WORKING MACHINE

Abstract

A working machine includes a machine body, a working device including a function portion to perform a function while in contact with a work target object, a hydraulic actuator to switch between a state in which the function portion contacts the work target object and a state in which the function portion is not in contact with the work target object, a manual operator to be operated in relation to actuation of the hydraulic actuator, and a controller configured or programmed to control the actuation of the hydraulic actuator. The controller is configured or programmed to derive a degree of contact of the function portion with the work target object based on a pressure of hydraulic fluid supplied to the hydraulic actuator, and if the derived degree matches or substantially matches a preset optimal degree, change an actuation state of the hydraulic actuator in action.

Claims

1. A working machine comprising: a machine body; a working device connected to the machine body and including a function portion to perform a function corresponding to a content of work while in contact with a work target object; a hydraulic actuator to switch between a first state in which the function portion is in contact with the work target object and a second state in which the function portion is not in contact with the work target object; a manual operator to be operated by a user in relation to actuation of the hydraulic actuator; and a controller configured or programmed to control the actuation of the hydraulic actuator; wherein the controller is configured or programmed to: derive a degree of contact of the function portion with the work target object based on a pressure of hydraulic fluid supplied to the hydraulic actuator; and if the derived degree of contact matches or substantially matches a preset optimal degree of contact, change an actuation state of the hydraulic actuator in action.

2. The working machine according to claim 1, wherein the controller is configured or programmed to change the actuation state of the hydraulic actuator in action while the manual operator is operated in relation to the actuation of the hydraulic actuator.

3. The working machine according to claim 1, wherein changing the actuation state of the hydraulic actuator in action by the controller includes reducing an actuation speed of the hydraulic actuator from an actuation speed corresponding to an instruction provided by operation of the manual operator.

4. The working machine according to claim 1, further comprising: a hydraulic pump to supply hydraulic fluid to the hydraulic actuator; and a prime mover to drive the hydraulic pump; wherein changing the actuation state of the hydraulic actuator in action by the controller includes reducing an actuation speed of the hydraulic actuator in action from an actuation speed corresponding to a combination of a drive rotational speed of the prime mover and an instruction provided by operation of the manual operator.

5. The working machine according to claim 2, wherein the hydraulic actuator includes a hydraulic cylinder including a tubular cylinder and a piston rod inserted in the tubular cylinder such that the piston rod is extendable out of and retractable into the tubular cylinder, the hydraulic cylinder being operable to switch between the first state and the second state by extending or retracting via extension of the piston rod out of the tubular cylinder or retraction of the piston rod into the tubular cylinder; the hydraulic cylinder includes a first port to allow hydraulic fluid to be supplied to the tubular cylinder to move the piston rod in a direction in which the piston rod extends out of the tubular cylinder and a second port to allow hydraulic fluid to be supplied to the tubular cylinder to move the piston rod in a direction in which the piston rod retracts into the tubular cylinder; and the controller is configured or programmed to, while the manual operator is operated in relation to extension or retraction of the hydraulic cylinder that is the actuation of the hydraulic actuator: derive the degree of contact of the function portion with the work target object based on the pressure of hydraulic fluid at least at the first port or the second port of the hydraulic cylinder; and if the derived degree of contact matches or substantially matches the preset optimal degree of contact, change a movement state of the piston rod of the hydraulic cylinder that is the actuation state of the hydraulic actuator in action.

6. The working machine according to claim 5, wherein the controller is configured or programmed to, while the manual operator is operated in relation to the extension or retraction of the hydraulic cylinder, reduce a movement speed of the piston rod of the hydraulic cylinder in action as the derived degree of contact approaches the preset optimal degree of contact.

7. The working machine according to claim 6, wherein the controller is configured or programmed to, while the manual operator is operated in relation to the extension or retraction of the hydraulic cylinder, cause the piston rod to stop moving when the derived degree of contact changes from a degree other than the preset optimal degree of contact to a degree matching or substantially matching the preset optimal degree of contact.

8. The working machine according to claim 7, wherein the controller is configured or programmed to, after changing the actuation state of the hydraulic cylinder while the manual operator is operated in relation to the extension or retraction of the hydraulic cylinder, when the operation of the manual operator in relation to the extension or retraction of the hydraulic cylinder is stopped and then the operation is resumed, cause the piston rod to move in accordance with an instruction provided by the resumed operation of the manual operator.

9. The working machine according to claim 5, wherein the working device includes: an arm extending from the machine body and connected to the machine body such that the arm is swingable up and down; and a bucket which is the function portion swingably connected to a distal portion of the arm; the hydraulic cylinder includes a first hydraulic cylinder to swing the arm and a second hydraulic cylinder to swing the bucket; and the controller is configured or programmed to, while the manual operator is operated to move the piston rod of the first hydraulic cylinder to lower the arm or to move the piston rod of the second hydraulic cylinder to bring the bucket into a discharging posture after the derived degree of contact reaches a value equal to or less than a specified value corresponding to a state in which the bucket is not in contact with a ground which is the work target object: derive the degree of contact of the bucket with the ground which is the work target object based on the pressure of hydraulic fluid at least at the first port or the second port of the first hydraulic cylinder or the second hydraulic cylinder in which the piston rod is moved by operating the manual operator; and if the derived degree of contact matches or substantially matches the preset optimal degree of contact, reduce a movement speed of the piston rod.

10. The working machine according to claim 9, wherein the controller is configured or programmed to derive the degree of contact of the bucket with the ground which is the work target object based on a relationship between the pressure of hydraulic fluid at the first port and the pressure of hydraulic fluid at the second port.

11. The working machine according to claim 5, wherein the function portion includes an attachable and detachable work attachment to be attached such that the work attachment is replaceable with another work attachment having a different function; and the controller is configured or programmed to recognize the work attachment which is attached, and, if the recognized work attachment is a specific function portion, change the movement state of the piston rod of the hydraulic cylinder in action when the derived degree of contact matches or substantially matches the preset optimal degree of contact.

12. The working machine according to claim 11, further comprising: an attachment selector to be used by the user to select a work attachment to be used from a plurality of types of work attachments having different functions; wherein the controller is configured or programmed to recognize the work attachment selected by the user via the attachment selector as the work attachment which is attached.

13. The working machine according to claim 11, wherein the controller is configured or programmed to compare the derived degree of contact with one of a plurality of the preset optimal degrees of contact corresponding to the respective functions of the plurality of types of work attachments that corresponds to the recognized work attachment.

14. The working machine according to claim 5, further comprising: one or more supply-discharge passages connected to the first port and/or the second port of the hydraulic cylinder; and one or more sensors to detect a pressure of hydraulic fluid in the one or more supply-discharge passages; wherein the controller is configured or programmed to, if a detection result from the one or more sensors exceeds a predetermined pressure while the manual operator is operated in relation to the extension and retraction of the hydraulic cylinder, change the movement state of the piston rod of the hydraulic cylinder in action to a state differing from an instruction provided by the operation of the manual operator.

15. The working machine according to claim 5, wherein the working device includes: an arm extending from the machine body and connected to the machine body such that the arm is swingable up and down; and a bucket which is the function portion swingably connected to a distal portion of the arm; the hydraulic cylinder includes a first hydraulic cylinder to swing the arm and a second hydraulic cylinder to swing the bucket; and the controller is configured or programmed to, if the pressure of hydraulic fluid at the first port or the second port of the first hydraulic cylinder exceeds a threshold for a certain period of time while the manual operator is operated on the first hydraulic cylinder to lower the arm, cause the piston rod of the first hydraulic cylinder to stop moving.

16. The working machine according to claim 5, further comprising: one or more supply-discharge passages connected to the first port and/or the second port of the hydraulic cylinder; a control valve to adjust a flow rate of hydraulic fluid flowing through the one or more supply-discharge passages; and one or more sensors to detect the pressure of hydraulic fluid in the one or more supply-discharge passages; wherein the manual operator includes an operator to receive input relating to actuation of the working device and to control a flow rate of the control valve based on the received input; and the controller is configured or programmed to, if the controller recognizes the attached function portion as a specific function portion and a detection result from the one or more sensors exceeds a threshold for a certain period of time while the input is received by the operator, control the control valve such that the flow rate of hydraulic fluid achieved by the control valve is zero or is lower than a flow rate of hydraulic fluid corresponding to the input received by the operator.

17. The working machine according to claim 16, wherein the controller is configured or programmed to, from when the input received by the operator starts being kept constant or substantially constant to when a change in the input received by the operator is detected, control the control valve such that the flow rate of hydraulic fluid achieved by the control valve is lower than the flow rate of hydraulic fluid corresponding to the input received by the operator that is kept constant or substantially constant.

18. The working machine according to claim 16, wherein the controller is configured or programmed to, in a case that the input is received by the operator for a certain period of time or more also after the detection result from the one or more sensors exceeds the threshold while the input is received by the operator and then the input received by the operator is kept constant or substantially constant, repeat the following until next time input received by the operator is detected: actuating the control valve when the detection result from the one or more sensors is less than the threshold; and stopping actuation of the control valve when the detection result from the one or more sensors exceeds the threshold.

19. The working machine according to claim 5, wherein the working device includes: an arm extending from the machine body and connected to the machine body such that the arm is swingable about a first shaft perpendicular to an up-and-down direction; and an earth auger connected to a distal portion of the arm such that the earth auger is swingable about a second shaft perpendicular to the up-and-down direction, the earth auger being the function portion and including a digging drill and a hydraulic motor to rotate the digging drill, the digging drill including a shaft body including a pointed end and a helical blade attached around the shaft body; the hydraulic cylinder includes a first hydraulic cylinder to swing the arm about the first shaft and a second hydraulic cylinder to swing the earth auger about the second shaft; and the controller is configured or programmed to, while the hydraulic motor is stopped; derive a degree of contact of the earth auger with soil which is the work target object based on a pressure of hydraulic fluid supplied to at least one of the hydraulic cylinder or the second hydraulic cylinder; and change the movement state of the piston rod of the hydraulic cylinder and set a digging depth of the earth auger in the soil to zero if the derived degree of contact matches or substantially matches the preset optimal degree of contact, wherein changing the movement state of the piston rod of the hydraulic cylinder includes stopping movement of the piston rod of the first hydraulic cylinder and the piston rod of the second hydraulic cylinder.

20. The working machine according to claim 19, wherein the working device includes an arm posture detector to detect a posture of the arm; and the controller is configured or programmed to, under a condition in which the set digging depth is zero, recognize a current digging depth of the earth auger in the soil based on a detection result from the arm posture detector.

21. The working machine according to claim 20, wherein the arm posture detector includes an angle sensor to sense an angle of rotation of the arm about the first shaft; and the controller is configured or programmed to, under the condition in which the set digging depth is zero, recognize the current digging depth of the earth auger in the soil based on a detection result from the angle sensor.

22. The working machine according to claim 20, wherein the arm posture detector includes a stroke sensor to detect a degree of extension or retraction of the first hydraulic cylinder; and the controller is configured or programmed to, under the condition in which the set digging depth is zero, recognize the current digging depth of the earth auger in the soil based on a detection result from the stroke sensor.

23. The working machine according to claim 20, further comprising at least one of a display or a speaker; wherein the controller is configured or programmed to, after determining that the current digging depth of the earth auger in the soil is a preset digging depth, cause at least one of the display or the speaker to provide a notification indicating that the current digging depth of the earth auger in the soil is the preset digging depth.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] A more complete appreciation of example embodiments of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings described below.

[0032] FIG. 1 is a general side view of a working machine according to a first example embodiment of the present invention that has attached thereto a bucket as a work attachment.

[0033] FIG. 2 is a general side view of a working machine according to the first example embodiment of the present invention that has attached thereto a sweeper as a work attachment.

[0034] FIG. 3 is a general side view of a working machine according to the first example embodiment of the present invention that has attached thereto a grapple as a work attachment.

[0035] FIG. 4 is a partial side view of a working machine according to the first example embodiment of the present invention that has attached thereto a hydraulic breaker as a work attachment.

[0036] FIG. 5 is a partial side view of a working machine according to the first example embodiment of the present invention that has attached thereto an earth auger as a work attachment.

[0037] FIG. 6 schematically illustrates a hydraulic circuit (first hydraulic circuit) of a working machine according to the first example embodiment of the present invention.

[0038] FIG. 7 schematically illustrates a hydraulic circuit (second hydraulic circuit) of a working machine according to the first example embodiment of the present invention.

[0039] FIG. 8 is a block diagram schematically illustrating an electrical system of a working machine according to the first example embodiment of the present invention.

[0040] FIG. 9 is a conceptual diagram of an attachment list stored in a storing unit of a working machine according to the first example embodiment of the present invention.

[0041] FIG. 10 schematically illustrates a display of a working machine according to the first example embodiment of the present invention that displays icons of the attachment list.

[0042] FIG. 11 is a flowchart schematically illustrating a process performed by a controller of a working machine according to the first example embodiment of the present invention.

[0043] FIG. 12 schematically illustrates a hydraulic circuit (second hydraulic circuit) of a working machine according to a second example embodiment of the present invention.

[0044] FIG. 13 schematically illustrates a hydraulic circuit (second hydraulic circuit) of a working machine according to another example embodiment of the present invention.

[0045] FIG. 14 schematically illustrates a hydraulic circuit (second hydraulic circuit) of a working machine according to another example embodiment of the present invention.

[0046] FIG. 15 schematically illustrates a hydraulic circuit (second hydraulic circuit) of a working machine according to another example embodiment of the present invention.

[0047] FIG. 16 schematically illustrates a hydraulic circuit (second hydraulic circuit) of a working machine according to another example embodiment of the present invention.

[0048] FIG. 17 schematically illustrates a hydraulic circuit (second hydraulic circuit) of a working machine according to another example embodiment of the present invention.

[0049] FIG. 18 schematically illustrates a hydraulic circuit (second hydraulic circuit) of a working machine according to another example embodiment of the present invention.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

[0050] Example embodiments will now be described with reference to the accompanying drawings, wherein like reference numerals designate corresponding or identical elements throughout the various drawings. The drawings are to be viewed in an orientation in which the reference numerals are viewed correctly.

[0051] The following description discusses example embodiments of the present invention with reference to the drawings as necessary.

[0052] As illustrated in FIG. 1, a working machine 1 includes a machine body 2, a pair of traveling devices 3 to support left and right side portions of the machine body 2 such that the machine body 2 is allowed to travel, and a working device 4 connected to the machine body 2. The working machine 1 also includes hydraulic actuators 50, 51, and 52 to actuate the traveling devices 3 and the working device 4. That is, the working machine 1 includes a hydraulic circuit 5 (hydraulic system) including the hydraulic actuators 50, 51, and 52 to actuate the traveling devices 3 and the working device 4 and hydraulic pump(s) to supply hydraulic fluid to the hydraulic actuators 50, 51, and 52. Accordingly, the working machine 1 includes a prime mover 10 to drive the hydraulic pump. The working machine 1 further includes manual operators 11 and 12 operated by a user in relation to the actuation of the hydraulic actuators 50, 51, and 52 and a controller 13 to control the actuation of the hydraulic actuators 50, 51, and 52. In the present example embodiment, the working machine 1 includes a display 14 to display information relating to work.

[0053] The machine body 2 includes a frame chassis 20, a seat 21 provided on the frame chassis 20, and a seat-protecting mechanism 22 to protect the seat 21.

[0054] The frame chassis 20 is made of sheet metal, has a three-dimensional shape suitable for the shape and size of the working machine 1, and defines a prime mover chamber ER that contains the prime mover 10 at a rear portion in a front-rear direction.

[0055] The seat 21 is located forward of the prime mover chamber ER (prime mover 10) and is fixed to the frame chassis 20. In the present example embodiment, the seat-protecting mechanism 22 is a so-called cabin that surrounds the seat 21. The seat 21 is located forward of the prime mover chamber ER as described above, and therefore the cabin 22 is also located forward of the prime mover chamber ER. That is, the cabin 22 defines an operation room RM in which the user who sits on the seat 21 stays at a position forward of the prime mover chamber ER.

[0056] The cabin 22 has front, back, left, and right windows, and the manual operators 11 and 12 operated by the user are provided in the cabin 22 (in the operation room RM). The manual operators 11 and 12 included in the working machine 1 according to the present example embodiment include a manual operator (hereinafter referred to as a first manual operator) 11 to control the traveling devices 3 and a manual operator (hereinafter referred to as a second manual operator) 12 to control the working device 4. The first manual operator 11 and the second manual operator 12 are provided in the operation room RM such that they can be operated by the user who sits on the seat 21. In the present example embodiment, the first manual operator 11 and the second manual operator 12 are provided at a front portion in the seat 21.

[0057] The first manual operator 11 and the second manual operator 12 are respective mechanical lever devices. That is, the first manual operator 11 and the second manual operator 12 include operation levers 110 and 120 pivotable along the front-rear direction and left-right direction. The traveling devices 3 and the working device 4 are actuated based on the degree and direction of pivot of the operation levers 110 and 120. In the following description, the operation lever 110 of the first manual operator 11 is referred to as a first operation lever, and the operation lever 120 of the second manual operator 12 is referred to as a second operation lever.

[0058] More specifically, the first manual operator 11 changes the direction of travel of the traveling devices 3 when the direction of pivot of the first operation lever 110 is changed, and controls the travel speed of the traveling devices 3 based on the degree of pivot of the first operation lever 110. The second manual operator 12 changes upward/downward movement of arm(s) 40 of the working device 4 (described later) or upward/downward swinging (rotational) movement of a work attachment 41a or the like which is a function portion of the working device 4 (described later) when the direction of pivot of the second operation lever 120 is changed, and controls the speed of the upward/downward movement of the arm(s) 40 or the speed of the upward/downward pivot of the work attachment 41a or the like based on the degree of pivot of the second operation lever 120. Note that, with regard to the working machine 1 according to the present example embodiment, in the case where the work attachment includes a hydraulic actuator (such as a hydraulic cylinder) to perform its own function (its independent function), another manual operator (AUX switch 75 in the present example embodiment) that differs from the second operation lever 120 may be operated in relation to the function (actuation of the hydraulic actuator) of the work attachment 41a.

[0059] The pair of traveling devices 3 support the opposite side portions of the frame chassis 20. In the present example embodiment, the pair of traveling devices 3 are crawler traveling devices. Specifically, each of the pair of traveling devices 3 includes idler(s) 30, driving wheel(s) 31, a plurality of rollers 32, an endless crawler belt 33, and traveling motor(s) 34. FIG. 1 illustrates a left side surface of the working machine 1, and therefore only one of the traveling devices 3 that supports the left side portion of the frame chassis 20 is illustrated.

[0060] A pair of the idlers 30 are provided at an interval in the front-rear direction. The plurality of rollers 32 are provided between the pair of idlers 30. The driving wheel(s) 31 is/are located higher than the rollers 32. The crawler belt 33 is wound around the idlers 30, the driving wheel(s) 31, and the rollers 32.

[0061] The traveling motors 34 drive the driving wheels 31 to rotate. In the present example embodiment, each traveling motor 34 is a hydraulic motor. Accordingly, the traveling motor 34 as a hydraulic actuator 50 for travel is connected in the hydraulic circuit 5. The left and right pair of traveling devices 3 rotate and drive the driving wheels 31 to cause the crawler belts 33 to turn.

[0062] The working device 4 includes the arm(s) 40 connected to the machine body 2 and a work attachment 41a as a function portion directly or indirectly connected to the arm(s) 40.

[0063] More specifically, the working device 4 includes the arm(s) 40 which is/are connected to the machine body 2 rotatably about a first shaft S1 extending perpendicularly to the up-and-down direction and which extend(s) to a position forward of the machine body 2, the work attachment 41a as a function portion to perform a function corresponding to specific work, and coupler(s) 45 to which the work attachment 41a is detachably attached, and the coupler(s) 45 is connected to the distal portion(s) of the arm(s) 40 rotatably about a second shaft S2 extending perpendicularly to the up-and-down direction.

[0064] In the present example embodiment, the working machine 1 further includes a plurality of hydraulic actuators 51 and 52 to actuate the working device 4. The plurality of hydraulic actuators 51 and 52 include hydraulic actuators 51 and 52 to switch between a state in which the work attachment (function portion) 41a or the like is in contact with a work target object and a state in which the work attachment (function portion) 41a or the like is not in contact with the work target object. In the present example embodiment, the hydraulic actuators 51 and 52 to actuate the working device 4 are fluidly connected in the hydraulic circuit 5 and are also mechanically connected in the working device 4.

[0065] The arm(s) 40 extends in one direction. Each arm 40 includes a proximal portion directly or indirectly connected to the machine body 2 rotatably about the first shaft S1 and a distal portion at the opposite end of the arm 40 from the proximal portion. The proximal portion and the distal portion are arranged in the one direction. In the present example embodiment, the distal portion of the arm 40 bends downward. The proximal portion of the arm 40 is indirectly connected to the machine body 2. Specifically, the working machine 1 includes link(s) 46 connected to a rear portion of the frame chassis 20 and extending in the up-and-down direction. Each link 46 includes a lower end portion and an upper end portion. The lower end portion of the link 46 is connected to the frame chassis 20 via a lateral shaft S3 extending perpendicularly to the up-and-down direction. On the other hand, a corresponding arm 40 is rotatably connected to the upper end portion of the link 46 via the first shaft S1. Accordingly, the working machine 1 includes an arm posture detector SE1 to detect the posture of the arm(s) 40. The arm posture detector SE1 may be a detector to directly detect the posture of the arm(s) 40, and may be a detector to detect something whose parameter changes in relation to (in proportion to) changes in posture (tilt angle) of the arm(s) 40. Specifically, examples of the arm posture detector SE1 include a stroke sensor to detect the degree of extension or retraction of the first hydraulic cylinder(s) 51 to rotate (swing) the arm(s), and a first angle sensor SE1 to sense the angle of rotation of the arm(s) 40 about the first shaft S1. In the present example embodiment, the arm posture detector SE1 is an angle sensor SE1 electrically connected to the controller 13 to sense the angle of rotation of the arm(s) 40 about the first shaft S1 (such an angle sensor is hereinafter referred to as a first angle sensor).

[0066] In the present example embodiment, such arms 40 configured as described above are provided on left and right sides of the cabin 22. That is, the working device 4 includes a pair of arms 40 arranged with the cabin 22 therebetween. The shapes and arrangement of the pair of arms 40 are each symmetrical with respect to the widthwise (lateral) center of the cabin 22. Accordingly, a left and right pair of the links 46 are connected to the arms 40. FIG. 1 illustrates the left side surface of the working machine 1, and therefore only the arm 40 and the link 46 provided on the left side are illustrated similarly to the traveling devices 3.

[0067] The working device 4 includes, as the hydraulic actuators 51 and 52 to actuate the working device 4, first hydraulic cylinder(s) 51 to rotate the arm(s) 40 about the first shaft S1 to raise/lower the distal portion of the arm(s) 40, and second hydraulic cylinder(s) 52 to rotate the coupler(s) 45 (work attachment 41a) about the second shaft S2. Accordingly, the working machine 1 includes an angle sensor SE2 electrically connected to the controller 13 to sense the angle of rotation of the coupler(s) 45 (work attachment 41a or the like) about the second shaft S2 (such an angle sensor is hereinafter referred to as a second angle sensor).

[0068] The first hydraulic cylinder(s) 51 and the second hydraulic cylinder(s) 52 can each be used to bring the work attachment 41a or the like into contact with a work target object T. In the working machine 1 according to the present example embodiment, the first hydraulic cylinder(s) 51 is/are used as hydraulic actuator(s) to automatically adjust the degree of contact when the work attachment 41a is brought into contact with the work target object T.

[0069] The first hydraulic cylinder(s) 51 and the second hydraulic cylinder(s) 52 include hydraulic cylinders which include hydraulic actuators, and are therefore connected in the hydraulic circuit 5. The first hydraulic cylinder(s) 51 and the second hydraulic cylinder(s) 52 each include a tubular cylinder 510, 520, and a piston rod 511, 521 inserted in the tubular cylinder 510, 520 such that the piston rod is extendable out of and retractable into the tubular cylinder. Each hydraulic cylinder includes a first port Pa1, Pb1 to allow hydraulic fluid to be supplied to the tubular cylinder 510, 520 to move the piston rod 511, 521 in a direction in which the piston rod 511, 521 extends out of the tubular cylinder 510, 520, and a second port Pa2, Pb2 to allow hydraulic fluid to be supplied to the tubular cylinder 510, 520 to move the piston rod 511, 521 in a direction in which the piston rod 511, 521 retracts into the tubular cylinder 510, 520. That is, the first hydraulic cylinder(s) 51 and the second hydraulic cylinder(s) 52 are double-acting hydraulic cylinders.

[0070] More specifically, the piston rod 511, 521 includes a piston 511a, 521a fitted in the tubular cylinder 510, 520 movably in an axial direction and a rod 511b, 521b connected to the piston 511a, 521a and extending out of one end of the tubular cylinder 510, 520. Accordingly, the first port Pa1, Pb1 is located at the opposite end (the end opposite the one end of the tubular cylinder 510, 520 from which the rod 511b, 521b extends out) of the tubular cylinder 510, 520, and the second port Pa2, Pb2 is located at the one end (the one end of the tubular cylinder 510, 520 from which the rod 511b, 521b extends out) of the tubular cylinder 510, 520. With this, the first hydraulic cylinder(s) 51 and the second hydraulic cylinder(s) 52 are each configured such that hydraulic fluid is supplied and discharged to and from two spaces in the tubular cylinder 510, 520 divided by the piston 511a, 521a via the first port Pa1, Pb1 and the second port Pa2, Pb2 to cause the piston rod 511, 521 to extend out of and retract into the tubular cylinder 510, 520, so that the hydraulic cylinder as a whole extends and retracts.

[0071] Such a first hydraulic cylinder 51 is provided for each arm 40. That is, the working device 4 includes a pair of first hydraulic cylinders 51 provided on opposite sides of the cabin 22. The pair of first hydraulic cylinders 51 are symmetrical with respect to the widthwise (lateral) center of the cabin 22 to correspond to the respective pair of arms 40.

[0072] Each of the pair of first hydraulic cylinders 51 connects a corresponding arm 40 and the frame chassis 20. That is, the distal end (end of the rod 511b) of the piston rod 511 of the first hydraulic cylinder 51 is connected to the arm 40 rotatably about an axis perpendicular to the up-and-down direction, and the end of the tubular cylinder 510 of the first hydraulic cylinder 51 is connected to the frame chassis 20 rotatably about an axis perpendicular to the up-and-down direction.

[0073] In the present example embodiment, a pair of the second hydraulic cylinders 52 are provided at an interval in the width direction. The pair of second hydraulic cylinders 52 are symmetrical with respect to the widthwise (lateral) center of the cabin 22. Each of the pair of second hydraulic cylinders 52 connects a corresponding arm 40 and a corresponding coupler 45 to each other. That is, the distal end (end of the rod 521b) of the piston rod 521 of the second hydraulic cylinder 52 is connected to the couplers 45 rotatably about an axis perpendicular to the up-and-down direction, and the end of the tubular cylinder 520 of the second hydraulic cylinder 52 is connected to the arm 40 rotatably about an axis perpendicular to the up-and-down direction.

[0074] With this, the arm 40 rotates about the first shaft S1 and the distal portion is raised and lowered as the first hydraulic cylinder 51 extends or retracts. The work attachment 41a attached to each coupler 45 rotates about the second shaft S2 and swings up or down as the second hydraulic cylinder 52 extends or retracts. Note that, in many cases, a bucket 41a is used as the work attachment 41a or the like connected to the couplers 45. Since the second hydraulic cylinders 52 cause the bucket 41a to swing (rotate), the second hydraulic cylinders 52 are also referred to as bucket cylinders when the couplers 45 are connected to the bucket 41a.

[0075] FIG. 1 illustrates a bucket to excavate soil etc. as the work attachment 41a. In addition to the bucket 41a, examples of the work attachment also include a sweeper 41b as illustrated in FIG. 2, a grapple 41c as illustrated in FIG. 3, a hydraulic breaker 41d as illustrated in FIG. 4, and an earth auger 41e as illustrated in FIG. 5, as well as a dozer blade, a brush cutter, a tree puller, a hydraulic crusher, an angle broom, a pallet fork, a mower, and a snow blower (which are not illustrated). Such work attachment 41a are attachable and detachable (replaceable) to and from the couplers 45.

[0076] A bucket and a dozer blade which excavate or carry earth and sand etc. are obtained by forming sheet metal into a shape that can be used to perform a function. The sweeper 41b (see FIG. 2) to clean a road surface (ground surface), the grapple 41c (see FIG. 3) to hold lumber etc., the hydraulic breaker 41d (see FIG. 4) to break bedrock etc., and the earth auger 41e (see FIG. 5) to dig a hole in soil etc. each include hydraulic actuator(s) (a hydraulic motor 411b, 411d, a hydraulic cylinder 411c) to perform a function relating to specific work. Specifically, the sweeper 41b includes the hydraulic motor 411b to rotate a brush 410b rotatable in contact with the road surface, and the hydraulic breaker 41d includes the hydraulic motor 411d to apply vibrations to a rod-shaped crushing chisel 410d which comes into contact with rock etc. The earth auger 41e includes a digging drill 410e including a shaft body including a pointed end and a helical blade attached around the shaft body, and a hydraulic motor 411e to rotate the digging drill 410e, and is configured such that the helical blade of the digging drill 410e drills a hole in the soil by the hydraulic motor 411e rotating the digging drill 410e with the pointed end at the bottom (with the pointed end stuck in the soil). The grapple 41c includes the hydraulic cylinder 411c to cause a pair of jaws 410c, which hold an object therebetween, to approach and move away from each other. Such hydraulic actuators 411b, 411c, 411d, and 411e of the work attachments 41b and the like are each connected in the hydraulic circuit 5. This will be described together with the hydraulic circuit 5.

[0077] As illustrated in FIGS. 6 and 7, the hydraulic circuit 5 according to the present example embodiment includes a first hydraulic circuit (hydraulic system for travel) 5A to drive the traveling devices 3 (traveling motor(s) 34 (50)) and a second hydraulic circuit (hydraulic system for work) 5B to drive the working device 4.

[0078] The following first discusses the first hydraulic circuit 5A. As illustrated in FIG. 6, the first hydraulic circuit 5A includes a hydraulic pump (hereinafter referred to as a first hydraulic pump) 53 driven by the prime mover 10 to deliver hydraulic fluid and hydrostatic transmission(s) (hereinafter referred to as HST) 54 hydraulically controlled by the pressure of hydraulic fluid delivered by the first hydraulic pump 53 to drive the driving wheel(s) 31 of the traveling device(s) 3. The first hydraulic circuit 5A includes a hydraulic fluid tank 55 to store hydraulic fluid.

[0079] The first hydraulic pump 53 is a fixed displacement pump. The first hydraulic pump 53 includes an input shaft. The input shaft of the first hydraulic pump 53 is connected to the output shaft of the prime mover 10. With this, the first hydraulic pump 53 rotates synchronously with the output rotation of the prime mover 10. The first hydraulic pump 53 is driven by the prime mover 10 to suck hydraulic fluid from the hydraulic fluid tank 55 and deliver it toward a downstream portion.

[0080] A pair of HSTs 54 are provided for the respective left and right pair of traveling devices 3. Each of the pair of HSTs 54 includes a hydraulic pump (hereinafter referred to as a second hydraulic pump) 56, a traveling motor 34 which is a hydraulic motor 50, and a pair of fluid passages R1a and R1b provided between the second hydraulic pump 56 and the traveling motor 34. Specifically, the first hydraulic circuit 5A includes a first driver DR to drive one of the pair of traveling devices 3 (right traveling device 3) and a second driver DL to drive the other of the pair of traveling devices 3 (left traveling device 3). The first driver DR and the second driver DL each include a HST 54, a second hydraulic pump 56, a hydraulic motor 50 which is a traveling motor 34, and a pair of fluid passages R1a and R1b. Note that the first driver DR and the second driver DL have the same structure. Accordingly, in the following description, the first driver DR and the second driver DL are collectively referred to as drivers D. Drivers D indicate the first driver DR and the second driver DL (and a driver D indicates the first driver DR or the second driver DL).

[0081] In the HST 54 of the driver D, the second hydraulic pump 56 includes an input shaft. The input shaft of the second hydraulic pump 56 is connected to the output shaft of the prime mover 10. In the present example embodiment, the output from the prime mover 10 is inputted into the first hydraulic pump 53 and the second hydraulic pump 56. That is, the prime mover 10 is used to drive both the first hydraulic pump 53 and the second hydraulic pump 56. Accordingly, the output shaft of the prime mover 10, the input shaft of the first hydraulic pump 53, and the input shaft of the second hydraulic pump 56 are connected to each other coaxially in a line.

[0082] With this, the second hydraulic pump 56 rotates synchronously with the output rotation of the prime mover 10. That is, the first hydraulic pump 53 and the second hydraulic pump 56 each rotate synchronously with the output rotation of the same prime mover 10. A third hydraulic pump 64 of a second hydraulic circuit 5B (described later) also receives the output from the same prime mover 10. The third hydraulic pump 64 includes an output shaft, and therefore the output shaft of the third hydraulic pump 64, the output shaft of the prime mover 10, the input shaft of the first hydraulic pump 53, and the input shaft of the second hydraulic pump 56 are also connected to each other coaxially in a line (in series).

[0083] In the HST 54 of the driver D, the second hydraulic pump 56 is a variable displacement pump including a movable swash plate 56a. Accordingly, the second hydraulic pump 56 includes a pair of pressure receivers 56b and 56c. The pair of pressure receivers 56b and 56c receive pilot hydraulic fluid. With this, the tilt angle and direction of the movable swash plate 56a of the second hydraulic pump 56 are controlled.

[0084] The second hydraulic pump 56 is driven by the prime mover 10 to suck hydraulic fluid from the hydraulic fluid tank 55 to deliver it toward a downstream portion. In the present example embodiment, the second hydraulic pump 56 delivers hydraulic fluid toward the HST 54 located downstream thereof. With this, hydraulic fluid delivered by the second hydraulic pump 56 is partially introduced into the HST 54.

[0085] In the present example embodiment, the first hydraulic pump 53 delivers hydraulic fluid toward the pressure receivers 56b and 56c of the second hydraulic pump 56 of the driver D via pump control valve(s) 57 and shuttle valve(s) 58 operably connected to the first operation lever 110. With this, the pressure of hydraulic fluid from the first hydraulic pump 53, as pilot hydraulic fluid to control the movable swash plate 56a of the second hydraulic pump 56 of the driver D, acts on the pressure receiver(s) 56b and 56c of the second hydraulic pump 56.

[0086] As described earlier, the first operation lever 110 is capable of pivoting along the front-rear and left-right directions, and its neutral position N is an intermediate position in the left-right direction and an intermediate position in the front-rear direction. In connection with this, in the case where the first operation lever 110 is in the neutral position N, the movable swash plate 56a of the second hydraulic pump 56 is in the neutral position, so that the second hydraulic pump 56 does not deliver hydraulic fluid. With this, the traveling motor 34 stays in the stopped state. That is, the pair of traveling devices 3 are in the stopped state, and the working machine 1 (machine body 2) is in the stopped state.

[0087] On the other hand, in the case where the first operation lever 110 is pivoted in any of the front-rear and left-right directions, the angle (degree of pivot) and the direction of pivot from the neutral position N determine the angle and direction of tilt of the movable swash plate 56a of the second hydraulic pump 56. This determines to drive/stop the traveling motor 34, and determines the direction and the speed of driving/rotating. With this, the direction in which the working machine 1 (machine body 2) travels (turns) and the travel speed are controlled based on the operation (degree of pivot and the direction of pivot) of the first operation lever 110.

[0088] In the driver D, the traveling motor 34 (50) is a variable displacement motor including a movable swash plate 50a. The movable swash plate 50a can be switched between a high-speed tilt state in which the movable swash plate 50a is tilted a small angle (small-displacement position) and a low-speed tilt state in which the movable swash plate 50a is tilted a large angle (large-displacement position).

[0089] In the driver D, the traveling motor 34 (50) includes a swash plate control actuator 59 operably connected to the movable swash plate 50a. A switching valve 60 is fluidly connected to the swash plate control actuator 59 of the traveling motor 34.

[0090] The switching valve 60 can be switched between a hydraulic fluid supply state in which hydraulic fluid is supplied to the swash plate control actuator 59 and a hydraulic fluid discharge state in which hydraulic fluid is discharged from the swash plate control actuator 59. Accordingly, the manner in which the movable swash plate 50a of the traveling motor 34 (50) is tilted is changed according to a change in the state of the switching valve 60.

[0091] The switching valve 60, upon receipt of the pressure (hydraulic pressure) of pilot hydraulic fluid, enters the hydraulic fluid supply state. The switching valve 60, upon release from pilot hydraulic fluid, returns to the hydraulic fluid discharge state. Hydraulic fluid from the first hydraulic pump 53, as pilot hydraulic fluid to the switching valve 60, is supplied to the switching valve 60 via an electromagnetic switching valve 61 for speed change.

[0092] The electromagnetic switching valve 61 for speed change can be switched between an open state in which hydraulic fluid is allowed to flow through a flow passage and a closed state in which hydraulic fluid is blocked from flowing through the flow passage. The electromagnetic switching valve 61 for speed change includes a solenoid 61a and a spring and is normally biased by the spring in the closed state. In the closed state, the electromagnetic switching valve 61 for speed change blocks hydraulic fluid from flowing from the first hydraulic pump 53 to the switching valve 60 and brings the switching valve 60 into the hydraulic fluid discharge state.

[0093] The solenoid 61a of the electromagnetic switching valve 61 for speed change is electrically connected to the controller 13. With this, the electromagnetic switching valve 61 for speed change, upon receipt of a control signal from the controller 13, enters the open state by energization of the solenoid 61a, allowing hydraulic fluid from the first hydraulic pump 53 to be discharged as pilot hydraulic fluid to the switching valve 60. With this, the switching valve 60 enters the hydraulic fluid supply state.

[0094] The working machine 1 includes a transmission switch 80 electrically connected to the controller 13 to switch between a high-speed mode in which the traveling devices 3 travel at high speed and a low-speed mode in which the traveling devices 3 travel at low speed.

[0095] When the transmission switch 80 is operated to select the high-speed mode, the controller 13 causes the electromagnetic switching valve 61 for speed change to enter the closed state, so that the switching valve 60 enters the hydraulic fluid discharge state. Accordingly, the movable swash plate 50a of the traveling motor 34 enters the high-speed tilt state, and the traveling motor 34 (50) rotates at high speed. On the contrary, when the transmission switch 80 is operated to select the low-speed mode, the controller 13 causes the electromagnetic switching valve 61 for speed change to enter the open state, so that the switching valve 60 enters the hydraulic fluid supply state. Accordingly, the movable swash plate 50a of the traveling motor 34 (50) enters the low-speed tilt state, and the traveling motor 34 (50) rotates at low speed.

[0096] In the present example embodiment, the traveling motor 34 (50) is provided with a braking actuator 62 which is a hydraulic actuator. The braking actuator 62, upon receipt of hydraulic fluid, brakes the traveling motor 34 (50). Hydraulic fluid from the first hydraulic pump 53 is supplied to the braking actuator 62 of the traveling motor 34 via an electromagnetic switching valve 63 for braking.

[0097] The electromagnetic switching valve 63 for braking can be switched between an open state in which hydraulic fluid is allowed to flow through a flow passage and a closed state in which hydraulic fluid is blocked from flowing through the flow passage. The electromagnetic switching valve 63 for braking includes a solenoid 63a and a spring and is normally biased by the spring in the closed state. In the closed state, the electromagnetic switching valve 63 for braking blocks hydraulic fluid from the first hydraulic pump 53 from flowing toward the braking actuator 62 of the traveling motor 34 (50).

[0098] The solenoid 63a of the electromagnetic switching valve 63 for braking is electrically connected to the controller 13. The electromagnetic switching valve 63 for braking, upon receipt of a control signal from the controller 13, enters the open state by energization of the solenoid 63a, allowing hydraulic fluid from the first hydraulic pump 53 to be supplied to the braking actuator 62. With this, the traveling motor 34 (50) is braked.

[0099] The working machine 1 includes a brake pedal 79 electrically connected to the controller 13 to switch between braking and not braking the traveling motor 34 (50). When the brake pedal 79 is not depressed by the user, the controller 13 keeps the electromagnetic switching valve 63 for braking in the closed state. Therefore, the traveling motor 34 (50) is not braked. On the other hand, when the brake pedal is depressed by the user, the controller 13 brings the electromagnetic switching valve 63 for braking into the open state. With this, the traveling motor 34 (50) is braked.

[0100] The second hydraulic circuit 5B (system) will now be described. As illustrated in FIG. 7, the second hydraulic circuit 5B includes the third hydraulic pump 64 which is driven by the prime mover 10 to deliver hydraulic fluid and which supplies hydraulic fluid to the hydraulic actuators 51 and 52 (first hydraulic cylinder(s) 51, the second hydraulic cylinder(s) 52, and/or the hydraulic actuator 411b or the like of the work attachment 41b or the like) of the working device 4. The second hydraulic circuit 5B includes the hydraulic fluid tank 55 to store hydraulic fluid. The hydraulic fluid tank 55 is shared by the first hydraulic circuit 5A and the second hydraulic circuit 5B. In the present example embodiment, the second hydraulic circuit 5B includes a pump controller (so-called load sensing system (LS system)) 81 to control the delivery flow rate of the third hydraulic pump 64 depending on work.

[0101] The third hydraulic pump 64 is a variable displacement pump capable of changing the delivery flow rate. The third hydraulic pump 64 includes an input shaft. The input shaft of the third hydraulic pump 64 is connected to the output shaft of the prime mover 10.

[0102] In the present example embodiment, the input shaft of the third hydraulic pump 64 is connected coaxially in a line (in series) with the input shaft of the first hydraulic pump 53 and the input shafts of the second hydraulic pumps 56 of the first hydraulic circuit 5A (see FIGS. 6 and 7). That is, in the hydraulic circuit 5 according to the present example embodiment, a plurality of hydraulic pumps (first hydraulic pump 53, second hydraulic pumps 56, third hydraulic pump 64) are driven by the same prime mover 10. With this, the third hydraulic pump 64 rotates synchronously with the output rotation of the prime mover 10. The third hydraulic pump 64 is driven by the prime mover 10 to suck hydraulic fluid from the hydraulic fluid tank 55 and deliver it toward a downstream position.

[0103] The second hydraulic circuit 5B includes a plurality of AUX ports 65a, 65b, and 65c to which pipes leading to the hydraulic actuator 411b, 411c or the like of the work attachment 41b, 41c or the like are connected detachably. The second hydraulic circuit 5B includes a control valve (hereinafter referred to as a first control valve) 66 to control the flow of hydraulic fluid supplied to the first hydraulic cylinders 51 and a control valve (hereinafter referred to as a second control valve) 67 to control the flow of hydraulic fluid supplied to the second hydraulic cylinders 52, as well as a control valve (hereinafter referred to as a third control valve) 68 to control the flow of hydraulic fluid supplied to and discharged from the hydraulic actuator of the work attachment 41b or the like via two of the plurality of AUX ports 65a, 65b, and 65c. The second hydraulic circuit 5B includes pressure detectors 69a1, 69a2, 69b1, 69b2, 69c1, and 69c2 electrically connected to the controller 13 to detect the pressure of hydraulic fluid in the hydraulic actuators 51, 52, 411b, 411c and/or the like (first hydraulic cylinders 51, the second hydraulic cylinders 52, and/or the hydraulic actuator 411b, 411c or the like of the work attachment 41b, 41c or the like) attached to the working device 4.

[0104] The second hydraulic circuit 5B includes a pipe (hereinafter referred to as a delivery fluid passage) R2 connected to the delivery port of the third hydraulic pump 64 and a plurality of pipes (hereinafter referred to as supply fluid passages) R3a, R3b, and R3c branching from the delivery fluid passage R2 in parallel and connected to the pump ports of the first control valve 66, the second control valve 67, and the third control valve 68, respectively. The second hydraulic circuit 5B also includes a pipe (hereinafter referred to as a bleed-off fluid passage) R4 which branches from the delivery fluid passage R2 at a position located upstream of the positions at which the plurality of supply fluid passages R3a, R3b, and R3c branch to reach the hydraulic fluid tank 55 and which is provided with a flow rate adjustment valve 70 at an intermediate position thereof, and pipes (hereinafter referred to as drain fluid passages) R5a, R5b, and R5c connected downstream of the tank ports of the first control valve 66, the second control valve 67, and the third control valve 68 and the flow rate adjustment valve 70 of the bleed-off fluid passage R4. With this, the flow rate of hydraulic fluid in the delivery fluid passage R2 is adjusted by the flow rate adjustment valve 70 of the bleed-off fluid passage R4.

[0105] In the present example embodiment, the working device 4 includes the first hydraulic cylinders 51 and the second hydraulic cylinders 52 as the hydraulic actuators 51 and 52. When the work attachment 41b, 41c or the like including the hydraulic actuator 411b, 411c or the like is attached to the working device 4, the working device 4 includes, as hydraulic actuators thereof, not only the first hydraulic cylinders 51 and the second hydraulic cylinders 52 but also the hydraulic actuator 411b, 411c or the like of the work attachment 41b, 41c or the like.

[0106] Accordingly, the second hydraulic circuit 5B includes, as the pressure detectors 69a1, 69a2, 69b1, 69b2, 69c1, and 69c2, first pressure detectors 69al and 69a2 electrically connected to the controller 13 to detect the pressure of hydraulic fluid in the first hydraulic cylinders 51, second pressure detectors 69b1 and 69b2 electrically connected to the controller 13 to detect the pressure of hydraulic fluid in the second hydraulic cylinders 52, and third pressure detectors 69c1 and 69c2 electrically connected to the controller 13 to detect the pressure of hydraulic fluid in the hydraulic actuator of the work attachment 41b or the like.

[0107] As described earlier, the first hydraulic cylinders 51 and the second hydraulic cylinders 52 are each a double-acting hydraulic cylinder and include the first port Pa1, Pb1 and the second port Pa2, Pb2 via which hydraulic fluid enters and exits. Accordingly, the first pressure detectors 69a1 and 69a2 are connected to a pair of supply-discharge passages (hereinafter referred to as first supply-discharge passages) R6a and R6b which are pipes connected to the first ports Pa1 and the second ports Pa2 of the first hydraulic cylinders 51, and the second pressure detectors 69b1 and 69b2 are connected to a pair of supply-discharge passages (hereinafter referred to as second supply-discharge passages) R7a and R7b which are pipes connected to the first ports Pb1 and the second ports Pb2 of the second hydraulic cylinders 52. The third pressure detectors 69c1 and 69c2 are connected to a pair of supply-discharge passages (hereinafter referred to as third supply-discharge passages) R8a and R8b which are pipes to connect the third control valve 68 and two AUX ports 65a and 65c (hydraulic fluid ports) to each other.

[0108] In the present example embodiment, the pair of first pressure detectors 69a1 and 69a2 are provided near the first ports Pa1 and the second ports Pa2 of the first hydraulic cylinders 51 in the pair of first supply-discharge passages R6a and R6b. The pair of second pressure detectors 69b1 and 69b2 are provided near the first ports Pb1 and the second ports Pb2 of the second hydraulic cylinders 52 in the pair of second supply-discharge passages R7a and R7b. The pair of third pressure detectors 69c1 and 69c2 are provided near the AUX ports 65a and 65c in the pair of third supply-discharge passages R8a and R8b.

[0109] With this, the pair of first pressure detectors 69a1 and 69a2 detect the pressure of hydraulic fluid at the first port Pa1 of each first hydraulic cylinder 51 and the pressure at the second port Pa2 of the first hydraulic cylinder 51, and the pair of second pressure detectors 69b1 and 69b2 detect the pressure of hydraulic fluid at the first port Pb1 of each second hydraulic cylinder 52 and at the second port Pb2 of the second hydraulic cylinder 52. That is, the first pressure detectors 69a1 and 69a2 and the second pressure detectors 69b1 and 69b2 detect the pressure of hydraulic fluid (pressure of hydraulic fluid in the inner spaces divided by the piston 511a, 521a) in the tubular cylinders 510, 520 of the hydraulic cylinders 51, 52. On the contrary, the pair of third pressure detectors 69c1 and 69c2 detect the pressure of hydraulic fluid supplied to and discharged from the hydraulic actuator 411b, 411c or the like of the work attachment 41b, 41c or the like via the pair of AUX ports 65a and 65c.

[0110] The pressure detectors 69a1, 69a2, 69b1, 69b2, 69c1, and 69c2 (first pressure detectors 69a1 and 69a2, second pressure detectors 69b1 and 69b2, third pressure detectors 69c1 and 69c2), upon detecting the pressure of hydraulic fluid, output the detection result as a signal to the controller 13.

[0111] The control valves 66, 67, and 68 (first control valve 66, second control valve 67, third control valve 68) are pilot-pressure-controlled direction switching valves each including a spool with pressure receivers 66a, 66b, 67a, 67b, 68a, and/or 68b to receive pilot pressure at opposite sides thereof. The first hydraulic pump 53 of the first hydraulic circuit 5A is configured to supply hydraulic fluid for control (pilot hydraulic fluid) also to the control valves (first control valve 66, second control valve 67, third control valve 68) of the second hydraulic circuit 5B. That is, the first hydraulic pump 53 is used by both the first hydraulic circuit 5A and the second hydraulic circuit 5B and supplies hydraulic fluid for control (pilot hydraulic fluid) to target positions in the entire hydraulic circuit 5.

[0112] In the present example embodiment, the second hydraulic circuit 5B includes operation valves 71a, 71b, 71c, and 71d to actuate the first hydraulic cylinders 51 and the second hydraulic cylinders 52 based on the operation of the second operation lever 120. In the present example embodiment, the second operation lever 120 is pivotable about the lower end thereof. Based on this, the plurality of operation valves 71a, 71b, 71c, and 71d are provided around the lower portion of the second operation lever 120. Specifically, the second operation lever 120 is pivotable along the front-rear and left-right directions about the lower end thereof. Accordingly, a pair of (two of) the operation valves 71a, 71b, 71c, and 71d are provided forward and rearward of the second operation lever 120, and the other pair of (other two of) the operation valves 71a, 71b, 71c, and 71d are provided leftward and rightward of the second operation lever 120. Among the plurality of (four) operation valves 71a, 71b, 71c, and 71d, one or more of the operation valves 71a, 71b, 71c, and 71d at position(s) corresponding to the direction of pivot of the second operation lever 120 is/are actuated. That is, when the second operation lever 120 is pivoted in forward, rearward, leftward, or rightward, one or more of the operation valves 71a, 71b, 71c, and 71d at position(s) corresponding to the direction of pivot of the second operation lever 120 is/are actuated, so that hydraulic fluid from the first hydraulic pump 53 as pilot hydraulic fluid is discharged from the one or more of the operation valves 71a, 71b, 71c, and 71d corresponding to the pivot of the second operation lever 120 toward the control valve(s) (first control valve 66, second control valve 67).

[0113] Specifically, the neutral position N of the second operation lever 120 is an intermediate position in the front-rear direction and an intermediate position in the left-right direction, similarly to the first operation lever 110. When the second operation lever 120 is pivoted in the forward direction F from the neutral position N, the corresponding operation valve 71a allows pilot hydraulic fluid (hydraulic fluid) in an amount corresponding to the pivot angle (operation amount) of the second operation lever 120 to flow. Accordingly, pilot hydraulic fluid (hydraulic fluid) is supplied to one pressure receiver 66a of the first control valve 66 via a pilot fluid passage, and the spool of the first control valve 66 moves in one direction. With this, hydraulic fluid is supplied from the first control valve 66 to the second ports Pa2 of the first hydraulic cylinders 51 via the supply-discharge passage R6a, and hydraulic fluid is discharged into the first control valve 66 via the supply-discharge passage R6b from the first ports Pa1 of the first hydraulic cylinders 51. With this, the first hydraulic cylinders 51 retract, and the arms 40 are lowered.

[0114] In contrast, when the second operation lever 120 is pivoted in the rearward direction B from the neutral position N, the corresponding operation valve 71b allows pilot hydraulic fluid (hydraulic fluid) in an amount corresponding to the pivot angle (operation amount) of the second operation lever 120 to flow. Accordingly, pilot hydraulic fluid (hydraulic fluid) is supplied to the opposite pressure receiver 66b of the first control valve 66 via a pilot fluid passage, and the spool of the first control valve 66 moves in the opposite direction. With this, hydraulic fluid is supplied from the first control valve 66 to the first ports Pa1 of the first hydraulic cylinders 51 via the supply-discharge passage R6b, and hydraulic fluid is discharged into the first control valve 66 via the supply-discharge passage R6a from the second ports Pa2 of the first hydraulic cylinders 51. With this, the first hydraulic cylinders 51 extend, and the arms 40 are raised.

[0115] Thus, with the working machine 1 according to the present example embodiment, when the second operation lever 120 is pivoted in the forward F or rearward B direction, pilot hydraulic fluid is supplied from the operation valve 71a or 71b corresponding to the operation (pivot) of the second operation lever 120 to the first control valve 66, so that the spool of the first control valve 66 moves and the first hydraulic cylinders 51 extend or retract (arms 40 are raised or lowered) in response to the operation of the second operation lever 120. Based on this, the working machine 1 according to the present example embodiment is configured such that, when the degree of contact between the work attachment 41a or the like and the work target object Tis the optimal degree of contact, the spool of the first control valve 66 moves and the action state of the first hydraulic cylinders 51 (raised/lowered state or stopped state of the arms 40) is brought to a state not corresponding to the instruction provided by the user operation of the second operation lever 120.

[0116] Specifically, the second hydraulic circuit 5B includes a pilot control valve 72 to change the flow state of pilot hydraulic fluid, in a pair of pipes (pilot fluid passages) R9a and R9b to connect a pair of operation valves 71a and 71b located forward F and rearward B of the second operation lever 120 and a pair of pressure receivers 66a and 66b of the first control valve 66. The pilot control valve 72 is a solenoid valve. Solenoids 72a and 72b of the pilot control valve 72 are connected to the controller 13. The pilot control valve 72 can be switched between (i) a first state in which upstream portions and downstream portions of the respective pair of pilot fluid passages R9a and R9b are in communication with each other, (ii) a second state in which the upstream portions and downstream portions of the pair of pilot fluid passages R9a and R9b are blocked from each other, and (iii) a third state in which the upstream portion of the pilot fluid passage R9a is in communication with the downstream portion of the pilot fluid passage R9b, and the upstream portion of the pilot fluid passage R9b is in communication with the downstream portion of the pilot fluid passage R9a. The spool is in the neutral position in the first state. Based on this, the spool moves in one direction in the second state, and the spool moves in the opposite direction in the third state.

[0117] With this, the following is achieved. In the case where the second operation lever 120 is pivoted in the forward direction F, hydraulic fluid is supplied into the tubular cylinders 510 of the first hydraulic cylinders 51 via the second ports Pa2 so that the arms 40 are lowered and that pilot hydraulic fluid acts on the pressure receiver 66a of the first control valve 66 so that hydraulic fluid in the tubular cylinders 510 of the first hydraulic cylinders 51 is discharged via the first ports Pa1. When the degree of contact between the work attachment 41a or the like and the work target object T is an appropriate degree of contact, the controller 13 transmits an electrical signal to the solenoid 72a or 72b of the pilot control valve 72 to change the state of the pilot control valve 72. That is, the pilot control valve 72 switches from the first state to the second state or the third state in response to an instruction corresponding to the current situation from the controller 13. This results in a state in which a flow passage of pilot hydraulic fluid (hydraulic fluid) is blocked or a state in which the flow path is changed.

[0118] When the pilot control valve 72 blocks the pair of pilot fluid passages R9a and R9b (the pilot control valve 72 enters the second state), the pressure receivers 66a and 66b of the first control valve 66 are released from pilot hydraulic fluid. With this, the spool of the first control valve 66 returns to neutral, and the supply of hydraulic fluid to the first hydraulic cylinders 51 is stopped. With this, the first hydraulic cylinders 51 are maintained in a certain extended state, so that the arms 40 are maintained in a certain position (posture). In contrast, when the pilot control valve 72 changes the route of the pair of pilot fluid passages R9a and R9b (the pilot control valve 72 enters the third state), the flow path of hydraulic fluid is changed, and pilot hydraulic fluid acts on the pressure receiver 66b of the first control valve 66.

[0119] With this, the spool of the first control valve 66 moves, hydraulic fluid is supplied into the tubular cylinders 510 of the first hydraulic cylinders 51 via the first ports Pa1, whereas hydraulic fluid in the tubular cylinders 510 of the first hydraulic cylinders 51 is discharged via the second ports Pa2, so that the arms 40 are raised. Accordingly, when the user continues to operate the second operation lever 120, the degree of contact of the work attachment 41a or the like with the work target object T is not excessive but is appropriate.

[0120] Furthermore, when the second operation lever 120 is pivoted in the rightward direction R from the neutral position N, the corresponding operation valve 71d allows pilot hydraulic fluid (hydraulic fluid) in an amount corresponding to the pivot angle (operation amount) of the second operation lever 120 to flow. Accordingly, pilot hydraulic fluid (hydraulic fluid) is supplied to the pressure receiver 67a of the second control valve 67 via a pilot fluid passage R9d, and the spool of the second control valve 67 moves in one direction. With this, hydraulic fluid is supplied from the second control valve 67 to the first ports Pb1 of the second hydraulic cylinders 52 via the supply-discharge passage R7b, and hydraulic fluid is discharged into the second control valve 67 via the supply-discharge passage R7a from the second ports Pb2 of the second hydraulic cylinders 52. With this, the second hydraulic cylinders 52 extend, and the work attachment 41a or the like rotates downward with respect to the arms 40 (counterclockwise in the drawing). That is, in the case where the work attachment 41a or the like is a bucket, the bucket is brought into a dumping posture (discharging posture) in which the bucket discharges earth and sand etc.

[0121] On the contrary, when the second operation lever 120 is pivoted in the leftward direction L from the neutral position N, the corresponding operation valve 71c allows pilot hydraulic fluid (hydraulic fluid) in an amount corresponding to the pivot angle (operation amount) of the second operation lever 120 to flow. Accordingly, pilot hydraulic fluid (hydraulic fluid) is supplied to the pressure receiver 67b of the second control valve 67 via a pilot fluid passage R9c, and the spool of the second control valve 67 moves in the opposite direction. With this, hydraulic fluid is supplied from the second control valve 67 to the second ports Pb2 of the second hydraulic cylinders 52 via the supply-discharge passage R7a, and hydraulic fluid is discharged into the second control valve 67 via the supply-discharge passage R7b from the first ports Pb1 of the second hydraulic cylinders 52. With this, the second hydraulic cylinders 52 retract, and the work attachment 41a or the like rotates upward with respect to the arms 40 (clockwise direction in the drawing). That is, in the case where the work attachment 41a or the like is a bucket, the bucket is brought into a shoveling posture in which the bucket scoops earth and sand etc.

[0122] In the present example embodiment, the second hydraulic circuit 5B includes a plurality of pilot pressure detectors 73a, 73b, 73c, and 73d electrically connected to the controller 13 to detect the hydraulic pressure in the pilot fluid passages R9a, R9b, R9c, and R9d connected to the plurality of operation valves 71a, 71b, 71c, and 71d. The plurality of pilot pressure detectors 73a, 73b, 73c, and 73d input signals indicating the detection result (values of the hydraulic pressure in the pilot fluid passages R9a, R9b, R9c, and R9d) into the controller 13.

[0123] Accordingly, the controller 13 determines whether the first control valve 66 or the second control valve 67 is actuated (first hydraulic cylinder(s) 51 or the second hydraulic cylinder(s) 52 are extending or retracting) based on the signals inputted from the plurality of pilot pressure detectors 73a, 73b, 73c, and 73d. That is, the controller 13 determines whether the second operation lever 120 is operated to actuate the arm(s) 40 or the second hydraulic cylinder(s) 52 (whether the second operation lever 120 is pivoted from the neutral position N). The controller 13 recognizes the state (position) of the first control valve 66 or the second control valve 67, i.e., the direction and extent (operation amount) of pivot of the second operation lever 120 (angle and direction of pivot from the neutral position), based on the signals from the plurality of pilot pressure detectors 73a, 73b, 73c, and 73d.

[0124] The second hydraulic circuit 5B includes a pair of solenoid valves 74a and 74b to control the third control valve 68. Accordingly, the working machine 1 includes the AUX switch 75 electrically connected to the controller 13 that changes the states of the solenoid valves 74a and 74b.

[0125] The solenoid valves 74a and 74b are supplied with, as hydraulic fluid functioning as pilot hydraulic fluid for the third control valve 68, hydraulic fluid from the third hydraulic pump 64 via, for example, a delivery fluid passage. Note that, in FIG. 7, the source of pilot hydraulic fluid (hydraulic fluid) to the solenoid valves 74a and 74b is not illustrated.

[0126] The AUX switch 75 may be any of various switches such as a seesaw switch, a slide switch, or a push switch. The AUX switch 75, when operated by the user, inputs an electrical signal corresponding to the operation into the controller 13, as a signal. The controller 13, upon receiving the signal based on the operation of the AUX switch 75, outputs electric current corresponding to the signal as a control signal to one of the solenoid valves (solenoids) 74a and 74b. That is, the AUX switch 75 determines which of the solenoid valves 74a and 74b to actuate, in response to the user operations.

[0127] When the AUX switch 75 is operated to actuate the solenoid valve 74a, and the solenoid of the solenoid valve 74a receives a control signal from the controller 13 and is energized. Accordingly, pilot hydraulic fluid (hydraulic fluid) is supplied from the solenoid valve 74a to the pressure receiver 68a of the third control valve 68. With this, the state of the third control valve 68 is changed, hydraulic fluid is supplied from the third control valve 68 to the hydraulic actuator of the work attachment 41b or the like via the AUX port 65a which is one of the two AUX ports 65a and 65c, whereas hydraulic fluid from the hydraulic actuator of the work attachment 41b or the like is returned to the third control valve 68 via the AUX port 65c.

[0128] On the contrary, when the AUX switch 75 is operated to actuate the solenoid valve 74b, the solenoid of the solenoid valve 74b receives a control signal from the controller 13 and is energized. Accordingly, pilot hydraulic fluid (hydraulic fluid) is supplied from the solenoid valve 74b to the pressure receiver 68b of the third control valve 68. With this, the state of the third control valve 68 is changed, hydraulic fluid is supplied from the third control valve 68 to the hydraulic actuator of the work attachment 41b or the like via the AUX port 65c of the two AUX ports 65a and 65c, whereas hydraulic fluid from the hydraulic actuator of the work attachment 41b or the like is returned to the third control valve 68 via the AUX port 65a. With this, the direction of supply (flow) of hydraulic fluid to the hydraulic actuator of the work attachment 41b or the like is changed, and the actuation of the work attachment 41b is changed.

[0129] As illustrated in FIG. 8, the controller 13 is a so-called ECU and includes an arithmetic controller 130, a storing unit 131 (storage and/or memory) to store information used for processing by the arithmetic controller 130, an input 132 electrically connected to the arithmetic controller 130 to input an electrical signal as input information from external electrical device(s) into the arithmetic controller 130, and an output 133 electrically connected to the arithmetic controller 130 to output an instruction signal (electrical signal) as output information from the arithmetic controller 130 to external electrical device(s).

[0130] The arithmetic controller 130 is a CPU (MPU) and includes a calculator 130a and a controller 130b. In the controller 13 according to the present example embodiment, the storing unit 131 includes a first storing unit 131a to store information for use in processing performed by the arithmetic controller 130 (calculator 130a and controller 130b) temporarily or in the short term and a second storing unit 131b to store information for use in processing performed by the arithmetic controller 130 (calculator 130a and controller 130b) in the long-term. The first storing unit 131a may be a so-called memory. The second storing unit 131b may be a storage such as a hard disk or a solid state drive (SSD).

[0131] The input 132 and the output 133 are so-called interfaces. Electrical device(s) to output an electrical signal as information is connected to the input 132. On the contrary, electrical device(s) to receive an electrical signal as information is connected to the output 133.

[0132] Specifically, as devices relating to the first hydraulic circuit 5A, the transmission switch 80 and the brake pedal 79 etc. are connected to the input 132, and, as devices relating to the second hydraulic circuit 5B, the AUX switch 75, the pressure detectors 69a1 and 69a2 etc., the pilot pressure detectors 73a, 73b, 73c, and 73d, a posture detector, the arm posture detector (first angle sensor SE1), and the second angle sensor SE2 etc. are connected to the input 132. On the other hand, as devices relating to the first hydraulic circuit 5A, the electromagnetic switching valve 61 for speed change (solenoid 61a) and the electromagnetic switching valve 63 for braking (solenoid 63a) etc. are connected to the output 133, and, as devices relating to the second hydraulic circuit 5B, the LS system 81, the pilot control valve 72 (solenoids 72a and 72b), and the solenoid valves 74a and 74b etc. are connected to the output 133.

[0133] In the present example embodiment, the display 14 is a touchscreen monitor. Accordingly, the display 14 is connected to the input 132 and the output 133 in order to transmit and receive information to and from the controller 13 (arithmetic controller 130).

[0134] The working machine 1 according to the present example embodiment is configured such that, when the degree of contact of the work attachment 41a or the like with the work target object T is appropriate when the user is operating the second operation lever 120, such a state is maintained. That is, the controller 13 compares the actual degree of contact (state) of the work attachment 41a or the like with the work target object T and the preset optimal degree of contact (state), and, if the actual degree of contact (state) matches or substantially matches the preset optimal degree of contact (state), changes the actuation state of the hydraulic actuators 51 and/or 52 which are being continuously actuated to bring the work attachment 41a or the like into appropriate contact with the work target object T.

[0135] As described earlier, there are various types of work attachments 41a and the like, and the optimal degree of contact with the work target object T differs from one type to another. Specifically, the optimal degree of contact (state) as a reference differs between different types of work attachments 41a and the like. Accordingly, as illustrated in FIG. 9, the optimal degree of contact with the work target object T, as a reference based on which to determine whether the state of contact of the work attachment 41a or the like with the work target object Tis appropriate or not, is preset based on the function of the work attachment 41a or the like and is stored in the storing unit 131 (second storing unit 131b). That is, the optimal degree of contact with the work target object T, as a threshold based on which to determine whether the state of contact of the work attachment 41a or the like with the work target object T is appropriate, is set as the value of a contact pressure against the work target object T in consideration of work conditions, work environments, and work loads etc. of the work attachment 41a or the like.

[0136] In the present example embodiment, the storing unit 131 (second storing unit 131b) stores a list of work attachment(s) 41a and/or the like attachable to the arm(s) 40 (coupler(s) 45) (hereinafter referred to as an attachment list) including pictogram(s) (icon(s)) representing the work attachment(s) 41a and/or the like and their associated optimal degree(s) of contact of the work attachment(s) 41a and/or the like with the work target object T. In the present example embodiment, each optimal degree of contact stored in the storing unit 131 (second storing unit 131b) is the relationship P1, P2 or the like between the pressure of hydraulic fluid at the first port Pa1 of the first hydraulic cylinder(s) 51 and the pressure of hydraulic fluid at the second port Pa2 of the first hydraulic cylinder(s) 51 applied when the work attachment 41a or the like and the work target object T come into contact with each other (contact under pressure).

[0137] As illustrated in FIG. 10, the attachment list displayed on the display 14 includes one or more icons including pictogram(s) representing the work attachment(s) 41a and/or the like and selectable by a touch gesture. Note that the icons in the attachment list illustrated in FIGS. 9 and 10 are example icons including an icon including the pictogram of a bucket 41a, an icon including the pictogram of a sweeper 41b, an icon including the pictogram of a grapple 41c, an icon including the pictogram of a hydraulic breaker 41d, and an icon including the pictogram of the earth auger 41e. The optimal degrees of contact of the work attachments 41a and the like and their corresponding icons of the work attachments 41a and the like are associated with each other and stored in the storing unit 131 (second storing unit 131b).

[0138] As described earlier, the display 14 is a touchscreen monitor, and therefore the display 14 functions as an attachment selector for the user to select the work attachment 41a, 41b, or the like to use from a plurality of types of work attachments 41a, 41b and the like which have different functions. Accordingly, the controller 13 (arithmetic controller 130) is configured or programmed to, when the user selects (touches) the work attachment 41a or the like to use (icon of the work attachment to be connected to the arm(s) 40) from the plurality of types of work attachments 41a and the like (attachment list) displayed on the display (attachment selector) 14, recognize the selected work attachment 41a or the like and retrieve (read) the optimal degree of contact of the recognized work attachment 41a or the like (work attachment 41a or the like corresponding to the selected icon) from the storing unit 131 (second storing unit 131b). The optimal degree of contact and conditions to achieve the optimal degree of contact (state) are obtained through actual testing.

[0139] On the other hand, the actual degree (state) of contact of the work attachment 41a or the like is derived based on the pressure condition of hydraulic fluid in the first hydraulic cylinder(s) 51. That is, the controller 13 derives the current degree of contact between the work attachment 41a, 41b, or the like and the work target object T based on the detection result from the first pressure detectors 69a1 and 69a2.

[0140] The working machine 1 according to the present example embodiment, as described above, is configured such that, when specific work is performed, the degree of contact of the attached work attachment 41a with the work target object T is prevented from excessively exceeding (greatly exceeding) the optimal degree of contact. That is, in the working machine 1 according to the present example embodiment, the controller 13 performs the following control so that the degree of contact of the work attachment 41a or the like with the work target object T approaches the optimal degree.

[0141] Note that the work target object T for the work attachments 41a, 41b, 41d, and 41e other than the grapple 41c, among the work attachments 41a and the like described as examples in the present example embodiment, is the ground surface of soil (such as bedrock on the ground surface), and therefore the degree of contact with the work target object T is affected by loads in the up-and-down direction. Therefore, with regard to the control to adjust the degree of contact of the work attachments 41a and the like other than the grapple 41c among the above example work attachments with the work target object T, the controller 13 performs control relating to the first hydraulic cylinder(s) 51.

[0142] On the contrary, with regard to the grapple 41c, the degree of contact between a pair of jaws 410c and an object to be held therebetween (work target object T) is adjusted. Accordingly, with regard to the control to adjust the degree of contact, the controller 13 performs control relating to the hydraulic cylinder 411c of the grapple 41c.

[0143] Specifically, as illustrated in FIG. 11, when work is performed using the work attachment 41a or the like, the user first selects the icon of the work attachment 41a or the like attached to the distal portion of the arm(s) 40 from the attachment list displayed on the display (attachment selector) 14. Accordingly, the controller 13 (arithmetic controller 130) recognizes the selected type of the work attachment 41a or the like (S1) and extracts the optimal degree of contact associated with the work attachment 41a or the like of the selected icon from the storing unit 131 (second storing unit 131b) (S2). Note that, in the case where the controller 13 automatically recognizes the work attachment 41a or the like connected to the coupler(s) 45, the optimal degree of contact associated with the automatically recognized work attachment is extracted from the storing unit 131 (second storing unit 131b) instead of the user selecting the work attachment 41a (S2).

[0144] Next, the user operates the second operation lever 120 (which is an operator) such that the work attachment 41a or the like approaches or comes into contact with the work target object T (S3). In the present example embodiment, the user pivots the second operation lever 120 in the forward direction F to cause the first hydraulic cylinder(s) 51 to retract, thus lowering the arm(s) 40 (S3). The user, as needed, operates the second operation lever 120 to cause the second hydraulic cylinder(s) 52 to extend, thus rotating (pivoting) the work attachment 41a or the like. In the case where the selected work attachment 41a or the like is the work attachment 41c including a hydraulic actuator (hydraulic cylinder) 411c such as the grapple 41c, the user operates the AUX switch 75 to actuate the hydraulic actuator 411c of the work attachment 41c, thus also performing the function of the work attachment 41c.

[0145] In such conditions, the controller 13 receives information relating to the pressure of hydraulic fluid in the first hydraulic cylinder(s) 51 and the second hydraulic cylinder(s) 52 (S4). In the case where the work attachment 41a or the like includes the hydraulic cylinder 411c as a hydraulic actuator such as the grapple 41c, the controller 13 receives information relating to the pressure of hydraulic fluid in the hydraulic cylinder 411c of the work attachment 41c (S4). That is, the controller 13 receives, as measured results, the value of the pressure of hydraulic fluid at the first ports Pa1 of the first hydraulic cylinders 51 and the value of the pressure of hydraulic fluid at the second ports Pa2 of the first hydraulic cylinders 51 from the pair of first pressure detectors 69a1 and 69a2, and receives, as measured results, the value of the pressure of hydraulic fluid at the first ports Pb1 of the second hydraulic cylinders 52 and the value of the pressure of hydraulic fluid at the second ports Pb2 of the second hydraulic cylinders 52 from the pair of second pressure detectors 69b1 and 69b2 (S4). In the case where the AUX switch 75 is operated, the controller 13 receives, as measured results, the value of the pressure of hydraulic fluid at a first port Pc1 of the hydraulic cylinder 411c of the work attachment 41a or the like and the value of the pressure of hydraulic fluid at a second port Pc2 of the hydraulic actuator 411c from the pair of third pressure detectors 69c1 and 69c2.

[0146] Next, the controller 13 calculates (derives) a load on the work attachment 41a (degree of contact with the work target object T) based on the inputted (received) information (pressure of hydraulic fluid in the first hydraulic cylinders 51, the second hydraulic cylinders 52, and/or the hydraulic actuator 411c) (S5).

[0147] Specifically, the controller 13 derives the load (degree of contact with the work target object T) on the work attachment 41a or the like based on the value of the pressure of hydraulic fluid (detection result) at the first port(s) Pa1, Pb1, Pc1 of the hydraulic cylinder(s) 51, 52, 411c which extends and retracts in response to the operation of the manual operator (second manual operator, AUX switch) 12, 75 and the value of the pressure of hydraulic fluid (detection result) at the second port(s) Pa2, Pb2, Pc2 of the hydraulic cylinder(s) 51, 52, 411c (S5).

[0148] In the present example embodiment, in the case where the work attachment 41a or the like does not include the hydraulic cylinder 411c, the controller 13 derives a load on the work attachment 41a (degree of contact with the work target object T) based on the relationship between the value of the pressure of hydraulic fluid (detection result) at the first ports Pa1, Pb1 of at least one of the first hydraulic cylinders 51 or the second hydraulic cylinders 52 and the value of the pressure of hydraulic fluid (detection result) at the second ports Pa2, Pb2 of the at least one of the first hydraulic cylinders 51 or the second hydraulic cylinders 52 (S5). Note that, as described earlier, many of the plurality of types of work attachment 41a and the like come into contact with the work target object T as the arms 40 are lowered, thus adjusting the degree of contact. Therefore, in the present example embodiment, the controller 13 derives the load on the work attachment 41a (degree of contact with the work target object T) based on the relationship between the value of the pressure of hydraulic fluid (detection result) at the first ports Pa1 of the first hydraulic cylinders) 51 and the value of the pressure of hydraulic fluid (detection result) at the second ports Pa2 of the first hydraulic cylinders 51.

[0149] On the contrary, in the case where the work attachment 41c includes the hydraulic cylinder 411c, the controller 13 derives a load on the work attachment 41c (degree of contact with the work target object T) based on the relationship between the value of the pressure of hydraulic fluid (detection result) at the first port Pc1 of the hydraulic cylinder 411c of the work attachment 41c and the value of the pressure of hydraulic fluid (detection result) at the second port Pc2 of the hydraulic cylinder 411c (S5).

[0150] Specifically, when the user operates the second operation lever 120, the work attachment 41a or the like comes into contact with the work target object T, and, if the user continues operating the second operation lever 120 (operation to lower the arms 40), the first hydraulic cylinders 51 continue to retract in response to the operation of the second operation lever 120. If the user continues operating the second operation lever 120 (operation to cause the work attachment 41a or the like to rotate), the second hydraulic cylinders 52 continue to extend in response to the operation of the second operation lever 120.

[0151] Accordingly, the work attachment 41a or the like continues to descend, so that the degree of contact (contact pressure) of the work attachment 41a or the like with the work target object T increases. Accordingly, the measured results relating to the pressure of hydraulic fluid from the first pressure detectors 69a1 and 69a2 and the second pressure detectors 69b1 and 69b2 change (increase).

[0152] Specifically, each first hydraulic cylinder 51 has the end of the rod 511b thereof connected to the corresponding arm 40, and has the end of the tubular cylinder 510 connected to the frame chassis 20. Therefore, when the arm 40 is lowered, hydraulic fluid is supplied to the second port Pa2 at the end of the rod, whereas hydraulic fluid is discharged via the first port Pa1 at the end of the tubular cylinder. Therefore, in the first hydraulic cylinder 51 trying to lower the arm 40 (first hydraulic cylinder 51 to retract), the pressure of hydraulic fluid at the second port Pa2 increases due to the influence of the reaction force of the contact pressure (load) between the work attachment 41a or the like and the work target object T that acts via the arm 40 and/or a force to push out hydraulic fluid via the first port Pa1. The hydraulic fluid at the first port Pa1 in the tubular cylinder 510 is discharged via the first port Pa1 by the piston 511a receiving the pressure of hydraulic fluid at the second port Pa2 in the tubular cylinder 510. With this, the pressure of hydraulic fluid (change in pressure) at the first port Pa1 and the pressure of hydraulic fluid (change in pressure) at the second port Pa2 correspond to (agree with) each other.

[0153] Note that, in the first hydraulic cylinder 51 according to the present example embodiment, there is the rod 511b of the piston rod 511 in the second port Pa2-side inner space of the tubular cylinder 510, whereas there is no the piston rod 511 (rod 511b) in the first port Pa1-side inner space of the tubular cylinder 510. Therefore, the area of a pressure-receiving surface of the piston 511a that receives the pressure of hydraulic fluid is smaller at the second port Pa2 side than at the first port Pa1 side. Therefore, even if the pump pressure is the same, the pressure of hydraulic fluid at the second port Pa2 is higher than the pressure of hydraulic fluid at the first port Pa1. The pressure of hydraulic fluid at the first port Pa1 and the pressure of hydraulic fluid at the second port Pa2 are also affected by a load that would occur during movement of the piston rod 511 (load that would occur when the arm 40 is raised or lowered).

[0154] However, since the pressure of hydraulic fluid at the first port Pa1 and the pressure of hydraulic fluid at the second port Pa2 have a correlation as described earlier, the thrust of the piston rod 511 of the first hydraulic cylinder 51 can be derived from the relationship in the pressure of hydraulic fluid, and a pressing force (actual degree of contact) to press the work attachment 41a or the like against the work target object T can be derived based on the thrust (S5). The same applies to the hydraulic cylinder 411c of the work attachment 41c. The pressing force (contact force, or the actual degree of contact) to press the work attachment 41c against the work target object T is derived (S5). Note that, in the present example embodiment, the controller 13 corrects values in consideration of the sliding resistance of the piston 511a sliding within the tubular cylinder 510 when calculating the thrust of the piston rod 511.

[0155] After calculating the actual degree of contact as described above, the controller 13 compares the calculated degree of contact and the optimal degree of contact extracted from the storing unit 131 (S6). As described earlier, if the second operation lever 120 continues to be operated, the first hydraulic cylinders 51 continue to retract (continue to receive hydraulic fluid at the second port Pa2), and the pressure of hydraulic fluid in the first hydraulic cylinders 51 changes. Accordingly, the controller 13 continuously derives the degree of contact while the second operation lever 120 is being operated. The controller 13 repeatedly compares the derived degree of contact and the extracted optimal degree of contact (S6). If the AUX switch 75 continues to be operated, the hydraulic cylinder 411c of the work attachment 41c continues to extend (continues to receive hydraulic fluid at the first port Pc1), and the pressure of hydraulic fluid in the hydraulic cylinder 411c changes. Therefore, the controller 13 continuously derives the degree of contact while the AUX switch 75 is being operated. The controller 13 repeatedly compares the derived degree of contact and the extracted optimal degree of contact (S6).

[0156] That is, the pressure detectors 69a1, 69a2, 69c1, and 69c2 continuously measure pressure, and therefore the controller 13 derives the load on the work attachment 41a (degree of contact with the work target object T) upon each receipt of measured results from the pressure detectors 69a1, 69a2, 69c1, and 69c2 (S5). Also, the controller 13 compares the derived degree of contact and the optimal degree of contact (threshold) extracted from the storing unit 131 (second storing unit 131b) (S6).

[0157] As a result of comparison between the derived degree of contact and the extracted optimal degree of contact, if the controller 13 determines that the degree of contact has approached the optimal degree of contact (threshold) (YES at S7), the controller 13 reduces the speed of retraction of the first hydraulic cylinders 51 (movement speed of the piston rods) (S8). That is, if the controller 13 determines that the degree of contact has approached the optimal degree of contact (threshold) (YES at S7), the controller 13 actuates control valve(s) (first control valve, third control valve) 66, 68 to perform control so that the flow rate of hydraulic fluid toward the hydraulic cylinder(s) 51, 411c is reduced (S8).

[0158] Also in such conditions, if the user continues to operate the manual operator (second manual operator 12, AUX switch 75), the hydraulic cylinder(s) 51, 52, 411c continues to be actuated, so that the work attachment 41a or the like comes into contact with the work target object T and the degree of contact further increases. If the controller 13 determines that the calculated degree of contact matches or substantially matches the extracted optimal degree of contact (YES at S9) and the manual operator (second manual operator, AUX switch) 12, 75 is operated (YES at S10), the controller 13 changes the actuation state of the hydraulic cylinder 51, 411c. That is, the controller 13 causes the actuation state of the hydraulic cylinder(s) 51 or 411c to differ from that indicated by the operation of the manual operator (second manual operator, AUX switch) 12, 75 (user intention) (S12). In the present example embodiment, if the controller 13 determines that the calculated degree of contact matches or substantially matches the extracted optimal degree of contact (threshold), the controller 13 stops the actuation of the hydraulic cylinder(s) 51, 52, 411c (movement of the piston rods 511 and/or the piston rods 521) even if the manual operator (second manual operator, AUX switch) 12, 75 is being operated. If the actuation of the hydraulic cylinder(s) 51, 411c (extension, retraction) is stopped here, the lowering of the arms 40 and/or the actuation of the work attachment 41c are stopped based on the result of determination by the controller 13. Accordingly, the work attachment 41a or the like is in contact with the work target object T to have the optimal degree of contact. Note that the targets to have their actuation state changed include the first hydraulic cylinder(s) 51, the second hydraulic cylinder(s) 52, and the hydraulic cylinder 411c or the like of the work attachment 41c which are hydraulic actuators in action.

[0159] In the present example embodiment, in the case where a certain period of time has passed since when it was determined that the derived degree of contact matched or substantially matched the extracted optimal degree of contact (threshold) and the manual operator (second manual operator, AUX switch) 12, 75 is being operated, the controller 13 performs control differently from an instruction provided by the operation of the manual operator. That is, the controller 13 reduces the actuation speed of the hydraulic cylinder(s) 51, 52, 411c (movement speed of the piston rods 511, 521) or stops the actuation of the hydraulic cylinder(s) 51, 52, 411c (the movement of the piston rods 511, 521). In the present example embodiment, in the case where the second manual operator 12 (second operation lever 120) is operated, the controller 13 stops the actuation of the first hydraulic cylinders 51 and the second hydraulic cylinders 52 (movement of the piston rods 511, 521). In the case where the work attachment 41c is a grapple, however, in order to maintain the force to grip the work target object T (to prevent a reduction in the gripping force), when the AUX switch 75 is being operated, the controller 13 reduces the actuation speed of the hydraulic cylinder 411c (movement speed of the piston rod). The actuation of the hydraulic cylinder(s) 51, 411c (movement of the piston rods 511) is discussed here, which indicates that the controller 13 actuates a control valves (first control valve 66, third control valve 68).

[0160] On the other hand, in the case where it is determined that the calculated degree of contact matches or substantially matches the extracted optimal degree of contact (YES at S9) and the manual operator (second manual operator, AUX switch) 12, 75 is not operated (NO at S10), the controller 13 waits until the user operates the manual operator (second manual operator, AUX switch) 12, 75 (S14). That is, in the case where the user is stopping the operation while keeping the manual operator (second manual operator, AUX switch) 12, 75 stationary or substantially stationary (for example, when the user pivots the second operation lever 120 in a certain direction to a certain degree and keeps it in that state: NO at S10), the state of the manual operator (second manual operator, the AUX switch) is kept constant or substantially constant, and the controller 13 wails until the operation of the manual operator (second manual operator, AUX switch) 12, 75 is resumed (movement relating to operation is resumed) (S14). In such conditions, the controller 13 reduces the flow rate of hydraulic fluid supplied to the hydraulic cylinder(s) 51, 411c from the flow rate of hydraulic fluid corresponding to the state of the manual operator (second manual operator, AUX switch) kept constant or substantially constant or reduces the flow rate to 0 (zero), until the operation of the manual operator (second manual operator, AUX switch) 12, 75 is resumed (movement relating to the operation is resumed) (S15). That is, the controller 13 reduces the flow rate of hydraulic fluid supplied to the hydraulic cylinder(s) 51, 411c or stops the supply of hydraulic fluid (S15). In the present example embodiment, the controller 13 stops the supply of hydraulic fluid to the first hydraulic cylinders 51 to stop the retraction of the first hydraulic cylinders 51, whereas the controller 13 reduces the flow rate of hydraulic fluid supplied to the hydraulic cylinder 411c of the work attachment 41c to reduce the speed of extension (S15). That is, the controller 13 brings the flow rate of hydraulic fluid at the first control valve 66 to 0 (zero) (blocks the flow) and reduces the flow rate of hydraulic fluid at the third control valve 68 (S15). Next, when the user resumes the operation of the manual operator (second manual operator, AUX switch) 12, 75 (YES at S14), the controller 13 stops the control performed so far and actuates the hydraulic cylinder(s) 51, 52, 411c in response to the operation of the manual operator (second manual operator, AUX switch) 12, 75 (S16). That is, the controller 13 actuates the hydraulic cylinder(s) 51, 52, 411c in accordance with the user's intention (S16).

[0161] It is noted that, when work is performed using the work attachment 41a or the like, the degree of contact of the work attachment 41a or the like with the work target object T may change. In particular, in the case of the work attachment 41a or the like such as a bucket 41a or a dozer blade, the degree of contact of the work attachment 41a or the like with the work target object T may change depending on travel environments or the conditions of the work target object T because the work is perform during the travel. That is, when the work attachment 41a or the like such as a bucket or a dozer blade moves in contact with soil (work target object T) during travel, the work attachment 41a or the like may run over a stone or rock in the ground etc., resulting in excessive contact. On the contrary, the degree of contact with the work target object T may decrease due to, for example, unevenness (recess) in soil etc.

[0162] Therefore, the pressure of hydraulic fluid in the hydraulic cylinders 51, 411c (relationship between the pressure of hydraulic fluid at the first port Pa1, Pc1 and the pressure of hydraulic fluid at the second port(s) Pa2, Pc2) may also change. Accordingly, in the case where it is determined that the derived degree of contact matches the optimal degree of contact (YES at S9) and that the user continues to operate the second manual operator 12 (YES at S10), the controller 13 determines whether the pressure of hydraulic fluid in the hydraulic cylinder(s) 51, 411c has exceeded a predetermined threshold for a certain period of time (S11). Note that the threshold may be a numeral, but has an appropriate range with the upper limit and the lower limit in the present example embodiment.

[0163] Accordingly, if the degree of contact of the work attachment 41a or the like with the work target object T has exceeded the threshold (outside an appropriate range) for a certain period of time (if it is determined that the degree of contact is not the optimal degree of contact, YES at S11), the controller 13 controls the control valve 66, 68 such that the flow rate of hydraulic fluid is lower than the flow rate of hydraulic fluid corresponding to the input received by the second operation lever (operator) 120 or the flow rate is 0 (zero) to change the actuation state of the hydraulic cylinder(s) 51, 411c (S12). That is, the controller 13 reduces the speed of movement of the work attachment 41a or the like toward the work target object T or stops the movement of the work attachment 41a or the like. In the present example embodiment, in the case where the work attachment 41a or the like is a bucket etc., the descending arms 40 are decelerated or stopped and are raised if the degree of contact exceeds the appropriate degree of contact, the arms 40 are lowered if the degree of contact have not reached the appropriate degree of contact (including the cases where the work attachment 41a or the like is separated from the work target object T), and the ascending/descending arms 40 are stopped if the degree of contact is the appropriate degree of contact.

[0164] In the case where the work attachment 41c is a grapple, the controller 13 changes the degree of opening/closing of the jaws 410c and/or stops the opening/closing of the jaws 410c. Note that, in the present example embodiment, in the case where the work attachment 41c is a grapple, the controller 13 reduces the amount of hydraulic fluid supplied to the hydraulic cylinder 411c so that, although the pair of jaws 410c do not appear to perform opening or closing movement, the pair of jaws 410c exert a force to hold the work target object T between them. The controller 13 then, until it determines that work is about to end (NO at S13), repeats acquiring the detected values relating to the pressure of hydraulic fluid in the hydraulic cylinder(s) 51, 411c (S4), deriving the current degree of contact (S5), and the like, in the above-described order, and, when the work ends (YES at S13), ends the process (END).

[0165] It is noted that during the work performed by the bucket 41a, the arms 40 are repeatedly raised and lowered and the bucket 41a during work comes into contact with and moves away from (out of contact with) the ground (which is a work target object T). In view of this, the controller 13 is configured or programmed to, in the case where a work attachment 41a or the like which contacts/moves away from the work target object T during work like the bucket 41a is selected, recognize whether the work attachment 41a or the like is not in contact with the work target object T. That is, the controller 13 recognizes that the work attachment 41a or the like is not in contact with the work target object T when the degree of contact derived based on the pressure of hydraulic fluid at the first ports Pa1 of the first hydraulic cylinders 51 and the pressure of hydraulic fluid at the second ports Pa2 of the first hydraulic cylinders) 51 is equal to or less than a specified value corresponding to non-contact of the work attachment 41a or the like with the work target object (ground) T.

[0166] Accordingly, in the above-described process, after the controller 13 according to the present example embodiment derives the degree of contact (S5), the controller 13 compares the derived degree of contact and the optimal degree of contact (S6), and also compares the derived degree of contact and the specified value based on which to determine whether the work attachment is in the non-contact state, to determine whether the work attachment 41a and the work target object T are in contact with each other.

[0167] Next, after the controller 13 determines whether the work attachment 41a and the work target object T are in contact with each other (after recognizing that the work attachment 41a is not in contact with the work target object T or that the work attachment 41a is in contact with the work target object T), when the second manual operator 12 continues to be operated to lower the arms 40 to cause the bucket 41a to approach or come into contact with the ground (contact under pressure) and the derived degree of contact matches or substantially matches the preset optimal degree of contact (YES at S9 and YES at S10), the controller 13 changes the actuation state of the first hydraulic cylinders 51, i.e., reduces the movement speed of the piston rods 511 of the first hydraulic cylinders 51 (S12). Note that, if the controller 13 according to the present example embodiment determines that the degree of contact has approached the optimal degree of contact (threshold) (YES at S7), the controller 13 actuates the control valve(s) (first control valve, third control valve) 66, 68 to perform control such that the flow rate of hydraulic fluid to the hydraulic cylinder(s) 51, 52, 411c decreases (S8), thus reducing the movement speed of the piston rods 511. Therefore, since the controller 13 changes the actuation state of the first hydraulic cylinders 51 as described above, i.e., the controller 13 reduces the movement speed of the piston rods 511 of the first hydraulic cylinders 51 (S12) as described above, the movement speed of the piston rods 511 of the first hydraulic cylinders 51 decreases stepwise. With this, the speed of lowering of the arms 40 also decreases stepwise, and the impact which would result when the work attachment 41a comes into contact with the work target object T is prevented or reduced.

[0168] Note that the switching between raising and lowering the arms 40 is performed in the following manner. The controller 13 determines whether the degree of contact is appropriate or not, and based on the result thereof, switches the state of the pilot pressure control valve, the first control valve 66, and/or the first hydraulic cylinders 51 to switch between, raising, lowering, and stopping of the arm(s) 40.

[0169] This allows the work attachment 41a or the like connected to the distal portion of the arms 40 to perform predetermined work while in contact with the work target object T, while ensuring an optimal degree of contact with the work target object T without excessive contact with the work target object T. That is, the work attachment 41a or the like is in a predetermined contact state (optimal degree of contact) in which it is in contact with the work target object T while applying a predetermined (target) contact pressure to the work target object T, and is prevented from being in an insufficient contact state in which the work attachment 41a or the like does not apply a sufficient contact pressure to the work target object T because, for example, the work attachment 41a or the like is separated from the work target object T or in an excessive contact state in which the work attachment 41a or the like applies an excessive contact pressure like, for example, the work attachment 41a or the like is stuck into the work target object T such as soil.

[0170] With this, the work attachment 41a or the like for use in work sufficiently performs its function. Specifically, in the case where the work attachment 41a or the like is the bucket 41a as illustrated in FIG. 1 and performs leveling (soil leveling) using the bucket 41a, the controller 13 causes the actuation state of the arms 40 to differ from an instruction provided by the operation of the second operation lever 120 (raises/lowers or stops the arms 40) while the working machine 1 is performing travel/work, so that the bucket 41a is not excessively pressed against the soil, and excavates the soil and achieves the optimal degree of contact.

[0171] In the case where the work attachment 41a or the like is the sweeper 41b as illustrated in FIG. 2 and performs cleaning etc. on the road surface using the sweeper 41b, the controller 13 causes the actuation state of the arms 40 to differ from an instruction provided by the operation of the second operation lever 120 (raises/lowers or stops the arms 40) while the working machine 1 is performing travel/work, so that the brush 410b of the sweeper 41b is not excessively pressed against the road surface (work target object T) but the sweeper 41b (brush 410b) makes contact with the road surface in the optimal (preferable) contact state (degree of contact, contact posture). This makes it possible to prevent or reduce excessive damage to the brush of the sweeper and appropriately remove dust etc.

[0172] In the case where the work attachment 41a or the like is the grapple 41c as illustrated in FIG. 3, the AUX switch 75 is operated instead of the second manual operator 12 as described earlier. In the case where the work target object (object to be crushed) T such as lumber is held by the grapple 41c, it is possible to cause the jaws 410c to contact the work target object T with the optimal degree of contact to hold the work target object T between them.

[0173] Note that, although not described earlier, pilot hydraulic fluid supplied to the pressure receivers 68a and 68b of the third control valve 68 is controlled using the solenoid valves 74a and 74b actuated in response to an instruction from the controller 13. Since the degree of contact of the pair of jaws 410c with the work target object Tis brought to the optimal degree of contact in such a manner, the work target object (object to be crushed) T is prevented from being damaged or falling and the work target object (object to be crushed) T can be held in the appropriate state and transported.

[0174] In the case where the work attachment 41a or the like is the hydraulic breaker 41d including the rod-shaped crushing chisel 410d as illustrated in FIG. 4 and the work target object (object to be crushed) T such as a concrete block is crushed using the hydraulic breaker 41d, the controller 13 causes the actuation state of the arms 40 to differ from an instruction provided by the operation of the second operation lever 120 (raises/lowers or stops the arms 40) to allow the hydraulic breaker 41d (crushing chisel 410d) to contact with the work target object T with the optimal degree of contact to crush the work target object T.

[0175] Specifically, the hydraulic breaker 41d is a work attachment to be connected to the AUX ports 65a and 65b while in connection with the couplers 45. Hydraulic fluid is supplied to and discharged from the hydraulic breaker 41d via the AUX ports 65a and 65b, and therefore the crushing chisel 410d reciprocates (vibrates). Accordingly, when the degree of contact between the crushing chisel 410d and the work target object T is lower than the optimal degree of contact, vibrations applied by the crushing chisel to the work target object T may be weak or may result in idle strokes.

[0176] When the degree of contact between the crushing chisel 410d and the work target object T is greater than the optimal degree of contact, the work target object T can be crushed, but some other objects behind the work target object T may be damaged or the working device 4 may be damaged due to large loads on the arms 40 etc. However, since the controller 13 causes the actuation state of the arms 40 to differ from an instruction provided by the operation of the second operation lever 120 (raises/lowers or stops the arms 40) as described above to bring the degree of contact of the hydraulic breaker 41d (crushing chisel 410d) with the work target object T to the optimal degree of contact, it is possible to efficiently and effectively crush the work target object T (object to be crushed) while preventing or reducing damage to the working device 4.

[0177] In the case where the work attachment 41a or the like is the earth auger 41e as illustrated in FIG. 5 and soil is excavated (hole is made) using the earth auger 41e, the controller 13 causes the actuation state of the arms 40 to differ from an instruction provided by the operation of the second operation lever 120 (raises/lowers or stops the arms 40) to bring the degree of contact of the earth auger 41e with the soil (work target object T) to the appropriate degree of contact, making it possible to suitably excavate the soil without causing damage to the earth auger 41e.

[0178] In the present example embodiment, in a case that the earth auger 41e as a work attachment is connected to the couplers 45 and the hydraulic motor 411e is stopped (hydraulic fluid is not supplied from the AUX ports 65a, 65b, 65c), when the degree of contact of the earth auger 41e with the soil is an appropriate degree, the controller 13 determines that the pointed end of the earth auger 41e is stuck in the soil (determines that the earth auger 41e is in the preliminary stage before the helical blade digs a hole in the soil).

[0179] Specifically, while the hydraulic motor 411e is stopped (hydraulic fluid is not supplied from the AUX ports 65a, 65b, 65c), when the arms 40 are rotated (lowered) by the operation of the second operation lever 120, the pointed end of the digging drill 410e sticks into the soil, and the helical blade of the digging drill 210e contacts the soil. Even if the arms 40 are caused to be lowered further, the arms 40 are not lowered but are subjected to loads (hydraulic cylinders 51, 52 is/are subjected to loads) because the helical blade makes surface contact with the soil (ground surface). Accordingly, the pressure of hydraulic fluid in the first and second hydraulic cylinders 51 and 52 (the relationship between the pressure of hydraulic fluid at the first ports Pa1, Pb1 and the pressure of hydraulic fluid at the second ports Pa2, Pb2) also changes. The controller 13 derives the degree of contact of the earth auger 41e (digging drill 411e) with the soil (ground surface) T based on the pressure of hydraulic fluid in at least one of the first hydraulic cylinders 51 or the second hydraulic cylinders 52. In the present example embodiment, the controller 13 derives the degree of contact based on the pressure of hydraulic fluid in the first and second hydraulic cylinders 51 and 52 (the relationship between the pressure of hydraulic fluid at the first port first ports Pa1, Pb1 and the pressure of hydraulic fluid at the second ports Pa2, Pb2). Then, the controller 13 compares the derived degree of contact with the preset optimal degree of contact and, if the derived degree of contact matches or substantially matches the preset optimal degree of contact, stops the movement of the piston rods 511 of the first hydraulic cylinders 51 to stop the rotation (swinging) of the arms 40 (such stopping corresponds to changing the actuation state of the first hydraulic cylinders 51).

[0180] If the controller 13 determines that the derived degree of contact matches or substantially matches the preset optimal degree of contact, the controller 13 recognizes that the earth auger 41e (digging drill 410e) is located at the position at which the digging depth of the earth auger 41e (digging drill 410e) in the soil is zero, and stores information thereof. Next, the controller 13 drives the hydraulic motor 411e of the earth auger 41e (rotates the digging drill 411e) while, automatically or based on the operation of the second operation lever 120, causing the first hydraulic cylinders 51 to extend or retract (retract in the present example embodiment) to rotate the arms 40 about the first shaft S1 and causing the second hydraulic cylinders 52 to extend or retract (retract in the present example embodiment) to rotate the couplers 45 about the second shaft S2 such that the earth auger 41e is lowered while maintained in the upright position.

[0181] In so doing, the arm posture detector (first angle sensor) SE1 and the second angle sensor SE2 detect the angle of the arms 40 and the angle of the couplers 45, and the controller 13 obtains the degree of the downward movement of the earth auger 41e (digging drill 411e) from the ground surface based on the detection result from the arm posture detector (first angle sensor) SE1. Note that, in the present example embodiment, the controller 13 controls the extension and retraction of the second hydraulic cylinders 52 so that the earth auger 41e being lowered is maintained in the upright position based on the detection results from the first angle sensor SE1 and the second angle sensor SE2.

[0182] When the degree of the downward movement of the earth auger 41e from the ground surface (digging depth of zero) reaches a preset digging depth, the controller 13 causes a display 14 to display an indication that the present digging depth has been reached. Note that, if the display 14 includes an audio output or the working machine 1 includes a speaker, the controller 13 may cause the audio output and/or the speaker to output a sound indication that the preset digging depth has been reached, in addition to or instead of the indication displayed by the display 14. The controller 13 may be configured or programmed to cause the display 14 to display the current degree of the downward movement of the earth auger 41e from the ground surface (digging depth is zero) while the earth auger 41e (digging drill 411e) is digging a hole in the soil. This allows the user to keep the digging depth of the earth auger 41e (digging drill 411e) in the soil at the planned depth based on the indication displayed on the display 14.

[0183] The controller 13 may be configured or programmed to stop the hydraulic motor 411e when the degree of the downward movement of the earth auger 41e from the ground surface (the degree of downward movement from a digging depth of zero) reaches the present digging depth. The controller 13 may be configured or programmed to, while rotating or stopping the hydraulic motor 411e, cause the arms 40 to be raised (cause the first hydraulic cylinders 51 to extend) to pull the earth auger 41e (digging drill 411e) from the soil (ground). Thus, the controller 13 recognizes that the earth auger 41e (digging drill 410e) is located at the position (reference position) at which the digging depth of the earth auger 41e (digging drill 410e) in the soil is zero (stores the information thereof) when the derived degree of contact matches or substantially matches the present optimal degree of contact. By digging a hole in the soil based on the reference position, it is possible to achieve the intended excavation (hole digging).

[0184] The following description discusses a working machine according to a second example embodiment of the present invention. The basic structure of the working machine according to the present example embodiment is the same as the first example embodiment except for the hydraulic circuit (a portion of the second hydraulic circuit). Accordingly, only elements that differ from those according to the first example embodiment will be described below, the elements which are the same or correspond to those according to the first example embodiment are assigned identical names and reference signs, and such elements are not described here. Note that, as the description for the elements not described herein that are the same as those in the first example embodiment, the corresponding description in the first example embodiment can be used.

[0185] As illustrated in FIG. 12, in the working machine 1 according to the present example embodiment, the second manual operator 12 differs from that according to the first example embodiment. Accordingly, a portion of the second hydraulic circuit 5B of the hydraulic circuit 5 differs from that according to the first example embodiment.

[0186] Specifically, in the present example embodiment, the second manual operator 12 is a digital joystick (hereinafter referred to as a joystick).

[0187] The second manual operator (joystick) 12 includes an operation lever which is an operator operated by the user and is pivotable about the lower end thereof (which is referred to as a second operation lever also in the present example embodiment) 120. The second manual operator (joystick) 12 outputs an electrical signal corresponding to the direction and extent (angle) of pivot (operation) of the second operation lever 120. That is, the second manual operator (joystick) 12 is connected to the controller 13 (arithmetic controller 130) communicably in a wired wireless manner. In the present example embodiment, the second manual operator 12 is connected to the controller 13 in a wired manner and outputs the electrical signal corresponding to the direction and extent (angle) of pivot of the second operation lever 120 to the controller 13. Note that, when the second manual operator 12 is connected to the controller 13 communicably in a wireless manner, it is possible to change the arrangement of the second manual operator 12 or locate the second manual operator 12 in consideration of other devices such that the user can easily operate the second manual operator 12 without having to consider how to guide communication cables etc. Furthermore, when the second manual operator (joystick) 120 is connected to the controller 13 in a wireless manner, external remote control can be achieved. That is, the second manual operator (joystick) 120 can be used as a remote controller to remote control the working machine 1 (at least the working device 4). In the present example embodiment, the second manual operator 12 is connected to the controller 13 via a communication cable (in a wired manner) to maintain communication stability.

[0188] Specifically, the second manual operator 12 (joystick) includes the second operation lever 120 pivotable in the front-rear and left-right directions about the lower end thereof and a lever position detector 121 to detect the direction and extent (angle) of pivot of the second operation lever 120 and to output the detection result of the direction and extent (angle) of pivot of the second operation lever 120. Accordingly, the lever position detector 121 is electrically connected to the controller 13 (arithmetic controller 130) in a wired or wireless manner (in a wired manner, in the present example embodiment), and outputs, as electric information (signal), the detection result relating to the direction and extent (angle) of pivot of the lever toward the controller 13 (arithmetic controller 130).

[0189] In the working machine 1 according to the present example embodiment, the directions of pivot of the second operation lever 120 are assigned different actuations of the working device 4.

[0190] The working machine 1 according to the present example embodiment is configured such that the arms 40 are lowered (first hydraulic cylinders 51 are retracted) in the case where the second operation lever 120 is pivoted forward, and the arms 40 are raised (first hydraulic cylinders 51 are extended) in the case where the second operation lever 120 is pivoted rearward. The working machine 1 is also configured such that the work attachment 41a or the like is rotated in one direction about the second shaft S2 (rotated counterclockwise downward in the drawing) in the case where the second operation lever 120 is pivoted left, and the work attachment 41a or the like is rotated in the opposite direction about the second shaft S2 (rotated clockwise upward in the drawing) in the case where the second operation lever 120 is pivoted right.

[0191] That is, the controller 13 performs control such that the first hydraulic cylinders 51 are retracted in the case where a signal indicating that the second operation lever 120 is pivoted forward is received from the joystick 12 (lever position detector 121), and the first hydraulic cylinders 51 are extended in the case where a signal indicating that the second operation lever 120 is pivoted rearward is received from the joystick 12 (lever position detector 121). The controller 13 performs control such that the second hydraulic cylinders 52 are retracted in the case where a signal indicating that the second operation lever 120 is pivoted left is received from the joystick 12 (lever position detector 121), and the second hydraulic cylinders 52 are extended in the case where a signal indicating that the second operation lever 120 is pivoted right is received from the joystick 12 (lever position detector 121).

[0192] In the second hydraulic circuit 5B according to the present example embodiment, the first control valve 66, the second control valve 67, and the third control valve 68 are pilot control valves. That is, the first control valve 66, the second control valve 67, and the third control valve 68 include the pressure receivers 66a, 66b, 67a, 67b, 68a, and 68b to receive the pressure (hydraulic pressure) of pilot hydraulic fluid, and change their state (the manner in which hydraulic fluid flows) upon the pressure receivers 66a, 66b, 67a, 67b, 68a, and/or 68b receiving the pressure (hydraulic pressure) of pilot hydraulic fluid. This is the same as the first example embodiment.

[0193] In the second hydraulic circuit 5B according to the first example embodiment, the combination of the operation valves 71a, 71b, 71c, and 71d linked with the second operation lever 120 and the pilot control valve 72 actuated based on an instruction from the controller 13 is used to control pilot hydraulic fluid supplied to the first control valve 66 and the second control valve 67, whereas the combination of the operation of the AUX switch 75 and the pair of solenoid valves 74a and 74b actuated based on an instruction from the controller 13 based on that operation is used to control pilot hydraulic fluid supplied to the third control valve 68.

[0194] On the contrary, in the second hydraulic circuit 5B according to the present example embodiment, however, pilot hydraulic fluid supplied to the first control valve 66, the second control valve 67, and the third control valve 68 is controlled by solenoid valves 76a, 76b, 77a, 77b, 78a, and 78b actuated based on an instruction from the controller 13.

[0195] Specifically, the second hydraulic circuit 5B according to the present example embodiment includes a pair of solenoid valves (hereinafter referred to as first solenoid valves) 76a and 76b to control pilot hydraulic fluid supplied to the first control valve 66, a pair of control valves (hereinafter referred to as second solenoid valves) 77a and 77b to control the flow of pilot hydraulic fluid to the second control valve 67, and a pair of solenoid valves (hereinafter referred to as third solenoid valves) 78a and 78b to control pilot hydraulic fluid supplied to the third control valve 68.

[0196] More specifically, the second hydraulic circuit 5B according to the present example embodiment includes a pair of first solenoid valves 76a and 76b provided in a respective pair of pilot fluid passages connected to the pair of pressure receivers 66a and 66b of the first control valve 66 to open and block the pilot fluid passages based on an instruction from the controller 13, a pair of second solenoid valves 77a and 77b provided in a respective pair of pilot fluid passages connected to the pair of pressure receivers 67a and 67b of the second control valve 67 to open and block the pilot fluid passages based on the instruction from the controller 13, and a pair of third solenoid valves 78a and 78b provided in a respective pair of pilot fluid passages connected to the pair of pressure receivers 68a and 68b of the third control valve 68 to open and block the pilot fluid passages based on an instruction from the controller 13.

[0197] In the second hydraulic circuit 5B according to the present example embodiment, when one of the pair of first solenoid valves 76a and 76b opens or blocks the pilot fluid passages based on an instruction from the controller 13, the pressure (hydraulic pressure) of pilot hydraulic fluid is applied to one of the pair of pressure receivers 66a and 66b of the first control valve 66, so that the state of the first control valve 66 (supply state of hydraulic fluid to the first hydraulic cylinders 51) is changed. When one of the pair of second solenoid valves 77a and 77b opens or blocks the pilot fluid passages based on an instruction from the controller 13, the pressure (hydraulic pressure) of pilot hydraulic fluid is applied to one of the pair of pressure receivers 67a and 67b of the second control valve 67, so that the state of the second control valve 67 (supply state of hydraulic fluid to the second hydraulic cylinders 52) is changed. When one of the pair of third solenoid valves 78a and 78b opens or blocks the pilot fluid passages based on an instruction from the controller 13, the pressure (hydraulic pressure) of pilot hydraulic fluid is applied to one of the pair of pressure receivers 68a and 68b of the third control valve 68, so that the state of the third control valve 68 (supply state of hydraulic fluid to the AUX ports 65a, 65b, and 65c) is changed.

[0198] With this, in the working machine 1 according to the present example embodiment, when the controller 13 outputs a signal (electric current) to the first solenoid valves 76a and 76b and the second solenoid valves 77a and 77b based on the signal from the second manual operator (joystick) 12, the first control valve 66 and the second control valve 67 are actuated in response to the operation of the second manual operator 12, and the first hydraulic cylinders 51 and the second hydraulic cylinders 52 extend or retract. Accordingly, the arms 40 are raised or lowered in response to the operation of the second manual operator 12, and the work attachment 41a or the like rotates (pivots). When the controller 13 outputs a signal (electric current) to the third solenoid valves 78a and 78b based on the signal from the AUX switch 75, the third control valve 68 is actuated in response to the operation of the AUX switch 75, and the hydraulic actuator 411c of the work attachment 41c is actuated. Accordingly, the work attachment 41c performs a function in response to the operation of the AUX switch 75.

[0199] Also in the working machine 1 according to the present example embodiment, the first hydraulic cylinders 51, the second hydraulic cylinders 52, and the hydraulic actuator 411b or the like of the work attachment 41b or the like can be actuated in accordance with an instruction from the controller 13, regardless of the operation of the second manual operator 12, and therefore the work attachment 41a or the like can be brought into contact with the work target object T with the optimal degree of contact similarly to the first example embodiment.

[0200] Note that the control performed to bring the work attachment 41a or the like into contact with the work target object T with the optimal degree of contact is the same as the first example embodiment, and therefore is not described here. Since the same process can be performed, the working machine 1 according to the second example embodiment can achieve the same effects as the first example embodiment.

[0201] The working machines 1 according to the first example embodiment and the working machines 1 according to the second example embodiment of the present invention have been described so far. Example embodiments included in the first example embodiment and second example embodiment of the present invention achieve the effect of bringing the function portion (work attachment) 41a or the like into contact with the work target object T in the optimal contact state.

[0202] In each example embodiment as has been described, a working machine 1 includes a machine body 2, a working device 4 connected to the machine body 2 and including a function portion (work attachment) 41a, 41b or the like to perform a function corresponding to content of work while in contact with a work target object T, a hydraulic actuator (hydraulic cylinder) 51, 52, 411c to switch between a first state in which the function portion (work attachment) 41a, 41b or the like is in contact with the work target object T and a second state in which the function portion (work attachment) 41a, 41b or the like is not in contact with the work target object T, a manual operator (second manual operator, AUX switch) 12, 75 to be operated by a user in relation to actuation of the hydraulic actuator (hydraulic cylinder) 51, 52, 411c, and a controller 13 configured or programmed to control the actuation of the hydraulic actuator (hydraulic cylinder) 51, 52, 411c, wherein the controller 13 is configured or programmed to derive a degree of contact of the function portion (work attachment) 41a, 41b or the like with the work target object T based on a pressure of hydraulic fluid supplied to the hydraulic actuator (hydraulic cylinder) 51, 52, 411c, and if the derived degree of contact matches or substantially matches a preset optimal degree of contact, change an actuation state of the hydraulic actuator (hydraulic cylinder) 51, 52, 411c in action.

[0203] With the configuration described above, the hydraulic actuator(s) (hydraulic cylinder(s)) 51, 52, 411c performs switching between the first state in which the function portion (work attachment) 41a, 41b or the like is in contact with the work target object T and the second state in which the function portion is not in contact with the work target object T. The contact of the function portion (work attachment) 41a, 41b, or the like with the work target object T results in a load on the hydraulic actuator(s) (hydraulic cylinder(s)) 51, 52, 411c, and the pressure of hydraulic fluid supplied to the hydraulic actuator(s) (hydraulic cylinder(s)) 51, 52, 411c changes depending on the load. Therefore, the controller 13 derives the degree of contact of the function portion (work attachment) 41a, 41b, or the like with the work target object T based on the pressure of hydraulic fluid supplied to the hydraulic actuator(s) (hydraulic cylinder(s)) 51, 52, 411c, so that the actual degree of contact can be derived.

[0204] The function portion (work attachment) 41a, 41b, or the like of the working device 4 performs the function that corresponds to the content of work, and therefore the state of contact with the work target object T during the work differs from one function portion to another and the optimal value of the degree of contact (optimal degree of contact) also differs from one function portion to another. The controller 13 uses the preset optimal degree of contact as a reference for comparison with the actual degree of contact, and is therefore capable of determining whether the actual degree of contact is appropriate. When the derived degree of contact matches or substantially matches the preset optimal degree of contact, the controller 13 changes the actuation state of the hydraulic actuator(s) (hydraulic cylinder(s)) 51, 52, 411c in action, so that the function portion (work attachment) 41a, 41b, or the like is prevented from continuously contacting the work target object T in an inappropriate manner. Note that, for example, changing the actuation state of the hydraulic actuator(s) (hydraulic cylinder(s)) 51, 52, 411c in action indicates switching between extension and retraction (changing extension to retraction or changing retraction to extension), changing the acting state to the stopped state, and/or changing the speed of the extension or the retraction. Accordingly, the degree of contact of the function portion (work attachment) 41a, 41b, or the like with the work target object Tis prevented from exceeding the optimal degree of contact (reference for contact). That is, the working machine 1 configured as described above makes it possible to bring the work attachment (function portion) 41a or the like into contact with the work target object T such that the work attachment can perform the function without causing excessive loads on the work attachment 41a or the like (which is the function portion).

[0205] The controller 13 may be configured or programmed to change the actuation state of the hydraulic actuator (hydraulic cylinder) 51, 52, 411c in action while the manual operator (second manual operator, AUX switch) 12, 75 is operated in relation to the actuation of the hydraulic actuator (hydraulic cylinder) 51, 52, 411c. The state in which the manual operator (second manual operator, AUX switch) 12, 75 is operated in relation to the actuation of the hydraulic actuator (hydraulic cylinder) 51, 52, 411c indicates the state in which the degree of contact of the function portion (work attachment) 41a or the like with the work target object T is increasing while the function portion (work attachment) 41a or the like is in contact with the work target object T. Thus, the controller 13 changes the actuation state of the hydraulic actuator(s) (hydraulic cylinder(s)) 51, 52, 411c in action while the manual operator(s) (second manual operator, AUX switch) 12, 75 is operated in relation to the actuation of the hydraulic actuator(s) (hydraulic cylinder(s)) 51, 52, 411c, thus changing the actuation state of the hydraulic actuator(s) (hydraulic cylinder(s)) 51, 52, 411c in action before the optimal degree of contact is exceeded. This makes it possible to allow the function portion (work attachment) 41a, 41b or the like to perform a predetermined function without being brought into excessive contact with the work target object T.

[0206] In one or more example embodiments described above, changing the actuation state of the hydraulic actuator (hydraulic cylinder) 51, 411c in action by the controller 13 may include reducing an actuation speed of the hydraulic actuator (hydraulic cylinder) 51, 411c from an actuation speed corresponding to an instruction provided by operation of the manual operator (second manual operator, AUX switch) 12, 75. With this, the actuation speed of the work attachment 41a, 41b or the like decreases, making it possible to prevent the work attachment 41a, 41b or the like from being brought into excessive contact with the work target object T.

[0207] Specifically, the working machine 1 according to one or more example embodiments described above may further include a hydraulic pump (third hydraulic pump) 64 to supply hydraulic fluid to the hydraulic actuator (hydraulic cylinder) 51, 411c, and a prime mover 10 to drive the hydraulic pump (third hydraulic pump) 64. Changing the actuation state of the hydraulic actuator (hydraulic cylinder) 51, 411c in action by the controller 13 may include reducing an actuation speed of the hydraulic actuator (hydraulic cylinder) 51, 411c in action from an actuation speed corresponding to a combination of a drive rotational speed of the prime mover 10 and an instruction provided by the operation of the manual operator (second manual operator, AUX switch) 12, 75. With this, the actuation state of the hydraulic actuator(s) (hydraulic cylinder) 51, 411c in action is changed based not only on the operation state of the manual operator(s) (second manual operator, AUX switch) 12, 75 but also on the actuation speed of the work attachment 41a, 41b or the like in consideration of the drive state of the prime mover 10 (manner in which hydraulic fluid is delivered by the hydraulic pump (third hydraulic pump) 64). With this, the actuation speed of the work attachment 41a, 41b or the like is lower than the reference actuation speed, making it possible to prevent the work attachment 41a, 41b or the like from being brought into excessive contact with the work target object T.

[0208] The hydraulic actuator may include a hydraulic cylinder 51, 52, 411c including a tubular cylinder 510, 520 and a piston rod 511, 521 inserted in the tubular cylinder 510, 520 such that the piston rod 511, 521 is extendable out of and retractable into the tubular cylinder 510, 520, the hydraulic cylinder 51, 52, 411c being operable to switch between the first state and the second state by extending or retracting via extension of the piston rod 511, 521 out of the tubular cylinder 510, 520 or retraction of the piston rod 511, 521 into the tubular cylinder 510, 520. The hydraulic cylinder 51, 52, 411c may include a first port Pa1, Pb1, Pc1 to allow hydraulic fluid to be supplied to the tubular cylinder 510, 520 to move the piston rod 511, 521 in a direction in which the piston rod 511, 521 extends out of the tubular cylinder 510, 520 and a second port Pa2, Pb2, Pc2 to allow hydraulic fluid to be supplied to the tubular cylinder 510, 520 to move the piston rod 511, 521 in a direction in which the piston rod 511, 521 retracts into the tubular cylinder 510, 520. The controller 13 may be configured or programmed to, while the manual operator (second manual operator, AUX switch) 12, 75 is operated in relation to extension or retraction of the hydraulic cylinder that is the actuation of the hydraulic actuator (hydraulic cylinder) 51, 52, 411c, derive the degree of contact of the function portion (work attachment) 41a, 41b or the like with the work target object T based on the pressure of hydraulic fluid at least at the first port Pa1, Pb1, Pc1 or the second port Pa2, Pb2, Pc2 of the hydraulic cylinder 51, 52, 411c, and, if the derived degree of contact matches or substantially matches the preset optimal degree of contact, change a movement state of the piston rod 511, 521 of the hydraulic cylinder that is to the actuation state of the hydraulic actuator (hydraulic cylinder) 51, 52, 411c in action.

[0209] The hydraulic cylinder(s) 51, 52, 411c as a whole extends or the retracts by extending or retracting the piston rod 511, 521 out of or into the cylinder 510, 520 by receiving or discharging hydraulic fluid via the first port Pa1, Pb1, Pc1 or the second port Pa2, Pb2, Pc2. With the extension or the retraction, the hydraulic cylinder(s) 51, 52, 411c exerts a driving force in the direction in which the piston rod 511, 521 moves, and exerts the driving force or a component of the driving force as a force to cause the function portion (work attachment) 41a, 41b, or the like to contact the work target object T. With this, the reaction force resulting when the function portion (work attachment) 41a, 41b, or the like comes into contact with the work target object T acts on the piston rod 511, 521. It follows that the pressure of hydraulic fluid at the first port Pa1, Pb1, Pc1 and the second port Pa2, Pb2, Pc2 of the hydraulic cylinder(s) 51, 52, 411c changes according to the degree of contact of the function portion (work attachment) 41a, 41b, or the like with the work target object T.

[0210] Therefore, as described above, when the controller 13 derives the degree of contact of the function portion (work attachment) 41a, 41b, or the like with the work target object T based on the pressure of hydraulic fluid at least at the first port Pa1, Pb1, Pc1 or the second port Pa2, Pb2, Pc2 of the hydraulic cylinder(s) 51, 52, 411c and, if the derived degree of contact matches or substantially matches the preset optimal degree of contact, changes the movement state of the piston rod 511, 521 of the hydraulic cylinder(s) that is the actuation state of the hydraulic actuator (hydraulic cylinder) 51, 52, 411c in action, the movement state of the piston rod(s) 511, 521 of the hydraulic cylinder(s) 51, 52, 411c is changed such that there is no or little difference between the optimal degree of contact and the actual degree of contact (with no or little error).

[0211] The controller 13 changes the movement state of the piston rod 511, 521 of the hydraulic cylinder(s) 51, 52, 411c while the manual operator (second manual operator, AUX switch) 12, 75 is operated in relation to the extension or retraction of the hydraulic cylinder 51, 52, 411c that is the actuation of the hydraulic actuator (hydraulic cylinder) 51, 52, 411c. Therefore, the controller 13 allows the function portion (work attachment) 41a or the like to perform the predetermined function while further reducing the likelihood that the function portion will come into excessive contact with the work target object T.

[0212] The controller 13 may be configured or programmed to, while the manual operator (second manual operator, AUX switch) 12, 75 is operated in relation to the extension or retraction of the hydraulic cylinder, reduce a movement speed of the piston rod 511, 521 of the hydraulic cylinder in action as the derived degree of contact approaches the preset optimal degree of contact. This makes it possible to prevent or reduce the likelihood that the degree of contact will increase in a short period of time, and therefore the piston rod 511, 521 would be moving at low speed when the derived degree of contact matches or substantially matches the preset optimal degree of contact. Thus, it is possible to more reliably change the actuation state of the hydraulic cylinder(s) 51, 52, 411c.

[0213] The controller 13 may be configured or programmed to, while the manual operator (second manual operator, AUX switch) 12, 75 is operated in relation to the extension or retraction of the hydraulic cylinder, cause the piston rod 511, 521 to stop moving when the derived degree of contact changes from a degree other than the preset optimal degree of contact to a degree matching or substantially matching the preset optimal degree of contact. With this, the piston rod 511, 521, which increases the degree of contact of the function portion (work attachment) 41a, 41b or the like with the work target object T, stops when the derived degree of contact has changed from a degree other than the preset optimal degree of contact to a degree matching or substantially matching the preset optimal degree of contact. This makes it possible to prevent or reduce the likelihood that the preset optimal degree of contact will be exceeded when the function portion (work attachment) 41a, 41b or the like is in contact with the work target object T.

[0214] The controller 13 may be configured or programmed to, after changing the actuation state of the hydraulic cylinder 51, 52, 411c while the manual operator (second manual operator, AUX switch) 12, 75 is operated in relation to the extension or retraction of the hydraulic cylinder 51, 52, 411c, when the operation of the manual operator (second manual operator, AUX switch) 12, 75 in relation to the extension or retraction of the hydraulic cylinder is stopped and then the operation is resumed, cause the piston rod 511, 521 to move in accordance with an instruction provided by the resumed operation of the manual operator (second manual operator, AUX switch) 12, 75. This achieves the following. When the operation of the manual operator(s) (second manual operator, AUX switch) 12, 75 is stopped (operation is not changed and is kept constant), the piston rod 511, 521 is in the stopped state and the excessive degree of contact does not occur. However, the state of contact of the function portion (work attachment) 41a, 41b or the like with the work target object T may change as time passes. In this regard, by causing the piston rod 511, 521 to move as indicated by (in accordance with an instruction provided by) the operation of the manual operator(s) (second manual operator, AUX switch) 12, 75 when the operation is resumed, it is possible to perform work efficiently.

[0215] The working device 4 may include an arm 40 extending from the machine body 2 and connected to the machine body 2 such that the arm 40 is swingable up and down, and a bucket 41a which is the function portion (work attachment) 41a swingably connected to a distal portion of the arm 40. The hydraulic cylinder may include a first hydraulic cylinder 51 to swing the arm 40 and a second hydraulic cylinder 52 to swing the bucket 41a. The controller 13 may be configured or programmed to, while the manual operator (second manual operator) 12 is operated to move the piston rod 511 of the first hydraulic cylinder 51 to lower the arm 40 or to move the piston rod 521 of the second hydraulic cylinder 52 to bring the bucket 41a into a discharging posture after the derived degree of contact reaches a value equal to or less than a specified value corresponding to a state in which the bucket 41a is not in contact with a ground which is the work target object T, derive the degree of contact of the bucket 41a with the ground which is the work target object T based on the pressure of hydraulic fluid at least at the first port Pa1, Pb1 or the second port Pa2, Pb2 of the first hydraulic cylinder 51 or the second hydraulic cylinder 52 in which the piston rod 511, 521 is moved by operating the manual operator (second manual operator) 12, and if the derived degree of contact matches or substantially matches the preset optimal degree of contact, reduce a movement speed of the piston rod 511, 521.

[0216] With this, since the pressure of hydraulic fluid at least at the first port Pa1, Pb1 or the second port Pa2, Pb2 of the first hydraulic cylinder 51 or the second hydraulic cylinder 52 in which the piston rod 511, 521 is moved by operating the manual operator (second manual operator) 12 is produced based on the state of contact of the work attachment 41a, 41b, or the like (load), the degree of contact derived based on the pressure of this hydraulic fluid corresponds to the actual degree of contact. Therefore, by reducing the movement speed of the piston rod 511, 521 when the derived degree of contact matches or substantially matches the preset optimal degree of contact, it is possible to eliminate or reduce the likelihood that the degree of contact of the work attachment 41a, 41b, or the like with the work target object T will sharply exceed the optimal degree of contact.

[0217] The controller 13 may be configured or programmed to derive the degree of contact of the bucket 41a with the ground which is the work target object T based on a relationship between the pressure of hydraulic fluid at the first port Pa1, Pb1 and the pressure of hydraulic fluid at the second port Pa2, Pb2. The pressure of hydraulic fluid differs between the first port Pa1, Pb1 and the second port Pa2, Pb2, sPc2 of the first hydraulic cylinder 51 or the second hydraulic cylinder 52, because of, for example, the difference in inner capacity resulting from the presence/absence of the piston rod 511, 521 (rod), the difference in pressure receiving area of the piston rod 511, 521 (piston), and the characteristics of passages (such as throttles in the flow of hydraulic fluid).

[0218] Therefore, the degree of contact derived based on the pressure of hydraulic fluid at the first port Pa1, Pb1 or the pressure at the second port Pa2, Pb2 may differ from the actual degree of contact. However, the relationship between the pressure of hydraulic fluid at the first port Pa1, Pb1 and the pressure at the second port Pa2, Pb2 is constant or substantially constant. Therefore, by deriving the degree of contact of the bucket 41a with the ground (work target object T) based on the relationship between the pressure of hydraulic fluid at the first port Pa1, Pb1 and the pressure at the second port Pa2, Pb2, it is possible to obtain a result which has little or no difference from the actual degree of contact.

[0219] The function portion may include an attachable and detachable work attachment 41a, 41b or the like to be attached such that the work attachment is replaceable with another work attachment 41a, 41b or the like having a different function. The controller 13 may be configured or programmed to recognize the work attachment 41a, 41b or the like which is attached, and, if the recognized work attachment 41a, 41b or the like is a specific function portion (work attachment) 41a, 41b or the like, change the movement state of the piston rod 511, 521 of the hydraulic cylinder 51, 52, 411c in action when the derived degree of contact matches or substantially matches the preset optimal degree of contact. This achieves the following. The work attachment 41a, 41b or the like differs in terms of optimal degree of contact with the work target object T depending on the content of work.

[0220] Therefore, in the case where the work attachment 41a, 41b, or the like recognized by the controller 13 is the specific function portion (work attachment) 41a, 41b, or the like, by changing the movement state of the piston rod 511, 521 of the hydraulic cylinder 51, 52, 411c in action when the derived degree of contact matches or substantially matches the optimal degree of contact, it is possible to eliminate or reduce the likelihood that the work will be performed under the conditions in which the degree of contact of the work attachment 41a, 41b, or the like greatly exceeds the optimal degree of contact.

[0221] The working machine 1 according to one or more example embodiments described above may further include an attachment selector 14 to be used by a user to select a work attachment 41a, 41b or the like to be used from a plurality of types of work attachments 41a, 41b and the like having different functions. The controller 13 may be configured or programmed to recognize the work attachment 41a, 41b or the like selected by the user via the attachment selector 14 as the work attachment 41a, 41b or the like which is attached. With this, the work attachment 41a, 41b or the like selected by the user (used for work) is automatically identified, making it possible to also derive the optimal degree of contact suitable for the work attachment 41a, 41b or the like (optimal degree of contact in consideration of work conditions, work environments, work characteristics etc. of the work attachment 41a, 41b or the like) in a linked manner.

[0222] In particular, the controller 13 may be configured or programmed to compare the derived degree of contact with one of a plurality of the preset optimal degrees of contact corresponding to the respective functions of the plurality of types of work attachments 41a, 41b and the like that corresponds to the recognized work attachment 41a, 41b or the like. The plurality of optimal degrees of contact are preset according to the respective functions of the work attachments 41a, 41b and the like, which means that each optimal degree of contact is set in consideration of work characteristics, work load, etc. of the corresponding work attachment 41a, 41b or the like. Thus, by comparing the derived degree of contact with the optimal degree of contact corresponding to the work attachment 41a, 41b or the like, it is possible to accurately determine whether the derived degree of contact is suitable (is a suitable degree of contact) for the work attachment 41a, 41b or the like.

[0223] The working machine 1 may further include one or more supply-discharge passages R6a, R6b, R7a, R7b, R8a, R8b connected to the first port Pa1, Pb1, Pc1 and/or the second port Pa2, Pb2, Pc2 of the hydraulic cylinder 51, 52, 411c, and one or more sensors (first pressure detector, second pressure detector, third pressure detector) 69a1, 69a2 and/or the like to detect the pressure of hydraulic fluid in the one or more supply-discharge passages R6a, R6b, R7a, R7b, R8a, R8b. The controller 13 may be configured or programmed to, if a detection result from the one or more sensors (first pressure detector, second pressure detector, third pressure detector) 69a1, 69a2 and/or the like exceeds a predetermined pressure while the manual operator (second manual operator, AUX switch) 12, 75 is operated in relation to the extension and retraction of the hydraulic cylinder 51, 52, 411c, change the movement state of the piston rod 511, 521 of the hydraulic cylinder 51, 52, 411c in action to a state differing from an instruction provided by the operation of the manual operator (second manual operator, AUX switch) 12, 75.

[0224] With this, the sensor(s) (first pressure detector, second pressure detector, third pressure detector) 69a1, 69a2, and/or the like to detect the pressure of hydraulic fluid in the supply-discharge passage(s) R6a, R6b, R7a, R7b, R8a, R8b connected to the first port(s) Pa1, Pb1, Pc1 and the second port(s) Pa2, Pb2, Pc2 of the hydraulic cylinder(s) 51, 52, 411c measures the pressure of hydraulic fluid at the first port(s) Pa1, Pb1, Pc1 of the hydraulic cylinder(s) 51, 52, 411c and the pressure of hydraulic fluid at the second port(s) Pa2, Pb2, Pc2 of the hydraulic cylinder(s) 51, 52, 411c. In the case where the detection result from the sensor(s) (first pressure detector, second pressure detector, third pressure detector) 69a1, 69a2, and/or the like exceeds the predetermined pressure, the controller 13 changes the movement state of the piston rod 511, 521 of the hydraulic cylinder(s) 51, 52, 411c in action such that the movement state differs from the instruction provided by the operation of the manual operator(s) (second manual operator, AUX switch) 12, 75. It follows that, even when the manual operator(s) (second manual operator, AUX switch) 12, 75 continues to be operated, since the movement state of the piston rod 511, 521 of the hydraulic cylinder(s) 51, 52, 411c is changed such that the movement state differs from the instruction provided by the operation of the manual operator(s) (second manual operator, AUX switch) 12, 75, the direction in which the force acts due to the contact of the work attachment 41a, 41b, or the like with the work target object T is changed, so that the load acting on the work attachment 41a, 41b, or the like is reduced.

[0225] The working device 4 may include an arm 40 extending from the machine body 2 and connected to the machine body 2 such that the arm 40 is swingable up and down, and a bucket 41a which is the function portion (work attachment) 41a swingably connected to a distal portion of the arm 40. The hydraulic cylinder may include a first hydraulic cylinder 51 to swing the arm 40 and a second hydraulic cylinder 52 to swing the bucket 41a. The controller 13 may be configured or programmed to, if the pressure of hydraulic fluid at the first port Pa1 or the second port Pa2 of the first hydraulic cylinder 51 exceeds a threshold for a certain period of time while the manual operator (second manual operator) 12 is operated on the first hydraulic cylinder 51 to lower the arm 40, cause the piston rod 511 of the first hydraulic cylinder 51 to stop moving.

[0226] Thus, if the piston rod 511 of the first hydraulic cylinder(s) 51 stops moving when the pressure of hydraulic fluid at the first port Pa1 or the second port Pa2 of the first hydraulic cylinder(s) 51 has exceeded the threshold for the certain period of time while the manual operator (second manual operator) 12 is operated on the first hydraulic cylinder(s) 51 to lower the arm(s) 40, the following is achieved. During the certain period of time after the pressure of hydraulic fluid at the first port Pa1 or the second port Pa2 of the first hydraulic cylinder(s) 51 reaches the threshold, the piston rod 511 of the first hydraulic cylinder(s) 51 continues moving even if the pressure of hydraulic fluid at the first port Pa1 or the second port Pa2 of the first hydraulic cylinder 51 changes, so that the action of the descending arm(s) 40 is not fluctuated and the arm(s) 40 smoothly descends. After the certain period of time from when the pressure of hydraulic fluid at the first port Pa1 or the second port Pa2 of the first hydraulic cylinder 51 reaches the threshold, the piston rod 511 of the first hydraulic cylinder(s) 51 stops moving, and the arm(s) 40 stops descending, so that the work attachment 41a, 41b, or the like connected to the arm(s) 40 is prevented from coming into excessive contact with the work target object T.

[0227] The working machine 1 may further include one or more supply-discharge passages R6a, R6b, R7a, R7b, R8a, R8b connected to the first port Pa1, Pb1, Pc1 and/or the second port Pa2, Pb2, Pc2 of the hydraulic cylinder 51, 52, 411c, a control valve (first control valve, second control valve, third control valve) 66, 67, 68 to adjust a flow rate of hydraulic fluid flowing through the one or more supply-discharge passages R6a, R6b, R7a, R7b, R8a, R8b, and one or more sensors (first pressure detector, second pressure detector, third pressure detector) 69a1, 69a2 and/or the like to detect the pressure of hydraulic fluid in the one or more supply-discharge passages. The manual operator (second manual operator, AUX switch) 12, 75 may include an operator (second operation lever) 120 to receive input relating to actuation of the working device 4 and to control a flow rate of the control valve (first control valve, second control valve, third control valve) 66, 67, 68 based on the received input. The controller 13 may be configured or programmed to, if the controller 13 recognizes the attached function portion (work attachment) 41a, 41b or the like as a specific function portion (work attachment) 41a, 41b or the like and a detection result from the one or more sensors (first pressure detector, second pressure detector, third pressure detector) 69a1, 69a2 exceeds a threshold for a certain period of time while the input is received by the operator (second operation lever) 120, control the control valve (first control valve, second control valve, third control valve) 66, 67, 68 such that the flow rate of hydraulic fluid achieved by the control valve (first control valve, second control valve, third control valve) 66, 67, 68 is zero or is lower than a flow rate of hydraulic fluid corresponding to the input received by the operator (second operation lever) 120.

[0228] With this, the sensor(s) (first pressure detector, second pressure detector, third pressure detector) 69a1, 69a2, and/or the like to detect the pressure of hydraulic fluid in the supply-discharge passage(s) R6a, R6b, R7a, R7b, R8a, R8b connected to the first port Pa1, Pb1, Pc1 and the second port Pa2, Pb2, Pc2 of the hydraulic cylinder(s) 51, 52, 411c measures the pressure of hydraulic fluid at the first port Pa1, Pb1, Pc1 of the hydraulic cylinder(s) 51, 52, 411c and the pressure of hydraulic fluid at the second port Pa2, Pb2, Pc2 of the hydraulic cylinder(s) 51, 52, 411c.

[0229] In the case where the detection result from the sensor(s) (first pressure detector, second pressure detector, third pressure detector) 69a1, 69a2, and/or the like has exceeded the threshold for the certain period of time, the controller 13 controls the control valve(s) (first control valve, second control valve, third control valve) 66, 67, 68 such that the flow rate of hydraulic fluid achieved by the control valve(s) (first control valve, second control valve, third control valve) 66, 67, 68 is lower than the flow rate of hydraulic fluid corresponding to the input received by the operator (second operation lever) 120 or is the flow rate is 0 (zero). It follows that, during the certain period of time after the pressure of hydraulic fluid at the first port Pa1, Pb1, Pc1 or the second port Pa2, Pb2, Pc2 of the hydraulic cylinder(s) 51, 52, 411c reaches the threshold, even when the pressure of hydraulic fluid at the first port Pa1, Pb1, Pc1 or the second port Pa2, Pb2, Pc2 of the hydraulic cylinder(s) 51, 52, 411c changes, the state of supply of hydraulic fluid to the hydraulic cylinder(s) 51 (supply state also includes whether hydraulic fluid is supplied or not) is kept constant.

[0230] With this, the action of the work attachment 41a, 41b, or the like is not fluctuated and continues without causing an awkward feeling. On the other hand, after the certain period of time from when the pressure of hydraulic fluid at the first port Pa1, Pb1, Pc1 or the second port Pa2, Pb2, Pc2 of the hydraulic cylinder(s) 51, 52, 411c reaches the threshold, the amount (flow rate) of hydraulic fluid supplied to and discharged from the hydraulic cylinder(s) 51 decreases below the flow rate of hydraulic fluid corresponding to the input received by the operator (second operation lever) 120 or decreases to 0 (zero). Accordingly, the moving speed of the work attachment 41a, 41b, or the like decreases low or the work attachment 41a, 41b, or the like stops (moving speed decreases to 0 (zero)), making it possible to eliminate or reduce the likelihood that the work attachment 41a, 41b, or the like will come into excessive contact with the work target object T.

[0231] The controller 13 may be configured or programmed to, from when the input received by the operator (second operation lever) 120 starts being kept constant or substantially constant to when a change in the input received by the operator (second operation lever) 120 is detected, control the control valve (first control valve, second control valve, third control valve) 66, 67, 68 such that the flow rate of hydraulic fluid achieved by the control valve (first control valve, second control valve, third control valve) 66, 67, 68 is lower than the flow rate of hydraulic fluid corresponding to the input received by the operator (second operation lever) 120 kept constant or substantially constant.

[0232] With this, the control valve(s) (first control valve, second control valve, third control valve) 66, 67, 68 is controlled such that the flow rate of hydraulic fluid achieved by the control valve(s) (first control valve, second control valve, third control valve) 66, 67, 68 is lower than the flow rate of hydraulic fluid corresponding to the input received by the operator (second operation lever) 120 until a change in the input received by the operator (second operation lever) 120 is detected (until the operation of the operator (second operation lever) 120 is resumed (until the operator 120 is operated to perform actuation again). This makes it possible to keep an appropriate degree of contact without bringing the work attachment 41a, 41b, or the like into excessive contact with the work target object T.

[0233] The controller 13 may be configured or programmed to, in a case that the input is received by the operator (second operation lever) 120 for a certain period of time or more also after the detection result from the one or more sensors (first pressure detector, second pressure detector, third pressure detector) 69a1, 69a2 exceeds the threshold while the input is received by the operator (second operation lever) 120 and then the input received by the operator (second operation lever) 120 is kept constant or substantially constant, repeat the following until next time input received by the operator (second operation lever) 120 is detected: actuating the control valve (first control valve, second control valve, third control valve) 66, 67, 68 when the detection result from the one or more sensors (first pressure detector, second pressure detector, third pressure detector) 69a1, 69a2 is less than the threshold; and stopping actuation of the control valve (first control valve, second control valve, third control valve) 66, 67, 68 when the detection result from the one or more sensors (first pressure detector, second pressure detector, third pressure detector) 69a1, 69a2 exceeds the threshold.

[0234] If the operator (second operation lever) 120 receives input for a certain period of time or more even after the detection result from the sensor(s) (first pressure detector, second pressure detector, third pressure detector) 69a1, 69a2, and/or the like exceeds the threshold while the operator (second operation lever) 120 is receiving input, the degree of contact of the work attachment 41a, 41b, or the like with the work target object T increases. However, if the input received by the operator (second operation lever) 120 thereafter is kept constant or substantially constant and the detection result from the sensor(s) (first pressure detector, second pressure detector, third pressure detector) 69a1, 69a2, and/or the like decreases below the threshold, the degree of contact of the work attachment 41a, 41b, or the like with the work target object T decreases.

[0235] However, since the control valve(s) (first control valve, second control valve, third control valve) 66, 67, 68 is actuated when the detection result from the sensor(s) (first pressure detector, second pressure detector, third pressure detector) 69a1, 69a2, and/or the like is less than the threshold, the amount of hydraulic fluid supplied to and discharged from the hydraulic cylinder 51, 52, 411c increases, and the degree of contact of the work attachment 41a, 41b, or the like with the work target object Tis restored.

[0236] On the contrary, if the detection result from the sensor(s) (first pressure detector, second pressure detector, third pressure detector) 69a1, 69a2, and/or the like in the hydraulic circuit 5 (second hydraulic circuit 5B) exceeds the threshold, the degree of contact of the work attachment 41a, 41b, or the like with the work target object T increases. In this regard, when the detection result from the sensor(s) (first pressure detector, second pressure detector, third pressure detector) 69a1, 69a2, and/or the like in the hydraulic circuit 5 (second hydraulic circuit 5B) exceeds the threshold, the actuation of the control valve(s) (first control valve, second control valve, third control valve) 66, 67, 68 is stopped, so that the amount of hydraulic fluid supplied to and discharged from the hydraulic cylinder(s) 51, 52, 411c decreases, and the degree of contact of the work attachment 41a, 41b, or the like with the work target object Tis restored. Thus, the degree of contact of the work attachment 41a, 41b, or the like with the work target object T is maintained at the optimal value (optimal degree of contact) by repeating the above until next input is received by the operator is detected.

[0237] The working device 4 may include an arm 40 extending from the machine body 2 and connected to the machine body 2 such that the arm 40 is swingable about a first shaft S1 perpendicular to an up-and-down direction, and an earth auger 41e connected to a distal portion of the arm 40 such that the earth auger 41e is swingable about a second shaft S2 perpendicular to the up-and-down direction, the earth auger 41e being the function portion and including a digging drill 411e and a hydraulic motor 411e to rotate the digging drill 411e, the digging drill 411e including a shaft body including a pointed end and a helical blade attached around the shaft body. The hydraulic cylinder 51, 52 may include a first hydraulic cylinder 51 to swing the arm 40 about the first shaft S1 and a second hydraulic cylinder 52 to swing the earth auger 41e about the second shaft S2. The controller 13 may be configured or programmed to, while the hydraulic motor 411e is stopped, derive a degree of contact of the earth auger 41e with soil T which is the work target object based on a pressure of hydraulic fluid supplied to at least one of the hydraulic cylinder 51 or the second hydraulic cylinder 52, and change the movement state of the piston rod 511, 521 of the hydraulic cylinder 51, 52 and set a digging depth D of the earth auger 41e in the soil T to zero if the derived degree of contact matches or substantially matches the preset optimal degree of contact, wherein changing the movement state of the piston rod 511, 521 of the hydraulic cylinder 51, 52 includes stopping movement of the piston rod 511 of the first hydraulic cylinder 51 and the piston rod 521 of the second hydraulic cylinder 52.

[0238] With this, the reference (digging depth D) based on which the earth auger 41e excavates the soil T is clear, making it possible to excavate the soil T using the set digging depth.

[0239] The working device 4 may include an arm posture detector SE1 to detect a posture of the arm 40. The controller 13 may be configured or programmed to, under a condition in which the set digging depth D is zero, recognize a current digging depth D of the earth auger 41e in the soil based on a detection result from the arm posture detector SE1.

[0240] With this, the reference position (digging depth D) based on which the excavation of soil T starts is clear, and the earth auger 41e (digging drill 411e) starts excavating the soil T from the reference position (at which the digging depth D is zero).

[0241] The arm posture detector SE1 may include an angle sensor to sense an angle of rotation of the arm 40 about the first shaft S1. The controller 13 may be configured or programmed to, under the condition in which the set digging depth D is zero, recognize the current digging depth D of the earth auger 41e in the soil T based on a detection result from the angle sensor SE1.

[0242] The working device 4 may include a first angle sensor SE1 to sense an angle of rotation of the arm 40 about the first shaft S1, and a second angle sensor SE2 to sense an angle of rotation of the earth auger 41e about the second shaft S2. The controller 13 may be configured or programmed to, under the condition in which the set digging depth D is zero, recognize the current digging depth D of the earth auger 41e in the soil T based on detection results from the first angle sensor SE1 and the second angle sensor SE2.

[0243] With this, the angle sensor SE1 senses the angle of the arm(s) 40 to the machine body 2, and the controller 13 determines the position (heightwise position) of the earth auger 41e based on the angle of the arm(s) 40. Specifically, since the length of the arm(s) 40 (the distance from the first shaft S1 to the distal end of the arm(s) 40) is constant, the angle of the arm(s) 40 has a constant relationship with the height of the distal end of the arm(s) 40, making it possible to determine the position (heightwise position) of the earth auger 41e connected to the distal portion of the arm(s) 40. Thus, the reference position (digging depth D) from which excavation starts is clear and the position of the earth auger 41e (depth in the soil T) is appropriate, making it possible to dig a hole having the preset digging depth D.

[0244] The arm posture detector may include a stroke sensor to detect a degree of extension or retraction of the first hydraulic cylinder 51. The controller 13 may be configured or programmed to, under the condition in which the set digging depth D is zero, recognize the current digging depth D of the earth auger 41e in the soil T based on a detection result from the stroke sensor.

[0245] With this, the angle sensor senses the extension or retraction of the first hydraulic cylinder(s) 51, and the controller 13 determines the position (heightwise position) of the earth auger 41e based on the extension or retraction (length) of the first hydraulic cylinder(s) 51 sensed by the stroke sensor. Specifically, the length of the arm(s) 40 (the distance from the first shaft S1 to the distal end of the arm(s) 40) is constant, and therefore the angle of the arm(s) 40 has a constant relationship with the height of the distal end of the arm(s) 40, and the angle of the arm(s) 40 also has a constant relationship with the degree of extraction or retraction of the first hydraulic cylinder(s) 51 to rotate (swing) the arm(s) 40. It follows that it is possible to determine the position (heightwise position) of the earth auger 41e connected to the distal portion of the arm(s) 40. Thus, the reference position (digging depth D) from which excavation starts is clear and the position of the earth auger 41e (depth in the soil T) is appropriate, making it possible to dig a hole having the preset digging depth D.

[0246] The working machine 1 may further include at least one of a display 14 or a speaker. The controller 13 may be configured or programmed to, after determining that the current digging depth D of the earth auger 41e in the soil T is a preset digging depth D, cause at least one of the display 14 or the speaker to provide a notification indicating that the current digging depth D of the earth auger 41e in the soil T is the preset digging depth D.

[0247] With this, the indication (notification) displayed by the display 14 and/or the sound indication (notification) provided by the speaker allows the user to recognize that the digging depth in the soil T has reached the preset digging depth D.

[0248] Note that the present invention is not limited to the first example embodiment and the second example embodiment described above and can be modified without departing from the spirit of the present invention.

[0249] For example, in the first and second example embodiments, a compact track loader in which the traveling device 3 is a crawler traveling device 3 is described as an example of the working machine 1. The working machine 1, however, is not limited thereto. For example, the working machine 1 may be a working machine in which the traveling device 3 is a tire (wheeled) traveling device.

[0250] In such a case, the traveling device 3 may include front and back pairs of left and right wheels, one of the front and back pairs of left and right wheels may be driving wheels, and the other of the front and back pairs of left and right wheels may be steered wheels. The tyer (wheeled) traveling device 3 may be a traveling device in which the front and back pairs of left and right wheels are driving wheels and the direction of movement is changed using the difference between the rotational speeds of the wheels (so-called skid-steer loader). The working machine 1 may be another construction machine, an agriculture machine, a utility vehicle (UV), or the like, provided that the working machine 1 includes the working device 4 including a function portion.

[0251] In the first and second example embodiments, the working machine 1 includes, as the seat-protecting mechanism 22, the cabin 22 which defines the operation room RM (space having specified dimensions in the widthwise direction, front-rear direction, and height direction) including the seat 21. Note, however, that this does not imply any limitation. For example, the seat-protecting mechanism 22 may be a so-called canopy or ROPS which includes pillars extending upward from the frame chassis 20 and a roof supported by the pillars above the seat 21.

[0252] In the first and second example embodiments, the prime mover 10 to drive the hydraulic pump(s) is a diesel engine. Note, however, that this does not imply any limitation. The prime mover 10 may be another internal combustion engine such as a gasoline engine or a hydrogen engine. The prime mover 10 may be an electric motor instead of or in addition to an internal combustion engine.

[0253] In the first and second example embodiments, the second operation lever 120 is pivotable in the front-rear and left-right directions from the neutral position. Note, however, that this does not imply any limitation. For example, the second operation lever 120 may be pivotable also diagonally in four directions from the neutral position, and may be configured to actuate the hydraulic actuator(s) 51, 52 according to the direction in which the second operation lever 120 is pivoted diagonally in such directions. The second operation lever 120 may be pivotable in the front-rear and left-right directions and diagonally in four directions from the neutral position, and may be configured to actuate the hydraulic actuator(s) 51, 52 according to the direction in which the second operation lever 120 is pivoted. Thus, the second operation lever 120 pivotable in the front-rear and left-right directions and diagonally in the four directions makes it possible to increase the number of movement patterns of the hydraulic actuator(s) 51, 52.

[0254] In the first and second example embodiments, the control valves to control the hydraulic actuators 51, 52, and 411c (first hydraulic cylinder(s) 51, second hydraulic cylinder(s) 52, and hydraulic cylinder(s) 411c of the work attachment(s) 41c and/or the like) are pilot pressure control valves actuated by the pressure of pilot hydraulic fluid (hydraulic fluid). Note, however, that this does not imply any limitation. For example, control valves to control the hydraulic actuators 51, 52, and 411c (first hydraulic cylinder(s) 51, second hydraulic cylinder(s) 52, and hydraulic cylinder(s) 411c of the work attachment(s) 41c and/or the like) may be solenoid valves (electromagnetic control valves) actuated in response to an electrical signal (electric current).

[0255] In the first and second example embodiments, the hydraulic cylinder 411c of the work attachment 41c is actuated by operating the AUX switch 75, but this does not imply any limitation. For example, the hydraulic cylinder 411c of the work attachment 41c may be actuated by using an operation lever instead of the AUX switch 75 such that the function of the work attachment 41c is performed. In such a case, the second manual operator 12 may also be operated to actuate the work attachment 41c. A feature similar to the second manual operator 12 may be provided separately to actuate the work attachment(s) 41c and/or the like.

[0256] In the first and second example embodiments, the icon of the work attachment 41a or the like used by the user is selected from the attachment list displayed on the display 14, and the controller 13 retrieves (extracts) the optimal degree of contact of the work attachment 41a or the like corresponding to the selected icon from the storing unit 131. Note, however, that this does not imply any limitation. For example, the controller 13 may automatically recognize the attachment (work attachment) 41a or the like to be connected to the arm(s) 40 and may retrieve (extract) the optimal degree of contact of the recognized work attachment 41a or the like from the storing unit 131. In such a case, for example, the controller 13 need only recognize the work attachment 41a or the like based on an attachment ID (identification information relating to the attachment 41a or the like) contained in a wireless signal (advertisement signal) transmitted from a beacon transmitter attached to the work attachment 41a or the like.

[0257] In the second hydraulic circuit 5B according to the first example embodiment, the control valve (first control valve) 66 to control the actuation (extension and the retraction) of the first hydraulic cylinder 51 is a pilot-pressure-controlled directional switching valve, whereas the pilot control valve 72 to receive an instruction from the controller 13 that stops and changes (switches) the direction of the flow (flow path) of pilot hydraulic fluid supplied to the control valve (first control valve) 66 is provided to actuate the first hydraulic cylinder 51 (control valve (first control valve) 66) differently from when the manual operator (second manual operator) 12 is operated. The pilot control valve 72, however, is not limited to this kind.

[0258] For example, as illustrated in FIGS. 13 and 14, the pilot control valve 72 may switch between a state in which pilot hydraulic fluid supplied to the control valve (first control valve) 66 flows in response to the operation of the manual operator (second manual operator) 12 and a state in which the flow of pilot hydraulic fluid supplied to the control valve (first control valve) 66 is blocked (stopped). In such a case, as illustrated in FIG. 14, the pilot control valve 72 may be a proportional electromagnetic control valve to switch between not only the state in which pilot hydraulic fluid supplied to the control valve (first control valve) 66 flows in response to the operation of the manual operator (second manual operator) 12 and the state in which the flow of pilot hydraulic fluid supplied to the control valve (first control valve) 66 is blocked (stopped) but also a state in which the flow rate of pilot hydraulic fluid supplied to the control valve (first control valve) 66 is adjusted (state in which the flow rate is reduced). Accordingly, the use of the pilot control valve 72 illustrated in FIG. 14 makes it possible not only to raise/lower the arm 40 (extend/retract the first hydraulic cylinder 51) and stop the arm 40 but also to change the speed at which the arm 40 is raised/lowered (speed of the extension and retraction of the first hydraulic cylinder 51) in accordance with an instruction from the controller 13.

[0259] The second hydraulic circuit 5B according to the first example embodiment includes the pump controller (so-called load sensing system (LS system)) 81 to control the delivery flow rate of the third hydraulic pump 64 depending on work. Note, however, that this does not imply any limitation. For example, the second hydraulic circuit 5B may use a configuration including no LS system 81, such as the second hydraulic circuit 5B illustrated in FIGS. 15 to 18.

[0260] Note that, in the case where the control valve(s) (first control valve, the second control valve, the third control valve) 66, 67, and/or 68 of the second hydraulic circuit 5B are pilot-pressure-controlled directional switching valves, the second hydraulic circuit 5B is configured such that the control valve(s) (first control valve, the second control valve, the third control valve) 66, 67, and/or 68 are actuated in accordance with an instruction from the controller 13. That is, the second hydraulic circuit 5B, as illustrated in FIGS. 15 and 17, is configured such that the pilot control valve 72 to operate in accordance with an instruction from the controller 13 is able to change the state of supply of pilot hydraulic fluid to the control valve (first control valve) 66 to control the extension and retraction of the hydraulic cylinders (first hydraulic cylinder, second hydraulic cylinder, a hydraulic cylinder of a work attachment 41a and/or the like) 51, 52, 411c similarly to the first example embodiment, and that the solenoid valve(s) 76, 76a, 76b, 77a, 77b to operate in accordance with an instruction from the controller 13 are able to change the state of supply of pilot hydraulic fluid to the control valve (first control valve) 66 to control the extension and retraction of the hydraulic cylinder (first hydraulic cylinder, second hydraulic cylinder, a hydraulic cylinder of a work attachment 41a and/or the like) 51, 52, 411c similarly to the second example embodiment illustrated in FIGS. 16 and 18.

[0261] In the case where the controller 13 controls a plurality of hydraulic cylinders (first hydraulic cylinder, the second hydraulic cylinder, and the hydraulic cylinder of the work attachment 41a and/or the like) 51, 52, and 411c, as illustrated in FIG. 17, the pilot control valve 72 and the solenoid valves 77a and 77b may be used to control pilot hydraulic fluid to the plurality of control valves (first control valve, the second control valve, and the third control valve) 66, 67, and 68 to control the supply of hydraulic fluid to the hydraulic cylinders 51, 52, and 411c.

[0262] In the first example embodiment, a single first manual operator 11 and a single second manual operator 12 are provided as the manual operators 11 and 12, but this does not imply any limitation. For example, a plurality of first manual operators 11 and a plurality of second manual operators 12 may be provided for subdivided operations. For example, the first manual operators 11 included in the working machine 1 may include a first manual operator 11 to be operated in relation to forward movement and backward movement and a first manual operator 11 to be operated in relation to steering (right turn, left turn), and the second manual operators 12 included therein may include a second manual operator 12 to be operated in relation to the arm 40 and a second manual operator 12 to be operated in relation to the work attachment 41a or the like (coupler(s) 45) swinging. In the case where the plurality of first manual operators 11 and the plurality of second manual operators 12 are provided, as illustrated in FIGS. 15, 17, and 18, the combination of one of the first manual operators 11 and one of the second manual operators 12 may be used as a single manual operator 11 or 12.

[0263] In the first example embodiment, the working machine 1 includes the first angle sensor SE1 as an arm posture detector, and the controller 13 determines the degree of downward movement of the earth auger 41e (digging drill 411e) from the ground surface based on the detection result from the first angle sensor SE1, for example, Note, however, that the controller 13 may be configured or programmed to determine the degree of downward movement of the earth auger 41e from the ground surface based on detection result(s) from other arm posture detector(s) (sensor(s)) without relying on the detection result from the first angle sensor SE1. For example, the first hydraulic cylinder(s) 51 may be provided with a stroke sensor to detect the degree of extension or retraction thereof, and the controller 13 may be configured or programmed to determine the degree of downward movement of the earth auger 41e from the ground surface based on the detection result from the stroke sensor.

[0264] While example embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.