HYDRAULIC CONTROL SYSTEM, WORK MACHINE AND METHOD FOR CONTROLLING OPERATION OF A WORK ATTACHMENT

Abstract

The invention refers to a hydraulic control system for controlling operation of a work attachment of a work machine, comprising a controller configured to output a work attachment control value controlling the operation of the work attachment, an operator input device configured to output a command signal depending on the amount of actuation of the operator input device for setting the work attachment control value, a save input device configured to generate a save command signal upon actuating the save input device and a mode select input device configured to select a first mode and a second mode, wherein the controller is configured to save a constant work attachment control value, wherein the constant work attachment control value is the work attachment control value as set by the command signal upon receiving the save command signal.

Claims

1: A hydraulic control system for controlling operation of a work attachment of a work machine, comprising a controller configured to output a work attachment control value controlling the operation of the work attachment, an operator input device operatively connected to the controller, wherein the operator input device is configured to output a command signal depending on the amount of actuation of the operator input device for setting the work attachment control value, a save input device operatively connected to the controller, wherein the save input device is configured to generate a save command signal upon actuating the save input device, wherein the controller is configured to save a constant work attachment control value, wherein the constant work attachment control value is the work attachment control value as set by the command signal upon receiving the save command signal.

2: The hydraulic control system according to claim 1 characterized by a mode select input device operatively connected to the controller and configured to select a first mode and a second mode, wherein in the first mode, the controller outputs the work attachment control value based on the command signal, and in the second mode, the controller outputs the constant work attachment control value when the command signal reaches a predetermined threshold.

3: The hydraulic control system according to claim 2 characterized in that, in the second mode, the controller terminates outputting the constant work attachment control value when the command signal falls below the predetermined threshold.

4: The hydraulic control system according to claim 2 characterized in that the controller only saves the constant work attachment control value upon receiving the save command signal, when the first mode is selected.

5: The hydraulic control system according to claim 2 characterized in that at least one of the save input device, the operator input device and the mode select input device is a movable switch movable between different positions.

6: The hydraulic control system according to claim 2 characterized in that the operator input device is a slide switch and that the save input device and the mode select input device is a button switch.

7: The hydraulic control system according to claim 2 characterized by a lever, wherein the operator input device, the save input device and/or the mode select input device is/are arranged on the lever.

8: The hydraulic control system according to claim 1 characterized by a hydraulic pump for providing hydraulic fluid to the work attachment, wherein the controller controls the hydraulic pump to set a flow of the hydraulic fluid according to the work attachment control value.

9: The hydraulic control system according to claim 8 characterized by an engine, wherein the hydraulic pump is a fixed displacement pump which is driven by the engine, and wherein the controller outputs the work attachment control value to the engine to set the flow of the hydraulic fluid.

10: The hydraulic control system according to claim 8 characterized in that the hydraulic pump is a variable displacement pump, wherein the controller outputs the work attachment control value to the variable displacement pump to control the displacement of the variable displacement pump to set the flow of the hydraulic fluid.

11: The hydraulic control system according to claim 1 characterized by a control valve for setting a flow of hydraulic fluid to the work attachment, wherein the controller outputs the work attachment control value to the control valve to set the flow of the hydraulic fluid.

12: The hydraulic control system according to claim 10 characterized by an electromagnetic valve which provides pilot pressure based on an EPC signal, wherein the work attachment control value is the EPC signal.

13: A work machine, comprising a work attachment, a hydraulic circuit for supplying hydraulic fluid to the work attachment, and a hydraulic control system according to claim 1 for controlling a flow of the hydraulic fluid in the hydraulic circuit.

14: A method for controlling operation of a work attachment of a work machine, comprising the following steps: controlling the work attachment in a first mode based on an amount of actuation of an operator input device, saving the current amount of actuation, and controlling the work attachment in a second mode based on saved amount of actuation.

15: The method according to claim 14, characterized in that controlling the work attachment in the second mode is started by actuating the operator input device beyond a predetermined threshold, wherein controlling the work attachment in the second mode is stopped by moving the operator input device below the predetermined threshold.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0056] FIG. 1 shows a perspective view of a work machine.

[0057] FIG. 2 shows a perspective view of a front end of the work machine with a bucket removed.

[0058] FIG. 3 shows a perspective view of rear end of the work machine.

[0059] FIG. 4 shows a perspective view of a work attachment.

[0060] FIG. 5 shows a block diagram of a first embodiment of a hydraulic control system and the work attachment.

[0061] FIG. 6 shows a block diagram of a second embodiment of a hydraulic control system and the work attachment.

[0062] FIG. 7 shows a block diagram of a third embodiment of a hydraulic control system and the work attachment.

[0063] FIG. 8 shows a fourth embodiment of a hydraulic control system and the work attachment.

[0064] FIG. 9 shows a flow chart showing a method for controlling a work attachment according to the invention.

[0065] FIG. 10 shows several diagrams highlighting the functioning of the hydraulic control system.

[0066] FIG. 11 shows a front perspective view of a lever.

[0067] FIG. 12 shows a rear perspective view of the lever.

[0068] FIG. 13 shows a fifth embodiment of a hydraulic control system and the work attachment.

DESCRIPTION OF EMBODIMENTS

[0069] FIG. 1 shows a wheel loader which is an example of a work machine 10. The work machine 10 comprises a vehicle body 12 which has a cab 14 arranged thereon. The cab 14 comprises a driver seat and a plurality of control instruments for controlling the functioning of the work machine 10. The work machine 10 further comprises a boom 16 and a bucket 18. The boom 16 can be raised and lowered using a hydraulic cylinder (not visible in FIG. 1). The bucket 18 is removably attached to the boom 16. The bucket 18 can be tilted with regard to the boom 16 using a tilting hydraulic cylinder 19.

[0070] The work machine 10 further comprises two front wheels 20 and two rear wheels 22. The rear wheels 22 and/or the front wheels 20 are powered by means of an engine 24, which is not visible in FIGS. 1 and 2, since it is arranged in an engine compartment covered by an engine hood 26. The engine 24 and the engine compartment are arranged behind the cab 14 in a front-rear direction of the work machine 10.

[0071] The engine 24 may be a combustion engine and/or can be constituted by an electric motor. The engine 24 provides power for driving the work machine 10, for raising and lowering the boom 16 as well as for tilting the bucket 18.

[0072] FIG. 2 shows a front end of the work machine 10 with the bucket 18 removed. The bucket 18 is attached to the boom 16 by means of a bucket fastening structure 28. The bucket fastening structure 28 can also be used to attach a work attachment 30 which will be explained in the following. The bucket attachment structure 28 in the embodiment shown comprises two bucket openings 28a arranged on the boom 16 and a tilt fastening structure 28b which the bucket 18 can be tilted. Furthermore, two hydraulic lines 32 are arranged on the boom 16 which can be connected to the work attachment 30. Hydraulic fluid can be fed to the work attachment 30 by means of the hydraulic lines 32.

[0073] FIG. 4 shows a manhole cutter as an example of the work attachment 30. The work attachment 30 comprises a cutter 38 which can be rotated around an axle (not visible). The cutter 38 comprises a plurality of cutting teeth with which the cutter 38 may cut into tarmacadam. The cutter 38 is rotatably attached to a frame 40. The frame 40 holds a hydraulic motor 42 for driving the cutter 38. The hydraulic motor 42 is not visible in FIG. 4, since it is covered by the frame 40. The hydraulic motor 42 can be directly connected to the cutter 38 or indirectly, for example via a transmission.

[0074] The work attachment 30 further comprises an attachment structure 44 fixed to the frame 40 for attaching the work attachment 30, for example, to the bucket fastening structure 28. To this end, the attachment structure 44 may comprise pins which engage with the bucket openings 28a. The attachment structure 44 allows a removable attachment of the work attachment 30 to the work machine 10. Furthermore, the work attachment 30 also comprises hydraulic lines 32 (not shown) for connecting the hydraulic motor 42 to the hydraulic lines 32 of the work machine 10.

[0075] FIG. 5 shows an exemplary embodiment of a hydraulic control system 46 which controls the amount of hydraulic fluid fed to the work attachment 30. The hydraulic control system 46 comprises an operator input device 48, a save input device 50, a mode select input device 52, a controller 54 and a hydraulic circuit 56. The operator input device 48 is operatively connected to the controller 54, for example, by means of a wire. The operator input device 48 can be actuated such that the amount of actuation can be changed. For example, the operator input device 48 is device which can be moved between different positions, as will be discussed in the following with reference to FIGS. 11 and 12. The operator input device 48 outputs a command signal, which is indicative of the amount of operation. The command signal is forwarded to the controller 54.

[0076] The save input device 50 is also operatively connected to the controller 54, for example, by means of a wire. The save input device 50 is movable between a first position and a second position, wherein the save input device 50 generates a save command signal upon reaching the second position. For example, the save input device 50 is a button whereby the first position is the non-pressed position and the second position is reached when the button is pressed. Embodiments of the save input device 50 are discussed in conjunction with FIGS. 11 and 12 in the following. The save input device 50 generates a save command signal which is forwarded to the controller 54.

[0077] The mode select input device 52 is operatively connected to the controller 54, for example, by means of a wire. The mode select input device 52 is provided to select between a first mode and a second mode. The mode select input device 52 may be configured as a button, wherein pressing the button switches between the first mode and the second mode. Furthermore, the mode select input device 52 may be configured to have two different positions, wherein each position indicates a respective mode. For example the mode select input device 52 is configured as a button having two positions, wherein each position indicates a respective mode. The mode select input device 52 generates a selection command signal which is forwarded to the controller 54.

[0078] The controller 54 outputs a work attachment control value which is forwarded to the hydraulic circuit 56 for setting the flow of hydraulic fluid which is supplied to the work attachment 30. The controller 54 may be configured as a computer, a microprocessor or any other suitable electronic device.

[0079] The controller 54 is capable of working in two different modes. In a first mode, also referred to as a proportional mode, the controller 54 outputs a work attachment control value which is indicative of the command signal generated by the operator input device 48. For example, the work attachment control value linearly increases with an increase in the command signal. Preferably, the more the operator input device 48 is actuated, the higher the command signal gets and the more the work attachment control value increases. For example, there is a linear relationship between the amount of actuation and the work attachment control value.

[0080] In a second mode, also often referred to as a continuous mode, the controller 54 outputs a constant work attachment control value. The constant work attachment control value is set by operating the controller 54 in the proportional mode and actuating the save input device 50. Upon receiving the save command signal from the save input device 50, the controller 54 saves the current work attachment control value based on the current command signal generated by the operator input device 48 as the constant work attachment control value. Upon actuating the mode select input device 52, the controller 54 then switches to the continuous mode. The working principle of the hydraulic control system 46 according to the invention will be discussed in the following, in particular in conjunction with FIG. 9.

[0081] The hydraulic circuit 56 of the embodiment shown in FIG. 5 comprises a control valve 58, a hydraulic pump 60, and a fluid reservoir 62. The hydraulic pump 60 may be a fixed displacement pump and sucks hydraulic fluid from the fluid reservoir 62. The hydraulic pump 60 pumps the hydraulic fluid through the hydraulic line 32 in which the control valve 58 is arranged. For changing the amount of hydraulic fluid which is fed to the hydraulic motor 42 of the work attachment 30, the degree of opening of the control valve 58 is changed. Hence, in this embodiment, the work attachment control value is a signal for setting the opening degree of the control valve 58. The control valve 58 may be a solenoid valve (electromagnetically operated valve), which is controlled by an EPC signal (EPC: Electronic Pressure Control). Thus, in this particular embodiment, the work attachment control value is an EPC signal.

[0082] A further embodiment of the hydraulic control system 46 is depicted in FIG. 6. The hydraulic control system 46 of FIG. 6 is identical to the hydraulic control system 46 of FIG. 5 except for the following differences. The hydraulic circuit 56 of the hydraulic control system 46 of FIG. 6 does not comprise a control valve 58 compared to the hydraulic circuit 56 as shown in FIG. 5. The hydraulic pump 60 of the hydraulic control system 46 of FIG. 6 is a fixed displacement pump which is connected to the engine 24. For setting the flow of hydraulic fluid fed to the hydraulic motor 42 of the work attachment 30, the engine speed of the engine 24 is accordingly set. For example, the amount of fuel for the engine 24 is changed depending on the work attachment control value. Hence, in this embodiment, the work attachment control value defines the amount of fuel which is supplied to the engine 24. By setting the engine speed, the amount of hydraulic fluid supplied to the hydraulic motor 42 is set.

[0083] The hydraulic control system 46 of the embodiment shown in FIG. 7 is identical to the hydraulic control system 46 as shown in FIG. 5 except for the following differences. The hydraulic circuit 56 of the embodiment shown in FIG. 7 comprises a variable displacement pump as the hydraulic pump 60 but no control valve 58. Furthermore, the hydraulic circuit 56 comprises an actuator 64 for changing the displacement of the hydraulic pump 60. In particular, the hydraulic pump 60 comprises a swashplate whose angle can be changed using the actuator 64. By changing the angle of the swashplate, the amount of hydraulic fluid displaced by the hydraulic pump 60 can be changed while maintaining a constant engine speed. The work attachment control value in the embodiment as shown in FIG. 7 is a signal driving the actuator 64 for setting the angle of the swashplate of the hydraulic pump 60.

[0084] FIG. 8 shows another embodiment of a hydraulic circuit 56. The hydraulic circuit 56 as shown in FIG. 8 is identical to the hydraulic circuit 56 as shown in FIG. 5 except for the following differences. The hydraulic circuit 56 of the hydraulic control system 46 as shown in FIG. 8 comprises a control valve 58 whose degree of opening is set by pilot pressure. The pilot pressure is changed using a pilot pressure control valve 66. Hence, the hydraulic circuit 56 of FIG. 8 comprises a pilot pressure line 68 which guides some hydraulic fluid from the pilot pressure control valve 66 to the control valve 58. The pilot pressure control valve 66 may be an electromagnetic valve (solenoid valve) which changes its degree of opening depending on an EPC signal. Hence, in the current embodiment, the work attachment control value is an EPC signal. By changing the opening degree of the pilot pressure control valve 66, the amount of hydraulic fluid in the pilot pressure line 68 is changed, which in turn changes the degree of opening of the control valve 58. In this way, the amount of hydraulic fluid fed to the hydraulic motor 42 can be set.

[0085] The working principle of the hydraulic control system 46 of the current invention will be discussed in the following in conjunction with FIGS. 9 and 10. To start, an operator presses the mode select input device 52 to select the first mode (see step S1). Upon actuation, the mode select input device 52 outputs the selection command signal to the controller 54 such that the controller 54 works in the first mode or proportional mode.

[0086] For setting the rotation speed of the hydraulic motor 42 and thus of the cutter 38 of the work attachment 30, the operator changes the amount of operation of the operator input device 48 (see step S2). Depending on the amount of operation of the operator input device 48, a respective command signal is generated which is forwarded to the controller 54. The controller 54 outputs a work attachment control value depending on the amount of the command signal. In particular, as shown in FIG. 10, the work attachment control value linearly depends on the amount of the command signal. For example, the work attachment control value increases upon an increase in the value of the command signal. By changing the amount of actuation of the operator input device 48, the operation of the work attachment 30 is set. In particular, it is possible to adjust the rotation speed of the cutter 38 of the work attachment 30 by changing the amount of operation of the operator input device 48.

[0087] After setting the amount of operation of the operator input device 48 as required, the operator presses the save input device 50. The save input device 50 then generates the save command signal. Upon receiving the save command signal, the controller 54 saves the work attachment control value as currently outputted to the hydraulic circuit 56 as the current work attachment control value (see step S3).

[0088] If the operator decides to operate the work attachment 30 no longer in the proportional mode, the operator operates the mode select input device 52 upon which it generates the selection command signal (see step S4). Upon receiving the selection command signal, the controller 54 operates in the second mode, i.e. the continuous mode.

[0089] To initiate the controller 54 to output the constant work attachment control value, the operator operates the operator input device 48 by an amount of actuation which is greater than a predetermined threshold (see step S5). If the controller 54 receives a command signal whose value is beyond the predetermined threshold, the controller 54 starts outputting the constant work attachment control value as indicated in FIG. 10 (see step S6). The controller 54 stops outputting the constant work attachment control value, if the amount of actuation of the operator input device 48 falls below the predetermined threshold (see step S7).

[0090] Alternatively, as indicated by the dotted lines in FIG. 10, the controller 54 outputs the current work attachment control value even in the second mode, if the command signal is below the predetermined threshold. If the command signal, i.e. the amount of actuation is beyond the predetermined threshold, the controller 54 outputs the constant work attachment control value irrespective whether the command signal further increases. Hence, in the continuous mode, the work attachment control value outputted by the controller 54 does not linearly depend on the amount of the command signal. In this embodiment, if the amount of the command signal falls below the predetermined threshold, the controller 54 outputs a work attachment control value depending on the command signal, i.e. as done in the proportional mode.

[0091] FIGS. 11 and 12 show a front and rear perspective view of a lever 70. The lever 70 may be arranged in the cab 14. The lever 70 can be tilted for controlling the travel of the work machine 10, for raising/lowering the boom 16, and/or for tilting the bucket 18.

[0092] The operator input device 48, the save input device 50 and the mode select input device 52 are arranged on the lever 70. In the embodiment shown in FIGS. 11 and 12, the operator input device 48 is a slide switch which can be actuated in the left-right direction. The amount of displacement from the rest position as shown in FIGS. 11 and 12 defines the amount of actuation. The operator input device 48 is arranged on the rear side of the lever 70 to be actuated by a middle finger of the operator.

[0093] The save input device 50 preferably is a push button arranged on the lever 70. Similarly, the mode select input device 52 preferably is also a push button arranged on the same lever. The save input device 50 and mode select input device 52 are arranged on the front side of the lever 70 to be actuated by a thumb of the operator. The lever 70 may be part of a remote control for remotely controlling the work machine 10.

[0094] Since all input devices 48, 50 and 52 necessary for controlling the work attachment 30 are arranged on the lever 70, it is not necessary to remove the hand from the lever 70 for controlling the work attachment 30 both in the first mode as well as in the second mode.

[0095] The hydraulic control system 46 of the embodiment shown in FIG. 13 is identical to the hydraulic control system 46 as shown in FIG. 5 except for the following differences. The save command signal, the command signal, and the selection command signal are wireless transmitted to the controller 54. To this end, the operator input device 48, the save input device 50, and the mode select input device 52 could be connected to a transmitter 72, such as infrared radiation (IR) transmitter or a radio transmitter, by means of wires. The operator input device 48, the save input device 50, the mode select input device 52, and the transmitter 72 could be components of the lever 70. The transmitter 72 wirelessly outputs the save command signal, the command signal, and the selection command signal. It is also possible that the operator input device 48, the save input device 50, and the mode select input device 52 each comprise a transmitter 72 for sending the save command signal, the command signal, and the selection command signal, respectively.

[0096] The save command signal, the command signal, and the selection command signal sent by the transmitter 72 are received by a receiver 74 which is adapted to receive the signals emitted by the transmitter 72. The receiver 74 is connected to the controller 54 by means of a wire and forwards the received signals to the controller 54.

[0097] An advantage of the hydraulic control system of the present invention is that the constant work attachment control value is set using the operator input device 48. This simplifies the control of the work attachment 30, since the operator can use the operator input device 48 for setting both the work attachment control value in the proportional mode and the constant work attachment control value for controlling the work attachment 30 in the continuous mode. For example, the operator can use the operator input device 48 in the proportional mode for setting the control of the operation of the work attachment 30 depending on the specific requirements. Upon reaching the desired state of operation of the work attachment 30, for example the speed of the rotation of the work attachment 30, this setting can be saved using the save input device 50. Upon switching to the continuous mode, this finely adjusted setting of the operation of the work attachment 30 is executed. In contrast to the commonly known hydraulic control systems, the constant work attachment control value for controlling the operation of the work attachment 30 in the continuous mode is not set in advance, but can be tuned to the current requirements. Thus, the constant work attachment control value can be better adjusted to the given circumstances.

[0098] Furthermore, the operator does not need to release the operator input device 48 for setting the constant work attachment control value, but uses the same operator input device 48 for both setting the work attachment control value in the proportional mode and in the continuous mode.

REFERENCE SIGNS LIST

[0099] 10 work machine; 12 vehicle body; 14 cab; 16 boom; 18 bucket; 19 tilting hydraulic cylinder; 20 front wheel; 22 rear wheel; 24 engine; 26 engine hood; 28 bucket fastening structure; 28a bucket opening; 28b tilt fasting structure; 30 work attachment; 32 hydraulic line; 38 cutter; 40 frame; 42 hydraulic motor; 44 attachment structure; 46 hydraulic control system; 48 operator input device; 50 save input device; 52 mode select input device; 54 controller; 56 hydraulic circuit; 58 control valve; 60 hydraulic pump; 62 fluid reservoir; 64 actuator; 66 pilot pressure control valve; 68 pilot pressure line; 70 lever.