A working machine includes: a plurality of hydraulic actuators including a high-load hydraulic actuator and a low-load hydraulic actuator whose hydraulic pressure for actuation thereof is lower than that of the high-load hydraulic actuator; a plurality of direction switching valves each of which switches a direction of a hydraulic fluid for a corresponding one of the hydraulic actuators, the plurality of direction switching valves including a low-load direction switching valve that switches a direction of hydraulic fluid for the low-load hydraulic actuator; and a dummy-load forming unit that forms a dummy load in the low-load direction switching valve to suppress a variation in an actuation speed of the low-load hydraulic actuator between a time when the high-load hydraulic actuator and the low-load hydraulic actuator are operated in combination and a time when the low-load hydraulic actuator is operated singly.

A hoist valve assembly for a work machine cylinder includes a main control valve, a counterbalance valve and a counterbalance shutoff valve. A main control valve raise position connects a head end of the cylinder with a pressurized fluid source and a rod end of the cylinder to a low pressure reservoir to extend the cylinder. The counterbalance valve is between the rod end and the main control valve, is biased to a closed position and has an open position connecting the rod end to the low pressure reservoir. Rod end and head end pressure signals apply force to the counterbalance valve toward the open position. The counterbalance shutoff valve is positioned between the head end and the counterbalance valve, and has a normal position to apply the head end pressure signal to the counterbalance valve and a shutoff position that blocks the head end pressure signal from the counterbalance valve.

When a machine-control ON/OFF switch is switched to the ON position, a controller outputs either a first control signal generated by an operation lever or a second control signal that operates a boom cylinder in accordance with a predetermined condition; when the ON/OFF switch is switched to the OFF position, the controller outputs the first control signal; when a control signal has been switched from one of the first control signal and the second control signal to the other control signal by the operation of the ON/OFF switch, the controller applies a rate limit to the control signal, and controls the boom cylinder on the basis of the control signal obtained after the limitation.

A boom system including a hoist boom pivoted to a machine base; a stick boom having a proximal end pivoted to the hoist boom and a distal end configured to carry a working tool; at least one hydraulic hoist cylinder mounted between the machine base and the hoist boom; a first stick cylinder mounted between the hoist boom and the stick boom; a second stick cylinder mounted similarly and mechanically linked with the first stick cylinder; and a hydraulic circuit for supplying hydraulic fluid to the hoist cylinder and stick cylinders, wherein the hydraulic circuit includes a hydraulic conduit line connecting a base end of the at least one hoist cylinder with a base end of the second stick cylinder to allow hydraulic fluid to shunt between the base ends of the hoist cylinder and the second stick cylinder.

A controller acquires current position data indicative of a current position of a work machine. The controller acquires an inclination angle of an actual topography to be dug. The controller acquires a maximum climbing angle when the work machine travels in reverse. The controller determines a digging angle with respect to the actual topography based on the inclination angle and the maximum climbing angle. The controller determines a target digging trajectory based on the digging angle. The controller controls a work implement according to the target digging trajectory.

A working machine includes: a machine body provided thereon with a traveling pump and a traveling motor; a traveling change-over valve shiftable between a first state where a rotation speed of the traveling motor is set to a first speed and a second state where the rotation speed is set to a second speed; an actuation valve operable to control a flow of operation fluid to an operation valve that changes a pressure of operation fluid to be applied to the traveling pump according to operation of an operation member; and a controller to perform a shock-mitigation control for reducing an opening degree of the actuation valve when the traveling change-over valve is shifted from the first state to the second state. The controller determines a reduction amount of the opening degree of the actuation valve reduced by the shock-mitigation control, based on a straight-traveling degree of the machine body.

An attachment is attached to an upper turning body. During a normal operation, a drive means drives the attachment according to an input of an operator to a manipulation device. A sensor detects a motion of an excavator. Based on an output of the sensor, the slip suppression unit detects slip of a traveling body in an extension direction of the attachment and corrects an operation of the attachment performed by the drive means.

A working machine includes a machine body, a traveling device provided on the machine body, a traveling motor configured to provide power to the traveling device and to be switched between a first speed and a second speed, a traveling operation member to be operated by an operator, an operation detector to detect an operation extent of the traveling operation member, a traveling pump driven in response to the operation extent to supply operation fluid to the traveling motor, a revolution detector to detect a motor revolving speed, and a controller configured to switch the traveling motor from the second speed to the first speed when the motor revolving speed is equal to or less than a deceleration threshold, and then to switch the traveling motor from the first speed to the second speed when the motor revolving speed is equal to or greater than a return threshold.

A hydraulic system of a construction machine includes: control valves interposed between a variable displacement main pump and hydraulic actuators; and first solenoid proportional valves connected to pilot ports of the control valves. The hydraulic system further includes: a regulator that changes a displacement of the main pump; and a second solenoid proportional valve connected to an auxiliary pump by a primary pressure line, the second solenoid proportional valve outputting a secondary pressure to the regulator through a secondary pressure line. A switching valve is interposed between the auxiliary pump and the first solenoid proportional valves, and includes a pilot port that is connected to the secondary pressure line by a pilot line.

Systems to control movement of a motor grader include a sensor for providing a bounce signal indicative of a bouncing movement of the motor grader, and a controller programmed with instructions that, when executed: receive the bounce signal from the sensor; analyze the bounce signal from the sensor; determine whether the maximum amplitude of the bouncing movement exceeds a threshold; in response to determining whether the maximum amplitude exceeds the threshold, generate an articulation angle command signal to change an articulation angle of the motor grader; and transmit the articulation angle command signal to change the articulation angle.