A hydraulic system for a work machine includes a hydraulic bump to output an operation fluid, a hydraulic switch valve to be switched among switching positions in accordance with a pressure of the operation fluid, a proportional valve to change the pressure of the operation fluid applied to the hydraulic switch valve, a travel hydraulic device to change a thrust power in accordance with the switching positions of the hydraulic switch valve. And, the hydraulic system includes a controller to control the proportional valve in accordance with a state of the travel hydraulic device.

A work machine includes systems and methods for stability control based on operating values. The work machine includes a control system having a sensor system with a load sensor, an arm position sensor, and an articulation angle sensor. A controller is in communication with the sensor system. The controller is configured to receive a movement command and to receive a set of values from the sensor system. The controller is configured to determine an operational window for normal operation of the work vehicle based on the received set of values, determine a movement limit based on the received set of values, and limit movement of a component beyond the movement limit.

To reduce load on the operator and to establish traveling stability in the steering operation of a construction machine that has a pair of right and left traveling devices, and an engine as a driving power to the right and left traveling devices, a controller is provided which is responsive to a switch for traveling to drive or stop both a right and a left traveling devices. A switch for steering causes the controller to change the direction of travel of the construction machine, and the controller also acts to reduce the engine speed in accordance with the operation amount of the switch for steering.

An excavator includes a lower travelling body; an upper turning body mounted on the lower travelling body; a hydraulic pump installed in the upper turning body; a travelling hydraulic motor that is a variable displacement type motor configured to move the lower travelling body by being driven by hydraulic oil discharged by the hydraulic pump; and a control device configured to control a motor capacity of the travelling hydraulic motor so as to be switchable between a plurality of levels. The control device switches the motor capacity to a low rotation setting upon detecting that an operation for changing a travelling direction of the lower travelling body is performed.

A travel control system for construction machinery includes first and second hydraulic pumps, a first travel motor and a second travel motor operable by a working oil discharged from the first hydraulic pump or the second hydraulic pump, at least one actuator operable by the working oil discharged from the first hydraulic pump or the second hydraulic pump, a straight travel valve to be switched between a first position and a second position, first and second travel motor control valves configured to control amounts of the working oil supplied to the first and second travel motors, first and second spool displacement adjusting valves supplying pilot signal pressures to the spools of the first and second travel motor control valves respectively, and a controller configured to output a control signal to each of the first and second spool displacement adjusting valves corresponding to a manipulation signal of an operator.

A track-type machine includes first and second ground-engaging track assemblies, each having a drive motor, and a propulsion system including an operator station with first and second joysticks, and a travel control system including input devices resident on the first and second joysticks. The input devices are adjustable to vary at least one of a speed or a direction of the drive motors in the track assemblies. Adjustment of the drive motor speed can be in proportion to an adjustment of the corresponding input device.

The present invention relates to a vertical lift type loader comprising a power transmission arrangement with an engine, a hydraulic power system for powering work hydraulics of the loader and a drivetrain power system for powering locomotion of the loader, both being feedable with power from the engine, the hydraulic power system including a power limiter for limiting the power supply of the engine to the hydraulic power system to different power limit values, a determining device for determining an operational state of the loader, and a controller configured to control the power limiter to limit the power supply of the engine to the hydraulic power system to different power limit values, these power limit values being set depending on the operational state of the loader determined by the determining device.

A variable displacement pump supplies hydraulic oil to turning motor via a turning control valve; pair of supply/discharge lines connect turning motor and turning control valve; a pair of make-up lines connect pair of supply/discharge lines to tank, each line having check valve; turning operation device including operating lever and outputting operation signal corresponding to inclination angle of operating lever; a flow rate adjuster adjusts tilting angle of pump; and controller controls flow rate adjuster, such that tilting angle of pump increases in accordance with increase in operation signal outputted from turning operation device. Controller: turning acceleration and at time of constant speed turning, controls flow rate adjuster such that discharge flow rate of pump changes on first regulation line; turning deceleration, controls flow rate adjuster such that discharge flow rate of pump changes on second regulation line, second regulation line having slope less than slope of first regulation line.

A work vehicle includes a first frame, a second frame pivotally coupled to the first frame at an articulation joint, and a control circuit operable to control relative movement of the first and second frames about the articulation joint. The control circuit includes a pump, an actuator in fluid communication with the pump, and a first valve assembly coupled to a user-manipulable control. The first valve assembly is configured to direct fluid from the pump to the actuator in response to movement of the user-manipulable control to pivot the first and second frames. The control circuit also includes a second valve assembly configured to direct fluid from the pump to the actuator in response to receiving an electronic control signal to pivot the first and second frames.

A vehicle steering assembly for controlling movement of a vehicle having independently rotatable left and right ground-engaging traction elements. The steering assembly comprises a steering handle coupled to the panel support structure and extending generally upwardly from the panel support structure. The steering handle comprises a laterally-extending crossmember and at least one upright extension member. The crossmember and the upright extension member are rigidly connected to one another so that shifting of the crossmember relative to the extension member is substantially prevented. The steering handle is shiftable in forward and rearward directions to thereby cause corresponding forward and rearward rotation of both of the left and right traction elements. The steering handle is rotatable in clockwise and counterclockwise directions to thereby cause a change in the relative speeds and directions of rotation of the left and right traction elements.