A hydraulic system for a work vehicle includes a first pump providing a first flow to a first circuit. A first pressure sensor measures a first pressure in the first circuit. A first swashplate angle sensor measures a first angle of a first swashplate of the first pump. A supplemental pump provides a supplemental flow to a supplemental circuit. A supplemental pressure sensor measures a supplemental pressure in the supplemental circuit. A supplemental valve adjusts the load sense signal provided to a supplemental load sensing compensator of the supplemental pump. A first valve selectively enables flow from the supplemental circuit to the first circuit when the supplemental pressure is equal to or greater than the first pressure. A controller determines to operate the supplemental pump in one of a standby condition and a use condition based in part on the first angle of the first swashplate.

Hydraulic valve circuitry adapted for hydraulic connection to a lift truck having a mast and at least one lift cylinder for alternately raising and lowering the mast. The hydraulic assembly is also adapted for hydraulic connection to an attachment to the lift truck, the attachment having opposed clamps actuated by respective clamp cylinders. The hydraulic assembly preferably comprises a valve circuit capable of causing the at least one lift cylinder to be an accumulator.

A balancing valve includes four ports. While the pressures at a pair of balancing ports of a hydraulic balancing valve are equal, the valve maintains two other ports in a closed position. Upon a pressure differential between the balancing ports, fluid communication can occur between one of the balancing ports and either of the other ports based upon the direction of the pressure differential. A hydraulic ride control system utilizes the balancing valve together with other control valves to provide ride control functionality.

A method for controlling a hydraulic actuator (2) of a system (1) by means of a valve having a valve element is described. A position of the valve element determines a pressure supplied to a hydraulic actuator (2). In such a method a variable dead band should be minimized. To this end a start position of the valve element is preadjusted as a function of at least one parameter outside the hydraulic actuator (2).

A pressure regulator includes an outlet pressure sensor, loading and unloading electromagnetic valves, and a regulator control circuit operatively connected to the loading and unloading electromagnetic valves and configured to pilot the loading and unloading electromagnetic valves to cancel an error signal given by a difference between an inlet signal corresponding to a desired outlet pressure and a feedback signal provided by the outlet pressure sensor. The pressure regulator includes an engaging current analysis circuit to detect and store reference characteristics of the engaging current of the solenoid of the loading electromagnetic valve in a stable inlet pressure condition, monitor the engaging current to detect any variation of its characteristics with respect to the corresponding reference characteristics, and, in the event of variation, provide a pilot modulation signal to at least one of the loading or unloading electromagnetic valves or a pressure variation signal to the regulator control circuit.

A hydraulic control apparatus includes an output-side oil passage into which oil from a first oil passage and oil from a second oil passage flow, and a pressure regulating check valve regulating a hydraulic pressure in the second oil passage. The pressure regulating check valve includes first and second elastic portions housed in a spool hole between a valve body and a bottom of the spool hole. A natural length of the second elastic portion is shorter than a distance between the valve body and the bottom when the valve body closes an inflow hole. The second elastic portion applies an elastic force to the valve body in a state in which the valve body opens the inflow hole.

A system for controlling hydraulic fluid flow within a work vehicle includes a pilot conduit configured to receive a pilot flow of hydraulic fluid from a fluid supply conduit such that the operation of a compensator valve is controlled based on a pressure of the pilot flow within the pilot conduit. Furthermore, a pilot conduit valve is configured to adjust the pressure of the pilot flow within the pilot conduit. In addition, the system includes a load sense conduit configured to receive a bleed flow of the hydraulic from the fluid supply conduit such that the operation of the pump is controlled based on a pressure of the bleed flow within the load sense conduit. Moreover, a load sense valve is configured to adjust the pressure of the bleed flow within the load sense conduit.

A hydraulic system includes a hydraulic pump to output an operation fluid, first and second hydraulic devices to be operated by the operation fluid, first and second control valves to control the first and second hydraulic device, respectively, first and second communication tubes connecting the first hydraulic device to the first control valve, a supply fluid tube connecting the first control valve to the second control valve, the supply fluid tube being configured to supply the return fluid to the second control valve, first and second connection fluid tubes disposed on the first control valve, a discharge fluid tube connected to the first control valve, first and second branching fluid tubes branched from the first and second connection fluid tubes, respectively, first and second throttles disposed on the first and second branching fluid tubes, respectively, the second throttle being smaller than the first throttle.

A control device generates an operation signal for controlling a pressure of hydraulic oil on a downstream side of the swing motor in a hydraulic device based on an azimuth direction, a swing speed, and a target stopping azimuth direction of a swing body during braking of a swing motor.

Hydraulic valve circuitry adapted for hydraulic connection to a lift truck having a mast and at least one lift cylinder for alternately raising and lowering the mast. The hydraulic assembly is also adapted for hydraulic connection to an attachment to the lift truck, the attachment having opposed clamps actuated by respective clamp cylinders. The hydraulic assembly preferably comprises a valve circuit capable of causing the at least one lift cylinder to be an accumulator.