A hydraulic system for controlling an implement on a work machine may include a hydraulic reservoir, a hydraulic pump in fluid communication with the reservoir, a central valve in fluid communication with the pump and configured for controlling the implement, a load sense pressure relief system, and a controller. The controller may be configured for controlling the central valve and the load sense pressure relief system and selecting between operating the hydraulic system at a first pressure and a second pressure based on a factor relating to implement position.

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.

A hydraulic system for a work vehicle includes a first pump with a first swashplate providing a first flow in a first circuit and a second pump with a second swashplate providing a second flow in a second circuit. A supplemental pump with a supplemental swashplate provides a supplemental flow to a supplemental circuit. A first valve selectively enables flow from the supplemental circuit to the first circuit. A second valve selectively enables flow from the supplemental circuit to the second circuit. A controller determines to operate the supplemental pump in one of a standby condition and a use condition based in part on a first angle of the first swashplate and a second angle of the second swashplate.

A hydraulic system for a work vehicle includes a first pump providing a first flow in a first circuit having a first pressure. A first load sense circuit connected to a first load sensing compensator of the first pump. The first load sense circuit having a first load sense pressure. A supplemental pump provides a supplemental flow to a supplemental circuit having a supplemental pressure. A supplemental load sense circuit connected to a supplemental load sensing compensator of the supplemental pump. A first supplemental valve selectively enables flow from the first load sense circuit to the supplemental load circuit based in part on a first pressure differential between the first pressure and the first load sense pressure. 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 preselection valve is for a hydraulic valve assembly with a switching element, a pressure input line, a first pressure output line and a first load pressure line with a load pressure inlet and output. The switching element is switchable from neutral to a first switching position. The pressure input line is connected to the first pressure output line in the first position. The preselection valve has a second and third load pressure line and a load pressure increasing device. The second load pressure line branches off the pressure input line upstream of the switching element. The load pressure increasing device is connected to the third load pressure line, which connects the pressure increasing device to the first load pressure line. The second load pressure line is connected to the pressure increasing device in the first switching position and the second load pressure line is blocked in the neutral position.

A system for operating a work vehicle includes a hydraulic control assembly and a controller. The hydraulic control assembly includes a pump, accumulator, boom hydraulic cylinder, pin hydraulic cylinder, pin control valve, and ride control valve assembly. The boom hydraulic cylinder moves a boom of the work vehicle. The pin hydraulic cylinder moves a pin on the boom. The ride control valve assembly includes a charge valve and discharge valve. The charge valve is in fluid communication with the pump and the accumulator. The discharge valve is in fluid communication with the accumulator and a reservoir. The controller operates the work vehicle in a ride control mode and pin actuation mode. The pin actuation mode includes opening the charge valve with the discharge valve closed, and directing hydraulic fluid through the pin control valve.

To achieve reduction of fuel consumption and enhancement of operability, in a hydraulic control circuit provided with a bypass oil passage formed by being branched from a discharge line of a hydraulic pump and extending to an oil tank, and a bypass valve having variable opening area for controlling a flow rate of the bypass oil passage, and to accurately perform pump pressure control through opening area control of the bypass valve without being affected by a condition of each time. The hydraulic control circuit is configured to perform closed-loop control of the opening area of the bypass valve so that the pump pressure is maintained at a set pressure, during nonoperation of the operation lever; on the other hand, to perform open-loop control for reducing the opening area of the bypass valve depending on the operation input of the operation lever, during an operation of the operation lever, and further configured to correct on the basis of the opening area of the bypass valve during the closed-loop control, the correspondence relationship between the operation input of the operation lever and the opening area of the bypass valve during the open-loop control.

The present invention provides an engineering machinery hydraulic system with compensation differential pressure controllable, uses an electronic pressure compensating valve to solve the problem of flow mismatch under conditions of pressure over-limit and flow saturation, and realizes proportional shunt control and high-precision flow distribution of the system. The engineering machinery hydraulic system disclosed in the present invention has the advantages of low energy consumption, fast response speed, and high flow control precision.

A hydraulic system includes first and second valve assemblies connected to a common pump. The first valve assembly includes a main valve housed inside a manifold. A pressure compensator valve maintains a constant pressure drop across a variable orifice of the main valve. A pressure limiter valve is in communication with the main valve and the pressure compensator valve, and allows an actuator connected to the first valve assembly to operate independently of the second valve assembly so that fluid flow to a work port of the first valve assembly is not interrupted by operation of the second valve assembly.

A hydraulic device having: a plurality of main piston-cylinder arrangements, each of the respective pistons having a fixed stroke length and configured for axial reciprocation within their respective cylinder; a plurality of flow control valves for switching between a lockdown state and an unlocked state of one or more of the plurality of main piston cylinder arrangements during operation of the hydraulic device; and one or more control valves for directing the plurality of flow control valves between their respective unlock and lock positions.