An example valve includes: a pressure compensation spool configured to be subjected to a first fluid force of fluid received at a first port acting in a proximal direction; a pressure compensation spring disposed in a pressure compensation chamber and applying a biasing force on the pressure compensation spool in a distal direction; a turbine configured to rotate as fluid flows through the valve; and a flow area configured to throttle fluid flow from the first port to the pressure compensation chamber, wherein fluid in the pressure compensation chamber applies a second fluid force on the pressure compensation spool in the distal direction, such that the pressure compensation spool moves to a particular axial position based on force equilibrium between the first fluid force, the second fluid force, and the biasing force to throttle fluid flow from the pressure compensation chamber to a second port.

A hydraulic system includes a pump in communication with a fluid reservoir and powered by a motor. A pressure compensator is adapted to adjust a position of a variable displacement mechanism of the pump. A load sensing line is adapted to communicate a highest load sensing pressure from a plurality of valves to the pressure compensator. The pressure compensator adjusts the variable displacement mechanism of the pump based on the highest load sensing pressure for maintaining a constant pressure drop across one or more work ports in each of the plurality of valves. The plurality of valves each include a load sense port having an integrated check valve that includes a metering orifice.

A spool valve is provided. A valve housing has a pilot fluid passage, and a first portion and a second portion lengthwisely spaced apart from each other. A spool is movably inserted in the valve housing, and includes a plug able to enter the pilot fluid passage between the first portion and the second portion to change a flow area of the pilot fluid passage following movement of the spool. A hydraulic machine provides that when pilot fluid is supplied to the pilot fluid passage through the first portion, at least a portion of the supplied pilot fluid is provided to the holding valve through the second portion. The holding valve allows a flow of working fluid from the first chamber to the spool valve, and the spool moves to a third position to forward working fluid to the second chamber.

The present disclosure relates to systems that use a single proportional valve to control raising and lowering of a load. The present disclosure also relates to proportional valves that provide proportional flow control in first and second opposite flow directions through the proportional valve.

A lift arm lifting and lowering mechanism cylinder case provided with a cylinder portion into which oil is fed, a piston slidable inside the cylinder portion to define a hydraulic chamber and receiving hydraulic pressure of the hydraulic chamber on a front surface, a safety valve provided to the piston to discharge the oil inside the hydraulic chamber to the outside when the hydraulic pressure of the hydraulic chamber becomes greater than or equal to a predetermined value, and a lift arm supported by the cylinder case and rotatable in conjunction with movement of the piston, in which the piston includes an oil passage allowing communication between a rear surface of the piston and the front surface, and the oil passage includes a containing portion provided to open on the axially front surface side and capable of containing the safety valve, and a non-containing portion provided on the axially rear surface side relative to the containing portion and incapable of containing the safety valve.

A valve unit (V) has a valve housing (50) that includes a supply oil passage (55) configured to receive operating oil from a hydraulic pump, and a pressure adjustment valve (Va) configured to adjust the pressure of the supply oil passage (55). The pressure adjustment valve (Va) includes a pressure adjustment valve body (61) configured to open and close the supply oil passage (55), a compression coil spring (62) that keeps the pressure adjustment valve body (61) at a closed position when the pressure of the supply oil passage (55) is smaller than a set value and allows the pressure adjustment valve body (61) to open when the pressure of the supply oil passage (55) is not smaller than the set value, and a restriction member (63) configured to, when the pressure adjustment valve body (61) becomes open against the urging force of the spring (62) in response to a pressure of the operating oil, abut against the pressure adjustment valve body (61) to restrict movement of the pressure adjustment valve body (61).

There is provided a work machine which can improve accuracy of control of an actuator when a pressure difference between a hydraulic pump and the actuator is large and the demanded flow rate of the actuator is small. An auxiliary flow rate controller is configured such that an opening area of a main valve changes between a maximum opening area and zero according to the opening area of a pilot variable restrictor when the opening area of the pilot variable restrictor is equal to or more than a predetermined opening area and that the opening area of the main valve is zero irrespective of the opening area of the pilot variable restrictor when the opening area of the pilot variable restrictor is less than the predetermined opening area.

A fluid pressure valve according to an embodiment of the present invention is applicable to a fluid pressure servo mechanism. The fluid pressure valve includes a housing having a housing member, the housing member being formed integrally so as to have a first port, a second port, and a flow path connecting between the first port and the second port.

An electrohydraulic poppet valve device control system includes a main body, an extend poppet valve, a retract valve body, a retract poppet valve, and an actuator. The actuator is movable to an extend position, a retract position, and a null position, and moves to, or remains in, the null position when electrical power is not supplied to the actuator. In the extend position, the extend poppet valve is in its open position and the retract poppet valve is in its closed position. In the retract position, the extend poppet valve is in its closed position and the retract poppet valve is in its open position. In the null position, the extend poppet valve is in its closed position and the retract poppet valve is in its closed position.

A valve device includes: a flow path forming member having a first flow path through which a fluid is to flow, and a conical second flow path formed on a downstream side of the first flow path and having an outer diameter increasing in a flow direction of the first flow path; a spherical valve body capable of blocking a flow of the fluid in the first flow path by contacting an inner surface of the flow path forming member, which forms the second flow path; a holding member configured to hold the valve body in a conical concave part; and a coil-shaped spring configured to apply a force in a direction of causing the valve body to contact the inner surface via the holding member and arranged so that a direction of a center line of the coil is tilted with respect to the flow direction.