A control valve device includes a valve block that switches the flowing direction of a working fluid supplied to and discharged from a boom cylinder and an arm cylinder (actuators). The valve block includes an actuator port connected to the boom cylinder, and a supply port, a discharge port, and a regeneration port communicating with the actuator port. A supply valve is provided between the actuator port and the supply port, and a discharge valve is provided between the actuator port and the discharge port.

A fluid pressure control device includes a load holding mechanism that is configured to hold the load pressure of the load side pressure chamber. The load holding mechanism includes a switching valve having a communication passage configured to be blocked from the third pressure chamber by the second land section in a case where the spool is closed, and providing communicate between the second supply port and the discharge port in accordance with the movement of the spool in the valve opening direction. In a case where the spool is moved in the valve opening direction, at the same time when or after the second supply port communicates with the discharge port via the communication passage, the first land section is brought into sliding contact with the annular projecting section and the first supply port and the discharge port are blocked from each other.

A turning control apparatus includes a turning body and a hydraulic motor to turn the turning body. A high-pressure relief circuit relieves hydraulic pressure of a first hydraulic line at a first relief pressure, the first hydraulic line supplying an operating oil to drive the hydraulic motor. A hunting reduction circuit relieves a hydraulic pressure of a second hydraulic line at a pressure lower than the first relief pressure, the second hydraulic line being connected to a deceleration-side hydraulic port from which the operating oil is discharged when the hydraulic motor is being driven. The hunting reduction circuit connected to the deceleration-side hydraulic port is caused to open before an operation lever to operate turning of the turning body returns to a neutral position.

A turning control apparatus includes a turning body and a hydraulic motor to turn the turning body. A high-pressure relief circuit relieves hydraulic pressure of a first hydraulic line at a first relief pressure, the first hydraulic line supplying an operating oil to drive the hydraulic motor. A hunting reduction circuit relieves a hydraulic pressure of a second hydraulic line at a pressure lower than the first relief pressure, the second hydraulic line being connected to a deceleration-side hydraulic port from which the operating oil is discharged when the hydraulic motor is being driven. The hunting reduction circuit connected to the deceleration-side hydraulic port is caused to open before an operation lever to operate turning of the turning body returns to a neutral position.

A valve assembly includes a valve body having at least a first bore and a second bore, a flow passage connecting the first bore to the second bore, a plurality of ports opening to each bore respectively, the first bore being upstream of the second bore. First and second spools are disposed in the first and second bores, respectively, for controlling the flow of fluid to and from the respective ports. A check valve is disposed in the flow passage and configured to prevent fluid flow from the second spool towards the first spool through the flow passage while allowing fluid flow from one of the ports in the first bore towards the second spool through the flow passage.

A valve assembly includes a valve body having at least a first bore and a second bore, a flow passage connecting the first bore to the second bore, a plurality of ports opening to each bore respectively, the first bore being upstream of the second bore. First and second spools are disposed in the first and second bores, respectively, for controlling the flow of fluid to and from the respective ports. A check valve is disposed in the flow passage and configured to prevent fluid flow from the second spool towards the first spool through the flow passage while allowing fluid flow from one of the ports in the first bore towards the second spool through the flow passage.

An electric fluid pressure cylinder is provided with: a driving unit integrally provided with an electric motor, a pump configured to discharge working oil by being driven by the electric motor, and a tank; a hydraulic cylinder configured to be extended and contracted by the working oil supplied from the driving unit; and a first hose pipe and a second hose pipe configured to guide the working oil between the driving unit and the hydraulic cylinder. The driving unit is further provided with: a valve block configured to control the flow of working fluid between the fluid pressure cylinder and the pump; and a connecting plate attached to the valve block and formed with a connecting port to which the pipe member is connected, the connecting port being configured such that the working fluid supplied to and discharged from the fluid pressure cylinder passes through the connecting port.

An electric fluid pressure cylinder is provided with: a driving unit integrally provided with an electric motor, a pump configured to discharge working oil by being driven by the electric motor, and a tank; a hydraulic cylinder configured to be extended and contracted by the working oil supplied from the driving unit; and a first hose pipe and a second hose pipe configured to guide the working oil between the driving unit and the hydraulic cylinder. The driving unit is further provided with: a valve block configured to control the flow of working fluid between the fluid pressure cylinder and the pump; and a connecting plate attached to the valve block and formed with a connecting port to which the pipe member is connected, the connecting port being configured such that the working fluid supplied to and discharged from the fluid pressure cylinder passes through the connecting port.

An example method includes identifying an operating state at which a velocity of a hydraulic actuator configured to operate a movable member of a robot is less than a threshold velocity and an actuator force is less than a threshold force, determining a valve command that corresponds to the operating state, such that the valve command is provided to a valve configured to control flow to and from the hydraulic actuator, and the valve includes a spool movable within a body of the valve, and the valve command causes the spool to move within the body of the valve to a position that induces the operating state, and determining a null bias signal based on the valve command.

A dual pressure margin priority circuit and method for controlling flow from a pump to steering valve and low priority inlets. A steering pressure valve controls flow from pump to steering valve inlets, and provides a steering valve load sense pressure. A priority valve controls flow from pump to low priority inlets. A load sense cutoff valve has a first inlet receiving the steering valve load sense pressure. The load sense cutoff valve controls flow through the priority valve based on steering valve load sense pressure at the first cutoff valve inlet. The cutoff valve can include a second inlet coupled to tank, and a load sense input coupled to the steering valve load sense pressure. The cutoff valve can be a pressure limiter valve. The priority and steering pressure valves can be 2-way proportional flow spool valves with bias springs, and contributing and opposing load sense inputs.