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.

A hydraulic valve assembly having a regeneration circuit, where the hydraulic valve assembly is switchable between a regenerative mode and a non-regenerative mode as the valve assembly supplies fluid to operate a hydraulic device. The hydraulic valve assembly may be automatically switchable between the regenerative mode and the non-regenerative mode, such as by utilizing a pressure control valve in the hydraulic circuit that is activatable at a predetermined pressure setpoint, or by utilizing a variable pressure reducing valve that actuates a spool in the hydraulic circuit. In other embodiments, the hydraulic valve assembly may be manually switchable between the regenerative mode and non-regenerative mode by utilizing a valve member operatively coupled to a solenoid in cooperation with one or more check valves in the regeneration circuit.

A hydraulic boosting and regulating system includes an intensifier circuit and a regulator and employs low leak, low crossover valves.

A work machine that can keep the control accuracy of actuators irrespective of temperature variation of a hydraulic operating fluid that passes through flow rate controllers that control the flow rates of supply to the actuators is provided. For this purpose, the flow rate controllers each have a valve body that is disposed on a main hydraulic line connecting a delivery line of a hydraulic pump and the actuator and that moves according to an operation pressure from a solenoid proportional pressure reducing valve, a sampling hydraulic line that branches from the main hydraulic line, and a temperature sensor set on the sampling hydraulic line. The controller is configured to correct a command electrical signal to the solenoid proportional pressure reducing valve according to a signal from the temperature sensor.

A hydraulic system includes at least two hydraulic circuits with hydraulic circuit lines and at least one hydraulic component connected to each hydraulic circuit or to a hydraulic circuit line thereof via a respective switch valve used for pressure build-up and release. At least one pressure supply device can build up pressure in both hydraulic circuits. At least one circuit separating valve blocks or releases a hydraulic connection line connecting the two hydraulic circuits. At least one outlet valve selectively connects an accumulator container to at least one hydraulic circuit. A hydraulic connection between a pump of the pressure supply device and a respective hydraulic circuit connects a return flow from the hydraulic circuit into the pressure supply device or its pump. A controlled feed valve or a non-return valve controls the hydraulic connection. A pressure supply device or outlet valve releases pressure in at least one hydraulic component.

Apparatus for generating braking force in a vehicle brake system has at least two pressure supply devices and first and second hydraulic brake circuits, each having at least one or two hydraulic wheel brakes. Pressure in at least one brake circuit can be both built up and released by the pressure supply devices, which include a piston pump or gear pump driven by an electric motor drive and deliver continuous volume. At least one valve arrangement may adjust wheel brake pressures individually and/or disconnect/connect the wheel brakes from/to a brake circuit and/or a pressure supply device. At least one electronic control unit enables open-loop and closed-loop control. Pressure increase is enabled in one or both brake circuits, independently or in combination, using first and/or second pressure supply devices that produce changes in pressure simultaneously or temporally offset or overlapping.

A brake system may include: two hydraulic brake circuits, each having at least one wheel brake; a first pressure supply device for pressure build-up and release in at least one brake circuit via forward and return travel of a piston; a second pressure supply device with a continuous delivery, electromotively-driven piston pump, gear pump, or eccentric piston pump; at least one valve assembly with valves for adjusting pressure for each wheel brake and/or for connecting/disconnecting the wheel brakes and at least one of the pressure supply devices; at least one electronic control unit; a connection line connecting the two brake circuits; and at least one outlet valve for pressure release. The wheel brakes are paired with dedicated switch valves. Each brake circuit has a hydraulic main line to connect the switch valves to the first and second pressure supply devices, which provide different maximum pressures and/or delivery volumes.

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.

An electro-hydraulic control apparatus for construction machinery includes a control valve installed in a hydraulic line between a hydraulic pump and an actuator to control operations of the actuator according to a displacement amount of a spool therein, a spool displacement adjusting valve configured to output a secondary pressure in proportion to an inputted pressure command signal to the spool of the control valve to control the displacement amount of the spool of the control valve, a pressure sensor to detect the secondary pressure outputted from the spool displacement adjusting valve, and a controller configured to output the pressure command signal to the spool displacement adjusting valve according to a manipulation signal of the construction machinery, and to correct the pressure command signal when a pressure difference between the detected secondary pressure and a design pressure predetermined by the pressure command signal is out of a preset allowable range.

A hydraulic control unit (4) includes a valve bush (12), a valve cover (15) partially closing the valve bush (12) on an end face (S1), a valve slide (13) guided in a longitudinal direction (L) within the valve bush (12), and a housing part (6). The housing part (6) includes a recess (8) matching an external contour of the valve bush (12). An intermediate plate (7) is configured to partially cover the valve cover (15). A spring (14) is arranged within the valve bush (12) and preloads the valve slide (13) in a starting position. The valve bush (12) is inserted, together with the valve cover (15), the valve slide (13), and the spring (14), into the recess (8) of the housing part (6) and jointly form a hydraulic valve (9). The valve bush (12) forms an inlet (19), and the valve cover (15) forms an outlet (31).