The present disclosure relates to a hydraulic valve arrangement comprising a first pilot operated proportional directional control valve having a first valve member that is displaceable in a first and a second axial direction for controlling direction of supply and discharge of hydraulic fluid to and from a hydraulic actuator, a first proportional electro-hydraulic control valve for controlling displacement of the first valve member in the first axial direction, a second proportional electro-hydraulic control valve for controlling displacement of the first valve member in the second axial direction, and a second pilot operated proportional control valve having a second valve member configured to be controlled by the first and second proportional electro-hydraulic control valves via a shuttle valve arrangement. Individual meter-in and meter-out control of the hydraulic actuator is providable by having the second pilot operated proportional control valve configured to operate as a meter-in valve of the hydraulic actuator and the first pilot operated proportional directional control valve configured to operate as a meter-out valve of the hydraulic actuator, or by having the first pilot operated proportional directional control valve configured to operate as a meter-in valve of the hydraulic actuator and the second pilot operated proportional control valve configured to operate as a meter-out valve of the hydraulic actuator. The present disclosure also relates to a vehicle comprising a hydraulic actuator and a hydraulic valve arrangement for controlling the motion of the hydraulic actuator.

A construction machine that precisely enables derivation of the operation characteristics of hydraulic actuators in a high-velocity area with less calibration operation is provided. A controller (10) has a calibration mode in which the controller (10) derives operation characteristics (α(xs)) representing a relation among a spool position (xs) of a meter-in valve (8a1), an operation velocity (Va) of a hydraulic actuator (4a), and a differential pressure (ΔP) across the meter-in valve (8a1), and is configured to, in a case where the spool position (xs) of the meter-in valve (8a1) has changed in a direction to increase the opening area of the meter-in valve (8a1) in the calibration mode, output a command signal to increase the opening area of a bleed-off valve (8b1) to a bleed-off solenoid proportional pressure-reducing valve (8b2) as a command signal to reduce the differential pressure (ΔP).

Universal control circuitry for an electro-hydraulic valve actuator system includes logic gate circuitry to control one or more of a closing solenoid valve, an opening solenoid valve, an emergency shutdown solenoid valve, and a hydraulic fluid pump motor to route hydraulic fluid through a hydraulic circuit to actuate a valve via a hydraulic actuator according to received commands. The universal control circuitry is configured to control operation for multiple different configurations of a hydraulic valve actuator system including double-acting configurations, single-acting spring-to-open configurations, and single-acting spring-to-close configurations, each with or without an emergency shutdown arrangement (which may be configured to trip based on an external shutdown input alone or in combination with a local system power failure), a hydraulic accumulator, and maintained or momentary input commands.

This hydraulic drive system includes: a hydraulic pump capable of changing a discharge flow rate of a working fluid; a meter-in control valve that controls a meter-in flow rate of the working fluid flowing from the hydraulic pump to a hydraulic actuator; a meter-out control valve that is provided separately from the meter-in control valve and controls a meter-out flow rate of the working fluid being drained from the hydraulic actuator into a tank; an operation device that outputs an operation command; a first pressure sensor that detects a drainage pressure of the hydraulic actuator; and a control device that sets a target meter-out flow rate according to the operation command from the operation device and controls an opening degree of the meter-out control valve on the basis of the drainage pressure detected by the first pressure sensor and the target meter-out flow rate.

This hydraulic drive system includes: first and second circuit systems; first and second hydraulic pumps; a merge valve that opens and closes a merge passage connecting the hydraulic pumps; an operation device that outputs an operation command corresponding to an amount of operation specifying an amount of actuation of first and second hydraulic actuators; and a control device that controls the merge valve according to the operation command from the operation device. The first circuit system includes: a first meter-in control valve that controls a meter-in flow rate of the working fluid that flows to the first hydraulic actuator; and a first meter-out control valve that controls a meter-out flow rate of the working fluid that is drained from the first hydraulic actuator into a tank. The control device controls an opening degree of the first meter-in control valve and an opening degree of the first meter-out control valve.

Problem to be solved: To provide a hydraulic circuit for the construction machine which enables to use the relief valve of low capacity in the work tool circuit. Solution: The hydraulic circuit 2 for a construction machine has: a hydraulic pump 4 of variable capacity, a work tool 6 operated by hydraulic oil delivered by the hydraulic pump 4, a work tool operating device 10 to output a signal for operating the work tool 6, a control valve 14 allowing the hydraulic pump 4 to supply the hydraulic oil to the work tool 6 based on the signal output from the work tool operating device 10, a tool's relief valve 44 to release the hydraulic oil flowing between the control valve 14 and the work tool 6, a pressure sensor 46 to detect a pressure of hydraulic oil flowing into the work tool 6, and a controller 48 to reduce a delivery rate from the hydraulic pump 4 when the pressure detected by the pressure sensor 46 exceeds a predetermined value.

A hydraulic circuit includes a pump connected to a tank for supplying hydraulic liquid under pressure to a component via a directional control slide valve provided with a feed port connected to an inlet of the component and with a return port connected to an outlet of the component. The hydraulic circuit further includes a pressure limiter connected to the inlet of the component and the tank, and a feed control system for the hydraulic component including a pressure sensor installed upstream of the hydraulic component downstream of the feed port for supplying information about the pressure of the hydraulic liquid and a setpoint pressure. The feed control system further including an actuator for controlling the movement of the directional control slide valve, and a control unit for generating a control signal for the actuator based on information about the pressure measured at the feed port.

A hydraulic system can include a hydraulic actuator including a piston rod slidably disposed within a housing having a base-side port and a rod-side port, a hydraulic pump, a hydraulic reservoir, an accumulator, a first control valve operable to selectively control flow from the pump to the base-side port and from the base-side port to the reservoir, a second control valve operable to selectively control flow from the pump to the rod-side port and from the rod-side port to the reservoir, a third control valve operable to selectively allow flow between the base-side port and the accumulator, and a controller for operating the hydraulic system and including a ride control mode in which damping is provided to the hydraulic actuator by operation of the first, second, and third control valves.

A hydraulic system for a working vehicle, the hydraulic system includes a hydraulically actuated device; a hydraulic pump assembly for supplying a variable output of hydraulic fluid to the hydraulically actuated device; and a proportional control valve, wherein the hydraulic system is arranged such that hydraulic fluid exiting the hydraulically actuated device flows through a restriction of the proportional control valve; and wherein the hydraulic system is configured to control a flow of hydraulic fluid supplied to the hydraulically actuated device by varying the output of hydraulic fluid from the hydraulic pump assembly, and to control a flow of hydraulic fluid exiting the hydraulically actuated device via adjusting a restriction area of the proportional control valve.

A fluid pressure control device includes a neutral passage, a control valve provided in the neutral passage, a first supply passage, and a discharge passage, the control valve has, a switching valve configured to control a flow of a working fluid to the discharge passage from the first actuator in accordance with a pressure in a pilot chamber to which a part of the working fluid supplied from the first supply passage to the first actuator is led, and a throttle portion configured to throttle the flow of the working fluid supplied to the first actuator from the first supply passage, and the pressure on an upstream side of the throttle portion is led to the pilot chamber.