A valve device includes a valve body, a drain chamber wall configured to define a drain chamber, a drain port formed in the drain chamber wall facing the valving element, and a drain passage configured to guide drain fluid from another valve device to the drain chamber, wherein at least one of the drain chamber wall and the valving element includes a communicating passage configured to allow the drain port to communicate with the drain chamber when the movement of the valving element is restricted by the drain chamber wall.

A work machine includes directional control valves 43 and 44 each controlling a direction and a flow rate of a pressurized fluid supplied to each a boom cylinder 32 and a bucket cylinder 36; operation amount sensors 51a, 52a, and 52b detecting operation amounts of operation devices 51 and 52; a variable flow control valve 45 that can restrict the flow rate of the pressurized fluid in a meter-in passage of the directional control valve 44 related to the bucket cylinder 36; and a controller 60 controlling the variable flow control valve on the basis of the detection results by the operation amounts from the operation amount sensors, and the controller changes over an action mode to any one of a normal mode for restricting the flow rate of the pressurized fluid by the variable flow control valve and a responsiveness priority mode for not restricting the flow rate of the pressurized fluid by the variable flow control valve in response to the detection results of the operation amounts of the plurality of operation devices. It is thereby possible to enhance responsiveness in an action that requires responsiveness such as an action in which an operation amount of an operation lever frequently changes in a short period of time and to suppress a decline in work efficiency.

A shovel includes a hydraulic pump, multiple hydraulic actuators, a center bypass oil passage supplied with hydraulic oil discharged from the hydraulic pump, multiple directional control valves, and a bleed-off valve. The directional control valves are arranged in tandem in the center bypass oil passage and configured to supply the hydraulic actuators with the hydraulic oil from the center bypass oil passage. At least a directional control valve other than the most downstream directional control valve in the center bypass oil passage among the directional control valves opens the center bypass oil passage. The bleed-off valve is connected to part of the center bypass oil passage upstream of at least one of the directional control valves.

An actuator includes a cylinder, a first 2/2-way solenoid valve, a second 2/2-way solenoid valve, a fuzzy block, a controller, a source, a silencer, and a sensor. The cylinder is configured to receive a piston. The piston defines a first chamber and a second chamber inside the cylinder. The first 2/2-way solenoid valve includes an input terminal and a plurality of ports. The second solenoid valve includes an input terminal and a plurality of ports. The fuzzy block includes a plurality of phases each phase including a 2/2-way solenoid valve and a flow control valve for controlling the speed of movement of the piston within the cylinder. The controller is configured to issue a control signal for controlling the first and second 2/2-way solenoid valves and the 2/2-way solenoid valves included within the plurality of phases.

A flow control manifold that routes pressurized fluid from one of a first fluid manifold connection and a second fluid manifold connection of the flow control manifold to an input of a work tool and directs return fluid from an outlet of the work tool to the other of the first and second fluid manifold connections not receiving pressurized fluid.

An object to reduce a relief amount at the start of turning. A hydraulic drive system of a construction machine includes: a turning control valve disposed on a first circulation line extending from a first pump; a boom control valve disposed on a second circulation line extending from a second pump; first and second regulators, which change tilting angles of the first and second pumps; and a controller, which controls one or more solenoid proportional valves, which output a secondary pressure to the first and second regulators. While a turning operation is being performed, if a discharge pressure of the first pump is higher than a first setting value and a discharge pressure of the second pump is lower than a second setting value, the controller lowers first and second horsepower control lines that restrict discharge flow rates of the first and second pumps.

A work machine has a controller which has an area limiting control section correcting the pilot pressures of pilot lines, a regeneration control section adjusting the flow rate of the hydraulic fluid caused to flow from a tank side line of an arm cylinder into a pump side line thereof between zero and a predetermined upper limit value, and a regeneration control switching section that issues an order to the regeneration control section to set the predetermined upper limit value to a first set value when the function of the area limiting control section is invalid and that issues an order to the regeneration control section to set the predetermined upper limit value to a second set value that is smaller than the first set value when the function of the area limiting control section is effective.

A fluid pressure control device includes a first circuit system having a first pump and a first control valve. The first circuit system includes an intermediate cut valve provided downstream of the first control valve in a first intermediate passage and which connects and disconnects a connection between the first intermediate passage and the tank, and an external output port communicating at a part downstream of the first control valve in the first intermediate passage and upstream of the intermediate cut valve, the external output port being capable of externally supplying working fluid discharged from the first pump.

The present disclosure relates to a hydraulic control circuit for crane slewing gear having directional valves arranged in work lines and controllable separately for the inflow and outflow to the hydraulic motor for the carrying out of a rotational movement of the slewing gear, wherein an inflow valve serves the control of the oil inflow from a hydraulic pump via the work line to the hydraulic motor and an outflow valve is provided via which the hydraulic motor can be relieved to the tank, wherein the work lines are each connected via at least one check valve to a common inlet of the outflow valve to relieve the hydraulic motor independently of the direction of rotation of the slewing gear via an outflow valve into the tank.

To keep operability of a hydraulic actuator excellent even in a state pressure has been sufficiently accumulated in a pressure accumulator. In a hydraulic driving device of a work machine including a hydraulic actuator, a tank, a flow control valve, and a pressure accumulator, there are further provided with a first pressure compensation valve that is for controlling difference between front and back pressures of the flow control valve constant and a second pressure compensation valve that is arranged between the pressure accumulator and the tank and is for controlling difference between front and back pressures of the flow control valve and the first pressure compensation valve constant.