It is made possible to suppress variations of the speed of an actuator into which a regeneration flow rate flows, regardless of variations of the regeneration flow rate caused by posture changes of the front part and to enhance the operability when the front part moves in the free fall direction, and hydraulic fluid discharged from an actuator driving the front part is regenerated. Accordingly, a controller 19 of a hydraulic system is provided with a regeneration control calculation section 19b, and a pump flow rate control calculation section 19c, and when the regeneration control calculation section controls a regeneration valve 12 to perform regeneration, the pump flow rate control calculation section controls a pump flow rate regulation device 20 to increase the delivery flow rate of a hydraulic pump 1 as the angle of an arm 16 approaches the vertically downward direction based on posture information about the arm 16 acquired by an inertial measurement unit 31.

A hydraulic work machine is provided which can improve the finishing accuracy in a horizontally leveling work, a slope face shaping work and so forth by preventing sudden acceleration of an arm when the excavation load decreases suddenly. The hydraulic work machine includes an arm velocity-control valve device 22 capable of adjusting a meter-out opening of the arm cylinder independently of a first arm directional control valve 23. A controller 100 is configured to control, when correcting and increasing an operation amount instructed by the first arm directional control valve, the arm velocity-control valve device to decrease the meter-out opening of the arm cylinder in response to the increase of load pressure of the arm cylinder.

A hydraulic system includes a hydraulic pump, a first hydraulic actuator, a second hydraulic actuator, a first control valve to control the first hydraulic actuator, a second control valve to control the second hydraulic actuator, a return fluid tube in which a return fluid discharged from the first hydraulic actuator flows, the return fluid tube connecting the first control valve and the first hydraulic actuator, a first inner fluid tube provided in the first control valve and connected to the return fluid tube, an outer fluid tube connected to the first inner fluid tube, the outer fluid tube connecting the first control valve and the second control valve, a return-discharge fluid tube to discharge the return fluid, the discharge fluid tube being branched from the outer fluid tube, and a throttle provided in the return-discharge fluid tube.

A construction machine includes: one or more hydraulic pumps discharging a working fluid; an engine supplying a rotational power to the hydraulic pumps; a hydraulic line through which the working fluid discharged by the hydraulic pumps moves; a main control valve provided on the hydraulic line and controlling supply of the working fluid to a traveling device or one or more of various working devices, which require the working fluid; a bypass cut valve provided on the hydraulic line at a lower side thereof than the main control valve to open and close the hydraulic line; an automatic warm-up switch generating a warm-up operation signal for raising a temperature of the working fluid before an operation starts; and a control device performing a warm-up operation for increasing the number of revolutions of the engine and opening the bypass cut valve to increase a flow rate along the hydraulic line, when the warm-up operation signal is received from the automatic warm-up switch.

A direction control valve group for a construction machine that controls an amount of pressure oil supplied to a hydraulic actuator from a hydraulic pump that discharges the pressure oil is provided. The direction control valve includes a cylinder port that supplies the pressure oil to the hydraulic actuator, a bridge passage that is switchably connected and disconnected to the cylinder port according to a change in position of a first spool, and an internal passage that supplies the pressure oil discharged from the hydraulic pump to the bridge passage. The first spool is provided in the internal passage.

A hydraulic boom control system for a forestry machine includes a pump for pressurizing a hydraulic fluid on a high pressure side, a reservoir for storing hydraulic fluid on a low pressure side, and a first hydraulic cylinder including a cap end and a rod end. The first hydraulic cylinder is configured to actuate the hoist of the boom. A second hydraulic cylinder includes a cap end and a rod end and is configured to actuate the stick of the boom. A first control valve is operable to control the first hydraulic cylinder. A second control valve is operable to control the second hydraulic cylinder. A variable return metering valve is fluidly connected to at least one of the first or second control valves. The variable return metering valve is operable to modulate shared hydraulic fluid flow between the first hydraulic cylinder and the second hydraulic cylinder.

A flow rate control apparatus for construction equipment includes: a boom cylinder driven by hydraulic fluid; a first control valve for controlling a hydraulic fluid flow supplied to the boom cylinder; an option actuator driven by hydraulic fluid; a second control valve for controlling a hydraulic fluid flow supplied to the option actuator; a boom cylinder manipulation lever and an option actuator manipulation lever; a confluence line selectively confluence the hydraulic fluid supplied to the boom cylinder with the hydraulic fluid of the option actuator; a center bypass switching valve provided at the furthest downstream side of a fluid supply path of the first hydraulic pump; a confluence switching valve selectively opening and closing the confluence line; a confluence selection valve applying a pilot pressure to the confluence switching valve; and a controller for controlling the confluence selection valve.

A fluid pressure cylinder driving device includes a switch valve, a high pressure air supply source, an exhaust port and a check valve. When the switch valve is at a first position, a head side cylinder chamber communicates with the high pressure air supply source, and a rod side cylinder chamber communicates with the exhaust port. When the switch valve is at a second position, the head side cylinder chamber communicates with the rod side cylinder chamber via the check valve, and the head side cylinder chamber communicates with the exhaust port.

An example valve includes: a seat member; a spool configured to be seated on the seat member to block fluid flow from a first port to a second port when the valve is in a closed state, wherein fluid at the first port applies a fluid force on the spool; a spring applying a biasing force on the spool toward the seat member, wherein as the fluid force overcomes the biasing force, the spool moves in the proximal direction off the seat member, thereby allowing fluid flow from the first port to the second port through a flow area formed between the spool and the seat member; a turbine configured to rotate as fluid flowing through the flow area flows downstream across the turbine; and an electric generator coupled to the turbine, such that rotation of the turbine causes the electric generator to generate electric power.

The invention relates to a discharge pressure scale (30) consisting of at least one valve housing (41) having at least three fluid connection points in the form of a functional connector (A), a return flow connector (T) and a control connector (28), wherein a valve piston (52) is guided such that it moves longitudinally against the effect of an energy accumulator (42), moving from a respective opening or regulating position, against a valve seat (94), into a closed position, wherein the control (28) and return flow connectors (T) are separated from one another, characterised in that the fluid pressure present at the control connector (28) can be guided onto a pressure-active surface (A.sub.1*) of the valve piston (52) by means of a pressure compensation device (70) in such a way that it moves into its respective opening or regulating position in a pressure-compensated manner due to the force of the energy accumulator (42).