A control system for a work machine includes a plurality of hydraulic pumps that discharge hydraulic oil, a hydraulic cylinder that moves a working equipment element, a plurality of flow rate control valves that are respectively connected to the hydraulic pumps and adjust a flow rate of the hydraulic oil supplied to the hydraulic cylinder, a plurality of supply flow paths respectively connected to the of flow rate control valves, a meter-in flow path that connects a collective part of the supply flow paths and an inlet of the hydraulic oil in the hydraulic cylinder, a plurality of discharge flow paths respectively connected to the flow rate control valves, a meter-out flow path that connects a collective part of the discharge flow paths and an outlet of the hydraulic oil in the hydraulic cylinder, and a throttle disposed in the meter-out flow path.

A combined valve for insertion into an elongated bore of a power unit body of a hydraulic power unit may have an elongated carrier for receiving a relief and a check valve. The valve may also have a register arranged at a first axial position of a longitudinal axis of the carrier for calibration of the relief valve. The valve may also have a check valve coupled to the carrier at a second axial position along the longitudinal axis of the carrier. The valve may also have a relief valve coupled to the carrier at a third axial position along the longitudinal axis of the carrier. A minimal distance between the first and the second axial position may be less than a minimal distance between the first and the third axial position.

A hydraulic pressure amplifier arrangement (1) comprising a supply port (IN), a return port (R), a high pressure port (H1), and a pressure amplifier unit (2) having a low pressure inlet (3) connected to the supply port (IN) and a high pressure outlet (4) connected to the high pressure port (H1) is described, wherein the pressure amplifier unit (2) comprises an amplification factor. In such a hydraulic pressure amplifier arrangement it should be possible to allow simply releasing off pressure at the high pressure port while keeping small unnecessary energy consumption. To this end a control valve (8) is arranged in a connection between the high pressure port (H1) and the return port (R).

An apparatus includes a hydraulic circuit that is configured to selectively open fluid communication between one portion of the hydraulic circuit and another portion of the hydraulic circuit, such as a reservoir, based on the flow of the hydraulic fluid in the one portion. When the flow of hydraulic fluid exceeds a selected threshold in the one portion of the hydraulic circuit, the flow of fluid urges the opening of a hydraulic component of the hydraulic circuit to allow fluid communication between the one portion and the reservoir to discharge fluid from the one portion.

It is an object of the present invention to provide a construction machine capable of efficiently driving a hydraulic cylinder by an accumulator. Thus, the construction machine includes a first control valve disposed in a first hydraulic fluid line connecting a bottom-side fluid chamber of a hydraulic cylinder with an accumulator, and a second control valve disposed in a second hydraulic fluid line connecting a rod-side fluid chamber of the hydraulic cylinder with a tank. The construction machine further includes a third control valve disposed in a third hydraulic fluid line connecting the rod-side fluid chamber with the accumulator, and a fourth control valve disposed in a fourth hydraulic fluid line connecting a line part of the first hydraulic fluid line, which connects the bottom-side fluid chamber with the third control valve, and a line part of the third hydraulic fluid line, which connects the rod-side fluid chamber with the third control valve, with each other.

Provided is a work machine which can increase the operation speed of an actuator by a regeneration function while securing the position control accuracy of the actuator. A controller is configured to calculate a regeneration flow rate on the basis of an input amount of an operation lever and a target actuator flow rate, subtract the regeneration flow rate from the target actuator flow rate to calculate a target actuator supply flow rate, calculate a target flow rate control valve opening amount on the basis of the target actuator supply flow rate, calculate a target pump flow rate that is equal to or higher than a total target actuator supply flow rate, control a selector valve on the basis of the input amount of the operation lever, control a flow rate control valve according to the target flow rate control valve opening amount, and control a hydraulic pump according to the target pump flow rate.

A fail-safe actuation system comprising an actuator having first and second chambers, a working circuit with a motor/pump device configured to actuate the actuator in an operative state, and a safety circuit configured to move the actuator into the safety position in a failure state, the safety circuit having a tank that holds pressurized fluid and that, in the failure state, is automatically connected to the first chamber via a switching valve, and having a drain valve that, in the failure state, is moved into a through-flow position in order to drain fluid out of the second chamber, the safety circuit configured such that, in the operative state, an inflow into the actuator—in a manner that is decoupled from the tank—is established by the working circuit, and, in the failure state, an inflow from the tank into the first chamber—in a manner that is completely decoupled from the working circuit—is created by the safety circuit, whereby a short-circuit fluid connection is provided between the first and second chambers that, in the failure state, is through-connected in order to generate a short-circuit flow between the first and second chambers.

A control system of a hybrid construction machine includes fluid pressure pumps configured to supply a working fluid to a fluid pressure actuator, a regeneration unit having a regeneration motor for regeneration to be rotated by the working fluid discharged from a load side pressure chamber of the fluid pressure actuator, a rotating electric motor coupled to the regeneration motor, and a storage battery configured to store electric power generated by the rotating electric motor, and a variable throttle configured to bleed a portion of the working fluid obtained by excluding a flow rate of the working fluid guided to the regeneration motor from the working fluid discharged from the load side pressure chamber.

A method of controlling a float function of a cylinder 25 having a first side and a second side includes connecting the second side of the cylinder to a reservoir 15; connecting the first side of the cylinder to an output of a pump 20 and to the reservoir; and supplying an amount of flow from a pump less than an amount supplied by the pump under loaded conditions. A three-position directional control valve 30 having a pump port, a reservoir port, a first cylinder port, and a second cylinder port may be provided to effectuate aspects of this method.

The present disclosure relates to a hydraulic drive system having a hydraulic circuit architecture operable in first and second modes. In a first mode, a main hydraulic pump (22) is used to drive a hydraulic actuator (24) via a closed hydraulic circuit, and a charge pump (42) provides charge flow to the closed hydraulic circuit. In a second mode the main pump set to zero displacement and the charge pump (42) is used to drive the hydraulic actuator (24).