A fluid circuit includes a pressure fluid source configured to supply pressure fluid, multiple actuators connected to the pressure fluid source, a direction switching valve configured to switch a supply destination of the pressure fluid supplied from the pressure fluid source, and a discharge amount control mechanism configured to control the output pressure of the pressure fluid source such that a pressure difference ΔP between the output pressure of the pressure fluid source and the maximum load pressure of the load pressures of the multiple actuators reaches a target value ΔPt. The fluid circuit further includes an accumulator configured to accumulate part of return fluid from the actuators.

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, the second control valve being arranged on a downstream side of the first control valve, and a discharge fluid tube in which the operation fluid flows. The hydraulic system further includes a first fluid tube in which a return fluid flows toward the second control valve. The hydraulic system further includes a second fluid tube in which a supply fluid flows toward the first hydraulic actuator, a third fluid tube coupling the first fluid tube to the discharge fluid tube, and a fourth fluid tube in which the return fluid flows toward the second fluid tube, the fourth fluid tube being connected to the first fluid tube.

In a hydraulic system for a working machine, a controller is configured or programmed to increase an output-port pressure of one activation valve for one hydraulic device and an output-port pressure of another activation valve for another hydraulic device to a normal pressure higher than a preloading pressure from a state where the output-port pressure of the one activation valve is equal to the preloading pressure and the output-port pressure of the other activation valve is lower than the preloading pressure, by causing the output-port pressure of the one activation valve to be lower than the preloading pressure and increasing the output-port pressure of the other activation valve to the normal pressure.

A valve for controlling a hydraulic cylinder on a work machine may include a raising position configured for placing a pump in fluid communication with a cap end of the hydraulic cylinder. The valve may also include closed center position configured for closing off fluid communication to the cap end line and the rod end line. The valve may also include a lowering position configured for placing the pump in fluid communication with the rod end of the hydraulic cylinder. The valve may also include a snubbing position configured for placing the cap end in restricted flow fluid communication with the tank and for placing the rod end in restricted flow fluid communication with the tank.

An engine control system controls a work machine including an engine, a fuel injection device that injects fuel into the engine, and a hydraulic pump that is driven by the engine. The rotation state amount specification unit specifies a rotation state amount related to rotation of the engine. The injection amount determination unit determines a fuel injection amount by the fuel injection device based on the rotation state amount.

A hydraulic machinery may include: a boom actuator including a large chamber and a small chamber; a tank; and an energy recovery circuit provided between the boom actuator and the tank, wherein the energy recovery circuit includes: a discharge valve provided between the large chamber and the tank to allow or block the flow of fluid from the former to the latter; a regeneration valve connecting the large chamber and the small chamber to allow or block the flow of fluid from the former to the latter; a recovery part for recovering energy; and a first valve provided between the large chamber and the recovery part to allow or block the flow of fluid from the former to the latter.

The present invention relates to a switching valve block for a hydraulically actuable work machine that comprises a plurality of valve block inputs for a respective connection to a pressure output of one or more hydraulic fluid pumps, a plurality of valve block outputs for outputting a pressurized hydraulic fluid, and at least one valve that is arranged between valve block inputs and valve block outputs and is adapted to selectively produce a fluid connection between a first valve block input and a first valve block output or between a first valve block input and a second valve block output. The invention is characterized in that the first valve block output furthermore already has a fixed fluid connection to a second valve block input.

A control valve of hydraulic system for a working machine is provided, which includes a main body and a spool. The main body includes first, second, third, fourth and fifth ports, and first second, third, fourth and fifth inner fluid paths connected to the first, second, third, fourth and fifth ports, respectively. The spool is configured to move between a neutral position and a communicating position allowing fluid communication between the second inner fluid path and the fifth inner fluid path or between the first inner fluid path and the fifth inner fluid path. The spool includes a communicating hole configured to allow the fluid communication between the second port and the fourth port, or between the first port and the fourth port, when the spool is in a position between the communicating position and the neutral position.

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 system includes a first output fluid tube connecting between a hydraulic pump to output operation fluid and a first operation valve to change a first pilot pressure of the operation fluid, a second output fluid tube connected between the hydraulic pump and a second operation valve to change a second pilot pressure of the operation fluid, a switching valve provided in the second output fluid tube, and a warm-up fluid tube connected between the first operation valve and the switching valve, wherein the switching valve is switched between a first position allowing the operation fluid to be drained through the first output fluid tube, the first operation valve, the warm-up fluid tube and the switching valve, and a second position allowing the operation fluid to be supplied through second output fluid tube to the second operation valve.