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.

Disclosed is an energy-recycling hydraulic control main valve, which is provided with end covers, a valve core, a left one-way valve and a right one-way valve; the left one-way valve is composed of a left valve seat, a left cone valve core and a left spring; a conical surface of the left cone valve core is closely attached to a left conical surface of the valve core by the spring force; the right one-way valve is composed of a right valve seat, a right cone valve core and a right spring; and a conical surface of the right cone valve core is closely attached to a right conical surface of the valve core by spring force. The hydraulic main control valve can not only limit the falling speed of a piston, but use the potential energy generated by the gravity action on the piston, thereby achieving energy recycling.

A control valve has a first and second pilot chambers facing both ends of a spool, a signal pressure passage configured to lead a pilot pressure of the first and second pilot chambers to another device other than the control valve as a signal pressure, a communication groove configured to allow the first pilot chamber and the signal pressure passage to communicate with each other, a communication hole configured to allow the second pilot chamber and the signal pressure passage to communicate with each other, and a check valve interposed in the communication hole, and the check valve has a poppet portion configured to open or close the communication hole and a spacer portion configured to regulate a moving amount of the poppet portion in an open direction, and the control valve further includes a movement regulating portion configured to regulate movement of the spacer portion toward the poppet portion.

Disclosed is a flow control valve for construction machinery, the flow control valve being adapted to reduce pressure loss due to flow on return to a hydraulic tank during the boom-down operation of a large-scale excavator. The flow control valve for construction machinery according to the present invention comprises: first and second boom spools which are respectively coupled to first and second boom valve blocks, and which regulate working fluid that is respectively supplied from first and second hydraulic pumps to a boom cylinder during direction reversal; a boom-up flow-adjusting means which, in direction reversal of the first and second boom spools for boom-up drive, supplies working fluid from the first and second hydraulic pumps into a large chamber of the boom cylinder via the first and second boom spools respectively, and causes part of the flow of working fluid from the second hydraulic pump to pass via the second boom spool so as to be combined with working fluid being supplied from the first hydraulic pump to the large chamber of the boom cylinder due to direction reversal of the first boom spool; and a boom-down flow-adjusting means which, in direction reversal of the first and second boom spools for boom-down drive, causes part of the flow of working fluid coming back from the large chamber of the boom cylinder to return to the hydraulic tank via the first and second boom spools respectively, and causes part of the flow of working fluid coming back from the large chamber of the boom cylinder to combine as respective regenerative flows for working fluid on the small chamber side of the boom cylinder.

A switching valve includes a spool, a first cylinder port that communicates with the piston side chamber, a second cylinder port that communicates with the rod side chamber, a bridge passage having a first opening which is adjacent to the first cylinder port and a second opening which is adjacent to the second cylinder port, a regeneration passage formed in the spool to connect the second cylinder port communicating with the rod side chamber to the first cylinder port in accordance with a switching position of the spool, and a first communication port and a second communication port formed in the spool to communicate with the regeneration passage. The first communication port communicates with the second opening of the bridge passage, which is adjacent to the second cylinder port, and the second communication port communicates with the second cylinder port in accordance with the switching position of the spool.

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 control system for construction machinery includes a hydraulic cylinder operable by a working oil discharged from a hydraulic pump, a control valve arranged between the hydraulic pump and the hydraulic cylinder to control an operation of the hydraulic cylinder according to a position of a spool therein, the control valve having a first spool position for draining the working oil discharged from a chamber of the hydraulic cylinder to a drain tank, and a pressure compensated valve installed in a return hydraulic line through which the working oil discharged from the control valve at the first spool position is drained to the drain tank, the pressure compensated valve being configured to control a flow rate of the working oil passing through the pressure compensated valve according to a pressure difference between a front end and a rear end of the 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.

An interlocked single function activation valve for hydraulic systems is disclosed. The hydraulic valve prevents unsafe tie-down or safety override situations by requiring the safety mechanism to be reset each time the hydraulic system is used. The hydraulic valve includes an interlock spool that moves to an extension position when the hydraulic system is de-pressurized and then re-pressurized while the control lever is engaged (i.e., tied down). When the interlock spool is in the extension position, it prevents the system from reaching a working pressure, thereby forcing a reset of the control lever before the system can reach working pressure.

An interlocked single function activation valve for hydraulic systems is disclosed. The hydraulic valve prevents unsafe tie-down or safety override situations by requiring the safety mechanism to be reset each time the hydraulic system is used. The hydraulic valve includes an interlock spool that moves to an extension position when the hydraulic system is de-pressurized and then re-pressurized while the control lever is engaged (i.e., tied down). When the interlock spool is in the extension position, it prevents the system from reaching a working pressure, thereby forcing a reset of the control lever before the system can reach working pressure.