A drive device of a construction machine includes a pump passage connected to a hydraulic pump, first and second supply passages connected to the pump passage, first and second passages connected to the first supply passage, third and fourth passages connected to the second supply passage, a first valve connected to the first and third passages, a second valve connected to the second and fourth passages, a first bucket passage connecting the first passage to a cap-side space of the bucket cylinder through the first valve, a second bucket passage connecting the third passage to a rod-side space of the bucket cylinder through the first valve, a first arm passage connecting the second passage to a rod-side space of an arm cylinder through the second valve, and a second arm passage connecting the fourth passage to a cap-side space of the arm cylinder through the second valve.

Provided is a working machine capable of regenerating and utilizing surplus energy. The working machine related to the present invention is provided with a branching flow path (150) through which hydraulic oil flows between a hydraulic actuator (24) and a hydraulic pump-motor (14), an accumulator (30) arranged in the branching flow path, a first opening/closing valve (31) arranged between the accumulator and the hydraulic pump-motor, and a second opening/closing valve (32) arranged between the accumulator and the hydraulic actuator. A control device (41) selectively introduces the hydraulic oil from the hydraulic actuator and the hydraulic oil from the hydraulic pump-motor to the accumulator and accumulates the same by controlling opening/closing of the first opening/closing valve and the second opening/closing valve.

A control system for construction machinery includes a first hydraulic pump, first and second actuators connected to the first hydraulic pump through first and second hydraulic lines respectively, first and second control valves installed in the first and second hydraulic lines respectively and configured to control operations of the first and second actuators, and a controller configured to adjust a spool displacement amount of the first control valve according to an amount of working oil to be supplied to the first actuator when the first actuator performs a single or multiple operation by self-load.

A hydraulic circuit for a construction machine including a direction control valve group including direction control valves provided in tandem to a center bypass passage, a bleed-off valve provided to the center bypass passage downstream of the direction control valve group, and a control valve controlling an amount of pressure oil to be supplied to the direction control valve.

A fluid power system includes an electro-hydraulic variable displacement fluid pump driving fluid at a first displacement value. The system further includes a directional control valve, a sensor, and a controller. The directional control valve includes a valve member movable between a neutral position and at least one actuated position. The directional control valve diverts at least some fluid to an actuator while the valve member is in an actuated position, and the directional control valve exhausts fluid at an exhaust pressure through an outlet port to the fluid reservoir while the valve member is in the neutral position. The sensor measures a difference between the exhaust pressure and a nominal pressure and generates a signal based on the measured difference. The controller generates a flow command at least partially based on the pressure signal to modify the operation of the pump to drive fluid at a second displacement value.

In a method of controlling a main control valve of an excavator, when speeds of a boom cylinder and an arm cylinder is increased by handling a boom joystick and an arm joystick, a second arm control spool between a first hydraulic pump and the arm cylinder may be closed. A first boom control spool between the first hydraulic pump and the boom cylinder may be opened to supply a first flux generated from the first hydraulic pump to the boom cylinder. A second boom control spool between a second hydraulic pump and the boom cylinder may be closed. A first arm control spool between the second hydraulic pump and the arm cylinder may be opened to supply a second flux generated from the second hydraulic pump to the arm cylinder.

A hydraulic system for a work machine includes a first control valve including a first direction switch to switch a direction in which the operation fluid is to flow through a first hydraulic actuator and a pressure compensator to maintain a differential pressure to a constant pressure, the differential pressure being a difference between a pressure of the operation fluid to be inputted to the pressure compensator and a pressure of the operation fluid to be outputted from the pressure compensator. And, the hydraulic system includes a second control valve including a second direction switch to switch a direction in which the operation fluid is to flow through a second hydraulic actuator and a flow rate prioritizer to prioritize a flow rate of the operation fluid to be outputted to the second hydraulic actuator.

Provided is a working machine capable of regenerating and utilizing surplus energy. The working machine related to the present invention is provided with a branching flow path (150) through which hydraulic oil flows between a hydraulic actuator (24) and a hydraulic pump-motor (14), an accumulator (30) arranged in the branching flow path, a first opening/closing valve (31) arranged between the accumulator and the hydraulic pump-motor, and a second opening/closing valve (32) arranged between the accumulator and the hydraulic actuator. A control device (41) selectively introduces the hydraulic oil from the hydraulic actuator and the hydraulic oil from the hydraulic pump-motor to the accumulator and accumulates the same by controlling opening/closing of the first opening/closing valve and the second opening/closing valve.

A drive device of a construction machine includes a pump passage connected to a hydraulic pump, first and second supply passages connected to the pump passage, first and second passages connected to the first supply passage, third and fourth passages connected to the second supply passage, a first valve connected to the first and third passages, a second valve connected to the second and fourth passages, a first bucket passage connecting the first passage to a cap-side space of the bucket cylinder through the first valve, a second bucket passage connecting the third passage to a rod-side space of the bucket cylinder through the first valve, a first arm passage connecting the second passage to a rod-side space of an arm cylinder through the second valve, and a second arm passage connecting the fourth passage to a cap-side space of the arm cylinder through the second valve.

A hydraulic system for a work machine includes a hydraulic pump to supply a pilot fluid, and a hydraulic switch valve to be switched to a plurality of switching positions based on a pilot pressure. The pilot pressure is a pressure of the pilot fluid supplied from the hydraulic pump. The hydraulic system includes a direction switch valve to apply a first pilot pressure to the hydraulic switch valve to switch the hydraulic switch valve into one of the plurality of switching positions. The hydraulic system includes a pressure applying device to apply a second pilot pressure to the hydraulic switch valve. The second pilot pressure is lower than the first pilot pressure.