A hydraulic excavator drive system includes a regeneration line, which connects an arm pushing and an arm crowding supply line, each of which extends between an arm cylinder and arm control valve. The regeneration line includes regeneration and switching valves. A release line that is branched off from the regeneration line at a position between the regeneration valve and the switching valve is provided with a release valve. A secondary pressure from a first solenoid proportional valve is fed to a pilot port of the regeneration valve such that the regeneration valve opens at a time of arm crowding. A secondary pressure from a second solenoid proportional valve is fed to a pilot port of the release valve such that release valve opens at a time of arm pushing. An arm pushing pilot pressure for moving the arm control valve is led to a pilot port of the switching valve.

A swiveling working machine includes a swivel base; a working device provided on a front side of the swivel base; a battery unit; an electric motor that is driven by electric power output by the battery unit; and a hydraulic pump that delivers a hydraulic fluid by driving of the electric motor. The battery unit is disposed at a rear portion of the swivel base. The electric motor and the hydraulic pump are disposed sideward of the battery unit side by side in a front-rear direction.

A work vehicle includes: a hydraulic pump driven by an engine; a hydraulic actuator that is driven by hydraulic oil supplied from the hydraulic pump; a switching valve configured to switch from one to the other of a first state in which the hydraulic oil supplied from the hydraulic pump is supplied to a first channel and a second state in which the hydraulic oil supplied from the hydraulic pump is supplied to a second channel; a restriction operation device configured to generate an operation signal that restricts the drive of the hydraulic actuator; and a controller that controls the switching valve. The controller includes: an operation signal acquisition unit configured to acquire the operation signal; and an instruction output unit configured to output, to the switching valve, a control instruction that restricts the drive of the hydraulic actuator with the engine driving, in response to the operation signal.

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.

A construction machine including a boom; an engine; a main pump discharging a working fluid; a working fluid tank storing the working fluid; a boom cylinder raising or lowering the boom and comprising a head side and a rod side; a regeneration line connected to the head side of the boom cylinder and moving the working fluid discharged from the head side of the boom cylinder; a regeneration motor operated by the working fluid moved through the regeneration line and assisting the engine; an accumulator connected to the regeneration line accumulating the working fluid discharged from the boom cylinder; a boom regeneration valve opening or closing the regeneration line; a main control valve controlling a supply of the working fluid, to the boom cylinder and discharge a part of the working fluid, which is discharged from the head side of the boom cylinder, to the working fluid tank.

In a hydraulic excavator including a main controller that can execute area restriction control, the main controller is configured to calculate an operation velocity Vfx of a front work device in a machine body coordinate system and a movement velocity (dragging velocity) Vu of a machine body in a gravity coordinate system and correct a direction of a calculated target velocity vector Vt upward away from a construction target surface when generation of dragging is detected during execution of the area restriction control based on the calculated operation velocity Vfx of the front work device 2 and the calculated movement velocity Vu of the machine body.

A work machine includes a machine body, a travel device, a hydraulic drive, a pedal for performing a braking operation, an inching valve that changes a flow rate of a hydraulic fluid, and an adjuster that adjusts a stroke of an operation of the pedal. The adjuster includes a swing member that swings in coordination with an operation of the pedal and that is at a first position when the pedal is at an initial position of the stroke, a movement member that is capable of performing movement in contact with the swing member and that changes the first position by performing the movement in contact with the swing member, and a switching mechanism that is switchable between a first state in which the switching mechanism allows the movement of the movement member and a second state in which the switching mechanism prohibits the movement of the movement member.

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.

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 pressure increasing portion to increasing a pressure of the operation fluid, a first discharge fluid tube connected to any one of the first control valve and the second control valve and connected to the pressure increasing portion, a second discharge fluid tube connected to the first discharge fluid tube and configured to discharge the operation fluid, a float switching valve having an allowance position, a prevention position, and a float position, the allowance position blocking the second discharge fluid tube and allowing the operation fluid to flow to the pressure increasing portion, the prevention position unblocking the second discharge fluid tube and preventing the operation fluid from flowing to the pressure increasing portion.

The present invention provides an engineering machinery hydraulic system with compensation differential pressure controllable, uses an electronic pressure compensating valve to solve the problem of flow mismatch under conditions of pressure over-limit and flow saturation, and realizes proportional shunt control and high-precision flow distribution of the system. The engineering machinery hydraulic system disclosed in the present invention has the advantages of low energy consumption, fast response speed, and high flow control precision.