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.

An example valve includes: a first port fluidly coupled to a chamber of an actuator; a second port fluidly coupled to a reservoir; a third port configured to provide an output pilot fluid signal and receive an input pilot fluid signal; a fourth port fluidly coupled to a source of fluid; a main poppet configured to be subjected to a first fluid force of fluid received at the first port acting on the main poppet in a proximal direction to cause the main poppet to be seated at a main poppet seat to block fluid flow to and from the first port; a piston configured to move axially to contact the main poppet; and a spool that is axially movable between a first position and a second position to operate the valve in either a pilot-operated check valve mode of operation or a proportional flow control mode of operation.

A ride control valve includes a valve body defining a work passage, a pump passage, a tank passage, and an accumulator passage configure to couple to an accumulator. A ride control spool is movably disposed within the valve body and configured to move between a a first ride control position to discharge the accumulator, a second ride control position configured to charge the accumulator at a variable charge rate, a third ride control configured to balance the accumulator pressure with the work passage pressure, and a fourth ride control position configured to couple the accumulator to the work passage. A pressure balancing spool is movably disposed within the ride control spool to selectively couple the accumulator passage with each of the pump passage and the tank passage to balance the accumulator pressure. The ride control valve is configured couple to a directional control valve without external conduit.

A regeneration valve includes a housing defining a first port, a second port, a third port, and a chamber fluidly communicating with the first, second, and third ports. The chamber has a valve element movable between a first position, in which the second port fluidly communicates with the first port, and a second position, in which the second port fluidly communicates with the third port. A resilient member biases the valve element towards the first position. In operation, a flow restrictor element moves between the first port and the second port for restricting fluid flow from the second port to the first port. At a predetermined flow rate between the second port and the first port, if a supply pressure of fluid at the actuation chamber exceeds the bias of the resilient member, the valve element moves to the second position for fluidly communicating the second and third ports.

An example valve includes: a first port fluidly coupled to a chamber of an actuator; a second port fluidly coupled to a reservoir; a third port configured to provide an output pilot fluid signal and receive an input pilot fluid signal; a fourth port fluidly coupled to a source of fluid; a main poppet configured to be subjected to a first fluid force of fluid received at the first port acting on the main poppet in a proximal direction to cause the main poppet to be seated at a main poppet seat to block fluid flow to and from the first port; a piston configured to move axially to contact the main poppet; and a spool that is axially movable between a first position and a second position to operate the valve in either a pilot-operated check valve mode of operation or a proportional flow control mode of operation.

A hydraulic driving device of an industrial vehicle includes: a tank which stores hydraulic oil; a hydraulic pump which includes a suction port sucking the hydraulic oil and a discharge port discharging the hydraulic oil; a hydraulic cylinder which is driven by the hydraulic oil discharged from the discharge port of the hydraulic pump; a direction switching valve which is disposed among the hydraulic pump, the tank, and the hydraulic cylinder and switches a hydraulic oil flow direction in response to an operation state of operation means for driving the hydraulic cylinder; in which the direction switching valve includes a main spool which moves in response to the operation state of the operation means and a flow regulator which is disposed inside the main spool to control a flow rate of the hydraulic oil flowing from the hydraulic cylinder to the tank.

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 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.

A regeneration valve includes a housing defining a first port, a second port, a third port, and a chamber fluidly communicating with the first, second, and third ports. The chamber has a valve element movable between a first position, in which the second port fluidly communicates with the first port, and a second position, in which the second port fluidly communicates with the third port. A resilient member biases the valve element towards the first position. In operation, a flow restrictor element moves between the first port and the second port for restricting fluid flow from the second port to the first port. At a predetermined flow rate between the second port and the first port, if a supply pressure of fluid at the actuation chamber exceeds the bias of the resilient member, the valve element moves to the second position for fluidly communicating the second and third ports.

A valve member having a supply pressure and a method of controlling the supply pressure in the valve member includes a valve body having a fluid inlet, a fluid outlet, and a controlled port. The valve member includes a spool moveable within the valve body to fluidly connect at least one of the fluid inlet and the fluid outlet with the controlled port. The spool includes an end in fluid communication with a control pressure port and a pin received within the end of the spool that is moveable relative to the spool. Fluid flow through the control pressure port acts against a cross-sectional area of the pin and an annular area of the spool to modulate the supply pressure through the valve member.