A hydraulic system includes a hydraulic circuit, a heater, a temperature sensor, and a controller. The hydraulic circuit includes a reservoir configured to store hydraulic fluid, a pump coupled to the reservoir, a driver positioned to drive the pump to pump the hydraulic fluid from the reservoir and throughout the hydraulic circuit, and an actuator positioned to selectively receive the hydraulic fluid from the pump to operate a controllable machine component. The driver is independent of a prime mover of the machine. The heater is positioned to facilitate selectively heating the hydraulic fluid. The temperature sensor is positioned to acquire temperature data indicative of a temperature of the hydraulic fluid. The controller is configured to monitor the temperature of the hydraulic fluid and selectively activate at least one of the heater or the pump to thermally regulate the hydraulic fluid to maintain the hydraulic fluid within a target temperature range.

A hydraulic drive system includes control valve and operating devices, a variable displacement pump, and a flow regulator. When an operating lever inclination angle becomes a value, a control valve opening area becomes a reference. When the operating lever inclination angle maximizes, the opening area maximizes. The flow regulator: until the operating lever inclination angle becomes the value, increases the pump discharge flow rate with the inclination angle, so a differential pressure between pump discharge and actuator load pressures is constant; when the operating lever inclination angle becomes the value, controls the pump discharge flow rate, so a control valve passing flow rate is an actuator maximum flow rate when the differential pressure is constant; and when the operating lever inclination angle is between the value and the maximum, defines a maximum pump discharge flow rate, so the pump discharge flow rate is kept to the actuator maximum flow rate.

A hydraulic jack including a load cylinder, a pump, a release valve and a flow regulator. The pump is configured to provide pressurized fluid to the load cylinder. The release valve is in fluid communication with the pressurized fluid. The flow regulator is configured to alter a flow path of the fluid therethrough as an inverse function of a pressure drop of the fluid across the flow regulator. The fluid regulator being in fluid communication with the release valve.

A hydraulic machine includes an actuator, a tank, a directional control valve disposed between the actuator and the tank, and an adjustable return check valve disposed between the directional control valve and the tank. The directional control valve includes an attachment actuator directional control valve disposed between an attachment actuator of the actuator and the tank and a swing actuator directional control valve disposed between a swing actuator of the actuator and the tank. The adjustable return check valve allows fluid to flow from the attachment actuator directional control valve toward the tank while applying the low back pressure but blocks a flow, and allows fluid to flow from the swing actuator directional control valve toward the tank while applying the high back pressure but blocks a reverse flow.

A system for braking a displacement-controlled drive system (10), which can be driven by means of an inflow pressure and an outflow pressure at an inflow end and an outflow end thereof, respectively, for a motion, characterized in that by means of an electro-proportional adjustment of at least one valve element (26, 28, 126, 128) an outflow volume flow of the drive system (10) is controlled such that the outflow pressure is decoupled from the motion of the drive system and can be freely preset and coupled to the inflow pressure, which can in that way be lowered to the extent necessary for the motion of the drive system (10).

A control system for a construction machine includes: a boom cylinder; a boom switching valve; a fluid pressure motor adapted to drive a motor generator by being rotated by means of a return fluid guided from a piston side chamber; a regeneration control valve adapted to adjust a first supply amount serving as a supply amount of a working fluid supplied from the piston side chamber to the boom switching valve, and a second supply amount serving as a supply amount of the working fluid supplied from the piston side chamber to the fluid pressure motor; and a controller adapted to control the regeneration control valve so that the second supply amount becomes smaller than the first supply amount in a case where a stroke amount of a spool becomes an upper limit value or more.

A work machine includes: a hydraulic actuator that is driven by a hydraulic fluid from a hydraulic pump; an open-center directional control valve that is arranged on a center bypass line, and controls a flow of the hydraulic fluid to be supplied to the hydraulic actuator; a CB cut valve arranged between a directional control valve and a hydraulic working fluid tank on the center bypass line; and a machine controller that controls an opening of the CB cut valve. The machine controller restricts the opening of the CB cut valve when operation on the hydraulic actuator is in a fine operation state in which the operation on the hydraulic actuator is within a predetermined range representing a region of fine operation, and the fine operation state is continued longer than a predetermined period, and fully opens the CB cut valve otherwise.

An object of the invention is to achieve a travel speed known in the art during travelling operation, improve energy efficiency by reducing energy loss, and obtain favorable travel operability less susceptible to effects from variations in a travel load and changes in a pump delivery pressure when travelling operation is performed through operation of a travel lever over a half stroke range or less. A variable restrictor valve 80 is disposed in parallel with a flow sensing valve 50 of an engine speed sensing valve unit 13. A travel pilot pressure is adapted to act in an opening direction of the variable restrictor valve 80. The variable restrictor valve 80 is set to have a continuously increasing opening area from a full closure to a maximum with an increasing travel pilot pressure. Travel flow control valves 6d and 6e have an opening area that allows a predetermined flow rate QT required for traveling to be obtained even when a target LS differential pressure is decreased to a second specified value Pa3 when the travel lever is fully operated. In a first half of a spool stroke, the travel flow control valves 6d and 6e have an opening area approximate to an opening area of comparative example 1.

A hydraulic system is provided for controlling one or more piston-cylinders of an implement. An implement valve includes at least one spool operable to transition between a neutral position and an open position. A variable displacement pump is operable to move a fluid from a reservoir into a supply conduit and to the at least one spool. A flow control valve, distinct and separate from the at least one spool is located in-line with the supply conduit between the variable displacement pump and the at least one spool, and is operable to simultaneously provide the fluid to the implement valve and to a bypass pathway. The bypass pathway extends from the flow control valve to the reservoir without intervening valving. Each of the at least one spool is operable to permit increased fluid flow to a corresponding piston cylinder of the implement when in the open position. The variable displacement pump is operable to vary a flow rate to maintain a predetermined pump margin across the flow control valve.

A control system of a hybrid construction machine includes fluid pressure pumps, a regeneration motor, a rotating electric motor coupled to the regeneration motor, a storage battery configured to store electric power generated by the rotating electric motor, an assist pump provided coaxially to the regeneration motor to be driven by the rotating electric motor, the assist pump being configured to supply a working fluid to a fluid pressure actuator, and load adjusting units configured to change a load of the assist pump in accordance with a state of the storage battery.