A fluid system includes a variable-speed and/or a variable-torque pump to pump a fluid, at least one proportional control valve assembly, an actuator that is operated by the fluid to control a load, and a controller that establishes a speed and/or torque of the pump and a position of the at least one proportional control valve assembly. The pump includes at least one fluid driver that provides fluid to the actuator, which can be, e.g., a fluid-actuated cylinder, a fluid-driven motor or another type of fluid-driven actuator that controls a load. Each fluid driver includes a prime mover and a fluid displacement assembly. The fluid displacement assembly can be driven by the prime mover such that fluid is transferred from the inlet port to the outlet port of the pump.

The hydraulic system according to the invention comprises a hydraulic circuit with a low-pressure region and a high-pressure region; a volume- and/or speed-variable hydraulic machine, which is driven by a first electric motor and has an inlet and an outlet and provides a volume flow of a hydraulic fluid in the high-pressure region of the hydraulic circuit. The hydraulic system according to the invention further comprises at least one movable shaft, which is arranged in the high-pressure region of the hydraulic circuit; at least one valve, which separates the high-pressure region from the low-pressure region; and at least one hydraulic fluid container, which is hydraulically connected to the low-pressure region of the hydraulic circuit. The hydraulic system according to the invention also has a discharge line, which discharges hydraulic fluid from the leakage of the hydraulic machine, and a cooling line for transporting the hydraulic fluid in order to cool the electric motor, the discharge line and the cooling line being fluidically connected to at least one of the hydraulic fluid containers.

A method and control system operable to control movement of a work implement of a work vehicle. The control system includes a reservoir that retains fluid, a pump in fluid communication with the reservoir, and an actuator in fluid communication with the pump. The actuator has a first side and a second side. A control valve is fluidly positioned between the pump and the actuator, a first proportional relief valve is fluidly positioned between the pump and the first side of the actuator, and a second proportional relief valve is fluidly positioned between the pump and the second side of the actuator. The first proportional relief valve is configured to permit flow of fluid from the first side of the actuator to the reservoir when a pressure at the first side of the actuator exceeds a pressure set point.

A hydraulic drive system of a construction machine includes: a boom control valve connected to a boom cylinder by a boom raising supply line and a boom lowering supply line; a pump that sucks hydraulic oil through a suction line, and delivers the hydraulic oil through a delivery line; a regenerative valve that brings the boom raising supply line and the suction line into communication with each other through a regenerative line when a boom lowering operation is performed; and a controller that controls an accumulator switching valve. The controller: switches the accumulator switching valve to a pressure accumulation position when a pressure accumulation condition is satisfied; switches the accumulator switching valve to a pressure release position when a pressure release condition is satisfied; and switches the accumulator switching valve to a neutral position when neither the pressure accumulation condition nor the pressure release condition is satisfied.

A method and apparatus for remotely positioning a stabilizer wheel of a towable agricultural implement simultaneously, cooperatively and proportionally control the flow of hydraulic fluid to and from both the rod and base ends of the bore of a double-acting hydraulic cylinder, to hold the piston of the hydraulic cylinder at a target position determined from a desired position input signal corresponding to a desired position of the stabilizer wheel with respect to a frame of the agricultural implement.

Disclosed embodiments include hydraulic systems which provide power to lift, tilt and auxiliary (e.g., implement) functions, including high-flow auxiliary functions, with increased efficiency. Disclosed embodiments incorporate a single variable displacement pump that supplies pressurized fluid to a main control valve (e.g., for lift, tilt, and auxiliary functions) and a bypass circuit. The main control valve supplies fluid to control lift, tilt, and auxiliary flow for implements. The bypass circuit combines flow with the output of the auxiliary section of the main control valve to optionally provide high-flow for selected implements. The single variable displacement pump can then be set to different output flow levels, with the bypass circuit functioning differently under different conditions to optimize hydraulic flow to carryout various tasks under various conditions.

A fluid system includes a variable-speed and/or a variable-torque pump to pump a fluid, at least one proportional control valve assembly, an actuator that is operated by the fluid to control a load, and a controller that establishes a speed and/or torque of the pump and a position of the at least one proportional control valve assembly. The pump includes at least one fluid driver that provides fluid to the actuator, which can be, e.g., a fluid-actuated cylinder, a fluid-driven motor or another type of fluid-driven actuator that controls a load. Each fluid driver includes a prime mover and a fluid displacement assembly. The fluid displacement assembly can be driven by the prime mover such that fluid is transferred from the inlet port to the outlet port of the pump.

An apparatus includes a housing, a piston, an input cavity, a first actuating shaft, a first output cavity, and a second output cavity. The housing comprises an input port, a first output port, a second output port, a first end, a second end, a first wide wall having a first internal surface, and a chamber at least partially defined by the first end and the first internal surface. The piston is able to actuate along the first internal surface of the first side wall. The input cavity is in fluid communication with the input port. The first output cavity is in fluid communication with the first output port. The second output cavity is in fluid communication with the second output port. The first actuating shaft is fixed to the piston and helps fluidly isolate the first output port from the second output port.

A linear actuator system includes a linear actuator and at least one integrated pump assembly connected to the linear actuator to provide fluid to operate the linear actuator. The integrated pump assembly includes a pump with at least one fluid driver comprising a prime mover and a fluid displacement assembly to be driven by the prime mover such that fluid is transferred from a first port of the pump to a second port of the pump. The pump assembly also includes two valve assembles to isolate the pump from the system. The linear actuator system also includes a controller that establishes at least one of a speed and a torque of the at least one prime mover to exclusively adjust at least one of a flow and a pressure in the linear actuator system to an operational set point.

An object of the present invention is to provide a construction machine capable of suppressing lugging down of an engine irrespective of contents of operation of an operator and the load state of a hydraulic actuator. A controller 50 includes: a demanded torque estimating section 50c configured to estimate demanded torque as torque demanded from an engine 9 by the first hydraulic pump on the basis of a demanded velocity of a first hydraulic actuator 1 and a load pressure on the first hydraulic actuator; a demanded velocity limiting section 50d configured to, in a case in which a demanded torque change rate as a change rate of the demanded torque exceeds a predetermined change rate, limit the demanded velocity such that the demanded torque change rate becomes equal to or lower than the predetermined change rate; and a command calculating section 50e configured to calculate a delivery flow rate of the first hydraulic pump on the basis of the demanded velocity of the first hydraulic actuator, the demanded velocity being limited by the demanded velocity limiting section.