초록 ▼

A hydrostatic drive system includes a hydraulic motor driven by a variable displacement axial piston pump with alternative intake and output ports. A charge pump generates a charge pressure which is communicated only to the pump intake port via a charge valve unit. The pump displacement is controlle

A hydrostatic drive system includes a hydraulic motor driven by a variable displacement axial piston pump with alternative intake and output ports. A charge pump generates a charge pressure which is communicated only to the pump intake port via a charge valve unit. The pump displacement is controlled by a swashplate which is moved by servo pistons which receive fluid from a displacement control valve. A three check valve unit communicates the higher of pump intake, outlet and charge fluid pressures to an inlet of the displacement control valve.

대표청구항 ▼

A hydraulic pressure pump stroking assist for use with a hydraulic pump having intake and output ports, movable means for varying pump displacement, servo means for controlling the position of the movable means, and control valve means for controlling the flow of pressurized fluid to and exhaust of

A hydraulic pressure pump stroking assist for use with a hydraulic pump having intake and output ports, movable means for varying pump displacement, servo means for controlling the position of the movable means, and control valve means for controlling the flow of pressurized fluid to and exhaust of fluid from the servo means, the stroking assist comprising: charge means for providing a pressurized charge fluid; charge valve means for communicating the charge means with the pump intake port and for preventing communication between the charge means and the pump output port; and differentiating means for receiving fluid pressure from the charge means, from the pump intake port and from the pump output port and for communicating the higher of said pressures to the control valve means, the differentiating means including first, second and third check valves, a first passage directly communicating charge fluid from an inlet of the charge valve to the first check valve, a second passage communicating only the pump intake port to the second check valve, a third passage communicating only the pump output port to the third check valve and a fourth passage communicating all of the check valves to the control valve means.