Abstract: A fluid pumping system for a power transmission device includes a variable displacement vane pump having a housing containing a rotor, a plurality of vanes coupled to the rotor and a linearly translatable slide for varying the displacement of the pump. A control system varies the displacement of the pump and provides a fluid output pressure selected from a continuously variable range of output pressures which are independent from the operating speed of the pump. The control system includes a linear actuator for moving the slide between minimum and maximum pump displacement positions. The linear actuator includes an electric stepper motor for bi-directionally translating an actuator shaft acting on the slide.

Abstract: A gear pump is provided and includes an inlet port which terminates, in the pumping direction of the rotor set, in a radially inwardly extending ramp portion. The ramp portion operates to direct working fluid from an inlet radially inwardly into a pumping chamber of the rotor set which is passing over the ramp portion. By closing the pumping chamber at a radially inwardly point, the filling efficiency of the pumping chamber is improved, reducing cavitation and/or operating noise of the pump.

Abstract: With a traditional gear pump inlet design it is difficult to fill the pumping chamber when the inlet pressure is low or the operating speed is high A gear pump (100) is provided and includes an inlet port (116) which terminates, in the pumping direction of the rotor set (104) in a radially inwardly extending ramp portion (132) The ramp portion (132) operates to direct working fluid from the inlet (116) radially inwardly into the pumping chamber (126) of the rotor set (104) which is passing over the ramp portion (132) By closing the pumping chamber (126) at a radially inwardly point, the filling efficiency of the pumping chamber (126) is improved, reducing cavitation and/or operating noise of the pump.