Direct control linear variable displacement vane pump

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.

1 . A fluid pumping system for a power transmission device, comprising:
 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; and   a control system for varying the displacement of the pump and providing 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 including a linear actuator for moving the slide between minimum and maximum pump displacement positions, the linear actuator including an electric stepper motor for bi-directionally translating an actuator shaft acting on the slide.   
     
     
         2 . The fluid pumping system of  claim 1  wherein the housing includes a pressure balance chamber in communication with the slide and in receipt of pressurized working fluid, the fluid balancing forces acting on the slide wherein the resultant force on the slide approaches zero. 
     
     
         3 . The fluid pumping system of  claim 2  wherein the control system includes a controller in communication with a drive providing electrical pulses to the stepper motor. 
     
     
         4 . The fluid pumping system of  claim 1  wherein the slide includes a first arm having substantially parallel opposite faces positioned proximate substantially parallel opposite walls of a recess formed in the housing, the first arm restricting relative rotation between the slide and the housing. 
     
     
         5 . The fluid pumping system of  claim 4  wherein the slide includes a second arm having substantially parallel opposite faces positioned proximate substantially parallel opposite walls of another recess formed in the housing, the second arm restricting relative rotation between the slide and the housing, wherein the first and second arms are diametrically opposed to one another. 
     
     
         6 . The fluid pumping system of  claim 5  wherein the second arm includes a pocket in receipt of the actuator shaft. 
     
     
         7 . The fluid pumping system of  claim 6  further including a clip interconnecting the actuator shaft and the second arm. 
     
     
         8 . The fluid pumping system of  claim 2  wherein the slide includes a bore in receipt of the vanes and the pressure balance chamber extends along one side of the slide to allow fluid to act on portions of the slide on opposite sides of a centerline extending through the slide bore. 
     
     
         9 . The fluid pumping system of  claim 1  wherein the actuator shaft and the slide each translate parallel to one another. 
     
     
         10 . The fluid pumping system of  claim 9  wherein the slide includes a bore in receipt of the vanes, the translation line of the actuator shaft intersecting a centerline of the slide bore. 
     
     
         11 . The fluid pumping system of  claim 1  further including a spring urging the slide into contact with the actuator shaft, wherein the actuator shaft is not fixed to the slide. 
     
     
         12 . A fluid pumping system for a power transmission device, comprising:
 a variable displacement vane pump including a linearly moveable slide for varying the displacement of the pump;   a linear actuator for moving the slide between maximum and minimum pump displacement positions, the linear actuator including an electric motor for rotating a drive member, the drive member engaging a driven actuator shaft to cause linear translation of the actuator shaft in response to rotation of the drive member; and   a control system including a controller for signaling the actuator to extend or retract the actuator shaft to vary the pump displacement.   
     
     
         13 . The fluid pumping system of  claim 12  wherein the controller operates in an open loop control mode and is not in receipt of a signal indicative of the pressure being output by the pump. 
     
     
         14 . The fluid pumping system of  claim 12  wherein the controller operates in a closed loop mode in response to a signal indicative of the pressure output by the pump. 
     
     
         15 . The fluid pumping system of  claim 12  wherein the electric motor is a stepper motor operable to position the slide at various positions between the minimum and maximum displacement positions. 
     
     
         16 . The fluid pumping system of  claim 12  wherein the pump includes a housing with a pressure balance chamber in communication with the slide and in receipt of pressurized working fluid, the fluid balancing forces acting on the slide wherein the resultant force on the slide approaches zero. 
     
     
         17 . The fluid pumping system of  claim 16  wherein the slide includes a first arm having substantially parallel opposite faces positioned proximate substantially parallel opposite walls of a recess formed in the housing, the first arm restricting relative rotation between the slide and the housing. 
     
     
         18 . The fluid pumping system of  claim 17  wherein the slide includes a second arm having substantially parallel opposite faces positioned proximate substantially parallel opposite walls of another recess formed in the housing, the second arm restricting relative rotation between the slide and the housing, wherein the first and second arms are diametrically opposed to one another. 
     
     
         19 . The fluid pumping system of  claim 18  wherein the second arm includes a pocket in receipt of the actuator shaft. 
     
     
         20 . The fluid pumping system of  claim 19  further including a clip interconnecting the actuator shaft and the second arm. 
     
     
         21 . The fluid pumping system of  claim 12  further including a spring urging the slide into contact with the actuator shaft, wherein the actuator shaft is not fixed to the slide. 
     
     
         22 . The fluid pumping system of  claim 12  wherein the actuator shaft and the slide each translate along the same line.