Variable displacement vane pump with enhanced discharge port

Abstract

A variable displacement vane pump which includes an enhanced discharge port. The enhanced discharge port reduces areas of high pressure in the discharge port which would otherwise occur as the pressurized working fluid reverses its direction of flow to enter the discharge port. By reducing the areas of high pressure, the back torque on the pump rotor is reduced and the energy efficiency of the pump is enhanced. In one embodiment, the pivot for the pump control ring is located radially outwardly from a conventional location, to allow for a discharge recess to be formed in the control ring, adjacent the discharge port, and extending past the pivot to the pump outlet. In a second embodiment, the discharge recess is formed in the control ring around the pivot and a seal is provided on the control ring to inhibit leakage of pressurized working fluid past the control ring. In a third embodiment, a secondary discharge port is provided adjacent the discharge recess formed in the control ring and pressurized working fluid in the discharge recess can exit the discharge recess through the secondary discharge port which is in fluid communication with the pump outlet.