Multiple Pressure Variable Displacement Pump with Mechanical Control

Abstract

A variable displacement vane pump that includes a biasing assembly that applies a first biasing force to a pump control ring when the pump control ring is located a first position and a second position and applies a second biasing force when the pump control ring is located between the second position and a third position. The first position of the pump control ring corresponds to a maximum volumetric capacity of the pump, the second position corresponds to an intermediary volumetric capacity of the pump, and the third position corresponds to a minimum volumetric capacity of the pump. Fluid pressure within a control chamber urges the pump control ring toward the third position.

What is claimed is: 
     
         1 . A variable displacement vane pump having a housing with a pump chamber, the pump chamber having a fluid inlet, a fluid outlet, a pump control ring, and a vane pump rotor, the pump control ring disposed within the housing for altering the displacement of the pump by rotating between a first position that corresponds to a maximum volumetric capacity of the pump, a second position that corresponds to an intermediary volumetric capacity of the pump, and a third position that corresponds to a minimum volumetric capacity of the pump, the vane pump rotor rotatably mounted within the pump control ring and having a plurality of slidably mounted vanes engaging an inside surface of the pump control ring, the vane pump rotor having an axis of rotation eccentric from a center of the pump control ring, the vane pump rotor rotating to pressurize fluid as the fluid moves from the fluid inlet to the fluid outlet, comprising:
 a biasing assembly for urging the pump control ring toward the first position, wherein the biasing assembly applies a first biasing force to the pump control ring when the pump control ring is located between the first position and the second position and applies a second biasing force to the pump control ring when the pump control ring is located between the second position and the third position; and   a control chamber formed between the housing and the pump control ring, wherein fluid pressure within the control chamber urges the pump control ring toward the third position.   
     
     
         2 . The variable displacement vane pump of  claim 1 , further comprising:
 a needle bearing mounted between the pump control ring and the housing to allow the pump control ring to pivot relative to the needle bearing.   
     
     
         3 . The variable displacement vane pump of  claim 1 , further comprising
 a feedbath path in communication with the fluid outlet supplying a pressurized fluid to the control chamber.   
     
     
         4 . The variable displacement vane pump of  claim 1 , further comprising:
 a spring chamber formed between the housing and the pump control ring, wherein the spring chamber has a maximum volume when the pump control ring is in the first position and a minimum volume when the pump control ring is in the third position.   
     
     
         5 . The variable displacement vane pump of  claim 4 , wherein the biasing assembly is disposed within the spring chamber. 
     
     
         6 . The variable displacement vane pump of  claim 1 , wherein the biasing assembly further comprises:
 a first spring having a first spring load;   a second spring having a second spring load; and   a control pin having a substantially T-shaped configuration with a first leg extending through the radial center of the first spring and a second leg located between the first spring and the second spring.   
     
     
         7 . The variable displacement vane pump of  claim 6 , wherein the first spring and the second spring are substantially coaxially aligned. 
     
     
         8 . The variable displacement vane pump of  claim 6 , wherein the second spring load of the second spring is greater than the first spring load of the first spring. 
     
     
         9 . The variable displacement vane pump of  claim 6 , wherein the pump control ring engages the first spring and the second spring engages the housing. 
     
     
         10 . The variable displacement vane pump of  claim 6 , further comprising:
 a spring chamber formed between the housing and the pump control ring, wherein the spring chamber has a maximum volume when the pump control ring is in the first position and a minimum volume when the pump control ring is in the third position.   
     
     
         11 . The variable displacement vane pump of  claim 10 , wherein the first spring, the second spring, and the control pin are disposed within the spring chamber. 
     
     
         12 . The variable displacement vane pump of  claim 11 , wherein the second spring engages the spring chamber. 
     
     
         13 . The variable displacement vane pump of  claim 6 , wherein the first spring and the second spring are compression springs. 
     
     
         14 . The variable displacement vane pump of  claim 13 , wherein the first compression spring and the second compression spring are substantially coaxially aligned, and the second spring load of the second compression spring is greater than the first spring load of the first compression spring. 
     
     
         15 . The variable displacement vane pump of  claim 14 , wherein the second leg of the control pin compresses the second compression spring when the pump control ring engages the first leg of the control pin. 
     
     
         16 . The variable displacement vane pump of  claim 15 , further comprising:
 a spring chamber formed between the housing and the pump control ring, wherein the spring chamber has a maximum volume when the pump control ring is in the first position and a minimum volume when the pump control ring is in the third position.   
     
     
         17 . The variable displacement vane pump of  claim 16 , wherein the first compression spring, the second compression spring, and the control pin are disposed within the spring chamber. 
     
     
         18 . The variable displacement vane pump of  claim 17 , wherein the second compression spring engages the spring chamber. 
     
     
         19 . A variable displacement vane pump having a housing with a pump chamber, the pump chamber having a fluid inlet, a fluid outlet, a pump control ring, and a vane pump rotor, the pump control ring disposed within the housing for altering the displacement of the pump by rotating between a first position that corresponds to a maximum volumetric capacity of the pump, a second position that corresponds to an intermediary volumetric capacity of the pump, and a third position that corresponds to a minimum volumetric capacity of the pump, the vane pump rotor rotatably mounted within the pump control ring and having a plurality of slidably mounted vanes engaging an inside surface of the pump control ring, the vane pump rotor having an axis of rotation eccentric from a center of the pump control ring, the vane pump rotor rotating to pressurize fluid as the fluid moves from the fluid inlet to the fluid outlet, comprising:
 a biasing assembly for urging the pump control ring toward the first position, wherein the biasing assembly applies a first biasing force to the pump control ring when the pump control ring is located between the first position and the second position and applies a second biasing force to the pump control ring when the pump control ring is located between the second position and the third position;   a control chamber formed between the housing and the pump control ring, wherein fluid pressure within the control chamber urges the pump control ring toward the third position;   a feedback path in communication with the fluid outlet supplying a pressurized fluid to the control chamber; and   a spring chamber formed between the housing and the pump control ring, wherein the spring chamber has a maximum volume when the pump control ring is in the first position and a minimum volume when the pump control ring is in the third position, and the biasing assembly is disposed within the spring chamber.   
     
     
         20 . The variable displacement vane pump of  claim 19 , wherein the biasing assembly further comprises:
 a first compression spring having a first spring load;   a second compression spring having a second spring load, wherein the second spring load of the second compression spring is greater than the first spring load of the first compression spring; and   a control pin having a substantially T-shaped configuration with a first leg extending through the radial center of the first compression spring and a second leg located between the first compression spring and the second compression spring, wherein the second leg of the control pin compresses the second compression spring when the pump control ring engages the first leg of the control pin.