Adaptive pivot for variable displacement vane pump

Abstract

Variable displacement pumps and methods of pumping a fluid are provided. An example pump may include a housing having an inlet and an outlet, a rotor fixed for rotation with a shaft, the shaft rotatably mounted within the housing, and a plurality of radially extending vanes slidably disposed in the rotor. The pump may further include a pivotable ring member defining at least in part a control chamber about the rotor, wherein the ring member is pivotable within the housing to vary an eccentricity of the ring member with respect to the rotor. The ring member is configured to shift a pivot position of the ring member from a first pivot position to a second pivot position displaced from the first pivot position.

What is claimed is: 
     
         1 . A variable displacement pump, comprising:
 a housing having an inlet and an outlet;   a rotor fixed for rotation with a shaft, the shaft rotatably mounted within the housing;   a plurality of radially extending vanes slidably disposed in the rotor; and   a pivotable ring member defining at least in part a control chamber about the rotor, wherein the ring member is pivotable within the housing to vary an eccentricity of the ring member with respect to the rotor, wherein the ring member is configured to shift a pivot position of the ring member from a first pivot position to a second pivot position displaced from the first pivot position.   
     
     
         2 . The pump of  claim 1 , further comprising a resilient element engaged with the ring member, thereby biasing the ring member in a first pivot direction opposed to a second pivot direction, the control chamber positioned such that an external pressure introduced into the control chamber applies a force to the ring member tending to pivot the ring member in the second pivot direction. 
     
     
         3 . The pump of  claim 1 , wherein the radially extending vanes define one or more vane chambers configured to develop pressure during operation of the pump, the pressure in the one or more vane chambers imparting a force to the ring member offset from a pivot pin of the ring member by an offset distance, wherein the pivot position is shiftable to reduce the offset distance. 
     
     
         4 . The pump of  claim 1 , further comprising a pivot pin configured to define the first and second pivot positions. 
     
     
         5 . The pump of  claim 4 , further comprising a pivot anchor fixed to the ring member. 
     
     
         6 . The pump of  claim 1 , wherein the housing defines at least first and second undulations corresponding to the first and second pivot positions of the ring member, respectively. 
     
     
         7 . The pump of  claim 1 , further comprising a cam rotatably fixed within the housing. 
     
     
         8 . The pump of  claim 7 , wherein the cam defines the first pivot position of the ring member when placed in a first rotational position, and the cam defines the second pivot position of the ring member when rotated from the first rotational position to a second rotational position. 
     
     
         9 . A variable displacement pump, comprising:
 a housing having an inlet and an outlet;   a rotor fixed for rotation with a shaft, the shaft rotatably mounted within the housing;   a plurality of radially extending vanes slidably disposed in the rotor;   a pivotable ring member defining at least in part a control chamber about the rotor, wherein the ring member is pivotable within the housing to vary an eccentricity of the ring member with respect to the rotor, wherein the ring member is configured to shift a pivot position of the ring member from a first pivot position to a second pivot position displaced from the first pivot position; and   a resilient element engaged with the ring member, thereby biasing the ring member in a first pivot direction about the first and second pivot positions.   
     
     
         10 . The pump of  claim 9 , wherein the radially extending vanes define one or more vane chambers configured to develop pressure during operation of the pump, the pressure in the one or more vane chambers imparting a force to the ring member offset from a pivot pin of the ring member by an offset distance, wherein the pivot position is shiftable to reduce the offset distance. 
     
     
         11 . The pump of  claim 9 , further comprising a pivot pin configured to define the first and second pivot positions. 
     
     
         12 . The pump of  claim 9 , wherein the housing defines first and second undulations corresponding to the first and second pivot positions of the ring member, respectively. 
     
     
         13 . The pump of  claim 9 , further comprising a cam rotatably fixed within the housing. 
     
     
         14 . A method of pumping a fluid, comprising:
 providing a housing having an inlet and an outlet;   rotatably mounting a rotor within the housing upon a shaft;   positioning a plurality of radially extending vanes in the rotor, the vanes each slidably disposed in the rotor;   defining a control chamber about the rotor with a pivotable ring member, wherein the ring member is pivotable within the housing to vary an eccentricity of the ring member with respect to the rotor; and   shifting a pivot position of the ring member from a first pivot position to a second pivot position displaced from the first pivot position.   
     
     
         15 . The method of  claim 14 , further comprising biasing the ring member in a first pivot direction by engaging the ring member with a resilient element. 
     
     
         16 . The method of  claim 14 , wherein the radially extending vanes define one or more vane chambers configured to develop pressure during operation of the pump, the pressure in the one or more vane chambers imparting a force to the ring member offset from a pivot pin of the ring member by an offset distance; and
 wherein shifting the pivot position reduces the offset distance.   
     
     
         17 . The method of  claim 16 , wherein the offset is eliminated by the reduction in the offset distance. 
     
     
         18 . The method of  claim 14 , wherein shifting the pivot position includes shifting a pivot pin within the housing. 
     
     
         19 . The method of  claim 14 , further comprising providing first and second undulations in the housing corresponding to the first and second pivot positions of the ring member, respectively. 
     
     
         20 . The method of  claim 14 , further comprising providing a cam rotatably fixed within the housing, wherein the pivot position is shifted by rotating the cam.