Variable displacement vane pump

Abstract

A variable displacement vane pump includes a pump housing, a drive shaft supported in the pump housing, a rotor rotated by the drive shaft, a plurality of vanes mounted to the rotor, a cam ring disposed movably around the pump element and a pressure plate arranged facing the rotor and the cam ring. The pressure plate has formed therein a discharge hole and a drive shaft insertion hole. The pump housing has formed therein a suction hole, a high-pressure chamber and a low-pressure chamber. The variable displacement vane pump further includes a first seal member disposed on a pressure receiving surface of the pressure plate so as to separate the drive shaft insertion hole from the high-pressure chamber and a second seal member disposed on the pressure receiving surface of the pressure plate so as to separate the low-pressure chamber from the high-pressure chamber and the drive shaft insertion hole.

What is claimed is: 
     
         1 . A variable displacement vane pump for supplying a hydraulic fluid from a fluid reservoir, comprising:
 a pump housing provided with a pump element storage part;   a drive shaft supported rotatably in the pump housing;   a pump element placed in the pump element storage part, the pump element comprising: a rotor rotated by the drive shaft and having a plurality of slots formed therein at positions in a circumferential direction around a rotation axis of the rotor; and a plurality of vanes retractably mounted in the respective slots;   an annular cam ring disposed movably around the pump element in the pump element storage part, thereby defining a plurality of pump chambers by the rotor, the vanes and the cam rings; and   a pressure plate arranged in the pump element storage part, with the driving shaft being inserted through a drive shaft insertion hole of the pressure plate in an axial direction along the rotation axis of the rotor, and having a rotor-side surface facing the rotor and the cam ring and a pressure receiving surface opposite the rotor-side surface,   the pressure plate defining a discharge hole extending therethrough in the axial direction and open to a discharge area in which the pump chambers decrease in volume with rotation of the rotor,   the pump housing defining: a suction hole open to a suction area in which the pump chambers increase in volume with rotation of the rotor; a suction passage connecting the suction port to the fluid reservoir; a high-pressure chamber located at a position facing the pressure receiving surface of the pressure plate and adapted to allow introduction of a discharge pressure thereto through the discharge port and bias the pressure plate toward the rotor and the cam ring by the action of the discharge pressure; and a low-pressure chamber located at a position corresponding to the suction area in the circumferential direction and adapted to allow introduction of a suction pressure thereto, and   the variable displacement vane pump further comprising:   an annular first seal member disposed on the pressure receiving surface of the pressure plate so as to surround the drive shaft insertion hole and separate the drive shaft insertion hole from the high-pressure chamber; and   an annular second seal member disposed on the pressure receiving surface of the pressure plate so as to surround the suction area and separate the suction area from the high-pressure chamber and the drive shaft insertion hole.   
     
     
         2 . The variable displacement vane pump according to  claim 1 ,
 wherein the pump element storage part is in communication with the outside of the pump housing through a clearance between the pump housing and the drive shaft.   
     
     
         3 . The variable displacement vane pump according to  claim 2 ,
 wherein the pump housing has a drain passage formed therein so as to allow therethrough the hydraulic fluid leaked to the vicinity of the drive shaft to be drained to the outside of the pump housing.   
     
     
         4 . The variable displacement vane pump according to  claim 3 ,
 wherein an outer end of the fluid drain passage is situated vertically below an inner end of the fluid drain passage.   
     
     
         5 . The variable displacement vane pump according to  claim 1 ,
 wherein the pump housing comprises:   a first housing body having a cup shape including a cylindrical portion and a bottom portion formed integral with the cylindrical portion so as to close one end of the cylindrical portion; and   a second housing body fixed to the first housing body so as to close the other end of the cylindrical portion; and   wherein an outer end of the suction passage is open at the cylindrical portion of the first housing body.   
     
     
         6 . The variable displacement vane pump according to  claim 1 ,
 wherein the suction passage is brought into communication with the suction area from both sides in the axial direction; and   wherein the pump housing has a lubrication groove formed therein at a position opposite the pressure plate with respect to the rotor and facing the rotor so as to allow introduction of the discharge pressure thereto.   
     
     
         7 . The variable displacement vane pump according to  claim 1 ,
 wherein the first and second seal members are formed as separate pieces.   
     
     
         8 . The variable displacement vane pump according to  claim 7 ,
 wherein the pump housing has a high-pressure introduction groove formed therein at a position between the first and second seal members so as to allow introduction of the discharge pressure thereto.   
     
     
         9 . The variable displacement vane pump according to  claim 7 ,
 wherein the pump housing has, formed therein, first and second seal grooves in which the first and second seal members are fitted, respectively.   
     
     
         10 . The variable displacement vane pump according to  claim 7 ,
 wherein the pump housing has, formed therein, first and second seal grooves in which the first and second seal members are fitted, respectively; and   wherein the first and second seal grooves are continuous at adjacent parts thereof with each other.   
     
     
         11 . The variable displacement vane pump according to  claim 11 ,
 wherein the first and second seal members are formed integral with each other.   
     
     
         12 . The variable displacement vane pump according to  claim 11 ,
 wherein the first seal member is formed such that the size of a low-pressure region between the first insertion hole and the drive shaft insertion hole in the circumferential direction is larger in the discharge area than in the suction area.   
     
     
         13 . The variable displacement vane pump according to  claim 11 , further comprises a plane bearing disposed around the drive shaft,
 wherein the plane bearing has a helical groove formed in an inner circumferential surface thereof so as to allow therethrough the hydraulic fluid between the plane bearing and the drive shaft to be fed away from the pump element storage part by relative rotation of the drive shaft and the plane bearing.   
     
     
         14 . A variable displacement vane pump for supplying a hydraulic fluid from a fluid reservoir, comprising:
 a pump housing provided with a pump element storage part;   a drive shaft supported rotatably in the pump housing and driven by an engine of a vehicle;   a pump element placed in the pump element storage part, the pump element comprising: a rotor rotated by the drive shaft and having a plurality of slots formed at positions in a circumferential direction around a rotation axis of the rotor;   and a plurality of vanes retractably mounted in the respective slots;   an annular cam ring disposed movably around the pump element in the pump element storage part, thereby defining a plurality of pump chambers by the rotor, the vanes and the cam ring; and   a pressure plate arranged in the pump element storage part, with the drive shaft being inserted through a drive shaft insertion hole of the pressure plate in an axial direction along the rotation axis of the rotor, and having a rotor-side surface facing the rotor and the cam ring and a pressure receiving surface opposite the rotor-side surface,   the pressure plate defining a discharge hole extending therethrough in the axial direction at a position vertically above the drive shaft and open to a discharge area in which the pump chambers decrease in volume with rotation of the rotor,   the pump housing defining: a suction hole extending at a position vertically below the drive shaft and open to a suction area in which the pump chambers increase in volume with rotation of the rotor; a suction passage connecting the suction port to the fluid reservoir; a high-pressure chamber located at a position facing the pressure receiving surface of the pressure plate and adapted to allow introduction of a discharge pressure thereto through the discharge port and bias the pressure plate toward the rotor and the cam ring by the action of the discharge pressure; and a low-pressure chamber located at a position corresponding to the suction area in the circumferential direction and adapted to allow introduction of a suction pressure thereto, and   the variable displacement vane pump further comprising:   an annular drive-shaft-side seal member disposed on the pressure receiving surface of the pressure plate so as to surround the drive shaft insertion hole and separate the drive shaft insertion hole from the high-pressure chamber; and   an annular low-pressure-chamber-side seal member disposed on the pressure receiving surface of the pressure plate so as to surround the suction area and separate the suction area from the high-pressure chamber and the drive shaft insertion hole.   
     
     
         15 . The variable displacement vane pump according to  claim 14 ,
 wherein the pump element storage part is in communication with the outside of the pump housing through a clearance between the pump housing and the drive shaft.   
     
     
         16 . The variable displacement vane pump according to  claim 15 ,
 wherein the pump housing has a drain passage formed therein so as to allow therethrough the hydraulic fluid leaked to the vicinity of the drive shaft to be drained to the outside of the pump housing.   
     
     
         17 . The variable displacement vane pump according to  claim 16 ,
 wherein an outer end of the fluid drain passage is situated vertically below an inner end of the fluid drain passage.   
     
     
         18 . The variable displacement vane pump according to  claim 14 ,
 wherein the pump housing comprises:   a first housing body having a cup shape including a cylindrical portion and a bottom portion formed integral with the cylindrical portion so as to close one end of the cylindrical portion; and   a second housing body fixed to the first housing body so as to close the other end of the cylindrical portion; and   wherein an outer end of the suction passage is open at the cylindrical portion of the first housing body.   
     
     
         19 . The variable displacement vane pump according to  claim 14 ,
 wherein the suction passage is brought into communication with the suction area from both sides in the axial direction; and   wherein the pump housing has a lubrication groove formed therein at a position opposite the pressure plate with respect to the rotor and facing the rotor so as to allow introduction of the discharge pressure thereto.   
     
     
         20 . The variable displacement vane pump according to  claim 14 ,
 wherein the drive-shaft-side seal member and the low-pressure-chamber-side seal member are formed as separate pieces.