Vane pump

Abstract

A vane pump includes: a rotor with slots; vanes mounted in the slots, and adapted to project from the slots; a cam ring surrounding the rotor; and a plate defining pump chambers in cooperation with the rotor, vanes and cam ring. The plate includes: a suction port; a discharge port; a first back pressure port that receives a suction-side fluid pressure, and hydraulically communicates with a first back pressure chamber corresponding to a first vane positioned in a suction region; and a second back pressure port that hydraulically communicates with a second back pressure chamber corresponding to a second vane whose distal end portion is positioned at a terminal end portion of the suction port. The second back pressure port includes: a first portion arranged to receive a discharge-side fluid pressure; and a throttling portion for restricting a fluid flow between the first portion and second back pressure chamber.

1 . A vane pump comprising:
 a rotor adapted to be rotated by a drive shaft, the rotor including a plurality of slots at an outside periphery of the rotor;   a plurality of vanes mounted in corresponding ones of the slots, and adapted to project from, and travel inwards and outwards of the corresponding slots;   a cam ring adapted to be eccentric with respect to the rotor, the cam ring surrounding the rotor; and   a plate arranged to face an axial end of the rotor, and define a plurality of pump chambers in cooperation with the rotor, the vanes, and the cam ring, wherein the plate includes at a side facing the rotor:
 a suction port opened in a suction region in which each pump chamber gradually expands while moving along with rotation of the rotor; 
 a discharge port opened in a discharge region in which each pump chamber gradually contracts while moving along with rotation of the rotor; 
 a first back pressure port arranged to receive a suction-side fluid pressure, and hydraulically communicate with a proximal end portion of at least a first one of the slots corresponding to a first one of the vanes positioned in the suction region; and 
 a second back pressure port arranged to hydraulically communicate with a proximal end portion of at least a second one of the slots corresponding to a second one of the vanes whose distal end portion is positioned at a terminal end portion of the suction port, wherein the second back pressure port includes:
 a first portion arranged to receive a discharge-side fluid pressure; and 
 a throttling portion arranged to restrict a flow of fluid between the first portion and the proximal end portion of the second slot. 
 
   
     
     
         2 . The vane pump as claimed in  claim 1 , wherein the throttling portion has a cross-sectional flow area that is substantially constant as followed in a direction of rotation of the rotor. 
     
     
         3 . The vane pump as claimed in  claim 1 , wherein the throttling portion has a cross-sectional flow area that increases as followed in a direction of rotation of the rotor. 
     
     
         4 . The vane pump as claimed in  claim 1 , wherein the throttling portion has a cross-sectional flow area that decreases as followed in a direction of rotation of the rotor. 
     
     
         5 . The vane pump as claimed in  claim 1 , wherein:
 the second vane is behind in a direction of rotation of the rotor and adjacent to a third one of the vanes whose distal end portion is positioned between a terminal end of the suction port and a beginning end of the discharge port; and   the second back pressure port is arranged to supply the proximal end portion of the second slot at least with an amount of working fluid, during a period before the second vane passes through the terminal end of the suction port after the proximal end portion of the second slot starts to hydraulically communicate with the second back pressure port, wherein the amount of working fluid is sufficient to bring the distal end portion of the second vane into contact with an inside peripheral surface of the cam ring.   
     
     
         6 . The vane pump as claimed in  claim 1 , wherein:
 each of the vanes extends in a radial direction of the rotor; and   the second back pressure port overlaps with the suction port in a circumferential direction of the plate.   
     
     
         7 . The vane pump as claimed in  claim 1 , wherein the throttling portion has a cross-sectional flow area that changes as followed in a direction of rotation of the rotor. 
     
     
         8 . The vane pump as claimed in  claim 7 , wherein the cross-sectional flow area of the throttling portion changes with a change in depth of the throttling portion. 
     
     
         9 . The vane pump as claimed in  claim 1 , wherein the throttling portion has a smaller depth than the first portion.