Variable Displacement Vane Pump

Abstract

A variable displacement vane pump has an inner peripheral face of a cam ring formed so that in a maximum eccentric state, a radius vector gradually shortens according to the rotation of a rotor in an area from a starting point of a first seal interval to an intermediate point of the first seal interval and an area from an intermediate point of a second seal interval to an end point of the second seal interval. The inner peripheral face of the cam ring is formed so that in a minimum eccentric state, the radius vector is substantially fixed or gradually lengthens according to the rotation of the rotor in other areas.

1 . A variable displacement vane pump for transmitting steering operation on a steering wheel to a steered wheel and supplying working fluid to a steering gear for a vehicle that generates steering assist force by hydraulic pressure of the working fluid, the variable displacement vane pump comprising:
 a pump housing provided with a pump element storage part;   a driving shaft journaled to the pump housing;   a rotor provided in the pump housing, rotatively driven by the driving shaft and provided with a plurality of slots in a circumferential direction;   a plurality of vanes provided in a freely projecting/retreating manner in the plurality of slots;   a cam ring annularly formed movably on/over the pump element storage part and forming a plurality of pump rooms together with the rotor and the plurality of vanes on an inner peripheral side; and   a cam ring control mechanism that is provided to the pump housing and controls eccentricity to the rotor of the cam ring, wherein:   the pump housing is provided with a suction port open to an area in which volume of the plurality of pump rooms increases according to rotation of the rotor and a discharge port open to an area in which the volume of the plurality of pump rooms decreases; and   an inner peripheral face of the cam ring is formed to be a state that in a maximum eccentric state that in which eccentricity to the rotor of the cam ring is maximum, a distance to the rotational center of the rotor gradually shortens according to the rotation of the rotor in at least one of an area from a termination of the suction port to an intermediate point of the termination of the suction port and a starting end of the discharge port and an area from an intermediate point of a termination of the discharge port and a starting end of the suction port to the starting end of the suction port in a rotational direction of the rotor, and the inner peripheral face of the cam ring is formed to be a state that in a minimum eccentric state in which the eccentricity to the rotor of the cam ring is minimum, the distance to the rotational center of the rotor is substantially fixed or gradually lengthens according to the rotation of the rotor in at least one of at least a part of an area from the intermediate point of the termination of the suction port and the starting end of the discharge port to the starting end of the discharge port and at least a part of an area from the termination of the discharge port to the intermediate point of the termination of the discharge port and the starting end of the suction port.   
     
     
         2 . The variable displacement vane pump according to  claim 1 , wherein:
 the driving shaft is rotatively driven by an engine of the vehicle; and   the inner peripheral face of the cam ring is formed to be a state that when the vehicle is run, the distance to the rotational center of the rotor is substantially fixed or gradually lengthens according to the rotation of the rotor in at least one of at least a part of the area from the intermediate point of the termination of the suction port and the starting end of the discharge port to the starting end of the discharge port and at least a part of the area from the termination of the discharge port to the intermediate point of the termination of the discharge port and the starting end of the suction port.   
     
     
         3 . The variable displacement vane pump according to  claim 1 , wherein:
 the driving shaft is rotatively driven by the engine of the vehicle; and   the inner peripheral face of the cam ring is formed to be a state that when engine speed is 1500 rpm or more every minute, the distance to the rotational center of the rotor is substantially fixed or gradually lengthens according to the rotation of the rotor in at least one of at least a part of the area from the intermediate point of the termination of the suction port and the starting end of the discharge port to the starting end of the discharge port and at least a part of the area from the termination of the discharge port to the intermediate port of the termination of the discharge port and the starting end of the suction port.   
     
     
         4 . The variable displacement vane pump according to  claim 1 , wherein:
 the inner peripheral face of the cam ring is formed to be a state that in the maximum eccentric state, at least one of the area from the termination of the suction port to the intermediate point of the termination of the suction port and the starting end of the discharge port and the area from the intermediate point of the termination of the discharge port and the starting end of the suction port to the starting end of the suction port and areas before and after at least the one that connect with at least the one are connected by a higher order curve; and   the inner peripheral face of the cam ring is formed to be a state that in the minimum eccentric state, at least one of the area from the intermediate point of the termination of the suction port and the starting end of the discharge port to the starting end of the discharge port and the area from the termination of the discharge port to the intermediate point of the termination of the discharge port and the starting end of the suction port and areas before and after at least the one that connect with at least the one are connected by the higher order curve.   
     
     
         5 . The variable displacement vane pump according to  claim 1 , wherein:
 the inner peripheral face of the cam ring is formed to be a state that in the minimum eccentric state, the distance to the rotational center of the rotor gradually lengthens according to the rotation of the rotor in at least one of at least a part of the area from the intermediate point of the termination of the suction port and the starting end of the discharge port to the starting end of the discharge port and at least a part of the area from the termination of the discharge port to the intermediate point of the termination of the discharge port and the starting end of the suction port.   
     
     
         6 . The variable displacement vane pump according to  claim 1 , wherein:
 the eccentricity to the rotor of the cam ring is controlled by swinging or rolling the cam ring in a state in which the cam ring is supported by a supporting face provided on a side of the discharge port of an inner peripheral face of the pump element storage part.   
     
     
         7 . The variable displacement vane pump according to  claim 6 , wherein:
 the center of an inside diameter of the cam ring is located on the side of the suction port apart from the center of the rotor in an unloaded condition in which differential pressure between pressure on the side of the suction port and pressure on the side of the discharge port does not act on the driving shaft, the rotor and the cam ring, and in a state in which the driving shaft is elastically deformed on the side of the suction port by the action of the differential pressure, a relative position of the center of the inside diameter of the cam ring to a port reference line is located on the side of the discharge port apart from a relative position in the unloaded condition;   the cam ring is rollably supported by a supporting face provided on the side of the discharge port of the inner peripheral face of the pump element storage part; and   the supporting face is formed to be a state that as the cam ring is rolled in a direction from the maximum eccentric state to the minimum eccentric state, the center of the inside diameter of the cam ring gradually separates on the side of the discharge port from the port reference line.   
     
     
         8 . The variable displacement vane pump according to  claim 1 , wherein:
 the inner peripheral face of the cam ring is formed to be a state that in the maximum eccentric state, the distance to the rotational center of the rotor gradually shortens according to the rotation of the rotor in the area from the termination of the suction port to the intermediate point of the termination of the suction port and the starting end of the discharge port in a rotational direction of the rotor; and   the inner peripheral face of the cam ring is formed to be a state that in the minimum eccentric state, the distance to the rotational center of the rotor is substantially fixed or gradually lengthens according to the rotation of the rotor in at least a part of the area from the intermediate point of the termination of the suction port and the starting end of the discharge port to the starting end of the discharge port.   
     
     
         9 . The variable displacement vane pump according to  claim 8 , wherein:
 the inner peripheral face of the cam ring is formed to be a state that in the maximum eccentric state, the distance to the rotational center of the rotor gradually shortens according to the rotation of the rotor in the area from the termination of the suction port to the intermediate point of the termination of the suction port and the starting end of the discharge port and in the area from the intermediate point of the termination of the discharge port and the starting end of the suction port to the starting end of the suction port in the rotational direction of the rotor; and   the inner peripheral face of the cam ring is formed to be a state that in the minimum eccentric state, the distance to the rotational center of the rotor is substantially fixed or gradually lengthens according to the rotation of the rotor in at least a part of the area from the intermediate point of the termination of the suction port and the starting end of the discharge port to the starting end of the discharge port and in at least a part of the area from the termination of the discharge port to the intermediate point of the termination of the discharge port and the starting end of the suction port.   
     
     
         10 . The variable displacement vane pump according to  claim 1 , wherein:
 the plurality of odd pieces of slots and the plurality of odd pieces of vanes are provided to the rotor.   
     
     
         11 . A variable displacement vane pump for transmitting steering operation on a steering wheel to a steered wheel and supplying working fluid to a steering gear for a vehicle that generates steering assist force by hydraulic pressure of the working fluid, the variable displacement vane pump comprising:
 a pump housing provided with a pump element storage part;   a driving shaft journaled to the pump housing;   a rotor provided in the pump housing, rotatively driven by the driving shaft and provided with a plurality of slots in a circumferential direction;   a plurality of vanes provided in a freely projecting/retreating manner in the plurality of slots;   a cam ring annularly formed movably on/over the pump element storage part and forming a plurality of pump rooms together with the rotor and the plurality of vanes on an inner peripheral side; and   a cam ring control mechanism that is provided to the pump housing and controls eccentricity to the rotor of the cam ring, wherein:   the pump housing is provided with a suction port open to an area in which volume of the plurality of pump rooms increases according to rotation of the rotor and a discharge port open to an area in which the volume of the plurality of pump rooms decreases; and   an inner peripheral face of the cam ring is formed to be a state that in a maximum eccentric state in which eccentricity to the rotor of the cam ring is maximum, a distance to the rotational center of the rotor gradually shortens according to the rotation of the rotor in at least one of an area from a termination of the suction port to a starting end of the discharge port in a rotational direction of the rotor and an area from a termination of the discharge port to a starting end of the suction port, and the inner peripheral face of the cam ring is formed to be a state that in a minimum eccentric state in which the eccentricity to the rotor of the cam ring is minimum, the distance to the rotational center of the rotor is substantially fixed or gradually lengthens according to the rotation of the rotor in at least one of at least a part of the area from the termination of the suction port to the starting end of the discharge port and at least a part of the area from the termination of the discharge port to the starting end of the suction port.   
     
     
         12 . The variable displacement vane pump according to  claim 11 , wherein:
 the driving shaft is rotatively driven by an engine of the vehicle; and   the inner peripheral face of the cam ring is formed to be a state that when the vehicle is run, the distance to the rotational center of the rotor is substantially fixed or gradually lengthens according to the rotation of the rotor in at least one of at least a part of the area from the termination of the suction port to the starting end of the discharge port and at least a part of the area from the termination of the discharge port to the starting end of the suction port.   
     
     
         13 . The variable displacement vent pump according to  claim 11 , wherein:
 the driving shaft is rotatively driven by the engine of the vehicle; and   the inner peripheral face of the cam ring is formed to be a state that when engine speed is 1500 rpm or more every minute, the distance to the rotational center of the rotor is substantially fixed or gradually lengthens according to the rotation of the rotor in at least one of at least a part of the area from the termination of the suction port to the starting end of the discharge port and at least a part of the area from the termination of the discharge port to the starting end of the suction port.   
     
     
         14 . The variable displacement vane pump according to  claim 11 , wherein:
 the eccentricity to the rotor of the cam ring is controlled by swinging or rolling the cam ring in a state in which the cam ring is supported by a supporting face provided on a side of the discharge port of an inner peripheral face of the pump element storage part.   
     
     
         15 . The variable displacement vane pump according to  claim 14 , wherein:
 the center of an inside diameter of the cam ring is located on the side of the suction port based upon a port reference line that joins an intermediate point of the termination of the suction port and the starting end of the discharge port and the center of the rotor in an unloaded condition in which differential pressure between pressure on the side of the suction port and pressure on the side of the discharge port does not act on the driving shaft, the rotor and the cam ring, and a relative position of the center of the inside diameter of the cam ring based upon the port reference line in a state in which the driving shaft is elastically deformed on the side of the suction port by the action of the differential pressure is located on the side of the discharge port apart from a relative position in the unloaded condition;   the cam ring is rollably supported by a supporting face provided on the side of the discharge port of the inner peripheral face of the pump element storage part; and   the supporting face is formed to be a state that as the cam ring is rolled in a direction from the maximum eccentric state to the minimum eccentric state, the center of the inside diameter of the cam ring gradually separates from the port reference line.   
     
     
         16 . A variable displacement vane pump for transmitting steering operation on a steering wheel to a steered wheel and supplying working fluid to a steering gear for a vehicle that generates steering assist force by the hydraulic pressure of the working fluid, the variable displacement vane pump comprising:
 a pump housing provided with a pump element storage part;   a driving shaft journaled to the pump housing;   a rotor provided in the pump housing, rotatively driven by the driving shaft and provided with a plurality of slots in a circumferential direction;   a plurality of vanes provided in a freely projecting/retreating manner in the plurality of slots;   a cam ring annularly formed movably on/over the pump element storage part and forming a plurality of pump rooms together with the rotor and the plurality of vanes on an inner peripheral side; and   a cam ring control mechanism that is provided to the pump housing and controls eccentricity to the rotor of the cam ring, wherein:   the pump housing is provided with a suction port open to an area in which volume of the plurality of pump rooms increases according to rotation of the rotor and a discharge port open to an area in which the volume of the plurality of pump rooms decreases; and   an inner peripheral face of the cam ring is formed to be a state that in a state in which the cam ring is relatively moved from the side of the suction port to the side of the discharge port by the action on the driving shaft, the rotor and the cam ring of differential pressure between pressure on the side of the suction port and pressure on the side of the discharge port, compared with an unloaded condition in which no differential pressure acts and in a maximum eccentric state in which the eccentricity to the rotor of the cam ring is maximum, a distance to the rotational center of the rotor gradually shortens according to the rotation of the rotor in at least one of an area from a termination of the suction port to a starting end of the discharge port and an area from a termination of the discharge port to a starting end of the suction port in a rotational direction of the rotor, and the inner peripheral face of the cam ring is formed to be a state that in a minimum eccentric state in which the eccentricity to the rotor of the cam ring is minimum, the distance to the rotational center of the rotor is substantially fixed or gradually lengthens according to the rotation of the rotor in at least one of at least a part of the area from the termination of the suction port to the starting end of the discharge port and at least a part of the area from the termination of the discharge port to the starting end of the suction port.   
     
     
         17 . The variable displacement vane pump according to  claim 16 , wherein:
 the driving shaft is rotatively driven by an engine of the vehicle; and   the inner peripheral face of the cam ring is formed to be a state that when the vehicle is run, the distance to the rotational center of the rotor is substantially fixed or gradually lengthens according to the rotation of the rotor in at least one of at least a part of the area from the termination of the suction port to the starting end of the discharge port and at least a part of the area from the termination of the discharge port to the starting end of the suction port.   
     
     
         18 . The variable displacement vane pump according to  claim 16 , wherein:
 the driving shaft is rotatively driven by the engine of the vehicle; and   the inner peripheral face of the cam ring is formed to be a state that when engine speed is 1500 rpm or more every minute, the distance to the rotational center of the rotor is substantially fixed or gradually lengthens according to the rotation of the rotor in at least one of at least a part of the area from the termination of the suction port to the starting end of the discharge port and at least a part of the area from the termination of the discharge port to the starting end of the suction port.   
     
     
         19 . The variable displacement vane pump according to  claim 16 , wherein:
 the eccentricity to the rotor of the cam ring is controlled by swinging or rolling the cam ring in a state in which the cam ring is supported by a supporting face provided on a side of the discharge port of an inner peripheral face of the pump element storage part.   
     
     
         20 . The variable displacement vane pump according to  claim 19 , wherein:
 the center of an inside diameter of the cam ring is located on the side of the suction port based upon a port reference line that joins an intermediate point of the termination of the suction port and the starting end of the discharge port and the center of the rotor in an unloaded condition in which differential pressure between pressure on the side of the suction port and pressure on the side of the discharge port does not act on the driving shaft, the rotor and the cam ring, and a relative position based upon the port reference line in a state in which the driving shaft is elastically deformed on the side of the suction port by the action of the differential pressure is located on the side of the discharge port apart from a relative position in the unloaded condition;   the cam ring is rollably supported by the supporting face provided on the side of the discharge port of the inner peripheral face of the pump element storage part; and   the supporting face is formed to be a state that the center of the inside diameter of the cam ring gradually separates from the port reference line as the cam ring is rolled in a direction from the maximum eccentric state to the minimum eccentric state.