Variable displacement vane pump and method of controlling the same

Abstract

A variable displacement vane pump includes: a cam ring defining first and second fluid pressure chambers on both sides thereof; and a rotor mounted inside the cam ring, the rotor defining an annular chamber outside thereof. Arranged outside of the rotor, vanes divide the annular chamber into a plurality of pump chambers. A suction port is defined in a section of the annular chamber in which each of the pump chambers expands with the rotation of the rotor, while a discharge port is defined in a section of the annular chamber in which each of the pump chambers contracts with the rotation of the rotor. A first fluid passage is connected to one of the first and second fluid pressure chambers. A second fluid passage is connected to one of the suction port and the discharge port. An electromagnetic valve controls fluid communication between the first and second fluid passages.

1 . A variable displacement vane pump comprising:
 a pump body;   a cam ring movably mounted within the pump body, the cam ring and the pump body defining first and second fluid pressure chambers therebetween, the first fluid pressure chamber having a volumetric capacity that increases when the cam ring moves toward a first end position, the second fluid pressure chamber having a volumetric capacity that increases when the cam ring moves toward a second end position;   a rotor mounted inside the cam ring at least for rotation about an axis in a direction, the rotor defining an annular chamber outside thereof;   a plurality of vanes arranged circumferentially at an outer radial periphery of the rotor for movement with the rotation of the rotor, the vanes extending radially and dividing the annular chamber into a plurality of pump chambers;   a suction port defined in a first section of the annular chamber in which each of the pump chambers expands with the rotation of the rotor;   a discharge port defined in a second section of the annular chamber in which each of the pump chambers contracts with the rotation of the rotor, the discharge port defining a third section of the annular chamber from the suction port to the discharge port along the direction of rotation of the rotor, the third section having a larger volumetric capacity when the cam ring is in the second end position than when the cam ring is in the first end position;   a first fluid passage hydraulically connected to one of the first and second fluid pressure chambers;   a second fluid passage hydraulically connected to one of the suction port and the discharge port; and   an electromagnetic valve hydraulically connected to the first and second fluid passages for controlling fluid communication therebetween.   
   
   
       2 . The variable displacement vane pump as claimed in  claim 1 , further comprising:
 a discharge passage downstream with respect to the discharge port, the discharge passage including an orifice; and   a control valve hydraulically connected to upstream and downstream portions of the discharge passage with respect to the orifice and hydraulically connected to one of the first and second fluid pressure chambers for controlling an internal pressure of the one of the first and second fluid pressure chambers.   
   
   
       3 . The variable displacement vane pump as claimed in  claim 2 , wherein:
 the second fluid pressure chamber is hydraulically connected to the suction port;   the control valve is hydraulically connected to the suction port; and   the control valve hydraulically connects the first fluid pressure chamber selectively to one of the suction port and the discharge port.   
   
   
       4 . The variable displacement vane pump as claimed in  claim 2 , wherein the control valve hydraulically connects the first fluid pressure chamber to the upstream portion of the discharge passage, and hydraulically connects the second fluid pressure chamber to the downstream portion of the discharge passage. 
   
   
       5 . The variable displacement vane pump as claimed in  claim 4 , wherein:
 the first fluid passage is hydraulically connected to the first fluid pressure chamber;   the second fluid passage is hydraulically connected to the discharge port; and   the electromagnetic valve controls fluid communication between the first fluid pressure chamber and the discharge port.   
   
   
       6 . The variable displacement vane pump as claimed in  claim 4 , wherein:
 the first fluid passage is hydraulically connected to the first fluid pressure chamber;   the second fluid passage is hydraulically connected to the suction port; and   the electromagnetic valve controls fluid communication between the first fluid pressure chamber and the suction port.   
   
   
       7 . The variable displacement vane pump as claimed in  claim 2 , wherein:
 the control valve is hydraulically connected to the suction port; and   the control valve hydraulically connects the second fluid pressure chamber selectively to one of the suction port and the discharge port.   
   
   
       8 . The variable displacement vane pump as claimed in  claim 7 , wherein:
 the first fluid passage is hydraulically connected to the second fluid pressure chamber;   the second fluid passage is hydraulically connected to the discharge port; and   the electromagnetic valve controls fluid communication between the second fluid pressure chamber and the discharge port.   
   
   
       9 . The variable displacement vane pump as claimed in  claim 2 , further comprising:
 a separator mounted in contact with the cam ring within the pump body, the separator defining a third fluid pressure chamber and the second fluid pressure chamber on both sides thereof, the third fluid pressure chamber having an internal pressure acting on the cam ring in a direction to move the cam ring toward the second end position; and   a third fluid passage hydraulically connected to the third fluid pressure chamber,   
     wherein the electromagnetic valve is hydraulically connected to the third fluid passage for controlling fluid communication through the third fluid passage. 
   
   
       10 . The variable displacement vane pump as claimed in  claim 1 , wherein the first fluid passage has an opening in one of axial end surfaces of the one of the first and second fluid pressure chambers. 
   
   
       11 . The variable displacement vane pump as claimed in  claim 10 , wherein the opening of the first fluid passage is defined in a position such that, when the cam ring is in any position between the first and second end positions, at least part of the opening is constantly open to the one of the first and second fluid pressure chambers. 
   
   
       12 . The variable displacement vane pump as claimed in  claim 1 , further comprising a fourth fluid passage hydraulically connects the electromagnetic valve to the discharge port, wherein the one of the suction port and the discharge port is the suction port, wherein the electromagnetic valve hydraulically connects the first fluid passage selectively to one of the second and fourth fluid passages. 
   
   
       13 . The variable displacement vane pump as claimed in  claim 12 , wherein the one of the first and second fluid pressure chambers is the first fluid pressure chamber. 
   
   
       14 . The variable displacement vane pump as claimed in  claim 12 , wherein the one of the first and second fluid pressure chambers is the second fluid pressure chamber. 
   
   
       15 . The variable displacement vane pump as claimed in  claim 12 , further comprising:
 a separator mounted in contact with the cam ring within the pump body, the separator defining a third fluid pressure chamber and the second fluid pressure chamber on both sides thereof, the third fluid pressure chamber having an internal pressure acting on the cam ring in a direction to move the cam ring toward the second end position; and   a third fluid passage hydraulically connecting the electromagnetic valve to the third fluid pressure chamber,   
     wherein the electromagnetic valve hydraulically connects the third fluid passage selectively to one of the second and fourth fluid passages. 
   
   
       16 . The variable displacement vane pump as claimed in  claim 1 , wherein the electromagnetic valve includes a valve mechanism disposed between the first and second fluid passages, and an electromagnetic actuator for controlling the valve mechanism. 
   
   
       17 . The variable displacement vane pump as claimed in  claim 16 , further comprising a suction passage defined within the pump body, and hydraulically connected to the suction port and an outside suction pipe, wherein the electromagnetic actuator is arranged close to the opening of the suction passage. 
   
   
       18 . The variable displacement vane pump as claimed in  claim 17 , wherein the electromagnetic actuator has a longitudinal axis perpendicular to the axis of the rotor. 
   
   
       19 . The variable displacement vane pump as claimed in  claim 16 , wherein the valve mechanism of the electromagnetic valve is closed when the electromagnetic actuator is subject to a malfunction. 
   
   
       20 . The variable displacement vane pump as claimed in  claim 19 , wherein the valve mechanism of the electromagnetic valve is closed when the electromagnetic actuator is de-energized. 
   
   
       21 . The variable displacement vane pump as claimed in  claim 1 , further comprising:
 a drive shaft rotatably supported on the pump body and mechanically coupled to the rotor for rotation with the rotation of the rotor;   a seal disposed radially outside of the cam ring, the seal defining the first and second fluid pressure chambers on both sides thereof;   a first member mounted within the pump body and disposed at an axial end of the cam ring; and   a second member mounted within the pump body and disposed at another axial end of the cam ring,   
     wherein:
 the rotor includes a plurality of slots arranged circumferentially at the outer radial periphery of the rotor, each of the slots extending radially and accommodating a respective one of the vanes for allowing longitudinal movement thereof; 
 the suction port is defined in one of the first and second members; 
 the discharge port is defined in one of the first and second members; and 
 the electromagnetic valve controls fluid communication between the first fluid pressure chamber and the discharge port and between the second fluid pressure chamber and one of the suction port and the discharge port. 
 
   
   
       22 . A variable displacement vane pump comprising:
 a pump body;   a cam ring movably mounted within the pump body, the cam ring and the pump body defining first and second fluid pressure chambers therebetween, the first fluid pressure chamber having a volumetric capacity that increases when the cam ring moves toward a first end position, the second fluid pressure chamber having a volumetric capacity that increases when the cam ring moves toward a second end position;   a rotor mounted inside the cam ring at least for rotation about an axis in a direction, the rotor defining an annular chamber outside thereof;   a plurality of vanes arranged circumferentially at an outer radial periphery of the rotor for movement with the rotation of the rotor, the vanes extending radially and dividing the annular chamber into a plurality of pump chambers;   a suction port defined in a first section of the annular chamber in which each of the pump chambers expands with the rotation of the rotor;   a discharge port defined in a second section of the annular chamber in which each of the pump chambers contracts with the rotation of the rotor, the discharge port defining a third section of the annular chamber from the suction port to the discharge port along the direction of rotation of the rotor, the third section having a larger volumetric capacity when the cam ring is in the second end position than when the cam ring is in the first end position;   a separator mounted in contact with the cam ring within the pump body, the separator defining a third fluid pressure chamber and the second fluid pressure chamber on both sides thereof, the third fluid pressure chamber having an internal pressure acting on the cam ring in a direction to move the cam ring toward the second end position;   a third fluid passage hydraulically connected to the third fluid pressure chamber; and   a first valve hydraulically connected to the third fluid passage for controlling fluid communication through the third fluid passage.   
   
   
       23 . The variable displacement vane pump as claimed in  claim 22 , further comprising:
 a second fluid passage hydraulically connected to the suction port; and   a fifth fluid passage hydraulically connecting the third fluid pressure chamber to the discharge port,   
     wherein the first valve is hydraulically connected to the second fluid passage for controlling fluid communication between the second and third fluid passages. 
   
   
       24 . The variable displacement vane pump as claimed in  claim 22 , further comprising a fourth fluid passage hydraulically connected to the discharge port, wherein the first valve is hydraulically connected to the fourth fluid passage for controlling fluid communication between the third and fourth fluid passages. 
   
   
       25 . A method of controlling a variable displacement vane pump for a vehicle, the variable displacement vane pump comprising: a pump body; a cam ring movably mounted within the pump body, the cam ring defining at least a pump chamber and a first fluid pressure chamber having an internal pressure acting on the cam ring; a suction port; a discharge port; a discharge passage downstream with respect to the discharge port, the discharge passage including an orifice; a control valve for controlling the internal pressure of the first fluid pressure chamber, the control valve operating in response to pressures from upstream and downstream portions of the discharge passage with respect to the orifice; an electromagnetic valve for controlling fluid communication among the first fluid pressure chamber, the suction port and the discharge port, the method comprising:
 adjusting the controlled internal pressure of the first fluid pressure chamber in accordance with an operating state of the vehicle by the electromagnetic valve.   
   
   
       26 . The method as claimed in  claim 25 , further comprising closing the electromagnetic valve during a failed condition thereof.