Vane pump including outer side plate defining high and low pressure notch grooves of differing lengths adjacent the high and low discharge ports for improved noise performance

1. A vane pump comprising:

a rotor which is connected to a rotating shaft pivoted to an inner portion of a housing so as to rotate;

a cam ring which is arranged in such a manner as to surround the rotor in the inner portion of the housing, said cam ring being fixed with respect to the housing;

a plurality of movingly rotatable vanes which are slidably arranged in a plurality of vane grooves provided in a radial direction of the rotor;

a plurality of pump chambers which are defined by the adjacent vanes around the rotor;

a high pressure discharge port and a low pressure discharge port defined in said cam ring corresponding to the pump chambers carrying out a compression stroke, the high pressure discharge port being opposingly disposed from the low pressure discharge port along a diameter direction of the rotor; and

a high pressure notch groove and a low pressure notch groove defined in an outer side plate of the vane pump, the high pressure notch groove extending in a direction away from an edge of the high pressure discharge port and the low pressure notch groove extending in a direction away from an edge of the low pressure discharge port,

a length of the high pressure notch groove is greater than a length of the low pressure notch groove, and a first vane and a second vane of the plurality of movingly rotatable vanes are respectively positioned on opposite portions of the rotor so as to be opposed one-to-another along the diameter direction of the rotor, the rotor having two positions during operation of the vane pump, a first unshifted position and a second shifted position, the shifting occurring due to a force applied to the rotor resulting from differing pressures occurring respectively at the high pressure discharge port and the low pressure discharge port as the vane pump transitions from a static state to an operating state, and when the rotor is disposed in the second shifted position the center of the rotor is disposed closer to the low pressure discharge port on the side of the vane pump having the low discharge pressure, wherein when the rotor is disposed in said second shifted position said first vane of the plurality of movingly rotatable vanes encounters a leading end of the high pressure notch groove at the high pressure discharge port in a side of the vane pump having the high discharge pressure in a rotation direction of the rotor at the same moment at which said second vane of the plurality of movingly rotatable vanes encounters a leading end of the low pressure notch groove at the low pressure discharge port in a side of the vane pump having the low discharge pressure in the rotation direction of the rotor.

2. The vane pump according to claim 1 , wherein the high pressure notch groove and the low pressure notch groove are V-shaped, respectively, and the open end of the V-shape of the high pressure notch groove is disposed adjacent the edge of the high pressure discharge port and the open end of the V-shape of the low pressure notch groove is disposed adjacent the edge of the low pressure discharge port.

3. The vane pump according to claim 2 , wherein the different respective lengths of said V-shaped high pressure notch groove and said V-shaped low pressure notch groove correspond to an amount of a play between the rotating shaft and the rotor manifested from a pressure difference of a discharge pressure between the high pressure discharge port and the low pressure discharge port.

4. The vane pump according to claim 3 , wherein the vane pump is a fixed displacement vane pump.

5. The vane pump according to claim 2 , wherein the vane pump is a fixed displacement vane pump.

6. The vane pump according to claim 1 , wherein the vane pump is a fixed displacement vane pump.