Pump device

Abstract

A pump device includes: a main pump and a sub pump; and a switching valve that switches so as to supply the hydraulic oil discharged from the sub pump to the hydraulic device, or to return the hydraulic oil discharged from the sub pump to the suction side. The main pump and the sub pump each include: a rotor, a discharge port into which the hydraulic oil discharged from a pump chamber is led, and a groove-shaped discharge-side notch formed from an opening edge of the discharge port toward a direction opposite to a rotation direction of the rotor. The switching valve switches according to a rotation speed of the drive shaft. At least one discharge-side notch of the sub pump is formed so that a resistance applied to the flow of the hydraulic oil passing therethrough is greater than that of the discharge-side notch of the main pump.

1 . A pump device for supplying working fluid to a fluid pressure device, the pump device comprising:
 a main pump configured to supply the working fluid to the fluid pressure device through a first discharge passage;   a sub pump configured to supply the working fluid to the fluid pressure device through a second discharge passage that joins with the first discharge passage;   a return passage configured to return the working fluid discharged from the sub pump to a suction side; and   a switching valve configured to switch regarding whether or not to return the working fluid discharged from the sub pump to the suction side through the return passage,   wherein the main pump and the sub pump each comprise:
 a rotor connected to a common drive shaft; 
 a plurality of vanes provided so as to be capable of reciprocating in a radial direction relative to the rotor; 
 a cam ring having an inner peripheral surface, wherein distal ends of the vanes being configured to be in sliding contact with the inner peripheral surface in accordance with rotation of the rotor; 
 pump chambers defined by the rotor, the cam ring, and adjacent pair of the vanes; 
 a discharge port into which the working fluid discharged from the pump chamber is led; and 
 a groove-shaped discharge-side notch formed from an opening edge of the discharge port toward a direction opposite to a rotation direction of the rotor, 
   wherein the switching valve is configured to switch according to a rotation speed of the drive shaft, and   wherein at least one discharge-side notch of the sub pump is formed so that a resistance applied to the flow of the working fluid passing therethrough is greater than that of the discharge-side notch of the main pump.   
     
     
         2 . The pump device according to  claim 1 , wherein the main pump and the sub pump each further comprise a suction port configured to lead the working fluid to the pump chamber,
 and an opening area of the discharge-side notch of the sub pump at a position separated from a reference position by a predetermined angle is formed to be smaller than an opening area of the discharge-side notch of the main pump at a position separated from the reference position by a predetermined angle, the reference position being a position of the vane that is on the front side in the rotation direction among the pair of vanes that define the pump chamber when communication between the pump chamber and the discharge port is blocked in accordance with the rotation of the rotor.   
     
     
         3 . The pump device according to  claim 1 , wherein the main pump and the sub pump each further comprise a groove-shaped suction-side notch formed from an opening edge of the suction port toward the direction opposite to the rotation direction of the rotor, the suction port being configured to lead the working fluid to the pump chamber,
 wherein at least one suction-side notch of the sub pump is formed so that a resistance applied to the flow of the working fluid passing therethrough is greater than that of the suction-side notch of the main pump.   
     
     
         4 . The pump device according to  claim 1 , wherein the switching valve configured to switch so as to return the working fluid to the suction side through the return passage when the rotation speed of the drive shaft is at or above a predetermined pump rotation speed.