Pump device

Abstract

A pump device includes a pump, a flow control valve having a spool that returns a part of working fluid discharged from the pump to a suction side, and a differential pressure adjusting device that adjusts a differential pressure acting on both end portions of the spool to a target differential pressure, and the differential pressure adjusting device includes a pressure regulating chamber that communicates with a second fluid pressure chamber and a pilot chamber into which pressure in the discharge channel is guided: and a pressure in the pressure regulating chamber is adjusted such that a differential pressure between the pressure in the pressure regulating chamber and a pressure in the pilot chamber becomes the target differential pressure.

1 . A pump device for supplying working fluid to a fluid pressure apparatus comprising:
 a pump configured to discharge the working fluid into a discharge channel by sucking and pressurizing the working fluid;   a flow control valve having a first valve body configured to operate in accordance with a differential pressure acting on both end portions thereof to return a part of the working fluid discharged from the pump to a suction side; and   a differential pressure adjusting device configured to adjust the differential pressure acting on both end portions of the first valve body to a target differential pressure; wherein   the flow control valve comprises:   a first fluid pressure chamber provided so as to face against a first-side end portion of the first valve body, the first fluid pressure chamber communicating with the discharge channel;   a second fluid pressure chamber provided so as to face against a second-side end portion of the first valve body, the second fluid pressure chamber communicating with the discharge channel; and   a biasing member accommodated in the second fluid pressure chamber in a compressed state, the biasing member being configured to bias the first valve body in a valve-closing direction; and   the differential pressure adjusting device has:   a second valve body;   a pressure regulating chamber provided so as to face against a first-side end portion of the second valve body, the pressure regulating chamber communicating with the second fluid pressure chamber; and   a pilot chamber provided so as to face against a second-side end portion of the second valve body, a pressure in the discharge channel being guided into the pilot chamber; and wherein   a pressure in the pressure regulating chamber is adjusted such that a differential pressure between the pressure in the pressure regulating chamber and a pressure in the pilot chamber becomes the target differential pressure.   
     
     
         2 . The pump device according to  claim 1 , wherein
 the pump device further comprises   an orifice provided in a communicating passage that allows the discharge channel to communicate with the second fluid pressure chamber.   
     
     
         3 . The pump device according to  claim 1 , wherein
 the differential pressure adjusting device further comprises:   a biasing member accommodated in the pressure regulating chamber in a compressed state, the biasing member being configured to bias the second valve body in a valve-opening direction; and   a proportional solenoid configured to bias the second valve body in the valve-closing direction, the proportional solenoid being capable of changing the biasing force biasing the second valve body in the valve-closing direction.   
     
     
         4 . The pump device according to  claim 1 , wherein
 the target differential pressure is adjusted in accordance with a rotation speed of the pump.   
     
     
         5 . The pump device according to  claim 1 , wherein
 the target differential pressure is adjusted in accordance with pressure required by the fluid pressure apparatus.