Electric pump and fluid supply apparatus

Abstract

An electric pump includes a pump body, an intake port formed in the pump body, a discharge port formed in the pump body for discharging fluid pumped from the intake port, a rotor housed in the pump body, a brushless sensorless motor which rotates the rotor, and a mechanism for preventing losing synchronism of the brushless sensorless motor by controlling hydraulic pressure in the discharge port not to exceed a predetermined pressure.

1 . An electric pump comprising: 
 a pump body;    an intake port formed in the pump body;    a discharge port formed in the pump body for discharging fluid pumped from the intake port;    a rotor housed in the pump body;    a brushless sensorless motor which rotates the rotor; and    a mechanism for preventing losing synchronism of the brushless sensorless motor by controlling hydraulic pressure in the discharge port not to exceed a predetermined pressure.    
   
   
       2 . An electric pump according to  claim 1 , wherein the mechanism for preventing losing synchronism includes: 
 a cylinder having an opening portion at discharge side which is in communication with the discharge port and an opening portion at intake side which is in communication with the intake port; and    a piston configured to be biased towards the opening portion at the discharge side by means of a biasing member; wherein    the opening portion at the discharge side and the opening portion at the intake side are configured to establish a communication when the piston is displaced exceeding a predetermined position against the biasing force of the biasing member by means of hydraulic pressure from the discharge port.    
   
   
       3 . The electric pump according to  claim 2 , wherein the piston includes a communication passage including plural holes which establishes the communication between the opening 
 portion at the intake side and the opening portion at the discharge side when the piston is displaced exceeding the predetermined position against the biasing force of the biasing member.    
   
   
       4 . The electric pump according to  claim 1 , wherein the mechanism for preventing losing synchronism controls the hydraulic pressure in the discharge port by returning a part of fluid discharged from the discharge port to the intake port.  
   
   
       5 . The electric pump according to  claim 4 , wherein the mechanism for preventing losing synchronism includes: 
 a cylinder having an opening portion at discharge side which is in communication with the discharge port and an opening portion at intake side which is in communication with the intake port; and    a piston configured to be biased towards the opening portion at the discharge side by means of a biasing member; wherein    the opening portion at the discharge side and the opening portion at the intake side are configured to establish a communication when the piston is displaced exceeding a predetermined position against the biasing force of the biasing member by means of hydraulic pressure from the discharge port.    
   
   
       6 . The electric pump according to  claim 5 , wherein the piston includes a communication passage including plural holes which establishes the communication between the opening portion at the intake side and the opening portion at the discharge side when the piston is displaced exceeding the predetermined position against the biasing force of the biasing member.  
   
   
       7 . The electric pump according to  claim 1 , wherein the mechanism for preventing losing synchronism controls the hydraulic pressure in the discharge port by discharging the fluid discharged from the discharge port to outside of the pump body.  
   
   
       8 . The electric pump according to  claim 7 , wherein the mechanism for preventing losing synchronism includes: 
 a cylinder having an opening portion at discharge side which is in communication with the discharge port and an opening portion at intake side which is in communication with the intake port; and    a piston configured to be biased towards the opening portion at the discharge side by means of a biasing member; wherein    the opening portion at the discharge side and the opening portion at the intake side are configured to establish a communication when the piston is displaced exceeding a predetermined position against the biasing force of the biasing member by means of hydraulic pressure from the discharge port.    
   
   
       9 . The electric pump according to  claim 8 , the piston includes a communication passage including plural holes which establishes the communication between the opening portion at the intake side and the opening portion at the discharge side when the piston is displaced exceeding the predetermined position against the biasing force of the biasing member.  
   
   
       10 . A fluid supply apparatus comprising: 
 a first pump which pumps fluid from a fluid reservoir;    a first supply passage for conveying pumped fluid to a destination of the fluid to be supplied;    a relief valve provided on the first supply passage, the relief valve preventing an increase of fluid pressure in the first supply passage to be equal to or greater than a predetermined pressure;    an intake port which pumps fluid from either the fluid reservoir or a separately provided fluid reservoir;    an electric driven second pump having a discharge port for discharging pumped fluid;    a second supply passage merged with the first supply passage between the first pump and the relief valve;    a rotor provided on the second pump and electrically driven by a brushless sensorless motor; and    a mechanism for preventing losing synchronism of the brushless sensorless motor by controlling hydraulic pressure in the discharge port not to exceed a predetermined pressure value lower than operational pressure of the relief valve.    
   
   
       11 . The fluid supply apparatus according to  claim 10 , wherein the mechanism for preventing losing synchronism controls hydraulic pressure by returning the fluid discharged from the discharge port to the intake port.  
   
   
       12 . The fluid supply apparatus according to  claim 10 , wherein the mechanism for preventing losing synchronism controls hydraulic pressure by discharging the fluid discharged from the discharge port to outside of the second pump.