Electric pump unit

Abstract

A pump body is formed of a pump housing and a pump plate provided in front of the pump housing. A motor housing is fixed to a rear end of the pump housing, and accommodates a pump driving electric motor. A bearing device that supports a motor shaft includes a first bearing that is arranged in a closed-end hole formed in a rear face of the pump plate and supporting a front end portion of the motor shaft, and a second bearing that is arranged radially inward of a cylindrical bearing support portion formed in the pump housing and extending inside the motor housing and that supports a middle portion of the motor shaft. A pump rotor is arranged between the first bearing and the second bearing.

1 . An electric pump unit, comprising:
 a pump body of a pump that sucks in and discharges fluid, wherein the pump body includes a pump housing and a pump plate, the pump housing forms a pump chamber that accommodates a pump rotor, and the pump plate is provided at one end of the pump housing;   a motor housing that is fixed to the other end of the pump housing and that accommodates a pump driving electric motor; and   the electric motor that includes a motor shaft that is supported by a bearing device and that rotates the pump rotor, a motor rotor that is fixed to a motor housing-side end portion of the motor shaft, and a motor stator that is fixed to the motor housing,   wherein the bearing device includes a first bearing that is arranged in a closed-end hole formed in the pump plate and that supports a pump housing-side end portion of the motor shaft, and a second bearing that is arranged radially inward of a cylindrical bearing support portion formed in the pump housing and extending inside the motor housing, and that supports a middle portion of the motor shaft, and   wherein the pump rotor is arranged between the first bearing and the second bearing.   
     
     
         2 . The electric pump unit according to  claim 1 , wherein the first bearing is a plain bearing. 
     
     
         3 . The electric pump unit according to  claim 1 , wherein:
 the pump rotor is formed of an outer gear and an inner gear;   the inner gear is fixed to the motor shaft with axial and radial movements of the inner gear restricted;   the second bearing is a rolling bearing that includes an inner ring, an outer ring and rolling elements; and   the inner ring is fitted to a middle portion of the motor shaft by interference fit.   
     
     
         4 . The electric pump unit according to  claim 2 , wherein:
 the pump rotor is formed of an outer gear and an inner gear;   the inner gear is fixed to the motor shaft with axial and radial movements of the inner gear restricted;   the second bearing is a rolling bearing that includes an inner ring, an outer ring and rolling elements; and   the inner ring is fitted to a middle portion of the motor shaft by interference fit.   
     
     
         5 . The electric pump unit according to  claim 3 , wherein the outer ring of the second bearing is fitted to the bearing support portion by interference fit. 
     
     
         6 . The electric pump unit according to  claim 4 , wherein the outer ring of the second bearing is fitted to the bearing support portion by interference fit. 
     
     
         7 . The electric pump unit according to  claim 3 , wherein:
 the first bearing is formed of a cylindrical metal member;   the motor shaft is fitted to the first bearing by clearance fit;   the outer ring of the second bearing is fitted to the bearing support portion by clearance fit; and   the motor shaft is fitted to the first bearing such that an axis of the motor shaft is located closer to an oil discharge port side than an axis of the cylindrical metal member is.   
     
     
         8 . The electric pump unit according to  claim 4 , wherein:
 the first bearing is formed of a cylindrical metal member;   the motor shaft is fitted to the first bearing by clearance fit;   the outer ring of the second bearing is fitted to the bearing support portion by clearance fit; and   the motor shaft is fitted to the first bearing such that an axis of the motor shaft is located closer to an oil discharge port side than an axis of the cylindrical metal member is.