Fuel pump

Abstract

A fuel pump includes a motor ( 20 ), an impeller ( 39 ) that includes a fitting hole ( 44; 71 ) fitted to an output end portion ( 37 ) of a rotary shaft ( 31 ) of the motor ( 20 ), and a case ( 48 ) that includes a pump chamber ( 41 ) receiving the impeller ( 39 ), a suction hole ( 13 ) passing through the case ( 48 ) from the pump chamber ( 41 ) to one side in an axial direction of the rotary shaft ( 31 ), and a discharge hole ( 47 ) passing through the case ( 48 ) from the pump chamber ( 41 ) to the other side in the axial direction. An outer wall surface of the output end portion ( 37 ) includes a pair of first plane surfaces ( 51, 52 ) that are parallel to each other. An inner wall surface of the fitting hole ( 44; 71 ) includes a pair of second plane surfaces ( 61, 62; 72, 73 ), which are parallel to each other on their cross section perpendicular to an axial center (AX 2 ) of the impeller ( 39 ) and each of which is engaged with one ( 51 ) of the pair of first plane surfaces or the other one ( 52 ) of the pair of first plane surfaces when the rotary shaft ( 31 ) rotates in a predetermined rotational direction. When a distance between the pair of first plane surfaces ( 51, 52 ) is referred to as a two-surface width (S), a value obtained by dividing the two-surface width (S) by an outer diameter (D) of the output end portion ( 37 ) is 0.75 or smaller.

1 . A fuel pump comprising:
 a motor;   an impeller that includes a fitting hole fitted to an output end portion of a rotary shaft of the motor; and   a case that includes:
 a pump chamber receiving the impeller; 
 a suction hole passing through the case from the pump chamber to one side in an axial direction of the rotary shaft; and 
 a discharge hole passing through the case from the pump chamber to the other side in the axial direction, wherein: 
   an outer wall surface of the output end portion includes a pair of first plane surfaces that are parallel to each other;   an inner wall surface of the fitting hole includes a pair of second plane surfaces, which are parallel to each other on their cross section perpendicular to an axial center of the impeller and each of which is engaged with one of the pair of first plane surfaces or the other one of the pair of first plane surfaces when the rotary shaft rotates in a predetermined rotational direction; and   when a distance between the pair of first plane surfaces is referred to as a two-surface width, a value obtained by dividing the two-surface width by an outer diameter of the output end portion is 0.75 or smaller.   
     
     
         2 . The fuel pump according to  claim 1 , wherein in a state where the one of the pair of first plane surfaces and one of the pair of second plane surfaces are in contact, a value obtained by dividing a clearance between the other one of the pair of first plane surfaces and the other one of the pair of second plane surfaces by the two-surface width is 0.011 or smaller. 
     
     
         3 . The fuel pump according to  claim 1 , wherein:
 the inner wall surface of the fitting hole further includes a pair of third plane surfaces, which are parallel to each other and each of which is engaged with the one of the pair of first plane surfaces or the other one of the pair of first plane surfaces when the rotary shaft rotates in a direction opposite to the rotational direction; and   a distance between one of the pair of third plane surfaces and the other one of the pair of third plane surfaces is larger than a distance between one of the pair of second plane surfaces and the other one of the pair of second plane surfaces.