Fuel pump having an impeller

Abstract

A fuel pump includes an impeller having a plurality of front and rear blades and a plurality of front and rear blade ditches, a pump passage around the impeller, a fuel suction port and a fuel discharge port. Each of the front and rear blade ditches has a concave surface. Each of the front blade ditches has a tip depth at the tip of the front blade and a bottom depth at a portion adjacent to the tip. The fuel discharged from the front ditches is turned by the concave surface inwardly, thereby forming circulating flow effectively.

What is claimed is:  
     
         1 . A fuel pump including an impeller having a plurality of front and rear blades and a plurality of front and rear blade ditches, a passage member having a pump passage around said impeller, a fuel suction port and fuel discharge port, 
 wherein each of said front blade ditches has a front concave surface that has a first tip depth at the tip of said blade and a bottom depth that is deeper than said first tip depth at a portion adjacent to said tip.    
     
     
         2 . The fuel pump as claimed in  claim 1 , 
 wherein said first tip depth is larger than a half of a thickness of said impeller.    
     
     
         3 . The fuel pump as claimed in  claim 1 , 
 wherein said front concave surface has a tangential line inclining toward the front end of said impeller at the portion that crosses said blade tip.    
     
     
         4 . The fuel pump as claimed in  claim 1 , 
 wherein each of said rear blade ditches has a rear concave surface that has a second tip depth at the tip of said blade and a bottom depth that is deeper than said second tip depth at a portion adjacent to said tip.    
     
     
         5 . The fuel pump as claimed in  claim 4 , 
 wherein said second tip depth is smaller than a half of the thickness of said impeller.    
     
     
         6 . The fuel pump as claimed in  claim 1 , 
 wherein said front concave surface is a partially cylindrical surface.    
     
     
         7 . The fuel pump as claimed in  claim 6 , 
 wherein said rear concave surface is a partially cylindrical surface.    
     
     
         8 . The fuel pump as claimed in  claim 6 , 
 wherein said partially cylindrical surface has its center inside said front blade ditch.    
     
     
         9 . The fuel pump as claimed in  claim 7 , 
 wherein said front and rear cylindrical surfaces respectively have centers inside said blade ditches.    
     
     
         10 . The fuel pump as claimed in  claim 1 , 
 wherein each of said front and rear blades inclines forward in the rotation direction of said impeller.    
     
     
         11 . The fuel pump as claimed in  claim 1 , 
 wherein said front blades are disposed at the peripheral portion of the front end of said impeller at equal pitches in the circumferential direction and said rear blades are disposed at the peripheral portion of the rear end of said impeller at equal pitches in the circumferential direction, and    wherein said front and rear blades are a half-pitch shifted from each other in a circumferential direction.