Fuel pump

Abstract

A fuel pump improved in pump efficiency is provided. An impeller rotating in a pump casing has an approximately disk-shaped configuration with a group of recesses formed in a region extending along the outer peripheries of the obverse and reverse sides of the impeller. The recesses are repeatedly arranged at a distance between each other in the circumferential direction with a partition provided between each pair of adjacent recesses. The radially inner and outer end portions of the partition are positioned on the same radius, and the radially middle portion of the partition is curved rearward in the direction of rotation of the impeller. With this fuel pump, the incidence of separation or vortex formation in the flow of fuel is minimized, and a high pump efficiency can be obtained. It is preferable that the maximum amount of curvature of the partition should be from 0.1 to 1.0 mm, and the curved configuration of the rotation direction forward side of each partition on the obverse and reverse sides should be a circular arc with a radius of from 2.3 to 4.3 mm, and/or the curved configuration of the rotation direction rearward side of each partition should be a circular arc with a radius of from 3.0 to 5.0 mm.

What is claimed is:  
     
         1 . A fuel pump having an impeller rotating in a pump casing, said impeller having an approximately disk-shaped configuration with a group of recesses formed in a region extending along outer peripheries of obverse and reverse sides of said impeller, said recesses being repeatedly arranged at a distance between each other in a circumferential direction with a partition provided between each pair of adjacent recesses, 
 wherein radially inner and outer end portions of said partition are positioned on a same radius, and a radially middle portion of said partition is curved rearward in a direction of rotation of said impeller.    
     
     
         2 . A fuel pump according to  claim 1 , wherein a diameter of the impeller is from 30 to 36 mm; a radial length of each partition is from 2.9 to 4.5 mm; a circumferential distance between each pair of adjacent partitions is from 1.5 to 2.5 mm; a thickness of each partition is from 0.2 to 1.5 mm; a thickness of the impeller is from 3.0 to 4.5 mm, and a maximum amount of curvature of said partition is from 0.1 to 1.0 mm.  
     
     
         3 . A fuel pump according to  claim 1 , wherein a diameter of the impeller is from 30 to 36 mm; a radial length of each partition is from 2.9 to 4.5 mm; a circumferential distance between each pair of adjacent partitions is from 1.5 to 2.5 mm; a thickness of each partition is from 0.2 to 1.5 mm; a thickness of the impeller is from 3.0 to 4.5 mm, and a curved configuration of a rotation direction forward side of each partition on the obverse and reverse sides is a circular arc with a radius of from 2.3 to 4.3 mm.  
     
     
         4 . A fuel pump according to  claim 1 , wherein a diameter of the impeller is from 30 to 36 mm; a radial length of each partition is from 2.9 to 4.5 mm; a circumferential distance between each pair of adjacent partitions is from 1.5 to 2.5 mm; a thickness of each partition is from 0.2 to 1.5 mm; a thickness of the impeller is from 3.0 to 4.5 mm, and a curved configuration of a rotation direction rearward side of each partition on the obverse and reverse sides is a circular arc with a radius of from 3.0 to 5.0 mm.  
     
     
         5 . A fuel pump according to  claim 1 , wherein said partition is inclined rearward in the direction of rotation as a distance from the obverse and reverse sides increases inward in a direction of thickness.  
     
     
         6 . A fuel pump according to  claim 5 , wherein said partition is inclined at from 40° to 60° from a middle plane in the direction of thickness.  
     
     
         7 . A fuel pump according to  claim 5 , wherein said partition continuously extends while defining a gently arcuate surface at a rotation direction forward side of a middle plane in the direction of thickness.  
     
     
         8 . A fuel pump according to  claim 1 , wherein a thickness of said partition increases as a distance from the obverse and reverse sides increases inward in a direction of thickness.  
     
     
         9 . A fuel pump according to  claim 8 , wherein the thickness of said partition at a middle plane in the direction of thickness is greater than a thickness thereof at the obverse and reverse sides by from 0.1 to 0.4 mm.  
     
     
         10 . A fuel pump according to  claim 1 , wherein a radially inner end face of each of said recesses has two arcuate surfaces contacting each other at a middle plane in a direction of thickness.  
     
     
         11 . A fuel pump according to  claim 10 , wherein a radius of said arcuate surfaces is from 0.7 to 2.2 mm.  
     
     
         12 . A fuel pump according to  claim 1 , wherein a radially outer end face of each of said recesses is slanted to face toward the obverse and reverse sides from a middle plane in a direction of thickness.  
     
     
         13 . A fuel pump according to  claim 12 , wherein the radially outer end face of each of said recesses is slanted to face toward the obverse and reverse sides from the middle plane in the direction of thickness at an open angle of not more than 20°.  
     
     
         14 . A fuel pump according to  claim 12 , wherein the radially outer end face of each of said recesses has two arcuate surfaces contacting each other at the middle plane in the direction of thickness.  
     
     
         15 . A fuel pump according to  claim 14 , wherein a radius of said arcuate surfaces is from 0.2 to 1.0 mm.  
     
     
         16 . A fuel pump according to  claim 1 , wherein said partition is inclined rearward in the direction of rotation as a distance from the obverse and reverse sides increases inward in a direction of thickness and continuously extends while defining a gently arcuate surface at a rotation direction forward side of a middle plane in the direction of thickness; a thickness of said partition increases as a distance from the obverse and reverse sides increases inward in the direction of thickness; a radially inner end face of each of said recesses has two arcuate surfaces contacting each other at the middle plane in the direction of thickness; and a radially outer end face of each of said recesses is slanted to face toward the obverse and reverse sides from the middle plane in the direction of thickness.