Fuel pump

Abstract

The invention relates to a fuel pump comprising an electromotive drive that has a commutator ( 20 ) and carbon brushes ( 24, 26 ) that brush alternately against commutator segments ( 16, 18 ) when the commutator ( 20 ) is rotated. The aim of the invention is to improve the corrosion resistance and to clean the carbon brushes ( 24, 26 ). To achiever this, the commutator segments ( 16, 18 ) contain graphite and at least one commutator segment ( 16, 18 ) contains graphite and an admixture of a material ( 30 ) that has a greater hardness than graphite.

1 . A fuel pump comprising an electromotive drive that has a commutator and carbon brushes which brush alternately against commutator segments as the commutator rotates, characterized in that the commutator segments ( 16 ,  18 ) contain graphite and at least one commutator segment ( 16 ,  18 ) contains graphite and an admixture of a material ( 30 ) that has a greater hardness than graphite.  
   
   
       2 . The fuel pump as claimed in  claim 1 , characterized in that the admixture material ( 30 ) occurs in the form of individual particles ( 28 ) in the graphite.  
   
   
       3 . The fuel pump as claimed in  claim 2 , characterized in that the particles ( 28 ) are uniformly dispersed in the respective commutator segments ( 16 ,  18 ).  
   
   
       4 . The fuel pump as defined in  claim 1 , characterized in that the admixture material ( 30 ) is aluminum oxide.  
   
   
       5 . The fuel pump as defined in  claim 1 , characterized in that the proportion of admixture material ( 30 ) in the respective commutator segments ( 16 ,  18 ) is approximately 0.2%.  
   
   
       6 . The fuel pump as defined in  claim 1 , characterized in that the commutator segments ( 16 ,  18 ) are oriented radially in relation to the commutator axis and that the carbon brushes ( 24 ,  26 ) bear axially against the commutator segments ( 16 ,  18 ).  
   
   
       7 . The fuel pump as defined in  claim 4  or  5 , characterized in that the commutator segments are oriented axially in relation to the commutator axis and that the carbon brushes bear radially against the commutator segments.  
   
   
       8 . The fuel pump as defined in  claim 4 , characterized in that all commutator segments ( 16 ,  18 ) coming into contact with the carbon brushes ( 24 ,  26 ) contain the admixture material ( 30 ).