A STUDY ON BRUSH WEAR UNDER COMMUTATION ARCS IN GASOLINE

The dc motor for an automotive fuel pump has a distinctive feature in that its commutation is carried out in a gasoline environment. The stu dy of brush wear under commutation Is generally important from the poi nt of view of its reliability and durability. In this paper, the wear of the copper-graphite brush sliding against the copper commutator und er commutation arcs in gasoline and air is reported. It was made clear that the brush wear in gasoline was more severe than that in air on b oth polarities when the commutation current was set to 10 A including arcs. In order to make the influence of arcs clear on the brush wear, we also examined the brush wear with load current but no arcing and th e material transfer in switching contacts with arcing, which gave us t he information of electrical erosion. In addition, we analyzed worn br ush surfaces after these tests with scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). As a result, the are has a s erious influence on the brush wear in both environments, but how to er ode the brush surface by arcing in gasoline is different from that in air.