Mechanical Wear and Arc Erosion of Brush and Commutator in DC Motor for Automotive Fuel Pump

A carbon flat commutator is widely used in a DC motor driving an automotive fuel pump. The authors have reported the commutation phenomena such as arc duration and wear/erosion of brush and commutator in alternative fuels, ethanol and others. As well-known, the brush and commutator wear/erosion increases when the arc occurs. Generally, it is difficult to divide the experimentally obtained wear/erosion into mechanical wear and arc erosion. From the previous authors' works, the arc erosion on the commutator can be clearly recognized for carbon flat commutators. In this paper, by analyzing the commutator surface by the laser microscope the mechanical wear and the arc erosion can be separately estimated. Consequently, it can be made clear that the arc discharge not only generates arc erosion, but also increases the mechanical wear. Furthermore, it is examined why the mechanical wear increases when the arc discharge occurs. As basic data, mechanical wear without arc is tested and it can reveal that the mechanical wear stays almost constant up to 10A load. Based on those results a model is discussed to explain why the mechanical wear increases when the arc discharge takes place.