An influence of commutation arc in gasoline on brush wear and commutator

Many DC motors are used for automotive electrical equipment. In particular, a motors for fuel pumps have the distinctive feature that their commutation is carried out in gasoline. Our previous studies (Sawa and Shimoda, 1992; Shimoda et al, 1993; Yamamoto et al, 1996; Nagakura and Sawa, 1997) reported that brush wear in gasoline was much greater than that in air, and also that carbon brushes were sometimes severely worn under negative polar conditions. In this paper, the wear of carbon brushes for negative polar conditions, sliding against the copper commutator in gasoline and air is reported. In order to find the cause of severe wear on the carbon brush, we examined the range of brush wear, arc energy and the influence of the arc on the commutator with changing commutation current from 5 A to 10 A. As a result, arc energy in air is larger than that in gasoline, but the range of brush wear is narrow. The commutator surface in gasoline is rougher than that in air, and excessive film is observed on the commutator surface when severe wear takes place.