Recently many small D.C. motors have been used for automotive electrical equipment. In particular, motors for fuel pumps play an important role of supplying the engine with gasoline. Therefore, high reliability and long life are required for the motors. The feature of these motors is that gasoline flows inside the motor and commutation is done in gasoline. This paper is a fundamental investigation of the commutation phenomena in gasoline. We have already reported in a previous paper on fundamental characteristics of the commutation arc such as arc duration, arc voltage and residual current. In this paper, the experimental results of arc duration, residual current and arc voltage are reported for both commutator materials of Cu and Ag/Ni. And the wear of a brush made of metallic-carbon is measured, respectively on Cu and Ag/Ni commutators. When the silver-nickel commutator is used, brush wear is slighter in gasoline than in air. When the copper commutator is used, brush wear in gasoline is similar to that in air. The influence of gasoline on commutation arc voltage is also described.
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