Sliding contacts are widely used in motors of various types and applications. Recently motors have become more and more downsized, while longer life and higher reliability are demanded. In such a background, many difficult problems remain to be solved. One of the most difficult problems is the behavior of the sliding contacts used in brushes and commutators. This study is intended to achieve satisfactory characteristics and long life of metal brushes and commutators. This is a report on the general idea of solving the problem by using a vapor lubricant. Polyhydric alcohols were used as vapor lubricants, and various types of small power motors tested. As a result, the surfaces of the brushes and commutators were found to be free of carbonaceous deposits, such as black powder and brown powder. Motors lubricated with vapor lubricants of this system have already been manufactured and used in quantity.
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