特集 Lead - Free Brush Materials for Starter Motors *

This paper reports the development of a lead-free brush material for high-load starter motors. These brushes can be used in much more extreme conditions --at a PV-value (the product of the brush contact pressure and sliding velocity) approximately three times that of conventional starter motor brushes, and double the electrical current density. The major technical requirement for this development was the ability to reduce the electrical wear in brushes caused by commutation sparking. We developed a brush material that reduces electrical wear by adding a phosphorous compound. Because the phosphorous compound can improve both the lubricity at high-temperatures and the contact stability of the brushes, the developed brush reduces commutation sparks. The life of the developed brush is about 1.5 times longer than that of conventional brushes containing lead.