Trial Manufacture of Functionally Graded Commutator Mado from Copper and Resin

Joining between copper and resin on commutator of electromotor is usually executed by injection molding method and copper is embedded in resin. In this case, clear boundary exists between copper and resin because copper and resin are not combined chemically. This boundary will change to be gaps or cracks after a long time use. In most cases, an abrupt fracture occurs when a force is greater than a certain value applied to this cracks or crack-like defects. In this study, so as to solve this problem, trial manufacture of functionally graded commutator made from copper and resin powder has been executed by spark plasma sintering method. The third element is added into resin powder and resin powder is prepared so that the coefficient of linear thermal expansion may become low. Several mechanical and thermophysical properties have been investigated. The value of shearing stress between copper and copper-resin mixed layer is more than 50Mpa. It shows that the joint strength between copper and resin of this functionally graded commutator without clear boundary is high enough. The more the content of resin increases, the higher the coefficient of thermal expansion becomes. The thermal conductivity in onedimensional and non-steady state at 296K indicates that the change is due to the mixing ratio of copper and resin.