| 摘要 |
PURPOSE:To deepen a groove between commutator segments and thus to improve strength against abnormal sparks by a method wherein a narrow step is formed on inner periphery of a head of the commutator segment, and a projection on inner periphery of a molding fixture is kept higher than the commutator segment head excluding the step. CONSTITUTION:A hoop material is shaped to form a commutator segment 2 consisting of a head 5, a tail 9 and a neck 7 connecting both parts and having a step 11 narrower than the head on head side of the neck 7. On the other hand, a projection 13 extending axially is provided plurally at equal pitch on inner periphery of a cylindrical part 12 of a molding fixture 1, and each projection 13 is formed higher than the height a1 of the commutator segment head 5. The commutator segment 2 is inserted between the projections 13, arranged in a mold, and then a molding material is given therein to make a mold commutator. A groove between the commutator segments is deepened thereby, and abnormal sparks, if arising, will not reach the mold surface consequently, thus improving mechanical strength. |
