YOKE OF PLANETARY GEAR-TYPE STARTER, MANUFACTURING APPARATUS THERFOR AND MANUFACTURING METHOD

摘要

In a cylindrical yoke 1 of a planetary gear-type starter which acts as the magnetic field of the motor of a planetary gear-type starter for reducing the rotation of a motor output shaft 31 and transmitting the reduction rotation to a starter output shaft 21 so that an inner peripheral gear portion is improved in precision by suppressing a material remaining in the yoke 1 and gear noise is reduced in operation, the yoke 1 comprises an opening formed at the bottom portion of the yoke for journaling the starter output shaft of the planetary gear-type starter, an inner peripheral gear portion 11 formed in the vicinity of the bottom portion 12 of the yoke, and an annular thick portion 18 formed between the inner peripheral gear portion and the bottom portion on the inner peripheral side thereof, wherein the yoke 1 incorporates the flange 2 of the starter output shaft and planetary gears 4 which are rotatably mounted to the flange as well as engaged with the outer peripheral gear portion 32 of the motor output shaft and the inner peripheral gear portion. There are also provided a manufacturing apparatus and a manufacturing method of the yoke.