Patent ID: 6857984

Claim:
A starter comprising: a motor having a motor shaft; an output shaft arranged coaxially with the motor shaft; a planetary gear reduction device for transmitting rotation of the motor shaft to the output shaft in reduced rotation speeds; and a ball disposed at a first thrust receiving location between the motor shaft and the output shaft for receiving thrust load and allowing relative rotational movement between the motor shaft and the output shaft, wherein the motor shaft and the output shaft have respective end faces opposing each other, with a spacing therebetween in an axial direction, at a second thrust receiving location between the motor shaft and the output shaft, wherein a thrust receiving member is disposed in the spacing between the end faces of the motor shaft and the output shaft at the second thrust receiving location, the thrust receiving member being thinner than the spacing to be able to contact both end faces of the shafts and receive thrust only when one of the shafts wear more than a predetermined length, whereby initially only the ball receives thrust, and subsequently, after wearing of the one of the shafts to more than the predetermined length, both the ball and the thrust receiving member receive thrust, and the thrust receiving member also being disposed between the output shaft and the planetary gear reduction device, and wherein one of the shafts has a wear characteristic at a position where the ball contacts.