Starter motor and process of forming pinion shaft used in the starter

Abstract

The starter motor includes a first output shaft with a pinion gear in mesh with a ring gear of an engine. A first reduction mechanism outputs power from a motor shaft through the first output shaft. A second output shaft and a second reduction mechanism output power from the first output shaft through the second output shaft. The second output shaft is rotatably coupled onto the first output shaft and made coaxial therewith. Power can be taken out on the side of the pinion gear. Both output shafts are associated with each other through a stop member for regulating relative displacement in the axial directions, so that thrusts in directions opposite to the above directions different from each other, which have not been borne, can be borne by each of the output shafts on the other side, respectively. The second reduction mechanism has a plurality of planetary gears orbitally revolving around a sun gear, a stopper for locking against fall-off of the planetary gears from pin shafts is formed on the side of the outer periphery of the planetary gears, being clamped between the ring gear and a case bracket. An annular seal ring partitions the first and second reduction mechanisms. The second output shaft at one end is formed from a cylindrical slug into a pinion shaft with a large diameter flanged portion.