Coaxial electric starter motor for IC engine

摘要

A coaxial starter motor has pinion (6) running on a splined shaft. There is a magnet device (9) around the shaft 94) to drive the pinion into engagement with the ring gear (15) of the engine. The magnet device comprises an excitation coil (24) with an inner bore hole, a yoke (25) which surrounds the coil in order to conduct a magnetic flux axially along an inner surface of the coil's bore hole. A cylindrical outer armature part (27) can slide in the bore of the coil, a cylindrical inner armature part (28) can slide telescopically inside the outer part, return springs (35, 21) force the outer and inner armature parts in a direction in order to open magnetic gaps relative to the yoke, a spiral spring (36) forces the two armature parts apart and an annular spring holder (8) is fitted to the bore of the outer armature part in order to engage a corresponding end of the spiral spring.