Dc motor for automotive engine starter

摘要

An engine starter includes a motor having a tubular armature rotation shaft, and a rotation output shaft arranged on one axial end side of the motor coaxially therewith to be axially slidably supported. A clutch mechanism is included for transmitting torque from the armature rotation shaft to a rotation output shaft and an electromagnetic switch which has a shifting member to push the aforementioned rotation output shaft by an electromagnetic force in the axial direction to slidably move it. The switch also brings movable contacts in touch with fixed contacts to supply power to the aforementioned motor. A rear part of the rotation output shaft and the front part of the shifting member are inserted into the armature rotation shaft tube from opposite directions. The shifting member of the electromagnetic switch, the armature rotation shaft and the rotation output shaft are all coaxially arranged to reduce the length of the starter. The coaxial arrangement is highly effective in preventing invasion of dust into the contact chamber of the electromagnetic switch. To ensure a compact size for the starter a compact spring is provided for restoring the rotation shaft to a rest position after the engine has started.