Both types of starter motors used on Toyota starting systems have a one-way clutch, or overrunning clutch. This clutch prevents damage to the starter motor once the engine has been started. It does so, by disengaging its housing (which rotates with the motor armature) from an inner race which is combined with the pinion gear. Spring loaded wedged rollers are used.
Without an over-running clutch, the starter motor would be quickly destroyed if engine torque was transferred through the pinion gear to the armature.
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