To ease shock load such as meshing shock, and reduce noise caused by a backlash at the time of starting an engine.
A starter has a planetary gear reduction mechanism 6 which is composed of an internal gear 2 movably held inside the center cas 12 of a driving housing 1; a sun gear 3 rotatingly driven by a motor; a planetary gear 4; and a driving shaft 5 to hold the planetary gear 4. An irregular face 7 having irregularities arranged in a peripheral direction is formed on the front end face of the internal gear 2, and a spring 8 formed of a plate spring is fixed in the center case 12 opposite to the irregular face 7. The spring 8 is pressingly energized to abut against the irregular face 7. When excessive torque acts on the internal gear 2, it rotates to ease shock load. When the torque fluctuates within a fixed range, the internal gear 2 is reciprocatingly rotated by the elastic force of the spring 8, and backlash noise is thereby prevented.
HOSOYA AKIFUMI
OMI MASANORI
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