Motor reducer broken shaft of internal factors include the following:

1. shaft fracture stress reducer design time is too large;

2. the reducer input shaft the shaft shoulder is not thinking of fillet radius and curves to make extensive fatigue damage of stress concentration;

3. speed reducer for vertical shaft form, first-level input shaft bevel gear shaft, bearing in the transition of the bevel gear shaft shoulder appear more serious stress concentration and fatigue damage;

4. speed reducer for hard surface reducer, reducer input shaft diameter is fine, although calculating the strength through, due to shaft itself is fine, the same shaft diameter serious stress concentration and fatigue damage;

5. input shaft heat treatment quality is unqualified;

6. improper input shaft material choice.