Patent ID: 8900091

Claim:
A planetary gear reduction mechanism comprising an input shaft rotatable about a first rotational axis, an output shaft, at least one planetary gear driven by the input shaft, the planetary gear having a first and a second gear of the same shape but having different rotational phase angles and integrated together rotatably about a third rotational axis, a fixed sun gear meshed with the first gear of the planetary gear, and a driven sun gear meshed with the second gear of the planetary gear and coaxially integrated with the output shaft, the driven sun gear having a different gear teeth number than the fixed sun gear, the planetary gear comprising: the fixed sun gear and the driven sun gear are external gears; the input shaft is provided with an eccentric rotary plate rotatable about a second rotational axis offset from the first rotational axis by a predetermined distance; and the planetary gear is provided with a shaft mechanism which is offset in the same eccentricity direction as the eccentric rotary plate from the third rotational axis by the predetermined distance and operably coupled to the eccentric rotary plate such that the shaft mechanism eccentrically rotates about the third rotational axis in synchronism with the eccentric rotary plate.