| 摘要 |
An object is to provide a compact power transmission device which comprises a small number of parts and is compact in size, and which can transmit the rotation of a rotary shaft to a wheel with a high reduction ratio. A rotary shaft 11 is provided so as to be coaxial with an inner member 11 which comprises a hub ring 4 and a bearing inner ring 5. External gears 16a and 16b are rotatably provided around eccentric portions 14a and 14b formed on the rotary shaft 11. The external gears 16a and 16b mesh with internal teeth 18 formed on the inner periphery of a casing 1. When the rotary shaft 11 rotates, the external gears 16a and 16b mesh with the internal teeth 18 one after another, so that their centers rotate about the axis of the rotary shaft. When the rotary shaft 11 rotates once, the external gears 16a and 16b rotate about their own axes by an amount corresponding to the difference in number between the external teeth 17 and the internal teeth 18. The rotation of the external gears about their axes is transmitted through a torque transmission means 20 to the inner member 3, thereby rotating the inner member 3 at a reduced speed. |
