| 摘要 |
A bicycle transmission includes a shaft, a driving part supported about the shaft for coupling to the input part, a driven part supported about the shaft for coupling to the output part, and a planetary gear mechanism disposed between the driving part and the driven part for changing the transmission ratio of the motive force applied from the driving part to the driven part. The planetary gear mechanism comprises a sun gear installed about the shaft, an output gear for transmitting motive force to the driven part, a frame part installed about the shaft and coupled to the driving part, and a planetary gear rotatably coupled to the frame part and disposed between the sun gear and the output gear for engaging the sun gear and the output gear. A clutch comprising a roller is disposed at an intermediate point along the transmission path between the driving part and the driven part for transmitting the motive force from the driving part to the driven part in one direction only. A first clutch of this type may be disposed between the output gear and the driven part, and a second clutch of this type may be disposed between the frame part and the driven part for directly coupling the frame part to the driven part. In another embodiment of the invention, the planetary gear mechanism further includes a switching unit for selectively coupling the frame part to the driving part and decoupling the frame part form the driving part In this embodiment, a first clutch of the above type may be disposed between the output gear and the driven part, a second clutch of the above type may be disposed between the frame part and the driven part, and a third clutch of the above type may be disposed between the driving part and the output gear.
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