Patent ID: 8100810

Claim:
An internal hub transmission comprising: a hub axle; a driver rotatably supported by the hub axle; a hub shell rotatably supported by the hub axle; a power transmission mechanism disposed between the driver and the hub shell for transmitting rotational power from the driver to the hub shell through a plurality of power transmission paths, the power transmission mechanism having at least one planetary gear mechanism that includes a sun gear, a planetary gear and a ring gear, the planetary gear being supported by a gear rack, the planetary gear having helical gear teeth and at least one of the sun gear and the ring gear being provided with helical gear teeth that mesh to the helical gear teeth of the planetary gear, the power transmission mechanism further having a first ball bearing assembly operably disposed between the gear rack and the ring gear to support smooth rotation therebetween; and a shift mechanism for selecting one of the plurality of power transmission paths.