| 摘要 |
A power driving device for a bicycle has a planetary gear assembly mounted with a driving axle shaft, including a housing fixed to the bicycle frame with a side wall rotatably mounting the driving axle shaft and a flange wall projecting laterally from the side wall which contains the planetary gear assembly and has a ring gear fixed thereto, a pinion gear carrier fixed to the driving axle shaft for rotation together therewith upon application of a driving force to the pedals, and a sun gear fixedly connected to a driving sprocket wheel for transmitting power from the pedals to the rear wheel of the bicycle. The planetary gear assembly can provide a power changing ratio in the range of about 3.5, so that the driving sprocket wheel can have a number of teeth substantially less than the number of teeth on a conventional sprocket wheel yet, when multiplied by the power changing ratio of the planetary gear assembly, is equivalent to more than double that of the conventional sprocket wheel. In other embodiments, the planetary gear assembly is provided at the rear wheel axle shaft of the bicycle, which is fixed to the pinion gear carrier and is driven by a rear sprocket wheel linked by a chain to a front sprocket wheel driven by the pedals, and the sun gear is fixed to a hub for the rear wheel. Alternatively, two planetary gear assemblies are used, one at the pedal position and the other at the rear axle shaft, to provide a combined power changing ratio that is doubled. |
