| 摘要 |
The present invention relates to a power transmission device for a chainless bicycle, which uses a planetary gear device having multiple gear sets to achieve a variety of changes in gear ratio, and which enables easy gear-changing and reliable power transmission, and which enables the easy attachment and detachment of a rear wheel. To accomplish this, the power transmission device for a chainless bicycle according to one embodiment of the present invention comprises: a first gear change unit installed on a pedal shaft to increase the rotating speed of the pedal shaft and to output the increased rotating speed; a first bevel gear installed on the pedal shaft to rotate at the speed outputted by the first gear change unit; a power transmission shaft, on one end of which a second bevel gear which is to engage with a first bevel gear is arranged; a fourth bevel gear which is to engage with a third bevel gear arranged at the other end of the power transmission shaft; a second transmission unit which increases the rotating speed of the fourth bevel gear and outputs the increased rotating speed; and a rear wheel which rotates at the speed output by the second transmission unit. Both the first transmission unit and the second transmission unit have: a carrier connected to the pedal shaft and to the fourth bevel gear; a planetary gear group which has at least three support members protruding from a virtual circumference of one surface of the carrier, wherein at least three pairs of planetary gear groups are installed on the support members such that the three pairs of planetary gear groups are independently and freely rotatable, and wherein the planetary gear group consists of at least three planetary gears having different diameters; a ring gear group consisting of ring gears which are brought into internal contact and engagement with the respective planetary gears such that the ring gears are independently and freely rotatable; a sun gear group consisting of sun gears which are brought into external contact and engagement with the respective planetary gears, and which have different diameters and are formed into a unitary body; and gear change lock means for selectively locking either an output shaft or the ring gear connected to the sun gear group.
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