To make a motor-assisted bicycle compact and light in weight by adopting a flat motor as a driving source, directly assembling this motor on a crankshaft and further assembling also a reduction gear of a single stage oscillating inscribed engagement type planetary gear structure on the crankshaft by combining the motor and the reduction gear.
A flat motor 30 which is one of main elements of a motor driving system MD is assembled on a crankshaft 12 coaxially with the crankshaft 12. The flat motor 30 is connected with an eccentric body 51 used as also an input shaft of a reduction gear 50 via a one-way clutch 40. This reduction gear 50 has an oscillating inscribed engagement type planetary gear structure. The eccentric body 51 is assembled on the outer periphery of a torque ring 91 via a bearing 51b by decentering the shaft center 02 of the body 51 itself for the shaft center 01 of the crankshaft 12 by e. Thus, both of the motor 30 and the reduction gear 50 can be stored in a range of the size of a sprocket 62 on the crankshaft 12.
EGAWA MASANORI
ISHIKAWA TETSUZO
