Stepless speed change device for bicycle

Abstract

A stepless speed change device for a bicycle comprises a plurality of planetary members journaled in a carrier fixed to a crankshaft of the bicycle in two parallel planes perpendicular to the crankshaft, planetary gears respectively fitted on the planetary members through one-way clutches so as to rotate in one direction, an eccentric shifter having a circular track for guiding rocking pins extending from and eccentric to the planetary members, the eccentric shifter capable of changing its eccentricity relative to the crankshaft and a sun gear connected to a crank gear as an output portion of the device, thereby making it possible to make the diameters of the planetary gears much larger than that of the sun gear so as to make much larger the speed-up transmission ratio and at the same time increase the number of planetary gears to make small pulsations in transmission force. According to the invention, the device includes a speed change operating device having for itself a performance of a reverse input allowing device so as to effectively bring the stepless speed change device into practical use. In this manner, the stepless speed change device becomes light weight and small-sized as a whole.