Driving apparatus with a speed changer for a bicycle

Abstract

A driving apparatus with a speed changer for a bicycle using a pair of non-circular gears for performing an exponential function angular velocity modulation for the speed changer. The driving apparatus is provided with a primary angular velocity modulating mechanism having a first non-circular gear fixed to a first rotary shaft receiving driving power and a second non-circular gear supported to a second rotary shaft, a secondary angular velocity modulating mechanism having the second non-circular gear and a third non-circular gear supported to a third rotary shaft generating driving power through a one-way clutch, and a spring for increasing a relative angle between the first and the third rotary shafts around the second rotary shaft. The driving apparatus performs an exponential function continuous increasing mode or an exponential function continuous decreasing mode using the primary and secondary angular velocity modulating mechanisms and transmits only one-directional rotation to the third rotary shaft (output shaft) through interposition of the one-way clutch. The driving apparatus continuously changes the angular velocity ratio of a rear wheel shaft with respect to a pedal crank shaft in a substantially stepless manner.