Patent ID: 8100424

Claim:
A bicycle driving assistance device comprising: a crank having two pedals connected to two ends thereof; a first chainwheel unit having a first chainwheel connected to the crank on a first side of a bicycle; a gear box having an input shaft, an output shaft, a vortex spring, a case, a first gear, an idle gear and a second gear, the input shaft connected to a second chainwheel of the first chainwheel unit, a first chain engaged between the first and second chainwheels, a free end of the input shaft connected with a first one-direction bearing so that the input shaft is restrict to rotate in a pre-set direction, the vortex spring, the case, the first gear respectively mounted to the input shaft, a first end of the vortex spring fixed to the input shaft and a second end of the vortex spring fixed to the case, the case fixed to the first gear which is engaged with the idle gear, the idle gear engaged with the second gear which is connected to the output shaft; a second chainwheel unit having an output chainwheel which is fixed to the output shaft on a second side of the bicycle, and a third chainwheel of the second chainwheel unit connected to a fourth chainwheel of a rear chainwheel unit, a second chain engaged between the third chainwheel and the output chainwheel, the fourth chainwheel connected to the crank by a second one-direction bearing, a third chain engaged between a rear chainwheel of the rear chainwheel unit and the fourth chainwheel, an energy stored in the vortex spring being released when the force applied to the pedals is less than the energy stored in the vortex spring.