3 A Split Power Continuously Variable Transmissions (SPCVT) for Bicycle Use 2002-32-1772

Fine packaging is important for the bicycle transmission design. We are proposing a split power continuously variable transmission (SPCVT) operated with one mode. The planetary gear unit (PGU) in the SPCVT consists of two epicyclic gear trains. Both epicyclic gear trains do not include any ring gears to minimize the overall diameter of the transmission. A variator is connected to the PGU as a type of variable bridge. The variator involves two rotor pairs contacting on concave-convex spherical surfaces. This new mechanism of the variator shows a strong possibility to get high power density in comparison with other existing traction drives. A four-bar linkage is used to locate the counter rotor assembly exactly in the contact points of the rotor pair and extend the range of variator speed ratio. The crank is pulled by the wire connected to the speed control lever on the handle of bicycle. The theoretical performances of SPCVT were investigated and a SPCVT was designed to install at the rear wheel, based on the regular input power and speed for bicycle, in which the overall width and diameter between hub and frame were within around 55mm and 200mm, respectively. And CAD was finished by Pro-E.