New automatic hybrid transmissions for motorcycles

This paper presents a systematic approach to designing new automatic transmission systems for motorcycles, including conceptual design, kinematic design, efficiency analysis, engine and transmission matching, and prototype developing and testing. The basic concept is to combine a stepped design and a stepless one into a hybrid transmission system. Four hybrid transmission systems, consisting of a two degrees of freedom planetary gear train and a rubber V-belt drive unit, are synthesized. Two operating regimes over the full speed ratio range are obtained by means of engaged clutches. Kinematic design of the hybrid transmission systems is employed to obtain the major dimensions. Based on the power flow and efficiency analysis, formulas for the mechanical efficiency of the transmission systems are derived. The transmission theory of the V-belt drive unit is studied. The design procedure for matching the power source and transmission is presented. A testing rig was designed and constructed. A prototype of this new hybrid transmission system was developed to measure the transmission efficiency and test the operating characteristics. The results show that the proposed design is theoretically correct and practically feasible.