An analysis on the characteristics of electromechanical transmission with multi-planetary gearing

The characteristics of the speed, torque and split ratio of multi-planetary power split transmission are analyzed for input split, output split and compound split three power coupling mechanisms of vehicle electromechanical variable transmission (EVT), and the combinations of different power-split modes are analyzed. The results show that the characteristic of multi-planetary power split transmission is the same as the dual-planetary one. The input split transmission has one mechanical point, before which the split ratio is relatively low, is suitable for low-speed start-up stage. The output split mode has one mechanical point with a symmetric distribution of split ratio, and when transmission ratio is lower than mechanical point, the efficiency is high, suitable for high speed stage. The compound split has two mechanical points, between which the split ratio is relatively low with high efficiency, suitable for medium and high speed stages. For multi-mode EVT, it is recommended to adopt input split mode at low-speed start-up stage and adopt compound split mode at medium and high speed stages for achieving switch without speed difference.