Topology design of multi-row series-parallel multi-speed planetary gear automatic transmission based on extended lever method

Abstract

Abstract With the urgent need of saving energy, reducing emissions, reducing shifting frustration and improving driving quality, the number of gears of automatic transmissions used in automobiles is increasing. However, the traditional lever method is insufficient in designing multi-row parallel-series multi-speed planetary gear automatic transmissions. In this study, an extended lever method is proposed, which can design and analyze the transmission state of planetary gears with multiple input elements, multiple output elements and no fixed elements. Then, based on the extended lever method, a series of multi-speed planetary gear automatic transmissions are designed, among which a twelve-speed planetary gear automatic transmission is selected, and the kinematics and dynamics are analyzed by using the lever method. The results show that the designed twelve-speed transmission has a wide range of speed ratios, with up to seven overdrive gears and a smaller speed ratio interval of each overdrive gear. The results further prove that the extended lever method is an important direction for the design of multi-row series-parallel multi-speed planetary gear automatic transmission.