Synthesis of six-speed planetary gear trains for vehicles

This paper presents a systemic method for synthesis of six-speed automatic planetary gear trains with three-degree-of-freedom and three-planetary-gear-set. Firstly, a deduced model is proposed based on the analysis of degree of freedom and a graph generation algorithm based on graph theory and lever analogy is developed to synthesize the two-degree-of-freedom planetary gear trains. Next, the design methods of multi-degree-of-freedom, such as the switched-input and variable fixed interconnection, are applied to synthesize six-speed planetary gear trains with three degrees of freedom. Finally, according to the requirements, such as the ratio step, efficiency, mechanism planarity and single-transition shift, seventeen valid schemes are selected for six-speed automatic transmissions with planetary gear trains.