An epicyclic gear mechanism for automobile transmissions is a device which is connected from engine to driving wheels, and the main purpose is to maintain the revolution speed of engine to be in a desired working range while accelerating or decelerating the automobile. The epicyclic gear mechanisms for automobile transmissions in production are mostly Ravigneaux-type, Parallel-connected type and Lepelletier epicyclic mechanisms, and the Lepelletier epicyclic gear mechanisms is a device which is connected with a simple epicyclic gear mechanism besides the input end to increase the total number of speed ratios of an automatic transmission. For the incompletion in the relative design methodology, a systematic methodology of designing Lepelletier epicyclic gear mechanisms for automobile transmission is described. At first, fundamental and gear-shifting operations of the Lepelletier-type automatic transmissions is introduced, and the basic principles of lever analogy is explained, the gear ratio¡¦s analysis for Lepelletier epicyclic gear mechanisms is illustrated to establish the design requirements. Secondly, gearing-sequence is devised base on the lever analogy diagrams, and a systematical procedure to arrange desired clutches and brakes into epicyclic gear mechanisms is provided, then the number of the teeth of all gears can be calculated. At last, the six-speed and eight-speed Lepelletier automatic transmissions are designed base on the above design procedure. The results of this work obtain 19 types of automatic transmission which could reach six-speed.

An epicyclic-type automatic transmission is a device that is connected to the back of an engine and sends the power from the engine to the drive wheels. Its job is to keep the engine within a certain angular velocity. For the development of multi-speed parallel-connected automatic transmission for automobiles, the related configuration design methods are still tedious and prone to human error. Therefore, the purpose of this research is to present an efficient methodology for the systematic design of the parallel-connected automatic transmission for automobiles. First, fundamentals and gear-shifting operations of the parallel-connected automatic transmission are illustrated to establish the design requirements, and the theory of the analysis of speed ratios for epicyclic-type automatic transmission is derived based on the concept of lever analogy. Next, one simple clutching-sequence synthesis methods are proposed and illustrated, based on the lever analogy, and the design theory and the procedure of clutch configuration of epicyclic-type automatic transmission are developed. With the above methods, designs of six-speed and eight-speed parallel-connected automatic transmission. Finally, the complete atlas of six-speed and eight-speed parallel-connected automatic transmission can be systematically synthesized from the data of given speed ratios. This proposed design method can also be applied to the development and design of multi-speed parallel-connected automatic transmissions.