Analysis of multi-speed transmission and electrically continuous variable transmission using lever analogy method for speed ratio determination

Abstract

The planetary gear trains are commonly used in automotive transmissions. A practical method to analyze planetary gear train for speed ratio determination is lever analogy. The classical lever analogy provides an easy way to study the kinematics and determine the power flow of a three- or four-speed automatic transmission. However, the classical approach becomes very complex and not easy to use in analyzing transmissions having three or more planetary gear trains. This article presents a systematical approach of an improved lever analogy method to simplify the analysis. Two higher multi-speed automatic transmissions and several hybrid powertrain transmissions are discussed as examples to demonstrate the determination of speed or torque ratios using the method. The developed technique can be further applied to optimize the designs of component sizing, configuration, and power control of many types of automotive transmissions.