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.
Highlights
The planetary gear sets, or epicyclic gear drives, are commonly used to transform torque and speed in many automotive, aerospace, and marine applications
This article presents a systematical approach of an improved lever analogy method to simplify the analysis
The structure of this EVT has two planetary gear sets where the engine drives the carrier 1, MG1 and MG2 connect to sun gear S1 and S2, respectively, two ring gears are on a common output shaft, and the planetary carrier 2 is constrained to the transmission housing
Summary
The planetary gear sets, or epicyclic gear drives, are commonly used to transform torque and speed in many automotive, aerospace, and marine applications. The structure of this EVT has two planetary gear sets where the engine drives the carrier 1, MG1 and MG2 connect to sun gear S1 and S2, respectively, two ring gears are on a common output shaft, and the planetary carrier 2 is constrained to the transmission housing. For a desired engine speed, the speed of MG1 in the third-generation EVT is lower than that in the original EVT
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