Application of Multi-speed Gearbox in Infinitely Variable Transmission

Abstract

One way to reduce vehicles’ fuel consumption (FC) is to optimize different parts of its powertrain. Among different modern powertrains, continuously variable transmission (CVT) is one of the common types which changes speed ratio between engine and wheels, continuously. Therefore, the CVT allows the engine to operate at its fuel-optimal speed. Due to the limited power transmission capacity and speed ratio range of the CVT, researchers attempted to combine the CVT with a planetary gear train and a fixed ratio mechanism. This mechanism is called infinitely variable transmission (IVT). In this study, a multi-speed gearbox (MSG) is used in the IVT and its impact on the powertrain performance and the vehicle’s FC is investigated. After extracting the governing dynamics of the system, an optimization on the parameters which affect the IVT performance is implemented to minimize the vehicle’s FC. It is observed that the vehicle’s FC for the case of using the optimized IVT equipped with two-speed MSG is almost 5% less than the case of using the optimized six-speed AT transmission in different driving cycles.