TWINSPEED POWERSHIFT GEARBOX FOR FULL AND RANGE EXTENDED EVs

摘要

Up to recent, gearboxes for EVs are only single speed solutions and some technical solutions even aim at no gearbox at all, by having 2 or 4 direct drive in-wheel motors for each wheel. However, there is also a trend to design multi-speed gearboxes in order to overcome a number of technical and functional drawbacks of single motor EV solutions. This paper describes the analysis, design and control of a powershifting two-speed transmission for EVs. The study and prototyping pursued is based on static and dynamic vehicle performance and energy flow simulations. Efficiency maps of the battery, e-motor and gearbox are incorporated in the simulation models. Furthermore, the vehicle mass (incl. batteries, e-motor, inverter, etc.) is included to evaluate the vehicle launch and speed performance as a function of road inclination. Efficiency optimization of the entire drivetrain is performed through gear ratio design/selection as well as shifting strategy (when to shift). Finally, for compactness and light weight design purpose, it is chosen to use a unique combination of planetary gearsets and lower cost shifting elements instead of multiple gear stages as seen in manual transmissions or multiple wet-plate clutch as seen in automatic transmissions. One of the main challenges was to enable smooth control using this new combination of planetary gearsets and shifting elements.