Specifications and Design of a PM Electric Variable Transmission for Toyota Prius II

This paper focuses on an analysis of technical requirements for the design of a permanent-magnet-type electric variable transmission (PM-EVT), which is a novel series-parallel hybrid electric vehicle (HEV) powertrain concept. Similar to the planetary gear train used in Toyota Prius II, the EVT also realizes the power-split function. However, it is implemented in an electromagnetic way rather than in a mechanical way, as is the case for Prius II with a planetary gear. In this paper, a procedure to define the technical requirements of an EVT is presented. Since Toyota Prius II is a well-known series-parallel HEV, this vehicle is chosen as a reference. The engine, battery, and other necessary components are kept as input data. A dynamic simulation was performed to take into account different driving cycles. Then, based on an analysis of the simulation results (torque, speed, and power) the technical requirements of the PM-EVT are defined. Finally, the PM-EVT machine is designed. The PM-EVT design results are presented and validated using the finite-element method (FEM).