Parameters design of powertrain system of electric vehicle with two-speed gearbox

A scheme of two-speed transmission is proposed based on an electric vehicle(EV) with a settled gear ratio.A new traction motor is chosen and a two-speed automatic gearbox without clutch is designed,and matching design between the motor and the two-speed gearbox is carried out.In order to improve operation efficiency of the motor,speed ratios of the two-speed gearbox are optimized aiming at lest energy consumption of the motor over the ECE drive cycle under the condition of ensuring the dynamic performance of the EV.A shifting strategy to guarantee high operation efficiency of the motor is drew up.The simulation results indicate that the energy consumption is decreased by 6.6% and the driving range is extended by 7.1% compared with the EV with a settled gear ratio.