在一款采用固定速比减速器的电动汽车的基础上，改用两挡变速传动方案，对驱动电机进行参数匹配设计，并设计了不带离合器的两挡自动变速器。为了提高电机工作效率，对传动系统的速比进行了以整车动力性要求为约束、以ECE(欧洲城市经济)循环工况下电机能量消耗最小为目标的优化设计，制定了以电机高效运行为原则的换挡控制策略，并与采用固定速比减速器的电动汽车进行了ECE运行循环下的能耗和续驶里程的对比。结果表明，整车能耗降低了6.6%，续驶里程延长了7.1%。

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.

国家863高技术研究发展计划资助项目(2008AA11A145)