Efficiency And Shift Strategy Study Of The 2-speed AMT For Pure Electric Vehicle In Consideration Of Driving Modes And Transmission Efficiency

Pure electric vehicle(PEV) is an important type of new energy vehicles. Many countries and major automobile companies are paying more and more attention on it.Transmission adoption has a significant effect on the performance of pure electric vehicles. Recently, the application of 2-speed Automatic Manual Transmission(AMT) for pure electric vehicle has become a hot topic to many auto companies. The 2-speed AMT has a good application prospect in the PEV, which can decrease the performance requirement of the motor and make the motor operating at the high efficiency area. Therefore, it is necessary for the study on the 2-speed AMT.In this paper, based on the research project cooperating with the company about the efficiency and shift strategy of 2-speed AMT, the efficiency of 2-speed AMT has been tested and analyzed. On the basis of the efficiency research and traditional shift schedule analysis, the integrated shift schedule has been proposed in consideration of driving modes and transmission efficiency. The torque compensation control strategy during the torque recovery process of shifting has been put forward, which improves the driving comfort of the PEV with 2-speed AMT effectively. The main research work is as follows:(1) The theory of efficiency loss of transmission has been analyzed, and the power losses including gear mesh, oil churning and bearing friction have been researched in detail. The efficiency calculation model of the 2-speed AMT has been established.(2)The efficiency test bench for 2-speed AMT has been established. The efficiency experiment for 2-speed AMT has been conducted. The experiment result is highly agreeable to the simulation result of efficiency model of 2-speed AMT. Therefore, the effectiveness of the theoretical efficiency model has also been proved. According to the simulation analysis on the power losses of gear mesh, oil churning and bearing friction, the variation laws and influence factors of test data of 2-speed AMT efficiency have been researched. The influence of the input speed, input torque and lubricant temperature to the transmission efficiency has been analyzed, and the influence difference of the above factors between the first gear and second gear of the 2-speed AMT has also been analyzed.(3) Based on the analysis of transmission efficiency and the defect of traditional shift schedule of 2-speed AMT, the integrated shift schedule has been proposed in consideration of driving modes and transmission efficiency. The simulation analysis for the 2-speed AMT using the proposed shift schedule has been conducted. The results show that the integrated shift schedule is advanced and effective.(4)The reason of fluctuation of driving force after shifting has been analyzed. Then the torque compensation control strategy after shifting has been put forward according to the characteristic of the powertrain of PEV. The driving force control strategy after torque compensation has been achieved according to the shift strategy of the 2-speed AMT in consideration of driving modes and transmission efficiency. The simulation result show that the fluctuation of driving force of 2-speed AMT has been reduced after torque compensation and the driving comfort has also been improved.