Research On Parameter Matching And Performance Of Two-speed Transmission For Pure Electric Vehicle

In order to meet the increasingly severe requirements of energy conservation and environmental protection,the new energy automobile industry represented by pure electric vehicles has achieved rapid development in recent years.At present,pure electric vehicles mostly use traditional single-speed transmissions,which is insufficient in terms of the power performance and energy economy.In order to improve the matching efficiency of the drive motor and improve the vehicle performance,a new two-speed automatic transmission for the pure electric vehicle is proposed in this paper,which is matched with the single-row planetary gear set and torque converter.First of all,the unique structure of the transmission in this subject is illustrated,in which the pump wheel of hydraulic torque converter is connected with the sun gear of planetary gear set,and the turbine is connected with the carrier shaft,and the output shaft is connected with the ring gear.The realization process of direct gear and high gear is analyzed theoretically and the motion relationship is solved and proved by using the transformation method.Secondly,parameter matching is carried out for the main components,and the models of the transmission and the vehicle are establishment by using the parameters.The basic parameters of planetary gear set are calculated according to the limiting conditions and checked.According to the output characteristics of the drive system,the file is written for simulation,and the stable common working area of the torque converter and the drive motor was determined.The gear shift strategy is proposed,and a 2-AT transmission model and a pure electric vehicle model are established based on the shift strategy,combined with the above parameters.Under the 80-second test condition,the expected 6 automatic shifts are achieved,which illustrates that the transformation scheme is accurate and feasible.The gear shift quality under the test condition is analyzed in terms of three aspects: sliding power,shift time,and shift shock.Finally,two aspects from power performance and energy economic are carried out to evaluate the performance of the vehicle.The power performance of the vehicle model matched with the two-speed hydraulic automatic transmission is studied by comparing the single speed transmission and the two-speed transmission without hydraulic torque converter in terms of maximum gradeability,maximum speed,and acceleration time.Then the driver model is built,and the SOC is used as an indicator to compare the economy of the vehicles matching the different transmissions under the FTP-72 and US06 cycle conditions.The simulation results show that the two-speed hydraulic automatic transmission can effectively improve the shift quality,and enhance the power performance and energy economy of the pure electric vehicle.