The Design And Development Of Two-speed Automatic Transmission For Electric Vehicle

The development of electric vehicle is the only way to reduce vehicle fuel consumption and emission, improve the atmospheric environment and meet the emission regulations. The drive system of electric vehicle has a key role in this regard. But nowday, all of the electric car on the market are matched with single-speed gearbox, however there are some restrictions on its electrical drive means in power performance and electrical efficiency. Therefore, the R&D of dual speed automatic transmission used on the electric cars has important practical application value to improve the electric car’s power performance and electrical efficiency, and reduce motor costs.Designing dual speed automatic transmission which in line with the needs of electric car drive is the goal of this paper. Aiming at the development status of transmission technology of modern electric vehicle, and combined with the actual project needs, this paper focus on the system parameters and structure design of dual speed automatic transmission, modeling and test of the virtual prototypes, dynamics model of power shifting process, optimal control of the gear shifting.In chapter 1, according to the research background and status of the electric vehicle transmission system, the necessity to carry out research work of this paper has discussed, the characteristics of various types of the existing traditional car ’s transmission and the characteristics requirements of the electric vehicle transmission were analyzed.The second chapter has completed the system design and calculation of dual speed automatic transmission. Firstly, the overall structure of the system has been designed and demonstrated, a new type of clutch / brake integrated planetary shifting structure was proposed. And then the integrated structure and parameters of planetary gear mechanism, integration of the clutch/brake shift mechanism, electro-hydraulic control system has been designed. Finally, the strength of the main parts were checked with the finite element method.In chapter 3, the dual speed automatic transmission was simulated based on the Romax commercial software. According to the drawings of structural design of dual-speed automatic transmission, a virtual prototype model of dual speed automatic transmission was established with Romax. By setting the simulation parameters in line with actual operating conditions to simulate the operation of each gear, the stress state, fatigue life and strength situation were obtained under the earch gear. The result verified the correctness of design of the dual speed automatic transmission.In chapter 4, the dynamics model of dual speed automatic transmission was established. Firstly, through the establishment of a simplified physical model of the system, using lagrange equation has established and solved the differential equations of motion of transmission system, and has established input, output and friction torque model. Then focus on building the dynamic model of the hydraulic actuator which is closely related with shifting performance. Linear proportional pressure solenoid valve were tested, in order to gain the output pressure- input current curve which is very important to the performance of shifting control. A vehicle model of the motor fixed with speed ratio reducer and two-speed automatic transmission is established in the simulation environment of Matlab/Simulink.