Performance analysis and optimization design of variant CR-CR 9-speed automatic transmission

With the growing demand of people for fuel economy, driving comfort and environmental friendliness of automobiles, the development of high-gear automatic transmissions (ATs) with outstanding performance has become a research focus in the automotive field. However, the lack of systematic research methods has impeded the progress in this field. This paper presents a performance analysis and optimization method for high-gear variant CR-CR 9-speed AT. Firstly, the lever method was employed to calculate the transmission ratios of each gear position, the relative rotational speeds of each component, and the internal and external torques of the transmission, and a general formula for transmission efficiency was derived. Secondly, in order to enhance the performance and efficiency of the transmission, a scaled optimization algorithm was programmed, obtaining the optimal scheme of transmission structure with the highest efficiency and the optimal speed ratio step value ranges for the reduction and acceleration gears. Finally, three-dimensional modeling and simulation were carried out to verify the correctness of the theoretical derivation and the feasibility of the most efficient structure scheme. This method can provide a theoretical foundation and technical support for the improvement and preferred application of high-gear ATs.