Study of the shift process of a hydrodynamic automatic transmission considering the vehicle driveline system

The hydrodynamic automatic transmission is the most widely used automatic transmission, which is the core assembly of automobile to achieve automatic manoeuvring. Its shift quality is ultimately reflected as the vehicle's driving status through the transmission system. In this paper, based on analysing the power transmission route of the transmission system and the structural principle of the six-speed automatic transmission. It discusses its mathematical model and the evaluation index of shift quality in the process of shifting and establishes the AMESim model of the whole power transmission system including the automatic transmission. By simulating the process of accelerator pedal depressing and releasing, the heat generation of each clutch and brake is calculated. The changes of parameters such as engine torque output, vehicle speed, acceleration and impact degree during the gear shift were obtained. The effects of different torsion spring stiffnesses of the transmission system on the degree of impact are analysed to provide theoretical basis and reference for the subsequent structural design of the hydrodynamic automatic transmission.