The Study And Simulation On The Shift Quality Of Automatic Transmission

As the development of automobile technology, the convenience and comfort are highly desired by people. Automatic transmission is the main part of the vehicle driving system, so it has much influence on the performance of the vehicle. Automatic transmission shift up and down through the joint and with drawing of the unite components, so the shift process is actually the process jointing and withdrawing of the unite components.Because of the different speed ratios, the state of the driving system has a sudden change, but the joint components can't act in time; And at sometime the friction moment of the components change; All These will cause a impact of the vehicle and the increase of the components temperature.In this paper the influence of Automatic transmission's shift process to vehicle driving smoothness, drive system load and the life of the unite components is analyzed. The evaluation method and index of shift quality are introduced from subjective and objective points. Also the methods to improve the shift quality are brought forward based on the influencing factors.To simplify the planetary mechanism of automatic transmission to equivalent lever, the engagement and disengage-ment of the clutch, the operational condition of shifting component and the transmission path of power are judged straightly applying to the force diagram and revolution relation chart It will simplify the structure of the planet gear to apply the lever analogy to planet gear system, and the dynamics equations are easy to get. The dynamics model of the automatic transmission's shift process is built up through simplifying the engine-torque converter model. So the dynamics equations are obtained from the mechanics model. The shift process and the oil pressure regulations are studied and many conclusions are got to improve the shift quality.The simulation model is built up.AG4's shift up process and shift down process are studied based on this model. The result of which shows the change in amplitude of the output shaft angular acceleration and that of the degree of jerk are noticeably reduced when applying the new oil pressure pattern to control the process in the AG4 automatic transmission. Therefore, the smooth shifting control is achieved by reducing the shock subjected during gear-shift, and thus the gear-shift process is greatly improved.