A study of the shifting transients of a torque converter equipped vehicle

A torque converter, the major component of an automatic transmission, is a hydrodynamic device that has a great influence on the transient characteris tics of a vehicle during gear shifting. To predict accurately the vehicle c haracteristics, detailed analysis of the torque converter is required. In t his study, the classical one-dimensional modelling of the torque converter, based on the concept of the mean flow path, is used to analyse the shiftin g transients. It is proved that the equivalent parameters included in the m odelling can be determined from the experimental results by using nonlinear optimization methods. Dynamic modelling of power transmission components, such as clutches and planetary gear systems, are also considered The clutch engagement condition, which determines the degree of freedom of the system during shifting, is proposed. In the modelling of the power transmission s ystem, the stiffness of the shaft and various control logics are included. Using the developed simulation method, the effects of the design variables and the control conditions are evaluated. Finally, the results of the drivi ng simulation are compared with those of the dynamometer-based experiments.