Influence of the Flatness Ratio of a Torque Converter on Hydrodynamic Performance

Passenger car torque converters have been designed with an increasingly flatter profile in recent years for the purpose of achieving a weight saving and more compact size. However, a flatter design has tended to result in reduced hydrodynamic performance and the basic mechanism involved is still not fully understood. In this study, four torque converters with different flatness ratios were manufactured and tested in order to evaluate the effect of the flatness ratio on overall performance. The internal flow characteristics of the torque converters were numerically investigated using a CFD code. It was found that performance deteriorated when the flatness was less than about 0.2. The main cause of this performance deterioration can be attributed to nonuniformity of the velocity fields of the pump. Such nonuniformity occurs not only from the inlet to the exit, but also from the shell to the core in the flow passage.