Prediction of Drag Torque in a Disengaged Wet Clutch of Automatic Transmission by Analytical Modeling

Abstract

In the automotive industry one of the crucial issues is reduction of CO2 emission to protect environment. A lot of researches have been done to reduce the CO2 emission of cars by improving efficiency of engine and engine parts or lowering the weight. However, a significant reduction of CO2 emission of cars can also be obtained from improvement of efficiency of transmission by reducing drag torque or spin loss in disengaged wet clutch. The reduction of drag torque can be achieved by introducing groove on facing of clutch disk and further reduction can be obtained by optimizing the shape of groove. Generally, the optimum shape of groove is decided by trial and error method which requires time, making sample, conducting a lot of tests and wasting a lot of raw materials. In this research, we proposed a new analytical model to predict the drag torque characteristics of a disengaged wet clutch of transmission without making any samples and performing any tests. The feature of the model: It bases on continuity and Navier-Stokes equation, a real time visualization investigation and laminar flow. The model is validated with tests results and the comparison result shows that they are very close to each other. The significance of the model is: it captures the multiphase drag torque characteristic which changes with changing gaps, speeds and oil flow rates. Moreover, the model is a green environment friendly tool to estimate drag torque characteristics without making any samples or conducting any drag tests.