Dry Dual Clutch Transmission (DCT) Thermal Model 2015-01-1144

Dual Clutch Transmissions (DCT) for passenger cars are being developed by OEMs and suppliers. The driving force is the improvement in fuel economy available from manual transmissions together with the comfort of automatic transmissions. A dry clutch system (dDCT) is currently the subject of research, development, and production implementation. One of the key issues in the development of a dDCT is clutch durability. In dry clutches with current linings, above a critical temperature, the friction system starts to suffer permanent damage. In addition, the clutch friction characteristics are a function of the clutch interface temperature. Because a reliable, low-cost temperature sensor is not available for this application, the clutch control engineers rely on a good thermal model to estimate the temperature of the clutches.

A thermal model was developed for dry dual clutch transmissions to predict operating temperature of both pressure and center plates during all maneuvers. The model is intended to be used to a) prevent clutch plate over-heating during abusive driving scenarios such as hill holding or multiple GCVW launches in both forward and reverse on grades and b) estimate clutch friction characteristics for control purposes. It is a Simulink based model that is integrated into the transmission controller to notify drivers and take corrective actions in case of overheating. The model also predicts the initial conditions for the temperature of the clutches during engine startups. The thermal model was validated fully in a test cell environment as well as in vehicles using slip ring and telemetry hardware. The thermal model has seven states that include both bell housing air and skin temperatures. Other parameters that affect cooling performance of a dry DCT, such as ambient temperature, and engine coolant and transmission oil temperatures, are also taken into consideration.