Clutch Energy — A Criteria of Thermal Failure

A method is presented for computing the energy dissipation rate in a wet clutch that is part of a vehicle transmission system. This method takes into account the transients in the vehicle prime mover, the hydraulic torque converter, the powershift transmission, and the vehicle load.

The clutch energy rate is then used as an input to attempt to predict the interface temperature at the clutch surface.

The solution of the Fourier-Poisson unsteady state heat conduction equation is carried out using a finite difference method. The calculation of this interface temperature, called temperature index, is then correlated to actual clutch failure through experimental laboratory clutch testing. Results show a temperature index level above which failure is likely to occur regardless of the variation of clutch parameters.