Modeling Torque Converter Clutch Viscous Damper Performance

A viscous damper is used as part of the automatic transaxle torque converter in some new passenger cars for improved driveability and fuel economy. A viscous silicone fluid is a critical component of the damper. Fluid viscosity-shear rate characteristics were determined in the laboratory for temperatures of 25 to 150 °C at shear rates from 400 to over 6000 reciprocal seconds. Using these data, and the dimensions of the viscous damper, a mathematical model was developed which predicts viscous damper output torque. Correlation between model predictions and actual measured torques from dynamometer tests was excellent. As a result, the mathematical model is useful for predicting viscous damper performance from measured fluid viscosity-shear rate characteristics. Also, since the model includes the critical viscous damper dimensions, it can be used for determining effects of damper design modifications on damper performance.