Search Results

An integrated approach to modeling end of useful life of an automatic transmission fluid (ATF) has been developed. The flexible fluid life model allows either predictive or real-time calculations of the end of useful fluid life under different transmission design strategies and customer driver behaviors as reflected in operating temperatures, shift characteristics, fluid volume and fluid distribution throughout the transmission. An estimation of remaining useful fluid life is monitored using two metrics, namely bulk oxidation, as a general indicator of fluid quality, and frictional degradation, as an indicator of shift quality. As operating conditions increase in severity, ATF is subjected to conditions that may shorten its life. Using the developed technique, ATF useful life can be better predicted.

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.