6 Speed Automatic Transmission Vibration Magnitude Prediction and Whine Noise Improvement through Transmission System Modeling 2011-01-1553

As automotive technology has been developed, gear whine has become a prominent contributor for cabin noise as the masking has been decreased. Whine is not the loudest source, but it is of high tonal noise which is often highly unpleasant. The gear noise originates at gear mesh. Transmission Error acts as an excitation source and these vibrations pass through gears, shafts and bearings to the housing which vibrates to produce noise on surrounding air. As microgeometry optimization target to reduce the fundamental excitation source of the noise, it has been favored method to tackle gear whine noise, especially for manual transmission. However, practicality of microgeometry optimization for the planetary gear system has been still in question, because of complex system structure and interaction among multi mesh gear sets make it hard to predict and even harder to improve.

In this paper, successful case of whine noise improvement by microgeometry is presented. System level simulation model with accurate details of actual test system condition such as clearances, measured microgeometry and test rig condition were constructed. The vibration at the accelerometer location at the housing was predicted using the model. The comparison of the result to test result showed very good correlation. Especially, the absolute housing vibration level matched very well, which allowed engineers to use the simulation result during optimization process to make decision quickly without having to run the actual test to know if the improvement was sufficient enough to meet the vibration target. Microgeometry optimization was done for all gear sets in the rear planetary. The predicted result of vibration showed 3 m/s₂ reduction at the target speed range under target torque condition. The noise test result confirmed that the noise was reduced by 5~6 dBA and the design target could be satisfied.