Predicting Variation in the NVH Characteristics of an Automatic Transmission using a Detailed Parametric Modelling Approach 2007-01-2234

Generally within engineering design, the current emphasis is on biasing the development process towards increased virtual prototyping and reduced “real” prototyping.

Therefore there is a requirement for more CAE based automated optimisation, Design of Experiments and Design for Six Sigma. The main requirements for these processes are that the model being analysed is parametric and that the solution time is short. Prediction of gear whine behaviour in automatic transmissions is a particularly complex problem where the conventional FEA approach precludes the rapid assessment of “what if?” scenarios due to the slow model building and solution times. This paper will present an alternative approach, which is a fully parametric functionality-based model, including the effects of and interactions between all components in the transmission. In particular the time-varying load sharing and misalignment in the planetary gears will be analysed in detail. It will be shown how the transmission error in all gear pairs can be predicted and how this can be used to excite the transmission model dynamically to predict the vibration response in any part of the system, including the housing.

This will be illustrated with a model of a 6-speed automatic transmission showing correlation of the model with test data. An example will be given to demonstrate the ability of this approach to rapidly investigate the variation in manufacturing tolerances in parameters such as gear micro-geometry and how this impacts on the variability of the predicted transmission error and housing vibration.