Lai K., Yang C.

In recent vehicle development, the noise and vibration reduction is an important design index to fit customer expectation. It is also well understood that the vehicle sound is not only about 'sound pressure' but also about 'sound quality'. Powertrain system vibration can result in an increase in vehicle interior noise when excited by engine loads through the vehicle body. To evaluate the powertrain system vibration, the finite element method was applied to calculate the normal modes of the powertrain system. In this paper, Hybrid CAE technology combined numerical and experimental analysis is applied for the passenger car to improve the NVH characteristics caused by normal mode of powertrain system. The target to enhance the performance of noise and vibration is to improve the sound quality. Using Hybrid analysis technology, the difference between the experimental frequencies and analysis frequencies are about 3%. Updating CAE model can be applied to modify and optimize the characteristics of powertrain system. In order to reduce the powertrain vibration, the powertrain stay was designed to increase the stiffness of powertrain system. The vibration level of first bending and torsion mode will affect the interior sound quality directly. From the result of modal analysis, the natural frequencies of first bending and torsion mode were increased significantly. The run-up testing was used to verify the effect of the powertrain stay. From this test results, the vibration magnitude of 3rd to 6th order were decreased, especially for 4th and 6th order. In addition, the Index of sound quality was also become better than original condition.