Testing Analysis On Auto Transmission Nvh And Improvement For Transmission

With the improvement of automobile technology, people have higher requirements for automobile comfort, so vehicle NVH (Noise, Vibration and Harshness) becomes a general item to measure the vehicle quality. The vibration and noise of the automobile mostly comes from the engine and transmission system. However, automobile's transmission system is mostly comprised of gearbox. So it shows the especial crucial significance to knock down the vibration and noise of the whole car, by depressing the vibration and noise resulting from the transmission.Based on retrospect of all the nation and oversea progress in the automobile transmission vibration and noise research, whether in the past years or nowadays, the importance and necessity of testing research of transmission NVH is made very clear. Firstly, the dominating factor of the vibration and noise of the transmission is analyzed, and the analysis on the transmission mechanism of the influencing factor is also carried through. They provide theoretical support for testing analysis. Then, taking a certain type gearbox produced by the company as research object, two different test plans which include NVH target testing and NVH noise source testing, are marked out. In addition, Wave filtering analysis, order analysis, FFT analysis, etc, all of these the analysis by synthesis methods are chosen. Through analysis, the reason that causes the vibration and noise was found out and the methods for controlling the vibration and noise are designed. Finally, according to the NVH target testing results, the transmissions by modeling are analyzed, and load spectrum analysis on one transmission whose sound pressure level is not eligible is carried out. And the influence factors on NVH are found out and relevant improvement is made. After that, the improved transmission is tested by NVH target testing and the new testing result is analyzed. At last, it is proved the diagnose result is correct.In this dissertation, the principle of the causing reasons for transmission's vibrating noise is studied and the testing schedule for transmission's NVH is designed. It offers effective help for enterprises about solving NVH problems. At the same time, the modal analyzing method is given in this dissertation, which is of practical significance for analyzing and improving transmission's NVH problem.