The Research Of Vibration Isolation And Noise Reduction In Automobile Engine

The good performance of NVH is the target of automobile comfortability,and the exemplification of a top quality engine.However,the conflict between the demand of the NVH technology and the supply of it is critical.So the systemic research of NVH is essential to engine and automobile.In this background,the paper deepens the research of NVH on a certain engine mainly about the idetification of sound and vibration,including some NVH control technology.Solving the pollution problem of sound and vibration have already been one of the challenging issues.Lowing noise and vibration isolation are significance in the process.Theory analysis ,experiment doing and virtual design are hired in the paper for the research of sound and vibration of the engine.There are two aspects of the research content, as follow:Firstly, engine mounting is one of the research objects. There are two kinds of mounting, including rubber mounting and passive hydraulic mounting. The elements effecting the dynamic characteristics of the mountings are analysed.with the use of experiment-doing method, the frequency respond characteristics and dynamic stiffness of rubber mounting are studied. Simulation calculation of rubber mounting renders a clear direction for the improving of the mounting performance. Through reasonable design of construction, the isolation ratio of the mounting is lowed to 0.1.Meanwhile,the mounting obtains the good performance of bending, squeezing, shearing. Due to more and more demanding of comfortability and smoothness from customers, the development of NVH technology within engine is limited by the short of deep research .Because of so, comparison of dynamic stiffness and phases characteristics of three passive hydraulic engine mounts in the low frequency domain (0~50Hz) and high frequency domain (50Hz~250Hz) respectively is the main task in the paper. It shows that the dynamic stiffness of the HEM with only one inertia track is the highest among the three. In the low frequency domain, the dynamic stiffness of floating-decoupler hydraulic mount increases faster than the others. The characteristic of'hard'and'soft'in the low frequency domain and high frequency domain respectively is distinguished among the three.Secondly, the optimization and improving of engine NVH characteristics within the engine system is another important content which focuses on oilpan. According to the NVH analysis results report of the engine, oilpan contribute a lot to overall noise level, therefore the noise level of which is abnormal. It is priority to building model of the oilpan by using the software of LMS.virtual.lab.After that, the author does some model tests by LMS.lab test system. The noise density power reports are given out to verify the optimization of oilpan. In the process of developing superior NVH characteristics, the pattern, dampness, frequency of model are analyzed. The result report of pattern and tranfer function shows that the area of aberrant sound and vibration is obvious in the oilpans. Based on the result, some measures are taken up to improving the dynamic characteristics.