Research On The Test And Evaluation Method Of The Vibration Isolation Performance Of The Automotive Engine

With the on-going prosperity and development of the auto industry, NVH problems attract more and more people’s attention. As one of the core problems of NVH, the vibration isolation performance of engine mountings has became the focus concern in some vehicle research and design center. The engine mounting with good vibration isolation performance can not only largely reduce the random vibration transmitted to the car body which is produced by the engine, but also can effectively block the vibration transmitted to the engine which is caused by the road excitation.The former can improve the comfort of passengers and drivers, and the latter can guarantee the reliability of the engine. However, currently our country lacks a set of systematic and complete test and evaluation plan of engine mounting vibration isolation performance, and most of the engine mounting vibration isolation performance test plans are still at unit test level.In order to more effectively and accurately test and evaluate the engine mounting vibration isolation performance, in this paper, the engine mounting vibration isolation performance test and evaluation mehods are studied, and the details are as follows:(1) As for the test method, this paper presents "direct test method" and "indirect test method". The direct test method is targeted at testing the sample car, and pick up the random vibration signals from the upper and lower engine mounting under different conditions. The indirect test method is for testing 3 different engine mountings of the same engine, and pick up the random vibration signal from the driver seat’s guidance rail.(2) As for the evaluation method, this paper presents "rough evaluation method" and "precise evaluation method".With rough evaluation method, the maximum values of the random vibration signal amplitude of the upper and lower engine mounting are compared, and the engine mounting vibration isolation performance are evaluated. With the precise evaluation method, the statistical algorithm is used process the random vibration signal in time domain and frequency domain.(3) With rough evaluation method and precise evaluation method, the random vibration signals of the sample and test cars picked with direct test method are processed." The conclusion sre obtained as follows:the engine mounting vibration isolation performance of the sample car is better than the test car when the car is under idling condition, and worse than the test car when the car is under even-speed and acceleration condition.(4) With rough evaluation method and precise evaluation method, the random vibration signals picked from the driver seat’s guidance rail with indirect test method. The conclusion sre obtained as follows:the vibrarion isolation ability of Mounting C is better than that of Mounting B, and the vibrarion isolation ability of Mounting B is better than that of Mounting A.This paper established an engine mounting vibration isolation performance test and evaluation system, and formed a complete set of engine mounting test procedures, which can test and evaluate the vibration isolation performance of auto engine mounting more accurately and effectively. This set of engine mounting vibration isolation performance test and evaluation system can provide a reference for the future study of auto NVH and some related issues.