Optimization Design Of Mounting System Of YBL685OH Bus Engine

With the development of the society, the request of the comfort performance is more and more high, the vehicle's high-speed has been improved, but at the same time the vibration problem is increasingly serious. High ride and low noise are very important, the noise is one compellent item. Therefore, the optimization of the engine mounting is an important research in the world, and the engine mounting system's design directly affects the transfer of the vibration energy and the vehicle's NVH(Noise, Vibration and Harshness).This paper based on lots of the references and the deep study about the isolation vibration. The engine mounting system primarily contains three functions(support, limiting position, isolation vibration).By analyzing the single-freedom-degree vibration system , when the frequency of outside excitation meets the natural frequency of the engine mounting system, resonance will take place and enhances vibration of system which will cause the bad result. From the diagram of amplitude-frequency respond curves, we can know that system produces the effect of vibration isolation, the ratio of excitation frequency to natural frequency must be larger than 2.The most important excitation is firing pulse in idle, therefore , the natural frequency of the engine mounting system is 1/2 time than the firing frequency..The engine mounting system is a complex multi-freedom degrees vibration system. We must consider its natural characteristics of three axes directions and three rotary directions. We establish the six-freedom-degrees vibration model, deduce the solution of the vibration equation and write out the related program which is convenient to the result of the natural characteristics of system.General, the vibration coupling exists in every vibration model of the engine mounting system. The vibration coupling is related to the centroid position of the engine, the position of the main inertial axis, the stiffness and position of the engine mounting. The vibration coupling extends the range of the resonance frequency ,then increases the difficulty of the isolation vibration. Therefore, we must reduce he degree of the vibration coupling. In order to improve the decoupling level and the degree of vibration, we properly adjust the system parameters by the energy theory.Because of the influence of the whole vehicle arrangement, it's difficult to change the mounting position and the installed angle, we compare three mounting projects of the different stiffness in order to improve performance of the isolation vibration. We adopt the most suitable project by the subjective evaluation from three optimized projects.In this paper, we apply the optimized program to the natural characteristics of the mounting system ,which provide the reasonable matching of the mounting system, reduce the cost of product development and shorten the period of the product design. At the same time, this paper can also provide the precious experience to the future work.