The Parameter Optimization Of Engine Mount System

The engine mounting system which can reduce the vibration from engine to vehicle body as well as the inside noise has attained significant attention, and it is also the critical factor which control the vibration and noise of vehicle. During the working condition, the exciting forces from engine and road are two main vibration sources that cause vehicle vibration; the high performance of engine mounting system can largely isolation the vibration of vehicle body and noise caused by vibration of relevant components, thus improve the endurance and comfort of vehicle.Presently, there are two main methods to design mount system, one is the traditional method—mode decoupling, which controls the system response by changing the stiffness matrix to arrange system modes; the other one controls force transfer between the engine and body by optimizing the parameters of mounts with dynamic response as objective directly. With the two methods, optimization of engine mount system of some national FF car is studied in this paper. The following content is included:①The mathematic model of engine mount system that is used to mode decoupling is set up, the disturbance frequencies of engine mount system are analyzed and engine mount system mode frequencies are proper arranged. With energy mode decoupling theory, the modes of engine mount system are decoupled.②Analyze the influence of main components of engine exciting force on the NVH performance and transmission path, which provide basic exciting data for dynamic analysis model. The main work includes the simplification of calculating formulation, compilation of calculating program using the Matlab language, the application manner of excitation force in the dynamic model.③Established the multi-body dynamic analysis model of engine mounting system, and check the validity of the established model through comparison of response between the results obtained from the established dynamic model and similar measurement. Simultaneously, the modeling and realization method in Adams of rubber mounts and hydraulic mounts were also analyzed.④Based on the above, dynamic optimization of the engine mounting system was carried out restrict to boundary and frequency restrict. The mount stiffness, fixing orientation and hydraulic force parameters were taken as design variables, the reduce of acceleration was taken as optimization object. The optimization results of three optimization methods indicated that the isoceles triangle manner proposed in this paper, which put the centroid of the triangle at the centroid of the engine and made the plane of left mount and right mount parallel to the XZ plane of crankshaft coordinate is very effective in reducing the dynamic response of engine mounting system, and obtained the purpose of improve the isolation vibration performance of engine mounting system.