Research On Matching Of A Powertrain Mounting System With Effect Of A Flexible Base

The engine is one of the major vibration sources of vehicle when it is running. Reducing exciting force which is transferred from engine to support has significance meaning in vehicle noise, vibration and harshness research. Engine and transmission rigidly connected, generally referred to as the Powertrain. The Powertrain mounting system is the only one that connected the Powertrain to the frame. So it has great significance in promoting the vehicle riding comfort through reasonable design of powertrain mounting system.In this paper, the research object is a commercial vehicle powertrain mounting system. First, discussing the existing research results in matching powertrain mounting system, analyzed the characteristics of this result. On this basis, the author adopted the reduction theory to build the Powertrain mounting research model which contains the flexible foundation and conduct the corresponding research.The traditional six degrees of freedom mathematical model of powertrain mounting system is established. And then the correctness of the model is verified by comparing six degrees of freedom model with the corresponding multi-body model. Through analyzing the model characteristi cs include frequency, vibration mode, energy distribution and reaction force, this work reveals that the original powertrain mounting system can’t meet the requirements of vibration isolation theory. In order to improve the vibration isolation performances, taking the minimum reaction force as the optimized goal and system energy distribution as restriction, a set of optimum parameters is obtained. After optimization, the model energy of powertrain mounting system is highly decoupling, moreover the reaction force is significantly reduced.Traditional six degrees of freedom model regarded the frame as absolutely rigid, but in fact the frame is a large deformable str ucture and the flexibility can’t be neglected. Considering this shortage, flexible frame struct ure is taken into account in the mounting system to explore the modeling and optimization method of powertrain mounting. This paper adopted the GUYAN reduction method to reduce frame finite element model. The reduced model retained the original frame model of flexible features(modal frequency and vibration mode, etc.). According to the dynamics relationship, the coupling model which contains the flexible frame is established. The coupling model is not only has more modal information than six degrees of freedom model, but it also has higher computing efficiency than the multi-body model.The author applied optimization result of the six degrees of freedom model to the coupling model, the result reveals the optimization results the optimization model can improve the vibration isolation performance in the commonly used speed range, but it can’t increasing the vibration isolation performance in the idle speed condition. Finally, basis on the coupling model, this paper optimize the mounting system parameter, and get a good vehicle vibration isolation performance. The optimization result also shows that the optimization model has good robustness.