Optimum Design Of Engine Mounting System Based On Improved Transfer Path Analysis

With the rapid development of industrialization, the vibration and noise have been one of the pollute sources, and influence the people's life,work and study, even the health and psychology, leading to many psychogenic and physiological diseases. During the one hundred years of automotive naissance, the science and technology has been rapid developed, and many newest research production have been applied on the vehicle, the total number of vehicle in the world is increasing, so the pollute problem caused by vehicle is universal and serious. At the same time, with the improvement of people's living standard, they do not settle for the walking instrument only, especially they also need vehicles have better ride and traveling comfort of vehicle, so the NVH of vehicle (Noise,Vibration and Harshness) have been paid attention more and more in the world. The noises of vehicle include two parts, one is the interior noise, and the other is the exterior noise, and the developed nations have established many statutes and measurement methods based on the characteristic of country, even these rules prohibit selling the vehicle which does not meet the criterion of the vibration and noise rules. These methods make the interior and exterior noise become lower and lower, and the statutes have become rigid more and more. At the same time, these methods also accelerate the development of NVH technology and measurement technology.In china, the research of NVH is only carried out in recent years, and Chinese government has established correlative statutes, but they are not rigorous as the developed country. In these years, the total number of vehicle in China is increasing rapidly, and Chinese government has to amend the correlative statutes and keep the same step with the development of world, so all of these needs the auto manufacturer and research institute try their best to achieve farther detailed understanding of the compartment vibration generation mechanisms and the measurement methods, only by this way, it can confirm the indigenous automotive production can have a room in the international competition, and improve the technology level of independent research and development of Chinese vehicle.There are many elements can lead to NVH problems and generation mechanism is very complicated, the interior and exterior noise is caused by vibration of vehicle, and the powertrain is the main source of vibration and noise, so the control of vibration and noise of powertrain is the main aspect of improving the NVH and traveling comfort. In a national project of Jilin University (863 Program), the goal of this work was to achieve farther detailed understanding of the compartment vibration generation mechanisms. Through the test, an innovative optimum method of identification parameters of powertrain rigid body based on operation modal method was improved, and the vehicle vibration and analysis model was built based on transfer path analysis of vibration energy. By the method of test and simulation, the main vibration source can be found, and an innovative optimum method of engine mounting system based on transfer path analysis was introduced. Then the method was applied to optimize engine mounting system, and the optimum results were contrasted with the traditional energy decoupling method, finally, the effectiveness of the proposed method was validated through optimum of engine mounting system of the car.The control of the interior noise is a complicated system project. The background knowledge of transfer path analysis and the transfer function relation of complicated subsystem were introduced, and then the mathematical equations of improved transfer path analysis method were introduced, the Accuracy of transfer function was improved in theory, so the test period of traditional transfer path analysis can be shorted. With the method, under laboratory conditions, the vehicle was located and accelerated slowly, the acceleration data (engine mounts/chair rail/steering wheel/board/gearshift) were obtained, and the vehicle vibration transfer path analysis model was built and amended by these data, . Then the transfer function model of engine mount was built too. These data were put into the vehicle vibration model and predicted the interior vibration, by the contrast of predict results and test results, the effectiveness of the proposed approach was validated.By analysis the vibration generation mechanisms of interior vibration, the vehicle interior vibration model of transfer path analysis was built. The structure of each vibration transfer path and the calculational method of transfer function were analyzed, the each essentials and step in the process of building the vehicle model were analyzed in detail. After the analysis of the vibration source of interior aim point and transfer function of each vibration transfer path, the main vibration transfer paths of interior aim point were picked out.By the vehicle model based on the test data, an innovative optimum method of engine mounting system, which based on transfer path analysis, was introduced. Then the optimum of transfer functions of engine mounting system can be carried out based on this method, and the optimization results of stiffness were obtained, at the same time, an innovative criterion of engine mounting system also was improved under real vehicle operation conditions. So it is not necessary to use the general criterion of engine mount system (20dB) to evaluate the mount system.An innovative optimum method of identification parameters of powertrain rigid body based on operation modal method was improved. With the method, under real vehicle operation condition, the modal parameters and inertia parameters of the powertrain were identified, and these parameters are more accurate and can be used to optimize the engine mounting system. At the same time, these parameters also can be used to evaluate the rigid body modal design of powertrain. The original stiffness of engine mounts was tested and the stiffness can be the preliminary data in optimum of engine mounting system.The mount system of the car was decoupled and optimized. The results of energy decoupling method were contrasted with the results of transfer path analysis method in following aspects, such as stiffness, energy decoupling, vibration transfer rate, interior vibration and so on. The contrast results show the transfer path analysis method is better in vibration transfer rate and interior vibration, but is worse in energy decoupling. So the effectiveness of the transfer path analysis method was validated in theory. Finally, the samples of the mount were made by the results of transfer path analysis method, and assembled them on the car. By the real car testing, the results show that the interior vibration can be controlled effectively, and the effectiveness of the proposed approach was validated.In the paper, the vibration energy transfer characteristic relations of vehicle different subsystems were built by vehicle test data and the main vibration sources and transfer paths of interior vibration were picked out by the model, the engine mounting system was optimized by an innovative transfer path analysis optimum method, then an innovative criterion of engine mounting system also was improved under real vehicle operation conditions for different kind of vehicle.