Study On The Dynamic Characteristics And Parameter Identification Of Hydraulic Engine Mount In Automative Powertrain Mouting System

As the elastic link device between the vehicle powertrain and chassis, the vehicle powertrain mounting system is an important part to isolate the vehicle vibration and reduce vehicle noise, and its characteristic has an important influence on the Noise, Vibration and Harshness (NVH) characteristics of the vehicle. Hydraulic engine mounts (HEMs) are the most usually used isolation parts in the vehicle powertrain mounting system, and the researches on the vibration isolation characteristics of HEMs are the main research aspect of the vibration isolation of the vehicle powertrain.The abilities on the Resarch&Development (R&D), manufacturing and application of HEMs in the domestic-made automobiles are still in the initial stages nowadays. The structures of mounts in most domestic-made automobiles are simple and their characteristics are unideal. With more demand for riding comfort and the automotive industry's shift to small, four cylinder engines and transversely mounted front-wheel-drive powertrains, it is urgent that the design methods and techniques for HEMs be studied extensively and systemically.The modeling, parameter identification, performance analysis, test verification and parameter optimum of the HEM with inertia track and decoupler were studied to disclose its'vibration isolation mechanism and deduce the relations between the vibration isolation characteristics of the HEM and its'structure. All these work are aim to give some references to the design and research, structure improvement and performance optimum of HEMs. The main research contents are listed as follows:1. The modelings of the hydraulic engine mount were developed. Dynamic stiffness and equivalent damping coefficient are adopted as the indexes to evaluate the dynamic characteristics of the HEM in this study. The lumped parameter models of the HEM at low frequency, large amplitude drive and high frequency, small amplitude drive were developed based on the analysis of the structure and work principle of the HEM. The relations between the dynamic characteristic feature points of the HEM and the lumped parameters were deduced too. And the nonlinear model of the HEM considering the nonlinearities of the flow of the liquid in the inertia track and decoupler were developed in the end.2. The methods to identify the lumped parameters of the HEM were discussed. A new parameter identification method based on the dynamic characteristic feature points was proposed. In this new method, the dynamic characteristic feature points were obtained by tests of the HEM's dynamic characteristic firstly, and then the lumped parameters were calculated by the relation developed between the feature points and the lumped parameters. To validate the results by the new parameter identification method based on the dynamic characteristic feature points, the parameter identification method coupled fluid–structure interaction (FSI) and finite element analysis (FEA) was introduced. The simulated dynamic characteristics utilizing the parameters derived by the above two methods consists well with the tested dynamic characteristics,and it is implied that the lumped model developed and the parameter identification methods proposed can describe the dynamic characteristics of the HEM with inertia track and decoupler well. The simulated dynamic characteristic curve by the parameter identification method based on the dynamic characteristic feature points are more approaching to the tested dynamic characteristics, and it is implied that the parameters derived by this method are more precise.3. The dynamic characteristics of rubber mounts and HEMs were analyzed and compared and the dynamic characteristic features of rubber mounts and HEMs were deduced. The rules which the lumped parameters and structural parameters including the dynamic stiffness and damping of the rubber spring, the equivalent piston area of the rubber spring, the volume stiffness of the upper chamber, the length and cross-sectional area of the inertia track, the inertia coefficient and damping coefficient of the decoupler affect the dynamic characteristics of the HEM were studied and analyzed theoretically and experimentally.4. The multi-objective optimum method of the HEM was developed. The parameters including the dynamic stiffness and damping of the rubber spring, the volume stiffness of the upper chamber, the length and cross-sectional area of the inertia track, the inertia coefficient and damping coefficient of the decoupler were selected as the design parameters, and the peak dynamic stiffness and equivalent damping , the frequencies which the peak dynamic stiffness and equivalent damping emerge, and the dynamic stiffness and equivalent damping at high frequency approaches to infinite were adopted as the optimum objectives, and thus the multi-objective optimum model of the HEM was developed. The model was solved using the Pareto GA combined the fuzzy penalty function method and the optimum solution was validated experimentally. The objective function values of the optimal result are decreased remarkably. The optimal result is more satisfied with the vibration isolation requirements of the engine mounting system and has better vibration isolation characteristics.