Research On Nonlinear Dynamic Characteristics And Parameters Optimization Of Automotive Transmission

Automotive transmission noise is one of the main noise source of the car, the vibration of transmission often lead to the vibration of the other parts connected to the transmission,which may affect the NVH(Noise, Vibration, Harshness) of the complete vehicle, therefore, controlling the vibration noise of transmission and improving the dynamic performance and vehicle ride comfort, is one of the key ways to inhence the competitiveness of the automobile enterprises. At the same time, the whole world is facing huge social problems of harmonious development in energy and environment, especially our country is facing a very grim situation to achieve the goal of energy saving and emission reduction, which brings about urgent demand on the automotive lightweight and energy saving technology in the power machinery industry in our country. Mechanical manual automotive transmission has its own special advantages, that is widely used in different types of cars, in the future for a long time, it will occupy an important position in the automobile transmission industry. In recent years, according to the automobile transmission vibration and noise problems of dynamics, lots of scholars and automobile enterprises invested a great effort, manpower and material resource in the research, with the development of computer technology, modern design theory and method, such as finite element method, virtual prototype technology have been applied widly in the development and design of transmission products, which can not only greatly shorten the the research and development period, but also improve the accuracy of simulation, in order to meet the need of the constant changing market.The dissertation mainly from the analysis of dynamics characteristic of a transmission power train assembly system, according to some dynamic problems needed to be solved urgently, based on theoretical analysis, numerical simulation, virtual prototype, experimental verification means, the related problems of dynamic characteristic optimization and vibration and noise reduction have been studied deeply. The main works are as following:According to virtual prototype model of the typical car transmission assembly, the factors affecting solution of the modal of the transmission gear system are discussed, based on the explicit dynamic finite element method, the dynamic meshing characteristics of the transmission gears and effect of different simulation model on meshing characteristics are studied. The relation of dynamic stiffness with load frequency, the magnitude of load and temperature and other parameters are obtained by using the finite element simulation test. The dynamic model with whirling-swing coupling vibration of a different offset disk rotor system supported on ball bearings is established, and the paper puts emphasis on discussing the effect of disk swing, rotor offset and ball bearing clearance on critical speed and vibration amplitude of the rotor system. Rattle noise of the transmission gear system are gradually becoming the key problem the design process of transmission, on the basis of predecessors research, in the paper the gear rattle dynamic model of the transmission is established by simplifing the incentive effect of driving gear tooth into simple harmonic excitation that the fundamental frequency is gear meshing frequency, the effects of gear parameters and working conditions on the rattle characteristics are analyzed, the parameters of each gear clearance and idler gear equivalent mass are optimized to reduce the rattle noise of the whole transmission system, the research provides the basis for the similar product improved design. Finally, the stiffness and strength of the transmission gearbox is calculated under the bearings reaction force, and the topology optimization design of the transmission gearbox is carried out based on the structural strength analysis, and the gearbox lightweight is realized.In this dissertation, from the view of engineering application, in-depth and detailed research of some dynamic problems of a typical car transmission are carried out through the simulation analysis and optimization of the structure, the new dynamic models of the related issues are established, and the related analysis method and process have been developed, some research results obtained will play an important role in shortening development cycle of the similar products and improve the performance of domestic transmission.