Simulation Analysis And Optimization Of Noise And Vibration Characteristics Of The Transmission Assembly

Noise pollution is recognized as the third largest environmental pollution,in which the noise caused by cars occupies a large proportion,so as early as the 1960 s,some countries began to introduce a series of measurement methods and laws related to car noise Regulations,vehicle vibration and noise characteristics and become an important evaluation index of the automobile development process.Cars will produce a variety of noises during driving.Gearbox vibration noise is the main one among many noise sources.Under various complex working conditions,due to the processing and installation errors of the gear itself and other uncertain factors,the transmission noise problem has gradually become prominent.Therefore,how to improve the NVH performance of the transmission has also become a problem of concern.First of all,from the causes and transmission channels,the noise types of the gearbox are classified in detail,and the knowledge of transmission vibration noise is systematically sorted out.According to the different noise generation reasons,the vibration noise generation mechanism of the transmission gear transmission system and the box body is analyzed.It is pointed out that the main excitations of the gear vibration noise are stiffness excitation,error excitation and meshing shock excitation,etc.which provide a theoretical basis for the simulation analysis of the transmission.Secondly,Hypermesh was used to establish the finite element model of the transmission system.Based on the established finite element model,the modal simulation analysis of the box body and the gearbox system was carried out respectively.From the results of the modal analysis,the box body is free The modal formation under unconstrained conditions provides a strong basis for gearbox noise reduction optimization.The method of comparison between experiment and simulation was used to verify the experiment,which verified the correctness of the establishment of the finite element model,and also proved the accuracy of the modal simulation results.Calculate the other excitations that the gearbox may withstand during the vehicle's working process,such as the natural frequency of the gearbox system obtained by comparing the modal simulation of the engine excitation frequency,road load frequency and gear meshing frequency,and explore whether the gearbox will appear during the work process Resonance phenomenon.Then,multi-body dynamics simulation analysis is performed based on AVL Excite PU software to simulate the vibration characteristics of the gearbox during normal operation.In this paper,the coupling finite element method and the multi-body dynamics method are combined to perform a single-piece finite element modal reduction on the established finite element model.As the input conditions of the body elements of the multi-body dynamics model,a flexible multi-body dynamics Learning model is established.In this paper,nine speed conditions are selected to simulate the dynamic coupling mechanism,and the data such as the speed of each shaft of the gearbox,the meshing force of each group of gears,and the vibration speed of the surface of the housing are calculated.Fitting the vibration acceleration curve of the shell surface on multiple working conditions to the Vibration acceleration Cambil diagram,and analyzing the vibration of the gearbox shell,the result shows that there is howling in the fifth gear,and the remaining four gears have sporadic knocks.Data recovery is performed on the reduced shell surface vibration velocity as a boundary condition for sound radiation calculation.Finally,the accuracy of the simulation is verified by the vibration test.Thirdly,the software AVL Acoustics is used as the acoustic analysis platform to generate acoustic grids and field point grids,and the shell surface vibration velocity obtained by multi-body dynamics simulation is used as the boundary condition.Acoustic radiation sound field radiation sound pressure cloud diagram and sound pressure value curve.The acoustic radiation verification test was also conducted on the gearbox.The change trend of the sound pressure level was basically the same,which also verified the accuracy of the simulation.Finally,on the basis of the above simulation analysis,two kinds of transmission vibration and noise reduction schemes are proposed.The first is to optimize the macro parameters of the gear pair that produces howling noise,so as to reduce the transmission error and excessive excitation generated when the gear is meshed,and reduce the noise from the excitation source.The second is to reinforce and thicken the gearbox body,increase the rigidity of the box,reduce the vibration transmitted to the box,and achieve the purpose of reducing noise from the propagation path.