| With the continuous development of the automobile industry,countries continue to formulate more stringent noise regulations and standards to reduce the harm of noise outside the car to the environment,and the new generation of vehicle users gradually put forward higher sound quality requirements.Driven by these factors,the level of automobile research and development has been continuously improved,and the R＆D personnel have effectively treated the previously prominent engine noise and tire noise.Because of the change of shielding situation,the problem of transmission gear noise has become increasingly prominent.Therefore,more efforts are needed to reduce noise of transmission.In this paper,the transmission of a heavy commercial vehicle with main and auxiliary box structure is taken as the research object,by means of simulation analysis and experimental test,the generation and propagation mechanism of transmission gear noise are studied,the dynamic analysis model is established,the key factors of vibration and noise are studied,and the vibration characteristic analysis method of transmission considering power shunt and shell flexibility is put forward,and the noise produced by gear meshing is predicted and optimized,which has certain reference significance for noise reduction of transmission.Firstly,aiming at the problem of high noise in individual gears of the existing transmission under a certain working condition,the structural characteristics and power transmission route of the transmission are analyzed.Based on MASTA software,the transmission system is modeled,and the load sharing characteristics of power shunt structure and the influence of the phase between meshing pairs on the dynamic meshing of gears are simulated and analyzed.The transmission error caused by the meshing of each transmission twist gear pair on the transmission line is used as excitation to study the dynamic response of the transmission system under the speed-up condition,analyze the vibration spectrum characteristics and determine the root of noise.Secondly,in order to reduce static transmission error and meshing misalignment of the gear pair as the optimization goal,the optimization scheme of tooth surface modification of main box gear is explored,and the peak-to-peak value of transmission error,meshing misalignment,tooth contact and bearing vibration response characteristics before and after optimization are compared to evaluate the feasibility of the optimization scheme.Then,the shell is made flexible,and the rigid-flexible coupling model of gear shafting-shell is established.The deformation at the bearing hole of the shell and the corresponding gear meshing situation are analyzed,as well as the influence on the transmission error of the main box gear pair and the dynamic response of the rigid-flexible coupling system.By analyzing the vibration of the bearing and the mode of the coupling system,the dynamic response position and the peak frequency of the vibration are determined.Finally,in order to improve the stiffness of the supporting bearing hole and change the modal frequency of the shell,the shell is optimized by increasing the wall thickness and setting stiffeners.The data of shell deformation,gear meshing transmission error,coupling system modal frequency and dynamic response before and after optimization are compared to verify the feasibility of the optimization scheme to suppress the vibration and noise of the transmission.At last,the transmission with tooth surface modification and shell optimization is tested on the bench,and compared with the original noise test data,to evaluate and verify the effectiveness of the transmission whine noise research solutions. |
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