Study On Noise Control For High-speed Gears

In modern life, vehicle on one side is the traffic tool that is absolutely necessary, on the other side it is a heavy noise source. It is very important to control the vehicle noise. The running gear's noise enhances sharply and it becomes one of the engine noise sources as the speed increases. The gear noise control becomes very valuable. This paper is a research on high speed gear noise control while taking primary gear of motorbike as an example. The dynamic character of the gear meshing, the vibration and the noise radiation are simulated based on the FEM and BEM. The relationship between the gear parameter, the meshing noise and the parameter optimization are present in this paper, which is a reference for low noise design. Finally, all the simulation conclusions are justified by the physical experiment.The mainly contents and conclusions are as follows:The mechanism of the gear mesh noise is analyzed. The impact, which is the main reason for the high speed gear noise, is caused by the wrong mesh relationship when the gear is meshing. The alternate force leads to a distortion of gear tooth and brings the wrong mesh relationship. So, the effective way for gear noise control is to reduce the impact force while joggling.Based on the tooth profile modification and the fluctuant torque, the model of the gear and the axes is established in this paper. A dynamic analysis in Ls-Dyna for the gear and the axes model is simulated to gain the mesh force and the impact force of the bearing. The force are used to simulated the noise radiation and the output of the sound power for the block and gear model. The simulation conclusion is verified by a vibration and noise experiment.As the torque of the engine changes, the noise enhances with the speed; the influence of the tooth profile modification curve indicates that the one time tooth profile modification curve does the best for the decrease of noise, next come the tooth profile modification curve of line and arc, And the worst is the two times tooth profile modification, which is also better than the gear with no tooth profile modification. The noise and vibration of gear pair caused by varying torque has the same influencing trend with constant torque. So it is feasible to predict change law of gear pair's noise and vibration caused by varying torque using constant torque influence.For the gear with no tooth profile modification, a different modification coefficient brings different noise decrease. The noise test shows that, the modification coefficient 0.82 does best for the noise decrease, the 0.39 one takes second place and the 0.54 one is the worst. This paper chooses the modification coefficient 0.54 for the motorbike gear while considering the intensity of the small gear and avoiding sharpness of the gear. The gear after tooth profile modification must have a good performance of noise decrease. Comparing the gear with the modification coefficient of 0.82 and the coefficient of 0.54, the 0.54 one has a 10~20% decrease of the acceleration, and the sound power level decreased by 1~2dB. And this paper chooses the one with one time tooth profile modification for the ultimate measure.