Optimization On The Radiation Noise Of Electric Bus Under The Acceleration Conditions

With the advancement of science and technology and the shortage of petroleum resources in China,Chinese vehicle industry is developing rapidly towards to new energy vehicle.However,because the new energy vehicle lacks the masking effect of the internal combustion engine,and the motor has the characteristics of transient changes under the acceleration conditions,the acceleration noise of the new energy vehicle transmission system is more prominent.In this paper,a 4-speed mechanical gearbox used to a pure electric bus is taken as the research object,and the radiation noise optimization of the gearbox under the acceleration conditions is studied based on the response surface method and the gear tooth micro-modification method.Based on the multi-body dynamics theory of the gearbox,the generation mechanism of the radiation noise,and the micro-modification of gear tooth,the radiation noise of the gearbox under the acceleration conditions is studied in this paper.The cabin crew reported that the electric bus had abnormal vibration and noise under the 2-gear and 3-gear acceleration conditions.In order to determine the noise source of the electric bus,the near-field noise and the gearbox front end vibration of the whole vehicle under the 2-gear and 3-gear acceleration conditions was carried out.It was found that the vibration and noise under the 3-gear acceleration condition was greater than that under the 2-gear acceleration condition by comparing the test results.Subsequently,based on the order analysis method,the near-field noise of the whole vehicle gearbox under the 3-gear acceleration condition was analyzed.The analysis showed that the 3-gear pair was the main noise source of the gearbox,so the shifted gear pair was optimized as an object under the 3-gear acceleration condition.The bench noise tests of the gearbox under the acceleration conditions,the bench noise tests of the gearbox and the meshing spot tests under steady-state conditions and the modal tests of the gearbox housing were carried out based on the industry standard of the bench test.The gearbox multi-body dynamics model and the acoustic boundary element model was established and verified by above test results.Subsequently,the overall sound pressure level of the gearbox measuring point was optimized as the objective function under the3-gear acceleration condition.The noise optimization of the gearbox was studied based on the gear tooth micro-modification and response surface method.When the gear lead crown modification and the gear involute modification of the shifted gear of the 3-gear were selected as –2 μm and 24 μm respectively,the gearbox measuring point noise was reduced by 2～4 d B(A)under the 3-gear acceleration condition.