Research On Gearbox Noise Reduction Technology Based On Gear Modification And Shell Optimization

The gearbox is an important part of the vehicle transmission system.The vibration and noise level of the gearbox is one of the important factors affecting the performance of the vehicle NVH.This paper studies and analyzes the vibration and noise of the gearbox based on the NVH performance improvement project of a SUV car gearbox.There is a strong howling noise in the second gear of this model,which seriously affects the driving experience of consumers.In this paper,through the combination of theoretical analysis and experimental simulation,the root cause of the problem is found out.Finally,the modification scheme is proposed and verified.Firstly,the whole vehicle hub test is carried out in the semi-anechoic chamber.The subjective evaluation shows that there is obvious howling noise in the sliding stage after the acceleration of the second gear WOT and POT conditions.The noise signal at the inner ear of the main driver is performed by order tracking.Analysis and analysis found that the order signal of the gear is abnormal.The bench test of the gearbox shows that the value of the gear step curve in the speed range of 2762 rpm,3000 rpm,and 3610 rpm is almost equal to the overall noise(OA curve)of the gearbox,which is prone to whistling.It is thus determined that the gearbox second gear is the source of the howling problem.The forced vibration of the housing is the main source of radiated noise from the transmission,and the housing is modally analyzed in order to understand the dynamic characteristics of the transmission housing.The finite element model of the gearbox housing is built in Hypermesh,and the modal solution of the shell is solved by Nastran.The modal test of the shell was carried out by hammering method.The maximum error of the test mode and the simulation mode was less than 7%,which verified the accuracy of the finite element model.Then the dynamic model of the gearbox is established in Romax Designer,the transmission error and the meshing spot condition under the typical working condition of the gearbox second gear are simulated,and the dynamic force at each bearing seat of the gearbox input torque-40 Nm and the speed of 3000 rpm is extracted.As the excitation force of the gearbox housing,the acoustic finite element model of the gearbox is then established in the LMS Virtual lab.The simulation shows that the dynamic force of the bearing overlaps with the modal order of the gearbox housing,resulting in the housing The first-order,eighth-order,and sixteenth-order modal participation factors are large,thereby determining the order to be optimized of the casing.Finally,the micro-geometry parameters of the gears were studied by Romax Designer,and the tooth profile and tooth orientation of the gears were determined.The results of the modification showed that the gear transmission error and meshing condition were significantly improved,and the gear transmission error was earlier than that.By 85%,the maximum load on the tooth flanks is reduced by 37.5%.Combined with the simulation analysis of radiated noise,the gearbox housing is structurally optimized to strengthen the stiffness at its weak position and reduce the smooth large surface of the casing that is easy to radiate external noise.Comparing the radiation noise level before and after the optimization of the gearbox,the results show that the overall noise of the gearbox is reduced by 7dB under the comprehensive control of gear shaping and shell optimization,which indicates that the overall noise of the gearbox is effectively controlled,and the howling problem is basically solved.The noise level of the gearbox is greatly reduced.