Study On Vibration Mode Of A Gearbox Housing

The gearbox housing supports and protects the normal operation of the parts inside the gearbox,and is in the operating environment under sinusoidal excitation force from the engine.The gearbox housing with poor vibration performance produces excessive vibration noise,and the center line deviation of the transmission shaft caused by the gearbox housing deformation reduces the power transmission performance of the automobile,which will directly lead to poor NVH performance of the automobile.By analyzing the modal parameters and operational data of the gearbox housing,the weak vibration position of the gearbox housing is determined,and the specific vibration mode change and vibration amplitude of the gearbox casing are determined by the steady-state response of the gearbox housing under the effect of sinusoidal excitation force,so as to evaluate the vibration performance of the gearbox housing.This paper takes gearbox housing of an automobile as an example.Firstly,the lower order modal parameters of the gearbox housing are obtained by calculating the free mode of the gearbox housing.Then,based on the results of the finite element modal analysis of the gearbox housing,the free modal test of the gearbox housing is carried out based on the principle of reciprocity.The dynamic modal model of the gearbox housing is modified by combining the calculation and experiment.Finally,vibration test bench and LMS system are combined to carry out the operational deflection shape test of the gearbox housing under the effect of sinusoidal excitation force.The result of constrained mode calculation of the dynamic modal model of the gearbox housing is taken as the operational deflection shape pre-test,and the measuring point with the maximum amplitude variation is determined by calculating the operational deflection shape of the gearbox housing.The dynamic modal model of the gearbox housing is determined by the free modal analysis of the gearbox housing,and the constrained modal parameters of the gearbox housing based on the experiment environment are obtained.Based on the operating data of the gearbox housing under the effect of sinusoidal excitation force,the vibration mode variation and specific amplitude of the gearbox housing at the peak of representative frequency are obtained.The analysis shows that the gearbox housing does not resonate under the sinusoidal excitation force from the engine,and the connection between the rear gearbox head and the gearbox housing is the weakest part of the gearbox housing.When the maximum vibration amplitude occurs,the gearbox housing is bent,and the deflection of the center line of the transmission shaft caused by the deformation of the gearbox housing will have a small impact on the power transmission of the automobile.Thus,a systematic research method combining modal parameters and operating data for the vibration problem of gearbox housing structure is presented,and this research method can be used as a reference for other parts.