Light Load Loader Transmission Vibration And Noise Estimation

Due to the complex structure of the gearbox and the influence of a variety of excitation factors,the gearbox may produce significant vibration and noise during operation,which not only affects the stability of the machine,but also poses a health hazard to the operator,so it is important to study the vibration and noise of the gearbox.This thesis takes a light-duty loader gearbox as the research object,establishes the dynamics model of the mutual coupling of the box and the transmission system,studies the influence of the box flexibility on the dynamic response of the transmission system,and also combines the finite element analysis method and the acoustic boundary element method to propose a practical method of gearbox vibration and noise prediction.The main research work is as follows:(1)By building a three-dimensional model of the gearbox,the basic macro parameters of the components in the gearbox are obtained and the meshing stiffness of each gear pair is modelled according to the energy method.The static transfer error between each gear pair is modelled by the harmonic function.A finite element model of the box is built and imported into Romax software for reduction,the stiffness matrix and mass matrix of the box are extracted,and the dynamics equations of the box are established in preparation for solving the dynamics model of the gearbox.(2)Based on the above parameters,the drive line dynamics model and the drive line dynamics model of the coupled box were established respectively,and the dynamics model before and after the coupled box was solved by Runge Kutta method.The changes of the gear meshing dynamics and bearing support dynamics before and after the coupled box were analysed at multiple speeds,and the influence of the box flexibility on the dynamic response of the drive line was investigated.The dynamic bearing support reaction force after the box coupling is solved and used as the excitation factor for the box vibration response analysis.The results show that the dynamic response of the transmission system after the box coupling has a certain degree of change,and the change of bearing support reaction force is greater than the change of gear meshing force.At 1500r/min,the variation in bearing 3 support reaction force reaches 41%.Therefore,the influence of box flexibility should be considered in the dynamic analysis of the drive system.(3)A finite element model of the box was established in ANSYS Workbench software and modal analysis of the box was carried out to obtain the intrinsic frequencies and the modes of vibration of each order of the box.On the basis of the modes,the harmonic response of the box was analysed using the mode superposition method with the dynamic response of the transmission system as the excitation.The vibration response of the box surface is obtained.Observation points are selected on the box surface and the vibration acceleration and corresponding vibration modes of the measured points are analysed.The results show that the peak frequencies of vibration acceleration at each observation point are 540 Hz,640Hz,1300 Hz and 2600 Hz respectively,which are similar to the meshing frequencies of each gear pair in the transmission system.There is a large deformation in the bearing housing at the bottom of the box and the back cover of the box housing.These parts of the box can be optimised if improvements are made to the box.(4)The acoustic model of the box was established in LMS Virtual.Lab software using the vibration response of the box surface as the boundary condition.The noise on the surface of the box and the sound field around the box were calculated using the boundary element method,and the radiated noise on the surface of the box and the sound field around the box were obtained.The noise of the gearbox was tested and the sound pressure values of the box surface were obtained.The simulation results were compared with the experimental results.The results show that the maximum sound pressure levels at 1300 Hz are 124 d B and 102 d B for the box surface and external sound field respectively.there are differences between the experimental and simulated results,but the correctness of the simulated results is verified within acceptable limits.