Research On Vibration And Noise Reduction Of Gearbox Under External Excitation Force

The application of gear transmission systems in industrial products is becoming more and more widespread.During the meshing process,the required kinetic energy can be generated,which also causes vibration of the system.In addition,the production accuracy of equipment during gear production leads to errors in the accuracy of the output gears,it exacerbates the vibration of the gear system during the meshing process,and in addition,there are errors in the assembly process between bearings and shafts,bearings and boxes,and shafts and gears.It also exacerbates the vibration of the gear system.The vibration generates radiate noise from the box.This article analyses existing methods of noise and vibration control,and base on the active vibration control method,select the gearbox of a secondary gear transmission system of a weeding machine as the research object,and by changing the external excitation force to study the effect of noise and vibration control,the main research content is as follows:(1)Analysis of gearbox vibration characteristics: Using finite element method to conduct modal analysis on the gearbox,obtain the natural vibration mode and natural frequency;Establish a dynamic model of the gearbox system and obtain the bearing support forces of the six bearings in the gearbox.Use the obtained bearing support forces as the load boundary conditions of the gearbox finite element model to perform harmonic response analysis on the gearbox.(2)Gearbox vibration and noise testing: A gearbox vibration and noise experimental testing platform is established.Three axis acceleration sensors are used to collect surface vibration data of the gearbox under working conditions,and a decibel meter is used to collect radiated noise data of the gearbox under working conditions.the location of secondary force sources is determined by combining with finite element analysis results and experimental results.(3)Active vibration control simulation experiment: Based on the two control mechanisms of modal suppression and modal reconstruction,four types of external excitation forces were proposed: applying an external excitation force with the same amplitude in opposite phase,an external excitation force with 1.5 times the amplitude in opposite phase,an external excitation force with 0.5 times the amplitude in opposite phase,and suppressing the dominant amplitude external excitation force.These four external excitation forces are applied to the secondary force source to suppress box vibration and analyze their vibration reduction and noise reduction effects,The finite element method is used to simulate the vibration of the gearbox under the action of four kinds of external forces,and the four kinds of box surface vibration data obtained from the simulation after the box vibration control are imported into the LMS Virtual.Lab acoustic software as boundary conditions,and the noise radiated from the external acoustic field of the gearbox is calculated using the direct boundary element method.The simulation results of active vibration show that applying an external excitation force with opposite phase and the same amplitude has the best vibration control effect.The displacement curve of an external excitation force with opposite phase and multiple amplitude only reduces the vibration displacement amplitude without changing the trend of the displacement curve.However,applying an external excitation force to suppress the dominant amplitude reduces the amplitude of the dominant amplitude,and the amplitudes of other frequencies may not necessarily be reduced;The acoustic simulation results show that the gearbox noise can be reduced to a certain extent when the opposite phase multiple amplitude external excitation force is applied,and the trend of the sound pressure level frequency curve remains unchanged.The peak sound pressure is mainly concentrated in the frequency range of 1000 Hz to 1500 Hz.The best noise reduction effect is achieved when the external excitation force is applied to suppress the dominant mode,and there is a good noise reduction effect at each octave of the gear meshing frequency,with the highest noise reduction reaching 50.13 d B at 1191 Hz.