Study On The Friction-Induced-Noise Of Flexible Bearings Under Different Lubrication Conditions

Harmonic reducer,as the core component of robot joint,an important development direction is to reduce vibration and noise in order to improve the processing quality and protect the health of workers in production site.The flexible bearing of harmonic reducer is a thin-walled bearing.Its function is to transfer the fluctuation of the wave generator cam to the flexible wheel through deformation.Especially in the case of high torque load,the lubrication of the flexible bearing is particularly important.If the ball contacts abnormally with the raceway,harmful friction noise will appear.In this paper,the influencing factors of friction noise of flexible bearings under different lubrication conditions are studied.The research is mainly carried out in the following aspects:Based on the theory of complex modal analysis,the friction noise of point contact balldisk friction pair is simulated by finite element method,and the coupled modal frequency is obtained.According to the theory of transient dynamics,the dynamic simulation of ball-disk friction model is carried out,and the vibration frequency of the model is obtained by Fourier transform.The frequency of friction noise can be effectively predicted by combining the two simulation methods.The test environment of point contact ball-disk friction noise is built,which includes UMT-3 friction and wear tester,high precision microphone and data acquisition system.GCr15 steel disc specimens were processed,and the surface morphology of the disc specimens was tested.DLC and four kinds of nitrides(titanium nitride,chromium nitride,zirconium nitride,aluminum titanium nitride)were coated on the surface of some specimens,and the hardness of the solid film was tested.Afterwards,the frictional noise under different linear velocities,loads,roughness and working conditions of solid films were measured,and the sound pressure level and frequency were analyzed.The contact stress and relative sliding speed of flexible bearing ball and ring are calculated.Four greases are selected as lubricants for measuring friction noise under grease lubrication.The rheology and thixotropy of four greases are tested.The elastohydrodynamic lubrication of flexible bearing is calculated by the viscosity parameters of base oil.Finally,the friction and wear test of UMT-3 is carried out.The influence of lubricating grease on friction noise was tested under two large load conditions.The test-bed of flexible bearing and harmonic reducer is developed,and the acquisition conditions of noise,vibration and torque are set up.DLC coating was carried out on a flexible bearing and a flexible wheel,rigid wheel and wave generator of LHD-25-100-CI harmonic reducer.The multi-speed noise measurement of flexible bearings with different greases,DLC and dry friction under 200 N radial load was carried out.Three types of harmonic reducer were tested with different input speed and load noise in the original grease,and LHD-25-100-C-I harmonic reducer was tested with variable speed and load noise.