Analysis On Influence Of Lubrication To Gearbox Vibration Signal

The gear box is an important mechanical part of rotating machinery equipment,and is widely used in various fields of machinery industry.Its working state plays an important role in improving the production efficiency of whole equipment.The transmission state of gear is also affected by the properties of lubricating oil in gearbox.And it will lead to transmission failure if the lubrication state is bad.However,the feature information of working state in transmission process is contained in vibration signal.Then the lubrication condition and transmission state can be better reflected.Therefore,the vibration signal is analyzed by using a reasonable method.Meanwhile,the connection between lubrication and vibration is built,which has an important meaning for reducing the vibration and prolonging the life of gearbox.In this paper,different basic oils are used for friction experiments and several typical lubricating oils are selected to do the vibration experiment.Based on the the method of normal distribution statistics and wavelet analysis,the vibration signal of gearbox in different working conditions is studied and the properties of lubricating oils are verified.The main content of the paper is as follow:(1)The lubricating properties of several single biodegradable base oils and mixed base oils are identified by analyzing the scar SEM image from four balls test and friction-wear test.(2)The relationship between the friction coefficient and the thickness ratio of oil film is obtained by studying the failure characteristics of gear teeth in gear transmission based on EHL theory.Considering the interaction relationship between friction and vibration,the friction coefficient is discussed into the vibration model of gear transmission system and the dynamic equation of transmission system with two degrees freedom is analysd.And the hypothesis that reflecting the variation of friction coefficient by monitoring the variation of vibration amplitude from gearbox is proposed.(3)The vibration mechanism of gear transmission system is analyzed and the structure and test scheme of vibration experiment platform are described.Several common methods of signal analysis are listed and the vibration amplitudes are analyzed by normal distribution statistics.The vibration signal before loading is compared with it after loading from the output position in two different base oils lubrication states.And the frequency graph of vibrationsignal after loading is analyzed and the signal in key frequency domain is decomposed by three layers of wavelet packet.Then the power spectrum of sub regions is obtained.For this,the specific frequency and variation difference of amplitude in frequency can be judged by observing the power spectrum and comparing the characteristic frequencies of two groups.