| In recent years,with the development of science and technology and the improvement of people's living standard,the requirement to reliability and ride comfort of an automobile becomes higher.As one of the most important parts of the automobile transmission system,the reliability of the driving axle assembly and the noise radiation level are important in the drive system designing.The torque transmitted by the hypoid gears of main reducer of automobile driving axle is high,which causes so large alternating load that affects the fatigue life of the driving axle gear and the noise radiation,and is one of the most abominable parts of the working conditions in the transmission system.Due to the complex meshing principle and manufacturing techniques,the manufacturers of the driving axle are still facing many difficulties with the fatigue and noise radiation of the the driving axle hypoid gears(DAHG)design.Based on the project” Study on the fatigue and noise radiation mechanism of DAHG of a light truck” cooperated between Jilin University and a automobile company,a further study on the fatigue and noise radiation mechanism of DAHG has been carried out.An investigation method has been established in this thesis,by which the root stress distribution of DAHG can be analyzed and the gears time-varying transmission error and meshing parameters can be obtained with FEM,which provides a solid theory fundamental for the further and comprehensive investigation on reliability and vibro-noise radiation of driving axle.The main research contents of this thesis include the following aspects:1.The geometry models are the basis of the research on the reliability and dynamic performance of DAHG,and this thesis presents a surface geometry modeling method of HFT hypoid gears based on numerical calculation method.Firstly,the coordinate transform matrix from the tool to the workpiece is obtained by the Gleason machine.Secondly,the solution equations of tooth surface coordinate are established according to the gear machining parameters and the tooth germ parameters,then for the nonlinear equations of initial value problems,according to the gear machining process,a method for estimating the gearmeshing points based on the simulated annealing algorithm,which can be taken as the initial value to solve other points coordinate values.A programme SURFACE based on MATLAB code was established for hypoid gear teeth surface coordinate.Finally,the gear teeth surface coordinates are obtained,which can be imported into CATIA to generate the 3D-models of gear pairs.2.The teeth root fatigue life of hypoid gears of driving axle inducer is not only related to the gears geometry,but also to the gear load and boundary conditions.In order to simulate the real boundary conditions of DAHG accurately,a finite element modeling method for driving axle has been established,which is that establishing the substructures models of driving axle supporting structure and mapping the interior DOF of substructure components onto restraint joints position.This modeling method can not only simulate the nonlinear contact relationship between driving axle gears and bears accurately,but also take the influence the deformation of components like driving axle housing,differential housing and main reducer housing exerted on the teeth root bending stress of DAHG into consideration.3.The prediction model of the teeth root bending stress of DAHG is established by using the driving axle FEM model established,and also been compared with the test rig results of the teeth root bending stress of DAHG.The results show that the established models can predict the teeth stress under loads of DAHG accurately.In order to further analyzed the effect of installation error have on bending stress of DAHG,the sensitivity of gear teeth root bending stress to different installation errors is analyzed.Based on the stress changing course of teeth root week points obtained,a method which can fast predict the bending fatigue of driving axle gears is proposed,which has been used to analyze the sensitivity of different kinds of installation error of driving axle gears to bending fatigue parameters.4.The time-varying dynamic characteristics in the drive axle have hypoid gear meshing process,such as transmission error,time-varying mesh stiffness,is one of the main factors affecting the driving axle noise radiation.In this chapter,the load meshing of hypoid gears(LTCA)is analyzed by ABAQUS to obtain the static and dynamic transmission error of gears,and the relationship discussion between them shows there is little differencebetween the static and dynamic transmission error of hypoid gears.Then,the influence of load and installation error on static transmission error and dynamic transmission error on the rotating speed fluctuating is analyzed comparatively.Finally,an finite element method is established to calculate the gear meshing stiffness.The influence of different loads on gear meshing stiffness is analyzed to lay the foundation for dynamic analysis of hypoid gear system.5.The automobile driving axle noise is the dynamic response induced by DAHG.In this thesis,the noise radiation prediction model of driving axle is established based on the coupling between DAHG and driving axle housing dynamic response.Firstly,the 14-DOF vibration model of hypoid gear by using conventional lumped parameter method to obtain the dynamic load at the bear position of driving axle.Secondly,the dynamic response of driving axle housing is obtained by mode superposition method.Then the finite element calculation results are imported to predict the driving axle noise radiation by boundary element method.Finally,the test rig is built to measure the vibration noise of driving axle,which is also compared with the prediction results.The comparative results showed that the vertical vibration of driving axle housing surface can represent the noise radiation level of driving axle,which is the result caused by the dynamic coupling between driving axle gear system and driving axle housing.There is little difference between experimental results and prediction results,also the prediction model can predict the vibration and noise radiation accurately.The fatigue and noise generation mechanism of drive axle hypoid gears is studied.By finite element method,lumped parameter method and boundary element method.A complete analysis of drive axle hypoid gear meshing was researched,which includes building the three-model and predicting the fatigue life of the gear system.The research ideas,methods and results can provide good reference and guidance for the reliability and noise research of driving axle industry,engineering design and other automobile transmission system design,such as the Transmission. |
PDF Full Text Request