Key Technology Of Shaft And Rear Axle Vibration

The shaft-final drive assembly is a nonlinear coupling vibration system which iscomposed of several subsystems with different natural vibration characteristics, andthis system can be described as a general mode ‘universal joint-shaft-gears’. As theflexible transmission system can meet the needs of floating output and the blacklashof the structure will cause the vibration, impact and the energy losses, how to reducethe vibration and impact in this variable axial transmission system and finding a wayto realize the energy-saving and noise-reduction are hot issues for researchersworldwide. The focus of this thesis is on the coupling nonlinear dynamics problem ofthe shaft-final drive assembly system. Through analysis of the vibration transfer path,the mechanism of the dynamic excitation during the power transmission process isdiscussed and the results show that the vibration and noise can be reduced effectivelywhen the bearing stiffness coefficient is1.2or blacklash is0.1mm based oncombination of theory model, virtual prototype simulation and experiment. The majorworks of this thesis are listed as follow:The coupled vibration model with7degrees of freedom of the hypoid gears areestablished based on mechanical analysis. The excitation parameters of the timevarying stiffness, meshing impact and deviation are included in the equations and thelateral vibration, axial vibration and torsional vibration are considered in the model.The coupled vibration mathematical model is solved using the Runge-Kuttanumerical simulation method and the dynamic response of the gear system is got.Atthe same time, the analysis and comparison of the steady state responses are proposedwith different stiffness variation coefficient and different blacklash variationcoefficient.The Lateral-torsional vibration nonlinear dynamics model with14DOF forshaft-final drive assembly system is founded by the method of lumped mass. Thetorque ripple from engine, the alternant load from universal joint and the dynamicexcitation from gear system are all considered in the model. According to the motiontransmitting characteristics of universal joint, the degree of freedom of the system isreduced to11DOF and a new set of uniform non-linear dimensionless differentialequations of the system is constructed. The impacts of transmission shaft and gearsystem on the dynamic response of the shaft-final drive assembly are analyzed and the influence rules of bearing stiffness and blacklash on the assembly system dynamicresponse are studied.The dynamics simulation model is built with ADAMS and the shaft parts are setas flexible bodies with ANSYS FEA software so that an integrated rigid-flexiblecoupling vibration model for the shaft-final drive assembly system is established.Then the influence of the bearing stiffness on the vibration characteristics is analyzedeither under the same speed or under an increased speed and a better range of valuesfor stiffness coefficient is proposed. A better gear locating distance is derived as theimpact of the blacklash is analyzed in the same way. Finally, the results of vibrationtests and the NVH tests are compared and analyzed via changing the bearing stiffnessor the blacklash. The correctness of the theoretical analysis and the simulationanalysis is proved.