| Since the geared rotor-bearing system has the characteristics of higher energy density,higher efficiency,lower vibration and noise,it is widely used in vehicles.And its work performance has a crucial effect on the vehicle NVH performance.Therefore,how to establish an effective dynamic model is one of the most important topics to be solved urgently in the current engineering application,for the accurate prediction of its dynamic characteristics.In this thesis,the research object is the geared rotor-bearing system consisted of hypoid gear pair,shafts and tapered roller bearings from an automobile main reducer.Considering the coupled vibration of gears,bearings and shafts,and other various factors,the nonlinear dynamic model of a geared rotor-bearing system is established.The modern analytical techniques are applied to study the dynamic behavior of the system in depth,and reveal the underlying vibration and noise physics of the hypoid geared rotor system.The major works of this dissertation are as follows.Firstly,considering the effect of dynamic mesh force on shaft vibration,the lateral-torsional vibration mathematical model of the shaft is obtained,based on the vibration theory of continuous beam.And then,the pinion and gear coupled dynamic model of lateral-torsional-axial-pendulant degree of freedom is established by lumped parameter method.This model takes into account synthesized engine output torque,road resistance and other external excitation,piecewise-nonlinear dynamic mesh force,tooth friction drag,and bearing dynamic load expressed as a non-linear power function and other internal excitation,and the dynamic bending deformation of the shaft.Besides,the bearing vibration analysis model in view of the flexible rotor effect is proposed.Secondly,an adaptive step size control for Runge-Kutta algorithm is performed for solving the differential equations,and a variety of steady state response is presented.Then,a series of important dynamic and geometric influence on dynamic behavior,bifurcation and chaos characteristics are examined by using multiple analysis techniques based on time domain,frequency domain and phase space.Simultaneously,by applying the method of multiple scales to the reduced system,the first approximation steady state solutions and their boundary condition of instability for the primary resonance and secondary resonance of the system are obtained.Thirdly,the 3-D finite element model of pinion and gear is presented by employing CAE software,then its inherent characteristics and tooth contact pattern are investigated.Simultaneously,an entire geared rotor-bearing model based on the virtual prototype technology of Romax Designer software is introduced to characterize the potential interaction between dynamic bearing load and gear tooth contact force,so the steady state response analysis of gear and bearing are conducted.Finally,the experimental correlation process for main reducer is presented under different operating conditions.The housing surface acceleration of main reducer and sound pressure level inside the vehicle are measured.The influence of load torque and backlash on the vibration of hypoid geared rotor-bearing system are analyzed and discussed,so the best backlash is identified.In addition,the actual effect of bearing stiffness optimized on vibration and noise reduction is verified.The comparison of dynamic simulation results and experimental measurements plays a significant role in validation for the proposed analytical models and procedures.Therefore,the parallel research line based on theoretical modeling,simulation analysis and experimental verification for a geared rotor-bearing system dynamics provides a theoretical basis for the main reducer dynamic design and optimization. |
