| The elastic gear,which consists of outer ring gear,rubber ring and wheel,is an important transmission component in a three-cylinder engine balancing system.It directly affects the balance of the quality of the system and its mechanical properties have a great influence in the running stability,vibration and noise of the engine.Therefore,good static characteristics and dynamic performance for elastic gears must be ensured.In view of the static characteristics and dynamic performance of elastic gears,the following works were mainly researched in this thesis.(1)The structure,function,working conditions and performance requirements of elastic gear used in three-cylinder engine balance system had been analyzed to study the static and dynamic characteristics of elastic gears.Based on secondary development function of Visual Basic 6.0 and Solidworks,parametric modeling,assembly and window operations and other functions of elastic gears were achieved,which lays the foundation for the static characteristics and the dynamic characteristic analysis.(2)Based on setting parameters of the Hertz elastic contact theory in finite element analysis,the stress and strain characteristics of elastic gears and metal gears under the same working conditions were analyzed and compared.The difference between the static characteristics of the elastic gear and the metal gear was obtained.Based on the idea of orthogonal experiment design,the influence of rubber hardness,thickness and width on the stress and strain characteristics of elastic gears were analyzed.The influences of rubber parameters on the stress and strain of elastic gears were obtained by analyzing the difference and variance of the experimental results,which determines the significant influence of each factor on the results and its optimal combination.(3)Regarding the rubber ring as merely elastic damping structure without inertia,simplifying the outer ring and the hub as rigid structure only with inertia but without elastic,taking transmission error and tooth side gap into account,the torsional vibration model of elastic gears was established,which is based on lumped mass method to solve the elastic gear dynamic equation and corresponding dimensionless processing considering the transmission error and backlash factors.By changing thetorsional rigidity of the rubber to the displacement stiffness in the direction of the meshing line,the equivalent meshing stiffness model of elastic gear meshing was established based on the lumped mass method.Then based on the model and Weber elastic mechanics,the formula of the equivalent meshing stiffness of elastic gears is obtained.(4)The first six order modes of elastic gears and metal gears were analyzed by finite element analysis method,and changing the thickness,width of the rubber and rotational speed of gear,the laws of the variation of the natural characteristics for the elastic gear with parameters were analyzed,which provide a reference for gears to avoid meshing resonance.The dynamic response characteristics of the two kinds of gears under the same working condition were analyzed and compared by using the rigid metal model of the rigid gear drive and the rigid/flexible coupling virtual prototyping model of the elastic gear drive,and the damping effect of elastic gears was studied.Comparing with the theoretical results,the reliability of the simulation was verified.The dynamic response characteristics of the elastic gear were analyzed at different rubber thicknesses,widths and rotating speeds.The laws of dynamic response characteristics of elastic gears with the parameters were obtained.The technical basis for the design and manufacture of the elastic gear used in three-cylinder engine balance system was presented in this thesis,which is helpful to improve the quality of the elastic gear and improve the performance of the balance system. |
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