| Helical bevel gear including hypoid gear and spiral bevel gear are widely used in power and motion transmission of the machines and equipments. It is one of the most complex types of gear drive system, which has the advantages of smooth working, high ratio of transmission, high efficiency advantages of transmission, compact structure, saving more space, resistant abrasion, long service life and low noise. With the development of high-speed and precision mechanical transmission, the demand of dynamic characteristics and stability of gear transmission system continues to increase. A more accurate prediction of gear dynamic characteristics becomes more and more important. Due to the complexity of gear mesh, such as time-vary mesh stiffness, impaction of tooth mesh in and out, backlash, friction drag, manufacturing and assembly errors and the comprehensive effect of the entire gear transmission system vibration caused by vibration coupling several kinds of vibrations from shaft, gear pair, gear box, engine and nonlinear characteristics, all this factors make the research of gear dynamics quite complicated. Therefore, in-depth theoretical and experimental studying the dynamic characteristics of gearing system and finding the general rule of vibration calculation has current significance at present stage.The goal of this dissertation research is to establish more effective mathematical model and analytical techniques to characterize the mesh and dynamic behavior, predict vibratory response, and reveal the underlying physics of helical bevel geared rotor system. The major works of this dissertation are listed as follow.Firstly, the 3-D geometrical model and finite element analysis is conducted by a special and professional finite element analysis software package for helical bevel gear. The different processing methods of face-milled and face-hobbed are investigated. The tooth-surface equation of pinion and gear is established according to these two different types of methods. The principal curvatures, principal direction and contact ellipse of contact path is obtained by unload tooth contact analysis (ULTCA).The method of representation for geometry, mechanics and physics variables in the dynamic equation of spiral bevel gears and hypoid gear drives lay the roots for dynamic analysis.The 3-D quasi-static loaded tooth contact analysis model is established to obtain the transmission error, contact pattern, time-varying mesh stiffness and mesh point and line of action under different load. Secondly, the multi-body and multiple-degree-of-freedom (MDOF) dynamic model of helical bevel is established. By applying modern analytical theory and method and analyzing mesh model and dynamic excitation, the bend-torsion-axes-swing degree of freedom and load, engine, pinion and gear multi-body model of vibration is obtained by lumped parameter method. This model takes into account synthesized transmission error, time varying stiffness, backlash, and gyroscopic effect. The differential equations of motion of gear system are solved by using advanced nonlinear algorithm and computer software.Thirdly, the effect of time-varying friction coefficient and friction force on helical bevel gear dynamics is investigated. The elastohydrodynamic lubrication (EHL) theory was used to differentiate the different lubrication situation. Mixed EHL model is also proposed to predict the instantaneous friction coefficient at each contact grid cell along the contact zone under different load and speed condition. Comparison of different frictional behavior and dynamic response for hypoid gear and spiral bevel gear is made.Finally, the effect of assembly error is qualitative analyzed. The misalignment error including hypoid offset error, shaft angle error, pinion axial position error, gear axial position error of hypoid and spiral bevel gear sensitivities are identified. At the same time, the effect of assembly error on frictional behavior and dynamic response are examined and differentiated. The influence of assembly error and time-varying friction force on gear system dynamic are compared and analyzed.
|
PDF Full Text Request