Meshing Efficiency Calculation And Macro And Micro Parameters Optimization Of Double Helical Star Gear System

Double helical star gear transmission device is the core component of the geared turbofan(GTF)engine,which has the characteristics of compact structure,strong bearing capacity and high transmission efficiency.Transmission efficiency is an important evaluation index of GTF engine gear transmission.The meshing power loss of gear pair has a great influence on the transmission efficiency,and the friction power loss is the main part of meshing power loss.Especially for high-speed and heavy-load gear transmission,the teeth bear high load,the relative sliding speed is high,the teeth are in the state of mixed EHL,and the friction power loss of the tooth surface is serious.Therefore,the research on meshing efficiency calculation,macro and micro parameter optimization of double helical star gear system has important theoretical significance and engineering value for improving meshing efficiency of gear system.Double helical star gear system is taken as the research object in this paper.The friction excitation analysis of double helical gear pair,dynamics modeling and dynamic meshing force analysis of gear system,meshing efficiency calculation of gear system,and optimization of macro and micro parameters based on efficiency improvement are carried out.The main contents of this paper can be summarized as follows:(1)According to the geometric parameters of the modified double helical gear pair and the position of the entry and exit,the contact ratio of the gear pair was calculated.The formulas for calculating time-varying contact line length,comprehensive curvature radius,entrainment speed and relative sliding speed of internal and external meshing double helical gear pairs were derived.Based on the theory of mixed EHL and the contact line segmentation method,the comprehensive friction coefficient,time-varying friction force and friction torque of tooth surface were obtained.(2)Considering the factors of time-varying meshing stiffness,tooth surface friction,meshing phase and meshing error,a bending-torsion-axial coupling dynamic model of double helical star gear system was established by using the lumped parameter method,the dynamic meshing forces of gear pair were obtained and the influence law of meshing stiffness on meshing force was analyzed.It is concluded that the variation of dynamic meshing force on left and right sides of double helical gear is similar,and the meshing force of internal and external meshing gear pairs is different in phase.(3)Considering the sliding friction and rolling friction power losses of the internal and external meshing double helical gear pairs,the total friction power loss and meshing efficiency of the double helical star gear system were calculated,and the rationality of results was verified by comparing with Niemann formula.The influences of macro and micro parameters of gear on meshing efficiency were studied.The meshing efficiency increases with the increase of the number of teeth,pressure angle and tooth profile modification,while decreases with the increase of module and surface roughness.(4)Macro and micro parameters,such as number of teeth,module,pressure angle and tooth profile modification,were used as design variables.Taking the transmission ratio,assembly and fatigue strength as the constraint conditions,and reducing the mass,reducing the static transmission error and improving the meshing efficiency as goal,the macro and micro parameter optimization model of double helical star gear system was established.The optimal design parameters were searched based on genetic algorithm,and the evaluation result shows that the optimization effect of gear system is good.