Analysis Of Compound Modification And Meshing Performance Of High Speed And Heavy Load Double Helical Gear Pair

With the advantages of high contact ratio,low axial force,high load carrying capacity and smooth transmission,double helical gears are widely used in high-speed,high-load sharing transmissions.Double helical gear is influenced by thermoelastic deformation,machining error and other factors in the meshing process.The gear teeth will be interfered at the meshing-in and meshing-out positions,deteriorate the meshing performance,and aggravate the vibration and noise of the gear system.While tooth modification can effectively reduce the meshing shock of gear teeth,it will also have a great impact on dynamic excitations,such as time-varying meshing stiffness,tooth surface normal load distribution,tooth surface friction force and torque,then the dynamic characteristics of the gear system will be influenced.The research on compound modification and its influence on meshing performance has important theoretical significance and engineering value for the vibration and noise reduction of high-speed heavy-load gear devices.Focusing double helical star gear system of the aerial geared turbofan(GTF)engine,the low slip ratio parameter optimization of the double helical gear pair,the design of the compound modification parameters,the calculation of the time-varying meshing stiffness and the system dynamic characteristics are carried out.The main researches in this paper can be summarized as follows:(1)Based on the motion relationship of the gear pair meshing,the slip rate of double helical gear pair was calculated,and the influence of gear parameters on the gear pair slip ratio were analyzed.The design parameters of double helical star gear pairs were optimized with the basic design parameters as the design variable and the low slip ratio as the objective function;the distribution of heat flux on the tooth surface before and after optimization was compared and analyzed.The temperature field and thermoelastic coupling simulation of double helical star gear system was analyzed,and parameters with optimization of low slip ratio can significantly reduce the gear temperature rise.(2)Based on gear tooth deformation interference amount and tooth surface temperature of the double helical star gears thermoelastic coupling simulation,the modification parameters of the gear pair were calculated;the modification curve is used instead of the straight tooth profile and controling grinding feed movement of grinding wheel to achieve tooth modification,the tooth profile equation of double helical gear with compound modification was derived,and an accurate parameterized model of the compound modification gearr was established.According to the finite simulation of gears before and after modification,it is found that the contact area of the tooth surface decreased,the contact stress is equalized and decreased after modification.(3)Considering the influence of profile modification and load deformation on the gear pair contact ratio and contact state,an algorithm for mesh stiffness of double helical gear taking the modification parameters and width of run-out groove into account was proposed and numerical verified.Then the influence of different width of run-out groove,modification parameters,and the input torque on mesh stiffness of double helical gear was analyzed,and the contact ratio and meshing stiffness of double helical gears with modification decresed.(4)Based on the time-varying meshing stiffness of the double helical gear and the idea of slicing,the tooth surface normal load and the tooth surface friction excitation distribution law of the double helical gear were solved.Cosidering the meshing phase of sun-planet gear pairs and planet-ring gear pairs,time-varying meshing stiffness,frictional excitation,machining error and other factors,a double helical star gear system dynamics model was established using the centralized parameter method,and the double helical star gear system dynamics characteristics were analyzed.Gear tooth modification can improve the load distribution of the tooth surface,and reduce meshing impact and system vibration.