Optimization Design And Dynamic Analysis Of High-Contact-Ratio Gear

High-contact-ratio(HCR)gear is a kind of involute spur gear with the value of contact ratio greater than 2.The contact ratio of HCR gear is increased mainly by reducing the value of modulus,tooth addendum coefficient and increasing the value of pressure angle.HCR gear has become a hot research field in gear industry because of the greater bearing capacity and smaller transmission noise.At present,there is no systematic theoretical material of HCR gear which is still in the exploratory stage.The main contents of this thesis are the optimal design of the parameters and the dynamic analysis of HCR gear.The specific contents are as follows:(1)The meshing characteristics of HCR gear are investigated.The influence of contact ratio on the contact strength of tooth surface,the bending strength of tooth root and the transmission noise is analyzed.And the pressure angle,addendum coefficient,modulus and displacement coefficient are studied.Besides,the influence of bending root transition curve on the bending strength of tooth root is investigated.(2)The optimization design of HCR gear is studied.First of all,the optimization design mathematical model is established,including selecting the modulus,tooth number,pressure angle,addendum coefficient and displacement coefficient as design variables,establishing 2 different objective functions and listing 7 constraint conditions about contact ratio,addendum coefficient,tooth thickness,undercut avoiding,transition curve,tooth contact strength and bending strength.Then,the results show that the multi-objective optimization is more reasonable which consider the maximum of the contact ratio and the minimum volume of the gear as objective functions.Moreover,the parameters of internal and external meshing HCR gears are calculated respectively.(3)The geometric model of HCR gear is established.The tooth profile equations of HCR gear are studied,including the involute equation,involute cylindrical surface equation and transition curve equation.According to the optimization design results of the HCR gear,the three-dimensional modeling software SolidWorks is used to establish the HCR gear and the standard gear models.(4)The dynamic analysis of HCR gear are investigated.Firstly,the finite element method and finite element software ANSYS Workbench are introduced.Then,the modal analysis are completed.Thus,the 20 natural frequencies and the 10 modes are obtained.The transient dynamics analysis of HCR gear are completed and the stress nephogram of different moments are listed.Besides,the results of the HCR gear and the standard gear are compared.The results show that the maximum stress value of the HCR gear decreases 10.98% and the average stress value decreases 13.46%,which verifies the HCR gear can improve the bearing capacity of gears.According to the stress change of different nodes on the tooth profile of driving gear and driven gear,the maximum value appeared on the root and the middle of the tooth profile.The effects of driving gear acceleration,pressure angle and addendum coefficient of HCR gear stress are investigated.