Research On The Global Design Method Of High-speed Spiral Bevel Gear With High Contact Ratio

Spiral bevel gear has become the key part of helicopter power transmission system because of its smooth transmission,low noise,high loading capacity,and the power transmission of cross-axle at any angle.The meshing quality of spiral bevel gear shows a very important influence on the performance of the whole system.High level dynamic modeling analysis and tooth surface design of high-speed spiral bevel gear with high contact ratio are of great theoretical and practical significance for improving the design level of helicopter power system in China.In this paper,the global optimization design of high-speed spiral bevel gears with high contat ratio is carried out aiming at reducing the vibration and noise of gears.The main research results are as follows:(1)The impact excitation of spiral bevel gear is studied.Firstly,based on the mechanism of meshing impact of gear,the calculation method of initial meshing point and meshing stiffness is analysed with the method of TCA and LTCA,and the impact velocity and impact force are also calculated accurately.Secondly,the influence of load torque and rotational speed on meshing impact is analyzed in detail.Finally,the dynamic response of high contact ratio spiral bevel gear with meshing impact and loaded transmission error is analyzed based on 8-DOF dynamic model.(2)The global design technology of spiral bevel gear with high contact ratio based on ease-off is studied.Firstly,the ease-off target tooth surface of pinion is designed by presupposing geometric transmission error and the contact path meeting the requirement of high contact ratio;Secondly,the machine settings are taken as the optimization variable and the sum of squares of normal deviations between the pinion tooth surface and ease-off target tooth surface is treated as the optimization objective,the pinion tooth surface and the corresponding machine settings are calculated via the genetic algorithm.Finally,the meshing performance of the spiral bevel gears designed by global design method is analyzed with the TCA method,and it is also compared with the preset meshing performance.The simulation results show that the spiral bevel gears obtained by the ease-off global design method meet the design requirements.(3)The tooth surface design technology of spiral bevel gear with high contact ratio based on tooth length curvature correction is researched.Firstly,the basic principle of tooth surface modification technology of high contact ratio spiral bevel gear based on tooth length curvature correction is described detailedly.Secondly,the corrections of the locus of grinding wheel are taken as the optimization variable,and the sum of squares of normal deviations between the pinion tooth surface and ease-off target tooth surface is regard as the optimization objective,the pinion tooth surface is computed by the genetic algorithm.Finally,the meshing performance of the spiral bevel gear designed by the tooth length curvature correction method is analyzed with the TCA method,and it is compared with the preset meshing performance,as well as with the meshing performance of the spiral bevel gear designed with the constant processing parameters in the previous paper.The simulation results show that the meshing performance of spiral bevel gear with high contact ratio designed by the tooth length curvature correction method is much closer to the preset meshing performance.Based on the ease-off technology and the tooth length curvature correction method,the optimal design of spiral bevel gears with high contact ratio is carried out with the objective of minimizing the loaded transmission error amplitude and meshing impact.The simulation results show that the loaded transmission error amplitude and meshing impact of second-order spiral bevel gear with high contact ratio are reduced after optimization,while the seventh-order transmission error can further decrease the loaded transmission error amplitude and meshing impact of spiral bevel gear with high contact ratio.(4)The tooth surface design technology of spiral bevel gear with high contact ratio based on the grinding wheel profile modification is discussed.The tooth surface design principle of spiral bevel gear based on grinding wheel profile modification is described in detail.Firstly,the mathematical model of the novel grinding wheel profile is established,and the design method of the novel grinding wheel profile is introduced.Secondly,based on the principle of gear mesh and the theory of differential geometry,the tooth surfaces of pinion and gear are deduced.Finally,the meshing performance of the high contact ratio spiral bevel gear designed by the grinding wheel profile modification method is analyzed according to the method of TCA,and the meshing performance of the spiral bevel gear is compared with the preset spiral bevel gear under the same working conditions to verify the effectiveness and rationality of the tooth surface design method.The simulation results show that the grinding wheel profile modification method can effectively avoid edge contact of high contact ratio spiral bevel gear and improve the meshing performance.(5)The influence of the design contact ratio on the dynamic performance of spiral bevel gear is analyzed.Firstly,the definition and calculation method of the design contact ratio and the actual contact ratio are given,and the relationship between the design contact ratio and the contact path is analyzed,the variation of the actual contact ratio with load torque is also studied.Secondly,the advantages of the global design method in improving meshing performance of spiral bevel gears with high contact ratio are analyzed.Finally,the influence of the design contact ratio on the loaded transmission error,meshing impact,dynamic characteristics of spiral bevel gear are analyzed.The simulation results show that the global design method could significantly improve the meshing performance of spiral bevel gears with high contact ratio.And increasing the design contact ratio can effectively reduce the loaded transmission error,meshing impact and dynamic load coefficient,and then improve the dynamic performance of spiral bevel gears.(6)The tooth surface design methods of spiral bevel gears with high contact ratio are verified by simulation and test methods.The tooth surface acquired by the theoretical modeling method is compared with that obtained by KIMOS software to verify the accuracy of the tooth surface modeling method.The geometric transmission error obtained with the TCA method is compared with the result of KIMOS software,which verifies the correctness of the TCA method.The contact path obtained with the LTCA method is compared with the result of KIMOS software,which verifies the correctness of the LTCA method.The cutting experiment and hobbing experiment of the seventh-order spiral bevel gear with high contact ratio are carried out.Experimental method is utilized to verify the correctness of the seventh-order design theory and the feasibility of processing seventh-order spiral bevel gear with high contact ratio.The loaded transmission error obtained by the LTCA method is in comparison with the result of the FEA method to verify the accuracy of the LTCA method.It also verifies that the seventh-order transmission error can further lower the loaded transmission error amplitude of spiral bevel gear with high contact ratio.By using ABAQUS software,the finite element modeling analysis of the preset spiral bevel gear and the spiral bevel gear designed by the grinding wheel profile modification method are carried out,which verifies the correctness and feasibility of the design method of the high contact ratio spiral bevel gear based on the grinding wheel profile modification.