| With the steady progress of "Made in China 2025" plan,machinery building industry has a rapidly growth in the last few years.Precision and heavy-duty gearbox is used in construction machinery and heavy-load equipment fields extensively.With China’s gradual transformation from a manufacturing power to a manufacturing power,the know-how affecting gear transmission characteristics are also demand prompt solution.Compared with foreign advanced level,the domestic precision gear box still has the disadvantages of low transmission efficiency and large vibration noise.As the kernel parts of precision gear box,the vibration properties,level of precision and reliability of heavy load or precision equipment were directly determined by the gears.The key technology of gear and gear transmission system is the bottleneck restricting the development of precision gear box in China.At present,the gearbox produced in China has large vibration and noise in the running process,and the transmission performance needs to be improved.Gear modification is a main method to effectively improve gear meshing characteristics.By adopting reasonable gear modification can greatly achieve the purpose of small vibration and low noise of the gearbox on a large degree,so as to ameliorate the contact capability.In this paper,the gear pair in a certain type of precision gear box is taken as the research object,and a new modification method for obtaining accurate modification amount is proposed.The calculation model of time-varying meshing stiffness after gear modification is established,and the affecting law of modification on the vibration characteristics of gear system is deeply studied.The main research contents of this dissertation are as follows :(1)Based on the existing gear modification methods,a new tooth profile modification method is proposed which have obtained the accurate modification amount previously.Through the contact finite element simulation,the actual interference of gear meshing is taken as the accurate modification amount of gear,and the simulation model of the gear systems is established by Romax.The condition of the load distribution and contact temperature of tooth surface,and transmission error before and after modification are compared and analyzed.(2)Considering the direct influence of gear modification have produced on gear meshing stiffness,the calculation formula of gear loading deformation after tooth profile modification is deduced based on material mechanics method,and the computation module of time-varying meshing stiffness of modified gear is built and further been solved by Matlab,and the results are compared with results of the finite element simulation and ISO6336 standard.(3)Considering the combined effects of various factors such as the modified stiffness,tooth separation and input torque of gear transmission system,the nonlinear dynamic modele of modified tooth is built by using the centralized quality method.The stiffness considering the influence of modification is binomial fitted and combined to expand the expression into the Fourier series.The dynamic equation was solved by the changed-step fourth-order Runge-Kutta method,and the vibration characteristics of the gear system before and after modification were obtained.(4)The gearboxes rigging unmodified and modified gears were tested and verified,respectively.The criterion that can directly reflect the dynamic performance of the gearbox such as noise and vibration were mainly tested.The noise and vibration data of the gearbox unmodified and modified were collected,and the influence of gear modification on the vibration and acoustic noise characteristics of the transmission system was analyzed. |
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