| Non-circular gears transmit gear ratio motion in a meshing manner,and the development and application of their related derivatives are receiving extensive attention.There are design and application cases in the fields of vehicles,radar,oil exploration,robots,agricultural machinery,engines,and automation equipment.With the gradual maturity of the non-circular gear design and application technology,the manufacturing problem is becoming the bottleneck problem restricting its popularization and use.Generating manufacturing,as an efficient gear manufacturing method,has the advantages of low cost and high precision,and has great application advantages in solving non-circular gear manufacturing problems.In terms of generating motion realization,Electronic Gearbox(EGB)technology can realize high-precision nonlinear synchronous motion control of multi-axis CNC machine tools,and is an effective and reliable solution for generating motion with variable speed ratios.In this paper,the related problems of high-precision tooth profile of non-circular gear,generating motion model,electronic gearbox interpolation error,generating envelope error and cutting force fluctuation were studied.Related research was also carried out on flexible hobbing processing technology for non-circular gears with different shapes and non-circular gear finishing technology.The main contents of the paper are as follows:1.The meshing transmission and tooth profile calculation of parallel-shaft non-circular gears were studied.Considering the application advantages of variable tooth thickness design ideas in the field of backlash adjustment and precision transmission,a conjugate meshing model of variable tooth thickness helical rack and non-circular gear pair was constructed.The meshing transmission characteristics of helical non-circular gear pair,variable tooth thickness non-circular gear pair,and variable tooth thickness helical non-circular gear pair were studied.The transmission feasibility and backlash adjustment characteristics of variable tooth thickness spur non-circular gear pair were demonstrated.The non-circular gear high-precision tooth profile/tooth surface construction method was researched based on the graphic method,focusing on the selection and extraction of the characteristic points of the tooth profile obtained by the graphic method,accuracy analysis,error convergence characteristics,and the general envelope rule of the graphic method.According to the generation and disappearance rules of tooth profile characteristic points in the envelope process,an accurate graphic method for judging whether undercutting occurs and the degree of undercutting was proposed,and compared with the equivalent tooth profile method.2.The error of non-circular gear NC generated electronic gearbox was analyzed and optimized.Firstly,the principle of multi-axis linkage machining of non-circular gears and the linkage mode of main and driven shafts based on variable-speed flexible electronic gearbox were analyzed.Then the EGB processing transmission scheme based on the linkage model was built,and the interpolation error and its causes in the processing process deeply studied.Finally,the optimization plan of the EGB interpolation error of the gear ratio was carried out,and an improved processing transmission plan was proposed.Furthermore,the shortcomings of the interpolation error generation of the EGB constructed based on the variable displacement ratio linkage model were analyzed,and the implementation scheme of the EGB constructed based on the variable displacement ratio linkage model was proposed.The proposed optimization scheme can effectively improve the calculation accuracy of the interpolation process and restrain the error accumulation phenomenon in the multi turn continuous machining process of the gear blank.3.The key technology of NC flexible hobbing of non-circular gears was studied.A machining linkage model considering additional motion was constructed by taking the helical non-circular gear as the object,and the correctness of the model was verified based on the rigid body kinematics method.The analysis flow of the non-circular gear hobbing processing scheme was constructed,and a method to realize the universality of the interpolation operation module of the electronic gearbox was proposed.This method pre-calculates the displacement relationship equation of the EGB slave axis and the master axis through the system,and expresses it regularly in the form of segmented spline coefficients,and then uses the coefficient array as the processing code reading item to realize the universal motion interpolation calculation module.The calculation process in the interpolation process was studied,and a data structure method was proposed to avoid looking up the table and homogenizing the calculation time of each interpolation period,and the effectiveness of the proposed scheme was verified by interpolation calculation simulation.Aiming at the matching characteristics of non-circular gear pairs,the position characteristics of the projection rack corresponding to the different installation postures of the hob were studied,and a flexible and efficient tool setting solution was proposed.4.The generative machining strategy with comprehensive constraints of cutting force and envelope error was studied.Based on the theory of Kienzle-Vector formula,the positive correlation between undeformed chip volume and peak rolling force was established,and the simulation method of intermittent chip generation was studied.By obtaining the geometric shape and volume change law of the undeformed chip entity,the location of the peak force was determined.A method for analyzing the envelope error of non-circular gear hobbing using equivalent gear and equivalent hob was proposed,and the numerical value of the envelope error and the position distribution of the pitch curve were studied.Aiming at the shortcomings of the basic hobbing linkage model in terms of cutting force fluctuations and uneven distribution of envelope errors,a hob global cutting tool machining linkage model was proposed.This model can realize the equal arc length development of the non-circular pitch curve under the condition of the constant speed of the hob.It is of great significance for the control of the peak cutting force,the suppression of the fluctuation of the cutting force,the control of the envelope error and the uniformity of the distribution.5.The precision machining technology of non-circular gear tooth surface was studied,gear grinding,gear shaving,gear honing processing plan was analyzed,and different processing forms suitable for non-circular gear were discussed.Research the applicability of forming method and generative method for tooth grinding to non-circular gears,focusing on the analysis of the machining motion principle of worm grinding wheel and tapered grinding wheel and the realization of EGB.The axial shaving processing plan suitable for non-circular gears was analyzed,the processing linkage model of the axial shaving and the tooth surface margin homogenization plan were analyzed,and the special G code for high-end elliptical gear shaving was developed.The applicability of internal and external powerful honing to the processing of non-circular gears was analyzed,and its process characteristics and processing motion models were also studied. |
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