Research On Design And Continuous Generating Machining Method Of Crossed Beveloid Gears With High Meshing Performance

Crossed beveloid gears has the advantages of small size,compact structure,high accuracy,insensitivity to installation error,low transmission noise and smooth movement,which has broad application prospects in high-speed ships and all-drive vehicles.However,the correlation law between tooth meshing performance and gear parameters and installation errors is complex,which leads the traditional design method cannot effectively solve the problems of high sliding speed between tooth surfaces,severe wear of gears,low load capacity and short service life caused by point contact between tooth surfaces.Moreover,beveloid gears also are faced with the problems including the immature precision manufacturing theory and lack of precision machining methods for that with modifications,which brings great challenges to ensure the meshing performance of tooth surfaces.Focusing on the above technical difficulties and aiming at achieving the design and manufacturing of cross beveloid gears with high meshing performance including high bearing capacity,large contact ratio and smooth transmission characteristics,the thesis conducted the research on geometric parameter design,contact analysis method and continuous spreading machining method,where a controllable design model of contact angle and numerical analysis method of loaded contact were proposed,which innovated a parameter optimization scheme for crossed beveloid gears.The adaptive design model and analytical meshing model of continuous generating machining were established,and the forming law of tooth surface in continuous generating machining is revealed.(1)A controlled design model for contact angle of crossed beveloid gears was established.Based on the generation principle of beveloid gears,the calculation formula of the tooth surface geometry parameters was derived,and the relationship that the rack parameters should satisfy for correct meshing with beveloid gears was analyzed.By introducing the concept of common rack,the spatial position model and contact angle calculation formula of crossed beveloid gears were established.On the basis of the geometric design model of crossed beveloid gears,the contact angle controllable design model was established by introducing the contact angle control relationship,and the improvement method was proposed to improve the robustness of the design model.The proposed design method provides theoretical support for the continuous optimization of the geometric parameters of the crossed beveloid gears.(2)The contact analysis method of crossed beveloid gears was studied.Based on the generating principle of beveloid gears,an accurate model of beveloid gears with tooth root fillet and a model of beveloid gears with consideration of rack tool modificaiton were established.Further,a meshing model was established,which included a numerical method to determine the contact ellipse.The numerical method of load contact analysis of crossed beveloid gears was proposed for the demand of load contact analysis.The mathematical model to determine the flexibility was established,where the finite element method and the Boussinesq elastic half space force displacement relationship was applied to calculate the global and local deformation.The transmission error coordination condition is added on the basis of the deformation coordination condition by considering the multi-tooth contact situation,and the loaded contact analysis solution model was established by using the influence coefficient method.The proposed method provides support for the optimization of geometric parameters and modification parameters.(3)The continuous optimization method for crossed beveloid gears for high meshing performance was studied in two stages: geometric parameter design and tooth surface modification parameter design.In the geometric parameter optimization,the geometric parameter optimization model is established based on the contact angle controllable design method,considering the installation error and its variation characteristics,and the overall performance of the contact performance within the variation range of the installation error as the optimization target.In the optimization of the modificaiton parameters,the strategy of determining tooth surface flexibility for continuous modificaiton optimization was proposed,and the method of determining tooth surface contact order in the case of multi-tooth contact,the calculation method of potential meshing points of non-contact tooth surfaces and tooth surface parting distance were proposed considering the influence of tooth surface modification.The optimization model was established with the modification parameters as the design parameters and the contact performance as the optimization target.NSGA-Ⅱ algorithm is used to solve the model according to the discrete and non-differentiable characteristics of the optimized model.(4)The processing method of beveloid gears was studied.According to the generating principle of beveloid gears and gear generating processing theory,an adaptive design model for generating processing of beveloid gears was proposed,which solves the problems of mounting parameter design and motion model design faced in manufacturing on conventional gear generating processing machines.For beveloid gears with soft tooth surfaces,the plunge shaving method was proposed,and the design model for plunge shaving tool and undercut control equation were established.Based on the singleparameter envelope principle,a mathematical model of the plunge shaving of beveloid gears was established,and the influence law of shaving cutter parameters on root cut and machining accuracy is analyzed.The continuous generating grinding process was studied for hardened beveloid gears,and a worm wheel-beveloid gear analytical meshing model was established for the first time to solve the problem of the design of the grinding process parameters and to elucidate the movement law of the grinding contact traces on the tooth surface.(5)The machining verification of beveloid gears was carried out.Aiming at the plunge shaving of beveloid gears,based on Vericut software,a simulation processing platform was built,and the simulation processing of a beveloid gear with compound modification was verified.For continuous generative grinding,the grinding module was developed under SIEMENS 840 Dsl CNC system.The module contains perfect HMI human-machine interface and NC control program.On this basis,the grinding experiment of variable thickness gear was carried out.