Research On 3D Parametric Design Of Automobile Steering Non-circular Gear Sector And Rack Pair

The spatially staggered shafts of automobile steering shafts and horizontal rocker shafts often use tapered non-circular gear sector and rack pairs to achieve non-uniform speed transmission.The profile and gear direction parameters of the cross section of each end of non-circular gear sectors are also different(spiral thickened gear),the gear surface is complex,and there is no mature three-dimensional modeling method at present,which hinders the smooth development of the three-dimensional parametric design of the non-circular gear sector and rack pair.Most companies use empirical methods or parameter trial.The product development cycle is long,and the cost is high.Therefore,this paper studies the three-dimensional modeling method of the non-circular gear sector and the extraction algorithm of the cross-sectional contour coordinates of the three-dimensional model based on the meshing principle of the non-circular gear sector and rack pair.The design realizes the three-dimensional parametric modeling of the non-circular gear sector,which lays the foundation for the finite element analysis of the steering gear steering shaft,three-dimensional measurement and enterprise information construction.The main work is as follows:The geometric motion process of two non-circular gear racks with different transmission ratios have been studied,based on the meshing principle of non-circular gear racks,analyze the pure rolling law of the gear rack joints for different transmission ratios.The synthetic method analyzes the instantaneous center trajectory of the non-circular gear rack pair under the eccentric state.The results show that if there is eccentricity,the instantaneous center trajectory is discontinuous at this time,which inevitably brings motion interference.The above research provides a theoretical basis for the three-dimensional modeling of non-circular gear sector and rack.The three-dimensional modeling method of non-circular gear sector has been studied.Adopt the principle of non-circular gear rack and spline curve rolling,based on SolidWorks,establish a three-dimensional model of non-circular gear sector through solid Boolean.Study the method of extracting the coordinates of irregular or discontinuous surfaces through SolidWorks.Extract the gear profile of non-circular gear through the macro,and save the coordinate of the tooth profile to txt text,import it into MATLAB simulation program for 3D gear surface reconstruction,and obtain the 3D non-circular gear sector through the bilinear interpolation algorithm.Develop 3D parametric design software for non-circular gear,study the secondary development of SolidWorks.Through the SolidWorks API,the parameterized modeling interface is written in VB,and the SolidWorks three-dimensional entity Boolean is used to perform the three-dimensional modeling of the non-circular gear sector,and a set of non-circular gear sectors for automobile steering shafts produced is developed.Analyze the accuracy of the three-dimensional modeling of non-circular gear sectors.By comparing the gear profile of the three-dimensional model with the theoretically calculated gear profile,the gear pitch error at the corresponding point is calculated to be less than 0.00238mm.The finite element analysis of the non-circular gear sectors is performed by ANSYS Workbench.The maximum stress value of the gear sector is within the allowable range.The detection method of the non-circular gear sector is studied.Use the P26 to detect the non-circular gear sector,and the maximum gear error is 0.0465mm.The results show that the three-dimensional parametric modeling method is feasible.