Research On Forming Theory And Machining Method Of Spiral Bevel Gear With Line Contact Reduction Tooth

In this thesis,the forming principle and processing method(half-spiral-generating method)of spiral bevel gear pair with line contact,are presented,and the forming principle of half-spiral-generating for machining conjugate tooth surface is expounded.Based on the numerical control machine tool,the gear cutting motion model and the corresponding tooth surface solving model were established.With the help of numerical simulation,finite element contact simulation,virtual machining simulation,numerical control machining test and meshing test,the design and machining of the spiral bevel gear with reduced-tooth line contact were realized.The main research contents and results are as follows:(1)Based on the basic principle of gear meshing,it is explained that the relative motion of a point on the conjugate meshing tooth surface of a gear pair is the spiral motion of the point around the instantaneous axis.Based on the principle of generating gear,the conjugate surface forming methods(direct forming method and indirect forming method|)are analyzed.The reason that the conjugate tooth surfaces with line contact can not be obtained by the current machining method of spiral bevel gears with reduced teeth is expounded.(2)Based on the forming theory of generating gear,the forming principle of line contact spiral bevel gear pair and half-spiral-generating machining method are presented.In order to solve the non-linear contact problem in machining spiral bevel gears,a forming principle of spiral bevel gear pair with linear contact was put forward.By using the generating gear that overlapped with gear to generate the tooth surface of the pinion,the spiral bevel gear pair with reduced-tooth line contact conjugate was completely fabricated based on the generating gear principle.The machining principle of half-spiral-generating method and the movement required for gear cutting were described.Based on the direct forming method,the tooth surface of gear was machined,and the control method of each axis of CNC machine tool to r ealize the gear cutting movement was explained.By establishing the gear cutting coordinate system,the basic calculation formula of adjusting parameters were determined,the tool motion equation was deduced,and the complete gear cutting model of half-spiral-generating method was constructed.(3)The solving method of tooth surface is expounded.According to the established cutting model,a mathematical model was established to solve the coordinate of tooth surface points.The three-dimensional model of the spiral bevel gear pair with reduced teeth were constructed by using the solved tooth surface points,and the finite element contact simulation analysis was carried out.The simulation results of linear contact and nearly full tooth contact were obtained.(4)A numerical control machining experiment of spiral bevel gears with reducedtooth line contact was carried out based on the half-spiral-generating method.The CNC machining program was written,the machining simulation of spiral bevel gear was carried out,and the CNC machining trial production of spiral bevel gear with line contact was carried out.The feasibility and correctness of the cutting model,the machining method motion control and the NC program were verified.The meshing meshing test results of the spiral bevel gear pair obtained by machining show that the contact area covers most of the tooth surface,which is completely consistent with the contact distribution of linear contact conjugate gear pair,which verifies the correctness of the forming principle of linear contact spiral bevel gear pair and the half-spiralgenerating method proposed in this paper.