Research On Machining Method For Spiral Bevel Gear Of Half-spread-out Helix Modified Roll

To solve the problems of the bias of tooth and low machining efficiency of spiral bevel gears,this paper studies a simple method for adjustment and correction,machining method of half-spread-out helix modified roll.According to this method,the passive gear is machined by generating method and the drive gear is machined by the method of helix modified roll.This paper carries out researches on meshing characteristics of gears based on half-spread-out helix modified roll,cutting principle,tooth contact analysis,error correction of tooth surface and experiment of machining.The main results and innovations of this paper are listed as follows:(1)According to principle of the half-spread-out helix modified roll and traditional and machining methods,the geometry model are established for the solution of cutters pressure angle respectively.Through comparative analysis,the reason of the bias of tooth contact of traditional generating method is summarized and the principle that the bias of tooth can be eliminated by the half-spread-out helix modified is interpreted.(2)Taking half-spread-out helix modified as research objects,normal vector and curvature of the calculation point on gear tooth surface can be solved according to cutting principle and machine tool motion.Then,by applying principle of gearing and differential geometry,normal vector and curvature of the calculation point on pinion tooth surface are determined.Finally,the machine settings of pinion are calculated and determined based on the above analysis.(3)Based on wheel blank parameters of gear pair,structural parameter of cutter and machine setting,the relative position and motion among head-cutter,machine and workpiece are determined.Using the principle of gearing,the equations of gear and pinion are established respectively.Then,based on the assembly relation,gear pair mounting coordinate system is established and the tooth contact analysis is conducted.And the tooth contact trace and transmission error curve are obtained.(4)Based on the theoretical tooth surface equation of pinion,its equation with machine tool adjustment parameter errors is established.Then,the solution model of tooth surface normal errors is given and the connection between machine tool adjustment parameter errors and surface normal errors is gained.On this basis,the value of weight coefficient for the machine tool adjustment parameters is determined and the weight coefficient parametrical modification method is proposed.Finally,the validity of the method is tested by applying tooth contact analysis.(5)On the YKT2250 machine tools,experiment of machining based on the methods mentioned and machine tool adjustment parameters is performed and a pair of spiral bevel gears are acquired,which indicates the accuracy of the machine settings and the feasibility of half-spread-out helix modified roll.