Research On Machining And Modeling Methods Of Line-Contact Spiral Bevel Gears

Aiming at the problem that only a local contact area can be obtained by traditional designing and machining methods,the adjustment of contact area is difficult and the bearing capacity of gear pair is limited,based on the theory of tooth surface formation of line-contact spiral bevel gears and taking full advantage of multi-axis NC machining technology,the machining and corresponding tooth surface modeling methods of linecontact spiral bevel gears were studied in this thesis.Based on the study of milling principle,simulation methods such as finite element contact analysis and numerical control cutting simulation and testing methods such as actual NC machining and gear rolling test were carried out to verify the proposed machining and modeling methods.Thus the designing and machining of line-contact spiral bevel gears were realized.The main contents of this thesis can be summarized as follows:(1)According to the principle of crown generating gear,the reason why a linecontact area can’t be obtained by traditional methods was analyzed,the basic principle of machining line-contact spiral bevel gears with conical finger-type cutter was explained and the kinematic analysis of machining process was carried out.Based on five-axis machining center with dual rotary tables,the machining coordinate systems and motion models for the cutter were established and the machining parameters were solved.(2)Based on the established coordinate systems and motion models for the cutter,a set of non-linear equations for solving the line-contact tooth surface points were constructed by the meshing principle of gears.Aiming at the shortcomings of this method,the principle and method for solving tooth surface points based on digital simulation principle of conjugate surfaces were studied.The problem of solving tooth surface points was transformed into a non-linear programming problem under multidimensional constraints,and the corresponding mathematical models were established.Using the obtained discrete points,the 3D models of line-contact spiral bevel gear pair were constructed and the finite element contact analysis was carried out.(3)A program control method for generating line-contact spiral bevel gears was studied,the control of the rotation for the blank,the curvilinear motion for the cutter in machining concave and convex surfaces and the rotation for the crown generating gear were realized by macro programming technique.Besides,the tooth cutting procedures were worked out.The models of tools,blanks,fixtures and cutters for five-axis NC machining were established and the simulation of NC machining was carried out in simulation software to verify the machining method,the curvilinear motion for the cutter and the tooth machining procedures.(4)The conical finger-type cutter was manufactured and the actual machining experiments were carried out using five-axis machining center with dual rotary tables so that the machining coordinate systems,motion models for the cutter and tooth machining procedures were verified.Then actual contact area detection was carried out by bevel gear rolling machine and it showed that the proposed machining principle and the established machining models were correct.