Research On Meshing Characteristics And Tooth Surface Design Of Aero Spiral Bevel Gears

Spiral bevel gears are widely used in aeronautical transmission system, which can offer many advantages in terms of smooth transmission, high loading capacity and compact structure. As the key part of aero-engine accessory drive, the meshing performances of spiral bevel gears have great influences over the whole transmission system. Contact pattern and transmission error are two key indexes for meshing quality evaluation. With the aid of TCA(Tooth Contact Analysis), LTCA(Loaded TCA), as well as experimental tests, high-order transmission error curve design, meshing performance analysis, and redesign of pinion tooth surface based on the shifting of contact pattern are studied for aero spiral bevel gears in this paper. In addition, software systems are also developed for the design and manufacture of high-performance spiral bevel gears, which have been successfully applied in the development of aero gears.The main contributions of this dissertation are listed as follows:(1) An inversion algorithm of machining parameter for pinion tooth surface of spiral bevel gears is investigated. Taking pinion digital tooth surface as known, a least squares optimization model is established to obtain target surface, which can be solved by using the Levenberg-Marquardt(L-M) method with trust region strategy. This iterative algorithm can be used for active modification design of spiral bevel gears.(2) The design methods of transmission error for spiral bevel gears are proposed. 1.Based on the local synthesis method, the optimization design of second-order parabolic transmission error is proposed. 2. Considering gear as an imaginary cutter tool, active modification design of pinion tooth surface is investigated. According to the predesigned high-order transmission error(forth-order parabola, seventh-order dished curve), the pinion target tooth surface is built on the base of pinion reference tooth surface that fully conjugated with gear tooth surface. The pinion machining parameters then can be reversed by tooth surface approximation algorithm mentioned above. 3. Based on second-order parabolic transmission error, revision method of modified roll coefficients is put forward to design high-order function of transmission error(seventh-order dished curve) for spiral bevel gears.The constraint equations are established by controlling special meshing point of high-order transmission error curve directly, while modified roll coefficients can be obtained by solving the nonlinear equations. And the rest of the machining parameters are the same as second-order parabolic transmission error.(3) Loaded meshing performance of three kinds of pinion tooth surface with the style of transmission error including second-order parabola, forth-order parabola, and seventh-order dished curve which roughly have the same contact ratio and lower end amplitude are investigated quantitatively. Comparative studies are show that high-order transmission error design can improve the dynamic and strength performance of gears effectively.(4) The inversion of misalignment based on the shifting of contact pattern and redesign of pinion tooth surface are proposed for spiral bevel gears. The relationship among different groups of misalignment which can lead to the same contact pattern is studied. The digital features of contact pattern are extracted, and the equivalent misalignment can be obtained by an optimal method according to the minimum sum of contact path deviation. Pinion tooth surface is redesigned considering the misalignment by using optimal design of second-order parabolic transmission error.(5) Experimental results are presented to verify tooth surface design method and meshing performance analysis for spiral bevel gears. Machining, meshing testing, loaded contact pattern forming process as well as vibration acceleration testing are investigated separately for spiral bevel gears with three types of transmission error curves including second-order parabola, forth-order parabola and seventh-order dished curve respectively. Experimental results show good consistency with the theoretical analysis.