Spiral bevel gear has the advantages of stable transmission, low vibration and noise and large bearing capacity, which makes it the power input device of main reducer of high-power helicopter. In the early design of spiral bevel gear, the contact path is similar to that of spur gear and perpendicular to the root cone. There are some problems, such as small coincidence degree, poor tooth strength and large vibration and noise, which can not meet the current transmission requirements of high-speed and heavy load.
In this regard, scholars at home and abroad have proposed a method to improve the design coincidence degree by reducing the angle between the contact path and the root cone, that is, the so-called “inner diagonal design”. Fang Zongde et al. Combined with local comprehensive parameters, meshing simulation and load-bearing meshing simulation, aiming at the controllability of the tooth surface and meshing performance of spiral bevel gear, that is, by adjusting the direction of contact path, carried out large degree of fit design to improve the meshing performance of spiral bevel gear, and verified that it has good dynamic performance in a wide load range. Deng Xiaozhong and others improved the coincidence degree of spiral bevel gear by reducing the included angle between the contact path and the root cone, and analyzed its strength performance and dynamic performance. It shows that the spiral bevel gear with large coincidence degree can significantly reduce the contact stress and vibration noise on the tooth surface. Mou Yanming and others proposed a design method of spiral bevel gear with large coincidence degree based on tooth length curvature correction, which improved the load distribution and meshing performance of tooth surface. Based on the local synthesis method, Fuentes and others in the United States optimized the angle between the contact path and the root cone, designed the contact path along the approximate tooth length direction, and obtained the spiral bevel gear with high strength and low noise. Before that, Fuentes et al. Established the target tooth surface considering transmission error and tooth surface impression, obtained the corresponding small wheel machining parameters through the Levenberg Marquardt optimization method based on confidence interval strategy, realized the tooth surface impression along the approximate tooth length direction of the contact path, and analyzed the tooth strength performance by finite element method.
(1) By optimizing the local comprehensive parameters, the design of the contact path of spiral bevel gear as the large coincidence of inner diagonal and along the tooth length is realized under the condition of meeting the preset meshing performance.
(2) Compared with the inner diagonal design, the large coincidence design along the contact path of the tooth length has lower error sensitivity. When there is installation error, the tooth surface impression of spiral bevel gear will shift along the tooth height direction, but it is more sensitive to the deviation of shaft spacing. Therefore, higher requirements are put forward for the installation accuracy of the center distance between the two axes.
(3) The tooth surface marks along the tooth length contact path cover the whole tooth surface, which is conducive to improve the bending strength and contact strength of spiral bevel gear teeth and reduce the fluctuation of load-bearing transmission error of spiral bevel gear pair.
By optimizing the local comprehensive parameters, the meshing performance of spiral bevel gears can be pre controlled. On this basis, two kinds of large coincidence designs with inner diagonal contact path and along the tooth length direction are proposed. Through tooth contact analysis (TCA) and tooth load contact analysis (LTCA), the sensitivity, strength performance and fluctuation of load transmission error of tooth mark under two kinds of large coincidence design are compared respectively.