Spiral bevel gear based on the generation principle of spherical involute tooth surface

Spiral bevel gears are widely used in aviation, ships, national defense technical equipment, machine tools, automobiles, engineering machinery, mining machinery and other mechanical products because of their high coincidence coefficient, stable transmission and high strength. Spiral bevel gear is one of the most widely used spiral bevel gears, and has basically become a synonym of spiral bevel gear. As an ideal spherical involute tooth profile, the tooth surface of spiral bevel gear belongs to spatial spiral surface, and the mathematical model of tooth surface is more complex, which makes the existing tooth surface cutting process extremely complex and the cost of machine tools and cutting tools expensive. In the actual gear cutting process, the setting of machine tool and tool parameters, assembly error and cutting force deformation in the machining process will affect the tooth surface bearing capacity and meshing performance of the processed spiral bevel gear, which makes the quality control of spiral bevel gear design and manufacturing more difficult. Therefore, the research on the milling of high-precision spherical involute spiral bevel gear has always been an important and difficult problem in the field of gear manufacturing at home and abroad. At present, there are two main processing systems of spiral bevel gears: Gleason system and Oerlikon system. The high-precision spiral bevel gear processing technology and equipment are also basically monopolized by foreign companies with these two kinds of teeth, which makes China’s high-precision spiral bevel gears basically rely on the purchase of foreign machine tools for processing.

In principle, the spherical involute spiral bevel gear pair carries out conjugate transmission by line contact, but the existing tooth cutting methods all adopt the engineering approximation method, and the tooth surface of the spiral bevel gear is point contact quasi conjugate transmission. Gleason’s spiral bevel gear tooth profile is approximately replaced by the hypothetical equivalent cylindrical gear tooth profile on the back cone expansion plane, and pursues the simplicity of tool design and manufacturing. The spiral surface formed by the rotation of the straight edge is used as the cutting surface of the blade, and the spiral bevel gear tooth surface is processed in the way of envelope expansion. Strictly speaking, the tooth surface processed in this way is not a spherical involute tooth surface, which loses many properties such as interchangeability, constant instantaneous transmission ratio and so on. Due to the incorrect meshing of the cut tooth surface, there are some disadvantages, such as high transmission noise, poor contact area, reduced strength and so on. In order to obtain better tooth surface contact performance, the machine tool and tool parameters must be adjusted repeatedly, which makes the cost of precision spiral bevel gear more expensive, and it takes a lot of time to adjust the rolling of bevel gear tooth surface.

With the continuous development and improvement of computer technology and control system, the gear milling machine tool of spiral bevel gear has been improved from Gleason No.116 gear milling machine based on mechanical rigid transmission to Phoenix II multi axis linkage NC gear milling machine tool, which cancels the lengthy mechanical transmission chain, adjustment link, tool tilting mechanism and shaking table mechanism, The structure of the machine tool is simplified to a certain extent. However, the tooth surface forming is still based on the original Gleason tooth cutting technology, using the engineering approximation method. The adjustment of tooth contact area, the parameter design of machine tool and cutting tool and the control of gear cutting motion are still complex and difficult problems to be solved.

Based on the generation principle of the tooth surface of spherical involute spiral bevel gear, breaking through the existing Gleason system of spiral bevel gear processing, a new milling method is innovatively proposed, which takes the tooth surface generating line as the cutting edge and the inverse motion of the tooth surface generating motion as the cutting motion, and only needs three-axis linkage to cut the tooth surface of spiral bevel gear. Based on the research of the new method of three-axis linkage gear cutting, the gear cutting motion is further simplified, and a two-axis linkage milling method is innovatively proposed. Using the new method of spiral bevel gear milling proposed in this paper, the gear cutting machine and tool are significantly simplified and the motion control is simple. This paper attempts to explore a new path in the field of bevel gear processing and realize the independent innovation of spiral bevel gear processing technology.

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