Gear is one of the important mechanical transmission parts, widely used in aerospace, automobile industry, ship machinery, equipment manufacturing and other equipment. For a long time, in order to improve the bearing capacity of ordinary spur gears, researchers have made a lot of improvement on the traditional gears in the aspects of tooth profile and tooth line, and developed many new transmission gears, among which circular arc tooth line cylindrical gear is one of them. The main structural feature of the gear is that the tooth alignment is a space arc curve, and the tooth profile is different according to different machining methods. Due to the advantages of no axial force, smooth transmission and large bearing capacity, the gear has a good application prospect.
The main machining methods of circular arc tooth line cylindrical gear include round broaching cutter head method, three cutter head rotary cutting method, CNC rolling cutting method, parallel connecting rod processing method and rotary cutter head milling method. Among them, the quality of the products obtained by the round broaching disc method is unstable and the cost is high; the three cutter head rotary cutting method has the defects of low efficiency and difficult to guarantee the accuracy; while in the process of NC Hobbing, the interference between the cutter flank and the machined tooth surface is easy to occur, which makes it easier to process the gears with smaller radius.
At present, the research focus on the machining method of circular arc tooth line cylindrical gear is mainly parallel connecting rod machining method and rotary cutter head milling method. Therefore, the research on the transmission characteristics of the gear is mainly carried out around the above two processing methods. For example, Ma Zhenqun studied the transmission theory and manufacturing system of the cylindrical gear with symmetrical arc-shaped tooth profile, analyzed the real tooth contact problem of the gear, and proposed the CNC machining method of the whole tooth surface modification; Di Yutao and others studied the influence of meshing interference, axis parallelism error and center distance on meshing performance, and proposed the calculation method of tooth surface stress and bending stress and the concept of displacement; Xiao Huajun and Wang Shaojiang realized the three-dimensional modeling and rapid prototyping manufacturing for manufacturing through relevant research work; Al-fonso FA et al. Compared the contact stress and transmission error of spur gear, helical gear and circular arc tooth line cylindrical gear transmission, and the results showed that circular arc tooth line cylindrical gear had certain advantages and disadvantages; based on finite element method, Chen YC analyzed the contact stress distribution and transmission error of curve gear under loading; In addition, tsengrt, Zhang XG, Wei Yongqiao and others have carried out relevant research on the three-dimensional modeling, undercutting conditions, transmission error, lubrication and other aspects of the circular arc gear. These research results promote the practical engineering application of the gear to a certain extent.
As we all know, according to the different gear processing methods, the curve of gear tooth profile will be different: one is that the profile of any section is involute; the other is that the section of tooth profile is involute, the other is hyperbola, and the whole tooth profile is a variable hyperbola family.
At present, there is no targeted research on the problem of tooth profile difference caused by different machining methods, which restricts the in-depth research on the modification and lubrication of the gear.
Therefore, the author adopts the main processing methods (parallel connecting rod machining and rotary cutter head milling) This paper analyzes the technological characteristics of the two processing methods of the gear, deduces the tooth surface and tooth profile equation of the gear obtained by the two processes, and then obtains the gear tooth thickness equation, and analyzes the influence of design parameters on the tooth thickness deviation, so as to provide theoretical basis for the research of gear system noise reduction, lubrication, fault diagnosis and tooth profile modification.
