After nearly 70 years of development, the technology of hypoid gear has been continuously improved, but as one of the most complex gear transmission forms, the design and processing of hypoid gear has always been a difficulty. Scholars at home and abroad have done a lot of work in these aspects, most of which are for arc involute hypoid gear, and there is less research on cycloid hypoid gear with equal high teeth.
In the 1970s, the former Ministry of machinery industry of China specially organized various scientific research institutes and universities to tackle the key problems of Gleason circular arc involute gear technology, which not only deciphered the calculation and design method of Gleason adjustment card, but also made a lot of improvement and development on its basis, and established the industrial and technical system of spiral bevel gear design and manufacturing in China. Later, with the establishment of diplomatic relations between China and the United States, the United States gradually lifted the export restrictions of Gleason equipment to China, and a large number of Gleason processing and supporting equipment were introduced into China, thus forming a situation in which circular arc involute bevel gears and hypoid gears have occupied a dominant position in China for a long time. At present, China still uses this set of technical system. During this period, although China also introduced a number of SKM2 gear milling machines (as shown in the figure) from the former Oricon company in Switzerland, due to the small number of imports and single products, only a small amount of them were used for the processing of drive axle gears and industrial gears of passenger cars. Moreover, at that time, the precision of Oricon machine tools was not high and the calculation and adjustment were complex, so they did not form a scale. After 1986, China’s Huainan coal mining machinery plant, Shenyang Mining machinery plant, northwest coal mining machinery plant No. 1, Tangshan metallurgical machinery plant, etc. have successively introduced AMK series processing and inspection equipment and related technology from the former West Germany, developed a series of products and applied them to tunneling machines, belt conveyors, scraper conveyors and other equipment, but they have not formed a scale.
Cycloid constant height tooth system (hereinafter referred to as cycloid tooth) hypoid gear is processed by face hobbing (FH) method with continuous indexing, and only two machine tools, two knives and two loading and unloading are required to complete rough and fine cutting of large and small wheels. Compared with face milling (FM) method of arc involute hypoid gear, it not only saves processing equipment, but also reduces loading and unloading times and shortens production cycle, Thus, it is very beneficial to reduce costs and improve production efficiency. With the successful development and production application of advanced cycloid gear numerical control processing equipment (such as Klinger Oricon’s C series and Gleason’s Phoenix Series), its processing accuracy has been significantly improved, and the special design and analysis software developed by the two companies has greatly simplified the previous complex calculation and adjustment. Therefore, in recent years, the application of cycloid gear in developed countries such as Europe, America, Japan and South Korea has become more and more common. Enterprises such as Daimler Chrysler, BMW, Mann and Volkswagen in Germany, general motors, Ford, American axle, John Deere and Dena in the United States, Iveco in Italy, Toyota in Japan, Hyundai in South Korea, gaz group in Russia and Tata Motors in India have begun to turn to the production and application of cycloid and other high teeth.
As we all know, machining error and heat treatment deformation will lead to the deviation of the actually machined tooth surface from the theoretical design tooth surface, which sometimes even reaches hundreds of microns, which will make the actual contact area deviate from the design position, and the transmission is unstable, resulting in vibration, noise and intensity problems. Because the tooth surface of cycloid hypoid gear is an undevelopable ruled surface, and the tooth line is an epicycloid, the tooth groove shrinks, so it is impossible to carry out grinding, so the process of tooth cutting heat treatment tooth grinding is mostly adopted. Grinding can improve the tooth surface finish and reduce the noise of hypoid gear pair, but the ability to modify the tooth surface is limited, and the radial runout, pitch error and tooth shape error caused by the heat treatment deformation of hypoid gear cannot be eliminated. When the tooth surface deformation is large, the deviation between the actual machined tooth surface and the theoretically designed tooth surface cannot be effectively reduced, and the position of the contact area cannot be changed. Circular arc involute gear and “gram” cycloid gear can reduce this kind of tooth surface deviation by grinding and scraping after heat treatment respectively, but “Austria” cycloid gear cannot eliminate tooth surface deviation by finishing after heat treatment, so it is necessary to find other methods, such as tooth surface error pre correction.
Due to the inexorability of machining error and heat treatment deformation, how to minimize the meshing performance deviation caused by it has become a research hotspot in recent years. The traditional adjustment method is to adjust the machine tool settings according to the contact marks obtained from the roll inspection test and the corresponding adjustment cards, but this method largely depends on the experience of technicians, requires repeated trial cutting, and is time-consuming and unreliable. With the emergence of the latest high-precision hypoid gear measuring center and coordinate measuring instrument, it is possible to control the tooth surface error without relying on the roll inspection test. By analyzing the sensitivity of the tooth surface error to various processing parameters (including tool parameters, cutter head parameters, machine tool setting parameters, auxiliary shaping motion parameters, etc.), select the processing parameter combination that has a great impact on the tooth surface, and then calculate the error between the measured actual tooth surface and the theoretically designed tooth surface to obtain the corresponding processing parameter inverse adjustment, which is fed back to the processing machine tool for tooth cutting again, In this way, only two trial cuts are needed to obtain the actual tooth surface approaching the theoretical design tooth surface. For the mass-produced hypoid gears, in the trial production stage, through the statistical analysis of the measurement results after heat treatment, the approximate machining error and heat treatment deformation law are found. Adopting this pre correction method will greatly improve the production efficiency and is very beneficial to reducing the cost. Gleason expert manufacturing system gems (Gleason expert manufacturing system) and Klingelnberg integrated manufacturing of spiral bevel gears (kimos5), the latest spiral bevel gear integrated manufacturing system of Klingelnberg Oricon group, have integrated this function, but as its core technology, they are not disclosed to the public.
Using this pre correction method, the height of the machined tooth surface can approach the theoretical design tooth surface, but the first designed tooth surface is often not the optimal tooth surface, so it is particularly important to study how to obtain the optimal mating tooth surface and its corresponding processing method. Active tooth surface design technology can enable designers to design tooth surface topology according to the required meshing performance, so it is a very effective way to obtain the optimal mating tooth surface.
Because high-precision tooth surface coordinate data can be obtained, through the surface fitting technology, we can easily get the fitting tooth surface and its expression that is highly close to the actual tooth surface. Using the digital tooth surface obtained by this fitting to carry out tooth contact analysis instead of the traditional roll inspection test, we can obtain the transmission error curve while obtaining the contact mark of the actual tooth surface. A large number of studies have shown that, Transmission error is an important cause of vibration and noise. The contact analysis of the actual tooth surface comprehensively reflects the meshing information of the hypoid gear pair, and avoids the inconsistency between the design and inspection evaluation criteria, which is very useful in production. This simulation and analysis technology of actual tooth surface meshing based on accurate measurement of tooth surface (or digital roll Inspection Technology) can be compiled into a general computer program and integrated into the closed-loop manufacturing system, which can reduce the inspection equipment and shorten the production cycle. It is also applicable to other types of hypoid gear transmission. At the same time, the high-precision fitting of the actual tooth surface also lays the foundation for the further active design based on the actual tooth surface.