Development and types of Involute Gears

Gears are widely used in mechanical transmission devices and are one of the common mechanical parts. Human beings began to use gears in agricultural production and military before BC. At first, the tooth profile of the gear was not involute shape, but dial and hang tooth profile, without considering the tooth profile and tooth pitch. Fig. 1 shows the gear device and its dial and hang tooth profile used in ancient times. With the development of history and the progress of science and technology, the tooth profile of gear has developed from equal pitch tooth profile to cycloid shape. In the 1860s, the use of involute as the tooth profile of the gear was proposed, but the involute gear was not widely used until a century later, the involute gear was widely used all over the world after the generation processing method was used to produce the involute tooth profile gear, as shown in Figure 2.

Involute gear transmission is one of the most commonly used mechanical transmission modes in modern industrial production. It is mainly used to transmit power and motion. Various transmission forms of involute gear are shown in Figure 3. Compared with other mechanical transmission such as chain transmission, belt transmission, hydraulic transmission and friction transmission, involute gear transmission has a series of advantages, such as high efficiency, large power range, accurate transmission ratio, long service cycle, space saving and so on. By adjusting the ratio of teeth and the number of gears between involute gears, the transmission ratio of any value can be obtained in theory; It can also be applied to parallel, orthogonal and other staggered transmission relationships by changing the spatial position relationship of each transmission shaft. Involute gears are widely used, ranging from clocks and watches to aircraft and ships, all need to rely on involute gears to transmit power. At present, involute gears are widely used in more than 20 fields, such as instruments and meters, engineering machinery, machine tools, mining, hoisting equipment, automobile and motorcycle agricultural machinery, electric energy, aviation, ships, weapons and equipment, rail transit, cement construction, petrochemical industry and so on, Involute gear is the most important transmission component in mechanical products, and its transmission mode has become an indispensable transmission form in mechanical transmission. Due to the important position of involute gear in industrial development, it is regarded as one of the symbols of the process of social industrialization.

(a) Spur gear transmission
(b) Helical cylindrical gear transmission
(c) Herringbone cylindrical gear transmission
(d) Rack and pinion transmission
(e) Hypoid gear transmission
(f) Helical gear transmission
(g) Screw transmission
(h) Straight bevel gear transmission
(i) Bevel gear transmission
(j) Curve tooth bevel gear transmission
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