According to historical records, in 400 ~ 200 BC in ancient China has already started to use gear, shanxi unearthed bronze gears in our country is so far have found zui old gear, reflecting the ancient science and technology achievements of this work is to gear mechanism as the core mechanism. The 17th century, people started to research, can be delivered right tooth shape of the movement. The 18th century, Europe after the industrial revolution, the application of gear transmission is increasing day by day widely; First the development of cycloidal gear, then the involute gear, until the beginning of the 20th century, involute gear has set up a file in the application. In order to improve the service life of the power transmission gear and reduce its size, from material, heat treatment and structure improvement, the circular arc tooth profile of gear obtained the development. Gear is to be able to mesh each other toothed machine part, its application in the field of mechanical transmission and the whole mechanical qi is extensively. Modern gear technology has reached: the module of gear O. 004 ~ 100 mm; Gear diameter by 1 mm ~ 150 m; Transmitted power can reach hundreds of kilowatts; Speed up to thousands of revolutions per minute; Zui the circumference of the high speed of 300 m/SEC. In the application of transmission gear appeared very early. More than three hundred years BC, the ancient Greek philosopher Aristotle in the mechanical problems, it expounds the bronze or iron gear transmission problem of rotary motion. Invented in ancient China, has been applied in the entire gear train. However, the ancient gear is made of wood or with gold of moulds, the only transmission shaft between the rotary motion, cannot guarantee the stability of transmission, the bearing capacity of the gear are also small. With the development of production, the gear operation stability. 1674 Danish astronomer roemer song ci with outer cycloid tooth profile curve is put forward, in order to get stable running gear. This article by polyurethane industrial synchronous belt arc-gear synchronous belt original, reproduced please indicate the copyright: http://www. lilainuo。 com