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 the oldest gear have been found so far, as a reflection of 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.

As early as in 1694, French scholar Philippe De La Hire forward involute tooth shape curve can be used as in the first place. In 1733, the French M.C amus put forward the common normal of tooth contact must be on the center of the node. A auxiliary instantaneous center line respectively along the big wheel and little wheel

Instantaneous center line (pitch) for pure rolling, and the auxiliary instantaneous center line solid coupling of auxiliary tooth shape on the big wheel and little wheel envelope formed by two tooth profile curve is conjugated to each other, this is Camus theorem. It takes into account the two tooth surface meshing state; Clear modern about the trajectory of the contact point is established

Concept. In 1765, Swiss L.E uler involute profile analytic research mathematical foundation, illustrates a pair of meshing gears, the tooth profile curve of the radius of curvature and curvature center position. Later, babies' further complete the method, and is now the Eu - let - babies' equation. Can contribute to the application of involute tooth profile is Roteft WUlls, he put forward the centre distance change when involute gear has the advantages of the angular speed ratio unchanged. In 1873, a German engineer Hoppe is put forward, with different number of teeth of involute tooth profile of gear in the pressure Angle is changed, thus laid the ideological basis of modern shift gear.

The end of the 19th century, generative principle of gear cutting method and using the principle of gear cutting machine and cutting tool appeared, after making the gear machining with the more comprehensive means, involute profile shows high more optimal sex. Teeth mesh as long as the gear cutting tools from the normal position when moving slightly, can use the standard cutter cut out the corresponding shift gears in machine tool. In 1908, the Swiss MAAG displacement method is studied and manufacturing export as processing gear shaper, later, the BSS, American AGMA, Germany DIN successively put forward many kinds of method to calculate the deflection of gear.

In order to improve the service life of the power transmission gear and reduce its size, in addition to from material, heat treatment and structure improvement, the circular arc tooth profile of gear obtained the development. In 1907, the British Frank Humphris published a circular arc tooth profile at the earliest. In 1926, rui natives Eruest Wildhaber a patent on the method of surface arc tooth profile helical gears. In 1955, the Soviet union's M.L.N ovikov completed practical research of arc tooth profile gear and get the order of Lenin. In 1970, the British Rolh - Royce company engineers R.M.S tuder achieved double circular arc gear patent in the United States. This kind of gear is now increasingly attention by people, has played a significant benefit in the production.

Gear is to be able to mesh each other toothed machine part, its application in the field of mechanical transmission and the whole machinery is extremely broad. Modern gear technology has reached: the module of gear o. 004 ~ 100 mm; Gear diameter by 1 mm ~ 150 m; The transmitted power can reach Hundreds of kilowatts; Speed up to thousands of revolutions per minute; The circumference of the highest speed of 300 m/SEC.

Gear is to be able to mesh each other toothed machine part, its application in the field of mechanical transmission and the whole machinery is extremely broad. Modern gear technology has reached: the module of gear o. 004 ~ 100 mm; Gear diameter by 1 mm ~ 150 m; The transmitted power can reach Hundreds of kilowatts; Speed up to thousands of revolutions per minute; The circumference of the highest 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.