The history of gears

In the west, the ancient Greek philosopher Aristotle expounded the problem of transmission of rotating motion by bronze or cast iron gears in his mechanical problem in 300 BC. The famous Greek scholars Aristotle and Archimedes studied cogwheels, and the famous Greek inventor gutisibius put even pins on the edge of a circular table to engage it with the pin wheel. This was about 150 BC. In 100 BC, heron, an alexandrian inventor, invented the speedometer, in which gears were used. Gears were also used in the first century AD in the mill mill made by the Roman architect bidopis. By the 14th century, gears were used on clocks.Iron bronze gear at the end of the warring states periodIron bronze gear at the end of the warring states periodEarly eastern han dynasty (the first century AD) has been the word gear. The south-pointing cart and ji li drum cart in The Three Kingdoms period had adopted a gear drive system. The water rotary mill invented by du yu in jin dynasty transfers the power of water wheel to stone mill through gears. One of the earliest records of the gear drive system in the history books is a description of the armillary sphere made in 725 by liang lizan, a member of the tang dynasty. Built in the northern song dynasty (see ancient Chinese timepieces), the water-moving table used a complex gear system. A rack and pinion drive was recorded in the book wu bei zhi (1621) by MAO yuanyi of the Ming dynasty. In 1956, in the ancient ruins of anwuji city, hebei province, iron spined gear with a diameter of about 80 mm was found. Although it was incomplete, the iron quality was good. Through research, it was confirmed to be the product from the end of the warring states period (3rd century BC) to the western han dynasty (206 BC ~ 24 AD). In 1954, bronze ratchet gear was unearthed in tiljia ya, yongji county, Shanxi Province. Referring to the unearthed objects in the same pit, we can conclude that they are relics from the early years of the qin dynasty (221 ~ 206 BC) or the western han dynasty. As for the use of ratchet gear, no written record has been found so far, and it is speculated that it may be used for braking to prevent the wheel shaft from reversing. In 1953, a pair of bronze herringbone gears were unearthed in hongqing village, chang 'an county, shaanxi province. According to the analysis of tomb structure and burial items, it can be concluded that the gear from the early eastern han dynasty. Both wheels have 24 teeth and are about 15 mm in diameter. Hengyang and other places also found the same herringbone gear.As early as 1694, French scholar PHILIPPE DE LA HIRE first proposed that the involute can be used as tooth curve. In 1733, m. ciamus, a Frenchman, proposed that the public normal at the contact point of a wheel tooth must pass through nodes on the central link. When an auxiliary instantaneous center line (nodal circle) rolls pure along the instantaneous center line (nodal circle) of the large wheel and the small wheel respectively, the two tooth profile curves formed by the auxiliary tooth shape of the fixed connection with the auxiliary instantaneous center line on the large wheel and the small wheel are conjugate to each other, which is CAMUS theorem. It takes into account the meshing state of the two tooth surfaces; Clearly established the modern concept of contact point trajectory. L, Switzerland, 1765. EULER put forward the mathematical basis for the analytic study of involute tooth profile, and clarified the relationship between the curvature radius and the curvature center of a pair of meshing gears. Later, SAVARY further completed this method and became eu-let-savary equation. ROTEFT WULLS contributed to the application of involute tooth profile. He proposed that the angular velocity ratio of involute gear is constant when the center distance changes. In 1873, the German engineer HOPPE put forward the involute tooth shape of gears with different number of teeth when the pressure Angle changes, thus laying the ideological foundation of modern displacement gears.At the end of the 19th century, the principle of developing tooth cutting method and the use of this principle of special machine tools and cutting tools have emerged, so that the gear processing has a more complete means, the involute tooth shape shows great advantages. As long as the gear is slightly moved from the normal meshing position, the standard cutter can be used to cut out the corresponding gear on the machine. In 1908, Swiss MAAG studied the displacement method and manufactured the developing gear shaper. Later, British BSS, American AGMA and German DIN successively proposed a variety of calculation methods for gear displacement.Bronze herringbone gear in the early han dynastyBronze herringbone gear in the early han dynastyIn order to improve the service life of power transmission gear and reduce its size, arc-toothed gear has been developed in addition to material improvement, heat treatment and structure improvement. In 1907, FRANK HUMPHRIS, a Briton, first published the arc-toothed shape. In 1926, the retur ERUEST WILDHABER patented the circular tooth helical gear. In 1955, M. L. NOVIKOV completed the practical research of arc-toothed gear and won the Lenin medal. 1970 engineer r. at rolh-royce, United Kingdom. M. STUDER has a us patent for double arc gears. This kind of gear has been paid more and more attention to, and has brought about remarkable benefit in production.Gears are mechanical parts with teeth that can mesh with each other. They are widely used in mechanical transmission and the whole mechanical field. Modern gear technology has reached: gear modulus 0.004 ~ 100 mm; Gear diameter from 1 mm to 150 m; Transfer power up to 100, 000 kilowatts; Speed up to several hundred thousand RPM; The maximum circumferential velocity is 300 m/s.With the development of production, the smoothness of gear operation is valued. In 1674, Danish astronomer romer first proposed to use epicycloid as tooth profile curve to get smooth gear.During the industrial revolution in the 18th century, gear technology developed rapidly, and a lot of research was done on gear. In 1733, French mathematician cami published the basic law of tooth profile engagement. In 1765, euler, a Swiss mathematician, suggested using involute as tooth profile curve.The gear hobbing and gear shaper appeared in the 19th century solved the problem of producing high precision gear in large quantities. In 1900, pufort gear hobbing machine equipped with a differential device, can be processed in the gear hobbing helical gear, since the hobbing gear hobbing gear has been popular, generating processing gear accounted for the overwhelming advantage, the involute gear has become the most widely used gear.In 1899, rusher was the first to implement the idea of shifting gears. The gear can not only avoid the root cutting, but also match the center distance and improve the bearing capacity of the gear. In 1923, Wilder haber in the United States first put forward the gear with circular arc tooth profile. In 1955, sunovikov made an in-depth study on the circular arc gear, and the circular arc gear was applied in production. This kind of gear has high bearing capacity and efficiency, but it is not as easy to manufacture as involute gear, and needs further improvement.