【正文】 were probably “thought” experiments of Heron of Alexandria (ca. ), who wrote on the subjects of theoretical mechanics and the basic elements of mechanism. The oldest surviving relic containing gears is the Antikythera mechanism, so named because of the Greek island of that name near which the mechanism was discovered in a sunken ship in 1900. Professor Price of Yale University has written an authoritative account of this mechanism. The mechanism is not only the earliest relic of gearing, but it also is an extremely plex arrangement of epicyclic differential gearing. The mechanism is identified as a calendrical puting mechanism for the sun and moon, and has been dated to about 87 .The art of gearing was carried through the European dark ages after the fall of Rome, appearing in Islamic instruments such as the geared astrolabes which were used to calculate the positions of the celestial bodies. Perhaps the art was relearned by the clockand instrumentmaking artisans of fourteenthcentury Europe, or perhaps some crystallizing ideas and mechanisms were imported from the East after the crusades of the eleventh through the thirteenth centuries.It appears that the English abbot of ’s monastery, born Richard of Wallingford, in . 1330, reinvented the epicyclic gearing concept. He applied it to an astronomical clock, which he began to build at that time and which was pleted after his death.A mechanical clock of a slightly later period was conceived by Giovanni de Dondi(13481364). Diagrams of this clock, which did not use differential gearing, appear in the sketchbooks of Leonardo da Vinci, who designed geared mechanisms himself. In 1967 two of da Vinci’s manuscripts, lost in the National Library in Madrid since 1830, were rediscovered. One of the manuscripts, written between 1493 and 1497 and known as “Codex Madrid I” , contains 382 pages with some 1600 sketches. Included among this display of Lenardo’s artistic skill and engineering ability are his studies of gearing. Among these are tooth profile designs and gearing arrangements that were centuries ahead of their “invention”.2 Beginning of Modern Gear Technology In the period 1450 to 1750, the mathematics of geartooth profiles and theories of geared mechanisms became established. Albrecht Durer is credited with discovering the epicycloidal shape(ca. 1525). Philip de la Hire is said to have worked out the analysis of epicycloids and remended the involute curve for gear teeth (ca. 1694). Leonard Euler worked out the law of conjugate action(). Gears deigned according to this law have a steady speed ratio.Since the industrial revolution in midnineteenth century, the art of gearing blossomed, and gear designs steadily became based on more scientific principles. In 1893 Wilfred Lewis published a formula for puting stress in gear teeth. This formula is in wide use today in gear design. In 1899 George , the founder of five gear manufacturing panies, published “A Treatise on Gear Wheels” . New inventions led to new applications for gearing. For example, in the early part of this century (1910), parallel shaft gears were introduced to reduce the speed of the newly developed reaction steam turbine enough to turn the driving screws of oceangoing vessels. This application achieved an overall increase in efficiency of 25 percent in sea travel.The need for more accurate and quietrunning gears became obvious with the advent of the automobile. Although the hypoid gear was within our manufacturing capabilities by 1916, it was not used practically until 1926, when it was used in the Packard automobile. The hypoid gear made it possible to lower the drive shaft and gain more usable floor space. By 1937 almost all cars used hypoidgeared rear axles. Special lubricant antiwear additives were formulated in the 1920s which made it practical to use hypoid gearing. In 1931 Earle Buchingham, chairman of an American Society of Mechanical Engineers (ASME) research mittee on gearing, published a milestone report on geartooth dynamic loading. This led to a better understanding of why fasterrunning gears sometimes could not carry as much load as slowerrunning gears.Highstrength alloy steels for gearing were developed during the 1920s and 1930s . Nitriding and casehardening was introduced in 1950. Extremely clean steels produced by vacuum melting processes introduced in1960 have proved effective in prolonging gear life.Since the early 1960s there has been increased use of industrial gas turbines for electric power generation. In the range of 1000 to 14000 hp, epicyclic gear systems have been used successfully. Pitchline velocities are form 50 to 100m/s(10000 to 20000 ft/min). These gear sets must work reliably for 10000 to 30000 hp between overhaule.In 1976 bevel gears produced to drive a pressor test stand ran stand ran successfully for 235h at 2984kw and 200m/s. form all indications these gears could be used in an industrial application if needed. A reasonable maximum pitchline velocity for mercial spiralbevel gears with curved teeth is 60m/s.Gear system development methods have been advanced in which lightweight, highly loaded gears are used in aircraft applications. The problems of strength and dynamic loads, as well as resonant frequencies for such gearing, are now treatable with techniques such as finiteelement analysis, siren and impulse testing for mode shapes, and application of damping treatments where required.齒 輪李洪光（譯） 直齒輪和斜齒輪 輪齒是直的、而方向又與其軸平行的齒輪稱作直齒輪。感謝學(xué)院圖書館工作人員對我此次設(shè)計提供文獻資料。參考文獻[1]孫恒，陳作模. 機械原理 [M].北京：高等教育出版社，2001[2]濮良貴，[M].北京：高等教育出版社，2001[3]王伯惠，[M].北京：人民交通出版社，1999[4]吳宗澤，羅圣國. 機械設(shè)計課程設(shè)計[M].北京：高等教育出版社，1999[5]鄒慧君. 機械原理課程設(shè)計手冊[M].北京：高等教育出版社， 1998[6] 范欽珊. 材料力學(xué)[M].北京：高等教育出版社，[7]《現(xiàn)代機械傳動手冊》[M].北京：機械工業(yè)出版社，2002[8](第5卷) [M].北京：化學(xué)工業(yè)出版社，2002[9]劉古岷，王渝，[M].北京：機械工業(yè)出版社，2001[10] 成大先. 機械設(shè)計圖冊(第5卷)[M].北京：化學(xué)工業(yè)出版社，2000[11]《機械工程手冊》(第11卷機械產(chǎn)品(一)) [M]. 北京：機械工業(yè)出版社，1982 [12][M].北京：經(jīng)濟日報出版社，1991[13]日