外文翻譯--齒輪和齒輪傳動-其他專業(yè)-文庫吧資料
2025-01-27 00:34本頁面
【正文】 s, size, and quality, industrial practice is to follow standards set up by the American Gear Manufactures Association (AGMA). Tooth form Standards published by AGMA establish gear proportions and tooth profiles. Tooth geometry is determined primarily by pitch, depth, and pressure angle. Pitch： Standards pitches are usually whole numbers when measured as diametral pitch P. Coarsepitch gearing has teeth larger than 20 diametral pitch –usually to . Finepitch gearing usually has teeth of diametral pitch 20 to 200. Depth: Standardized in terms of pitch. Standard fulldepth have working depth of 2/p. If the teeth have equal addenda(as in standard interchangeable gears) the addendum is 1/p. Stub teeth have a working depth usually 20% less than fulldepth teeth. Fulldepth teeth have a larger contract ratio than stub teeth. Gears with small numbers of teeth may have undercut so than they do not interfere with one another during engagement. Undercutting reduce active profile and weakens the tooth. Mating gears with long and short addendum have larger loadcarrying capacity than standard gears. The addendum of the smaller gear (pinion) is increased while that of larger 蘭州交通大學畢業(yè)設計（論文） 2 gear is decreased, leaving the whole depth the same. This form is know as recessaction gearing. Pressure Angle: Standard angles are 020 and 025 . Earlier standards include a 14 02/1 pressure angle that is still used. Pressure angle affects the force that tends to separate mating gears. High pressure angle decreases the contact ratio (ratio of the number of teeth in contact) but provides a tooth of higher capacity and allows gears to have fewer teeth without undercutting. Backlash: Shortest distances between the noncontacting surfaces of adjacent teeth . Gears are monly specified according to AGMA Class Number, which is a code denoting important quality characteristics. Quality number denote toothelement tolerances. The higher the number, the closer the tolerance. Number 8 to 16 apply to finepitch gearing. Gears are heattreated by casehardening, throughhardening, nitriding, or precipitation hardening. In general, harder gears are stronger and last longer than soft ones. Thus, hardening is a device that cuts the weight and size of gears. Some processes, such as flamehardening, improve service life but do not necessarily improve strength. Design checklist The larger in a pair is called the gear, the smaller is called the pinion. Gear Ratio: The number of teeth in the gear divide by the number of teeth in the pinion. Also, ratio of the speed of the pinion to the speed of the gear. In reduction gears, the ratio of input to output speeds. Gear Efficiency: Ratio of output power to input power. (includes considerat
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