Gears are vital factors in machinery. One of the first mechanism invented using gears was the clocks. In fact, a clock is little more than a train of gears.Considerable study and research have been made on gears in recent years because of their wide use under exacting conditions. They have to transmit heavier loads and run at higher speeds than ever before. The engineers and the machinists all consider gearing the prime elementin nearly all classes of machinery.齿轮在机械中占有极其重要的作用。第一个利用齿轮做成的机械装置就是钟表，事实上，它只不过是用了一系列的齿轮。对于它可以在严格的条件下的广泛使用，在齿轮上做了大量的学习和研究。相比过去，它们现在必须在更高的速度下传递更重的负荷。工程师和机器操纵工人都认为齿轮在几乎所有的机器的零件中占有首要的因素。1. Spur gearsSpur gears are used to transmit power and rotary motion between parallel shafts. Theteeth are cut parallel to the axis of the shaft on which the gears are mounted. The smaller of two gears in mesh is called the pinion and the larger is customarily Designated as the gear. In most applications, the pinion is the driving element whereas the gear is the driven element.1.直齿圆柱齿轮直齿圆柱齿轮用于平行轴之间传递力和回转运动，轮齿被切制成与安装齿轮的轴之轴线相平行。两啮合齿轮中较小的叫小齿轮，大的习惯上叫齿轮，在大多数情况下，小齿轮是主动轮，大齿轮叫从动轮。2. Helical gearsHelical gears have certain advantages, for example, when connecting parallel shafts they have a higher load-carrying capacity than spur gear with the same tooth numbers and cut with the same cutter.2斜齿圆柱齿轮斜齿圆柱齿轮具有特定的优点，比如，当连接平行轴的用相同刀具切削出来的并齿数相同的斜齿轮比直齿轮具有较高的承载能力。斜齿轮也能用于连接相互成任意角度的非平行轴。Helical gears can also be used to connect nonparallel , non-intersecting shaftsat any angle to one another.斜齿轮也能用于连接相互成任意角度的非平行轴。The maximum gear ratio obtainable with a single pair of gears varies with the type of gear and the application. The following are approximate maxim a for the various type for average load conditions: spur, 8; parallel-shaft helical, 10; straight bevel , 6; spiral bevel, 8;hypoid , 12; and worm , 80. For lightly loaded, instrument, and positioning gears, these rations can be exceeded. Rations as high as 400 or higher can be obtained with gears that resemble tapered worms meshing with hypoid gear. For heavily loaded gear, the given rations may be so high that a reasonable gear size precludes a satisfactory pinion.一对齿轮能获得的最大传动比随齿轮类型和应用的变化而变化，以下是各种类型的齿轮的平均载荷条件的近似最大化，直齿是8，平行轴斜齿轮是10，直齿锥齿是6，曲线齿锥齿轮8，准双曲面12，蜗轮蜗杆8，对于轻载荷和定位齿轮这些传动比被超出，类似于成锥形的蜗轮蜗杆，和准双曲面齿轮能够获得的传动比高达400 或更高，如此高以至于00 的齿轮尺寸不可能令人满意。Since the ratio in a single pair of gears is the quotient of the tooth number, and since there usually are limitations on both the minimum and maximum numbers of teeth on the available gears,it follows that the number of ratios obtainable in a single pair is limited. To enlarge the coverage it is necessary to use multiple pairs, or trains. The overall speed ratio in a train is the product of the ratios in each pair. In certain cases an exact ratio cannot be obtained with gears, but by using two or more parts, the desired ratio can be approximated to any degree of precision.一对齿轮的传动比齿数的商，它们通常是限制在有效齿轮的最大和最小齿数之间，因此，一对齿轮获得的传动比是受限制的，为了扩大范围，用多级齿轮副或系列是必要的，在一个系列中，总速比是每对齿轮产生的传动比。As a convenience for machine builders and users, packaged speed reducers, following an industry-accepted pattern , are manufactured in a wide variety of types,configurations , speed ratios, and capacities; these consist of a box or housing containing bearings, shafts, lubricant and shaft oil seals. Speed increasers are usually custom build.在某种情况下，一个确切的传动比不能由齿轮副获得，但是用两对或更多对时，要求的传动比能达到精确等级，为了对机器制造者和使用者方便起见，各种整装式减速器，根据工业通用的试样被大量的多样化的类型的组合的速度比的生产制造，这些由箱子组成或给含有轴承轴润滑剂和轴油封装外罩增速器通常被定别。All speed reducers when operating continuously become hot because of friction in the teeth, in the lubricant, in the bearings, and in the oil seals. If the heat is generated at a faster rate than it can be dissipated to the atmosphere, the lubricant may deteriorate and the gear or bearing fail.所有的减速器当被连续使用时，由于轮齿在润滑剂轴承和油封件的摩擦会变热，如果热量的产生在空气中散逸的速度还快的话，润滑剂不能损坏，并且轴承和齿轮失效。Worm gear sets are widely used because of the many advantages obtained by their tooth action and load carrying capacity. A large speed reduction or a high increase oftorque can be attained with the worm gear set. Compactness of design is easy to obtain with such a combination, Worm gear drives are quiet and vibration free.蜗轮装置由于啮合作用和传递载荷能力获得的许多优点而被广泛应用，大量转矩的减速或增速装置由蜗轮装置完成，设计的紧凑，用这样一个结合体是容易得到的，蜗轮是平稳且无振动的。A worm gear set consists of the worm, which is very similar to a screw, and the wormgear, which is a helical gear. The shafts upon which the worm and the gear are mounted are usually at right angels but not in the same plane. The usual practice is to have the worm drive the worm gear. With same ratios, it is possible to have a gear driver the worm. However, with large ratios, it is impossible for the gear to drive the worm.一个蜗轮装置由蜗杆非常类似于螺丝和蜗轮一个斜齿轮组成的，安装蜗杆和蜗轮的轴通常相互垂直而不在同一平面中，通常习惯上使蜗杆驱动蜗轮。小的传动比，使一个齿轮驱动蜗杆是有可能的，但是，大的传动比，使一个齿轮驱动蜗杆是不可能的。The worm can be made with either right-hand or left-hand thread. Also, like a screw, it can be made with single, double, triple, or quadruple thread