英文文獻(xiàn)GearsGears are vital factors in machinery ,which are uses to transmit power or motion from one shaft to another .They may be used only to transmit motion from one part of a machine to another,or they may be used to change the speed or the torque of one shaft with with relation to another.One of the first mechanism invented using gears wad the clock.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 high speeds than ever before.The engineers and the machinists all consider gearing the prime element in nearly all classes of machinery.Super Gears Spur gears will be considered first for several reasons.In the first place, hey are simplest and the least expensive of gears and they may be used to transmit power between parallel shafts, also spur gears definitions are usually applicable to other types .It is important go understand the following definitions, since they are important factors in the design of any equipment utilizing gears.Diametric Pitch The number of teeth per inch of pitch cirle diameter .The diameter pitch is usually an integer .A small number for the pitch implies a large tooth size.Meshing spur gears must have the same diameter pitch .The speed ratio is based on the fact that meshing gears may have different-sized pitch circles and hence different number of teeth.Circular Pitch The distance from a point on one tooth to the corresponding point on an adjacent tooth, is measrued along the pitch circle.This is a liner dimension and thus bas liner units.Pitch Circle The circle on which the ratio of the gear set is based, when two gears are meshing, the two pitch circles must be exactly tangent if the gears are to function properly.The tangency point is known as the pitch point.Pressure Angle The angle between the line of action and a line perpendicular to the centerlines of the two gears in mesing .Pressure Angles for spur gears are usually 14.5 or 20 degrees, although other values can be used.Meshing gears must have the same pressure angles.In the case of a rack, the teeth have the straight sides inclined at an angle corresponding to the pressure angle.Base CircleA circle tangent to the line of action (or pressure line ) .The base circle is the imaginary circle about which an involutes cure is developed .Most spur gears follow an involutes cure from the base circle to the top of the tootch,this cure can be visualized by observing a point on a taut cord an it is unwound from a cylinder .In a gear ,the cylinder is the best circle.AddendumThe radial distance is from the pitch circle to the top of the tooth. DedendumThe radial distance from file pitch circle to the root of the tooth.ClearanceThe difference between gear addendum and dedendum face width.Face WidthThe width of the tooth measured axially.Face The surface is between the pitch circle and top of tooth.Flank The surface is between the pitch circle and the bottom of the tooth.Helical Gears These gears have their tooth element at an angle or helix to the axis of the gear. They are more difficult and expensive to make than spur gears, ut are quieter and stronger. They may be used to transmit power between parallel shafts at an angle to each in the same or different planes.Herringbone GearsA herringbone gear is equivalent to a right-hand and a left-hand helical gear placed side by side.Because of the angle of the tooth, elical gears create considerable side thrust on the shaft. A herringbone gear corrects this thrust by neutralizing it, allowing the use of a small thrust bearing instead of a large one and perhaps eliminating one altogether.Often a central groove is made round the gear for ease in machining.Bevel Gears Bevel gears are used to connect shafts, which are not parallel to each other.Usually the shafts are 90 deg.To each other, but they may be more or less than 90 deg.The two meshing gears may have the same number of teeth for the purpose of changing direction of motion only,or they may have a different number of teeth for the purpose of changing both speed and direction .The faces of the teeth lie on the surface of the frustum of a cone,therefore the teeth elements are not parallel to each other it can be seen that this lack of parallelism creates a machining problem so that two passes with a tool must be made.The tooth elements may be straight or spiral ,so that we have plain anti spiral evel gears.Worm and Worm GearsA worm-and-worm-gear combination is used chiefly where it is desired to obtain a high gear reduction in a limited space, normally the worm drivers the worm gear and is not reversible, that is to say, the worm gear can not drive the worm.Most worms can be rotated in either direction, clockwise or counterclockwise.Racks A rack is a gear with an infinite radius, or a gear with its perimeter stretched out into a straight line.It is used to change reciprocating motion to rotary motion or vice versa.A lathe rack and pinion is a good example of this mechanism.Various materials are used in manufacturing gears .Usually,the materials selected depends on the method used for making the gear and the application to which it will be put.Gears can be cast,cut,or extruded.Typical materials include cast iron,cast steel,plain carbon steel,alloy steel aluminum,phosphor bronze,laminated phonetics,and nylon.中文翻譯齒輪齒輪是機(jī)器中的動(dòng)力元件,用來傳遞軸與軸之間的運(yùn)動(dòng)及動(dòng)力。它們可能僅被用來傳遞運(yùn)動(dòng),即機(jī)器的一個(gè)部分到另一個(gè)部分,或者被用來改變軸與軸之間相對(duì)速度和轉(zhuǎn)矩,第一個(gè)被發(fā)現(xiàn)用齒輪的機(jī)器是鐘表,事實(shí)上,鐘表的齒輪與火車上的齒輪相比是非常小的。由于齒輪在實(shí)際環(huán)境中的廣泛應(yīng)用,人們?cè)邶X輪的應(yīng)用方面進(jìn)行了許多的研究和調(diào)查?，F(xiàn)在,齒輪傳動(dòng)比起以前來不得不傳遞很重的載荷,和在高速度下運(yùn)轉(zhuǎn)。目前工程師和機(jī)械師都在考慮存在于機(jī)械中的這種因素。直齒圓柱齒輪直齒圓柱齒輪被作為傳動(dòng)中的首選有許多原因。它們是最簡(jiǎn)單也是最廉價(jià)的，并且它們可以被用作傳動(dòng)平行軸之間的力，還有它的概念同于其它類型的齒輪，以下的幾個(gè)定義是非常重要的，因?yàn)?，它們?cè)谠O(shè)計(jì)任何與齒輪有關(guān)的方面都是非常重要的。徑節(jié)節(jié)圓直徑單位距離上的齒數(shù)，徑節(jié)通常是一個(gè)整數(shù)。小小的一段齒距包括了許多的齒形。直齒圓柱齒輪嚙合的條件是必須有相同的徑節(jié)，齒輪的傳動(dòng)比決定于嚙合齒輪的不同的節(jié)圓和不同數(shù)目的齒數(shù)。齒距沿著節(jié)圓從齒上的一點(diǎn)到臨近齒上對(duì)應(yīng)相同的另一點(diǎn)的距離，這是一個(gè)線尺寸和線性單位。節(jié)圓作為齒輪比率設(shè)定基礎(chǔ)的圓。若要是互相嚙合的齒輪正常運(yùn)行，則兩節(jié)圓必須精確相切。壓力角運(yùn)動(dòng)方向與垂直于兩嚙合齒輪中心線的直線所形成的夾角。對(duì)于直齒圓柱齒輪壓力角為 14.5 度或 20 度，因此可以有許多的用途，相嚙合的齒輪必須有相同的壓力角。對(duì)于齒條，齒相對(duì)于直邊有與壓力角相同的傾斜角度。基圓與運(yùn)動(dòng)方向相切（或與壓力角方向相切）的圓。基圓是產(chǎn)生漸開線所假想的圓。許多直齒圓柱齒輪都是漸開線從基圓到齒頂，當(dāng)繃緊繩索從一個(gè)圓柱體展開時(shí)，仔細(xì)觀察繩索上某點(diǎn)的運(yùn)動(dòng)，即可想象出此段漸開線的形狀。在齒輪中，基圓是最主要的圓。齒頂高從節(jié)圓到齒頂?shù)膹较蚓嚯x。齒根高從節(jié)圓到齒底的徑向距離。間隙齒頂高與齒根高之間的不同。面寬齒在軸向的寬度。面 節(jié)圓和齒頂之間的表面。齒腹節(jié)圓和齒底之間的表面。斜齒輪這些齒輪的齒相對(duì)于齒輪軸線由一個(gè)角度或螺旋角度，它們比直齒圓柱齒輪的制造更難，造價(jià)更昂貴，但是它們傳動(dòng)無噪音并且可靠。它們可以用來在相同或不同平面中構(gòu)成一定角度的相兩軸之間的力的傳遞。人字形齒輪人字形齒輪是在齒輪兩邊有相同數(shù)量在左旋和右旋形的齒輪。由于齒輪有角度，齒輪制造時(shí)需要考慮軸受到的軸向力，人字形齒輪是用平衡的方法來抵消軸向推力的，固而允許選用輕系列軸承取代重系列軸承，甚至可以完全取消軸承，通常在切削加工中在齒輪的周圍有一個(gè)中心槽來抵消。錐齒輪錐齒輪用作互相不平行的軸之間的連接。通常軸之間的夾角是 90 度，但它們比 90 多或少，相嚙合的兩齒輪僅改變運(yùn)動(dòng)方向，或者為改變速度具有不同的齒數(shù)，齒的表面沿著圓錐的表面，圓頭齒之間不相互平行，它就使得在機(jī)械加工中產(chǎn)生類似的問題及必須要一套夾具。齒輪的線可能是直的或螺旋的，因此有平直的錐齒和螺旋的錐齒。蝸桿和蝸輪蝸桿蝸輪機(jī)構(gòu)主要用作有限空間需較小齒輪的體積的情況。通常蝸桿為主動(dòng)件并且不能顛倒，也就是說，蝸輪不能作為主動(dòng)件。許多蝸桿能左右移動(dòng)，轉(zhuǎn)動(dòng)為順時(shí)針或逆時(shí)針。齒條齒條是有無窮半徑的齒輪或是邊緣隨著直線擴(kuò)展的齒輪，它被用來往復(fù)運(yùn)動(dòng)改變?yōu)槁菪\(yùn)動(dòng)或反過來，車床齒條和小齒輪是這種機(jī)器的最好例子。各種材料被用于制造齒輪。通常被選用的材料取決于齒輪的制造與齒輪將來的實(shí)現(xiàn)用途，齒輪能被鑄，軋或擠壓出來。材料類型包括：鑄鐵碳素鋼，合金鋼，鋁，青銅，尼龍。