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发动机部件

www.bysj580.com / 2017-02-21
发动机部件
 了解操作或各部分的目的是必要的,一个完整的理解整个引擎。每个部分或单位有自己的特殊功能来执行和配合其他部分组成一个柴油发动机。一个人谁想操作,或其他服务的柴油引擎必须能够识别不同的部分用即期和知道他们的特定的功能。
   柴油发动机不同出外观、尺寸大小、数量及布置的汽缸、和施工细节。然而,他们都有相同的主要部分,尽管他们可能看起来不同,所有执行相同的功能。每个柴油发动机只有几个主要工作部件、辅助零件必须抓住工作部件在一起或协助主要工作部件性能。主要的工作部件是缸,圆筒,通常持有进口和排气阀门、活塞、连杆、曲轴、曲轴箱和燃料泵和燃料喷嘴
   汽缸引擎的核心是缸,燃料燃烧和电力发达。里面的缸是由班轮或套筒。缸的内径称为孔。汽缸头关闭的一头缸,常常包含阀门在空气和燃料是承认和废气排放
   活塞的另一端的工作空间是封闭的气缸活塞,传送到曲轴电力开发的燃烧的燃料。活塞环润滑机油产生一个气密密封活塞和气缸之间的衬垫。远处,活塞从气缸的一端,另一个是称为中风
  连杆的一端,称为同一年底连杆,附加到活塞销和活塞销位于活塞。其他或大端有一个轴承为曲柄销
  在曲轴转动的作用下活塞通过连杆和曲柄销位于曲柄臂之间,或脸颊,和传递工作从活塞到驱动轴。曲轴的部分支持在主轴承和旋转称为轴径。
  一个飞轮足够分量的是固定在曲轴和商店动能在电力存储并返回它在其他斯托克斯。飞轮有助于启动引擎,也可以用来使曲轴的旋转或多或少的统一
    一个凸轮轴驱动从曲轴链条传动或定时齿轮操作进、排气阀门通过凸轮,凸轮的追随者,把鱼竿,摇杆武器。气门弹簧用来关闭阀门。
   一个曲轴箱用来维系气缸,活塞,曲轴,以保护所有移动部件和轴承,并提供一个水库润滑油。的下部曲轴箱叫做台板。
  燃料是交在燃烧的空间注入系统包括泵、燃油管路、燃油喷射嘴或称为喷嘴。
 
  齿轮
  齿轮在机械是至关重要的因素,这是用来传输电力或运动从一个轴到另一个。他们可能只用于传输运动从一个地区到另一个机器,或者他们可能被用来改变速度或转矩一轴与关系到另一个。第一个机制是时钟发明使用齿轮。事实上,一个时钟只不过是一连串的齿轮。相当大的学习和研究有了齿轮近年来因为他们严格的条件下广泛使用。他们已经发送重负荷和运行速度比以往任何时候都极强。工程师和机械师都认为传动装置的主要元件在几乎所有类型的机械
直齿圆柱齿轮
  直齿圆柱齿轮将首先被考虑几个原因。首先,他们是最简单的和最昂贵的齿轮和他们可能被用来传输电力,也平行轴之间,直齿圆柱齿轮的定义通常适用于其他类型。重要的是要理解下面的定义,因为他们都是重要的因素在设计的任何设备利用齿轮
径节
  牙齿的数量每寸节圆直径。径节通常是一个整数。少量的沥青意味着一个大牙齿大小。啮合直齿圆柱齿轮必须有相同的螺距。速度比是基于啮合齿轮可能有不同的节圆和不同数量的牙齿的事实。
周节
  从一个点的距离在一个齿上的相应的点一个相邻的齿,测量沿节圆。这是一个衬套尺寸,因此具有衬管单
节圆
  圆上的比率齿轮组是建立。当两个齿轮啮合,这两个节圆必须恰好切线如果齿轮正常功能。这个切点是知道作为节点
压力角
  两齿轮在啮合时作用线和中心线垂直的夹角。对直齿圆柱齿轮压力角通常是14.5或20度,虽然可以使用其他值。啮合齿轮必须具有相同的压力角。对于一个架,牙齿有直边倾斜角度对应的压力角
基圆
  一个圆的切线作用线。基圆是虚圆,而渐开线疗法是发达。遵循一个渐开线直齿圆柱齿轮最治愈的基圆齿的顶部,这种治疗能可视化通过观察一个点在一个紧绳,因为它是用一个圆筒解除。在一个齿轮,气缸是最好的圈。
斜齿轮
  这些齿轮有牙齿的元素在一个角度或螺旋的轴齿轮
  他们是更加困难和昂贵的比直齿圆柱齿轮,但更安静、更强。他们可能被用来传输电力平行轴之间的角度,每一个在相同或不同的飞机
人字形齿轮
  一个人字齿轮是相当于一个右斜齿轮并排放置。因为牙齿的角度,斜齿轮创造了可观的侧推力轴上。一个人字齿轮纠正这个推力通过中和它,允许使用一个小推力轴承代替一个大家庭,也许一个完全消除。通常一个中央沟是在齿轮为便于在加工
锥齿轮
  锥齿轮是用来连接轴,不互相平行。通常轴是90度到对方,但是他们可能或多或少地超过90度的两个啮合齿轮可能具有相同数量的牙齿为目的,改变运动方向,或者它们可能只有一个不同的牙数为目的的改变速度和方向都。牙齿的脸躺在表面的圆台,因此牙齿元素并不互相平行。可以看出,这种缺乏并行创建一个加工问题,这样两个传递必须工具。牙齿的元素可能是直或螺旋,这样我们有平原和螺旋锥齿轮
蜗杆 蜗杆齿轮
  一个蜗杆蜗轮组合使用,主要是想获得一个高齿轮减速在一个有限的空间。通常,蜗杆驱动蜗轮和是不可逆的,也就是说,蜗轮不能驱动蜗杆。大多数蠕虫可以在任意方向旋转,顺时针或逆时针方向

   架是一个齿轮与无限半径,或一个齿轮与周长伸出成一条直线。它是用来改变往复运动来回转运动或反之亦然。一个车床齿条和齿轮是一个很好的例子,这种机制
  各种材料用于制造齿轮。通常,所选材料取决于方法用于使齿轮和应用程序,它将。齿轮可以投、切、或挤压。典型的材料包括铸铁、铸钢、碳素钢、合金钢、铝、青铜,叠层酚醛塑料,尼龙
  齿轮制造
  
  齿轮通常采用以下一般过程铣削,发电,或成型。在铣削方法制造,铣刀形状以便符合形状的牙齿之间的空间。刀具是然后穿过面对齿轮毛坯,因此剪一个牙齿之间的空间。齿轮毛坯的然后自动旋转,直到下一个空间被削减的刀线。这个过程一直持续到所有的空间都被切断,因此完全成形齿轮
  铣刀的缺点是,不同的刀具必须使用,不仅为不同的音高也为不同数量的牙齿。齿轮制造商通常形状的铣刀,这样他们是正确的对齿轮的最小齿数,在每个齿的八个范围数字,对于一个给定的音高。这意味着,当齿轮有更多的牙齿切与这铣刀,误差在齿廓的结果。错误增加向高端每个范围的牙数字,但误差通常是可接受的对大多数应用程序
  它是很难达到一个高精确度在切削齿的铣削过程。齿轮用于高速、高负荷的应用不削减足够精确的铣削过程。发电的方法被描述下应该使用每当高精度是必需的
  发电过程的齿轮加工需要使用要么滚刀或一个塑造者。一个滚刀类似于一个蠕虫病毒,使其轴平行裂缝提供切削刃figure2-1所示。的脸滚刀的牙齿松了一口气的间隙。切割过程中可以通过移动滚刀在齿轮毛坯平行齿轮轴作为齿轮毛坯和滚刀旋转
  从这个方法得到更好的精确结果,因为两者的同步旋转的刀具和齿轮毛坯。换句话说,铣刀徒几乎以相同的方式被削减到齿轮,将最终啮合齿轮。有未来的生成方法利用不需要一个不同的铣刀对齿轮的像距但不同数量的牙齿
  第二个方法生成齿轮是由成形过程。刀具用于成型方法要么是一个齿条刀或一个小齿轮铣刀。齿条刀的,牙齿直边,有其附录了等于齿根的齿轮被削减。角的方向侧架等于压力角的齿轮被削减。图2 - 2显示了一个齿轮毛坯和齿条刀。切割过程开始当齿轮毛坯已经搬进了铣刀直到节圆的齿轮毛坯是节线的切线的齿条刀。刀具是然后给定一个往复运动的脸的齿轮毛坯,毛坯慢慢旋转和机架翻译。切空间在两个牙齿没有完成一遍,而是需要经过几个平行的刀具齿轮轴。切割和滚动动作一直持续到结束的架是达到。此时,齿轮毛坯和切割架是重新定位,轧制和切割行动一直持续到所有的牙齿在齿轮被切断
  有两个主要优点使用生成刀而不是铣刀。首先,一个更高的精确度能达到切割过程。第二,一个刀可以用来切任何相同齿数的节圆
  
  第三一般方法制造齿轮的成型。而铸造齿轮曾经是一个很常见的方法,它现在的应用仅限于齿轮用在非常低的速度。注塑、压铸时使用大量的齿轮是必需的。注塑时使用的材料是塑料,而压铸过程通常是金属,如铜和铝
  如果齿轮用于应用程序涉及高速度和高负载,它通常需要有更高的精确度,所得从切削过程。一个方法的整理是剃须。在这个方法中,齿轮的运行有硬配对齿轮或剃齿刀。这个结果在去除少量的表面的齿轮
  另一个流行的方法用于齿轮精加工是磨削。在这种方法中,一个表单磨床或砂轮用于获得高精确度。的两个,磨削方法产生最精确的完成。其他整理方法包括研磨,研磨和抛光。
  

Engine  Parts
    An  understanging  of  the operation or purpuse of the various parts is necessary for a complete understanding of the whole engine.Each part or unit having its own special function to perform and in conjunction with other parts makes up a diesel engine.A person who wants to operate,repair,or otherwise service diesel engines must be able to recognize the different parts by sight and know what their particular functions are.
    Diesel engines vary in out appearance ,size,number and arrangement of cylinders,and details of construction.However,they all have the same main parts which,though they may look different,all perform the same functions.Each diesel engine has only a few main working parts,the auxiliary parts are necessary to hold the working parts together or to assist the main working parts performance.The main working parts are the cylinder,the cylinderhead,usually holding inlet and exhaust valves,the piston,the connecting rod,the crankshaft,the crankcase and the fuel pump and fuel nozzle.
     Cylinder  The heart of the engine is the cylinder,where the fuel is burned and the power developed.The inside of the cylinder is formde by the liner,or sleeve.The inside diameter of the cylinder is called the bore.The cylinder head closes one end of the cylinder and often contains the valves through which air and fuel are admitted and the exhaust gases discharged.
     Piston The other end of the working space of the cylinder is closed by the piston that transmits to the crankshaft the power developed by the burning of the fuel. Piston rings lubricated with engine oil produce a gastight seal between the piston and the cylinder liner . The distance that the piston travels from one end of the cylinder to the other is called the stroke  
     Connecting Rod One end,called the same end of the connecting rod,is attached to the wrist pin or piston pin located in the piston. The other or big end has a bearing for the crankpin
      Crankshaft The crankshaft turns under the action of the piston through the connecting rod and crankpin located between crankwebs,or cheeks,and transmits the work from the piston to the driven shaft. The parts of the crankshaft supported by and rotating in the main bearings are called journal
      A flywheel of sufficient weight is fastened to the crankshaft and stores kinetic energy during the power stores and returns it during the other stokes. The flywheel helps to start the engine and also serves to make the rotation of the crankshaft more or less uniform
      A camshaft driven from the crankshaft by a chain drive or by a timing gears operates the intake and exhaust valves through cams,cam followers,push rods,and rocker arms. Valve springs serve to close the valves.
      A crankcase serves to hold together the cylinder,piston,and crankshaft,to protect all moving parts and their bearings,and to provide a reservoir for lubricating oil.The lower part of the crankcase is called a bedplate.
      Fuel is delivered into the combustion space by an injection system consisting of a pump,fuel line,and called fuel-injection nozzle or spray nozzle.  
Gears
     Gears are vital factors in machinery,which are used 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 relation to another. One of the first mechanism invented using gears was 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 higt speeds than ever before. The engineers and the machinists all consider gearing the prime element in nearly all classes of machinery
Spur Gears
   Spur gears will be considered first for several reasons. In the first place,they are the 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 to understand the following definitions,since they are important factors in the design of any equipment utilizing gears
Diametral Pitch
    The number of teeth per inch of pitchcircle diameter. The diameteral pitch is usually an integer. A small number for the pitch implies a large tooth size. Meshing spur gears must have the same diameteral pitch. The speed ratio is based on the fact that meshing gears may have differentsized pitch circles and hence different numbers of teeth
Circular Pitch
    The distance from a point on one tooth to the corresponding point on an adjacent tooth,measured along the pitch circle. This is a liner dimension and thus has 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 know 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 meshing. 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 Circle
   A circle tangent to the line of action. The base circle is the imaginary circle about which an involute cure is developed. Most spur gears follow an involute cure from the base circle to the top of the tooth,this cure can be visualized by observing a point on a taut cord as it is unwound from a cylinder. In a gear,the cylinder is the best circle.
Addendum
   The radial distance from the pitch circle to the top of the tooth
Dedendum
    The radial distance from the pitch circle to the root of the tooth
Clearance
     The difference between the addendum and the addendum
Face Width
     The width of the tooth measured axially
Face
     The surface between the pitch circle and the top of the tooth
 
Flank
    The surface 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 gearThey are more difficult and expensive to make than spur gears,but 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 Gears
    A herringbone gear is equivalent to a right-hand helical gear placed side by side. Because of the angle of the tooth,helical 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 around 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 and spiral bevel gears
Worm and Worm Gears
    A 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 drives 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,phospor bronze,laminated phenolics,and nylon.
Gear  Manufacture
  Gears are usually manufactured by one of the following general processes.milling,generating,or molding. In the milling method of manufacture,the milling cutter is shaped so as to conform to the shape of the space between the teeth. the cutter is then moved across the face of the gear blank,thus cutting out a space between teeth. the gear blank is then automatically rotated until the next space to be cut lines up with the cutter. this process is continued until all the spaces have been cut out,thus completely forming the gear
  The disadvantage of the milling cutter is that a different cutter must be used,not only for different pitches but also for different number of teeth. Gear manufacturers usually shape the milling cutters so that they are correct for the gear with the smallest number of teeth,in each of eight ranges of tooth numbers,for a given pitch. this means that when gears having a greater number of teeth are cut with this milling cutter,an error in the tooth profile results. the error increases toward the high end of each range of tooth numbers,but the error is usually acceptable for most applications
  It is extremely difficult to attain a high degree of accuracy in cutting teeth by the milling process. gears to be used for high-speed,high-load applications are not cut accurately enough by the milling process. the generating method to be described next should be used whenever high accuracy is required
  The generating process of gear cutting entails the use of either a hob or a shaper. A hob which resembles a worm,with gashes made parallel to its axis to provide cutting edges is shown in figure2-1. the faces of the hob teeth are relieved for clearance. the cutting process is accomplished by moving the hob across the gear blank parallel to the gear axis as both the gear blank and the hob are rotated
  Better accuracy results from this method because of the simultaneous rotation of both the cutter and the gear blank. in other words,the cutter acts in much the same manner to the gear being cut,as will the eventual meshing gear. the generating method has the future advantage of not requiring a different cutter for gears of like pitch but different number of teeth
  A second method of generating gears is by the shaping process. the cutting tool used in the shaping method is either a rack cutter or a pinion cutter. the rack cutter,which has teeth with straight sides,has its addendum made equal to the dedendum of the gear being cut. the angular orientation of the side of the rack is equal to the pressure angle of the gear to be cut. figure 2-2 shows a gear blank and a rack cutter. the cutting process is started when the gear blank has been moved into the cutter until the pitch circle of the gear blank is tangent to the pitch line of the rack cutter. the cutter is then given a reciprocating motion across the face of the gear blank,as the blank slowly rotate and the rack translates. the cutting of the space between two teeth is not accomplished in one pass but rather requires several passes of the cutter parallel to the gear axis. the cutting and rolling action is continued until the end of the rack is reached. at this point ,the gear blank and the cutting rack are repositioned,and the rolling and cutting action continued until all the teeth on the gear have been cut
  there are two principal advantage to using generating cutter rather than milling cutters. the first is that a much higher degree of accuracy can be obtained in the cutting process. second,a single cutter can be used to cut gears with any number of teeth of the same pitch
  The third general method of manufacturing gears is molding. while the casting gears was once a very common method,its present-day application is limited to gears used at very low speeds. injection molding and die casting is used when a large number of gears are required. injection molding is used when the material is a plastic,while die casting is often the process for metals such as brass and aluminum
  If gears are to be used in applications involving high speeds and high loads,it is usually necessary to have a higher degree of accuracy than that obtained from cutting process. one method of finishing is shaving. in this method,the gear is run with a hard mating gear or a shaving cutter. this results in the removal of small amounts of the surface of the gear
  Another popular method used for finishing gears is grinding. in this method,a form grinder or grinding wheel is used to obtain a high degree of accuracy. of the two,the grinding method produces the most accurate finish. other finishing methods include honing,lapping,and burnishing 
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