1、Crank rod systemCrank rod system is the main mechanisms reciprocating internal combustion engine. Crank rod system is realizing work cycle engine, and complete the energy conversion major sports parts. In doing work stroke, it will fuel burning the heat energy produced is the piston reciprocating mo
2、tion, crankshaft rotation movement into mechanical energy, foreign power output; In other stroke, relies on the rotation of the flywheel crank and inertia, through the connecting rod driving the piston movement up and down, to create the conditions for the next to do work. The function of the crank
3、rod system Crank rod system role is to provide burning the place, after burning fuel gas in the piston top role inflationary pressure in the rotation of the crankshaft into torque, and constantly power output. (1) will gas pressure into crankshaft of torque (2) the reciprocating movement of the pist
4、on to the rotary motion of the crankshaft The composition of the crank rod system Crank rod system by the bodys group, the piston connecting rod group, crankshaft fly wheel of three parts. (1) the body groups: the cylinder block, cylinder cushion, the cylinder, and the crankcase oil sump (2) the pis
5、ton linkage groups: the piston, piston, piston pins, connecting rod (3) the crankshaft fly wheel: the crankshaft flywheel 1. The group The body is a skeleton of the engine, is the engine agencies and the system installation, which the foundation, the installation of all the major engine parts and ac
6、cessories, under various load. Therefore, the body must have the enough strength and rigidity. The cylinder block The cylinder block is the engine of all agencies and system, is in the engine assembly was one of the most important components. The cylinder block have water-cooled air-filled type cyli
7、nder and the cylinder block. Water-cooled the cylinder block in general and cast integrative crankcase. The cylinder block upper took out all cylinder, air cylinder surrounding cavity mutual connected make water sets. The lower part is used to support of the crankshaft crankcase. The cylinder block
8、have inline, V and level to the three kinds of forms, in cars and V inline commonly used two. The lower part of the cylinder block structure general type, gantry gate, and tunnel type three forms of the air-filled type the cylinder block and the crankcase adopt fission style structure, the cylinder
9、block and the crankcase separate, then assembled into casting together. The cylinder block and the surface of cylinder head cast has many heat sink to ensure sufficient heat dissipation, the cylinder block of materials with grey cast iron, in order to improve the general the wear resistance of the c
10、ylinder, and sometimes in cast iron to add a small amount of alloy elements such as nickel, molybdenum, chromium, phosphorus, etc. But, in fact, besides the piston and cylinder wall surface with the other part, to request is not high wear resistance. In order to the economy of the material, widely u
11、sed the cylinder inserted into the cylinder liner to form in cylinder surface. So, cylinder liner wear resistance can better alloy cast iron or steel alloy manufacture, in order to prolong the service life, and cylinder cylinder of low price can be used ordinary cast iron and aluminum alloy material
12、s manufacturing. The cylinder liner is dry and wet type two kinds. Dry cylinder liner outside surface are not direct with cold water contact, the wall thickness general for 1 3 mm. On the surface of the cylinder liner and assembly of the cylinder body surface using interference fitted. Wet cylinder
13、liner surface directly contact with the cooling water and good cooling effect. The wall thickness than dry cylinder liner, generally for 5 to 9 mm. Cylinder head The cylinder head is the main purpose of the piston and cylinder, closed the top and cylinder walls together make up the combustion chambe
14、r. General water-cooled engine within the cylinder head cast a jacket, under the cylinder head end and cylinder for top corresponding to the water jacket is the same, use water to cool the circulation of the combustion chamber wall of high temperature, such as part; The air-filled type engine cylind
15、er head on many heat sink, cast by increasing heat area to reduce the temperature of the combustion chamber. The engine cylinder head shall have the exhaust port a catheter hole and into the exhaust passage, etc. The gasoline engine cylinder head also should have the spark plug hole, and also has in
16、stalled the diesel engine injector do holes. Cylinder cushion The cylinder and the cylinder block with cylinder liner, the between the role is to ensure that the cylinder and the cylinder block of between sealed to prevent leakage of combustion chamber, water leaking. Oil pan is The oil pan is main
17、effect is to be stored and sealed the crankcase oil. The oil pan is force is small, generally USES the thin stamping steel and into. 2. The pistons connecting rod group The piston connecting rod group of piston, piston, piston pins, connecting rod, connecting rod bearings etc. piston The piston is t
18、he role of cylinder head, cylinder walls with together, and heirs of the combustion chamber of gas cylinder pressure, through the piston pins will force to the connecting rod, in order to promote the rotation of the crankshaft. The piston can be divided into the head, ring groove department and the
19、skirt three parts. The piston head the piston is part of the combustion chamber, its shape depends on the form of the combustion chamber. Common piston head shape has flattened type, concave and convex roof top type type. Piston ring grooves installed in the ring grooves inside. The gasoline engine
20、is general by 2 3 word ring groove, above 1 2 way used to install the gas ring, realize the cylinder seal; The most the following a used to install the oil. In oil ring ring groove bottom drilling has many radial return oil hole, when the pistons downward motion, oil the cylinder wall of redundant r
21、ing scratched off the oil back to KongLiu oil pan. If the temperature too high, a the ring easy to produce carbon, overheating jammed phenomenon. The piston skirt piston skirt up guiding role. Piston rings Piston ring installation in the ring grooves inside, used to seal between piston and cylinder
22、walls, prevent channeling the clearance between the piston and make the gas, and the movement along. Piston ring are divided into gas ring and oil ring two kinds. Piston pins The piston pin role is to connect the piston and rod assembly small head, and by the gas forces the pistons to the connecting
23、 rod. The piston pin for hollow cylinder, usually sometimes to make the required strength tubular body structure section. The piston pin generally USES low carbon steel or low carbon alloy. The piston pin and piston pins a hole and connecting rod small head bushing of hole is used to connect the who
24、le serving and half serving the connection. Adopts full serving the connection, the piston pin can be in the hole of the free rotation; Using half a serving the connection, pin and connecting rod between small head, work with full term is not happen relatively rotation; Pin and piston pins between a
25、 hole for clearance fit. Connecting rod The connecting rod is the role of the piston inherit the crankshaft the force, and make the reciprocating movement of the piston into the rotary motion of the crankshaft. By connecting rod connecting rod body, connecting rod, connecting bolts and cover bearing
26、 parts, such as connecting rod connecting rod body and cover is divided into small head, connecting rod connecting rod body and the big end. The connecting rod small head used to install the piston pins to link the piston. Rod body usually make it workers or H form, in order to meet in section stren
27、gth and rigidity requirements under the premise of reducing quality. The big end and of the crankshaft connecting rod shaft neck linked. Generally do component open type, and stem body cut half called connecting rod cover, both by connecting rod bolt connection as one. The connecting rod axle bush i
28、nstalled in the big end in a hole, and the crankshaft connecting rod shaft neck outfit and together, is the most important in the engine with one of vice. Commonly used reduce integration mainly white gold alloy, copper alloy and aluminum alloy lead. 3. The crankshaft fly wheel The crankshaft fly wh
29、eel mainly by the crankshaft, flywheel and some accessories composition. crankshaft Fly wheel mainly by the crankshaft and the flywheel and other different parts and the role of the flywheel and other different role of parts and accessories. The crankshaft is the most important part of one of the en
30、gine. Its role is to group the gas from the piston connecting rod force into the rotation of the crankshaft foreign output torque, and drive the engine of the gas distribution institution and other auxiliary devices work. The front of the crankshaft is mainly used to drive the gas distribution insti
31、tution, water pump and fan etc subsidiary, front axle are installed on timing gear (or synchronous belt wheel), fan and pump pulley, reverse shock absorber and start claw, etc. After the end of the crankshaft lugs structure, used to install the flywheel. Spindle neck and neck in the engine connectin
32、g rod shaft is the most critical slip fits, vice general surface are quenched, shaft neck transition occurred at the shall also rolling process, the strengthening to improve its anti-fatigue strength. The crankshaft axial orientation general use of the thrust piece or turn over the side bearings, po
33、sitioning device installed in front a the main bearing place or a bearing place. The crankshaft general selection high strength, high impact toughness and wear resistance of high quality carbon steel, good quality of carbon steel alloy or high strength nodular cast iron to forging or casting. The cr
34、ankshaft assembly must pass before dynamic balance of the calibration, balance the crankshaft, often in its emphasis on one side of the balance weight or crank drilling to part of the quality, in order to achieve the requirements of balance. flywheel The flywheel is a rotating inertia big disc, pres
35、sure on the outer circle, and a tooth of starter gear drive, for the starter when the engine use. The flywheel is often the first cylinder ignition timing marks with, so that the calibration ignition moment. Many of the cylinder engines should go into crankshaft and the action balance tests. In orde
36、r to guarantee the disassembling the process does not damage the flywheel transfers to the assembly relation between, the pins or asymmetric bolt arrangement, when installation should be pay attention to. 曲柄连杆机构曲柄连杆机构是往复式内燃机的主要工作机构。曲柄连杆机构是发动机实现工作循环，完成能量转换的主要运动零件。在作功冲程，它将燃料燃烧产生的热能活塞往复运动、曲轴旋转运动而转变为机械能
37、对外输出动力；在其他冲程，则依靠曲柄和飞轮的转动惯性、通过连杆带动活塞上下运动，为下一次作功创造条件。曲柄连杆机构的功用曲柄连杆机构的作用是提供燃烧场所，把燃料燃烧后气体作用在活塞顶上的膨胀压力转变为曲轴旋转的转矩，不断输出动力。 （1）将气体的压力变为曲轴的转矩 （2）将活塞的往复运动变为曲轴的旋转运动 曲柄连杆机构的组成曲柄连杆机构由机体组、活塞连杆组、曲轴飞轮组三部分组成。 （1）机体组：气缸体、气缸垫、气缸盖、曲轴箱及油底壳 （2）活塞连杆组：活塞、活塞环、活塞销、连杆 （3）曲轴飞轮组：曲轴飞轮 1.机体组 机体是构成发动机的骨架，是发动机各机构和各系统的安装基础，其内、外安装着发
38、动机的所有主要零件和附件，承受各种载荷。因此，机体必须要有足够的强度和刚度。 气缸体气缸体是发动机各个机构和系统的装配基体，是发动机中最重要的一个部件。气缸体有水冷式缸体和风冷式气缸体。 水冷式气缸体一般与上曲轴箱铸成一体。气缸体上部拍了出所有气缸，气缸周围的空腔相互连通构成水套。下半部分是用来支承曲轴的曲轴箱。 气缸体有直列、V形和水平对置三种形式，在汽车上常用直列和V形两种。气缸体下部的结构有一般式、龙门式、和隧道式三种形式风冷式气缸体和曲轴箱采用分体式结构，气缸体和曲轴箱分开铸造，然后再装配到一起。气缸体和气缸盖外表面铸有许多散热片来保证充分散热，缸体的材料一般用灰铸铁，为提高气缸的耐磨
39、性，有时在铸铁中加入少量合金元素如镍、钼、铬、磷等。但是，实际上除了与活塞配合的气缸壁表面外，其他部分对耐磨性要求并不高。为了材料上的经济性，广泛采用缸体内镶入气缸套来形成气缸工作表面。这样，缸套可用耐磨性较好的合金铸铁或合金钢制造，以延长气缸使用寿命，而缸体可用价格较低的普通铸铁或铝合金材料制造。气缸套有干式和湿式两种。 干式气缸套外表面不直接与冷水接触，其壁厚一般为13mm。缸套外表面与其装配的气缸体内表面采用过盈配合。 湿式缸套外表面直接与冷却水接触，冷却效果好。其壁厚比干式缸套，一般为59mm。 气缸盖气缸盖的主要作用是封闭气缸上部，与活塞顶部和气缸壁一起构成燃烧室。 一般水冷式发动机
40、气缸盖内铸有冷却水套，缸盖下端面与缸体上端面向所对应的水套是相通的，利用水的循环来冷却燃烧室壁等高温部分；风冷式发动机气缸盖上铸有许多散热片，靠增大散热面积来降低燃烧室的温度。 发动机的气缸盖上应有进排气门座导管孔和进排气通道等。汽油机气缸盖还应有火花塞孔，而柴油机则设有安装喷油器的做孔。 气缸垫气缸盖与气缸体之间装有气缸衬垫，其作用是保证气缸盖与气缸体间的密封，防止燃烧室漏气、水套漏水。 油底壳油底壳的主要作用是储存机油并封闭曲轴箱。油底壳受力很小，一般采用薄钢板冲压而成。 2.活塞连杆组 活塞连杆组由活塞、活塞环、活塞销、连杆、连杆轴瓦等组成。 活塞活塞的作用是与气缸盖、气缸壁等共同组成燃
41、烧室，并承受气缸中气体压力，通过活塞销将作用力传给连杆，以推动曲轴旋转。 活塞可分为头部、环槽部和裙部三部分。 活塞头部 活塞是燃烧室的组成部分，其形状取决于燃烧室的形式。常见的活塞头部形状有平顶式、凹顶式和凸顶式。 活塞环槽 活塞环安装在活塞环槽内。汽油机一般由23道环槽,上面12道用来安装气环,实现气缸的密封;最下面的一道用来安装油环.在油环槽底面上钻有许多径向回油孔,当活塞向下运动时,油环把气缸壁上多余的机油刮下来经回油孔流回油底壳。若温度过高，第一道环容易产生积碳，出现过热卡死现象。 活塞裙部 活塞裙部起导向作用。 活塞环 活塞环安装在活塞环槽内，用来密封活塞与气缸壁之间的间隙，防止窜
42、气，同时使活塞往复运动便顺捷。活塞环分为气环和油环两种。 活塞销 活塞销的作用是连接活塞和连杆小头，并将活塞所受的气体作用力传给连杆。 活塞销通常为空心圆柱体，有时也按等强度要求做成截面管状体结构。 活塞销一般采用低碳钢或低碳合金制造。 活塞销与活塞销座孔和连杆小头衬套孔的连接采用全浮式和半浮式连接。采用全浮式连接，活塞销可以在孔内自由转动；采用半浮式连接，销与连杆小头之间为过盈配合，工作中不发生相对转动；销与活塞销座孔之间为间隙配合。 连杆连杆的作用是将活塞承受的力传给曲轴，并使活塞的往复运动转变为曲轴的旋转运动。 连杆由连杆体、连杆盖、连杆螺栓和连杆轴瓦等零件组成，连杆体与连杆盖分为连杆小
43、头、杆身和连杆大头。 连杆小头用来安装活塞销，以连接活塞。杆身通常做成“工”或“H”形断面，以求在满足强度和刚度要求的前提下减少质量。 连杆大头与曲轴的连杆轴颈相连。一般做成分开式，与杆身切开的一半称为连杆盖，二者靠连杆螺栓连接为一体。 连杆轴瓦 安装在连杆大头孔座中，与曲轴上的连杆轴颈装和在一起，是发动机中最重要的配合副之一。常用的减磨合金主要有白合金、铜铅合金和铝基合金。 3.曲轴飞轮组 曲轴飞轮组主要由曲轴、飞轮和一些附件组成。 曲轴飞轮组主要由曲轴和飞轮以及其他不同作用的零件和飞轮以及其他不同作用的零件和附件组成。 曲轴是发动机最重要的机件之一。其作用是将活塞连杆组传来的气体作用力转变
44、成曲轴的旋转力矩对外输出，并驱动发动机的配气机构及其他辅助装置工作。 曲轴前端主要用来驱动配气机构、水泵和风扇等附属机构，前端轴上安装有正时齿轮(或同步带轮)、风扇与水泵的带轮、扭转减振器以及起动爪等。 曲轴后端采用凸缘结构，用来安装飞轮。 主轴颈和连杆轴颈是发动机中最关键的滑动配合副，一般均进行表面淬火，轴颈过渡圆角处还须进行滚压强化等化等工艺，以提高其抗疲劳强度。 曲轴的轴向定位一般采用止推片或翻边轴瓦，定位装置装在前端第一道主轴承处或中部某轴承处。 曲轴一般选用强度高、耐冲击韧度和耐磨性能好的优质中碳结构钢、优质中碳合金钢或高强度球墨铸铁来锻造或铸造。 曲轴在装配前必须经过动平衡校验，对不平衡的曲轴，常在其偏重的一侧平衡重或曲柄上钻去一部分质量，以达到平衡的要求。 飞轮飞轮是一个转动惯量很大的圆盘，外缘上压有一个齿圈，与起动机的驱动齿轮啮合，供起动机发动机时使用。 飞轮上通常还刻有第一缸点火正时记号，以便校准点火时刻。 多缸发动机的飞轮应与曲轴一起进行动平衡试验。为了保证在拆装过程中不破坏飞轮与曲轴间的装配关系，采用定位销或不对称螺栓布置方式，安装时应加以注意。
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