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1、,Review 1:Engine Terms,TDC（top dead center）:the position of the crank and piston when the piston is farther away from the crankshaft.,BDC（bottom dead center）:the position of the crank and piston when the piston is nearest away from the crankshaft.,2.1:principle of operation,Stroke:the distance betwe
2、en BDC and TDC;stroke is controlled by the crankshaft.Four-stroke Two-stroke,swept volume:the volume between TDC and BDC.,Bore:the internal diameter of the cylinder.,engine capacity,compression ratio,Clearance volume:the volume of space above the piston when it is at TDC.,Engine capacity:this is the
3、 swept volume of all cylinders.,Compression ratio:(swept vol+clearance vol)/(clearance vol),The spark-ignition engine is an internal combustion engine with externally supplied in ignition,which converts the energy contained in the fuel to kinetic energy.The cycle of operations is spread over four pi
4、ston strokes.To complete the full cycle it takes two revolutions of the crankshaft.火花点火式发动机是一个外部提供点火的内燃发动机，它把燃料中的能量转化成动能工作循环分布在活塞的四个行程，完成整个行程曲轴需要转两周,Intake(induction)stroke,Review 2:List the four strokes of a four-stroke engine.,Compression stroke,Power stroke,Exhaust stroke,Crankshaft and connectin
5、g rods system,Review 3:List the main systems of a gasoline engine.,Valve system,Fuel system,Ignition system,Lubrication system,Cooling system,Starting system,Energy and power:Engines used in automobiles are internal combustion heat engines.They convert the chemical energy of the gasoline into heat w
6、ithin a power chamber that is called a combustion chamber.Heat energy released in the combustion chamber raises the temperature of the combustion gases within the chamber.The increase in gas temperature causes the pressure of the gases to increase.The pressure developed within the combustion chamber
7、 is applied to the head of a piston to produce a usable mechanical force,which is then converted into useful mechanical power.,Engine terms:Linking the piston by a connecting rod to a crankshaft causes the gas to rotate the shaft through half a turn.The power stroke uses up the gas,so means must be
8、provided to expel the burnt gas and recharge the cylinder with a fresh petrol-air mixture:this control of gas movement is the duty of the valves;,活塞通过连杆和曲轴连接，使得气体带动曲轴旋转半圈。作功冲程耗尽了所有的气体，这样就必须采取相应的措施排出废气以及向气缸内充入新鲜的可燃混合气：气体的运动由气门来控制。,2.2：engine block and cylinder head Basic words（）,曲轴箱,汽缸盖罩,汽缸,汽缸套,汽缸体,油
9、底壳,汽缸盖,衬垫,水套,油道,Engine block:The engine block is the basic frame of the engine.All other engine parts either fit inside it or fasten to it.It holds the cylinders,water jackets,and oil galleries.The engine block also holds the crankshaft,which fastens to the bottom of the block.The camshaft also fits
10、 inside the block,except on overhead-cam-engines(OHC).In most cars,this block is made of gray iron,or an alloy(mixture)of gray iron and other metals,such as nickel or chromium.,气缸体是发动机的基体。发动机其它的部件都安装在缸体内或固定在缸体上，它包含了气缸、水套和油道，以及固定在缸体底部的曲轴等。除凸轮轴顶置发动机外，凸轮轴也装在汽缸体中大多数汽车汽缸体由灰铸铁或灰铸铁与其它金属如镍、铬的合金制造而成。,The blo
11、ck can be made of one kind of iron that is light and easy to cast while the sleeves uses another that is better able to stand up wear and tear.汽缸体由质量较轻且易于铸造的一种铸铁制成，而缸套则用另一种抗磨和抗拉缸能力较好的铸铁,The dry sleeve can be cast in or pressed into a new block or used to recondition badly worn or damaged cylinders t
12、hat cannot easily be rebored.,干缸套可以铸在或压入新缸体中，或者用于严重磨损或损坏而又不易重镗的缸体的修复。,wet sleeve,dry sleeve,Cylinder sleeve:,Cylinder head:The cylinder head fastens to the top of the block,just as a roof fits over a house.The underside forms the combustion chamber with the top of the piston.In-line engines of light
13、 vehicles have just one cylinder head for all cylinders;larger in-line engines can have two or more.,气缸盖扣在缸体的顶部，就像屋顶安在房子上一样。缸盖的下方和活塞顶部形成燃烧室。轻型车的直列发动机所有缸仅有一个气缸盖，较大的直列发动机有两个或更多缸盖。,hemi,Semi-hemi,wedge,桑塔纳夏利富康,切诺基,捷达奥迪,Cylinder head:The cylinder head carries the valves,valve springs and the rockers on
14、the rocker shaft,this part of the valve gear being worked by push-rods.,缸盖上装有气门、气门弹簧和摇臂轴上的摇臂，推杆推动这部分气门传动机构工作。,The oil pump in the lubricating system draws oil from the oil pan and sends it to all working parts in the engine.The oil drains off and runs down into the pan.Thus,there is constant circula
15、tion of oil between the pan and the working parts of the engine.,润滑系的机油泵从油底壳抽出机油，并把机油输送给发动机的所有工作部件。机油从油底壳流进流出。因而机油在油底壳和发动机的工作部件之间不断循环流动。,Oil pan:,2.3 piston,connecting rod and crankshaft,活塞环,活塞（头部裙部）,活塞销,连杆,飞轮,曲轴,曲柄轴径,Basic words:,Piston assembly:Most pistons are made from cast aluminum.The piston,t
16、hrough the connecting rod,transfers to the crankshaft the force created by the burning fuel mixture.This force turns the crankshaft.,大多数活塞由铝铸造而成。通过连杆，活塞把可燃混合气燃烧所产生的力传递给曲轴，并带动曲轴旋转。,Piston:,In disel engines,the combustion chamber may be formed totally or in part in the piston crown,depending on method
17、 of injection.,柴油机发动机根据喷油方法不同，活塞头部可以形成全部燃烧室，也可以是燃烧室的一部分,Piston rings:In modern engines,each piston has three rings.(Piston in older engines sometimes had four rings,or even five.)The inside surface of the ring fits in the groove on the piston.The rings outside surface presses against the cylinder wa
18、lls.,在新型发动机上，每个活塞有三个活塞环。（在老式发动机上，每个活塞有四个甚至五个活塞环。）环的内边面紧贴在活塞的环槽里，环的外表面紧压在气缸壁上。,Connecting rod:The connecting rod little end is connected to the piston pin.A bush made from a soft metal,such as bronze,is used for this joint.The lower end of the connecting rod fit the crankshaft journal.This is called
19、the big end.,连杆小头与活塞销连接，用在连接处的衬套是由诸如青铜这种较软材料所制成的。连杆下端连接在曲轴的轴径处，称为连杆大头。,Small enough to be withdrawn through the cylinder bore.,Cylinder number and firing order:N.B.No.4 piston is always performing the companion stroke to No.1:when the inlet valve in No.4 cylinder is fully open,No.1 cylinder inlet va
20、lve is fully closed-this feature is useful to remember when checking valve clearances.,注意4号活塞和1号活塞总是成对运行：4号气缸进气门全闭时，1号气缸进气门全开这个特点在检查气门间隙时是很有用的。,Crank arrangement of engines:,four cylinders,six cylinders,Torsional vibration balancer:,As each cylinder fires,it causes the crank throw to speed up.The inertia of the rest of shaft cause it to stay slightly behind,resulting in a twisting action on the crankshaft.,当一缸点火时，使曲轴摆幅的速度提高，而其它轴的惯性阻碍它，使其滞后，从而导致曲轴扭转。,
