1、汽车实用英语Unit 3 Engine Mechanical System ServiceUpon completion of this unit,you should be able to:Overall Objectives 总体目标总体目标 Learn key terms about engine mechanical system in this unit Understand the repairing process of every assembly Use maintenance manual to deal with the practical problemsTask 3.
2、1 Inspecting Engine Assembly 发动机总成的检查 Task 3.2 Replacing Chain Sub-assembly 正时链条的更换Task 3.3 Inspecting Crankshaft and Piston 曲轴和活塞的检查 Task 3.4 Overhauling Cylinder Head 气缸盖的检修 Task 3.5 Replacing Camshaft 更换凸轮轴Tasks Introduction 任务导入任务导入 Task 3.1 Inspecting engine assembly 发动机总成检修Task 3.2 Overhauling
3、 cylinder block assembly 气缸体检修Task 3.3 Inspecting crankshaft and piston Task 3.4 Overhauling cylinder head Task 3.5 Replacing camshaftTask 3.6 Replacing chain sub-assemblyTasks Introduction 任务导入任务导入 Servicing engine mechanical system describes the act of inspecting the condition of engine assembly a
4、nd replacing parts.Proper operation is critical to ensure the engine running safely,smoothly and correctively.The following tasks(e.g.overhauling cylinder block assembly,inspecting crankshaft and piston,replacing camshaft,replacing chain sub-assembly etc.)are the important items in engine mechanical
5、 system to avoid major damage or for safety reasons.Task Description 任务描述任务描述 Task3.1 Inspecting engine assemblyLearning Preparation 学习准备学习准备 inspecting 检查engine assembly 发动机总成cooling system 冷却系统radiator cap 散热器盖install 安装reinstall 重新安装 Key terms:Learning Preparation 学习准备学习准备 fin 散热器片compressed air
6、压缩空气oil pressure 油压socket wrench 套筒扳手oil pressure switch 油压开关Key terms:Step 1 A maintenance case is provided;Step 2 Learn the process of inspecting engine assembly via a maintenance manual;Step 3 Require students to grasp the key terms in this task;Step 4 Try to describe the process of engine assemb
7、ly inspection;Step 5 Students read relative material;Step 6 AssessmentPlan and Implement 计划和实施计划和实施()1.The engine coolant level should be between the”LOW”and”FULL”line.()2.You can remove the radiator cap while the engine and radiator are still hot,as fluid and steam can be blown out under pressure.(
8、)3.Oil level should be between the”L”and”F”marks on the oil level gage.()4.Check idle speed with cooling fan ON.()5.If adding oil helps the compression,it is likely that the piston rings and/or cylinder bore are worn or damaged.Assessment and Feedback 评价和反馈评价和反馈 True or False()6.If compression press
9、ure stays low,there may be leakage past the gasket.()7.The minimum compression pressure is 1,500 kPa(10.2 kgfcm2,145 psi).()8.The engine idle speed is 700800 rpm.()9.If the distance between the steam cleaner and core is too close,there is a possibility of damaging the fins.()10.If fins are clogged,w
10、ash them with gasoline cleaner and dry with compressed air.Assessment and Feedback 评价和反馈评价和反馈True or False An engine which is called the“heart”of a vehicle is used to supply power for an automobile.Generally,an automobile is operated by internal combustion engine（内燃机）.Most internal combustion engine
11、s operate on the four stroke cycle.This type of engine is also known as Otto cycle,after the name of its inventor,Nikolaus Otto.Each cylinder of the four stroke cycle engine has a piston which reciprocates（往复运动）within the cylinder.The power production cycle consists of four strokes of the piston in
12、a reciprocating engine.These four strokes are intake stroke,compression stroke,power stroke and exhaust stroke,shown in Fig.3-1.3.1.1 Brief Introduction to Engine3.1.1 Brief Introduction to Engine Fig.3-1 working principle The intake stroke,as the piston moves downward to the Bottom Dead Center,a va
13、cuum is created in the cylinder.The intake valve opens and air-fuel mixture（混合气）enters the cylinder.The compression stroke,the air-fuel mixture is compressed as the piston moves upward.The spark plug is fired to ignite the air-fuel mixture prior to the piston being at the Top Dead Center.Note that b
14、oth valves are closed.3.1.1 Brief Introduction to Engine The power stroke,the air-fuel mixture explodes（爆炸，膨胀）,which forces the piston downward.Note that both valves are closed.The exhaust stroke,as the piston starts to move upward,the exhaust valve is opened.The piston moving up forces the exhaust
15、gases out of the cylinder.This four stroke cycle of piston within the cylinder is repeated time and again to push the vehicle forward.3.1.1 Brief Introduction to Engine The most common engine comprises crankshaft and connecting rod mechanism,valve gear,cooling system,lubricating system,fuel system,s
16、tarting system,ignition（点火）system(there is no ignition system in diesel engines),shown in Fig.3-2.3.1.2 Main Components of Engine The power mechanism of the engine is actually called the crankshaft and connecting rod mechanism.Its function is to convert heat energy into mechanical energy used to dri
17、ve the vehicles.The valve gear provides timely admission of the fresh charge into the cylinders and exhaust of spent gases from them.The function of the cooling system is to maintain the highest and most efficient operating temperature within the engine and to remove excess heat（余热）from the engine.3
18、.1.2 Main Components of Engine The lubrication system is designed to keep all the engine parts lubricated so that friction（摩擦）is reduced.The fuel system works according to the requirements of the engine as it provides an air-fuel mixture which must be in proportion to the speed and load placed on th
19、e engine.The fuel system sends the air-fuel mixture to the cylinder for burning and simultaneously（同时地）exhausts the effluent gas through the exhaust pipe.3.1.2 Main Components of Engine The ignition system is designed to ignite the air and fuel that have been mixed in the fuel system.The starting sy
20、stem provides the power to turn the internal combustion engine over until it can operate under its own power.3.1.2 Main Components of EnginePractice Maintenance Manual Reading Inspecting engine assemblyPractice Maintenance Manual Reading 1.Inspect coolant 1)INSPECT COOLING SYSTEM FOR LEAKSWarning!To
21、 avoid the danger of being burned,do not remove the radiator cap while the engine and radiator are still hot,as fluid and steam can be blown out under pressure.(a)Fill the radiator with coolant and attach a radiator cap tester.(b)Warm up the engine.(c)Pump it to 118 kPa(1.2 kgf/cm2,17.1 psi),and che
22、ck that the pressure does not dropPractice Maintenance Manual Reading Note!If the pressure drops,check the hoses,radiator or water pump for leaks（泄露）（泄露）.If no external leaks are found,check the heater core,cylinder block and head.Practice Maintenance Manual Reading 2)CHECK ENGINE COOLANT LEVEL AT R
23、ESERVOIR(a)The engine coolant level should be between the”LOW”and”FULL”lineNote!If low,check for leaks and add”Toyota Long Life Coolant”or equivalent（相等的）（相等的）up to the”FULL”line.Practice Maintenance Manual Reading 3)CHECK ENGINE COOLANT QUALITY (a)Remove the radiator cap.Warning!To avoid the danger
24、 of being burned,do not remove the radiator cap while the engine and radiator are still hot,as fluid and steam can be blown out under pressure.Practice Maintenance Manual Reading Note!If excessively dirty,replace the coolant.(c)Reinstall the radiator cap.(b)Check if there is any excessive deposits o
25、f rust or scale around the radiator cap and radiator filler hole;the coolant should be free from oil.Practice Maintenance Manual Reading 4)INSPECT FINS BLOCKAGE (a)If fins are clogged（堵塞）,wash them with water or a steam cleaner and dry with compressed air.Practice Maintenance Manual Reading Warning!
26、If the distance between the steam cleaner and core is too close,there is a possibility of damaging the fins,so keep the following injection distance.If the fins are bent,straighten them with a screwdriver or pliers.Be careful not pour water directly onto electronic components.Practice Maintenance Ma
27、nual Reading 2.Inspect engine oil 1)CHECK ENGINE OIL LEVEL (a)After warming up the engine and then 5 minutes after the engine stops,oil level should be between the”L”and”F”marks on the oil level gage（油位表）.If low,check for leakage and add oil up to the”F”mark.Warning!Do not fill with engine oil above
28、 the”F”mark.Practice Maintenance Manual Reading 2)CHECK ENGINE OIL QUALITY (a)Check the oil for deterioration,entry of water,discoloring or thinning.If the quality is visibly poor,replace the oil.Oil grade:Use API grade SL”EnergyConserving”,or ILSAC multigrade engine oil.SAE 5W30 is the best choice
29、for good fuel economy,and good starting in cold weather.Practice Maintenance Manual Reading If SAE 5W30 is not available,SAE 10W30 may be used.However,it should be replaced with SAE 5W30 at the next oil replacement.Practice Maintenance Manual Reading 3)INSPECT OIL PRESSURE(a)Disconnect the oil press
30、ure switch connector.(b)Using a 24 mm deep socket wrench,remove the oil pressure switch.Practice Maintenance Manual Reading(c)Install the oil pressure gauge.(d)Warm up the engine.(e)Inspect the oil pressure.Practice Maintenance Manual Reading Oil pressure:(f)Apply adhesive to 2 or 3 threads of the o
31、il pressure switch.Adhesive:Part No.0883300080,THREE BOND 1344,LOCTITE（乐泰，一种美国品牌胶水）242 or equivalentPractice Maintenance Manual Reading(g)Using a 24 mm deep socket wrench,install the oil pressure switch.Torque:15 Nm(153 kgfcm,11 ftlbf)(h)Connect the oil pressure switch connector.(i)Check for the eng
32、ine oil leaks.Practice Maintenance Manual Reading 3.Inspect fan and generator V belt Note!You dont need to check the belt deflection（挠曲）（挠曲）because auto tensioner is adopted.Practice Maintenance Manual Reading 4.Inspect engine idle speed (a)Warm up engine.(b)When using handheld tester or OBDII scan
33、tool.(1)Connect the handheld tester or OBDII scan tool to the DLC3.Note!Please refer to the handheld tester or OBDII scan tool operators manual for further details.(c)Check the idle speed.Idle speed:650750 rpmPractice Maintenance Manual Reading (c)Check the idle speed.Idle speed:650750 rpmWarning!Ch
34、eck idle speed with cooling fan OFF.Switch off all accessories and air conditioning.Practice Maintenance Manual Reading 5.Inspect compression(a)Warm up and stop engine.(b)Remove ignition coil.(c)Remove spark plugs.(d)Inspect cylinder compression pressure.SST 0999200500(1)Insert a compression gauge i
35、nto the spark plug hole.(2)Fully open the throttle.(3)While cranking the engine,measure the compression pressure.Practice Maintenance Manual Reading 5.Inspect compressionCompression pressure 1,300 kPa(13.3 kgfcm2,189 psi)Minimum pressure:1,000 kPa(10.2 kgfcm2,145 psi)Difference between each cylinder
36、:100 kPa(1.0 kgfcm2,15 psi)Practice Maintenance Manual Reading Warning!Always use a fully charged battery to obtain engine speed of 250 rpm or more.Check other cylinders compression pressure in the same way.This measurement must be done in as short a time as Possible.(4)If the cylinder compression i
37、n one more cylinders is low,pour a small amount of engine oil into the cylinder through the spark plug hole and repeat steps(1)through(3)for cylinders with low compression.Practice Maintenance Manual Reading Note!If adding oil helps the compression,it is likely that the piston rings and/or cylinder
38、bore are worn or damaged.If pressure stays low,a valve may be sticking or seating is improper,or there may be leakage past the gasket（衬垫）（衬垫）.Task 3.2 Replacing chain sub-assemblyLearning Preparation 学习准备学习准备 revolve 旋转valve 气门hexagonal wrench 六角扳手 align 对齐，排列chain tensioner 链条张紧器slipper 滑块Key terms
39、:Step 1 A maintenance case is provided;Step 2 Learn the process of replacing chain sub-assembly via a maintenance manual;Step 3 Require students to grasp the key terms in this task;Step 4 Try to describe the process of chain sub-assembly replacement;Step 5 Students read relative material;Step 6 Asse
40、ssmentPlan and Implement 计划和实施计划和实施()1.Timing chain must be replaced at the manufacturers recommended distance and/or time periods.()2.The owners manual maintenance schedule is the source of timing chain replacement intervals,typically every 30,000 to 50,000 miles.()3.Dont replace the timing chain t
41、ensioner at the same time as the chain is replaced.Assessment and Feedback 评价和反馈评价和反馈True or False()4.In case of revolving the camshafts with the chain off the sprockets,turn the crankshaft 1/5 revolution for valves not to touch the pistons.()5.Two yellow color links are on the chain.()6.Timing chai
42、ns are generally more durable than timing belts.()7.Failure to replace the chain can result in complete breakdown or catastrophic engine failure.Assessment and Feedback 评价和反馈评价和反馈True or False()8.Remove the timing chain with the crankshaft timing gear plying screwdrivers.()9.When Installing chain su
43、b-assy,Using a crankshaft pulley bolt,turn the crankshaft and set the set key on the crankshaft upward.()10.Install the timing chain on the crankshaft timing sprocket with the yellow color link aligned with the timing mark on the crankshaft timing sprocket.Assessment and Feedback 评价和反馈评价和反馈True or F
44、alse 3.6.1 Chain(Timing Belt)A timing belt or timing chain is a part of an internal combustion engine that synchronizes（同步）the rotation of the crankshaft and the camshaft(s)so that the engines valves open and close at the proper times during each cy linders intake and exhaust strokes,shown in Fig.3.
45、2.1.In an interference engine the timing belt or chain is also critical to preventing the piston from striking the valves.3.6.1 Chain(Timing Belt)A timing belt is a belt that usually features teeth on the inside surface,while a timing chain is a roller chain.3.6.1 Chain(Timing Belt)Most modern produ
46、ction automobile engines utilize（使用）a timing belt or chain to synchronize crankshaft and camshaft rotation;some engines instead utilize gears to directly drive the camshafts.The use of a timing belt or chain instead of direct gear drive enables engine designers to place the camshaft(s)further from t
47、he crankshaft,and in engines with multiple camshafts a timing belt or chain also enables the camshafts to be placed further from each other.3.6.1 Chain(Timing Belt)Timing chains were common on production automobiles through the 1970s and 1980s,when timing belts became the norm,but timing chains have
48、 seen a resurgence（复活）in recent years.Timing chains are generally more durable than timing belts though neither is as durable as direct gear drive however,timing belts are lighter,less expensive,and operate more quietly.3.6.2 Chain Failure Timing belts must be replaced at the manufacturers recommend
49、ed distance and/or time periods.Failure to replace the belt can result in complete breakdown or catastrophic（毁灭性的）engine failure,especially in interference engine.The owners manual maintenance schedule is the source of timing belt replacement intervals（周期）,typically every 60,000 to 100,000 miles.It
50、is common to replace the timing belt tensioner at the same time as the belt is replaced.3.6.2 Chain Failure The usual failure modes of timing belts are either stripped teeth(which leaves a smooth section of belt where the drive cog will slip)or delamination（剥落）and unraveling（变形）of the fiber cores.Br
