英文版汽车构造

英文版汽车构造是一本讲解汽车结构的书,也是一本英文的书,对于汽车专业的有大智慧

CHAPTER 1 AUTOMOTIVE BASICS

1.1 Principal Components

Today's average car contains more than 15,000 separate, individual parts that must work

together. These parts can grouped into four major categories: engine, body, chassis and

electrical equipment.

1.2 Engine

The engine acts as the power unit. The internal combustion engine is most common: this

obtains its power by burning a liquid fuel inside the engine cylinder. There are two types of

engine :gasoline(also called a spark-ignition engine) and diesel(also called a

compression-ignition engine).Both engines are called heat engines; the burning fuel

英文版汽车构造是一本讲解汽车结构的书,也是一本英文的书,对于汽车专业的有大智慧

generates heat which causes the gas inside the cylinder to increase its pressure and supply

power to rotate a shaft connected to the transmission.

1.3 Body

An automobile body is a sheet metal shell with windows, doors, a hood, and a trunk deck built

into it. It provides a protective covering for the engine, passengers, and cargo. The body is

designed to keep passengers safe and comfortable. The body styling provides an attractive,

colorful, modern appearance for the vehicle.

1.4 Chassis

The chassis is an assembly of those systems that are the major operating part of a vehicle.

The chassis includes the transmission, suspension, steering, and brake systems.

Transmission systems ― conveys the drive to the wheels. The main components are clutch,

gearbox, driveshaft, final drive, and differential.

Suspension― absorbs the road shocks.

Steering― controls the direction of the movement.

Brake― slows down the vehicle.

1.5 Electrical Equipment

The electrical system supplies electricity for the ignition, horn, lights, heater, and starter. The

electricity level is maintained by a charging circuit. This circuit consists of the battery,

alternator (or generator). The battery stores electricity. The alternator changes the engine's

mechanical energy into electrical energy and recharges the battery.

New Words

Principal component 主要部件

category 种类，类型

body 车身

chassis 底盘

layout 布置

power unit 动力装置

internal combustion engine 内燃机

cylinder 汽缸

gasoline 汽油

spark 火花

ignition 点燃，点火

diesel 柴油机

compression 压缩

英文版汽车构造是一本讲解汽车结构的书,也是一本英文的书,对于汽车专业的有大智慧

shaft 轴

transmission 传动系

sheet metal 金属板

shell 外壳

hood （发动机）罩

trunk deck 行李舱盖

cargo 货物

styling 样式

assembly 总成，装配

suspension 悬挂，悬置

shock 冲击

steering 转向，操纵

brake 刹车，制动器

clutch 离合器

gearbox 变速器

driveshaft 传动轴

final drive 主减速器，后桥

differential 差速器

slow down （使）慢下来，减速

horn 喇叭

starter 起动机

charge 充电

alternator 交流发电机

Review Questions

1.

2.

3.

4. List the main parts of an automobile? What are the common types of a vehicle according to body styling? Which systems does a chassis include and what are the main functions of the chassis? Why are suspension systems used on vehicles?

CHAPTER2 INTERNAL COMBUSTION ENGINE

2.1 principle of operation

2.1.1 Engine and power

Engine is used to produce power. The chemical energy in fuel is converted to heat by the

burning of the fuel at a controlled rate. This process is called combustion. If engine combustion

occurs with the power chamber. ,the engine is called internal combustion engine. If combustion

takes place outside the cylinder, the engine is called an external combustion engine.

Engine used in automobiles are internal combustion heat engines. Heat energy released in the

combustion chamber raises the temperature of the combustion gases with the chamber. The

increase in gas temperature causes the pressure of the gases to increase. The pressure developed

within the combustion chamber is applied to the head of a piston to produce a usable mechanical

force, which is then converted into useful mechanical power.

2.1.2 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 provided to expel the burnt gas

英文版汽车构造是一本讲解汽车结构的书,也是一本英文的书,对于汽车专业的有大智慧

and recharge the cylinder with a fresh petrol-air mixture :this control of gas movement is the duty

of the valves ;an inlet valve allows the new mixture to enter at the right time and an exhaust valve

lets out the burnt gas after the gas has done its job. Engine terms are :

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 to the

crankshaft.

Stroke : the distance between BDC and TDC; stroke is controlled by the crankshaft.

Bore : the internal diameter of the cylinder.

Swept volume : the volume between TDC and BDC.

Engine capacity : this is the swept volume of all the cylinder e.g. a four-stroke having a capacity

of two liters(2000cm) has a cylinder swept volume of 50cm.

Clearance volume: the volume of the space above the piston when it is at TDC.

Compression ratio = (swept vol + clearance vol)\(clearance vol)

Two-stroke : a power stroke every revolution of the crank.

Four-stroke : a power stroke every other revolution of the crank..

2.1.3 The Four-stroke Spark-ignition Engine Cycle

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 piston strokes. To complete the full cycle it takes

two revolutions of the crankshaft.

The operating strokes are :

英文版汽车构造是一本讲解汽车结构的书,也是一本英文的书,对于汽车专业的有大智慧

This stroke introduces a mixture of atomized gasoline and air into the cylinder. The stroke

starts when the piston moves downward from a position near the top of the cylinder. As the

piston moves downward, a vacuum, or low-pressure area, is created.

During the intake stroke, one of the ports is opened by moving the inlet valve. The exhaust

valve remains tightly closed.

Compression stroke

As the piston moves upward to compress the fuel mixture trapped in the cylinder, the valves

are closed tightly. This compression action heats the air/fuel mixture slightly and confines it

within a small area called the combustion chamber.

Power stroke

Just before the piston reaches the top of its compression stroke, an electrical spark is

introduced from a spark plug screwed into the cylinder head.

The spark ignites the compressed, heated mixture of fuel and air in the combustion chamber

to cause rapid burning. The burning fuel produces intense heat that causes rapid expansion

of the gases compressed within the cylinder. This pressure forces the piston downward. The

downward stroke turns the crankshaft with great force.

Exhaust stroke

Just before the bottom of the power stroke, the exhaust valve opens. This allows the piston,

as it moves upward, to push the hot, burned gases out through the open exhaust valve.

Then, just before the piston reaches its highest point, the exhaust valve closes and the inlet

valve opens. As the piston reaches the highest point in the cylinder, known as TDC, it starts

back down again. Thus, one cycle ends and another begins immediately.

2.1.4 Engine Overall Mechanics

The engine has hundreds of other parts . The major parts of engine are engine block , engine

heads, pistons, connecting rods, crankshaft and valves. The other parts are joined to make systems.

These systems are the fuel system, intake system, ignition system, cooling system, lubrication

system and exhaust system. Each of these systems has a definite function. These systems will

discussed in detail later.

NEW WORD

Piston 活塞

Connecting rod 连杆

Crankshaft 曲轴

Power stoke 活塞行程

英文版汽车构造是一本讲解汽车结构的书,也是一本英文的书,对于汽车专业的有大智慧

Expel 排出

Valve 气阀

inlet(intake) valve 进气阀

exhaust valve 排气阀

term 术语

TDC 上止点

BDC 下止点

Bore 缸径

swept volume 有效容积

engine capacity 发动机排量

clearance volume 余隙容积,燃烧室容积

compression ratio 压缩比

revolution 旋转,转数

every other 每隔一个

cycle 循环

spread over 分布,遍及

intake stroke 进气行程

compression stroke 压缩行程

knock 敲缸,敲打

exhaust stroke 排气行程

engine block 发动机缸体

lubrication 润滑

2.2 Engine Block and Cylinder Head

2.2.1 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 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. Engine blocks

are castings.

Some engine blocks, especially those in smaller cars, are made of cast aluminum. This metal

is much lighter than iron. However, iron wears better than aluminum. Therefore, the cylinders

in most aluminum engines are lined with iron or steel sleeves. These sleeves are called

cylinder sleeves. Some engine blocks are made entirely of aluminum.

英文版汽车构造是一本讲解汽车结构的书,也是一本英文的书,对于汽车专业的有大智慧

2.2.2 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. The most common

cylinder head types are the hemi, wedge, and semi-hemi. All three of these terms refer to the

shape of the engine's combustion chamber. The cylinder head carries the valves, valve

springs and the rockers on the rocker shaft, this part of the valve gear being worked by the

push-rods. Sometimes the camshaft is fitted directly into the cylinder head and operates on

the valves without rockers. This is called an overhead camshaft arrangement. Like the

cylinder block, the head is made from either cast iron or aluminum alloy.

2.2.3 Gasket

The cylinder head is attached to the block with high-tensile steel studs. The joint between the

block and the head must be gas-tight so that none of the burning mixture can escape. This is

achieved by using cylinder head gasket. This is a sandwich gasket, i.e. a sheet of asbestos

between two sheets of copper, both these materials being able to withstand the high

temperature and pressures within the engine.

英文版汽车构造是一本讲解汽车结构的书,也是一本英文的书,对于汽车专业的有大智慧

2.2.4 Oil Pan or Sump

The oil pan is usually formed of pressed steel. The oil pan and the lower part of the cylinder

block together are called the crankcase; they enclose, or encase, the crankshaft. 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 circulation

of oil between the pan and the working parts of the engine.

New Words

engine block 缸体

cylinder head 气缸盖

fasten 使固定

water jacket 水套

oil gallery 油道

camshaft 凸轮轴

overhead-cam(OHC) 顶置凸轮

gray iron 灰铸铁

alloy 合金

nickel 镍

chromium 铬

casting 铸件

head cover 汽缸盖罩

intake manifold 进气总管

distributor 分电器

oil pan 油底壳

aluminum 铝

be lined with 镶有

cylinder sleeve 气缸套

hemi 半球形

wedge 楔型，楔入

semi-hemi 准半球形

rocker 摇臂

push-rod 推杆

gasket 衬垫

high-tensile 高强度的

stud 螺栓

gas-tight 密封的

asbestos 石棉

crankcase 曲轴箱，曲柄箱

英文版汽车构造是一本讲解汽车结构的书,也是一本英文的书,对于汽车专业的有大智慧

encase 封闭，把…包起来

drain off 排出，流出

1.

2.

3.

4.

5.

2.3 Piston Connecting Rod and Crankshaft

2.3.1 Piston Assembly

The piston is an important part of a four-stroke cycle engine. Most pistons are made

from cast aluminum. The piston , through the connecting rod, transfers to the

crankshaft the force create by the burning fuel mixture. This force turns the

crankshaft .Thin, circular , steel bands fit into grooves around the piston to seal the

bottom of the combustion chamber. These bands are called piston rings. The grooves

into which they fit are called ring grooves. A piston pin fits into a round hole in the

piston . The piston pin joins the piston to the connecting rod . The thick part of the

piston that holds the piston is the pin boss.

The piston itself , its rings and the piston pin are together called the piston

assembly.

2.3.2.Piston

To withstand the heat of the combustion chamber, the piston must be strong. It

also must be light, since it travels at high speeds as it moves up and down inside the

cylinder. The piston is hollow. It is thick at the top where it take the brunt of the heat

and the expansion force. It is thin at the bottom, where there is less heat. The top part

of the piston is the head , or crown . The thin part is the skirt The sections between the

ring grooves are called ring lands.

The piston crown may be flat , concave ,dome or recessed . In diesel engine , the

combustion chamber may be formed totally or in part in the piston crown , depending

on the method of injection . So they use pistons with different shapes. Review Question What do TDC, BDC, stroke, compression ratio and engine capacity stand for? How do you calculate swept volume and compression ratio? What controls the length of the stroke? List the main parts of the engine overall mechanics? What are the main function of the engine block?

英文版汽车构造是一本讲解汽车结构的书,也是一本英文的书,对于汽车专业的有大智慧

2.3.3Piston Rings

As Fig.2-9 shows , piston rings fit into ring grooves near the of the piston. In

simplest terms, piston rings are thin, circular pieces of metal that fit into grooves in the tops of the pistons.

In modern engines ,each piston has three rings. (Piston in older engines

sometimes had four rings, or even five.) The ring’s outside surface presses against the

cylinder walls. Rings provide the needed seal between the piston and the cylinder

walls. That is, only the rings contact the cylinder walls. The top two rings are to keep

the gases in the cylinder and are called compression rings. The lower one prevents the

oil splashed onto the cylinder bore from entering the combustion chamber , and is

called an oil ring. Chrome-face cast-iron compression rings are commonly used in

automobile engines. The chrome face provide a very smooth , wear-resistant surface.

During the power stoke , combustion pressure on the combustion rings is very

high. It causes them to untwist . Some of the high-pressure gas gets in back of the

rings. This force the ring face into full contact with the cylinder wall. The combustion

pressure also holds the bottom of the ring tightly against the bottom of the ring groove.

Therefore , high combustion pressure causes a tighter seal between the ring face and

the cylinder wall.

2.3.4 Piston Pin

The piston pin holds together the piston and the connecting rod . This pin fits

into the piston pin holes and into a hole in the top end of the connecting rod. The top

end of is much smaller than the end that fits on the crankshaft . This small end fits

inside the bottom of the piston . The piston pin

fits through one side of the piston , through the

small end of the rod , and then through the other

side of the piston . It holds the rod firmly in place in

the center of the piston. Pins are made of

high-strengh steel and have a hollow center . Many

pins are chrome-plated to help them wear better.

2.3.3 Connecting rod

The connecting rod is made of forged

high-strength

英文版汽车构造是一本讲解汽车结构的书,也是一本英文的书,对于汽车专业的有大智慧

steel . It transmits and motion from the piston to the crankpin on the crankshaft . 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 fits the crankshaft journal . This is called the big end . For this big-end bearing , steel-backed lead or tin shell bearing are used . These are the same as those used for the main bearings . The split of the big end is sometimes at an angle , so that it is small enough to be withdrawn through the cylinder bore . The connecting rod is made from forged alloy steel .

2.3.5 Crankshaft

The crankshaft , in conjunction with the connecting rod , coverts the reciprocating motion of the piston to the rotary motion needed to drive the vehicle . It is usually made from carbon steel which is alloyed with a small proportion of nickel .The main bearing journals fit into the cylinder block and the big end journals align with the connecting rods .At the rear end of the crankshaft is attached the flywheel , and at the front end are the driving whells for the timing gears , fan , cooling water and alternator .

The throw of the crankshaft , the distance between the main journal and the big end centers , controls the length of the stroke . The stroke is double the throw , and the stroke-length is the distance that the piston travels from TDC to BDC and vice

versa .

2.3.6 Flywheel

The flywheel is the made from carbon steel . It fit s onto the rear of the crankshaft . As well as keeping the engine rotating between power strokes it also carries the clutch , which transmits the drive to the transmission , and has the starter ring gear around its circumference . There is only one working stroke in four so a flywheel is needed to drive the crankshaft during the time that the engine is performing the non-power strokes .

英文版汽车构造是一本讲解汽车结构的书,也是一本英文的书,对于汽车专业的有大智慧

New Words

Comprise 由。。。。。。。组成，包含

Inter 惯性，惯量

Radius 半径，范围

Circular 圆形的

Steel band 钢圈

Fit into 放入，放进

Groove 凹槽

Piston pin 活塞销

Pin boss 活塞销凸台

Withstand 抵抗

Hollow 空的

Brunt 冲力

Crown 活塞顶

Skirt 裙部

Ring land 环带

Concave 凹的，凹入的

Dome 圆顶

Recessed 隐蔽的

Cylinder wall 气缸壁

Cylinder bore 缸筒

Splash 飞溅

chrome-face 表面镀银的

Untwist 朝相反方向的

In place 在适当位置

Chrome-plated 镀铬的

Forge 伪造，仿造

Crankpin 曲轴销

Bush 轴瓦，套筒

Bronze 青铜

Crankshaft journal 曲轴轴颈

Steel-backed 钢背的

Lead 铅

英文版汽车构造是一本讲解汽车结构的书,也是一本英文的书,对于汽车专业的有大智慧

Tin 锡

Splint 切口，中断，分配，分离

In conjunction with 连同

Reciprocating motion 往复运动

Rotary 旋转的

Carbon steel 碳钢

Journal 轴颈

Align with 匹配

Overlap 重叠

Timing gear 正时齿轮

Throw 摆幅

Vice verse 反之亦然

Impulse 脉冲

Space out 隔开，分隔

Through out 遍及

Diagram 图表

Firing order 点火顺序

Companion 成对

Circumference 圆周

2.4 Valve System

The valve system is made up of those parts needed to open and close the valves at just the right time .

2.4.1 Valve Operation

To coordinate the four-stroke cycle , a group parts called the valve train opens and closes the valves ( moves them down and up , respectively ) . These valve movements must take place at exactly the right moments . The opening of each valve is controlled by a camshaft .

1. Camshaft(OHC) Valve Train Overhead

The cam is an egg-shaped piece of metal on a shaft that rotates in coordination with the crankshaft . The metal shaft , called the camshaft , typically has individual cams for each valve in the engine . As the camshaft rotates , the lobe , or high spot of the cam , pushes against parts connected to the stem of the valve . This action forces the valve to move downward . This action could open an inlet valve , or open an exhaust valve for an exhaust stroke .

As the camshaft continues to rotate , the high spot moves away from the valve mechanism . As this occurs , valve spring pull the valve tightly closed against its opening , called the valve seat .

Valve in modern car engines are located in the cylinder head at the top the engine . This is known as an overhead valve (OHC) configuration . In addition , when the camshaft is located over the cylinder head , the arrangement is known as overhead camshaft (OHC) design . Some high-performance engine have two separate camshafts , one for each set of inlet and exhaust valves . These engines are known as overhead-camshaft (DHOC) engine .

2. Push-rod Valve Train

The camshaft also can be located in the lower part of the engine , within the engine block . To transfer the motion of the cam upward to the valve , additional parts are needs .

In this arrangement , the cam lobs push against round metal cylinders called follower

英文版汽车构造是一本讲解汽车结构的书,也是一本英文的书,对于汽车专业的有大智慧

upward ( away from the camshaft ) . The cam follower rides against a push rod , which pushes against a rocker arm . The rocker arm pivots on a shaft through its center . As one side of the rocker arm moves up , the other side moves down , just like a seesaw . The downward-moving side of the rocker arm pushes on the valve stem to open the valve .

Because a push-rod valve train has additional parts , it is more difficult to run at high

speeds . Push-rod engines typically run at slower speeds and , consequently , produce less horsepower than overhead-camshaft designs of equal size . ( Remember , power is the rate at which work is done .)

2.4.2 Valve Clearance

When the engine runs in compression stroke and power stroke , the valves must close tightly on their seats to produce a gas-tight seal and thus prevent the gases escaping from the combustion chamber . If the valves do not close fully the engine will not develop fill power . Also the valve heads will be liable to be brunt by the passing hot gases , and there is the likelihood of crown touching an open valve , which can seriously damage the engine .

So that the valves can close fully some clearance is needed in the operating mechanism . This means that the operating mechanism must be able to move sufficiently far enough away from the valve t allow the valves to be fully closed against its seat by the valve spring . However , if the clearance is set too great this will cause a light metallic taping noise .

2.4.3 Valve Timing

The time at which valves open and close ( valve timing ) and the duration of the valve opening in stated in degrees of crankshaft rotation . For example , the intake valve normally begins to open just before the piston has reached the top dead center . The valve remains open as the piston travels down to BDC and even past BDC . This is intake valve duration .An example of this could be stated as follows : IO at 17BTDC , IC at 51ABDC ( or , intake opens 17before top dead center , intake closes 51after bottom dead center ) . Intake valve duration in this case is 248 of crankshaft rotation .

This leaves 129 duration for the compression stroke since compression ends when the piston reaches TDC . At this point the power stroke begins . The power stroke ends when the exhaust valve begins to open approximately at 51 before bottom dead center . The duration of the power stroke in this case is also 129 .

Since the exhaust valve is opening at 51 BBDC , this begins the exhaust stroke . The exhaust stroke continues as the piston passes BDC and moves upward to past TDC . With the exhaust valve closing at 17 TTDC , the duration of the exhaust stroke is 248 .

It is apparent from this description that the exhaust valve stays open for a short period of time during which the intake valve is also open . In other words , the end of the exhaust stroke and the beginning of the intake stroke overlap for a short period of time . This is called valve overlap . Valve timing and valve overlap vary on different engines.

Opening the intake valve before TDC and closing it after BDC increase the fill of air-fuel mixture in the cylinder . Opening the intake valve early helps overcome the static inertia of the air-fuel mixture at the beginning of the intake stroke , while leaving the intake valve open after BDC takes advantage of the kentia of the moving air-fuel mixture . This increase volumetric efficiency .

As the piston moves down on the power stroke past the 90 ATDC position , pressure in the cylinder has dropped , and the leverage to the crankshaft has decreased due to connecting rod

英文版汽车构造是一本讲解汽车结构的书,也是一本英文的书,对于汽车专业的有大智慧

angle and crankshaft position . This ends the effective length of the power stroke , and the exhaust valve can now be opened to begin expelling the burned gases . The exhaust valve remains open until the piston has moved up past the TDC position . This helps to remove as much of the burned gases as is possible and increase volumetric efficiency .

2.4.4 Cam Design and Control Dynamics

The function of the cam is to open and close the valves as far as possible , as fast as possible and as smoothly as possible . The closing force for the valves is applied by the valve spring which also maintain contact between the cam and the valves . Dynamic force impose limits on cam and valve lift .

The entire valve-train assembly can be view as a spring \mass system in which the conversion from stored to free energy causes force vibration . Valve-train assemblies with overhead camshafts can be represented with sufficient accuracy by a 1-mass system ( consisting of the moving mass , the valve-train assembly stiffness and corresponding damping ) .

For system with valve bottom-mounted camshaft and push rods , a 2-mass system is being increasingly used .

The maximum permissible contact stress , usually regarded as the parameter which limits cam-lobe radius and the rate of opening on the flank , currently lies between 600-700Mpa depending upon the material parings used .

2.4.5 Camshaft Drive Mechanism

Each cam must revolve once during the four-stroke cycle to open a valve. A cycle, remember, corresponds with two revolutions of the crankshaft . Therefore, the camshaft must revolve at exactly half the speed of the crankshaft . This is accomplished with a 2:1 gear ratio .A gear connected to the camshaft has twice the number of teeth as a gear connected to the crankshaft. The gears are linked in one of three ways:

1.Belt Drive

A cog-type belt can be used .Such belts are made of synthetic rubber and reinforced with internal steel or fiberglass strands. The belts have teeth ,or slotted spaces to engage and drive teeth on gear wheels. A belt typically is used on engines with overhead-cam valve trains.

2.Chain Drive

On some engines, a metal chain is used to connect the crankshaft and camshaft gears. Most push-rod engines and some OHC engines have chains.

3.Gear Drive

The camshaft and crankshaft gears can be connected directly, or meshed. This type of operating linkage commonly is used on older six-cylinder, inline engines.

A camshaft driven by a chain or belt turns in the same direction as the crankshaft . But a Camshaft driven directly by the crankshaft gear turns in the opposite direction. Timing belts are used because they cost less than chains and operate more quietly. A typical timing belt is made of neoprene (synthetic rubber) reinforced with fiberglass.

2.4.6 Electronic Valve Control System

An electronic value control (EVC) system replaces the mechanical camshaft, controlling

each value with actuators for independent value timing. The EVC system controls the opening and closing time and lift amount of each intake and exhaust valve with independent actuators on each value. Changing from a mechanical camshaft driven value into

英文版汽车构造是一本讲解汽车结构的书,也是一本英文的书,对于汽车专业的有大智慧

independently controlled actuator valves provides a huge amount of flexibility in engine control strategy. Vehicles utilizing EVC can realize several benefits including:

1) increases engine power and fuel economy,

2) allows centralized and distributed EVC systems to perform at their full potential,

3) adapts to engines of varied cylinder counts.

With all of the improved efficiencies and consumer benefits, auto manufacturers are

eager to get their first EVC systems on the road. The EVC system is targeted to operate

in temperatures up to 125, while the actuator is targeted to run up to 6000 r/min. The

actuator can be controlled in a centralized system with a high-speed multiplex bus (up

to 10Mbps) or in a distributed system with a nominal speed bus.

EVC systems must be compact in size, specifically the actuators that must be small

enough to fit in the engine space. A vehicle that uses a 42V system is ideal for EVC

because it requires high voltage to control the value actuators, and EVC is targeted for

V8 and V12 engines. The EVC system is also highly flexible, allowing adaptability for a number of cylinder engines.

New Words

coordinate 协调

valve train 气阀传动

respectively 分别的，各自的

overhead camshaft 顶置凸微轮轴

guide 导管

tappet 挺杆

valve insert 气门座

cotter 锁销，锁片

opening 口

lobe 凸起

spot 点，位置

stem 杆

dual 双的

cam follower 凸轮挺杆

seesaw 跷跷板，杠杆

value clearance 气门间歇

gas-tight seal 气封

liable to 容易

likelihood 可能

tapping 轻敲

valve timing 配气正时

intake valve 进气阀

exhaust valve 排气阀

static 静态的，静力的

kinetic （运）动的，动力（学）的

volumetric 测定体积的

leverage 杠杆作用

offset 偏移量

英文版汽车构造是一本讲解汽车结构的书,也是一本英文的书,对于汽车专业的有大智慧

dynamics 动力学

valve lift 气门挺杆

valve…as… 把…..看成……

parameter 参数，参量

radius 半径，范围

flank 侧面

pairing 配对，成对

correspond with 相当于

gear ratio 传动比

cog-type belt 齿型带

synthetic rubber 合成橡胶

reinforce 加强

fiberglass 玻璃纤维

strand 绳，线，绞合

slotted 有槽的，切槽的

mesh 相啮合

linkage 联动

inline engine 直列发动机

neoprene 氯丁（二稀）橡胶

electronic valve control (EVC) 电子式气阀控制

centralized system 集中系统

distributed system 分布系统

varied cylinder count 可变的汽缸数

architecture 结构，构造

processor 处理器

local node 局域节点

communication layer 通信层

synchronization 同步

Review Question

1. List the main parts of the OHC valve train .

2. How does a push-rod valve train work ?

3. how are the valve clearance adjusted by hand ?

4. Why do the intake valves open before TDC and close after BDC ?

5. What do we mean by “ valve overlap “

6. Why do most cars use timing belts rather than chains ?

7. What are the advantage of the electronic valve control (EVC) ?

2.5 Gasoline Fuel System

2.5.1 Gasoline

Gasoline is distilled from crude petroleum . Gasoline is highly flammable , meaning it burns easily in the presence of air .

Gasoline must vaporize easily . This characteristic , called volatility , is important . However , it must not vaporize too easily , or it will turn to vapor inside the fuel tank or fuel lines . Inside the

英文版汽车构造是一本讲解汽车结构的书,也是一本英文的书,对于汽车专业的有大智慧

fuel line , fuel vapor may block the flow of liquid gasoline . This is called vapor lock . Vapor lock is common in fuel lines where the inlet side of the pump is exposed to high temperatures .

The flammability of gasoline varies with its quality and the additives mixed with the gasoline The way gasoline burns inside the combustion chamber is most important .

Increasing the pressure of the fuel mixture in the combustion chamber before ignition helps to increase the power of an engine . This is done by compression the fuel mixture to a smaller volume . Higher compression ratio not only boost power but also give more efficient power . But as the compression ratio goes up , knocking tendency increase . The octane number of a gasoline is a measure of its antiknock quality or ability to resist detonation during combustion . Detonation , sometimes referred to as knock , can be defined as an uncontrolled explosion of the last portion of the burning fuel-air mixture due to excessive temperature and pressure condition in the combustion chamber . Since detonation creates shock pressure waves , and hence audible knock , rather tan smooth combustion and expansion of the fuel-air mixture , it result in loss of power , excessive localized temperatures , and engine damage if sufficiently severe .

There are two commonly used methods of determining the octane number of motor gasoline the motor method and the research method . Both used the same type of laboratory single –cylinder engine , which is equipped with a variable head and a knock meter to indicate knock intensity . Using the test sample as fuel , the engine compression ratio and the air-fuel mixture are adjusted to develop a specified knock intensity . Two primary standard reference fuels , normal heptane and iso-octane , arbitrarily assigned 0 and 100 octane numbers , respectively , are then blended to produce the same knock intensity as the test sample . Thus , if the matching reference blend is made up of 15 n-heptane and 85 iso-octane , the test sample , the test sample is rate 85 motor or research octane number , according to the test method used .

2.5.2 Adaptation to Operating Condition

In certain operation conditions , the fuel requirement differs greatly from the basic injection-fuel quantity so that corrective is required in mixture formation .

1.Cold Start

During a cold start , the air-fuel mixture drawn in by the engine leans off . This is due to

the low turbulence at cranking speeds causing poor mixture of the fuel particles with the air , and to the minimal evaporation of the fuel and wetting of the cylinder walls and intake ports with fuel at low temperature . In order to compensate for these phenomena , and thus facilitate staring of the cold engine , additional fuel must be injected during cranking .

2.Post-start Phase

After staring at low temperatures , it is necessary to enrich the mixture for a short period in order to compensate for poor mixture formation and wetting of the cylinder and intake-port walls with fuel . In addition , the rich mixture results in higher torque and therefore better throttle response when accelerating from idle .

3.Warm-up

The warm=up phase follows the cold-start and the post-start phase . The engine needs extra fuel during the warm-up phase because some of the fuel condenses on the still cold cylinder walls . At low temperatures , mixture formation is poor due to the large fuel droplets concerned , and due to the inefficient mixing of the fuel with the air drawn in by the engine , The result is that fuel condenses on the intake valves and in the intake manifold , and only evaporates at higher temperatures .

英文版汽车构造是一本讲解汽车结构的书,也是一本英文的书,对于汽车专业的有大智慧

The above factors all necessitate an increasing enrichment of the mixture along with decreasing temperature .

4.Acceleration

If the throttle is opened abruptly , the air-fuel mixture is momentarily leaned-off , and a short period of mixture enrichment is needed to ensure good transitional response .

5 . Part Load

During part-load operation , achieving maximum air-fuel economy and observing the emission values are the crucial factors .

6.Full Load

The engine delivers maximum power at full load , when the air-fuel mixture must

be enriched compared to that at part load .

This enrichment depends on engine speed and provide maximum possible torque

over the entire engine-speed range . This also ensure optimum fuel-economy figures during full-load operation .

7.Idling

In addition to the efficiency of the engine , the engine idle speed principally

determines the fuel consumption at idle .

The higher frictional resistances in the cold engine must be overcome by increasing

the air-fuel mixture input . In order to achieve smoother running at idle , the idle-speed control increases the idle speed . This also leads to more rapid warm-up of the engine . Close-loop idle-speed control prevents too high an idle speed . The mixture quantity corresponds to the quantity required for maintaining the idle speed at the relevant load ( e.g.. cold engine and increased friction ) . It also permits constant exhaust-gas emission values for a long period without idle adjustment . Closed-loop idle-speed control also partially compensates for charges in the engine resulting from aging and ensures stable engine idling throughout the service life .

8.Overrun

Cutting off the fuel during deceleration reduces fuel consumption not merely on

long downhill runs and during braking , but also in town traffic . Because no fuel is burnt , there are no emission .

9.Engine-speed Limiting

When a presser engine speed is reached , the ECU suppresses the fuel-injection pulses .

10.Adaptation of the Air-fuel Mixture at High Altitudes

The low density of air at high altitudes necessitates a leaner air-fuel mixture . At high altitudes , due to the lower air density , the volumetric floe measured by the air-fuel sensor corresponds to a lower air-mass floe . This error can compensated for by correcting the fuel quantity . Over-enrichment is avoided and , therefore , excessive fuel consumption .

2.5.3 Carburetor

As shown in Fig.2-20 , the fuel system has a fuel tank , fuel tank , fuel pump , fuel filter and carburetor . These parts store gasoline and deliver it to the carburetor as needed . Stated simply , the fuel tank stores the gasoline . The fuel lines carry the fuel from the tank to the carburetor . The fuel pump moves gasoline from the tank and through the fuel lines to carburetor . the fuel filter removes impurities from the gasoline . Then the carburetor sends the fuel ━ a mixture of air and gasoline ━ into the combustion chamber .

英文版汽车构造是一本讲解汽车结构的书,也是一本英文的书,对于汽车专业的有大智慧

2.5.4 Motronic Combine Ignition and Fuel Injection System

The carburetor sends the correct air-fuel mixture to the engine . However , not all cars have carburetors . Fuel-injection systems are used on many modern cars .

Fuel-injection systems have many advantages over carburetors . For example , they provide more exact fuel control . Thus , they can better match air-fuel ratios to changing engine conditions . They also provide better economy and emission control . Furthermore , fuel-injection system do not need many of the parts that carburetor have .

The Motronic system is an engine-management system comprising a control unit ( ECU ) which implements at least the two basic function ignition and fuel injection , but which , however may contain additional subsystems as required for improves engine control .

1. Detection of Measured Valves

The combustion process in the cylinder is influenced not only by fuel management , mixture quantity and air-fuel ratio , but also by the ignition advance and the energy contained in the ignition spark . An optimized engine control the air-fuel ratio λ throughout the injection time t ( i.e. the quantity of injected fuel ) as well as the ignition advance angle α and the dwell angle β . The main parameters which effect the combustion process are detected as measure values and processed together such that the optimum ignition and injection timing is calculated for instantaneous engine operating conditions

2. Actuating Variables/Sensors

Engine speed and load are the main actuating variables . Because a specific ignition

advance angle and a specific injection time correspond to each point of the engine speed/load map , it is important that all variables which pertain to the same point are calculate on the same speed /load area . This is only possible if the ignition advance and the injection time are calculated with the same speed and load valves ( engine speed detected only once with the same sensors ) .

This avoids statistical errors which can result , for example , from tolerances of different load sensor devices . Whereas a slightly different allocation in the part-load rage normally only increases consumption or exhaust emission , at full load near the knock limit the susceptibility t engine knocking increase . Clear allocation of the ignition timing angle and the injection time is provide by Motronic Systems , even under conditions of dynamic engine operation .

3. Motronic System

The Motonic system comprise a series of subsystem , the two basic subsystem being ignition and fuel injection . The combined system is more flexible and can implement a greater number of functions than the corresponding individual system . An important feature of the Motronic system is its implementation of a large number of freely programmable maps as desired for most sub-functions .

The exhaust gas recirculation (EGR) function has not been used in Europe to date , and is therefore provide only as an alternative systems . The lambda control system can only be considered today if used in conjunction with an adaptive precontrol for reasons of reduced exhaust emissions .

The knock control is either connected to the Motronic system via a defined interface , or integrated into the system . This combination of subsystem makes sense a physical standpoint : it enables a basic system ( ignition and fuel injection ) with open-loop functional control in a management system .

The idle speed control is realized by means of data from the ignition system and the fuel

英文版汽车构造是一本讲解汽车结构的书,也是一本英文的书,对于汽车专业的有大智慧

emissions .

The knock control is either connected to the Motronic system via a defined interface , or integrated into the system . This combination of subsystem makes sense a physical standpoint : it enables a basic system ( ignition and fuel injection ) with open-loop functional control in a management system .

The idle speed control is realized by means of data from the ignition system and the fuel injection system and is part of the overall system of control which includes tank ventilation and camshaft control .

Microcomputer-controlled systems today are required to perform self-diagnosis of the control unit itself , as well as of the entire system to a certain extent . Motronic system of the future will thus include a diagnostic feature .

An engine-management system should include at least those function described here . The addition of other functions is practical if they can be implemented without the need for a number of additional inputs and outputs . System which use input and output signals different from those used by the Motronic system are not integrated but rather are connected with the Motronic system via interfaces . Typical examples of such systems are the transmission control system and the traction control system which access the ignition and injection system via corresponding interfaces .

4. System Configuration

Fig 2-22 is a typical Motronic system which shows the fuel circuit and the acquisition of load and temperature data . The system dose not include the cold-start valve or the thermo-time switch whose function are performed by the control unit . The auxiliary-air device has been replaced by the idle-speed actuator . In addition to the ignition coil , the ignition section also include the high-volt-age distributor which is normally mounted directly on the camshaft . In contrast to the conventional ignition distributor , the high-voltage distributor only incorporate the high-voltage distributor function . The control unit electronically determines the proper ignition timing as a function of engine speed and load .

5. Control Unit ( ECU )

The ECU detects the instantaneous condition of the engine at very short intervals ( milliseconds ) via a number of sensors . The signals output by the sensors are fed to the ECU where input circuits remove any signal interference and convert the signals to a uniform voltage range . An A/D converter then transforms these signals to their signal equivalents . This information is then processed by the microcomputer , which generates output signals . The output stages amplify the low power lever of microcomputer outputs to the lever required by the actuators . All programs and maps are resident in a semiconductor memory . Digital signal level or component tolerance fluctuations . Digital accuracy is governed by word length , quartz-clock frequency constancy and the algorithms used for processing . Analog accuracy is determined by constancy and accuracy of the reference volt-ages , and by the components used in the input circuits . Program configuration must allow for the extreme real-time requirements of the engine : the interval between two ignition pulse in a 6-cylinder engine is only about 3ms at maximum speed . All essential calculation must be performed during this period . In addition to crankshaft-synchronous control processing , the ECU also has to calculate time-synchronous events .Both then functions have to wait if an interrupt occurs .

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