汽车构造(英文版)

CHAPTER 1 AUTOMOTIVE BASICS
第一章 汽车原理

1.1 Principal Components
1.1 汽车主要组成部分
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.
现代汽车有超过15000个零件组成，分成 几个必须在一起工作的功能部分。主要包括4个功能部分：引
擎，车身，底盘和电控。



1.2 Engine

1.2引擎

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
generates heat which causes the gas inside the cylinder to increase its pressure and supply
power to rotate a shaft connected to the transmission.
引擎为汽车提供能源。一般是内燃 机：通过在引擎缸内燃烧液体燃料获得能量。引擎有两种：汽油机和柴
油机。两种引擎都叫热机。燃烧的 燃料产生大量大热，热量使缸内的气体产生大的压力，通过连杆使曲轴
旋转。



1.3 Body
1.3 车身

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.
车身有窗户，门，盖，内饰等组成，它为发动机，乘客及货物提供空间和保 护。车身的设计要让乘客安全
并乘坐舒适。对于乘用汽车，车身要动感，色彩绚丽，现代化。




1.4 Chassis
1.4 底盘

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.
底盘是一个组合体，主要由汽车的操纵部分，传动系统，悬架，转向部分，制动系统组成。
Transmission systems ― conveys the drive to the wheels. The main components are clutch,
gearbox, driveshaft, final drive, and differential.
传动系统用来驱动车轮。主要有离合器，变速箱，驱动轴，最后驱动和差速器组成。

Suspension― absorbs the road shocks.
悬架主要用来吸收路面冲击。
Steering― controls the direction of the movement.
转向系统控制汽车的行驶方向。
Brake― slows down the vehicle.
制动系统使汽车停下来。

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.

电动系统主要为点火系统，喇叭，灯，加热器，及启动系 统提供电能。电压通过一个电路保
持恒定。这个电路有电池，发电机组成。电池储存电能，发电机把引擎 的机械能转化为电能，
给电池充电。
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

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. List the main parts of an automobile?汽车的主要部分有哪些？
2. What are the common types of a vehicle according to body styling?根据车身，汽车的一般类
型有哪些？

3. Which systems does a chassis include and what are the main functions of the chassis?汽车底
盘有哪些系统，底盘的功用是那些？
4. Why are suspension systems used on vehicles?汽车为什么用悬架系统？
CHAPTER2 INTERNAL COMBUSTION ENGINE
第二章 引擎燃烧室
2.1 principle of operation
2.1原理
2.1.1 Engine and power
2.1.1引擎和能量
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.
引擎为汽车 提供能量，燃料的化学能通过燃烧，转化为热能，这个过程叫燃烧。假如燃
烧在燃烧室，这样的发动机叫 内燃机。假如燃烧在气缸外，这样的发动机叫外燃机。
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.
用在汽车上的一般是内燃机，热能在燃烧室释放，燃烧室气体温度升高。气体温度的升< br>高使气体的压力曾加，燃烧室内的高压气体作用在活塞头部产生可以利用的化学能，化学能
转化为 机械能。
2.1.2 Engine Terms
2.2.1引擎冲程

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
and recharge the cylinder with a fresh petrol-air mixture :this control of gas movement is the duty
of the valves an intake 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 :
连接活塞和曲轴的连杆，是气体推动曲轴旋转的原因。做功冲程利用气体，也就意味着吧废气排出缸体，同时燃烧室吸入新鲜的燃油和空气：这个功能是气门的职责；进气门使新
鲜的混合 气在合适的时刻进入，排气门使燃烧过的混合气排除缸外。
TDC(Top Dead Center):the position of the crank and piston when the piston is farther away
from the crankshaft.
上止点：当活塞离曲轴最远时，活塞或曲轴的位置。
BDC(Bottom Dead Center):the position of the crank and piston when the piston is nearest to the
crankshaft.
下止点：当活塞距离曲轴最近时，活塞或曲轴的位置。
Stroke : the distance between BDC and TDC; stroke is controlled by the crankshaft.
冲程：上止点和下止点的距离；冲程被曲轴控制。
Bore : the internal diameter of the cylinder.
缸经：缸筒的内经。

Swept volume : the volume between TDC and BDC.
有效容积：上止点和下止点直接的容积。
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.
发动机的排量：指发动机所以缸的排量，一个四冲程2升发动机每个气缸的排量是50.
Clearance volume: the volume of the space above the piston when it is at TDC.
燃烧室：当活塞在上止点时，活塞上面的容积。
Compression ratio = (swept vol + clearance vol)(clearance vol)
压缩比=（有效容积+燃烧室容积）燃烧室容积

Two-stroke : a power stroke every revolution of the crank.
两冲程发动机：曲轴旋转一周，一个做功冲程。
Four-stroke : a power stroke every other revolution of the crank..
四冲程发动机：曲轴旋转两圈，一个做功冲程。











2.1.3 The Four- stroke Spark-ignition Engine Cycle
2.1.3四冲程发动机的点火系统

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.
四冲程点火发动机是一个具备外部点火系统的把燃料的能量转化为机械能的机械。
The cycle of operations is spread over four piston strokes. To complete the full cycle it takes
two revolutions of the crankshaft.
一个循环包括四个冲程。每个循环曲轴要旋转两圈。
The operating strokes are :
吸气冲程：

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.
吸气冲程吧雾化的汽油和新鲜空气吸入缸内。吸气冲程开始时，活塞在上止点。当活塞 向下运动时，
产生真空和低压，混合气体被吸入。
在吸气冲程，进气门打开，排气门闭合。

Compression stroke
压缩冲程
As the piston moves upward to compress the fuel mixture trapped in the cylinder, the valves
are closed tightly. This compression action heats the airfuel mixture slightly and confines it
within a small area called the combustion chamber.
当活塞向上运动时，气门紧闭，活塞压缩混合可燃气。压缩混合气在燃烧室温度升高。


Power stroke
做功冲程
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.
在活塞到达压缩冲程的上止点前，缸盖上螺纹固定的火花塞产生火星，点火。
火花点燃在燃烧 室高压高温的燃油混合气体使其快速燃烧。快速燃烧的燃气产生大量的热，在缸体内
迅速扩散产生压力。 高压气体推动活塞向下运动。向下的运动使曲轴旋转。


Exhaust stroke
排期冲程
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.
在做工冲程即将结束时，排气门打开。活塞向上运动，将热燃烧后的混合气通过排气门排除缸体外。 < br>在活塞到达上止点前排气门关闭，进气门开启。当活塞到达所谓的上止点时，活塞又开始向下运动，

这样一个循环结束，另一个循环开始。
2.1.4 Engine Overall Mechanics
2.1.4 发动机的总体构造
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.
发 动机有说百个部件，发动机的主要部件是缸体，缸盖，活塞，连杆，曲轴和气门。其
它部分组合成系统， 这些系统包括，燃油供给系统，进气系统，点火系统，冷却系统，润滑
系统，和排气系统。每个系统都有 一定的功能。这些系统将在以后的的章节详细讨论。
NEW WORD
Piston 活塞
Connecting rod 连杆
Crankshaft 曲轴
Power stroke 活塞行程
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发动机缸体和缸盖
2.2.1 Engine Block
2.2.1缸体
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.
缸体是发动机的基础，其它的部 件要么装在缸体内，要么固定在缸体上。水套和油道在缸体内。当然
缸体也固定曲轴，曲轴固定在缸体的 底部。凸轮轴也固定在缸体上，除非是顶置凸轮轴固定在缸盖上。在
大多数汽车上，缸体的材料是灰铸铁 或者是灰铸铁和其它金属的合金，例如镍镉合金，缸体是铸件。
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.
一些发动机缸体，特别是小汽车缸体是铸铝。这种金属比铸铁轻。虽然，铸铁的耐 久性比驴占优势。
因此，铝合金缸体的气缸被镶上铸铁或钢质圆桶，那些桶被叫做缸套。还有一些发动机 全部是铝缸体。
2.2.2 Cylinder Head
2.2.2缸盖

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.
缸盖固定在缸体上，就像房子的屋顶。 缸盖下面空间和活塞形成燃烧室。一般气缸盖的燃烧室是半球
形，楔形，半独立燃烧室。三种燃烧室形状 都影响发动机燃烧室。缸盖上安装气门，气门弹簧和气门摇臂，
这个气门通过推杆工作。有时候，缸盖上 的凸轮轴不经过摇臂直接气门。被叫做顶置凸轮轴结构。就像缸
体，缸盖的材料是铸铁或铸铝。

2.2.3 Gasket
2.2.3气缸垫
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.

缸盖被高强度螺钉固定在缸体上。在缸体和缸盖的结合处有耐气的垫片，防止燃烧的混合气体 外溢。
缸垫可以实现这一功能。气缸垫就像是三明治，一层石棉夹在铜材料的中间，这两种材料都能承受 发动机
高温和高压。
2.2.4 Oil Pan or Sump
2.2.4油底壳

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.
油底壳一般是钢铁冲 压件，油底壳和缸体下面部分被叫做曲轴箱，它们把曲轴密封，包裹起来。润滑
系统的油泵吸取油底壳的 油输送到发动机的工作部分润滑。油流经油道又回到油底壳。这样，机油在发动
机工作部分和油底壳之间 始终有一个连续的循环。

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
encase 封闭，把…包起来
drain off 排出，流出
Review Question
问题回顾

1. What do TDC, BDC, stroke, compression ratio and engine capacity stand for?
,BDC冲程，压缩比，引擎排量是什么意思？
2. How do you calculate swept volume and compression ratio?
2.怎么计算排气容积及压缩比？
3. What controls the length of the stroke?
3.行程是怎么控制的？
4. List the main parts of the engine overall mechanics?
4.说出发动机的主要部分？
5. What are the main function of the engine block?

5.缸体的作用是什么？
2.3 Piston Connecting Rod and Crankshaft
2.3活塞连杆和曲轴
2.3.1 Piston Assembly
2.3.1活塞总成
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.
活塞是四冲程发动机的一个重要部件。大多数的活塞是铝合金浇注而成。 活
塞通过连杆把燃烧混合气体的能量传给曲轴。这种能量使曲轴旋转，薄的，圆筒
钢片安装在活 塞队环槽内来密封燃烧室的底部。这些薄片叫做活塞环。活塞上的
槽被叫做活塞环槽。活塞销装在活塞的 圆孔内。活塞销吧活塞和连杆链接起来。
用来支撑活塞销厚道活塞部分叫活塞销凸台。
The piston itself , its rings and the piston pin are together called the piston
assembly.
活塞和活塞销在一起被叫做活塞总成。

2.3.2活塞
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.
为了能承受燃烧室的热量，活塞必须有一定的强度。活塞要轻，因为它以很
高的 速度在缸体里上下运动。因此，活塞是空的。活塞的头部很厚，因为，活塞
头部要承受燃烧和膨胀的热量 。活塞底部很薄，因为那里几乎没有热。活塞的顶
部叫做活塞顶或活塞头。活塞的薄部分叫活塞裙部。
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.
活塞头可能是平的，凹的，圆的。在柴油机中，今天活塞头是组 成燃烧室的
一部分，这取决于喷射的方式。所以，柴油机活塞有的形状很自由。

2.3.3Piston Rings
2.3.3活塞环
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.
正像2-9所展示的，活塞环装在活 塞顶部的的活塞环槽里。一般的活塞环是
薄的，圆环金属片，正好贴在活塞头部的活塞环里。
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.
现代发动机，每个 活塞都有三个活塞环（近代发动有时候有四个活塞环，甚
至五个）。活塞环的外表面贴在缸筒的壁面上。 活塞环在活塞和缸筒之间形成密
封。也就是说，只有活塞环和岗壁接触。活塞上面的两道环使气体早缸筒 里，叫
做气环。第三道环使机油流回阻止机油进入燃烧室，被叫做油环。
ring 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.
做工冲程中，燃烧室里气环的压力很高。压力使气环 错开。一些高压气体进
入气环背隙。这样使气环完全和缸壁接触。燃烧压力当然使气环的底部紧紧的贴< br>在活塞环槽里。因此，高的压力使活塞环在缸体和活塞间形成了密封。

2.3.4 Piston Pin
2.3.4活塞销
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.
活塞 销连接活塞和连杆。活塞销要穿进活塞销空和连杆小头。连杆头部的孔
比连杆和曲轴链接的孔小，连杆小 头安装活塞底内部。活塞销通过活塞孔，连杆
小头孔，活塞的另一侧销孔。销使连杆紧紧的固定在活塞中 间。活塞销是高强度
金属制成，并且是空心的。许多活塞销镀烙提高其耐磨性。
2.3.3 Connecting rod
2.3.3连杆
The connecting rod is made of forged
high-strength 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 .
连杆是高强度金属锻造的。它把活塞的运动
传递给曲轴的曲柄销 。连杆小头连接活塞销。在
连接处的衬套有软金属制成，例如青铜。比较低
的连杆头叫做连杆大 头，安装在曲轴上。对于大
头轴承，金属背轴承或锡轴承。它们和发动机主
轴承是一样的。连杆 大头有时一定的角度分开
的，分开裂口很小，为了适应气缸。连杆式有铸

造合金 铸成。


2.3.5 Crankshaft
2.3.5曲轴
The crankshaft , in conjunction with the connecting rod , converts 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 .
曲轴链接连杆，把活塞的 往复运动变成驱动汽车的旋转运动。一般情况下，
曲轴是碳及小量的金属镍的合金做成的。主轴承轴安装 在缸径和大头
主要轴承曲
颈安装在气缸体和与连杆大头末端匹配的曲颈上。

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 .

New Words
Comprise 由。。。。。。。组成，包含
Inertia 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
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
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
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:
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.
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.
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
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 rmin. 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
tappet
valve insert
cotter
opening
lobe
spot
stem
dual
cam follower
seesaw
value clearance
gas-tight seal
liable to
likelihood
tapping
valve timing
intake valve
exhaust valve
static
kinetic
volumetric
leverage
offset
dynamics
valve lift
valve…as…
parameter
radius
flank
pairing
correspond with
gear ratio
cog-type belt
synthetic rubber
导管
挺杆
气门座
锁销，锁片
口
凸起
点，位置
杆
双的
凸轮挺杆
跷跷板，杠杆
气门间歇
气封
容易
可能
轻敲
配气正时
进气阀
排气阀
静态的，静力的
（运）动的，动力（学）的
测定体积的
杠杆作用
偏移量
动力学
气门挺杆
把…..看成……
参数，参量
半径，范围
侧面
配对，成对
相当于
传动比
齿型带
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
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 .
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 .
-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 .
-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 .
The above factors all necessitate an increasing enrichment of the mixture along with
decreasing temperature .
ration
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 .
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 .

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 .
n
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 .

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


tion 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 .
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 VariablesSensors
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 speedload 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
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 AD 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 .

2.6 Engine Cooling
The purpose of the engine?s cooling system is to remove excess heat from the engine , to
keep the engine operation at its most efficient temperature , and to get the engine up to the correct
temperature as soon as possible after staring .Ideally , the cooling system keeps the engine running
at its most efficient temperature no matter what the operation are .
There are two types of cooling systems liquid cooling and air cooling . Most auto
engines are cooled by the liquid type air cooling is used more frequently for airplanes ,
motorcycles and lawnmowers .
2.6.1 Liquid Cooling
This system consists of several interdependent parts that function together to maintain
proper engine temperature . The cooling system of a water –cooled engine consists of the engine?s

water jacket , a thermostat , a water pump , radiator and radiator cap , a cooling fan ( electric or
belt-drive) , hoses , and usually an expansion ( overflow ) tank .
To dissipate excess engine heat , the cooling system performs four function :
1) absorption
2) circulation
3) radiation
4) control
Absorption occurs as coolant moves through the engine block . Heat energy from the
burning fuel in the cylinders passes into the cylinder walls and cylinder head . Liquid coolant
circulates through hollow spaces within the engine block and head to absorb the heat from the
metal parts of the engine . The hollow spaces are known as the water jacket .
After absorbing the heat , the hot coolant passes out through the cylinder head and eaters
the radiator . As the coolant circulates through the radiator , it gives up its heat to the metal tubes
of the radiator . The radiator is made of brass or aluminum , metals that conduct heat well . As air
passes through the radiator fins and around the tubes , heat is transferred to air .
However , if coolant circulated at all times from the engine to radiator , the engine
would run very cool on cold days . Remember that chemical reaction , including the burning of the
fuel , occur more efficiently at high temperature . Thus , for the engine to operate efficiently , there
must be a control mechanism .
This control system is the thermostat . It regulates hoe much coolant is permitted to flow
through the radiator . After you start the engine , it should heat an efficient operating temperature
as quickly as possible and maintain that temperature without overheating .
2.7 Engine Lubrication
The purpose of the lubrication system is to circulate oil through the engine . An engine
must have a good lubrication system . Without it , the friction heat from the contact of moving
parts would wear the parts and cause power loss . Oil , when placed between two moving parts ,
separates them with a film . This oil film prevents the parts from rubbing against between each
other . This oil film also cushions the parts , giving quieter and smoother engine operating .
Besides lubricating engine parts , oil is also used to :
1) clean the inside of the engine
2) help cool the engine
3) from a seal between the cylinder walls and piston rings .
Friction between engine components is reduced by :
1) boundary lubricating – relies on oil being splashed up onto the surfaces .
2) full film lubricating – an oil film is maintained by forcing the oil between the
surfaces by an oil pump .
The system used on a modern engine combines both methods : pistons are lubricated by
splash and bearing are pressure fed .
The main parts of a lubrication system are : pump , main oil gallery , relief valve and
filters .
2.7.1 Pump
In most cars , the oil pump is in the crankcase above the sump . It draws oil through a
tube that extends downward oil through a tube that extends downward into the sump .This tube
has a filter screen over its bottom end . The screen keeps large pieces of sludge and dirt from

being drawn into the pump . The tube may be hinged on the pump end so that it can move up and
down as the oil level change in the sump . Thus , the pump always draws oil from the top of the
sump , not from the bottom where the dirt and sludge tend to settle . Modern cars use one of two
common types of oil pump – the gear – type and the rotor – type .

2.7.2 Main Oil Gallery and Relief Valve
This runs the length of the engine . Drilling from the gallery allow oil to be supplied
to the bearing surfaces .
Generally fitted in the gallery , this spring loaded valves opens when the pressure
reaches the maximum allowed .

2.7.3 Filters
Besides the gauze screen that prevents pieces of the metal entering the pump there is
an external filter which can be renewed periodically . A modern engine uses a full – flow filtering
system . In this system , the output of the oil pump flows through the oil filter before each trip
through the engine . When an engine runs at 3000rmin its entire five quarts of oil pass through the
filter at least once every minutes . Thus the oil filter ensures that only clean oil enters the engine .
New Words

Cushion 缓冲，减振
Relief valve 溢流阀
Sludge 油泥渣，残渣
Hinge 依。。。。。。。而转移
Gauze screen filter 金属滤网滤清器
Review Question
1.
2.
3.
4.
5.
What is the purpose of the cooling system ?
List the main parts a liquid – cooling system ?
Why is thermostat need is a liquid – cooling system ?
What are the main function of the lubrication system ?
List the main parts of the lubrication system ?
2.8 Exhaust System
The exhaust system carries exhaust gases from the engine?s combustion chamber to the
atmosphere and reduces , or muffles , engine noise . Exhaust gases leave the engine the engine in a
pipe , traveling through a catalytic converter and a muffler before exiting through the tailpipe .
2.9.1 The Tailpipe
The tailpipe is a long metal tube attached to the muffler . It sticks out from under the body of a
car , at the rear , in order to discharge the exhaust gases from the muffler of the engine into the air
outside the car .
2.8.2 The Muffler
Exhaust gases leave the engine under extremely high pressure . If these gases escaped directly
from the engine , the noise would be tremendous . For the reason , the exhaust manifold sends the
gases to a muffler where they go through metal plates , or tubes , with a series of holes . The
pressure of the gases is reduced when they pass through the muffler , so they go out of the tailpipe
quietly .
The muffler is made of metal and is located underneath the body a car . it?s connected
between the tailpipe and the catalytic converter .

There are two types of muffler design . One type uses several baffled chambers to reduce
noise . The other type sends the gases straight through perforate pipe wrapped in metal or
fiberglass This type of muffler is designed for the purpose of reducing backpressure and ,
consequently , makes slightly more noise .
The muffler quests the noise of the exhaust by “ muffling ” the sound waves creates by the
opening and closing of the exhaust valves . When an exhaust valve opens , it discharge the burned
gases at high pressures into exhaust pipe , which is at low pressure . This type of action creates
sound waves that travel through the flowing gas , moving much faster than the gas itself ( up to
1400 m. p . h . ) that the muffler must silence . It generally does this by converting the sound wave
energy into heat by pasting the exhaust gas and through perforated chambers of varied sizes .
Passing into the perforation and reflectors within the chamber forces the sound waves to dissipate
their energy .
Car manufacturers are experimenting with an electronic muffler , which uses sensors to
monitor the sound waves of the exhaust noise . The sound wave data are sent to a computer that
controls speaker near the tailpipe . The system generates sound waves 180 degrees of phase with
the engine noise . The sound waves from the electronic muffler collide with the exhaust sound
waves and they cancel each other out , leaving only low – lever heat to emerge from the tailpipe .
2.8.3 The Exhaust Manifold And Header
The exhaust manifold , usually constructed of cast iron , is a pipe that conducts the exhaust
gases from the combustion chambers to the exhaust pipe . It has smooth cures in it for improving
the flow of exhaust .
The exhaust manifold is bolted to the cylinder head , and has entrances for the air that is
injected into it . It is usually is located under the intake manifold .
A header is a different type of manifold , it is made of separate equal – length tubes .
2.8.4 Manifold to Exhaust Pipe Gasket
There are several types of that connect the exhaust pipe to manifold .
One is a flat surface gasket . Another type uses a ball and socket with spring to maintain
pressure . This type allows some flexibility without breakage of the seal or the manifold . A third
type is the full ball connector type , which also allows a little flexibility .
2.8.5 Exhaust Pipe Hangers
Hangers hold the exhaust system in place . They give the system flexibility and reduce the
noise lever . The hanger system consists of rubber rings , tubes and clamps .
2.8.6 Exhaust pipe
The exhaust pipe is the bent – up or convoluted pipes underneath a car . Some are shaped to
go over the rear axle allowing the rear axle to move up and down without bumping into the
exhaust pipe ; some are shaped to bend around under the floor of the car , connecting the catalytic
converter with the muffler . Exhaust pipes are usually made out of stainless steel , since the high
heat conditions involved with the muffler system will cause rust .
2.8.7 Dual Exhaust System
The advantage of a dual exhaust system is that the engine exhausts more freely ,thereby
lowering the backpressure , which is inherent in an exhaust system . With a dual exhaust system ,
a sizable increasing in engine horsepower can be obtained because the “ breathing ” capacity of
the engine is improved , leaving less exhaust gases in the engine at the end of each exhaust stroke .
This , in turn , leaves more room for en extra intake of the air – fuel mixture .

New Word
Tremendous 巨大的，极大的
Perforated 多孔的
Muffler 消音器
Tailpipe 尾管
Hanger 吊耳，吊钩
Manifold 歧管
Fiberglass 玻璃纤维
Speaker 扬声器
Header 集气管
Baffled 用挡板隔开的
Convoluted 回旋状的
Flat 平面
Sizable 相当大的，大小相当的
Room 空间
Bump 碰撞
Catalytic converter 催化转换器
Backpressure 背压

2.9The Ignition System
There are many different ignition systems . Most of these systems can be placed into one of
three distinct : the conventional breaker point type ignition systems ( in use since the early
1900s ) the electronic ignition systems ( popular since the mid 70s ) and the distributorless
ignition system ( introduces in the mid 80s ) .
The automotive ignition system has two basic functions it must control the spark and
timing of the spark plug firing to match varying engine requirements , and it must increase battery
voltage to a point where it will overcome the resistance offered by the spark plug gap and fire the
plug .
2.9.1 Point – Type Ignition System
An automotive ignition system is divided into two electrical circuits – the primary and
secondary circuits . The primary circuit carries low voltage . This circuit operates only on battery
current and is controlled by the breaker points and the ignition switch . The secondary circuit coil
( commonly called the coil wire ) , the distributor cap the distributor rotor , the spark plug leads
and the spark plugs .
The distributor is the controlling element of the system . It switches the primary current on
and off and distributes the current to the proper spark plug each time a spark is needed . The
distributor is a stationary housing surrounding a rotating shaft . The shaft is driven at one – half
engine speed by the engine?s camshaft through the distributor drive gears . A cam near the top of
the distributor shaft has on lobe for each cylinder of the engine . The cam operates the contact
points , which are mounted on a plate within the distributor housing .
A rotor is attached to the top of the distributor shaft . When the distributor cap is in
place , a spring – loaded piece of metal in the center of the cap makes contact with a metal strip on
top of the rotor . The outer end of the rotor passes very close to the contacts connected to the spark
plug leads around the outside of the distributor cap .
The coil is the heart of the ignition system . Essentially , it is nothing more than a

transformer which takes the relatively low voltage ( 12 volts ) available from the battery and
increasing it to a point where it will fire the plug as much as 40000 volts . The term “coil” is
perhaps a misnomer since there are actually two coils of wire wound about an iron cone . These
coils are insulated from each other and the whole assembly is enclosed in an oil – filled case . The
primary coil , which consists of relatively few turns of heavy wire , is connected to the two
primary terminals located on top of the coil . The secondary coil consists of many turns of fine
wire. It is connected to the high – tension connection on top of the coil ( the tower into which the
coil wire from the distributor is plugged ) .
Under normal operating conditions , power from the battery is fed through a resistor or
resistance wire to the primary circuit of the coil and is then grounded through the ignition points in
the distributor ( the points are closed ) . Energizing the coil primary circuit with battery voltage
produces current flow through the primary winding , which induces a very large , intense magnetic
filed . This magnetic filed remains as long as current flows and the points remain closed .
As the distributor cam rotates , the points are pushed apart , breaking the primary circuit
and stopping the flow of current . Interrupting the flow of primary current causes the magnetic
filed to collapse . Just as current flowing through a wire produces a magnetic filed , moving a
magnetic filed across a wire will produce a current . As the magnetic filed collapses , its lines of
wire in the secondary winding , inducing a current in them . Since there are many more turns of
wire in the secondary windings , the voltage from the primary winding is magnified considerably
up to 40000volts .
The voltage from the coil secondary winding flows through the coil high – tension lead to
the center of the distributor cap , where it is distributed by the rotor to one of the outer terminals in
the cap . From there , it flows through the spark plug lead to the spark plug . This process occurs
in a split second and is repeated every time the points open and close , which is up to 1500 times a
minute in a 4 – cylinder engine at idle .
2.9.2 Electronic Ignition Systems
The need for higher mileage , reduced emissions and greater reliability has led to the
development of the electronic ignition system . These system generate a much stronger spark ,
which is needed to ignite leaner fuel Breaker point system needed a resistor to reduce the
operating voltage of the primary circuit in order to prolong the life of the points . The primary
circuit of the electronic ignition system operates on full battery voltage , which helps to develop a
stronger spark . Spark plug gaps have winded due to the ability of the increased voltage to jump
the large gap . Cleaner combustion and less deposits have led to longer spark plug life .
On some systems , the ignition coil has moved inside the distributor cap . This system is
said to have an internal coil opposed to the complicated external .
Electronic ignition systems are not as complicated as they may first appear . In fact , they
differ only slightly from conventional point ignition systems . Like conventional ignition systems ,
electronic systems have two circuits : a primary circuit and a secondary circuit . The entire
secondary circuit is the same as in a conventional ignition system . In addition , the section of the
primary circuit from the battery to the battery terminal at the coil is the same as in a conventional
ignition system .
Electronic ignition system differ from conventional ignition system in the distributor
component area . Instead of a distributor cam , breaker plate , points , and condenser , an
electronic ignition system has an armature ( called by various names such as a trigger wheel ,

redactor , etc . ) , a pickup coil ( stator , sensor , etc. ) , and an electronic module .
2.9.3 Distributorless Ignition System ( DIS )
The third type of ignition system is the distributorless ignition . The spark plugs are fired
directly from the coils . The spark timing is controlled by an Ignition Control Unit ( ICU ) and the
Engine Control Unit ( ECU ) . The distributorless ignition system may have one coil per cylinder ,
or one coil for each pair of cylinders .
Some popular systems use one ignition coil per two cylinders . This type of system is often
known as the waste spark distribution method . In this system , each cylinder is paired with the
cylinder opposite it in the firing order ( usually 1 – 4 – 2 – 3 on 4 – cylinder engines or 1 – 4 – 2 –
5 – 3 – 6 on V6 engines ) . The ends of each coil secondary leads are attached to spark plugs for
the paired opposites . These two plugs are on companion cylinder , cylinders that are at Top Dead
Center ( TDC ) at the sane time . But , they are paired opposites , because they are always at
opposing ends of the 4 – stroke engine cycle . When one is at TDC of the compression stroke , the
other is at TDC of the exhaust stroke . The one that is on compression is said to be the event
cylinder and one on the exhaust stroke , the waste cylinder . When the coil discharges , both plugs
fire at the same time to complete the series circuit .
Since the polarity of the primary and the secondary windings are fixed , one plug always
fires in a forward direction and the other in reverse . This is different than a conventional system
firing all plugs the same direction each time . Because of the demand for additional energy the
coil design , saturation time and primary current flow are also different . This redesign of the
system allows higher energy to be available from the distributorless coils , greater than 40
kilovolts at the rpm ranges .
The distributorless ignition system uses either a magnetic crankshaft sensor , camshaft
position sensor , or both , to determine crankshaft position and engine speed . This signal is sent to
the ignition control module or engine control module , which then energizes the appropriate coil .
The advantage of no distributor , in theory , is :
1. No timing adjustments .
2. No distributor cap and rotor .
3. No moving parts to wear out .
4. No distributor to accumulate moisture and cause staring problems .
5. No distributor to drive thus providing less engine drag .
The major components of a distributorless ignition are :
1. ECU or Engine Control Unit .
2. ICU or Ignition Control Unit .
3. Magnetic Triggering Device such as the Crankshaft Position Sensor and the Camshaft
position Sensor .
4. Coil Pack .
New Words
Distributor 分电器
Condenser 电容器
Wear 磨损
Saturation 磁饱和
Series 串联
Wind 缠绕

Coil （ 点火 ）线圈
Transformer 变压器
Turn 匝数
Term 术语， 学期，条件
Breaker point type ignition system 触点型点火系统
Distributorless ignition system 无分电器点火系统
Primary and secondary circuits 初级和次级电路
Magnetic filed 磁场
High tension lead 高压导线
Distributor rotor 分火头
Spark plug 火花塞
Chaper3 Chassis
3.1clutch
The engine produces the power to drive the vehicle . The drive line or drive train transfer the
power of the engine to the wheels . The drive train consists of the parts from the back of the
flywheel to the wheels . These parts include the clutch , the transmission ,the drive shaft ,and the
final drive assembly .
The clutch which includes the flywheel ,clutch disc , pressure plate , springs , pressure plate
cover and the linkage necessary to operate the clutch is a rotating mechanism between the engine
and the transmission . It operates through friction which comes from contact between the parts .
That is the reason why the clutch is called a friction mechanism . After engagement, the clutch
must continue to transmit all engine torque to transmission depending on the friction without
slippage . The clutch is also used to disengage the engine from the drive train whenever the gears
in the transmission are being shifted from gear ratio to another .
To start the engine or shift the gears , the driver has to depress the clutch pedal with the
purpose of disengagement the transmission from the engine . At that time , the driven members
connected to the transmission input shaft are either stationary or rotating at a speed that is slower
of faster than the driving members connected to engine crankshaft . There is no spring pressure on
the clutch assembly parts . So there is no friction between the driving members and driven
members . As the driver lets loose the clutch pedal , spring pressure increase on the clutch parts .
Friction between the parts also increases . The pressure exerted by the springs on the driven
members is controlled by the driver through the clutch pedal and linkage . The positive
engagement of the driving and driven members is made possible the friction between the surfaces
of the members . When full spring pressure is applied , the speed of the driving and driven
members should be the same . At the moment , the clutch must act as a coupling device and
transmit all engine power to the transmission , without slipping .
However , the transmission should be engaged to the engine gradually in order to operate the
car smoothly and minimize torsional shock on the drive train because an engine at idle just
develop little power . Otherwise , the driving members are connected with the driven members too
quickly and the engine would be stalled .
The flywheel is a major part of the clutch . The flywheel mounts to the engine?s crankshaft and
transmits engine torque to the clutch assembly . The flywheel , when coupled with the clutch disc
and pressure plate makes and breaks the flow of power the engine to the transmission .

The flywheel provides a mounting location for the clutch assembly as well . When the clutch
is applied , the flywheel transfers engine torque to the clutch disc . Because of its weight , the
flywheel helps to smooth engine operation . The flywheel also has a large ring gear at its outer
edge , which engages with a pinion gear on the starter motor during engine cranking .
The clutch disc fits between the flywheel and the pressure plate . The clutch disc has a splined
hub that fits over splines on the transmission input shaft . A splined hub has grooves that match
splines on the shaft . These splines fit in the grooves . Thus , the two parts held together .
However , back – and – forth movement of the disc on the shaft is possible . Attached to the input
shaft , the disc turns at the speed of the shaft .
The clutch pressure plate is generally made of cast iron . It is round and about the same
diameter as the clutch disc . One side of the pressure plate is machined smooth . This side will
press the clutch disc facing are against the flywheel . The outer side has shapes to facilitate
attachment of spring and release mechanism . The two primary types of pressure plate assemblies
are coil spring assembly and diaphragm spring .
In a coil spring clutch the pressure plate is backed by a number of coil springs and housed
with them in a pressed – steed cover bolted to the flywheel . The spring push against the cover .
Neither the driven plate nor the pressure plate is connected rigidly to the flywheel and both can
move either towards it o away . When the clutch pedal is depressed a thrust pad riding on a carbon
or ball thrust bearing is forced towards the flywheel . Levers pivoted so that they engage with the
thrust pad at one end and the pressure plate tat the other end pull the pressure plate back against its
springs . This releases pressure on the driven plate disconnecting the gearbox from the engine .
Diaphragm spring pressure plate assemblies are widely used in most modern cars . The
diaphragm spring is a single thin sheet of metal which yields when pressure is applied to it . When
pressure is removed the metal spring back to its original shape . The center portion of the
diaphragm spring is slit into numerous fingers that act as release levers . When the clutch
assembly rotates with the engine these weights are flung outwards by centrifugal plate and cause
the levers to press against the pressure plate . During disengagement of the clutch the fingers are
moved forward by the release bearing . The spring pivots over the fulcrum ring and its outer rim
moves away from the flywheel . The retracting spring pulls the pressure plate away from the
clutch plate thus disengaging the clutch .
When engaged the release bearing and the fingers of the diaphragm spring move towards the
transmission . As the diaphragm pivots over the pivot ring its outer rim forces the pressure plate
against the clutch disc so that the clutch plate is engaged to flywheel .
The advantages of a diaphragm type pressure plate assembly are its compactness , lower
weight , fewer moving parts , less effort to engage , reduces rotational imbalance by providing a
balanced force around the pressure plate and less chances of clutch slippage .
The clutch pedal is connected to the disengagement mechanism either by a cable or , more
commonly , by a hydraulic system . Either way , pushing the pedal down operates the
disengagement mechanism which puts pressure on the fingers of the clutch diaphragm via a
release bearing and causes the diaphragm to release the clutch plate . With a hydraulic mechanism ,
the clutch pedal arm operates a piston in the clutch master cylinder . This forces hydraulic fluid
through a pipe to the cutch release cylinder where another operates the clutch disengagement
mechanism by a cable .
The other parts including the clutch fork , release bearing , bell – housing , bell housing

cover , and pilot bushing are needed to couple and uncouple the transmission . The clutch fork ,
which connects to the linkage , actually operates the clutch . The release bearing fits between the
clutch fork and the pressure plate assembly . The bell housing covers the clutch assembly . The
bell housing cover fastens to the bottom of the bell housing . This removable cover allows a
mechanic to inspect the clutch without removing the transmission and bell housing . A pilot
bushing fits into the back of the crankshaft and holds the transmission input shaft .
New Word
Clutch 离合器
Flywheel 飞轮
Stationary 静止的，不动的，不变的，固定的
Torsional 扭转的，扭力的
Crankshaft 曲轴，机轴
Stall 停止，停转，迟延
Mount 安放，设置，装上
Groove 凹槽，沟
Lever 杆，杠杆，控制杆
Pivot 支点
Gearbox 变速器
Retract 缩回，缩进，收回，
Compactness 紧密，简洁
Drive train 传动系
Drive shaft 传动轴
Pressure plate 压盘
Clutch disc 离合器从动盘，离合器摩擦片
Gear ratio 传动比
Release bearing 分离轴承
Release fork 分离拨叉
Master cylinder 主缸
Clutch pedal 离合器踏板
Coupling device 结合装置
At idle 空转。空闲
Couple with 与。。。。。。。结合
Ring gear 外形齿轮，齿圈
Pinion gear 小齿轮
Splined hub 花键毂
Cast iron 铸铁
Diaphragm spring 膜片弹簧
Thrust pad 止推片
Engage with 结合
Centrifugal force 离心力
Fulcrum ring 支撑环
Pilot bushing 导轴衬
Bell housing 钟形外壳，离合器壳

3.2 AUTOMATIC TRANSMISSION
The modern automatic transmission is by far , the most complicated mechanical component in
today?s automobile . It is a type of transmission that sifts itself . A fluid coupling or torque
converter is used instead of a manually operated clutch to connect the transmission to the engine .
There are two basic types of automatic transmission based on whether the vehicle is rear wheel
drive or front wheel drive . On a rear wheel drive car , the transmission is usually mounted to the
back of the engine and is located under the hump in the center of the floorboard alongside the gas
pedal position . A drive shaft connects the transmission to the final drive which is located in the
rear axle and is used to send power to the rear wheels . Power flow on this system is simple and
straight forward going from the engine , through the torque converter , then trough the
transmission and drive shaft until it reaches the final drive where it is split and sent to the two rear
transmission .
On a front wheel drive car , the transmission is usually combined with the final drive to form
what is called a transaxle . The engine on a front wheel drive car is usually mounted sideways in
the car with the transaxle tucked under it on the side of the engine facing the rear of the car . Front
axles are connected directly to the transaxle and provide power to front wheels . In this example ,
power floes from the engine , through the torque converter to a larger chain that sends the power
through a 180 degree turn to the transmission that is along side the engine . From there , the power
is routed through the transmission to the final drive where it is split and sent to the two front
wheels through the drive axles .
There are a number of other arrangements including front drive vehicles where the engine is
mounted front to back instead of sideways and there are other systems that drive all four wheels
but the two systems described here are by far the most popular . A much less popular rear and is
connected by a drive shaft to the torque converter which is still mounted on the engine . This
system is found on the new Corvette and is used in order to balance the weight evenly between the
front and rear wheels for improved performance and handling . Another rear drive system mounts
everything , the engine , transmission and final drive in the rear . This rear engine arrangement is
popular on the Porsche.
The modern automatic transmission consists of many components and systems that designed to
work together in a symphony of planetary gear sets , the hydraulic system, seals and gaskets , the
torque converter , the governor and the modulator or throttle cable and computer controls that has
evolved over the years into what many mechanical inclined individuals consider to be an art from .
Here try to used simple , generic explanation where possible to describe these systems .
3.2.1 Planetary gear sets
Automatic transmission contain many gears in various combinations . In a manual
transmission , gears slide along shafts as you move the shift lever from one position to another ,
engaging various sizes gears as required in order to provide the correct gear ratio . In an automatic
transmission , how ever , the gears are never physically moved and are always engaged to the
same gears . This is accomplished through the use of planetary gear sets .
The basic planetary gear set consists of a sun gear , a ring and two or more planet gears , all
remaining in constant mesh . The planet gears are connected to each other through a common
carrier which allows the gears to spin on shafts called “pinions” which are attached to the carrier .
One example of a way that this system can be used is by connecting the ring gear to the input

shaft coming from the engine , connecting the planet carrier to the output shaft , and locking the
sun gear so that it can?t move . In this scenario , when we turn the ring gear , the planets will
“walk” along the sun gear ( which is held stationary ) causing the planet carrier to turn the output
shaft in the same direction as the input shaft but at a slower speed causing gear reduction ( similar
to a car in first gear ) .
If we unlock the sun gear and lock any two elements together , this will cause all three elements
to turn at the same speed so that to output shaft will turn at the same rate of speed as the input
shaft . This is like a car that is third or high gear . Another way we can use a planetary gear set is
by locking the planet carrier from moving , then applying power to the ring gear which will cause
the sun gear to turn in opposite direction giving us reverse gear .
The illustration in Figure shows how the simple system described above would look in an actual
transmission . The input shaft is connected to the ring gear , the output shaft is connected to the
planet carrier which is also connected to a “Multi-disk” clutch pack . The sun gear is connected to
drum which is also connected to the other half of the clutch pack . Surrounding the outside of the
drum is a band that can be tightened around the drum when required to prevent the drum with the
attached sun gear from turning .
The clutch pack is used , in this instance , to lock the planet carrier with the sun gear forcing
both to turn at the same speed . If both the clutch pack and the band were released , the system
would be in neutral . Turning the input shaft would turn the planet gears against the sun gear , but
since noting is holding the sun gear , it will just spin free and have no effect on the output shaft .
To place the unit in first gear , the band is applied to hold the sun gear from moving . To shift from
first to high gear , the band is released and the clutch is applied causing the output shaft to turn at
the same speed as the input shaft .
Many more combinations are possible using two or more planetary sets connected in various
way to provide the different forward speeds and reverse that are found in modern automatic
transmission .
3.2.2
Clutch pack
A clutch pack consists of alternating disks that fit inside a clutch drum . Half of the disks are
steel and have splines that fit into groves on the inside of the drum . The other half have a friction
material bonded to their surface and have splines on the inside edge that fit groves on the outer
surface of the adjoining hub . There is a piston inside the drum that is activated by oil pressure at
the appropriate time to squeeze the clutch pack together so that the two components become
locked and turn as one .
3.2.3 One-way Clutch
A one-way clutch ( also known as a “sprag” clutch ) is a device that will allow a component
such as ring gear to turn freely in one direction but not in the other . This effect is just like that
bicycle , where the pedals will turn the wheel when pedaling forward , but will spin free when
pedaling backward .
A common place where a one-way clutch is used is in first gear when the shifter is in the drive
position . When you begin to accelerate from a stop , the transmission starts out in first gear . But
have you ever noticed what happens if you release the gas while it is still in first gear ? The
vehicle continues to coast as if you were in neutral . Now , shift into Low gear instead of Drive .

When you let go of the gas in this case , you will feel the engine slow you down just like a
standard shift car . The reason for this is that in Drive , one-way clutch is used whereas in Low , a
clutch pack or a band is used .
3.2.4 Torque Converter
On automatic transmission , the torque converter takes the place of the clutch found on standard
shift vehicles . It is there to allow the engine to continue running when the vehicle comes to a stop .
The principle behind a torque converter is like taking a fan that is plugged into the wall and
blowing air into another fan which is unplugged . If you grab the blade on the unplugged fan , you
are able to hold it from turning but as soon as you let go , it will begin to speed up until it comes
close to speed of the powered fan . The difference with a torque converter is that instead of using
air it used oil or transmission fluid , to be more precise .
A torque converter is a lager doughnut shaped device that is mounted between the engine and
the transmission . It consists of three internal elements that work together to transmit power to the
transmission . The three elements of the torque converter are the pump , the Turbine , and the
Stator . The pump is mounted directly to the torque housing which in turn is bolted directly to the
engine?s crankshaft and turns at engine speed . The turbine is inside the housing and is connected
directly to the input shaft of the transmission providing power to move the vehicle . The stator is
mounted to a one- way clutch so that it can spin freely in one direction but not in the other . Each
of the three elements has fins mounted in them to precisely direct the flow of oil through the
converter .
With the engine running , transmission fluid is pulled into the pump section and is pushed
outward by centrifugal force until it reaches the turbine section which stars it running . The fluid
continues in a circular motion back towards the center of the turbine where it enters the stator . If
the turbine is moving considerably slower than the pump , the fluid will make contact with the
front of the stator fins which push the stator into the one way clutch and prevent it from turning .
With the stator stopped , the fluid is directed by the stator fins to re-enter the pump at a “help”
angle providing a torque increase . As the speed of the turbine catches up with the pump , the fluid
starts hitting the stator blades on the back-side causing the stator to turn in the same direction as
the pump and turbine . As the speed increase , all three elements begin to turn at approximately the
same speed . Sine the ?80s , in order to improve fuel economy , torque converters have been
equipped with a lockup clutch which locks the turbine to the pump as the vehicle reaches
approximately 40-50 mph . This lockup is controlled by computer and usually won?t engage
unless the transmission is in 3
rd
or 4
th
gear .
3.2.5 Hydraulic System
The hydraulic system is a complex maze of passage and tubes that sends that sends
transmission fluid and under pressure to all parts of the transmission and torque converter and .
Transmission fluid serves a number of purpose including : shift control ,general lubrication and
transmission cooling . Unlike the engine ,which uses oil primary for lubrication ,every aspect of a
transmission ?s function is dependant on a constant supply of fluid is send pressure . In order to
keep the transmission at normal operating temperature , a portion of the fluid is send to through
one of two steel tubes to a special chamber that is submerged in anti-freeze in the radiator . Fluid
passing through this chamber is cooled and then returned to the transmission through the other
steel tube . A typical transmission has an avenge of ten quarts of fluid between the transmission ,
torque converter , and cooler tank , In fact , most of the components of a transmission are

constantly submerged in fluid including the clutch packs and bands . The friction surfaces on these
parts are designed to operate properly only when they are submerged in oil .
3.2.6 Oil Pump
The transmission oil pump ( not to confused with the pump element inside the torque
converter ) is responsible for producing all the oil pressure that is required in the transmission .
The oil pump is mounted to front of the transmission case and is directly connected to a flange on
the engine crankshaft , the pump will produce pressure whenever the engine is running as there is
a sufficient amount of transmission fluid available . The oil enters the pump through a filter that is
located at bottom of the transmission oil pan and travels up a pickup tube directly to the oil pump .
The oil is then sent , under pressure to the pressure regulator , the valve body and the rest of the
components , as required .
3.2.7 Valve Body
The valve body is the control center of the automatic transmission . It contains a maze of
channels and passages that direct hydraulic fluid to the numerous valves which when activate the
appropriate clutch pack of band servo to smoothly shift to the appropriate gear for each driving
situation . Each of the many valves in the valve body has a specific purpose and is named for that
function . For example the 2-3 shift valve activates the 2
nd
gear up-shift or the 3-2 shift timing
valve which determines when a downshift should occur .
The most important valve and the one that you have direct control over is the manual valve. The
manual valve is directly connected to the gear shift handle and covers and uncovers various
passages depending on what position the gear shift is paced in . When you place the gear shift in
Drive , for instance , the manual valve directs fluid to the clutch pack ( s ) that activates 1
st
gear . It
also sets up to monitor vehicle speed and throttle position so that it can determine the optimal time
and the force for the 1-2 shift . On computer controlled transmission , you will also have electrical
solenoids that are mounted in the valve body to direct fluid to the appropriate clutch packs or
bands under computer control to more precisely control shift points .
3.2.8 Computer Controls
The computer uses sensors on the engine and transmission to detect such things as throttle
position , vehicle speed , engine speed , engine load , stop light switch position , etc . to control
exact shift points as well as how soft or firm the shift should be . Some computerized transmission
even learn your driving style and constantly adapt to it so that every shift is timed precisely when
you would need it .
Because of computer controls , sports models are coming out with the ability to take manual
control of the transmission as through it were a stick shift lever through a special gate , then
tapping it in one direction or the other in order to up-shift at will . The computer monitors this
activity to make sure that the driver dose not select a gear that could over speed the engine and
damage it .
Another advantage to these “ smart” transmission is that they have a self diagnostic mode which
can detect a problem early on and warn you with an indicator light on the dash . A technician can
then plug test equipment in and retrieve a list of trouble codes that will help pinpoint where the
problem is .
3.2.9 Seals and Gaskets
An automatic transmission has many seals and gaskets to control the flow of hydraulic fluid and
to keep it from leaking out . There are two main external seals : the front seal and the rear seal .

The front seal seals the point where the torque converter mounts to the transmission case . This
seal allows fluid to freely move from the converter to the transmission but keeps the fluid from
leaking out . The rear seal keeps fluid from leaking past the output shaft .
A seal is usually made of rubber ( similar to the rubber in a windshield wiper blade ) and is used
to keep oil from leaking past a moving part such as a spinning shaft . In some cases , the rubber is
assisted by a spring that holds he rubber in close contact with the spinning shaft .
A gasket is a type of seal used to seal two stationary parts that are fasted together . Some
common gasket materials are : paper , cork , rubber , silicone and soft metal .
Aside from the main seals , there are also a number of other seals and gasket that vary from
transmission to transmission . A common example is the rubber O-ring that seals the shaft for the
shift control lever . This is the shaft that you move when you manipulate the gear shifter . Another
example that is common to most transmission is the oil pan gasket . In fact , seals are required
anywhere that a device needs to pass through the transmission case with each one being a potential
source for leaks .
New Words
Hump 圆形隆起
Transaxle 变速器驱动桥
Tuck 把一端塞进
Gasket 垫圈
Governor 油压调节器
Modulator 调制器
Spline 花键
Bond 结合
Strap 带,皮带
Doughnut 圆环图
Stator 定子,固定片
Maze 曲径
Submerge 浸没,淹没
Quart 夸脱
Downshift 调低速档
Optimal 最佳的
Solenoid 螺线管
Retrieve 重新得到
Cork 塞住
Manipulate 操作,使用
Fluid coupling 液力偶合器
Torque converter 液力变矩器
Planetary converter 行星齿轮组
Throttle cable 节气门拉线
Ring gear 齿圈
High gear 高速档
Reverse gear 倒档
Sprag clutch 锲块式单向离合器
Centrifugal force 离心力

Gear up 促进
Stick shift 顶杆档
Vacuum hose 真空软管
Throttle valve 节气阀
Leak out 泄露
Windshield wiper 风窗玻璃刮水器
3.3 The Differential System
When a vehicle is cornered the inner wheel moves through a shorter distance than the outer
wheel . This means that the inner wheel must slow down and the outer wheel must speed up .
During this period it is desirable that each driving maintains its driving action . The differential
performs these two tasks . The principle of the bevel type differential can be seen if the unit is
considered as two discs and a lever .
When the vehicle is traveling straight , the lever will divide the diving force equally and both
discs will move the same amount .
When the vehicle corners , the driving will still be divided equally but the inner disc will now
move through a smaller distance this will cause the lever to pivot about its center which will prize
forward the outer disc to give it a greater movement . This action shows that the torque applied to
each driving wheel is always equal – hence the differential is sometimes called a torque equalizer .
New Word
Desirable 想知道的
Disc 盘片,轮盘,轮圈
Prize 撬动,推动
Equalizer 平衡装置
3.4 Brake System
The breaking system is the most important system in cars . If the brakes fail , the result can be
disastrous . Brakes are actually energy conversion devices , which convert the kinetic energy
( momentum ) of the vehicle into thermal ( heat ) . When stepping on the brakes , the driver
commands a stopping force ten times as powerful as the force that puts the car in motion . The
braking system can exert thousands of pounds of pressure on each of the four brakes .
The brake system is composed of the following basic components : the “master cylinder” which
is located under the hood , and is directly connected to the brake pedal , converts driver foot?s
mechanical pressure into hydraulic pressure . Steel “brake lines” and flexible “brake hoses”
connect the master cylinder to the “slave cylinders” located at each wheel . Brake fluid , specially
designed to work in extreme condition , fills the system . “Shoes” and “Pads” are pushed by the
salve cylinders to contact the “drum” and “rotors” thus causing drag , which ( hopefully ) slows
the car .
The typical brake system consists of disk brakes in front and either disk or drum brakes in the
rear connected by a system of tubes and hoses that link the brake at each wheel to the master
cylinder .
Stepping on the brake pedal , a plunger is actually been pushing against in the master cylinder
which forces hydraulic oil ( brake fluid ) through a series of tubes and hoses to the braking unit at
each wheel . Since hydraulic fluid ( or any fluid for that matter ) cannot be compressed , pushing
fluid through a pipe is just like pushing a steel bar through pipe . Unlike a steel bar , however ,
fluid can be directed through many twists and turns on its way to its destination , arriving with the

exact same motion and pressure that it started with . It is very important that the fluid is pure
liquid and that there are no air bubbles in it . Air can compress , which causes a sponginess to the
pedal and severely reduced braking efficiency . If air is suspected , then the system must be bled to
remove the air . There are “bleeder screws” at each wheel and caliper for this purpose .
On a disk brakes , the fluid from the master cylinder is forced into a caliper where it pressure
against a piston . The piton , in-turn , squeezes two brake pads against the disk ( rotor ) which is
attached to the wheel , forcing it to slow down or stop . This process is similar to the
wheel ,causing the wheel to stop . In either case , the friction surface of the pads on a disk brake
system , on the shoes on a drum brake convert the forward motion of the vehicle into heat . Heat is
what causes the friction surfaces ( lining ) of the pads and shoes to eventually wear out and require
replacement .
Brake fluid is a special oil that has specifics properties . It is designed to withstand cold
temperatures without thickening as well as very high temperatures without boiling . ( If the brake
fluid should boil , it will cause you to have a spongy pedal and the car will be hard to stop ) .
The brake fluid reservoir is on top of the master cylinder . Most cars today have a transparent
reservoir so that you can see the level without opening the cover . The brake fluid lever will drop
slightly as the brake pads wear . This is a normal condition and no cause for concern . If the lever
drops noticeably over a short period of time or goes down to about two thirds full , have your
brakes checked as soon as possible . Keep the reservoir covered expect for the amount of time you
need to fill it and never leave a can of brake fluid uncovered . Brake fluid must maintain a very
high boiling point . Exposure to air will cause the fluid to absorb moisture which will lower that
boiling point .
The brake fluid travels from the master cylinder to the wheels through a series of steel tubes and
reinforced rubber hoses . Rubber hoses are only used in places that require flexibility , such as at
the front wheels , which move up and down as well as steer . The rest of the system uses
non-corrosive seamless steel tubing with special fittings at attachment points . If a steel line
requires a repair , the best procedure is to replace the complete line . If this is nit practical , a line
can be repaired using special splice fittings that are made for brake system repair . You must never
use brass “compression” fittings or copper tubing repair a brake system . They are dangerous and
illegal .
3.4.1 Other Components in the Hydraulic System
Proportioning Valve or Equalizer Valve
These valves are mounted between the master cylinder and the rear wheels . They are designed
to adjust the pressure between the front and the rear brakes depending on how hard you are
stopping . The shorter you stop , the more of the vehicle?s weight is transferred to the front wheels ,
in some cases , causing the rear to lift and the front to dive . These valves are designed to direct
more pressure to the front and less pressure to the harder you stop . This minimizes the chance of
premature lockup at the rear wheels .
Pressure Differential Valve
This valve is usually mounted just below the master and is responsible for turning the brake
warning light on when it detects a malfunction . It measures the pressure from the two sections of
the master cylinder and compares them . Since it is mounted ahead of the proportioning or
equalizer valve , the two pressure it detects should be equal . If it detects a difference , it means
that there is probably a brake fluid leak somewhere in the system .

Combination Valve
The Combination valve is simply a proportioning valve and a pressure differential valve that is
combine into one unit .
The parking brake system controls the rear brakes through a series of steel cables that are
connected to either a hand lever or a foot pedal . The ideal is that the system is fully mechanical
and completely bypasses the hydraulic system so that the vehicle can be brought to a stop even if
there is a total brake failure .
New Word
Disastrous 灾难性的
Hood 发动机罩
Plunger 活塞,柱塞
Sponginess 轻软有弹性的
Malfunction 故障
Bypass 设旁路,与会
Corkscrew 活塞推杆
Inoperative 不起作用的
Booster 调压器,助力器
Slam 砰地踏下
Screech 发出尖锐的声音
Thumping 极大的
Momentarily 即刻
Thermal energy 热能
Master cylinder 制动主缸
Brake pedal 制动踏板
Brake hose 制动软管
Salve cylinder 轮缸
Drum brake 鼓式制动器
Brake shoe 制动蹄
Bleeder screw 放气螺钉
Spongy pedal 踏板发软
Panic stop 紧急停车,紧急制动
Friction lining 摩擦衬片
Proportioning valve 比列阀
Equalizer valve 平衡阀
Pressure differential valve 差压阀
Combination valve 组合阀
3.5 Steering System
3.5.1 Basic Parts of Steering System
The steering converts the steering –wheel rotary motion into a turn motion of the steered
wheels of the vehicle .
The basic steering system in most cars is the same . The steering gear of steering box is the
heart of the steering system .This is usually next to the engine . A shaft extends from the back of
the steering gear . This shaft is connected to the steering column or steering shaft . The steering
wheel is at the top of the steering column . Another shaft comes from the bottom of the steering

gear . This shaft connects to the arms , rods , and links . This parts assembly , called the steering
linkage , connects the steering gear to the parts at the wheels . The wheels and tires mount to the
steering knuckles , As shown in fig , the knuckles are pivoted at the top and bottom . Thus , the
wheels and rites can turn from side top side .
While the steering system may look complicated , it works quite simply . When a driver drives
a car straight down the road , the steering gear is centered . The gear holds the linkage centered so
that the wheels and tires point straight ahead . When the driver turns the steering wheel , the
steering shaft rotates and the steering gear moves toward that side . The shaft coming out the
bottom of the steering gear turns , as well . When the shaft turns , it pulls the linkage to one side
and makes the steering knuckles turn slightly about their pivot points . Thus , the steering knuckle ,
spindle , wheels , and tires turn to one side , causing the car to turn .
The type of steering layout depends on the suspension system . The beam axle used on heavy
commercial vehicle has a king pin fitted at each end of the axle and this pin is the pivot which
allows the wheels to be steered . Cars have independent suspension and this system has ball joints
to allow for wheel movement .
New Word
Steering box 转向器
Steering column 转向柱管
Steering linkage 转向传动机构
Steering knuckle 转向节
King pin 主销
Track rod 转向杆
Drop arm 摇臂
Stub axle 转向轴
Turn about 绕…….转动
Spindle 转向节(轴端)
Swivel joint 转向节
Types of Steering System
A steering box must have the following qualities :
1) no play in the straight-ahead position
2)low friction , resulting in high efficiency
3)high rigidity ,
4 readjustability
For these reasons , these are several different types of steering gears . However , there are only
two types of steering systems : manual steering systems and power steering systems . In the
manual type , the driver dose all the work of turning the steering wheel , steering gear , wheels and
tires . In the power , hydraulic fluid assists the operation so that driver effort is reduced .
On today?s cars , two types of steering systems commonly are used to provide steering control :
1) recirculating ball
2) rack and pinion
Either of these two types of steering mechanisms may be a fully mechanical systems or a power
–assisted system .
3.6 Front Suspension
The front suspension is more complicated than the rear suspension . This is because the front

wheels must move in several different directions . The wheels must move up and down with the
suspension and turn left to right with the steering . Since the car goes in the direction in which the
front wheels point , the alignment of the front wheels is important . The wheels must point in just
the right direction for the car to move straight down the road and turn properly .
Modern cars uses an independent front suspension . In this system , each wheel mounts
separately to the frame and has its own individual spring and shock absorber . Thus , the wheels
act independently of one another . When one wheel hits a bump or hole in the road , the other
wheel dose no9t deflect .
3.6.1 Front Wheel Alignment
As a car moves down the high-way , the suspension moves the front wheels up and down . At the
same time , the steering mechanism moves the front wheels , sometimes to make turns and
sometimes to make the travel straight . The angular relationship between the wheels and
suspension parts during this motion is the front-end geometry . Since the geometry can change the
alignment of front wheels is adjustable . You can change the adjustment to compensate for spring
sag .
The alignment of the front wheels affects the operation of a car . Poor alignment ca make a car
pull to one side and stop the front wheels from returning to the straight-ahead position after a turn .
The three normally adjustable angles are caster , camber , and toe .
1. Toe-in
Toe-in specifies the degree to which non-parallel front wheels are closer together at the front
than at the rear measured at the edges of the rims at the wheel center height . front non-driven
wheels , toe-in is approximately 2-3 mm , and between +3mm and-2 mm for driven wheels .
Toe- in reduces the tendency of the wheels to shimmy .
2. Kingpin Angle
The kingpin angle is the inclination of the steering axis relative to the longitudinal plane ,
measured in the transverse plane of the vehicle . Kingpin angle is 2°-16°and determines the
steering aligning torque in conjunction with steering offset and wheel caster . It is measured only
with the vehicle loaded .
3. Camber
Camber is the inward or outward tilt of the wheel at the top . Inward tilt is negative camber and
outward tilt is positive camber . The tilt of the wheel is measured inn degrees and is adjustable on
many vehicles .
4. Caster
Caster is the forward or backward of spindle or steering the knuckle at the top when viewed
from the side . Forward tilt is negative caster and backward tilt positive caster . Caster is measured
in the number of degrees that it is forward or backward from true vertical and is adjustable on
many vehicle .
New Word
Front wheel alignment 前轮定位
Sag 倾斜
Caster 主销倾角
Camber 车轮倾角
Toe 轮胎缘距
Toe-in 轮胎前束

Kingpin 主销
Align 矫正,对准
Positive camber 车轮外倾角
Negative camber 车轮内倾角
Deviate 偏离
Positive caster 主销正倾角
Negative caster 主销负倾角
3.6.2 Rear Suspension
The purpose of the rear suspension is to support the weight of the rear of the vehicle . As with
the front suspension , this system contributes to the stability and ride of the vehicle . Rear
suspension may be of the solid axle or independent design . Many cars have solid axle rear
suspension . Either design may have different kinds of springs , including torsion bars . However ,
the coil spring and leaf spring types are most popular .
3.7 Wheels and Tires
To maintain grip when a vehicle is traveling at speed over a bumpy surface , a wheel must be
light in weight . Also it must be strong , cheap to produce , easy to clan and simple to remove .
3.7.1. Wheels
The structure of the wheel is shown in Fig . The rim is made in one piece , with the wheel
center welded or riveted to it . Most modern vehicles use the drop center type . This drop center
provides a well for tire bead to drop into for tire removal . A slight hump at the head ledge holds
the tire in place should it go flat while driving .
3.7.2. tires
Tires are important to your safety and comfort . They transmit the driving and braking power to
the road . The car?s directional control , road- ability and riding comfort are greatly dependent on
the tires . Tires should be selected and maintained with great care .
There are two basic types of tires – those with inner tubes and those without ( called “tubeless”
tires ) . Most modern automobile tires are of the tubeless type . Truck and bus tire are usually of
the tube type .
Tires are made of several layers of nylon , rayon , or polyester fabric bonded together with belts
of rayon , fiberglass , or steel cord . The rubber used in tires is a blend of natural and synthetic
rubber .

New Words
Rim 轮缘
Bead 胎边,轮缘
Hump 凸起
Inner tube 内胎
Rayon 人造丝
Polyester 多元脂
Casing plies 帘布层
Rubber chafer 橡胶胎圈