CHAPTER 1 AUTOMOTIVE BASICS
1.1 Principal Components
Today's average car contains more than 15,000 separate, individual parts that must work
together. These parts can grouped into four major categories: engine, body, chassis and
electrical equipment.
1.2 Engine
The engine acts as the power unit. The internal combustion engine is most common: this
obtains its power by burning a liquid fuel inside the engine cylinder. There are two types of
engine :gasoline(also called a spark-ignition engine) and diesel(also called a
compression-ignition engine).Both engines are called heat engines; the burning fuel
Administrator
铅笔
generates heat which causes the gas inside the cylinder to increase its pressure and supply
power to rotate a shaft connected to the transmission.
1.3 Body
An automobile body is a sheet metal shell with windows, doors, a hood, and a trunk deck built
into it. It provides a protective covering for the engine, passengers, and cargo. The body is
designed to keep passengers safe and comfortable. The body styling provides an attractive,
colorful, modern appearance for the vehicle.
1.4 Chassis
The chassis is an assembly of those systems that are the major operating part of a vehicle.
The chassis includes the transmission, suspension, steering, and brake systems.
Transmission systems ― conveys the drive to the wheels. The main components are clutch,
gearbox, driveshaft, final drive, and differential.
Suspension― absorbs the road shocks.
Steering― controls the direction of the movement.
Brake― slows down the vehicle.
1.5 Electrical Equipment
The electrical system supplies electricity for the ignition, horn, lights, heater, and starter. The
electricity level is maintained by a charging circuit. This circuit consists of the battery,
alternator (or generator). The battery stores electricity. The alternator changes the engine's
mechanical energy into electrical energy and recharges the battery.
New Words
Principal component 主要部件
category 种类,类型
body 车身
chassis 底盘
layout 布置
power unit 动力装置
internal combustion engine 内燃机
cylinder 汽缸
gasoline 汽油
spark 火花
ignition 点燃,点火
diesel 柴油机
compression 压缩
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?
2. What are the common types of a vehicle according to body styling?
3. Which systems does a chassis include and what are the main functions of the chassis?
4. Why are suspension systems used on vehicles?
CHAPTER2 INTERNAL COMBUSTION ENGINE
2.1 principle of operation
2.1.1 Engine and power
Engine is used to produce power. The chemical energy in fuel is converted to heat by the
burning of the fuel at a controlled rate. This process is called combustion. If engine combustion
occurs with the power chamber. ,the engine is called internal combustion engine. If combustion
takes place outside the cylinder, the engine is called an external combustion engine.
Engine used in automobiles are internal combustion heat engines. Heat energy released in the
combustion chamber raises the temperature of the combustion gases with the chamber. The
increase in gas temperature causes the pressure of the gases to increase. The pressure developed
within the combustion chamber is applied to the head of a piston to produce a usable mechanical
force, which is then converted into useful mechanical power.
2.1.2 Engine Terms
Linking the piston by a connecting rod to a crankshaft causes the gas to rotate the shaft through
half a turn. The power stroke “uses up” the gas , so means must be provided to expel the burnt gas
and recharge the cylinder with a fresh petrol-air mixture :this control of gas movement is the duty
of the valves ;an inlet valve allows the new mixture to enter at the right time and an exhaust valve
lets out the burnt gas after the gas has done its job. Engine terms are :
TDC(Top Dead Center):the position of the crank and piston when the piston is farther away
from the crankshaft.
BDC(Bottom Dead Center):the position of the crank and piston when the piston is nearest to the
crankshaft.
Stroke : the distance between BDC and TDC; stroke is controlled by the crankshaft.
Bore : the internal diameter of the cylinder.
Swept volume : the volume between TDC and BDC.
Engine capacity : this is the swept volume of all the cylinder e.g. a four-stroke having a capacity
of two liters(2000cm) has a cylinder swept volume of 50cm.
Clearance volume: the volume of the space above the piston when it is at TDC.
Compression ratio = (swept vol + clearance vol)\(clearance vol)
Two-stroke : a power stroke every revolution of the crank.
Four-stroke : a power stroke every other revolution of the crank..
2.1.3 The Four-stroke Spark-ignition Engine Cycle
The spark-ignition engine is an internal-combustion engine with externally supplied in
ignition , which converts the energy contained in the fuel to kinetic energy.
The cycle of operations is spread over four piston strokes. To complete the full cycle it takes
two revolutions of the crankshaft.
The operating strokes are :
This stroke introduces a mixture of atomized gasoline and air into the cylinder. The stroke
starts when the piston moves downward from a position near the top of the cylinder. As the
piston moves downward, a vacuum, or low-pressure area, is created.
During the intake stroke, one of the ports is opened by moving the inlet valve. The exhaust
valve remains tightly closed.
Compression stroke
As the piston moves upward to compress the fuel mixture trapped in the cylinder, the valves
are closed tightly. This compression action heats the air/fuel mixture slightly and confines it
within a small area called the combustion chamber.
Power stroke
Just before the piston reaches the top of its compression stroke, an electrical spark is
introduced from a spark plug screwed into the cylinder head.
The spark ignites the compressed, heated mixture of fuel and air in the combustion chamber
to cause rapid burning. The burning fuel produces intense heat that causes rapid expansion
of the gases compressed within the cylinder. This pressure forces the piston downward. The
downward stroke turns the crankshaft with great force.
Exhaust stroke
Just before the bottom of the power stroke, the exhaust valve opens. This allows the piston,
as it moves upward, to push the hot, burned gases out through the open exhaust valve.
Then, just before the piston reaches its highest point, the exhaust valve closes and the inlet
valve opens. As the piston reaches the highest point in the cylinder, known as TDC, it starts
back down again. Thus, one cycle ends and another begins immediately.
2.1.4 Engine Overall Mechanics
The engine has hundreds of other parts . The major parts of engine are engine block , engine
heads, pistons, connecting rods, crankshaft and valves. The other parts are joined to make systems.
These systems are the fuel system, intake system, ignition system, cooling system, lubrication
system and exhaust system. Each of these systems has a definite function. These systems will
discussed in detail later.
NEW WORD
Piston 活塞
Connecting rod 连杆
Crankshaft 曲轴
Power stoke 活塞行程
Expel 排出
Valve 气阀
inlet(intake) valve 进气阀
exhaust valve 排气阀
term 术语
TDC 上止点
BDC 下止点
Bore 缸径
swept volume 有效容积
engine capacity 发动机排量
clearance volume 余隙容积,燃烧室容积
compression ratio 压缩比
revolution 旋转,转数
every other 每隔一个
cycle 循环
spread over 分布,遍及
intake stroke 进气行程
compression stroke 压缩行程
knock 敲缸,敲打
exhaust stroke 排气行程
engine block 发动机缸体
lubrication 润滑
2.2 Engine Block and Cylinder Head
2.2.1 Engine Block
The engine block is the basic frame of the engine. All other engine parts either fit inside it or
fasten to it. It holds the cylinders, water jackets, and oil galleries. The engine block also holds
the crankshaft, which fastens to the bottom of the block. The camshaft also fits inside the
block, except on overhead-cam engines (OHC). In most cars, this block is made of gray iron,
or an alloy (mixture) of gray iron and other metals, such as nickel or chromium. Engine blocks
are castings.
Some engine blocks, especially those in smaller cars, are made of cast aluminum. This metal
is much lighter than iron. However, iron wears better than aluminum. Therefore, the cylinders
in most aluminum engines are lined with iron or steel sleeves. These sleeves are called
cylinder sleeves. Some engine blocks are made entirely of aluminum.
2.2.2 Cylinder Head
The cylinder head fastens to the top of the block, just as a roof fits over a house. The
underside forms the combustion chamber with the top of the piston. The most common
cylinder head types are the hemi, wedge, and semi-hemi. All three of these terms refer to the
shape of the engine's combustion chamber. The cylinder head carries the valves, valve
springs and the rockers on the rocker shaft, this part of the valve gear being worked by the
push-rods. Sometimes the camshaft is fitted directly into the cylinder head and operates on
the valves without rockers. This is called an overhead camshaft arrangement. Like the
cylinder block, the head is made from either cast iron or aluminum alloy.
2.2.3 Gasket
The cylinder head is attached to the block with high-tensile steel studs. The joint between the
block and the head must be gas-tight so that none of the burning mixture can escape. This is
achieved by using cylinder head gasket. This is a sandwich gasket, i.e. a sheet of asbestos
between two sheets of copper, both these materials being able to withstand the high
temperature and pressures within the engine.
2.2.4 Oil Pan or Sump
The oil pan is usually formed of pressed steel. The oil pan and the lower part of the cylinder
block together are called the crankcase; they enclose, or encase, the crankshaft. The oil
pump in the lubricating system draws oil from the oil pan and sends it to all working parts in
the engine. The oil drains off and runs down into the pan. Thus, there is constant circulation
of oil between the pan and the working parts of the engine.
New Words
engine block 缸体
cylinder head 气缸盖
fasten 使固定
water jacket 水套
oil gallery 油道
camshaft 凸轮轴
overhead-cam(OHC) 顶置凸轮
gray iron 灰铸铁
alloy 合金
nickel 镍
chromium 铬
casting 铸件
head cover 汽缸盖罩
intake manifold 进气总管
distributor 分电器
oil pan 油底壳
aluminum 铝
be lined with 镶有
cylinder sleeve 气缸套
hemi 半球形
wedge 楔型,楔入
semi-hemi 准半球形
rocker 摇臂
push-rod 推杆
gasket 衬垫
high-tensile 高强度的
stud 螺栓
gas-tight 密封的
asbestos 石棉
crankcase 曲轴箱,曲柄箱
encase 封闭,把…包起来
drain off 排出,流出
Review Question
1. What do TDC, BDC, stroke, compression ratio and engine capacity stand for?
2. How do you calculate swept volume and compression ratio?
3. What controls the length of the stroke?
4. List the main parts of the engine overall mechanics?
5. What are the main function of the engine block?
2.3 Piston Connecting Rod and Crankshaft
2.3.1 Piston Assembly
The piston is an important part of a four-stroke cycle engine. Most pistons are made
from cast aluminum. The piston , through the connecting rod, transfers to the
crankshaft the force create by the burning fuel mixture. This force turns the
crankshaft .Thin, circular , steel bands fit into grooves around the piston to seal the
bottom of the combustion chamber. These bands are called piston rings. The grooves
into which they fit are called ring grooves. A piston pin fits into a round hole in the
piston . The piston pin joins the piston to the connecting rod . The thick part of the
piston that holds the piston is the pin boss.
The piston itself , its rings and the piston pin are together called the piston
assembly.
2.3.2.Piston
To withstand the heat of the combustion chamber, the piston must be strong. It
also must be light, since it travels at high speeds as it moves up and down inside the
cylinder. The piston is hollow. It is thick at the top where it take the brunt of the heat
and the expansion force. It is thin at the bottom, where there is less heat. The top part
of the piston is the head , or crown . The thin part is the skirt The sections between the
ring grooves are called ring lands.
The piston crown may be flat , concave ,dome or recessed . In diesel engine , the
combustion chamber may be formed totally or in part in the piston crown , depending
on the method of injection . So they use pistons with different shapes.
2.3.3Piston Rings
As Fig.2-9 shows , piston rings fit into ring grooves near the of the piston. In
simplest terms, piston rings are thin, circular pieces of metal that fit into grooves in
the tops of the pistons.
In modern engines ,each piston has three rings. (Piston in older engines
sometimes had four rings, or even five.) The ring’s outside surface presses against the
cylinder walls. Rings provide the needed seal between the piston and the cylinder
walls. That is, only the rings contact the cylinder walls. The top two rings are to keep
the gases in the cylinder and are called compression rings. The lower one prevents the
oil splashed onto the cylinder bore from entering the combustion chamber , and is
called an oil ring. Chrome-face cast-iron compression rings are commonly used in
automobile engines. The chrome face provide a very smooth , wear-resistant surface.
During the power stoke , combustion pressure on the combustion rings is very
high. It causes them to untwist . Some of the high-pressure gas gets in back of the
rings. This force the ring face into full contact with the cylinder wall. The combustion
pressure also holds the bottom of the ring tightly against the bottom of the ring groove.
Therefore , high combustion pressure causes a tighter seal between the ring face and
the cylinder wall.
2.3.4 Piston Pin
The piston pin holds together the piston and the connecting rod . This pin fits
into the piston pin holes and into a hole in the top end of the connecting rod. The top
end of is much smaller than the end that fits on the crankshaft . This small end fits
inside the bottom of the piston . The piston pin
fits through one side of the piston , through the
small end of the rod , and then through the other
side of the piston . It holds the rod firmly in place in
the center of the piston. Pins are made of
high-strengh steel and have a hollow center . Many
pins are chrome-plated to help them wear better.
2.3.3 Connecting rod
The connecting rod is made of forged
high-strength steel . It transmits and motion from the piston to the crankpin on
the crankshaft . The connecting rod little end is connected to the piston pin . A bush
made from a soft metal , such as bronze , is used for this joint . The lower end of the
connecting rod fits the crankshaft journal . This is called the big end . For this big-end
bearing , steel-backed lead or tin shell bearing are used . These are the same as those
used for the main bearings . The split of the big end is sometimes at an angle , so that
it is small enough to be withdrawn through the cylinder bore . The connecting rod is
made from forged alloy steel .
2.3.5 Crankshaft
The crankshaft , in conjunction with the connecting rod , coverts the
reciprocating motion of the piston to the rotary motion needed to drive the vehicle . It
is usually made from carbon steel which is alloyed with a small proportion of
nickel .The main bearing journals fit into the cylinder block and the big end journals
align with the connecting rods .At the rear end of the crankshaft is attached the
flywheel , and at the front end are the driving whells for the timing gears , fan ,
cooling water and alternator .
The throw of the crankshaft , the distance between the main journal and the
big end centers , controls the length of the stroke . The stroke is double the throw ,
and the stroke-length is the distance that the piston travels from TDC to BDC and vice
versa .
2.3.6 Flywheel
The flywheel is the made from carbon steel . It fit s onto the rear of the crankshaft .
As well as keeping the engine rotating between power strokes it also carries the
clutch , which transmits the drive to the transmission , and has the starter ring gear
around its circumference . There is only one working stroke in four so a flywheel is
needed to drive the crankshaft during the time that the engine is performing the
non-power strokes .
New Words
Comprise 由。。。。。。。组成,包含
Inter 惯性,惯量
Radius 半径,范围
Circular 圆形的
Steel band 钢圈
Fit into 放入,放进
Groove 凹槽
Piston pin 活塞销
Pin boss 活塞销凸台
Withstand 抵抗
Hollow 空的
Brunt 冲力
Crown 活塞顶
Skirt 裙部
Ring land 环带
Concave 凹的,凹入的
Dome 圆顶
Recessed 隐蔽的
Cylinder wall 气缸壁
Cylinder bore 缸筒
Splash 飞溅
chrome-face
表
关于同志近三年现实表现材料材料类招标技术评分表图表与交易pdf视力表打印pdf用图表说话 pdf
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 , wit