CHAPTER1AUTOMOTIVE BASICS
1.1Principal Components
Today's average car contains more than15,000separate,individual parts that must work together.These parts can grouped into four major categories:engine,body,chassis and electrical equipment.
1.2Engine
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.
1.3Body
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.
1.4Chassis
The chassis is an assembly of those systems that are the major operating part of a vehicle. The chassi
s 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.
1.5Electrical 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
CHAPTER2INTERNAL COMBUSTION ENGINE
2.1principle of operation
2.1.1Engine 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.
2.1.2Engine 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 a four-stroke having a capacity of two liters(2000cm)has a cylinder swept volume of50cm.
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..
2.1.3The
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 t
he 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
汽车构造
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 compr
essed 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.
2.1.4Engine 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