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
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 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.
1.5  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 th
e 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 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.
汽车构造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 r
eaches 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