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An individual cycle comprises four strokes: 1, intake stroke; 2, compression stroke; 3, power stroke and 4, exhaust stroke.. The intake stroke on the diesel engine draws only air into th

TECHNICAL ENGLISH for

AUTOMOTIVE ENGINEERING

(FIRST EDITION)

Edited by: Nguyen Tuan Hung, MEng

Mechanical Engineering Faculty

Ho Chi Minh City University of Industry

Ministry of Industry

Ho Chi Minh City, September-2007

AUTOMOTIVE INTRODUCTION 1

Chapter 1: Automotive Introduction

1 What are the main functions of automobile nowadays?

2 How automobile can be classified?

3 How many major systems in automobile?

II. READING

Part a: Automobile Introduction

Automobile, self-propelled vehicle used primarily on public roads but adaptable to other

surfaces Automobiles changed the world during the 20th century From the growth of suburbs to the development of elaborate road and highway systems, the so-called horseless carriage has forever altered the modern landscape The manufacture, sale, and servicing of automobiles have become key elements of industrial economies But along with greater mobility and job creation, the automobile has brought noise and air pollution, and automobile accidents rank among the leading causes of death and injury throughout the world But for better or worse, the 1900s can be called the Age of the Automobile, and cars will no doubt continue to shape our culture and economy well into the 21st century

Automobiles are classified by size, style, number of doors, and intended use The typical automobile, also called a car, auto, motorcar, and passenger car, has four wheels and can carry

up to six people, including a driver Larger vehicles designed to carry more passengers are called vans, minivans, omnibuses, or buses Those used to carry cargo are called pickups or trucks, depending on their size and design Minivans are van-style vehicles built on a passenger car frame that can usually carry up to eight passengers Sport-utility vehicles, also known as SUVs, are more rugged than passenger cars and are designed for driving in mud or snow

The automobile is built around an engine Various systems supply the engine with fuel, cool it during operation, lubricate its moving parts, and remove exhaust gases it creates The engine produces mechanical power that is transmitted to the automobile’s wheels through a drivetrain, which includes a transmission, one

or more driveshafts, a differential gear, and axles Suspension systems, which include springs and shock absorbers, cushion the ride and help protect the vehicle from being damaged by bumps, heavy loads, and other stresses

Fig1.1: The drive-train

Wheels and tires support the vehicle on the roadway and, when rotated by powered axles, propel the vehicle forward or backward Steering and braking systems provide control over direction and speed

An electrical system starts and operates the engine, monitors and controls many aspects

of the vehicle’s operation, and powers such components as headlights and radios Safety features such as bumpers, air bags, and seat belts help protect occupants in an accident

Fig 1.3: Four-bar twist beam

axle by Renault, with 2

torsion bar springs both for

the left and right axle sides

Fig 1.2: A multi-link rear axle, – a type of suspension system which is progressively replacing the semi-trailing arm axle, and consists of at least one trailing arm on each side

Fig 1.4: Steering and suspension system

AUTOMOTIVE INTRODUCTION 1

Part b: Automobile Physical Configuration

Fig 1.5: Automobile systems

The automobile configuration is depicted in Figure 1.5, in which many of the important

automotive systems are illustrated These systems include the following:

on

III. NEW WORDS

Look up for the new words

Self-propelled vehicle (n) Doubt (n, v) Carriage (n) Differential (n) Suspension systems (n) Shape (v, n) Rugged (a) Gear (n)

Steering system (n) Classify (v) Mud (n) Axles (n)

Sport-utility vehicles (n) Van (n) Snow (n) So-called (a)

braking system (n) Omnibuses (n) Wheel (n) Springs (n)

For better or worse (exp) Pickup (n) Drive-train (n) shock absorbers (n) Element (n) Landscape (n) Transmission (n) cushion (n)

Elaborate (a) bumps (n) electrical system (n) headlight (n)

Answer these questions:

Why do we call automobiles as self-propelled vehicles?

Decide if these statements are True or False:

1 Automobiles can be use primarily on public roads ( True False)

2 Servicing of automobiles has become key elements of industrial economies.( True False)

3 Automobile industries create only mobilities and jobs ( True False)

4 The 21st

century can be called the Age of the Automobile ( True False)

5 Vans are designed to carry people ( True False)

6 Minivans can carry more than 9 people ( True False)

7 Sport-utility vehicles are more rugged than passenger cars ( True False)

8 Sport-utility vehicle can be drived in mud or snow ( True False)

AUTOMOTIVE INTRODUCTION 1

9 The engine produces mechanical power ( True False)

10 Drivetrain consist of a transmission, one or more driveshafts, a differential gear, and axles ( True False)

11 Suspension systems includes springs and shock absorbers and cushion ( True False)

12 Wheels and tires are rotated by powered axles ( True False)

13 Steering and braking systems provide control over direction and speed ( True False)

14 Electrical system only starts and operates the engine ( True False)

15 Bumpers, air bags, and seat belts are safety features of automobile ( True False)

VI WORD(S) SELECTIONS

Select ONE word(s) in the below box and fill in the gap in column B with its meaning word in column A

Self-propelled

vehicle

g The system locates car’s position

i Vehicles used to carry cargo

b Capable of d The system

transmit engine’s power to the wheels

f The system controls car’s direction

h

Double-deck bus

j The system cools the engine during its operation

Chapter 2: The Engine

1 Name some kinds of engines you know

2 Do you have a four-stroke engine in your house? How powerful is it?

3 What type of fuel does a four-stroke engine run on?

II. READING

1 The reciprocating engine

The engine is the heart of a car although it is normally hidden under the bonnet The engine is exposed in a motorcycle but the detailed mechanisms are not visible

There are two main types of reciprocating engine, the four-stroke and the two-stroke engine:

1.1 The petrol engine

1.1.1 Four-stroke engine

Fig2.2: Basic operations of four-stroke cycle engine

Fig 2.1: Cutaway of four- stroke cycle petrol engine (courtesy of Volvo Car Corporation)

THE ENGINE 2

The four-stroke engine is also referred to as the Otto cycle engine after its inventor N.A Otto Most cars use the four-stroke engine An individual cycle comprises four strokes: 1, intake stroke; 2, compression stroke; 3, power stroke and 4, exhaust stroke These four strokes repeat to generate the crankshaft revolution

+ Intake stroke: the intake stroke draws air and fuel into the combustion chamber The piston

descends in the cylinder bore to evacuate the combustion chamber When the inlet valve opens, atmospheric pressure forces the air-fuel charge into the evacuated chamber As a result, the combustible mixture of fuel and air fills the chamber

+ Compression stroke: at the end of the intake stroke, both inlet and exhaust valves are

closed The inertial action of the crankshaft in turn lifts the piston which compresses the mixture The ratio of the combustion chamber volume before and after compression is called the compression ratio

+ Power stroke: when the piston ascends and reaches top dead center, an electric current

ignites the spark plug and as the mixed gas burns, it expands and builds pressure in the combustion chamber The resulting pressure pushes the piston down with several tons of force

+ Exhaust stroke: during the exhaust stroke, the inlet valve remains closed whilst the exhaust

valve opens The moving piston pushes the burned fumes through the now open exhaust port and another intake stroke starts again

During one cycle, the piston makes two round trips and the crankshaft revolves twice The inlet and exhaust valves open and close only once The ignition plug also sparks only once A

petrol engine, whether four- or two-stroke, is called a Spark Ignition (SI) engine because it

fires with an ignition plug The four-stroke-cycle engine contains the lubricating oil in the crankcase The oil both lubricates the crankshaft bearings and cools the hot piston

1.1.2 The two-stroke engine

The two-stroke engine is similar to that of the four-stroke-cycle engine in its reciprocating mechanism It uses the piston-crankshaft mechanism, but requires only one revolution of the crankshaft for a complete power-producing cycle The two-stroke engine does not use inlet and exhaust valves The gas exchange is implemented by scavenging and exhaust port-hole openings in the bore wall The upward and downward motion of the piston simultaneously opens and closes these port-holes The air-fuel mixture then goes in or out of the combustion chamber through the port-holes Combustion takes place at every rotation of the crankshaft

In the two-stroke engine, the space in the crankcase works as a pre-compression chamber for each successive fuel charge The fuel and lubricating oil are premixed and introduced into the crankcase, so that the crankcase cannot

be used for storing the lubricating oil When combustion occurs in the cylinder, the combustion pressure compresses the new gas

in the crankcase for the next combustion The burnt gas then exhausts while drawing in new gas The lubricating oil mixed into the air-fuel mixture also burns

Since the two-stroke engine does not use a valve system, its mechanism is very simple The power output is fairly high because it achieves one power stroke per two revolutions

of the crankshaft However, although the power output is high, it is used only for small motorcycle engines and some large diesel

applications Since the new gas pushes out the burnt gas, the intake and exhaust gases are not clearly separated As a result, fuel consumption is relatively high and cleaning of the exhaust gas by a catalytic converter is difficult

1.2 The diesel engine

The name diesel comes from the inventor of the diesel engine, R Diesel There are both four- and two-stroke-cycle diesel engines Most automotive diesels are four-stroke engines The intake stroke on the diesel engine draws only air into the cylinder The air is then compressed during the compression stroke At near maximum compression, finely atomized diesel fuel (a gas oil having a high flashpoint) is sprayed into the hot air, initiating auto ignition of the mixture During the subsequent power stroke, the expanding hot mixture works

on the piston, then burnt gases are purged during the exhaust stroke

Since diesel engines do not use a spark plug, they are also referred to as compression ignition (CI) engines In the case of petrol engines, too high a temperature in the combustion

chamber ignites the petrol spontaneously When this occurs, the plug cannot control the moment of ignition This unwanted phenomenon is often referred to as ‘knocking’

The diesel is an injection engine A petrol engine normally needs a throttle valve to control airflow into the cylinder, but a diesel engine does not Instead, the diesel uses a fuel injection pump and an injector nozzle sprays fuel right into the combustion chamber at high pressure The amount of fuel injected into the cylinder controls the engine power and

speed There are two methods by which

fuel is injected into a combustion chamber, direct or indirect injection

With direct injection engines (DI)

the fuel is injected directly into the cylinder and initial combustion takes place within the bowl that is machined

into the piston head itself With indirect injection engines (IDI) the fuel is

injected and initial combustion takes place in a small pre combustion chamber formed in the cylinder head The burning gases then expand into the cylinder where combustion continues

2 Advantages and disadvantages of reciprocating engines

-> An engine with a piston-cylinder mechanism has the following advantages:

a It is possible to seal the gap between the piston and the cylinder, resulting in high compression ratio, high heat efficiency and low fuel consumption

b The piston ring faces the cylinder bore wall, separated by an oil film The resulting hydrodynamic lubrication generates low friction and high durability

c The piston loses speed at the dead-center points where the travelling direction reverses, which gives enough time for combustion and intake as well as for exhaust

-> However, the reciprocating engine also has disadvantages:

a The unbalanced inertial force and resulting piston ‘slap’ can cause noise and vibration

b It is difficult to reuse the exhaust heat

Fig 2.4: Basic parts of a diesel engine

THE ENGINE 2

3 The rotary engine (Wankel engine)

The rotary-piston engine (or Wankel engine, named by its inventor) generates power by the compression, ignition, and expansion of gasoline/air mixture in a 4-stroke cycle in the same way as conventional internal combustion engines The completely different mechanical design allows all moving parts to have a continuous rotary motion instead of a reciprocating movement The rotor (or piston) is roughly triangular shaped and rotates on an eccentric on the output shaft within a housing of epitrochoid shape The term is given to the path described

by a point within a circle rolling around another circle

Fig 2.5: The Wankel rotary engine cycle

III. NEW WORDS

Look up for the new words

Valve lifter Lambda sensor Valve spring Inlet valve

Camshaft Catalytic converter Fuel injector Spark ignition (SI)

engineValve seat Exhaust manifold Intake manifold Ignition plug

Camshaft drive chain Piston Combustion

chamber Scavenge (v) Cylinder Connecting rod Crank case Air-fuel mixture

Compression ignition

(CI) engines Spontaneously Phenomenon Referred to

Knocking Injector nozzle Direct injection

engines (DI)

Indirect injection engines (IDI)

1 What is the role of engine in cars?

THE ENGINE 2

-

V. QUIZ

1 Most automobile engines are

a large and heavy

b gasoline-fueled, spark-ignited, liquid-cooled internal combustion type

c unable to run at elevations that are below sea level

d able to operate with any fuel other than gasoline

2 An exhaust valve is

a a hole in the cylinder head

b a mechanism for releasing the combustion products from the cylinder

c the pipe connecting the engine to the muffler

d a small opening at the bottom of a piston

3 Power is produced during

a intake stroke

b compression stroke

c power stroke

d exhaust stroke

4 The air–fuel ratio is

a the rate at which combustible products enter the engine

b the ratio of the mass of air to the mass of fuel in a cylinder before ignition

c the ratio of gasoline to air in the exhaust pipe

d intake air and fuel velocity ratio

5 An SI engine is

a a type of internal combustion engine

b a Stirling engine

c always fuel injected

d none of the above

VI. TRUE/FALSE

Decide if these statements are True or False:

1 We can see the detailed mechanisms of a engine in a car ( True False)

2 The four-stroke engine is also referred to as the Otto cycle engine when petrol is used as fuel ( True False)

3 In four-stroke petrol engine, only air is intaken in induction stroke ( True False)

4 Two-stroke engine uses inlet and exhaust valves ( True False)

5 The name diesel comes from the inventor of the diesel engine, R Diesel ( True False)

6 The intake stroke on the diesel engine draws air/diesel mixture into the cylinder ( True False)

7 A diesel engine uses a spark plug for ignition ( True False)

8 A petrol engine normally needs a throttle valve to control airflow into the cylinder and a diesel engine does ( True False)

9 In DI engine, the fuel is injected directly into the cylinder ( True False)

10 In IDI engine, the fuel is injected and initial combustion takes place in a small ombustion chamber formed in the cylinder head ( True False)

pre-VII. SUBSTITUTION

1. “The engine is the heart of a car although it is normally hidden under the bonnet” (paragraph 1) It refers to:

a the man’s heart

b The engine’s heart

c The car’s heart

d All correct

2 “Power stroke: when the piston ascends and reaches top dead center, an electric current

ignites the spark plug and as the mixed gas burns, it expands and builds pressure in the combustion chamber” (paragraph 2, part 1.1.1) It refers to:

a spark plug

b air

c Fuel

d Air/fuel mixture

3 “Compression stroke: at the end of the intake stroke, both inlet and exhaust valves are

closed The inertial action of the crankshaft in turn lifts the piston which compresses the mixture” (paragraph 2, part 1.1.1) Which refers to:

a The inertial action

a the way to control engine power

b the way to inject fuel into cylinder

c the way to control engine speed

d All correct

5 “The piston loses speed at the dead-center points where the travelling direction reverses,

which gives enough time for combustion and intake as well as for exhaust” (paragraph 3, part 2) Which refers to:

a the travelling direction reverses

b the dead-center points

c the loosen speed of the piston

d all correct

DRIVETRAIN 3

Chapter 3: The Drivetrain

1 How to transmit motive power from the engine to the wheels?

2 How to adjust the ratio of engine speed to wheel speed?

3 In the front-engine car, how to transmit the power from the engine to the rear wheels?

4 When the vehicle turn a corner, what component allows each driven wheel to turn at a different speed?

II. READING

The engine drivetrain system of the automobile consists of the engine, clutch, transmission, drive shaft, differential and driven wheels We have already discussed the SI

engine and we know that it provides the motive power for the automobile Now let’s examine

the clutch, transmission, drive shaft and differential in order to understand the roles of these

devices

1. CLUTCH

A clutch is a releasable coupling connecting the adjacent ends of two coaxial shafts

Mechanical clutches fall into two main categories: positive engagement and progressive engagement

The former is either positively disengaged, so that no torque can be transmitted from the driving to the driven shaft, or positively engaged, in which case the shafts rotate together,

connected by some mechanical devices such as splines, keys In contrast, the progressive type

is gradually engaged, so that the speed of the driving shaft falls while, simultaneously, that of the driven shaft rises from its initial stationary state until both are rotating at equal speeds Positive engagement clutches are unsuitable for connecting the engine to the gearbox

For road vehicles, a progressive engagement clutch of the friction type is interposed

between the engine and the gearbox To illustrate the basic principles applicable to all progressive engagement clutches, a simple clutch stripped of all complications such as friction linings and actuation mechanism is shown in Fig 3.1 The two plates E and F are keyed on the ends of shafts A and B, which are carried in bearings C and D All rotate about a common axis XY

At high rotational speeds, problems can arise with multi-spring clutches owing to the effects of centrifugal force on both the springs themselves and the levers of the release mechanism These problems are obviated when diaphragm-type springs are used, and a number of other advantages are experienced

Fig 3.3: Clutch components

DRIVETRAIN 3

2. TRANSMISSION

The transmission is a gear system that adjusts the ratio of engine speed to wheel speed Essentially, the transmission enables the engine to operate within its optimal performance range regardless of the vehicle load or speed It provides a gear ratio between the engine speed and vehicle speed such that the engine provides adequate power to drive the vehicle at any speed

Fig 3.8: Transmission position in car

To understand the basic idea behind a standard transmission, the Fig 3.11 shows a very simple two-speed transmission in neutral:

Fig 3.7: The diaphragm-spring clutch

Fig 3.9: Mercedes-Benz C-class sport coupe,

six-speed manual transmission

Fig 3.10: Mercedes-Benz Actros, manual

transmission

Fig 3.11: Two-speed transmission

The shaft 1 comes from the engine through the clutch The shaft 1 and gear 1 are connected as a single unit

The shaft 2 and gears in this shaft are called the layshaft These are also connected as a single

piece, so all of the gears on the layshaft and the layshaft itself spin as one unit The shaft 1 and the shaft 2 are directly connected through their meshed gears so that if the shaft 1 is spinning, so is the shaft 2 In this way, the layshaft receives its power directly from the engine whenever the clutch is engaged

The shaft 3 is a splined shaft that connects directly to the drive shaft through the differential to the drive wheels of the car If the wheels are spinning, the shaft 3 is spinning

The gears 3 ride on bearings, so they spin on the shaft 3 If the engine is off but the car is coasting, the shaft 3 can turn inside the gears 3 while the gears 3 and the layshaft are motionless

The purpose of the collar is to connect one of the two gears 3 to the drive shaft 3 The collar is

connected, through the splines, directly to the shaft 3 and spins with the shaft 3 However, the collar

can slide left or right along the shaft 3 to engage either of the gears 3 Teeth on the collar, called dog

teeth, fit into holes on the sides of the gears 3 to engage them

The five-speed manual transmission is fairly standard on cars today Internally, it looks something like Fig 3.12

Fig 3.12: Five-speed manual transmission

DRIVETRAIN 3

Manual transmissions in modern passenger cars use synchronizers to eliminate the need for double-clutching A synchro's purpose is to allow the collar and the gear to make frictional contact before the dog teeth make contact This lets the collar and the gear synchronize their speeds before the teeth need to engage, like Fig 3.13

The cone on the gear fits into the cone-shaped area in the collar, and friction between the cone and the collar synchronize the collar and the gear The outer portion of the collar then slides so that the dog teeth can engage the gear Every manufacturer implements transmissions and synchros in different ways, but this is the general idea

3. DRIVE SHAFT

The drive shaft is used on front-engine, rear wheel drive vehicles to couple the transmission output shaft to the differential input shaft (fig 3.8) Flexible couplings, called

universal joints, allow the rear axle housing and wheels to move up and down while the

transmission remains stationary In front wheel drive automobiles, a pair of drive shafts

couples the transmission to the drive wheels through flexible joints known as constant velocity (CV) joints

Fig 3.14 The drive shaft and universal joints

4. DIFFERENTIAL

The differential serves three purposes (see Figure 1.13)

• The most obvious is the right angle transfer of the rotary motion of the drive shaft

to the wheels

• The second purpose is to allow each driven wheel to turn at a different speed This

is necessary because the “outside” wheel must turn faster than the “inside’’ wheel when the vehicle is turning a corner

• The third purpose is the torque increase provided by the gear ratio

This gear ratio can be changed in a repair shop to allow different torque to be delivered to the wheels while using the same engine and transmission The gear ratio also affects fuel economy

Fig 3.13: Synchronizers