giáo trình anh văn chuyên ngành ô tô

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


Technical English for AUTOMOTIVE ENGINEERING. 1

Chapter 1: Automotive Introduction.
I. PRE-READING QUESTION:
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 21
st
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.
AUTOMOTIVE INTRODUCTION. 1


Technical English for AUTOMOTIVE ENGINEERING. 2

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


Technical English for AUTOMOTIVE ENGINEERING. 3

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:
1. Engine
2. Drivetrain (transmission, differential,
axle)
3. Suspension
4. Steering
5. Brakes
6. Instrumentation
7. Electrical/electronic
8. Motion control
9. Comfort/convenience
10.Entertainment/communication/navigati
on.
III. NEW WORDS
Look up for the new words
Automobile (n) Rank (n) Truck (n) Driveshafts (n)
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)

Suburbs (n)

bumper (n) occupant (n)
adaptable to (a)

Highway (n) Primary (a)
IV. COMPREHENSION QUESTION
Answer these questions:

1. Why do we call automobiles as self-propelled vehicles?
AUTOMOTIVE INTRODUCTION. 1


Technical English for AUTOMOTIVE ENGINEERING. 4


2. What are the key elements of industrial economies?

3. What are advantages of automobile in our life?

4. What are disadvantages of automobile in our life?

5. What are the main functions of the engine?

6. What are the main functions of Suspension systems?

7. What are the main functions of wheels and tires?

8. What are the main functions steering and braking systems?

9. What are the main functions of electrical system?

10. What component(s) makes automobiles safer?

V. TRUE/FALSE
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 21
st
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


Technical English for AUTOMOTIVE ENGINEERING. 5

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
a. The system
protects vehicles
from bumps, loads,
and stresses
c. Cars designed
for driving in
mud or snow.
e. 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.

No

Column A Column B No Column A Column B
1 Automobile

6 Sport-utility vehicles

2 Pickups

7 Omnibus

3 Adaptable to

8
Drivetrain system

4 Steering system

9
Navigation system

5 Suspension system


10 Coolant system

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Technical English for AUTOMOTIVE ENGINEERING. 6
Chapter 2: The Engine
I. PRE-READING QUESTION
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).

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Technical English for AUTOMOTIVE ENGINEERING. 7
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

Fig2.3: Two-stroke engine

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Technical English for AUTOMOTIVE ENGINEERING. 8
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

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Technical English for AUTOMOTIVE ENGINEERING. 9
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
Bonnet (n) Crankshaft Cylinder head Exhaust valve
Valve lifter Lambda sensor Valve spring Inlet valve
Camshaft Catalytic converter Fuel injector
Spark ignition (SI)
engine
Valve 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)
IV. COMPREHENSION QUESTION
1. What is the role of engine in cars?

2. How many types of reciprocating engine?

3. Name 4 strokes of the 4-stroke engine?

4. How are the air and fuel mixture drawn into combustion chamber in intake stroke?

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Technical English for AUTOMOTIVE ENGINEERING. 10

5. In compression stroke, how the mixture is compressed?

6. Why is the piston pushed down in power stroke?

7. Why can we call a petrol engine as a Spark Ignition (SI) engine?

8. What is the same feature of the two-stroke engine and the four-stroke-cycle engine?

9. Does two-stroke engine use inlet and exhaust valves?

10. In the two-stroke engine, what is the function of the space in the crankcase?

11. Why is a two-stroke engine mechanism very simple?

12. How about a two-stroke engine power? Is it more than or less than the same capacity of
four-stroke engine? Why?

13. Why isn’t a two-stroke engine as popular as four-stroke one?

14. What kind of mixture is intaken in intake-stroke of a diesel engine?

15. Why doesn’t a diesel engine have a spark plug?

16. How many methods for injecting fuel into a combustion chamber in diesel engine?

17. Advantages and disadvantages of reciprocating engines?

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Technical English for AUTOMOTIVE ENGINEERING. 11


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 pre-
ombustion chamber formed in the cylinder head ( True  False).

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Technical English for AUTOMOTIVE ENGINEERING. 12
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.
b. the crankshaft.
c. the piston.
d. the mixture
4. “There are two methods by which fuel is injected into a combustion chamber, direct or
indirect injection” (paragraph 4, part 1.2). Which refers to:
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



Technical English for AUTOMOTIVE ENGINEERING. 13
Chapter 3: The Drivetrain.
I. PRE-READING QUESTION
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.

Fig 3.1: Basic principle of the
friction-type clutch

Fig 3.2: Clutch position in car.

DRIVETRAIN 3



Technical English for AUTOMOTIVE ENGINEERING. 14
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


Fig 3.4: Single-plate
clutch
Fig 3.5: Multi-spring single-plate
clutch

Fig 3.6: Triple-plate clutch


DRIVETRAIN 3

Technical English for AUTOMOTIVE ENGINEERING. 15
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


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Technical English for AUTOMOTIVE ENGINEERING. 16

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

Technical English for AUTOMOTIVE ENGINEERING. 17
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

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Technical English for AUTOMOTIVE ENGINEERING. 18
III. NEW WORDS
clutch stationary disc Release bearing
coaxial shafts state flywheel Release fork
positive engagement unsuitable crankshaft spring
progressive
engagement
gearbox
Pilot
bearing/bushing
centrifugal force
splines friction type Front/rear
diaphragm-type

springs
keys interposed seal transmission
gradually principles
Transmission input
shaft
gear ratio
simultaneously stripped Bearing retainer regardless
adequate meshed cone front-engine
neutral collar implements couple
layshaft dog teeth synchros differential
spin synchronizers Drive Shaft universal joints
constant velocity
joints
obvious right angle torque
IV. COMPREHENSION QUESTION
1. What is a clutch?

2. How many types of clutch?

3. How many types of positive engagement clutch?


Fig 3.15: Differential

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Technical English for AUTOMOTIVE ENGINEERING. 19
4. Are ositive engagement clutches suitable for connecting the engine to the gearbox?

5. What is the typical type of progressive engagement clutch?

6. What is/are the main problem(s) for the multi-spring clutches at high rotational speeds?

7. And how can we solve that (those) problem(s)?

8. What is the main function of transmission?

9. What is the layshaft?

10. What is the main purpose of the collar?

11. What is the name of the teeth on the collar?

12. What is the main function of synchronizer?

13. How does the synchronizer operate?

14. What is the drive shaft function?

15. What is the Universal joint?

16. What are the purposes of differential?


DRIVETRAIN 3

Technical English for AUTOMOTIVE ENGINEERING. 20
V. TRUE/FALSE
1. Engine, clutch, transmission, drive shaft, differential and driven wheels are elements of
drivetrain system. ( True  False)
2. A clutch is a releasable coupling. ( True  False)
3. There are two main categories of mechanical clutches. ( True  False)
4. Progressive engagement clutch is friction type. ( True  False)
5. Centrifugal force is the main problem which arises with multi-spring clutches. ( True 
False)
6. Diaphragm-type springs obviate the problems in the multi-spring clutches at high
rotational speeds. ( True  False)
7. The transmission enables the engine to operate within its optimal performance range. (
True  False)
8. By providing a gear ratio between the engine speed and vehicle speed of the clutch,
engine provides adequate power to drive the vehicle at any speed. ( True  False)
9. Layshaft is a intermidiate shaft in gear box. ( True  False)
10. Synchronizers add the need for double-clutching in cars. ( True  False)
11. Transmissions and synchros are implemented in the same way by all auto manufacturer.
( True  False)
12. The drive shaft is used to couple the transmission output shaft to the differential input
shaft. ( True  False)
13. Universal joints a rigid couplings. ( True  False)
14. Differential allows each driven wheel to turn at a different speed. ( True  False)
15. Differential is the torque decrease provided by the gear ratio. ( True  False)

SUSPENSION SYSTEM 4



Technical English for AUTOMOTIVE ENGINEERING. 21

Chapter 4: Suspension System.
I. PRE-READING QUESTION
1. How to maximize the friction between the tires of a car and the road surface?
2. How to provide steering stability with good handling and to ensure the comfort of the
passengers?
3. How to absorb the vibration in moving of the cars?
II. READING
Another major automotive sub-system is the suspension system, which is the mechanical
assembly that connects each wheel to the car body. The primary purpose of the suspension
system is to isolate the car body from the vertical motion of the wheels as they travel over the rough
road surface. The suspension system can be understood with reference to Figure 4.1, which illustrates
the major components.

Fig 4.1: Major components of suspension system.
1. SPRINGS
Notice that the wheel assembly is connected through a movable assembly to the body. The weight
of the car is supported by SPRINGS. Today's springing systems are based on one of four basic
designs:
1.1. Coil springs: this is the most common type of spring and is, in essence, a heavy-duty torsion
bar coiled around an axis. Coil springs compress and expand to absorb the motion of the wheels (Fig
4.1).
1.2. Leaf springs: this
type of spring consists of
several layers of metal
(called "leaves") bound
together to act as a single
unit. Leaf springs were
first used on horse-drawn
carriages and were found
on most American

automobiles until 1985.
They are still used today
on most trucks and heavy-
duty vehicles (Fig 4.2)



Fig 4.2: Leaf spring.

SUSPENSION SYSTEM 4



Technical English for AUTOMOTIVE ENGINEERING. 22


1.3 Torsion bars: torsion bars
use the twisting properties of a steel
bar to provide coil-spring-like
performance. The short torsion bar
springs grip into the guide tubes 2 and
3 in the centre of the vehicle (Fig 4.4).
Parts 2, 3 and 4 are jointly subjected
to torsional stresses and so the
torsional stiffness of the transverse
tubes contributes to the spring rate. On
the outside, the cast trailing arms 1
are welded to the transverse tubes,
which (pushed into each other) support
each other on the torsionally elastic

bearings 5 and 6. This creates a
sufficiently long bearing basis, which
largely prevents camber and toe-in
changes when forces are generated.
The entire assembly is fixed by the
brackets 7 which permits better force
transfer on the body side sill. Guide tubes 2 and 3 are mounted in the brackets and can rotate, as well
as the outer sides of the two torsion bars 4. The two arms thus transfer all vertical forces plus the
entire springing moment to the body. The anti-roll bar 8 is connected to the two trailing arms via two
U-shaped tabs. The two rubber bearings 5 and 6 located between the tubes 2 and 3 also contribute
to the stabilizing effect. The bump and rebound travel stops are fitted into the shock absorber 9.

1.4 Air springs: The air-spring bellows
are supplied by an electrically powered
compressor. The individual wheel
adjustment permits the lowering or lifting of
the vehicle as well as a constant vehicle
height, regardless of – even onesided –
loading. It is also possible to counteract
body tilt during cornering. The damping
properties of the shock absorbers are
affected by spring bellow pressure
depending on the load (Fig 4.5)


Fig 4.4: Torsion bars in suspension system

Fig 4.3: Leaf spring assembly

Fig 4.5: Air springs in suspension system

SUSPENSION SYSTEM 4



Technical English for AUTOMOTIVE ENGINEERING. 23
2. SHOCK ABSORBER (sometimes a strut)
(Fig 4.6), which is in effect a viscous damping
device. There is a similar assembly at each wheel,
although normally there are differences in the
detailed configuration between front and rear
wheels.
Enter the shock absorber, or snubber, a
device that controls unwanted spring motion
through a process known as dampening. Shock
absorbers slow down and reduce the magnitude
of vibratory motions by turning the kinetic
energy of suspension movement into heat
energy that can be dissipated through hydraulic
fluid.
A shock absorber is basically an oil pump
placed between the frame of the car and the
wheels. The upper mount of the shock connects
to the frame (i.e., the sprung weight), while the
lower mount connects to the axle, near the wheel (i.e., the unsprung weight). In a twin-tube
design, one of the most common types of shock absorbers, the upper mount is connected to a
piston rod, which in turn is connected to a piston, which in turn sits in a tube filled with
hydraulic fluid. The inner tube is known as the pressure tube, and the outer tube is known as
the reserve tube. The reserve tube stores excess hydraulic fluid.
When the car wheel encounters a bump in the road and causes the spring to coil and

uncoil, the energy of the spring is transferred to the shock absorber through the upper mount,
down through the piston rod and into the piston. Orifices perforate the piston and allow fluid
to leak through as the piston moves up and down in the pressure tube. Because the orifices are
relatively tiny, only a small amount of fluid, under great pressure, passes through. This slows
down the piston, which in turn slows down the spring.
Shock absorbers work in two cycles the compression cycle and the extension cycle.
The compression cycle occurs as the piston moves downward, compressing the hydraulic
fluid in the chamber below the piston. The extension cycle occurs as the piston moves toward
the top of the pressure tube, compressing the fluid in the chamber above the piston. A typical
car or light truck will have more resistance during its extension cycle than its compression
cycle. With that in mind, the compression cycle controls the motion of the vehicle's unsprung
weight, while extension controls the heavier, sprung weight.

SUSPENSION TYPES
3.1 Dependent Suspensions
3.1.1 Dependent front suspensions: have a
rigid front axle that connects the front
wheels. Basically, this looks like a solid bar
under the front of the car, kept in place by leaf
springs and shock absorbers. Common on
trucks, dependent front suspensions haven't
been used in mainstream cars for years.



Fig 4.6: Shock Absorber.

Fig 4.7: Dependent front
suspensions

SUSPENSION SYSTEM 4



Technical English for AUTOMOTIVE ENGINEERING. 24

3.1.2 Dependent rear suspensions





Contrary to the front version of
this system, many cars are still
designed and built with
dependant (linked) rear
suspension systems.





3.2 Independent Suspensions
3.2.1 Independent front Suspensions
So-named because the front wheel's
suspension systems are independant of
each other (except where joined by an
anti-roll bar). These came into existance
around 1930 and have been in use in one

Fig 4.8: Solid-axle, leaf-spring

Fig 4.9: Solid-axle, coil-spring

Fig 4.10: Beam Axle

Fig 4.11: Macpherson strut

Fig 4.12
:
Coil Spring type 1


Fig 4.13: Coil Spring type 2