Mechanisms of an Automobile

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Mechanisms of an Automobile


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Contents

1. Introduction2. Basic vehicle layout

3. Mechanisms of an automobile

3.1 Power transmission

3.2 Steering mechanism

3.3 Braking system

3.4 Coolant system

3.5 Fuel injection system

4. Engine and it's types4.1 SI engine

4.2 CI engine

5. Future advancements inan automobile


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The means of transport provided by nature to man is severely

limited in regards to the load he could carry and the distances hecould carry them as well as the speed of travel with or without aload. Moreover, the physical exertion involved was not to hisliking. Initially, the man tamed and trained certain animals forcarrying heavier loads to greater distances at speeds higher than

the man could attain. These means of transport were alsolimited with regard to the load carried and the speed as well asdistances travelled and the physical exertion involved.Automobile has found an important place in everywhere of ourcommercial and social existence .

Introduction to Automobile


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In general, modern motor vehicle is a complex piece of machinerynecessitating a careful attention to make it perform in a safe,economical and efficient manner. The automobile is essentially atransportation equipment unit. It is made up of a frame supporting thebody and certain power developing and transmitting units. These arefurther supported by tyres and, wheels, through the springs and axles.The engine supplies the power. It is delivered by the transmission

system and rear axles through the clutch or fluid coupling to the rearwheels. The automobile is propelled through the friction of the contactbetween the road and the wheels. The various units are held togetherin proper arrangement on the frame. The protection and comfort isprovided by the body of the vehicle.

Introduction to Automobile


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Basic Vehicle Layout


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The basic structure or the framework

The engine or power plant or source of power

The power train or the transmission system

The body or the super- structure

The auxiliaries

The controls

Components of an Automobile


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This is the unit on which the other units are mounted.

It consists of:-

Frame

The Suspension system

Axles

Wheels

The Basic Structure (Chassis)


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The engine provides the power to move the vehicle The engine is classified as

- Petrol engine

- Oil engine

The Power Plant (Engine)


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The transmission system consists of a

Clutch,

Gear box,

Propeller shaft, and

Differential Gear

The Transmission System


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* To protect from atmospheric effect

* To streamline the vehicle

The body or the super structure


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* Fuel system

* Ignition system

* Lubrication system

* Cooling system

* Electrical system

The Auxiliaries


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* Footboard :clutch, brake pedal, accelerator pedal

and dimmer switch

* Dashboard : ignition switch, self-starter switch,lighting switch, throttle control, choke control,

speedo-meter, ammeter oil gauge, fuel gauge,temperature gauge, warning light and electric bellswitch.

Controls


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AUTOMOMOBILE

COOLING SYSTEMS


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Purpose of theCooling system

Control temperature of hot

combustion.4000 degree temps. couldseriously damage engine parts.

Provide Heat for passengerCompartment.

Cool trans fluid & oil.Heat moves from warm to cold.


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Cooling System TypesAir Cooling

Oil Cooling

Liquid or Water Cooled


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Cooling system parts

Water jackets

Water pump

Radiators

Radiator fans

Radiator cap

Thermostat

Coolant recovery tank


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Water jacketsSurrounds the cylinders withwater passage.

Absorbs heat from the cylinder

wall.Pump move water to radiatorwhere heat is exchanged to the air.


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RadiatorsA radiator is a heat exchanger.

Tube and fin style the most

popular.Made of copper and brass oraluminum and plastic

Types

1 Down flow2 Cross flow


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Radiator FansKeeps air moving through the radiatorwhen the car is not moving.

Several types:

rigid,

flex (not used much anymore),

viscous clutch and electric.


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ThermostatControls coolant temperature.Uses a temperature sensor and avalve.

Usually opens around 195 degrees F.


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Water PumpNon-positive displacement pumpwhich circulates coolant around coolingsystem.

Simple impeller design.

Usually driven by drive belt fromcrankshaft.


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Radiator CapThe cap allows access to the cooling system forfilling and testing.

The cap has two valves: a pressure relief valve

set at around 15 PSI and a vacuum valve which isneeded when the engine cools down.

Raises boiling point of fluid

Able to take on more heat


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Coolant Recovery TankKeeps the coolant level full in the system at alltimes.Works in conjunction with the radiator cap.When the engine heats up the coolant

expands and flows to the recovery tank.When the engine coolant the coolantcontracts and creates a vacuum and draws thefluid back into the radiator.Reduces air in systemReduces rust

Less need to open radiator


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Coolant typeSeveral types of anti-freezeavailable.

Ethylene glycol most common.

(itsgreen)Dexcool (its orange)

Propylene glycol (non-toxic)


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Typical Braking System


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Types of Brakes

Brake

Hydraulics


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DrumBrake

Disk BrakeParking

brake


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Master Cylinder

Brake fluid and brakeline

Other Components in theHydraulic System.eg-Proportioning valve orEqualizer Valve,Pressure

Differential Valve,ElectronicBrake Force Distribution

Rotor,caliper,support and

braking pads


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Anti-Lock Brakes (ABS)

power brake booster


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AUTOMOBILE POWERTRANSMISSION


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POWER TRANSMITTING

DEVICES1.CLUTCH2.GEARBOX

3.PROPELLER SHAFT

4.DIFFERENTIAL5.DIFFERENTIAL


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Fuel injection system


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ObjectivesThe functional objectives for fuel injection systems can vary. All share the central task

of supplying fuel to the combustion process, but it is a design decision how a particularsystem is optimized. There are several competing objectives such as:

Power output

Fuel efficiency

Emissions performance

Ability to accommodate alternative fuels

Reliability

Driveability and smooth operation

Initial cost

Maintenance cost

Diagnostic capabilityRange of environmental operation

Engine tuning

The modern digital electronic fuel injection system is more capable at optimizing thesecompeting objectives consistently than earlier fuel delivery systems (such as

carburettors). Carburettors have the potential to atomize fuel better (see Pogue and

Allen Caging patents)


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Types of fuel injection system

1. Mechanical injection system

2. Electronic fuel injection system


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Mechanical injection systemThe fuel injection system is the most vital component in the working of CI

Engine. The engine performance is greatly dependent on the effectiveness ofthe fuel injection system. The injection system has to perform the important

duty of initiating and controlling the combustion process

In this fuel injection system, the amount of fuel delivered into the air streamgoing to the engine is controlled by a pump which forces the fuel under

pressureWhen the fuel is injected into the combustion chamber towards the end ofcompression stroke, it is atomized into very fine droplets. These dropletsvaporize due to heat transfer from the compressed air and forms fuel air

mixture. Due to continues heat transfer from hot air to the fuel thetemperature reaches a value higher than its self ignition temperature. This

causes the fuel to ignite spontaneously initiating the combustion process.


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Gasoline injector
http://en.wikipedia.org/wiki/File:Injector3.gif


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Types of mechanical fuel Ignitionsystem

AIR INJECTION SYSTEM

SOLID INJECTION SYSTEM


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Electronic fuel injection system

Various injection schemes

Single point fuel injection system

Multi point fuel injection system


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Steering system

Introduction: This system provides thedirectional change in the movement of

an Automobile and maintain in a position as perthe drivers decision without

much strain on him.


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Functions of steering system

1. It helps in swinging the wheels to the left orright.

2. It helps in turning the vehicle at the will of thedriver.

3. It provides directional stability.

4. It is used to minimize the tyre wear and tear.

5. It helps in achieving self centering efforts.

6. It absorbs major part of the road shocks.


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Requirements of steering system

a. It must keep the wheel at all times in to rolling motionwith out

rubbing on the road.

b. This system should associate to control the speed.

c. It must light and stable.

d. It should also absorb the road shocks.

e. It must easily be operated with less maintenance.

f. It should have self-centering action to some extent.


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Davis gear mechanism


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Ackermaans steering gearmechanism


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Types of

Engine

S.I.Engine

Fourstroke

Twostroke

C.I.Engine

Engine and it's types


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S.I. Engine


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Cylinder Components


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The Four stroke engine, as the name suggests, consists

of four strokes of the piston, namely Intake Stroke

Compression Stroke

Combustion/Power Stroke

Exhaust Stroke

Working (four stroke)


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Working (four stroke)


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The working of two stroke engine is similar to that of

the four stroke one. The difference is the number ofstrokes.

Where the Four stroke completes two cycles in fourstroke, the two stroke engine completes one cycle in

two strokes.

Working (two stroke)


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Construction


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Working

Diff b t f t k


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Difference between four strokeand two stroke engines


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The only difference between diesel engine and a four-stroke gasoline engine is:

No sparkplug on Diesel engine.

Has a higher compression ratio i.e. (14:1 to 25:1)

Better fuel mileage.

CI engine


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The CI engine consists of four strokes, namely

Intake Stroke Compression Stroke

Power Stroke

Exhaust Stroke

Working


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Both valves stay closedPiston moves from BDC toTDC, compressing air to 22:1Compressing the air tothis extent increases thetemperature inside thecylinder to above 1000degree F.

CompressionStroke


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Both valves stay closed

When the piston is at the end of

compression stroke(TDC) the injector

sprays a mist of diesel fuel into the

cylinder.

When hot air mixes with diesel fuel

an explosion takes place in thecylinder.

Expanding gases push the piston

from TDC to BDC

Power Stroke


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Piston moves fromBDC to TDC

Exhaust valve opensand the exhaust gasesescape

Exhaust valve opensand the

exhaust gases escape

Exhaust Stroke


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Difference between SI and CI engines


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Automobile propulsion technology under developmentinclude gasoline/electric and plug-in hybrids, batteryelectric vehicles, hydrogen cars,biofuels, and

various alternative fuels. Research into future alternativeforms of power include the development of fuelcells, Homogeneous Charge Compression Ignition(HCCI), Stirling engines, and even using the stored energyof compressed air or liquid nitrogen.

New materials which may replace steel car bodiesinclude duralumin, fiberglass, carbon fibres, and carbonnanotubes.

Telematics technology is allowing more and more peopleto share cars, on a pay-as-you-go basis, through car

share and carpool schemes.Communication is also evolving due to connectedcar systems.

S f h i


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Some future techniques

Autonomous cars

Communicating cars

Pre collision system

Night visionTraction control

Active head restraints

Proximity warning system

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Mechanisms of an Automobile

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