Major Systems and Components of an Automobile(Automotive fundamentals, Automobile parts explanation , function, requirements and sketches)

Introduction

In the previous Units, we learnt about the different  types of automobile. In this Unit, we will discuss the  major systems and components of an automobile. An automobile is made of several components, assemblies  and systems. The growing automotive industry has 

given rise to a growing auto component industry also.  India has emerged as a global outsourcing hub for  manufacturing of various automobile components. All 

major companies like Toyota, Hyundai, Ford, Volvo,  Renault and others are now sourcing their automotive  components from Indian manufacturers. The auto components industry is predominantly 

divided into five segments.

(i) Engine parts 

(ii) Drive transmission and steering parts 

(iii) Suspension and brake parts 

(iv) Electrical parts 

(v) Body and chassis

Automotive Fundamentals

Picture yourself in the not-too-distant future driving your new car along a rural interstate highway on a business trip. You are traveling along one of the new automated highways in which individual cars are controlled electronically to maintain a fixed spacing in a lane at a preferred speed. Typically, these cars are traveling at 70mph and are spaced about 25ft apart. The cars are computer controlled via a digital communication link, including a cable buried in the center of the “cruise” lane and follow one another in a pattern known as platooning. Your car will automatically remain in this cruise control lane until you approach your destination exit. You press a button on the steering column and an image of a road map appears faintly visible (so as not to obscure the road ahead) on the windshield

in front of you. This map shows your present position and the position of the

destination city. The distance to your destination and the approximate arrival

time are displayed on the digital instrument cluster.

You are talking on your cellular phone to your office about some changes in a contract that you hope to negotiate. You are wearing a lightweight headset that enables you to use the cell phone “hands free” to drive. Dialing is accomplished by voice command using voice recognition software in your cell phone controller. After the instructions for the contract changes are completed, a printer in your car generates a copy of the latest contract version. Your spouse (in the passenger seat) is sending e-mail messages using the on-board computer that is linked by radio to the Internet. Your son (in the rear

seat) is watching a movie via an interactive digital link, while your daughter

(also in a rear seat) is doing a math lesson from an education center with an

interactive video link.

After you finish your phone call, the onboard entertainment system starts

playing music for you at a comfortable level relative to the low-level wind and

road noise in the car. After completing your phone conversation, you press

another button on the steering wheel and the music is replaced by a recorded lesson in French verb conjugation, which you have been studying. Suddenly, the French lesson is interrupted by a message delivered in natural-sounding

synthesized speech. “You have fuel remaining for another 50 miles at the

present speed. Your destination is 23 miles away. Recommend refueling after

exiting the highway. There is a station that accepts your electronic credit near

the exit (you know, of course, that the electronic credit is activated by inserting

the fuel nozzle into the car). Also, the left rear tire pressure is low and the engine control system reports that the mass air flow sensor is intermittently malfunctioning and should be serviced soon.’’ After this message has been delivered, the French lesson returns.

Chassis and Auto Body

Chassis

Chassis is a French term and was initially used to denote the frame or main structure of a vehicle. The chassis.contains all the major units necessary to propel the vehicle, guide its motion, stop it and allow it to run smoothly over uneven surfaces. It is the main mounting for all the components including

the body. It is also known as the carrying unit. The chassis includes the following major components.

(i) A steel frame, which is a major part.

(ii) In case of a passenger car, the whole body is also an integral part of the chassis. However, in commercial vehicles like trucks and buses, the body is not a part of the chassis. Therefore, a chassis is almost a complete vehicle except the body and other accessories, which are not involved in the movement of the vehicle.

Functions of the chassis

The functions of the chassis includes

(i) carrying the weight of the vehicle and its passengers,

(ii) withstanding the engine and transmission torque and thrust stresses, as well as accelerating and braking torque,

(iii) withstanding the centrifugal force while taking a turn and

(iv) withstanding the bending load and twisting due to the rise and fall of the front and rear axles.

Automobile Body or Superstructure

In case of integral or frameless construction, the body is an integral part of the chassis. But, in case of the conventional chassis, the body or superstructure is made after receiving

the chassis from the manufacturer. The shape of the body depends upon the ultimate use for which the vehicle is meant. The body of a car  is made of a sheet of metal or fibre glass, so that passengers can sit in it.

Requirements of automobile body

The body of a motor vehicle should fulfill certain requirements. It should

(i) be light weight.

(ii) have minimum number of components.

(iii) have long fatigue life.

(iv) have uniformly distributed load.

(v) have sufficient space for passengers and luggage.

(vi) have good access to the engine and suspension system.

(vii) have minimum vibrations when the vehicle is running.

(viii) have minimum resistance to air.

(ix) be cheap and easy in manufacturing.

(x) have clear all-round vision through glass areas.

(xi) have an attractive shape and colour.

Engine and Its Components

An engine is complex unit in which different components are assembled together, and fuel is burned to produce power or energy. The engine converts chemical energy (heat energy) into mechanical energy, which is then utilised for vehicular movement. There are different processes of fuel combustion. When the fuel is burned within the engine, it is called an Internal Combustion (IC) engine, and when it is burned externally and the produced steam is used for the mechanical movement, it is called an External Combustion (EC) engine.

automobile engines are quite economical

due to the developments taking place in

the field of internal combustion engine.

On the basis of the process of ignition,

the automobile engines are classified into spark ignition engine (petrol or gas) and compression ignition engine(diesel). In an IC engine, the reciprocating motion of the

piston is converted into rotary motion of the crankshaft and the produced power is then transmitted to move the vehicle. In case of a rotary engine or Wankel engine, the rotor rotates and completes the process of combustion and produces the power, which helps the vehicular movement. The spark ignition engine can be differentiated from the compression ignition engine as per the following factors.

(i) The type of fuel used.

(ii) The way the fuel enters in the combustion chamber.

(iii) The way in which fuel is ignited.

Components of an IC Engine

 1.Cylinder: The cylinder or cylinder liner of an IC engine is fitted in the cylinder block, which is a single casted unit and is considered to be the main body of an engine. The block has cylinder liners.

The piston reciprocates up and down from Top Dead Centre (TDC) to Bottom Dead Centre (BDC) to generate power.

 The cylinder liner and the cylinder block have to withstand very high pressure (about 70 bar) and temperature (about 700C) during power stroke. The material used for the cylinder block must withstand such heat and also disperse it effectively. The cylinder block is well-designed

with water passages to remove the excess heat and separate oil passages are provided for the circulation of lubricating oil. The top portion of the cylinder block is covered by the cylinder head. The crankcase is an integral part of the cylinder block which houses the crankshaft and the lower portion is dipped in an oil pan.

2.Cylinder Head: 

The cylinder head is also single-

casted unit and bolted to the top portion of the cylinder block. The combustion chamber is a part of the cylinder head, where the combustion of gases takes

place. The water passages are provided to remove the heat from the cylinder head. In latest engines, the cylinder head also houses the camshaft which

has the inlet and exhaust valves with supportive valve mechanism. This provision is made to fix spark

plug in SI engines and nozzle in CI engines. The lower portion of the cylinder head is well-machined to ensure there is no leakage of gases. Cylinder head

gasket is usually cast as one piece and bolted to the top of the cylinder (engine block). Copper and asbestos gaskets are provided between the cylinder

and cylinder-head to obtain a gas-tight joint. The charge enters the combustion chamber through the inlet valve connected to the inlet manifold, and the exhaust gases are removed through the exhaust

valves connected to the exhaust manifold.

3.Piston and Piston Rings: 

Piston is a cylindrical unit,used to compress the charge during compressionstroke and to transmit the gas force to the connecting rod and then to the crankshaft duringpower stroke. The pistons of IC engines are usuallymade of aluminium alloy, which has high thermal conductivity and is light in weight. The material of piston must have the ability for higher heat transfer.The piston moves up and down (from TDC to BDC)and assists in completing the engine cycle.

4.Connecting Rod: 

It is usually manufactured by using drop-forged steel. It is made in the shape

of ‘I’ so as to reduce its weight and to withstand strength. Its small end is connected to the piston with the help of gudgeon pin and the big end is connected to the crankpin with shell bearings. It

has a passage for the transfer of lubricating oil from the big end bearing to the small end bearing (gudgeon pin). The major function of the connecting rod is to convert the reciprocating motion of piston to the rotary motion of the crankshaft.

5.Crank and Crankshaft: 

The crankshaft  is called the backbone of an engine because it converts the reciprocating motion of piston into the

rotary motion of the crankshaft. The crankshaft is a single casted unit and is made of drop-forged steel main journals which are placed and supported in

the crank case. The main journal and connecting journals are machined to a smooth finish to reduce

6.Camshaft: 

The major function of the camshaft is

to operate the intake and exhaust valves through the cam lobe, the gear drive transmits the power for the rotation of oil pump, therefore the oil pump sucks the oil from the oil sump and transits the same to the oil gallery. The camshaft is driven by crankshaft at half the speed of the crankshaft.

 7.Cam Lobe and Tappet:

The cam lobe of the camshaft is placed directly above the bucket tappet, such that the lobe comes around it and pushes down the bucket tappet and the valve, thus opening the valve. In an overhead

camshaft with rocker arm, the cam lobe comes under the valve lifter, and causes the rocker arm to rock or turn the lobe and pushes down the valve steam and it moves down to open

8.Crank Case: 

The crank case is an integrated

part of the cylinder block. The casing is provided to hold the crankshaft. The crankshaft is allowed to rotate freely and transmit the power to the flywheel

9.Water Pump and Water Jacket: 

The function of water pump is to draw water from the radiator and supply it to the water passages provided in the cylinder block and cylinder head with certain pressure. The circulation of coolant removes the excessive heat from an engine. This helps in maintaining the

engine temperature and also the

life of an engine 

10.Radiator: 

The major function of the radiator is to radiate the heat from the coolants. It

has two tanks located at the top and bottom. The upper tank is connected to the lower tank with the core through the passages for easy radiation of the heat. The radiator also stores the coolant

11.Carburettor: 

The major function of the carburetor is to supply carburised fuel as per speed and the engine load. In petrol engines the carburettor is mounted on the induction pipe or on the induction manifold. The quantity of fuel air mixture in appropriate ratio is controlled by the throttle valve and the movements of the throttle valve are connected to the accelerator.

12.Spark Plug: 

The function of the spark plug is to ignite the fuel air mixture after completion of the

compression stroke in an engine. It is generally placed in the combustion chamber of the cylinder head. This is only used in petrol engine.

13.Fuel Injection Pump: 

In case of diesel engine the diesel oil from the fuel tank is sucked by the fuel feed pump. The pump first sends the diesel oil to the fuel filter and then to the transfer pump. The transfer pump increase the pressure of the fuel.The high pressure of fuel is then sent to the distributor

rotor through the metering valve and from rotor the fuel is sent to the injector In case of a multi point fuel injection system, the electric fuel pump is used and placed in the fuel tank. The pump generates the injection pressure and sends it to the fuel filter, and then to the common rail at a

pressure of 3 to 4 bar. The common rail or fuel rail is connected to the fuel injector.

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