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Class 9 Automotive Service Technician Chapter 3 Major Systems and Components of an Automobile
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Major Systems and Components of an Automobile
Chapter: 3
Session – 1: Chassis and Auto Body
Check Your Progress
A. Fill in the blanks:
1. A chassis is almost a complete _________ mounting body.
Ans: Vehicle.
2. The shape of the chassis depends upon the ultimate use of the _________.
Ans: Vehicle.
3. Major part of a chassis is the __________frame.
Ans: Steel.
4. In commercial vehicles like trucks and buses the body is not a _________ of the chassis.
Ans: Part.
5. In most of the cases, it is an open body, whereas for liquid material like water, milk and fuel a __________ is mounted on the chassis.
Ans: Tank.
B. Multiple choice questions:
1. Chassis is a French term and was initially used to denote ___________.
(a) Main structure of a vehicle.
(b) Fixing the automobile body.
(c) Transmission system, front and rear axle.
(d) Carrying the bolt.
Ans: (a) Main structure of a vehicle.
2. What are the functions of the chassis frame?
(a) To carry the weight of the vehicle and its passengers.
(b) To withstand the engine and transmission torque.
(c) To withstand the centrifugal force while cornering.
(d) All of the above.
Ans: (d) All of the above.
3. Automobile body is made of ________________.
(a) Sheet metal or fiberglass.
(b) Iron.
(c) Copper.
(d) Gun metal.
Ans: (a) Sheet metal or fiberglass.
4. The body is fixed to the chassis with the help of ________.
(a) I or U bolts.
(b) Rivet.
(c) Welding.
(d) Threaded bolt.
Ans: (a) I or U bolts.
5. Automobile body should fulfill which of the following requirements?
(a) The body should be light.
(b) It should have a long fatigue life.
(c) Both (a) and (b).
(d) None of the above.
Ans: (c) Both (a) and (b).
C. Short answer questions:
1. Differentiate between chassis frame and automobile body.
Ans: The differences between chassis frame and automobile body are:
| Chassis frame | Automobile body |
| Chassis is a French term and was initially used to denote the frame or main structure of a vehicle. | The body or superstructure is made after receiving the chassis from the manufacturer (in conventional chassis construction). |
| It includes a steel frame which is a major part. | The body of a car is made of a sheet of metal or fiberglass. |
| 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. | The body provides space for passengers and cargo, protects from dust and rain, and makes the journey comfortable with cushioned seats and glass panes. |
| Supports vehicle weight, absorbs shocks, and provides stability. | Protects occupants, provides comfort, and enhances aesthetics. |
| Strength, durability, and stability. | Aerodynamics, styling, and functionality. |
2. Explain the use of the chassis frame.
Ans: The chassis frame is used to provide structural support to the vehicle, and its functions include:
(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.
(iv) Withstanding the bending load and twisting due to the rise and fall of the front and rear axles.
3. How does auto body help in transport?
Ans: 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 fiberglass, so that passengers can sit in it. To make the journey comfortable, cushioned seats are provided. The body is provided on all sides with glass panes fixed to protect the passengers from dust and rain.
| Session – 2: Engine and Its Components |
| Check Your Progress |
A.Fill in the blanks:
1. Engine is the __________ of an automobile. Its role is very important.
Ans: Heart.
2. Engine converts the Chemical Energy (heat energy) to ___________ Energy.
Ans: Mechanical.
3. Major parts of engine are ___________, ____________, _________ and ___________.
Ans: Crankshaft, connecting rod, piston, cylinder.
4. The function of the carburettor is to supply uniform ___________ to the cylinder of a _______ through the intake manifold.
Ans: Air-fuel, petrol engine.
5. Sparkplug is used to ____________.
Ans: Ignite the mixture.
B. Multiple choice questions:
1. The compression-ignition engine air is compressed so that its temperature goes up to ____________.
(a) 538 °C (1000 °F) or higher.
(b) 348 °C.
(c) 2480 °C.
(d) None of the above.
Ans: (a) 538 °C (1000 °F) or higher.
2. The cylinder of an IC engine is generally made of _____________.
(a) Cast iron.
(b) Copper.
(c) Iron.
(d) Fibre.
Ans: (a) Cast iron.
3. The charge (fuel and air mixture for SI engine and only air for CI engine) enters through the _____________.
(a) Inlet valve.
(b) Spark plug.
(c) Outlet valve.
(d) Piston.
Ans: (a) Inlet valve.
4. The heart of the engine is the _____________.
(a) Piston.
(b) Cylinder head.
(c) Connecting rod.
(d) All of the above.
Ans: (a) Piston.
C. Short answer questions:
1. Explain the role of engine and its components.
Ans: An engine is a 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 utilized 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.
2. Explain the difference between compression ignition engine and spark ignition engine?
Ans: The spark ignition engine uses a highly volatile fuel, such as gasoline, which turns into vapor easily. The fuel is mixed with air before it enters the combustion chamber and forms a combustible air-fuel mixture. This mixture then enters the cylinder and gets compressed with the help of a piston. An electric spark is produced by the ignition system which ignites the combustible air-fuel mixture. The combustible gases burn and expand, which forces the piston downwards for generating power.
Whereas, In the compression ignition engine or diesel engine, only fresh air enters the cylinder, which is compressed to a very high pressure and temperature, which could go up to 1000°F (538°C). The diesel is then injected or sprayed into the engine combustion chamber. This spray contains very fine and tiny particles of diesel in an atomized form. The hot air or heat of compression ignites the fuel and generates the power stroke.
| Session – 3: Lubrication System |
| Check Your Progress |
A. Fill in the blanks:
1. Dry or solid friction is produced in _____________.
Ans: Two metallic surfaces.
2. Dry friction creates lot of ______________.
Ans: Heat.
3. The objective of lubrication is to reduce __________.
Ans: Friction.
4. Lubrication provides ________ and ______ effect.
Ans: Cushioning, cooling.
B. Multiple choice questions:
1. Viscosity is measured using a _____________.
(a) Barometer.
(b) Thermometer.
(c) Viscometer.
(d) Fathometer.
Ans: (c) Viscometer.
2. Lubricating oil is used for ______________.
(a) Minimising wear in moving parts.
(b) Help in keeping parts cool.
(c) Both (a) and (b).
(d) None of the above.
Ans: (a) Minimising wear in moving parts.
3. Which type of lubrication system is used in a two-stroke engine?
(a) Petrol system.
(b) Wet sump system.
(c) Dry sump system.
(d) All of the above.
Ans:(d) All of the above.
4. Viscosity index is a measure for the change of viscosity with change in ______________.
(a) Pressure.
(b) Temperature.
(c) Volume.
(d) Mass.
Ans: (b) Temperature.
C. Short answer questions:
1. Explain the importance of lubrication in engine.
Ans: The importance of lubrication are:
(i) To reduce friction between moving parts to its minimum value so that power loss is minimized.
(ii) To reduce wear and tear of the moving parts as much as possible.
Apart from these objectives, lubrication also serves other important purposes, which may be called secondary. These are as follows:
(a) To provide cooling effect: The lubricating oil takes heat from the hot moving parts during its circulation and delivers it to the surrounding air through the crank case.
(b) To provide cushioning effect: The lubricating oil also serves as a good cushion against the shocks experienced by the engine. For example, instant combustion of the fuel in the combustion chamber produces a sudden rise of pressure in the cylinder and the shock goes to the bearings through the piston, gudgeon pin and the connecting rod. This shock is then absorbed by the layer of oil present in the main bearings.
(c) To provide cleaning action: The lubricating oil serves another useful purpose of providing a cleaning action. During its circulation, it carries away many impurities, such as carbon particles, etc.
(d) To provide a sealing action: The lubricating oil also helps the piston rings in maintaining an effective seal against the high-pressure gases in the cylinder thus preventing leakage towards the crankcase.”
2. List the properties of lubricant.
Ans: A good lubricant should possess the following properties:
(i) Viscosity: It should have sufficient viscosity to form a lubricating film between moving parts.
(ii) Viscosity Index: The viscosity of the lubricant should not change much with the change in temperature.
(iii) Oiliness: The lubricant should possess adequate oiliness to adhere to the surfaces.
(iv) Pour Point: It should have a low pour point to remain fluid at low temperatures.
(v) Corrosion Resistance: A good lubricant should protect metallic surfaces from corrosion, which can occur due to chemical reactions.
(vi) Thermal Stability: The lubricant should be able to withstand high temperatures without breaking down or forming harmful deposits, says Petro Online.
| Session – 4: Cooling System |
| Check Your Progress |
A. Fill in the blanks:
1. The cooling system removes excess __________ from the engine.
Ans: Heat.
2. Cooling_____________a constant engine operating temperature.
Ans: Maintains.
3. The objective of cooling is to reduce_____________.
Ans: Temperature.
4. Liquid cooling is employed in most ___________engines.
Ans: IC.
B. Multiple choice question:
1. Which of the following type of cooling system is used in a motorcycle?
(a) Air cooling system.
(b) Water cooling system.
(c) Both (a) and (b).
(d) None of the above.
Ans: (b) Water cooling system.
2. The cooling fan is _______________.
(a) Driven by belt and pulleys.
(b) Fitted between the engine and the radiator.
(c) Driven from the camshaft.
(d) All of the above.
Ans: (a) Driven by belt and pulleys.
3. In water cooling, the water in the jacket obtains heat from the cylinder due to _______________.
(a) Conduction.
(b) Convection.
(c) Radiation.
(d) All of the above.
Ans: (a) Conduction.
C. Short answer questions:
1. How does a cooling system work?
Ans: The cylinders of internal combustion engines require cooling because the engine cannot convert all the heat energy released by combustion into useful work. Liquid cooling is employed in most of the IC engines, whether they are used in automobiles or elsewhere. The water (coolant) is circulated around the cylinders to pick up heat and then dissipate it through a radiator. As the temperature increases from 71 to 82 degrees centigrade, the thermostat valve opens and sends water to the radiator to radiate the heat. When the temperature rises above 82 degrees, the thermostat switch operates the cooling fan to support the cooling process in the radiator.
2. What is the role of coolants?
Ans: The role of coolants in an engine is to regulate temperature and prevent overheating. Coolants are specially formulated liquids that circulate through the engine to absorb excess heat and maintain optimal operating temperatures.
Roles of Coolants:
(i) Heat Absorption and Dissipation: Coolants absorb the heat generated by the engine during combustion and transfer it to the radiator, where it is released into the atmosphere. This prevents the engine from overheating.
(ii) Corrosion Protection: Coolants contain additives that prevent corrosion and rust in the engine’s cooling system components, such as the radiator, water pump, and engine block.
(ii) Freezing Prevention: Coolants contain antifreeze additives that lower the freezing point of the coolant, preventing it from turning to ice and potentially damaging the engine in cold weather.
(iv) Lubrication: Coolants help lubricate components like the water pump, reducing friction and wear.
| Session – 5: Fuel Supply System |
| Check Your Progress |
A. Fill in the blanks:
1. Air and fuel are _______ outside the engine.
Ans: Mixed.
2. The fuels, such as petrol, benzol and alcohol are used in ___________ engine.
Ans: IC.
3. Oil fuels which are used in CI engines do not _________ easily.
Ans: Mix.
4. The fuel system is controlled by the ______________.
Ans: ECM.
B. Multiple choice questions:
1. Which of these is used as a fuel in IC engine?
(a) Methanol.
(b) LPG.
(c) Benzoyl.
(d) All of the above.
Ans: (d) All of the above.
2. The carburettor is used to _____________.
(a) Mix petrol and air in correct proportion.
(b) Supply fuel air mixture to the engine.
(c) Both (a) and (b).
(d) None of the above.
Ans: (c) Both (a) and (b).
3. In a multi-point fuel injection the injector is used for how many cylinder engines?
(a) Five.
(b) Two.
(c) Four.
(d) Six.
Ans: (d) Six.
4. Which of the following is not an injector fault?
(a) Blue nozzle body.
(b) Nozzle wetness blue nozzle body.
(c) Excessive leak off.
(d) Blow holes.
Ans: (d) Blow holes.
C. Short answer questions.
1. Write the importance of a fuel supply system.
Ans: In petrol engines, the fuel and air mixture is supplied to the combustion chamber of an engine. This mixture is atomised and then vapourised by the carburettor. Then the mixture is ignited by the spark plug. The fuels, such as petrol, benzoyl, and alcohol are used in an SI engine. Nowadays, fuel is injected in the flow of air at a certain temperature and pressure, and the fuel vaporises faster, leading to better combustion with low emissions and improved fuel efficiency.
In the case of a compression ignition engine (diesel), the fuel is sent through the fuel pump to the injector, which sprays the fuel at the end of the compression stroke. The oil fuels used in CI engines do not vaporise easily. Therefore, a separate injection system is used consisting of a fuel injection pump (FIP) and injectors. These injectors atomise the fuel, and it is then sent for combustion.
2. Explain the correct method of injecting fuel in an automobile.
Ans: Fuel Injection Pump: In the case of a 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 increases the pressure of the fuel. This high-pressure fuel is then transferred to the distributor rotor through the metering valve. From the rotor, the fuel is sent to the injector. In the case of a multi-point fuel injection (MPFI) system, the electric fuel pump is used. 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.
| Session – 6: Transmission System |
| Check Your Progress |
A. Fill in the blanks:
1. Transmission system consists of ___________ components.
Ans: Three.
2. The main parts of a clutch are _________ and ___________.
Ans: Driving members and driven members.
3. Different gear ratios in the _________ makes the vehicle move at different speeds.
Ans: Gear box.
4. The clutch assembly consist of flywheel, pressure plate and ____________.
Ans: Clutch disc.
B. Multiple choice questions:
1. Which of these systems is used in motor vehicles to supply the output of the internal combustion engine to drive wheels?
(a) Transmission system.
(b) Power system.
(c) Torque system.
(d) None of the above.
Ans:(a) Transmission system.
2. Which type of transmission system is used for a disengagement and engagement between the engine and the remainder of transmission system?
(a) Clutch.
(b) Differential.
(c) Propeller shaft.
(d) None of the above.
Ans: (a) Clutch.
3. In a four-wheel drive there is __________.
(a) One live axle.
(b) No live axle.
(c) Two live axle.
(d) None of the above.
Ans: (c) Two live axle.
4. ____________ produces different gear ratios in automobiles.
(a) Transmission system.
(b) Differential.
(c) Steering.
(d) Gear box.
Ans: (d) Gear box.
C. Short answer questions:
1. Discuss the role of a transmission system.
Ans: The transmission system is used in motor vehicles to supply the output of the internal combustion engine to drive wheels. It provides different gear ratios that make the vehicle move at different speeds. The clutch is used to engage and disengage the engine from the transmission system smoothly.
2. Explain the function of a gear box.
Ans: Functions of a gear box:
(i) To provide a means to vary the leverage or torque ratio between the engine and the road wheels as required.
(ii) The transmission also provides a neutral position so that the engine and the road wheels are disconnected even with the clutch in the engaged position.
(iii) It provides a means to reverse the car by selecting the reverse gear.
| Session – 7: Front and Rear Axle |
| Check Your Progress |
A. Fill in the blanks:
1. Axle and steering system transmit ______ to the wheel.
Ans: Power.
2. Front and rear axle system is used for __________.
Ans: Power transmission.
3. Differential mechanism enables the __________ to move faster than the inner wheel while taking a turn.
Ans: Outer wheel.
4. Rear axle ________ the weight of vehicle body.
Ans: Bears.
B. Multiple choice questions:
1. The central portion of the front axle is made of__________.
(a) I section.
(b) T section.
(c) Q section.
(d) U section.
Ans: (a) I section.
2. The end of the front axle is mounted with ____________.
(a) Stub axles.
(b) King pin.
(c) Piston ring.
(d) Axle shaft.
Ans: (a) Stub axles.
3. What kind of load does the axle take due to the load of the vehicle?
(a) Bending load.
(b) Frictional load.
(c) Torsional load.
(d) None of these.
Ans: (a) Bending load.
C. Short answer questions:
1. What is the role of a front axle?
Ans: Front axle carries the weight of the front portion of the automobile as well as facilitates steering and controls the rolling of wheels. It also absorbs road shocks arising due to road surface variations.
In case of a commercial vehicle the front axles are generally dead axles. The front axle is designed to transmit the weight of the automobile from the springs to the front wheels, turning right or left as required.
To prevent interference due to front engine location, and for providing greater stability and safety at high speeds by lowering the centre of gravity of the road vehicles, front axle includes the axle-beam, stub-axles with brake assemblies.
It is made of drop forged alloy steel consisting of 0.4% carbon steel and 1.3% nickel steel.
The axle is made of I-section at centre and of circular or elliptical section in the ends since it has to bear the bending stress and torsional stress. In order to lower the chassis height a downward sweep is provided at the centre of the beam axle.
The main beam axle is connected to the stub axle with a king pin. The front road wheels are mounted on the stub axle.
For smooth steering effects and maintaining proper control, the front axle of a car is supported with an independent suspension system, such as Mac-pherson. The strut and coil spring allows the wheel to move up and down but does not allow to change the driving angle of axle shaft to transmit the drive smoothly. It also allows the wheel to rotate freely. This supports in steering the vehicle.
2. Why are rear axles required?
Ans: Like the front axle, the rear axle is also made of drop forged steel. The rear axle bears the weight of the vehicle body and load with springs. It enables to transmit the driving and braking torque to the chassis frame and body of the vehicle. It also bears the side thrust or pull due to any side load on the wheel. It supports various parts like bevel pinion, bevel gear, cage of sun gear and star pinions, axle shafts, and different support bearings.
It is important to note that rear road wheels are mounted on the axle shaft and the differential mechanism enables the outer wheel to move faster than the inner wheel while taking a turn.
| Session – 8: Steering and Suspension System |
| Check Your Progress |
A. Fill in the blanks:
1. Steering system is used for __________.
Ans: Controlling the vehicle.
2. Main parts of steering system are __________and steering column.
Ans: Steering wheel.
3. A suspension system consists of springs, __________ and linkages that connect a vehicle to its wheels.
Ans: Shock absorbers.
4. A suspension system keeps vehicle occupants ____________.
Ans: Safe.
B. Multiple choice questions:
1. The tilting of the front wheels away from the vertical is called _____________.
(a) Camber.
(b) Caster.
(c) Toe-in.
(d) Toe- out.
Ans: (b) Caster.
2. Which of the following types of mechanism is used in a steering system?
(a) Rack and pinion steering.
(b) Rotary motion is turning.
(c) Reciprocating motion.
(d) Power steering system.
Ans: (d) Power steering system.
3. Leaf spring absorbs shocks by ___________.
(a) Tension.
(b) Compression.
(c) Twisting.
(d) Bending.
Ans: (d) Bending.
4. Compressed air is used for ______________.
(a) Air suspension system.
(b) Hydraulic suspension.
(c) Mechanical suspension.
(d) None of the above.
Ans: (a) Air suspension system.
C. Short answer questions:
1. How does a steering system work?
Ans: The steering mechanism permits the driver to control the car on a straight road and turn right or left as desired. The steering mechanism includes a steering wheel, which the driver controls, a steering gear, which converts rotary motion of steering wheel into straight line motion and steering linkages. In modern cars, the manually operated steering system is assisted by power and is called power steering. The electric power drawn from the battery or hydraulic power is used.
Functions of a Steering System:
(i) It provides directional stability to the vehicle when moving in a straight (ahead) direction.
(ii) It provides perfect steering condition, i.e., perfect rolling motion of the wheels at all times.
(iii) It facilitates straight ahead recovery after completion of turn.
(iv) It controls the wear and tear of the tyre.
(v) It is used to turn the vehicle as per the will of the driver.
(vi) It converts the rotary motion of the steering wheel into angular displacement of the front wheel.
(vii) It multiplies the effort of the driver to ease operation.
(viii) It absorbs road shocks and prevents them from reaching the driver.
2. What is a power steering system?
Ans: A power steering system is a mechanism that uses engine power to assist the driver in turning the steering wheel, reducing the effort required to steer the vehicle. It uses external power, usually hydraulic pressure or electric power, to assist the driver in turning the wheels, especially at low speeds or when the vehicle is stationary.
| Session – 9: Wheel, Tyre and Brake |
| Check Your Progress |
A. Fill in the blanks:
1. Wheel is an important component of the ___________.
Ans: Vehicle.
2. Tyre is fitted on the _____________.
Ans: Rim.
3. Brake should work _________ on roads.
Ans: Equally well.
4. Hand brake is also known as ___________ brake.
Ans: Emergency.
B. Multiple choice questions:
1. The most important component of a vehicle is __________.
(a) Wheel.
(b) Rim.
(c) Disk.
(d) Tyre.
Ans: (a) Wheel.
2. The tyre is mounted on the ____________.
(a) Vehicle.
(b) Disc.
(c) Wheel rim.
(d) None of the above.
Ans: (c) Wheel rim.
3. The main component of the generating or charging system is (are) ____________.
(a) Generator/alternator.
(b) Ammeter.
(c) The battery.
(d) All of the above.
Ans: (a) Generator/alternator.
C. Short answer questions:
1. What are the components of a wheel?
Ans: The wheel is an important component of a vehicle. Wheel of a four-wheeler vehicle is mounted on a hub and consists of parts like rim, tyre and tube. The wheels not only support the weight of the vehicle, but also protect it from road shocks. All the four wheels must resist the braking stresses and withstand side thrust. A wheel should be light and easily removable.
2. How does the brake system function?
Ans: A braking system uses friction to slow down or stop a vehicle. When the brake pedal is pressed, the brake shoes or pads are pressed against the rotating drum or disc of the wheel. This creates friction that slows down or stops the wheel from turning. The braking force is transmitted through hydraulic or mechanical means.
| Session – 10: Electrical or Electronic and Air Conditioning Systems |
| Practical Exercises |
A.Fill in the blanks:
1. ________ is the main component of a refrigeration system.
Ans: Evaporator.
2. Battery is used for _______ vehicle.
Ans: Charging.
3. Starting system consist of battery and starting_________.
Ans: Motor.
4. Warm temperature in the car is maintained by ____________.
Ans: Heater.
B. Multiple choice questions:
1. The starting motor is driven by means of the current taken from the________________.
(a) Battery.
(b) Stabiliser.
(c) Ignition coil.
(d) None of the above.
Ans: (a) Battery.
2. The function of the ignition system is __________.
(a) To produce a spark in the engine combustion chamber.
(b) To generate, regulate and supply the electrical energy.
(c) To produce a current for charging.
(d) None of the above.
Ans: (a) To produce a spark in the engine combustion chamber.
3. List the electrical accessories used in vehicle.
| S. No. | List of accessories |
| 1. | |
| 2. | |
| 3. |
Ans:
| S. No. | List of accessories |
| 1. | Horns. |
| 2. | Electric fuel pump. |
| 3. | Heater. |
4. Air conditioner losses energy from the ____________.
(a) Battery system.
(b) Condenser.
(c) Engine.
(d) None of the above.
Ans: (a) Battery system.
C. Short answer questions:
1. Discuss the importance of electrical and electronic system in automobiles.
Ans: Nowadays, all the automobiles run with the help of electrical and electronic system, and therefore, it plays an important part in the functioning of an automobile.
The electrical and electronic systems consist of the following.
(i) Starting system: The starting motor is driven by means of the current taken from the battery.
(ii) Ignition system: The function of the ignition system is to produce a spark in the engine combustion chamber at the end of the compression stroke.
(iii) Generating or charging system: The function of the charging system in an automobile is to generate, regulate and supply the electrical energy for charging the battery.
(iv) Lighting system: It consists of various types of lighting used during the vehicle running, such as head light, tail light, fog light, brake light, reversing light, left and right indicators, parking light, cabin light, panel board lights, etc.
(v) Connections for other accessories.
2. What are the components of an air conditioning system?
Ans: Different Components of Automobile Air Conditioning System:
(i) Compressor.
(ii) Magnetic clutch.
(iii) Condenser.
(iv) Receiver-drier (or dehydrator).
(v) Expansion valve.
(vi) Evaporator.
(vii) Throttling valve.
(i) Compressor: A compressor is unit driven by the engine. It has a low pressure side port which is connected to the evaporator and a high pressure side port which is connected to the condenser using rubber hoses. The compressor is the main mechanical part of the system. In hybrid engines the compressor is electrically powered. A small electric motor is fitted inside the compressor which pressurises the refrigerant. These compressors have a pair of large gauge wires which form the compressor controller. In latest cars, where the climetrons are used the electric power supply is controlled by ECU as per the temperature settings.
(ii) Clutch: The compressor is always fixed with a clutch. The major function of the clutch is to transmit the power smoothly to the compressor when the system is operated.
(iii) Condenser: The major function of this device will be to change the high-pressure refrigerant vapour to a liquid. The condenser is mounted in front of the engine’s radiator, and it looks similar to a radiator. The condenser is a cooling device in which the vapour is condensed to a liquid because of the high pressure that is driving it in, and this generates a great deal of heat. The heat is then in turn removed from the condenser by air flowing through the condenser on the outside.
(iv) Receiver-drier: The main function of this device is to filter refrigerant. The liquid refrigerant moves to the receiver-drier. This is a small reservoir vessel for the liquid refrigerant, which removes any moisture that may have leaked into the refrigerant and also stores excess quantity of refrigerant.
(v) Expansion Valve: The pressurised refrigerant flows from the receiver-drier to the expansion valve. The expansion valve is a controlling device which controls the varying load when there are pressure changes in the evaporator, as it may increase or decrease. The valve maintains a constant pressure throughout the varying load on the evaporator controlling the quantity of refrigerant flowing into the evaporator.
(vi) Evaporator: It is the main component of a refrigeration system and is also called the cooling coil. It has tubes and fins or freezing coil. It is usually placed inside the passenger compartment above the footwell. As the cold low-pressure refrigerant is passed into the evaporator, it vapourises and absorbs heat from the air in the passenger compartment. The blower fan inside the passenger compartment pushes air over the outside of the evaporator, so cold air is circulated inside the car. On the ‘air-side’ of the evaporator, the moisture in the air is reduced, and the ‘condensate’ is collected.
(vii) Throttling Device: It is a part of refrigeration system and air conditioning system. When refrigerant comes out from the condenser at a medium temperature and high pressure, it enters the throttling valve. In the throttling valve, the pressure and temperature of the refrigerant are decreased suddenly and the cooling effect is provided to the evaporator.
| Session – 11: Active and Passive Safety |
| Check Your Progress |
A. Fill in the blanks:
1. Air bags are used for ___________.
Ans: Safety.
2. Seat belt is also known as a __________ belt.
Ans: Safety.
3. Passive safety system helps __________.
Ans: Automatically.
4. Active safety system is used for avoiding ____________.
Ans: Accidents.
B. Multiple choice questions:
1. Which types of anti-theft devices are available in a vehicle?
(a) Locking devices.
(b) Disabling devices.
(c) Alarm systems.
(d) All of the above.
Ans: (d) All of the above.
2. Tempered glass is used for _____________.
(a) Side and rear window glass.
(b) Auto window and door.
(c) Head light.
(d) All of the above.
Ans: (a) Side and rear window glass.
3. Which of these safety systems are operated automatically?
(a) Passive safety system.
(b) Active safety system.
(c) Energy-absorber safety.
(d) None of the above.
Ans: (a) Passive safety system.
4. Impact sensors are used in ________________.
(a) Electrical system.
(b) Mechanical system.
(c) Auto-mechanical system.
(d) None of the above.
Ans: (a) Electrical system.
C. Short answer question:
1. Discuss the components of the active and passive safety system.
Ans: There are different safety and security systems for automobiles available in the market and some of which are fitted by the manufacturer.
Some of the active and passive security systems are mentioned as follows.
(a) Safety Glass: Safety glass is used in all windows and doors of automotives. The safety glass used in today’s vehicles is of two types — laminated and tempered. These are considered as safety glass because of their varying strength.
Laminated plate glass is used to make windshields. It consists of two thin sheets of glass with a thin layer of clear plastic between them. Some glass manufacturers increase the thickness of the plastic material for better strength. When this type of glass breaks, the plastic material tends to hold the shattered glass in place and thus, prevents it from causing injury.
Tempered glass is used for side and rear window glass but rarely for windshields. It is a single piece of heat-treated glass and has more resistance to impact than the regular glass of the same thickness. Thus, it has greater strength compared to a laminated plate glass.
(b) Seat belts: A seat belt is also called a safety belt. It is a harness designed to protect the occupant of a vehicle from harmful movement, during a collision or when the vehicle stops suddenly.
A seat belt reduces the likelihood and severity of injury in a traffic collision. It prevents the vehicle occupant from hitting hard against the interior elements of the vehicle or other passengers, and keeps the occupants positioned in place for maximum benefit from the airbag.
The passenger must fasten the seat belt for crash protection. However, in case of a passive safety system, such as the inflation of air bags at the time of an accident, is automatic. No action is required of the occupant to make it functional. Nowadays, seat belts are also provided for rear seat occupants.
(c) Airbags: An airbag is one of the passive safety systems for the occupants of a four-wheeler. The electrical system of airbags includes impact sensors and an electronic control module. In case of an accident, the sensor detects the impact and the airbag opens up to save the driver and other occupants.
(d) Energy-absorber Safety Bumpers: Modern bumpers are designed to absorb the energy of a low-speed impact, minimizing the shock directed to the frame and to the occupants of the vehicle. Most energy absorbers are mounted between the bumper face bar or bumper reinforcement bar and the frame.
(e) Security Devices: There are three basic types of security devices available — locking devices, disabling devices and alarm systems.
In automobile vehicles, an anti-theft system or device is installed to prevent theft of a vehicle. Many car security devices are available in the market. These are mechanical devices and ignition cut off devices, intelligent computerized anti-theft devices, satellite tracking system, engine control module, etc. Vehicle owners may select as per risk and install it in their vehicles. Prior to purchasing, the customers should check that these theft devices are duly approved from the Automobile Research Association of India (ARAI).
Important features of these devices are explained below:
(i) Alarm: In the case of vehicle tampering, audible warning sounds emerge.
(ii) Keyless Lock Device: To use the vehicle, electronic coding device is required.
(iii) Electronic Immobilisers: These built-in transponders send signals to the ignition and fuel pump system. The vehicle remains in stationary or inoperable state if the ignition starters do not get correct signals.
(iv) Steering Wheel Lock: This device is fitted in the steering of the vehicle and it locks it in one place so that no one can drive it without removing the lock.
(v) Vehicle Tracking: Even if a thief steals a vehicle, the tracking technologies can help trace it. Tracking devices offer real-time location of the stolen vehicle with the help of the global positioning system (GPS).
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