What is an Automobile?
"Automobile", a
classical compound derived from Ancient Greek autós (αὐτός) "self"
and Latin mobilis "movable", entered English from French and was
first adopted by the Automobile Club of Great Britain in 1897. An automobile is
a self-propelled vehicle that has a power source for its propulsion and is used
to carry passengers and goods on land, such as cars, buses, trucks, etc.
Automobiles are classified on the purpose of the vehicle depending on whether
the vehicle is used to carry passengers or used for transportation of goods or
USD for any special purpose. Passenger vehicle – Car, bus, taxi, etc.
Commercial vehicle – Trucks, tempos, containers, etc.
A automobile is a motor
vehicle with wheels. A self-propelled
passenger vehicle that usually has four wheels and an internal-combustion
engine using a volatile fuel., used for land transport. An automobile (or car)
is a land vehicle used to carry passengers. The most common engine types the
four-cylinder, the boxer-four, straight-six, V6 and V8
Cars were invented in
1886, when German inventor Carl Benz patented his Benz Patent-Motorwagen.
most important part of an
automobile is Engine. It makes sense to start with the most important part
under the hood of a vehicle, which is the engine. modern vehicles run on
internal combustion engines, which generate energy by igniting a mixture of air
and fuel that moves pistons, which in turn move the car. 4 stages of an engine
are fuel injection, ignition, expansion (work is done), exhaust.
3 types of engines are
Internal combustion engines., Hybrid engine (Internal combustion engine +
electric engine), Electric engine.
A vehicle is composed of
basic mechanical parts and devices making up its systems; each of them fulfills
a specific function such as Fuel supply system, Transmission system, Suspension
system, Braking system, Steering system, Cooling system, Electrical system,
Exhaust system.
Automobile engineering is
a branch study of engineering which teaches manufacturing, designing,
mechanical mechanisms as well as operations of automobiles. It is an
introduction to vehicle engineering which deals with motorcycles, cars, buses,
trucks, etc.
An 'Automobile' is a word that derived from Greek means auto, self and Latin mobilis meaning moving, a vehicle that moves itself rather than being moved by another vehicle or animal or motor car is a wheeled passenger vehicle that carries its own motor.
Most definitions of the term specify that automobiles are designed to run primarily on roads, to have seating for people, to typically have four wheels, and to be constructed principally for the transport of people and goods.
An “automobile” is a self-propelled vehicle driven by an internal combustion engine and is used for transportation of passengers and goods on the ground.
Automobile engineering deals with the various types of automobiles, their mechanism of transmission systems and its applications.
Automobiles are the different types of vehicles used for transportation of passengers, goods, etc. All the types of vehicles work on the principle of internal combustion processes or sometimes the engines are called as internal combustion engines. Different types of fuels are burnt inside the cylinder at higher temperature to get the transmission motion in the vehicles.
Automobile engineering is a branch of mechanical engineering which deals with everything about automobiles and practices to propel them.
CLASSIFICATION OF VEHICLES
Automobiles or vehicles can be classified on different bases as given below:
On the Basis of Load
(a) Heavy transport vehicle (HTV) or heavy motor vehicle (HMV),
e.g. trucks, buses, tractor etc.
(b) Light transport vehicle (LTV),
e.g. pickup, station wagon, etc.
(c) Light motor vehicle (LMV),
e.g., cars, jeeps, etc.
WHEELS
(a) Two-wheeler vehicle,
eg: Scooter, motorcycle, etc.
(b) Three-wheeler vehicle,
eg:: Autorickshaw,
(c) Four-wheeler vehicle,
eg: Car, jeep, trucks, buses, etc.
(d) Six-wheeler vehicle,
eg: Big trucks with two gear axles each having four wheels.
FUEL USED
(a) Petrol vehicle,
e.g., motorcycle, scooter, cars, etc.
(b) Diesel vehicle,
e.g., trucks, buses, etc.
(c) Electric vehicle which use battery to drive.
(d) Steam vehicle,
e.g. steam boat etc.
(e) Gas vehicle,
e.g. LPG and CNG vehicles, where LPG is liquefied petroleum gas and CNG is compressed natural gas.
BODY
On the basis of body, the vehicles are classified as:
(a) Sedan with two doors
(b) Sedan with four doors
(c) Station wagon
(d) Convertible,
e.g. jeep, etc.
(e) Van
(f) Special purpose vehicle,
e.g. ambulance, milk van, etc.
TRANSMISSION
(a) Conventional vehicles with manual transmission,
e.g. car with 5 gears.
(b) Semi-automatic
(c) Automatic: Gears are not required to be changed manually. It automatically changes as speed increases or decrease in automobiles.
POSITION OF ENGINE
Engine in Front
eg: cars, buses, trucks in India.
Engine in the Rear Side
eg:: Nano car.
LAYOUT OF AN AUTOMOBILE CHASIS
Introduction of Chassis Frame: Chassis is a French term and was initially used
to denote the frame parts or Basic Structure of the vehicle. It is the back bone
of the vehicle. A vehicle without body is called Chassis. The components of
the vehicle like Power plant, Transmission System, Axles, Wheels and Tyres,
Suspension, Controlling Systems like Braking, Steering etc., and also electrical
system parts are mounted on the Chassis frame. It is the main mounting for all
the components including the body. So, it is also called as Carrying Unit.
The automobile can be considered to consist of five basic components:
(a) The Engine or Power Plant: source of power.
(b) The Frame and Chassis: supports the engine, wheels, body, braking system, steering, etc.
(c) The transmission which transmits power from the engine to the car wheels.
It consists of clutch, transmission, shaft, axles and differential.
(d) The body.
(e) Accessories including light, air conditioner/heater, stereo, wiper, etc.
The following main components of the Chassis are
1. Frame: is made up of long two members called side members riveted together with the help of number of cross members.
2. Engine or Power plant: It provides the source of power
3. Clutch: It connects and disconnects the power from the engine flywheel to the transmission system.
4. Gear Box
5. U Joint
6. Propeller Shaft
7. Differential
FUNCTIONS OF THE CHASSIS FRAME:
1. To carry load of the passengers or goods carried in the body.
2. To support the load of the body, engine, gear box etc.,
3. To withstand the forces caused due to the sudden braking or
acceleration
4. To withstand the stresses caused due to the bad road condition.
5. To withstand centrifugal force while cornering
TYPES OF CHASSIS FRAMES:
There are three types of frames
1. Conventional frame
2. Integral frame
3. Semi-integral frame
1. Conventional frame: It has two long side members and 5 to 6 cross
members joined together with the help of rivets and bolts. The frame sections
are used generally.
a. Channel Section - Good resistance to bending
b. Tabular Section - Good resistance to Torsion
c. Box Section - Good resistance to both bending and Torsion
2. Integral Frame: This frame is used now a days in most of the cars. There is
no frame and all the assembly units are attached to the body. All the
functions of the frame carried out by the body itself. Due to elimination of
long frame it is cheaper and due to less weight most economical also. Only
disadvantage is repairing is difficult.
3. Semi - Integral Frame: In some vehicle’s half frame is fixed in the front end
on which engine gear box and front suspension is mounted. It has the
advantage when the vehicle is met with accident the front frame can be
taken easily to replace the damaged chassis frame. This type of frame is
used in FIAT cars and some of the European and American cars.
VARIOUS LOADS ACTING ON THE FRAME:
Various loads acting on the frame are
1.Short duration Load - While crossing a broken patch.
2. Momentary duration Load - While taking a curve.
3. Impact Loads - Due to the collision of the vehicle.
4. Inertia Load - While applying brakes.
5. Static Loads - Loads due to chassis parts.
6. Over Loads - Beyond Design capacity.
The Automobile bodies are divided in two groups:
- Passenger Body
- Commercial body
According to Chassis design the body can divided into:
1. Conventional Type
2. Integral Type
3. Semi- Integral Type
According to other usage:
1. Light vehicle Bodies - cars, jeeps
2. Heavy vehicle Bodies – Busses, Lorries
3. Medium vehicle Bodies - Vans, Matadors
REQUIREMENTS OF BODIES FOR VARIOUS TYPES OF VECHILE:
The body of the most vehicle should fulfil the following requirements:
1. The body should be light.
2. It should have minimum number of components.
3. It should provide sufficient space for passengers and luggage.
4. It should withstand vibrations while in motion.
5. It should offer minimum resistance to air.
6. It should be cheap and easy in manufacturing.
7. It should be attractive in shape and color.
8. It should have uniformly distributed load.
9. It should have long fatigue life
10.It should provide good vision and ventilation.
FUNCTIONS OF MAJOR COMPONENTS OF AN AUTOMOBILE
CHASSIS AND FRAME:
The frame is usually made of box, tubular and channel members that are welded or riveted together. It comprises of the springs with the axles and wheels, the steering system and the brakes, the fuel tank, the exhaust system, the radiator, the battery and other accessories.
ENGINE OR POWER PLANT:
The engine is the power plant of the vehicle. Internal combustion engine with petrol or diesel fuel is used to run a vehicle. An engine may be either a two-stroke engine or a four-stroke engine.
An engine consists of a cylinder, piston, valves, valve operating mechanism, carburetor, fan, fuel feed pump and oil pump, etc.
TRANSMISSION
SYSTEM:
The mechanism that transmits the power developed by the engine of automobile to the engine to the driving wheels is called the TRANSMISSION SYSTEM (or POWER TRAIN).
IT IS COMPOSED OF:
- Clutch
- The gear boxes
- Propeller shaft
- Universal joints
- Rear axle
- Wheel
- Tyres
REQUIREMENTS OF TRANSMISSION SYSTEM: -
- Provide means of connection and disconnection of engine with rest of power train without shock and smoothly.
- Provide a varied leverage between the engine and the drive wheels
- Provide means to transfer power in opposite direction.
- Enable power transmission at varied angles and varied lengths.
- Enable speed reduction between engine and the drive wheels in the ratio of 5:1.
- Enable diversion of power flow at right angles.
- Provide means to drive the driving wheels at different speeds when required.
- Bear the effect of torque reaction, driving thrust and braking effort effectively.
The above requirements are fulfilled by the following main units of transmission system: -
- Clutch
- Gear Box
- Transfer Case
- Propeller Shaft and Universal Joints.
- Final Drive
- Differential
- Torque Tube
- Road Wheel
- Wheel Tyre
A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its Centre, facilitating movement or transportation while supporting a load (mass), or performing labor in machine.
While tyre is the outer part of the wheel made up with rubber and mostly use in vehicles for smooth movement.
Power developed by the engine is transferred to the wheels by transmission system.
(a) It must provide varying gear ratios. Number of gear ratios are equal to number of gears in a vehicle.
(b) It must provide a reverse gear for moving vehicle in reverse direction.
(c) It must provide a neutral or disconnecting arrangement so that the engine can be uncoupled from the wheels of the vehicle.
In a conventional transmission system, there is a clutch, a manually operated transmission (gear box), a propeller shaft and a differential or final drive.
MANUAL TRANSMISSION SYSTEM: -
In this type of transmission system, the driver has to manually select and engage the gear ratios.
CLUTCH FULLY DEPRESSED
The clutch is fully disengaged when the pedal is fully depressed. There will be no torque being transferred from the engine to the transmission and wheels. Fully depressing the clutch allows the driver to change gears or stop the vehicle.
CLUTCH SLIPS
The clutch slips are the point that vary between being fully depressed and released. The clutch slip is used to start the vehicle from a stand still. It then allows the engine rotation to adjust to the newly selected gear ratio gradually. It is recommended not to slip the clutch for a long time because a lot of heat is generated resulting in energy wastage.
CLUTCH FULLY RELEASED
The clutch is fully engaged when the pedal is fully released. All the engine torque will be transmitted to the transmission. This results in the power being transmitted to the wheels with minimum loss.
Automatic transmission: -Automatic transmission system is the most advanced system in which drives mechanical efforts are reduced very much and different speeds are obtained automatically. This system is
generally, also called hydromantic transmission. It contains epicyclic gear arrangement, fluid coupling and torque converter. In this
planetary gears sets are placed in series to provide transmission. This type of transmission is used by Skoda, Toyota, Lexus, etc
Epicyclic gearing (planetary gearing): - it is a gear system consisting of one or more outer gears, or planet gears, revolving about a central gear. By using epicyclic gear, different torque speed ratio can be obtained. It also compacts the size of gear box.
STAGES OF AUTOMATIC TRANSMISSION: -
Park(P): -
selecting the park mode will lock the transmission, thus restricting the vehicle
from moving.
Reverse(R): -
selecting the reverse mode puts the car into reverse gear, allowing the vehicle to move backward.
Neutral (N): - selecting neutral mode disconnects the transmission from the wheel.
Low (L): - selecting the low mode will allow you to lower the speed to move on hilly and middy areas.
Drive (D): - selecting drive mode allows the vehicle to move and accelerate through a range of gears.
CLUTCH:Clutch allows the driver to couple or decouple the engine and transmission. When clutch is in engaged position, the engine power flows to the transmission through clutch. When gears are to be changed while vehicle is running, the clutch permits temporary decoupling of engine and wheels so that gears can be shifted.
FUNCTION OF A CLUTCH:-
a) To permit engagement or disengagement of a gear when the vehicle is stationary and the
engine is running
b) To transmit the engine power to the road wheels smoothly without shock to the transmission
system while setting the wheel in motion.
c) To permit the engaging of gears when the vehicle is in motion without damaging the gear
wheels.
PRINCIPLE OF OPERATION OF A CLUTCH: -
The clutch principle is based on friction. when two friction surfaces are brought in contact with each other and pressed they are united due to friction between them. If one is revolved the other will also revolve. The friction between the two surfaces depends upon.
Area of the surface,
ii. Pressure applied upon them,
iii. Coefficient of friction of the surface materials
one surface is considered as driving member and the other as driven member.
The driving member of a clutch is the flywheel mounted on the crank shaft; the driven member is the pressure plate mounted on the transmission shaft. Friction surfaces (clutch plates) are between the two members (driving and driven). On the engagement of the clutch, the engine is connected to the transmission (gear box) and the power flows from the engine to the rear wheels through the transmission system. when the clutch is disengaged by pressing a clutch pedal, the engine is disconnected from the transmission and consequently the power does not flow to the rear wheels while the engine is still running.
TYPES OF TRANSMISSION SYSTEM :-
HYDRAULIC TRANSMISSION SYSTEM: -
Fluid coupling : A fluid coupling is a hydrodynamic device used to transmit rotating mechanical power. It has been used in automobile transmissions as an alternative to a mechanical clutch. It consists of a pump-generally known as impeller and a turbine generally known as rotor, both enclosed suitably in a casing. They face each other with an air gap. The impeller is suitably connected to the prime mover while the rotor has a shaft bolted to it. This shaft is further connected to the driven machine through a suitable arrangement. Oil is filled in the fluid coupling from the filling plug provided on its body.
There is no mechanical interconnection between the impeller and the rotor and the power is transmitted by virtue of the fluid filled in the coupling. The impeller when rotated by the prime mover imparts velocity and energy to the fluid, which is converted into mechanical energy in the rotor thus rotating it. The fluid follows a closed circuit of flow from impeller to rotor through the air gap at the outer periphery and from rotor to impeller again through the air gap at the inner periphery. To enable the fluid to flow from impeller to rotor it is essential that there is difference in the "heat" between the two and thus it is essential that there is difference in R.P.M., known as slip between the two. As the slip increases more and more fluid can be transferred from the impeller to the rotor and more torque is transmitted.
Torque Converter: - Torque converter is a hydraulic transmission which increases
the torque of the vehicle reducing its speed. It provides a continuous variation of
ratio from low to high. The key characteristic of a torque converter is its ability to
multiply torque when there is a substantial difference between input and output
rotational speed, thus providing the equivalent of a reduction gear. cars with
an automatic transmission has no clutch that disconnects the transmission from
the engine. So, they use an amazing device called a torque converter.
There are four components inside the very strong housing of the torque converter:
- Pump
- Turbine
- Stator
- Transmission fluid
The housing of the torque converter is bolted to the flywheel of the engine, so it turns at whatever speed the engine is running at. The pump inside a torque converter is a type of centrifugal pump. As it spins, fluid is flung to the outside. As fluid is flung to the outside, a vacuum is created that draws more fluid in at the centre. The fluid then enters the blades of the turbine, which is connected to the transmission. The turbine causes the transmission to spin,which basically moves your car. The blades of the turbine are curved. This means that the fluid, which enters the turbine from the outside, has to change direction before it exits the centre of the turbine. It is this directional change that causes the turbine to spin. n o r der to change the direction of a moving object, you must apply a force to that object -- it doesn't matter if the object is a car or a drop of fluid. And whatever applies the force that causes the object to turn must also feel that force, but in the opposite direction. So as the turbine causes the fluid to change direction, the fluid causes the turbine to spin. The fluid exits the turbine at the centre, moving in a different direction than when it entered. The fluid exits the turbine moving opposite the direction that the pump (and engine) is turning. If the fluid were allowed to hit the pump, it would slow the engine down, wasting power. This is why a torque converter has a stator. The stator resides in the very centre of the torque converter. Its job is to redirect the fluid returning from the turbine before it hits the pump again. This dramatically increases the efficiency of the torque converter. The stator has a very aggressive blade design that almost completely reverses the direction of the fluid. A one-way clutch (inside the stator) connects the stator to a fixed shaft in the transmission (the direction that the clutch allows the stator to spin is noted in the figure above). Because of this arrangement, the stator cannot spin with the fluid -- it can spin only in the opposite direction, forcing the fluid to change direction as it hits the stator blades.
Final drive is the last stage in transferring power from engine to wheels. It reduces the speed of the propeller shaft to that of wheels
The propeller shaft has a small bevel pinion which meshes with crown wheel. The crown wheel gives rotary motion to rear axles. The size of crown wheel in bigger than that of bevel pinion, therefore, the speed of rear axles lower than the speed of pinion.
Brakes are used to slow down or stop the vehicle. Hydraulic brakes are generally used in automobiles, where brakes are applied by pressure on a fluid. Mechanical brakes are also used in some vehicles. These brakes are operated by means of leavers, linkages, pedals, cams, etc. Hand brake or parking brake is usually a mechanical brake. These are used for parking the vehicles on sloppy surfaces and also in case of emergency.
Gear Box
Gear box contain gearing arrangement to get different speeds. Gears are used to get more than one speed ratios. When both mating gears have same number of teeth, both will rotate at same number speed. But when one gear has less teeth than other, the gear with less number of teeth will rotate faster than larger gear. In a typical car, there may be six gears including one reverse gear. First gear gives low speed but high torque. Higher gears give progressively increasing speeds. Gears are engaged and disengaged by a shift lever.
Steering System
Front wheels can be turned to left and right by steering system so that the vehicle can be steered. The steering wheel is placed in front of driver. It is mechanically linked to the wheels to provide the steering control. The primary function of the steering system is to provide angular motion to front wheels so that vehicle can negotiate a turn. It also provides directional stability to vehicle when the vehicle moves ahead in straight line.
many vehicles are equipped with power steering which uses pressure of a fluid to reduce steering effort. When driver turns the steering wheel, a hydraulic mechanism comes into play to provide most of the effort needed to turn the wheel.
Front Axle
Front axles are mounted at the end of front axle. A part of the weight of vehicle is transmitted to the wheels through this axle. The front axle performs several functions.
It carries the weight of the front of the vehicle and also takes horizontal and vertical loads when vehicle moves on bumpy roads. When brakes are provided on front wheels, it endures bending stresses and torsional stresses. It is generally made from steel drop forging. It is robust in construction.
Suspension System
Suspension system of an automobile separates the wheel and axle assembly of the automobile from its body. Main function of the suspension system is to isolate the body of the vehicle from shocks and vibrations generated due to irregularities on the surface of roads. Shock absorbers are provided in the vehicles for this purpose. It is in the form of spring and damper. The suspension system is provided both on front end and rear end of the vehicle.
A suspension system also maintains the stability of the vehicle in pitching or rolling when vehicle is in motion.