GuruIntroduction
Cars, the wonders of contemporary engineering, are complex mechanisms consisting of various components cooperating to offer a dependable form of travel. In this article, we will delve into the inner workings, examining the various vital parts that make up a car. From the robust engine to the detailed interior, each element is crucial for a seamless and secure driving experience.
Parts of an automobile
An automobile has several numbers of component. But there are four basic components.These are:
- The Chassis
- The Engine
- The Transmission System
- The Body
- Lubrication System
- Cooling System
- Fuel System
- Ignition System
- Electrical System
- Suspension System
- Power Train
- Clutch
- Drive Shaft
- Differential
- Axles
- Wheels
- Steering System
- Braking System
- Accessories
Apart from these four basic components, there are controls and auxiliaries. The controls are meant for controlling the movement of vehicle. The auxiliaries are additional components meant for providing comfort to the user of the automobile.
1.The Chassis
The chassis of an automobile incorporates all the major assemblies consisting of engine,components of transmission system such as clutch, gear box, propeller shaft, axles, control system such as brakes and steering and suspension system of the vehicle. In other words,it is the vehicle without its body.
The chassis of an automobile has the frame, suspension system, axles and wheel as the main components (Shown in Fig 1). The frame could be in the form of conventional chassis or unit construction may be adopted. In conventional chassis frame, the frame forms the main skeleton of vehicle. It supports engine, power transmission and car body. The frame is supported on wheels and axles through springs.
The frame carries the weight of the vehicle and passengers, withstands engine, transmission, accelerating and braking torques.It also withstands the centrifugal forces while cornering and takes up stresses due to rise and fall of axles. In unit construction type there is no frame (Shown in Fig 2).
The structure of body of the automobile is first formed and then different components such as engine, transmission system and other parts are placed at suitable places in the body structure. The transmission system itself consists of a number of parts such as clutch assembly, gear box, propeller shaft, differential and axles. The other parts include the interior details which are utilized by the passengers and driver of the vehicle. Through suitable designing, the parts are so arranged that they provide maximum comfort and make journeys in the automobile enjoyable.
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The other part of chassis are suspension system, axles and wheel. The suspension system absorbs the vibrations due to up and down movement of wheels. Springs and shock absorbers connecting the frame and the axle perform this function. The springs can be leaf spring, coil spring or torsion bar. Even rubber or air can form the material of springs. The wheels of the vehicle can be suspended independently on springs or on spring suspended axles.
The axle may be ‘live’ if power from the engine is transmitted to it. It may be a ‘dead’ axle if no power is supplied to it and it is just supporting the weight of the vehicle. In ‘four wheel drive’, the power is supplied to both the axles and therefore both the axles are ‘live’.In addition to providing support to the weight of the vehicle, the axle also resists the stresses due to braking and driving torque.
The Engine
The engine is the source of motive power to an automobile. Obviously it is very important part of the automobile because in the absence of engine the automobile may not move at all and its basic function of transporting passengers or goods would be defeated. The power of the engine determines the working of the automobile. In the same manner, the efficiency of engine determines the efficiency of automobile.
The engine, now-a-days, is invariably an internal combustion engine. This may be spark ignition engine consuming petrol as fuel. Alternatively, it could be a compression ignition engine using diesel as fuel.
The engines used are multi-cylinder engines. A single cylinder engine, though capable of providing the desired power may become very heavy and therefore may be unsuitable. In multi-cylinder engine each cylinder handling smaller amount of power may keep engine light in weight.
In an internal combustion engine, total heat produced by the burning of fuel is not converted into work. Part of it causes over-all heating of engine which is undesirable.This heat is to be dissipated properly. Coolant in the form of air or water may be used to take away this heat. So an engine can be air cooled or water cooled. These days some chemicals have been developed which have cooling property and these remain unaffected for a longer period of time.
These chemicals are being used as coolants and these do not require frequent replacement. Apart from their longer life they are more efficient also. Similarly lubrication is another aspect to be taken care of in an engine requiring periodic attention from the user. The moving parts in an engine need regular lubrication to reduce unwanted friction. The chemistry of lubricant is now highly developed. There is standard rating for lubricants and for every purpose a specific lubricant is available.
The Transmission System
The transmission system transmits power developed by the engine to the road wheels. The power available as output from engine is in the form of rotation of crankshaft. This movement is to be transferred to the road wheels to cause their rotary motion. Their rotary motion makes possible the movement of vehicle. The transmission system consists of different parts. These include clutch, gear box, propeller shaft, differential and axle, live axle to be more precise. The road wheels are at the ends of axle. The motion is transmitted through these parts. Every part of transmission system performs its own function.
The clutch, part of transmission system is next to crankshaft. It is a mechanism enabling the rotary motion of one shaft transmitted to the second shaft ‘at will’. When the engine starts it should not be connected to road wheels i.e., these should not start moving as soon as the engine starts. Secondly, this motion should be transferred smoothly so that passengers in car do not feel discomfort and its mechanism is not spoiled. It case of vehicles used for the transportation of goods smooth transmission process is essential as otherwise it may cause damage to goods.
Gear box is the component of transmission system next to clutch. It has got gear train and it provides different gear ratios. These ratios determine the rotary speed of output shaft from gear box. The torque transmitted to the road wheels give rise to a propulsive force (or tractive effort) between these and the road. When starting from rest large tractive effort is required.
This makes essential the introduction of considerable ‘leverage’ between engine and the wheels so that torque from engine, which is almost constant, produces large tractive effort. This ‘leverage’ is provided by the gear box. Different gear ratios available in the gear box can provide the required tractive effort to overcome the resistance faced by the automobile under different conditions.
Propeller shaft transmits the output from the gear box to the axle. This axle may be in the rear or in the front or in some cases both the rear and front axle may receive output from gear box (Shown in Fig. 4,5,6). The output from the gear box is in the form of rotary motion of the shaft and this motion is transferred to the axle.
Differential is the next component of the transmission system. The motion of propeller shaft is fed to the differential which turns it through 90 degrees. This is essential as the axle is at 90 degrees to the propeller shaft. The function is performed with the help of a pinion and a gear. Another important function of differential it to reduce the speed of inner wheels and at the same time enhance the speed of outer wheels by the same amount. This is required when the automobile is moving on a curved path.
On a curved path, the outer wheels are required to traverse a circle of bigger radius than the inner wheels. This means that the outer wheels are required to traverse larger distance as compared to inner wheels.
As the automobile is to move as a single unit, all the four wheels must travel together.Therefore, the outer wheels should travel larger distance and inner wheels should travel smaller distance in the same time period. Hence the variation in speed of inner and outer wheels is needed. This is performed by the differential with the help of sun and planet gear system. Further details of differential to be taken up later.
Axle is the next component of transmission system. The axle receiving power from the engine is termed as ‘live’ axle. It is in two halves. The ends of the axle have road wheels connected to it. These road wheels are in direct contact with the road surface. The body of the automobile is above the axle. The axle also takes up the various loads including the weight of the automobile. It also transmits motion to the road wheels.
The Body
The use of a separate frame to which the body structure is attached is now almost obsolete except for some applications for commercial heavy duty vehicles. Many heavy vehicles now use ‘sub-frames’ of simple construction to which the engine and gear box is attached. The sub-frame is supported on the main frame and is fixed on it through some suitable rubber connections to isolate the engine vibrations.
Due to development in spot welding and sheet pressing techniques most of the vehicles have integral construction. All the assembly units of the vehicles are attached to the body which also acts the frame. It makes the vehicle compact, light weight and also its cost is reduced. Some intermediate designs using a light chassis and a pressed steel body are also in use. The light chassis, in such designs, is strengthened by using platform made of sheet of steel.
Apart from the four basic components described above, the automobile has the control systems and auxiliaries. The control systems are used to control the motion of an automobile and therefore are essential in an automobile.These include
(b) Braking system or brakes.
Steering system
Braking system
The Auxiliaries
Lubrication System
An engine has many moving parts which eventually develop wear, as they move against each other.The engine circulates oil between these moving parts to prevent the metal-to-metal contact that results in wear. Parts that are oiled can move more easily with less friction and hence power loss due to friction is minimized. The secondary function of a lubricant is to act as a coolant and also as a sealing medium to prevent leakages. Finally, a film of lubricant on the cylinder walls helps the rings in sealing and thus improves the engine’s compressions.
Cooling System
Fuel System
Ignition System
The purpose of the ignition system is to provide assistance for the combustion of fuel either by a high voltage spark or self-ignition in each of the engine’s cylinders at the right time so that the air-fuel mixture can burn completely.
The fuel supplied to the combustion chamber must be ignited to deliver power. In a spark-ignition engine an electric spark is used for this purpose. The compression-ignition engine does not require a separate ignition system because the ignition is affected by compression of the mixture to a high pressure.
Electrical System
Suspension System
- Rigid system
- Independent system
In the rigid system,the road springs are attached to a rigid beam axle. It is mostly used in the front axle of commercial vehicles and in the rear axle of all types of vehicles.
Power Train
Clutch
ratio or while stopping the vehicle.
Drive Shaft
has universal joints at its ends.
Differential
axle shaft. It allows the rear wheels to be driven at different speeds when the vehicle takes a bend
or falls into a ditch.
Axles
required drive through these axles.
Wheels
vehicle. The wheels are also used for retardation and for stopping the vehicle.
Steering System
Braking System
Brakes are required for slowing down or stopping a moving vehicle. The braking system is essential for the safety of passengers, and passers-by on roads. The braking system may be operated mechanically or hydraulically. 95 per cent of the braking systems in use today are of the hydraulic type.
All brakes consist of two members, one rotating and the other stationary. There are various means by which the two members can be brought in contact, thus reducing the speed of the vehicle. Figure 9 shows the simplified layout of a hydraulic braking system.
The major components of the braking system are: brake pedal, master cylinder, wheel cylinders,brake drum, brake pipe, brake shoes, brake packing plant and linkages. As the load on the vehicle and the vehicle speed has increased according to recent trends, in modern days, the importance of the brake system has also increased and power brakes are now being preferred. Power brakes utilize vacuum and air pressure to provide most of the brake-applying effort.
