An Engine is a type of device that converts chemical energy of the fuel supplied into heat energy and then converts this Heat energy into Mechanical energy. This energy can be used for doing some useful work. Th. functioning of an engine is that the fuel supplied is burnt and the energy released is converted into Mechanical energy. Engine is also known as Power Unit.
The major parts of an Internal Combustion Engine are-
1. Cylinder Block-
It is also called as foundation of the engine. The surfaces of cylinder are finished very smooth by using accurate grinding and honing processes. Sometimes liners are used inside the blocks where the piston always moves up and down. The cylinder block is generally made of grey cast iron and sometimes may be added with nickel and chromium. Aluminium Cylinder blocks are also used. Cylinder Head is fitted to the Cylinder block on the top of it. Crankcase is placed at the bottom of Cylinder Head.
2. Cylinder Head-
It is a separate casting placed on the top of cylinder block and supported by studs and nuts. It contains the upper end of combustion chambers and has a provision for a spark plug. Copper, asbestos or steel gasket is commonly placed between the head and block to retain compression. On the top of the cylinder head, a rocker arm assembly unit is placed for operating overhead valves. This is usually made of aluminium alloy or grey cast iron.
Crankcase is fitted to the bottom portion of the cylinder block. It supports both the crankshaft and camshaft. It is also called as oil pan because it holds oil for lubrication purposes. Gaskets are also used to seal joint between Cylinder block and Crankcase. Three parts Cylinder Block, Cylinder Head and crankcase form the foundation and the main body of an automobile engine.
Piston is the most important part of an I.C.Engine which helps to convert the heat energy into mechanical energy. It is a cylindrical part that move up and down in the cylinder. The space between the cylinder wall and the piston is known as piston clearance, which provides space for a thin film of lubricant. Piston is subjected to a very greater thrust and higher temperature during power stroke. So, piston must be strong and light to reduce the inertia loads on the bearings. Pistons are made of aluminium alloys, cast steel, cast iron or chrome nickel. Grooves are cut around the piston outer circumference to accommodate piston rings to seal the compressed and expansion of gases above the piston. The top of the piston is called as head, the part below the ring grooves is known as the skirt. The portions of the pistons that separate the grooves are called the lands. Piston has bosses to hold piston pin or gudgeon pin.
The piston must possess these four qualities-
- Light in weight
- Good heat conductivity
- Smooth and silent operation
- Withstand high temperature and pressure
5. Piston Pin-
The piston pin or wrist pin connects piston to the small end of the connecting rod. It is also cylindrical piece made of case hardened steel. Piston pin is supported in the piston boss.
6. Piston Rings-
The purpose of the piston rings is to be provide a sealing to compressed and expanding gases above the piston. They also prevent the oil from entering into the combustion space. They help in transmitting the heat of the cylinder.
7. Connecting Rod-
Connecting rod is that part of the engine which provides connection between the piston and crankshaft. It has one end small which is connected to the piston by means of gudgeon pin and the other end known as big end connected to the crankpin of the crankshaft. It has I-beam cross-section. The big end of the connecting rod is made split to permit it being clamped around the crankpin of the crankshaft. Connecting rod carries the power (thrust) from the piston to the crankpin of the crankshaft.
Reciprocating motion of the piston present in the engine is directly converted into the rotary motion by the only means of connecting rod and crankshaft arrangement. Crankshaft is a strong one piece casting of heat
treated alloy steel. It consists of crankpins. crank arms or webs. main journals. Big end cap of the connecting rod of the engine is directly connected to the crankpin of the crankshaft. Main journals of the
crankshaft pass through main bearings. Crankshafts have drilled passages through which oil can flow to the connecting rod from main bearings. Rear end of the crankshaft carries
flywheel and the front end of the crankshaft carries gears that drives the crankshaft, vibration dampers and drive belt pulleys.
9. Valves and Valve Mechanisms-
Valve is a device used to close or open a passage to admit air-fuel mixture or air during suction stroke and expel the burnt gases during exhaust stroke. There are two types of valves used for each cylinder i.e. inlet valve and exhaust valve. Valve must seal the combustion space tightly when closed otherwise leakage may result. Movement of the valve is actuated 13 an eccentric projection called ‘cam’ of a camshaft. This camshaft driven by crankshaft in a specified gear ratio. Due to the rotation of the camshaft, the cam lifts a tappet above it. This causes the push rod to move up, so the valve lifts against a spring from its seat. In this order the up or down movement of the push rod due to the rotation of the camshaft causes the valve to retain to its original place or seat. The valves are sometimes known as Poppet valves
Flywheel is a device mounted on the rear end of the crankshaft, used to store energy necessary to carry the engine over the points at which it is not receiving power from the explosions. The size of the flywheel varies as per the number of cylinders of the engine. It is a heavy steel body attached to the flange of the crank shaft with nuts and bolts. It carries a clutch plate assembly with it.
It is a device which power up from the Crankshaft, operates the valves by the cams mounted on it. Camshaft is either placed above the cylinder head or in the cylinder block depending upon the valve mechanism. Camshaft has a number of cams along its length. Two cams for each cylinder is placed, where one operates inlet valve and the other operates exhaust valve. Camshaft operates pump, distributor and oil pump.
12. Vibration Dampers–
During the power strokes power impulses tend to set up twist and untwist actions in the connecting rod, crankshaft and crank pins. These twist and untwist actions repeated every power impulse turbine tends to set up torsional vibrations in the crankshaft. If these torsional vibrations are not controlled, it may cause the breakage of crankshaft at certain speed. To control these torsional vibrations, a device known as vibrational damper is used which is generally mounted on the front end of the crankshaft.
These are the major parts of an Internal Combustion Engine.