WHAT ARE THE PRINCIPAL PARTS OF AN I.C. ENGINE?

Diagram shows the principal parts of an I.C. engine. The details regarding the various parts of the engine are as follow:

1. Cylinder
2. Cylinder head
3. Piston Rings
4. Connecting rod
5. Crank
6. Crank case
7. Valves
8. Cams
9. Flywheel

1. Cylinder: It is the cylindrical vessel in which the fuel is burnt and the power is developed. It is considered as heart of the engine. The primary functions of cylinder is:
   • To contain the working fluid under pressure and
   • To guide the piston while reciprocating inside the cylinder.
2. Cylinder head: The top end of the cylinder is closed by a removable cylinder head. The cylinder head consists of two valves ‘inlet valve’ and ‘exhaust valve’.
3. Piston Rings: The rings which are placed in the grooves cut towards top of the piston are called Piston Rings. There are two set of rings inserted into the groves. They are compression rings and oil rings.
   • Compression rings: The compression rings press hard with the cylinder walls forming a tight seal between the piston and the cylinder. This prevents escaping of the high pressure gases into the crankcase.
   • Oil rings: The function of oil rings is to extract the lubricating oil from the cylinder walls and send it back to oil sump through the holes provided on the piston.
4. Connecting rod: The connecting rod is a link that connects the piston and the crankshaft. Its function is to convert the reciprocating motion of the piston into rotary motion of the crankshaft.
5. Crank: The crank is a lever with one of its end connected to the connecting rod by a pin joint with other end connected rigidly to the crankshaft. The other end of the crank is connected to the crankshaft. The power required for any useful purpose is taken from the crankshaft.
6. Crank case: It encloses the crankshaft and serves as a sump for the lubricating oil.
7. Valves: The valves are control devices that allow the air/fuel to enter into the cylinder and also to discharge the burnt gases to atmosphere. There are two valves.
   • Inlet valve and
   • Exhaust valve
     • ‘Inlet valve’ is the one through which fresh charge (air and fuel or air) enters into the cylinder.
     • ‘Exhaust valve’ through which the burnt gases are discharged out of the cylinder.
   • These valves are actuated by means of cams.
8. Cams: It is an element designed to control the movement of both the inlet and exhaust valves.
9. Flywheel: It is a heavy mass of rotating wheel mounted on the crankshaft and is used as an energy storing device. The flywheel stores energy received during the power stroke and supplies the same during other strokes.

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