MAIN COMPONENTS OF I.C. ENGINE

The principal parts of an internal combustion engine.

a) Cylinder

In an internal combustion engine, the main part is the cylinder in which combustion takes place. The cylinder has to withstand high temperature and high pressure. Normally the cylinder is made of cast iron or steel alloy.

b) Cylinder Head

This is a block placed as a cover on the cylinder. The cylinder head has provision for setting the inlet and exhaust valves. A hole is also provided to screw in a spark plug or injection nozzle. The cylinder head is normally made of cast iron. When head is mounted on the cylinder, an asbestos gasket is provided in between the cylinder and the cylinder head.

c) Valves

The valves are placed in the correct setting in the provision made specially for them in the cylinder head. Two valves are provided. Through the inlet valve the mixture of air and fuel vapour is sent in. The exhaust valve is for discharging the products of combustion. The valves are held in position by valve springs. The opening and these valves are performed with the help of cam mechanisms.

d)Piston

The piston is the main active part of the engine as shown in Figure 2.1. It has a close fit with the cylinder. The movement of the piston changes the volume of the cylinder and provides the combustion space. Generally pistons are made up of aluminum alloy. Aluminum alloy is the lightest one and has good heat conductive properties. A hole is centrally provided to insert a pin to connect the small end of the connecting rod. Circumferential grooves are provided on the surface of the piston to accommodate piston rings.

e) Piston Rings

Piston rings are made up of special steel alloys to retain elastic properties at high temperature. These are circular rings fitted in the circumferential grooves of the piston There are two sets of rings. Upper rings are called compression rings, which provide an airtight seal. This will prevent the leakage of the burnt gases into the casing. The lower rings are called oil scrapper rings. These are provided to remove the oil film from the engine cylinder and to prevent the leakage of oil into the cylinder.

f) Connecting rod

This is the connecting link between the piston and the crankshaft. The reciprocating motion of the piston is converted into rotary motion of the crankshaft. Upper end of the connecting rod is called small end, which carries the piston by means of a floating pin called piston pin or gudgeon pin. The lower end is called big end of the connecting rod, which connects the crankshaft through the crank pin.

g) Crank shaft

Crankshafts are made up of special steel alloys. The crankshaft is the main member from which we obtain the rotary power. This shaft is build up with one or more eccentric parts called crank or crank throws. This crank throws are mainly responsible for producing reciprocating motion of the piston.

h) Crank case

This is the main housing at the bottom of the engine, providing support for the cylinder and crankshaft bearings. The other engine parts are arranged in proper alignment on this crankcase. The crankcase provides protection to the parts described above from dirt and also it acts as a lubricant sump.

i) Fly wheel

This is a larger solid wheel mounted on the crankshaft. This acts as an energy reservoir to store excess energy during power stroke and delivers during the compression stroke.

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