Farm Power And Machinery (1+1)

Four Stroke Cycle Engine

• In four stroke cycle engine, all the events taking place inside the engine cylinder are completed in four strokes of the piston. This engine has got valves for controlling the charges and exhaust gases. The opening and closing of the valve is controlled by cams, fitted on camshaft. The camshaft is driven by crankshaft with the help of suitable gears or chains. The camshaft runs at half the speed of the crankshaft.

The events taking place in I.C. engine are as follows :
I. Air or air-fuel mixture (charge) is taken in the cylinder.
II. The charge is compressed in the cylinder by the piston.
III. If charge is only air, the fuel is injected at the end of compression.
IV. The charge is ignited at a predetermined time under specified pressure inside the engine cylinder.
V. The power developed due to expansive forces of gases inside the cylinder is transferred to the crankshaft through the connecting rod.
VI. Exhaust gases go out of the cylinder at regular interval of time.
The complete cycle covers all these events in systematic manner. Four stroke cycle engines complete all these events in four strokes of the piston, whereas the two stroke cycle engine covers all these events in two strokes of the piston.
The four strokes of the piston are:
I. Suction stroke
II. Compression stroke
III. Power stroke or expansion stroke
IV. Exhaust stroke