A camshaft is the element of an internal combustion engine the purpose of which is to open and close the valves. Working in conjunction with the crankshaft, the camshaft rotates at half the speed of the crankshaft in a 4-stroke engine cycle and at the same speed in a 2-stroke engine.
4-Stroke Engine Cycle
The four cycles of a 4-stroke engine are intake, compression, power and exhaust. The crankshaft rotates twice for these steps while the camshaft rotates once. The smooth working of an engine requires precision parts and timing of the components. There are several cams attached to one or more camshafts–one controlling the intake valve and another controlling the exhaust valve–for each piston. The intake valve is opened by the rotating cam as the crankshaft pulls the piston down. At the compression stage, the intake valve is closed while the piston is pushed back up. The fuel and air mixture ignites as the piston moves downward again. Lastly, as the piston is pushed back up the cylinder, the exhaust valve is opened by the rotating cam to release the byproduct of the explosion.
A properly working engine requires precise timing between the rotation of the camshaft and crankshaft. The cams attached to the camshaft are instrumental in the harmonious opening and closing of the valves that provide an engine with its power.