It is a mechanical element provided with a bar or shaft, on which there is at least one lobe that operated by the crankshaft through gears, chains or belts opens and closes in turn, the intake and exhaust valves at similar intervals . The bar revolves around its own axis by opening and closing by means of the lobes or cams, these valves. It is generally applied to combustion engines but also has application in hydraulic hammers, mills or looms.

Its history comes from ancient times. Already in the 11th century this technology of transmission from circular motion to linear motion was applied. Both on the axis of a mill and by the pressure of its cams, hammers and rollers were rising again when the cam made the circular motion.

The application of the camshaft in the automotive industry is to control the valves, making force on it, it opens and through damping when the cam moves it closes again. The cam does not make force in the center of the valve if not with a certain laterality, with this it is achieved that the valve rotates on itself avoiding wear. A cam can actuate several valves, even the activation of both an intake and exhaust valve by a single cam has been achieved. But the disadvantage is that the time intervals are not adjustable then.

In common four-stroke engines, the camshaft rotates at half the speed of the crankshaft, of which it is secured by means of a chain or belt. They are placed parallel to the crankshaft. The camshafts are manufactured in cast iron, in exceptional cases in steel.

Several types of camshaft are distinguished . Thus there camshaft bar , double overhead camshaft or camshafts single butt . In the development of the well-known Valvetronic , we find a completely variable valve control. That is, each valve is activated in an electrohydraulic manner (MultiAir technology), so it combines the regulation of distribution times with a continuous regulation of the intake valve stroke.