A camshaft is a shaft to which a cam is fastened or of which a cam forms an integral part. The camshaft was described in 1206 by Turkish engineer Al-Jazari. He employed it as part of his automata, water-raising machines and water clocks such as the castle clock. Among the first cars to utilize engines with single overhead camshafts were the Maud slay designed by Alexander Craig and introduced in 1902and the Marr Auto Car designed by Michigan native Walter Lorenzo Marr in 1903.
Uses of Camshaft:
The camshaft is used to operate poppet valves in internal combustion engines with pistons. It consists of a cylindrical rod running the length of the cylinder bank with a number of oblong lobes protruding from it, one for each valve. The cam lobes force the valves open by pressing on the valve, or on some intermediate mechanism, as they rotate.
A camshaft acts as a timing device that controls the opening and closing of the intake and exhaust valves, as well as setting the valve overlap that occurs at the top dead centre on the exhaust stroke. The shaft is constructed with several journals that ride on bearings within the engine. It has egg-shaped lobes that actuate the valve train, either by moving lifters and pushrods or by pushing directly on the valve stems. The camshaft is bound to crankshaft rotation by a timing chain, timing belt or timing gears, and failures in the camshaft drive can allow the valves to contact the piston crowns, causing extensive internal damage.
Additional Functions of a Camshaft:
In older engines camshafts may also have gears machined into them that operate the distributor and the oil pump. In newer engines, the camshaft may have a position sensor mounted on the end that sends information to the power train control module to help the module properly time your fuel injection pulses and ignition. Some engines may have multiple camshafts, as is the case with some overhead cam engines, particularly ones built in a “V” configuration. Engines with a desmodromic valve train use at least two cams, as there is a push-open cam and a pull-close cam, instead of the traditional push-open cam with valve springs to pull the valve shut as the cam rotates past the lobe and back onto the base circle.
The relationship between the rotation of the camshaft and the rotation of the crankshaft is of critical importance. Since the valves control the flow of the air/fuel mixture intake and exhaust gases, they must be opened and closed at the appropriate time during the stroke of the piston.