A camshaft is a rotating cylindrical shaft used to regulate the injection of vaporized fuel in an internal combustion engine. These are occasionally confused with the crankshaft of the engine, where the reciprocating motion of the pistons is converted into rotational energy. Instead, camshafts are responsible for the accurately-timed fuel injections required by internal combustion engines. Camshafts have multiple cams on them, which are used to open valves through either direct contact or pushrods. A camshaft is directly coupled to the crankshaft, so that the valve openings are timed accordingly.
Camshafts can be found in many different types of machines that require mechanical timing. Most of the time, they are found in internal combustion engines and perform the essential task of timing fuel injection. Even though camshafts can be found in different types of machines, they are typically used for valve-timing purposes. An example of this would be a fuel burner which injects fuel in timed intervals to help reduce fuel consumption. Camshafts have also played a role in older machines, such as water pumps and mechanical clocks.
An engine camshaft can be made from many different types of materials. The materials used in the camshaft depend upon the quality and type of engine being manufactured. For most mass-produced automobiles, chilled cast iron is used. Not only is it cheap, but chilled cast iron is also extremely durable and reliable. This is because cold treating increases the strength and hardness of any metal that undergoes the process.
For higher-quality camshafts, billet steel is used. While far superior to chilled cast iron in performance, the manufacturing process is both laborious and expensive— thus, billet steel is seldom found outside of high-performance or luxury cars. Camshafts made from this material are often made through the use of computerized numerical control (CNC) machines to ensure precision.
Camshaft timing is incredibly important for internal combustion engine performance. The rotation of the camshaft opens both the intake and exhaust valves of the cylinder, so proper timing is necessary for making sure fuel is injected and exhausted at the correct times. Since the camshaft is often coupled directly to the crankshaft itself, it can be timed in accordance with the position of the crankshaft. The two shafts are coupled through either a belt or gear arrangement, depending on the location of the camshaft.
The location of the camshaft can vary and depends on whether or not the cams—or lobes—of the shaft come in direct contact with the valves or open the valves through pushrods. Ideally, it will be positioned directly above the cylinder head, which eliminates the need for pushrods. For this reason, many internal combustion engines have camshafts located directly above the cylinder heads.