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A camshaft operating two valves. A camshaft is a shaft that contains a row of pointed cams in order to convert rotational motion to reciprocating motion.Camshafts are used in piston engines (to operate the intake and exhaust valves), [1] [2] mechanically controlled ignition systems and early electric motor speed controllers.
Pushrods are long, slender metal rods that are used in overhead valve engines to transfer motion from the camshaft (located in the engine block) to the valves (located in the cylinder head). The bottom end of a pushrod is fitted with a lifter, upon which the camshaft makes contact. The camshaft lobe moves the lifter upwards, which moves the ...
In most piston engines, the camshaft(s) are mechanically connected to the crankshaft. The crankshaft drives the camshaft (via a timing belt, timing chain or gears), which in turn actuates the intake and exhaust valves. [1] These valves allow the engine to inhale air (or an air/fuel mixture) and exhale the exhaust gasses. [2]
With traditional fixed valve timing, an engine will have a period of "valve overlap" at the end of the exhaust stroke, when both the intake and exhaust valves are open. The intake valve is opened before the exhaust gases have completely left the cylinder, and their considerable velocity assists in drawing in the fresh charge.
The cam can be seen as a device that converts rotational motion to reciprocating (or sometimes oscillating) motion. [clarification needed] [3] A common example is the camshaft of an automobile, which takes the rotary motion of the engine and converts it into the reciprocating motion necessary to operate the intake and exhaust valves of the cylinders.
Late intake valve closing (LIVC) The first variation of continuous variable valve timing involves holding the intake valve open slightly longer than a traditional engine. This results in the piston actually pushing air out of the cylinder and back into the intake manifold during the compression stroke.
The active valve control system (AVCS) is an automobile variable valve timing technology used by Subaru. It varies the timing of the valves by using hydraulic oil pressure to rotate the camshaft, known as "phasing", [1] in order to provide optimal valve timing for engine load conditions. The system is closed loop using the camshaft sensors ...
The rocker ratio is the distance travelled by the valve divided by the distance travelled by the pushrod effective. The ratio is determined by the ratio of the distances from the rocker arm's pivot point to the point where it touches the valve and the point where it touches the pushrod/camshaft.