For OHC and DOHC engines, the camshaft operates the valve directly or via a short rocker arm. In an overhead valve engine, the camshaft presses on a pushrod which transfers the motion to the top of the engine, where a rocker opens the intake/exhaust valve. Therefore a V6 engine with a total of four camshafts (two per cylinder bank) is usually referred to as a double overhead camshaft engine, although colloquially they are sometimes referred to as "quad-cam" engines. The valvetrain layout is defined according to the number of camshafts per cylinder bank. Note that many modern industrial and automotive engines continue to use the overhead valve design (with the cam mounted low in the engine block) which allows lower overall engine height than a similar overhead cam design. As engine speeds increased through the 20th century, single overhead camshaft (SOHC) engines- where the camshaft is located within the cylinder head near the top of the engine- became increasingly common, followed by double overhead camshaft (DOHC) engines in more recent years. In an overhead valve engine, which came later, the cam follower (lifter) transfers its motion to valves at the top of the engine via a pushrod and a rocker arm lever.
Early flathead engines locate the valves in the block and the cam acts directly on those valves. Most early internal combustion engines used a cam-in-block layout (such as overhead valves), where the camshaft is located within the engine block near the bottom of the engine. Main articles: Cam-in-block and Overhead camshaft engine
It gives a surface hardness of 55-60 HRC, suitable for use in high-performance engines. When manufacturing a camshaft from EN40b, the camshaft will also be heat treated via gas nitriding, which changes the micro-structure of the material. Different types of steel bar can be used, one example being EN40b. The method of construction is usually either forging, machining (using a metal lathe or milling machine), casting or hydroforming. This is a much more time-consuming process, and is generally more expensive than other methods. Billet steel: When a high-quality camshaft or low-volume production is required, engine builders and camshaft manufacturers choose steel billet.Other elements are added to the iron before casting to make the material more suitable for its application. Cast iron: Commonly used in high volume production, chilled iron camshafts have good wear resistance since the chilling process hardens them.The materials used for a camshaft are usually either: Camshafts are made from metal and are usually solid, although hollow camshafts are sometimes used.
0 kommentar(er)
