Camshafts are essential components in a combustion engine, but What Is A Camshaft, and why is it so vital? Let’s delve into the details.
A Look Back at Camshaft Technology
Most people are familiar with the basic principles of a combustion engine. Fuel and air are mixed and ignited in a cylinder, creating an explosion that drives a piston. This motion is then converted into rotational energy via the crankshaft and transmission.
While the core concept might seem straightforward, the internal combustion engine has undergone extensive development. The camshaft, however, is a relatively old technology that has been used since the early days of engine invention. The concept of the cam dates back to 13th century Turkey, where Ismail al-Jazari used it in various mechanisms, as described in his ‘Book of Knowledge of Ingenious Mechanical Devices’. Despite technological advancements, the fundamental principles of operation remain unchanged.
Synchronization and Cam Shape
A camshaft is a relatively simple component: a shaft with shaped lobes, known as ‘cam lobes‘, positioned along its length. As the shaft rotates, the shape of the cam lobe interacts with a valve or switch, and the speed of rotation determines the rate of action.
In modern internal combustion engines, camshafts are typically positioned above the cylinder banks where they control the valves. Their calibration precisely manages the air-fuel mixture entering the cylinder and the efficient expulsion of exhaust gases.
The precise synchronization between valve opening/closing and piston movement is critical for engine performance. Camshafts are connected to the crankshaft via a timing belt or chain to ensure this precise timing. The shape of the cam lobes also controls the speed at which the valves open and close, known as variable valve timing.
The basic action of a cam.
Advantages of Multiple Camshafts
The number of camshafts in an engine varies depending on the cylinder arrangement and valve operation. Inline engines typically have one camshaft, while V-shaped engines require at least two. Some engines utilize double overhead camshafts (DOHC), resulting in four camshafts across two cylinder banks.
Using an additional shaft per bank offers several advantages over a single overhead camshaft design (SOHC), despite the added weight and cost. These advantages include ideal component placement for improved efficiency, increased top-end power, and a less complex valve operation, particularly when using more than two valves per cylinder.
Four valves per cylinder is a common configuration for its efficiency, maximizing the use of cylinder head space. While a SOHC can operate four valves per cylinder, it requires a more complex system of rods and cams. Therefore, DOHC is often preferred.
The complete system in operation.
Innovations in Valve Technology
DOHC configurations enable the use of sophisticated valve technology, allowing adjustments to the timing, duration, and lift of the valves. This advanced control can enhance fuel efficiency, increase power, and reduce emissions.
Virtually every car manufacturer has developed their own version of variable valve timing. Some systems use multiple cam profiles, switching between them based on engine load. Others adjust the timing between the crankshaft and camshafts. One of the earliest systems used oil pressure to control valve operation.
The optimal system remains to be seen, but these technologies will likely become more prevalent as the automotive industry strives for greater efficiency and power, leading to further reimagining of the camshaft’s design and role.
