Learning the Basics of Camshafts - Purpose and Operation
We've talked about engines and the combustion process they go through in order to power your vehicle. In essence, fuel goes into the combustion chamber, the spark plug triggers a small explosion contained within the chamber, and the resulting exhaust exits. The entry of the fuel and the departure of the exhaust are controlled, in large part, by camshafts. Below, I'll explain what they are and describe how they perform their jobs.
Camshafts Described
A camshaft is a rod on which cams sit. The cams (sometimes called lobes) are oblong in shape with one end noticeably protruding outward from the rod. As the rod turns, so too, do the cams. The protruding end of each lobe is what ultimately allows them to perform their job.
Understanding Their Jobs
First, to better understand the role of the camshaft, let's review the 4-step process that happens within your car's combustion chamber. When the intake stroke begins, a piston sits near the top of the chamber. The piston descends, the intake valve opens, and the chamber fills with the air-fuel mixture. Next, the compression stroke begins and the piston rises, compressing the air-fuel mixture within the chamber.
The power stroke begins as the piston reaches the top of the chamber. At the top sits a spark plug. The spark plug ignites the compressed air-fuel mixture, creating an explosion. The force of the explosion pushes the piston toward the bottom of the chamber. As it descends, the exhaust stroke begins as the exhaust valve opens. The piston rises and forces the exhaust from the combustion chamber.
The above description of the 4-stroke process your engine goes through is necessary to fully appreciate the job of the camshafts. I mentioned that the intake valve opens during the intake stroke. As it does, a fuel injector pushes gasoline into the chamber. The intake valve opens as the result of one of the cams on the camshaft. As the rod turns, the oblong cam's protruding end pushes against the tip of the intake valve. As it does, it forces the valve downward and thereby, creates an opening to the combustion chamber for the fuel.
You'll remember that the exhaust valve opens in order that the rising piston can force out the exhaust that exists after the power stroke. This happens in the same manner as with the intake camshaft. An exhaust camshaft turns and one of the oblong cams on the rod pushes down on the tip of the exhaust valve. That creates the opening in the chamber through which the gases are pushed out.
This process happens hundreds of times each minute while you're on the road. The entire system is designed around flawless timing. While engines attract most of the attention from consumers, they wouldn't work properly without the camshafts.
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