Automobile engines utilize both crankshafts and camshafts to drive their power generation mechanisms. These two shafts serve distinct purposes, have varying constructions, and are positioned differently within the engine.
A significant distinction between a crankshaft and a camshaft lies in their functions: the camshaft is responsible for activating the intake and exhaust valves, whereas the crankshaft plays a crucial role in converting the back-and-forth movement of the piston into rotational motion.
What is a Camshaft?
The engine’s vital component is the crankshaft, which, in conjunction with the connecting rod, converts the piston’s back-and-forth motion into rotational motion. To gauge the camshaft’s position and speed, a camshaft position sensor is employed.
Positioned within the crankcase along with bearings, the crankshaft derives power from the piston and subsequently transmits it to propel the vehicle’s wheels.
Meanwhile, the camshaft features multiple cam units that facilitate the engine’s intake and exhaust processes. Specifically, when the piston reaches top dead center, the inlet valve opens, permitting the entry of air or an air-fuel mixture into the cylinder.
Subsequently, as the piston fills with spent charge, the exhaust valve opens, enabling the discharge of exhaust gases into the atmosphere. The camshaft is responsible for orchestrating the precise timing of these valve movements.
Typically crafted from cast iron or steel, the camshaft is positioned above the cylinder, though it can also be located at the cylinder’s bottom. The motion of this shaft is transferred to the valves through a rocker arm mechanism.
What is a Crankshaft?
The camshaft plays a crucial role in precisely timing the opening and closing of the engine’s intake and exhaust valves. Its motive power is derived from the crankshaft, facilitated by either a timing belt or chain. To monitor the crankshaft’s position and speed, a crankshaft position sensor is employed.
Due to the speed-reducing nature of the timing mechanism, the camshaft’s rotation occurs at half the speed of the crankshaft.
Utilizing its lobes, the camshaft actuates rocker arms, which in turn are linked to both the intake and exhaust valves.
Engines can incorporate either one or two camshafts. In the case of a single camshaft, it handles the task of operating both intake and exhaust valves. Conversely, engines equipped with two camshafts have separate camshafts for the inlet and exhaust valves.
During the power stroke of the engine’s operation, the piston engages in reciprocating motion within the cylinder. Acting as the connecting link, the piston is affixed to the crankshaft by means of a connecting rod. As the piston descends, it imparts a rotational shift to one half of the crankshaft’s motion, while the reverse occurs as the piston ascends. This mechanism effectively converts the piston’s to-and-fro motion into rotational motion. Notably, in a four-stroke engine, the crankshaft completes two revolutions over the course of a single power stroke.
Fabricated typically from forged alloy steel, this shaft’s construction is geared towards resilience. Given its continuous exposure to high fatigue loads, it necessitates considerable strength to withstand such stresses. Positioned beneath the cylinders, one extremity of the crankshaft interfaces with the flywheel, serving to regulate and smooth out the engine’s rotational motion.
How Do Camshafts and Crankshafts Work Together?
The coordination between the camshaft and crankshaft is facilitated by a timing chain, akin to a bicycle chain, or a timing belt, resembling a toothed drive belt. An alternative is a mesh gear set, where two interlocking gears are employed. This synchronization is established at the “front end” of the engine and is imperative for precise valve timing, a requisite for optimal combustion control.
In the course of the four-stroke combustion cycle encompassing intake, compression, power, and exhaust phases, the crankshaft completes two rotations, consequently driving each piston through two cycles of upward and downward movement. In contrast, the camshaft undergoes one revolution. This configuration ensures that each valve undergoes one cycle of opening and closing over every two revolutions of the crankshaft, relative to the piston’s motion. As a result, during the intake stroke, solely the intake valve(s) open.
Throughout the compression and combustion strokes, both valves remain shut, with only the exhaust valve(s) being active during the exhaust stroke.
It’s important to acknowledge that timing components like belts, chains, and gears are subject to wear and tear. Regular checks of your vehicle’s owner’s manual are advised to determine the recommended intervals for replacements.
