What is crankshaft? Everything you need to know
The most important part of a car is the engine. It is the heart of the car. However, the crankshaft is one of the most important parts of the engine. In other words, without the crankshaft, your car cannot run.
So, what is the crankshaft? How does it work? We will discuss everything about the crankshaft in depth, so read on carefully.
What is a crankshaft?
The crankshaft is a rotating shaft driven by the crank mechanism. It is a key component in the engine that converts the reciprocating motion of the piston into rotational motion.
The crankshaft is an important part of the engine power transmission system, connected to the piston through a connecting rod and working with components such as the flywheel and pulley.
How Does the Crankshaft Work?
Step 1: Piston Downward Movement
The engine piston moves from top dead center to bottom dead center. During this movement, the piston, which is connected to the crankshaft through a connecting rod, transmits its movement to the crankshaft.
Step 2: Motion Conversion
The piston's linear motion is converted into rotational motion through the crankshaft. The crankshaft then transmits the converted rotational motion to the camshaft.
Step 3: Compression
The crankshaft continues to rotate, pushing the connecting rod upward, causing the intake valve to open, allowing the air-fuel mixture to enter the engine combustion chamber, causing the piston to compress the fuel-air mixture.
In addition, as the piston moves upward again, the exhaust gas is pushed out of the cylinder. The first rotation of the crankshaft is completed.
Step 4: Ignition
The ignition stage is the next stage after compression is completed. The heat released causes the piston to enter a downward stroke, and the piston transmits its linear motion to the connecting rod fixed to the crankshaft.
Step 5: Flywheel Movement
One end of the crankshaft is connected to the flywheel. It converts the linear motion of the piston into rotational motion, and then transmits the rotational motion to the flywheel, which transmits it to the gearbox, which further transmits the power to the transmission shaft, and finally drives the vehicle.
Step 6: Balance and shock absorption
The balance block on the crankshaft is used to reduce the vibration generated during rotation, and ensures the smooth operation of the engine through precise balance correction.
Crankshaft Types
There are many types of crankshafts, depending on the engine design. They come in a variety of designs and materials to suit different engine configurations and vehicle types.
Let's look at these crankshafts in more detail to find the right crankshaft for your vehicle.
Flat Plane Crankshafts
Flat plane crankshafts are commonly used in V8 engines, especially racing and sports engines. They are named because their crank pins are oriented flat or 180 degrees. This design is lighter and can speed higher, but it produces more vibration.
Crossplane
Another design for V8 engines, the crossplane crankshaft has crank pins that are 90 degrees to each other. This design allows for smoother running and better balance, but usually adds weight.
V-Type
This crankshaft design is used in V-type engines and is suitable for engines with an odd number of cylinders on each side. V-type crankshafts can meet the unique firing order and balance requirements of such machines.
Inline Crankshafts
Inline crankshafts are commonly used in inline engines and are a simpler design, commonly found in four-cylinder or six-cylinder engines.
Common parts of a crankshaft
A crankshaft consists of several parts that work together to make it run smoothly. The parts of a crankshaft include main journals, connecting rod journals, cranks, balance weights, and flanges.
Main journals
The main journals are the main bearings that support the crankshaft and are mounted on the engine block. The engine rotates around these journals. There are two main types of bearings for the main journals: journal bearings and plain bearings.
Connecting rod journals
The connecting rod journals are offset from the axis of rotation and attached to the big end of the piston rod. They are also commonly called crankpins or connecting rod bearing journals. Some connecting rods have oil passages drilled in them to spray oil onto the cylinder wall.
Cranks
Link the main journals with the connecting rod journals to form the eccentric part of the crankshaft.
Balance weights
These are counterweights mounted on the crankshaft arms, and their main function is to apply reaction forces. In other words, the counterweights provide the much-needed stability and balance to the crankshaft.
In addition, when the crankshaft rotates, the reaction force may reduce the engine speed. However, counterweights help to eliminate these reaction forces, helping the crankshaft achieve high RPMs.
Flywheel Mounting Flange
The flywheel is attached to the crankshaft via a flange. When the clutch or torque converter is engaged, the crankshaft turns the flywheel, which in turn turns the gears in the transmission.
How are crankshafts made?
There are two main methods for making crankshafts: forging and casting.
Forged crankshafts are made by heating the metal to a high temperature and using pressure to work it into the desired shape, which increases the strength of the crankshaft.
Casting crankshafts are made by introducing liquid metal into a mold and cooling it to solidify, which is a less expensive method.
These processes are essential to making a crankshaft that can withstand the pressure of engine rotation, and parts such as the crankshaft journal are also treated with surface hardening to achieve optimal performance.
Summary
The crankshaft is an important part of the engine. Understanding the working principle of the crankshaft and the parts that make up the crankshaft will help you choose the crankshaft that suits you more quickly.
It is worth noting that crankshaft manufacturing is a process that requires technology. Komotashi is a leading Chinese auto parts manufacturer and provides high-quality products that meet international standards.