Dual Mass Flywheel (DMF) Technology - Explained
A flywheel is a component on the engine attached to the back of the crankshaft. When the engine is off, the flywheel is first driven by the starter motor, which will rotate the crankshaft so that the engine works. When the engine is working, the flywheel still has a role in generating the inertial force of each piston's working stroke, which is used to move the other pistons.
The flywheel is also a component that transmits power from the engine to the transmission through the clutch. So, although it looks simple, the flywheel has a myriad of functions for the power generated by the engine.
Previous cars still rely on conventional flywheels. This flywheel only consists of serrations and metal disks that are heavyweight. Although conventional, it can do all of the above functions well.
What is a Dual Mass Flywheel?
Along with technology and innovation, automotive engineers continue to develop their engines to be more efficient and produce maximum power. One of many engine components, the flywheel also have an improvement. So, the Dual Mass Flywheels (DMF) are created not only performed by the above functions but also have the purpose of increasing fuel efficiency and power.
Yes, the Dual Mass Flywheel consists of two flywheels. The first is the primary disk in direct contact with the crankshaft. At the same time, the other part is a second disk attached to the primary disk. Although connected, they are not fixed attachments. Sometimes, one of the disks will rotate independently, supported by the arc springs and bearings.
However, the disk rotation has a limit by a set of springs. These springs absorb the effects of the difference in rotation and as a component that also reduces engine vibration.
Why is Dual Mass Flywheel Needed?
When we see a flywheel rotating, we assume that it rotates at a constant speed. But it is not absolutely true. The flywheel doesn't turn constantly. Why? For example, suppose the engine has four cylinders. In that case, the one that works in one rotation period is only one piston, while the other three pistons do not. This imbalance will cause vibration and uneven distribution of power from the engine to the transmission.
In practice, the piston does not provide power in the Top Dead Center (TDC) position, mainly in the power stroke step. It is the initial movement to exert force as it moves past TDC. This force gradually increases until it reaches 90 degrees after TDC. After exceeding 90 degrees, the piston's force decreases until it reaches the Bottom Dead Center (BDC), where it no longer exerts any force on the crankshaft.
To overcome this, you can design a flywheel with a larger size and weight. But unfortunately, this will also cause other effects. The flywheel's large and heavy dimensions will require a lot of power to rotate, impacting engine performance and reducing fuel efficiency.
How does a Dual Mass Flywheel Work
This dual flywheels (DMF) design can eliminate the above problems based its design. This dual mass flywheels can eliminate the above issues. Since the primary disk is attached directly to the crankshaft, it follows an uneven angular speed of the crankshaft.
Because the secondary disk is not a fixed connection to the primary disk, the spring between the two disks will absorb the uneven rotation of the crankshaft before transferring the energy to the secondary disk. In turn, the secondary disk transfers the rotation of the crankshaft to the transmission via the clutch.
How well the springs dampen uneven crankshaft rotation depends on the design and arrangement. As long as the engine is running normally and the DMF is not damaged, DMF will absorb the vibrations caused by the crankshaft movement.
We need to know that the Clutch Plate used in DMF does not have a spring-like conventional clutch disk. It is because the function of the DMF spring replaces its function. So we can not install a conventional clutch disk on the Dual Mass Flywheel.
Advantages of Using Dual Mass Flywheels
DMF was created to reduce engine vibration, which can damage manual transmissions in a variety of ways. With a degree of damage that is largely proportional to the amplitude of the movement.
We need to note that we cannot immediately detect that the DMF is damaged if there is any damage to the transmission. It could be due to a wrong driving pattern or service history.
However, other benefits of DMF include smoother clutch operation, increased gearshift, the overall reduction of vibration throughout the vehicle, and in some applications, even a slight increase in fuel economy efficiency.
Read also:Disadvantages of Using Dual Mass Flywheels
It is undeniable that the Dual Mass Flywheel has drawbacks which are determined by several factors. The DMF brand used by the vehicle, the pattern of use of the vehicle (whether it is used to tow or not), the distance travelled by the vehicle, and the driving conditions. In addition, external factors can also be affecting DMF usabilities, such as the frequency of cars crossing gravel and dusty roads.
Some objective weaknesses in DMF are as follows:
- Very high replacement costs compared to conventional flywheel and clutch kit replacement costs. Most manufacturers recommend replacing the DMF along with the clutch.
- A damaged DMF cannot be repaired and cannot be replaced with a conventional flywheel.
- The service life of DMF depends on its brands and quality. If routinely checked, we can use up the service life of DMF to a distance of about 95,000 miles or more. In contrast, some other brands of DMF have been damaged even less than 30,000 miles.