Dual mass flywheel
A Dual mass flywheel or DMF is a rotating mechanical device that is used to provide continuous energy (rotational energy) in systems where the energy source is not continuous, the same way as a conventional flywheel acts, but damping any violent variation of torque or revolutions that could cause an unwanted vibration. The vibration reduction is achieved by accumulating stored energy in the two flywheel half masses over a period of time but damped by a series of strong springs, doing that at a rate that is compatible with the energy source, and then releasing that energy at a much higher rate over a relatively short time. The compact dual-mass flywheel also includes the whole clutch, (with the pressure plate and the friction disc).[1]
History
The Dual Mass Flywheels were developed to address the escalation of torque and power, especially at low revs. The growing concern for the environment and the adoption of more stringent regulations have marked the development of new engines, more efficient, lowering the cylinder number even to 3 or 2 cylinders-, and allowing to deliver more torque and power at low revolutions. The counterpart has been an increase in the level of vibration that traditional clutch discs are unable to absorb. This is where the Dual Mass Flywheels play a key role, making these mechanical developments more viable .[2]
The absorption capacity of the vibration depends on the moving parts of the DMF, obviously, they are subject to a certain wear. So when replacing the clutch -for a vehicle over 100,000 miles-, it is highly recommended that a competent workshop replace the dual mass flywheel when replacing the clutch. Otherwise, both the new clutch and the gearbox or crankshaft may suffer in excess.[2]
Types
Red: flywheel-crankshaft side-
Blue:. flywheel-transmission side
The main type is called a "planetary DMF". The planetary gear and the torsional damper are incorporated into the main Flywheel. For this purpose, the main flywheel is divided into primary and secondary mass pignon connected, hence the name "planetary DMF" and between them there are four different types of bent springs:
Individual bent spring
The simplest form of the bent spring is the standard single spring.
One phase bent spring in parallel
The standard springs are called parallel springs of one phase. Consist of an outer and an inner spring, both with a length almost equal. The two springs are connected in parallel. The curves individual characteristics of the two springs are added to form its own characteristic curve of the spring pair.
Two phase bent spring in parallel
In the case of two-stage spring there are two curved parallel springs, one inside the other, but the internal spring is shorter so that will act later. The characteristic curve of the outer spring is adapted to increase when the engine is started. Here only intervenes softer outer spring so that the problematic resonance frequency range can go faster. When the torque increases, reaching the maximum value, then also acts the internal spring. In this second phase, the outer spring and the inner one work together. The collaboration of both springs can thus ensure good acoustic insulation at all engine speeds.
Three-phase bent spring
This curved spring consists of an outer and two inner docks with different elastic characteristics connected in series. This category of bent spring uses the two concepts together: parallel and series dock in order to ensure optimum torsional compensation for each value of torque.
See also
- Centrifugal pendulum absorber
- Clutch
- Flywheel
- Flywheel energy storage
- Harmonic balancer
- List of moments of inertia
References
External links
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