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A dual-mass flywheel (DMF or DMFW) is a rotating mechanical device that is used to provide continuous energy (
rotational energy Rotational energy or angular kinetic energy is kinetic energy due to the rotation of an object and is part of its total kinetic energy. Looking at rotational energy separately around an object's axis of rotation, the following dependence on the ob ...
) in systems where the energy source is not continuous, the same way as a conventional
flywheel A flywheel is a mechanical device which uses the conservation of angular momentum to store rotational energy; a form of kinetic energy proportional to the product of its moment of inertia and the square of its rotational speed. In particular, as ...
acts, but
damping Damping is an influence within or upon an oscillatory system that has the effect of reducing or preventing its oscillation. In physical systems, damping is produced by processes that dissipate the energy stored in the oscillation. Examples i ...
any violent variation of
torque In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of th ...
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 arc 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. A compact dual-mass
flywheel A flywheel is a mechanical device which uses the conservation of angular momentum to store rotational energy; a form of kinetic energy proportional to the product of its moment of inertia and the square of its rotational speed. In particular, as ...
often includes the whole
clutch A clutch is a mechanical device that engages and disengages power transmission, especially from a drive shaft to a driven shaft. In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). ...
, including the pressure plate and the friction disc.


History

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 more efficient new engines, lowering the cylinder number to 3 or even 2 cylinders, and allowing the delivery of more torque and power at low revolutions. The counterpart has been an increase in the level of vibration which traditional
clutch A clutch is a mechanical device that engages and disengages power transmission, especially from a drive shaft to a driven shaft. In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). ...
discs are unable to absorb. This is where the dual-mass flywheels play a key role, making these mechanical developments more viable.LUK Symposia
/ref> The absorption capacity of the vibration depends on the moving parts of the DMF, these parts are subject to wear. Whenever the clutch is replaced, the DMF should be checked for wear. The two key wear characteristics are freeplay and sideplay (rock). These should be measured to determine whether the flywheel is serviceable. The wear limit specifications can be found in vehicle or flywheel manufacturer's published documentation. Other failure modes are severely grooved/damaged clutch mating surface, grease loss, and cracking.


Types

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 pinion-connected masses, 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 arc spring.


One-phase bent springs in parallel

The standard arc springs are called parallel springs of one phase. These consist of an outer and an inner arc spring of almost equal lengths and connected in parallel. The individual characteristic curves of the two arc springs are added to form the characteristic curve of the spring pair.


Two-phase bent springs in parallel

In the case of two-stage spring there are two curved parallel arc springs, one inside the other, but the internal arc spring is shorter so that it acts later. The characteristic curve of the outer arc spring is adapted to increase when the engine is started. The softer outer arc spring only acts to increase the problematic resonance frequency range. When the torque increases, reaching the maximum value, the internal arc spring also acts. In this second phase, the inner and outer arc springs work together. The collaboration of both arc springs thus ensures good acoustic isolation at all engine speeds.


Three-phase bent spring

This curved spring consists of an outer and two inner arc springs with different elastic characteristics connected in series. This category of bent spring uses the two concepts together: parallel and series connection in order to ensure optimal torsional compensation for each value of torque.


See also

* Centrifugal pendulum absorber *
Clutch A clutch is a mechanical device that engages and disengages power transmission, especially from a drive shaft to a driven shaft. In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). ...
*
Flywheel A flywheel is a mechanical device which uses the conservation of angular momentum to store rotational energy; a form of kinetic energy proportional to the product of its moment of inertia and the square of its rotational speed. In particular, as ...
*
Flywheel energy storage Flywheel energy storage (FES) works by accelerating a rotor (flywheel) to a very high speed and maintaining the energy in the system as rotational energy. When energy is extracted from the system, the flywheel's rotational speed is reduced as a c ...
*
Harmonic balancer A harmonic damper is a device fitted to the free (accessory drive) end of the crankshaft of an internal combustion engine to counter torsional and resonance vibrations from the crankshaft. This device must be interference fit to the crankshaft i ...
*
List of moments of inertia Moment of inertia, denoted by , measures the extent to which an object resists rotational acceleration about a particular axis, it is the rotational analogue to mass (which determines an object's resistance to ''linear'' acceleration). The momen ...


References


External links


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