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What is Dual Mass Flywheel | types , Working

A dual-mass flywheel (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. A compact dual-mass flywheel often includes the whole clutch, including the pressure plate and the friction disc.

Dual Mass Flywheel, and What Does It Do?

A dual mass flywheel, or DMF, acts the same way a conventional flywheel acts. There are some advantages, and disadvantages to using this design. Here’s what you need to know about the purpose of a dual mass flywheel.

The dual mass flywheel is primarily designed to reduce noise and vibration. The DMF is sort of a mechanical “sponge”, where vibrations and harshness in the driveline are dampened by two flywheel masses that are connected to one another by a series of high strength springs. Any roughness is absorbed (at least partially) by the springs between the flywheel masses.

It may help to think of a dual mass flywheel as a shock absorber: each flywheel is a solid connection, but between there is a “soft” spring that takes some of the jolts out of accelerations, gear changes, etc.

Types Of Dual Mass Flywheel :

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 spring.

One-phase bent springs in parallel

The standard springs are called parallel springs of one phase. These consist of an outer and an inner spring of almost equal lengths and connected in parallel. The individual characteristic curves of the two 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 springs, one inside the other, but the internal spring is shorter so that it acts later. The characteristic curve of the outer spring is adapted to increase when the engine is started. The softer outer spring only acts to increase the problematic resonance frequency range. When the torque increases, reaching the maximum value, the internal spring also acts. In this second phase, the inner and outer springs work together. The collaboration of both springs thus ensures good acoustic isolation at all engine speeds.

Three-phase bent spring

This curved spring consists of an outer and two inner 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.