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Dual-mass Flywheel

The Sachs dual-mass flywheel (planetary DMF) provides first-class driving properties in passenger cars. This is particularly noticeable in the reduction of noise in the powertrain and body, as well as in a more comfortable ride and easier shifting. The use of innovative and multifunctional components makes the Sachs dual-mass flywheel a practical choice even for the lower mid-size category of cars.

Less noise – a more pleasant ride
Sachs dual-mass flywheel (planetary DMF)

Problem:
Ignition-dependent rotational irregularities of the engine cause torsional vibrations in a car‘s powertrain. At a specific engine speed, the ignition frequency equals the natural frequency of the powertrain. This condition induces vibrations of particularly large amplitude that can trigger rattle noises in the transmission and humming in the body shell. The rattle is caused by the meshing of slack gears and synchronizing rings outside the power flow in the transmission. Noise in the body is caused by vibrations that may be transmitted to the body through the supports of the engine-transmission unit and of the drive axle. These noises can be eliminated or at least greatly reduced by a torsion damper that allows a degree of elastic distortion between the crankshaft and the input shaft.
A basic rule: The softer the springs in the damper and the greater the moment of inertia associated with the transmission, the better the damping of vibrations. In a conventional clutch, the damper is integrated in the clutch disk. But in many contemporary cars, this solution no longer ensures a comfortable noise level, since the residual rotational irregularities are relatively large.

Solution:
In the Sachs planetary DMF, the planetary transmission and the torsion damper are integrated in the flywheel. In this arrangement, the total mass of the flywheel is divided into a primary and a secondary flywheel. That‘s why this component is called a planetary DMF. This design allows the use of much softer springs and an approximately one hundred percent increase in the moment of inertia associated with the transmission. This means a marked reduction in speed variations. The result: Annoying rattles and hum noises are a thing of the past.

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