User Guide

Benefits of the arc spring:
• High friction at large rotation angle (start-up process)
and low friction at low rotation angle (overrun)
• Loweractuationforce(springrate)becauseofthe
flexible space utilisation (in comparison with systems
with multiple single springs)
• Impactdampingcanbeintegrated(dampingspring))
. Friction control disc
During the start-up process, the DMF operates briefly in
the resonant frequency range. When this happens, the
flange wings repeatedly hit the arc springs with unbraked
force, producing noise as they do so. An eective
countermeasure here is an additional friction device, the
friction control plate. This has the eect of delaying the
rotation of the flange within a dened working range.
As a result, the flange can be rotated over the secondary
mass in the range of clearance angle (
a) without
noticeable resistance. Only outside the clearance angle,
i.e. at greater angles of rotation, does the additional
friction come into eect. In this way, the noises
produced when starting up or changing the load can
be eliminated.
DMF systems help to improve the noise behaviour of the
vehicle by using special torsion damper designs. As a
direct result, less noise is generated and fuel consumption
is reduced.
In order to make ideal use of the available space, a coil
spring with a large number of coils is fitted in a semicir-
cular position. The arc spring lies in the spring channel
of the DMF and is supported by a guide. Under operation,
the coils of the arc spring slide along the guide and
generate friction and thereby damping. In order to pre-
vent wear on the arc springs, the contact surfaces are
smeared with grease. The optimised shape of the spring
guides helps to reduce friction significantly. Besides
improved vibration damping, arc springs help to reduce
wear.
Thanks to the diversity of arc spring designs, a DMF sys-
tem can be manufactured to precisely match the individ-
ual load characteristics of each vehicle type. Arc springs
of various designs and characteristics are used. The most
frequent types are:
• Single-stage springs
• Two-stage springs
either in a parallel arrangement in one of various differ-
ent layouts, or in-line arrangement
• Damping springs
In practice, the spring types are applied in various different
combinations.
a
1
2
1 Guide
2 Arc spring
. Arc springs