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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
casing lining made of fibers having a layer of self-supporting sound absorbing airborne sound.
BACKGROUND OF THE INVENTION Such a casing lining is known from DE-A 36 21 658. The
casing lining consists of a complex fiber material mixed with a binder medium, which is pressed
into a grid by means of pressure and heat to form a self-supporting unit. The casing lining has
individual pillow-shaped parts which each have a compression which increases from the center
towards its limit. However, the stabilization of the shape of the casing lining mainly tends to
absorb high frequency sound waves. That is because the range of low fibers after compression is
relatively small. In order to eliminate this drawback, it has been proposed to arrange several
layers of known casing lining up and down. However, the space required for that is relatively
SUMMARY OF THE INVENTION It is an object of the present invention to improve the casing
lining of the known type to increase the absorption area if the required area is equal, and in
particular the sound waves of low-frequency sound. The goal is to be able to achieve improved
SUMMARY OF THE INVENTION According to the invention, the fibers are compressed and
bonded to a substantially bubble-free support frame at least in the region of the rim surrounding
the layer on the outside, said layer being bowl-shaped in at least one place. The above-mentioned
problems can be solved by providing the curved portion, and the curved portion being limited by
the absorbing surface having a flow resistance of 20 to 200 Rayl.
Further advantageous configurations are described in the subclaims.
Within the framework of the present invention, the fibers are compressed and bonded to the
substantially bubble-free support frame in the area of the edge surrounding the layer at least on
the outside, and the layer is at least one first. It has a bowl-shaped curve in position, and the
curve is limited by an absorbing surface having a flow resistance of 20 Rayl to 200 Rayl. The
compressed and bonded support frame consisting of fibers makes it possible to form a stabilized,
self-supporting structure in the form of a casing lining, and a device for fixing to a support, such
as a cover hood, for example. Is simplified by this configuration. The support frame comprises,
for example, a first fixing member engageable with a second fixing member of the carrier. A
particularly simple connection between the casing lining and the carrier can be achieved by
means of a snap connection. By means of the bending, an enlargement of the absorption area is
necessarily realized, such that it can be achieved for the frequency spectrum of the noise source
by the flow resistance between 20 Rayl and 200 Rayl, preferably between 50 Rayl and 150 Rayl.
The absorption rate defined in can be achieved. One rayl corresponds to 10 Ns / m 3.
The fibers are made of cotton, for example.
In the partial region of the layer arranged inwardly of the support frame, further fibers are
compressed and bonded to the substantially air-free support frame.
The support member arranged inside the support frame is formed as a support web which has a
functional curve and supports the support frame in the form of an X, for example. Furthermore, if
a substantially bubble-free support member is used inside the support frame, the majority of the
casing lining consists of fibers of relatively low degree of compression, whereby sound waves of
frequencies higher than 800 Hz can be achieved. Absorption is to be performed well.
Intersecting support members enhance the rigidity of the shape of the casing lining.
Another reinforcement of the shape rigidity is achieved by the fact that the curve is arranged on
the support frame and / or the support member and extends parallel to the longitudinal direction
of its profile.
The substantially U-shaped design of the support frame and / or the support member necessarily
increases the bending strength and the torsional strength.
According to an advantageous embodiment of the invention, the layer comprises an at least
partially air-impermeable, sheet-like coating at least at one point on the side opposite to the
airborne sound, the curved part comprising the coating being air Each is pierced by a passage
opening to form a Helmholtz resonator on the side facing the transmission. By means of a onepiece construction of a Helmholtz resonator with a casing lining, it is possible to realize sound
absorption of various frequencies, preferably less than 800 Hz. The Helmholtz resonator can
change its volume, the diameter of its outlet opening and its neck length. Hereby, very good
sound absorption, which is adaptable to the respective given conditions of the use case, over a
wide frequency range, advantageously in the connection with the bend having a flow resistance
between 50 Rayl and 150 Rayl. Is possible. It is very advantageous if the Helmholtz resonator is
formed integrally with the fiber layer from the point of view of the simple manufacture of the
casing lining.
In order to achieve as wide a sound absorption as possible, the bends cover 10 to 90% of the
total area of the layer, and 10 to 90% of the bends are configured as Helmholtz resonators.
The bends are arranged in the support frame and / or in the support member and are arranged
continuously and densely, with the successive bends overlapping one another in the end region.
This configuration forms an area of the support frame and / or low compression fiber for
absorption of high frequency waves located outside the support member and an area for
absorbing higher frequency vibrations formed as a bend. can do.
The closely continuous curvatures and their arrangement form a large absorption area.
The curved portion has a basic contour configured substantially V-shaped to form an overlap.
As a result, the mutually adjacent curves can be engaged with one another in the formation of the
housing lining, so that an additional reinforcement can be realized. In addition to the
substantially V-shaped basic contour, the curved portion may be U-shaped. The support frame
and / or the support member may have a U-shaped profile which is open in the direction of the
holding member, whereby it is possible to combine the bowl-shaped curve with a chamber to be
used for sound absorption It can be formed. The casing lining according to the invention may be
glued to each optional base plate or clipped or screwed onto the base plate. The holding member
is formed, for example, by the motor hood of a motor vehicle, the housing lining being fixed on
the side of the motor hood facing the motor.
The casing lining according to the invention can be used, for example, as a cover lining for the
interior of a motor vehicle, but there is also the possibility that the casing lining can be covered
by a surface covering made of porous open-pore material on the acoustic source side. ing. In
particular in the high frequency range, this can achieve a further improvement of the sound
BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention will now be illustrated
in the drawings and will now be described in detail.
1 and 2 show a first embodiment of a casing lining, which is fixed to the inside of the engine
The casing lining consists of a fiber, an air-borne sound absorbing layer 1, wherein the rim 3 of
the casing lining is compressed and bonded to the support frame 4. By way of example, phenolic
resins or thermoplastic binder media are used as adhesives. In order to additionally reinforce the
casing lining relative to the support frame 4, another fiber 2 located inside the support frame 4 is
compressed and bonded to the substantially X-shaped support member 7. In the frame of the
present embodiment, both the support frame 4 and the support member 7 are configured to
have a large number of curved portions 5 in consideration of the fact that the surface becomes as
large as possible for sound absorption over a wide area. In the embodiment according to FIGS. 1,
2 and 4, the bending portion 5 is at least partially formed as a Helmholtz resonator 10. This
Helmholtz resonator 10 has at least one passage opening 12 arranged in the direction of the
acoustic source for the air and the frequency of the airborne sound to be absorbed is defined and
also different volumes And / or have different opening cross sections of the passage opening 12.
The curved part, which is designed as a Helmholtz resonator, is provided on the other side 8 of
the airborne sound with an air-impermeable sheet-like covering 9 which can be glued to it. The
coating 9 is also penetrated in the region of the passage opening 12. The bending portion 5
which is not embodied as a Helmholtz resonator consists of compressed and bonded fibers,
whose absorption surface 6 preferably has a flow resistance located in the region between 50
Rayl and 150 Rayl. Have. In order to achieve as wide a sound absorption as possible, the bends
have, for example, different wall thicknesses and different flow resistances synthesized
The flexures 5 are substantially rectangular in the region of the support frame 4 and are
connected closely to one another. An additional reinforcement of the casing lining is that, in the
embodiment according to FIG. 1, the continuous curves disposed along the support member 7
overlap one another in the area of their end faces. Is achieved by
As can be seen from FIG. 2, substantially the entire surface of the casing lining facing the
airborne sound is utilized for the absorption of the airborne sound. The entire casing lining is
made in one piece and consists of fibers 2 which are compressed and bonded in the region of the
support frame 4 and the support member 7 in order to form the curve 5, while being bonded In
the non-area, it consists of a layer 1 of airborne sound absorbing, which consists of fibers.
A second embodiment different from the first embodiment based on FIG. 1 is illustrated in FIG.
The bend 5 has various wall thicknesses, the flow resistance of the bend 5 reaching 50 Rayl to
150 Rayl. The majority of the absorbing surface 6 of the curved section 5 enables the absorption
of airborne sound in the frequency range from 50 Hz to 10000 Hz.
A cross section similar to that of FIG. 3 is shown in FIG. 4 in which the sheet 8 which is
impermeable to air is arranged on the side 8 of the Helmholtz resonator 10 opposite to the
airborne sound. The coating 9 is penetrated in the region of the passage opening 12 of the
Helmholtz resonator 10. The sheath 9 extends only in the region of the Helmholtz resonator 10
so that the pot-like bend 5 closed on the side 11 facing the airborne sound has the desired flow
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description, jph06266365
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