METHOD AND DEVICE FOR REDUCING OR PREVENTING NOISE DEVELOPMENT OF FRICTION BRAKES AND FRICTION CLUTCHES

PROCEDE ET DISPOSITIF SERVANT A REDUIRE OU A EVITER LA FORMATION DE BRUITS SUR DES FREINS ET DES EMBRAYAGES A FRICTION

English Abstract

The friction brake is provided with a
brake lining. The support plate (1) of said
brake lining is provided with a friction lining
(2). Two resonators (3) which are diagonally
displaced against each other are formed in the
material of the support plate (1). The natural
frequency of the resonators (3) is adjusted
to the friction induced excitation frequency
of the support plate (1). The surfaces of
the resonators (3) are dimensioned in such
a way that the sound waves thus generated
lie beyond the human hearing range. The
resonators (3) use the vibration energy which
is supplied to the support plate (1) without
causing audible noises. Hence, the brake is
acoustically attenuated.

French Abstract

L'invention concerne un frein à friction présentant une garniture de frein dont la plaque support (1) est pourvue d'une garniture de friction (2). Deux résonateurs (3), décalés en diagonale l'un par rapport à l'autre, sont façonnés dans le matériau de la plaque support (1). Leur fréquence fondamentale est réglée sur la fréquence d'excitation de la plaque support (1) induite par la friction et leur surface est dimensionnée de telle manière que les ondes sonores générées se situent hors de la gamme audible pour l'homme. Les résonateurs (3) consomment l'énergie de vibration enregistrée dans la plaque support (1) sans générer de bruits audibles, ce qui stabilise le frein acoustiquement.

Claims

8
The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. ~A friction device comprising a plurality of components,
said components having surfaces, which are so dimensioned that
sound waves generated in a frictional process are audible,
wherein at least one of the components is connected to at
least one vibratory element; and
wherein the vibratory element is constructed in the form
of a resonator, said resonator having a first resonant
frequency set to a friction-induced excitation frequency of
the device, said resonator having surfaces dimensioned so as
to generate sound waves that are inaudible.
2. ~The friction device as claimed in claim 1, wherein the
resonator is constructed in the form of a beam that is fixed
on one end.
3. ~The friction device as claimed in claim l, wherein the
resonator is constructed in the form of a beam that is fixed
on both ends.
4. ~The friction device as claimed in claim 1, wherein said
at least one resonator being connected to a wall of said at
least one component and being formed over the entire width of
said wall.
5. ~The friction device as claimed in claim 1, wherein said
at least one component and said at least one resonator are
composed of the same material.

9
6. ~The friction device as claimed in claim 5, wherein the
resonator is integrally formed with said component.
7. ~The friction device as claimed in claim 1, wherein at
least one of said components is connected to a plurality of
resonators, each having a first resonant frequency, the first
resonant frequencies of said plurality of resonators are set
to different friction-induced excitation frequencies of the
device.
8. ~The friction device as claimed in claim 1, wherein two
resonators are connected to one component and are arranged
diagonally offset from each other in a common recess of said
component.
9. ~The friction device as claimed in claim 1, wherein a
plurality of resonators are connected to one component of said
device, said resonators being angularly offset from each other
in a star-shaped orientation.
10. ~The friction device as claimed in claim 9, wherein four
resonators are disposed offset from one another by 90°.
11. ~The friction device of claim 1, wherein said friction
device is a friction brake.
12. ~The friction device of claim 1, wherein said friction
device is a friction clutch.
13. ~The friction device according to any one claims 1 to 12
wherein said friction device engages a revolving body.

Description

CA 02360086 2001-07-30
x
Method and Apparatus for Reducing or Preventing the Generation of
Norse by Friction Brakes and Friction Clut~6es
The invention relates to a friction brake or friction clutch with a plurality
of
components, the surfaces of which are so dimensioned that the sound waves
generated in a frictional process are audible, at least one of the components
being connected to at least one vibratory element.
rt is known that friction brakes tend to generate noise in an irregular
fashion
when they are actuated, which is perceived by people as unpleasant. The
production of such noise is due to the fact that the friction bearing deforms
in
the range of its elasticity, the degree of deformation constantly changing and
thus producing vibrations. If the frequency of these vibrations extends into
the
range of the resonant frequencies of large area brake components, the latter
are
induced to vibrate with large amplitudes occurring over a large area, as
occurs
in the case of resonance vibration in the event of relatively little damping.
The
pressure waves in the surrounding atmosphere resulting therefrom intrude into
human hearing in the form of disruptive noises.
As a countermeasure, it has been attempted to shift the resonant frequencies
occurring in the braking installation. This concept may, however, be realised
constructionally only with difficulty, and even then only incompletely, as a
result of the plurality of layers.
Attempts have also been made to increase the damping by coupling
modifications or by material variations. This is, however, also realisable
only

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2
with difficulty and even then only incompletely as a result of tight safety
and
constructional restrictions.
Thus WO 97/31195 discloses damping the frictional vibrations between a brake
housing and the associated brake lining. The brake housing can have pegs
capable of vibration for laterally supporting the brake lining. Alternatively,
the
carrier plate of the brake lining can be provided with lateral tongues capable
of
vibration.
Furthermore, DE 3811222 A1 discloses a device of~the type referred to above in
which a brake disk is provided with vibration caneellers. These are plates
fined
on one side, which have merely a single degree of freedom. In order to fulfil
their function, they must be excited to perform out of phase vibration. This
results in the necessity of setting their resonant frequency to the resonant
frequency of the brake disk and so determining the damping that the necessary
phase shifting occurs. The additional consideration of the damping requires a
very considerable additional computation complexity in matching the vibratory
elements to the desired target frequency.
2Q Starting from this prior art, the circumstances of which are comparable to
those
of friction clutches, it is the object of the invention to provide a
computationally
more simple and eonstructionally flexible possibility reducing or preventing
the
generation of noise by friction brakes and friction clutches.
This object is solved in accordance with the invention with the friction brake
ar
friction clutch referred to above if the vibratory element is constructed in
the
form of a resonator, the first resonant frequency of which is set to a
friction-

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3
induced excitation frequency of the brake or clutch and whose area is so
dimensioned that the noises which are generated are inaudible.
important embodiments of the invention are characterised in the dependent
claims.
The resonator is a vibratory element rigidly connected to one of the brake or
clutch components, the resonant Frequency of wrhich is set to that friction-
induced excitation frequency which would i~rapart resonance vibrations to a
main ~uv'al1 surface of the brake or clutch. The resonator vibrates in
synchronism
with this frequency and converts the vibrational energy introduced into the
brake or clutch by the frictional process so as to dissipate it without the
main
wall surfaces of the installation being induced to ~ribrate in an acoustically
disruptive manner. The area of the resonator is not sufficiently large to
transmit
disruptive noise arrnospherically. The installation is thus acoustically
calmed
such that noise is not sene~rated at all in the vicinity of the resonant
freqiuency of
the resonator.

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3a
The resonant frequency, to which the resonator should be set, is determined
analytically, numerically or experimentally. Additionally, there is the
possibility of equipping the brake or clutch with a plurality of resonators,
which
are set to different excitation frequencies. The entire critical region rnay
thus be
covered in this manner without complex tests being necessary.
One or more large area components of the installation, .which can generate
friction-induced noise, arc generally equipped with one or more resonators.
The entire installation can be acoustically stabilised in this manner.
It is of substantial advantage that the resonators do not require a defined
ambient air space. They must merely be able to vibrate freely-
Best results were achieved with resonators which are constructed in the form
of
beams fixed on one side. They can be arranged in openings which completely
pass through the wall thickness of the associated component. They can,
however, also be located in niche-like recesses, provided that their freedom
to
vibrate is ensured.

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The choice of materials may be made at will. rt is advantageous to construct
the
resonators from the material of the associated component and thus to work them
out of the material of the component, for instance by wire erosion or die
cuts.
Other rigid connections can equally be considered.
A particularly simple arrangement consists of arranging two resonators
diagonally offset from one another, namely in rectangular or approximately
rectangular main surfaces of the component. With circular main surfaces, a
star-shaped orientation with an appropriate angular offset, preferably of
90°, is
suitable. An unequal angular offset is also possible.
The invention is applicable to disk brake installations, which have at least
one
brake disk, at least two brakes linings, at least one brake calliper, at least
one
clamping unit and at least one holder. In this case, the lining carrier plates
will
be equipped with one or more resonators in a central arrangement or in an
upwardly, downwardly or laterally offset arrangement with respect to the
centre
of the inner circle of the brake piston. The brake disks will further also be
equipped with resonators arranged in a star shape, these being constructed in
the
form of beams fixed at the radially inner end. In the case of an internally
ventilated brake disk, the resonators arc positioned, for instance, at the
positions
of a few internal ventilation passages. Finally, the question arises of also
equipping the brake calliper with resonators may also be considered. Disk
clutches can be constructed xn a corresponding manner.
z5
The invention is also applicable to drum brake installations with at least one
brake drum, at least one brake lining, at least one brake shoe, at least one
anchor

CA 02360086 2005-O1-12
plate, at least one clamping unit and at least one holder.
In this case, the anchor plate, the brake drum (in recesses
on the inner or outer surface) and the brake shoe are
preferably equipped with resonators.
5
All friction brakes and friction clutches are suitable for
using the invention.
The possible uses of the braking installations or clutch
installations with resonators are very varied, both in
vehicles and in stationary machines. Reference is made to
passenger carrying vehicles, freight vehicles, trailers,
semi-trailers, special vehicles of all types including
agricultural and military land vehicles, rescue and safety
vehicles, extraterrestrial vehicles, track vehicles of all
types, flying devices in driving operation and two-wheeled
vehicles, also lifts, moving belts and conveyor belts,
escalators, agricultural and military devices and
entertainment carousels together with the associated
installation (temporary structures).
The example is given of a disk brake system, which is
excited with a friction-induced frequency of 2000 Hz. As a
result of the provision of resonators the system is free of
resonant wall vibrations in the frequency range of ca. 1750
Hz to 2650 Hz and thus free of sound radiation.
In one aspect, the present invention resides in a
friction device comprising a plurality of components,
said components having surfaces, which are so dimensioned
that sound waves generated in a frictional process are

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5a
audible, wherein at least one of the components is
connected to at least one vibratory element; and wherein
the vibratory element is constructed in the form of a
resonator, said resonator having a first resonant
frequency set to a friction-induced excitation frequency
of the device, said resonator having surfaces dimensioned
so as to generate sound waves that are inaudible.
The invention will be explained below in more detail by way
of preferred exemplary embodiments in conjunction with the
accompanying drawings, in which:
Figure 1 is a perspective view of a brake lining for a disk
brake;
Figure 2 is a perspective view of a brake disk;

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Figure 3 is a sectional view along the line A-A in Figure 2;
Figure 4 is a side view of a brake calliper.
In Figure 1, a carrier plate 1 is provided for a .fiiction lining 2. The
carrier plate
1 has two resonators 3. These are constructed in the form of beams fixed on
one side and are worked out of the material of the carrier plate 1. Their
thickness corresponds to that of the carrier plate 1. The arrangement is such
that the resonators 3 are diagonally offset from one another.
The first resonant frequency of the resonators 3 is set to the friction-
induced
excitation frequency of the carrier plate 1, the surfaces of the resonators
being
so dimensioned that the sound waves which are produced are inaudible. T"he
resonators 3 convert the vibrational energy introduced into the carrier plate
1.
The result is that the brake lining is acoustically stabilised. No disruptive
noises
are emitted into the environment.
Figures 2 and 3 show an internally ventilated brake disk 4, which includes a
resonator 5. The latter replaces one of the internal ventilating passages,
which
are not shown. The resonator S is also constructed in the form of a beam fixed
on one side, the fixing point being situated radially inwardly.
Figure 4 shows a brake calliper 6 with screw connections 7, a vent 8 and a
hydraulic connection 9. Two resonators 10 are also provided whose
arrangement and construction correspond to the resonators 3 of Figure 1.
Modifications are of course possible within the scope of the invention. This
relates above all to the construction and arrangement of the resonators. A
star-

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7
shaped arrangement is, for instance, possible. Tt should be stressed that
resonators of different frequencies can also be used.
The applicability of the in~rention is not limited to disk brakes. Above all,
drum
brakes can also be equipped With resonators. The invention may basically be
used with all friction brakes and friction clutches.

Representative Drawing