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DESCRIPTION JP2007328347

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DESCRIPTION JP2007328347
PROBLEM TO BE SOLVED: To provide a vibration / noise reduction device capable of suppressing
vibration or noise in a wide frequency range over a wide area. A piezoelectric speaker (2) in
which a diaphragm (21) made of a piezoelectric ceramic or the like is supported on an elastic
support (22) on a suppression target (1) and electrodes are connected to the diaphragm. Is
provided as an acousto-electric converter or a vibration-electric converter, and provided with
energy consumption means (3) for converting the electric energy obtained from the piezoelectric
speaker into heat energy and consuming it. [Selected figure] Figure 1
Vibration and noise reduction device
[0001]
The present invention relates to a vibration / noise reduction device that suppresses the
generation of vibration or noise of a relatively lightweight object such as a wall of a vehicle, a
wall of a building, a machine itself, or a casing of the machine. An object of suppression of
vibration or noise generation is herein referred to as a suppression object. The present invention
is particularly suitable for reducing the vibration and noise of an object to be suppressed which
exists in an environment susceptible to vibration or noise in the audible range.
[0002]
Generation of vibration or noise due to extraneous vibration such as the wall surface of a railway
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vehicle or other vehicle, wall surface of a building, etc It can interfere with stability and impair
health. In addition, noise generation due to external vibration or self vibration of the machine
itself or its housing etc. or vibration generation due to extraneous sound not only hinders the
performance of the inherent function of the machine but also mental stability of the machine
driver or operator. Threatens and increases the risk of an accident. For this reason, there is a
demand for a technique for effectively suppressing the generation of vibration or noise of
relatively lightweight objects such as walls of vehicles and buildings, machines or their casings.
[0003]
Among the conventional vibration / noise reduction devices, the energy conversion system
includes an energy conversion system for converting vibration or noise into electricity, and an
energy consuming means that consumes the converted electricity as heat energy. As a system, a
microphone is generally used as a noise-electric converter, and a vibration-electric converter is
recently known that uses a piezoelectric material. A shunt circuit including a coil and a resistor is
used as the energy consuming means, and a resonant circuit is configured by the capacitance C
of the piezoelectric material, the coil inductance L of the shunt circuit, and the resistor R. Energy
is consumed by supplying current to the resistor of this shunt circuit to release Joule heat (see,
for example, Non-Patent Document 1)
[0004]
Journal of Sound & Vibration Vol. 146 No. 2 p24, 52,68 1991
[0005]
The above-described conventional vibration / noise reduction device has the following problems
in the above energy conversion system and energy consumption means.
(1) Problems of energy conversion system The energy conversion system using a microphone
only converts the sound pressure in the space of a minute range near the position where the
microphone is attached into an electric signal, and the acoustic energy of the intrusion sound Can
not be efficiently converted into electrical energy (the energy conversion local range is narrow,
and the efficiency is low). In addition, when a piezoelectric material such as piezoelectric ceramic
is used as a converter from vibrational energy to electrical energy, the frequency range that can
be converted is narrow due to the characteristics of the piezoelectric material itself (that is, the
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piezoelectric material has frequency dependence on energy conversion performance) High sex).
The frequency or level of vibration or noise transmitted to it varies depending on the type of
vehicle or a wall of a building or the type of object to be suppressed such as a motor or its casing,
or the acoustic environment. Therefore, practically, it can not be expected to exhibit conversion
performance of wide band vibration or noise in the wide frequency range in the field.
[0006]
(2) Problems of Energy Consumption Means The conventional resonance circuit constituting the
energy consumption means is generally constituted by the inductance L possessed by the coil
and the capacitance C possessed by the piezoelectric element, and 1 / (2π√ Resonance occurs
at the frequency due to (LC). That is, in the vicinity of the resonant frequency determined by L
and C, it is possible to effectively dissipate the power with a resistor for energy consumption, but
the dissipation of power is small at other frequencies (the current of the resonant circuit
Frequency dependence of amplification). The frequency band of vibration or noise transmitted to
the object to be suppressed may vary widely depending on the environment. Therefore, the
vibration / noise reduction device using the conventional shunt circuit that constitutes the
resonance circuit can not exhibit a sufficient energy consumption effect with respect to vibration
or noise in a wide band.
[0007]
(3) Necessity of using individual signal converter When converting the noise and vibration into
electricity because the signal or energy converter so far is a single system converter of noiseelectricity and vibration-electricity respectively Needs to use each dedicated converter.
[0008]
(4) Problems Related to the Mounting Method Generally, when the vibration / noise reduction
device is attached to the object to be suppressed, it is common to bond the device to the object to
be suppressed or mechanically attach it with a screw or the like.
Depending on the object to be suppressed or the use environment, the strength or the direction
of the vibration or sound may change. In such a case, it is desirable to change, move or add the
attachment position of the vibration / noise reduction device, but conventionally it has been
impossible to remove once attached, or it takes time and effort to loosen and remove screws and
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the like.
[0009]
(5) Problems in damping effect The damping materials and various ANC systems (Active Noise
Control System) that are already commercially available are used for each narrow band, and only
the damping effect in a single system is exhibited . In general, the damping material is effective
only in the high frequency region, and the ANC system is effective in the low frequency region.
Therefore, when the wall of a vehicle, the wall of a nearby building such as an expressway, a
railway track, a speaker for public notification, etc. is subjected to vibration or noise in a wide
frequency band, a satisfactory damping or soundproofing effect can be obtained In order to
achieve this, it is necessary to install multiple types of vibration and noise reduction devices,
which is expensive and thus difficult to achieve.
[0010]
The present invention has been made in view of the above problems, and the problem to be
solved is to solve the problem of the above energy conversion system, that is, to cover as wide a
wide area as possible. An object of the present invention is to provide a vibration / noise
reduction device capable of efficiently converting vibration or noise in a frequency range into
electrical energy (expansion of a regional range capable of energy conversion and improvement
of conversion efficiency).
[0011]
When a piezoelectric speaker is attached to a wall or the like as an energy conversion system, the
noise can be efficiently converted to electricity by vibrating the diaphragm of the piezoelectric
speaker against the intruding sound. In the case where the device is not implemented, the
acoustic energy incident on the piezoelectric speaker is converted to electrical energy, or the
secondary radiation sound from the wall is converted to electricity, so the vibration energy of the
object to be suppressed is made efficient Can not be converted into electrical energy (problems
when using a piezoelectric speaker for the energy conversion system).
Therefore, it is desirable to attach the piezoelectric speaker as an energy conversion system so
that the vibration is efficiently transmitted from the object to be suppressed when the
piezoelectric speaker is attached to a wall or the like to the diaphragm of the piezoelectric
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speaker.
[0012]
In the case where the object to be suppressed is a piezoelectric speaker for sound, it is desirable
to reduce unnecessary noise generated on the back side.
[0013]
In order to solve the above-mentioned problems, the present invention relates to a vibration /
noise reduction device comprising an energy conversion system for converting vibration or noise
into electricity and energy consumption means for consuming the converted electricity as heat
energy. The conversion system is composed of a plurality of piezoelectric speakers formed by
supporting a diaphragm made of piezoelectric ceramic or the like on an elastic support and
connecting electrodes to the diaphragm, and a flat surface on the suppression target or in the
space It is characterized in that the energy consuming means is connected in series between the
two electrodes connected to the respective diaphragms of the piezoelectric speaker, as well as
being attached.
[0014]
The energy consumption means may be one constituted by a shunt circuit including a coil and a
resistor connected in series between both electrodes connected to the diaphragm of the
piezoelectric speaker (claim 2).
[0015]
When attaching a piezoelectric speaker to an object to be suppressed, a post for interposing the
vibration of the object to be suppressed directly to the diaphragm is interposed between the
object to be suppressed and the diaphragm of the piezoelectric speaker to improve conversion
efficiency. It is desirable to do (claim 3).
[0016]
Moreover, in order to improve the conversion efficiency, it is desirable to overlap and attach a
plurality of piezoelectric speakers on the suppression target (Claim 4).
[0017]
In addition, when a plurality of piezoelectric speakers are stacked and attached, in order to
improve conversion efficiency, a support is interposed only between the diaphragm of the
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piezoelectric speaker directly attached to the suppression target and the suppression target, and
piezoelectrics are superimposed It is desirable not to interpose a support between the
diaphragms of the speaker of this type (claim 5).
[0018]
Further, in the present invention, it is desirable that the piezoelectric speaker be attached to the
sheet-like damping material, and that the damping material be attached to the suppression target
(claim 6).
[0019]
Then, when the object to be suppressed is a piezoelectric speaker for sound, a piezoelectric
speaker as an acoustic-electric converter is attached to the back of the piezoelectric speaker for
sound, and non-generation occurs on the back of the piezoelectric speaker for sound It is
desirable to suppress the required noise (claim 7).
[0020]
As described above, according to the invention of claim 1, (a) a plurality of energy conversion
systems are formed by supporting a diaphragm made of piezoelectric ceramic or the like on an
elastic support and connecting electrodes to the diaphragm The energy conversion system has a
wider area than that of the conventionally used piezoelectric element, and is constituted by a
single piezoelectric speaker and attached to the suppression target planarly on the suppression
target or in space. It can be efficiently converted to electrical energy in a wide frequency band.
And since (i) the converted electric energy is converted into heat energy by the energy
consumption means and consumed, the damping or sound absorbing effect is exhibited over a
wide area and in a wide frequency band.
That is, the effect of the expansion of the regional range which can be energy-converted, the
reduction of frequency dependence, and the improvement of conversion efficiency is acquired.
Furthermore, since the piezoelectric speaker is thin-walled unlike conventional energy
conversion systems, vibration or noise generation of relatively lightweight objects such as a
vehicle wall, a wall of a building, a machine itself or a casing of a machine Is useful as a vibration
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/ noise reduction device that suppresses noise.
That is, the damping or sound absorbing effect can be exhibited without the need to particularly
increase the thickness of the wall of the vehicle, the wall of the building, the machine itself or the
housing of the machine.
This is an effect that can not be realized by conventional energy conversion systems such as
microphones and dynamic speakers.
[0021]
According to the second aspect of the invention, since the electrical energy extracted from the
piezoelectric speaker is converted into heat energy by the resistor and emitted, the vibration of
the object to be suppressed and the secondary radiation are attenuated.
[0022]
According to the third aspect of the invention, since the vibration of the suppression target is
directly transmitted to the diaphragm, the vibration transmission efficiency from the suppression
target to the diaphragm of the piezoelectric speaker is significantly improved.
[0023]
According to the invention of claim 4, when the amount of noise input to the object to be
suppressed is large, the plurality of piezoelectric speakers sequentially convert the noise that has
passed through the piezoelectric speaker in the previous stage into electrical energy, and the
previous speaker Since the transmitted noise is further converted to electric energy by a later
speaker, the energy conversion efficiency is improved.
[0024]
According to the invention of claim 5, the vibration is mainly converted to electricity through the
column attached between the piezoelectric speaker directly attached to the suppression target
and the suppression target, and the piezoelectric speaker on the intrusion sound side Noise and
vibration can be efficiently converted to electricity with the same strain-electric converter
because noise is mainly converted to electricity by not having a support.
[0025]
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According to the sixth aspect of the present invention, it is possible to achieve a damping effect
in which the damping effect in the high frequency range of the damping material and the
damping effect in the low frequency range of the piezoelectric speaker are combined.
[0026]
According to the invention of claim 7, the piezoelectric speaker as the acoustic-electric converter
can be attached to the back side of the acoustic piezoelectric speaker to suppress unnecessary
noise generated on the back side of the acoustic piezoelectric speaker. Therefore, a clear sound
that is not affected by noise can be produced on the front side of the acoustic piezoelectric
speaker.
[0027]
Next, embodiments of the present invention will be described based on the drawings.
FIG. 1 is a conceptual diagram showing the basic configuration of the first embodiment, FIG. 2 is
a circuit diagram showing an example of a piezoelectric speaker and an energy consumption
means, and FIG. 3 shows an example of an attachment structure of the piezoelectric speaker to a
suppression target (A) is a front view, (b) is a cross-sectional view, FIG. 4 is a conceptual view
showing a mounting structure in the case where piezoelectric speakers are overlapped and
attached, (a) is a simple overlapping of piezoelectric speakers (B) is a cross-sectional view of the
first piezoelectric speaker provided with a support, and (c) is a cross-sectional view showing the
mounting structure of the piezoelectric speaker damping sheet.
FIG. 5 is a graph showing the vibration reduction effect together with a comparative example,
FIG. 6 is a conceptual diagram showing another installation example of the piezoelectric speaker,
and FIG. 7 is a case where a support is not provided between the diaphragm and the suppression
target plate FIG. 8 is a graph showing the frequency dependency of the piezoelectric
performance of the piezoelectric element and the piezoelectric speaker (the energy conversion
characteristic graph of the piezoelectric element and the piezoelectric speaker).
[0028]
The basic configuration of the vibration / noise reduction device according to the present
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invention is, as shown in FIG. 1, a piezoelectric speaker 2 attached to the object 1 to be
suppressed, and energy consumption means for consuming electric energy extracted by the
piezoelectric speaker It consists of three.
The suppression target 1 is a relatively lightweight object or member such as a wall surface of a
railway vehicle or other vehicle, a wall surface of a building, a machine itself, or a casing of a
machine, and the effects of the present invention are effectively exhibited. It is a case where
these suppression objects exist in an environment susceptible to vibration or noise of a relatively
wide band frequency.
The piezoelectric speaker 2 has a diaphragm 21 made of piezoelectric ceramic or the like
supported on an elastic support 22 and an electrode connected to the diaphragm, and when used
as an original speaker for sound, the electrode is used. When an audio signal is received via the
diaphragm, it vibrates at a predetermined frequency to generate a sound wave. In the present
invention, the piezoelectric effect of the diaphragm 21 of the piezoelectric speaker 2 (the
phenomenon of generating charge when receiving mechanical vibration) Is used as a kind of
energy conversion system that converts distortion due to received vibration or noise into
electrical energy.
[0029]
One of the methods of attaching the piezoelectric speaker 2 to the suppression target 1 is a
method of directly attaching the elastic support plate 22 or the casing of the piezoelectric
speaker 2 to a wall or the like, or a method of fixing using an adhesive tape or the like , And
fixing methods using fasteners such as screws.
Although it has been proposed to use a piezoelectric element to convert acoustic energy or
vibrational energy into electrical energy, as shown in FIG. 8, this piezoelectric element is
generally near the natural frequency (100 to 300 Hz) determined by the shape Although energy
conversion is efficiently performed, energy conversion efficiency is low at other frequencies.
[0030]
FIG. 8 is a graph showing the frequency characteristics of the output of the piezoelectric element
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and the piezoelectric speaker. The thin line indicates the output of the piezoelectric element, and
the thick line indicates the output of the piezoelectric speaker.
As shown in the figure, while the piezoelectric element has a low output level in the vicinity of
500 Hz and 1000 to 2000 Hz, the piezoelectric speaker has a slightly low output level in a
narrow range of 750 to 1100 Hz and 1700 to 2000 Hz. It can be seen that good output can be
obtained over a wide range of
[0031]
The piezoelectric speaker 2 is manufactured on the premise that it is used as an acoustic speaker,
and is designed to widen the frequency band of acoustic radiation.
When this piezoelectric speaker 2 is used as a strain-electric converter, it is possible to convert
distortion due to vibration or noise in a wide frequency band of 50 to 1700 Hz into electricity as
shown in FIG.
The present invention is most characterized in that acoustic energy and vibration energy can be
converted into electrical energy in a wide band by using a piezoelectric speaker having this wide
frequency band as an energy converter.
[0032]
When the magnitude of vibration or noise applied to the suppression target 1 is large, it is
preferable to use a plurality of piezoelectric speakers and couple the positive electrode and the
negative electrode of each piezoelectric speaker in parallel or in series.
[0033]
The electrical energy consuming means 3 is constituted by a known shunt circuit S1 including a
coil 31 and a resistor 32 connected in series between both electrodes connected to the
diaphragm of the piezoelectric speaker 2 as illustrated in FIG. can do.
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Since the shunt circuit S1 is connected to the piezoelectric speaker 2, an LCR resonance circuit is
formed by the capacitance (C) of the diaphragm, the inductance (L) of the coil 31 and the
resistance (R) of the resistor 32. There is.
According to the above configuration, when the external vibration or noise enters the
suppression target 1, the vibration or noise is transmitted to the diaphragm 21 of the
piezoelectric speaker 2, and the distortion generated on the diaphragm 21 is converted into
electric charge. The resonant current flows through the shunt circuit S1, and the current is
converted into Joule heat in the resistor 32 and released to the atmosphere, whereby energy is
consumed.
[0034]
As described above, when the shunt circuit S1 constituting the resonance circuit is used, the
maximum current flows from the piezoelectric speaker 2 to the shunt circuit S1 when the
suppression target 1 vibrates at the same frequency as the resonance frequency. Good vibration
damping effect can be obtained, but when vibration of other frequency is received, the vibration
damping effect becomes low.
[0035]
When the piezoelectric speaker is used as an energy conversion system, the quality of vibration
transmission from the object to be suppressed to the diaphragm of the piezoelectric speaker
affects the damping effect or the sound absorbing effect.
In a preferred embodiment, as shown in FIG. 3, a support 5 is preferably provided between the
center of the diaphragm 21 and the object to be suppressed, so that the vibration of the object 1
is transmitted to the diaphragm 21 of the piezoelectric speaker 2. I am trying to communicate
directly. The support 5 may be a rigid body such as metal or an elastic body such as rubber. In
the piezoelectric speaker alone, basically only the acoustic energy to be applied is converted into
electric energy, but by connecting the diaphragm 21 of the piezoelectric speaker 2 and the
suppression target 1 with the support 5, the suppression target 1 is obtained. Since vibrational
energy can be directly transmitted to the diaphragm 21 of the piezoelectric speaker 2,
improvement in energy conversion efficiency is expected. Furthermore, it is possible to convert
not only the component excited by the acoustic energy to which the vibration of the suppression
object is applied, but also the solid propagation vibration of the vibration due to other factors
into electric energy. As shown in FIG. 7, comparing the output when the support 5 is not
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provided between the diaphragm 21 and the suppression target plate 1 (FIG. 7A) and the output
when the support 5 is provided (FIG. 7B). In the case of the presence of a support, it can be seen
that an output faithfully following the vibration of the suppression target plate is obtained.
[0036]
When a plurality of piezoelectric speakers 2 are used, the piezoelectric speakers 2a, 2b, and 2c
are overlapped not only in a planar manner on the target surface of the suppression target 1, but
also as illustrated in FIG. It is possible to use. In order to increase the energy conversion
efficiency, it is possible to convert vibration or noise to electrical energy in multiple steps with
respect to the sound incident direction by overlapping piezoelectric speakers on the same
surface, and the overall energy conversion efficiency improves.
[0037]
As described above, in the case of using the piezoelectric speaker in an overlapping manner, as
illustrated in FIG. 4B, the pillar 5 is attached to the piezoelectric speaker 2a directly attached to
the suppression target 1, and pasted thereon The piezoelectric speaker 2b is preferably used
without a support. By attaching the support 5 to the piezoelectric speaker 2a directly attached to
the suppression target 1, the vibration energy of the suppression target 1 is mainly converted
into electric energy by the piezoelectric speaker 2a, and the support is provided on the
piezoelectric speaker 2b thereon. By not attaching it, it is possible to convert acoustic energy to
electrical energy, and it is possible to convert different energy to electrical energy.
[0038]
With regard to the attachment structure of the piezoelectric speaker 2, all of the abovementioned examples directly attached the suppression target 1, but as another preferable
attachment structure, when high frequency vibration and low frequency vibration are applied to
the suppression target 1, As shown in FIG. 4 (b), the piezoelectric speaker 2 is attached to a
damping sheet (sheet-like damping material) 7, and the damping sheet 7 is fixed to the
suppression target 1 with an adhesive tape or an adhesive. That's good. Thus, by attaching to the
vibration damping sheet 7, it is possible to combine the performance of the piezoelectric speaker
2 and the performance of the vibration damping material, as schematically shown in FIG. In
particular, the damping effect of the high frequency band possessed by the damping material can
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be exhibited.
[0039]
In the above description, although a device for damping and reducing noise when the
suppression target 1 vibrates or generates sound due to extraneous noise has been considered,
the present invention relates to the sound of the piezoelectric speaker 2- Since the basic principle
is to perform damping noise control using electrical conversion or vibration-electrical conversion
(piezoelectric effect), it can not be applied to the case where the suppression target 1 itself
generates vibration or noise. . Further expanding, if applied to the case where the suppression
target 1 is a piezoelectric speaker provided for an original application of sound generation, the
function of the piezoelectric speaker for sound generation can be further improved. That is, as
illustrated in FIG. 6, the noise suppressing piezoelectric speaker 2B is provided on the back
surface of the sound generating piezoelectric speaker 2A corresponding to the suppression
object, and energy is supplied to the diaphragm 21 of the latter speaker 2B through the
electrodes. By connecting the consumption means 4, it is possible to reduce the reverse phase
sound radiated to the back side of the sound generating speaker 2A, that is, the noise, whereby
the front side of the sound generating speaker 2A has no noise or is very Less clear and clear
sound is provided. By connecting a control circuit (not shown) for adjusting a reactance (L) or a
resistance value (R) for setting a resonance frequency corresponding to the frequency to be
reduced instead of the energy consuming means 3 for generating sound It is possible to suppress
or eliminate noise outside the necessary range emitted from the back side of the speaker 2A.
[0040]
BRIEF DESCRIPTION OF THE DRAWINGS The conceptual diagram which shows the basic
composition of 1st Embodiment. The circuit diagram which shows an example of a piezoelectric
speaker and an energy consumption means. It is a figure which shows an example of the
attachment structure with respect to the suppression target object of a piezoelectric speaker, (a)
is a front view, (b) is sectional drawing. It is a figure which shows the attachment structure in the
case of overlapping and attaching a piezoelectric speaker, (a) is a conceptual diagram in the case
of only overlapping and attaching a piezoelectric speaker, (b) is a case where the first
piezoelectric speaker is provided with a support Conceptual illustration. The graph which shows
a vibration reduction effect with a comparative example. The conceptual diagram which shows
the other example of installation of a piezoelectric speaker. The measurement graph which shows
the difference of the output in the case (a) and the case (b) of not providing a support | pillar
between a diaphragm and a suppression object board. The output comparison figure of a
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piezoelectric element and a piezoelectric type speaker.
Explanation of sign
[0041]
Reference Signs List 1 suppression target 2 piezoelectric speaker 3 energy consumption means
S1, S2 shunt circuit 31 coil 32 resistor 5 post
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