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JP2011171790

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DESCRIPTION JP2011171790
In any of the conventional configurations, a temperature change of air around a heat source is
generated to reproduce a sound wave, but none of them has been able to reproduce a sufficient
sound pressure. The present invention, on the other hand, comprises an activated carbon 1 and a
signal source 2 and by causing a temperature change in the activated carbon 1 by the signal
source 2, only by causing a thermal change in air around the activated carbon. Instead, the
amount of adsorption of the gas adsorbed by the activated carbon changes, and by adsorbing and
desorbing the gas, a highly efficient speaker can be realized. Moreover, since it is the simple
structure which sends electricity to activated carbon, it is possible to reproduce ¦ regenerate a
sound by the simple structure which does not have a vibration system or a magnet. [Selected
figure] Figure 1
Speaker device
[0001]
The present invention relates to a speaker device using activated carbon.
[0002]
A speaker converts electric energy into mechanical vibration, and a system in which sound is
reproduced by vibrating a medium such as air is the mainstream.
In addition to an electrodynamic type in which the diaphragm is driven by Lorentz force, the
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electrostatic drive type using electrostatic force, a piezoelectric type using a piezoelectric
element, an electromagnetic type using a magnetic attraction force, etc. Although there are
various drive systems, they all share the point of converting electrical energy into mechanical
vibration of the diaphragm and generating sound.
[0003]
The diaphragm of the speaker is vibratably supported by a support means generally called an
edge or a damper. Therefore, due to the weight of the vibration system and the stiffness of the
support means, resonance occurs at a specific frequency. At high frequencies, a plurality of
resonance modes are generated according to the rigidity of the diaphragm. Due to the resonance
due to the above two factors, it is extremely difficult to flatten the sound pressure-frequency
characteristics.
[0004]
Further, when the speaker using the diaphragm vibrates, a sound of the opposite phase of the
sound generated from the front surface of the diaphragm is generated from the back surface of
the diaphragm. This back sound wraps around the front of the speaker and cancels the sound
generated from the front of the speaker. The lower the frequency, the greater the effect of this
wraparound. For this reason, in many cases, the speaker cabinet is used to prevent the sound on
the back surface of the diaphragm from turning around on the front surface. However, the
problem with using a cabinet is the effect of air stiffness (stiffness) inside the cabinet. The
mechanical impedance Zair of this stiffness is expressed by Equation 1 and acts as a "spring"
which acts in the direction of inhibiting the movement of the diaphragm. Here, ρ is the density
of the medium, ρ is the speed of sound in the medium, a is the effective radius of the diaphragm,
V is the cabinet volume, and ω is the angular frequency.
[0005]
[0006]
Therefore, the smaller the speaker cabinet volume and the lower the frequency, the greater the
impedance of air that impedes the movement of the diaphragm, making it difficult to reproduce
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bass.
Therefore, there has been a problem that it is difficult to reproduce the bass with a small speaker.
[0007]
Therefore, as a device that generates sound without using mechanical vibration, a device that
causes temperature change to the air layer on the surface of the heat generator by the heat
generator and generates sound using thermal expansion and contraction (for example, Patent
Documents 1 to 3) There is. FIG. 9 shows the substrate 101, the heat insulating layer 102, and
the heating element thin film 103 in Patent Document 1 mentioned above.
[0008]
When a signal current is allowed to flow through the heating element thin film 103, Joule heat is
generated in accordance with the electric resistance value, and sound waves are generated due to
thermal expansion and contraction of air on the front surface of the thin film. The heating
element 103 is formed into a thin film to increase the surface area, and the heat insulating layer
102 is provided between the heating element 103 and the substrate 101 to thermally insulate
the heating element 103 from the substrate 101. Sound generation efficiency is improved by
increasing the temperature change on the surface. Moreover, in patent document 2, thermal
reliability is improved by improving heat dissipation. Furthermore, in Patent Document 3, a
Helmholtz resonator is provided in front of the heat generating element to improve the bass
reproduction capability.
[0009]
Patent Document 4 discloses a thermoacoustic device using carbon nanotubes. In patent
document 4, the electrode is provided in the both ends of a carbon nanotube, and it connects to
the sound wave generator. The carbon nanotube structure is heated to generate sound waves by
heating the surrounding medium. Due to the size of the specific surface area of the carbon
nanotube and the small heat capacity, it is characterized in that sound waves are generated more
efficiently than in the past.
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[0010]
JP-A-11-300274 JP-A-2006-094398 JP-A-2008-167252 JP-A-2009-268108
[0011]
However, although all of the above-mentioned conventional configurations cause temperature
change of the air around the heat source to reproduce the sound wave, none of them has resulted
in reproducing sufficient sound pressure.
The present invention solves the above-mentioned conventional problems, and uses activated
carbon that adsorbs gas, and in addition to causing temperature change in the surrounding air as
in the conventional case, by the temperature change generated in activated carbon, the
adsorption amount of activated carbon By changing the temperature according to the
temperature, a sound wave can be generated by adsorption and desorption of gas molecules to
provide a speaker device with higher efficiency.
[0012]
In order to solve the above-mentioned conventional problems, the speaker device of the present
invention comprises activated carbon which adsorbs molecules of gas contained in air at normal
temperature and normal pressure, a signal source for supplying electric energy for changing the
temperature of the activated carbon, Electrical energy from a signal source generates heat, and
the heating element generates a temperature change in the activated carbon, and in response to
the temperature change of the activated carbon, the volume change due to the temperature
change of the surrounding gas simultaneously occurs, and the activated carbon The speaker
device is characterized in that the adsorption equilibrium of the adsorbed gas is moved, and the
adsorption and desorption of the gas generated by the change of the adsorption amount due to
the adsorption and desorption of the gas generates a sound. According to this configuration, in
addition to the sound reproduction due to the temperature change of the surrounding gas in the
related art, the sound reproduction due to adsorption and desorption of the gas occurs, so that
more efficient sound reproduction can be realized.
[0013]
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The activated carbon has a specific surface area of 1000 m <2> / g or more.
[0014]
The activated carbon has a nitrogen adsorption performance of 5 cc or more per 1 g of activated
carbon at 1 atmosphere (760 mmHg) and 25 ° C.
[0015]
The activated carbon itself may be used as a heating element by supplying electrical energy from
the signal source to the activated carbon through an electrode.
A conductive paste may be disposed between the electrode and the activated carbon to reduce
the electrical resistance between the electrode and the activated carbon.
[0016]
The heating element may be provided separately from the activated carbon.
At this time, a resistor using nichrome wire, carbon or the like is used as an example of the
heating element. For the thermal connection between the heating element and the activated
carbon, a material having a high thermal conductivity, such as a resin containing silicone or a
metal filler, may be used.
[0017]
The activated carbon may be fibrous activated carbon, and the form thereof is, for example, cloth
(cloth), felt, fiber (yarn), paper (paper), etc.
[0018]
The activated carbon may be granular activated carbon or may be molded with a binder or the
like.
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As for the particle size of granular activated carbon, it is desirable to use the material with the
highest efficiency.
[0019]
By arranging a plurality of the electrodes, narrowing the interval, and arranging the activated
carbon between them, it becomes possible to apply a high electric field even at a low voltage.
[0020]
The efficiency of the speaker device is reduced when the activated carbon adsorbs water vapor.
For this reason, in order not to adsorb water vapor, it drives at the temperature which does not
adsorb water vapor. It is desirable that the moisture absorption of activated carbon does not
exceed 20% of its own weight.
[0021]
According to the speaker device of the present invention, more efficient sound reproduction can
be realized by adsorption / desorption of gas due to temperature change of the adsorption
amount of activated carbon.
[0022]
The block diagram of the speaker apparatus in Embodiment 1 of this invention The figure which
shows the adsorption ¦ suction characteristic in normal temperature of the activated carbon in
Embodiment 1 of this invention The structural cross section of the electrode in Embodiment 1 of
this invention Embodiment of this invention 2 is a block diagram of the speaker apparatus in FIG.
2 is a block diagram of the speaker apparatus in the third embodiment of the present invention.
FIG. 8 is a block diagram of the speaker apparatus in the fourth embodiment of the present
invention. Of the speaker apparatus according to the sixth aspect is a structural diagram of a
television equipped with the speaker apparatus according to the related art.
[0023]
Hereinafter, embodiments of the present invention will be described with reference to the
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drawings.
[0024]
First Embodiment FIG. 1A is a configuration diagram of a speaker device according to a first
embodiment of the present invention.
In FIG. 1 (a), 1 is fibrous activated carbon, 2 is a signal source, and 3 is an electrode.
The activated carbon 1 has a characteristic of adsorbing a gas at normal temperature.
An example of the adsorption characteristics of nitrogen at 25 ° C. is shown in FIG. The abscissa
represents the pressure, and the ordinate represents the amount of adsorption. Samples 1 and 2
are granular activated carbon and sample 3 is fibrous activated carbon. The pore diameter and
specific surface area of each are shown in Table 1.
[0025]
[0026]
It can be seen that nitrogen is adsorbed at 25 ° C. and 1 atm (760 mmHg).
In addition, although the measurement example at 25 ° C. is shown here, it is not particularly
limited to 25 ° C. as long as it is a material having a gas adsorption ability at a temperature at
which a speaker is generally used. Activated carbon is a carbonaceous granular or powdery
substance that exhibits particularly high adsorption ability to gas and dye molecules, and is made
of coconut charcoal, brown charcoal, peat, etc. as a raw material. As a rule, it generally refers to
one having a specific surface area of 1000 m <2> / g or more.
[0027]
Oxygen and nitrogen, which are the main components of air, are critical gases at room
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temperature, and their adsorption characteristics are expressed by Equation 2 from the variation
of the DR (Dubinin-Radshkevich) equation.
[0028]
[0029]
Here, WL is an absolute saturated adsorption amount, W is an adsorption amount, R is a gas
constant, T is an absolute temperature, β is an affinity factor, E0 is a characteristic adsorption
energy, Psq is a pseudosaturation vapor pressure, and P is a barometric pressure.
From this equation, the amount of adsorption W is shown as a function of the absolute
temperature T, and the amount of adsorption changes with temperature change.
The relationship between the absolute temperature T and the adsorption amount W is such that
the adsorption amount W decreases as the absolute temperature T rises, and the adsorption
amount increases as the absolute temperature T falls. Therefore, since the gas is released when
the temperature rises, it works in the direction of increasing the reproduced sound in
combination with the volumetric expansion of the gas due to the temperature rise. On the other
hand, when the temperature is lowered, the surrounding gas is adsorbed, and this acts in the
direction of increasing the reproduction sound in combination with the volume contraction of the
gas due to the temperature decrease.
[0030]
From the above, it becomes possible to drive the speaker using the change of the adsorption
amount according to the temperature change of the activated carbon of the present application
with high efficiency.
[0031]
FIG. 1 (b) shows an example of sound pressure measurement in which a voltage is actually
applied to fibrous activated carbon to generate sound.
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The measurement conditions are: applied voltage 5 V, measurement distance is 25 mm, shape of
activated carbon between electrodes is 110 mm × 20 mm, and electrodes are attached on both
sides of 110 mm so as to sandwich fibrous activated carbon between two electrodes. There is.
[0032]
FIG. 3 shows a cross-sectional view of an electrode attached to fibrous activated carbon. 1 is a
fibrous activated carbon, 3 is an electrode, and 4 is a conductive paste or a conductive adhesive.
By using the conductive paste 3, the electrical resistance between the fibrous activated carbon 1
and the electrode 3 can be suppressed to a low level, the heat generation in the portion other
than the activated carbon can be suppressed, and the loss of electrical energy can be prevented.
[0033]
As the shape of the fibrous activated carbon, it is desirable to use a thin fiber in order to enhance
the thermal conductivity to the surrounding air and to better follow the signal source. Fibrous
activated carbon has high adsorption speed and low acoustic resistance because only micropores
are regularly formed on the surface, so it is easy to reproduce high-frequency sound and the
acoustic loss due to activated carbon material is also minimized. Can be limited. In addition,
fibrous activated carbon includes all those which are fibrous activated carbon which comprises
activated carbon, such as felt-like, cloth-like, and cotton-like. Examples of raw materials of fibrous
activated carbon include phenol resin fiber, acrylonitrile, cellulose and the like.
[0034]
On the other hand, the adsorption capacity of activated carbon to oxygen and nitrogen may be
lowered by adsorption of water vapor to pores under high humidity (for example, a humidity of
65% or more). Therefore, the temperature of the activated carbon may be raised to 100 ° C. or
higher, preferably 110 ° C. or higher, by the electrical energy from the signal source. The water
vapor in the pores can be desorbed and removed, and the decrease in the efficiency of adsorption
and desorption can be prevented. The activation of the activated carbon to a temperature of 100
° C. or higher or 110 ° C. or higher may be temporary during speaker regeneration or may be
always performed. Furthermore, by providing a hygrometer, temperature control may be
performed according to the indication value of the hygrometer.
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[0035]
Note that the signal of the sound reproduced by the activated carbon 1 is the square of the signal
of the signal source 2 because it is due to Joule heat caused by the current flowing through the
electric resistance of the activated carbon 1. Therefore, in the signal source, it is preferable to
add a DC bias to the sound to be reproduced and to use a square root as the signal source. As a
method, software for creating the above signal source may be used in advance, or the above
signal conversion function may be incorporated in the signal source. Furthermore, in order to
prevent the influence of the temperature of the regeneration environment on the cooling rate of
the activated carbon, the signal source 2 may be a signal source in which a DC bias is further
added to the signal current so as to obtain a high temperature difference with the regeneration
environment temperature.
[0036]
As described above, according to the present invention, more efficient sound reproduction can be
realized by adsorption and desorption of gas due to temperature change of the amount of
adsorption of activated carbon. Moreover, since it is the simple structure which sends electricity
to activated carbon, it is possible to reproduce ¦ regenerate a sound by the simple structure
which does not have a vibration system or a magnet. Since there is no vibration part, it is possible
to realize high reliability without any change in material characteristics and fatigue failure in the
vibration part. In addition, since no diaphragm is used, a back noise does not occur, and a cabinet
or baffle plate is unnecessary. For this reason, miniaturization is possible. In addition, not using a
magnet is suitable for use in places such as MRI where non-magnetism is required.
[0037]
Furthermore, an efficient speaker device can be realized by using a material having a high
specific surface area of 1000 m <2> or more per 1 g, which has high air adsorption capacity at
normal temperature.
[0038]
Furthermore, by using activated carbon having a central pore diameter of 3 nm or less, nitrogen
and oxygen, which are main components of air, can be effectively adsorbed, and an efficient
speaker device can be realized.
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[0039]
Moreover, the loss of the electrical energy by contact resistance can be prevented by using a
conductive paste between the electrode provided between the signal source and the activated
carbon and the activated carbon.
[0040]
Second Embodiment FIG. 4 is a configuration diagram of a speaker device according to a first
embodiment of the present invention.
1 is activated carbon, 2 is a signal source, and 5 is a heating element.
The signal source 2 drives the heating element 5 to cause the activated carbon 1 to generate a
thermal change according to the signal.
The method of reproducing sound with respect to the temperature change of the activated
carbon 1 is the same as that of the first embodiment, and thus will not be described.
[0041]
Examples of the heating element 5 include high-resistance materials such as nichrome wire,
Peltier elements, and the like. In the case of a Peltier element, the heat generation side and the
cooling side are alternately arranged on the same surface, and current can be alternately
supplied to efficiently cool. For this reason, it is also possible to lower the operating temperature.
[0042]
Here, a material having high thermal conductivity, such as silicone grease, silicone sheet, heat
dissipating gel, metal as a filler, resin having high thermal conductivity, adhesive, etc., is used for
the contact portion between heating element 5 and activated carbon 1 It is good to do.
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[0043]
Although granular activated carbon used as activated carbon 1 has a broad pore diameter
distribution and some acoustic loss, it is cheaper than fibrous activated carbon.
There are many varieties, and the raw materials are coconut shell, coal, charcoal, resin including
phenol resin, and the like. Furthermore, it is possible to reduce the acoustic loss due to particles
by using a molding technique of granular activated carbon. In addition, scattering of particles can
be prevented.
[0044]
Activated carbon adsorbs water vapor when the relative humidity is high. When water vapor is
adsorbed, the amount of adsorption of nitrogen and oxygen decreases, and the sound pressure of
the speaker device decreases. Therefore, by raising the driving temperature of the speaker
device, the amount of saturated water vapor around the activated carbon increases, and the
relative humidity decreases. Moisture absorption of water vapor can be reduced. Specifically, it is
desirable that the water adsorption amount of the activated carbon does not exceed 20% of the
weight of the activated carbon.
[0045]
Although granular activated carbon is drawn as the activated carbon 1 in FIG. 4, other forms of
activated carbon such as fibrous activated carbon and felt-like activated carbon may be used.
[0046]
As described above, according to the present invention, it is possible to design the activated
carbon and the activated carbon not to be caught by the electrical impedance by generating the
temperature change of the activated carbon by the heating element.
[0047]
Third Embodiment FIG. 5 is a block diagram of a speaker device according to a third embodiment
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of the present invention.
1 is activated carbon and 2 is a signal source.
The activated carbon 1 is molded into an arbitrary shape.
[0048]
The operation of the speaker is the same as that of the first embodiment and is therefore omitted.
[0049]
Although a resin material is often used as a binder for molding the activated carbon 1, it is
desirable that the pores of the activated carbon 1 be as unobstructed as possible.
Further, as a binder for molding the activated carbon 1, a paste or an adhesive having high
electric conductivity or thermal conductivity may be used. In addition, activated carbon with the
most suitable particle size may be used so that the binder can be molded without blocking the
pores.
[0050]
As activated carbon 1, granular activated carbon may be used or fibrous activated carbon may be
used.
[0051]
As described above, according to the present invention, since the shape of the activated carbon 1
can be arbitrarily determined, it is possible to form a free-form speaker which is not confined to
the shape of a conventional speaker.
For example, even if the space for arranging the speakers is very limited, the shape of the
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activated carbon 1 is formed in accordance with the shape of the arranged space to arrange the
speakers in the space which could not be arranged conventionally. It becomes possible to realize.
[0052]
Fourth Embodiment FIG. 6 is a block diagram of a speaker device according to a fourth
embodiment of the present invention. 1 is activated carbon, 2 is a signal source, 3 is a plurality of
electrodes, and 6 is an insulator. One granular activated carbon was placed on top of six
insulators. The electrodes alternately arrange the poles to apply a high voltage between the
electrodes.
[0053]
The operation of the speaker is the same as that of the first embodiment and is therefore omitted.
[0054]
With this configuration, when the speaker device of the present invention has a large area, high
sound pressure can be obtained at a lower voltage than when the electrodes are disposed at both
ends of activated carbon as described in the first embodiment.
[0055]
Granular activated carbon having a small particle size may be used to reduce the contact
resistance between the granular activated carbons.
Also, in order to reduce the contact resistance between the granular activated carbons,
conductive paste or particles of a conductor may be used.
[0056]
Fifth Embodiment FIG. 7 is a configuration diagram of a speaker apparatus according to a fourth
embodiment of the present invention.
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1 is activated carbon, 2 is a signal source, 3 is a plurality of electrodes. The activated carbon 1 is
in the form of fibers, and a voltage is applied between the activated carbon 1 and the electrode 3.
The operation of the speaker is the same as that of the first embodiment and is therefore omitted.
[0057]
The operation of the speaker is the same as that of the first embodiment and is therefore omitted.
[0058]
With this configuration, when the speaker device of the present invention has a large area, high
sound pressure can be obtained at a lower voltage than when the electrodes are disposed at both
ends of activated carbon as described in the first embodiment.
[0059]
Sixth Embodiment FIG. 8 shows an example when the speaker device of the present invention is
used for a television.
When using for a television, since the water adsorption amount of the activated carbon is likely
to increase while the speaker device is not used, it is necessary to have a configuration that does
not increase the water adsorption amount of the activated carbon.
For example, it is conceivable to provide a configuration in which activated carbon is disposed in
a closed space, or a configuration in which the temperature of activated carbon is increased
instantaneously to reduce the amount of adsorbed water as described in the first embodiment.
[0060]
It is also possible to apply the speaker device of the present invention to products other than
televisions, for example, speakers for rack theaters, mobile phones, automobiles and the like.
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[0061]
With this configuration, it is possible to realize highly efficient sound reproduction even in an
environment where there is a high possibility that the moisture adsorption amount of the
activated carbon increases.
[0062]
The speaker device according to the present invention has activated carbon and a signal source,
and is useful as a speaker or the like that can reproduce sound without having a vibrating
portion.
The application can be applied to home AV, mobile, car, etc.
[0063]
1 activated carbon 2 signal source 3 electrode 4 conductive paste or conductive adhesive 5
heating element 6 insulator
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