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JP2010004537

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DESCRIPTION JP2010004537
The present invention relates to a thermoacoustic apparatus, and more particularly to a
thermoacoustic apparatus using carbon nanotubes. An apparatus of the present invention
includes a signal device, an acoustic wave generator including a carbon nanotube structure, and a
support. At least a portion of the sound wave generator is supported by the support. The carbon
nanotube structure is connected to the signal device. The heat capacity per unit area of the
carbon nanotube structure is 0 (not including 0) to 2 × 10 J / cm · K. [Selected figure] Figure 1
Thermoacoustic device
[0001]
The present invention relates to a thermoacoustic apparatus, and more particularly to a
thermoacoustic apparatus using carbon nanotubes.
[0002]
In general, an acoustic device comprises a signal device and a sound generator.
The signaling device transmits a signal to the sound generator (e.g. a speaker). The speaker can
convert an electrical signal to sound as an electroacoustic transducer.
[0003]
05-05-2019
1
According to the principle of operation, speakers are classified into various types such as
dynamic speakers, magnetic speakers, electrostatic speakers, and piezoelectric speakers. The
various types of speakers all produce mechanical sound by means of mechanical vibration, that
is, they realize electro-mechanical force-sound conversion. Here, dynamic speakers are widely
used.
[0004]
Referring to FIG. 21, the conventional dynamic speaker 100 includes a voice coil 102, a magnet
104 and a cone 106. The voice coil 102 is disposed between the magnets 104 as a conductive
component. When a current is supplied to the voice coil 102, the cone 106 is vibrated by the
interaction of the electromagnetic field of the voice coil 102 and the magnetic field of the magnet
104 to continuously generate pressure fluctuation of air, thereby generating a sound wave. it
can. However, the dynamic speaker 100 relies on the action of the magnetic field.
[0005]
Thermoacoustic phenomenon is a phenomenon in which sound and heat are related, and there
are two aspects, energy conversion and energy transport. Transferring the signal to the
thermoacoustic device generates heat in the thermoacoustic device and propagates to the
surrounding media. Sound waves can be generated due to thermal expansion and pressure waves
generated by the transferred heat.
[0006]
H.D.Arnold、I.B.Crandall, The thermophone as a
precision source of sound , Phys. 1917, 10, 22-38, Kaili Jiang,
Qunqing Li, Shoushan Fan, "Spinning continuous carbon nanotube yarns", Nature, 2002, 419, p.
801
[0007]
05-05-2019
2
Non-Patent Document 1 discloses a thermophone manufactured by a thermoacoustic
phenomenon. Here, a platinum piece having a thickness of 7 × 10 <-5> cm is used as a
thermoacoustic component. However, for a platinum piece having a thickness of 7 × 10 <-5> cm,
the heat capacity per unit area is 2 × 10 <-4> J / cm <2> · K. Since the heat capacity per unit
area of platinum pieces is very high, there is a problem that the thermophone using platinum
pieces has very weak sound when used outdoors.
[0008]
The present invention provides a lightweight thermoacoustic device in order to solve the abovementioned problems. The thermoacoustic apparatus of the present invention can generate sound
independently of a magnetic field and not by mechanical vibration.
[0009]
The thermoacoustic device of the present invention includes a signal device, a sound wave
generator including a carbon nanotube structure, and a support. At least a portion of the sound
wave generator is supported by the support. The carbon nanotube structure is connected to the
signal device.
[0010]
The heat capacity per unit area of the carbon nanotube structure is 0 (not including 0) to 2 × 10
<-4> J / cm <2> · K.
[0011]
One part of the sound wave generator is placed on the support and the other part is suspended.
[0012]
In the carbon nanotube structure, carbon nanotubes are connected by intermolecular force and
uniformly distributed.
[0013]
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The carbon nanotube structure includes at least one carbon nanotube film.
[0014]
The carbon nanotube structure includes a plurality of carbon nanotube wires.
[0015]
The device comprises at least two electrodes, the at least two electrodes being separated by a
predetermined distance and respectively electrically connected to the sound generator.
[0016]
The thermoacoustic system of the present invention includes a signal device, a carbon nanotube
structure in contact with a medium, and a support.
At least a portion of the carbon nanotube structure is supported by the support.
The carbon nanotube structure is connected to the signal device.
[0017]
The carbon nanotube structure generates a sound by heating the medium.
[0018]
Compared to the prior art, the thermoacoustic apparatus of the present invention has the
following advantages.
First, since the thermoacoustic apparatus of the present invention includes a carbon nanotube
structure, the structure is simple and the weight and size can be reduced as compared with the
conventional speaker.
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Second, since the thermoacoustic apparatus of the present invention generates an acoustic wave
by heating the carbon nanotube structure, it is not necessary to use a magnet.
Third, since the carbon nanotube structure has a small heat capacity per unit area, a large
specific surface area, and a high rate of heat exchange, sound can be generated favorably.
Fourth, since the carbon nanotube structure is thin, a transparent acoustic device can be
manufactured.
[0019]
It is a schematic diagram of the thermoacoustic apparatus in Example 1 of this invention.
It is a SEM photograph of the carbon nanotube film in Example 1 of this invention. It is a
schematic diagram of the carbon nanotube segment in Example 1 of this invention. It is a SEM
photograph of the carbon nanotube film in Example 1 of this invention. It is a SEM photograph of
the segment of the carbon nanotube film in Example 1 of the present invention. It is a SEM
photograph of the carbon nanotube wire in Example 1 of this invention. It is a SEM photograph
of the twisted carbon nanotube wire in Example 1 of the present invention. It is a schematic
diagram of textiles which consist of a plurality of carbon nanotube films and / or carbon
nanotube wires in Example 1 of the present invention. It is a frequency response curve of the
thermoacoustic apparatus in Example 1 of this invention. It is a schematic diagram of the
thermoacoustic apparatus in Example 1 of this invention. It is a schematic diagram of the
thermoacoustic apparatus in Example 2 of this invention. It is a schematic diagram of the
thermoacoustic apparatus in Example 3 of this invention. It is a schematic diagram of the
thermoacoustic apparatus in Example 4 of this invention. It is a schematic diagram of the
thermoacoustic apparatus in Example 5 of this invention. It is a schematic diagram of the
thermoacoustic apparatus in Example 6 of this invention. It is a circuit diagram in Example 6 of
this invention. It is a graph which shows the bias voltage which used the power amplifier in
Example 6 of this invention. It is a schematic diagram of the thermoacoustic apparatus in
Example 7 of this invention. It is a schematic diagram of the thermoacoustic apparatus in
Example 7 of this invention. It is a chart of the sound wave generation method of the present
invention. It is a schematic diagram of the conventional speaker.
[0020]
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5
Hereinafter, embodiments of the present invention will be described with reference to the
drawings.
[0021]
Example 1 Referring to FIG. 1, the thermoacoustic device 10 of the present invention includes a
signal device 12, a sound wave generator 14, a first electrode 142, and a second electrode 144.
The first electrode 142 and the second electrode 144 are each electrically connected to the
sound wave generator 14 so as to be separated by a predetermined distance. The first electrode
142 and the second electrode 144 are electrically connected to the signal device 12 respectively.
The first electrode 142 and the second electrode 144 transfer the signal from the signal device
12 to the sound generator 14.
[0022]
The sound wave generator 14 includes a carbon nanotube structure. The carbon nanotube
structure has a large specific surface area (eg, 100 m <2> / g or more). The heat capacity per unit
area of the carbon nanotube structure is 0 (not including 0) to 2 × 10 <-4> J / cm <2> · K, but
preferably 0 (not including 0). It is -1.7 * 10 <-6> J / cm <2> * K, and it is 1.7 * 10 <-6> J / cm
<2> * K in a present Example. Furthermore, a metal layer can be formed on the surface of the
carbon nanotube structure. A plurality of carbon nanotubes are uniformly dispersed in the
carbon nanotube structure. The plurality of carbon nanotubes are connected by intermolecular
force. The carbon nanotube structure needs to contain metallic carbon nanotubes. In the carbon
nanotube structure, the plurality of carbon nanotubes are arranged in an oriented manner or not
oriented. The carbon nanotube structures are classified into two types of non-oriented carbon
nanotube structures and oriented carbon nanotube structures according to the arrangement of
the plurality of carbon nanotubes. In the non-oriented carbon nanotube structure in this
embodiment, the carbon nanotubes are arranged or entangled along different directions. In the
oriented carbon nanotube structure, the plurality of carbon nanotubes are arranged along the
same direction. Alternatively, in the oriented carbon nanotube structure, when the oriented
carbon nanotube structure is divided into two or more regions, a plurality of carbon nanotubes in
each region are arranged along the same direction. In this case, the alignment directions of
carbon nanotubes in different regions are different. The carbon nanotube is a single-walled
carbon nanotube, a double-walled carbon nanotube, or a multi-walled carbon nanotube. When
the carbon nanotube is a single-walled carbon nanotube, the diameter is set to 0.5 nm to 50 nm,
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and when the carbon nanotube is a double-walled carbon nanotube, the diameter is set to 1 nm
to 50 nm, and the carbon nanotube is a multilayer carbon In the case of nanotubes, the diameter
is set to 1.5 nm to 50 nm.
[0023]
The carbon nanotube structure is flat and has a thickness of 0.5 nm to 1 mm. The heat capacity
per unit area of the carbon nanotube structure increases as the specific surface area of the
carbon nanotube structure decreases. As the heat capacity per unit area of the carbon nanotube
structure is higher, the sound pressure of the thermoacoustic device is lower.
[0024]
The carbon nanotube structure includes at least one carbon nanotube film 143a shown in FIG.
The carbon nanotube film 143a is obtained by drawing from a super-aligned carbon nanotube
array (refer to Non-Patent Document 3). In the single carbon nanotube film, a plurality of carbon
nanotubes are connected end to end along the same direction. That is, the single carbon
nanotube film 143a includes a plurality of carbon nanotubes whose ends in the longitudinal
direction are connected by an intermolecular force. Referring to FIGS. 2 and 3, the single carbon
nanotube film 143a includes a plurality of carbon nanotube segments 143b. The plurality of
carbon nanotube segments 143b are connected end to end by intermolecular force along the
length direction. Each carbon nanotube segment 143b includes a plurality of carbon nanotubes
145 connected by intermolecular force in parallel to each other. The lengths of the plurality of
carbon nanotubes 145 are the same in the single carbon nanotube segment 143b. Toughness
and mechanical strength of the carbon nanotube film 143a can be enhanced by immersing the
carbon nanotube film 143a in an organic solvent. Since the heat capacity per unit area of the
carbon nanotube film immersed in the organic solvent is low, the thermoacoustic effect can be
enhanced. The carbon nanotube film 143a has a width of 100 μm to 10 cm and a thickness of
0.5 nm to 100 μm.
[0025]
The carbon nanotube structure may include a plurality of stacked carbon nanotube films. In this
case, the adjacent carbon nanotube films are bonded by an intermolecular force. The carbon
nanotubes in the adjacent carbon nanotube film cross each other at an angle of 0 ° to 90 °.
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When the carbon nanotubes in the adjacent carbon nanotube film intersect at an angle of 0 ° or
more, a plurality of micro holes are formed in the carbon nanotube structure. Alternatively, the
plurality of carbon nanotube films may be juxtaposed without gaps.
[0026]
Alternatively, the single carbon nanotube film may include a plurality of carbon nanotubes
having substantially the same length. In the single carbon nanotube film, the plurality of carbon
nanotubes are uniformly juxtaposed along the same direction. The thickness of the single carbon
nanotube film is 10 nm to 100 μm. The plurality of carbon nanotubes are arranged in parallel
on the surface of the plurality of carbon nanotube films, and are arranged in parallel to one
another. Adjacent ones of the carbon nanotubes are spaced apart at a predetermined distance.
The distance is 0 to 5 μm. When the distance is 0 μm, adjacent carbon nanotubes are
connected by an intermolecular force. The length of each of the carbon nanotubes in the carbon
nanotube film is the same as the length of the carbon nanotube film. The length of the single
carbon nanotube is 1 cm or more, and preferably 1 cm to 30 cm. Furthermore, each of the
carbon nanotubes 145 is free of knots. In the present embodiment, the carbon nanotube film has
a thickness of 10 μm. The length of the single carbon nanotube 145 is 10 cm.
[0027]
The carbon nanotube structure includes at least one carbon nanotube film. Referring to FIG. 4, in
the single carbon nanotube film, a plurality of carbon nanotubes are entangled and arranged
isotropically. In the carbon nanotube structure, the plurality of carbon nanotubes are uniformly
distributed. The plurality of carbon nanotubes are arranged without orientation. The length of
the single carbon nanotube is 100 nm or more, preferably 100 nm to 10 cm. The carbon
nanotube structure is formed in the shape of a free-standing thin film. Here, the self-supporting
structure is a mode in which the carbon nanotube structure can be independently used without
using a support material. The plurality of carbon nanotubes are formed close to each other by
intermolecular force and mutually intertwined to form a carbon nanotube network. The plurality
of carbon nanotubes are arranged without being oriented to form many minute holes. Here, the
diameter of the single minute hole is 10 μm or less. Since the carbon nanotubes in the carbon
nanotube structure are arranged to be entangled with each other, the carbon nanotube structure
is excellent in flexibility and can be formed to be curved in an arbitrary shape. Depending on the
application, the length and width of the carbon nanotube structure can be adjusted. The
thickness of the carbon nanotube structure is 0.5 nm to 1 mm.
05-05-2019
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[0028]
The carbon nanotube structure includes one carbon nanotube film segment. Referring to FIG. 5,
carbon nanotubes in the segments of the carbon nanotube film are parallel to each other and
arranged along a predetermined direction. In the carbon nanotube film segment, the length of at
least one carbon nanotube is the same as the entire length of the carbon nanotube film segment.
Accordingly, the dimensions of one of the segments of the carbon nanotube film are limited by
the length of the carbon nanotube. The carbon nanotube structure may include a plurality of
stacked carbon nanotube film segments. In this case, adjacent segments of the carbon nanotube
film are bonded by intermolecular force. The thickness of the segment of the carbon nanotube
film is 0.5 nm to 100 μm.
[0029]
The carbon nanotube structure includes at least one carbon nanotube wire. The heat capacity of
one carbon nanotube wire is 0 (not 0 included) to 2 × 10 <-4> J / cm <2> · K, 5 × 10 <-5> J /
cm <2> -It is preferable that it is K. The diameter of one carbon nanotube wire is 4.5 nm to 1 cm.
Referring to FIG. 6, the carbon nanotube wire comprises a plurality of carbon nanotubes
connected by intermolecular force. In this case, a single carbon nanotube wire includes a
plurality of carbon nanotube segments (not shown) connected end to end. The carbon nanotube
segments have the same length and width. Furthermore, a plurality of carbon nanotubes of the
same length are arranged in parallel to each of the carbon nanotube segments. The plurality of
carbon nanotubes are arranged parallel to the central axis of the carbon nanotube wire. In this
case, the diameter of one carbon nanotube wire is 1 μm to 1 cm. Referring to FIG. 7, the carbon
nanotube wire may be twisted to form a twisted carbon nanotube wire. Here, the plurality of
carbon nanotubes are arranged in a spiral shape with the central axis of the carbon nanotube
wire as an axis. In this case, the diameter of one carbon nanotube wire is 1 μm to 1 cm. The
carbon nanotube structure may be formed of any one of the non-twisted carbon nanotube wire,
the twisted carbon nanotube wire, or a combination thereof.
[0030]
In the case where the carbon nanotube structure includes a plurality of carbon nanotube wires,
the plurality of carbon nanotube wires may be arranged in parallel or in parallel, or may be
woven or twisted. A fabric comprising a plurality of carbon nanotube wires 146 is shown in FIG.
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A first electrode 142 and a second electrode 144 are respectively installed at opposite ends of
the fabric. The first electrode 142 and the second electrode 144 are electrically connected to the
carbon nanotube wire 146.
[0031]
Since the carbon nanotube structure is flexible, the carbon nanotube structure can be formed
into various shapes, and furthermore, the carbon nanotube structure can be placed on the
surface of a hard insulator or a flexible insulator (for example, a flag or cloth) can do. If the flag
on which the carbon nanotube structure is installed is windy, it can be used as the sound wave
generator 14. The cloth on which the carbon nanotube structure is installed can play music as a
player such as MP3. Furthermore, by using the cloth on which the carbon nanotube structure is
installed, it is possible to help disabled persons (e.g. deaf persons).
[0032]
Even when a part of the carbon nanotube structure used for the sound wave generator 14 is
broken, the carbon nanotube structure can generate sound waves. On the other hand, if the
diaphragm or cone of the conventional speaker is damaged, the sound wave can not be
generated.
[0033]
As shown in FIG. 1, the sound wave generator 14 of the present embodiment includes a carbon
nanotube structure. The carbon nanotube structure includes a carbon nanotube film. In the
carbon nanotube film, carbon nanotubes are arranged along the same direction. The sound wave
generator 14 has a length of 3 cm, a width of 3 cm, and a thickness of 50 nm. If the sound wave
generator 14 is provided thin (10 μm or less in thickness), the sound wave generator 14 has
excellent transparency. Therefore, by using the transparent sound wave generator 14, a
transparent thermoacoustic device can be manufactured. The transparent thermoacoustic device
can be installed, for example, on the surface of a mobile phone or LCD. Alternatively, the
transparent thermoacoustic device can be affixed to the surface of the picture. The use of the
transparent sound wave generator 14 has the merit of making the thermoacoustic device
compact and lightweight.
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[0034]
The first electrode 142 and the second electrode 144 are made of any conductive material of
metal, conductive adhesive, carbon nanotube, and ITO. In the present embodiment, the first
electrode 142 and the second electrode 144 are rod-like metal electrodes. The sound wave
generator 14 is electrically connected to the first electrode 142 and the second electrode 144,
respectively. Since the carbon nanotube structure used for the sound wave generator 14 has
adhesiveness, the sound wave generator 14 can be directly bonded to the first electrode 142 and
the second electrode 144. Furthermore, the first electrode 142 and the second electrode 144 are
connected to both ends of the signal device 12 by conductive wires 149, respectively.
[0035]
Conductivity between the first electrode 142 or the second electrode 144 and the sound wave
generator 14 in order to make a good electrical connection between the first electrode 142 or
the second electrode 144 and the sound wave generator 14 An adhesive layer (not shown) can
also be provided. The conductive adhesive layer may be disposed on the surface of the sound
wave generator 14. The conductive adhesive layer is made of silver paste.
[0036]
The signal device 12 is any one of an electrical signal device, a direct current pulsation signal
device, an alternating current device, and an electromagnetic wave signal device (for example, an
optical signal device, a laser). The signal transferred from the signal device 12 to the sound wave
generator 14 is, for example, an electromagnetic wave (for example, an optical signal), an electric
signal (for example, alternating current, direct current pulsation signal, audio electric signal) or a
mixed signal thereof. is there. The signal is received by the carbon nanotube structure and
emitted as heat. The radiation of heat changes the pressure intensity of the surrounding medium
(environment), so that a detectable signal can be generated. When the thermoacoustic device 10
is used for an earphone, the input signal is an AC electrical signal or an audio electrical signal.
When the thermoacoustic apparatus 10 is used for a photoacoustic spectrum device, the input
signal is an optical signal. In the present embodiment, the signal device 12 is a photoacoustic
spectrum, and the input signal is an electrical signal.
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[0037]
The placement of the first electrode 142 and the second electrode 144 is optional for different
types of the signal devices 12. For example, if the signal from the signal device 12 is an
electromagnetic wave or light, the signal device 12 can transfer the signal to the sound wave
generator 14 without using the first electrode 142 and the second electrode 144. .
[0038]
In the signal device 12, since the carbon nanotube structure of the sound wave generator 14
includes a plurality of carbon nanotubes and the heat capacity per unit area is small, the
temperature wave generated by the sound wave generator 14 causes pressure on the
surrounding medium. Vibration can be generated. When a signal (e.g., an electrical signal) is
transferred to the carbon nanotube structure of the sound wave generator 14, heat is generated
in the carbon nanotube structure by the signal strength and / or the signal. The diffusion of the
temperature wave thermally expands the surrounding air to produce a sound. This principle is
largely different from the principle of generating sound by the pressure wave generated by the
mechanical vibration of the diaphragm in the conventional speaker. If the input signal is an
electrical signal, the thermoacoustic device 10 operates according to an electrical-thermal-sound
conversion scheme, but if the input signal is an optical signal, the thermoacoustic device 10 may
-Operate by the sound conversion system. The energy of the optical signal is absorbed by the
sound generator 14 and emitted as heat. As the heat radiation changes the pressure intensity of
the surrounding medium (environment), a detectable signal can be generated.
[0039]
FIG. 9 is a frequency response curve of the thermoacoustic apparatus in Example 1 of the present
invention. In this case, an AC electrical signal of 50 V is provided to the carbon nanotube
structure. In order to detect the performance of the thermoacoustic apparatus 10, a microphone
is installed at a distance of 5 cm from the sound wave generator 14 so as to face one side of the
sound wave generator 14. It can be understood from FIG. 9 that the frequency response range of
the thermoacoustic device 10 is wide and the sound pressure level is high. The sound pressure
level of the thermoacoustic device 10 is 50 dB to 105 dB. When a voltage of 4.5 W is applied to
the thermoacoustic device 10, the frequency response range of the thermoacoustic device 10 is 1
Hz to 100 KHz. The harmonic distortion of the thermoacoustic device 10 can be very small, for
example reaching as low as 3% in the range of 500 Hz to 40 KHz.
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[0040]
When the carbon nanotube structure of the thermoacoustic device 10 includes five carbon
nanotube wires, the distance between adjacent carbon nanotube wires is 1 cm, and the diameter
of one carbon nanotube wire is 50 μm. It is. When transferring a 50 V AC electrical signal to the
carbon nanotube structure, the sound pressure level generated by the thermoacoustic device 10
is 50 dB to 100 dB. When a voltage of 4.5 W is applied to the thermoacoustic device 10, the
frequency response range of the thermoacoustic device 10 is 100 Hz to 100 KHz.
[0041]
Furthermore, because the carbon nanotube structure has excellent mechanical strength and
toughness, it is possible to provide the carbon nanotube structure in the desired shape and size,
whereby a large number of desired shapes and sizes can be obtained. It is possible to obtain a
thermoacoustic device 10. The thermoacoustic apparatus 10 can be used, for example, for an
acoustic system, a mobile phone, an MP3, an MP4, a TV, a computer, and the like.
[0042]
Example 2 Referring to FIG. 10, the thermoacoustic apparatus 20 of the present example
includes a signal apparatus 22, a sound wave generator 24, a first electrode 242, a second
electrode 244, and a third electrode 246; And a fourth electrode 248. The configuration,
characteristics, and functions of the thermoacoustic apparatus 20 of the present embodiment are
the same as those of the thermoacoustic apparatus 10 of the first embodiment. The difference
between the present embodiment and the first embodiment is that the thermoacoustic device 20
of the present embodiment includes four electrodes (first electrode 242, second electrode 244,
third electrode 246, fourth electrode 248). is there. The four electrodes are rod-shaped, and are
separately installed at predetermined distances. The sound wave generator 24 is electrically
connected to the four electrodes so as to surround the four electrodes. Furthermore, the first
electrode 242 and the third electrode 246 are electrically connected in parallel to one end of the
signal device 22 by a first conductive wire 249. The second electrode 244 and the fourth
electrode 248 are electrically connected in parallel to the other end of the signal device 22 by a
second conductive line 249 '. Since the electrodes are connected in parallel to the signal device
22, the voltage applied to the thermoacoustic device 20 is low.
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[0043]
Referring to FIG. 11, the four electrodes may be disposed in the same plane. In this case, the
plurality of electrodes can be installed in the thermoacoustic device 20 without being limited to
the four electrodes.
[0044]
Example 3 Referring to FIG. 12, the thermoacoustic apparatus 30 of the present example
includes a signal device 32, a sound wave generator 34, a first electrode 342, and a second
electrode 344. The configuration, characteristics, and functions of the thermoacoustic apparatus
30 of the present embodiment are the same as the thermoacoustic apparatus 10 of the first
embodiment. The difference between the present embodiment and the first embodiment is that
the thermoacoustic apparatus 20 of the present embodiment includes a support 36. The sound
wave generator 34 is mounted on the surface of the support 36. The shape of the support 36 is
determined according to the shape of the sound wave generator 34. The support 36 is flat or /
and curved. The support 36 is any one of a screen, a wall, a desk, and a display. The sound wave
generator 34 can be in contact with the support 36.
[0045]
The support 36 is made of a hard material such as diamond, glass or quartz, or a flexible material
such as plastic, resin or fabric. The support 36 is thermally insulating and can not absorb the
heat generated by the sound wave generator 34. Furthermore, it is preferable that the surface in
contact with the support 36 and the sound wave generator 34 be rough. As a result, the area in
which the sound wave generator 34 contacts the peripheral catalyst can be increased. Since the
carbon nanotube structure has a large specific surface area, the sound wave generator 34 can be
directly adhered to the support 36.
[0046]
An adhesive layer (not shown) may be provided between the sound wave generator 34 and the
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14
support 36 in order to make a good connection between the sound wave generator 34 and the
support 36. The adhesive layer may be disposed on the surface of the sound wave generator 34.
In this embodiment, the conductive adhesive layer is made of silver paste.
[0047]
The first electrode 342 and the second electrode 344 are disposed on the same surface of the
sound wave generator 34 or respectively on opposing surfaces of the sound wave generator 34.
A plurality of electrodes can be installed on the thermoacoustic device 20 without being limited
to the two electrodes. The signal device 32 is connected to the sound wave generator 34 by a
conductive wire 349.
[0048]
Example 4 Referring to FIG. 13, the thermoacoustic apparatus 40 of the present example
includes a signal apparatus 42, a sound wave generator 44, a support 46, a first electrode 442, a
second electrode 444, and It includes a three electrode 446 and a fourth electrode 448. The
configuration, characteristics, and functions of the thermoacoustic apparatus 30 of the present
embodiment are the same as the thermoacoustic apparatus 10 of the first embodiment. The
difference between the present embodiment and the third embodiment is that the sound wave
generator 44 is installed so as to surround the support 46. The support 46 is, for example, a
three-dimensional or two-dimensional structure such as a cube, a cone, or a cylinder. In the
present embodiment, the support 46 has a cylindrical shape, and the first electrode 442, the
second electrode 444, the third electrode 446, and the fourth electrode 448 are separated by a
predetermined distance, respectively. It is electrically connected to the sound wave generator 44.
The manner in which the first electrode 442, the second electrode 444, the third electrode 446,
and the fourth electrode 448 are connected to the signal device 42 is the same as in the first
embodiment. Of course, the plurality of electrodes can be installed on the thermoacoustic device
40 without being limited to the four electrodes.
[0049]
Example 5 Referring to FIG. 14, the thermoacoustic apparatus 50 of the present example
includes a signal device 52, a sound wave generator 54, a support 56, a first electrode 542, and a
second electrode 544. Including. The configuration, characteristics, and functions of the
05-05-2019
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thermoacoustic apparatus 50 of the present embodiment are the same as the thermoacoustic
apparatus 30 of the third embodiment. The difference between this embodiment and the third
embodiment resides in that a space for sound collection is formed from the sound wave
generator 54 and the support 56 by placing a part of the sound wave generator 54 on the
support 56. It is. Since the periphery of the sound wave generator 54 is fixed to the support 56
and the other part is suspended, the area where the suspended part of the sound wave generator
54 contacts the surrounding medium is large. Referring to FIG. 22, the two carbon nanotube
films shown in FIG. 2 are adhered to the frame portion 722. The space is a closed space or an
open space. The support 56 is U-shaped or L-shaped. The thermoacoustic device 50 can include
two or more of the supports 56. The support 56 is any one of wood, plastic, metal and glass.
Referring to FIG. 14, in the present embodiment, the support 56 is L-shaped, and the sound wave
generator 54 extends from the first end 562 of the support to the second end 564 so that the
sound wave generator is A space for sound collection can be formed from 54 and the support 56.
The first electrode 542 and the second electrode 544 are disposed on the surface of the sound
wave generator 54 and are electrically connected to the signal device 52. Thereby, the sound
generated by the sound wave generator 54 is reflected by the inner wall of the support 56, so
that the acoustic function of the thermoacoustic device 50 can be enhanced.
[0050]
Example 6 Referring to FIGS. 15 and 16, the thermoacoustic apparatus 60 of the present
example includes a signal device 62, a sound wave generator 64, two electrodes 642, and a
power amplifier 66. The configuration, characteristics, and functions of the thermoacoustic
apparatus 60 of the present embodiment are the same as those of the thermoacoustic apparatus
10 of the first embodiment. The difference between the present embodiment and the first
embodiment is that the thermoacoustic apparatus 60 of the present embodiment includes a
power amplifier 66. The power amplifier 66 is electrically connected to the signal device 62.
Furthermore, the signal device 62 includes a signal output device (not shown), and the signal
output device is electrically connected to the signal device 62. The power amplifier 66 can
amplify the output of the signal from the signal unit 62 and transfer it to the sound generator 64.
The power amplifier 66 includes two outputs 664 and an input 662. The input unit 662 is
electrically connected to the signal device 62, and the output unit 664 is electrically connected to
the sound wave generator 64.
[0051]
Referring to FIG. 17, when providing the thermoacoustic device 60 with an alternating current,
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the frequency of the output signal of the sound wave generator 64 may be twice as high as the
frequency of the input signal. The cause of this is that an alternating current flows through the
sound wave generator 64 to alternately heat the sound wave generator 64 with a positive current
and a negative current, so that double frequency temperature oscillation and double frequency
sound pressure are generated. Thus, when using a conventional power amplifier (e.g., a bipolar
amplifier), the output signal (human voice or music) sounds strange as it is twice as large as the
input signal.
[0052]
The power amplifier 66 can provide an amplified signal (e.g., a voltage signal) and a bias voltage
to the sound generator 64 to reduce the input signal. Referring to FIG. 16, the power amplifier
66 is a class A power amplifier, and includes a first resistor R1, a second resistor R2, a third
resistor R3, a capacitor, and a triode. The triode includes a base B, an emitter E, and a collector C.
The capacitor is connected to the signal output of the signal unit 62 and to the base B of the
triode. The DC voltage Vcc and the first resistor R1 are connected to the base B of the triode. The
base B of the triode is connected to the second resistor R2. The emitter E is electrically connected
to one output 664 of the power amplifier 66. The DC voltage Vcc is electrically connected to the
other output 664 of the power amplifier 66. The collector C is connected to the third resistor R3.
The two outputs 664 of the power amplifier 66 are connected to the two electrodes 642,
respectively. The resistors R2 and R3 are grounded.
[0053]
A plurality of electrodes may be electrically connected to the sound wave generator 64. Adjacent
ones of the electrodes are connected to different ends 664 of the power amplifier 66. When the
electrodes are not installed, the two output parts 664 of the power amplifier 66 are electrically
connected to the sound wave generator 64 by conductive wires.
[0054]
Referring to FIG. 15, in order to reduce the frequency of the signal from the signal device 62, a
frequency reduction circuit 69 is provided. The frequency reduction circuit 69 can transfer the
signal to the power amplifier 66, for example, after reducing the signal frequency to half. The
power amplifier 66 is, for example, a conventional power amplifier and does not provide an
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amplified voltage signal and a bias voltage to the sound wave generator 64. The frequency
reduction circuit 69 may be integrated with the power amplifier 66.
[0055]
Seventh Embodiment Referring to FIGS. 18 and 19, the thermoacoustic apparatus 60 of the
present embodiment includes a plurality of sound wave generators 64 and a calibration unit 68
as compared with the sixth embodiment. The calibrator 68 is connected to the input 662 or the
output 664 of the power amplifier 66. Referring to FIG. 18, when the calibrator 68 is connected
to the output 664 of the power amplifier 66, the calibrator 68 divides the amplified signal from
the power amplifier 66 into sub-signals of a plurality of frequency bands. The sub-signals are
transferred to the plurality of sound wave generators 64 respectively. Referring to FIG. 19, when
the calibrator 68 is connected to the input 662 of the power amplifier 66, the thermoacoustic
device 60 includes a plurality of power amplifiers 66. The calibrator 68 divides the signal from
the signal unit 62 into sub-signals of a plurality of frequency bands, and transfers the sub-signals
to the plurality of power amplifiers 66, respectively. Each power amplifier 66 corresponds to one
sound generator 64.
[0056]
Referring to FIG. 20, the method of generating an acoustic wave according to the present
invention comprises a first step of providing a carbon nanotube structure; The method includes
two steps, a third step in which heat is radiated to a medium in contact with the carbon nanotube
structure, and a fourth step in which a thermoacoustic effect is generated.
[0057]
In the first step, the carbon nanotube structure is the same as the carbon nanotube structure
used for the thermoacoustic device 10.
In the second step, the signal is transferred to the signal device by at least two electrodes. In the
third and fourth steps, the heat generated in the carbon nanotube structure heats the
surrounding medium. Sound waves can be generated by repeatedly heating the surrounding
medium. The above is the thermoacoustic effect.
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[0058]
DESCRIPTION OF SYMBOLS 10 thermoacoustic apparatus 100 speaker 102 voice coil 104
magnet 106 cone 12 signal apparatus 14 sound wave generator 142 1st electrode 143a carbon
nanotube film 143b carbon nanotube segment 144 2nd electrode 145 carbon nanotube 146
carbon nanotube wire 149 conductive wire 20 thermoacoustic apparatus Reference Signs List 22
signal device 24 sound wave generator 242 first electrode 244 second electrode 246 third
electrode 248 fourth electrode 249 first conductive wire 249 'second conductive wire 30
thermoacoustic device 32 signal device 34 sound wave generator 342 first electrode 344 Second
electrode 349 conductive wire 36 support 40 thermoacoustic device 42 signal device 44
acoustic wave generator 442 first electrode 444 second electrode 446 third electrode 448 fourth
electrode 449 conductive wire 50 thermoacoustic device 52 Signal device 54 Sound wave
generator 542 First electrode 544 Second electrode 549 Conductive wire 56 Support 562 First
end 564 Second end 60 Thermoacoustic device 62 Signal device 64 Sound wave generator 66
Power amplifier 662 Frequency reduction circuit
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