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JP2011083019

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DESCRIPTION JP2011083019
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 and an acoustic wave generator including a carbon nanotube structure.
The carbon nanotube structure is connected to the signal device. The heat capacity per unit area
of the carbon nanotube structure is 2 × 10 J / cm · K or less. In the carbon nanotube structure,
carbon nanotubes are connected by intermolecular force and uniformly distributed. [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.
05-05-2019
1
[0003]
According to the operating principle, there are many kinds of speakers 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 is propagated 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]
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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 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 device of the present invention comprises a signal device and a sound generator comprising
carbon nanotube structures. The carbon nanotube structure is connected to the signal device.
[0010]
The heat capacity per unit area of the carbon nanotube structure is 2 × 10 <-4> J / cm <2> · K or
less.
[0011]
The frequency response range of the sound generator is 1 Hz to 100 KHz.
[0012]
In the carbon nanotube structure, carbon nanotubes are connected by intermolecular force and
uniformly distributed.
[0013]
In the carbon nanotube structure, carbon nanotubes are aligned and arranged.
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[0014]
In the carbon nanotube structure, carbon nanotubes are arranged without being oriented.
[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]
A signal device, a carbon nanotube structure, and a mediator in contact with the carbon nanotube
structure.
The carbon nanotube structure is connected to the signal device.
[0017]
The carbon nanotube structure generates a sound by heating the medium.
[0018]
The acoustic system of the present invention comprises carbon nanotube structures.
In the acoustic system of the present invention, the carbon nanotube structure generates sound
according to the thermoacoustic principle.
[0019]
Compared to the prior art, the thermoacoustic apparatus of the present invention has the
following advantages.
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First, since the thermoacoustic apparatus of the present invention includes a carbon nanotube
structure, the structure is simple and light and compact can be realized as compared with the
conventional speaker.
Second, since the thermoacoustic apparatus of the present invention heats the carbon nanotube
structure to generate an acoustic wave, 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.
[0020]
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 piece 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 schematic diagram of the thermoacoustic apparatus in Example 6 of this
invention. It is a schematic diagram of the thermoacoustic apparatus in Example 6 of this
invention. It is a schematic diagram of the thermoacoustic apparatus in Example 6 of this
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invention. It is a chart of the sound wave generation method of the present invention. It is a
schematic diagram of the conventional speaker.
[0021]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings.
[0022]
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.
[0023]
The sound wave generator 14 includes a carbon nanotube structure. The heat capacity per unit
area of the carbon nanotube structure is 2 × 10 <-4> J / cm <2> · K or less, but 1.7 × 10 <-6> J
/ cm <2> · K Is preferred. 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. The plurality of
carbon nanotubes are aligned or aligned in the carbon nanotube structure. 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 aligned 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
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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, 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.
[0024]
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. The sound pressure of the thermoacoustic device may be
lower as the heat capacity per unit area of the carbon nanotube structure is higher.
[0025]
The carbon nanotube structure includes at least one carbon nanotube film. In the single carbon
nanotube film, a plurality of carbon nanotubes are connected end to end along the same
direction. Referring to FIGS. 2 and 3, the single carbon nanotube film includes a plurality of
carbon nanotube segments 143 connected end to end with intermolecular force. Each carbon
nanotube segment 143 includes a plurality of carbon nanotubes 145 connected by
intermolecular force in parallel to one another. Toughness and mechanical strength of the carbon
nanotube film can be enhanced by immersing the carbon nanotube film in an organic solvent (for
example, argon). Since the heat capacity per unit area of the carbon nanotube film immersed in
the organic solvent is high, the thermoacoustic effect can be enhanced. The carbon nanotube film
has a width of 100 μm to 10 cm and a thickness of 0.5 nm to 100 μm.
[0026]
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 °.
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.
[0027]
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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 aligned without orientation. The length of the
single carbon nanotube is 10 cm or more. 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 aligned
without orientation to form a large number of minute holes. Here, the diameter of the single
minute hole is 10 μm or less. The carbon nanotubes in the carbon nanotube structure are
arranged in a mutually entangled manner, so 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.
[0028]
The carbon nanotube structure includes one carbon nanotube segment. Referring to FIG. 5,
carbon nanotubes in the carbon nanotube segment are parallel to one another and arranged
along a predetermined direction. In the carbon nanotube segment, the length of at least one
carbon nanotube is the same as the entire length of the carbon nanotube segment. Thus, the
dimension of one dimension of the carbon nanotube segment is limited by the length of the
carbon nanotube. The carbon nanotube structure may include a plurality of stacked carbon
nanotube segments. In this case, the adjacent carbon nanotube segments are bonded by an
intermolecular force. The thickness of the carbon nanotube segment 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 2 × 10 <-4> J / cm <2> · K or less, preferably 5 × 10 <-5> J / cm
<2> · 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
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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 linear 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 carbon nanotube wire, the twisted carbon nanotube wire, or a
combination thereof.
[0030]
When the carbon nanotube structure includes a plurality of carbon nanotube wires, the plurality
of carbon nanotube wires may be parallelly juxtaposed, crosswise woven, or twisted. A fabric
comprising a plurality of carbon nanotube wires 146 is shown in FIG. 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. The flag on
which the carbon nanotube structure is installed may be used as the sound generator 14 if it is
windy. 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 (for example, persons with hearing impairment).
[0032]
Even when a part of the carbon nanotube structure used for the sound wave generator 14 is
ruptured, 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.
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[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 that the thermoacoustic device is compact
and light.
[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]
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10
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. As the heat radiation changes the pressure intensity of the surrounding medium
(the environment), 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.
[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, the carbon nanotube structure of the sound wave generator 14 includes a
plurality of carbon nanotubes, and the heat capacity of a unit area is small. 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. In contrast to this, the principle of generating sound by
pressure waves generated by mechanical vibration of the diaphragm in the conventional speaker
is largely different. If the input signal is an electrical signal, the thermoacoustic device 10
operates according to an electro-thermal-sound conversion scheme, but if the input signal is an
optical signal, the thermo-acoustic device 10 may be a photo-thermal device. -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 radiation of heat changes the pressure intensity of the surrounding
medium (the environment), a detectable signal can be generated.
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[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. Thermoacoustic Device 10 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.
[0040]
When the carbon nanotube structure of the thermoacoustic device 10 includes five carbon
nanotube wires, the distance between the 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. The thermoacoustic device 10 When applying a
voltage of 4.5 W 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]
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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.
[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 electricitys.
[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
provided by the shape of the sound wave generator 34. The support 36 is a flat or / and a curved
surface. The support 36 is any one of a screen, a wall, a desk, and a display. The sound wave
generator 34 may be in contact with the support 36.
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[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. Thereby, the area in
contact with the sound wave generator 34 and 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
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
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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 method of connecting the first electrode 442, the second electrode 444, the third electrode
446, and the fourth electrode 448 to the signal device 42 is the same as that of the first
embodiment. Of course, the plurality of electrodes can be installed in the thermoacoustic device
40 without being limited to the four electricitys.
[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
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. The space is a closed space or an open space. The support 56 is U-shaped or Lshaped. 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, a support 56, two electrodes
642, a power amplifier 66, ,including. 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
05-05-2019
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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 signal power 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,
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, and the sound wave generator 64 is alternately heated by the positive
current and the negative current, so that double frequency temperature oscillation and double
frequency sound pressure occur. 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 may 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 ADC voltage Vcc and the first resistor R1 are connected to the base B of the triode.
The berth 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 register R3. The two outputs 664 of the power amplifier 66 are connected to the two
electrodes 642, respectively. The register R2 and the register R3 are grounded.
[0053]
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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
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]
Sixth 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 fifth 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 recognizes the signals
from the signal unit 62 into sub-signals of a plurality of frequency bands and transfers the subsignals 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 includes a first step of providing
a carbon nanotube structure, and a second step of transferring a signal to the carbon nanotube
structure to generate heat in the carbon nanotube structure. And a third step in which heat is
emitted to the medium contacting the carbon nanotube structure, and a fourth step in which a
thermoacoustic effect is generated.
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[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.
[0058]
10 thermoacoustic device 100 speaker 102 voice coil 104 magnet 106 cone 12 signal device 14
acoustic wave generator 142 first electrode 143 carbon nanotube segment 144 second electrode
145 carbon nanotube 146 carbon nanotube wire 149 conductive wire 20 thermoacoustic device
22 signal device 24 Sound wave generator 242 First electrode 244 Second electrode 246 Third
electrode 249 First conductive wire 249 'Second conductive wire 30 Thermoacoustic device 32
Signal device 34 Sound generator 342 First electrode 344 Second electrode 349 Conductive wire
36 Support 40 Thermoacoustic device 42 Signal device 44 Sound wave generator 442 First
electrode 446 Second electrode 446 Third electrode 448 Fourth electrode 449 Conductive wire
50 Thermoacoustic device 52 Signal device 54 Sound wave generator 542 Electrode 544 second
electrode 549 conductive lines 56 support 562 first end 564 second end 60 thermoacoustic
device 62 signaling device 64 wave generator 66 power amplifier 662 input unit 664 output unit
69 frequency reduction circuit
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