JP2009268108A - Thermoacoustic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoacoustic device using carbon nanotubes. <P>SOLUTION: The device includes a signal device and a sound wave generator having a carbon nanotube structure. The carbon nanotube structure is connected to the signal device. Thermal capacity per unit area of the carbon nanotube structure is 2×10<SP>-4</SP>J/cm<SP>2</SP>K or below. In the carbon nanotube structure, the carbon nanotubes are connected with intermolecular force and distributed uniformly. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a thermoacoustic apparatus, and more particularly to a thermoacoustic apparatus using carbon nanotubes.

  In general, the acoustic device includes a signal device and a sound wave generator. The signal device transmits a signal to the sound wave generator (for example, a speaker). The speaker can convert an electrical signal into sound as an electroacoustic transducer.

  Depending on the principle of operation, there are various types of speakers such as dynamic speakers, magnetic speakers, electrostatic speakers, and piezoelectric speakers. The various types of speakers all generate sound waves by mechanical vibration, that is, realize electrical-mechanical force-sound conversion. Here, dynamic speakers are widely used.

  Referring to FIG. 21, a conventional dynamic speaker 100 includes a voice coil 102, a magnet 104, and a cone 106. The voice coil 102 is installed between the magnets 104 as a conductive component. When a current is supplied to the voice coil 102, the cone 106 vibrates due to the interaction between the electromagnetic field generated by the voice coil 102 and the magnetic field generated by the magnet 104, and air pressure fluctuations continuously occur. it can. However, the dynamic speaker 100 depends on the action of a magnetic field.

  The thermoacoustic phenomenon is a phenomenon in which sound and heat are involved, and has two aspects, energy conversion and energy transport. When a signal is transferred to the thermoacoustic device, heat is generated in the thermoacoustic device and propagated to surrounding media. Sound waves can be generated due to thermal expansion and pressure waves caused by the propagated heat.

H. D. Arnold, I.D. B. Crandall, “The thermophone as a precision source of sound”, Phys. 1917, Vol. 10, pp. 22-38, Kaili Jiang, Quung Li, Shuushan Fan, “Spinning continuous carbon nanotube yarns”, Nature, 2002, vol. 419, p. 801

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 the platinum piece is very high, a thermophone using the platinum piece has a problem that sound is very weak when used outdoors.

  In order to solve the above-mentioned problems, the present invention provides a light thermoacoustic apparatus. The thermoacoustic apparatus of the present invention does not depend on a magnetic field and can generate sound without depending on mechanical vibration.

  The apparatus of the present invention includes a signal device and a sound wave generator including a carbon nanotube structure. The carbon nanotube structure is connected to the signal device.

The carbon nanotube structure has a heat capacity per unit area of 2 × 10 ⁻⁴ J / cm ² · K or less.

  The frequency response range of the sound wave generator is 1 Hz to 100 KHz.

  In the carbon nanotube structure, the carbon nanotubes are connected by an intermolecular force and are uniformly distributed.

  In the carbon nanotube structure, the carbon nanotubes are aligned and arranged.

  In the carbon nanotube structure, the carbon nanotubes are arranged without being oriented.

  The apparatus includes at least two electrodes, the at least two electrodes being separated by a predetermined distance and electrically connected to the sound wave generator, respectively.

  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.

  The carbon nanotube structure generates sound by heating the medium.

  The acoustic system of the present invention includes a carbon nanotube structure. In the acoustic system of the present invention, the carbon nanotube structure generates sound according to the thermoacoustic principle.

  Compared with the prior art, the thermoacoustic device of the present invention has the following advantages. First, since the thermoacoustic device of the present invention includes a carbon nanotube structure, the structure is simpler than that of a conventional speaker, and a light and small size can be realized. Secondly, the thermoacoustic apparatus of the present invention generates a sound wave by heating the carbon nanotube structure, so there is no need 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 heat exchange rate, sound can be generated satisfactorily. Fourth, since the carbon nanotube structure is thin, a transparent acoustic device can be manufactured.

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 the present invention. It is a schematic diagram of the carbon nanotube segment in Example 1 of the present invention. It is a SEM photograph of the carbon nanotube film in Example 1 of the present 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 the present 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 the textile fabric which consists of a some carbon nanotube film in Example 1 of this invention or / and a carbon nanotube wire. 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 the present 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 invention. It is a chart of the sound wave generation method of the present invention. It is a schematic diagram of the conventional speaker.

  Embodiments of the present invention will be described below with reference to the drawings.

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 each electrically connected to the signal device 12. The signal from the signal device 12 is transferred to the sound wave generator 14 by the first electrode 142 and the second electrode 144.

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 is preferably 1.7 × 10 ⁻⁶ J / cm ² · K. 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 include metallic carbon nanotubes. The plurality of carbon nanotubes are aligned or not aligned in the carbon nanotube structure. According to the arrangement method of the plurality of carbon nanotubes, the carbon nanotube structure is classified into two types, a non-oriented carbon nanotube structure and an oriented carbon nanotube structure. In the non-oriented carbon nanotube structure in this example, 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 arrangement directions of the 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. When the carbon nanotube is a double-walled carbon nanotube, the diameter is set to 1 nm to 50 nm. In the case of a nanotube, the diameter is set to 1.5 nm to 50 nm.

  The carbon nanotube structure has a flat plate shape and a thickness of 0.5 nm to 1 mm. The smaller the specific surface area of the carbon nanotube structure, the higher the heat capacity per unit area of the carbon nanotube structure. The higher the heat capacity per unit area of the carbon nanotube structure, the lower the sound pressure of the thermoacoustic device.

  The carbon nanotube structure includes at least one carbon nanotube film. In the single carbon nanotube film, a plurality of carbon nanotubes are connected to each other along the same direction. 2 and 3, the single carbon nanotube film includes a plurality of carbon nanotube segments 143 that are connected to each other by an intermolecular force. Each carbon nanotube segment 143 includes a plurality of carbon nanotubes 145 connected in parallel to each other by intermolecular force. By immersing the carbon nanotube film in an organic solvent (for example, argon), the toughness and mechanical strength of the carbon nanotube film can be increased. Since the heat capacity per unit area of the carbon nanotube film immersed in the organic solvent is increased, 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.

  The carbon nanotube structure may include a plurality of stacked carbon nanotube films. In this case, the adjacent carbon nanotube films are bonded by intermolecular force. The carbon nanotubes in the adjacent carbon nanotube films intersect each other at an angle of 0 ° to 90 °. When the carbon nanotubes in the adjacent carbon nanotube films intersect at an angle of 0 ° or more, a plurality of micropores are formed in the carbon nanotube structure.

  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 isotropically arranged. In the carbon nanotube structure, the plurality of carbon nanotubes are uniformly distributed. The plurality of carbon nanotubes are arranged without being oriented. The length of the single carbon nanotube is 10 cm or more. The carbon nanotube structure is formed in the shape of a self-supporting thin film. Here, the self-supporting structure is a form in which the carbon nanotube structure can be used independently without using a support material. The plurality of carbon nanotubes are close to each other by intermolecular force and entangled with each other to form a carbon nanotube net. 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 so as to be entangled with each other, the carbon nanotube structure is excellent in flexibility and can be formed to be bent into an arbitrary shape. Depending on the application, the length and width of the carbon nanotube structure can be adjusted. The carbon nanotube structure has a thickness of 0.5 nm to 1 mm.

  The carbon nanotube structure includes one carbon nanotube segment. Referring to FIG. 5, the carbon nanotubes in the carbon nanotube segment are parallel to each other and arranged along a predetermined direction. In the carbon nanotube segment, the length of at least one carbon nanotube is the same as the total length of the carbon nanotube segment. Therefore, the one-dimensional dimension of the carbon nanotube segment is limited by the length of the carbon nanotube. The carbon nanotube structure may include a plurality of the carbon nanotube segments stacked. In this case, the adjacent carbon nanotube segments are bonded by an intermolecular force. The carbon nanotube segment has a thickness of 0.5 nm to 100 μm.

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, and 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 includes 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. Further, a plurality of carbon nanotubes having the same length are arranged in parallel in 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 can be twisted to form a twisted linear carbon nanotube wire. Here, the plurality of carbon nanotubes are arranged in a spiral shape around the central axis of the carbon nanotube wire. In this case, the diameter of one carbon nanotube wire is 1 μm to 1 cm. The carbon nanotube structure is formed of any one of the carbon nanotube wire, the twisted carbon nanotube wire, or a combination thereof.

  When the carbon nanotube structure includes a plurality of carbon nanotube wires, the plurality of carbon nanotube wires may be arranged in parallel, cross-woven, or twisted. FIG. 8 shows a fabric composed of a plurality of carbon nanotube wires 146. A first electrode 142 and a second electrode 144 are 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.

  Since the carbon nanotube structure is flexible, the carbon nanotube structure can be formed into various shapes, and the carbon nanotube structure is installed on the surface of a hard insulator or a flexible insulator (for example, a flag or cloth). can do. When the flag on which the carbon nanotube structure is installed flutters in the wind, it can be used as the sound wave generator 14. The cloth provided with the carbon nanotube structure can play music as a player such as MP3. Furthermore, by using the cloth in which the carbon nanotube structure is installed, it is possible to help a physically handicapped person (for example, a person with hearing impairment).

  Even when a part of the carbon nanotube structure used for the sound wave generator 14 is ruptured, sound waves can be generated by the carbon nanotube structure. On the other hand, when the diaphragm or cone of a conventional speaker is damaged, sound waves cannot be generated.

  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, the carbon nanotubes are arranged along the same direction. The acoustic wave generator 14 has a length of 3 cm, a width of 3 cm, and a thickness of 50 nm. When the sound wave generator 14 is thin (thickness is 10 μm or less), the sound wave generator 14 has excellent transparency. Accordingly, by using the transparent sound wave generator 14, a transparent thermoacoustic device can be manufactured. The transparent thermoacoustic device can be installed on the surface of a mobile phone or LCD, for example. Or the said transparent thermoacoustic apparatus can be affixed on the surface of a picture. By using the transparent sound wave generator 14, the thermoacoustic apparatus is excellent in that it is small and light.

  The first electrode 142 and the second electrode 144 are made of a conductive material of metal, conductive adhesive, carbon nanotube, or ITO. In the present embodiment, the first electrode 142 and the second electrode 144 are rod-shaped 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. Further, the first electrode 142 and the second electrode 144 are respectively connected to both ends of the signal device 12 by conductive wires 149.

  In order to satisfactorily electrically connect the first electrode 142 or the second electrode 144 and the sound wave generator 14, electrical conductivity is provided between the first electrode 142 or the second electrode 144 and the sound wave generator 14. An adhesive layer (not shown) can also be installed. The conductive adhesive layer may be installed on the surface of the sound wave generator 14. The conductive adhesive layer is made of a silver paste.

  The signal device 12 is one of an electric 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 electrical signal (for example, an alternating current, a direct current pulsation signal, an audio electrical signal) or a mixed signal thereof. is there. The signal is received by the carbon nanotube structure and emitted as heat. Since the ambient pressure (environment) pressure intensity changes due to heat radiation, a detectable signal can be generated. When the thermoacoustic device 10 is used for an earphone, the input signal is an AC electric signal or an audio electric signal. When the thermoacoustic apparatus 10 is used for a photoacoustic spectrum device, the input signal is an optical signal. In this embodiment, the signal device 12 is a photoacoustic spectrum, and the input signal is an electrical signal.

  The placement of the first electrode 142 and the second electrode 144 is selective with respect to the different types of the signal device 12. For example, when 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. .

  In the signal device 12, the carbon nanotube structure of the sound wave generator 14 includes a plurality of carbon nanotubes and has a small heat capacity per unit area. Therefore, the pressure wave is transmitted to the surrounding medium by the temperature wave generated in the sound wave generator 14. Can be generated. When a signal (for example, an electrical signal) is transferred to the carbon nanotube structure of the sound wave generator 14, heat is generated in the carbon nanotube structure depending on the signal intensity and / or the signal. Due to the diffusion of the temperature wave, the surrounding air is thermally expanded and a sound is generated. This is largely different from the principle of generating sound by pressure waves generated by mechanical vibration of the diaphragm in a conventional speaker. When the input signal is an electrical signal, the thermoacoustic device 10 operates according to an electrical-thermal-sound conversion method. When the input signal is an optical signal, the thermoacoustic device 10 -Operates according to the sound conversion method. The energy of the optical signal is absorbed by the sound wave generator 14 and radiated as heat. Since the ambient pressure (environment) pressure intensity changes due to the radiation of heat, a detectable signal can be generated.

  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 50V is provided to the carbon nanotube structure. In order to detect the performance of the thermoacoustic apparatus 10, a microphone is installed facing the one side of the sound wave generator 14 separated from the sound wave generator 14 by a distance of 5 cm. From FIG. 9, it can be understood that the thermoacoustic device 10 has a wide frequency response range and a high sound pressure level. 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 is very small, for example, it can reach only 3% in the range of 500 Hz to 40 KHz.

  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 an AC electric signal of 50 V to the carbon nanotube structure, the sound pressure level generated in 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.

  Furthermore, since the carbon nanotube structure has excellent mechanical strength and toughness, it is possible to provide the carbon nanotube structure in a desired shape and size. The thermoacoustic device 10 can be obtained. The thermoacoustic apparatus 10 can be used for, for example, an acoustic system, a mobile phone, MP3, MP4, TV, a computer, and the like.

(Example 2)
Referring to FIG. 10, the thermoacoustic apparatus 20 of the present embodiment includes a signal device 22, a sound wave generator 24, a first electrode 242, a second electrode 244, a third electrode 246, and a fourth electrode 248. ,including. The configuration, characteristics, and functions of the thermoacoustic device 20 of the present embodiment are the same as those of the thermoacoustic device 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 four electrodes (first electrode 242, second electrode 244, third electrode 246, and fourth electrode 248). is there. The four electrodes have a rod shape and are separated from each other by a predetermined distance. The sound wave generator 24 is electrically connected to the four electrodes so as to surround the four electrodes. Further, the first electrode 242 and the third electrode 246 are electrically connected in parallel to one end of the signal device 22 through a first conductive line 249. The second electrode 244 and the fourth electrode 248 are electrically connected in parallel to the other end of the signal device 22 through 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.

  Referring to FIG. 11, the four electrodes may be installed on the same plane. In this case, a plurality of electrodes can be installed in the thermoacoustic apparatus 20 without being limited to the four electricity.

(Example 3)
Referring to FIG. 12, the thermoacoustic device 30 of this embodiment 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 device 30 of the present embodiment are the same as those of the thermoacoustic device 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 installed on the surface of the support 36. The shape of the support 36 is provided according to the shape of the sound wave generator 34. The support 36 is a flat surface and / or a curved surface. The support 36 is one of a screen, a wall, a desk, and a display. The sound wave generator 34 can be in contact with the support 36.

  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 has a heat insulating property and cannot 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 is provided rough. Thereby, the area which contacts the said sound generator 34 and the surrounding catalyst can be increased. Since the carbon nanotube structure has a large specific surface area, the sound wave generator 34 can be directly bonded to the support 36.

  In order to connect the sound wave generator 34 and the support 36 satisfactorily, an adhesive layer (not shown) can be provided 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 a silver paste.

  The first electrode 342 and the second electrode 344 are installed on the same surface of the sound wave generator 34, or are respectively installed on opposite surfaces of the sound wave generator 34. The thermoacoustic device 20 can be provided with a plurality of electrodes without being limited to the two electrodes. The signal device 32 is connected to the sound wave generator 34 by a conductive wire 349.

Example 4
Referring to FIG. 13, the thermoacoustic device 40 of the present embodiment includes a signal device 42, a sound wave generator 44, a support 46, a first electrode 442, a second electrode 444, a third electrode 446, A fourth electrode 448. The configuration, characteristics, and functions of the thermoacoustic device 30 of the present embodiment are the same as those of the thermoacoustic device 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 has a three-dimensional or two-dimensional structure such as a cube, a cone, or a cylinder. In this embodiment, the support 46 is cylindrical, and the first electrode 442, the second electrode 444, the third electrode 446, and the fourth electrode 448 are separated from each other by a predetermined distance, and It is electrically connected to the sound wave generator 44. The first electrode 442, the second electrode 444, the third electrode 446, and the fourth electrode 448 are connected to the signal device 42 in the same manner as in the first embodiment. Of course, the thermoacoustic device 40 can be provided with a plurality of electrodes without being limited to the four electricity.

(Example 5)
Referring to FIG. 14, the thermoacoustic device 50 of this embodiment includes a signal device 52, a sound wave generator 54, a support 56, a first electrode 542, and a second electrode 544. The configuration, characteristics, and functions of the thermoacoustic device 50 of the present embodiment are the same as those of the thermoacoustic device 30 of the third embodiment. The difference between the present embodiment and the third embodiment is that a part of the sound wave generator 54 is installed on the support 56 to form a sound collection space from the sound wave generator 54 and the support 56. That is. The space is a closed space or an open space. The support 56 is U-shaped or L-shaped. The thermoacoustic device 50 may include two or more supports 56. The support 56 is one of wood, plastic, metal, and glass. Referring to FIG. 14, in this 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. A space for sound collection can be formed from 54 and the support 56. The first electrode 542 and the second electrode 544 are installed on the surface of the sound wave generator 54 and are electrically connected to the signal device 52. Thereby, since the sound generated by the sound wave generator 54 is reflected by the inner wall of the support 56, the acoustic function of the thermoacoustic device 50 can be enhanced.

(Example 6)
Referring to FIGS. 15 and 16, the thermoacoustic device 60 of the present embodiment includes a signal device 62, a sound wave generator 64, a support 56, two electrodes 642, and a power amplifier 66. The configuration, characteristics, and functions of the thermoacoustic device 60 of the present embodiment are the same as those of the thermoacoustic device 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. Further, 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 signal power from the signal device 62 can be amplified by the power amplifier 66 and transferred to the sound wave generator 64. The power amplifier 66 includes two output units 664 and an input unit 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.

  Referring to FIG. 17, when an alternating current is provided to the thermoacoustic device 60, the frequency of the output signal of the sound wave generator 64 can be about twice as high as the frequency of the input signal. This is because an alternating current flows through the sound wave generator 64, and the sound wave generator 64 is alternately heated with a positive current and a negative current, so that double frequency temperature vibration and double frequency sound pressure are generated. Therefore, when a conventional power amplifier (for example, a bipolar amplifier) is used, the output signal (human voice or music) is about twice that of the input signal, so it sounds strange.

  The power amplifier 66 can provide an amplified signal (eg, a voltage signal) and a bias voltage to the sound wave 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 terminal of the signal device 62 and 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 triode berth B 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 another output 664 of the power amplifier 66. The collector C is connected to the third register R3. Two output portions 664 of the power amplifier 66 are connected to the two electrodes 642, respectively. The registers R2 and R3 are each grounded.

  A plurality of electrodes may be electrically connected to the sound wave generator 64. Adjacent electrodes are connected to different ends 664 of the power amplifier 66. When the electrodes are not installed, the two output portions 664 of the power amplifier 66 are electrically connected to the sound wave generator 64 by conductive wires.

  Referring to FIG. 15, in order to reduce the frequency of the signal from the signal device 62, a frequency reduction circuit 69 is installed. The frequency reduction circuit 69 can transfer the signal to the power amplifier 66 after, for example, reducing the signal frequency by half. The power amplifier 66 is a conventional power amplifier, for example, and does not provide the amplified voltage signal and bias voltage to the sound wave generator 64. The frequency reduction circuit 69 can be integrated with the power amplifier 66.

(Example 6)
18 and 19, the thermoacoustic apparatus 60 of the present embodiment includes a plurality of sound wave generators 64 and a calibrator 68 as compared with the fifth embodiment. The calibrator 68 is connected to the input part 662 or the output part 664 of the power amplifier 66. Referring to FIG. 18, when the calibrator 68 is connected to the output unit 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 knows the signal from the signal device 62 as a plurality of frequency band sub-signals, and transfers the sub-signals to the plurality of power amplifiers 66, respectively. Each power amplifier 66 corresponds to one sound wave generator 64.

  Referring to FIG. 20, a method for generating sound waves 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. A third step in which heat is radiated to the medium contacting the carbon nanotube structure and a fourth step in which a thermoacoustic effect is generated.

  In the first step, the carbon nanotube structure is the same as the carbon nanotube structure used in 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.

DESCRIPTION OF SYMBOLS 10 Thermoacoustic apparatus 100 Speaker 102 Voice coil 104 Magnet 106 Cone 12 Signal apparatus 14 Sound wave generator 142 First electrode 143 Carbon nanotube segment 144 Second electrode 145 Carbon nanotube 146 Carbon nanotube wire 149 Conductive wire 20 Thermoacoustic apparatus 22 Signal apparatus 24 Sound wave generator 242 First electrode 244 Second electrode 246 Third electrode 248 Fourth electrode 249 First conductive line 249 ′ Second conductive line 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 Sound 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 body 562 First end 564 Second end 60 Thermoacoustic device 62 Signal device 64 Sound wave generator 66 Power amplifier 662 Input unit 664 Output unit 69 Frequency reduction circuit

Claims (10)

A signal device and a sound wave generator including a carbon nanotube structure,
The carbon nanotube structure is connected to the signal device. ^2. The apparatus according to claim 1, wherein a heat capacity per unit area of the carbon nanotube structure is 2 × 10 ⁻⁴ J / cm ² · K or less.   The apparatus according to claim 1, wherein the frequency response range of the sound wave generator is 1 Hz to 100 KHz.   The apparatus according to any one of claims 1 to 3, wherein in the carbon nanotube structure, the carbon nanotubes are connected by an intermolecular force and are uniformly distributed.   The apparatus according to claim 1, wherein carbon nanotubes are aligned and arranged in the carbon nanotube structure.   The device according to claim 1, wherein the carbon nanotubes are arranged without being oriented in the carbon nanotube structure. The device comprises at least two electrodes;
The apparatus according to claim 1, wherein the at least two electrodes are separated by a predetermined distance and are electrically connected to the sound wave generator, respectively. A signal device, a carbon nanotube structure, and a medium in contact with the carbon nanotube structure,
The acoustic system, wherein the carbon nanotube structure is connected to the signal device.   The apparatus of claim 8, wherein the carbon nanotube structure generates sound by heating the medium. Including carbon nanotube structures,
An acoustic system, wherein the carbon nanotube structure generates sound according to a thermoacoustic principle.