JP2018133625A - Thermoacoustic device and acoustic wave inspection device - Google Patents

Abstract

A thermoacoustic apparatus and a sound wave inspection apparatus having a relatively large strength of a heating element and a relatively high degree of design freedom are provided. The thermoacoustic device includes a heating element 2 formed from a nonwoven sheet containing fibrous carbon nanostructures. It is preferable that the heating element has a three-dimensional shape. The heating element is preferably formed by bending a nonwoven sheet. The thermoacoustic apparatus may further include a plurality of electrodes 3 that apply current to the heating element. The thermoacoustic device may include three or more electrodes and two or more heating elements. The thermoacoustic device may further include a heating device that irradiates the heating element with light or electromagnetic waves. The sound wave inspection apparatus includes a thermoacoustic device and a sound wave receiving element. [Selection] Figure 1

Description

  The present invention relates to a thermoacoustic apparatus and a sound wave inspection apparatus.

  As a device for generating sound waves, a sound wave generating device using mechanical vibration such as an electrodynamic conversion device including a magnet and a coil, a capacitor conversion device, and a conversion device using a piezoelectric material is widely used. In recent years, unlike these sound wave generators, development of sound wave generators (thermoacoustic devices) using a thermoacoustic effect that does not perform mechanical vibration at all has been underway.

  The thermoacoustic device instantaneously expands the air in the vicinity of the heating element by applying an electric current to the heating element to instantaneously generate heat, or stops the current applied to the heating element to reduce the temperature of the heating element. By reducing the air flow, the sound around the heating element is contracted to form an air density, thereby generating sound waves. Since such a thermoacoustic apparatus does not involve mechanical vibration, there are advantages such as a wide frequency band, being hardly affected by the surrounding environment, and being relatively easy to miniaturize.

  In the thermoacoustic apparatus, it has been proposed to use a structure in which a plurality of carbon nanotubes are connected by an intermolecular force as a heating element in order to increase the generation efficiency of sound waves (refer to Japanese Patent No. 4672783). According to this thermoacoustic apparatus, since the carbon nanotube structure having a small heat capacity and a large specific surface area is used as a heating element, a high-speed temperature change corresponding to an electric signal or the like is possible, and a sound wave is excellent. It is said that it can occur.

Japanese Patent No. 4672783

  However, the carbon nanotube structure used as a heating element in the above publication has the disadvantages of low mechanical strength and easy breakage.

  In addition, since the carbon nanotube structure having no rigidity needs to be stretched around a structure such as an electrode, the degree of freedom in design is small.

  In view of the above problems, an object of the present invention is to provide a thermoacoustic apparatus and a sound wave inspection apparatus in which the strength of the heating element is relatively large and the degree of freedom in design is relatively large.

  A thermoacoustic apparatus according to one embodiment of the present invention made to solve the above-described problems is a thermoacoustic apparatus including a heating element formed from a nonwoven sheet containing fibrous carbon nanostructures.

  In the thermoacoustic apparatus according to one aspect of the present invention, it is preferable that the heating element has a three-dimensional shape.

  In the thermoacoustic device according to one aspect of the present invention, the heating element may be formed by bending the nonwoven sheet.

  The thermoacoustic device according to an aspect of the present invention may further include a plurality of electrodes that apply a current to the heating element.

  The thermoacoustic device according to one embodiment of the present invention may include three or more electrodes and two or more heating elements.

  The thermoacoustic device according to one embodiment of the present invention may further include a heating device that irradiates the heating element with light or electromagnetic waves.

  The sound wave inspection apparatus which concerns on another aspect of this invention is a sound wave inspection apparatus provided with the above-mentioned thermoacoustic apparatus and a sound wave receiving element.

  In the present invention, the “fibrous carbon nanostructure” means, for example, a carbon nanotube, a carbon nanohorn, a carbon nanofiber, a carbon nanocoil, a carbon microcoil or the like having a fibrous shape having an outer diameter (fiber diameter) of less than 1 μm. Means a carbon structure. “Nonwoven sheet” means a sheet formed by bonding or intertwining fibers by thermal, mechanical, or chemical action without weaving the fibers. And a concept including not only a flat thing but also a thing formed to have a three-dimensional shape from the beginning like a pulp egg packaging container, for example.

  The thermoacoustic device of the present invention includes a heating element formed from a nonwoven sheet containing fibrous carbon nanostructures (carbon nanotubes, carbon nanohorns, graphene, carbon nanofibers, carbon nanocoils, carbon microcoils, etc.). Therefore, since the rigidity of the heating element can be increased, the strength of the heating element is large and the degree of freedom in design is relatively large.

It is typical sectional drawing which shows the thermoacoustic apparatus which concerns on one Embodiment of this invention. FIG. 2 is a schematic plan view of the thermoacoustic device in FIG. 1. It is a typical top view which shows the thermoacoustic apparatus different from FIG. 1 of this invention. It is typical sectional drawing which shows the thermoacoustic apparatus which concerns on embodiment different from FIG.1 and FIG.3 of this invention. It is typical sectional drawing which shows the thermoacoustic apparatus which concerns on embodiment different from FIG.1, FIG3 and FIG.4 of this invention. It is typical sectional drawing which shows the thermoacoustic apparatus which concerns on embodiment different from FIG.1 and FIG.3 thru | or FIG. 5 of this invention. FIG. 7 is a schematic plan view of the thermoacoustic device in FIG. 6. It is typical sectional drawing which shows the thermoacoustic apparatus which concerns on embodiment different from FIG.1 and FIG.3 thru | or FIG. 6 of this invention. FIG. 9 is a schematic plan view of the thermoacoustic device in FIG. 8. It is typical sectional drawing which shows the thermoacoustic apparatus which concerns on embodiment different from FIG. 1, FIG. 3 thru | or FIG. 6, and FIG. It is typical sectional drawing which shows the thermoacoustic apparatus which concerns on embodiment different from FIG.1, FIG.3 thru | or FIG.6, FIG.8 and FIG.10 of this invention. It is typical sectional drawing which shows the thermoacoustic apparatus which concerns on embodiment different from FIG. 1, FIG. 3 thru | or FIG. 6, FIG. 8, FIG. FIG. 13 is a schematic plan view of the thermoacoustic device in FIG. 12. It is typical sectional drawing which shows the thermoacoustic apparatus which concerns on embodiment different from FIG.1, FIG.3 thru | or FIG.6, FIG.8, FIG.10, FIG.11 and FIG. FIG. 15 is a schematic plan view of the thermoacoustic device in FIG. 14. 1 is a schematic cross-sectional view showing a sound wave inspection apparatus according to an embodiment of the present invention. It is typical sectional drawing which shows the sound wave inspection apparatus which concerns on embodiment different from FIG. 16 of this invention. FIG. 18 is a schematic cross-sectional view showing a sound wave inspection apparatus according to an embodiment different from FIGS. 16 and 17 of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

[First embodiment]
1 and 2 show a thermoacoustic apparatus according to an embodiment of the present invention.

  The thermoacoustic apparatus includes a base member 1 having a rectangular frame shape, a sheet-like heating element 2 disposed so as to span between two sides on both sides in the longitudinal direction of the base member 1, and both longitudinal sides of the heating element 2. And a pair of electrodes 3 provided along the side edges. In other words, in the thermoacoustic apparatus, the heating element 2 is disposed between the pair of electrodes 3. The thermoacoustic apparatus further includes a signal generator 5 that applies a drive current between the pair of electrodes 3 via the wiring 4. The thermoacoustic apparatus further includes a fixing member 6 that fixes the heating element 2 to the base member 1 and a conductive member 7 that connects the wiring 4 to the electrode 3.

  The thermoacoustic device expands a gas (for example, air, nitrogen, helium, etc.) around the heating element 2 by applying a current to the heating element 2 by the signal generator 5 to generate heat. By stopping the current application to the heating element 2 and lowering the temperature of the heating element 2, the gas around the heating element 2 is contracted. As a result, a pressure wave is generated in the gas around the heating element 2, and this is emitted as a sound wave.

[Base member]
The base member 1 is a member that supports the heating element 2, is formed of a sufficiently rigid material, and is substantially immovably arranged by its own inertia or by being fixed to another structure. Is preferred.

[Heating element]
The heating element 2 is formed from a nonwoven sheet containing a plurality of fibrous carbon nanostructures, and is stretched in a plane on the base member 1. Note that the base member 1 may be omitted by improving the rigidity of the end of the heating element 2. As a method of improving the rigidity of the end portion of the heating element 2, for example, the end portion can be bent into an L shape, a U shape, a □ shape, or a ○ shape, and can be bonded as necessary. Good. Further, the rigidity may be improved by increasing the thickness of the end portion of the heating element 2.

  The heating element 2 exhibits conductivity when a plurality of fibrous carbon nanostructures come into contact with each other, and generates heat due to Joule loss when energized.

  As the fibrous carbon nanostructure contained in the heating element 2, carbon nanomaterials such as carbon nanotubes, carbon nanohorns, carbon nanofibers, carbon nanocoils, and carbon microcoils can be used alone or in combination of two or more. . As the carbon nanotube, a single-wall single-wall nanotube (SWNT) or a multi-wall multi-wall nanotube (MWNT) can be used.

  The fibrous carbon nanostructures in the heating element 2 are preferably arranged randomly so as not to have orientation. That is, the heating element 2 preferably has isotropic electrical and mechanical properties in plan view. Thereby, manufacture and handling of the heating element 2 are facilitated, and restrictions on the shape of the heating element 2 are reduced. For example, in order to improve heat dissipation, electrical and mechanical restrictions when opening the heating element 2 are small, and it can be formed at any position with any size.

  The heating element 2 may include a binder. Since the heating element 2 includes a binder, the strength is improved and the scattering of the fibrous carbon nanostructure can also be prevented. Moreover, the freedom degree of the shaping | molding of the heat generating body 2 improves significantly because the heat generating body 2 contains a binder.

  The heating element 2 may contain fibers and additives other than the fibrous carbon nanostructure. The heat generating body 2 is improved in strength by including fibers other than the fibrous carbon nanostructure. Moreover, the electrical resistance of the heating element 2 can be adjusted by doping impurities into the fibrous carbon nanostructure or containing (mixing) fibers other than the fibrous carbon nanostructure.

  As a method for forming the heating element 2, wet papermaking using a fibrous carbon nanostructure, needle punch, stitch bond, chemical bond, or the like can be applied. Moreover, as a formation method of the heat generating body 2, it is good also as a method of producing a carbon nanofiber with the form of a nonwoven sheet from the beginning other than the method of producing a nonwoven sheet using a fibrous carbon nanostructure.

  The wet papermaking using fibrous carbon nanostructures forms a nonwoven fabric containing fibrous carbon nanostructures on the porous body by filtering the solution in which the fibrous carbon nanostructures are dispersed through the porous body, A method may be used in which a carbon nanotube non-woven fabric is peeled off from a porous material and dried. The heating element 2 having a desired three-dimensional shape can be obtained by selecting the surface shape of the porous body that filters the dispersion solution of the fibrous carbon nanostructure.

  Examples of the solvent for the dispersion solution of the fibrous carbon nanostructure include water, alcohols such as methanol, ethanol, and propanol, ketones such as acetone and methyl ethyl ketone, ethers such as tetrahydrofuran, dioxane, and diglyme, such as N Amides such as N, dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, sulfur-containing solvents such as dimethyl sulfoxide, sulfolane, etc. Species or a combination of two or more can be used.

  In addition to the binder, the dispersion solution of fibrous carbon nanostructures may contain, for example, a conductive additive, a dispersant, a surfactant, and the like. As these, known ones can be used as appropriate.

  As the binder, rubber or resin latex can be used.

  Examples of rubber latex include, but are not limited to, natural rubber latex, synthetic diene rubber latex (latex such as butadiene rubber, styrene butadiene rubber, acrylonitrile butadiene rubber, chloroprene rubber, and butyl rubber), ethylene vinyl acetate rubber latex, Examples thereof include vinyl pyridine rubber latex and fluorine rubber latex.

  The latex of the resin is not particularly limited, and for example, polyethylene, polypropylene, styrene resin, acrylic resin, methacrylic resin, organic acid vinyl ester resin, vinyl ether resin, halogen-containing resin, olefin resin And latex such as alicyclic olefin-based resin, polycarbonate, polyester, polyamide, thermoplastic polyurethane, polysulfone, polyphenylene ether, and silicone resin.

  As a method for obtaining carbon nanofibers in the form of a non-woven sheet from the beginning, first, an acrylic nanofiber non-woven sheet made of fibers having a nano-level diameter is obtained by blowing an acrylic solution from a nozzle with a direct current high voltage current and subdividing it. (Electrospinning method). Next, a flameproofing treatment is performed by heating the acrylic nanofiber nonwoven sheet at 220 ° C., for example. Furthermore, the acrylic nanofiber nonwoven sheet is heated, for example, at 1100 ° C. to be carbonized and fired (to form carbon nanofibers). Thereby, the carbon nanofiber nonwoven sheet which can be used as the heat generating body 2 is obtained.

〔electrode〕
It is preferable that the electrode 3 is laminated | stacked on the both ends of the heat generating body 2 over the whole width, respectively. Thereby, the density of the current flowing in the heating element 2 can be made uniform, the efficiency of sound wave generation can be improved, and the durability of the heating element can be improved.

  The electrode 3 may be formed of a conductive paste or the like, or may be a rod-shaped or strip-shaped conductor connected to the heating element 2 with a conductive adhesive or the like.

〔wiring〕
As the wiring 4, for example, a linear conductor such as a covered electric wire can be used, but a conductor containing a fibrous nanocarbon structure such as a carbon nanotube may be used.

[Signal generator]
The signal generator 5 generates a driving current that generates heat from the heating element 2 and supplies the driving current to the heating element 2 through the wiring 4 (and the electrode 3). The drive current is selected according to the application of the thermoacoustic apparatus, and may be a pulse current or a periodic current. The voltage of this drive current can be set to, for example, 5 V or more and 100 V or less. Moreover, as a waveform of a drive current, it can be set as a sine wave, a rectangular wave, a sawtooth wave etc., for example. Moreover, as a frequency in case a drive current is periodic, it can be set as 1 kHz or more and 20 MHz or less, for example.

[Fixing member]
As the fixing member 6, an adhesive can be used. When the base member 1 has conductivity, the base member 1 and the heating element 2 may be insulated by using an insulating adhesive as the fixing member 6, and the base member 1 is insulated from at least one of the base member 1 and the heating element 2. After providing the layer, it may be fixed using a conductive adhesive. Further, it is preferable to use an adhesive having high heat resistance as the fixing member 6.

[Conductive member]
For example, a conductive paste can be used as the conductive member 7. Further, when the electrode 3 is formed of a conductive paste, the conductive member 7 can be omitted.

〔advantage〕
The thermoacoustic device can be manufactured relatively easily and inexpensively by using the heating element 2 formed of a nonwoven sheet containing fibrous carbon nanostructures, so that the strength of the heating element 2 is relatively large. The output of the device can be increased and the size can be reduced.

[Second Embodiment]
FIG. 3 shows a thermoacoustic apparatus according to an embodiment different from FIG. 1 of the present invention.

  The thermoacoustic apparatus includes a rectangular frame-shaped base member 1, a plurality of heating elements 2 a arranged to extend in parallel between two longitudinal sides of the base member 1, and the heating element 2 a A plurality of pairs of electrodes 3a provided along side edges on both sides in the longitudinal direction. Further, the thermoacoustic apparatus includes a wiring 4 for applying a driving current between the electrodes 3a at both ends of each heating element 2a, a conductive member 7, and a signal generator (not shown).

  The thermoacoustic apparatus can generate a sound wave independently from each heating element 2a by individually applying a current from the signal generator to the plurality of heating elements 2a via the wiring 4.

[Base member]
The configuration of the base member 1 in the thermoacoustic device of FIG. 3 can be the same as the configuration of the base member 1 in the thermoacoustic device of FIG.

[Heating element]
The heating element 2a is a belt-like body formed from a nonwoven sheet containing a plurality of fibrous carbon nanostructures, and is stretched on the base member 1 in parallel with each other at equal intervals.

  The configuration of the heating element 2a in the thermoacoustic apparatus of FIG. 3 can be the same as that of the heating element 2 in the thermoacoustic apparatus of FIG. 1 except that the planar shape and the number are different.

〔electrode〕
It is preferable that the electrode 3a is laminated | stacked over the whole width | variety, respectively at the both ends of each heat generating body 2a. The configuration of the electrode 3a in the thermoacoustic device of FIG. 3 can be the same as the configuration of the electrode 3 in the thermoacoustic device of FIG. 1 except that the electrode 3a is provided in each heating element 2a.

〔advantage〕
In the thermoacoustic apparatus, each heating element 2a can individually generate sound waves by using a plurality of heating elements 2a formed from a nonwoven sheet containing fibrous carbon nanostructures. For this reason, the thermoacoustic apparatus can be used as a transmission probe for an ultrasonic flaw detector by a phased array method. Specifically, by separately controlling the energization timing of each heating element 2a, it is possible to transmit a plurality of ultrasonic waves from each heating element 2a and form a single wavefront running in the intended direction.

[Third embodiment]
FIG. 4 shows a thermoacoustic apparatus according to an embodiment different from FIGS. 1 to 3 of the present invention.

  The thermoacoustic device includes a rectangular frame-shaped base member 1, a heating element 2b arranged so as to span between two sides on both sides in the longitudinal direction of the base member 1, and side edges on both sides in the longitudinal direction of the heating element 2b. And a plurality of pairs of electrodes 3 provided along. Further, the thermoacoustic apparatus includes a wiring (not shown) for applying a driving current between the electrodes 3 at both ends of the heating element 2b and a signal generator.

[Base member]
The configuration of the base member 1 in the thermoacoustic apparatus of FIG. 4 can be the same as the configuration of the base member 1 in the thermoacoustic apparatus of FIG.

[Heating element]
The heating element 2b is formed from a non-woven sheet containing a plurality of fibrous carbon nanostructures, and has a three-dimensional shape that is curved in an arc shape in a sectional view so as to be recessed inside the base member 1.

  The configuration of the heating element 2b in the thermoacoustic apparatus of FIG. 4 can be the same as that of the heating element 2 in the thermoacoustic apparatus of FIG. 1 except that the cross-sectional shape is different.

〔electrode〕
The configuration of the electrode 3 in the thermoacoustic apparatus in FIG. 4 can be the same as the configuration of the electrode 3 in the thermoacoustic apparatus in FIG.

〔advantage〕
The thermoacoustic apparatus can maintain the shape of the cylindrical surface of the heating element 2b by using the plurality of heating elements 2b formed from a nonwoven sheet containing fibrous carbon nanostructures. Thereby, the acoustic device can converge the sound wave generated from the heating element 2b near the center line of the cylindrical surface of the heating element 2b. For this reason, the resolution can be greatly improved by using the said thermoacoustic apparatus for the transmission probe of an ultrasonic flaw detector.

[Fourth embodiment]
FIG. 5 shows a thermoacoustic apparatus according to an embodiment different from FIGS. 1 to 4 of the present invention.

  The thermoacoustic apparatus includes a rectangular frame-shaped base member 1, a heating element 2 c arranged so as to span between two sides on both sides in the longitudinal direction of the base member 1, and side edges on both sides in the longitudinal direction of the heating element 2 c. And a plurality of pairs of electrodes 3 provided along. Further, the thermoacoustic apparatus includes a wiring (not shown) for applying a driving current between the electrodes 3 at both ends of the heating element 2c and a signal generator.

[Base member]
The configuration of the base member 1 in the thermoacoustic device of FIG. 5 can be the same as the configuration of the base member 1 in the thermoacoustic device of FIG.

[Heating element]
The heating element 2c is formed from a non-woven sheet containing a plurality of fibrous carbon nanostructures, and is curved in a generally arcuate shape in a cross-sectional view so as to be recessed inside the base member 1, and periodically so as to have a fine waveform. It has a three-dimensional shape bent.

  The configuration of the heating element 2c in the thermoacoustic apparatus of FIG. 5 can be the same as that of the heating element 2 in the thermoacoustic apparatus of FIG. 1 except that the cross-sectional shape is different.

〔electrode〕
The configuration of the electrode 3 in the thermoacoustic device of FIG. 5 can be the same as the configuration of the electrode 3 in the thermoacoustic device of FIG.

〔advantage〕
The thermoacoustic device uses a plurality of heating elements 2c formed from a non-woven sheet containing a plurality of fibrous carbon nanostructures, so that the heating element 2c retains the shape of the undulating cylinder. be able to. Accordingly, the acoustic device can converge the sound wave generated from the heating element 2c near the center line of the cylindrical surface of the heating element 2c, and the sound pressure of the sound wave generated when the area of the heating element 2c is large. Is relatively large. For this reason, the thermoacoustic apparatus can be increased in output or reduced in size. Further, by adopting a waved shape, the rigidity of the non-woven sheet containing carbon nanotubes is increased to prevent deformation, and as a result, the position and sound pressure at which the sound waves converge can be maintained. Rigidity can be further increased by adopting an egg pack shape or a waffle shape instead of the wavy shape.

[Fifth embodiment]
6 and 7 show a thermoacoustic apparatus according to an embodiment different from FIGS. 1 to 5 of the present invention.

  The thermoacoustic apparatus includes a circular frame-shaped base member 1d, a substantially spherical heating element 2d whose outer periphery is held by the base member 1d, a first electrode 8 provided along the outer edge of the heating element 2d, A first electrode 8 and a concentric annular second electrode 9 provided on the back surface of the heating element 2d, and an edge-shaped or point-like third electrode 10 provided in the central portion in plan view of the back surface of the heating element 2d are provided.

  Further, the thermoacoustic device includes a wiring (not shown) that applies a drive current independently between the first electrode 8 and the second electrode 9 and between the second electrode 9 and the third electrode 10 of the heating element 2d. A signal generator. As this signal generator, for example, it is connected to the ground of the second electrode 9 and the magnitude of the current and the timing of energization between these ground and the first electrode 8 and the third electrode 10 can be controlled separately. can do.

[Base member]
The configuration of the base member 1d in the thermoacoustic device in FIG. 6 can be the same as the configuration of the base member 1 in the thermoacoustic device in FIG. 1 except for a planar shape.

[Heating element]
The heating element 2d is formed of a non-woven sheet containing a plurality of fibrous carbon nanostructures, has a spherical shape so as to be recessed inside the base member 1d, and a planar flange whose outer peripheral portion is supported by the base member 1d. It has a three-dimensional shape.

  The configuration of the heating element 2d in the thermoacoustic device in FIG. 6 can be the same as that of the heating element 2 in the thermoacoustic device in FIG. 1 except that the shape is different.

〔electrode〕
The configuration of the electrodes 6, 7, and 8 in the thermoacoustic device in FIG. 6 can be the same as the configuration of the electrode 3 in the thermoacoustic device in FIG. 1 except that the shape and the arrangement position are different.

〔advantage〕
The thermoacoustic apparatus can form the heating element 2d into a spherical shape by using the plurality of heating elements 2d formed from a nonwoven sheet containing a plurality of fibrous carbon nanostructures. Yes.

  The thermoacoustic apparatus can converge the sound wave generated by the heating element 2d to a substantially central point of the spherical surface by forming the heating element 2d into a spherical shape in this way. For this reason, the resolution can be greatly improved by using the said thermoacoustic apparatus for the transmission probe of an ultrasonic flaw detector.

  Further, as shown in FIG. 7, the thermoacoustic apparatus has the heating element 2 d substantially having a portion between the first electrode 8 and the second electrode 9 and a portion between the second electrode 9 and the third electrode 10. Two heating elements are provided. For this reason, a drive current can be individually applied to the portion between the first electrode 8 and the second electrode 9 and the portion between the second electrode 9 and the third electrode 10 to generate sound waves. In this way, in the thermoacoustic apparatus, since the heating element 2d is substantially divided into two heating elements, the energization amount of each can be increased and the sound pressure of the generated sound wave can be increased.

[Sixth embodiment]
8 and 9 show a thermoacoustic apparatus according to an embodiment different from FIGS. 1 to 7 of the present invention.

  The thermoacoustic apparatus includes a rectangular frame-shaped base member 1, a plurality of strip-shaped heating elements 2 e that are stretched in parallel between two sides on both sides in the longitudinal direction of the base member 1, and the plurality of heating elements 2 e in series. A plurality of intermediate electrodes 11 that alternately connect the end portions of two adjacent heating elements 2e, and a pair of external electrodes 12 that are provided at the ends where the intermediate electrodes 11 of the heating elements 2e at both ends are not provided. With. Further, the thermoacoustic apparatus includes a wiring (not shown) for applying a driving current between the pair of external electrodes 12 and a signal generator.

[Base member]
The configuration of the base member 1 in the thermoacoustic apparatus in FIG. 8 can be the same as the configuration of the base member 1 in the thermoacoustic apparatus in FIG.

[Heating element]
The plurality of heating elements 2e are formed by bending a non-woven sheet containing a plurality of fibrous carbon nanostructures into a bellows shape, and are supported on the base member 1 in parallel with each other at equal intervals.

  The configuration of the heating element 2e in the thermoacoustic device in FIG. 8 can be the same as that of the heating element 2 in the thermoacoustic device in FIG.

  The heating element 2e is bent so as to form a mountain shape (V shape) having a constant height in a sectional view, and the sound pressure of the generated sound wave is increased by increasing the area.

  The height of the chevron of the heating element 2e bent in this way is preferably smaller than the wavelength of the sound wave to be generated. Thereby, it is possible to generate sound waves having the same phase.

〔electrode〕
The intermediate electrode 11 and the external electrode 12 are preferably laminated over the entire width at both ends of each heating element 2e. The material of the intermediate electrode 11 and the external electrode 12 in the thermoacoustic apparatus of FIG. 8 can be the same as the material of the electrode 3 in the thermoacoustic apparatus of FIG.

〔advantage〕
Since the thermoacoustic apparatus includes the heating element 2e bent in a bellows shape, the output can be increased or reduced in size.

[Seventh embodiment]
FIG. 10 shows a thermoacoustic apparatus according to an embodiment different from FIGS. 1 to 9 of the present invention.

  The thermoacoustic apparatus includes a rectangular frame-shaped base member 1, a plurality of strip-shaped heating elements 2 f that are stretched in parallel between two sides on both sides in the longitudinal direction of the base member 1, and the plurality of heating elements 2 f in series. A plurality of intermediate electrodes 11 that alternately connect the ends of two adjacent heating elements 2f so as to be connected to each other, and a pair of external electrodes 12 that are provided at the ends where the intermediate electrodes 11 of the heating elements 2f at both ends are not provided. With. Further, the thermoacoustic apparatus includes a wiring (not shown) for applying a driving current between the pair of external electrodes 12 and a signal generator.

[Base member]
The configuration of the base member 1 in the thermoacoustic device of FIG. 10 can be the same as the configuration of the base member 1 in the thermoacoustic device of FIG.

[Heating element]
The plurality of heating elements 2f are supported on the base member 1 in parallel with each other at equal intervals. Each heating element 2f is formed by bending a non-woven sheet containing a plurality of fibrous carbon nanostructures into a rectangular wave shape in a sectional view.

  The configuration of the heating element 2f in the thermoacoustic apparatus of FIG. 10 can be the same as that of the heating element 2e in the thermoacoustic apparatus of FIG.

〔electrode〕
The electrode 3 in the thermoacoustic apparatus of FIG. 10 can be the same as the electrode 3 in the thermoacoustic apparatus of FIG.

〔advantage〕
Since the thermoacoustic apparatus includes the heating element 2f that is bent in a rectangular wave shape in a cross-sectional view, the output can be increased or the size can be reduced.

[Eighth embodiment]
FIG. 11 shows a thermoacoustic apparatus according to an embodiment different from FIGS. 1 to 10 of the present invention.

  The thermoacoustic apparatus includes a rectangular frame-shaped base member 1, a plurality of strip-shaped heating elements 2 g that are stretched in parallel between two sides on both sides in the longitudinal direction of the base member 1, and the plurality of heating elements 2 g in series. A plurality of intermediate electrodes 11 that alternately connect the end portions of two adjacent heating elements 2g so as to be connected to each other, and a pair of external electrodes 12 that are provided at the ends where the intermediate electrodes 11 of the heating elements 2g at both ends are not provided. With. Further, the thermoacoustic device is provided with a wiring and a signal generator (not shown) for applying a driving current between the pair of external electrodes 12 and a porous member disposed on the back surface of the base member 1 (the side opposite to the heating element 2b). And a member 13.

[Base member]
The configuration of the base member 1 in the thermoacoustic apparatus of FIG. 11 can be the same as the configuration of the base member 1 in the thermoacoustic apparatus of FIG.

[Heating element]
The plurality of heating elements 2g are supported on the base member 1 in parallel with each other at equal intervals. Each heating element 2g is formed by bending a nonwoven sheet containing a plurality of fibrous carbon nanostructures.

  The heating element 2g in the thermoacoustic device of FIG. 11 has a heat radiating fin by reducing the length (width) of the top of the heating element 2f in the thermoacoustic device of FIG. 10 and increasing the length (width) of the bottom. It also has a role.

  By increasing the height of each heating element 2g from the bottom to the top (convex part) and by taking a relatively large distance between the top and bottom of the heating element 2g (cooling in the region surrounded by the heating elements 2g). For better air flow. A fan may be used to increase the flow velocity in the vicinity of the convex portion of each heating element 2g, or a part of the convex portion of each heating element 2g may be cut to form a columnar convex.

〔electrode〕
The electrode 3 in the thermoacoustic apparatus of FIG. 11 can be the same as the electrode 3 in the thermoacoustic apparatus of FIG.

(Porous member)
The porous member 13 is connected to the base member 1 using an adhesive (not shown) or the like. For example, when the porous member 13 is used as a transmission probe for an ultrasonic flaw detector, a sound wave generated from the back surface of the heating element 2b is absorbed by the porous member 13, thereby reducing background noise. The N ratio can be improved.

〔advantage〕
Since the thermoacoustic device includes the heating element 2g that is bent in a rectangular wave shape in cross-sectional view and has a function of a heat radiating fin, the output can be increased or the size can be reduced. In addition, since the thermoacoustic apparatus has the porous member 13 that absorbs unnecessary sound waves from the back surface of the heating element 2g, it can be used as a transmission probe for an ultrasonic flaw detection apparatus so that ultrasonic flaw detection with a high S / N ratio can be performed. It becomes possible.

[Ninth embodiment]
12 and 13 show a thermoacoustic apparatus according to an embodiment different from FIGS. 1 to 11 of the present invention.

  The thermoacoustic device includes a plate-like base member 1h, and a plurality of through electrodes 14a and 14b disposed at a portion where the heating element 2h disposed on the surface of the base member 1h and the heating element 2h of the base member 1h are in contact with each other. , 14c, 14d, 14e, 14f, 14g, 14h, and 14i. A hole 15 is formed in the base member 1h. Further, the thermoacoustic device includes a wiring (not shown) for applying a driving current to the plurality of through electrodes 14a, 14b, 14c, 14d, 14e, 14f, 14g, 14h, and 14i and a signal generator.

[Base member]
The base member 1h in the thermoacoustic apparatus of FIG. 12 is formed of an insulating material, and holds the heating element 2h and the plurality of through electrodes 14a, 14b, 14c, 14d, 14e, 14f, 14g, 14h, and 14i.

  The base member 1h is formed in parallel at equal intervals and has a plurality of slit-like holes 15 penetrating the front and back.

[Heating element]
The plurality of heating elements 2h are formed by bending a single nonwoven sheet containing a plurality of fibrous carbon nanostructures, and a plurality of through electrodes 14a, 14b, 14c, 14d, and the like disposed on the base member 1h. 14e, 14f, 14g, 14h, 14i, a plurality of bottom portions 16, a plurality of wall portions 17 extending upward from the bottom portion 16, and a plurality of top portions 18 connecting the upper ends of the adjacent wall portions 17. Have.

  The bottom portion 16 and the wall portion 17 are planar, and the top portion 18 is curved upwardly. Further, the bending angle at the boundary between the bottom portion 16 and the wall portion 17 is larger than 90 degrees, and the bending angle at the boundary between the wall portion 17 and the top portion 18 is smaller than 90 degrees. The boundary between the wall portion 17 and the top portion 18 may be rounded and curved. Thereby, when the air in the space surrounded by the heating element 2h and the base member 1h in a cross-sectional view expands, the bending stress acting on the boundary between the wall portion 17 and the top portion 18 can be reduced.

  The plurality of top portions 18 of the heating element 2h are respectively disposed above the holes 15 of the base member 1h, and the plurality of bottom portions 16 of the heating element 2h are disposed so as not to overlap the hole 15 of the base member 1h. . Accordingly, the space surrounded by the opposing wall portion 17 and the top portion 18 of the heating element 2h in a cross-sectional view communicates with the external space on the back surface side of the base member 1h through the hole portion 15. Thereby, since the thermoacoustic device can discharge part of the air in the space to the outside when the air in the space surrounded by the wall portion 17 and the top portion 18 expands, the heating element 2h. The heat applied to the heat generating element 2h is excellent. For simplification of the structure, the hole 15 may be omitted.

〔electrode〕
Each penetration electrode 14a, 14b, 14c, 14d, 14e, 14f, 14g, 14h, 14i includes a strip-shaped distribution portion 19 disposed on the surface of the base member 1h, and one or a plurality of penetration portions penetrating the base member 1h. 20. The distribution unit 19 may be, for example, a conductive adhesive that fixes the bottom 16 of the heat generating element 2h to the base member 1h and electrically connects the bottom 16 and the through 20, and is connected to the through 20. It may have a strip-shaped conductor layer and a conductive adhesive or the like that connects the conductor layer and the bottom portion 16 of the heating element 2h.

〔advantage〕
The thermoacoustic apparatus is configured to bend a single non-woven sheet to form a plurality of bottom parts 16, wall parts 17 and top parts 18, thereby generating an acoustic wave of the heating element 2h as compared to the area in plan view. Therefore, it is possible to increase the output or reduce the size.

  In addition, since the thermoacoustic apparatus can be driven by dividing the heating element 2h into a plurality of portions, it can be used as a transmission probe for an ultrasonic flaw detector by a phased array method by sequentially driving them. For example, each through electrode 14a, 14c, 14e, 14g, 14i is connected to the ground, and the timing of energization between these ground and each through electrode 14b, 14d, 14f, 14h is controlled separately, thereby generating individual heat generation. A plurality of ultrasonic waves can be transmitted from the body 2h to form a single wavefront that runs in the intended direction.

[Tenth embodiment]
14 and 15 show a thermoacoustic apparatus according to an embodiment different from FIGS. 1 to 13 of the present invention.

  The thermoacoustic apparatus includes a plate-like base member 1i, and a plurality of through electrodes 14a and 14b disposed at a portion where the heating element 2i disposed on the surface of the base member 1i and the heating element 2i of the base member 1i are in contact. , 14c, 14d, 14e, 14f, 14g, 14h, and 14i. Further, the thermoacoustic apparatus includes a wiring (not shown) for applying a driving current between the pair of external electrodes 12 and a signal generator.

[Base member]
The base member 1i in the thermoacoustic apparatus of FIG. 14 is formed of an insulating material, and holds the heating element 2i and the plurality of through electrodes 14a, 14b, 14c, 14d, 14e, 14f, 14g, 14h, and 14i.

[Heating element]
The plurality of heating elements 2i are formed by bending a single nonwoven sheet containing a plurality of carbon nanotubes, and a plurality of through electrodes 14a, 14b, 14c, 14d, 14e, 14f, and the like disposed on the base member 1i. 14 g, 14 h, 14 i have a plurality of bottom portions 16, a plurality of wall portions 17 extending upward from the bottom portion 16, and a plurality of top portions 18 connecting between the upper ends of the adjacent wall portions 17.

  The bottom portion 16 and the wall portion 17 are planar, and the top portion 18 is curved upwardly. Further, the bending angle at the boundary between the bottom portion 16 and the wall portion 17 is larger than 90 degrees, and the bending angle at the boundary between the wall portion 17 and the top portion 18 is smaller than 90 degrees. The boundary between the wall portion 17 and the top portion 18 may be rounded and curved. Thereby, when the air in the space surrounded by the heating element 2i and the base member 1i expands in cross-sectional view, the bending stress acting on the boundary between the wall portion 17 and the top portion 18 can be reduced.

  The heating element 2 i has a plurality of ventilation holes 21 formed side by side at the tops 18. Thereby, since the said thermoacoustic apparatus can discharge some air in the said space outside when the air in the space enclosed by the wall part 17 and the top part 18 expand | swells, the heat generating body 2i In addition to reducing the stress applied to the heating element 2i, the heat dissipation of the heating element 2i is excellent.

  Instead of providing the vent hole 21 at the top portion 18, it may be formed at both the top portion 18 and the wall portion 17, at the wall portion 17, or at the boundary portion between the top portion 18 and the wall portion 17. Further, the air holes 21 may be omitted for the sake of simplification of the structure.

[Eleventh embodiment]
FIG. 16 shows a configuration of a sound wave inspection apparatus according to an embodiment of the present invention.

  The sound wave inspection apparatus includes a thermoacoustic device 31 that is another embodiment of the present invention and a sound wave receiving element 32, and a cylindrical workpiece disposed between the thermoacoustic device 31 and the sound wave receiving element 32. This is an ultrasonic flaw detection ultrasonic inspection apparatus that inspects W scratches using ultrasonic waves generated by the thermoacoustic apparatus 31.

[Thermoacoustic device]
The thermoacoustic device 31 includes a cylindrical base member 33, a heating element 34 disposed inside the base member 33, a plurality of fixing members 35 that connect the base member 33 and the heating element 34, and the base member 33. And a pair of through electrodes 36 connected to both ends of the heating element 34, wiring (not shown) for applying a drive current between the pair of through electrodes 36, and a signal generator.

<Base member>
The base member 33 is a structural material that is formed of a material having insulation and rigidity and supports the heating element 34. Note that a hole may be formed in the base member 33 in order to improve heat dissipation from the heating element 34.

<Heating element>
The heating element 34 is formed by bending one nonwoven sheet containing a plurality of fibrous carbon nanostructures. More specifically, the heating element 34 is attached to the inner peripheral surface of the base member 33 using a fixing member 35, and a plurality of strip-shaped bottom portions 37 extending in the axial direction of the base member 33, and the base member 33 from the bottom portion 37. A plurality of wall portions 38 extending toward the central axis side and a plurality of top portions 39 connecting the adjacent wall portions 38 and facing the central axis of the base member 33 are provided. In addition, in order to improve heat dissipation, you may form a vent hole in the heat generating body 34. FIG.

  The configuration of the nonwoven sheet forming the heating element 34 of the thermoacoustic device 31 of FIG. 16 can be the same as that of the nonwoven sheet forming the heating element 2 of the thermoacoustic device of FIG.

<Penetration electrode>
In the thermoacoustic device 31, the pair of through electrodes 36 are electrically connected to both ends of the heating element 34, but the plurality of through electrodes 36 are electrically connected to the bottoms 37 of the heating element 34, and It may be configured such that a current can be applied independently between the bottom portions 37 of the heating elements 34 by being connected to every other.

[Sound wave receiving element]
The sound wave receiving element 32 has a plurality of sensors that receive the sound wave generated by the thermoacoustic device 31 and passed through the workpiece W and convert it into an electrical signal.

〔advantage〕
Since the sound wave inspection apparatus includes the heating element 34 formed by bending a non-woven sheet containing a fibrous carbon nanostructure and includes the thermoacoustic apparatus 31 that efficiently generates sound waves, Defects such as bubbles can be detected relatively accurately.

[Twelfth embodiment]
FIG. 17 shows a configuration of a sound wave inspection apparatus according to an embodiment different from FIG. 16 of the present invention.

  The sound wave inspection apparatus includes a thermoacoustic device 31a which is another embodiment of the present invention and a sound wave receiving element 32a, and has a rectangular cylindrical shape disposed between the thermoacoustic device 31a and the sound wave receiving element 32a. It is an ultrasonic flaw detection sound wave inspection apparatus that inspects the scratches on the workpiece Wa with ultrasonic waves generated by the thermoacoustic device 31a.

[Thermoacoustic device]
The thermoacoustic device 31a includes a square cylindrical base member 33a, a heating element 34a disposed outside the base member 33a, a plurality of fixing members 35a connecting the base member 33a and the heating element 34a, and a base member A pair of through-electrodes 36a disposed between 33a and the heating element 34a, a wiring (not shown) for applying a drive current between the pair of through-electrodes 36a, and a signal generator are provided.

<Base member>
The base member 33a is a structural material that is formed of a material having insulation and rigidity and supports the heating element 34a. In order to improve heat dissipation, a hole may be formed in the base member 33a.

<Heating element>
The heating element 34a is formed by bending one nonwoven sheet containing a plurality of fibrous carbon nanostructures. More specifically, the heating element 34a is attached to the outer peripheral surface of the base member 33a, and adjacent to a plurality of strip-shaped bottom portions 37a extending in the axial direction of the base member 33a, and a plurality of wall portions 38a extending outward from the bottom portion 37a. And a plurality of top portions 39a connecting the wall portions 38a. In addition, in order to improve heat dissipation, you may form a vent hole in the heat generating body 34a.

  The configuration of the nonwoven sheet forming the heating element 34a of the thermoacoustic device 31a of FIG. 17 can be the same as that of the nonwoven sheet forming the heating element 2 of the thermoacoustic device of FIG.

<Penetration electrode>
In the thermoacoustic device 31a, the pair of through electrodes 36a are electrically connected to both ends of the heating element 34a, but the plurality of through electrodes 36a are electrically connected to the bottoms 37a of the heating element 34a, and It may be configured such that an electric current can be applied independently between the bottom portions 37a of the heating elements 34a by being connected to every other.

[Sound wave receiving element]
The sound wave receiving element 32a includes a plurality of sensors that are generated by the thermoacoustic device 31a and receive sound waves that have passed through the workpiece Wa and convert them into electrical signals.

〔advantage〕
Since the sound wave inspection apparatus includes a heating element 34a formed by bending a non-woven sheet containing fibrous carbon nanostructures and includes a thermoacoustic apparatus 31a that efficiently generates sound waves, Defects such as bubbles can be detected relatively accurately.

[Thirteenth embodiment]
FIG. 18 shows a configuration of a sound wave inspection apparatus according to an embodiment different from FIGS. 16 and 17 of the present invention.

  The sound wave inspection apparatus includes a thermoacoustic device 31b which is another embodiment of the present invention and a sound wave receiving element 32b, and is a cylindrical workpiece disposed between the thermoacoustic device 31b and the sound wave receiving element 32b. This is an ultrasonic flaw detection sound wave inspection apparatus that inspects Wb scratches with ultrasonic waves generated by the thermoacoustic apparatus 31b.

[Thermoacoustic device]
The thermoacoustic device 31 b includes a cylindrical heating device 40, a heating element 34 b disposed inside the heating device 40, wiring (not shown) that applies a drive current to the heating device 40, and a signal generator.

<Heating device>
The heating device 40 can heat the heating element 34b disposed inside the heating device 40 in a non-contact manner. As the heating device 40, for example, a light energy generating unit such as a lamp or a laser is provided, and the heating element 2 is irradiated with light energy from the light energy generating unit, thereby heating the entire surface of the heating element 34b or scanning a part thereof. (Scan) Heat.

  As the heating device 40, instead of using light energy generating means, electromagnetic wave generating means such as an IH coil for inductively heating the heating element 34b by irradiating the heating element 34b with an electromagnetic wave or a magnetron for microwave heating may be used.

<Heating element>
The heating element 34b is formed by bending one nonwoven sheet containing a plurality of fibrous carbon nanostructures into a cylindrical shape and joining both ends of the heating element 34b with a conductive member (not shown). In order to increase the surface area by bending the heating element 34b, to make the surface irradiated with light fluff, or to improve heat dissipation, a hole may be formed in the heating element 34b.

  When heating the heating element 34b using electromagnetic wave generating means such as magnetron, the heating element 34b preferably contains a carbon nanocoil or a carbon microcoil as a fibrous carbon nanostructure.

  The configuration of the nonwoven sheet forming the heating element 34b of the thermoacoustic device 31b of FIG. 18 can be the same as that of the nonwoven sheet forming the heating element 34b of the thermoacoustic device of FIG.

[Sound wave receiving element]
The sound wave receiving element 32a includes a plurality of sensors that are generated by the thermoacoustic device 31a and receive sound waves that have passed through the workpiece Wa and convert them into electrical signals.

〔advantage〕
Since these non-contact heating methods do not require wiring, electrodes, and joints in the heating element 34b, the structure of the thermoacoustic device 31b can be simplified, reduced in weight, reduced in size and arrayed (multiple pixels). . When used as a transmission probe for an ultrasonic flaw detector, the periphery of the work is used, there is a problem that the wiring is easily disconnected, and the risk of disconnection increases particularly when the probe is driven at high speed. For this problem, by fixing the heating device 40 and scanning the optical system, it is possible to generate an ultrasonic wave of a necessary sound pressure from an arbitrary place of the heating element 34b without a cable. The risk of disconnection can be greatly reduced and inspection speed can be increased easily. In addition, you may arrange | position the heat generating body 34b so that a movement is possible.

[Other Embodiments]
The said embodiment does not limit the structure of this invention. Therefore, in the above-described embodiment, components of each part of the above-described embodiment can be omitted, replaced, or added based on the description and common general knowledge of the present specification, and they are all interpreted as belonging to the scope of the present invention. Should.

  In the thermoacoustic apparatus, the three-dimensional shape of the heating element may be formed by papermaking.

  The sound wave inspection apparatus is not limited to one that inspects a cylindrical workpiece. The thermoacoustic apparatus may be formed by combining, for example, the thermoacoustic apparatus as described in the first to tenth embodiments and a sound wave detecting element. It may be a scanning type device that moves any of the above.

  The thermoacoustic apparatus according to the present invention can be particularly suitably used for an ultrasonic flaw detection sound inspection apparatus.

1, 1d, 1h, 1i, 33, 33a Base members 2, 2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h, 2i, 34, 34a, 34b Heating element 3, 3a Electrode 4 Wiring 5 Signal generator 6, 35, 35a Fixing member 7 Conductive member 8 First electrode 9 Second electrode 10 Third electrode 11 Intermediate electrode 12 External electrode 13 Porous members 14a, 14b, 14c, 14d, 14e, 14f, 14g, 14h, 14i, 36, 36a Through-electrode 15 Hole 16, 37, 37a Bottom 17, 38, 38a Wall 18, 39, 39a Top 19 Distributor 20 Through-hole 21 Vent 31, 31a, 31b Thermoacoustic device 32, 32a, 32b Sound wave Receiver 40 Heating device W, Wa, Wb Workpiece

Claims (7)

  A thermoacoustic apparatus provided with the heat generating body formed from the nonwoven sheet containing a fibrous carbon nanostructure.   The thermoacoustic device according to claim 1, wherein the heating element has a three-dimensional shape.   The thermoacoustic device according to claim 2, wherein the heating element is formed by bending the nonwoven sheet.   The thermoacoustic device according to claim 1, further comprising a plurality of electrodes for applying a current to the heating element.   The thermoacoustic device according to claim 4, comprising three or more electrodes and two or more heating elements.   The thermoacoustic device according to claim 1, further comprising a heating device that irradiates the heating element with light or electromagnetic waves. The thermoacoustic device according to any one of claims 1 to 6,
A sound wave inspection apparatus comprising: a sound wave receiving element.

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