WO2013190852A1 - Élément de mise en correspondance acoustique et son procédé de fabrication, émetteur/récepteur d'onde ultrasonore l'utilisant et débitmètre ultrasonore - Google Patents

Élément de mise en correspondance acoustique et son procédé de fabrication, émetteur/récepteur d'onde ultrasonore l'utilisant et débitmètre ultrasonore Download PDF

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Publication number
WO2013190852A1
WO2013190852A1 PCT/JP2013/003892 JP2013003892W WO2013190852A1 WO 2013190852 A1 WO2013190852 A1 WO 2013190852A1 JP 2013003892 W JP2013003892 W JP 2013003892W WO 2013190852 A1 WO2013190852 A1 WO 2013190852A1
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Prior art keywords
acoustic matching
matching member
particles
dry gel
ultrasonic
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PCT/JP2013/003892
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English (en)
Japanese (ja)
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永原　英知
佐藤　真人
足立　明久
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パナソニック株式会社
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Priority to JP2014520963A priority Critical patent/JPWO2013190852A1/ja
Publication of WO2013190852A1 publication Critical patent/WO2013190852A1/fr

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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/02—Mechanical acoustic impedances; Impedance matching, e.g. by horns; Acoustic resonators
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/66—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
    • G01F1/662—Constructional details

Definitions

  • the present invention relates to an acoustic matching member for an ultrasonic transducer and a method for manufacturing the same.
  • an acoustic matching member to which dry gel is applied in order to transmit and receive ultrasonic waves to and from various gases with high sensitivity, an acoustic matching member to which dry gel is applied, a manufacturing method thereof, an ultrasonic transducer and an ultrasonic flowmeter using the acoustic matching member.
  • Patent Document 1 is an ultrasonic transducer including a piezoelectric body and an acoustic matching layer, wherein the acoustic matching layer is made of a dry gel of an inorganic oxide or an organic polymer, and the solid skeleton portion of the dry gel is hydrophobized.
  • An ultrasonic transmitter / receiver is disclosed.
  • An object of the present invention is to provide an acoustic matching member having an acoustic impedance that is difficult to obtain with only a dry gel, using the dry gel.
  • an ultrasonic transducer including the acoustic matching member, a manufacturing method thereof, and an ultrasonic flowmeter including the ultrasonic transducer is there.
  • the acoustic matching member of the present invention is an acoustic matching member composed of dry gel particles and binding particles, and the dry gel particles have fine pores therein and hold interparticle voids between the dry gel particles.
  • the binding particles are present between the dry gel particles to bond the dry gel particles, and the average particle diameter of the binding particles is larger than the average size of the fine pores of the dry gel particles, It is smaller than the average size of the interparticle voids of the dried gel particles.
  • the dry gel particle may have a solid skeleton portion made of silica.
  • the average size of the fine holes may be 100 nm or less.
  • the average size of the fine holes may be less than 50 nm.
  • an average particle diameter of the dry gel particles may be 1 ⁇ m or more.
  • the average particle diameter of the binding particles may be 50 nm or more and 10 ⁇ m or less.
  • the binding particles may be an organic polymer.
  • the organic polymer may be epoxy.
  • the epoxy may have an average molecular weight of 1000 to 100,000.
  • the ultrasonic transducer of the present invention includes an electromechanical transducer having electrodes on both surfaces, and any one of the acoustic matching members bonded to the acoustic wave emitting surface of the electromechanical transducer.
  • the ultrasonic flowmeter of the present invention uses any of the ultrasonic transducers described above.
  • the method for producing an acoustic matching member of the present invention includes a step of removing the aqueous solvent from the dispersion obtained by mixing the dried gel particles and the emulsion resin dispersed in the aqueous solvent, and performing a heat treatment to integrate them.
  • the average particle diameter of the emulsion resin may be smaller than the average particle diameter of the dried gel particles.
  • the average size of the fine pores of the dried gel particles may be smaller than the average particle size of the emulsion resin.
  • the acoustic matching member of the present invention can provide an acoustic matching member having an acoustic impedance that is difficult to obtain by using only the dried gel, using the dried gel.
  • An acoustic matching member having various acoustic impedances, an ultrasonic transducer including the acoustic matching member, a manufacturing method thereof, and an ultrasonic flowmeter including the ultrasonic transducer can be provided.
  • FIG. 1 is a perspective view showing the appearance of the ultrasonic transducer according to the first embodiment.
  • FIG. 2 is a schematic diagram showing the fine structure of the acoustic matching member in the first embodiment.
  • FIG. 3 is a diagram illustrating a manufacturing process procedure of the ultrasonic transducer according to the first embodiment.
  • FIG. 4 is a diagram illustrating a manufacturing process procedure of the ultrasonic transducer according to the first embodiment.
  • FIG. 5 is a diagram showing the relationship between the binding particle size and the molecular weight in the first embodiment.
  • FIG. 6 is a diagram illustrating a casting jig for the acoustic matching member according to the first embodiment.
  • FIG. 7A is a diagram showing the transmission / reception characteristics of the ultrasonic transducer with respect to 1 atmosphere of air.
  • FIG. 7B is a diagram illustrating the transmission / reception characteristics of the ultrasonic transducer with respect to 1 atmosphere of air.
  • FIG. 8A is a diagram showing the transmission / reception characteristics of the ultrasonic transducer with respect to air at 50 atmospheres.
  • FIG. 8B is a diagram illustrating the transmission / reception characteristics of the ultrasonic transducer with respect to air at 50 atmospheres.
  • FIG. 9 is a cross-sectional view showing the structure of a conventional ultrasonic flowmeter.
  • FIG. 10 is a cross-sectional view showing the structure of a conventional ultrasonic transducer.
  • FIG. 9 shows a cross-sectional configuration diagram of the main part of this type of ultrasonic flowmeter.
  • the fluid to be measured whose flow rate is to be measured is arranged to flow in the pipe.
  • a pair of ultrasonic transducers 101a and 101b are installed facing each other.
  • the ultrasonic transducers 101a and 101b are configured using a piezoelectric material such as a piezoelectric ceramic as an electromechanical transducer, and exhibit resonance characteristics like a piezoelectric buzzer and a piezoelectric oscillator.
  • the ultrasonic transducer 101a is used as an ultrasonic transmitter and the ultrasonic transducer 101b is used as an ultrasonic receiver.
  • an alternating voltage having a frequency near the resonance frequency of the ultrasonic transducer 101a is applied to the piezoelectric body in the ultrasonic transducer 101a.
  • the ultrasonic transducer 101a functions as an ultrasonic transducer and radiates ultrasonic waves into a fluid (for example, natural gas or hydrogen gas).
  • the emitted ultrasonic wave propagates to the path L1 and reaches the ultrasonic wave receiver 101b.
  • the ultrasonic transmitter / receiver 101b functions as a receiver, and receives the ultrasonic wave and converts it into a voltage.
  • the ultrasonic transducer 101b functions as an ultrasonic transducer
  • the ultrasonic transducer 101a functions as an ultrasonic receiver. That is, by applying an AC voltage having a frequency near the resonance frequency of the ultrasonic transducer 101b to the piezoelectric body in the ultrasonic transducer 101b, ultrasonic waves are radiated from the ultrasonic transducer 101b into the fluid. .
  • the emitted ultrasonic wave propagates along the path L2 and reaches the ultrasonic transducer 101a.
  • the ultrasonic transducer 101a receives the transmitted ultrasonic wave and converts it into a voltage.
  • the ultrasonic transducers 101a and 101b are generally collectively referred to as “ultrasonic transducers” in order to alternately function as a transmitter and a function as a receiver.
  • the ultrasonic flow meter shown in FIG. 9 when alternating voltage is continuously applied, ultrasonic waves are continuously emitted from the ultrasonic transducer and it becomes difficult to measure the propagation time.
  • the burst voltage signal is used as the drive voltage so that only ultrasonic waves are transmitted.
  • an ultrasonic burst signal is radiated from the ultrasonic transducer 101a by applying a burst voltage signal for driving to the ultrasonic transducer 101a.
  • the ultrasonic burst signal propagates through the path L1 and reaches the ultrasonic transducer 101b after time t.
  • the distance of the path L1 is equal to the distance of the path L2, and is L.
  • the ultrasonic transducer 101b can convert only the transmitted ultrasonic burst signal into an electric burst signal with a high S / N ratio.
  • the flow velocity of the fluid flowing in the pipe is V
  • the velocity of the ultrasonic wave in the fluid is C
  • the angle between the direction of flow of the fluid and the propagation direction of the ultrasonic pulse is ⁇ .
  • the flow velocity V of the fluid can be obtained from the distance L of the propagation path of ultrasonic waves and the propagation times t1 and t2.
  • the flow rate can be determined from the flow velocity V and the cross-sectional area of the flow path.
  • the acoustic impedance of the acoustic matching member formed on the ultrasonic wave transmitting / receiving surface of the piezoelectric body in the ultrasonic wave transmitter / receiver is important.
  • the acoustic matching member plays an important role when the ultrasonic transducer radiates (transmits) an ultrasonic wave to a gas and receives an ultrasonic wave that has propagated through the gas.
  • FIG. 10 shows a cross-sectional configuration of a conventional ultrasonic transducer 103.
  • the illustrated ultrasonic transducer 103 includes a piezoelectric body 104 and an acoustic matching member 105 bonded to one surface of the piezoelectric body 103.
  • the acoustic matching member 105 is bonded to one surface of the piezoelectric body 105 with an epoxy adhesive.
  • the ultrasonic vibration of the piezoelectric body 104 is transmitted to the acoustic matching member 105 through the adhesive layer made of this adhesive. Thereafter, the ultrasonic vibration is radiated as a sound wave to a fluid (ultrasonic propagation medium) such as a gas or a liquid in contact with the acoustic matching member 105.
  • a fluid ultrasonic propagation medium
  • the role of the acoustic matching member 105 is to efficiently propagate the vibration of the piezoelectric body to the fluid.
  • the acoustic impedance Z of a substance is defined by the following formula (Formula 5) using the speed of sound C in the substance and the density ⁇ of the substance.
  • the acoustic impedance of the gas to be radiated by ultrasonic waves is significantly different from the acoustic impedance of the piezoelectric body.
  • An acoustic impedance Z 1 of a piezoelectric ceramic such as PZT (lead zirconate titanate) which is a general piezoelectric body is about 2.9 ⁇ 10 7 kg / m 2 / sec.
  • the acoustic impedance Z 3 of air is 4.0 ⁇ 10 2 kg / m of about 2 / sec.
  • the acoustic impedance Z 1 of the piezoelectric body is 2.9 ⁇ 10 7 kg / m 2 / sec and the acoustic impedance Z 3 of the air is 4.0 ⁇ 10 2 kg / m 2 / sec, (Equation 6) is satisfied.
  • the acoustic impedance Z 2 is about 1.1 ⁇ 10 5 kg / m 2 / sec.
  • the acoustic matching material disclosed in Patent Document 1 sufficiently satisfies (Equation 6).
  • This material is produced using a dry gel imparted with durability, has a low density ⁇ , and a low sound velocity C.
  • An ultrasonic transducer equipped with an acoustic matching member made of a material with extremely low acoustic impedance, such as dry gel, can transmit and receive ultrasonic waves efficiently and with high sensitivity to gas. The gas flow rate can be measured with high accuracy.
  • the dry gel as described above is a porous body formed by a sol-gel reaction, and a network is formed in such a way that particles of several nm are joined to each other, and a skeleton of about several nm and a size of about several nm. It is formed from holes.
  • an acoustic matching member suitable for such a gas is required, and this is an acoustic matching member having an acoustic impedance different from that of an acoustic matching member formed only of dry gel. Is required.
  • the present inventors have conceived the following embodiment as a result of the above examination.
  • FIG. 1 shows a section of the ultrasonic transducer according to the first embodiment.
  • the illustrated ultrasonic transducer 1 includes a piezoelectric body 2 (electromechanical transducer), a pair of electrodes 3a and 3b provided on both surfaces of the piezoelectric body 2, and the main body of the piezoelectric body 2 via the electrodes 3a. And an acoustic matching member 4 joined to a surface (ultrasonic wave transmitting / receiving surface).
  • the piezoelectric body 2 is formed of a piezoelectric material and is polarized in the thickness direction (vertical direction in FIG. 1).
  • a voltage signal is applied between the electrode 3 a provided on the upper surface side of the piezoelectric body 2 and the electrode 3 b provided on the lower surface side, the piezoelectric body 2 expands and contracts based on the voltage signal and Ultrasonic waves are emitted from the acoustic wave transmitting / receiving surface.
  • the ultrasonic waves are radiated to an ultrasonic propagation medium (for example, gas) 5 through the acoustic matching member 4.
  • the ultrasonic wave propagating through the propagation medium 5 reaches the piezoelectric body 2 via the acoustic matching member 4, and generates a voltage signal between the electrodes 3a and 3b.
  • the ultrasonic transducer 1 of this Embodiment can perform both transmission and reception of an ultrasonic wave with one.
  • the material of the piezoelectric body 2 used in the present embodiment is arbitrary, and a known piezoelectric material can be used. Further, instead of the piezoelectric body 2, an electrostrictive body may be used. Also when using an electrostrictive body, the material is arbitrary and a well-known material can be used.
  • the electrodes 3a and 3b are also formed from a known conductive material.
  • the acoustic matching member 4 plays a role of efficiently propagating the ultrasonic waves generated in the piezoelectric body 2 to the propagation medium 5 and also plays a role of efficiently transmitting the ultrasonic waves propagated in the propagation medium 5 to the piezoelectric body 2. .
  • the acoustic matching member 4 of the present embodiment is composed of a block body in which dry gel particles 8 to which silica particles of about several nanometers are bonded while having pores of the same level are bonded by the bonded particles 10.
  • the thickness of the acoustic matching member 4 in the sound wave propagation direction is set to be about 1 ⁇ 4 of the wavelength of ultrasonic waves to be transmitted and received.
  • FIG. 2 shows a schematic diagram of the internal structure of the acoustic matching member 4 of the present embodiment.
  • 6 is a solid particle constituting the skeleton portion
  • 7 is a void existing between the solid particles
  • 8 is a dry gel particle
  • a plurality of solid particles 6 have voids. It is formed by being held and held.
  • the binding particles 10 in the present embodiment have a size larger than the internal pores (fine pores) of the dry gel particles 8 and smaller than the gaps between the dry gel particles 8. Since the binding particles 10 having such a size are too small to enter the pores in the dry gel particles 8, the low density characteristics that are characteristic of the dry gel are not lost.
  • the average particle size of the bonded particles 10 is measured by a laser diffraction method (for example, SALD manufactured by Shimadzu Corporation).
  • the average particle diameter of the dried gel particles 8 is measured by a laser diffraction method (for example, SALD manufactured by Shimadzu Corporation).
  • the average size of the internal pores of the dried gel particles 8 is measured by a gas adsorption method (for example, BELSORP-miniII manufactured by Nippon Bell Co., Ltd.).
  • the intergranular space 9 of the dried gel particle 8 is measured by a mercury intrusion method (for example, Autopore manufactured by Shimadzu Corporation).
  • the binding particles 10 in the present embodiment are made of a resin material.
  • the acoustic matching member 4 of the present embodiment can realize various acoustic impedances by adjusting the ratio of the binding particles 10 as compared with the acoustic matching member composed only of the dry gel, An ultrasonic transducer that efficiently transmits and receives ultrasonic waves can be realized by realizing an appropriate acoustic impedance according to the characteristics.
  • the acoustic matching member according to the present embodiment is a composite material in which dry gel particles having micro to meso-sized pores are bound together with binding particles, and the binding particles binding the dry gel particles are the internal voids of the dry gel particles. It has a size larger than the pore size and smaller than the gap between the dried gel particles.
  • the binding particles cannot enter the pores in the dry gel particles, and can enter the gaps between the dry gel particles.
  • the binding particles cannot enter the fine pores of the dried gel, the low density characteristics of the dried gel are not lost. Moreover, since it can penetrate
  • a piezoelectric body 2 is prepared according to the wavelength of ultrasonic waves to be transmitted and / or received.
  • a material having high piezoelectricity such as piezoelectric ceramics or a piezoelectric single crystal may be used.
  • the piezoelectric ceramic lead zirconate titanate, barium titanate, lead titanate, lead niobate, or the like can be used.
  • the piezoelectric single crystal lead zirconate titanate single crystal, lithium niobate, quartz, or the like can be used.
  • lead zirconate titanate ceramics are used as the piezoelectric body 2, and the frequency of ultrasonic waves to be transmitted and received is set to 500 kHz.
  • the resonance frequency of the piezoelectric body 2 is designed to be about 500 kHz.
  • the piezoelectric body 2 resonates strongly when its thickness is set to half the wavelength of the ultrasonic wave, and the transmission / reception efficiency of the ultrasonic wave is improved. Since the sound velocity of the lead zirconate titanate ceramic is about 3800 m / sec, the wavelength of the ultrasonic wave having a frequency of 500 kHz in the piezoelectric body 2 is 7.6 mm. For this reason, in this embodiment, the piezoelectric body 2 having a cylindrical shape with a thickness of about 3.8 mm and a diameter of 12 mm is used.
  • the upper and lower surfaces of the piezoelectric body 2 are provided with silver electrodes 3a and 3b by baking, and the piezoelectric body 2 is polarized in this direction.
  • the acoustic matching member 4 has the same diameter 12 mm as that of the piezoelectric body 2 and has a thickness of 1 ⁇ 4 wavelength as described above. Since the sound velocity of the acoustic matching member used in the present embodiment is 1500 m / sec, it is about 0.75 mm, which is a quarter wavelength at 500 kHz. The density is 500 kg / m 3 and the acoustic impedance is 7.5 ⁇ 10 5 kg / m 2 / sec.
  • FIG. 3 shows a manufacturing flow of the dry gel particles 8 of the acoustic matching member 4
  • FIG. 4 shows a manufacturing flow of bonding the dry gel particles 8 with the binding particles 10.
  • the gel particle dispersion obtained by the flow of FIG. 3 is an input of the production flow in FIG. 4, and the process of FIG. 4 is serially followed after the process of FIG.
  • the overall flow of FIG. 3 is to prepare dry gel particles 8 by preparing a gel-like raw material liquid and forming a block-shaped dry gel and then pulverizing it.
  • a dry gel is used in which the solid particles 6 that are solid skeleton portions are made of silica (SiO 2 ).
  • the size of the solid particles serving as the skeleton part of the dried gel is about several nm, and the pore size in the dried gel particles 8 has a relatively wide dispersion of about several nm to several tens of nm.
  • the dried gel particles 8 may be alumina, chromium oxide, tin oxide, carbon, or a copolymer polymer of resorcinol and formaldehyde.
  • the size of the dried gel particles 8 finally formed is about several to several tens of ⁇ m.
  • a dry gel material solution is prepared.
  • a raw material liquid is prepared by mixing alkoxysilane such as tetraethoxysilane, which is a raw material of the skeleton portion of the dried gel, with ethanol, water, and a catalyst (ammonia, hydrochloric acid, etc.).
  • the mixing ratio of the gel raw material liquid may be 6% tetraethoxysilane, 20% ethanol, and 74% 0.1N ammonia water.
  • the volume ratio of tetraethoxysilane in the gel raw material solution directly affects the density of the dried gel formed.
  • the blending ratio of the gel raw material liquid is set to a density of about 0.1. Further, this density is set so as to be a density that can be easily handled and can maintain strength when bonded by the binding particles 10 in this process and used as an acoustic matching member.
  • the prepared gel raw material solution is heated in a thermostatic chamber or the like to start and accelerate the polymerization reaction.
  • the polymerization reaction is completed by leaving it in a constant temperature bath at 60 ° C. for 24 hours. Since the temperature and the rate of the polymerization reaction are in a substantially proportional relationship, and the rate of the polymerization reaction greatly affects the particle size of the gel raw material liquid, it is important to control the reaction temperature in order to obtain a desired gel.
  • the polymerization reaction rate is also related to the stability of the properties of the gel.
  • the particle size and the pore size tend to be small, and when the reaction rate is low, the particle size and the pore size tend to be large.
  • the sound speed is slower, so that the reaction rate, that is, the heating temperature, may be controlled so that the particle size is about several nanometers.
  • the specific gravity of the gel skeleton and pore particles is appropriately set to 0.1, and the internal pore size is about 1 to 20 nm A gel can be obtained.
  • the alkoxysilane remaining in the wet gel may start a polymerization reaction in an environment such as an external temperature.
  • decomposition and dissolution reactions may start together with the polymerization reaction in an environment where a catalyst such as ammonia exists. Therefore, these residual solutions may be removed.
  • the solvent to be substituted may be any solvent that does not affect the reaction of the gel skeleton, such as pure water, an alcohol solvent such as ethanol, or an organic solvent such as pentane or hexane, and any substitution solvent can be selected. .
  • pure water is selected as a solvent in consideration of mixing with an aqueous emulsion resin used in a later process.
  • the formed wet gel is taken out from the reaction vessel and left in a vessel containing pure water having a volume about 10 times that of the wet gel for 24 hours to remove residual alkoxysilane and catalyst in the wet gel.
  • the obtained block-shaped wet gel is pulverized by a ball mill in order to obtain particles having a desired size of about several ⁇ m.
  • the principle of pulverization with a ball mill is that it moves in a cylindrical container by filling a cylindrical container such as Teflon (registered trademark) with a wet gel and hard balls such as zirconia and rotating the cylindrical container. The gel is crushed by the collision of the zirconia balls.
  • the particle size decreases with time. Further, when the rotational speed of the cylindrical container is increased, the size of particles obtained in the same processing time is reduced, that is, the pulverization efficiency is increased.
  • the size (diameter) of the ball for grinding affects the grinding efficiency and the particle size after grinding.
  • the impact at the time of the collision of the ball is large, so that the grinding efficiency is increased. That is, the change in particle size per unit time is large.
  • a zirconia ball having a diameter of 3 mm is used.
  • Zirconia is suitable as a material for balls for grinding because it is hard and hard to wear.
  • alumina or the like can also be used.
  • the pulverization efficiency is improved. In this embodiment, it is about 60%.
  • 20% airgel and 20% zirconia balls are placed in a cylindrical container made of Teflon (registered trademark) having an inner diameter of 150 mm, and 20% zirconia balls are further added, followed by grinding at 90 rpm for 1 hour.
  • dry gel particles 8 having an average particle diameter of about 8 ⁇ m can be obtained.
  • the average particle diameter of the dried gel particles 8 was measured by a laser diffraction method (SALD manufactured by Shimadzu Corporation), and as a result, it was about 8 ⁇ m.
  • the average size of the fine pores of the dried gel particles 8 was measured by a gas adsorption method (BELSORP-mini II manufactured by Nippon Bell Co., Ltd.) and found to be about 10 nm.
  • the balls used for pulverization are removed from the dried gel particles 8 thus obtained to obtain a gel particle-dispersed solution having a constant average particle diameter. Since the grinding balls used as described above have a diameter of 3 mm and gel particles have a size of about 10 ⁇ m, they can be easily separated with a mesh having an opening of about 1 mm.
  • the gel particle dispersion thus obtained is subjected to a binding process using the binding particles 10 as the next process.
  • FIG. 4 shows a coupling process using the coupled particles 10 and a process from the acoustic matching member to the ultrasonic transducer.
  • an emulsion resin dispersion is added to the obtained gel particle dispersion.
  • the emulsion resin dispersion is obtained by dispersing fine particulate resin in an aqueous solvent such as water.
  • an acrylic resin, an epoxy resin, a urethane resin, a vinyl acetate resin, a styrene resin, an olefin resin, or the like can be used.
  • an emulsion resin dispersion in which an epoxy resin having a particle size of about 800 nm is dispersed is used.
  • FIG. 5 shows the relationship between the molecular weight of the epoxy resin and the size of the particle diameter.
  • the horizontal axis represents the particle diameter
  • the vertical axis represents the molecular weight.
  • FIG. 5 shows the maximum particle size that can be taken by the molecular weight. In other words, it shows the theoretical value when the chain molecule of epoxy, which is a polymer, is perfectly linear. In fact, the polymer is linear and hardly exists in the solution, and is bent. Or, it may be spherical like a rounded thread, and the size shown in FIG. 5 is the maximum size and is usually smaller than this.
  • the epoxy resin Since the epoxy resin is in a normal state and a liquid state when the average molecular weight is less than 600, it cannot be used in the acoustic matching member of the present embodiment. Further, there is a correlation between the molecular weight and the softening point (flow, curing), and the fluidity at the same temperature decreases as the molecular weight increases.
  • a homogenization process is performed.
  • the homogenization process can be performed with a normal stirrer or the like.
  • a rotary mixer or the like can be used.
  • the homogenization process is performed for 5 minutes using a rotary mixer.
  • the average molecular weight is measured by a liquid chromatographic method (for example, Nexera manufactured by Shimadzu Corporation).
  • the dispersion of the gel particles and the binding particles 10 thus obtained is molded into a necessary shape, and an operation of removing excess water is performed. For this reason, in this embodiment, a gypsum mold that simultaneously performs the functions of molding and removing excessive water is used.
  • a hollow 12 having substantially the same shape as the size of the acoustic matching member 4 is provided on a plaster plaster plate 11, and a gel particle / binding particle 10 dispersion is cast into this portion.
  • the diameter of the recess is 20 mm and the depth is 5 mm.
  • the mold made of gypsum does not completely block liquid such as water and has fine pores that block gel particles and binding particles 10, not only from the surface of the cast dispersion, Since it is possible to remove moisture from the gypsum body itself, it is possible to efficiently remove moisture.
  • the dispersion liquid cast into a plaster mold was left in a constant temperature bath at 40 ° C. for 2 days (STEP 11). By performing this treatment, 90% or more of the moisture can be removed. In this way, a dried product of the composite of the dried gel particles 8 and the binding particles 10 from which moisture has been removed can be obtained.
  • the dried gel particles 8 and the binding particles 10 are in a state of being joined only by a weak intermolecular force, and the strength is insufficient for use as an acoustic matching member.
  • the temperature of the thermostatic chamber is raised to 150 ° C. while being installed in the gypsum mold.
  • the temperature is about 150 ° C.
  • a component having a particularly small particle size of the bonded particles 10 is melted to be in a liquid state. Since only such a resin having a small particle diameter, that is, a binding particle 10 having a small molecular weight, selectively flows on the surface of the large resin, it does not enter the fine pores inside the dry gel particle 8. .
  • the dried gel particles 8 can be integrated with each other with a strong bond without substantially destroying the pores inside the dried gel particles 8. After the heat treatment, if there is an abrupt temperature change, the composite that becomes the formed acoustic matching member is distorted, which may cause cracking or chipping.
  • the composite block thus formed had a thickness of 2 mm and a diameter of 15 mm.
  • the outer periphery is processed and the thickness is adjusted.
  • the thickness of the sound wave emitting surface or the surface coupled with the piezoelectric body 2 is adjusted to a predetermined thickness of 1 mm by a polishing machine. Thereafter, the polished surface is held and outer periphery processing is performed.
  • the outer peripheral machining was adjusted by holding with a jig slightly smaller than a disk-shaped acoustic matching member having a diameter of 12 mm, and polishing the portion exposed from the jig while rotating with a file.
  • the acoustic matching member 4 thus obtained has a density of 0.50 and a sound velocity of 1500 m / s.
  • the acoustic matching member 4 thus obtained is joined to the sound wave emitting surface of the piezoelectric body 2 in STEP14.
  • an emulsion resin may be used for bonding to the piezoelectric body 2.
  • an emulsion resin is applied to the upper surface of the piezoelectric body 2, and water is removed by heating at a low temperature of 60 ° C.
  • a molded acoustic matching member is placed on the emulsion-like resin layer thus formed, and further heated to 150 ° C. while being pressurized.
  • an ultrasonic transducer in which the piezoelectric body 2 is provided with an acoustic matching member composed of the dried gel particles 8 and the binding particles 10 is obtained.
  • FIG. 7 and FIG. 7 and 8 An example of the characteristics of the ultrasonic transducer 1 formed in this way is shown in FIG. 7 and FIG. 7 and 8, the horizontal axis indicates time, and the vertical axis indicates the relative amplitude.
  • FIG. 7 is a diagram illustrating characteristics when ultrasonic waves are transmitted / received to / from air at 1 atmosphere.
  • FIG. 7A shows the result of the acoustic matching member (acoustic impedance 0.1 ⁇ 10 ⁇ 6) formed only with the dried gel
  • FIG. 7B shows the acoustic matching member (acoustic impedance) produced according to the present embodiment. 0.75 ⁇ 10 ⁇ 6). It can be seen that higher sensitivity can be obtained when using an acoustic matching member made of only a conventional dry gel for air at normal temperature and normal pressure.
  • FIG. 8 shows characteristics when ultrasonic waves are transmitted / received to / from air of 50 atm.
  • the gas density increases proportionally. Since the speed of sound has no correlation with pressure, when the pressure increases 50 times, the acoustic impedance increases 50 times. For this reason, the optimum acoustic impedance as the acoustic matching member is larger than that in the case of atmospheric pressure air.
  • FIG. 8A is a result of an acoustic matching member (acoustic impedance 0.1 ⁇ 10 ⁇ 6) formed only with a dry gel
  • FIG. 8B is an acoustic matching produced by the present embodiment. It is a result by a member (acoustic impedance 0.75 ⁇ 10 ⁇ 6).
  • the ultrasonic sensor using the acoustic matching member in the present embodiment can obtain higher sensitivity, that is, the measurement accuracy of the ultrasonic flowmeter can be improved.
  • an acoustic matching member having a wide range of characteristics can be formed by using a dry gel material combined with another material.
  • STEP 8 or later in which the particulate dry gel and the emulsion resin are mixed is performed.
  • such a method since the procedure up to STEP 7 can be omitted, such a method may be adopted in consideration of time cost. However, it is possible to select the optimum method in consideration of the total cost.
  • the acoustic matching member of the present invention can be widely used in devices for transmitting and receiving ultrasonic waves between various media centered on gas, and in particular, sensing and flow rate required to detect ultrasonic waves with high accuracy. It can be suitably used for a measuring device.
  • Ultrasonic transducer Piezoelectric body (electromechanical transducer) 3a, 3b Electrode 4 Acoustic matching member 5 Propagation medium 6 Solid particle 7 Fine pore 8 Dry gel particle 9 Interparticle void 10 Bonded particle

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  • Electromagnetism (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Transducers For Ultrasonic Waves (AREA)
  • Measuring Volume Flow (AREA)

Abstract

La présente invention porte sur un élément de mise en correspondance acoustique (4) comprenant des particules de gel sec (8) et des particules de liaison (10), les particules de gel sec ayant des micropores (7) dans celles-ci et maintenant des vides interparticulaires parmi les particules de gel sec, les particules de liaison qui sont présentes parmi les particules de gel sec liant les particules de gel sec conjointement, et le diamètre de particule moyen des particules de liaison étant plus grand que la dimension moyenne des micropores des particules de gel sec mais plus petit que la dimension moyenne des vides interparticulaires (9) des particules de gel sec.
PCT/JP2013/003892 2012-06-22 2013-06-21 Élément de mise en correspondance acoustique et son procédé de fabrication, émetteur/récepteur d'onde ultrasonore l'utilisant et débitmètre ultrasonore WO2013190852A1 (fr)

Priority Applications (1)

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JP2014520963A JPWO2013190852A1 (ja) 2012-06-22 2013-06-21 音響整合部材及びその製造方法、及びこれを用いた超音波送受波器、超音波流量計

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JP2012-140486 2012-06-22
JP2012140486 2012-06-22

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WO2013190852A1 true WO2013190852A1 (fr) 2013-12-27

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003158796A (ja) * 2001-11-21 2003-05-30 Matsushita Electric Ind Co Ltd 超音波発生器およびその製造方法
WO2003064980A1 (fr) * 2002-01-28 2003-08-07 Matsushita Electric Industrial Co., Ltd. Couche d'adaptation acoustique, emetteur/recepteur ultrasonore, leurs procedes de fabrication, et debitmetre ultrasonore
JP2004323752A (ja) * 2003-04-25 2004-11-18 Matsushita Electric Ind Co Ltd 乾燥ゲルを含む成形体およびその製造方法

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003158796A (ja) * 2001-11-21 2003-05-30 Matsushita Electric Ind Co Ltd 超音波発生器およびその製造方法
WO2003064980A1 (fr) * 2002-01-28 2003-08-07 Matsushita Electric Industrial Co., Ltd. Couche d'adaptation acoustique, emetteur/recepteur ultrasonore, leurs procedes de fabrication, et debitmetre ultrasonore
JP2004323752A (ja) * 2003-04-25 2004-11-18 Matsushita Electric Ind Co Ltd 乾燥ゲルを含む成形体およびその製造方法

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