JP2008193194A - Ultrasonic oscillator and ultrasonic current meter/flowmeter - Google Patents
Ultrasonic oscillator and ultrasonic current meter/flowmeter Download PDFInfo
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Abstract
Description
本発明は、気体液体などの流体の流量を計測する超音波振動子および超音波流速・流量計に関するものである。 The present invention relates to an ultrasonic transducer and an ultrasonic flow velocity / flow meter for measuring a flow rate of a fluid such as a gas liquid.
従来、この種の超音波振動子は、図９に示すような構成であった。図９は、超音波振動子１０１の断面図を示し、１０２は正方柱状の圧電体１０３を収納するキャップ状の缶ケ−スを示す。１０４は、缶ケ−ス１０２上の設けられた２層からなる音響整合層を示す。２層からなる音響整合層１０４を構成する、１０５はセラミック多孔体を、１０６は多孔性の有機ガラスの乾燥ゲルを示す。１０７は缶ケ−ス１０３と溶接接合された台座を、１０８は電極端子１０９と圧電体１０２とを電気的に接続する導電性ゴムを。１１０は電極端子１０９と台座１０７とを電気的に絶縁する封入ガラス部を、１１１は缶ケ−ス１０３、台座１０７とを電気的に接続する接地端子をそれぞれ示す（例えば、特許文献１参照）。
このような構成の従来の超音波振動子１０１では、２層からなる音響整合層１０４が、構成する２層、即ち、多孔性の有機ガラスからなる乾燥ゲルの層１０６、あるいは多孔性セラミック層１０５の一部部分が連続して形成されていたため、製造時の蒸発乾燥あるいは熱サイクルなどの温度変化により、熱膨張係数の違いによると思われる歪みにより、強度的に弱い有機ガラスの乾燥ゲル１０６にクラックなどのひび割れや、表面層の剥離などが発生し、信頼性に、特に長期信頼性に課題を有していた。 In the conventional ultrasonic transducer 101 having such a configuration, the acoustic matching layer 104 composed of two layers is composed of two layers, ie, a dry gel layer 106 made of porous organic glass, or a porous ceramic layer 105. Since a part of the glass was continuously formed, due to temperature changes such as evaporative drying or thermal cycle during manufacturing, due to distortion that seems to be due to the difference in thermal expansion coefficient, the strength of the organic glass dry gel 106 is reduced. Cracks such as cracks, peeling of the surface layer, and the like occurred, and there were problems in reliability, particularly in long-term reliability.
本発明は、前記従来の課題を解決するもので、強度的に弱い有機ガラスの乾燥ゲルを保護する構成からなる音響整合層を有する超音波振動子とし、信頼性、特に、長期信頼性に強い超音波振動子および超音波流速・流量計を提供することを目的とする。 The present invention solves the above-mentioned conventional problems, and is an ultrasonic vibrator having an acoustic matching layer having a structure that protects a dry gel of organic glass that is weak in strength, and has high reliability, particularly long-term reliability. An object is to provide an ultrasonic transducer and an ultrasonic flow velocity / flow meter.
前記従来の課題を解決するために、本発明の超音波振動子は、セラミック多孔体などからなる比較的強度の大きい音響インピ−ダンスの大きいな連続体からなる材料と、有機ガラスの乾燥ゲルなどからなる比較的強度の小さい音響インピ−ダンスの小さな連続体からなる材料との混合体からなる音響整合層を構成し、超音波振動子とした。 In order to solve the above-mentioned conventional problems, the ultrasonic transducer of the present invention includes a material composed of a continuous body having a relatively large acoustic impedance, such as a ceramic porous body, and a dry gel of organic glass. An acoustic matching layer made of a mixture with a material made of a continuum having a relatively small acoustic impedance and having a relatively low strength was constructed to form an ultrasonic vibrator.
この構成により、比較的強度の小さい有機ガラスの乾燥ゲルなどからなる音響インピ−ダンスの小さな材料を、比較的強度の大きいセラミック多孔体などからなる音響インピ−ダンスの大きな材料で保護することになる。従って、音響特性は主に音響インピ−ダンスの小さい材料に依存することになり、物理的強度は比較的強度の大きいセラミック多孔体に依存することになる。このため、高感度で、熱サイクルなどの温度変化に強い音響整合層とすることができ、信頼性、特に、長期信頼性に強い超音波振動子を構成することができる。また、この超音波振動子を用いることにより、信頼性の高い超音波流速・流量計をも構成することができる。 With this configuration, a material having a small acoustic impedance made of a dry gel of organic glass having a relatively low strength is protected by a material having a large acoustic impedance made of a porous ceramic body having a relatively high strength. . Therefore, the acoustic characteristics mainly depend on a material having a small acoustic impedance, and the physical strength depends on a ceramic porous body having a relatively high strength. For this reason, it is possible to provide an acoustic matching layer that is highly sensitive and resistant to temperature changes such as a thermal cycle, and an ultrasonic vibrator that is strong in reliability, particularly in long-term reliability, can be configured. Further, by using this ultrasonic transducer, a highly reliable ultrasonic flow velocity / flow meter can be configured.
本発明の超音波振動子は、上記構成であるため、音響特性に優れ、かつ、強度的にも強い、信頼性、特に長期信頼性に優れた特性を有することになる。また、この超音波振動子
を用いることにより、信頼性の高い超音波流速・流量計を構成することができる。
Since the ultrasonic transducer of the present invention has the above-described configuration, it has excellent acoustic characteristics and strength, and has excellent reliability, particularly long-term reliability. Also, by using this ultrasonic transducer, a highly reliable ultrasonic flow velocity / flow meter can be configured.
第１の発明は、比較的強度の大きい音響インピ−ダンスの大きいな連続体からなる材料と、比較的強度の小さい音響インピ−ダンスの小さな連続体からなる材料とを混合して音響整合層を構成し、超音波振動子とした。 In the first invention, an acoustic matching layer is formed by mixing a material composed of a continuous material having a relatively large acoustic impedance and a material having a relatively small acoustic impedance and a material having a relatively small acoustic impedance. An ultrasonic transducer was constructed.
この構成により、比較的強度の小さい音響インピ−ダンスの小さな連続体を、比較的強度の大きい音響インピ−ダンスの大きいな連続体で保護することができ、熱サイクルなどの温度変化に強い音響整合層とすることができ、信頼性、特に、長期信頼性に強い超音波振動子を構成することができる。 With this configuration, a continuum with a relatively small acoustic impedance can be protected by a continuum with a relatively large acoustic impedance, and acoustic matching that is resistant to temperature changes such as thermal cycling. It is possible to form an ultrasonic vibrator having high reliability and particularly long-term reliability.
第２の発明は、特に、第１の発明の音響整合層において、比較的強度の小さい音響インピ−ダンスの小さな連続体を、比較的強度の大きい音響インピ−ダンスの大きい連続体からなる材料に内包される構成とした。 In the second invention, in particular, in the acoustic matching layer of the first invention, a continuum having a relatively low acoustic impedance is changed to a material consisting of a continuum having a relatively high acoustic impedance. It was set as the structure included.
この構成により、比較的強度の小さい音響インピ−ダンスの小さな連続体の外部に、比較的強度の大きい音響インピ−ダンスの大きいな連続体を構成することができ、熱サイクルなどの温度変化などにさらに強い音響整合層とすることができ、信頼性、特に、長期信頼性に強い超音波振動子を構成することができる。 With this configuration, a continuum with a relatively large acoustic impedance can be formed outside a continuum with a relatively small acoustic impedance, which can be used for temperature changes such as thermal cycling. Furthermore, it is possible to form a stronger acoustic matching layer, and it is possible to configure an ultrasonic transducer that is strong in reliability, particularly in long-term reliability.
第３の発明は、特に、第１および第２の発明における音響整合層において、比較的強度の大きい音響インピ−ダンスの大きい連続体からなる材料を大きい気孔径で構成し、比較的強度の小さい音響インピ−ダンスの小さい連続体からなる材料を小さい気孔径で構成した。 In the third invention, in particular, in the acoustic matching layers in the first and second inventions, a material composed of a continuous body having a relatively large strength and a large acoustic impedance is formed with a large pore diameter, and a relatively small strength. A material consisting of a continuum with a small acoustic impedance was constructed with a small pore diameter.
この構成により、比較的強度の小さい音響インピ−ダンスの小さい連続体からなる材料を、比較的強度の大きい音響インピ−ダンスの大きいな連続体の内部に簡単・容易に形成することが可能となり、信頼性の高い超音波振動子を実現できる。 With this configuration, it is possible to easily and easily form a material composed of a continuum with relatively low acoustic impedance and within a continuum with relatively high acoustic impedance, A highly reliable ultrasonic transducer can be realized.
第４の発明は、特に、第１〜３の発明の音響整合層において、比較的強度の大きい音響インピ−ダンスの大きい連続体からなる材料を、セラミックなどの無機多孔体で構成し、比較的強度の小さい音響インピ−ダンスの小さい連続体からなる材料を有機ガラスなどの乾燥ゲルで構成した。この構成により、音響インピ−ダンスが小さく、音響特性に優れた有機ガラスなどの乾燥ゲルからなる比較的強度の小さい材料を、超音波振動子の音響整合層として実用可能とすることができ、高感度で、かつ、温度特性にも優れた超音波振動子を実現することができる。 In a fourth aspect of the invention, in particular, in the acoustic matching layers of the first to third aspects of the invention, a material composed of a continuous body having a relatively large strength and a large acoustic impedance is formed of an inorganic porous body such as ceramic. A material composed of a continuum having a low acoustic impedance and a low strength was composed of a dry gel such as organic glass. This configuration makes it possible to use a relatively low-strength material made of a dry gel such as organic glass with low acoustic impedance and excellent acoustic characteristics as an acoustic matching layer for an ultrasonic transducer. An ultrasonic transducer having high sensitivity and excellent temperature characteristics can be realized.
第５の発明は、特に、第１〜４の発明の音響整合層において、比較的強度の大きい音響インピ−ダンスの大きい連続体からなる材料の気孔径を用いる超音波波長の２０分の１以下とする構成とした。 In the fifth aspect of the invention, in particular, in the acoustic matching layer of the first to fourth aspects of the invention, the ultrasonic wave diameter is less than 1 / 20th of the ultrasonic wavelength using the pore diameter of the material composed of a continuum having a relatively large acoustic impedance and a relatively high strength. The configuration is as follows.
この構成により、音響特性に優れた高感度な超音波振動子を実現できる。 With this configuration, a highly sensitive ultrasonic transducer with excellent acoustic characteristics can be realized.
第６の発明は、特に、第１〜５の発明の整合層を、複数層から音響整合層を構成し、超音波振動子とした。 In the sixth aspect of the invention, in particular, the matching layer of the first to fifth aspects of the invention comprises an acoustic matching layer composed of a plurality of layers to form an ultrasonic transducer.
この構成により、超高感度で、信頼性の高い超音波振動子を実現できる。また、超音波流速・流量計に適した超音波振動子をも実現できる。 With this configuration, it is possible to realize an ultrasonic transducer with ultra-high sensitivity and high reliability. In addition, an ultrasonic transducer suitable for an ultrasonic flow velocity / flow meter can be realized.
第７の発明は、特に、第１〜６の発明の音響整合層表面にエラストマ−系材料を被覆し、超音波振動子とした。 In the seventh invention, in particular, the surface of the acoustic matching layer of the first to sixth inventions is coated with an elastomer material to obtain an ultrasonic vibrator.
この構成により、音響整合層の表面がより一層保護される構成となり、信頼性をより高くすることができる。 With this configuration, the surface of the acoustic matching layer is further protected, and the reliability can be further increased.
第８の発明は、特に、第７の発明のエラストマ−系材料の被覆層の厚さを１０ミクロン以下とする構成とした。この構成により、音響特性を著しく劣化させることなく音響整合層の表面を保護することができ、信頼性が高く、音響特性に優れた超音波振動子を実現できる。 In the eighth invention, in particular, the thickness of the coating layer of the elastomeric material of the seventh invention is set to 10 microns or less. With this configuration, the surface of the acoustic matching layer can be protected without significantly deteriorating the acoustic characteristics, and an ultrasonic transducer having high reliability and excellent acoustic characteristics can be realized.
第９の発明は、特に、第１〜８発明の超音波振動子を一対用いて超音波流速・流量計を構成することとした。この構成により、信頼性の高い、超音波流速・流量計を実現できる。 In the ninth invention, in particular, an ultrasonic flow velocity / flow meter is configured by using a pair of the ultrasonic vibrators of the first to eighth inventions. With this configuration, a reliable ultrasonic flow velocity / flow meter can be realized.
以下、本発明の実施の形態について、図面を参照しながら説明する。なお、この実施の形態によって本発明が限定されるものではない。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.
（実施の形態１）
図１は、本発明の実施の形態１における超音波振動子の断面図を示す。図１において、超音波振動子１は、キャップ状の缶ケ−ス２の内部にエポキシ樹脂などで接着された圧電体３と、前記缶ケ−ス２の外部に接着された音響整合層４とから構成されている。
(Embodiment 1)
FIG. 1 shows a cross-sectional view of an ultrasonic transducer in the first embodiment of the present invention. In FIG. 1, an ultrasonic transducer 1 includes a piezoelectric body 3 bonded to an inside of a cap-shaped can case 2 with an epoxy resin and an acoustic matching layer 4 bonded to the outside of the can case 2. It consists of and.
音響整合層４は、比較的強度の大きい音響インピ−ダンスの大きい連通孔からなる連続体材料と、比較的強度の小さい音響インピ−ダンスの小さい連通孔からなる連続体で構成されている。図２に、音響整合層４の詳細図を示す。図２（ａ）の５は比較的強度の大きな、音響インピ−ダンスの大きい連続体からなる連通孔で構成される材料を、図２（ｂ）の６は比較的強度の小さい音響インピ−ダンスの小さい連続体からなる連通孔で構成される材料を示す。図２（ｃ）の４は比較的強度の大きい音響インピ−ダンスの大きい連続体からなる材料５と、比較的強度小さい音響インピ−ダンスの小さい連続体からなる材料６とを混合して形成した音響整合層を示す。 The acoustic matching layer 4 is composed of a continuous material composed of a continuous hole having a relatively large strength and a large acoustic impedance, and a continuous body composed of a continuous hole having a relatively small strength and a small acoustic impedance. FIG. 2 shows a detailed view of the acoustic matching layer 4. 2 in FIG. 2A is a material composed of a continuous hole made of a continuous body having a relatively large strength and a large acoustic impedance, and 6 in FIG. 2B is a sound impedance having a relatively small strength. The material comprised by the communicating hole which consists of a small continuous body of is shown. 2c in FIG. 2 (c) is formed by mixing a material 5 made of a continuum having a relatively large acoustic impedance and a material 6 made of a continuum having a relatively small acoustic impedance. An acoustic matching layer is shown.
なお、図１において、音響整合層４の外径は約１２［ｍｍ］、厚さ０．３〜１．５［ｍｍ］とした。圧電体３は、約７．４［ｍｍ］角の角柱状とし、その上面、下面には焼き付け銀などで構成される電極が形成されている（図示せず）。また、台座部７は缶ケ−ス２と周辺部で溶接され、圧電体３を密封する構成とした。導電性のゴム８は圧電体３の下面電極と端子９とを電気的に接続している。端子９は、ハ−メチックシ−ルなどの絶縁性材料１０により台座７に固定されている。他方の端子１１は、台座７に直接固定され、缶ケ−ス２を介して、圧電体３の上面電極に接続される構成とした。 In FIG. 1, the outer diameter of the acoustic matching layer 4 is about 12 [mm] and the thickness is 0.3 to 1.5 [mm]. The piezoelectric body 3 has a prismatic shape of about 7.4 [mm] square, and electrodes made of baked silver or the like are formed on its upper and lower surfaces (not shown). The pedestal portion 7 is welded to the can case 2 at the peripheral portion to seal the piezoelectric body 3. The conductive rubber 8 electrically connects the lower surface electrode of the piezoelectric body 3 and the terminal 9. The terminal 9 is fixed to the base 7 with an insulating material 10 such as a hermetic seal. The other terminal 11 is directly fixed to the pedestal 7 and connected to the upper surface electrode of the piezoelectric body 3 through the can case 2.
なお、この構成において、音響整合層４と缶ケ−ス２とはエポキシ系接着剤を用いて接着固定した。 In this configuration, the acoustic matching layer 4 and the can case 2 are bonded and fixed using an epoxy adhesive.
一般に、超音波振動子の音響整合層として要求される特性は、音響インピ−ダンスが小さいことである。音響インピ−ダンスは、音速と密度との積として示されるので、音響インピ−ダンスの小さい材料は、密度が低く、且つ、音速の遅い材料となる。音速は、通常の場合、材料自身の結合が弱いほど、遅いと言われている。従って、超音波振動子に要求される音響インピ−ダンスの小さい材料は、比較的強度の弱い材料であることが多い。従って、音響インピ−ダンスの小さい材料を単独で構成材料として使用することは、実用上大変難しい。 In general, a characteristic required as an acoustic matching layer of an ultrasonic transducer is a small acoustic impedance. Since acoustic impedance is shown as the product of sound speed and density, a material with low acoustic impedance is a material with low density and low sound speed. The speed of sound is usually said to be slower as the bond of the material itself is weaker. Therefore, a material having a small acoustic impedance required for an ultrasonic transducer is often a material having a relatively low strength. Accordingly, it is practically difficult to use a material having a small acoustic impedance alone as a constituent material.
このように、本発明の音響整合層は、比較的強度の大きい音響インピ−ダンスの大きい連続体からなる材料と、比較的強度の小さい音響インピ−ダンスの小さい連続体からなる材料とを、混合して、新たな音響整合層とすることにより、音響インピ−ダンスも比較的小さく、音響特性に優れ、また、比較的強度が大きく、実用可能な音響整合層とすることができる。 As described above, the acoustic matching layer of the present invention is a mixture of a material composed of a continuum having a relatively large acoustic impedance and a material composed of a continuum having a relatively small acoustic impedance. Thus, by using a new acoustic matching layer, the acoustic impedance is relatively small, the acoustic characteristics are excellent, the strength is relatively high, and a practical acoustic matching layer can be obtained.
また、それぞれの材料を連続体で構成しているため、音、即ち、振動が効率よく伝播し、減衰の少ない音響整合層を形成できる。即ち、音響的に共振した場合に、感度を大きくとることのできる超音波振動子を実現できる構成となる。 In addition, since each material is composed of a continuous body, sound, that is, vibration, propagates efficiently and an acoustic matching layer with little attenuation can be formed. That is, an ultrasonic transducer capable of increasing sensitivity when acoustically resonated can be realized.
（実施の形態２）
上記構成において、比較的強度の大きい、音響インピ−ダンスの大きい連通孔からなる連続体材料を外側に構成し、その内部に比較的強度の小さい、音響インピ−ダンスの小さい連通孔からなる連続体材料を構成することにより、物理的強度の大きい音響整合層とすることが出来、実用可能な強度を確保することができる。即ち、セラミック多孔体などを、上記の比較的強度の大きい、音響インピ−ダンスの大きい連通孔からなる連続体として用い、有機ガラスの原料を上記セラミック多孔体に含浸させ、有機ガラスの乾燥ゲルを形成することにより、比較的強度の小さい、音響インピ−ダンスの小さい連通孔からなる連続体とすることができる。
(Embodiment 2)
In the above configuration, a continuous material composed of communication holes having relatively high strength and a large acoustic impedance is formed outside, and a continuous material consisting of communication holes having a relatively small strength and a small acoustic impedance is provided therein. By configuring the material, an acoustic matching layer having a high physical strength can be obtained, and a practical strength can be ensured. That is, a ceramic porous body or the like is used as a continuous body composed of communication holes having a relatively high strength and a large acoustic impedance, and an organic glass raw material is impregnated in the ceramic porous body, and a dry gel of organic glass is used. By forming, it can be set as the continuous body which consists of a communicating hole with comparatively small intensity | strength and small acoustic impedance.
（実施の形態３）
上記構成において、比較的強度の大きい、音響インピ−ダンスの大きい連通孔からなる連続体材料を気孔径の大きい材料で構成し、比較的強度の小さい、音響インピ−ダンスの小さい連通孔からなる連続体材料を気孔径の小さい材料で構成することにより、大きい気孔径の内部に小さい気孔径からなる材料を容易に構成することができる。即ち、セラミック多孔体などを、上記の比較的強度の大きい、音響インピ−ダンスの大きい連通孔からなる連続体として用い、連通孔からなる大きい気孔径の中に、有機ガラスの原料を含浸させ、有機ガラスの乾燥ゲルを形成することにより、より気孔径の小さい連通孔からなる連続体とすることができる。この構成により、実用可能な強度を確保するとともに、音響特性に優れた音響整合層を構成することができる。
(Embodiment 3)
In the above configuration, a continuous material composed of a communication hole having a relatively large strength and a large acoustic impedance is composed of a material having a large pore diameter, and a continuous material composed of a communication hole having a relatively small strength and a small acoustic impedance. By configuring the body material with a material having a small pore diameter, a material having a small pore diameter inside a large pore diameter can be easily configured. That is, a ceramic porous body or the like is used as a continuous body composed of communication holes having a relatively high strength and a large acoustic impedance, and the organic glass material is impregnated into a large pore diameter composed of the communication holes. By forming a dry gel of organic glass, it is possible to obtain a continuous body composed of communication holes having a smaller pore diameter. With this configuration, a practical strength can be ensured and an acoustic matching layer having excellent acoustic characteristics can be configured.
（実施の形態４）
この種の比較的強度が大きく、音響インピ−ダンスの大きい材料として無機質のセラミック多孔体が適している。密度の低いセラミックとして気孔率の大きい、多孔体が適している。セラミック多孔体として密度は、（０．２５〜０．５０）×１０３［ｋｇ／ｍ３］は容易に準備することができる。また、音速は２０００〜３５００［ｍ／ｓ］程度であり、音響インピ−ダンス（Ｚｉｍｐ）としては、（０．５０〜１．７５）×１０６［ｋｇ／（ｍ２・ｓ）］となる。また、この種の比較的強度が小さく、音響インピ−ダンスの小さい材料として有機ガラスの乾燥ゲルが適している。有機ガラスの乾燥ゲルは、密度（０．１５〜０．４０）×１０６［ｋｇ／ｍ３］ は容易に準備することができ、また音速は、２００〜５００［ｍ／ｓ］程度となる。音響インピ−ダンスとしては、（０．０３〜０．２０）×１０６［ｋｇ／ｍ３］となる。
(Embodiment 4)
An inorganic ceramic porous body is suitable as a material having a relatively large strength and a large acoustic impedance. A porous body having a high porosity is suitable as a low-density ceramic. A density of (0.25 to 0.50) × 10 3 [kg / m 3 ] can be easily prepared as a ceramic porous body. The sound speed is about 2000 to 3500 [m / s], and the acoustic impedance (Zimp) is (0.50 to 1.75) × 10 6 [kg / (m 2 · s)]. . In addition, a dry gel of organic glass is suitable as a material having a relatively low strength and a low acoustic impedance. The organic glass dry gel can be easily prepared with a density (0.15 to 0.40) × 10 6 [kg / m 3 ], and the sound velocity is about 200 to 500 [m / s]. . The acoustic impedance is (0.03 to 0.20) × 10 6 [kg / m 3 ].
以下に簡単にこの種の無機質のセラミック多孔体について説明する。 This kind of inorganic ceramic porous body will be briefly described below.
セラミック多孔体に要求される特性は、気孔率が大きく、気孔径分布が一様で、且つ、分布に偏りがないことが重要でとなる。このようなセラミック多孔体を形成するには、気泡を多く含むセラミックスラリ−を固化させ、焼成するゾルキャスティグ法が適している。 It is important that the characteristics required for the ceramic porous body are large porosity, uniform pore size distribution, and no uneven distribution. In order to form such a ceramic porous body, a sol casting method in which a ceramic slurry containing a large amount of air bubbles is solidified and fired is suitable.
簡単に、ゾルキャスティング法の工程を説明する。まず、セラミック粉末原料と、架橋剤、触媒、界面活性剤などを含むゲル化材料とを十分混合する。このとき混合媒体としては水あるいは有機溶媒などを用いるとよい。このようにしてセラミックスラリ−が形成される。このとき、分散剤、滑剤、増粘剤、糊剤などを添加してもよい。 The process of the sol casting method will be briefly described. First, a ceramic powder raw material and a gelling material containing a crosslinking agent, a catalyst, a surfactant and the like are sufficiently mixed. At this time, water or an organic solvent may be used as the mixing medium. In this way, a ceramic library is formed. At this time, a dispersant, a lubricant, a thickener, a paste, or the like may be added.
次に、このセラミックスラリ−に気泡剤を添加し、攪拌・混合し、スラリ−中に、気泡を所定量導入する。なお、気泡を導入する前には、セラミックスラリ−を予め充分脱気しておくと、気泡の導入量が安定する。このようにして気泡が導入されたセラミックスラリ−所定の形状となるよう型枠に入れ、成形する。乾燥後、脱型し、界面活性剤などの有機物を焼き飛ばすことにより多くの気泡を含むセラミック成型体が形成される。その後、所定の温度、時間により、セラミック成形体を焼成する。 Next, a foaming agent is added to the ceramic slurry, stirred and mixed, and a predetermined amount of foam is introduced into the slurry. If the ceramic slurry is sufficiently deaerated before introducing bubbles, the amount of bubbles introduced is stabilized. Ceramic slurry into which bubbles have been introduced in this manner is put into a mold so as to have a predetermined shape, and then molded. After drying, it is demolded, and a ceramic molded body containing many bubbles is formed by burning off organic substances such as surfactants. Thereafter, the ceramic molded body is fired at a predetermined temperature and time.
このとき、セラミック粉末材料として、アルミナ系、ムライト系、ジルコニア系などの酸化物系の材料を用いると、比較的簡単に、ゾルキャスティング法により、この種のセラミック多孔体を形成することができる。また、炭化珪素系、窒化珪素系、窒化アルミニウム系、窒化ホウ素系、グラファイト系などの非酸化物系のセラミック材料を用いても比較的簡単に、ゾルキャスティング法により、この種のセラミック多孔体を形成することができる。 At this time, when an oxide-based material such as alumina, mullite, or zirconia is used as the ceramic powder material, this kind of ceramic porous body can be formed by a sol-casting method relatively easily. In addition, this kind of ceramic porous body can be formed by a sol-casting method relatively easily using non-oxide ceramic materials such as silicon carbide, silicon nitride, aluminum nitride, boron nitride, and graphite. Can be formed.
また、非酸化物系のセラミック材料を用いると焼成前後の寸法変化が小さいため、成形性が良い。通常の酸化物系セラミック材料の場合、焼成前後の寸法は、１０〜５０［％］前後収縮するものが多いが、非酸化物系の材料の場合、焼成において若干酸化し、体積が増加するためか、焼成前後の寸法変化が、おおよそ１０［％］以下に収まる場合が多いので、この種の目的のセラミック多孔体として非常に適していることになる。 In addition, when a non-oxide ceramic material is used, since the dimensional change before and after firing is small, formability is good. In the case of a normal oxide ceramic material, the size before and after firing often shrinks around 10 to 50%. However, in the case of a non-oxide material, the volume is increased due to slight oxidation during firing. In many cases, the dimensional change before and after firing is within about 10 [%] or less, which is very suitable as a ceramic porous body of this kind.
次に、音響整合層としては、音速が遅く、密度の小さいことが要求され、有機ガラスの乾燥ゲルが適している。有機ガラスの乾燥ゲルは次のようにして準備する。エトキシシランあるいはメトキシシランなどの有機溶液からなるガラス原料を、塩酸系触媒を用い十分活性な状態で、メチルあるいはエチルなどのアルコ−ル系溶媒に分散させる。この分散された溶液をアンモニア水などの塩基性触媒を添加するとともに、テフロン（登録商標）などの反応しない材料で作成された型枠に流し込み、成形する。この状態で、４０〜５０［℃］、３〜６［ｈ］保持すると、成形された湿潤ゲルが得られる。 Next, the acoustic matching layer is required to have a low sound speed and a low density, and an organic glass dry gel is suitable. The organic glass dry gel is prepared as follows. A glass material made of an organic solution such as ethoxysilane or methoxysilane is dispersed in an alcohol solvent such as methyl or ethyl in a sufficiently active state using a hydrochloric acid catalyst. The dispersed solution is added with a basic catalyst such as aqueous ammonia and poured into a mold made of a non-reactive material such as Teflon (registered trademark) to be molded. In this state, when it is kept at 40 to 50 [° C.] and 3 to 6 [h], a shaped wet gel is obtained.
この湿潤ゲルを再度、エトキシシランあるいはメトキシシランなどの原料溶液とアンモニアなどの塩基性触媒とを用い、再度有機ガラスを形成すると、湿潤ゲルを乾燥させても、収縮しない、即ち、体積変化の殆どしない乾燥ゲルが得られる。この有機ガラスの乾燥ゲルを使用目的に応じて、疎水化処理などを施すことがある。疎水化処理は、ジメチルジエトキシシラン溶液とアンモニアなどの塩基性触媒などを用い実施した。このようにして成形された有機ガラスの乾燥ゲルを準備する。 When this wet gel is again formed using a raw material solution such as ethoxysilane or methoxysilane and a basic catalyst such as ammonia, and the organic glass is formed again, it does not shrink even when the wet gel is dried, that is, almost no volume change occurs. A dry gel is obtained. The organic glass dry gel may be subjected to a hydrophobizing treatment or the like depending on the purpose of use. The hydrophobization treatment was performed using a dimethyldiethoxysilane solution and a basic catalyst such as ammonia. An organic glass dry gel thus formed is prepared.
本発明の音響整合層では、上記で説明した無機質のセラミック多孔体を準備し、その多孔体に上記で説明した有機ガラスの原料を流し込み、セラミック多孔体にお内部に有機ガラスの乾燥ゲルを形成し、音響整合層とした。 In the acoustic matching layer of the present invention, the inorganic ceramic porous body described above is prepared, the organic glass raw material described above is poured into the porous body, and a dry gel of organic glass is formed inside the ceramic porous body. And an acoustic matching layer.
このようにして形成した音響整合層を有する超音波振動子の特性を図３（ａ），（ｂ）に示す。セラミック多孔体の密度は約０．３５［ｇ／ｃｍ３］、有機ガラスの乾燥ゲルの密度は約０．２５［ｇ／ｃｍ３］であった。図３（ａ）、（ｂ）は、超音波振動子の感度と周波数との関係を示し、横軸に周波数を、縦軸に感度を示す。図３（ａ）に音響整合層の厚さを変えて作成した比較的感度の大きいかった超音波振動子の周波数特性を示す。１
２は音響整合層が約１．１０［ｍｍ］、１３は約１．０５［ｍｍ］、１４は約１．００［ｍｍ］、１５は約０．９５［ｍｍ］、１５は約０．９０［ｍｍ］の場合の結果をそれぞれ示す。
The characteristics of the ultrasonic transducer having the acoustic matching layer formed as described above are shown in FIGS. The density of the ceramic porous body was about 0.35 [g / cm 3 ], and the density of the dried gel of organic glass was about 0.25 [g / cm 3 ]. 3A and 3B show the relationship between the sensitivity and frequency of the ultrasonic transducer, with the horizontal axis representing frequency and the vertical axis representing sensitivity. FIG. 3A shows the frequency characteristics of an ultrasonic transducer having a relatively high sensitivity, which was prepared by changing the thickness of the acoustic matching layer. 1
2, acoustic matching layer is about 1.10 [mm], 13 is about 1.05 [mm], 14 is about 1.00 [mm], 15 is about 0.95 [mm], 15 is about 0.90 The results in the case of [mm] are shown respectively.
音響整合層の厚さが厚いほど、中心周波数は低くなった。もっとも感度の大きい１４の中心周波数は約５００［ｋＨｚ］であった。この場合の超音波の音速は、（１／４）波長を１［ｍｍ］と考えることができるので、約２０００［ｍ／ｓ］であった。図３（ｂ）に音響整合層の厚さを変えて作成した比較的感度の小さかった超音波振動子の周波数特性を示す。１７は音響整合層が約１．１０［ｍｍ］、１８は約１．０５［ｍｍ］、１９は約１．００［ｍｍ］、２０は約０．９５［ｍｍ］、２１は約０．９０［ｍｍ］の場合の結果をそれぞれ示す。図３（ａ）の場合と同様に、音響整合層の厚さが厚いほど、中心周波数は低くなった。もっとも感度の大きい１９の中心周波数は約５００［ｋＨｚ］であった。この場合も超音波の音速は、（１／４）波長を１［ｍｍ］、即ち、波長を４［ｍｍ］と考えることができるので、約２０００［ｍ／ｓ］であった。 The thicker the acoustic matching layer, the lower the center frequency. The center frequency of 14 having the highest sensitivity was about 500 [kHz]. The speed of sound of the ultrasonic wave in this case was about 2000 [m / s] because the (1/4) wavelength can be considered as 1 [mm]. FIG. 3B shows the frequency characteristics of an ultrasonic transducer having a relatively low sensitivity, which was prepared by changing the thickness of the acoustic matching layer. 17 is about 1.10 [mm], 18 is about 1.05 [mm], 19 is about 1.00 [mm], 20 is about 0.95 [mm], and 21 is about 0.90. The results in the case of [mm] are shown respectively. Similar to the case of FIG. 3A, the thicker the acoustic matching layer, the lower the center frequency. The center frequency of 19 having the highest sensitivity was about 500 [kHz]. Also in this case, the sound speed of the ultrasonic wave was about 2000 [m / s] because the (1/4) wavelength can be considered as 1 [mm], that is, the wavelength is 4 [mm].
図４（ａ），（ｂ）に図３（ａ），（ｂ）に示した超音波振動子の音響整合層の表面写真を示す。図４（ａ）は、比較的感度の大きかった図３（ａ）に示した超音波振動子の音響整合層の表面写真を示し、２２ａおよび２２ｂは直径が約２００［μｍ］の気孔を示す。なお、気孔の中に有機ガラスの乾燥ゲルが存在しているのがわかる。写真より、セラミック多孔体の気孔径は、大きくても約２００［μｍ］で、全般的により細かい直径の気孔から構成されていることがわかる。 FIGS. 4A and 4B show photographs of the surface of the acoustic matching layer of the ultrasonic transducer shown in FIGS. 3A and 3B. FIG. 4A shows a surface photograph of the acoustic matching layer of the ultrasonic transducer shown in FIG. 3A having relatively high sensitivity, and 22a and 22b show pores having a diameter of about 200 [μm]. . In addition, it turns out that the dry gel of organic glass exists in a pore. From the photograph, it can be seen that the pore diameter of the ceramic porous body is about 200 [μm] at most, and is generally composed of pores with a finer diameter.
図４（ｂ）は、比較的感度の小さかった図３（ｂ）に示した超音波振動子の音響整合層の表面写真を示し、２３ａおよび２３ｂは直径が約３００［μｍ］の気孔を示す。また、２４ａは直径が約５００［μｍ］の気孔を示す。なお、気孔の中に有機ガラスの乾燥ゲルが存在しているのが分かる。写真より、セラミック多孔体は、気孔径が約３００［μｍ］以上のものを多く含み、大きいものでは５００［μｍ］程度であることがわかる。また、さらに大きい気孔径のものも散見され、図４（ａ）に示したものに比べ、不均一であることがわかる。 FIG. 4B shows a surface photograph of the acoustic matching layer of the ultrasonic transducer shown in FIG. 3B, which has a relatively low sensitivity, and 23a and 23b show pores having a diameter of about 300 [μm]. . Reference numeral 24a denotes a pore having a diameter of about 500 [μm]. In addition, it turns out that the dry gel of organic glass exists in a pore. From the photograph, it can be seen that the ceramic porous body contains a large number of pores having a pore diameter of about 300 [μm] or more and about 500 [μm] in the case of a large one. In addition, it is found that even larger pore diameters are found, which is not uniform as compared with that shown in FIG.
この結果より、比較的感度の大きい超音波振動子の音響整合層を構成するセラミック多孔体は、気孔径が大体均一で約２００［μｍ］以下であることが必要であるといえる。また、図４（ｂ）に示した不均一で大きい気孔径を含んでいる音響整合層を構成するセラミック多孔体を有する超音波振動子は、比較的感度が小さいと言える。 From this result, it can be said that the porous ceramic body constituting the acoustic matching layer of the ultrasonic transducer having relatively high sensitivity is required to have a uniform pore diameter of approximately 200 [μm] or less. In addition, it can be said that the ultrasonic transducer having the ceramic porous body constituting the acoustic matching layer including the nonuniform and large pore diameter shown in FIG. 4B has relatively low sensitivity.
なお、気孔径約２００［μｍ］は、超音波の波長４［ｍｍ］の（１／２０）に相当する。 The pore diameter of about 200 [μm] corresponds to (1/20) of the ultrasonic wavelength 4 [mm].
このようにして形成した音響整合層を有する超音波振動子に対し、熱サイクル試験を実施した結果を図５に示す。なお、熱サイクル試験には、図５（ａ）に示した比較的感度の大きい超音波振動子を用いた。同図において、横軸は熱サイクル試験におけるサイクル数を、縦軸に開始時を１．０とする超音波振動子の相対感度を示す。熱サイクル試験は、＋８０［℃］と、−４０［℃］の気相中に約３０分間、交互に保持する方法とした。図中の白丸で示される実線２２は本発明に基づく超音波振動子の結果（Ｎ＝１０個の平均）を、黒四角で示される破線２３は従来の超音波振動子の結果（Ｎ＝１０個の平均）を示す。 FIG. 5 shows the result of the thermal cycle test performed on the ultrasonic transducer having the acoustic matching layer formed as described above. In the thermal cycle test, an ultrasonic vibrator with relatively high sensitivity shown in FIG. 5A was used. In the figure, the horizontal axis represents the number of cycles in the thermal cycle test, and the vertical axis represents the relative sensitivity of the ultrasonic transducer with 1.0 at the start. The thermal cycle test was a method of alternately holding in a gas phase of +80 [° C.] and −40 [° C.] for about 30 minutes. The solid line 22 indicated by a white circle in the figure indicates the result of the ultrasonic transducer according to the present invention (N = 10 average), and the broken line 23 indicated by the black square indicates the result of the conventional ultrasonic transducer (N = 10). Average).
本発明に基づく超音波振動子では、熱サイクル２０００回においても、感度低下は約５［％］以下であり、実用上問題となる１０［％］以上感度低下するものは無かった。従来の超音波振動子では、１５００回以降に劣化するものが多く見られ、２０００回では、実用上問題となる１０［％］以上の感度低下が発生した。本発明に基づく超音波振動子では
、比較的強度の弱い、音響イオンピ−ダンスの小さい有機ガラスの乾燥ゲルが、比較的強度の大きい、音響インピ−ダンスの大きい無機質のセラミック多孔体で保護される構成であるためと考えられる。
In the ultrasonic vibrator according to the present invention, the sensitivity decrease was about 5 [%] or less even after 2000 thermal cycles, and there was no material whose sensitivity decreased by 10 [%] or more, which is a practical problem. Many conventional ultrasonic transducers deteriorate after 1500 times. At 2000 times, a sensitivity drop of 10% or more, which is a practical problem, occurred. In the ultrasonic transducer according to the present invention, a dry gel of organic glass having a relatively low strength and a low acoustic ion impedance is protected by an inorganic ceramic porous body having a relatively high strength and a high acoustic impedance. This is thought to be due to the configuration.
（実施の形態５）
図６は、本発明の実施の形態５における超音波振動子２４の断面図を示す。２５は上記で説明した本発明に基づく比較的強度の大きい音響インピ−ダンスの大きい連通孔からなる連続体材料と、比較的強度の小さい音響インピ−ダンスの小さい連通孔からなる連続体で構成された音響整合層を２層（２６、２７）備えた音響整合層を示す。２６と２７とは同じ構成の音響整合層であるが、表面に近い２７の方の音響インピ−ダンスが小さくなるように構成した。即ち、２６はセラミック多孔体の密度を０．８〜０．９［ｇ／ｃｍ３］程度とし、２７の方は０．３〜０．４［ｇ／ｃｍ３］程度とした。また、それぞれの内部に形成した有機ガラスの乾燥ゲルの密度は、２６は０．３０〜０．３５［ｇ／ｃｍ３］、２７は０．１５〜０．２５［ｇ／ｃｍ３］とした。なお、それぞれの厚さは、超音波波長の（１／４）となるように調整した。
(Embodiment 5)
FIG. 6 shows a cross-sectional view of the ultrasonic transducer 24 according to the fifth embodiment of the present invention. 25 is composed of a continuous material composed of a communication hole having a relatively large acoustic impedance and a large acoustic impedance based on the present invention described above and a continuous material composed of a communication hole having a relatively small acoustic impedance and a small acoustic impedance. 2 shows an acoustic matching layer having two acoustic matching layers (26, 27). Although 26 and 27 are acoustic matching layers having the same configuration, the acoustic impedance of 27 closer to the surface is configured to be smaller. That is, 26 has a density of the ceramic porous body of about 0.8 to 0.9 [g / cm 3 ], and 27 has a density of about 0.3 to 0.4 [g / cm 3 ]. Moreover, as for the density of the dry gel of the organic glass formed in each inside, 26 was 0.30-0.35 [g / cm < 3 >], 27 was 0.15-0.25 [g / cm < 3 >]. . Each thickness was adjusted to be (1/4) of the ultrasonic wavelength.
この構成により、超音波の出力特性は大幅に増加した。即ち、大きい音響インピ−ダンスを持つ圧電体３で発生した超音波は、第１の音響整合層２６、および、第２の音響整合層２７を通り外部に放出されるため、より効率よくインピ−ダンスマッチングが取れるためと考えられる。 With this configuration, the output characteristics of the ultrasonic wave are greatly increased. That is, since the ultrasonic wave generated by the piezoelectric body 3 having a large acoustic impedance is emitted to the outside through the first acoustic matching layer 26 and the second acoustic matching layer 27, the impedance is more efficiently introduced. It is thought that dance matching can be taken.
（実施の形態６）
図７は、本発明の実施の形態６における超音波振動子２８の断面図を示す。２９は音響整合層４の表面に設けた被覆層を示す。表面の被覆層２９は、シリコンゴムあるいはフッ素ゴムなどの硬化後も粘着力のあるエラストマ−系接着剤で構成した。
(Embodiment 6)
FIG. 7 is a sectional view of the ultrasonic transducer 28 according to the sixth embodiment of the present invention. Reference numeral 29 denotes a coating layer provided on the surface of the acoustic matching layer 4. The coating layer 29 on the surface was made of an elastomer-based adhesive having adhesive strength even after being cured such as silicon rubber or fluorine rubber.
この構成により、表面が滑らかとなり、超音波の出力感度がより大きくなった。即ち、図４で示した多孔体の凹凸がなくなり平滑となったため、超音波振動のエネルギ−がより効率よく外部へ伝達されるためと考えられる。また、表面がエラストマ−系材料で被覆されているため、組立て作業などで表面を損傷することもなくなり、また機械的な強度も向上し、作業効率が向上した。 With this configuration, the surface becomes smooth and the output sensitivity of the ultrasonic wave is increased. That is, it is considered that the energy of ultrasonic vibration is transmitted to the outside more efficiently because the porous body shown in FIG. In addition, since the surface is coated with an elastomeric material, the surface is not damaged during assembling work, and the mechanical strength is improved and the working efficiency is improved.
なお、被覆膜の厚さは、概ね１０［μｍ］以下とした。被覆膜が厚すぎると、音響インピ−ダンスの逆転層として作用するようになり、超音波の出力特性が低下するようになる。被覆膜が１０［μｍ］以下の場合には、音響整合層としては無視できるようになし、超音波出力特性が低下することはない。 Note that the thickness of the coating film was approximately 10 [μm] or less. If the coating film is too thick, it acts as an inversion layer of the acoustic impedance, and the output characteristics of the ultrasonic waves are degraded. When the coating film is 10 [μm] or less, the acoustic matching layer can be ignored and the ultrasonic output characteristics are not deteriorated.
（実施の形態７）
図８は、本発明の実施の形態７における超音波流速・流量計の断面図を示す。３０は超音波流速・流量計の断面図を示し、３１は流体の流れる流路、３２は上流側に設けられた本発明に基づく超音波振動子、３３は下流側に設けられた本発明に基づく超音波振動子。なお、実線の矢印３４は流体の流れる方向を、破線の矢印３５は上流側の振動子３２と、下流側の振動子３３との間での超音波の伝播する方向をそれぞれ示す。図中のθは、流体の流れる方向と、超音波の伝播する方向との交差角を示す。
(Embodiment 7)
FIG. 8 shows a sectional view of an ultrasonic flow velocity / flow meter according to the seventh embodiment of the present invention. 30 is a sectional view of an ultrasonic flow velocity / flow meter, 31 is a flow path through which a fluid flows, 32 is an ultrasonic transducer according to the present invention provided on the upstream side, and 33 is the present invention provided on the downstream side. Based ultrasonic transducer. A solid line arrow 34 indicates the direction of fluid flow, and a broken line arrow 35 indicates the direction in which ultrasonic waves propagate between the upstream vibrator 32 and the downstream vibrator 33. In the figure, θ represents the crossing angle between the direction in which the fluid flows and the direction in which the ultrasonic waves propagate.
この構成において、上流側の超音波変換器３２から超音波を送信し、下流側の超音波変換器３３で受信し、また下流側の超音波変換器３３から超音波を送信し、上流側の超音波変換器３２で受信するよう交互に繰り返している。このとき、上流側の超音波変換器３２から下流側の超音波変換器３３への超音波の伝播時間をＴｕｄ、下流側の超音波変換器３３から上流側の超音波変換器３２への超音波の伝播時間をＴｄｕとし、超音波が流体中を
伝搬する伝搬速度をＶｓ、流体の流速をＶｆとすると、
Ｔｕｄ＝Ｌｄ／［Ｖｓ＋Ｖｆ・ｃｏｓ（θ）］
Ｔｄｕ＝Ｌｄ／［Ｖｓ−Ｖｆ・ｃｏｓ（θ）］
となる。なお、Ｌｄは超音波振動子間の距離を示す。
In this configuration, ultrasonic waves are transmitted from the upstream ultrasonic transducer 32, received by the downstream ultrasonic transducer 33, and ultrasonic waves are transmitted from the downstream ultrasonic transducer 33. It is alternately repeated so as to be received by the ultrasonic transducer 32. At this time, the propagation time of the ultrasonic wave from the upstream ultrasonic transducer 32 to the downstream ultrasonic transducer 33 is Tud, and the ultrasonic wave is transmitted from the downstream ultrasonic transducer 33 to the upstream ultrasonic transducer 32. If the propagation time of the sound wave is Tdu, the propagation velocity of the ultrasonic wave in the fluid is Vs, and the flow velocity of the fluid is Vf,
Tud = Ld / [Vs + Vf · cos (θ)]
Tdu = Ld / [Vs−Vf · cos (θ)]
It becomes. Ld represents the distance between the ultrasonic transducers.
これらより、
Ｖｓ＋Ｖｆ・ｃｏｓ（θ）＝Ｌｄ／Ｔｕｄ
Ｖｓ−Ｖｆ・ｃｏｓ（θ）＝Ｌｄ／Ｔｄｕ
となり、これらの両辺を引き算すると、
２＊Ｖｆ・ｃｏｓ（θ）＝（Ｌｄ／Ｔｕｄ）−（Ｌｄ／Ｔｄｕ）
＝Ｌｄ＊［（１／Ｔｕｄ）−（１／Ｔｄｕ）］
となる。よって、
Ｖｆ＝｛Ｌｄ／［２・ｃｏｓ（θ）］｝＊［（１／Ｔｕｄ）−（１／Ｔｄｕ）］
となり、流体の流速Ｖｆが得られる。さらに、流路３１の断面積Ｓｒを乗じると、流量Ｑｍとなる。
From these,
Vs + Vf · cos (θ) = Ld / Tud
Vs−Vf · cos (θ) = Ld / Tdu
And subtracting both sides,
2 * Vf · cos (θ) = (Ld / Tud) − (Ld / Tdu)
= Ld * [(1 / Tud)-(1 / Tdu)]
It becomes. Therefore,
Vf = {Ld / [2 · cos (θ)]} * [(1 / Tud) − (1 / Tdu)]
Thus, the fluid flow velocity Vf is obtained. Furthermore, when the cross-sectional area Sr of the flow path 31 is multiplied, the flow rate becomes Qm.
即ち、Ｑｍ＝Ｓｒ＊Ｖｆが、計測した流量値となる。このように超音波振動子間の距離Ｌｐ、および流路３１の断面積Ｓｒは、予めわかっているので、上述のように流路３１を流れる流体の流速Ｖｆおよび流量Ｑｍが計測されることになる。 That is, Qm = Sr * Vf is the measured flow rate value. As described above, since the distance Lp between the ultrasonic transducers and the cross-sectional area Sr of the flow path 31 are known in advance, the flow velocity Vf and the flow rate Qm of the fluid flowing through the flow path 31 are measured as described above. Become.
本発明の超音波振動子を用いることにより、即ち、セラミック多孔体などからなる比較的強度の大きい音響インピ−ダンスの大きいな連続体からなる材料と、有機ガラスの乾燥ゲルなどからなる比較的強度の小さい音響インピ−ダンスの小さな連続体からなる材料との混合体からなる音響整合層を有しているので、感度が大きいので、Ｓ／Ｎよく流体の流速・流量を計測することができる。また、機械的強度も大きくので、信頼性の高い超音波流速・流量計を実現することができる。 By using the ultrasonic vibrator of the present invention, that is, a material composed of a continuous material having a relatively large acoustic impedance, such as a ceramic porous material, and a relatively strong material composed of a dried gel of organic glass, etc. Since it has an acoustic matching layer made of a mixture with a material made of a continuum having a small acoustic impedance, the sensitivity is high, so the flow velocity / flow rate of the fluid can be measured with good S / N. In addition, since the mechanical strength is large, a highly reliable ultrasonic flow velocity / flow meter can be realized.
以上のように、本発明にかかる超音波振動子は、感度が大きく、信頼性にも優れているので、高性能な超音波流速・流量計をも実現できる。従って、長期信頼性を要求される家庭用ガスメ−タ、水道用メ−タなどの用途の適用できる。 As described above, since the ultrasonic transducer according to the present invention has high sensitivity and excellent reliability, it is possible to realize a high-performance ultrasonic flow velocity / flow meter. Therefore, applications such as household gas meters and water meters that require long-term reliability can be applied.
１ 超音波振動子
２ 缶ケ−ス
３ 圧電体
４ 音響整合層
５ セラミック多孔体
６ 有機ガラス
DESCRIPTION OF SYMBOLS 1 Ultrasonic vibrator 2 Can case 3 Piezoelectric body 4 Acoustic matching layer 5 Ceramic porous body 6 Organic glass
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