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JP4291500B2 - Broadband transducer - Google Patents

Broadband transducer Download PDF

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Publication number
JP4291500B2
JP4291500B2 JP2000225069A JP2000225069A JP4291500B2 JP 4291500 B2 JP4291500 B2 JP 4291500B2 JP 2000225069 A JP2000225069 A JP 2000225069A JP 2000225069 A JP2000225069 A JP 2000225069A JP 4291500 B2 JP4291500 B2 JP 4291500B2
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Prior art keywords
transducer
matching layer
sound wave
wave propagation
length
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JP2002044787A (en
Inventor
裕徳 森
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Tokin Corp
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NEC Tokin Corp
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  • Transducers For Ultrasonic Waves (AREA)

Description

【0001】
【発明の属する技術分野】
本発明は、海洋での魚群探知や深度の海洋探知での使用に好適な広帯域送受波器であって、特に、圧電振動子を用いた電気音響変換素子を複数個、配列して構成される素子配列型の広帯域送受波器に関するものである。
【0002】
【従来の技術】
従来、海洋での魚群探知や深度の海洋探知での分野での、送受波器については、音響測定精度の向上のため、使用周波数の高周波数化による水中音波の短波長化、あるいは信号応答性の改善を図るための広帯域化等の技術が提案されてきた。特に、送受波器の広帯域化の技術に関しては、整合層の使用により、かなりの成果が上がっていた。
【0003】
一般に、送受波器の電気音響変換素子に使用される整合層は、整合層材料の音響インピーダンス密度に着目し、電気信号と音響信号の変換を行う圧電振動子と水中超音波送受波器における音波伝搬媒体である水の各々の音響インピーダンス密度の幾何平均値を目標として種々の材料から選択される。
【0004】
前記整合層の長さ寸法を圧電振動子の使用周波数における整合層中の音波伝搬波長λの1/4とし、圧電振動子の音響放射面に接着等の方法により、音波の伝搬方向と整合層の長さ方向が一致するように取り付けられる。
【0005】
図5は、1個の圧電振動子に1層の整合層を設けた電気音響変換素子を用いた従来の送受波器の上面及び側面から見た断面図である。図5(a)は、送受波器の正面図であり、図5(b)は、図5(a)でのBB断面図である。
【0006】
前記送受波器の整合層の改善による送受波器の広帯域化においては、図5(a)に示すように、1個の圧電振動子1aの音響放射面に整合層2aを1層設けた電気音響変換素子を使用する構成が基本の形である。整合層2aを1層設けて得られる帯域幅では充分でない場合には、図6に示すように、2層目の整合層2bあるいは3層目の整合層2cを、新たに設けて、多重整合層の構成をとることで、より一層の広帯域化を図っていた。
【0007】
また、図7に示すような素子配列型の送受波器において、圧電振動子1bに整合層2dを1層設けた電気音響変換素子を複数個、配列することで充分な帯域幅が得られなければ、図7に示す送受波器の場合と同様に、図8に示すように、2層目の整合層2eあるいは3層目の整合層2fを設けて多重整合層化することにより対処するのが一般的であった。
【0008】
即ち、図7、図8に示す従来構成の送受波器は、図9に示すような音響放射面形状の電気音響変換素子1個で構成する送受波器を、細分化した電気音響変換素子を16個配列して音響放射面の形状や外径寸法が等しくなるように構成し直したものである。
【0009】
ここで、16個の電気音響変換素子は、各々同一の特性を持つものであるから、素子配列した送受波器の共振特性は、図9の電気音響変換素子1個の送受波器と同様に、圧電振動子の使用周波数における単一共振が整合層1個の付与により1次及び2次の2つの共振点を持つ2重共振特性へと変化したものであり、電気音響変換素子を複数個、配列しても共振点がさらに増えることはない。
【0010】
【発明が解決しようとする課題】
従来の送受波器においては、以下の問題点があった。即ち、図7のように、多重整合層を設けた電気音響変換素子を複数個配列する構造の送受波器とする場合、各電気音響変換素子は1個の圧電振動子に接着等の方法で2層以上の整合層を取り付けていくことで形成されるため、整合層の各層間のずれの防止や接着剤層の厚さの管理等が必要になる等、組立の煩雑化を招き、圧電振動子や整合層間の境界となる接着剤層の増加に伴い特性のばらつきが顕著化する等の問題があった。
【0011】
さらには、2層目、3層目の整合層として音響インピーダンス密度の異なる材料を使用するが、各整合層の音波伝搬方向の長さ寸法は、それぞれの材料における音波伝搬波長λの1/4とすることが通例で、整合層を1層だけ設けた構成の電気音響変換 素子に対して長さ寸法が増大するために、結果として、送受波器の寸法も大きくせざるを得ないという問題もあった。
【0012】
従って、本発明の目的は、素子配列型の水中超音波送受波器において、従来、1層の整合層を設けることで得られていた広帯域化の効果に対し、多重整合層という電気音響変換素子の構造の複雑化や長さ寸法の増加を必要とせずに、整合層を1層設けた基本的な構成の電気音響変換素子を組み合わせて使用することで、より広帯域化を達成した広帯域送受波器を提供することである。
【0013】
【課題を解決するための手段】
本発明は、圧電振動子に1層の整合層を設けた電気音響変換素子を複数個、配列して構成される素子配列型の水中超音波送受波器において、前記整合層として音波伝搬方向の長さが各整合層中の音波伝搬波長λに対して異なる比率である2種類以上の整合層を使用し、各整合層の長さを送受波器の使用周波数と材料の音波伝搬速度とにより定まる整合層中の音波伝搬波長λの1/10から4/10の間の値とすることを特徴とする。
【0014】
本発明によれば、音波伝搬方向である長さ方向の寸法が異なる複数種類の整合層を一つの仕様の圧電振動子に付与することで、共振特性のずれた複数の電気音響変換素子が得られ、それらを組み合わせて素子配列を構成することにより感度特性のずれた電気音響変換素子群の特性を合成した感度特性を有する送受波器を得ることができる。
【0015】
即ち、本発明は、圧電振動子に1層の整合層を付与した電気音響変換素子を複数個、配列して構成した素子配列型の広帯域送受波器において、前記整合層の音波伝搬方向の長さが、各整合層中の音波伝搬波長λに対して、異なる比率である2種類以上の整合層を使用し、各整合層の長さは、送受波器の使用周波数と材料の音波伝搬速度とにより定まる音波伝搬波長λの1/10以上から4/10以下の範囲の間の長さとする広帯域送受波器である。
【0016】
【発明の実施の形態】
本発明の広帯域送受波器について、以下に説明する。
【0017】
図1に、本発明の広帯域送受波器の説明図を示す。図1(a)は、正面図を示し、図1(b)は、図1(a)でのAA断面図を示す。
【0018】
従来の構成では、図7のように、素子配列型の送受波器で圧電振動子に1層の整合層を設けた電気音響変換素子を複数個、配列する場合は、1種類の材料から同一の寸法に作られた整合層を各圧電振動子に接着等で付与するため、各々の電気音響変換素子は、同一の特性を持つものであった。
【0019】
これは、素子配列型の送受波器が、図6のように、圧電振動子1個で電気音響変換素子を構成する送受波器に対して、指向性の操作や振動子の外径寸法比に起因する結合振動の発生回避を達成するために、音響放射面を細分化した形状の電気音響変換素子を複数個、配列する形で置き換えることを当初の目的として構成されたためである。
【0020】
即ち、図7に示す従来構成の送受波器は、図9に示すような音響放射面形状の電気音響変換素子1個で構成する送受波器を、細分化した電気音響変換素子を16個配列して音響放射面の形状や外径寸法が等しくなるように構成し直したものと言える。
【0021】
ここで、16個の電気音響変換素子は、各々同一特性を持つものであるから、素子配列した送受波器の共振特性は、図9の電気音響変換素子1個の送受波器と同様に、圧電振動子の使用周波数における単一共振が整合層1個の付与により1次及び2次の2つの共振点を持つ2重共振特性へと変化したものであり、電気音響変換素子を複数個配列しても共振点がさらに増えることはない。
【0022】
これに対して、本発明の広帯域送受波器は、長さの異なる複数の整合層を使用することで、2重共振特性の共振点がずれた電気音響変換素子が複数得られ、これらを組み合わせることで3個以上の共振点を持つ広帯域送受波器を構成している。
【0023】
ここで、整合層の材料選択のために、種々の材料について特性が評価されているが、主に材料の音響インピーダンス密度特性に着目して圧電振動子と広帯域送受波器における音波伝搬媒体である水の各々の音響インピーダンス密度の幾何平均値に近い特性値を持つ材料が整合層材料として優先的に選択されている。これは、圧電振動子と音波伝搬媒体である水との間のインピーダンスマッチングを考慮しているためである。
【0024】
上記の整合層の寸法に関しては、特に音波伝搬方向の長さ寸法を定める必要があるが、選択した材料の使用周波数における音波伝搬波長λに対し、整合層としての音波伝搬方向の長さ寸法LをL=λ/4となるように設定するのが通例であった。本発明では、整合層の音波伝搬方向の長さ寸法を使用周波数における整合層中の音波伝搬波長λの1/4として一様な整合層を使用する従来の方法に対して、意識的に長さ寸法の異なる整合層を複数使用するものである。
【0025】
即ち、本発明の広帯域送受波器は、圧電振動子に1層の整合層を付与した電気音響変換素子を複数個、配列して構成した素子配列型の広帯域送受波器において、前記整合層として音波伝搬方向の長さが各整合層中の音波伝搬波長λに対して異なる比率である、2種類以上の整合層を使用し、各整合層の長さは、送受波器の使用周波数と材料の音波伝搬速度とにより定まる音波伝搬波長λの1/10以上から4/10以下の範囲の間の長さとする広帯域送受波器である。
【0026】
ここで、整合層の長さが、音波伝搬波長λの1/10未満であると、整合層での超音波の透過率が極端に低下し、また寸法上も、厚みが薄くなり、送受波器の性能が著しく低下する。また、整合層の長さが、音波伝搬波長λの4/10を超えると、超音波の透過率が極端に低下し、送受波器の性能が著しく低下する。従って、整合層の長さを、音波伝搬波長λの1/10以上から4/10以下の範囲とするものである。
【0027】
【実施例】
本発明の実施例による広帯域送受波器について、以下に説明する。
【0028】
本発明の広帯域送受波器では、整合層の材料として、ガラス布基材エポキシ樹脂積層板を使用している。図3は、ガラス布基材エポキシ樹脂積層板における音波伝搬方向と、同樹脂板から得る整合層の音波伝搬方向と長さ方向の関係を示した図である。ここで、ガラス布基材エポキシ樹脂積層板22は、積層構造となっている。
【0029】
図3より、ここで使用している整合層は2種類で、いずれもガラス布基材エポキシ樹脂積層板22から加工したものであり、同一の素材から長さ方向寸法のみ異なる整合層を加工して組合せた場合について説明している。
【0030】
ここでは、ガラス布基材エポキシ樹脂積層板22の繊維に沿った方向を整合層の音波伝搬方向として、1種類は整合層中の音波伝搬波長λの1/5の長さとし、もう1種類は波長λの3/10の長さとして2種類の整合層を加工した。この整合層を長さ方向に周波数70kHzで共振する圧電振動子21に接着により付与して、1層の整合層を有する電気音響変換素子23a、23bの2種類を得ている。
【0031】
ガラス布基材エポキシ樹脂積層板22の材料特性としては、密度ρ=1.9×10(kg/cm)、繊維に沿った方向の音波伝搬速度C=3150(m/sec)あることから、角柱状の圧電振動子21の使用周波数70kHzに対して整合層の音波伝搬方向の長さ寸法は、音波伝搬波長λの1/5で約La=9.0(mm)、音波伝搬波長λの3/10で約Lb=13.5(mm)となる。
【0032】
熱硬化型のエポキシ樹脂接着剤により圧電振動子と前記2種類の整合層22a、22bを接着して、図4に示す電気音響変換素子23a、23bを得る。併せて、図4には、電気音響変換素子23aのインピーダンス周波数特性24a、電気音響変換素子23bのインピーダンス周波数特性24bを示す。長さ寸法の大きい整合層22aを設けた電気音響変換素子23aの共振点は、長さ寸法の小さい整合層22bを設けた電気音響変換素子23bの共振点に対して、約10kHz低周波側へシフトする。
【0033】
これらの電気音響変換素子23a、23bを組み合わせれば、インピーダンス特性に4つの共振点を持つ送受波器が得られる。これに対して、整合層が1種類である従来の送受波器構成では、例えば電気音響変換素子23aだけを配列したものに等しいことから、インピーダンス周波数特性24aと同様に、2つの共振点を持つ特性となる。
【0034】
実施例では、この2種類の電気音響変換素子23a、23bを各々8個使用して、4列×4列の配列を構成し、素子間及び素子配列の周囲にコルク25を接着して素子の位置決めと周囲からの遮音処置を行い、信号ケーブル26と接続後にポリウレタンゴムモールド27により全体をモールドして水密性を持たせ、図1に示す素子配列型の水中超音波送受波器を製作した。
【0035】
この超音波送受波器における電気音響変換素子23a、23bの配置は、図1に示すように、それぞれが交互に配置されるようにしてある。このようにして得た超音波送受波器の感度特性は、図2の本発明の送受波器の周波数特性の送波感度周波数特性28、受波感度周波数特性30に示すようになる。
【0036】
図2には、従来例として、図7に示す送受波器に実施例で用いた整合層と同じ材質で、音波伝搬方向の長さ寸法を音波伝搬波長λの1/4とした整合層だけを使用した場合の送波感度周波数特性29、受波感度周波数特性31を併せて示した。従来の構成で得られる送受波器の感度特性に対して、本発明の実施例では、低周波側及び高周波側に帯域が広がった感度特性が得られている。
【0037】
これは、本発明の実施例で用いた電気音響変換素子23a、23bの感度特性が、従来の長さ寸法を整合層中の音波伝搬波長λの1/4とした整合層を設けた電気音響変換素子の感度特性に対して、それぞれ高周波側、低周波側にシフトした特性を示しており、帯域のずれた感度特性を重畳させることにより、低周波側・高周波側へそれぞれ帯域を拡げ、また帯域内の感度変化を抑制することで、送受波器としてより広帯域化の効果が得られるものである。
【0038】
従来の送受話器の構成では、1層の整合層を付与した場合に対して、さらに広帯域化を図るための多重整合層化という手法は、整合層を多層設けることで、圧電振動子を多重共振させ、共振周波数近傍での感度特性の持ち上がりを連続的に繋げ、なおかつ、帯域内の感度変化を抑制ることで広帯域化を達成する方法であった。
【0039】
しかし、本発明の送受話器では、複数の電気変換音響素子をいくつかの群に分けてそれぞれの素子群に共振特性のずれを与え、これらの素子群を組み合わせて素子配列を形成したときに、1つの送受波器として複数の共振周波数を持つことを可能にし、多重整合層による圧電振動子の多重共振化の場合と同様の効果を近似的に得られるように構成したものである。
【0040】
本発明の方法によれば、圧電振動子に多重整合層を付与した時のような複雑な特性推定計算は不要であり、1層の整合層を付与した時の特性推定を複数行い、これらの特性の組合せから、素子配列を行った後の送受波器としての感度特性が比較的容易に推定できる。
【0041】
上記の実施例では、ガラス布基材エポキシ樹脂積層板を整合層として使用し、整合層の音波伝搬方向の長さ寸法の異なる整合層を加工し、圧電振動子に付与して特性の異なる2種類の電気音響変換素子を得ることで、同一の整合層1種類のみ使用する場合に対して、広帯域化の効果が大きく得られることを示したが、本発明は、整合層の材料としてガラス布基材エポキシ樹脂積層板のみ規定するものではなく、他の組成が均一である一般の樹脂材料であっても、同様の効果が得られる。
【0042】
ただし、その効果の大小は、それぞれ使用する材料の特性と整合層の寸法設定に依存するもので、本実施例と異なる材料を使用した場合でも、本実施例と全く同じ程度の効果が得られることを保証するものではない。
【0043】
本実施例で述べたように、1種類の材料から複数種類の整合層を得る方法であれば、複数の材料について特性を調査して材料同士の組合せを考える作業を省略することができる。
【0044】
また、整合層として材料特性の異なる複数の樹脂材料を組み合わせて使用することでも問題なく、本発明のような効果を得ることができる。ただし、この場合、各整合層の長さをそれぞれの樹脂材料中の音波伝搬波長λに対して1/10から4/10の間で異なる比率となるように設定しても、使用する各材料の音波伝搬速度によって整合層の長さ寸法が等しくなる場合もあり得るが、問題はない。
【0045】
また、本実施例では、整合層の長さ寸法を樹脂材料中の音波伝搬波長λの1/4から意識的にずらしているが、整合層の長さ寸法として音波伝搬波長λの1/4となる設定を組合せの中に含めることは何の問題もない。
【0046】
【発明の効果】
本発明によれば、整合層付きとしては最も単純な形態である1層の整合層を設けた電気音響変換素子を配列する方式の送受波器であって、音波伝搬波長に対する整合層の長さ寸法の設定が異なる複数の整合層を使用するという簡単な方法で、より広帯域化の成された広帯域送受波器を提供できる。
【図面の簡単な説明】
【図1】本発明における素子配列型の広帯域送受波器の説明図。図1(a)は正面図、図1(b)は、図1(a)でのAA断面図。
【図2】本発明による広帯域送受波器と、従来の構成による広帯域送受波器の感度特性を示すグラフ。図2(a)は、送波電力感度と周波数との関係を示す図、図2(b)は、受波電力感度と周波数との関係を示す図。
【図3】ガラス布基材エポキシ樹脂積層板における音波伝搬方向と、同樹脂板から得る整合層の音波伝搬方向と長さ方向の関係を示す図。
【図4】異なる長さの整合層を付与した2種類の電気音響変換素子の外観図と特性の説明図。図4(a)は、整合層の長さをLaとした場合の電気音響変換素子の外観図、図4(b)は、整合層の長さをLbとした場合の電気音響変換素子の外観図、図4(c)は、図4(a)と図4(b)に示したそれぞれの電気音響変換素子のインピーダンス特性を示す図。
【図5】1個の圧電振動子に1層の整合層を設けた電気音響変換素子を用いた従来の送受波器の上面及び側面から見た断面図。図5(a)は、送受波器の正面図、図5(b)は、図5(a)でのBB断面図。
【図6】2層の整合層を加えて多重整合層化した電気音響変換素子を用いた従来の送受波器の側面から見た断面図。
【図7】1個の圧電振動子に1層の整合層を設けた電気音響変換素子を複数個配列した従来の素子配列型の送受波器の上面及び側面から見た断面図。図7(a)は、送受波器の正面図、図7(b)は、図7(a)でのCC断面図。
【図8】図7の送受波器に加えて、2層の整合層を加えて多重整合層化した電気音響変換素子を用いた従来の送受波器の断面図。
【図9】1個の圧電振動子に1層の整合層を設けた電気音響変換素子を用いた従来の送受波器で、図8と音響放射面の形状寸法が等しい構成とした送受波器の上面及び側面から見た断面図。図9(a)は、送受波器の正面図、図9(b)は、図9(a)でのDD断面図。
【符号の説明】
1a,1b,1c,21 圧電振動子
2a〜2g 整合層
22 ガラス布基材エポキシ樹脂積層板
22a,22b 整合層
23a,23b 電気音響変換素子
24a,24b インピーダンス周波数特性
25 コルク
26 信号ケーブル
27 ポリウレタンゴムモールド
28,29 送波感度周波数特性
30,31 受波感度周波数特性
[0001]
BACKGROUND OF THE INVENTION
The present invention is a broadband transmitter / receiver suitable for use in fish detection in the ocean and ocean detection at depth, and in particular, is configured by arranging a plurality of electroacoustic transducers using piezoelectric vibrators. The present invention relates to an element array type broadband transducer.
[0002]
[Prior art]
Conventionally, for transducers in the field of fish detection in the ocean and ocean detection at depth, in order to improve acoustic measurement accuracy, shortening the wavelength of underwater acoustic waves by increasing the frequency used, or signal response Techniques such as wideband have been proposed to improve this. In particular, with regard to the technology for widening the bandwidth of the transmitter / receiver, considerable results have been achieved by using the matching layer.
[0003]
In general, the matching layer used in the electroacoustic transducer of the transducer is focused on the acoustic impedance density of the matching layer material, and the acoustic wave in the piezoelectric transducer and the underwater ultrasonic transducer that converts electrical signals and acoustic signals. The material is selected from various materials with the target being the geometric mean value of the acoustic impedance density of each of the water as the propagation medium.
[0004]
The length dimension of the matching layer is set to 1/4 of the sound wave propagation wavelength λ in the matching layer at the use frequency of the piezoelectric vibrator, and the sound wave propagation direction and the matching layer are bonded to the acoustic radiation surface of the piezoelectric vibrator by a method such as adhesion. Are attached so that their length directions coincide.
[0005]
FIG. 5 is a cross-sectional view of a conventional transducer using an electroacoustic transducer in which a single matching layer is provided on one piezoelectric vibrator, as viewed from the top and side. FIG. 5 (a) is a front view of the transducer, and FIG. 5 (b) is a BB cross-sectional view in FIG. 5 (a).
[0006]
In widening the bandwidth of the transducer by improving the matching layer of the transducer, as shown in FIG. 5 (a), an electric circuit in which one matching layer 2a is provided on the acoustic radiation surface of one piezoelectric vibrator 1a. A configuration using an acoustic transducer is a basic form. If the bandwidth obtained by providing one matching layer 2a is not sufficient, a second matching layer 2b or a third matching layer 2c is newly provided as shown in FIG. By adopting a layer structure, a wider bandwidth was achieved.
[0007]
Further, in an element array type transducer as shown in FIG. 7, a sufficient bandwidth must be obtained by arranging a plurality of electroacoustic transducers each having a matching layer 2d on the piezoelectric vibrator 1b. For example, as in the case of the transducer shown in FIG. 7, as shown in FIG. 8, a second matching layer 2e or a third matching layer 2f is provided to form a multiple matching layer. Was common.
[0008]
That is, the conventional transducer shown in FIG. 7 and FIG. 8 is a subdivided electroacoustic transducer from a transducer composed of one electroacoustic transducer having an acoustic radiation surface shape as shown in FIG. Sixteen are arranged and reconfigured so that the shape and outer diameter of the acoustic radiation surface are equal.
[0009]
Here, since the 16 electroacoustic transducers have the same characteristics, the resonance characteristics of the transducers in which the elements are arranged are the same as those of the transducer of one electroacoustic transducer in FIG. The single resonance at the operating frequency of the piezoelectric vibrator is changed to a double resonance characteristic having two primary and secondary resonance points by providing one matching layer, and a plurality of electroacoustic transducers are provided. Even if arranged, the resonance point does not increase further.
[0010]
[Problems to be solved by the invention]
The conventional transducer has the following problems. That is, as shown in FIG. 7, when a transducer having a structure in which a plurality of electroacoustic transducers provided with multiple matching layers is arranged, each electroacoustic transducer is bonded to one piezoelectric vibrator by a method such as adhesion. Since it is formed by attaching two or more matching layers, it is necessary to prevent the gap between the matching layers and to manage the thickness of the adhesive layer. There has been a problem that the variation in characteristics becomes remarkable as the adhesive layer serving as a boundary between the vibrator and the matching layer increases.
[0011]
Further, materials having different acoustic impedance densities are used as the second and third matching layers, but the length dimension in the sound wave propagation direction of each matching layer is 1/4 of the sound wave propagation wavelength λ of each material. As a result, the length of the electroacoustic transducer having a single matching layer is increased, and as a result, the size of the transducer must be increased. There was also.
[0012]
Accordingly, an object of the present invention is to provide an electroacoustic transducer element called a multi-matching layer for the effect of widening the band obtained by providing a single matching layer in an element array type underwater ultrasonic transducer. Broadband transmission / reception that achieves a wider bandwidth by using a combination of electroacoustic transducers with a basic configuration with a single matching layer, without the need for complex structure and increased length. Is to provide a vessel.
[0013]
[Means for Solving the Problems]
The present invention provides an element array type underwater ultrasonic transmitter / receiver configured by arranging a plurality of electroacoustic transducers each having a single matching layer on a piezoelectric vibrator. Two or more types of matching layers having different lengths with respect to the sound wave propagation wavelength λ in each matching layer are used, and the length of each matching layer depends on the use frequency of the transducer and the sound wave propagation speed of the material. The value is set to a value between 1/10 and 4/10 of the sound wave propagation wavelength λ in the matching layer.
[0014]
According to the present invention, a plurality of electro-acoustic transducers with different resonance characteristics can be obtained by providing a plurality of types of matching layers having different dimensions in the length direction, which is the direction of sound wave propagation, to a piezoelectric vibrator of one specification. Thus, by combining them to form an element arrangement, it is possible to obtain a transducer having a sensitivity characteristic obtained by synthesizing the characteristics of the electroacoustic transducer elements having a shifted sensitivity characteristic.
[0015]
That is, the present invention relates to an element array type broadband transducer in which a plurality of electroacoustic transducers each having a single matching layer provided on a piezoelectric vibrator are arranged. However, two or more types of matching layers having different ratios with respect to the sound wave propagation wavelength λ in each matching layer are used, and the length of each matching layer is determined by the use frequency of the transducer and the sound wave propagation speed of the material. This is a broadband transmitter / receiver having a length between 1/10 and 4/10 of the sound wave propagation wavelength λ determined by
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The broadband transmitter / receiver of the present invention will be described below.
[0017]
FIG. 1 is an explanatory diagram of a broadband transducer according to the present invention. Fig.1 (a) shows a front view, FIG.1 (b) shows AA sectional drawing in Fig.1 (a).
[0018]
In the conventional configuration, as shown in FIG. 7, in the case of arranging a plurality of electroacoustic transducers having a single matching layer on a piezoelectric vibrator in an element array type transducer, the same material is used for one element. The electroacoustic transducers have the same characteristics because the matching layer having the dimensions of 1 is applied to each piezoelectric vibrator by bonding or the like.
[0019]
This is because, as shown in FIG. 6, the element arrangement type transducer is a directivity operation and the outer diameter size ratio of the transducer with respect to the transducer comprising the electroacoustic transducer element by one piezoelectric transducer. This is because, in order to achieve the avoidance of the generation of the coupling vibration caused by the above, it was configured as an initial purpose to replace a plurality of electroacoustic transducers having a shape obtained by subdividing the acoustic radiation surface with an array.
[0020]
That is, the conventional transmitter / receiver shown in FIG. 7 includes 16 subdivided electroacoustic transducers, each of which is composed of one electroacoustic transducer having an acoustic radiation surface shape as shown in FIG. Thus, it can be said that the acoustic radiation surface is reconfigured so that the shape and the outer diameter are equal.
[0021]
Here, since the 16 electroacoustic transducers have the same characteristics, the resonance characteristics of the transducers arranged in the element are the same as those of the transducer of one electroacoustic transducer in FIG. The single resonance at the operating frequency of the piezoelectric vibrator is changed to a double resonance characteristic having two primary and secondary resonance points by providing one matching layer, and a plurality of electroacoustic transducers are arranged. However, the resonance point does not increase further.
[0022]
On the other hand, the wideband transducer of the present invention uses a plurality of matching layers having different lengths, thereby obtaining a plurality of electroacoustic transducers with shifted resonance points of the double resonance characteristics and combining them. Thus, a wideband transducer having three or more resonance points is configured.
[0023]
Here, the characteristics of various materials have been evaluated for selecting the material for the matching layer, and the sound propagation medium in the piezoelectric vibrator and the broadband transducer is mainly focused on the acoustic impedance density characteristics of the material. A material having a characteristic value close to the geometric mean value of each acoustic impedance density of water is preferentially selected as the matching layer material. This is because the impedance matching between the piezoelectric vibrator and water which is a sound wave propagation medium is taken into consideration.
[0024]
Regarding the dimension of the matching layer, it is necessary to determine the length dimension in the sound wave propagation direction in particular, but the length dimension L in the sound wave propagation direction as the matching layer with respect to the sound wave propagation wavelength λ at the use frequency of the selected material. It was customary to set L = λ / 4. In the present invention, the length dimension in the sound wave propagation direction of the matching layer is consciously long compared to the conventional method using a uniform matching layer with 1/4 of the sound wave propagation wavelength λ in the matching layer at the operating frequency. A plurality of matching layers having different height dimensions are used.
[0025]
That is, the broadband transducer according to the present invention is an element array type broadband transducer configured by arranging a plurality of electroacoustic transducers each having a single matching layer provided on a piezoelectric vibrator. Two or more matching layers having different lengths in the sound wave propagation direction with respect to the sound wave propagation wavelength λ in each matching layer are used. The length of each matching layer is determined by the frequency and material of the transducer. This is a broadband transmitter / receiver having a length between 1/10 and 4/10 of the sound wave propagation wavelength λ determined by the sound wave propagation speed.
[0026]
Here, when the length of the matching layer is less than 1/10 of the sound wave propagation wavelength λ, the transmittance of the ultrasonic wave in the matching layer is extremely reduced, and the thickness is reduced in terms of dimensions, so that transmission and reception waves are transmitted. The performance of the vessel is significantly reduced. On the other hand, when the length of the matching layer exceeds 4/10 of the sound wave propagation wavelength λ, the transmittance of the ultrasonic wave is extremely lowered, and the performance of the transducer is significantly lowered. Therefore, the length of the matching layer is in the range from 1/10 to 4/10 of the sound wave propagation wavelength λ.
[0027]
【Example】
A broadband transducer according to an embodiment of the present invention will be described below.
[0028]
In the broadband transducer of the present invention, a glass cloth base epoxy resin laminate is used as a material for the matching layer. FIG. 3 is a diagram showing the relationship between the sound wave propagation direction in the glass cloth base epoxy resin laminate and the sound wave propagation direction and the length direction of the matching layer obtained from the resin plate. Here, the glass cloth base material epoxy resin laminated plate 22 has a laminated structure.
[0029]
From FIG. 3, there are two types of matching layers used here, both of which are processed from the glass cloth base epoxy resin laminate 22, and different matching layers are processed from the same material only in the length direction dimension. Are described.
[0030]
Here, the direction along the fiber of the glass cloth base epoxy resin laminate 22 is the sound wave propagation direction of the matching layer, one type is 1/5 the length of the sound wave propagation wavelength λ in the matching layer, and the other type is Two types of matching layers were processed with a length of 3/10 of the wavelength λ. The matching layer is applied by adhesion to the piezoelectric vibrator 21 that resonates in the length direction at a frequency of 70 kHz to obtain two types of electroacoustic transducers 23a and 23b having one matching layer.
[0031]
The material properties of the glass cloth base epoxy resin laminate 22 are: density ρ = 1.9 × 10 3 (kg / cm 3 ), acoustic wave propagation velocity C = 3150 (m / sec) along the fiber. Therefore, the length dimension in the sound wave propagation direction of the matching layer is about 1/5 of the sound wave propagation wavelength λ with respect to the use frequency of 70 kHz of the prismatic piezoelectric vibrator 21, and is approximately La = 9.0 (mm). At 3/10 of λ, approximately Lb = 13.5 (mm).
[0032]
The piezoelectric vibrator and the two types of matching layers 22a and 22b are bonded with a thermosetting epoxy resin adhesive to obtain electroacoustic transducers 23a and 23b shown in FIG. In addition, FIG. 4 shows the impedance frequency characteristic 24a of the electroacoustic transducer 23a and the impedance frequency characteristic 24b of the electroacoustic transducer 23b. The resonance point of the electroacoustic transducer 23a provided with the matching layer 22a having a large length is about 10 kHz lower than the resonance point of the electroacoustic transducer 23b provided with the matching layer 22b having a small length. shift.
[0033]
By combining these electroacoustic transducers 23a and 23b, a transducer having four resonance points in the impedance characteristic can be obtained. On the other hand, the conventional transducer configuration having one type of matching layer is equivalent to, for example, an arrangement in which only the electroacoustic transducers 23a are arranged, and thus has two resonance points as with the impedance frequency characteristic 24a. It becomes a characteristic.
[0034]
In the embodiment, each of the two types of electroacoustic transducer elements 23a and 23b is used to form a 4 × 4 array, and a cork 25 is bonded between the elements and around the element array to form the elements. Positioning and sound insulation treatment from the surroundings were performed, and after connection with the signal cable 26, the whole was molded with a polyurethane rubber mold 27 to give water tightness, and the element array type underwater ultrasonic transducer shown in FIG. 1 was manufactured.
[0035]
The arrangement of the electroacoustic transducers 23a and 23b in this ultrasonic transducer is arranged alternately as shown in FIG. The sensitivity characteristics of the ultrasonic transducer thus obtained are as shown in the transmission sensitivity frequency characteristic 28 and the reception sensitivity frequency characteristic 30 of the frequency characteristics of the transducer of the present invention shown in FIG.
[0036]
In FIG. 2, as a conventional example, only the matching layer made of the same material as the matching layer used in the embodiment of the transducer shown in FIG. 7 and having a length dimension in the sound wave propagation direction of ¼ of the sound wave propagation wavelength λ is shown. The transmission sensitivity frequency characteristic 29 and the reception sensitivity frequency characteristic 31 when using the are shown together. In contrast to the sensitivity characteristics of the transmitter / receiver obtained with the conventional configuration, in the embodiment of the present invention, the sensitivity characteristics having a wide band on the low frequency side and the high frequency side are obtained.
[0037]
This is because the electroacoustic transducers 23a and 23b used in the embodiment of the present invention have an electroacoustic transducer provided with a matching layer in which the conventional length dimension is ¼ of the sound wave propagation wavelength λ in the matching layer. The sensitivity characteristics of the conversion element are shown shifted to the high frequency side and the low frequency side, respectively. By superimposing the shifted sensitivity characteristics, the band is expanded to the low frequency side and the high frequency side, respectively. By suppressing the sensitivity change in the band, the effect of widening the band as a transducer is obtained.
[0038]
In the conventional handset configuration, compared to the case where a single matching layer is provided, the technique of multiple matching layers for further broadening the band is to provide multiple matching layers to provide multiple resonances for the piezoelectric vibrator. In this method, the increase in sensitivity characteristics in the vicinity of the resonance frequency is continuously connected, and the change in sensitivity within the band is suppressed to achieve a wider band.
[0039]
However, in the handset of the present invention, when a plurality of electrical conversion acoustic elements are divided into several groups to give a shift in resonance characteristics to each element group, and an element array is formed by combining these element groups, One transmitter / receiver can have a plurality of resonance frequencies, and is configured to approximately obtain the same effect as in the case of multiple resonance of a piezoelectric vibrator using multiple matching layers.
[0040]
According to the method of the present invention, it is not necessary to perform complicated characteristic estimation calculation as in the case where a multiple matching layer is added to the piezoelectric vibrator, and a plurality of characteristic estimations are performed when a single matching layer is added. From the combination of characteristics, it is possible to relatively easily estimate the sensitivity characteristics as a transducer after element arrangement.
[0041]
In the above embodiment, a glass cloth base epoxy resin laminate is used as a matching layer, a matching layer having a different length dimension in the sound wave propagation direction of the matching layer is processed, and applied to the piezoelectric vibrator to have different characteristics 2 Although it has been shown that by obtaining only one type of matching layer by obtaining various types of electroacoustic transducers, the effect of broadening the band can be greatly obtained. Only the base epoxy resin laminate is not specified, and the same effect can be obtained even with a general resin material having another uniform composition.
[0042]
However, the magnitude of the effect depends on the characteristics of the material used and the dimension setting of the matching layer. Even when a material different from this example is used, the same effect as this example can be obtained. It is not guaranteed.
[0043]
As described in the present embodiment, the method of obtaining a plurality of types of matching layers from one type of material can omit the work of investigating the characteristics of a plurality of materials and considering the combination of the materials.
[0044]
In addition, even when a plurality of resin materials having different material characteristics are used in combination as the matching layer, the effect of the present invention can be obtained without any problem. However, in this case, even if the length of each matching layer is set to have a different ratio between 1/10 and 4/10 with respect to the sound wave propagation wavelength λ in each resin material, Although the length of the matching layer may be equal depending on the sound wave propagation speed, there is no problem.
[0045]
In this embodiment, the length dimension of the matching layer is intentionally shifted from ¼ of the sound wave propagation wavelength λ in the resin material. However, the length dimension of the matching layer is ¼ of the sound wave propagation wavelength λ. There is no problem in including the setting to be included in the combination.
[0046]
【The invention's effect】
According to the present invention, there is provided a transducer of a system in which electroacoustic transducers having a single matching layer, which is the simplest form with a matching layer, are arranged, and the length of the matching layer with respect to the sound wave propagation wavelength A broadband transmitter / receiver with a wider bandwidth can be provided by a simple method using a plurality of matching layers having different dimension settings.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an element array type broadband transducer according to the present invention. 1A is a front view, and FIG. 1B is a cross-sectional view taken along line AA in FIG.
FIG. 2 is a graph showing sensitivity characteristics of a broadband transducer according to the present invention and a broadband transducer according to a conventional configuration. 2A is a diagram showing a relationship between transmission power sensitivity and frequency, and FIG. 2B is a diagram showing a relationship between reception power sensitivity and frequency.
FIG. 3 is a diagram showing a relationship between a sound wave propagation direction in a glass cloth base epoxy resin laminate and a sound wave propagation direction and a length direction of a matching layer obtained from the resin plate.
FIG. 4 is an external view of two types of electroacoustic transducers provided with matching layers having different lengths and an explanatory diagram of characteristics. 4A is an external view of the electroacoustic transducer when the matching layer length is La, and FIG. 4B is an external view of the electroacoustic transducer when the matching layer length is Lb. FIG. 4 and FIG. 4C are diagrams showing impedance characteristics of the respective electroacoustic transducers shown in FIG. 4A and FIG.
FIG. 5 is a cross-sectional view of a conventional transducer using an electroacoustic transducer in which one matching layer is provided in one piezoelectric vibrator, as viewed from the top and side. 5A is a front view of the transducer, and FIG. 5B is a BB cross-sectional view in FIG. 5A.
FIG. 6 is a cross-sectional view seen from the side of a conventional transducer using an electroacoustic transducer having a multi-matching layer by adding two matching layers.
FIG. 7 is a cross-sectional view seen from the top and side of a conventional element array type transducer in which a plurality of electroacoustic transducers each having a single matching layer provided on one piezoelectric vibrator are arrayed. 7A is a front view of the transducer, and FIG. 7B is a CC cross-sectional view in FIG. 7A.
FIG. 8 is a cross-sectional view of a conventional transducer using an electroacoustic transducer in which two matching layers are added to form a multiple matching layer in addition to the transducer shown in FIG.
9 is a conventional transducer using an electroacoustic transducer in which one piezoelectric vibrator is provided with one matching layer, and has a configuration in which the shape of the acoustic radiation surface is the same as that of FIG. Sectional drawing seen from the upper surface and side surface of this. 9A is a front view of the transducer, and FIG. 9B is a DD cross-sectional view in FIG. 9A.
[Explanation of symbols]
1a, 1b, 1c, 21 Piezoelectric vibrators 2a-2g Matching layer 22 Glass cloth base epoxy resin laminates 22a, 22b Matching layers 23a, 23b Electroacoustic transducers 24a, 24b Impedance frequency characteristics 25 Cork 26 Signal cable 27 Polyurethane rubber Mold 28, 29 Transmission sensitivity frequency characteristics 30, 31 Reception sensitivity frequency characteristics

Claims (1)

圧電振動子に1層の整合層を付与した電気音響変換素子を複数個配列して構成した素子配列型の広帯域送受波器において、前記整合層の音波伝搬方向の長さが、各整合層中の音波伝搬波長λに対して、異なる比率である2種類以上の整合層を使用し、各整合層の長さは、送受波器の使用周波数と材料の音波伝搬速度とにより定まる音波伝搬波長λの1/10以上から4/10以下の範囲の間の長さとすることを特徴とする広帯域送受波器。In an element arrangement type broadband transducer in which a plurality of electroacoustic transducers each having a single matching layer provided on a piezoelectric vibrator are arranged, the length of the matching layer in the sound wave propagation direction is set in each matching layer. Two or more types of matching layers having different ratios to the sound wave propagation wavelength λ of the sound wave are used, and the length of each matching layer is determined by the use frequency of the transducer and the sound wave propagation speed of the material. A wideband transducer having a length between 1/10 and 4/10.
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US11035954B2 (en) 2017-10-19 2021-06-15 Furuno Electric Company Limited Transducer

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JP4456644B2 (en) * 2007-12-26 2010-04-28 株式会社デンソー Ultrasonic sensor
JP7093154B2 (en) * 2016-11-01 2022-06-29 株式会社トーキン Ultrasonic transducer

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11035954B2 (en) 2017-10-19 2021-06-15 Furuno Electric Company Limited Transducer

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