JP3865835B2

JP3865835B2 - Piezoelectric transducer

Info

Publication number: JP3865835B2
Application number: JP26954296A
Authority: JP
Inventors: 眞佐男妹尾; 剛山下; 忠男砂原
Original assignee: Hokuriku Electric Industry Co Ltd
Current assignee: Hokuriku Electric Industry Co Ltd
Priority date: 1996-10-11
Filing date: 1996-10-11
Publication date: 2007-01-10
Anticipated expiration: 2016-10-11
Also published as: JPH10117398A

Description

【０００１】
【発明の属する技術分野】
本発明は、圧電変換器に関するものである。
【０００２】
【従来の技術】
最近は、電話の受話器、携帯電話、無線器、ラジオ、テープレコーダ等の発音電子機器の小形化がさらに進み、これに伴って発音電子機器の発音素子として用いられている圧電発音体を構成する圧電変換器の小形化がさらに要求されるようになってきている。一般に、圧電変換器は、圧電振動子が前気室と後気室とを区分けするように、絶縁樹脂製の絶縁ケースの内部に収納されて構成されている。圧電振動子は、板状の金属製振動板に圧電セラミック素子が接合された構成を有している。そして、金属製振動板の周縁部が絶縁ケースの周壁の内壁部に接着剤を用いて接着されて圧電振動子は絶縁ケースに対して固定されると共に前気室と後気室との気密性を保持している。
【０００３】
従来は、圧電振動子を次のようにして絶縁ケースに固定する。まず絶縁ケースの内壁部の金属製振動板固定部に接着剤を塗布してから、周縁部が金属製振動板固定部上に位置するように圧電振動子を絶縁ケースの内壁部上に載置する。そして、圧電振動子の金属製振動板を内壁部側に押し付け、自然に接着剤を硬化させる。このようにして金属製振動板の周縁部を絶縁ケースの内壁部の金属製振動板固定部に接合すると、前気室と後気室との気密性を保持した上で圧電振動子を絶縁ケースに固定することができる。いままでに小形の圧電変換器としては、例えば、金属製振動板の直径を１５ｍｍにしたものが実際に製造販売されている。
【０００４】
【発明が解決しようとする課題】
この種の圧電変換器では、金属製振動板の金属製振動板固定部に接着剤を介して接合される金属製振動板の周縁部は、実質的に振動しないため、その部分を除いた部分の直径が、金属製振動板の固有共振周波数を実質的に決定する実質直径になる。そのため従来の圧電変換器の構造では、接着剤の量を少なくしなければ、金属製振動板の実質直径を小さくすることはできない。しかしながら、接着剤の量を少なくすることは技術的に非常に難しいという問題がある。そのため、例えば、金属製振動板の直径寸法を更に小さくしようとした場合に、従来の構造を採用すると、金属製振動板の実質直径がさらに小さくなって、固有共振周波数が高くなる問題が発生する。そのため従来の圧電変換器の構造をそのまま採用したのでは、例えば圧電受話器で用いる圧電発音体に要求される特性を満足する圧電変換器を得ることができない問題がある。
【０００５】
本発明の目的は、金属製振動板の実質直径が小さくなるのを抑制することができて、小形化を図ることができる圧電変換器を提供することにある。
【０００６】
本発明の他の目的は、製造の簡素化を図ることができる圧電変換器を提供することにある。
【０００７】
【課題を解決するための手段】
本発明は、絶縁樹脂製の第１のケース半部及び第２のケース半部が組合わされてなる二つ割りの絶縁ケースの内部に、板状の金属製振動板に圧電セラミック素子が接合されてなる圧電振動子が収納されている圧電変換器を対象にする。本発明では、第１のケース半部としては、金属製振動板を露出させる開口部を備えた底壁部とこの底壁部の外周部を囲むようにこの外周部から延びる周壁部とを有するものを用いる。また第２のケース半部としては、板状の底壁部とこの底壁部から延びる周壁部とを有するものを用いる。そして、第１のケース半部の周壁部と第２のケース半部の周壁部とを嵌合させて絶縁ケースを構成する。第１のケース半部及び第２のケース半部のそれぞれの周壁部の内壁部の形状は、第１のケース半部及び第２のケース半部のそれぞれの周壁部が互いに嵌合された状態で、絶縁ケースの内側に開口し且つ絶縁ケースの周壁に沿って延びて金属製振動板の周縁部を受け入れる溝部を形成し、しかも、金属製振動板の実質直径を実質的に減少させないように金属製振動板の周縁部を厚み方向両側から挟むように構成する。
【０００８】
より具体的に表現すれば、第１のケース半部及び第２のケース半部のそれぞれの周壁部の内壁部に、第１のケース半部及び第２のケース半部のそれぞれの周壁部が互いに嵌合された状態で、金属製振動板の周縁部を受け入れる溝部を形成する第１及び第２のテーパ部をそれぞれ内壁部に沿って一体に形成する。第１及び第２のテーパ部は、溝部が絶縁ケースの中心部に向かって開口し且つ中心部に向かうに従って広がるように傾斜させ、第１及び第２のテーパ部の傾斜角度は、第１及び第２のテーパ部の間で金属製振動板の周縁部を挟持するように定める。
【０００９】
本発明によれば、圧電振動子の金属製振動板の周縁部を厚み方向両側から挟んむ二つ割りの絶縁ケース内に圧電振動子を収納するので、接着剤を用いることなく、絶縁ケースの内部に圧電振動子を確実に固定できる。なお、金属製振動板の周縁部は、二つ割りの絶縁ケースに挟まれた状態で絶縁ケースの内部と接触しているため、接着剤を用いることなく、前気室と後気室との気密を保持することができる。また、第１のケース半部及び第２のケース半部のそれぞれの周壁部の内壁部の形状は、絶縁ケースの内側に開口する溝部を形成するように構成されており、この溝部に金属製振動板が受け入れられるので、金属製振動板はその角部（表面及び裏面の端部）が第１のケース半部及び第２のケース半部のそれぞれの周壁部の内壁部（第１及び第２のテーパ部）に接触した状態で絶縁ケース内に収納できる。このように本発明では、接着剤を用いる必要がない上、金属製振動板は角部が絶縁ケースと接触するので、金属製振動板の実質直径を小さくせずに、圧電変換器の小形化を図ることができる。また接着剤を用いないことにより、製造の簡素化を図ることができる。
【００１０】
溝部の形状は適宜に定めればよく、横断面形状がＶ字形、Ｕ字型等を採用することができる。
【００１１】
第１のケース半部及び第２のケース半部のそれぞれの周壁部の内壁部の形状は、金属製振動板の表面及び裏面の最も外周側に位置する部分とこれら表面及び裏面をつなぐ外周面の少なくとも一部とに跨がって接触するように構成することができる。言い換えるならば、第１及び第２のテーパ部の傾斜角度は、金属製振動板の表面及び裏面の最も外周側に位置する部分とこれら表面及び裏面をつなぐ外周面の少なくとも一部とに跨がって第１及び第２のテーパ部が接触するように定めることができる。
【００１２】
金属製振動板の周縁部と隣接する第１のケース半部の内壁部の少なくとも一部が絶縁樹脂を溶かす溶剤によって溶かされ且つ溶剤が除かれて形成された絶縁樹脂溶融硬化部によって、金属製振動板の表面側に位置する空間と裏面側に位置する空間との連通を阻止する気密シール部を形成すると、前気室と後気室との気密をより確実に保持することができる。溶剤としては、例えば、絶縁ケースをＰＰＯ樹脂（ノリル樹脂）により形成した場合には、ＰＰＯ樹脂を溶かすトルエン、ジクロロメタン等を溶剤として用いることができる。
【００１３】
また、気密シール部は、接着剤を用いて形成することもできる。接着剤を用いる場合は、金属製振動板の実質直径を実質的に減少させることなく、気密シール部としての役割だけを果たせばよいので、シール部により金属製振動板と第１のケース半部の内壁部との機械的結合を維持する必要はない。そのため、シール部は、該シール部だけでは金属製振動板と第１のケース半部の内壁部との機械的結合を維持できない程度の厚みを有しているもので構わない。このことは、シール部だけでは金属製振動板と第１のケース半部の内壁部との機械的結合を維持できない程度に接着剤の濃度を定めればよい。接着剤としては、ゴム系接着剤を用いることができる。その場合、濃度［溶剤（トルエン，キシレン）に対する接着成分（固形成分）の重量％］は５〜１０重量％にすればよい。
【００１４】
【発明の実施の形態】
以下、本発明の実施の形態の一例を図面を参照して詳細に説明する。図１は本発明の実施の形態の一例の圧電変換器（圧電発音体または圧電スピーカ）を内部に配置した携帯電話の受話器の概略部分断面図であり、図２は図１で用いる本発明の実施の形態の一例の圧電変換器の概略断面図である。なお図２においては、理解を容易にするため、各部の厚みを誇張して描いている。
【００１５】
この電話の受話器は、図１に示すようにハウジング１に圧電変換器２が取付けられた構造を有している。ハウジング１はハウジング本体３の内壁部に圧電変換器取付用の嵌合部（突出部）４を一体に有している。この突出部４は円筒状をなしており、圧電変換器２の位置決め用突起半部７ｆが嵌合される切欠凹部４ａを有している。また、ハウジング本体３には、突出部４によって囲まれた内側部分に１ヶ以上の放音孔３ａ…が形成されている。突出部４の内周にはリング状スペーサ５が配置されている。突出部４には、位置決め用突起半部７ｆと切欠凹部４ａとが嵌合された状態でリング状スペーサ５を介して圧電変換器２の表側ケース６の端部が嵌合されている。具体的には、表側ケース６の開口部６ｃがハウジング本体３に形成した放音孔３ａ…と対向するように即ち開口部６ｃがハウジング本体３の壁部によって覆われるように、圧電変換器２は突出部４に嵌合されている。この状態でハウジング本体３の壁部と圧電変換器２の圧電振動子８との間に前気室Ｒ1 が構成される。
【００１６】
圧電変換器２は、図２に詳細に示すように、第１のケース半部を構成する表側ケース６に第２のケース半部を構成する裏側ケース７が嵌合されて構成される二つ割りの収納ケース（絶縁ケース）を有しており、この収納ケースの内部には、電気信号に応じて振動する圧電振動子８が収納されている。なお本実施例では、表側ケース６と裏側ケース７の嵌め合わせ部からの空気漏れを防ぐために、嵌め合わせ部を溶着等により接合している。表側ケース６は、図２及び図３（Ａ）〜（Ｃ）に詳細に示すように、環状の底壁部６ａとこの底壁部６ａの外周部を囲むようにこの外周部から延びる周壁部６ｂとを有しており、ＰＰＯ樹脂からなる絶縁樹脂材料により一体成形されている。なお図３（Ａ）〜（Ｃ）は、表側ケース６の平面図、断面図及び裏面図である。底壁部６ａには、圧電振動子８の金属製振動板８ａを露出させる開口部６ｃが形成されている。また底壁部６ａの外周部には、直方体の形状を有する位置決め用突起半部６ｄが一体に設けられている。周壁部６ｂは、切欠部６ｅを有するほぼ円筒形状を有している。切欠部６ｅは、位置決め用突起半部６ｄと対応する位置に形成されている。切欠部６ｅは、表側ケース６に裏側ケース７が嵌合された状態で、リード線１０ａ，１０ｂを導出する隙間を形成するためのものであり、最終的にはその内部は封止剤１１により封止される。周壁部６ｂの内壁には、開口部６ｃ寄りの位置に周方向に連続して延びる環状のリブ６ｆが一体に形成されている。このリブ６ｆの内壁部の外面には傾斜面即ち第１のテーパー部６ｇが形成されている。この第１のテーパ部６ｇは開口部６ｃから離れるに従って径方向外側に向かって広がる（即ち拡径する）向きに形成されている。
【００１７】
第２のケース半部を構成する裏側ケース７は、図２及び図４（Ａ）〜（Ｃ）に詳細に示すように、円板状の底壁部７ａとこの底壁部７ａの縁部７ａ1 を残すように底壁部７ａから立ち上がって延びる周壁部７ｂとを有しており、表側ケース６と同様にＰＰＯ樹脂からなる絶縁樹脂によって一体成形されている。なお図４（Ａ）〜（Ｃ）は、裏側ケース７の平面図、断面図及び裏面図である。底壁部７ａには、漏洩孔７ｃが形成されている。この漏洩孔７ｃは底壁部７ａの中心部に形成されており、漏洩孔７ｃの裏側ケース７の内側に位置する一端の開口部には、漏洩孔７ｃを覆うように制動布９が接合または貼り付けられている（図２）。また底壁部７ａの表側ケース６に対向する内面には、補強用リブ７ｄが形成されている。この補強用リブ７ｄは格子状に形成されており、裏側ケース７の強度を高められるような形状及び寸法を有している。また底壁部７ａの外周には、位置決め用突起半部７ｆが形成されている。この位置決め用突起半部７ｆは、２つの直方体の突出片７ｆ1 ，７ｆ2 と、底壁部７ａに連続する板状部７ｆ3 とから構成されている。表側ケース６に裏側ケース７が嵌合された状態で表側ケース６の位置決め用突起半部６ｄは、突出片７ｆ1 ，７ｆ2 に挟まれた状態で位置決め用突起半部７ｆに嵌合される。なお、表側ケース６に裏側ケース７が嵌合された状態でリード線１０ａ，１０ｂが圧電変換器２から外部に導出する隙間が位置決め用突起半部６ｄと板状部７ｆ3 との間に形成される。また板状部７ｆ3 には、リード線１０ａ，１０ｂの導出と封止剤の注入とが容易に行え、且つ突出片７ｆ1 ，７ｆ2 の底壁部７ａへの取付強度を高められるような半円弧状の切り込み７ｆ4 が形成されている。
【００１８】
また周壁部７ｂは、切欠部７ｇを有するほぼ円筒状を有している。この切欠部７ｇは、位置決め用突起半部７ｆと対応する位置に形成されている。切欠部７ｇは、表側ケース６に裏側ケース７が嵌合された状態で、リード線１０ａ，１０ｂを導出する隙間を形成し、その内部には、シリコンゴム系の接着剤からなる封止剤１１が充填される。周壁部７ｂの内壁部の外面には傾斜面即ち第２のテーパ部７ｈが形成されている。この第２のテーパ部７ｈは、表側ケース６の第１のテーパ部６ｅと同様に、底壁部７ａから離れるに従って径方向外側に向かって広がる（即ち拡径する）向きに形成されている。
【００１９】
絶縁ケースは、図２に示すように、周壁部６ｂの端面６ｂ1 が裏側ケース７の縁部７ａ1 と接触するように表側ケース６及び裏側ケース７のそれぞれの周壁部６ｂ，７ｂが嵌合されて構成されている。このように、周壁部６ｂ，７ｂが互いに嵌合された状態で、絶縁ケースの周壁の内壁部には溝Ｇが形成される。この溝Ｇは、絶縁ケースの内側に（中心部に向かって）開口し、即ち中心部に向かうに従って広がり且つ絶縁ケースの周壁に沿って延びて圧電振動子８の金属製振動板８ａの周縁部を受け入れる横断面形状がほぼＶ字形の溝部である。周壁部６ｂ，７ｂの内壁部の形状（または第１及び第２のテーパ部の形状）は、このような溝部Ｇを形成するようそれぞれ構成されている。
【００２０】
圧電振動子８は板状の金属製振動板８ａとこの金属製振動板８ａの外周部に第１の電極部８ａ1 を残すように金属製振動板８ａの上に設けられた圧電セラミック８ｂと、圧電セラミック８ｂの両面にそれぞれ設けられた接合電極層８ｃ及び非接合電極層８ｄとから構成されている。接合電極層８ｃは金属製振動板８ａと電気的に接続されるように接合している。第１の電極部８ａ1 及び非接合電極層８ｄには、それぞれリード線１０ａ，１０ｂが半田付けにより接続されており、圧電振動子８は第１の電極部８ａ1 及び非接合電極層８ｄ間に与えられる電気信号に応じて振動する。この圧電振動子８は、非接合電極層８ｄが収納ケースの内側（裏側ケース７側）に向くように第１及び第２のテーパ部（溝部Ｇを囲む壁部）６ｇ，７ｈに対して固定されている。
【００２１】
上記の構成で組み立てた場合、金属製振動板８ａの周縁部と第１及び第２のテーパ部６ｇ，７ｈとの接触状態は図５及び図６に示した２つの状態のいずれかまたは両者が混在した状態になっている。これは絶縁ケース及び金属製振動板の加工精度と材料の膨脹、収縮等によって発生する寸法誤差に基づくものである。設計上は図６の状態になるように各部の寸法を決定している。
【００２２】
図５に示す接触状態では、表側ケース６の第１のテーパ部６ｇの拡径した端部６ｇ1 と裏側ケース７の第２のテーパ部７ｈの拡径した端部７ｈ1 とは金属製振動板８ａの厚み分だけ離れている。端部６ｇ1 と端部７ｈ1 との間には、周壁部６ｂの第１のテーパ部６ｇに連続する接触内壁部６ｈが露出している。金属製振動板８ａの周縁部は、第１のケース半部６及び第２のケース半部７のそれぞれの第１及び第２のテーパ部６ｇ，７ｈによって厚み方向両側から挟まれた状態で溝部Ｇに受け入れらている。具体的には、表側ケース６の第１のテーパ部６ｇの端部６ｇ1 と金属製振動板８ａの表面の最も外周側に位置する表面部分８ａ1 とが接触し、裏側ケース７の第２のテーパ部７ｈの端部７ｈ1 と金属製振動板８ａの裏面の最も外周側に位置する表面部分８ａ2 とが接触し、周壁部６ｂの接触内壁部６ｈと金属製振動板８ａの表面及び裏面をつなぐ外周面８ａ3 とが接触している。また図６は金属製振動板８ａの周縁部と第１及び第２のテーパ部６ｇ，１７ｈとの別の接触状態の拡大図である。この例では表側ケース６の第１のテーパ部６ｇの拡径した端部６ｇ1 と裏側ケース１７の第２のテーパ部１７ｈの拡径した端部１７ｈ1 とが接触している。そして、表側ケース６の第１のテーパ部６ｇと金属製振動板８ａの表面部分８ａ1 とが接触し、裏側ケース１７の第２のテーパ部１７ｈと金属製振動板８ａの表面部分８ａ2 とが接触している。実際には、金属製振動板８ａは金属であり、テーパ部は樹脂により形成されているため、金属製振動板８ａの角部はテーパ部に食い込んだ状態になっている。図５及び図６の状態においては、周壁部６ｂ，７ｂは、金属製振動板８ａの表面部分８ａ1 ，８ａ2 と外周面８ａ3 とに跨がって接触するように構成されている。言い換えるならば、第１及び第２のテーパ部６ｇ，７ｈの傾斜角度は、金属製振動板８ａの表面部分８ａ1 ，８ａ2 と外周面８ａ3 とに跨がって第１及び第２のテーパ部６ｇ，７ｈが接触するように定められている。本実施例では、圧電変換器２の小形化の要求により厚みが０．０３ｍｍで直径が１４ｍｍの金属製振動板８ａを用いたため、第１のテーパ部６ｇと金属製振動板８ａとの角度及び第２のテーパ部７ｈと金属製振動板８ａとの角度はいずれもほぼ４０〜５０度とし、溝部Ｇの底部を構成する円（第１及び第２のテーパ部が突き合わせ部によって形成される円）の直径も１４ｍｍとした。但しこれらの寸法にはバラツキがあるため図５及び図６の接触状態が発生する。
【００２３】
金属製振動板８ａの周縁部と第１のケース半部６の内壁部６ｇと間には、金属製振動板の表面側に位置する空間（前気室Ｒ1 ）と裏面側に位置する空間（後気室Ｒ2 ）との連通を阻止する気密シール部（絶縁樹脂溶融硬化部）Ｋが形成されている。気密シール部Ｋは、第１のテーパ部６ｇのＰＰＯ樹脂を溶かす溶剤（例えばジクロロメタン）によって第１のテーパ部６ｇの壁部を溶かした後に、溶剤が気化して無くなることによって形成される。溶剤の塗布または滴下は、例えばノズルを有する注液器具を用いて行う。その場合には、金属製振動板８ａが水平状態になるように位置決めしておき、金属製振動板８ａの周縁部に沿って注液器具のノズルを移動させながら第１のテーパ部６ｇに絶縁樹脂を溶かす溶剤を塗布または滴下する。溶剤は、金属製振動板８ａの周囲部分の第１のテーパ部６ｇを溶かす。溶けた絶縁樹脂は、金属製振動板８ａの周縁部と第１のテーパ部６ｇとの間に出てくる。その後溶剤が気化して無くなると（除去されると）、溶け出た絶縁樹脂は硬化して気密シール部Ｋとなる。この気密シール部Ｋは、厚みが薄く、金属製振動板８ａの周縁部の表面に形成される部分などは膜のような状態になっている。そのためこの例によれば、気密シール部Ｋと金属製振動板８ａとの結合部分の距離を短くできる上、仮に気密シール部Ｋが金属製振動板８ａの周縁部の表面に広がっても、その厚みは非常に薄いために、金属製振動板の実質直径を実質的に小さくすることはない。
【００２４】
なお、気密シール部は、濃度の薄い接着剤を用いて形成することもできる。このような接着剤としては、トルエン，キシレンからなる溶剤と、クロロプレンゴムからなる接着成分とを含むゴム系接着剤等を用いることができる。接着剤を用いて形成する気密シール部は、金属製振動板の実質直径を実質的に減少させることなく、気密シール部としての役割だけを果たせばよいので、シール部だけでは金属製振動板と第１のケース半部の内壁部との機械的結合を維持できない程度に接着剤の濃度を定めればよい。その場合、濃度（溶剤に対する接着成分の重量％）は５〜１０重量％にすればよい。
【００２５】
表側ケース６に裏側ケース７が嵌合された状態で、絶縁ケース内に圧電振動子８が固定されることによって、圧電振動子８と裏側ケース７とにより囲まれた後気室Ｒ2 が形成される（図２）。
【００２６】
本実施例では、次のようにして圧電変換器２を作った。
【００２７】
まず、圧電振動子８の金属製振動板８ａを表側ケース６の第１のテーパ部６ｇの端部６ｇ1 に載置する。次に表側ケース６と裏側ケース７とを嵌合させながら溶着して両ケースを結合する。そして切欠部６ｅ，７ｇ内並びに突出片７ｆ1 ，７ｆ2 と板状部７ｆ3 との間に封止剤を兼ねる接着剤を充填する。なおこの封止剤の充填は溶剤の塗布の後でもよい。この状態で、金属製振動板８ａの周縁部は絶縁ケースの溝部Ｇ内に収納された状態になっている。次に、裏側ケース７を下にして金属製振動板８ａを水平にした状態で、表側ケース６の開口部６ｃから金属製振動板８ａの周縁部にジクロロメタンを滴下する。このように滴下すると、毛細管現象によって、金属製振動板８ａの周縁部の全周と第１のテーパ部６ｇとの間にジクロロメタンが入り込む。なお、遠心力を利用すれば、金属製振動板８ａの周縁部の回りと第１のテーパ部６ｇとの間にジクロロメタンを確実且つ均等に入り込ませることができる。即ち金属製振動板８ａの表面のほぼ中央部に所定量のジクロロメタンを滴下し、絶縁ケースを遠心力が金属製振動板８ａの周縁部に向かって働くように回転させると、その遠心力でジクロロメタンが金属製振動板８ａの周縁部の回りと第１のテーパ部６ｇとの間に広がるのである。次に第１のテーパ部６ｇが部分的に溶ける。これを自然乾燥すると、ジクロロメタンが揮発して金属製振動板８ａの周縁部と第１のテーパ部６ｇとの間に気密シール部Ｋが形成される。
【００２８】
なお、本実施例では、溶剤または接着剤を用いて気密シール部Ｋを形成したが、気密シール部は必ずしも形成しなくてもよい。
【００２９】
【発明の効果】
本発明によれば、圧電振動子の金属製振動板の周縁部を厚み方向両側から挟んむ二つ割りの絶縁ケース内に圧電振動子を収納するので、接着剤を用いることなく、絶縁ケースの内部に圧電振動子を確実に固定できる。また、金属製振動板の実質直径を小さくせずに、圧電変換器の小形化を図ることができる。
【００３０】
また、金属製振動板の周縁部と隣接する第１のケース半部の内壁部の少なくとも一部が絶縁樹脂を溶かす溶剤によって溶かされ且つ溶剤が除かれて形成された絶縁樹脂溶融硬化部によって、金属製振動板の表面側に位置する空間と裏面側に位置する空間との連通を阻止する気密シール部を形成すると、前気室と後気室との気密をより確実に保持することができる。
【図面の簡単な説明】
【図１】本発明の実施の形態の一例の圧電変換器を内部に配置した携帯電話の受話器の概略部分断面図である。
【図２】本発明の実施の形態の一例の圧電変換器の概略断面図である。
【図３】（Ａ）〜（Ｃ）は、本発明の実施の形態の一例の圧電変換器に用いる表側ケースの平面図、断面図及び裏面図である。
【図４】（Ａ）〜（Ｃ）は、本発明の実施の形態の一例の圧電変換器に用いる裏側ケースの平面図、断面図及び裏面図である。
【図５】本発明の実施の形態の一例の圧電変換器の圧電振動子と第１及び第２のテーパ部との固定部分の拡大図である。
【図６】本発明の実施の形態の一例の圧電変換器の圧電振動子と第１及び第２のテーパ部との別の固定部分の拡大図である。
【符号の説明】
２圧電変換器
６表側ケース（第１のケース半部）
６ａ底壁部
６ｂ周壁部
６ｃ開口部
６ｇ第１のテーパー部
７裏側ケース（第２のケース半部）
７ａ底壁部
７ｂ周壁部
７ｈ第２のテーパ部
８圧電振動子
８ａ金属製振動板
Ｇ溝部
Ｋ気密シール部（絶縁樹脂溶融硬化部）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric transducer.
[0002]
[Prior art]
Recently, electronic electronic devices such as telephone receivers, mobile phones, wireless devices, radios, tape recorders and the like have been further miniaturized, and accordingly, piezoelectric sounding bodies used as sounding elements of sounding electronic devices are formed. There is a further demand for miniaturization of piezoelectric transducers. In general, the piezoelectric transducer is configured to be housed in an insulating case made of an insulating resin so that the piezoelectric vibrator separates the front air chamber and the rear air chamber. The piezoelectric vibrator has a configuration in which a piezoelectric ceramic element is bonded to a plate-shaped metal diaphragm. The peripheral portion of the metal diaphragm is bonded to the inner wall portion of the peripheral wall of the insulating case using an adhesive, and the piezoelectric vibrator is fixed to the insulating case, and the airtightness between the front air chamber and the rear air chamber Holding.
[0003]
Conventionally, a piezoelectric vibrator is fixed to an insulating case as follows. First, apply adhesive to the metal diaphragm fixing part on the inner wall of the insulating case, and then place the piezoelectric vibrator on the inner wall part of the insulating case so that the peripheral edge is located on the metal diaphragm fixing part. To do. Then, the metal diaphragm of the piezoelectric vibrator is pressed against the inner wall side, and the adhesive is naturally cured. In this way, when the peripheral part of the metal diaphragm is joined to the metal diaphragm fixing part on the inner wall part of the insulating case, the piezoelectric vibrator is insulated from the insulating case while maintaining the airtightness between the front air chamber and the rear air chamber. Can be fixed to. To date, as a small piezoelectric transducer, for example, a metal diaphragm having a diameter of 15 mm is actually manufactured and sold.
[0004]
[Problems to be solved by the invention]
In this type of piezoelectric transducer, the peripheral portion of the metal diaphragm that is joined to the metal diaphragm fixing portion of the metal diaphragm via an adhesive does not substantially vibrate, so the portion other than that portion is excluded. Is a substantial diameter that substantially determines the natural resonant frequency of the metallic diaphragm. Therefore, in the structure of the conventional piezoelectric transducer, the substantial diameter of the metal diaphragm cannot be reduced unless the amount of the adhesive is reduced. However, there is a problem that it is technically difficult to reduce the amount of the adhesive. Therefore, for example, when trying to further reduce the diameter of the metal diaphragm, adopting the conventional structure causes a problem that the substantial diameter of the metal diaphragm is further reduced and the natural resonance frequency is increased. . Therefore, if the structure of the conventional piezoelectric transducer is adopted as it is, there is a problem that it is impossible to obtain a piezoelectric transducer that satisfies the characteristics required for a piezoelectric sounding body used in a piezoelectric receiver, for example.
[0005]
An object of the present invention is to provide a piezoelectric transducer that can suppress a substantial diameter of a metal diaphragm and can be reduced in size.
[0006]
Another object of the present invention is to provide a piezoelectric transducer capable of simplifying manufacture.
[0007]
[Means for Solving the Problems]
According to the present invention, a piezoelectric ceramic element is joined to a plate-shaped metal diaphragm inside a two-part insulating case formed by combining a first case half and a second case half made of insulating resin. The target is a piezoelectric transducer in which a piezoelectric vibrator is housed. In the present invention, the first case half has a bottom wall portion having an opening for exposing the metal diaphragm and a peripheral wall portion extending from the outer peripheral portion so as to surround the outer peripheral portion of the bottom wall portion. Use things. As the second case half, one having a plate-like bottom wall and a peripheral wall extending from the bottom wall is used. Then, the insulating case is configured by fitting the peripheral wall portion of the first case half and the peripheral wall portion of the second case half. The shape of the inner wall portion of each peripheral wall portion of the first case half portion and the second case half portion is such that the respective peripheral wall portions of the first case half portion and the second case half portion are fitted to each other. And forming a groove that opens inside the insulating case and extends along the peripheral wall of the insulating case to receive the peripheral edge of the metal diaphragm, and does not substantially reduce the substantial diameter of the metal diaphragm. The peripheral part of the metal diaphragm is configured to be sandwiched from both sides in the thickness direction.
[0008]
More specifically, the respective peripheral wall portions of the first case half portion and the second case half portion are provided on the inner wall portions of the respective peripheral wall portions of the first case half portion and the second case half portion. In a state of being fitted to each other, first and second taper portions that form a groove portion that receives the peripheral portion of the metal diaphragm are integrally formed along the inner wall portion. The first and second tapered portions are inclined so that the groove portion opens toward the central portion of the insulating case and expands toward the central portion, and the inclination angles of the first and second tapered portions are the first and second tapered portions, respectively. The peripheral portion of the metal diaphragm is determined to be sandwiched between the second tapered portions.
[0009]
According to the present invention, since the piezoelectric vibrator is housed in the split insulating case that sandwiches the peripheral portion of the metal diaphragm of the piezoelectric vibrator from both sides in the thickness direction, the adhesive case is used without using an adhesive. The piezoelectric vibrator can be securely fixed. Note that the peripheral edge of the metal diaphragm is in contact with the inside of the insulating case while being sandwiched between the two insulating cases, so that the front air chamber and the rear air chamber can be sealed without using an adhesive. Can be held. Moreover, the shape of the inner wall part of each surrounding wall part of the 1st case half part and the 2nd case half part is comprised so that the groove part opened inside an insulating case may be formed, and metal is formed in this groove part. Since the diaphragm is received, the metal diaphragm has corner portions (front and back end portions) of the inner wall portions (first and second) of the peripheral wall portions of the first case half portion and the second case half portion. 2 taper portion) and can be stored in the insulating case. Thus, in the present invention, it is not necessary to use an adhesive, and the corners of the metal diaphragm are in contact with the insulating case. Therefore, the piezoelectric transducer can be reduced in size without reducing the actual diameter of the metal diaphragm. Can be achieved. Further, by not using an adhesive, manufacturing can be simplified.
[0010]
The shape of the groove may be determined as appropriate, and a V-shaped, U-shaped or the like can be adopted as the cross-sectional shape.
[0011]
The shape of the inner wall part of each peripheral wall part of the first case half part and the second case half part is the outermost surface connecting the front and back surfaces of the metal diaphragm and the front and back surfaces thereof. It can comprise so that it may straddle over at least one part. In other words, the inclination angle of the first and second taper portions spans the portion located on the outermost peripheral side of the front and back surfaces of the metal diaphragm and at least a part of the outer peripheral surface connecting these front and back surfaces. Thus, the first and second taper portions can be determined to contact each other.
[0012]
At least a part of the inner wall portion of the first case half adjacent to the peripheral edge of the metal diaphragm is melted by a solvent that dissolves the insulating resin, and the insulating resin melt-cured portion formed by removing the solvent is used to form the metal. By forming an airtight seal portion that prevents communication between the space located on the front surface side and the space located on the back surface side of the diaphragm, the airtightness between the front air chamber and the rear air chamber can be more reliably maintained. As the solvent, for example, when the insulating case is formed of a PPO resin (noryl resin), toluene, dichloromethane or the like that dissolves the PPO resin can be used as the solvent.
[0013]
The hermetic seal portion can also be formed using an adhesive. In the case of using an adhesive, it is only necessary to serve as an airtight seal part without substantially reducing the substantial diameter of the metal diaphragm, so that the metal diaphragm and the first case half are sealed by the seal part. It is not necessary to maintain the mechanical connection with the inner wall portion. Therefore, the seal portion may have a thickness such that the mechanical connection between the metal diaphragm and the inner wall portion of the first case half cannot be maintained by the seal portion alone. This means that the concentration of the adhesive may be determined to such an extent that the mechanical connection between the metal diaphragm and the inner wall portion of the first case half cannot be maintained with the seal portion alone. A rubber-based adhesive can be used as the adhesive. In that case, the concentration [weight% of the adhesive component (solid component) with respect to the solvent (toluene, xylene)] may be 5 to 10% by weight.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic partial cross-sectional view of a handset of a mobile phone in which a piezoelectric transducer (piezoelectric sounding body or piezoelectric speaker) of an example of an embodiment of the present invention is disposed, and FIG. 2 is a diagram of the present invention used in FIG. It is a schematic sectional drawing of the piezoelectric transducer of an example of embodiment. In FIG. 2, the thickness of each part is exaggerated for easy understanding.
[0015]
This telephone handset has a structure in which a piezoelectric transducer 2 is attached to a housing 1 as shown in FIG. The housing 1 integrally has a fitting portion (protruding portion) 4 for mounting the piezoelectric transducer on the inner wall portion of the housing body 3. The protrusion 4 has a cylindrical shape and has a notch recess 4a into which the positioning protrusion half 7f of the piezoelectric transducer 2 is fitted. Further, the housing body 3 is formed with one or more sound emitting holes 3a... In the inner part surrounded by the protrusions 4. A ring-shaped spacer 5 is disposed on the inner periphery of the protrusion 4. The end of the front case 6 of the piezoelectric transducer 2 is fitted to the protrusion 4 via the ring-shaped spacer 5 in a state where the positioning projection half 7f and the notch recess 4a are fitted. Specifically, the piezoelectric transducer 2 is formed such that the opening 6c of the front case 6 faces the sound emission holes 3a formed in the housing body 3, that is, the opening 6c is covered by the wall portion of the housing body 3. Is fitted to the protrusion 4. In this state, a front air chamber R1 is formed between the wall portion of the housing body 3 and the piezoelectric vibrator 8 of the piezoelectric transducer 2.
[0016]
As shown in detail in FIG. 2, the piezoelectric transducer 2 is divided into two parts formed by fitting a front case 6 constituting the first case half with a back case 7 constituting the second case half. A housing case (insulating case) is provided, and a piezoelectric vibrator 8 that vibrates according to an electric signal is housed inside the housing case. In the present embodiment, in order to prevent air leakage from the fitting portions of the front case 6 and the back case 7, the fitting portions are joined by welding or the like. As shown in detail in FIGS. 2 and 3A to 3C, the front case 6 has an annular bottom wall portion 6 a and a peripheral wall portion extending from the outer peripheral portion so as to surround the outer peripheral portion of the bottom wall portion 6 a. 6b, and is integrally formed of an insulating resin material made of PPO resin. 3A to 3C are a plan view, a cross-sectional view, and a rear view of the front case 6. An opening 6c is formed in the bottom wall 6a to expose the metal diaphragm 8a of the piezoelectric vibrator 8. A positioning projection half 6d having a rectangular parallelepiped shape is integrally provided on the outer peripheral portion of the bottom wall 6a. The peripheral wall 6b has a substantially cylindrical shape having a notch 6e. The notch 6e is formed at a position corresponding to the positioning projection half 6d. The notch 6e is for forming a gap for leading out the lead wires 10a and 10b in a state in which the back case 7 is fitted to the front case 6, and finally the inside is sealed by the sealant 11 Sealed. An annular rib 6f extending continuously in the circumferential direction is integrally formed on the inner wall of the peripheral wall 6b at a position near the opening 6c. An inclined surface, that is, a first tapered portion 6g is formed on the outer surface of the inner wall portion of the rib 6f. The first taper portion 6g is formed in a direction that expands radially outward (that is, expands in diameter) as the distance from the opening 6c increases.
[0017]
As shown in detail in FIG. 2 and FIGS. 4 (A) to (C), the back case 7 constituting the second case half is a disc-shaped bottom wall portion 7a and an edge portion of the bottom wall portion 7a. A peripheral wall portion 7b that rises and extends from the bottom wall portion 7a so as to leave 7a1 and is integrally formed of an insulating resin made of PPO resin in the same manner as the front side case 6. 4A to 4C are a plan view, a cross-sectional view, and a back view of the back side case 7. A leakage hole 7c is formed in the bottom wall portion 7a. The leakage hole 7c is formed at the center of the bottom wall portion 7a, and a braking cloth 9 is joined to the opening at one end located inside the back side case 7 of the leakage hole 7c so as to cover the leakage hole 7c. Affixed (FIG. 2). A reinforcing rib 7d is formed on the inner surface of the bottom wall portion 7a facing the front case 6. The reinforcing ribs 7d are formed in a lattice shape and have a shape and dimensions that can increase the strength of the back side case 7. A positioning projection half 7f is formed on the outer periphery of the bottom wall 7a. The positioning projection half 7f is composed of two rectangular parallelepiped projecting pieces 7f1 and 7f2 and a plate-like part 7f3 continuous to the bottom wall 7a. The positioning projection half 6d of the front case 6 is fitted to the positioning projection half 7f while being sandwiched between the protruding pieces 7f1 and 7f2 in a state where the back case 7 is fitted to the front case 6. Note that a gap through which the lead wires 10a and 10b are led out from the piezoelectric transducer 2 with the back case 7 fitted to the front case 6 is formed between the positioning projection half 6d and the plate-like portion 7f3. The The plate-like portion 7f3 has a semicircular arc shape so that the lead wires 10a and 10b can be easily led out and a sealing agent can be injected, and the mounting strength of the protruding pieces 7f1 and 7f2 to the bottom wall portion 7a can be increased. The notch 7f4 is formed.
[0018]
The peripheral wall portion 7b has a substantially cylindrical shape having a notch portion 7g. The notch 7g is formed at a position corresponding to the positioning projection half 7f. The notch 7g forms a gap through which the lead wires 10a and 10b are led in a state where the back case 7 is fitted to the front case 6, and a sealant 11 made of a silicone rubber-based adhesive is formed therein. Is filled. An inclined surface, that is, a second taper portion 7h is formed on the outer surface of the inner wall portion of the peripheral wall portion 7b. Similar to the first taper portion 6e of the front case 6, the second taper portion 7h is formed in a direction that expands outward (that is, expands in diameter) toward the radially outer side as the distance from the bottom wall portion 7a increases.
[0019]
As shown in FIG. 2, the insulating case is fitted with the peripheral wall portions 6b and 7b of the front case 6 and the back case 7 so that the end surface 6b1 of the peripheral wall portion 6b contacts the edge portion 7a1 of the back case 7. It is configured. Thus, the groove | channel G is formed in the inner wall part of the surrounding wall of an insulating case in the state which the surrounding wall parts 6b and 7b were mutually fitted. The groove G opens inside the insulating case (toward the central portion), that is, expands toward the central portion and extends along the peripheral wall of the insulating case, and the peripheral portion of the metal diaphragm 8a of the piezoelectric vibrator 8 The cross-sectional shape that receives the groove is a substantially V-shaped groove. The shapes of the inner wall portions of the peripheral wall portions 6b and 7b (or the shapes of the first and second tapered portions) are configured to form such a groove portion G, respectively.
[0020]
The piezoelectric vibrator 8 includes a plate-like metal diaphragm 8a and a piezoelectric ceramic 8b provided on the metal diaphragm 8a so as to leave the first electrode portion 8a1 on the outer periphery of the metal diaphragm 8a. It is comprised from the joining electrode layer 8c and the non-joining electrode layer 8d which were each provided in both surfaces of the piezoelectric ceramic 8b. The bonding electrode layer 8c is bonded so as to be electrically connected to the metal diaphragm 8a. Lead wires 10a and 10b are connected to the first electrode portion 8a1 and the non-bonding electrode layer 8d by soldering, respectively, and the piezoelectric vibrator 8 is applied between the first electrode portion 8a1 and the non-bonding electrode layer 8d. It vibrates according to the electrical signal that is generated. The piezoelectric vibrator 8 is fixed to the first and second taper portions (wall portions surrounding the groove portion G) 6g and 7h so that the non-bonded electrode layer 8d faces the inner side of the storage case (the back case 7 side). Has been.
[0021]
When assembled in the above-described configuration, the contact state between the peripheral portion of the metal diaphragm 8a and the first and second tapered portions 6g and 7h is either or both of the two states shown in FIGS. It is in a mixed state. This is based on the processing accuracy of the insulating case and the metal diaphragm and the dimensional error caused by the expansion and contraction of the material. The dimensions of each part are determined so as to be in the state of FIG. 6 in design.
[0022]
In the contact state shown in FIG. 5, the enlarged end portion 6g1 of the first tapered portion 6g of the front case 6 and the enlarged end portion 7h1 of the second tapered portion 7h of the back case 7 are made of the metal diaphragm 8a. It is separated by the thickness of. Between the end portion 6g1 and the end portion 7h1, a contact inner wall portion 6h continuous with the first tapered portion 6g of the peripheral wall portion 6b is exposed. The peripheral portion of the metal diaphragm 8a is a groove portion sandwiched from both sides in the thickness direction by the first and second tapered portions 6g and 7h of the first case half 6 and the second case half 7, respectively. Accepted by G. Specifically, the end portion 6g1 of the first taper portion 6g of the front case 6 and the surface portion 8a1 located on the outermost side of the surface of the metal diaphragm 8a come into contact with each other, and the second taper of the back case 7 is reached. The outer periphery connecting the end portion 7h1 of the portion 7h and the surface portion 8a2 located on the outermost peripheral side of the rear surface of the metal diaphragm 8a and connecting the contact inner wall portion 6h of the peripheral wall portion 6b and the front and rear surfaces of the metal diaphragm 8a. The surface 8a3 is in contact. FIG. 6 is an enlarged view of another contact state between the peripheral portion of the metallic diaphragm 8a and the first and second tapered portions 6g and 17h. In this example, the enlarged end portion 6g1 of the first tapered portion 6g of the front case 6 and the enlarged end portion 17h1 of the second tapered portion 17h of the back case 17 are in contact with each other. The first taper portion 6g of the front case 6 and the surface portion 8a1 of the metal diaphragm 8a are in contact with each other, and the second taper portion 17h of the back case 17 and the surface portion 8a2 of the metal diaphragm 8a are in contact with each other. is doing. Actually, since the metal diaphragm 8a is made of metal and the tapered portion is formed of resin, the corner portion of the metal diaphragm 8a is in a state of being cut into the tapered portion. 5 and 6, the peripheral wall portions 6b and 7b are configured to contact over the surface portions 8a1 and 8a2 of the metallic diaphragm 8a and the outer peripheral surface 8a3. In other words, the inclination angles of the first and second taper portions 6g and 7h are such that the first and second taper portions 6g extend over the surface portions 8a1 and 8a2 and the outer peripheral surface 8a3 of the metal diaphragm 8a. 7h are in contact with each other. In the present embodiment, since the metal diaphragm 8a having a thickness of 0.03 mm and a diameter of 14 mm is used due to a demand for miniaturization of the piezoelectric transducer 2, the angle between the first taper portion 6g and the metal diaphragm 8a and The angle between the second taper portion 7h and the metal diaphragm 8a is approximately 40 to 50 degrees, and the circle constituting the bottom of the groove portion G (the circle in which the first and second taper portions are formed by the abutting portion). ) Also had a diameter of 14 mm. However, since these dimensions vary, the contact state shown in FIGS. 5 and 6 occurs.
[0023]
Between the peripheral part of the metallic diaphragm 8a and the inner wall part 6g of the first case half 6, a space (front air chamber R1) located on the front side of the metallic diaphragm and a space located on the back side ( An airtight seal portion (insulating resin melt-hardening portion) K that prevents communication with the rear air chamber R2) is formed. The hermetic seal portion K is formed by dissolving the wall portion of the first taper portion 6g with a solvent (for example, dichloromethane) that dissolves the PPO resin of the first taper portion 6g and then evaporating and eliminating the solvent. The application or dripping of the solvent is performed using, for example, a liquid injection device having a nozzle. In that case, the metal diaphragm 8a is positioned so as to be horizontal, and is insulated from the first taper section 6g while moving the nozzle of the liquid injection device along the peripheral edge of the metal diaphragm 8a. Apply or drop a solvent that dissolves the resin. The solvent dissolves the first taper portion 6g around the metal diaphragm 8a. The melted insulating resin comes out between the peripheral portion of the metal diaphragm 8a and the first tapered portion 6g. Thereafter, when the solvent evaporates and disappears (when removed), the melted insulating resin is cured to form an airtight seal portion K. The hermetic seal portion K is thin, and the portion formed on the surface of the peripheral portion of the metallic diaphragm 8a is in a film-like state. Therefore, according to this example, it is possible to shorten the distance of the coupling portion between the hermetic seal portion K and the metal diaphragm 8a, and even if the hermetic seal portion K spreads on the surface of the peripheral portion of the metal diaphragm 8a, Since the thickness is very thin, the substantial diameter of the metallic diaphragm is not substantially reduced.
[0024]
The hermetic seal portion can also be formed using an adhesive having a low concentration. As such an adhesive, a rubber-based adhesive containing a solvent composed of toluene and xylene and an adhesive component composed of chloroprene rubber can be used. Since the hermetic seal portion formed using the adhesive only has to serve as the hermetic seal portion without substantially reducing the substantial diameter of the metal diaphragm, the seal portion alone can be used as a metal diaphragm. What is necessary is just to determine the density | concentration of an adhesive agent to such an extent that a mechanical coupling | bonding with the inner wall part of a 1st case half cannot be maintained. In this case, the concentration (weight% of the adhesive component with respect to the solvent) may be 5 to 10% by weight.
[0025]
The rear air chamber R2 surrounded by the piezoelectric vibrator 8 and the back case 7 is formed by fixing the piezoelectric vibrator 8 in the insulating case with the back case 7 fitted to the front case 6. (FIG. 2).
[0026]
In this example, the piezoelectric transducer 2 was made as follows.
[0027]
First, the metal diaphragm 8a of the piezoelectric vibrator 8 is placed on the end 6g1 of the first taper 6g of the front case 6. Next, the front side case 6 and the back side case 7 are welded together so that both cases are joined. Then, an adhesive that also serves as a sealing agent is filled in the notches 6e and 7g and between the projecting pieces 7f1 and 7f2 and the plate-like part 7f3. The sealing agent may be filled after application of a solvent. In this state, the peripheral edge portion of the metal diaphragm 8a is housed in the groove portion G of the insulating case. Next, dichloromethane is dropped from the opening 6c of the front case 6 to the peripheral portion of the metal diaphragm 8a with the back case 7 facing down and the metal diaphragm 8a being horizontal. When dripped in this manner, dichloromethane enters between the entire circumference of the peripheral portion of the metallic diaphragm 8a and the first tapered portion 6g by capillary action. If the centrifugal force is used, dichloromethane can be surely and evenly introduced between the periphery of the metal diaphragm 8a and the first tapered portion 6g. That is, when a predetermined amount of dichloromethane is dropped on the substantially central portion of the surface of the metallic diaphragm 8a and the insulating case is rotated so that the centrifugal force works toward the peripheral edge of the metallic diaphragm 8a, the centrifugal force causes dichloromethane. Is spread between the periphery of the metal diaphragm 8a and the first taper portion 6g. Next, the first taper portion 6g is partially melted. When this is naturally dried, dichloromethane evaporates and an airtight seal portion K is formed between the peripheral portion of the metal diaphragm 8a and the first tapered portion 6g.
[0028]
In this embodiment, the hermetic seal portion K is formed using a solvent or an adhesive, but the hermetic seal portion is not necessarily formed.
[0029]
【The invention's effect】
According to the present invention, since the piezoelectric vibrator is housed in the split insulating case that sandwiches the peripheral portion of the metal diaphragm of the piezoelectric vibrator from both sides in the thickness direction, the adhesive case is used without using an adhesive. The piezoelectric vibrator can be securely fixed. In addition, the piezoelectric transducer can be reduced in size without reducing the substantial diameter of the metal diaphragm.
[0030]
In addition, by the insulating resin melting and hardening portion formed by dissolving at least a part of the inner wall portion of the first case half adjacent to the peripheral edge portion of the metal diaphragm and removing the solvent, By forming an airtight seal portion that prevents communication between the space located on the front surface side and the space located on the back surface side of the metal diaphragm, the airtightness between the front air chamber and the rear air chamber can be more reliably maintained. .
[Brief description of the drawings]
FIG. 1 is a schematic partial sectional view of a handset of a mobile phone in which a piezoelectric transducer according to an example of an embodiment of the present invention is disposed.
FIG. 2 is a schematic cross-sectional view of an example of a piezoelectric transducer according to an embodiment of the present invention.
FIGS. 3A to 3C are a plan view, a cross-sectional view, and a back view of a front case used in a piezoelectric transducer as an example of an embodiment of the present invention.
FIGS. 4A to 4C are a plan view, a cross-sectional view, and a back view of a back side case used in a piezoelectric transducer as an example of an embodiment of the present invention.
FIG. 5 is an enlarged view of a fixed portion between a piezoelectric vibrator and first and second taper portions of an example of a piezoelectric transducer according to an embodiment of the present invention.
FIG. 6 is an enlarged view of another fixed portion between the piezoelectric vibrator and the first and second tapered portions of the piezoelectric transducer according to the example of the embodiment of the present invention.
[Explanation of symbols]
2 Piezoelectric transducer 6 Front case (first case half)
6a bottom wall part 6b peripheral wall part 6c opening part 6g first taper part 7 back side case (second case half)
7a Bottom wall part 7b Peripheral wall part 7h Second taper part 8 Piezoelectric vibrator 8a Metal diaphragm G Groove part K Airtight seal part (insulating resin melting and hardening part)

Claims

A piezoelectric vibrator in which a piezoelectric ceramic element is bonded to a plate-shaped metal diaphragm is formed in a two-part insulating case formed by combining a first case half and a second case half made of insulating resin. A piezoelectric transducer housed therein,
The first case half has a bottom wall portion having an opening for exposing the metal diaphragm and a peripheral wall portion extending from the outer peripheral portion so as to surround the outer peripheral portion of the bottom wall portion. ,
The second case half includes a plate-shaped bottom wall and a peripheral wall extending from the bottom wall, and the peripheral wall of the first case half and the second case half And the insulating case is configured by being fitted with the peripheral wall portion of
The inner wall portions of the peripheral wall portions of the first case half portion and the second case half portion are respectively provided with the peripheral wall portions of the first case half portion and the second case half portion. First and second taper portions that form a groove portion that receives a peripheral edge portion of the metal diaphragm in a state of being fitted to each other, are integrally formed along the inner wall portion, respectively.
The first and second tapered portions are inclined such that the groove portion opens toward the center portion of the insulating case and expands toward the center portion,
The inclination angle of the 1st and 2nd taper part is a piezoelectric transducer set so that the peripheral part of the metal diaphragm may be pinched between the 1st and 2nd taper parts .

A piezoelectric vibrator in which a piezoelectric ceramic element is bonded to a plate-shaped metal diaphragm is formed in a two-part insulating case formed by combining a first case half and a second case half made of insulating resin. A piezoelectric transducer housed therein,
The first case half has a bottom wall portion having an opening for exposing the metal diaphragm and a peripheral wall portion extending from the outer peripheral portion so as to surround the outer peripheral portion of the bottom wall portion. ,
The second case half includes a plate-shaped bottom wall and a peripheral wall extending from the bottom wall, and the peripheral wall of the first case half and the second case half And the insulating case is configured by being fitted with the peripheral wall portion of
The inner wall portions of the peripheral wall portions of the first case half portion and the second case half portion are respectively provided with the peripheral wall portions of the first case half portion and the second case half portion. First and second taper portions that form a groove portion that receives a peripheral edge portion of the metal diaphragm in a state of being fitted to each other, are integrally formed along the inner wall portion, respectively.
The first and second tapered portions are inclined such that the groove portion opens toward the center portion of the insulating case and expands toward the center portion,
The inclination angle of the first and second taper portions extends over a portion located on the outermost peripheral side of the front and back surfaces of the metal diaphragm and at least a part of the outer peripheral surface connecting the front and back surfaces. A piezoelectric transducer defined so that the first and second taper portions are in contact with each other .

Insulating resin melt formed by dissolving at least a part of the inner wall portion of the first case half adjacent to the peripheral edge portion of the metal diaphragm with a solvent that dissolves the insulating resin and removing the solvent. 3. The piezoelectric transducer according to claim 1, wherein an airtight seal portion that prevents communication between a space located on the front surface side and a space located on the back surface side of the metal diaphragm is formed by the curing portion.

Adhesive is applied across the inner wall of the first case half and the metal diaphragm adjacent to the peripheral edge of the metal diaphragm, and is applied to the surface side of the metal diaphragm. An airtight seal portion is formed to prevent communication between the space located and the space located on the back side,
The sealing portion, only the seal portion according to claim 1 or 2 has a thickness that can not be maintained mechanical coupling between the inner wall portion of the said metallic diaphragm first casing half Piezoelectric transducer.