JP3885421B2

JP3885421B2 - Piezoelectric transducer and manufacturing method thereof

Info

Publication number: JP3885421B2
Application number: JP21829999A
Authority: JP
Inventors: 聡新家
Original assignee: Konica Minolta Inc
Current assignee: Konica Minolta Inc
Priority date: 1999-08-02
Filing date: 1999-08-02
Publication date: 2007-02-21
Anticipated expiration: 2019-08-02
Also published as: JP2001044525A

Description

【０００１】
【発明の属する技術分野】
この発明は圧電変換素子、特にシート状の圧電材料を筒状に形成した圧電変換素子の電極構造とその製造方法に関する。
【０００２】
【従来の技術】
圧電変換素子を使用したアクチエータは、供給される電気エネルギを駆動力に変換する変換効率が高く、小型軽量でありながら発生する駆動力が大きく、また、駆動力を容易に制御できるため、カメラ、計測機器、その他の精密機械の被駆動部材の駆動や位置決めに利用されるようになつてきた。
【０００３】
このようなアクチエータで使用される駆動源である圧電変換素子には、単位の圧電素子を複数枚積層して構成したものがある。これは、単位の圧電素子に発生する厚み方向の変位をできるだけ大きくして取り出すためである。
【０００４】
単位の圧電素子を複数枚積層して構成した圧電変換素子は、単位素子それぞれの表面に電極を設ける工程、積層して接着する工程、各層の電極を結線する工程という繁雑な作業を経て製造されるので、コストの高いものであつた。
【０００５】
このため、表面に電極が形成された２枚の薄板状の圧電素子を積層した積層体を中空筒状に巻いて構成した圧電変換素子が提案されている。
【０００６】
図１１は、このような２枚の薄板状の圧電素子を積層して筒状に形成した圧電変換素子の一例を示す斜視図で、図１２の（ａ）及び（ｂ）は、その電極形成面と積層状態を説明する図、図１３は、円筒状に形成された圧電変換素子の円筒軸方向の端面の状態を説明する平面図である。
【０００７】
圧電変換素子の製造工程を説明する。まず、図１２の（ａ）に示すように、薄板状に形成された圧電セラミックスからなる第１の圧電素子１０１及び第２の圧電素子１０２を準備する。ここで、第２の圧電素子１０２の巻き取り方向の長さを第１の圧電素子１０１よりも寸法ｄだけ長くしておく。
【０００８】
第１の圧電素子１０１の表面には第１電極１０３を形成し、裏面は電極非形成面とする。また、第２の圧電素子１０２の表面には第２電極１０４形成し、裏面は電極非形成面とする（図１２の（ａ）参照）。
【０００９】
次に、図１２の（ｂ）に示すように、第１の圧電素子１０１の電極非形成面と第２の圧電素子１０２の電極形成面が対向するように積層し、この積層体を巻き取つて、図１１に示すような筒状体に構成する。第１の圧電素子１０１の巻き取り方向の長さを第２の圧電素子１０２の巻き取り方向の長さよりも短くすることで、筒状に形成したとき、第１電極１０３と第２電極１０４の端部がずれ、容易にそれ等の電極にリード線１０３ａ及び１０４ａを接続することができる。
【００１０】
【発明が解決しようとする課題】
上記した構成の筒状体の圧電変換素子では、図１３に示すように、その構造から筒状体の最も内側の部分では、第２の圧電素子１０２は第１電極１０３と第２電極１０４に挟まれない部分Ｘが生じる。この部分は圧電変換素子の第１電極１０３と第２電極１０４の間に電圧を印加した場合も伸縮変位が発生せず、伸縮変位を阻害するから、可能な限り小さくすることが望ましい。
【００１１】
また、上記した構成の筒状体の圧電変換素子では、図１３に示すように、圧電変換素子の側面に露出した第１及び第２電極にリード線をハンダ付け或いは金属ペーストで接着して接続しているが、このような接続作業は量産に向いていないという不都合があつた。この発明は、上記課題を解決することを目的とするものである。
【００１２】
【課題を解決するための手段】
この発明は、上記課題を解決するもので、請求項１の発明は、第１電極を表面に第２電極を裏面に形成したシート状の圧電素子の長手方向略中央に連続部を形成し、該連続部を積層筒状体の内部空間の中央部に積層筒状体から離れた状態で残してシート状圧電素子を巻き上げて積層筒状体に形成した後に焼成したことを特徴とする圧電変換素子である。
【００１４】
そして、前記積層筒状体の内部空間の中央部に残された連続部に露出する第１電極及び第２電極には、それぞれ第１及び第２の電極端子を接触させるものとする。
【００１５】
請求項３の発明は、圧電セラミツクスを材料とするシート状の圧電素子の表面に第１電極を、裏面に第２電極を形成する工程と、軸方向に延びたスリットを有する巻取軸のスリットに前記電極の形成されたシート状の圧電素子の長手方向略中央の連続部を挟み、巻取軸の回りにシート状の圧電素子を巻上げて筒状体に形成する工程と、形成された筒状体を所定温度で焼成する工程とを含むことを特徴とする圧電変換素子の製造方法である。
【００１６】
そして、前記巻取軸は、圧電素子の焼成温度よりも高い融点の材料で構成するとよい。
【００１７】
また、前記巻取軸のスリットには、圧電素子の焼成温度よりも高い融点の材料で構成された電極端子を備えることで圧電素子への給電が容易に行える。
【００１８】
このほか、前記巻取軸を圧電素子を焼成したときに焼失する材料で構成するようにしてもよい。
【００１９】
【発明の実施の形態】
以下、この発明の実施の形態を説明する。
【００２０】
［第１の実施の形態］
第１の実施の形態の圧電変換素子は、１枚の薄板状の圧電素子の表裏両面に電極を形成し、これを略中央部で２つ折りして積層した積層体を筒状に巻き上げて筒状体に形成した圧電変換素子である。
【００２１】
図１及び図２は、第１の実施の形態の圧電変換素子の構成を説明する図で、図１は圧電変換素子の断面図、図２は圧電変換素子の外観を示す斜視図である。
【００２２】
圧電変換素子の構成の概略を説明する。図１に示すように、シート状の圧電素子１１の表面の全面に第１電極１２を形成し、裏面の全面に第２電極１３を形成する。
【００２３】
次に、この表裏両面に電極の形成されたシート状の圧電素子１１を、第２電極１３の面が相互に対向するように長手方向の略中央部で２つ折りにして連続部１４を形成し、この積層体を連続部１４を内側にして筒状に巻き上げて筒状体に形成し、筒状体を所定の温度で焼成し、電極間に電圧を印加して分極させて圧電変換素子１０が完成する。
【００２４】
次に、その製造工程の詳細を説明する。まず、圧電素子１１の材料としては、ＰＺＴ（ＰｂＺｒＯ₃・ＰｂＴｉＯ₃）を主成分とする圧電セラミックスを使用する。このセラミックス粉体を溶剤、分散剤、バインダ、可塑剤等と混合し、ブレード等を使用して均一な平面に作成して一定の厚さ、例えば２０〜１００μｍの厚さに引き伸ばす。溶剤を蒸発させて乾燥すると、グリーンシートと呼ばれる柔軟性のあるシートを得ることができる。
【００２５】
次に、このグリーンシート（圧電素子）の表面及び裏面に、スクリーン印刷等の手段で、ペースト状の電極材料、例えば白金（Ｐｔ）系、銀−パラジウム（Ａｇ−Ｐｄ）系の電極材料を適当な樹脂バインダでペースト状にした電極材料を、３〜７μｍの厚さに印刷し（焼成後は樹脂バインダが揮発して１〜３μｍ程度になる）、第１電極１２及び第２電極１３を形成する。
【００２６】
グリーンシートの表裏両面に第１電極１２及び第２電極１３が印刷形成された圧電素子１１を所定の大きさに切断し、第２電極１３の面が相互に対向するように長手方向の略中央部で２つ折りにして積層し、この積層体の折り返し部分である連続部１４を内側にして筒状に巻き上げて筒状体に形成する。
【００２７】
次に、前記筒状体を所定の温度条件で焼成し、第１電極１２及び第２電極１３にリード線を接続して所定の直流高電圧を印加して分極させると、圧電変換素子１０が完成する。
【００２８】
焼成する温度条件は、例えば、図３に示すように、５時間程度かけて５００℃まで序々に温度を高め、５００℃で一定時間焼成した後、最初から９時間後に１２００℃まで序々に温度を高める。さらに、１２００℃で約０．３時間焼成した後、６時間程度かけて常温まで冷却する。
【００２９】
分極の方向はシート状の圧電素子の厚み方向とし、例えば、６０℃の環境において、電極１２及び１３の間に１．５ｋＶ／ｍｍの電圧を２０分間印加して分極させる。圧電素子を分極させることで、圧電変換素子１０に筒状軸方向の変位を発生させることができる。
【００３０】
図４は、圧電変換素子へ印加する電圧（Ｖ）と発生する変位（ｎｍ）の関係を示す図で、線（ａ）は上記した第１の実施の形態の圧電変換素子の印加電圧（Ｖ）と発生変位（ｎｍ）の関係を示し、線（ｂ）は図１１に示す従来の圧電変換素子の印加電圧（Ｖ）と発生変位（ｎｍ）の関係を示す。
【００３１】
この図から明らかなように、この発明の第１の実施の形態の圧電変換素子は図１１に示す従来の圧電変換素子よりも同一印加電圧に対する発生変位が大きく、変換効率が良い。これは、従来の圧電変換素子は、その筒状体の最も内側に２つの電極に挟まれていない伸縮変位の発生を阻害する部分があるが、この発明の第１の実施の形態の圧電変換素子は、このような伸縮変位の発生を阻害する部分が無いからである。
【００３２】
［第２の実施の形態］
第２の実施の形態の圧電変換素子は、１枚の薄板状の圧電素子の表裏両面に電極を形成し、その略中央部を連結部として一定幅を残して圧電素子相互が積層されるように巻き上げて筒状体に形成した圧電変換素子である。
【００３３】
図５及び図６は、第２の実施の形態の圧電変換素子の構成を説明する図で、図５は圧電変換素子の断面図、図６は圧電変換素子の外観を示す斜視図である。
【００３４】
圧電変換素子の構成の概略を説明する。図５に示すように、シート状の圧電素子２１の表面の全面に第１電極２２を形成し、裏面の全面に第２電極２３を形成する。
【００３５】
次に、この表裏両面に電極の形成されたシート状の圧電素子２１の略中央部を連続部２４として一定幅を残し、圧電素子相互が積層されるように巻き上げて筒状体に形成する。
【００３６】
図７はシート状の圧電素子２１の巻き上げ方法の一例を示す斜視図である。図７に示すように、軸方向にスリット３２が形成された巻取軸３１を準備する。巻取軸３１の直径は、圧電変換素子２０の略中央部に形成される連続部２４に略一致する寸法とする。また、スリット３２の幅は表裏両面に電極の形成されたシート状の圧電素子２１の厚みよりも僅かに大きい幅とし、スリット３２の軸方向長さは圧電素子２１の幅よりも大きい寸法とするとよい。
【００３７】
なお、巻取軸３１の材質は、例えばセルロース、ポリカーボネート樹脂等を使用して、焼成により巻取軸３１が焼失するようにする。
【００３８】
次に、スリット３２に表裏両面に電極の形成されたシート状の圧電素子２１の略中央部の連続部２４を挟み、巻取軸３１を回転すると、シート状の圧電素子２１は、図５の断面図に示すように巻き上げられ、筒状部分では圧電素子２１の表面の第１電極２２と裏面の第２電極２３とが積層された筒状体が形成される。
【００３９】
完成した筒状体から巻取軸３１を抜き取ることなしに所定の温度で焼成する。焼成の際に、巻取軸３１がある状態で焼成を開始するので、焼成により筒状体の形状が変形するおそれがなく、また、焼成により巻取軸３１は焼失するから、電極間に電圧を印加して分極させて圧電変換素子２０が完成する。
【００４０】
焼成の完了した圧電変換素子２０の外側の略半分には第１電極２２が露出し、外側の他の略半分には第２電極２３が露出する。中心部分の連結部２４には、その一方の面に第１電極２２が露出し、他の面には第２電極２３が露出する。
【００４１】
図８は、完成した圧電変換素子２０の第１電極２２及び第２電極２３への給電端子の接続構造の一例を示す斜視図である。圧電変換素子２０の軸方向の両端に配置した適宜の電気絶縁性取付部材に、弾性材料で構成した端子２５及び２６を取り付け、圧電変換素子２０の連結部２４に露出した第１電極２２に端子２５を圧接させ、第２電極２３に端子２６を圧接させる。
【００４２】
これにより、圧電変換素子２０の第１電極２２及び第２電極２３へ給電することができる。この他、圧電変換素子２０の外側に露出した第１電極２２及び第２電極２３にリード線を接続して給電するように構成することができることは言うまでもない。
【００４３】
また、スリット３２を備えた巻取軸３１と同一形状の電気絶縁性取付部材を準備し、そのスリット部分の内面に弾性材料で構成した端子２５及び２６を取り付け、圧電変換素子２０の連結部２４に露出した第１電極２２に端子２５を圧接させ、第２電極２３に端子２６を圧接させるように構成することもできる。
【００４４】
さらに、巻取軸３１自体を給電端子とすることもできる。即ち、巻取軸３１のスリット３２の内側に第１電極２２及び第２電極２３へ給電する端子を配置しても給電することができる。この場合は、巻取軸３１を圧電素子の焼成温度に耐えるセラミック等の電気絶縁性材料で構成し、さらにスリットの内側に配置する給電端子は、圧電素子の焼成温度よりも融点が高く、弾力性を有する金属材料で構成するとよい。
【００４５】
圧電素子２１の材料は、第１の実施の形態と同じくＰＺＴ（ＰｂＺｒＯ₃・ＰｂＴｉＯ₃）を主成分とする圧電セラミックスを使用する。また、電極材料や電極の形成方法、焼成する温度条件、分極処理なども第１の実施の形態と同じであるから、ここでは説明を省略する。
【００４６】
次に、上記した圧電変換素子を使用したアクチエータの構成を、図９及び図１０を参照して説明する。以下の説明では第１の実施の形態の圧電変換素子１０を使用したアクチエータで説明するが、第２の実施の形態の圧電変換素子２０を使用した場合も同様である。
【００４７】
図９はアクチエータの構成を示す断面図である。図９において、４１は基台、４２、４３、４４は支持ブロツク、４５は駆動軸で、駆動軸４５は、圧電変換素子１０に発生する軸方向の変位により軸方向（矢印ａ方向、及びこれと反対方向）に変位可能に支持ブロツク４３と支持ブロツク４４により移動自在に支持されている。
【００４８】
１０は、前記した製造方法により製造された筒状の圧電変換素子である。圧電変換素子１０の一端は支持ブロツク４２に接着固定され、他端は駆動軸４５の一端に接着固定される。
【００４９】
なお、符号５０は緩やかな立上がり部と急速な立下がり部、或いは急速な立上がり部と緩やかな立下がり部を有する鋸歯状波パルスを発生する駆動パルス発生回路を示す。駆動パルス発生回路５０は、圧電変換素子１０の電極１２と１３との間に駆動パルスを供給し、圧電変換素子１０を駆動するものである。
【００５０】
４６はスライダで、スライダ４６と駆動軸４５とは適当な摩擦力で摩擦結合している。図１０は、スライダ４６と駆動軸４５との摩擦結合部の構成を示す断面図で、スライダ４６には駆動軸４５が貫通しており、スライダ４６の駆動軸４５が貫通している下部には、開口部４６ａが形成され、駆動軸４５の下半分が露出している。また、この開口部４６ａには駆動軸４５の下半分に当接するパツド４７が嵌挿され、パツド４７は板ばね４８により押し上げられていて、駆動軸４５とスライダ４６及びパツド４７は板ばね４８の付勢力Ｆにより圧接され、適当な摩擦力で摩擦結合している。また、スライダ４６には、図示しないテーブル等の被駆動部材が結合されているものとする。
【００５１】
その動作を説明する。圧電変換素子１０の電極１２と１３を駆動パルス発生回路５０に接続し、電極１２と１３の間に数１０ｋＨｚの鋸歯状波駆動パルスを印加すると、圧電変換素子１０には軸方向に伸縮変位が生じるので、圧電変換素子１０に結合した駆動軸４５には軸方向に速度の異なる往復振動が発生する。これにより駆動軸４５に摩擦結合したスライダ４６は、駆動軸４５上を滑りながら駆動軸の往復振動の非対称性により速度の遅い振動方向に移動し、スライダに結合されたテーブル等の被駆動部材を移動させることができる。
【００５２】
【発明の効果】
以上説明したとおり、この発明の請求項１に記載の圧電変換素子は、第１電極を表面に第２電極を裏面に形成したシート状の圧電素子の長手方向略中央に連続部を形成し、該連続部を積層筒状体の内部空間の中央部に積層筒状体から離れた状態で残してシート状圧電素子を巻き上げて積層筒状体に形成した後に焼成した圧電変換素子である。この構成により、伸縮変異の発生を阻害する圧電素子部分がないほか、積層筒状体の内部空間の中央部に露出する連続部に第１電極及び第２電極にそれぞれ第１及び第２の電極端子を接触させることができ、電極にリード線をハンダ付け或いは金属ペーストで接着する等の繁雑な作業を省き、リード線を安定して接続することができる。
【００５３】
そして、１枚のシート状の圧電素子の表裏両面に第１電極及び第２電極を形成した素子を使用するから、製造工程が従来のものより簡単になる。
【００５４】
さらに、請求項３に記載の圧電変換素子の製造方法によれば、軸方向に延びたスリットを有する巻取軸を使用することにより、シート状の圧電素子を巻き上げて積層筒状体に形成する工程が簡単で、高い作業効率を得ることができる。
【図面の簡単な説明】
【図１】第１の実施の形態の圧電変換素子の断面図。
【図２】第１の実施の形態の圧電変換素子の外観を示す斜視図。
【図３】圧電変換素子の焼成温度条件の一例を示す図。
【図４】圧電変換素子へ印加する電圧と発生する変位の関係を説明する図。
【図５】第２の実施の形態の圧電変換素子の断面図。
【図６】第２の実施の形態の圧電変換素子の外観を示す斜視図。
【図７】第２の実施の形態の圧電変換素子の巻き上げ方法を説明する斜視図。
【図８】第２の実施の形態の圧電変換素子の給電端子の接続構造を示す斜視図。
【図９】圧電変換素子を使用したアクチエータの構成を示す断面図。
【図１０】アクチエータのスライダと駆動軸との摩擦結合部の構成を示す断面図。
【図１１】従来の２枚の薄板状の圧電素子を積層して筒状に形成した圧電変換素子の一例を示す斜視図。
【図１２】図１１に示す従来の圧電変換素子の電極形成面と積層状態を説明する図。
【図１３】図１１に示す従来の圧電変換素子の円筒軸方向の端面を説明する平面図。
【符号の説明】
１０圧電変換素子
１１圧電素子
１２第１電極
１３第２電極
１４連続部
２０圧電変換素子
２１圧電素子
２２第１電極
２３第２電極
２４連続部
２５、２６端子
３１巻取軸
３２スリット[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrode structure of a piezoelectric conversion element, particularly a piezoelectric conversion element in which a sheet-like piezoelectric material is formed into a cylindrical shape, and a method for manufacturing the same.
[0002]
[Prior art]
An actuator using a piezoelectric transducer has a high conversion efficiency for converting supplied electric energy into a driving force, a small driving force, a large driving force that is generated, and the driving force can be easily controlled. It has come to be used for driving and positioning of driven members of measuring instruments and other precision machines.
[0003]
Some piezoelectric transducers that are driving sources used in such an actuator are configured by laminating a plurality of unit piezoelectric elements. This is because the displacement in the thickness direction generated in the unit piezoelectric element is taken out as much as possible.
[0004]
Piezoelectric transducers constructed by laminating a plurality of unit piezoelectric elements are manufactured through the complicated processes of providing electrodes on the surface of each unit element, laminating and bonding, and connecting the electrodes of each layer. Therefore, it was expensive.
[0005]
For this reason, a piezoelectric conversion element has been proposed in which a laminate in which two thin plate-like piezoelectric elements each having an electrode formed thereon are stacked is wound into a hollow cylinder.
[0006]
FIG. 11 is a perspective view showing an example of a piezoelectric transducer formed by laminating two such thin plate-like piezoelectric elements into a cylindrical shape, and FIGS. 12A and 12B show the electrode formation. FIG. 13 is a plan view for explaining the state of the end surface in the cylindrical axis direction of the piezoelectric transducer formed in a cylindrical shape.
[0007]
A manufacturing process of the piezoelectric transducer will be described. First, as shown in FIG. 12A, a first piezoelectric element 101 and a second piezoelectric element 102 made of piezoelectric ceramics formed in a thin plate shape are prepared. Here, the length of the second piezoelectric element 102 in the winding direction is made longer than the first piezoelectric element 101 by the dimension d.
[0008]
The first electrode 103 is formed on the surface of the first piezoelectric element 101, and the back surface is a non-electrode-formed surface. Further, the second electrode 104 is formed on the surface of the second piezoelectric element 102, and the back surface is a non-electrode-formed surface (see FIG. 12A).
[0009]
Next, as shown in FIG. 12 (b), lamination is performed so that the electrode non-formation surface of the first piezoelectric element 101 and the electrode formation surface of the second piezoelectric element 102 face each other, and this laminate is wound up. Therefore, it forms in a cylindrical body as shown in FIG. When the length of the first piezoelectric element 101 in the winding direction is made shorter than the length of the second piezoelectric element 102 in the winding direction, the first electrode 103 and the second electrode 104 are formed in a cylindrical shape. The ends are displaced and the lead wires 103a and 104a can be easily connected to these electrodes.
[0010]
[Problems to be solved by the invention]
In the cylindrical piezoelectric conversion element having the above-described configuration, as shown in FIG. 13, the second piezoelectric element 102 is connected to the first electrode 103 and the second electrode 104 in the innermost part of the cylindrical body from the structure. A portion X that is not sandwiched occurs. It is desirable to make this portion as small as possible because no expansion / contraction displacement occurs even when a voltage is applied between the first electrode 103 and the second electrode 104 of the piezoelectric transducer, and the expansion / contraction displacement is hindered.
[0011]
Moreover, in the cylindrical piezoelectric transducer having the above-described configuration, as shown in FIG. 13, the lead wires are exposed to the first and second electrodes exposed on the side surfaces of the piezoelectric transducer and are connected by soldering or bonding with a metal paste. However, there is a disadvantage that such connection work is not suitable for mass production. The present invention aims to solve the above-mentioned problems.
[0012]
[Means for Solving the Problems]
The present invention solves the above-mentioned problems, and the invention of claim 1 is to form a continuous portion substantially at the center in the longitudinal direction of a sheet-like piezoelectric element in which the first electrode is formed on the front surface and the second electrode is formed on the back surface, Piezoelectric conversion characterized in that the continuous portion is left in the center of the inner space of the laminated cylindrical body in a state of being separated from the laminated cylindrical body, the sheet-like piezoelectric element is wound up and formed into a laminated cylindrical body, and then fired It is an element.
[0014]
Then, the first and second electrode terminals are brought into contact with the first electrode and the second electrode exposed at the continuous portion left in the central portion of the internal space of the laminated cylindrical body, respectively.
[0015]
According to a third aspect of the present invention, there is provided a step of forming a first electrode on the surface of a sheet-like piezoelectric element made of piezoelectric ceramics and a second electrode on the back surface, and a slit of a winding shaft having a slit extending in the axial direction. Sandwiching the continuous portion at the substantially longitudinal center of the sheet-shaped piezoelectric element on which the electrode is formed, and winding the sheet-shaped piezoelectric element around the take-up shaft to form a cylindrical body, and the formed cylinder And a step of firing the shaped body at a predetermined temperature.
[0016]
The winding shaft is preferably made of a material having a melting point higher than the firing temperature of the piezoelectric element.
[0017]
Further, the slit of the winding shaft is provided with an electrode terminal made of a material having a melting point higher than the firing temperature of the piezoelectric element, so that the piezoelectric element can be easily fed.
[0018]
In addition, the winding shaft may be made of a material that burns out when the piezoelectric element is fired.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0020]
[First Embodiment]
The piezoelectric conversion element according to the first embodiment forms electrodes by forming electrodes on both front and back surfaces of a single thin plate-like piezoelectric element, and folds this into two at a substantially central portion and winds it up into a cylindrical shape. This is a piezoelectric conversion element formed in a shape.
[0021]
1 and 2 are diagrams for explaining the configuration of the piezoelectric transducer according to the first embodiment. FIG. 1 is a cross-sectional view of the piezoelectric transducer, and FIG. 2 is a perspective view showing the appearance of the piezoelectric transducer.
[0022]
An outline of the configuration of the piezoelectric transducer will be described. As shown in FIG. 1, the 1st electrode 12 is formed in the whole surface of the sheet-like piezoelectric element 11, and the 2nd electrode 13 is formed in the whole back surface.
[0023]
Next, the sheet-like piezoelectric element 11 having electrodes formed on both the front and back surfaces is folded in half at a substantially central portion in the longitudinal direction so that the surfaces of the second electrodes 13 face each other to form a continuous portion 14. The laminated body is rolled up into a cylindrical shape with the continuous portion 14 inside, and the cylindrical body is fired at a predetermined temperature, and a voltage is applied between the electrodes to polarize the piezoelectric conversion element 10. Is completed.
[0024]
Next, details of the manufacturing process will be described. First, as a material of the piezoelectric element 11, a piezoelectric ceramic whose main component is PZT (PbZrO ₃ · PbTiO ₃ ) is used. This ceramic powder is mixed with a solvent, a dispersant, a binder, a plasticizer, and the like, formed into a uniform plane using a blade or the like, and stretched to a certain thickness, for example, 20 to 100 μm. When the solvent is evaporated and dried, a flexible sheet called a green sheet can be obtained.
[0025]
Next, paste-like electrode materials such as platinum (Pt) -based and silver-palladium (Ag-Pd) -based electrode materials are appropriately applied to the front and back surfaces of the green sheet (piezoelectric element) by means such as screen printing. An electrode material made into a paste form with an appropriate resin binder is printed to a thickness of 3 to 7 μm (the resin binder volatilizes to about 1 to 3 μm after firing) to form the first electrode 12 and the second electrode 13. To do.
[0026]
The piezoelectric element 11 having the first electrode 12 and the second electrode 13 printed and formed on both the front and back sides of the green sheet is cut to a predetermined size, and the approximate center in the longitudinal direction so that the surfaces of the second electrode 13 face each other. The portion is folded in two and laminated, and the continuous portion 14 that is the folded portion of the laminate is wound inside to form a tubular body.
[0027]
Next, when the cylindrical body is fired under a predetermined temperature condition, a lead wire is connected to the first electrode 12 and the second electrode 13 and a predetermined DC high voltage is applied for polarization, the piezoelectric conversion element 10 becomes Complete.
[0028]
For example, as shown in FIG. 3, the temperature is gradually raised to 500 ° C. over about 5 hours. After firing at 500 ° C. for a certain time, the temperature is gradually raised to 1200 ° C. after 9 hours from the beginning. Increase. Furthermore, after baking at 1200 ° C. for about 0.3 hours, it is cooled to room temperature over about 6 hours.
[0029]
The direction of polarization is the thickness direction of the sheet-like piezoelectric element. For example, in an environment of 60 ° C., a voltage of 1.5 kV / mm is applied between the electrodes 12 and 13 for 20 minutes for polarization. By polarizing the piezoelectric element, the piezoelectric conversion element 10 can be displaced in the cylindrical axial direction.
[0030]
FIG. 4 is a diagram showing the relationship between the voltage (V) applied to the piezoelectric transducer and the displacement (nm) generated, and the line (a) shows the applied voltage (V) of the piezoelectric transducer of the first embodiment described above. ) And the generated displacement (nm), and the line (b) shows the relationship between the applied voltage (V) and the generated displacement (nm) of the conventional piezoelectric transducer shown in FIG.
[0031]
As is apparent from this figure, the piezoelectric transducer according to the first embodiment of the present invention has a larger generated displacement with respect to the same applied voltage and better conversion efficiency than the conventional piezoelectric transducer shown in FIG. This is because the conventional piezoelectric transducer has a portion that inhibits the occurrence of expansion / contraction displacement that is not sandwiched between two electrodes on the innermost side of the cylindrical body, but the piezoelectric transducer according to the first embodiment of the present invention. This is because the element has no part that hinders the occurrence of such expansion and contraction displacement.
[0032]
[Second Embodiment]
In the piezoelectric transducer according to the second embodiment, electrodes are formed on both front and back surfaces of a single thin plate-like piezoelectric element, and the piezoelectric elements are stacked so as to leave a certain width with a substantially central portion as a connecting portion. It is the piezoelectric conversion element which was wound up and formed in the cylindrical body.
[0033]
5 and 6 are diagrams for explaining the configuration of the piezoelectric transducer according to the second embodiment. FIG. 5 is a cross-sectional view of the piezoelectric transducer, and FIG. 6 is a perspective view showing the appearance of the piezoelectric transducer.
[0034]
An outline of the configuration of the piezoelectric transducer will be described. As shown in FIG. 5, the first electrode 22 is formed on the entire surface of the sheet-like piezoelectric element 21, and the second electrode 23 is formed on the entire back surface.
[0035]
Next, a substantially central portion of the sheet-like piezoelectric element 21 having electrodes formed on both front and back surfaces is left as a continuous portion 24, and the piezoelectric elements are wound up so as to be laminated to form a cylindrical body.
[0036]
FIG. 7 is a perspective view showing an example of a method for winding up the sheet-like piezoelectric element 21. As shown in FIG. 7, a winding shaft 31 having a slit 32 formed in the axial direction is prepared. The diameter of the winding shaft 31 is set to a dimension that substantially coincides with the continuous portion 24 formed at the substantially central portion of the piezoelectric conversion element 20. Further, the width of the slit 32 is slightly larger than the thickness of the sheet-like piezoelectric element 21 having electrodes formed on both front and back surfaces, and the axial length of the slit 32 is larger than the width of the piezoelectric element 21. Good.
[0037]
The material of the winding shaft 31 is, for example, cellulose, polycarbonate resin, or the like, so that the winding shaft 31 is burned off by firing.
[0038]
Next, when the continuous portion 24 at the substantially central portion of the sheet-like piezoelectric element 21 having electrodes formed on the front and back surfaces is sandwiched between the slits 32 and the take-up shaft 31 is rotated, the sheet-like piezoelectric element 21 is shown in FIG. Rolled up as shown in the cross-sectional view, a cylindrical body in which the first electrode 22 on the front surface of the piezoelectric element 21 and the second electrode 23 on the back surface are stacked is formed in the cylindrical portion.
[0039]
The winding shaft 31 is fired at a predetermined temperature without being extracted from the completed cylindrical body. During firing, since the firing is started in a state where the winding shaft 31 is present, there is no fear that the shape of the cylindrical body is deformed by firing, and the winding shaft 31 is burned away by firing, so there is no voltage between the electrodes. Is applied and polarized to complete the piezoelectric transducer 20.
[0040]
The first electrode 22 is exposed at approximately half of the outer side of the piezoelectric conversion element 20 that has been baked, and the second electrode 23 is exposed at approximately other half of the outer side. The first electrode 22 is exposed on one surface of the connecting portion 24 at the center, and the second electrode 23 is exposed on the other surface.
[0041]
FIG. 8 is a perspective view illustrating an example of a connection structure of a power supply terminal to the first electrode 22 and the second electrode 23 of the completed piezoelectric transducer 20. Terminals 25 and 26 made of an elastic material are attached to appropriate electrically insulating mounting members disposed at both ends in the axial direction of the piezoelectric transducer 20, and the terminals are connected to the first electrode 22 exposed at the connecting portion 24 of the piezoelectric transducer 20. 25 is pressed and the terminal 26 is pressed against the second electrode 23.
[0042]
Thereby, power can be supplied to the first electrode 22 and the second electrode 23 of the piezoelectric transducer 20. In addition to this, it goes without saying that the first electrode 22 and the second electrode 23 exposed to the outside of the piezoelectric transducer 20 can be connected to lead wires to supply power.
[0043]
Further, an electrically insulating mounting member having the same shape as the winding shaft 31 provided with the slit 32 is prepared, and terminals 25 and 26 made of an elastic material are mounted on the inner surface of the slit portion, and the connecting portion 24 of the piezoelectric transducer 20 is mounted. The terminal 25 may be pressed into contact with the first electrode 22 exposed to the first electrode 22, and the terminal 26 may be pressed into contact with the second electrode 23.
[0044]
Furthermore, the winding shaft 31 itself can be used as a power supply terminal. In other words, power can be supplied even if terminals for supplying power to the first electrode 22 and the second electrode 23 are arranged inside the slit 32 of the winding shaft 31. In this case, the winding shaft 31 is made of an electrically insulating material such as a ceramic that can withstand the firing temperature of the piezoelectric element, and the power supply terminal disposed inside the slit has a melting point higher than the firing temperature of the piezoelectric element and is elastic. It is good to comprise with the metal material which has property.
[0045]
The material of the piezoelectric element 21 is a piezoelectric ceramic mainly composed of PZT (PbZrO ₃ · PbTiO ₃ ) as in the first embodiment. In addition, since the electrode material, the electrode forming method, the firing temperature condition, the polarization treatment, and the like are the same as those in the first embodiment, the description thereof is omitted here.
[0046]
Next, the structure of an actuator using the above-described piezoelectric conversion element will be described with reference to FIGS. In the following description, an actuator using the piezoelectric transducer 10 of the first embodiment will be described, but the same applies to the case of using the piezoelectric transducer 20 of the second embodiment.
[0047]
FIG. 9 is a cross-sectional view showing the structure of the actuator. In FIG. 9, reference numeral 41 denotes a base, reference numerals 42, 43, and 44 denote support blocks, reference numeral 45 denotes a drive shaft, and the drive shaft 45 is axially moved by the axial displacement generated in the piezoelectric transducer 10 (in the direction of arrow a). The support block 43 and the support block 44 are movably supported so as to be displaceable in the opposite direction.
[0048]
Reference numeral 10 denotes a cylindrical piezoelectric transducer manufactured by the manufacturing method described above. One end of the piezoelectric transducer 10 is bonded and fixed to the support block 42, and the other end is bonded and fixed to one end of the drive shaft 45.
[0049]
Reference numeral 50 denotes a drive pulse generating circuit that generates a sawtooth wave pulse having a gradual rising portion and a rapid falling portion, or a rapid rising portion and a gradual falling portion. The drive pulse generation circuit 50 supplies a drive pulse between the electrodes 12 and 13 of the piezoelectric conversion element 10 to drive the piezoelectric conversion element 10.
[0050]
46 is a slider, and the slider 46 and the drive shaft 45 are frictionally coupled with each other by an appropriate frictional force. FIG. 10 is a cross-sectional view showing the configuration of the friction coupling portion between the slider 46 and the drive shaft 45. The drive shaft 45 passes through the slider 46, and the lower portion of the slider 46 through which the drive shaft 45 passes is shown. The opening 46a is formed, and the lower half of the drive shaft 45 is exposed. In addition, a pad 47 that is in contact with the lower half of the drive shaft 45 is fitted into the opening 46 a, and the pad 47 is pushed up by a leaf spring 48. The drive shaft 45, the slider 46, and the pad 47 are connected to the leaf spring 48. It is pressed by an urging force F and is frictionally coupled with an appropriate frictional force. Further, it is assumed that a driven member such as a table (not shown) is coupled to the slider 46.
[0051]
The operation will be described. When the electrodes 12 and 13 of the piezoelectric transducer 10 are connected to the drive pulse generation circuit 50 and a sawtooth wave drive pulse of several tens of kHz is applied between the electrodes 12 and 13, the piezoelectric transducer 10 is subjected to expansion and contraction in the axial direction. As a result, the drive shaft 45 coupled to the piezoelectric transducer 10 generates reciprocating vibrations having different speeds in the axial direction. As a result, the slider 46 frictionally coupled to the drive shaft 45 moves in a slow vibration direction due to the asymmetry of the reciprocating vibration of the drive shaft while sliding on the drive shaft 45, and the driven member such as a table coupled to the slider is moved. Can be moved.
[0052]
【The invention's effect】
As described above, the piezoelectric conversion element according to claim 1 of the present invention forms a continuous portion at a substantially longitudinal center of a sheet-like piezoelectric element in which the first electrode is formed on the front surface and the second electrode is formed on the back surface, The piezoelectric transducer is fired after the sheet-like piezoelectric element is wound up to form a laminated cylindrical body, leaving the continuous portion at the center of the internal space of the laminated cylindrical body in a state of being separated from the laminated cylindrical body. With this configuration, there is no piezoelectric element portion that inhibits the occurrence of expansion / contraction variation, and the first and second electrodes are respectively connected to the first electrode and the second electrode in the continuous portion exposed in the central portion of the internal space of the laminated cylindrical body. The terminals can be brought into contact with each other, and complicated operations such as soldering the lead wires to the electrodes or bonding them with a metal paste can be omitted, and the lead wires can be stably connected.
[0053]
And since the element which formed the 1st electrode and the 2nd electrode on the front and back both surfaces of one sheet-like piezoelectric element is used, a manufacturing process becomes simpler than the conventional one.
[0054]
Furthermore, according to the method for manufacturing a piezoelectric transducer according to claim 3 , by using a winding shaft having a slit extending in the axial direction, the sheet-like piezoelectric element is wound up to form a laminated cylindrical body. The process is simple and high working efficiency can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a piezoelectric transducer according to a first embodiment.
FIG. 2 is a perspective view showing an appearance of the piezoelectric conversion element according to the first embodiment.
FIG. 3 is a diagram illustrating an example of a firing temperature condition of a piezoelectric conversion element.
FIG. 4 is a diagram for explaining a relationship between a voltage applied to a piezoelectric transducer and a generated displacement.
FIG. 5 is a cross-sectional view of a piezoelectric transducer according to a second embodiment.
FIG. 6 is a perspective view showing an appearance of a piezoelectric conversion element according to a second embodiment.
FIG. 7 is a perspective view illustrating a method for winding up a piezoelectric transducer according to a second embodiment.
FIG. 8 is a perspective view illustrating a connection structure of power supply terminals of the piezoelectric transducer according to the second embodiment.
FIG. 9 is a cross-sectional view showing a configuration of an actuator using a piezoelectric transducer.
FIG. 10 is a cross-sectional view showing a configuration of a frictional coupling portion between an actuator slider and a drive shaft.
FIG. 11 is a perspective view showing an example of a piezoelectric conversion element formed by stacking two conventional thin plate-like piezoelectric elements into a cylindrical shape.
12 is a view for explaining an electrode forming surface and a laminated state of the conventional piezoelectric transducer shown in FIG.
13 is a plan view for explaining the end surface in the cylindrical axis direction of the conventional piezoelectric transducer shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Piezoelectric conversion element 11 Piezoelectric element 12 1st electrode 13 2nd electrode 14 Continuous part 20 Piezoelectric conversion element 21 Piezoelectric element 22 1st electrode 23 2nd electrode 24 Continuous part 25, 26 Terminal 31 Winding shaft 32 Slit

Claims

A continuous portion is formed at a substantially longitudinal center of a sheet-like piezoelectric element formed with the first electrode on the front surface and the second electrode on the back surface, and the continuous portion is formed in the central portion of the inner space of the stacked cylindrical body. A piezoelectric conversion element, wherein the piezoelectric element is fired after the sheet-like piezoelectric element is wound up and formed into a laminated cylindrical body, leaving it in a state separated from the substrate.

According to claim 1, characterized in that each contacting the first and second electrode terminals to the first electrode and the second electrode is exposed to a continuous portion left in the central portion of the inner space of the laminated tubular body Piezoelectric transducer.

Forming a first electrode on the front surface of a sheet-like piezoelectric element made of piezoelectric ceramics and a second electrode on the back surface;
A winding shaft having a slit extending in the axial direction is sandwiched between a continuous portion in the longitudinal center of the sheet-shaped piezoelectric element on which the electrode is formed, and the sheet-shaped piezoelectric element is arranged around the winding shaft. Winding and forming into a cylindrical body;
And a step of firing the formed cylindrical body at a predetermined temperature.

The method of manufacturing a piezoelectric transducer according to claim 3, wherein the winding shaft is made of a material having a melting point higher than a firing temperature of the piezoelectric element.

4. The method of manufacturing a piezoelectric transducer according to claim 3, wherein the slit of the winding shaft is provided with an electrode terminal made of a material having a melting point higher than the firing temperature of the piezoelectric element.

4. The method of manufacturing a piezoelectric transducer according to claim 3, wherein the winding shaft is made of a material that is burned off when the piezoelectric element is fired.