JP2004343967A

JP2004343967A - Ultrasonic motor and its manufacturing method, and electronic apparatus with this ultrasonic motor

Info

Publication number: JP2004343967A
Application number: JP2003140798A
Authority: JP
Inventors: Akihiro Iino; 朗弘飯野; Seiji Watanabe; 聖士渡辺
Original assignee: Seiko Instruments Inc
Current assignee: Seiko Instruments Inc
Priority date: 2003-05-19
Filing date: 2003-05-19
Publication date: 2004-12-02
Anticipated expiration: 2023-05-19
Also published as: JP4313610B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic motor and an electronic apparatus with the ultrasonic motor, capable of realizing low-voltage driving, size and cost reductions and high output using laminated piezoelectric elements. <P>SOLUTION: This ultrasonic motor is provided with a vibrating body formed by stacking a plurality of piezoelectric elements 9a, 9b, 9c and drives a moving body 7 coming into contact with the vibrating body. Internal electrodes 10a, 10b and 10c, 10d provided on the interfaces of the plurality of piezoelectric elements 9a, 9b, 9c have the same shape and external electrodes 11a, 11b, 11c, 11d, 11e which shorts the internal electrodes 10a, 10b, 10c, 10d. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、超音波モータ及びその製造方法、ならびに超音波モータを備えた電子機器に関する。
【０００２】
【従来の技術】
弾性体の共振モードを利用した超音波モータは制御性に優れ、近年特に精密位置決め用アクチュエータとしても注目されている。特に、各種ステージ用のアクチュエータとしてはリニヤ型の超音波モータが要求される場合が多く、多くのタイプが提案され研究されている。その中でも、矩形板の縦（伸縮）振動と屈曲振動の合成振動を利用した超音波モータは様々なものが研究されている（例えば、特許文献１参照。）。これらの中でも、例えば特許文献１に示す様に矩形状の圧電素子単板を厚み方向に分極処理すると共に４分割された電極を設け、対角と成る電極を組とし、一組の電極に駆動信号を印加することで圧電素子からなる振動体に縦振動と屈曲振動を励振し、これと接する移動体を駆動する原理のものは様々な用途に実用化も進められている。
【０００３】
【特許文献１】
特許２９８０５４１号公報（第７−８頁、第１図）
【０００４】
【発明が解決しようとする課題】
しかしながら従来の構造では振動体の駆動に極めて高い電圧を必要とし、大きな昇圧回路を必要とする為、駆動回路の大型化、複雑化を招き駆動回路の価格も高価なものになってしまった。そしてこの場合、小型な機器、特にバッテリーで駆動される用途への適用は難しかった。また、振動体の構造としては圧電素子の厚みが薄いと十分な出力が得られないと共に、機械的強度も低く破損につながる恐れもあった。逆に厚みを厚くすると分極電圧が極めて高く、製造プロセスが複雑になる等の問題があった。そして、本構成では圧電素子の圧電横効果を用いているために大きな出力が得られなかった。
【０００５】
【課題を解決するための手段】
そこで、本発明の第１の態様は、複数の圧電素子を積層して振動体を構成し、前記振動体と接する移動体を駆動する超音波モータにおいて、前記複数の圧電素子の界面に設けられた内部電極は同一形状であり、前記内部電極を短絡する外部電極は少なくとも三つ有する超音波モータにある。
【０００６】
本発明の第２の態様は、第１の態様において、前記複数の圧電素子のうち少なくとも一枚は電極を有さない圧電素子であることを特徴とする超音波モータにある。
【０００７】
本発明の第３の態様は、第１の態様において、前記複数の圧電素子のうち少なくとも一つは同一面内に存在する複数の内部電極を短絡することを特徴とする超音波モータにある。
【０００８】
本発明の第４の態様は、第１の態様において、前記複数の外部電極を短絡する複数の導通手段を有し、少なくとも一つの前記導通手段は、分極時に接地した外部電極と分極時に電位を加えた外部電極を短絡することを特徴とする超音波モータにある。
【０００９】
本発明の第５の態様は、第１の態様において、前記振動体は矩形形状であり、駆動信号を印加する外部電極を選択することにより、前記振動体に励振する縦振動と屈曲振動の位相を逆転させ前記移動体の移動方向を切り替えることを特徴とする超音波モータにある。
【００１０】
本発明の第６の態様は、第１の態様において、前記振動体は矩形形状であり、前記複数の外部電極は第一の駆動信号もしくは第二の駆動信号が印加され、前記第一の駆動信号により前記振動体には縦振動が励振され、前記第二の駆動信号により前記振動体には屈曲振動が励振され、前記移動体を駆動することを特徴とする超音波モータにある。
【００１１】
本発明の第７の態様は、複数の圧電素子を積層して振動体を構成し、前記振動体と接する移動体を駆動する超音波モータであって、前記振動体は複数の内部電極が設けられた同一の圧電素子シート材を面内方向に位置をずらしながら積層し、個々の振動体形状に分割した後で、前記分割した面に少なくとも三つの外部電極を設けることで前記内部電極を短絡する超音波モータの製造方法にある。
【００１２】
本発明の第８の態様は、第１から６のいずれかの態様の超音波モータを備えた電子機器にある。
【００１３】
【発明の実施の形態】
本発明の実施の形態を図面を基に説明する。
【００１４】
図１は本発明の積層圧電素子１を振動体として用いたリニヤ型超音波モータの構成例を示したものである。矩形状の積層圧電素子１には突起２ａ，２ｂ並びに凹部を有する支持部材３が設けられている。加圧部材４の軸部４ａは段部を有し、案内板５の案内穴５ａで、軸方向にのみ移動可能に案内されている。突起２ａ，２ｂの下には案内部材８ａ，８ｂに案内された移動体７が設けられ、支持部材３は加圧部材４の凹部に係合し、加圧部材４を加圧手段６で加圧することにより突起２ａ，２ｂと移動体７は接している。
【００１５】
ところで、積層圧電素子１は縦振動と屈曲振動を励振する。例えば、図２に積層圧電素子１の長手方向に対する振動振幅の様子を示したものであり、図２（ａ）は縦振動の様子を図２（ｂ）は屈曲振動の様子を示したものである。縦振動、屈曲振動共に積層圧電素子１の中央部が振動の節となり、この位置に支持部材３が設けられている。また屈曲振動の腹の位置に突起２ａ，２ｂが設けられている。この縦振動と屈曲振動を同時に励振することにより突起２ａ，２ｂは積層振動子１の長手方向の変位と、これと直交する幅方向の変位からなる楕円運動を行い移動体７を駆動する。ところで、二つの振動モードはその次数に制限を与えられるものではなく、他のモードを用いても構わない。また、移動体７を固定し、振動体自体を駆動させても構わない。
【００１６】
（実施の形態１）
具体的に積層圧電素子９の構成例を図３を基に説明する。図３（ａ），図３（ｃ）はそれぞれ矩形形状からなり、積層圧電素子９を表裏から見た図であり、図３（ｄ），図３（ｅ）は断面図である。即ち図３（ｄ），図３（ｅ）に示す様に、内部電極１０ａ、１０ｂもしくは内部電極１０ｃ、１０ｄを一方の面に有する圧電素子９ａ、９ｂを交互に積層した構造となっている。内部電極１０ａ、１０ｂ、１０ｃ、１０ｄは圧電素子９ａ、９ｂの長手方向にほぼ二分した形状となっており、積層圧電素子９の一つの面方向にのみ張り出しており、積層圧電素子９の側面で外部電極１１ａ、１１ｂ、１１ｃ、１１ｄ、１１ｅで短絡されている。外部電極１１ａ、１１ｂ、１１ｃ、１１ｄは積層圧電素子９の面内の向かい合う辺の中心を結ぶ線で分けられる四つの領域それぞれにおいて内部電極１０ａ、１０ｂを短絡している。外部電極１１ｅは内部電極１０ｃ、１０ｄ全てを短絡している。
【００１７】
ここで外部電極１１ｅをＧＮＤとして外部電極１１ａ、１１ｂ、１１ｃ、１１ｄに高電圧を加えることで積層方向に方向に分極処理がなされる。
【００１８】
本積層圧電素子９の駆動方法であるが、例えば次の二通りがある。外部電極１１ａ、１１ｄと外部電極１１ｅの間に、もしくは外部電極１１ｂ、１１ｃと外部電極１１ｅの間に駆動信号を印加することで積層圧電素子９の面内の向かい合う辺の中心を結ぶ線で分けられる四つの領域の対角にある二つの領域が伸縮することで積層圧電素子９に縦振動と屈曲振動が励振される。駆動信号を印加する領域を切り替えることで縦振動と屈曲信号の位相が逆転し、移動体７の移動方向も変化する。別の方法としては外部電極１１ｅをＧＮＤとして外部電極１１ａ、１１ｄと外部電極１１ｂ、１１ｃの間に位相の異なる駆動信号、例えば９０度もしくは−９０度異なる信号を印加することで積層圧電素子９に縦振動と屈曲振動が励振される。位相を逆転させることで縦振動と屈曲信号の位相が逆転し、移動体７の移動方向も逆となる。
【００１９】
ところで、この積層圧電素子９の製法を図４に示すが、例えば積層圧電素子９が複数取れる大きさの圧電素子のシート１２上に複数の積層圧電素子分の電極１０を印刷等によって設ける。このシート１２を複数枚重ねた後で電極を有さない圧電素子を最後に重ねて積層し、仮燒結してバインダーを飛ばした後、個々の積層圧電素子９にダイシング等によって分割され本焼成される。そして外部電極１１ａ、１１ｂ、１１ｃ、１１ｄ、１１ｅが付けられた後、分極処理がなされ完成となる。このように、同一のシート１２のみを積層すれば良いため、各シートの電極付けの工程も含め、全て同一作業の繰り返しとなり、製造時間の大幅な短縮並びに電極付けマスク等の治具も少なくて済む。
【００２０】
ここでダイシングによる分割部を点線５０で示したが、内部電極１０の一方の辺が交互に点線５０に位置し、分割後には内部電極１０ａ、１０ｂ、１０ｃ、１０ｄを構成する様に交互にシート１２は位置をずらして重ねられる。実際にはシート１２上の電極１０は実際の内部電極１０ａ、１０ｂ、１０ｃ、１０ｄの大きさよりも若干大きなものが設けられており、分割時の寸法の誤差が生じても分割面に張り出す様に設定される。そしてこの様に最上面に電極を有さない圧電素子９ｃを積層することで、最上面、最下面の圧電素子は駆動力を生じない為、振動のバランスがとれるため、不要振動が発生しにくい。
【００２１】
また、ここで積層圧電素子９は金属等の弾性体と接合して振動体を構成しても構わないし、各圧電素子の電極の短絡も積層圧電素子の側面に限るものではなく、スルーホール等を用いても構わない。
【００２２】
（実施の形態２）
次に、実施の形態１の変形例を以下に示す。ここでは積層圧電素子１３の積層方向に伸縮する為、圧電縦効果が使え大きな出力が得られる。
【００２３】
図５（ａ），図５（ｃ）はそれぞれ矩形形状からなる実施の形態２の積層圧電素子１３を表裏から見た図であり、図５（ｄ），図５（ｅ）は断面図である。即ち、図５（ｄ），図５（ｅ）に示す様に内部電極１４ａ、１４ｂもしくは内部電極１４ｃ、１４ｄを一方の面に有する圧電素子１３ａ、１３ｂを交互に積層した構造となっている。内部電極１４ａ、１４ｂ、１４ｃ、１４ｄは圧電素子１３ａ、１３ｂの長手方向にほぼ二分した形状となっており、積層圧電素子１３の一つの面方向にのみ張り出しており、積層圧電素子１３の側面で外部電極１５ａ、１５ｂ、１５ｃ、１５ｄ、１５ｅで短絡されている。外部電極１５ａ、１５ｂ、１５ｃ、１５ｄは積層圧電素子１３の面内の向かい合う辺の中心を結ぶ線で分けられる四つの領域それぞれにおいて内部電極１４ａ、１４ｂを短絡している。外部電極１５ｅは内部電極１４ｃ、１４ｄ全てを短絡している。
【００２４】
ここで外部電極１５ｅをＧＮＤとして外部電極１５ａ、１５ｂ、１５ｃ、１５ｄに高電圧を加えることで積層方向に分極処理がなされる。
【００２５】
本積層圧電素子１３の駆動方法であるが、例えば次の二通りがある。外部電極１５ａ、１５ｄと外部電極１５ｅの間に、もしくは外部電極１５ｂ、１５ｃと外部電極１５ｅの間に駆動信号を印加することで積層圧電素子１３の面内の向かい合う辺の中心を結ぶ線で分けられる四つの領域の対角にある二つの領域が伸縮し、積層圧電素子１３に縦振動と屈曲振動が励振される。駆動信号を印加する領域を切り替えることで縦振動と屈曲信号の位相が逆転し、移動体７の移動方向も変化する。別の方法としては外部電極１５ｅをＧＮＤとして外部電極１５ａ、１５ｄと外部電極１５ｂ、１５ｃの間に位相の異なる駆動信号、例えば９０度もしくは−９０度異なる信号を印加することで積層圧電素子１３に縦振動と屈曲振動が励振される。位相を逆転させることで縦振動と屈曲信号の位相が逆転し、移動体７の移動方向も逆となる。
【００２６】
（実施の形態３）
実施の形態３に示す積層圧電素子１６の構成を図６に示すが、基本的には実施の形態１に示したものと共通であり、違いは外部電極１７ａ、１７ｂ、１７ｃ、１７ｄと分極方向、駆動方法のみであるため、相違点のみを述べ共通点の説明を省略する。
【００２７】
外部電極１７ｅは積層圧電素子１６の一つの面の幅方向中央部で内部電極１０ａ、１０ｂと短絡される。外部電極１７ｅで短絡される圧電素子部分の両側の部分では外部電極１７ａ、１７ｂによって内部電極１０ａが、外部電極１７ｃ、１７ｄによって内部電極１０ｂが短絡される。また積層圧電素子１６の反対の面では外部電極１７ｆによって内部電極１０ｃ、１０ｄが短絡される。
【００２８】
ここで、外部電極１７ｆをＧＮＤとして外部電極１７ａ、１７ｂ、１７ｃ、１７ｄ、１７ｅに電圧を加えることにより分極処理を行う。この場合の駆動方法としては、外部電極１７ｆをＧＮＤとして外部電極１７ｅに第一の駆動信号を印加することにより縦振動を励振する。また外部電極１７ａ、１７ｄもしくは外部電極１７ｂ、１７ｃに第二の駆動信号を印加することにより屈曲振動が励振され、移動体７を駆動する。どちらの外部電極に信号を印加するかによって縦振動と屈曲信号の位相が反転し、移動体７の移動方向も変わる。
【００２９】
別な駆動方法としては、外部電極１７ｆをＧＮＤとして外部電極１７ａ、１７ｄ、１７ｅにプラス方向の、外部電極１７ｂ、１７ｃにマイナス方向の電圧を加えることにより分極処理を行う。この場合の駆動方法としては、外部電極１７ｆを共通電極（ＧＮＤ）として外部電極１７ａ、１７ｂ、１７ｃ、１７ｄと外部電極１７ｅの間に位相の異なる第一及び第二の駆動信号、例えば９０度もしくは−９０度異なる信号を印加することで積層圧電素子１６に縦振動と屈曲振動が励振される。位相を逆転させることで縦振動と屈曲信号の位相が逆転し、移動体７の移動方向も逆となる。この位相は任意であり、０度と１８０度の切り替えを行っても構わない。
【００３０】
また分極方向に付いても任意であり、分極方向に応じて駆動信号の位相を逆転すれば同じ振動が励振される。
【００３１】
（実施の形態４）
図７は本発明の積層圧電素子の別の例を示したものである。図７（ａ），図７（ｃ）はそれぞれ矩形形状からなる実施の形態４の積層圧電素子１８を表裏から見た図であり、図７（ｄ），図７（ｅ）は断面図である。即ち図７（ｄ）、図７（ｅ）に示す様に内部電極１９ａ、１９ｂ、１９ｃもしくは内部電極１９ｄ、１９ｅ、１９ｆを一方の面に有する圧電素子１８ａ、１８ｂを交互に積層した構造となっている。内部電極１９ａ、１９ｂ、１９ｃ、１９ｄ、１９ｅ、１９ｆは圧電素子１８ａ、１８ｂの長手方向にほぼ三等分した形状となっており、積層圧電素子１８の一つの面方向にのみ張り出しており、積層圧電素子１８の側面で外部電極２０ａ、２０ｂ、２０ｃ、２０ｄ、２０ｅ、２１ａ、２１ｂ、２１ｃ、２１ｄ、２１ｅで短絡されている。外部電極２０ｅは積層圧電素子１８の一方の面内で内部電極１９ｂを短絡している。外部電極２０ａ、２０ｂは積層圧電素子１８を長手方向に２分する領域で電極１９ａを短絡する。外部電極２０ｃ、２０ｄは積層圧電素子１８を長手方向に２分する領域で電極１９ｃを短絡する。
【００３２】
また、他方の面で外部電極２１ｅは積層圧電素子１８の一方の面内で内部電極１９ｅを短絡している。外部電極２１ａ、２１ｂは積層圧電素子１８を長手方向に２分する領域で電極１９ｄを短絡する。外部電極２１ｃ、２１ｄは積層圧電素子１８を長手方向に２分する領域で電極１９ｆを短絡する。例えば外部電極２０ａと２０ｂが短絡しない様に、その隙間に位置する場所に電極を有さない圧電素子１８ｃを入れても構わない。
【００３３】
ここで、外部電極２１ａ、２１ｂ，２１ｃ，２１ｄ，２１ｅをＧＮＤとして外部電極２０ａ、２０ｂ、２０ｃ、２０ｄ、２０ｅに高電圧を加えることで、積層方向に分極処理がなされる。
【００３４】
本積層圧電素子１３の駆動方法であるが、例えば外部電極２１ｃ、２１ｂ、２１ｅ、２０ｂ、２０ｃを図示しない導通手段により短絡し、ＧＮＤとして外部電極２０ｅと図示しない導通手段により短絡された外部電極２０ａ、２０ｄ、２１ａ、２１ｄとの間に位相の異なる駆動信号、即ち第一の駆動信号と第二の駆動信号、例えば９０度もしくは−９０度異なる信号を印加することで積層圧電素子１８に縦振動と屈曲振動が励振される。位相を逆転させることで縦振動と屈曲信号の位相が逆転し、移動体７の移動方向も逆となる。
【００３５】
本発明によれば、圧電縦効果を用いるので大きな出力が得られると共に、分極方向が同じ方向で良い為、工程が簡単になると共に高い電圧まで破壊せずに使用できる。また分極方向の違いにより生じる特性ばらつきも生じない。
【００３６】
（実施の形態５）
図８は本発明の積層圧電素子の別の例を示したものである。図８（ａ）、図８（ｃ）はそれぞれ矩形形状からなる実施の形態４の例に対応する積層圧電素子２２を表裏から見た図であり、図８（ｄ），図８（ｅ）は断面図である。即ち、図８（ｄ），図８（ｅ）に示す様に、内部電極２３ａ、２３ｂ、２３ｃもしくは内部電極２３ｄ、２３ｅ、２３ｆを一方の面に有する圧電素子２２ａ、２２ｂを交互に積層した構造となっている。内部電極２３ｂ、２３ｅは圧電素子２２ａ、２２ｂの長手方向の中央部に設けられ、その両側には内部電極２３ａ、２３ｃ、２３ｄ、２３ｆが設けられ、積層圧電素子２２の一つの面方向にのみ張り出しており、積層圧電素子２２の側面で外部電極２４ａ、２４ｂ、２４ｃ、２４ｄ、２４ｅ、２４ｆで短絡されている。外部電極２４ｅは積層圧電素子２２の一方の面内で内部電極２３ｂを短絡している。外部電極２４ａ、２４ｂは積層圧電素子１８を幅方向に２分する領域で電極２３ａを短絡する。外部電極２４ｃ、２４ｄは積層圧電素子１８を幅方向に２分する領域で電極２３ｃを短絡する。また他方の面で外部電極２４ｆは内部電極２３ｄ、２３ｅ、２３ｆを短絡している。
【００３７】
ここで、外部電極２４ｆをＧＮＤとして外部電極２４ａ、２４ｂ、２４ｅにプラス方向の高電圧を、外部電極２４ｂ、２４ｃにマイナス方向の高電圧を加えることで加えることで積層方向に分極処理がなされる。
【００３８】
本積層圧電素子２２の駆動方法であるが、例えば外部電極２４ｆをＧＮＤとして外部電極２４ｅと外部電極２４ａ、２４ｂ、２４ｃ、２４ｄとの間に位相の異なる駆動信号、即ち第一の駆動信号と第二の駆動信号、例えば９０度もしくは−９０度異なる信号を印加することで積層圧電素子１８に縦振動と屈曲振動が励振される。位相を逆転させることで縦振動と屈曲信号の位相が逆転し、移動体７の移動方向も変化する。
【００３９】
また本実施の形態の変形例を図９、図１０を用いて説明する。図９、図１０は図８（ａ）に対応させて示したものであり、即ち図９、図１０は積層圧電素子２２の一方の面の外部電極の違いだけを示したものである。図９において、外部電極２５ｅは積層圧電素子２２の幅方向中央部に設けられ、内部電極２３ａ、２３ｂ、２３ｃを短絡させる。外部電極２５ａ、２５ｂは外部電極２５ｅの両側で内部電極２３ａを短絡する。外部電極２６ｃ、２６ｄは外部電極２５ｅの両側で内部電極２３ｃを短絡する。ここで、外部電極２５ａ、２５ｂ、２５ｃ，２５ｄ，２５ｅは図８における外部電極２４ａ、２４ｂ、２４ｃ、２４ｄ、２４ｅに相当させて分極、駆動させれば良い。
【００４０】
図１０において外部電極２６ｅは積層圧電素子２２の幅方向および長手方向中央部に設けられ、内部電極２３ａ、２３ｂ、２３ｃを短絡させる。外部電極２６ａ、２６ｂは外部電極２６ｅの両側で内部電極２３ａを短絡する。外部電極２６ｃ、２６ｄは外部電極２６ｅの両側で内部電極２３ｃを短絡する。ここで、外部電極２６ａ、２６ｂ、２６ｃ，２６ｄ，２６ｅを図８における外部電極２４ａ、２４ｂ、２４ｃ、２４ｄ、２４ｅに相当させて分極、駆動させれば良い。
【００４１】
本実施の形態は同様の実施の形態をとる実施の形態３の場合と比べ、振動を効率的に励振出来るという大きな特徴を有する。縦振動の励振に効果的な節部、即ち積層圧電素子２２の長手方向中央部に電極を有している。そして図９の場合には、屈曲振動を励振する圧電素子の電極２３ｂは駆動に用いていないため、実質上の隙間となり、内部電極２３ａ、２３ｂ、２３ｃ及び２３ｄ，２３ｅ，２３ｆの間の隙間を小さくしても分極時や駆動信号印加の際の影響は受けない。従って電極２３ａ、２３ｂ、２３ｃ、２３ｄ、２３ｅ、２３ｆ全てを用いて行う縦振動の励振の効率が良い。また、この電極２３ｂ，２３ｅの部分は屈曲振動の励振にはあまり寄与しないからこの部分を使わないことにより無駄な電力を消費せずに済む。
【００４２】
（実施の形態６）
本発明の超音波モータを用いて電子機器を構成した例を図１１を基に説明する。
【００４３】
図１１は本発明の駆動回路により駆動される超音波モータ１００を電子機器の駆動源に適用したブロック図を示したものであり、積層圧電素子１、９、１３、１６、１８，２２と積層圧電素子１、９、１６、１９に接合された摩擦部材２により摩擦駆動される移動体７と移動体７と一体に動作する伝達機構３２と、伝達機構３２の動作に基づいて動作する出力機構３３からなる。ここでは移動体を回転体とし、移動体を回転動作させる例について説明する。
【００４４】
ここで、伝達機構３２は例えば歯車列、摩擦車等の伝達車を用いる。出力機構３３としては、プリンタにおいては紙送り機構、カメラにおいてはシャッタ駆動機構、レンズ駆動機構、フィルム巻き上げ機構等を、また電子機器や計測器においては指針等を、ロボットにおいてはアーム機構、工作機械においては歯具送り機構や加工部材送り機構等を用いる。
【００４５】
尚、本実施の形態における電子機器としては電子時計、計測器、カメラ、プリンタ、印刷機、ロボット、工作機、ゲーム機、光情報機器、医療機器、移動装置等を実現できる。さらに移動体７に出力軸を設け、出力軸からのトルクを伝達するための動力伝達機構を有する構成とすれば、超音波モータ駆動装置を実現できる。
【００４６】
【発明の効果】
本発明によれば、複数の圧電素子の界面に設けられた内部電極は同一形状であり、内部電極を短絡する外部電極は少なくとも三つ有することにより、同じ形状の内部電極のみを用いているために製造時のばらつきが発生しにくい。そして外部電極の一つを共通電極（ＧＮＤ）とし、例えば他の二つの外部電極の何れかに信号を印加して二つの異なる振動の位相を変えるか、あるいは他の二つの外部電極に別々の信号を印加することで二つの振動を独立に励振する等の様々な駆動方法が可能となる。
【００４７】
また、この振動体構造により、複数の内部電極が設けられた同一の圧電素子シート材を面内方向に位置をずらしながら積層し、個々の振動体形状に分割した後で、前記分割した面に外部電極を設けるという製造方法が採れるため製造プロセスが簡単で、しかも短い時間に大量の振動体を作製可能な為、大幅に製造コストを引き下げられる。
【００４８】
また、外部電極どうしの間には電極を有さない圧電素子を設けることにより、製造時の外部電極どうしの短絡の防止や、この外部電極で短絡された内部電極が設けられた部分の分極時の影響が少なくなる。
【００４９】
さらに、外部電極のうち少なくとも一つは同一面内に存在する複数の内部電極を短絡するようにすることにより、内部電極の形状は同じであっても実際には異なる内部電極を有した場合と同等になり様々な振動の励振が可能となる。
【００５０】
また、前記複数の外部電極を短絡する複数の導通手段を有し、少なくとも一つの導通手段は、分極時に接地した外部電極と分極時に電位を加えた外部電極を短絡させれば一度の分極で済むと共に、分極方向が異なる部分での圧電特性の違いや分極方向が異なる境界部での応力集中による強度低下等を防ぐことが出来る。
【００５１】
また、振動体は矩形形状であり、駆動信号を印加する外部電極を選択することにより前記振動体に励振する縦振動と屈曲振動の位相を逆転させ移動体の移動方向を切り替えるようにすれば駆動回路が簡単になる。
【００５２】
また、振動体は矩形形状であり、複数の外部電極は第一の駆動信号もしくは第二の駆動信号が印加され、第一の駆動信号により振動体には縦振動が励振され、第二の駆動信号により振動体には屈曲振動が励振されるようにすれば、縦振動と屈曲振動を独立に励振可能であり、移動体の速度、推進力等を広範囲に渡って可変可能となり、更には高精度な位置決め制御が可能となる。
【００５３】
また、これらの振動体を用いた超音波モータを備えた電子機器は、その小型・薄型化、低消費電力化が可能となる。
【００５４】
以上のように、本発明によれば、簡単な製造プロセスで作製可能な積層圧電素子を振動体として用いるため低電圧で駆動でき、小型で高出力が得られると共に安価な超音波モータが実現できる。特に積層素子全体を一体的に焼結して作製することにより製品個々の特性ばらつきが小さく、信頼性が高く、内部損失が小さくて効率の高い超音波モータが得られる。そしてこれを用いた電子機器の小型、薄型化並びに低消費電力化が実現できる。
【図面の簡単な説明】
【図１】本発明にかかわるリニヤ型超音波モータの構成例を示す図である。
【図２】本発明にかかわる積層圧電素子の振動モードを示す図である。
【図３】本発明の実施の形態１にかかわる積層圧電素子の構成を示す図である。
【図４】本発明にかかわる積層圧電素子の製法を示す図である。
【図５】本発明の実施の形態２にかかわる積層圧電素子の構成を示す図である。
【図６】本発明の実施の形態３にかかわる積層圧電素子の構成を示す図である。
【図７】本発明の実施の形態４にかかわる積層圧電素子の構成を示す図である。
【図８】本発明の実施の形態５にかかわる積層圧電素子の構成を示す図である。
【図９】本発明の実施の形態５にかかわる積層圧電素子の別の構成を示す図である。
【図１０】本発明の実施の形態５にかかわる積層圧電素子の別の構成を示す図である。
【図１１】本発明にかかわる超音波モータを用いた電子機器を示すブロック図である。
【符号の説明】
１、９、１３、１６、１８、２２積層圧電素子
２摩擦部材
３支持部材
４加圧部材
６加圧手段
７移動体
１０、１４、１９、２３内部電極
１１、１５、１７、２０、２１、２４、２５、２６外部電極[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ultrasonic motor, a method of manufacturing the same, and an electronic device including the ultrasonic motor.
[0002]
[Prior art]
Ultrasonic motors using the resonance mode of an elastic body have excellent controllability, and in recent years have attracted particular attention as precision positioning actuators. In particular, linear ultrasonic motors are often required as actuators for various stages, and many types have been proposed and studied. Among them, various ultrasonic motors utilizing the combined vibration of longitudinal (expanding / contracting) vibration and bending vibration of a rectangular plate have been studied (for example, see Patent Document 1). Among these, for example, as shown in Patent Document 1, a rectangular piezoelectric element single plate is polarized in the thickness direction and four-divided electrodes are provided, diagonal electrodes are grouped, and a pair of electrodes is driven. Principles that excite longitudinal and bending vibrations in a vibrating body made of a piezoelectric element by applying a signal and drive a moving body in contact with the vibrating body are being put to practical use in various applications.
[0003]
[Patent Document 1]
Japanese Patent No. 2980541 (pages 7-8, FIG. 1)
[0004]
[Problems to be solved by the invention]
However, the conventional structure requires an extremely high voltage to drive the vibrating body, and requires a large booster circuit, which results in an increase in the size and complexity of the drive circuit and an increase in the price of the drive circuit. In this case, it has been difficult to apply the device to a small device, particularly to an application driven by a battery. As for the structure of the vibrating body, if the thickness of the piezoelectric element is small, sufficient output cannot be obtained, and the mechanical strength is low, which may lead to breakage. Conversely, when the thickness is increased, there is a problem that the polarization voltage is extremely high and the manufacturing process becomes complicated. In this configuration, a large output could not be obtained because the lateral piezoelectric effect of the piezoelectric element was used.
[0005]
[Means for Solving the Problems]
Therefore, a first aspect of the present invention is directed to an ultrasonic motor configured to form a vibrator by laminating a plurality of piezoelectric elements and to drive a moving body in contact with the vibrator, provided at an interface between the plurality of piezoelectric elements. The internal motor has the same shape and the ultrasonic motor has at least three external electrodes that short-circuit the internal electrodes.
[0006]
A second aspect of the present invention is the ultrasonic motor according to the first aspect, wherein at least one of the plurality of piezoelectric elements is a piezoelectric element having no electrode.
[0007]
A third aspect of the present invention is the ultrasonic motor according to the first aspect, wherein at least one of the plurality of piezoelectric elements short-circuits a plurality of internal electrodes existing in the same plane.
[0008]
A fourth aspect of the present invention, in the first aspect, has a plurality of conducting means for short-circuiting the plurality of external electrodes, and at least one of the conducting means is configured to apply a potential to the external electrode grounded at the time of polarization. An ultrasonic motor characterized in that the added external electrode is short-circuited.
[0009]
According to a fifth aspect of the present invention, in the first aspect, the vibrating body has a rectangular shape, and by selecting an external electrode to which a drive signal is applied, the phase of the longitudinal vibration and the bending vibration excited in the vibrating body is selected. In which the moving direction of the moving body is switched by reversing the rotation direction.
[0010]
According to a sixth aspect of the present invention, in the first aspect, the vibrating body has a rectangular shape, and the first driving signal or the second driving signal is applied to the plurality of external electrodes, and the first driving An ultrasonic motor is characterized in that a longitudinal vibration is excited in the vibrating body by a signal, and a bending vibration is excited in the vibrating body by the second drive signal to drive the moving body.
[0011]
A seventh aspect of the present invention is an ultrasonic motor configured to form a vibrating body by laminating a plurality of piezoelectric elements and to drive a moving body in contact with the vibrating body, wherein the vibrating body includes a plurality of internal electrodes. After stacking the same piezoelectric element sheet material shifted in the in-plane direction and dividing it into individual vibrator shapes, the internal electrodes are short-circuited by providing at least three external electrodes on the divided surface. To manufacture an ultrasonic motor.
[0012]
An eighth aspect of the present invention is an electronic device including the ultrasonic motor according to any one of the first to sixth aspects.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings.
[0014]
FIG. 1 shows a configuration example of a linear type ultrasonic motor using the laminated piezoelectric element 1 of the present invention as a vibrator. The rectangular laminated piezoelectric element 1 is provided with a supporting member 3 having projections 2a and 2b and a concave portion. The shaft 4a of the pressure member 4 has a step, and is guided by a guide hole 5a of the guide plate 5 so as to be movable only in the axial direction. A moving body 7 guided by guide members 8a and 8b is provided below the projections 2a and 2b. The support member 3 is engaged with the concave portion of the pressing member 4, and the pressing member 4 is pressed by the pressing means 6. By pressing, the projections 2a, 2b are in contact with the moving body 7.
[0015]
Incidentally, the laminated piezoelectric element 1 excites longitudinal vibration and bending vibration. For example, FIG. 2 shows a state of vibration amplitude in the longitudinal direction of the laminated piezoelectric element 1, FIG. 2 (a) shows a state of longitudinal vibration, and FIG. 2 (b) shows a state of bending vibration. is there. In both the longitudinal vibration and the bending vibration, the central portion of the laminated piezoelectric element 1 serves as a vibration node, and the support member 3 is provided at this position. Protrusions 2a and 2b are provided at the positions of antinodes of the bending vibration. By simultaneously exciting the longitudinal vibration and the bending vibration, the projections 2a and 2b perform an elliptical motion composed of the displacement of the laminated vibrator 1 in the longitudinal direction and the displacement in the width direction orthogonal thereto, thereby driving the moving body 7. Incidentally, the order of the two vibration modes is not limited, and another mode may be used. Further, the moving body 7 may be fixed and the vibrating body itself may be driven.
[0016]
(Embodiment 1)
Specifically, a configuration example of the laminated piezoelectric element 9 will be described with reference to FIG. FIGS. 3A and 3C each have a rectangular shape, and are views of the laminated piezoelectric element 9 viewed from the front and back, and FIGS. 3D and 3E are cross-sectional views. That is, as shown in FIGS. 3D and 3E, the piezoelectric elements 9a and 9b having the internal electrodes 10a and 10b or the internal electrodes 10c and 10d on one surface are alternately laminated. The internal electrodes 10 a, 10 b, 10 c, and 10 d have a shape substantially bisected in the longitudinal direction of the piezoelectric elements 9 a, 9 b, protrude only in one surface direction of the laminated piezoelectric element 9, and The external electrodes 11a, 11b, 11c, 11d, and 11e are short-circuited. The external electrodes 11a, 11b, 11c, and 11d short-circuit the internal electrodes 10a and 10b in each of four regions divided by a line connecting the centers of opposing sides in the plane of the laminated piezoelectric element 9. The external electrode 11e short-circuits all the internal electrodes 10c and 10d.
[0017]
Here, by applying a high voltage to the external electrodes 11a, 11b, 11c, and 11d while using the external electrode 11e as GND, polarization processing is performed in the stacking direction.
[0018]
The driving method of the present laminated piezoelectric element 9 includes, for example, the following two methods. By applying a drive signal between the external electrodes 11a and 11d and the external electrode 11e or between the external electrodes 11b and 11c and the external electrode 11e, a line connecting the centers of opposing sides in the plane of the laminated piezoelectric element 9 is divided. As the two regions at the diagonal of the four regions expand and contract, longitudinal vibration and bending vibration are excited in the laminated piezoelectric element 9. By switching the region to which the drive signal is applied, the phases of the longitudinal vibration and the bending signal are reversed, and the moving direction of the moving body 7 also changes. Another method is to apply a drive signal having a different phase between the external electrodes 11a and 11d and the external electrodes 11b and 11c, for example, a signal different by 90 degrees or −90 degrees between the external electrodes 11a and 11d as GND, so that Longitudinal vibration and bending vibration are excited. By reversing the phase, the phases of the longitudinal vibration and the bending signal are reversed, and the moving direction of the moving body 7 is also reversed.
[0019]
FIG. 4 shows a method of manufacturing the laminated piezoelectric element 9. For example, electrodes 10 for a plurality of laminated piezoelectric elements are provided on a sheet 12 of a piezoelectric element having a size capable of taking a plurality of laminated piezoelectric elements 9 by printing or the like. After stacking a plurality of the sheets 12, the piezoelectric elements having no electrodes are finally stacked and laminated, and the binder is blown off by preliminary sintering. You. Then, after the external electrodes 11a, 11b, 11c, 11d, and 11e are attached, polarization processing is performed to complete the process. In this way, since only the same sheet 12 needs to be laminated, the same operation is repeated, including the step of attaching electrodes to each sheet, so that the manufacturing time is greatly reduced and the number of jigs such as an electrode attachment mask is reduced. I'm done.
[0020]
Here, the divided portion by dicing is indicated by a dotted line 50, but one side of the internal electrode 10 is alternately positioned at the dotted line 50, and after division, the sheets are alternately formed so as to form the internal electrodes 10a, 10b, 10c, and 10d. 12 are superimposed with their positions shifted. In practice, the electrodes 10 on the sheet 12 are slightly larger than the actual size of the internal electrodes 10a, 10b, 10c, and 10d. Is set to By laminating the piezoelectric element 9c having no electrode on the uppermost surface in this way, since the piezoelectric elements on the uppermost surface and the lowermost surface do not generate a driving force, the vibration can be balanced, so that unnecessary vibration is hardly generated. .
[0021]
Here, the laminated piezoelectric element 9 may be combined with an elastic body such as a metal to form a vibrating body, and the short circuit of the electrodes of each piezoelectric element is not limited to the side surface of the laminated piezoelectric element, but may be a through hole or the like. May be used.
[0022]
(Embodiment 2)
Next, a modified example of the first embodiment will be described below. Here, since the multilayer piezoelectric element 13 expands and contracts in the laminating direction, a large output can be obtained by using the piezoelectric longitudinal effect.
[0023]
5 (a) and 5 (c) are views of the laminated piezoelectric element 13 of the second embodiment having a rectangular shape as viewed from the front and back, and FIGS. 5 (d) and 5 (e) are cross-sectional views. is there. That is, as shown in FIGS. 5D and 5E, the piezoelectric elements 13a and 13b having the internal electrodes 14a and 14b or the internal electrodes 14c and 14d on one surface are alternately stacked. The internal electrodes 14a, 14b, 14c, and 14d have a shape that is substantially bisected in the longitudinal direction of the piezoelectric elements 13a and 13b, and protrude only in one surface direction of the laminated piezoelectric element 13; The external electrodes 15a, 15b, 15c, 15d, and 15e are short-circuited. The external electrodes 15a, 15b, 15c, and 15d short-circuit the internal electrodes 14a and 14b in each of four regions separated by a line connecting the centers of opposing sides in the plane of the laminated piezoelectric element 13. The external electrode 15e short-circuits all the internal electrodes 14c and 14d.
[0024]
Here, by applying a high voltage to the external electrodes 15a, 15b, 15c, and 15d with the external electrode 15e being GND, polarization processing is performed in the stacking direction.
[0025]
The driving method of the laminated piezoelectric element 13 includes, for example, the following two methods. By applying a drive signal between the external electrodes 15a and 15d and the external electrode 15e, or between the external electrodes 15b and 15c and the external electrode 15e, a line connecting the centers of opposing sides in the plane of the laminated piezoelectric element 13 is divided. The two diagonal regions of the four regions are expanded and contracted, and the laminated piezoelectric element 13 is excited in the longitudinal vibration and the bending vibration. By switching the region to which the drive signal is applied, the phases of the longitudinal vibration and the bending signal are reversed, and the moving direction of the moving body 7 also changes. Another method is to apply a drive signal having a different phase between the external electrodes 15a and 15d and the external electrodes 15b and 15c, for example, a signal different by 90 degrees or −90 degrees between the external electrodes 15a and 15d as GND, so that Longitudinal vibration and bending vibration are excited. By reversing the phase, the phases of the longitudinal vibration and the bending signal are reversed, and the moving direction of the moving body 7 is also reversed.
[0026]
(Embodiment 3)
FIG. 6 shows the configuration of the laminated piezoelectric element 16 according to the third embodiment, which is basically the same as that shown in the first embodiment, except that the external electrodes 17a, 17b, 17c, and 17d and the polarization directions are different. Since only the driving method is used, only the differences will be described and the description of the common points will be omitted.
[0027]
The external electrode 17e is short-circuited with the internal electrodes 10a and 10b at the center in the width direction of one surface of the laminated piezoelectric element 16. In both sides of the piezoelectric element portion short-circuited by the external electrode 17e, the internal electrode 10a is short-circuited by the external electrodes 17a and 17b, and the internal electrode 10b is short-circuited by the external electrodes 17c and 17d. On the other side of the laminated piezoelectric element 16, the internal electrodes 10c and 10d are short-circuited by the external electrode 17f.
[0028]
Here, the polarization process is performed by applying a voltage to the external electrodes 17a, 17b, 17c, 17d, and 17e while setting the external electrode 17f to GND. As a driving method in this case, the longitudinal vibration is excited by applying the first drive signal to the external electrode 17e while setting the external electrode 17f to GND. Further, by applying the second drive signal to the external electrodes 17a and 17d or the external electrodes 17b and 17c, the bending vibration is excited and the moving body 7 is driven. The phase of the longitudinal vibration and the bending signal is inverted depending on which external electrode the signal is applied to, and the moving direction of the moving body 7 also changes.
[0029]
As another driving method, polarization is performed by applying a positive voltage to the external electrodes 17a, 17d, and 17e and applying a negative voltage to the external electrodes 17b and 17c with the external electrode 17f set to GND. As a driving method in this case, the first and second driving signals having different phases between the external electrodes 17a, 17b, 17c, and 17d and the external electrode 17e using the external electrode 17f as a common electrode (GND), for example, 90 degrees or By applying signals different by -90 degrees, longitudinal vibration and bending vibration are excited in the laminated piezoelectric element 16. By reversing the phase, the phases of the longitudinal vibration and the bending signal are reversed, and the moving direction of the moving body 7 is also reversed. This phase is arbitrary, and switching between 0 degree and 180 degrees may be performed.
[0030]
The direction of the polarization is also arbitrary. If the phase of the drive signal is reversed according to the polarization direction, the same vibration is excited.
[0031]
(Embodiment 4)
FIG. 7 shows another example of the laminated piezoelectric element of the present invention. 7 (a) and 7 (c) are views of the laminated piezoelectric element 18 of Embodiment 4 each having a rectangular shape as viewed from the front and back, and FIGS. 7 (d) and 7 (e) are cross-sectional views. is there. That is, as shown in FIGS. 7 (d) and 7 (e), the piezoelectric elements 18a and 18b having the internal electrodes 19a, 19b and 19c or the internal electrodes 19d, 19e and 19f on one surface are alternately laminated. ing. The internal electrodes 19 a, 19 b, 19 c, 19 d, 19 e, and 19 f have a shape substantially equally divided into three in the longitudinal direction of the piezoelectric elements 18 a and 18 b, and project only in one surface direction of the laminated piezoelectric element 18. The external electrodes 20a, 20b, 20c, 20d, 20e, 21a, 21b, 21c, 21d, 21e are short-circuited on the side surface of the piezoelectric element 18. The external electrode 20e short-circuits the internal electrode 19b within one surface of the laminated piezoelectric element 18. The external electrodes 20a and 20b short-circuit the electrode 19a in a region that bisects the laminated piezoelectric element 18 in the longitudinal direction. The external electrodes 20c and 20d short-circuit the electrode 19c in a region that bisects the laminated piezoelectric element 18 in the longitudinal direction.
[0032]
On the other surface, the external electrode 21e short-circuits the internal electrode 19e in one surface of the laminated piezoelectric element 18. The external electrodes 21a and 21b short-circuit the electrode 19d in a region that bisects the laminated piezoelectric element 18 in the longitudinal direction. The external electrodes 21c and 21d short-circuit the electrode 19f in a region that bisects the laminated piezoelectric element 18 in the longitudinal direction. For example, a piezoelectric element 18c having no electrode may be placed at a position located in the gap so that the external electrodes 20a and 20b are not short-circuited.
[0033]
Here, by applying a high voltage to the external electrodes 20a, 20b, 20c, 20d, and 20e using the external electrodes 21a, 21b, 21c, 21d, and 21e as GND, polarization processing is performed in the stacking direction.
[0034]
In the driving method of the present laminated piezoelectric element 13, for example, the external electrodes 21c, 21b, 21e, 20b, and 20c are short-circuited by conductive means (not shown), and the external electrode 20a is short-circuited as GND by the external electrode 20e and conductive means (not shown). , 20d, 21a, and 21d, a driving signal having a different phase, that is, a first driving signal and a second driving signal, for example, signals different by 90 degrees or -90 degrees are applied to the laminated piezoelectric element 18 to cause longitudinal vibration. And the bending vibration is excited. By reversing the phase, the phases of the longitudinal vibration and the bending signal are reversed, and the moving direction of the moving body 7 is also reversed.
[0035]
According to the present invention, a large output can be obtained by using the piezoelectric longitudinal effect, and the polarization direction can be the same, so that the process can be simplified and high voltage can be used without breaking. Also, there is no characteristic variation caused by the difference in the polarization direction.
[0036]
(Embodiment 5)
FIG. 8 shows another example of the laminated piezoelectric element of the present invention. FIGS. 8 (a) and 8 (c) are front and back views of the laminated piezoelectric element 22 corresponding to the example of the fourth embodiment having a rectangular shape, and FIGS. 8 (d) and 8 (e). Is a sectional view. That is, as shown in FIGS. 8D and 8E, a structure in which the piezoelectric elements 22a and 22b having the internal electrodes 23a, 23b and 23c or the internal electrodes 23d, 23e and 23f on one surface is alternately laminated. It has become. The internal electrodes 23b and 23e are provided at the center in the longitudinal direction of the piezoelectric elements 22a and 22b, and the internal electrodes 23a, 23c, 23d and 23f are provided on both sides of the internal electrodes 23b and 23e. The external electrodes 24a, 24b, 24c, 24d, 24e, and 24f are short-circuited on the side surface of the laminated piezoelectric element 22. The external electrode 24e short-circuits the internal electrode 23b within one surface of the laminated piezoelectric element 22. The external electrodes 24a and 24b short-circuit the electrode 23a in a region that bisects the laminated piezoelectric element 18 in the width direction. The external electrodes 24c and 24d short-circuit the electrode 23c in a region that bisects the laminated piezoelectric element 18 in the width direction. On the other surface, the external electrode 24f short-circuits the internal electrodes 23d, 23e and 23f.
[0037]
Here, the external electrode 24f is set to GND, and a positive high voltage is applied to the external electrodes 24a, 24b, and 24e, and a negative high voltage is applied to the external electrodes 24b and 24c, whereby polarization is performed in the stacking direction. .
[0038]
The driving method of the present laminated piezoelectric element 22 is, for example, a driving signal having a different phase between the external electrode 24e and the external electrodes 24a, 24b, 24c, 24d, that is, the external electrode 24f is set to GND, that is, the first driving signal and the second driving signal. By applying two driving signals, for example, signals different by 90 degrees or −90 degrees, longitudinal vibration and bending vibration are excited in the laminated piezoelectric element 18. By reversing the phase, the phases of the longitudinal vibration and the bending signal are reversed, and the moving direction of the moving body 7 also changes.
[0039]
A modification of the present embodiment will be described with reference to FIGS. 9 and 10 correspond to FIG. 8A, that is, FIGS. 9 and 10 show only the difference of the external electrodes on one surface of the laminated piezoelectric element 22. FIG. In FIG. 9, an external electrode 25e is provided at the center in the width direction of the laminated piezoelectric element 22, and short-circuits the internal electrodes 23a, 23b, and 23c. The external electrodes 25a and 25b short-circuit the internal electrode 23a on both sides of the external electrode 25e. The external electrodes 26c and 26d short-circuit the internal electrode 23c on both sides of the external electrode 25e. Here, the external electrodes 25a, 25b, 25c, 25d, and 25e may be polarized and driven corresponding to the external electrodes 24a, 24b, 24c, 24d, and 24e in FIG.
[0040]
In FIG. 10, the external electrode 26e is provided at the center of the laminated piezoelectric element 22 in the width direction and the longitudinal direction, and short-circuits the internal electrodes 23a, 23b, and 23c. The external electrodes 26a and 26b short-circuit the internal electrode 23a on both sides of the external electrode 26e. The external electrodes 26c and 26d short-circuit the internal electrode 23c on both sides of the external electrode 26e. Here, the external electrodes 26a, 26b, 26c, 26d, and 26e may be polarized and driven so as to correspond to the external electrodes 24a, 24b, 24c, 24d, and 24e in FIG.
[0041]
The present embodiment has a significant feature that vibration can be efficiently excited compared to the third embodiment which employs the same embodiment. An electrode is provided at a node effective for exciting longitudinal vibration, that is, at a central portion in the longitudinal direction of the laminated piezoelectric element 22. In the case of FIG. 9, since the electrode 23b of the piezoelectric element for exciting the bending vibration is not used for driving, it becomes a substantial gap, and the gap between the internal electrodes 23a, 23b, 23c and 23d, 23e, 23f is formed. Even if it is made smaller, it is not affected at the time of polarization or application of a drive signal. Therefore, the efficiency of the longitudinal vibration excitation performed using all of the electrodes 23a, 23b, 23c, 23d, 23e, and 23f is high. Further, since the electrodes 23b and 23e do not contribute much to the excitation of the bending vibration, unnecessary power is not consumed by not using these parts.
[0042]
(Embodiment 6)
An example in which an electronic device is configured using the ultrasonic motor of the present invention will be described with reference to FIG.
[0043]
FIG. 11 is a block diagram in which the ultrasonic motor 100 driven by the drive circuit of the present invention is applied to a drive source of an electronic device, and includes a multilayer piezoelectric element 1, 9, 13, 16, 18, 22, and a multilayer piezoelectric element. A moving body 7 that is frictionally driven by a friction member 2 joined to the piezoelectric elements 1, 9, 16, and 19, a transmission mechanism 32 that operates integrally with the moving body 7, and an output mechanism that operates based on the operation of the transmission mechanism 32 It consists of 33. Here, an example in which the moving body is a rotating body and the moving body is rotated will be described.
[0044]
Here, the transmission mechanism 32 uses a transmission wheel such as a gear train or a friction wheel. The output mechanism 33 includes a paper feed mechanism in a printer, a shutter driving mechanism, a lens driving mechanism, a film winding mechanism in a camera, a pointer in electronic devices and measuring instruments, an arm mechanism and a machine tool in a robot. , A tooth feed mechanism, a working member feed mechanism, or the like is used.
[0045]
Note that, as the electronic device in the present embodiment, an electronic timepiece, a measuring instrument, a camera, a printer, a printing machine, a robot, a machine tool, a game machine, an optical information device, a medical device, a moving device, and the like can be realized. Further, if the moving body 7 is provided with an output shaft and has a power transmission mechanism for transmitting torque from the output shaft, an ultrasonic motor driving device can be realized.
[0046]
【The invention's effect】
According to the present invention, the internal electrodes provided at the interfaces of the plurality of piezoelectric elements have the same shape, and since there are at least three external electrodes that short-circuit the internal electrodes, only the internal electrodes having the same shape are used. It is unlikely that there will be variations during manufacturing. One of the external electrodes is used as a common electrode (GND). For example, a signal is applied to one of the other two external electrodes to change the phase of two different vibrations, or a separate one is applied to the other two external electrodes. Various driving methods such as independently exciting two vibrations by applying a signal become possible.
[0047]
Further, by this vibrating body structure, the same piezoelectric element sheet material provided with a plurality of internal electrodes is laminated while shifting the position in the in-plane direction, and divided into individual vibrating body shapes. Since the manufacturing method of providing external electrodes can be adopted, the manufacturing process is simple, and a large number of vibrators can be manufactured in a short time, so that the manufacturing cost can be significantly reduced.
[0048]
In addition, by providing a piezoelectric element having no electrode between the external electrodes, it is possible to prevent a short circuit between the external electrodes at the time of manufacturing, and to polarize a portion where the internal electrode shorted by the external electrode is provided. Influence is reduced.
[0049]
Furthermore, at least one of the external electrodes is configured to short-circuit a plurality of internal electrodes existing in the same plane, so that the internal electrodes have the same shape but actually have different internal electrodes. It becomes the same, and various vibrations can be excited.
[0050]
In addition, it has a plurality of conducting means for short-circuiting the plurality of external electrodes, and at least one conducting means requires only one polarization by short-circuiting the external electrode grounded at the time of polarization and the external electrode applied with a potential at the time of polarization. At the same time, it is possible to prevent a difference in piezoelectric characteristics in a portion having a different polarization direction and a reduction in strength due to stress concentration at a boundary portion having a different polarization direction.
[0051]
Further, the vibrating body has a rectangular shape, and by selecting an external electrode to which a driving signal is applied, the phases of the longitudinal vibration and the bending vibration to be excited in the vibrating body are reversed, and the moving direction of the moving body is switched so that the driving is performed. The circuit becomes simple.
[0052]
Further, the vibrating body has a rectangular shape, and the first driving signal or the second driving signal is applied to the plurality of external electrodes, longitudinal vibration is excited in the vibrating body by the first driving signal, and the second driving signal is applied. If the bending vibration is excited in the vibrating body by the signal, the longitudinal vibration and the bending vibration can be excited independently, and the speed and the propulsion force of the moving body can be varied over a wide range. Accurate positioning control becomes possible.
[0053]
Further, an electronic device including an ultrasonic motor using these vibrators can be reduced in size, thickness, and power consumption.
[0054]
As described above, according to the present invention, since a laminated piezoelectric element that can be manufactured by a simple manufacturing process is used as a vibrator, it can be driven at a low voltage, and a compact, high-output, and inexpensive ultrasonic motor can be realized. . In particular, by integrally sintering and manufacturing the entire stacked element, an ultrasonic motor with small variations in characteristics of individual products, high reliability, small internal loss, and high efficiency can be obtained. In addition, it is possible to reduce the size, thickness, and power consumption of an electronic device using the electronic device.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration example of a linear type ultrasonic motor according to the present invention.
FIG. 2 is a diagram showing a vibration mode of the laminated piezoelectric element according to the present invention.
FIG. 3 is a diagram showing a configuration of a laminated piezoelectric element according to Embodiment 1 of the present invention.
FIG. 4 is a diagram showing a method for manufacturing a laminated piezoelectric element according to the present invention.
FIG. 5 is a diagram showing a configuration of a laminated piezoelectric element according to Embodiment 2 of the present invention.
FIG. 6 is a diagram showing a configuration of a laminated piezoelectric element according to Embodiment 3 of the present invention.
FIG. 7 is a diagram showing a configuration of a laminated piezoelectric element according to a fourth embodiment of the present invention.
FIG. 8 is a diagram showing a configuration of a laminated piezoelectric element according to a fifth embodiment of the present invention.
FIG. 9 is a diagram showing another configuration of the laminated piezoelectric element according to the fifth embodiment of the present invention.
FIG. 10 is a diagram showing another configuration of the laminated piezoelectric element according to the fifth embodiment of the present invention.
FIG. 11 is a block diagram showing an electronic device using the ultrasonic motor according to the present invention.
[Explanation of symbols]
1, 9, 13, 16, 18, 22 laminated piezoelectric element
2 Friction member
3 support members
4 Pressing member
6 Pressurizing means
7 Moving body
10, 14, 19, 23 Internal electrode
11, 15, 17, 20, 21, 24, 25, 26 external electrodes

Claims

An ultrasonic motor configured to form a vibrator by laminating a plurality of piezoelectric elements and drive a moving body in contact with the vibrator,
An ultrasonic motor having an internal electrode provided at an interface between the plurality of piezoelectric elements and having at least three external electrodes for short-circuiting the internal electrodes.

The ultrasonic motor according to claim 1, wherein at least one of the plurality of piezoelectric elements is a piezoelectric element having no electrode.

The ultrasonic motor according to claim 1, wherein at least one of the plurality of piezoelectric elements short-circuits a plurality of internal electrodes existing in the same plane.

2. The device according to claim 1, further comprising: a plurality of conducting means for short-circuiting the plurality of external electrodes, wherein at least one of the conducting means short-circuits an external electrode grounded during polarization and an external electrode applied with a potential during polarization. The ultrasonic motor as described.

The vibrating body has a rectangular shape, and by selecting an external electrode to which a drive signal is applied, a phase of longitudinal vibration and bending vibration to be excited on the vibrating body is reversed to switch a moving direction of the moving body. The ultrasonic motor according to claim 1, wherein

The vibrator has a rectangular shape, a first drive signal or a second drive signal is applied to the plurality of external electrodes, and a longitudinal vibration is excited in the vibrator by the first drive signal. The ultrasonic motor according to claim 1, wherein a bending vibration is excited in the vibrating body by the second drive signal to drive the moving body.

An ultrasonic motor configured to form a vibrator by laminating a plurality of piezoelectric elements and drive a moving body in contact with the vibrator, wherein the vibrator uses the same piezoelectric element sheet material provided with a plurality of internal electrodes. A method of manufacturing an ultrasonic motor in which the layers are laminated while being displaced in the in-plane direction, divided into individual vibrator shapes, and the internal electrodes are short-circuited by providing at least three external electrodes on the divided surface.

An electronic device comprising the ultrasonic motor according to claim 1.