JP2005020951A

JP2005020951A - Ultrasonic motor and positioning device having the same

Info

Publication number: JP2005020951A
Application number: JP2003185062A
Authority: JP
Inventors: Etsuo Yamamoto; 悦夫山本
Original assignee: Hephaist Seiko Co Ltd
Current assignee: Hephaist Seiko Co Ltd
Priority date: 2003-06-27
Filing date: 2003-06-27
Publication date: 2005-01-20

Abstract

<P>PROBLEM TO BE SOLVED: To improve controlling responsiveness by reducing a microscopic change of a frictional drive force generated from a vibrator in a standing wave ultrasonic motor. <P>SOLUTION: The ultrasonic motor 10 includes a vibrating part 24 having one vibrator 14, and two pairs of exciting elements 16 mounted in the vibrator 14. A controller 22 controls the two pairs of the exciting elements 16 so that two exciting elements 16 which form each pair of the two pairs of the exciting elements 16 generate high frequency displacing operations of different phases from each other to create an elliptical motion in the drive surface 12 of the vibrator 14 and it becomes a state that phases of the high frequency displacing operations of all the exciting elements 16 become regularly deviated from each other. More particularly, a control of applying drive voltages of V=αsinäωt-(m-1)π}, V=αcosäωt-(m-1)π} to the two exciting elements 16 for forming the m-th (m=1 or 2)pair is performed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、超音波モータに関する。さらに本発明は、超音波モータを備えた位置決め装置に関する。
【０００２】
【従来の技術】
振動体の超音波振動を用いて摩擦駆動力を生成する超音波モータは、近年、特に小型精密機器の分野で、様々な被駆動要素を直線又は回転駆動する小型アクチュエータとして広く利用されている。一般に超音波モータは、駆動面を有する振動体と、振動体を励振する励振素子と、振動体の駆動面に当接配置され、振動体の振動に応じて振動体に対し一方向へ移動する可動体（被駆動体）とを備えて構成される。振動体は通常、金属、セラミックス等の硬質の弾性体から作製され、また励振素子は通常、圧電セラミックス等の圧電素子から作製される。さらに超音波モータでは、振動体と可動体との間で効率良く摩擦駆動力を発生させるために、振動体の駆動面を所定圧力下で可動体の表面に押し付ける予圧構造が設けられる。
【０００３】
この種の超音波モータにおいて、所望端面が駆動面として作用する短棒状の振動体と、振動体の駆動面以外の面に適宜配置で接合される複数の圧電素子とを備え、個々の圧電素子を所定位相差で変位動作させることにより、摩擦駆動力を発揮するための楕円運動を駆動面に生起させる構成を有した定在波型の超音波モータが知られている。この形式の超音波モータとしては従来、それぞれの一端に駆動面を有する１対の柱状脚部とそれら柱状脚部の他端同士を接続する梁状胴部とを有した門形の振動体を備え、振動体の両脚部と胴部との接続領域に形成される互いに略直交する１対の傾斜肩面に、２つの圧電素子をそれぞれ近傍の駆動面に対し４５°の角度を成すように接合したもの（いわゆるπ形：例えば特許文献１参照）と、一端に駆動面を有するとともに他端に互いに略直交する１対の傾斜肩面を有する柱形の振動体を備え、それら傾斜肩面に２つの圧電素子をそれぞれ駆動面に対し４５°の角度を成すように接合したもの（いわゆるＹ形：例えば特許文献２参照）とが提唱されている。
【特許文献１】
特開平６−２８４７５５号公報
【特許文献２】
実開平２−１３６４８５号公報
【０００４】
また、上記特許文献１は、ＸＹステージに用いられる直動案内（位置決め）装置の駆動部に、上記したπ形の超音波モータを組み込んだ構成を開示する。この案内装置では、リニアガイドを介して直線往復動作可能に組み合わされる１対の基台の一方に、超音波モータの振動体及び圧電素子が固定的に設置されるとともに、他方の基台が、振動体の駆動面に当接される表面を有する可動体を構成している。
【０００５】
【発明が解決しようとする課題】
前述した短棒状の振動体を有する定在波型の超音波モータでは、振動体の駆動面に生起される周期的な楕円運動（円運動及び直線運動を含む）が、摩擦力を介して局所的に可動体に伝達されることにより、楕円運動の方向に対応する方向へ可動体が相対移動する。したがって微視的には、振動体の駆動面と可動体表面との間に摩擦駆動力を実質的に生じない時間が周期的に存在する。また、摩擦駆動力は、振動体の駆動面を可動体表面に押し付ける予圧力に依存し、負荷の慣性の影響を実質的に受けない。その結果、可動体の移動速度が微視的には不安定になっており、このことが、可動体の位置決め精度等の制御応答性に限界をもたらす要因となっている。さらに、可動体に、移動方向とは反対方向への制動作用が及ぼされている場合には、摩擦駆動力が減少する周期的微小時間に、可動体が制動作用により押し戻される傾向があり、結果として出力及び移動速度が低下することが懸念される。
【０００６】
また、上記定在波型の超音波モータを搭載した従来の単軸や多軸のステージ等の案内／位置決め装置では、従来の超音波モータに内在していた上記諸課題に伴い、ステージの位置決め精度の限界や、ステージの出力及び移動速度の低下等の問題が生じていた。
【０００７】
本発明の目的は、定在波型の超音波モータにおいて、振動体が生じる摩擦駆動力の微視的変動を低減することにより、制御応答性を向上させることができるとともに、可動体への制動作用に抗して出力及び移動速度を維持できる超音波モータを提供することにある。
本発明の他の目的は、駆動部に超音波モータを採用した位置決め装置において、ステージの位置決め精度、出力及び移動速度を向上させることができる位置決め装置を提供することにある。
【０００８】
【課題を解決するための手段】
上記目的を達成するために、請求項１に記載の発明は、駆動面を有する振動体を備える振動部と、振動体の超音波振動を制御する制御部とを具備する超音波モータにおいて、振動部は、少なくとも１個の振動体と、少なくとも１個の振動体に取り付けられて、振動体を励振する複数対の励振素子とを備え、制御部は、複数対の励振素子のうち、各対を成す２個の励振素子が、振動体の駆動面に楕円運動を生起する互いに位相の異なる高周波変位動作を生じるとともに、全ての励振素子の高周波変位動作の位相が、互いに規則的にずれた状態になるように、複数対の励振素子を制御すること、を特徴とする超音波モータを提供する。
【０００９】
請求項２に記載の発明は、請求項１に記載の超音波モータにおいて、振動部が、１個の振動体と、１個の振動体に取り付けられる複数対の励振素子とを備える超音波モータを提供する。
【００１０】
請求項３に記載の発明は、請求項１に記載の超音波モータにおいて、振動部が、複数の振動体と、それら振動体の各々に１対ずつ取り付けられる複数対の励振素子とを備える超音波モータを提供する。
【００１１】
請求項４に記載の発明は、請求項１〜３のいずれか１項に記載の超音波モータを備えた位置決め装置を提供する。
【００１２】
【発明の実施の形態】
以下、添付図面を参照して、本発明の実施の形態を詳細に説明する。全図面に渡り、対応する構成要素には共通の参照符号を付す。
図１及び図２は、本発明の一実施形態による超音波モータ１０を概略で示す。超音波モータ１０は、駆動面１２を有する振動体１４と、振動体１４を励振する励振素子１６と、振動体１４の駆動面１２に当接配置され、振動体１４の振動に応じて振動体１４に対し移動する可動体１８と、駆動面１２を可動体１８に押し付けた状態で振動体１４を支持する押圧支持構造２０と、振動体１４の超音波振動を制御する制御部２２とを備えて構成される。振動体１４と励振素子１６とは、超音波モータ１０の振動部２４を構成する。
【００１３】
振動部２４は、１個の振動体１４と、振動体１４に取り付けられる２対の励振素子１６とを備える。振動体１４は、短棒状（角柱形又は薄板形）の形態を有し、所望の一端面に平坦な駆動面１２を備えるとともに、駆動面１２から離れた他端側に、互いに略直交する方向へ平坦に延設される１対の傾斜肩面２６と、それら肩面２６の間で外方へ突設される支承部２８とを備える。振動体１４の駆動面１２は、好ましくは図示のように、振動体１４の一端面に固着された炭素繊維強化プラスチック等からなる摩擦材料３０によって形成される。摩擦材料３０は、振動体１４の超音波振動による摩擦駆動力の発生効率を向上させるとともに、駆動面１２及び可動体１８の表面の寿命を向上させる効果を奏する。
【００１４】
振動体１４は、図１の正面視及び図２の側面視の双方で、一端の駆動面１２の中心と他端の支承部２８の中心とを通る軸線１４ａ、１４ｂに関して線対称の形状を有する。両肩面２６は、いずれも駆動面１２に対し略４５°の角度を成して、軸線１４ａに関し左右対称に配置される。支承部２８は、振動体１４の本体部分１４ｃ（超音波が伝搬する部分）よりも薄い厚み（図１紙面に直交する方向への寸法）を有して本体部分１４ｃから延長され、その末端に軸線１４ａ方向へ延びる雌ねじ２８ａが凹設される。このような構成を有する振動体１４は、アルミニウム、チタン、銅、鉄系金属等の金属材料や、酸化珪素、酸化アルミニウム、酸化ジルコニウム、これらの複合物等のセラミックスといった、硬質の弾性体から一体的に作製される。
【００１５】
２対の励振素子１６の各々は、振動体１４の各肩面２６に接合される圧電素子１６からなる。各圧電素子１６は、圧電セラミックス等の薄板状圧電材料を積層してなる角柱（薄板）状の形態を有し、積層方向一端面を振動体１４の肩面２６に密着させて、例えば接着剤により肩面２６に強固に接合される。振動体１４の各肩面２６には、２個の圧電素子１６が互いに離間して、振動体厚み方向へ位置的に重畳かつ整合して配置され、両肩面２６上で２個ずつの圧電素子１６が、軸線１４ａに関し対称位置に配置される。対称位置にある各１対の（すなわち制御上で対を成す）圧電素子１６は、それぞれの積層方向へ延びる中心線１６ａがいずれも駆動面１２に対し略４５°の角度を成して配置される。対を成す２個の圧電素子１６には、制御部２２を含む制御回路を介して正弦波電圧がそれぞれに所定（例えば９０°）の位相差で印加され、それによる両圧電素子１６の差動的な変位動作が振動体１４を励振して、摩擦駆動力を発揮するためのいわゆる楕円運動を駆動面１２に生起させる。
【００１６】
なお、各圧電素子１６は、ジルコン酸チタン酸鉛（ＰＺＴ）からなる薄板状圧電材料の積層体から構成することが、低電圧で大駆動力を得る点で有利である。また、各圧電素子１６を振動体１４に接合する接着剤としては、十分な接着力が得られるものであれば特に限定されないが、例えばガラスフィラー入りの熱硬化型エポキシ接着剤を使用することができる。
【００１７】
可動体１８は、金属、樹脂等の硬質材料からなり、図示しない案内支持構造を介して、超音波モータ１０の図示しない機台（又は外部構造体）上に所定方向へ移動可能に支持される。可動体１８は、その所定表面領域３２で、振動体１４の駆動面１２に所定圧力下で接触して配置され、振動体１４の駆動面１２に生起された楕円運動の方向に応じて、接触面間の摩擦力により一方向（図示矢印）へ移動する。可動体１８の移動方向及び移動速度は、上記した１対の励振素子（圧電素子）１６に印加する正弦波電圧の位相及び周波数制御により制御できる。
【００１８】
なお可動体１８は、案内支持構造の構成に応じて、直動及び回動のいずれかの出力動作を遂行できる。また、振動体１４と可動体１８との移動関係は相対的なものであり、可動体１８が構造体上で固定されていた場合には、振動体１４が押圧支持構造２０と共に可動体１８に対して移動する。さらに、振動体１４の駆動面１２を形成する摩擦材料３０は、それに加えて又はその代わりに、可動体１８の表面領域３２に設置することもできる。
【００１９】
上記した振動体１４と励振素子１６とを含む駆動部２４及び可動体１８の構成は、いわゆるＹ形の超音波モータにおいて採用されている構成に類似しているものであり、対を成す励振素子１６の位相を反転することにより、可動体１８の駆動方向を切り換えることができる。なお、本発明に係る駆動部及び制御部の構成は、このようなＹ形モータ構造に限らず、π形や他の種々のモータ構造に適用できるものである。
【００２０】
押圧支持構造２０は、基材３４と、基材３４と振動体１４との間に配置され、振動体１４を基材３４上で支持しつつ駆動面１２を可動体１８に押し付けるばね力を発揮する支持ばね部材３６と、支持ばね部材３６のばね力を調整する予圧調整機構３８とを備える。支持ばね部材３６は、両端の取付部４０及びそれら取付部４０の間に位置する中間固定部４２を有する板状組立体である。支持ばね部材３６は、中間固定部４２で振動体１４に固定的に連結されるとともに、両取付部４０で与圧調整機構３８を介して基材３４に取り付けられる。その状態で支持ばね部材３６は、振動体１４の駆動面１２を可動体１８の表面領域３２に押し付けるばね力を発揮する。
【００２１】
基材３４は、矩形薄板状の主部４４と、主部４４の略平坦な一表面４４ａ上でその矩形輪郭の一外縁４４ｂに沿って互いに離間配置される角柱状の１対の取付基部４６とを備える。主部４４及び取付基部４６は、金属、樹脂等の硬質材料からなり、両者が互いに一体に成形されるか、或いはボルト等によって互いに固定的に連結される。各取付基部４６には、支持ばね部材３６を取り付けるための雌ねじ４６ａが、主部４４の表面４４ａに略平行な方向へ凹設される。なお、基材３４の主部４４は、前述した可動体１８を可動支持する超音波モータ１０の図示しない機台（又は外部構造体）に、固定的に連結することができる。
【００２２】
支持ばね部材３６は、中間固定部４２を含む板ばね要素４８と、それぞれに取付部４０を含む１対の剛性支持要素５０とを組み合わせて構成される。板ばね要素４８は、平板状の金属板、樹脂板等のばね材からなり、長手方向中央の中間固定部４２にボルト挿通孔４８ａが、また長手方向両端にボルト挿通孔４８ｂが、それぞれ板厚方向（紙面に平行な方向）へ貫通形成される。一対の剛性支持要素５０は、図１の正面視で互いに同一の略Ｓ字のクランク状外形に成形された金属板、樹脂板等の硬質材からなり、各々の一端の取付部４０にボルト挿通孔５０ａが、かつ他端に雌ねじ５０ｂが、それぞれ板厚方向（紙面に平行な方向）へ貫通形成される。
【００２３】
支持ばね部材３６は、板ばね要素４８の両端に、取付部４０を外側（相互離反側）に向けた両剛性支持要素５０の他端を重ねて配置し、個々のボルト挿通孔４８ｂに挿通したボルト５２を雌ねじ５０ｂに螺着して両要素４８、５０を相互に連結することにより、中間固定部４２を中心として対称な基準組立体の形態を呈する。そして支持ばね部材３６は、板ばね要素４８の中間固定部４２のボルト挿通孔４８ａに挿通したボルト５４を、振動体１４の支承部２８に形成した雌ねじ２８ａに螺着することにより、振動体１４に固定される。後述するように超音波モータ１０を適正に組み立てたときに、板ばね要素４８は、無負荷状態で、振動体１４の軸線１４ａに直交する方向へ延設される。
【００２４】
予圧調整機構３８は、支持ばね部材３６の両取付部４０と基材３４の両取付基部４６との間にそれぞれ介在する一対の調整ばね５６と、調整ばね５６を介して支持ばね部材３６の両取付部４０を対応の取付基部４６に取り付ける一対の取付ボルト５８とを備える。一対の調整ばね５６は、図１の正面視で互いに同一の略Ｕ字の外形に曲成された金属板、樹脂板等のばね材からなり、各々のＵ字の両腕部分の対応箇所にボルト挿通孔５６ａが、それぞれ板厚方向（紙面に平行な方向）へ貫通形成される。それら調整ばね５６は、Ｕ字の中央部分を内側（相互対向側）に向けて、基材３４の両取付基部４６にそれぞれ載置される。その状態で、各取付ボルト５８を、支持ばね部材３６の各取付部４０のボルト挿通孔５０ａと、対応の調整ばね５６のボルト挿通孔５６ａとに、連続的に挿通して、対応の取付基部４６の雌ねじ４６ａに螺着することにより、支持ばね部材３６が基材３４に取り付けられる。予圧調整機構３８は、個々の取付ボルト５８の締付けトルクを調整することにより、支持ばね部材３６の板ばね要素４８が発揮する予圧の調整を遂行する。
【００２５】
超音波モータ１０の上記構成要素群は、以下のようにして組み立てられる。
基材３４は、その主部４４の外縁４４ｂが可動体１８の表面領域３２に非接触に近接して位置するように、可動体１８の近傍に設置される。また、２対の圧電素子１６を両肩面２６に接合した振動体１４は、基材３４の両取付基部４６の略中間位置で、駆動面１２を表面領域３２に当接させて可動体１８上に搭載される。支持ばね部材３６は、前述した基準組立体の形態で、ボルト５４により中間固定部４２を振動体１４の支承部２８に固定するとともに、両端の取付部４０を、前述したように予圧調整機構３８を介して、基材３４の両取付基部４６に取り付ける。
【００２６】
ここで、１対の取付ボルト５８を個々に調整ばね５６の付勢に抗して適当なトルクで締め込むことにより、それら取付ボルト５８から対応の取付部４０に適当な圧力を負荷しつつ、基材３４に対する両取付部４０の取付位置を、可動体１８に接近する方向へ変位させる。それにより、中間固定部４２を支点として支持ばね部材３６の板ばね要素４８を撓ませて、板ばね要素４８に中間固定部４２を中心に平衡したばね力を発揮させる。このようにして、振動体１４の駆動面１２が、支持ばね部材３６の予調整されたばね力による適当な接触圧力下で、可動体１８の表面領域３２に当接され、以って超音波モータ１０の組み立てが完了する。
【００２７】
本発明の特徴的構成として、超音波モータ１０の制御部２２は、２対の励振素子１６のうち、各対を成す２個の励振素子１６が、振動体１４の駆動面１２に楕円運動を生起する互いに位相の異なる高周波変位動作を生じるとともに、全ての励振素子１６の高周波変位動作の位相が、互いに規則的にずれた状態になるように、それら２対の励振素子１６を制御するように構成される。具体的には、一方の対を成す２個の励振素子１６（１ａ）、１６（１ｂ）に対し、制御部２２は、下記の駆動電圧を印加する制御を遂行する。
励振素子１６（１ａ）の駆動電圧Ｖ＝αｓｉｎωｔ
励振素子１６（１ｂ）の駆動電圧Ｖ＝αｃｏｓωｔ
（ただし、αは最大駆動電圧、ωは駆動角速度）
これら駆動電圧により生じた各励振素子１６（１ａ）、１６（１ｂ）の差動的変位動作により、振動体１４に合成超音波振動が励起され、その結果として駆動面１２に楕円運動が生起される。なお、駆動面１２を詳細に分析すると、軸線１４ａの位置では正円運動が生じ、軸線１４ａから離れた位置では楕円運動が生じている。
【００２８】
さらに制御部２２は、他方の対を成す２個の励振素子１６（２ａ）、１６（２ｂ）に対し、下記の駆動電圧を印加する制御を遂行する。
励振素子１６（２ａ）の駆動電圧Ｖ＝αｓｉｎ（ωｔ−π）
励振素子１６（２ｂ）の駆動電圧Ｖ＝αｃｏｓ（ωｔ−π）
これにより、振動体１４の駆動面１２には、前述した１対目の励振素子１６（１ａ）、１６（１ｂ）による楕円運動から半波長分位相がずれた楕円運動が生起される。そして、２対全ての励振素子１６に対して同時にこれら駆動電圧を印加すれば、振動体１４の駆動面１２には、互いに半波長だけ位相がずれた楕円運動が相補的かつ相乗的に相互作用しつつ生起される。その結果、振動体１４の駆動面１２と可動体１８の表面領域３２との間の摩擦駆動力の微視的周期変動は、一対の励振素子１６のみを備えた超音波モータに比べて、変動間隔が短縮されると共に変動幅が削減されることになる。
【００２９】
したがって、上記構成を有する超音波モータ１０によれば、可動体１８の移動速度を微視的にも安定化することができ、それにより、可動体１８の位置決め精度等の制御応答性を著しく向上させることができる。また、可動体１８に、移動方向とは反対方向への制動作用が及ぼされている場合にも、可動体１８が制動作用により押し戻されることが回避され、出力及び移動速度を安定して維持することができる。
【００３０】
上記した超音波モータ１０の振動部２４及び制御部２２の構成は、対を成す励振素子１６の数が増える程、振動体１４の駆動面１２による摩擦駆動力の微視的周期変動の低減効果が向上する。すなわち、駆動部２４が、１個の振動体１４と、振動体１４の一対の肩面２６に取り付けられる複数（ｎ）対の励振素子１６とを備える構成において、制御部２２は、ｎ対の励振素子１６のうち、各対を成す２個の励振素子１６が、振動体１４の駆動面１２に楕円運動を生起する互いに位相の異なる高周波変位動作を生じるとともに、全ての励振素子１６の高周波変位動作の位相が、互いに規則的にずれた状態になるように、それらｎ対の励振素子１６を制御するように構成される。このとき制御部２２は、第ｍ番目（１≦ｍ≦ｎ）の対を成す２個の励振素子１６（ｍａ）、１６（ｍｂ）に対し、下記の駆動電圧を印加する制御を遂行する。
励振素子１６（ｍａ）の駆動電圧Ｖ＝αｓｉｎ｛ωｔ−２π（ｍ−１）／ｎ｝
励振素子１６（ｍｂ）の駆動電圧Ｖ＝αｃｏｓ｛ωｔ−２π（ｍ−１）／ｎ｝
【００３１】
これら駆動電圧をｎ対の励振素子１６（ｍａ）、１６（ｍｂ）に同時に印加することにより、振動体１４の駆動面１２には、１／ｎ波長ずつ位相がずれたｎ種類の楕円運動が相補的かつ相乗的に相互作用しつつ生起される。その結果、振動体１４の駆動面１２と可動体１８の表面領域３２との間の摩擦駆動力の微視的周期変動の削減効果が著しく向上する。なお、励振素子１６の対数を増すほど、駆動部２４の寸法が増加するので、要求される制御応答性と許容モータ寸法との両者を考慮して励振素子１６の対数を選定すれば良い。
【００３２】
図３及び図４は、上記した超音波モータ１０を駆動部に採用した本発明の一実施形態による位置決め装置６０を示す。位置決め装置６０は、超音波モータ１０の押圧支持構造２０の基材３４を含む第１の基台６２と、超音波モータ１０の可動体１８を含む第２の基台６４と、それら第１及び第２の基台６２、６４を相対移動可能に相互支持して互いに直線状に案内するリニアガイド６６と、第１及び第２の基台６２、６４の相対位置を検出する位置検出機構６８とを備えて構成される。
【００３３】
第１の基台６２は、矩形平板状の固定ベース部材であって、それ自体、押圧支持構造２０の基材３４を構成し、その一表面６２ａの所定位置に１対の取付基部４６が立設される。これら取付基部４６には、前述したように押圧支持構造２０の支持ばね部材３６（図１）及び予圧調整機構３８（図１）を介して、超音波モータ１０の振動部２４が取り付けられる。第２の基台６４は、矩形平板状の移動ステージ部材であって、それ自体、超音波モータ１０の可動体１８を構成する。第２の基台６４は、可動体１８の表面領域３２を構成する平坦な側面６４ａと、側面６４ａに略直交する平坦なステージ面６４ｂとを有する。なお、第１及び第２の基台６２、６４は、いずれも金属、樹脂等の高い剛性を有する材料から作製される。
【００３４】
リニアガイド６６は、例えばボールスライドから構成され、第１の基台６２の略中央でその表面６２ａと第２の基台６４の裏面６４ｃとの間に設置されて、基台６４を基台６２上で所与の負荷の下で直線往復移動可能に円滑に案内する。位置検出機構６８は、第１の基台６２の表面６２ａ上で、リニアガイド６６を挟んで超音波モータ１０の反対側に設置される例えば光学式の位置センサ７０と、位置センサ７０に非接触に対向して第２の基台６４に設置されるリニアスケール７２とを備える。位置センサ７０は、信号線７４を介して、超音波モータ１０の制御部２２に接続される。
【００３５】
上記構成を有する位置決め装置６０は、駆動部に超音波モータ１０を採用したことにより、ステージとなる第２の基台６４の移動速度を微視的にも安定化することができ、それにより、基台６４の位置決め精度等の制御応答性を著しく向上させることができる。また、基台６４に、移動方向とは反対方向への制動作用が及ぼされている場合にも、基台６４の出力及び移動速度を安定して維持することができる。
【００３６】
図５及び図６は、本発明の第２の実施形態による超音波モータ８０及びそれを搭載した位置決め装置８２を示す。超音波モータ８０及び位置決め装置８２は、振動部８４の構成以外は、図１〜図４に示す超音波モータ１０及び位置決め装置６０と実質的同一の構成を有するので、対応する構成要素には共通の参照符号を付してその説明を省略する。
【００３７】
超音波モータ８０の振動部８４は、２個の振動体８６と、それら振動体８６の各々に１対ずつ取り付けられる２対の励振素子８８とを備える。各振動体８６は、前述した超音波モータ１０における振動体１４を肉薄化した構成を有するものであり、したがって一端の平坦な駆動面９０と、他端の互いに略直交する１対の傾斜肩面９２と、それら肩面９２の間に突設される支承部９４とを備える。１対の励振素子（圧電素子）８８の各々は、振動体８６の各肩面９２に接合される。対を成す２個の圧電素子８８には、制御部２２を含む制御回路を介して正弦波電圧がそれぞれに所定（例えば９０°）の位相差で印加され、それによる両圧電素子８８の差動的な変位動作が振動体８６を励振して、摩擦駆動力を発揮するためのいわゆる楕円運動を駆動面９０に生起させる。
【００３８】
超音波モータ８０は、２個の振動体８６の駆動面９０に当接配置され、それら振動体８６の振動に応じて振動部８４に対し移動する共通の可動体１８を備える。２個の振動体８６は、可動体１８の移動方向に略平行な方向へ互いに離間して配置され、個々の振動体８６がそれぞれの押圧支持構造２０により、駆動面９０を可動体１８に押し付けた状態で安定して支持される。
【００３９】
上記超音波モータ８０を駆動部に採用した位置決め装置８２は、押圧支持構造２０の基材３４を含む第１の基台６２と、可動体１８を含む第２の基台６４と、それら第１及び第２の基台６２、６４を相対移動可能に相互支持して互いに直線状に案内するリニアガイド６６と、第１及び第２の基台６２、６４の相対位置を検出する位置検出機構６８とを備える。第１の基台６２は、それ自体、個々の振動体８６に関連する押圧支持構造２０の共通の基材３４を構成し、その一表面６２ａの所定位置に３個の取付基部４６が立設される。これら取付基部４６には、前述したように押圧支持構造２０の支持ばね部材３６（図１）及び予圧調整機構３８（図１）を介して、超音波モータ８０の振動部８４が取り付けられる。
【００４０】
超音波モータ８０の制御部２２は、前述した超音波モータ１０の制御部２２と同様に、個々の振動体８６に接合された各１対の励振素子８８が、各振動体８６の駆動面９０に楕円運動を生起する互いに位相の異なる高周波変位動作を生じるとともに、全ての励振素子８８の高周波変位動作の位相が、互いに規則的にずれた状態になるように、２対の励振素子８８を制御する。この構成において、制御部２２の制御下で各対の励振素子８８に印加される駆動電圧は、前述した超音波モータ１０におけるものと同様である。超音波モータ８０では、２対全ての励振素子８８に対して同時にこれら駆動電圧を印加することにより、２個の振動体８６の駆動面９０に、互いに半波長だけ位相がずれた楕円運動が独立して生起される。
【００４１】
上記した制御部２２による駆動電圧制御の結果、２個の振動体８６の駆動面９０と、両振動体８６に共通する可動体１８の表面領域３２（すなわち第２の基台６４の側面６４ａ）との間の摩擦駆動力の微視的周期変動は、２個の駆動面９０の楕円運動の協働により、変動間隔が短縮されると共に変動幅が削減されることになる。このように、上記構成を有する超音波モータ８０及びそれを搭載した位置決め装置８２においても、前述した超音波モータ１０及び位置決め装置６０と同等の作用効果が奏されることは理解されよう。
【００４２】
上記第２実施形態のように互いに独立した複数個の振動体を有する振動部は、それら振動体の相対配置を変更することにより、種々の変形形態による超音波モータ及び位置決め装置を構成することができる。例えば図７に示すように、それぞれに１対の励振素子８８（図５）を接合した２個の振動体８６を、可動体１８（第２の基台６４）の移動方向に交差又は略直交する方向へ互いに離間して配置した振動部８４を構成できる。この場合、それら振動体８６は、両者に共通する基材３４（第１の基台６２）に立設された１対の取付基部４６に、それぞれの押圧支持構造２０の支持ばね部材３６（図１）及び予圧調整機構３８（図１）を介して取り付けられる。このような構成を有する超音波モータ１００及びそれを搭載した位置決め装置１０２においても、前述した超音波モータ１０及び位置決め装置６０と同等の作用効果が奏されることは理解されよう。さらにこの構成では、上記第２実施形態による超音波モータ８０及び位置決め装置８２に比べて、小型化が促進される。
【００４３】
また、図８及び図９に示すように、それぞれに１対の励振素子８８を接合した２個の振動体８６を、可動体１８（第２の基台６４）を挟んで互いに異なる側に配置した振動部８４を構成できる。この場合、それら振動体８６は、両者に共通する基材３４（第１の基台６２）に立設された２対の取付基部４６に、それぞれの押圧支持構造２０の支持ばね部材３６（図１）及び予圧調整機構３８（図１）を介して取り付けられる。また、可動体１８（第２の基台６４）の両側に、各振動体８６の駆動面９０を当接する表面領域３２（側面６４ａ）が設けられる。このような構成を有する超音波モータ１１０及びそれを搭載した位置決め装置１１２においても、前述した超音波モータ１０及び位置決め装置６０と同等の作用効果が奏されることは理解されよう。
【００４４】
なお、図８及び図９に示す位置決め装置１１２は、位置検出機構を備えないものである。これに対し、図１０及び図１１に示すように、位置検出機構６８を設置した位置決め装置１１４を構成することもできる。この場合には、第２の基台６４の一方の側面６４ａに長手方向へ隣接して、位置検出機構６８のリニアスケール７２が設置される。
【００４５】
以上、本発明の好適な実施形態を説明したが、本発明は図示実施形態の構成に限定されず、特許請求の範囲の記載内でさらに他の様々な修正及び変更を施すことができる。例えば、本発明に係る超音波モータの振動部及び制御部の特徴的構成は、超音波モータの分野で公知の、様々な形状の振動体や様々に配置した励振素子を有する構成に適用でき、同等の作用効果を奏するものである。また、本発明に係る位置決め装置の特徴的構成は、多軸の位置決め装置にも適用でき、同等の作用効果を奏するものである。
【００４６】
【発明の効果】
以上の説明から明らかなように、本発明によれば、定在波型の超音波モータにおいて、振動体が生じる摩擦駆動力の微視的変動を低減することにより、制御応答性を向上させることができるとともに、可動体への制動作用に抗して出力及び移動速度を維持できるようになる。
さらに本発明によれば、駆動部に超音波モータを採用した位置決め装置において、ステージの位置決め精度、出力及び移動速度を向上させることができるようになる。
【図面の簡単な説明】
【図１】本発明の第１実施形態による超音波モータの正面図である。
【図２】図１の超音波モータの主要部を線ＩＩ−ＩＩに沿って示す一部断面側面図である。
【図３】図１の超音波モータを搭載した本発明の第１実施形態による位置決め装置の平面図である。
【図４】図３の位置決め装置の側面図である。
【図５】本発明の第２実施形態による超音波モータ及びそれを搭載した位置決め装置の平面図である。
【図６】図５の超音波モータ及び位置決め装置の側面図である。
【図７】変形例による超音波モータ及びそれを搭載した位置決め装置の平面図である。
【図８】他の変形例による超音波モータ及びそれを搭載した位置決め装置の平面図である。
【図９】図８の超音波モータ及び位置決め装置の側面図である。
【図１０】さらに他の変形例による超音波モータ及びそれを搭載した位置決め装置の平面図である。
【図１１】図１０の超音波モータ及び位置決め装置の側面図である。
【符号の説明】
１０…超音波モータ
１２…駆動面
１４…振動体
１６…励振素子
１８…可動体
２０…押圧支持構造
２２…制御部
２４…振動部
３０…摩擦材料
３２…表面領域
３４…基材
３６…支持ばね部材
３８…予圧調整機構
４０…取付部
４２…中間固定部
４６…取付基部
５６…調整ばね
５８…取付ボルト
６０…位置決め装置
６２…第１の基台
６４…第２の基台
６６…リニアガイド
６８…位置検出機構
７０…位置センサ
７２…リニアスケール[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic motor. Furthermore, the present invention relates to a positioning device provided with an ultrasonic motor.
[0002]
[Prior art]
In recent years, ultrasonic motors that generate frictional driving force using ultrasonic vibrations of a vibrating body have been widely used as small actuators that linearly or rotationally drive various driven elements, particularly in the field of small precision equipment. In general, an ultrasonic motor is disposed in contact with a vibrating body having a driving surface, an excitation element that excites the vibrating body, and the driving surface of the vibrating body, and moves in one direction relative to the vibrating body according to the vibration of the vibrating body. And a movable body (driven body). The vibrating body is usually made from a hard elastic body such as metal or ceramics, and the excitation element is usually made from a piezoelectric element such as piezoelectric ceramics. Further, the ultrasonic motor is provided with a preload structure for pressing the driving surface of the vibrating body against the surface of the movable body under a predetermined pressure in order to efficiently generate a frictional driving force between the vibrating body and the movable body.
[0003]
This type of ultrasonic motor includes a short rod-like vibrating body having a desired end surface serving as a driving surface, and a plurality of piezoelectric elements that are appropriately arranged and bonded to a surface other than the driving surface of the vibrating body. 2. Description of the Related Art A standing wave type ultrasonic motor having a configuration in which an elliptical motion for exerting a frictional driving force is generated on a driving surface by performing a displacement operation with a predetermined phase difference is known. Conventionally, as this type of ultrasonic motor, a portal-shaped vibrator having a pair of columnar legs each having a driving surface at one end and a beam-shaped body connecting the other ends of the columnar legs is used. A pair of inclined shoulder surfaces formed in a connection region between the leg portions and the body portion of the vibrating body and orthogonal to each other so that the two piezoelectric elements form an angle of 45 ° with respect to the adjacent driving surfaces, respectively. A columnar vibrator having a joined surface (so-called π-type: see, for example, Patent Document 1) and a pair of inclined shoulder surfaces having a drive surface at one end and substantially orthogonal to each other at the other end. In addition, a structure in which two piezoelectric elements are joined to each other so as to form an angle of 45 ° with respect to the drive surface (so-called Y shape: see, for example, Patent Document 2) is proposed.
[Patent Document 1]
JP-A-6-284755
[Patent Document 2]
Japanese Utility Model Publication No. 2-136485
[0004]
Patent Document 1 discloses a configuration in which the above-described π-shaped ultrasonic motor is incorporated in a drive unit of a linear motion guide (positioning) device used for an XY stage. In this guide device, a vibrating body and a piezoelectric element of an ultrasonic motor are fixedly installed on one of a pair of bases that can be linearly reciprocated via a linear guide, and the other base is A movable body having a surface in contact with the drive surface of the vibrating body is configured.
[0005]
[Problems to be solved by the invention]
In the standing wave type ultrasonic motor having the short rod-like vibrator described above, the periodic elliptical motion (including circular motion and linear motion) generated on the drive surface of the vibrator is locally affected by the frictional force. By being transmitted to the movable body, the movable body relatively moves in a direction corresponding to the direction of the elliptical motion. Therefore, microscopically, there is a period in which frictional driving force is not substantially generated between the driving surface of the vibrating body and the surface of the movable body. Further, the friction driving force depends on the pre-pressure that presses the driving surface of the vibrating body against the surface of the movable body, and is not substantially affected by the inertia of the load. As a result, the moving speed of the movable body is microscopically unstable, and this is a factor that brings a limit to control responsiveness such as positioning accuracy of the movable body. Furthermore, when the movable body is subjected to a braking action in the direction opposite to the moving direction, the movable body tends to be pushed back by the braking action during a periodic minute time when the frictional driving force decreases. As a result, there is a concern that the output and moving speed may be reduced.
[0006]
In addition, in conventional guide / positioning devices such as single-axis and multi-axis stages equipped with the standing wave type ultrasonic motor, the positioning of the stage is accompanied by the above-mentioned problems inherent in the conventional ultrasonic motor. There have been problems such as a limit in accuracy and a decrease in the output and moving speed of the stage.
[0007]
It is an object of the present invention to improve control responsiveness and reduce braking to a movable body by reducing microscopic fluctuations of frictional driving force generated by a vibrating body in a standing wave type ultrasonic motor. An object of the present invention is to provide an ultrasonic motor capable of maintaining an output and a moving speed against an action.
Another object of the present invention is to provide a positioning device that can improve the positioning accuracy, output, and moving speed of a stage in a positioning device that employs an ultrasonic motor as a drive unit.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is directed to an ultrasonic motor including a vibration unit including a vibration body having a driving surface and a control unit that controls ultrasonic vibration of the vibration body. The unit includes at least one vibrating body and a plurality of pairs of excitation elements attached to the at least one vibrating body to excite the vibrating body, and the control unit includes each pair of the plurality of excitation elements. The two exciter elements that form the same cause high-frequency displacement operations with different phases that cause elliptical motion on the drive surface of the vibrating body, and the phases of the high-frequency displacement operations of all the exciter elements are regularly shifted from each other An ultrasonic motor characterized by controlling a plurality of pairs of excitation elements is provided.
[0009]
The invention according to claim 2 is the ultrasonic motor according to claim 1, wherein the vibration section includes one vibration body and a plurality of pairs of excitation elements attached to the one vibration body. I will provide a.
[0010]
According to a third aspect of the present invention, in the ultrasonic motor according to the first aspect, the vibration unit includes a plurality of vibration bodies and a plurality of pairs of excitation elements attached to each of the vibration bodies. A sonic motor is provided.
[0011]
A fourth aspect of the present invention provides a positioning apparatus including the ultrasonic motor according to any one of the first to third aspects.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Corresponding components are denoted by common reference symbols throughout the drawings.
1 and 2 schematically show an ultrasonic motor 10 according to an embodiment of the present invention. The ultrasonic motor 10 is disposed in contact with a vibrating body 14 having a driving surface 12, an excitation element 16 for exciting the vibrating body 14, and the driving surface 12 of the vibrating body 14, and according to the vibration of the vibrating body 14. 14, a movable body 18 that moves relative to 14, a pressing support structure 20 that supports the vibrating body 14 in a state where the driving surface 12 is pressed against the movable body 18, and a control unit 22 that controls ultrasonic vibration of the vibrating body 14. Configured. The vibrating body 14 and the excitation element 16 constitute a vibrating portion 24 of the ultrasonic motor 10.
[0013]
The vibration unit 24 includes one vibration body 14 and two pairs of excitation elements 16 attached to the vibration body 14. The vibrating body 14 has a short rod shape (a prismatic shape or a thin plate shape), and includes a flat driving surface 12 on a desired one end surface, and directions orthogonal to each other on the other end side away from the driving surface 12. A pair of inclined shoulder surfaces 26 extending flatly and a support portion 28 projecting outward between the shoulder surfaces 26 are provided. The driving surface 12 of the vibrating body 14 is preferably formed of a friction material 30 made of carbon fiber reinforced plastic or the like fixed to one end surface of the vibrating body 14 as shown in the drawing. The friction material 30 has an effect of improving the generation efficiency of the frictional driving force by the ultrasonic vibration of the vibrating body 14 and improving the life of the surfaces of the driving surface 12 and the movable body 18.
[0014]
The vibrating body 14 has a line-symmetric shape with respect to axes 14a and 14b passing through the center of the drive surface 12 at one end and the center of the support portion 28 at the other end in both the front view of FIG. 1 and the side view of FIG. . Both shoulder surfaces 26 form an angle of approximately 45 ° with respect to the drive surface 12 and are arranged symmetrically with respect to the axis 14a. The support portion 28 has a thickness (dimension in the direction perpendicular to the plane of FIG. 1) that is thinner than the main body portion 14c (a portion through which ultrasonic waves propagate) of the vibrating body 14, and is extended from the main body portion 14c. A female screw 28a extending in the direction of the axis 14a is recessed. The vibrating body 14 having such a configuration is integrally formed from a hard elastic body such as a metal material such as aluminum, titanium, copper, or an iron-based metal, or ceramics such as silicon oxide, aluminum oxide, zirconium oxide, or a composite thereof. Are produced.
[0015]
Each of the two pairs of excitation elements 16 includes the piezoelectric element 16 bonded to each shoulder surface 26 of the vibrating body 14. Each piezoelectric element 16 has a prismatic (thin plate) shape formed by laminating thin plate piezoelectric materials such as piezoelectric ceramics, and has one end surface in the laminating direction in close contact with the shoulder surface 26 of the vibrating body 14, for example, an adhesive. Thus, it is firmly bonded to the shoulder surface 26. Two piezoelectric elements 16 are arranged on each shoulder surface 26 of the vibrating body 14 so as to be spaced apart from each other and to be superimposed and aligned in position in the thickness direction of the vibrating body. The element 16 is arranged at a symmetrical position with respect to the axis 14a. Each pair of piezoelectric elements 16 in a symmetrical position (that is, a pair in terms of control) is arranged such that the center lines 16a extending in the respective stacking directions form an angle of approximately 45 ° with respect to the drive surface 12. The A sinusoidal voltage is applied to each of the two piezoelectric elements 16 forming a pair with a predetermined phase difference (for example, 90 °) via a control circuit including the control unit 22, and thereby the differential of the two piezoelectric elements 16. The displacement operation excites the vibrating body 14 to cause a so-called elliptical motion on the drive surface 12 to exert a frictional driving force.
[0016]
In addition, it is advantageous that each piezoelectric element 16 is composed of a laminate of thin plate piezoelectric materials made of lead zirconate titanate (PZT) in that a large driving force can be obtained at a low voltage. The adhesive for joining each piezoelectric element 16 to the vibrating body 14 is not particularly limited as long as sufficient adhesive force can be obtained. For example, a thermosetting epoxy adhesive containing a glass filler may be used. it can.
[0017]
The movable body 18 is made of a hard material such as metal or resin, and is supported on a machine base (or external structure) (not shown) of the ultrasonic motor 10 so as to be movable in a predetermined direction via a guide support structure (not shown). . The movable body 18 is arranged in contact with the driving surface 12 of the vibrating body 14 under a predetermined pressure in the predetermined surface area 32, and contacts according to the direction of the elliptical motion generated on the driving surface 12 of the vibrating body 14. It moves in one direction (arrow shown in the figure) by the frictional force between the surfaces. The moving direction and moving speed of the movable body 18 can be controlled by controlling the phase and frequency of the sinusoidal voltage applied to the pair of excitation elements (piezoelectric elements) 16 described above.
[0018]
The movable body 18 can perform either an output operation of linear movement or rotation according to the configuration of the guide support structure. Further, the moving relationship between the vibrating body 14 and the movable body 18 is relative, and when the movable body 18 is fixed on the structure body, the vibrating body 14 and the pressing support structure 20 are moved to the movable body 18. Move against. Further, the friction material 30 forming the drive surface 12 of the vibrating body 14 can be placed on the surface region 32 of the movable body 18 in addition to or instead of the friction material 30.
[0019]
The configuration of the drive unit 24 and the movable body 18 including the vibrating body 14 and the excitation element 16 is similar to the configuration employed in a so-called Y-shaped ultrasonic motor, and forms a pair of excitation elements. By inverting the phase of 16, the driving direction of the movable body 18 can be switched. The configuration of the drive unit and the control unit according to the present invention is not limited to such a Y-type motor structure, but can be applied to a π-type and other various motor structures.
[0020]
The pressing support structure 20 is disposed between the base material 34 and the base material 34 and the vibrating body 14, and exerts a spring force that presses the drive surface 12 against the movable body 18 while supporting the vibrating body 14 on the base material 34. And a preload adjusting mechanism 38 that adjusts the spring force of the support spring member 36. The support spring member 36 is a plate-like assembly having attachment portions 40 at both ends and an intermediate fixing portion 42 located between the attachment portions 40. The support spring member 36 is fixedly connected to the vibrating body 14 by an intermediate fixing portion 42, and is attached to the base material 34 by a pressure adjusting mechanism 38 at both attachment portions 40. In this state, the support spring member 36 exerts a spring force that presses the drive surface 12 of the vibrating body 14 against the surface region 32 of the movable body 18.
[0021]
The base material 34 includes a rectangular thin plate-shaped main portion 44 and a pair of prism-shaped mounting base portions 46 that are spaced apart from each other along one outer edge 44b of the rectangular outline on a substantially flat surface 44a of the main portion 44. With. The main portion 44 and the mounting base portion 46 are made of a hard material such as metal or resin, and both are formed integrally with each other, or are fixedly connected to each other by bolts or the like. A female screw 46 a for attaching the support spring member 36 is recessed in each attachment base portion 46 in a direction substantially parallel to the surface 44 a of the main portion 44. The main portion 44 of the base material 34 can be fixedly connected to a machine base (or external structure) (not shown) of the ultrasonic motor 10 that movably supports the movable body 18 described above.
[0022]
The support spring member 36 is configured by combining a leaf spring element 48 including the intermediate fixing portion 42 and a pair of rigid support elements 50 each including the attachment portion 40. The plate spring element 48 is made of a spring material such as a flat metal plate or a resin plate, and has a bolt insertion hole 48a in the middle fixed portion 42 at the center in the longitudinal direction and a bolt insertion hole 48b at both ends in the longitudinal direction. It penetrates in the direction (direction parallel to the paper surface). The pair of rigid support elements 50 are made of a hard material such as a metal plate or a resin plate formed into the same substantially S-shaped crank shape as viewed from the front in FIG. A hole 50a and a female screw 50b at the other end are formed penetrating in the plate thickness direction (direction parallel to the paper surface).
[0023]
The support spring member 36 is disposed at both ends of the leaf spring element 48 with the other ends of both rigid support elements 50 with the mounting portions 40 facing outward (relative to each other), and inserted into the respective bolt insertion holes 48b. The bolt 52 is screwed onto the female screw 50b and the elements 48 and 50 are connected to each other, thereby forming a symmetrical reference assembly with the intermediate fixing portion 42 as the center. The support spring member 36 is screwed into a female screw 28 a formed in the support portion 28 of the vibrating body 14 by screwing a bolt 54 inserted into the bolt insertion hole 48 a of the intermediate fixing portion 42 of the leaf spring element 48. Fixed to. As will be described later, when the ultrasonic motor 10 is properly assembled, the leaf spring element 48 is extended in a direction perpendicular to the axis 14a of the vibrating body 14 in an unloaded state.
[0024]
The preload adjusting mechanism 38 includes a pair of adjusting springs 56 interposed between the mounting portions 40 of the support spring member 36 and the mounting base portions 46 of the base member 34, and both of the support spring members 36 via the adjustment springs 56. And a pair of mounting bolts 58 for mounting the mounting portion 40 to the corresponding mounting base 46. The pair of adjustment springs 56 is made of a spring material such as a metal plate or a resin plate that is bent into the same substantially U-shaped outer shape when viewed from the front in FIG. Bolt insertion holes 56a are formed penetrating in the thickness direction (direction parallel to the paper surface). The adjustment springs 56 are respectively placed on both attachment bases 46 of the base material 34 with the central portion of the U-shape facing inward (mutually opposed sides). In this state, the mounting bolts 58 are continuously inserted into the bolt insertion holes 50a of the mounting portions 40 of the support spring member 36 and the bolt insertion holes 56a of the corresponding adjustment springs 56, so that the corresponding mounting bases. The support spring member 36 is attached to the base material 34 by being screwed onto the female screw 46 a 46. The preload adjusting mechanism 38 adjusts the preload exerted by the leaf spring element 48 of the support spring member 36 by adjusting the tightening torque of each mounting bolt 58.
[0025]
The component group of the ultrasonic motor 10 is assembled as follows.
The base material 34 is installed in the vicinity of the movable body 18 so that the outer edge 44b of the main portion 44 is positioned in close proximity to the surface region 32 of the movable body 18 in a non-contact manner. In addition, the vibrating body 14 in which the two pairs of piezoelectric elements 16 are joined to the both shoulder surfaces 26 has the driving surface 12 in contact with the surface region 32 at a substantially intermediate position between the two attachment bases 46 of the base material 34. Mounted on top. The support spring member 36 is in the form of the reference assembly described above, and the intermediate fixing portion 42 is fixed to the support portion 28 of the vibrating body 14 by the bolt 54, and the mounting portions 40 at both ends are fixed to the preload adjusting mechanism 38 as described above. And are attached to both attachment bases 46 of the base material 34.
[0026]
Here, by individually tightening the pair of mounting bolts 58 with an appropriate torque against the bias of the adjustment spring 56, while applying an appropriate pressure from the mounting bolts 58 to the corresponding mounting portions 40, The attachment positions of both attachment portions 40 with respect to the base material 34 are displaced in a direction approaching the movable body 18. Accordingly, the leaf spring element 48 of the support spring member 36 is bent with the intermediate fixing portion 42 as a fulcrum, and the leaf spring element 48 exerts a spring force balanced around the intermediate fixing portion 42. In this way, the drive surface 12 of the vibrating body 14 is brought into contact with the surface region 32 of the movable body 18 under an appropriate contact pressure due to the pre-adjusted spring force of the support spring member 36, and thus the ultrasonic motor. 10 assembly is completed.
[0027]
As a characteristic configuration of the present invention, the control unit 22 of the ultrasonic motor 10 includes two excitation elements 16 out of the two pairs of excitation elements 16, and the two excitation elements 16 make an elliptical motion on the drive surface 12 of the vibrating body 14. The two pairs of excitation elements 16 are controlled so that the generated high-frequency displacement operations having different phases occur and the phases of the high-frequency displacement operations of all the excitation elements 16 are regularly shifted from each other. Composed. Specifically, the control unit 22 performs control for applying the following drive voltage to the two excitation elements 16 (1a) and 16 (1b) forming one pair.
Driving voltage V of the excitation element 16 (1a) V = αsinωt
Drive voltage V of the excitation element 16 (1b) = α cos ωt
(Where α is the maximum drive voltage and ω is the drive angular velocity)
Synthetic ultrasonic vibration is excited in the vibrating body 14 by the differential displacement operation of each of the excitation elements 16 (1a) and 16 (1b) generated by these driving voltages, and as a result, elliptical motion is caused on the driving surface 12. The When the driving surface 12 is analyzed in detail, a circular motion occurs at the position of the axis 14a, and an elliptical motion occurs at a position away from the axis 14a.
[0028]
Further, the control unit 22 performs control to apply the following drive voltage to the two excitation elements 16 (2a) and 16 (2b) forming the other pair.
Drive voltage V of the excitation element 16 (2a) = αsin (ωt−π)
Driving voltage V of the excitation element 16 (2b) = α cos (ωt−π)
As a result, an elliptical motion whose phase is shifted by a half wavelength from the elliptical motion generated by the first pair of excitation elements 16 (1a) and 16 (1b) is generated on the drive surface 12 of the vibrating body 14. If these drive voltages are applied simultaneously to all of the two pairs of excitation elements 16, elliptical motions that are out of phase with each other by half a wavelength interact with each other on the drive surface 12 of the vibrating body 14 in a complementary and synergistic manner. It is born while doing. As a result, the microscopic periodic fluctuation of the frictional driving force between the driving surface 12 of the vibrating body 14 and the surface region 32 of the movable body 18 is more variable than that of an ultrasonic motor having only a pair of excitation elements 16. The interval is shortened and the fluctuation range is reduced.
[0029]
Therefore, according to the ultrasonic motor 10 having the above-described configuration, the moving speed of the movable body 18 can be stabilized microscopically, thereby significantly improving control responsiveness such as positioning accuracy of the movable body 18. Can be made. Further, even when the movable body 18 is subjected to a braking action in a direction opposite to the moving direction, the movable body 18 is prevented from being pushed back by the braking action, and the output and the moving speed are stably maintained. be able to.
[0030]
The configuration of the vibration unit 24 and the control unit 22 of the ultrasonic motor 10 described above has an effect of reducing the microscopic periodic fluctuation of the frictional driving force by the driving surface 12 of the vibrating body 14 as the number of excitation elements 16 forming a pair increases. Will improve. That is, in the configuration in which the drive unit 24 includes one vibrating body 14 and a plurality (n) pairs of excitation elements 16 attached to the pair of shoulder surfaces 26 of the vibrating body 14, the control unit 22 includes n pairs of Among the excitation elements 16, two pairs of excitation elements 16 generate high-frequency displacement operations with different phases that cause elliptical motion on the drive surface 12 of the vibrating body 14, and high-frequency displacements of all the excitation elements 16. The n pairs of excitation elements 16 are controlled so that the phases of operation are regularly shifted from each other. At this time, the control unit 22 performs control to apply the following drive voltage to the two excitation elements 16 (ma) and 16 (mb) forming the m-th (1 ≦ m ≦ n) pair.
Driving voltage of excitation element 16 (ma) V = α sin {ωt−2π (m−1) / n}
Driving voltage V of the excitation element 16 (mb) V = α cos {ωt−2π (m−1) / n}
[0031]
By simultaneously applying these drive voltages to n pairs of excitation elements 16 (ma) and 16 (mb), n types of elliptical motions whose phases are shifted by 1 / n wavelength are generated on the drive surface 12 of the vibrating body 14. It occurs while interacting in a complementary and synergistic manner. As a result, the effect of reducing the microscopic period fluctuation of the frictional driving force between the driving surface 12 of the vibrating body 14 and the surface region 32 of the movable body 18 is significantly improved. As the logarithm of the excitation element 16 is increased, the size of the drive unit 24 is increased. Therefore, the logarithm of the excitation element 16 may be selected in consideration of both required control response and allowable motor dimensions.
[0032]
3 and 4 show a positioning device 60 according to an embodiment of the present invention that employs the above-described ultrasonic motor 10 as a drive unit. The positioning device 60 includes a first base 62 including the base material 34 of the pressure support structure 20 of the ultrasonic motor 10, a second base 64 including the movable body 18 of the ultrasonic motor 10, the first and A linear guide 66 for mutually supporting the second bases 62 and 64 so as to be relatively movable and linearly guiding each other; and a position detection mechanism 68 for detecting the relative positions of the first and second bases 62 and 64; It is configured with.
[0033]
The first base 62 is a rectangular flat plate-like fixed base member, which itself constitutes the base material 34 of the pressing support structure 20, and a pair of mounting bases 46 stands at a predetermined position on one surface 62 a thereof. Established. As described above, the vibration part 24 of the ultrasonic motor 10 is attached to these attachment bases 46 via the support spring member 36 (FIG. 1) and the preload adjusting mechanism 38 (FIG. 1) of the pressing support structure 20. The second base 64 is a rectangular flat plate-shaped moving stage member, and itself constitutes the movable body 18 of the ultrasonic motor 10. The second base 64 has a flat side surface 64a constituting the surface region 32 of the movable body 18, and a flat stage surface 64b substantially orthogonal to the side surface 64a. Note that the first and second bases 62 and 64 are both made of a material having high rigidity such as metal or resin.
[0034]
The linear guide 66 is composed of, for example, a ball slide, and is installed between the front surface 62 a and the back surface 64 c of the second base 64 at the approximate center of the first base 62. The guide is smoothly guided so that it can move back and forth in a straight line under a given load. The position detection mechanism 68 is, for example, an optical position sensor 70 installed on the opposite side of the ultrasonic motor 10 across the linear guide 66 on the surface 62 a of the first base 62, and does not contact the position sensor 70. And a linear scale 72 installed on the second base 64. The position sensor 70 is connected to the control unit 22 of the ultrasonic motor 10 via the signal line 74.
[0035]
The positioning device 60 having the above configuration can microscopically stabilize the moving speed of the second base 64 serving as a stage by adopting the ultrasonic motor 10 in the drive unit, Control responsiveness such as positioning accuracy of the base 64 can be remarkably improved. Further, even when the base 64 is subjected to a braking action in a direction opposite to the moving direction, the output and moving speed of the base 64 can be stably maintained.
[0036]
5 and 6 show an ultrasonic motor 80 and a positioning device 82 on which the ultrasonic motor 80 is mounted according to the second embodiment of the present invention. Since the ultrasonic motor 80 and the positioning device 82 have substantially the same configuration as the ultrasonic motor 10 and the positioning device 60 shown in FIGS. The description is abbreviate | omitted and attached | subjected.
[0037]
The vibration unit 84 of the ultrasonic motor 80 includes two vibrating bodies 86 and two pairs of excitation elements 88 attached to each of the vibrating bodies 86. Each vibrating body 86 has a configuration in which the vibrating body 14 in the ultrasonic motor 10 described above is thinned. Therefore, the flat driving surface 90 at one end and a pair of inclined shoulder surfaces at the other end substantially orthogonal to each other. 92 and a support portion 94 projecting between the shoulder surfaces 92. Each of the pair of excitation elements (piezoelectric elements) 88 is joined to each shoulder surface 92 of the vibrating body 86. A sinusoidal voltage is applied to each of the two piezoelectric elements 88 forming a pair with a predetermined phase difference (for example, 90 °) via a control circuit including the control unit 22. A typical displacement operation excites the vibrating body 86 to cause a so-called elliptical motion on the drive surface 90 to exert a frictional driving force.
[0038]
The ultrasonic motor 80 includes a common movable body 18 that is disposed in contact with the drive surfaces 90 of the two vibrating bodies 86 and moves relative to the vibrating portion 84 in accordance with the vibrations of the vibrating bodies 86. The two vibrating bodies 86 are spaced apart from each other in a direction substantially parallel to the moving direction of the movable body 18, and the individual vibrating bodies 86 press the drive surface 90 against the movable body 18 by the respective pressing support structures 20. It is supported stably in the state.
[0039]
The positioning device 82 adopting the ultrasonic motor 80 as a drive unit includes a first base 62 including the base material 34 of the pressing support structure 20, a second base 64 including the movable body 18, and the first of them. And a linear guide 66 for supporting the second bases 62 and 64 so as to be movable relative to each other and guiding them linearly, and a position detection mechanism 68 for detecting the relative positions of the first and second bases 62 and 64. With. The first base 62 itself constitutes the common base material 34 of the pressing support structure 20 related to the individual vibrating bodies 86, and three mounting bases 46 are erected at a predetermined position on one surface 62a. Is done. As described above, the vibration portion 84 of the ultrasonic motor 80 is attached to these attachment base portions 46 via the support spring member 36 (FIG. 1) and the preload adjusting mechanism 38 (FIG. 1) of the pressing support structure 20.
[0040]
As with the control unit 22 of the ultrasonic motor 10 described above, the control unit 22 of the ultrasonic motor 80 includes a pair of excitation elements 88 joined to the individual vibration bodies 86. The two pairs of excitation elements 88 are controlled so that the phases of the high-frequency displacement operations of all the excitation elements 88 are regularly deviated from each other. To do. In this configuration, the drive voltage applied to each pair of excitation elements 88 under the control of the control unit 22 is the same as that in the ultrasonic motor 10 described above. In the ultrasonic motor 80, by applying these drive voltages to all two pairs of excitation elements 88 simultaneously, elliptical motions whose phases are shifted from each other by a half wavelength are independent on the drive surfaces 90 of the two vibrators 86. And is born.
[0041]
As a result of the drive voltage control by the control unit 22 described above, the drive surface 90 of the two vibrating bodies 86 and the surface region 32 of the movable body 18 common to both the vibrating bodies 86 (that is, the side surface 64a of the second base 64). The microscopic periodic fluctuation of the frictional driving force between the two is reduced by the cooperation of the elliptical motion of the two driving surfaces 90 and the fluctuation width is reduced. Thus, it will be understood that the ultrasonic motor 80 having the above-described configuration and the positioning device 82 equipped with the ultrasonic motor 80 have the same operational effects as the ultrasonic motor 10 and the positioning device 60 described above.
[0042]
The vibration part having a plurality of independent vibrators as in the second embodiment can constitute an ultrasonic motor and a positioning device according to various modifications by changing the relative arrangement of the vibrators. it can. For example, as shown in FIG. 7, two vibrating bodies 86 each joined with a pair of excitation elements 88 (FIG. 5) intersect or are approximately orthogonal to the moving direction of the movable body 18 (second base 64). It is possible to configure the vibrating portions 84 that are arranged to be spaced apart from each other in the direction to be moved. In this case, the vibrating bodies 86 are attached to the pair of attachment bases 46 erected on the base material 34 (first base 62) common to both the support spring members 36 (see FIG. 1) and a preload adjusting mechanism 38 (FIG. 1). It will be understood that the ultrasonic motor 100 having such a configuration and the positioning device 102 on which the ultrasonic motor 100 has the same effects as the ultrasonic motor 10 and the positioning device 60 described above can be obtained. Further, in this configuration, the miniaturization is promoted as compared with the ultrasonic motor 80 and the positioning device 82 according to the second embodiment.
[0043]
Further, as shown in FIGS. 8 and 9, two vibrating bodies 86 each having a pair of excitation elements 88 joined are arranged on different sides with the movable body 18 (second base 64) interposed therebetween. Thus, the vibrating portion 84 can be configured. In this case, the vibrating bodies 86 are provided on the two pairs of mounting bases 46 erected on the base material 34 (the first base 62) common to both the support spring members 36 (see FIG. 1) and a preload adjusting mechanism 38 (FIG. 1). Further, on both sides of the movable body 18 (second base 64), a surface region 32 (side surface 64a) that contacts the driving surface 90 of each vibrating body 86 is provided. It will be understood that the ultrasonic motor 110 having such a configuration and the positioning device 112 on which the ultrasonic motor 110 has the same effects as the ultrasonic motor 10 and the positioning device 60 described above can be obtained.
[0044]
Note that the positioning device 112 shown in FIGS. 8 and 9 does not include a position detection mechanism. On the other hand, as shown in FIGS. 10 and 11, a positioning device 114 provided with a position detection mechanism 68 may be configured. In this case, the linear scale 72 of the position detection mechanism 68 is installed adjacent to one side surface 64a of the second base 64 in the longitudinal direction.
[0045]
The preferred embodiment of the present invention has been described above, but the present invention is not limited to the configuration of the illustrated embodiment, and various other modifications and changes can be made within the scope of the claims. For example, the characteristic configuration of the vibration unit and the control unit of the ultrasonic motor according to the present invention can be applied to a configuration having various shapes of vibrators and variously arranged excitation elements, which are known in the field of ultrasonic motors. Equivalent effects are obtained. In addition, the characteristic configuration of the positioning device according to the present invention can be applied to a multi-axis positioning device, and has the same effect.
[0046]
【The invention's effect】
As is apparent from the above description, according to the present invention, in the standing wave type ultrasonic motor, the control responsiveness is improved by reducing the microscopic fluctuation of the frictional driving force generated by the vibrating body. In addition, the output and the moving speed can be maintained against the braking action on the movable body.
Furthermore, according to the present invention, the positioning accuracy, output, and movement speed of the stage can be improved in the positioning device that employs an ultrasonic motor for the drive unit.
[Brief description of the drawings]
FIG. 1 is a front view of an ultrasonic motor according to a first embodiment of the present invention.
FIG. 2 is a partial cross-sectional side view showing the main part of the ultrasonic motor of FIG. 1 along line II-II.
FIG. 3 is a plan view of a positioning device according to a first embodiment of the present invention on which the ultrasonic motor of FIG. 1 is mounted.
4 is a side view of the positioning device of FIG. 3;
FIG. 5 is a plan view of an ultrasonic motor and a positioning device on which the ultrasonic motor according to the second embodiment of the present invention is mounted.
6 is a side view of the ultrasonic motor and positioning device of FIG. 5. FIG.
FIG. 7 is a plan view of an ultrasonic motor according to a modification and a positioning device on which the ultrasonic motor is mounted.
FIG. 8 is a plan view of an ultrasonic motor and a positioning device on which the ultrasonic motor according to another modification is mounted.
9 is a side view of the ultrasonic motor and positioning device of FIG. 8. FIG.
FIG. 10 is a plan view of an ultrasonic motor and a positioning device on which the ultrasonic motor according to still another modification is mounted.
11 is a side view of the ultrasonic motor and positioning apparatus of FIG.
[Explanation of symbols]
10 ... Ultrasonic motor
12 ... Drive surface
14 ... Vibrating body
16 ... Excitation element
18 ... Movable body
20 ... Pressing support structure
22 ... Control unit
24. Vibrating part
30 ... friction material
32 ... surface area
34 ... Base material
36 ... Supporting spring member
38 ... Preload adjustment mechanism
40 ... Mounting part
42. Intermediate fixing part
46: Mounting base
56 ... Adjustment spring
58 ... Mounting bolt
60 ... Positioning device
62. First base
64 ... Second base
66 ... Linear guide
68. Position detection mechanism
70: Position sensor
72 ... Linear scale

Claims

In an ultrasonic motor including a vibration unit including a vibration body having a drive surface and a control unit that controls ultrasonic vibration of the vibration body,
The vibrating section includes at least one vibrating body, and a plurality of pairs of excitation elements attached to the at least one vibrating body to excite the vibrating body,
The control unit, among the plurality of pairs of excitation elements, two excitation elements forming each pair cause high-frequency displacement operations with different phases that cause elliptical motion on the drive surface of the vibrator, Controlling the pairs of excitation elements such that the phases of the high-frequency displacement operations of all the excitation elements are regularly shifted from each other;
Ultrasonic motor characterized by

2. The ultrasonic motor according to claim 1, wherein the vibration unit includes one of the vibration bodies and the plurality of pairs of excitation elements attached to the one vibration body.

The ultrasonic motor according to claim 1, wherein the vibration unit includes a plurality of the vibration bodies and the plurality of pairs of excitation elements attached to each of the vibration bodies.

The positioning apparatus provided with the ultrasonic motor of any one of Claims 1-3.