JP4179934B2

JP4179934B2 - Ultrasonic motor and positioning apparatus equipped with ultrasonic motor

Info

Publication number: JP4179934B2
Application number: JP2003185060A
Authority: JP
Inventors: 悦夫山本; 健一郎石井
Original assignee: Hephaist Seiko Co Ltd
Current assignee: Hephaist Co Ltd
Priority date: 2003-06-27
Filing date: 2003-06-27
Publication date: 2008-11-12
Anticipated expiration: 2023-06-27
Also published as: JP2005020950A

Description

【０００１】
【発明の属する技術分野】
本発明は超音波モータに関し、特に、励振素子によって励振される振動体を、その駆動面を可動体に押し付けた状態で支持する押圧支持構造を有する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】
従来の超音波モータでは、前述した予圧構造として一般に、振動体を可動体に接近する方向へ付勢するばねが採用されている。例えば、上記特許文献１に記載される超音波モータでは、門形振動体を収容するケースの上板に、先端を振動体に向けた付勢ピンが上下移動自在に設置され、ケース上板と付勢ピンとの間に配置されたばねが、付勢ピンを振動体に向けて常時付勢する構成を採用している。付勢ピンは、その先端を直接又は間接的に振動体の胴部上面に当接させて、ばねの付勢力を振動体に伝達し、それにより、振動体の１対の駆動面が可動体の表面にばね圧力下で押し付けられる。この予圧構造では、付勢ピンはケース上板に沿って上下方向へ案内支持されており、また付勢ピンと振動体との間には相対変位を抑制し得る相補的嵌合構造が採用されている。したがって、ばね及び付勢ピンは、振動体の駆動面を可動体表面に押し付けた状態で振動体を支持する押圧支持構造とみなすこともできる。
【０００５】
なお、上記特許文献１には、押圧支持構造の一形態として、付勢ピンを付勢するばね力を調整する調整機構を備えたものが開示されている。さらに特許文献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。
【０００６】
【発明が解決しようとする課題】
超音波モータにおいては、振動体の駆動面と可動体表面との間に所定の接触圧力を維持するとともに、振動体に励振される超音波振動を拘束することなく、振動体をモータ構造内の正規位置に安定的に支持することが要求される。超音波モータの特徴の１つである優れた制御応答性は、このような振動体の安定支持を確保することで、より確実なものとなる。この観点で、前述した特許文献１の超音波モータにおける振動体の予圧構造（押圧支持構造）は、振動体の上方でケースに担持された付勢ピンを振動体の胴部上面にばね圧力下で当接して振動体を支持する構成であるから、振動体の下部領域（すなわち両脚部の駆動面近傍領域）に横方向へ加わる外力に対し、振動体を安定支持することが困難となる傾向がある。しかし、一般に超音波モータは、特に駆動立ち上がり時に、摩擦駆動の反作用として可動体から振動体にその駆動面に沿った方向への反力が加わるものであり、したがって従来の押圧支持構造では、この駆動反力に起因して振動体のふらつきや傾倒が生じることが懸念される。このような問題は、駆動反力のモーメントが比較的大きくなる前述した短棒状（門形ないし柱形）の振動体を有する超音波モータにおいて、顕現することが予測される。
【０００７】
このような問題を解決するために、本願出願人は、本願の先願である特願平２００３−０２２５４８号の明細書及び図面で、押圧支持構造として、基材に固定される第１固定部及び第２固定部と、それら第１及び第２固定部の間に位置して振動体に固定的に連結される中間固定部とを有し、第１及び第２固定部と中間固定部との間に延びる延長部分で、振動体の駆動面を可動体に押し付けるばね力を発揮する支持ばね部材を採用するとともに、基材への支持ばね部材の第１及び第２固定部の固定位置を、駆動面を底とした振動体の高さの方向に見て、振動体の頂端よりも低く、可動体に近接して配置するように構成した超音波モータを提案している。この超音波モータによれば、支持ばね部材のばね力を発揮する延長部分の両端の固定支持箇所が、振動体の駆動面に近い高さに配置されるので、振動体の下部領域（すなわち駆動面の近傍領域）に横方向へ加わる外力に対しても、振動体が安定して支持されることになる。
【０００８】
ただし、上記先願に係る超音波モータの押圧支持構造においても、モータの各種構成要素の成形誤差や組立誤差に起因して、振動体と可動体との相対的位置関係が正規位置関係から逸脱していた場合には、振動体に負荷されるばね力の不均衡により振動体の支持が不安定になることが懸念される。また、そのような構造上の誤差等に起因して、振動体の駆動面と可動体表面との接触状態が、一様な面接触ではなく線接触に近い状態となっていた場合には、効率の低下や駆動力の不安定化が生じる危惧がある。さらに、例えば前述したＹ形又はπ形のモータ構造における２個の圧電素子の電歪特性や接合状態の相違、振動体自体の構造上の不均一性や非対称性等に起因して、振動体の駆動面に、設計上の理想の楕円運動から逸脱した運動が生じる場合がある。このような場合には、例えばＹ形又はπ形のモータ構造のように可動体の駆動方向を切り換え可能な構成において、駆動方向により可動体の移動速度に差が生じることが危惧される。
【０００９】
また、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、ステージの移動動作の不安定化、位置決め精度の低下、往復移動速度差の発生等の問題が生じていた。さらに、超音波モータの採用により小型化した駆動部に対応して、案内／位置決め装置の一層の小型化・薄型化が要求されている。
【００１０】
本発明の目的は、振動体の駆動面と可動体表面との間に所定の接触圧力を維持するとともに、振動体に励振される超音波振動を拘束することなく、振動体をモータ構造内の正規位置に安定的に支持することができ、しかも、構造上の誤差等に起因する振動体の支持の不安定化、効率の低下、駆動力の不安定化、駆動方向切換に伴う速度差の発生等の諸問題を解決できる超音波モータを提供することにある。
【００１１】
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、ステージの移動動作を安定化し、位置決め精度を向上させ、かつ往復移動速度差を排除できる、小型化・薄型化の容易な位置決め装置を提供することにある。
【００１２】
【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移動する可動体と、駆動面を可動体に押し付けた状態で振動体を支持する押圧支持構造とを具備し、押圧支持構造は、基材と、基材と振動体との間に配置され、振動体を基材上で支持しつつ駆動面を可動体に押し付けるばね力を発揮する支持ばね部材と、支持ばね部材のばね力を調整する予圧調整機構とを備えて構成される超音波モータにおいて、支持ばね部材は、基材に取り付けられる第１取付部及び第２取付部と、それら第１及び第２取付部の間に位置して振動体に固定的に連結される中間固定部と、第１及び第２取付部と中間固定部との間に延設されてばね力を生じる延長部分とを有し、基材への支持ばね部材の第１及び第２取付部の取付位置が、駆動面を底とした振動体の高さの方向に見て、振動体の頂端よりも低く、可動体に近接して配置され、予圧調整機構は、支持ばね部材の第１及び第２取付部の少なくとも一方と基材との間に介在して、第１及び第２取付部の少なくとも一方の取付位置を調整する取付位置調整部材を備えること、を特徴とする超音波モータを提供する。
【００１３】
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、支持ばね部材の第１及び第２取付部の取付位置が、振動体を中心として可動体の移動方向へ実質的対称に分散して配置され、取付位置調整部材は、第１及び第２取付部の少なくとも一方の取付位置を調整して、可動体に対する所要の予圧を振動体の駆動面の全体に一様に生じさせる超音波モータを提供する。
【００１４】
請求項３に記載の発明は、請求項１又は２に記載の超音波モータにおいて、押圧支持構造は、振動体の駆動面と可動体との相対位置を角度的に調整する角度調整機構をさらに備える超音波モータを提供する。
【００１５】
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内蔵した位置決め装置を提供する。
【００１６】
請求項５に記載の発明は、請求項４に記載の位置決め装置において、超音波モータの基材を含む第１の基台と、超音波モータの可動体を含む第２の基台と、それら第１及び第２の基台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と、第１及び第２の基台の相対位置を検出する位置検出機構とを備え、第１及び第２の基台が両者間に装置内部空間を形成するように互いに組み合わされ、超音波モータ及び位置検出機構がいずれも装置内部空間に収容される位置決め装置を提供する。
【００１７】
請求項６に記載の発明は、駆動面を有する振動体と、振動体を励振する励振素子と、振動体の駆動面を被駆動物体に押し付けた状態で振動体を支持する押圧支持構造とを具備し、押圧支持構造は、基材と、基材と振動体との間に配置され、振動体を基材上で支持しつつ駆動面を被駆動物体に押し付けるばね力を発揮する支持ばね部材と、支持ばね部材のばね力を調整する予圧調整機構とを備えて構成される超音波モータにおいて、支持ばね部材は、基材に取り付けられる第１取付部及び第２取付部と、それら第１及び第２取付部の間に位置して振動体に固定的に連結される中間固定部と、第１及び第２取付部と中間固定部との間に延設されてばね力を生じる延長部分とを有し、基材への支持ばね部材の第１及び第２取付部の取付位置が、駆動面を底とした振動体の高さの方向に見て、振動体の頂端よりも低く、被駆動物体に近接して配置され、予圧調整機構は、支持ばね部材の第１及び第２取付部の少なくとも一方と基材との間に介在して、第１及び第２取付部の少なくとも一方の取付位置を調整する取付位置調整部材を備えること、を特徴とする超音波モータを提供する。
【００１８】
【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とを備えて構成される。
【００１９】
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２２と、それら肩面２２の間で外方へ突設される支承部２４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２６によって形成される。摩擦材料２６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。
【００２０】
振動体１４は、図１の正面視で、一端の駆動面１２の中心と他端の支承部２４の中心とを通る軸線１４ａに関して線対称の形状を有する。両肩面２２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２４は、振動体１４の本体部分１４ｂ（超音波が伝搬する部分）と同一の厚さ（図１紙面に直交する方向への寸法）を有して本体部分１４ｂから延長され、その末端に軸線１４ａ方向へ延びる雌ねじ２８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。なお振動体１４は、厚さ数ｍｍ程度の薄型構造を有する。
【００２１】
励振素子１６は、振動体１４の１対の肩面２２にそれぞれ接合される１対の圧電素子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２２に密着させて、例えば接着剤により肩面２２に強固に接合される。それにより１対の圧電素子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。これら圧電素子１６には、図示しない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。
【００２２】
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。
【００２３】
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３０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。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。
【００２４】
振動体１４の駆動面１２を形成する摩擦材料２６は、それに加えて又はその代わりに、可動体１８の表面領域３０に設置することもできる。いずれの場合も、摩擦材料２６は、駆動面１２の接触相手となる表面の材料と対比して、互いに実質的同一の硬度を有することが、摩擦材料２６自体の摩耗を抑制する点で有利である。さらに、両者の面精度を高めた上で、面粗さも実質的同一にすれば、摩擦材料２６の耐摩耗性が著しく向上することが、本願発明者の実験により判明した。
【００２５】
上記した振動体１４と励振素子１６との接合体及び可動体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ものであり、１対の励振素子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、本発明に係る押圧支持構造の構成は、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。
【００２６】
押圧支持構造２０は、基材３２と、基材３２と振動体１４との間に配置され、振動体１４を基材３２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３４とを備える。支持ばね部材３４は、第１取付部３６、第２取付部３８及びそれら第１及び第２取付部３６、３８の間に位置する中間固定部４０を有する板状組立体である。支持ばね部材３４は、中間固定部４０で振動体１４に固定的に連結されるとともに、第１及び第２取付部３６、３８で基材３２に取り付けられる。その状態で支持ばね部材３４は、第１及び第２取付部３６、３８と中間固定部４０との間に延びる延長部分４２で、振動体１４の駆動面１２を可動体１８の表面領域３０に押し付けるばね力を発揮する。
【００２７】
基材３２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、図示実施形態では両取付基部４６が、ボルト４８によって主部４４の表面４４ａに固定される。或いは、各取付基部４６を主部４４に一体化することもできる。
【００２８】
各取付基部４６には、後述する予圧調整機構の一構成要素である調整ねじ５０を螺着する雌ねじ５２が、主部４４の表面４４ａに略平行な方向へ凹設される。また、基材３２の主部表面４４ａ上で両取付基部４６に近接する位置に、外縁４４ｂに略直交する方向へ直線状に延びる１対の溝５４がそれぞれ形成されるとともに、それら溝５４の近傍に図示しない雌ねじがそれぞれ凹設される。なお、基材３２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。
【００２９】
支持ばね部材３４は、中間固定部４０及び延長部分４２を含む板ばね要素５６と、それぞれに第１及び第２取付部３６、３８を含む１対の剛性支持要素５８とを組み合わせて構成される。板ばね要素５６は、図１の正面視で略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、Ｕ字の中心梁部分として、無負荷状態で平板形態を呈する延長部分４２が、中間固定部４０を中心として対称に延長される。中間固定部４０には、支持ばね部材３４を振動体１４に固定的に連結するためのボルト挿通孔４０ａが、板厚方向（紙面に平行な方向）へ貫通形成される。
【００３０】
また板ばね要素５６には、中間固定部４０から離隔した延長部分４２の両端に、Ｕ字の両腕部分として延長部分４２に略直交する方向へ曲成された連結片６０が一体に設けられ、それら連結片６０のそれぞれに、板厚方向へ貫通する第２のボルト挿通孔６０ａが形成される。板ばね要素５６は、中間固定部４０のボルト挿通孔４０ａに挿通したボルト６２を、振動体１４の支承部２４に形成した雌ねじ２８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５６が有する延長部分４２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。
【００３１】
支持ばね部材３４の１対の剛性支持要素５８は、図１の正面視で互いに同一の略Ｌ字の外形に成形された金属板、樹脂板等の硬質材からなり、それぞれのＬ字の短腕部分として、第１及び第２取付部３６、３８が設けられるとともに、Ｌ字の長腕部分となる連結部６４が、それぞれ段差を介して第１及び第２取付部３６、３８に一体に設けられる。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、各剛性支持要素５８は、第１又は第２取付部３６、３８が連結部６４に対し、基材３２に接近する方向へずれて配置されるように形成される（図２）。
【００３２】
両剛性支持要素５８の第１及び第２取付部３６、３８には、支持ばね部材３４を基材３２に取り付けるための長孔状のボルト挿通孔６６が、それぞれ厚さ方向（紙面に直交する方向）へ貫通形成される。また、第１及び第２取付部３６、３８の各々には、基材３２の主部表面４４ａに対向する表面上の所定位置に、ボルト挿通孔６６の長軸に平行に直線状に延びる突条６８が突設される。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、各突条６８は、基材３２の主部表面４４ａに形成した対応の溝５４に、摺動自在に嵌入される。また、各連結部６４は、突条６８に対し略平行な方向へ延設され、その末端に、板厚方向（紙面に平行な方向）へ雌ねじ７０が凹設される。
【００３３】
各剛性支持要素５８は、第１又は第２取付部３６、３８のボルト挿通孔６６に挿通された取付ボルト７２を、基材３２の主部表面４４ａに溝５４近傍で凹設した図示しない雌ねじに螺着することにより、基材３２に取り付けられる。また、各剛性支持要素５８は、板ばね要素５６の各連結片６０のボルト挿通孔６０ａに挿通された調整ボルト７４（後述する角度調整機構の一構成要素）を、連結部６４の雌ねじ７０に螺着することにより、板ばね要素５６に連結される。
【００３４】
上記構成を有する支持ばね部材３４は、板ばね要素５６の両連結片６０の内側（相互対向側）に、第１及び第２取付部３６、３８を外側（相互離反側）に向けた両剛性支持要素５８の連結部６４の末端を重ねて配置した状態で、調整ボルト７４を用いて板ばね要素５６と両剛性支持要素５８とを相互に連結することにより、中間固定部４０を中心として対称な基準組立体の形態を呈する。このとき、板ばね要素５６と剛性支持要素５８とは、前者の連結片６０と後者の連結部６４とが互いに直線状に整列するように、目視で、又は適当なゲージを用いて、正確に組み合わされる。
【００３５】
本発明の特徴的構成として、押圧支持構造２０は、支持ばね部材３４のばね力を調整する予圧調整機構７６と、振動体１４の駆動面１２と可動体１８との相対位置を角度的に調整する角度調整機構７８とをさらに備える。予圧調整機構７６は、支持ばね部材３４の第１及び第２取付部３６、３８の双方と基材３２との間に介在して、第１及び第２取付部３６、３８の静止基台３２に対する取付位置を調整する取付位置調整部材５０を備える。図示実施形態では、取付位置調整部材５０は、基材３２の１対の取付基部４６に形成した雌ねじ５２に螺着される１対の調整ねじ（止めねじ）５０から構成される。
【００３６】
予圧調整機構７６は、それら調整ねじ５０と、両調整ねじ５０の先端を当接する第１及び第２取付部３６、３８の表面（図で上端面）３６ａ、３８ａと、第１及び第２取付部３６、３８の双方に設けた長孔状のボルト挿通孔６６及び突条６８と、両ボルト挿通孔６６に挿通される１対の取付ボルト７２と、両突条６８が嵌入される基材３２の主部表面４４ａの１対の溝５４とを含んで構成され、それらの協働により後述する予圧調整を遂行する。また、角度調整機構７８は、支持ばね部材３４の板ばね要素５６及び１対の剛性支持要素５８と、板ばね要素５６と両剛性支持要素５８とを相互に連結する１対の調整ボルト７４とを含んで構成され、それらの協働により後述する角度調整を遂行する。
【００３７】
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３２は、その主部４４の外縁４４ｂが可動体１８の表面領域３０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。基材３２の１対の取付基部４６には、それぞれの雌ねじ５２に、調整ねじ５０がその先端を雌ねじ５２から外方へ突出させない非作用状態で螺着される。また、１対の圧電素子１６を両肩面２２に接合した振動体１４は、基材３２の両取付基部４６の略中間位置で、駆動面１２を表面領域３０に当接させて可動体１８上に搭載される。
【００３８】
支持ばね部材３４は、前述した基準組立体の形態で、ボルト６２により中間固定部４０を振動体１４の支承部２４に固定するとともに、第１及び第２取付部３６、３８を基材３２の両取付基部４６の下側（可動体１８に近い側）にそれぞれ配置する。そして、第１及び第２取付部３６、３８の突条６８を、基材３２の主部表面４４ａの対応の溝５４に嵌入すると、第１及び第２取付部３６、３８の長孔状のボルト挿通孔６６が、主部表面４４ａに形成した図示しない雌ねじに実質的に整合配置される。
【００３９】
そこで、１対の取付ボルト７２をそれぞれ、第１及び第２取付部３６、３８のボルト挿通孔６６に挿通して対応の雌ねじに緩く螺着し、支持ばね部材３４を基材３２に仮留めする。この仮留め状態で、支持ばね部材３４の第１及び第２取付部３６、３８の表面３６ａ、３８ａは、対応の取付基部４６の表面（図で下端面）に、好ましくは接触して配置される。また、第１及び第２取付部３６、３８の各々は、突条６８と溝５４との係合状態を維持しつつ、長孔状のボルト挿通孔６６と取付ボルト７２とによって規定される移動範囲内で、振動体１４の軸線１４ａに略平行な方向へ移動できるようになっている。
【００４０】
この仮留め状態から、１対の調整ねじ５０をそれぞれ、対応の取付基部４６の雌ねじ５２にさらに螺入して、それら調整ねじ５０の先端を、支持ばね部材３４の第１及び第２取付部３６、３８の表面３６ａ、３８ａに当接させる。そして、個々の調整ねじ５０を適当なトルクで締め込むことにより、それら調整ねじ５０から対応の第１及び第２取付部３６、３８に適当な圧力を負荷しつつ、基材３２に対する第１及び第２取付部３６、３８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４０を支点として支持ばね部材３４の延長部分４２を撓ませて、延長部分４２に中間固定部４０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３４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３０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。
【００４１】
このようにして組み立てた超音波モータ１０では、押圧支持構造２０における支持ばね部材３４の特徴的形状、及び振動体１４に対する基材３２の両取付基部４６の位置関係に起因して、基材３２への支持ばね部材３４の第１及び第２取付部３６、３８の取付位置が、駆動面１２を底とした振動体１４の高さの方向に見て、振動体１４の頂端に位置する支承部２４よりも低く、可動体１８に近接して配置される。つまり、この押圧支持構造２０によれば、支持ばね部材３４のばね力を発揮する延長部分４２の両端の固定支持箇所が、振動体１４の駆動面１２に近い高さに配置されるので、振動体１４の下部領域（すなわち駆動面１２の近傍領域）に横方向へ加わる外力に対しても、振動体１４が安定して支持されることになる。
【００４２】
しかも、図示実施形態では、基材３２への支持ばね部材３４の第１及び第２取付部３６、３８の取付位置が、振動体１４の高さの方向に見て、振動体１４の支承部２４への支持ばね部材３４の中間固定部４０の固定位置よりも低く配置されるから、振動体１４に負荷されるばね力は、駆動面１２を可動体１８の表面領域３０に押し付ける方向へ振動体１４を引き寄せる牽引力となる。その結果、振動体１４に対する安定支持効果が一層向上する。また、基材３２への支持ばね部材３４の第１及び第２取付部３６、３８の取付位置は、振動体１４を中心として可動体１８の移動方向へ実質的対称に分散して配置される。したがって、可動体１８の移動方向に左右されることなく、振動体１４を安定的に支持することができる。
【００４３】
ここで、超音波モータ１０において、各種構成要素の成形誤差や組立誤差に起因して、振動体１４と可動体１８との相対的位置関係が正規位置関係から僅かに逸脱している場合を想定する。このような場合には、支持ばね部材３４から振動体１４に負荷されるばね力の不均衡が生じ、その結果、振動体１４の支持が不安定になることが懸念される。特に、振動体１４と１対の励振素子１６との接合体において、両励振素子１６の総合的な特性の相違や振動体１４の構造上の不均一性等により、振動体軸線１４ａに関する可動体移動方向への構造的対称性が損なわれていた場合には、振動体１４の駆動面１２に、設計上の理想の楕円運動から逸脱した運動が生じることがある。このような場合には、可動体１８の駆動方向を切り換えたときに、駆動方向により可動体１８の移動速度に差が生じることが危惧される。
【００４４】
上記した諸課題に対し、押圧支持構造２０においては、予圧調整機構７６の取付位置調整部材を構成する１対の調整ねじ５０を、個々に適当な量だけ締め込むことにより、基材３２への支持ばね部材３４の第１及び第２取付部３６、３８の取付位置を、振動体１４の軸線１４ａに略平行な方向へ個別に微調整することができる。したがって、超音波モータ１０に上記した構造上の誤差等が内在する場合であっても、１対の調整ねじ５０を個々に微調操作することにより、振動体１４を中心に可動体移動方向両側へ延長される支持ばね部材３４の延長部分４２の撓みによるばね力を、中間固定部４０を中心として平衡させることができる。その結果、押圧支持構造２０によれば、構造上の誤差等の存在に関わらず、可動体１８に対する所要の予圧を振動体１４の駆動面１２の全体に一様に生じさせて、振動体１４を可動体１８に対し安定的に支持できるとともに、振動体１４の駆動面１２に理想の楕円運動を生起して、可動体１８の駆動方向による移動速度差を排除することができる。
【００４５】
他方、上記した構造上の誤差等に起因して、振動体１４の駆動面１２と可動体１８の表面領域３０との接触状態が、理想とされる一様な面接触ではなく、線接触に近い状態となる場合も予測される。具体的には、図２に示すように、基材３２の主部４４と取付基部４６との組立又は成形誤差、基材３２の主部４４に対する支持ばね部材３４の第１又は第２取付部３６、３８の取付誤差、支持ばね部材３４における板ばね要素５６と剛性支持要素５８との組立誤差等に起因して、主部表面４４ａに対する振動体１４の平行性が損なわれたときに、振動体１４の駆動面１２と可動体１８の表面領域３０とが「ずれ角θ」を成して相互に線接触することになる。或いは、超音波モータ１０の図示しない機台や他の外部構造体との位置関係の誤差に起因して、基材３２の主部表面４４ａと可動体１８の表面領域３０との直交性が損なわれたときにも、同様な線接触状態が生じる。
【００４６】
このような課題に対し、押圧支持構造２０においては、角度調整機構７８を構成する１対の調整ボルト７４を一時的に緩めて、支持ばね部材３４の板ばね要素５６と両剛性支持要素５８との相対位置関係を個々に微調整することにより、振動体１４の駆動面１２と可動体１８の表面領域３０との接触状態を一様な面接触状態へと修正することができる。その結果、押圧支持構造２０によれば、構造上の誤差等の存在に関わらず、振動体１４の駆動面１２と可動体１８の表面領域３０との間に摩擦駆動力の生成に必須の所定接触圧力を維持しながら、駆動面１２の楕円運動を確実に可動体１８に伝達でき、以って、効率の低下や駆動力の不安定化を防止することができる。
【００４７】
このように、超音波モータ１０では、構造上の誤差が内在する場合であっても、予圧調整機構７６及び角度調整機構７８の微調作用により、押圧支持構造２０が、可動体１８の駆動立ち上がり時や駆動中に生じる駆動反力等に抗して、振動体１４をモータ構造内の正規位置に安定的に支持でき、また、振動体１４の駆動面１２に理想の楕円運動を生起して、可動体１８の駆動方向による移動速度差を排除でき、さらに、効率の向上及び駆動力の安定化を達成できる。しかもこの構成では、振動体１４と支持ばね部材３４との連結部位が、圧電素子１６を接合する振動体１４の肩面２２よりも高く（すなわち駆動面１２からさらに離れて）配置されるから、押圧支持構造２０が振動体１４の超音波振動を拘束することは回避される。さらに、予圧調整機構７６及び角度調整機構７８のいずれも、押圧支持構造２０が本来の振動体押圧支持機能を発揮するに必要な構成要素群の外形寸法を、実質的に超えない範囲で構成されているから、超音波モータ１０の寸法増加が回避される。したがって、超音波モータ１０によれば、小型・薄型の特徴を維持しつつ、構造上の誤差が駆動特性に及ぼす影響を積極的に修正して、優れた制御応答性を高い信頼性の下に実現することができる。
【００４８】
本発明に係る超音波モータ１０では、上記した押圧支持構造２０の特徴的構成に加えて（又はその代わりに）、効率や駆動特性を改善するための、下記のような様々な方策を施すことができる。
【００４９】
１つの方策として、振動体１４と１対の励振素子１６との接合体において、両励振素子１６の総合的な特性（電歪特性や接合状態等）の相違、振動体１４自体の構造上の不均一性や非対称性等が内在した場合の、駆動面１２の楕円運動の調整法を提案する。ここでは、図３に模式図的に示すように、このような構造上の誤差等に起因して、振動体１４の駆動面１２に図で反時計方向の楕円運動を生起させて可動体１８を図で右方向へ駆動する際に、楕円運動が理想状態（破線）から逸脱した傾斜状態（実線）になっている場合を考察する（図３（ａ））。なお、励振素子１６から振動体１４の駆動面１２までの距離が、駆動面１２上で可動体１８の移動方向に沿って変わるので、図示のように駆動面１２上の諸点において楕円運動の軌跡は異なる。この誤差等が内在した構造のままで、１対の励振素子１６の位相を反転し、振動体１４の駆動面１２に図で時計方向の楕円運動を生起させて可動体１８を図で左方向へ駆動する際には、楕円運動が右方向駆動のときと見掛け上で同じ方向へ傾いた状態（実線）になる（図３（ｂ））。駆動面１２のこのような傾斜楕円運動は、左方向へ移動する可動体１８を制動するかのように作用し、結果として、可動体１８の左方向移動速度が右方向移動速度よりも遅くなる。
【００５０】
ここで、１対の励振素子１６に印加する高周波電圧の周波数を、共振周波数から僅かに変化させると、それに伴い、駆動面１２の中心点から離れた点における楕円運動の軌跡が変動する。この現象に着目し、上記した傾斜楕円運動が振動体１４の駆動面１２に生じているときに、前述した予圧調整機構７６による機械構造的な微調整に加えて（又はその代わりに）、駆動周波数の微調整を行うことにより、振動体１４の駆動面１２の傾斜楕円運動を適宜修正することができる。そして、このような駆動周波数の微調整により、可動体１８の左右移動速度差を低減できることが、本願発明者の実験により判明した。
【００５１】
別の方策として、振動体１４の駆動面１２を効率良く楕円運動させるための、振動体１４の構造的条件を提案する。ここでは、図４に模式図的に示すように、振動体１４の駆動面１２の可動体移動方向に沿った寸法Ｗ１、励振素子１６の幅方向（紙面に平行な方向）の寸法Ｗ２、振動体１４の中心線１４ａと励振素子１６の中心線１６ａとの成す角度α、及び励振素子１６から振動体１４を伝搬する超音波の伝搬路の長さＬについて考察する。図示のように、励振素子１６による波動Ｖが振動体１４の本体部分１４ｂを伝搬して駆動面１２に到達する間に、波動Ｖの主成分が効率良く伝搬するように、以下の条件で振動体１４の形状及び寸法を設計する。
【００５２】
（１）Ｗ１≦Ｗ２／ｃｏｓα
（２）Ｌ≒ｎ・λ／４（ｎは自然数）
波動Ｖの波長λ＝ｖ／ｆ（ｖは振動体１４の音速、ｆは振動体１４の共振周波数）。
（３）波動Ｖの反射回数・・・１回又は２回
【００５３】
図４（ａ）は、波動Ｖの反射回数を１回として上記条件１、２を満たすように設計した振動体１４を、また図４（ｂ）は、波動Ｖの反射回数を２回として上記条件１、２を満たすように設計した振動体１４を、それぞれ示す。このような構成を有する振動体１４により、超音波モータ１０の効率が向上し、駆動の安定性及び応答性が改善されることが、本願発明者の実験により判明した。なお、伝搬路の長さＬの増加及び反射回数の増加に従い、効率が低下する傾向があった。
【００５４】
図５〜図７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８０を示す。位置決め装置８０は、超音波モータ１０の基材３２を含む第１の基台８２と、超音波モータ１０の可動体１８を含む第２の基台８４と、それら第１及び第２の基台８２、８４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８６と、第１及び第２の基台８２、８４の相対位置を検出する位置検出機構８８とを備えて構成される。
【００５５】
第１の基台８２は、矩形平板状の固定ベース部材であって、その一部分が超音波モータ１０の基材３２として作用するとともに、その表面８２ａの所定位置に、超音波モータ１０を設置するための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３４を介して、超音波モータ１０の固定側の構成要素群が取り付けられる。また、基台８２の表面８２ａには、その長手方向へ延びる両縁に沿って、リニアガイド８６を設置する１対の縁壁９０が突設される。さらに基台８２には、超音波モータ１０の設置領域の外側で一方の取付基部４６に隣接して、位置検出機構８８の設置領域として略矩形平面形状の開口部９２が、板厚方向へ貫通形成される。１対の取付基部４６及び開口部９２は、いずれも両縁壁９０の間の領域に配設される。
【００５６】
第２の基台８４は、矩形平板状の移動ステージ部材であって、その一表面８４ａの所定位置に、超音波モータ１０の可動体１８が固定的に設置される。可動体１８は、基台８４と同一の材料で基台８４に一体に形成してもよいし、別体の可動体１８を基台８４に一体的に固定する構成としてもよい。また、基台８４の表面８４ａには、その長手方向へ延びる両縁に沿って、リニアガイド８６を設置する１対の縁壁９４が突設される。さらに基台８４の表面８４ａには、可動体１８から離隔して、可動体１８に平行に延びるリニアスケール９６が固定される。可動体１８及びリニアスケール９６は、いずれも両縁壁９４の間の領域に配設される。なお、第１及び第２の基台８２、８４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。
【００５７】
第１の基台８２と第２の基台８４とは、それらの表面８２ａ、８４ａ同士を対向させて、基台８２の両縁壁９０が基台８４の両縁壁９４の内側に位置するように、互いに相補的に組み合わされる。この状態で、それら基台８２、８４の間に、超音波モータ１０及び位置検出機構８８を収容する装置内部空間９８が形成される。リニアガイド８６は、図示実施形態では１対のクロスローラガイド８６からなり、基台８２の両縁壁９０の外面と基台８４の両縁壁９４の内面との間にそれぞれ介在して、基台８４を基台８２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。
【００５８】
位置検出機構８８は、基台８２の開口部９２内に設置される光学式の位置センサ１００と、基台８４の表面８４ａに固定されるリニアスケール９６とから構成される。位置センサ１００は、断面Ｌ字状の取付具１０２を用いて、基台８２に固定される。位置センサ１００の信号線１０４は、超音波モータ１０の制御線１０６と共に、基台８２の長手方向一端から位置決め装置８０の外部に導出され、図示しない制御装置に接続される。
【００５９】
基台８２、８４を適正に組み合わせた状態では、基台８２に設置した超音波モータ１０の振動体１４の駆動面１２が、基台８４に設置した可動体１８の表面領域３０に、押圧支持構造２０による所定の予圧下で当接される。また、基台８４に設置したリニアスケール９６は、基台８２に設置した位置センサ１００に対し、位置検出動作を可能にする所定位置に非接触に配置される。
【００６０】
上記構成を有する位置決め装置８０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８４の移動動作を安定化し、その位置決め精度を向上させ、かつ往復移動速度差を排除することができる。しかも、超音波モータ１０及び位置検出機構８８がいずれも、第１及び第２の基台８２、８４の間に画定される装置内部空間９８に収容されるので、ステージ面積を超える突出部分が実質的に排除され、位置決め装置８０の小型化・薄型化が促進される。なお、本実施形態に係る位置決め装置８０は、ストロークＳ＝１００ｍｍ、高さＨ＝１６ｍｍ、最大搬送負荷５ｋｇを実現した。
【００６１】
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特徴的構成要件である押圧支持構造は、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、予圧調整機構の取付位置調整部材は、支持ばね部材の第１及び第２取付部の少なくとも一方と基材との間に介在して、第１及び第２取付部の少なくとも一方の取付位置を調整するように構成すれば、やはり同等の作用効果を奏することが予期される。さらに、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。
【００６２】
なお、本発明に係る超音波モータは、可動体を含まない構成でも提供し得るものである。この場合、押圧支持構造は、振動体を基材上で支持しつつその駆動面を被駆動物体に押し付けるばね力を発揮する支持ばね部材と、支持ばね部材のばね力を調整する予圧調整機構とを備えて構成される。
【００６３】
【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、押圧支持構造を有する超音波モータにおいて、振動体の駆動面と可動体表面との間に所定の接触圧力を維持するとともに、振動体に励振される超音波振動を拘束することなく、振動体をモータ構造内の正規位置に安定的に支持することができ、しかも、構造上の誤差等に起因する振動体の支持の不安定化、効率の低下、駆動力の不安定化、駆動方向切換に伴う速度差の発生等の諸問題を解決できる。したがって本発明によれば、超音波モータの優れた制御応答性を高い信頼性の下に実現することができる。
【００６４】
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、ステージの移動動作を安定化し、位置決め精度を向上させ、かつ往復移動速度差を排除することができ、しかも小型化・薄型化が容易となる。
【図面の簡単な説明】
【図１】本発明の一実施形態による超音波モータの正面図である。
【図２】図１の超音波モータを矢印ＩＩの方向から示す側面図である。
【図３】図１の超音波モータにおける駆動面の楕円運動を示す図で、（ａ）右方向駆動時、及び（ｂ）左方向駆動時のそれぞれの状態を示す。
【図４】図１の超音波モータにおける波動伝搬状態を示す図で、（ａ）１回反射、及び（ｂ）２回反射のそれぞれの状態を示す。
【図５】本発明の一実施形態による位置決め装置の図で、（ａ）一部切欠き平面図、及び（ｂ）正面図である。
【図６】図５の位置決め装置の線ＶＩ−ＶＩに沿った断面図である。
【図７】図５の位置決め装置の線ＶＩＩ−ＶＩＩに沿った断面図である。
【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
２６…摩擦材料
３０…表面領域
３２…基材
３４…支持ばね部材
３６…第１取付部
３８…第２取付部
４０…中間固定部
４２…延長部分
４６…取付基部
５０…調整ねじ
５４…溝
５６…板ばね要素
５８…剛性支持要素
７２…取付ボルト
７４…調整ボルト
７６…予圧調整機構
７８…角度調整機構
８０…位置決め装置
８２…第１の基台
８４…第２の基台
８６…リニアガイド
８８…位置検出機構
９２…開口部
９６…リニアスケール
９８…装置内部空間
１００…位置センサ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic motor, and more particularly, to an ultrasonic motor having a pressing support structure that supports a vibrating body excited by an excitation element in a state where its driving surface is pressed against a movable body. 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]
In a conventional ultrasonic motor, a spring that urges the vibrating body in a direction approaching the movable body is generally employed as the preload structure described above. For example, in the ultrasonic motor described in Patent Document 1, an urging pin whose tip is directed to the vibrating body is movably installed on the upper plate of the case that houses the gate-shaped vibrating body. A configuration is adopted in which a spring disposed between the urging pins constantly urges the urging pins toward the vibrating body. The biasing pin has its tip directly or indirectly brought into contact with the upper surface of the body portion of the vibrating body to transmit the biasing force of the spring to the vibrating body, whereby the pair of driving surfaces of the vibrating body are movable. Pressed against the surface of the plate under spring pressure. In this preload structure, the urging pin is guided and supported in the vertical direction along the case upper plate, and a complementary fitting structure that can suppress relative displacement is adopted between the urging pin and the vibrating body. Yes. Therefore, the spring and the biasing pin can be regarded as a pressing support structure that supports the vibrating body in a state where the driving surface of the vibrating body is pressed against the surface of the movable body.
[0005]
In addition, the said patent document 1 is provided with the adjustment mechanism which adjusts the spring force which urges | biases an urging | biasing pin as one form of a press support structure. Further, 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.
[0006]
[Problems to be solved by the invention]
In an ultrasonic motor, a predetermined contact pressure is maintained between the driving surface of the vibrating body and the surface of the movable body, and the vibrating body is placed in the motor structure without restraining the ultrasonic vibration excited by the vibrating body. It is required to stably support the normal position. The excellent control responsiveness which is one of the features of the ultrasonic motor becomes more reliable by ensuring stable support of such a vibrating body. From this point of view, the preload structure (pressing support structure) of the vibrating body in the ultrasonic motor described in Patent Document 1 described above has an urging pin carried on the case above the vibrating body under the spring pressure on the upper surface of the trunk of the vibrating body. Since the structure is configured to abut on and support the vibrating body, it tends to be difficult to stably support the vibrating body against an external force applied in the lateral direction to the lower area of the vibrating body (that is, the area in the vicinity of the drive surface of both legs). There is. However, in general, an ultrasonic motor is one in which a reaction force in the direction along the driving surface is applied from the movable body to the vibrating body as a reaction of the friction drive, particularly at the time of driving startup. There is a concern that the vibration body may be staggered or tilted due to the driving reaction force. Such a problem is expected to be manifested in the ultrasonic motor having the above-described short rod-like (gate or columnar) vibrating body in which the moment of the driving reaction force is relatively large.
[0007]
In order to solve such a problem, the applicant of the present application described in the specification and drawings of Japanese Patent Application No. 2003-022548, which is a prior application of the present application, as a pressing support structure, a first fixing portion fixed to a substrate. And an intermediate fixing portion that is located between the first and second fixing portions and is fixedly connected to the vibrating body, and the first and second fixing portions and the intermediate fixing portion, A supporting spring member that exerts a spring force that presses the driving surface of the vibrating body against the movable body is an extension portion that extends between the first and second fixing portions of the supporting spring member to the base. In addition, an ultrasonic motor is proposed that is configured to be disposed close to a movable body, which is lower than the top end of the vibrating body when viewed in the height direction of the vibrating body with the drive surface as the bottom. According to this ultrasonic motor, since the fixed support portions at both ends of the extended portion that exerts the spring force of the support spring member are arranged at a height close to the drive surface of the vibration body, the lower region of the vibration body (that is, the drive) The vibrating body is stably supported even with respect to an external force applied in the lateral direction to the area in the vicinity of the surface.
[0008]
However, even in the pressing support structure of the ultrasonic motor according to the previous application, the relative positional relationship between the vibrating body and the movable body deviates from the normal positional relationship due to molding errors and assembly errors of various components of the motor. In such a case, there is a concern that the support of the vibrator becomes unstable due to an imbalance of the spring force applied to the vibrator. In addition, when the contact state between the driving surface of the vibrating body and the surface of the movable body is close to a line contact rather than a uniform surface contact due to such structural errors, There is a risk that the efficiency may be lowered and the driving force may become unstable. Further, for example, due to the difference in electrostriction characteristics and bonding state of the two piezoelectric elements in the Y-type or π-type motor structure described above, structural non-uniformity or asymmetry of the vibration body itself, the vibration body In some cases, a movement deviating from an ideal elliptical motion in design occurs on the driving surface. In such a case, for example, in a configuration in which the driving direction of the movable body can be switched, such as a Y-type or π-type motor structure, there is a concern that the moving speed of the movable body varies depending on the driving direction.
[0009]
In addition, in conventional guide / positioning devices such as single-axis and multi-axis stages equipped with an ultrasonic motor, the above-mentioned problems inherent in conventional ultrasonic motors have led to unstable movement of the stage. Problems such as a decrease in positioning accuracy and the occurrence of a reciprocating speed difference have occurred. Furthermore, the guide / positioning device is required to be further reduced in size and thickness in response to a drive unit that has been reduced in size by adopting an ultrasonic motor.
[0010]
An object of the present invention is to maintain a predetermined contact pressure between the driving surface of the vibrating body and the surface of the movable body, and to restrain the vibrating body in the motor structure without restraining the ultrasonic vibration excited by the vibrating body. It can be stably supported at the normal position, and in addition, the support of the vibrating body is unstable due to structural error, etc., the efficiency is lowered, the driving force is unstable, the speed difference due to the switching of the driving direction An object of the present invention is to provide an ultrasonic motor capable of solving various problems such as generation.
[0011]
Another object of the present invention is to reduce the size and thickness of a positioning device that employs an ultrasonic motor as a drive unit, which can stabilize the movement of the stage, improve the positioning accuracy, and eliminate the reciprocating speed difference. To provide an easy positioning device.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is provided in contact with a vibrating body having a driving surface, an excitation element for exciting the vibrating body, and the driving surface of the vibrating body. A movable body that moves in response to the vibrating body, and a pressing support structure that supports the vibrating body in a state where the driving surface is pressed against the movable body. The pressing support structure includes a base material, the base material, and the vibrating body. And a support spring member that exerts a spring force that presses the drive surface against the movable body while supporting the vibrating body on the base material, and a preload adjusting mechanism that adjusts the spring force of the support spring member. In the ultrasonic motor, the support spring member is positioned between the first and second attachment portions attached to the base material and the first and second attachment portions, and is fixedly connected to the vibrating body. Extending between the intermediate fixing portion, the first and second mounting portions, and the intermediate fixing portion. An extension portion that generates a force of force, and the attachment positions of the first and second attachment portions of the support spring member to the base material are viewed in the height direction of the vibration body with the drive surface as the bottom, and the vibration body The preload adjusting mechanism is disposed between at least one of the first and second mounting portions of the support spring member and the base material, and is disposed lower than the top end of the movable body and close to the movable body. Provided is an ultrasonic motor comprising an attachment position adjusting member for adjusting an attachment position of at least one of the attachment portions.
[0013]
According to a second aspect of the present invention, in the ultrasonic motor according to the first aspect, the mounting positions of the first and second mounting portions of the support spring member are substantially symmetrical with respect to the moving direction of the movable body about the vibrating body. The mounting position adjusting member adjusts the mounting position of at least one of the first and second mounting portions to uniformly generate a required preload for the movable body on the entire driving surface of the vibrating body. An ultrasonic motor is provided.
[0014]
According to a third aspect of the present invention, in the ultrasonic motor according to the first or second aspect, the pressing support structure further includes an angle adjusting mechanism that angularly adjusts a relative position between the driving surface of the vibrating body and the movable body. An ultrasonic motor is provided.
[0015]
According to a fourth aspect of the present invention, there is provided a positioning apparatus including the ultrasonic motor according to any one of the first to third aspects.
[0016]
The invention according to claim 5 is the positioning device according to claim 4, wherein the first base including the base material of the ultrasonic motor, the second base including the movable body of the ultrasonic motor, and those A linear guide that mutually supports the first and second bases so as to be relatively movable and linearly guides each other; and a position detection mechanism that detects the relative positions of the first and second bases; In addition, a positioning device is provided in which the second base is combined with each other so as to form an apparatus internal space therebetween, and both the ultrasonic motor and the position detection mechanism are accommodated in the apparatus internal space.
[0017]
According to a sixth aspect of the present invention, there is provided a vibrating body having a driving surface, an excitation element that excites the vibrating body, and a pressing support structure that supports the vibrating body in a state where the driving surface of the vibrating body is pressed against a driven object. The support spring member is provided between the base material and the base material and the vibrating body and exhibits a spring force that presses the driving surface against the driven object while supporting the vibrating body on the base material. And a preload adjusting mechanism that adjusts the spring force of the support spring member, the support spring member includes a first attachment portion and a second attachment portion that are attached to the base material, and the first attachment portion. And an intermediate fixing portion that is positioned between the second mounting portion and is fixedly connected to the vibrating body, and an extension portion that extends between the first and second mounting portions and the intermediate fixing portion to generate a spring force. The mounting positions of the first and second mounting portions of the support spring member to the base material are driven. When viewed in the height direction of the vibrating body with the bottom at the bottom, the preload adjusting mechanism is disposed closer to the driven object than the top end of the vibrating body, and the preload adjusting mechanism is provided on the first and second mounting portions of the support spring member. Provided is an ultrasonic motor comprising an attachment position adjusting member that is interposed between at least one and a base material and adjusts the attachment position of at least one of the first and second attachment portions.
[0018]
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. The movable body 18 that moves relative to the movable body 18 and the pressing support structure 20 that supports the vibrating body 14 in a state in which the drive surface 12 is pressed against the movable body 18 are configured.
[0019]
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 22 extending flatly and a support portion 24 projecting outward between the shoulder surfaces 22 are provided. The driving surface 12 of the vibrating body 14 is preferably formed of a friction material 26 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 26 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.
[0020]
The vibrating body 14 has a line-symmetric shape with respect to an axis 14a passing through the center of the driving surface 12 at one end and the center of the support portion 24 at the other end in the front view of FIG. Both shoulder surfaces 22 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 24 has the same thickness as the main body portion 14b (a portion through which ultrasonic waves propagate) of the vibrating body 14 (a dimension in a direction perpendicular to the plane of FIG. 1) and extends from the main body portion 14b. A female screw 28 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. The vibrating body 14 has a thin structure with a thickness of about several mm.
[0021]
The excitation element 16 includes a pair of piezoelectric elements 16 that are respectively joined to a pair of shoulder surfaces 22 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 22 of the vibrating body 14, for example, an adhesive. Thus, it is firmly bonded to the shoulder surface 22. As a result, the pair of piezoelectric elements 16 are arranged such that the center lines 16 a extending in the respective stacking directions form an angle of approximately 45 ° with respect to the drive surface 12. A sinusoidal voltage is applied to each of these piezoelectric elements 16 with a predetermined phase difference (for example, 90 °) via a control circuit (not shown), and the differential displacement operation of both piezoelectric elements 16 thereby causes the vibrating body 14. So that a so-called elliptical motion for exerting a frictional driving force is caused on the driving surface 12.
[0022]
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.
[0023]
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 region 30, 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. 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.
[0024]
The friction material 26 forming the drive surface 12 of the vibrating body 14 may be placed on the surface region 30 of the movable body 18 in addition to or instead of it. In any case, it is advantageous in terms of suppressing wear of the friction material 26 itself that the friction material 26 has substantially the same hardness as the material of the surface with which the drive surface 12 contacts. is there. Furthermore, it has been found through experiments conducted by the present inventor that the wear resistance of the friction material 26 is remarkably improved if the surface roughness is made substantially the same while increasing the surface accuracy of both.
[0025]
The structure of the joined body of the vibrating body 14 and the excitation element 16 and the movable body 18 described above is employed in a so-called Y-shaped ultrasonic motor, and the phase of the pair of excitation elements 16 is reversed. The driving direction of the movable body 18 can be switched. The configuration of the pressing support structure 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.
[0026]
The pressing support structure 20 is disposed between the base material 32 and the base material 32 and the vibration body 14 and exhibits a spring force that presses the drive surface 12 against the movable body 18 while supporting the vibration body 14 on the base material 32. And a supporting spring member 34. The support spring member 34 is a plate-like assembly having a first attachment portion 36, a second attachment portion 38, and an intermediate fixing portion 40 located between the first and second attachment portions 36, 38. The support spring member 34 is fixedly connected to the vibrating body 14 by the intermediate fixing portion 40 and attached to the base material 32 by the first and second attachment portions 36 and 38. In this state, the support spring member 34 is an extended portion 42 extending between the first and second attachment portions 36 and 38 and the intermediate fixing portion 40, and the driving surface 12 of the vibrating body 14 is moved to the surface region 30 of the movable body 18. Demonstrate the spring force to press.
[0027]
The base material 32 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. In the illustrated embodiment, both the mounting base portions 46 are fixed to the surface 44 a of the main portion 44 by bolts 48. Alternatively, each mounting base 46 can be integrated with the main portion 44.
[0028]
Each mounting base 46 is provided with a female screw 52 into which an adjusting screw 50, which is a component of a preload adjusting mechanism to be described later, is recessed in a direction substantially parallel to the surface 44a of the main portion 44. In addition, a pair of grooves 54 linearly extending in a direction substantially orthogonal to the outer edge 44 b are formed on the main surface 44 a of the base material 32 at positions close to the mounting bases 46, respectively. A female screw (not shown) is recessed in the vicinity. The main portion 44 of the base material 32 can be fixedly connected to a machine base (or an external structure) (not shown) of the ultrasonic motor 10 that movably supports the movable body 18 described above.
[0029]
The support spring member 34 is configured by combining a leaf spring element 56 including an intermediate fixing portion 40 and an extension portion 42 and a pair of rigid support elements 58 including first and second attachment portions 36 and 38, respectively. . The leaf spring element 56 is made of a spring material such as a metal plate or a resin plate bent into a substantially U-shape when viewed from the front in FIG. 1, and exhibits a flat plate shape as a U-shaped central beam portion in an unloaded state. The extended portion 42 is extended symmetrically about the intermediate fixing portion 40. A bolt insertion hole 40a for fixedly connecting the support spring member 34 to the vibrating body 14 is formed through the intermediate fixing portion 40 in the plate thickness direction (direction parallel to the paper surface).
[0030]
Further, the leaf spring element 56 is integrally provided with connecting pieces 60 bent in a direction substantially perpendicular to the extension portion 42 as both U-shaped arm portions at both ends of the extension portion 42 separated from the intermediate fixing portion 40. Each of the connecting pieces 60 is formed with a second bolt insertion hole 60a penetrating in the plate thickness direction. The leaf spring element 56 is fixed to the vibrating body 14 by screwing a bolt 62 inserted into the bolt insertion hole 40a of the intermediate fixing portion 40 to a female screw 28 formed in the support portion 24 of the vibrating body 14. As will be described later, when the ultrasonic motor 10 is properly assembled, the extended portion 42 of the leaf spring element 56 is extended in a direction perpendicular to the axis 14 a of the vibrating body 14 in an unloaded state.
[0031]
The pair of rigid support elements 58 of the support spring member 34 is made of a hard material such as a metal plate or a resin plate formed in the same substantially L-shaped outer shape when viewed from the front in FIG. First and second attachment portions 36 and 38 are provided as arm portions, and a connecting portion 64 that is an L-shaped long arm portion is integrally formed with the first and second attachment portions 36 and 38 through respective steps. Provided. As will be described later, when the ultrasonic motor 10 is properly assembled, the rigid support elements 58 are displaced in the direction in which the first or second attachment portions 36 and 38 approach the base material 32 with respect to the coupling portion 64. It is formed to be arranged (FIG. 2).
[0032]
The first and second attachment portions 36 and 38 of the both rigid support elements 58 have elongated hole insertion holes 66 for attaching the support spring member 34 to the base member 32 in the thickness direction (perpendicular to the paper surface). Direction). Further, each of the first and second attachment portions 36 and 38 has a protrusion extending linearly in parallel with the major axis of the bolt insertion hole 66 at a predetermined position on the surface facing the main surface 44a of the base member 32. Article 68 is projected. As will be described later, when the ultrasonic motor 10 is properly assembled, each protrusion 68 is slidably inserted into a corresponding groove 54 formed on the main surface 44a of the base 32. Each connecting portion 64 extends in a direction substantially parallel to the protrusion 68, and a female screw 70 is recessed at the end in the plate thickness direction (direction parallel to the paper surface).
[0033]
Each rigid support element 58 includes a female screw (not shown) in which a mounting bolt 72 inserted through the bolt insertion hole 66 of the first or second mounting portion 36 or 38 is recessed in the vicinity of the groove 54 on the main surface 44a of the base 32. It is attached to the base material 32 by screwing to the base material 32. Further, each rigid support element 58 has an adjustment bolt 74 (a component of an angle adjustment mechanism described later) inserted into the bolt insertion hole 60 a of each connection piece 60 of the leaf spring element 56 on the female screw 70 of the connection portion 64. The leaf spring element 56 is connected by screwing.
[0034]
The support spring member 34 having the above-described configuration is both rigid with the first and second mounting portions 36 and 38 facing outward (mutually separated side) on the inner side (mutually facing side) of both connecting pieces 60 of the leaf spring element 56. The leaf spring element 56 and both rigid support elements 58 are connected to each other using the adjusting bolt 74 in a state where the ends of the connection portions 64 of the support elements 58 are overlapped with each other, thereby symmetric about the intermediate fixing portion 40. It takes the form of a standard assembly. At this time, the leaf spring element 56 and the rigid support element 58 are accurately visually or using an appropriate gauge so that the former connecting piece 60 and the latter connecting portion 64 are linearly aligned with each other. Combined.
[0035]
As a characteristic configuration of the present invention, the pressing support structure 20 angularly adjusts the relative position between the preload adjusting mechanism 76 that adjusts the spring force of the support spring member 34 and the drive surface 12 and the movable body 18 of the vibrating body 14. And an angle adjustment mechanism 78 for performing the operation. The preload adjusting mechanism 76 is interposed between both the first and second mounting portions 36 and 38 of the support spring member 34 and the base 32, and the stationary base 32 of the first and second mounting portions 36 and 38. An attachment position adjusting member 50 that adjusts the attachment position with respect to is provided. In the illustrated embodiment, the attachment position adjusting member 50 includes a pair of adjustment screws (set screws) 50 that are screwed onto a female screw 52 formed on a pair of attachment bases 46 of the base material 32.
[0036]
The preload adjusting mechanism 76 includes the adjustment screw 50, the surfaces (upper end surfaces in the drawing) 36a and 38a of the first and second attachment portions 36 and 38 that contact the tips of both adjustment screws 50, and the first and second attachments. Long hole-shaped bolt insertion holes 66 and protrusions 68 provided on both the portions 36 and 38, a pair of mounting bolts 72 inserted into both bolt insertion holes 66, and a base material into which both protrusions 68 are fitted. 32 and a pair of grooves 54 on the main surface 44a, and the preload adjustment described later is performed in cooperation with them. The angle adjusting mechanism 78 includes a leaf spring element 56 and a pair of rigid support elements 58 of the support spring member 34, and a pair of adjustment bolts 74 that interconnect the leaf spring element 56 and both the rigid support elements 58. The angle adjustment which will be described later is performed by their cooperation.
[0037]
The component group of the ultrasonic motor 10 is assembled as follows.
The base material 32 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 30 of the movable body 18 in a non-contact manner. An adjustment screw 50 is screwed to each of the female bases 52 in a non-operating state so that the tip of the base screw 32 does not protrude outwardly from the internal thread 52. In addition, the vibrating body 14 in which the pair of piezoelectric elements 16 are joined to both the shoulder surfaces 22 has the driving surface 12 in contact with the surface region 30 at a substantially intermediate position between the both mounting bases 46 of the base material 32. Mounted on top.
[0038]
The support spring member 34 is in the form of the reference assembly described above, and the intermediate fixing portion 40 is fixed to the support portion 24 of the vibrating body 14 by the bolts 62, and the first and second attachment portions 36 and 38 are fixed to the base material 32. It arrange | positions at the lower side (side near the movable body 18) of both the attachment base parts 46, respectively. And if the protrusion 68 of the 1st and 2nd attachment parts 36 and 38 is inserted in the corresponding groove | channel 54 of the main part surface 44a of the base material 32, the long hole shape of the 1st and 2nd attachment parts 36 and 38 will be carried out. The bolt insertion hole 66 is substantially aligned with a female screw (not shown) formed in the main surface 44a.
[0039]
Therefore, the pair of mounting bolts 72 are respectively inserted into the bolt insertion holes 66 of the first and second mounting portions 36 and 38 and loosely screwed into the corresponding female screws, and the support spring member 34 is temporarily fastened to the base 32. To do. In this temporarily fastened state, the surfaces 36a, 38a of the first and second mounting portions 36, 38 of the support spring member 34 are preferably arranged in contact with the surface (lower end surface in the figure) of the corresponding mounting base 46. The Further, each of the first and second attachment portions 36 and 38 is moved by the elongated hole insertion hole 66 and the attachment bolt 72 while maintaining the engagement state between the protrusion 68 and the groove 54. Within the range, it is possible to move in a direction substantially parallel to the axis 14 a of the vibrating body 14.
[0040]
From this temporarily fixed state, the pair of adjusting screws 50 are further screwed into the female screws 52 of the corresponding mounting bases 46, and the tips of the adjusting screws 50 are connected to the first and second mounting portions of the support spring member 34. It is made to contact | abut to the surface 36a, 38a of 36,38. Then, by tightening the individual adjustment screws 50 with an appropriate torque, the first and second bases 32 are applied to the first and second attachment portions 36 and 38 while applying appropriate pressures from the adjustment screws 50 to the corresponding first and second attachment portions 36 and 38. The attachment positions of the second attachment portions 36 and 38 are displaced in a direction approaching the movable body 18. Thereby, the extension portion 42 of the support spring member 34 is bent with the intermediate fixing portion 40 as a fulcrum, and the extension portion 42 exerts a spring force balanced around the intermediate fixing portion 40. In this way, the drive surface 12 of the vibrating body 14 is brought into contact with the surface region 30 of the movable body 18 under an appropriate contact pressure due to the pre-adjusted spring force of the support spring member 34, and thus the ultrasonic motor. 10 assembly is completed.
[0041]
In the ultrasonic motor 10 assembled in this manner, the base material 32 is caused by the characteristic shape of the support spring member 34 in the pressing support structure 20 and the positional relationship between the mounting bases 46 of the base material 32 with respect to the vibrating body 14. The mounting position of the first and second mounting portions 36, 38 of the support spring member 34 to the support is located at the top end of the vibrating body 14 when viewed in the height direction of the vibrating body 14 with the drive surface 12 as the bottom. It is lower than the portion 24 and is disposed close to the movable body 18. That is, according to the pressing support structure 20, the fixed support portions at both ends of the extension portion 42 that exerts the spring force of the support spring member 34 are arranged at a height close to the drive surface 12 of the vibrating body 14, The vibrating body 14 is stably supported against an external force applied in the lateral direction to the lower region of the body 14 (that is, the region near the drive surface 12).
[0042]
Moreover, in the illustrated embodiment, the mounting positions of the first and second mounting portions 36 and 38 of the support spring member 34 to the base material 32 are viewed in the height direction of the vibrating body 14, and the supporting portion of the vibrating body 14 is supported. 24, the spring force applied to the vibrating body 14 vibrates in the direction of pressing the drive surface 12 against the surface region 30 of the movable body 18. The traction force attracts the body 14. As a result, the stable support effect for the vibrating body 14 is further improved. Further, the mounting positions of the first and second mounting portions 36 and 38 of the support spring member 34 to the base material 32 are arranged so as to be substantially symmetrically distributed in the moving direction of the movable body 18 with the vibrating body 14 as the center. . Therefore, the vibrating body 14 can be stably supported without being influenced by the moving direction of the movable body 18.
[0043]
Here, in the ultrasonic motor 10, it is assumed that the relative positional relationship between the vibrating body 14 and the movable body 18 slightly deviates from the normal positional relationship due to molding errors and assembly errors of various components. To do. In such a case, there is a concern that an imbalance of the spring force applied to the vibrating body 14 from the support spring member 34 occurs, and as a result, the support of the vibrating body 14 becomes unstable. In particular, in the joined body of the vibrating body 14 and the pair of excitation elements 16, the movable body related to the vibrating body axis 14 a due to the difference in the overall characteristics of the two excitation elements 16 and the structural non-uniformity of the vibrating body 14. If the structural symmetry in the moving direction is impaired, the drive surface 12 of the vibrating body 14 may have a motion deviating from the ideal elliptical motion in design. In such a case, when the drive direction of the movable body 18 is switched, there is a concern that a difference occurs in the moving speed of the movable body 18 depending on the drive direction.
[0044]
In response to the above-described problems, in the pressing support structure 20, the pair of adjusting screws 50 constituting the mounting position adjusting member of the preload adjusting mechanism 76 are individually tightened by an appropriate amount, whereby the base 32 is fixed. The attachment positions of the first and second attachment portions 36 and 38 of the support spring member 34 can be finely adjusted individually in a direction substantially parallel to the axis 14 a of the vibrating body 14. Therefore, even if the above-described structural error or the like is inherent in the ultrasonic motor 10, the fine adjustment operation of the pair of adjustment screws 50 is performed individually on both sides of the movable body moving direction around the vibrating body 14. The spring force due to the bending of the extended portion 42 of the extended support spring member 34 can be balanced around the intermediate fixing portion 40. As a result, according to the pressing support structure 20, the required preload for the movable body 18 is uniformly generated on the entire drive surface 12 of the vibrating body 14 regardless of the presence of structural errors, etc. Can be stably supported with respect to the movable body 18, and an ideal elliptical motion can be generated on the drive surface 12 of the vibrating body 14, thereby eliminating the movement speed difference depending on the drive direction of the movable body 18.
[0045]
On the other hand, due to the structural error described above, the contact state between the drive surface 12 of the vibrating body 14 and the surface region 30 of the movable body 18 is not an ideal uniform surface contact but a line contact. A close situation is also predicted. Specifically, as shown in FIG. 2, an assembly or molding error between the main portion 44 of the base material 32 and the mounting base portion 46, the first or second mounting portion of the support spring member 34 with respect to the main portion 44 of the base material 32. When the parallelism of the vibrating body 14 with respect to the main portion surface 44a is impaired due to an attachment error of 36, 38, an assembly error between the leaf spring element 56 and the rigid support element 58 in the support spring member 34, etc. The driving surface 12 of the body 14 and the surface region 30 of the movable body 18 form a “shift angle θ” and are in line contact with each other. Alternatively, the orthogonality between the main surface 44 a of the base material 32 and the surface region 30 of the movable body 18 is impaired due to an error in the positional relationship between the ultrasonic motor 10 and a machine base (not shown) or other external structure. When this occurs, a similar line contact state occurs.
[0046]
In response to such a problem, in the pressing support structure 20, the pair of adjustment bolts 74 constituting the angle adjustment mechanism 78 are temporarily loosened, and the leaf spring element 56 and the both rigid support elements 58 of the support spring member 34. By individually finely adjusting the relative positional relationship of each, the contact state between the drive surface 12 of the vibrating body 14 and the surface region 30 of the movable body 18 can be corrected to a uniform surface contact state. As a result, according to the pressing support structure 20, a predetermined indispensable for generating a frictional driving force between the driving surface 12 of the vibrating body 14 and the surface region 30 of the movable body 18 regardless of the presence of structural errors or the like. While maintaining the contact pressure, the elliptical motion of the drive surface 12 can be reliably transmitted to the movable body 18, thereby preventing a reduction in efficiency and instability of the drive force.
[0047]
As described above, in the ultrasonic motor 10, even when a structural error is inherent, the pressing support structure 20 is activated when the movable body 18 is driven by the fine adjustment of the preload adjusting mechanism 76 and the angle adjusting mechanism 78. Against the driving reaction force generated during driving or the like, the vibrating body 14 can be stably supported at a normal position in the motor structure, and an ideal elliptical motion is generated on the driving surface 12 of the vibrating body 14. It is possible to eliminate a difference in moving speed depending on the driving direction of the movable body 18, and it is possible to improve efficiency and stabilize driving force. In addition, in this configuration, the connecting portion of the vibrating body 14 and the support spring member 34 is disposed higher than the shoulder surface 22 of the vibrating body 14 that joins the piezoelectric element 16 (that is, further away from the driving surface 12). It is avoided that the pressing support structure 20 restrains the ultrasonic vibration of the vibrating body 14. Furthermore, both the preload adjusting mechanism 76 and the angle adjusting mechanism 78 are configured in a range that does not substantially exceed the outer dimensions of the component group necessary for the pressing support structure 20 to exhibit the original vibrating body pressing support function. Therefore, an increase in the size of the ultrasonic motor 10 is avoided. Therefore, according to the ultrasonic motor 10, while maintaining the small and thin features, the influence of the structural error on the driving characteristics is positively corrected, and excellent control responsiveness is highly reliable. Can be realized.
[0048]
In the ultrasonic motor 10 according to the present invention, in addition to (or instead of) the characteristic configuration of the pressing support structure 20 described above, the following various measures are taken to improve efficiency and driving characteristics. Can do.
[0049]
As one measure, in the joined body of the vibrating body 14 and the pair of excitation elements 16, a difference in overall characteristics (electrostrictive characteristics, bonding state, etc.) of both the excitation elements 16, the structure of the vibrating body 14 itself. A method for adjusting the elliptical motion of the drive surface 12 when non-uniformity or asymmetry is inherent is proposed. Here, as schematically shown in FIG. 3, due to such a structural error or the like, the movable body 18 is caused by causing an elliptical motion in the counterclockwise direction in the drawing on the driving surface 12 of the vibrating body 14. Is considered to be the case where the elliptical motion is in an inclined state (solid line) deviating from the ideal state (dashed line) (FIG. 3 (a)). Since the distance from the excitation element 16 to the driving surface 12 of the vibrating body 14 changes along the moving direction of the movable body 18 on the driving surface 12, the locus of elliptical motion at various points on the driving surface 12 as shown in the figure. Is different. While maintaining the structure in which this error and the like remain, the phases of the pair of excitation elements 16 are reversed, and the elliptical motion in the clockwise direction is caused on the driving surface 12 of the vibrating body 14 to move the movable body 18 leftward in the drawing. When driving to the elliptical state, the elliptical motion is apparently inclined in the same direction as that when driving in the right direction (solid line) (FIG. 3B). Such inclined elliptical motion of the drive surface 12 acts as if the movable body 18 moving in the left direction is braked, and as a result, the leftward movement speed of the movable body 18 is slower than the rightward movement speed. .
[0050]
Here, when the frequency of the high frequency voltage applied to the pair of excitation elements 16 is slightly changed from the resonance frequency, the locus of the elliptical motion at a point away from the center point of the drive surface 12 varies accordingly. Focusing on this phenomenon, in addition to (or instead of) the mechanical structural fine adjustment by the preload adjusting mechanism 76 described above when the tilted elliptical motion described above is generated on the drive surface 12 of the vibrating body 14, the drive is performed. By performing fine adjustment of the frequency, the tilted elliptical motion of the drive surface 12 of the vibrating body 14 can be appropriately corrected. And it became clear by experiment of this inventor that the left-right moving speed difference of the movable body 18 can be reduced by such fine adjustment of the drive frequency.
[0051]
As another measure, a structural condition of the vibrating body 14 for efficiently causing the drive surface 12 of the vibrating body 14 to elliptically move is proposed. Here, as schematically shown in FIG. 4, the dimension W1 along the moving body moving direction of the driving surface 12 of the vibrating body 14, the dimension W2 in the width direction (direction parallel to the paper surface) of the excitation element 16, and the vibration The angle α formed by the center line 14a of the body 14 and the center line 16a of the excitation element 16 and the length L of the propagation path of the ultrasonic wave propagating from the excitation element 16 to the vibrating body 14 will be considered. As shown in the figure, while the wave V generated by the excitation element 16 propagates through the main body portion 14b of the vibrating body 14 and reaches the driving surface 12, the main component of the wave V is vibrated under the following conditions. The shape and dimensions of the body 14 are designed.
[0052]
(1) W1 ≦ W2 / cosα
(2) L≈n · λ / 4 (n is a natural number)
Wavelength V of wave V = v / f (v is the speed of sound of vibrating body 14, and f is the resonance frequency of vibrating body 14).
(3) Number of reflections of wave V: once or twice
[0053]
FIG. 4A shows the vibrating body 14 designed to satisfy the above-described conditions 1 and 2 with the number of reflections of the wave V being one, and FIG. The vibrators 14 designed to satisfy the conditions 1 and 2 are shown respectively. It has been found by experiments of the present inventor that the vibration body 14 having such a configuration improves the efficiency of the ultrasonic motor 10 and improves the stability and responsiveness of driving. Note that the efficiency tended to decrease as the propagation path length L increased and the number of reflections increased.
[0054]
5 to 7 show a positioning device 80 according to an embodiment of the present invention that employs the above-described ultrasonic motor 10 as a drive unit. The positioning device 80 includes a first base 82 including the base material 32 of the ultrasonic motor 10, a second base 84 including the movable body 18 of the ultrasonic motor 10, and the first and second bases. 82 and 84 are supported by each other so that they can move relative to each other and linearly guide 86, and a position detection mechanism 88 that detects the relative positions of the first and second bases 82 and 84. The
[0055]
The first base 82 is a rectangular flat plate-shaped fixed base member, a part of which acts as the base material 32 of the ultrasonic motor 10, and the ultrasonic motor 10 is installed at a predetermined position on the surface 82a. A pair of mounting bases 46 are provided upright. As described above, the fixed base component group of the ultrasonic motor 10 is attached to these attachment bases 46 via the support spring members 34 of the pressing support structure 20. In addition, a pair of edge walls 90 on which the linear guide 86 is installed project from the surface 82a of the base 82 along both edges extending in the longitudinal direction. Further, an opening 92 having a substantially rectangular planar shape as an installation region of the position detection mechanism 88 passes through the base 82 in the thickness direction, adjacent to one mounting base 46 outside the installation region of the ultrasonic motor 10. It is formed. The pair of attachment bases 46 and the openings 92 are both disposed in the region between the two edge walls 90.
[0056]
The second base 84 is a rectangular flat plate-shaped moving stage member, and the movable body 18 of the ultrasonic motor 10 is fixedly installed at a predetermined position on one surface 84a thereof. The movable body 18 may be formed integrally with the base 84 using the same material as the base 84, or may be configured such that the separate movable body 18 is integrally fixed to the base 84. In addition, a pair of edge walls 94 on which the linear guide 86 is installed project from the surface 84a of the base 84 along both edges extending in the longitudinal direction. Further, a linear scale 96 that is spaced apart from the movable body 18 and extends in parallel with the movable body 18 is fixed to the surface 84 a of the base 84. Both the movable body 18 and the linear scale 96 are disposed in a region between both edge walls 94. Note that the first and second bases 82 and 84 are both made of a material having high rigidity such as metal or resin.
[0057]
The first base 82 and the second base 84 have their surfaces 82 a and 84 a facing each other, and both edge walls 90 of the base 82 are positioned inside both edge walls 94 of the base 84. Are combined in a complementary manner. In this state, an apparatus internal space 98 for accommodating the ultrasonic motor 10 and the position detection mechanism 88 is formed between the bases 82 and 84. The linear guide 86 is composed of a pair of cross roller guides 86 in the illustrated embodiment, and is interposed between the outer surface of both edge walls 90 of the base 82 and the inner surface of both edge walls 94 of the base 84, respectively. The base 84 is smoothly guided on the base 82 so as to be capable of linear reciprocation under a given load.
[0058]
The position detection mechanism 88 includes an optical position sensor 100 installed in the opening 92 of the base 82 and a linear scale 96 fixed to the surface 84 a of the base 84. The position sensor 100 is fixed to the base 82 using a fixture 102 having an L-shaped cross section. The signal line 104 of the position sensor 100 is led out from the longitudinal end of the base 82 together with the control line 106 of the ultrasonic motor 10 to the outside of the positioning device 80 and connected to a control device (not shown).
[0059]
In a state where the bases 82 and 84 are appropriately combined, the drive surface 12 of the vibration body 14 of the ultrasonic motor 10 installed on the base 82 is pressed and supported on the surface region 30 of the movable body 18 installed on the base 84. The contact is made under a predetermined preload by the structure 20. In addition, the linear scale 96 installed on the base 84 is arranged in a non-contact manner at a predetermined position that enables a position detection operation with respect to the position sensor 100 installed on the base 82.
[0060]
The positioning device 80 having the above configuration stabilizes the moving operation of the second base 84 serving as a stage by adopting the ultrasonic motor 10 as the driving unit, improves its positioning accuracy, and reciprocating movement speed difference. Can be eliminated. In addition, since both the ultrasonic motor 10 and the position detection mechanism 88 are accommodated in the apparatus internal space 98 defined between the first and second bases 82 and 84, the protruding portion exceeding the stage area is substantially free. Therefore, the positioning device 80 can be reduced in size and thickness. In addition, the positioning device 80 according to the present embodiment realizes a stroke S = 100 mm, a height H = 16 mm, and a maximum transport load 5 kg.
[0061]
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 pressing support structure, which is a characteristic component of the ultrasonic motor according to the present invention, can be applied to a configuration having variously-shaped vibrating bodies and variously arranged excitation elements, which are known in the field of ultrasonic motors. Equivalent effects are obtained. The attachment position adjusting member of the preload adjusting mechanism is interposed between at least one of the first and second attachment portions of the support spring member and the base material, and is attached to at least one of the first and second attachment portions. If it is configured so as to adjust, it is expected that the same effects can be obtained. Furthermore, 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.
[0062]
Note that the ultrasonic motor according to the present invention can be provided even in a configuration that does not include a movable body. In this case, the pressing support structure includes a supporting spring member that exerts a spring force that presses the driving surface against the driven object while supporting the vibrating body on the substrate, and a preload adjusting mechanism that adjusts the spring force of the supporting spring member. It is configured with.
[0063]
【The invention's effect】
As is apparent from the above description, according to the present invention, in the ultrasonic motor having a pressing support structure, a predetermined contact pressure is maintained between the driving surface of the vibrating body and the surface of the movable body, and Without restraining the excited ultrasonic vibration, the vibration body can be stably supported at the normal position in the motor structure, and the support of the vibration body is unstable due to structural errors, Various problems such as a decrease in efficiency, instability of driving force, and generation of a speed difference associated with switching of driving directions can be solved. Therefore, according to the present invention, the excellent control response of the ultrasonic motor can be realized with high reliability.
[0064]
Furthermore, according to the present invention, in a positioning device that employs an ultrasonic motor in the drive unit, the stage movement operation can be stabilized, positioning accuracy can be improved, and a reciprocating speed difference can be eliminated. Thinning becomes easy.
[Brief description of the drawings]
FIG. 1 is a front view of an ultrasonic motor according to an embodiment of the present invention.
2 is a side view showing the ultrasonic motor of FIG. 1 from the direction of arrow II. FIG.
FIGS. 3A and 3B are diagrams showing elliptical motion of a drive surface in the ultrasonic motor of FIG. 1, showing respective states during (a) right-hand drive and (b) left-hand drive.
4 is a diagram showing a wave propagation state in the ultrasonic motor of FIG. 1, showing (a) one-time reflection and (b) two-time reflection states.
FIGS. 5A and 5B are views of a positioning device according to an embodiment of the present invention, in which FIG. 5A is a partially cutaway plan view, and FIG. 5B is a front view.
6 is a cross-sectional view of the positioning device of FIG. 5 along line VI-VI.
7 is a cross-sectional view of the positioning device of FIG. 5 along line VII-VII.
[Explanation of symbols]
10 ... Ultrasonic motor
12 ... Drive surface
14 ... Vibrating body
16 ... Excitation element
18 ... Movable body
20 ... Pressing support structure
26 ... friction material
30 ... surface area
32. Base material
34 ... Supporting spring member
36: First mounting portion
38 ... Second mounting portion
40. Intermediate fixing part
42 ... Extension
46: Mounting base
50 ... Adjustment screw
54 ... Groove
56. Leaf spring element
58 ... Rigid support element
72 ... Mounting bolt
74 ... Adjustment bolt
76 ... Preload adjustment mechanism
78 ... Angle adjustment mechanism
80 ... Positioning device
82. First base
84 ... Second base
86 ... Linear guide
88 ... Position detection mechanism
92 ... opening
96 ... Linear scale
98 ... Internal space of the device
100: Position sensor

Claims

A vibrating body having a driving surface, an excitation element that excites the vibrating body, a movable body that is disposed in contact with the driving surface of the vibrating body and moves relative to the vibrating body in accordance with vibrations of the vibrating body; A pressing support structure that supports the vibrating body in a state in which the driving surface is pressed against the movable body, and the pressing support structure is disposed between the base material and the base material and the vibrating body, A support spring member that exerts a spring force that presses the drive surface against the movable body while supporting the vibrating body on the base material, and a preload adjusting mechanism that adjusts the spring force of the support spring member. In the ultrasonic motor
The support spring member includes a first attachment portion and a second attachment portion that are attached to the base material, and an intermediate fixing portion that is positioned between the first and second attachment portions and fixedly connected to the vibrating body. And an extension portion extending between the first and second attachment portions and the intermediate fixing portion to generate the spring force, and the first and second of the support spring member to the base member The mounting position of the mounting portion is lower than the top end of the vibrating body when viewed in the height direction of the vibrating body with the drive surface as the bottom, and is disposed close to the movable body,
The preload adjusting mechanism is interposed between at least one of the first and second mounting portions of the support spring member and the base material, and sets the mounting position of at least one of the first and second mounting portions. Including a mounting position adjusting member to be adjusted;
Ultrasonic motor characterized by

The mounting positions of the first and second mounting portions of the support spring member are distributed substantially symmetrically in the moving direction of the movable body around the vibrating body, and the mounting position adjusting member includes The superposition according to claim 1, wherein the mounting position of at least one of the first and second mounting portions is adjusted to uniformly generate a required preload for the movable body on the entire drive surface of the vibrating body. Sonic motor.

The ultrasonic motor according to claim 1, wherein the pressing support structure further includes an angle adjustment mechanism that angularly adjusts a relative position between the driving surface of the vibrating body and the movable body.

A positioning device incorporating the ultrasonic motor according to claim 1.

A first base including the base material of the ultrasonic motor, a second base including the movable body of the ultrasonic motor, and the first and second bases are mutually supported to be relatively movable. And a linear guide that linearly guides each other and a position detection mechanism that detects the relative positions of the first and second bases, and the first and second bases are provided in the internal space of the apparatus. The positioning device according to claim 4, wherein the ultrasonic motor and the position detection mechanism are both housed in the internal space of the device.

A vibration body having a driving surface; an excitation element that excites the vibration body; and a pressing support structure that supports the vibration body in a state where the driving surface of the vibration body is pressed against a driven object. The support structure is a support spring that is disposed between the base material and the base material and the vibrating body, and exerts a spring force that presses the driving surface against the driven object while supporting the vibrating body on the base material. In an ultrasonic motor comprising a member and a preload adjusting mechanism for adjusting the spring force of the support spring member,
The support spring member includes a first attachment portion and a second attachment portion that are attached to the base material, and an intermediate fixing portion that is positioned between the first and second attachment portions and fixedly connected to the vibrating body. And an extension portion extending between the first and second attachment portions and the intermediate fixing portion to generate the spring force, and the first and second of the support spring member to the base member The mounting position of the mounting portion is lower than the top end of the vibrating body when viewed in the height direction of the vibrating body with the driving surface as the bottom, and is disposed close to the driven object,
The preload adjusting mechanism is interposed between at least one of the first and second mounting portions of the support spring member and the base material, and sets the mounting position of at least one of the first and second mounting portions. Including a mounting position adjusting member to be adjusted;
Ultrasonic motor characterized by