JP4113732B2

JP4113732B2 - Air bearing

Info

Publication number: JP4113732B2
Application number: JP2002162966A
Authority: JP
Inventors: 久嘉境
Original assignee: Mitutoyo Corp
Current assignee: Mitutoyo Corp
Priority date: 2002-06-04
Filing date: 2002-06-04
Publication date: 2008-07-09
Anticipated expiration: 2022-06-04
Also published as: JP2004011686A

Description

【０００１】
【発明の属する技術分野】
本発明は空気軸受、特にそのロック機構の改良に関する。
【０００２】
【従来の技術】
従来より、例えば三次元測定機等の測定機器、非球面加工機や半導体製造装置等の超精密加工機等の送り装置の案内機構には、静圧スラスト空気軸受が多用されている。
この静圧空気軸受は、可動部を他から供給された圧縮空気の力で基部より浮かせることにより、該基部と可動部間の摩擦を小さくしている。
【０００３】
【発明が解決しようとする課題】
ところで、例えば前述のような送り装置等の案内機構においては、非常に高い位置決め精度が要求される。
しかしながら、前記案内機構に用いられる静圧空気軸受は、非接触であるため、基部と可動部間に摩擦力が作用しない。このため、静圧空気軸受では、振動等の外乱により、少なくとも位置検出単位分の位置決め誤差を発生し、位置検出単位以下の静止は難しい。
したがって、静圧空気軸受では位置決め精度の改善が急務であり、従来は、例えば空気軸受に摩擦部材を設ける技術（例えば特開昭６０−４５６２６号等）、空気軸受への圧縮空気の供給を遮断し基部と可動部を接触させる技術（例えば特開平４−２８５８０９号、特許２９８７５１７号等）等を用いることが考えられる。
【０００４】
しかしながら前記特開昭６０−４５６２６号等の技術は、振動等の外乱により、ロック指令後に可動部の位置が変動することがあるので、採用するには至らなかった。
また前記特開平４−２８５８０９号、特許２９８７５１７号等は、基部に対する可動部の位置及び姿勢変化の低減に関しては、より一層の改善が望まれていた。
本発明は前記従来技術の課題に鑑みなされたものであり、その目的は基部に対する可動部の特定部位の位置及び姿勢を変えることなく、基部に対し可動部をしっかりとロックすることのできる空気軸受を提供することにある。
【０００５】
【課題を解決するための手段】
前記目的を達成するために本発明にかかる空気軸受は、基部と、可動部と、浮上用圧縮空気供給手段と、を備えた空気軸受において、チャンバと、静止用圧縮空気供給手段と、を備える。そして、前記基部に対する可動部の静止を指示するロック指令により、前記浮上用圧縮空気供給手段による基部と可動部間への浮上用圧縮空気供給の解除と、前記静止用圧縮空気供給手段によるチャンバ内への静止用圧縮空気の供給を行い、
前記浮上用圧縮空気供給の解除により消失する前記基部と可動部間の空気膜の厚みと同じ量だけ、前記ダイアフラム外壁の特定部位を空気膜の厚み増大方向に変形させることにより、前記基部に対するダイアフラム外壁の特定部位の位置及び姿勢を変えることなく、前記基部と可動部を接触させ、該接触により生じる摩擦力により、前記基部に対する可動部の静止を行うことを特徴とする。
【０００６】
ここで、前記可動部は、該基部に空気膜を介して支持され、該基部に対し相対運動可能とする。
また前記浮上用圧縮空気供給手段は、前記基部と可動部間に前記空気膜を形成する浮上用圧縮空気を供給する。
前記チャンバは、前記可動部の空気膜と接する面と反対側の背面に設けられ、少なくともダイアフラムにより構成され、静止用圧縮空気が供給されると、ダイアフラム外壁の特定部位を空気膜の厚みの増大方向に変形させる。
前記静止用圧縮空気供給手段は、前記チャンバ内に前記静止用圧縮空気を供給する。
【０００７】
ここにいう軸受とは、回転運動等の特定の運動に限定されるものではなく、直線運動、揺動等の基部に対し可動部が相対運動可能なものに対し適用できるものをいう。
ここにいう可動部の空気膜と接する面と反対側の背面に設けられ、少なくともダイアフラムにより構成されるとは、可動部の背面とダイアフラムによりチャンバを構成すること、可動部の背面に既にチャンバを構成しているダイアフラムを設けること等を含めていう。
ここにいうダイアフラム外壁の特定部位とは、ダイアフラム外壁そのもの、ダイアフラム外壁の特定部位に支持されるものを含めていう。
【０００８】
なお、本発明において、前記浮上用圧縮空気供給手段は、前記圧縮空気の供給源よりの圧縮空気を浮上用圧縮空気として前記基部と可動部間に供給する浮上用給気管を含み、前記静止用圧縮空気供給手段は、前記圧縮空気の供給源よりの圧縮空気を静止用圧縮空気として前記チャンバに供給する静止用給気管を含み、また制御弁を備えることが好適である。
ここで、前記制御弁は、前記供給源と前記各給気管の間に設けられ、前記ロック指令により、前記浮上用給気管による浮上用圧縮空気の供給の解除と、前記静止用給気管による静止用圧縮空気の供給を行う。
【０００９】
ここにいう圧縮空気の供給源は、浮上用圧縮空気供給手段と、静止用圧縮空気供給手段が共通の供給源を用いること、別個の供給源を用いることを含めていう。なお、本発明において、前記制御弁の後段に設けられ、前記ロック指令における前記チャンバ内の静止用圧縮空気の圧力が所定の値となるように前記静止用給気管を介して前記チャンバ内に供給される静止用圧縮空気の圧力の調整を行う静止用レギュレータあるいは、前記ロック指令解除時における前記空気膜の厚みが所定の値となるように前記浮上用給気管を介して前記浮上用圧縮空気の圧力の調整を行う浮上用レギュレータの少なくとも何れかを更に備えることが好適である。
【００１０】
ここで、レギュレータは、制御弁が供給・解除に限らず、弁の開度を制御して圧力調整を行えるものであれば、この制御弁に換えることも含む。
また本発明においては、前記ダイアフラム外壁の特定部位と前記基部との距離を測定するセンサと、このセンサの出力によって前記レギュレータを制御する制御回路を更に備え、前記ロック指令の有無に拘わらず、前記特定部位と前記基部との距離が常に一定になるようにレギュレータを制御することが好適である。
【００１１】
さらに本発明においては、静止制御用メモリと、ダイアフラム制御情報取得手段と、レギュレータと、を備えることが好適である。
ここで、前記静止制御用メモリは、予め得ておいた少なくともチャンバ内での静止用圧縮空気の圧力と、該圧力での前記ダイアフラム外壁の特定部位の空気膜の厚み方向の変形量との関係を記憶している。
【００１２】
また前記ダイアフラム制御情報取得手段は、前記ロック指令により、前記浮上用圧縮空気供給の解除により消失する前記基部と可動部間の空気膜の厚みに対応する静止用圧縮空気の圧力の値を静止制御用メモリより求める。
前記レギュレータは、前記制御弁の後段に設けられ、前記チャンバ内での静止用圧縮空気の圧力が、前記ダイアフラム制御情報取得手段により求めた圧力の値となるように、前記静止用給気管を介して前記チャンバ内に供給される静止用圧縮空気の圧力の調整を行う。
【００１３】
さらに本発明において、前記圧縮空気供給手段は、前記可動部の空気膜と接する面に凹状に窪んで形成された圧縮空気供給溝を更に含み、また圧縮空気排気溝と、圧縮空気排気穴と、排気管と、を更に備え、前記浮上用圧縮空気を回収することが好適である。
ここで、前記圧縮空気排気溝は、前記圧縮空気供給溝の外側に前記浮上用圧縮空気を回収する凹状に窪んで形成されている。
【００１４】
また前記圧縮空気排気穴は、前記圧縮空気排気溝の壁面に開口されて前記回収された浮上用圧縮空気を排気する。
前記排気管は、前記圧縮空気排気穴と前記回収された浮上用圧縮空気を吸引する吸引手段とを接続する。
また本発明においては、前記圧縮空気排気溝の外周側に連続的に配置されかつ前記可動部の空気膜と接する面と略同一面上に配置された外周抵抗部を更に備えていることが好適である。
【００１５】
【発明の実施の形態】
以下、図面に基づき本発明の好適な一実施形態について説明する。
【００１６】
図１（Ａ）には本発明の一実施形態にかかる空気軸受を用いた送り装置の案内機構の概略構成が示されており、同図（Ｂ）には空気軸受本体を軸受面より見た図である。
同図に示すロック機構付き空気軸受（空気軸受）１０は、三次元測定機のＸ軸ガイド機構、Ｙ軸ガイド機構、Ｚ軸ガイド機構にそれぞれ設けられた静圧スラスト空気軸受の一例であり、案内面（基部）１２と、スライダ（可動部）１４と、空気軸受本体１６と、浮上用圧縮空気供給手段１８と、静止用圧縮空気供給手段２０を備える。
【００１７】
前記空気軸受本体１６は、チャンバ２２を構成するダイアフラム２４が設けられる。
前記浮上用圧縮空気供給手段１８は、圧縮空気供給源２６と、空気軸受側圧縮空気供給配管（浮上用給気管）２８と、空気軸受本体１６の空気軸受側圧縮空気供給通路３０を含む。
前記静止用圧縮空気供給手段２０は、前記圧縮空気供給源２６と、ロック機構側圧縮空気供給配管（静止用給気管）３２と、空気軸受本体１６のロック機構側圧縮空気供給通路３４を含む。
前記案内面１２は、三次元測定機のテーブル（図示省略）に設けられ、前記空気軸受本体１６は前記ガイド機構のスライダ（可動部）１４の下方に設けられている。
【００１８】
そして、本実施形態においては、スライダ１４は、例えばＹ軸ガイド機構であり、モータ等の駆動源３６よりの駆動力が、ボールねじ等の送り機構３８を介してスライダ１４に伝達されており、スライダ１４の運動は案内面１２により例えばＹ軸方向等の特定の方向に規定されている。
案内面１２上に空気膜３６を介して空気軸受本体１６が設けられ、該空気軸受本体１６の背面に、空気軸受本体１６の背面と共にチャンバ２２を構成するダイアフラム２４が設けられている。ダイアフラム２４上部の略中央（ダイアフラムの中心軸上）及びスライダ１４下部には、それぞれ剛球４０を設けるための穴４２，４４が設けられている。該剛球４０を介してダイアフラム２４上部の略中央にスライダ１４下部が支持されている。
【００１９】
本実施形態においては、ダイアフラム２４上壁の中央部をダイアフラム２４外壁の特定部位とすることもできるが、剛球４０の略中心も、ダイアフラム２４上壁の中央部の機能と等価であるので、剛球４０の略中心をダイアフラム２４外壁の特定部位としている。
該スライダ１４のダイアフラム２４中心軸上には、スライダ１４下面とダイアフラム２４上面間の離隔距離を調整する調整ねじ４６を設けるための穴４８が設けられており、該調整ねじ４６の先端部と剛球４０が当接している。調整ねじ４６の先端部と対向する頭部側はスライダ１４の上方よりナット５０が設けられており、該ナット５０によりスライダ１４の下面に剛球４０を介して空気軸受本体１６がしっかりと設けられている。ダイアフラム２４の中心軸に沿って、該スライダ１４、該スライダ１４により移動する門柱等（図示省略）の加重Ｗがかかっている。
【００２０】
空気軸受本体１６は、側壁より空気軸受側圧縮空気供給通路３０の入口３０ａが開口し、下壁より出口３０ｂが開口している。
また空気軸受本体１６は、空気軸受側圧縮空気供給通路３０と独立しているロック機構側圧縮空気供給通路３４が設けられており、側壁よりその入口３４ａが開口し、ダイアフラム２４と空気軸受本体１６背面により気密に構成されるチャンバ２２と対向する空気軸受本体１６背面より、その出口３４ｂが開口している。
またロック機構付き空気軸受１０は、制御弁５２と、レギュレータ５３と、コンピュータ５４を備える。
【００２１】
制御弁５２は少なくとも３ポート５６ａ，５６ｂ，５６ｃを備えており、前記圧縮空気供給源２６と制御弁５２の第三ポート５６ｃ間は主配管５８で接続されている。
前記制御弁５２の第一ポート５６ａと空気軸受本体１６の空気軸受側圧縮空気供給通路３０の入口３０ａ間は、空気軸受側圧縮空気供給配管２８で接続されている。
前記制御弁５２の第二ポート５６ｂと空気軸受本体１６のロック機構側圧縮空気供給通路３４の入口３４ａの間は、前記空気軸受側圧縮空気供給配管２８と独立しているロック機構側圧縮空気供給配管３２で接続されている。
前記制御弁５２とコンピュータ５４間は信号線６０で接続されている。
【００２２】
そして、コンピュータ５４より、浮上を指示する制御信号が制御弁５２に送られると、制御弁５２は、第一ポート５６ａを開の状態とし、第二ポート５６ｂを閉の状態とする。
すると、圧縮空気供給源２６よりの圧縮空気は、主配管５８、制御弁５２の第一ポート５６ａ、空気軸受側圧縮空気供給配管２８を介して、空気軸受本体１６の入口３０ａより、空気軸受側圧縮空気供給通路３０に供給され、空気軸受本体１６の軸受面１６ａより開口している出口３０ｂより案内面１２に向けて供給される。
【００２３】
空気軸受本体１６の軸受面１６ａの出口３０ｂより供給された圧縮空気の力で、案内面１２に対し空気軸受本体１６を浮かせている。
同図では、前記空気膜３６による案内面１２より空気軸受本体１６の軸受面１６ａまでの軸受すきまをｈとし、案内面１２より剛球中心４０までの軸受支持高さをＨとしている。
このように空気軸受１０を構成することにより、案内面１２と空気軸受本体１６の軸受面１６ａ間の始動摩擦ないし移動摩擦を小さくしており、スライダ１４を例えばＹ軸方向にスムースに移動することができる。
【００２４】
ところで、例えば三次元測定機等の測定機器、非球面加工機や半導体製造装置等の超精密加工機の送り装置の案内機構においては、非常に高い位置決め精度が要求される。
このために、例えばボールねじ駆動等においては、モータ軸をメカニカルに固定することが一般的に考えられるが、モータ軸から先のカップリング、ボールねじ、ボールナット、スライダとのジョイント部等がばね要素であり、振動等の外乱により弾性変形を生じ、スライダの位置の変動を生じることがある。
【００２５】
また従来は、位置決め完了後、空気軸受への圧縮空気を遮断し、スライダの軸受面と案内面とを接触させ、摩擦を生じさせることにより、スライダの完全静止状態を得ることが考えられる。この方法ではスライダの完全静止状態が得られる点では非常に優れているが、空気軸受への圧縮空気供給遮断前に形成されていた空気膜の消失に起因し、スライダの幾何位置、幾何姿勢を大きく崩してしまうので、この点はまだまだ改善の余地が残されていた。
そこで、本発明において特徴的なことは、軸受が支持するスライダの位置及び姿勢を損なうことなく、軸受面と案内面を接触させ、該軸受面と案内面間の接触により生じる摩擦力により、スライダを完全静止させたことである。
【００２６】
このために本実施形態においては、同図に示すように空気軸受本体１６に、ダイアフラム２４と、ロック機構側圧縮空気供給通路３４を設けている。またロック機構側圧縮空気供給通路３４の入口３４ａに、空気軸受側圧縮空気供給配管２８と独立しているロック機構側圧縮空気供給配管３２を設けている。
そして、図２に示すようにコンピュータ５４より、静止を指示する制御信号（ロック指令）が制御弁５２に送られると、制御弁５２は、第一ポート５６ａを閉の状態とし、第二ポート５６ｂを開の状態とする。
【００２７】
すると、前記静止を指示する制御信号（ロック指令）の直前まで、前記軸受面１６ａの出口３０ｂより案内面１２に向けて供給されていた圧縮空気供給が解除され、これにより圧縮空気により形成されていた空気膜が消失する。これにより空気軸受本体１６の軸受面１６ａが案内面１２と接触し、該軸受面１６ａと案内面１２との接触により生じる摩擦力により、スライダ１４を静止させる。
ここで、前記浮上用圧縮空気供給の解除と同時に、圧縮空気供給源２６よりの圧縮空気は、主配管５８、制御弁５２の第二ポート５６ｂ、ロック機構側圧縮空気供給配管３２を介して、空気軸受本体１６の入口３４ａより、ロック機構側圧縮空気供給通路３４に供給され、空気軸受本体１６の背面に開口している出口３４ｂよりチャンバ２２内に供給される。
【００２８】
チャンバ２２内に供給された圧縮空気の力で、ダイアフラム２４は上方（図中矢印＋Ｚ方向）に撓む。
同図では、前記ダイアフラム２４のたわみ量δを、前記図１に示した軸受すきまｈと同じとし、案内面１２より剛球４０中心までの軸受支持高さＨが、前記図１に示した浮上時の軸受支持高さＨと同じ高さとしている。
【００２９】
このように本実施形態においては、本来はスライダ１４の移動方向（Ｙ軸方向）には拘束力を持たない静圧スラスト空気軸受１６の背面に、軸受面１６ａへの給気とは独立した給気配管系統であるロック機構側圧縮空気供給配管３２をもつダイアフラム２２により構成されるチャンバ２２を設けている。
そして、スライダ１４に対するコンピュータ５４等の制御系よりの位置決め指令に対して、前記駆動源３６に停止命令を出すと共に、前記チャンバ２２への圧縮空気供給と空気軸受本体１６への圧縮空気供給の解除を行っている。
【００３０】
このとき、静圧スラスト空気軸受本体１６の軸受面１６ａと案内面１２との間に形成されていた空気膜が消失し、一方、チャンバ２２に圧縮空気が供給されることにより、消失前に形成されていた空気膜と同じ厚さ分のダイアフラム２４の変形を生じさせている。
したがって、空気軸受本体１６が支持するスライダ１４の幾何位置及び幾何姿勢を保持したまま、軸受面１６ａと案内面１２との接触を行い、その接触により生じる摩擦力が案内面１２に対するスライダ１４のＹ軸方向への相対移動を規制することができる。
【００３１】
＜制御弁＞
ところで、空気軸受では、スライダの完全静止状態をより簡易に実現することが重要である。
そこで、本発明において特徴的なことは、スライダの完全静止状態を簡易に実現するために、軸受面への圧縮空気供給の解除と前記チャンバへの圧縮空気供給を、軸受への配管の途中に設けられた制御弁に対する制御指令により行ったことである。
このために本実施形態においては、前述のように制御弁５２と、コンピュータ５４を備えている。そして、コンピュータ５４よりの制御指令により、制御弁５２の第一ポート５６ａ、第二ポート５６ｂの開閉制御を行っており、前記軸受面１６ａへの圧縮空気供給解除と、チャンバ２２への圧縮空気供給が、より簡易に行える。これにより前記スライダ１４の静止がより簡易に行える。
【００３２】
＜レギュレータ＞
前記静止時の、軸受１６が支持するスライダ１４の幾何位置、幾何姿勢の変化をより小さくするためには、ダイアフラム２４のたわみ量δが、浮上用圧縮空気供給により形成されていた空気膜（軸受すきまｈ）と同じ厚さ分となるように、チューニングする必要がある。
そこで、本実施形態においては、チューニング用レギュレータ５３と、コンピュータ５４を備え、前記ダイアフラム２４のたわみ量（変形量）δのチューニングを、ダイアフラム２４の形状とチャンバ２２に供給される圧力により行っている。
【００３３】
チューニング用レギュレータ５３は、制御弁５２の第二ポート５６ｂとロック機構側圧縮空気供給配管３２の間に設けられている。チューニング用レギュレータ５３は制御弁５２と信号線６２で接続され、またコンピュータ５４と信号線６４で接続されている。
前記コンピュータ５４は、メモリ６６と、ＣＰＵ（ダイアフラム制御情報取得手段）６８を備え、メモリ６６は浮上制御用メモリ７０と、静止制御用メモリ７２を備える。
前記浮上制御用メモリ７０は、予め得ておいた案内面１２と軸受面１６ａ間の浮上用圧縮空気の圧力と、該圧力での案内面１２と軸受面１６ａ間の空気膜の厚み（軸受すきまｈ）の関係を記憶している。
前記静止制御用メモリ７２は、予め得ておいたチャンバ２２内の静止用圧縮空気の圧力と、該圧力でのダイアフラム２４のたわみ量δの関係を記憶している。
【００３４】
ＣＰＵ６８は、前記静止を指示する制御信号（ロック指令）により、該静止指示の制御信号直前に案内面１２と軸受面１６ａ間に供給されていた浮上用圧縮空気の圧力に対応する空気膜の厚み（軸受すきまｈ）を浮上制御用メモリ７０より求める。該求めた空気膜の厚みに対応する静止用圧縮空気の圧力の値を静止制御用メモリ７２より求める。
そして、ＣＰＵ６８は、制御弁５２よりチャンバ２２内に供給される静止用圧縮空気圧が、静止制御用メモリ７２より求めた静止用圧縮空気圧となるように、チューニング用レギュレータ５３に指示を出す。
チューニング用レギュレータ５３は、制御弁５２よりチャンバ２２への圧縮空気の供給量を流路の開度等により調整することにより、チャンバ２２への静止用圧縮空気の圧力の値が、ＣＰＵ６８よりの指示値となるように調整している。
【００３５】
このように本実施形態においては、制御弁５２に加えて、チューニング用レギュレータ５３を設けることにより、チャンバ２２への静止用圧縮空気の圧力の、より詳細な制御が行える。これにより、ダイアフラム２４のたわみ量δの制御がより詳細に行えるので、静止時、つまり軸受面１６ａと案内面１２との接触時の、軸受１６が支持するスライダ１４の幾何位置及び幾何姿勢の変化を、より大幅に低減することができる。
なお、本実施形態においては、ダイアフラム２４のたわみ量δをより詳細に制御するために、チャンバ２２内の圧縮空気の圧力をモニタする圧力センサ（図示省略）、該圧力センサよりの圧力情報をコンピュータに送る信号線（図示省略）等を設け、チャンバ２２内の圧縮空気の圧力をより詳細に把握することが、より好ましい。
【００３６】
＜タイミング＞
なお、前記構成では、軸受面１６ａへの圧縮空気供給の解除とチャンバ２２への圧縮空気供給を同時に行う例について説明したが、軸受面１６ａへの圧縮空気供給解除により消失していく空気膜３６とダイアフラム２４のたわみ量δとの関係に、極僅かなずれがあり、これを補正したいときは、チューニング用レギュレータ５３の開度や制御時期の調整により、ロック時の、空気軸受本体１６が支持するスライダ１４の幾何位置および幾何姿勢の変化を、より大幅に低減することができる。
【００３７】
変形例
本発明は前記構成に限定されるものではなく、発明の要旨の範囲内の範囲で種々の変形が可能である。
【００３８】
＜メカニカルロック＞
例えば、本実施形態においては、ロック機構付き空気軸受１０に加えて、前記駆動用アクチュエータの動きをメカニカルに拘束することにより、スライダ１４の静止安定性をより得ることができる。
【００３９】
＜運動＞
前記構成では、Ｙ軸方向等の直線運動の例について説明したが、本実施形態のロック機構付き空気軸受は、これに限定されるものではなく、発明の要旨の範囲内であれば、そのほか、回転運動、揺動等の任意の運動に適用することも好ましい。
【００４０】
＜機械への適用例＞
本実施形態のロック機構付き空気軸受１０は、空気軸受を用いる任意の機械に用いることができるが、特に高い位置決め精度が要求される機械、例えば三次元測定機等の測定機器、非球面加工機や半導体製造装置等の超精密加工機等の各案内機構に用いることが、より好適である。これにより、あまり位置決め精度が要求されない一般的な機械に用いたものに比較し、前述のような本実施形態のロック機構付き空気軸受のもつ効果を、より顕著に発揮することができる。
以下にその一例を示す。
【００４１】
すなわち、最近の三次元測定機（以下、ＣＭＭという）に装着されるプローブとして、一般的な３Ｄ型接触・非接触プローブのほかに、１Ｄ（一方向）ではあるが、変位の分解能がＣＭＭの位置検出分解能に比較し著しく高いもの、例えば粗さや真円度の測定に用いられる変位計等がある。
この場合、ＣＭＭ側での位置決め精度は、前記変位計の検出ストローク（測定範囲）の１／１０程度で充分であるが、重要なことは、静止安定性である。その安定度は、前記変位計の検出分解能と同等か、もしくはそれ以下であることが望ましい。
【００４２】
しかしながら、これまでは、本発明のように非常に高い静止安定性と、ロック時のスライダ等の幾何位置及び幾何姿勢の変化の大幅な低減効果が得られる空気軸受が存在しなかったので、ＣＭＭに粗さや真円度の測定に用いられる変位計を装着し、粗さや真円度を高いレベルで計測した例はなかった。
そこで、本実施形態においては、図３（Ａ）に示すようなＣＭＭ７４のＸ軸ガイド機構７６、Ｙ軸ガイド機構７８、Ｚ軸ガイド機構８０等の空気軸受に、本実施形態にかかるロック機構付き空気軸受を採用している。
【００４３】
ＣＭＭ７４は、テーブル８２と、テーブル８２上に設けれた門柱８４と、門柱８４にＹ軸方向に移動自在に支持されたＸビーム８６と、該Ｘビーム８６にＸ軸方向に移動自在に支持されたスライダ８８と、該スライダ８８にＺ軸方向に移動自在に支持されたＺ軸スピンドル９０を備える。
Ｚ軸スピンドル９０の下端にはプローブ９２が設けられている。そして、入力デバイス（図示省略）よりの入力情報に基づき、プローブ９２をテーブル８２上に載置された被測定物９４に接触させ、その時に発生する接触信号により検出される位置情報を前記コンピュータで演算処理し、被測定物９４の寸法等を得ている。
【００４４】
このような三次元測定機のＸ軸ガイド機構７６、Ｙ軸ガイド機構７８、Ｚ軸ガイド機構８０等の案内に空気軸受に、本実施形態にかかるロック機構付き空気軸受を採用している。
すなわち、同図（Ｂ）に示すようにＹ軸ガイド機構７８は、空気軸受本体１６が門柱８４の下面に設けられており、該空気軸受本体１６、空気膜３６を介して門柱８４はテーブル２２に対しＹ軸方向に移動する。
【００４５】
また同図（Ｃ）に示すようにＸ軸ガイド機構７６は、空気軸受本体１６がスライダ８８の下面及び側面に設けられており、該空気軸受本体１６、空気膜３６を介してスライダ８８はＸビーム８６に対しＸ軸方向に移動する。
また同図（Ｄ）に示すようにＺ軸ガイド機構８０は、空気軸受本体１６がＺ軸スピンドル９０の各側壁に設けられており、該空気軸受本体１６、空気膜３６を介してＺ軸スピンドル９０はスライダ８８に対しＺ軸方向に移動する。
このようなＣＭＭ７４のガイド機構７６，７８，８０に、本実施形態にかかるロック機構付き空気軸受を適用することができる。
【００４６】
したがって、ＣＭＭ７４の一般的なプローブ９２に代えて、例えば粗さや真円度の測定に用いられる変位計を装着し、変位計を移動するＣＭＭのＸ軸ガイド機構７６、Ｙ軸ガイド機構７８、Ｚ軸ガイド機構８０等の空気軸受に、本実施形態にかかるロック機構付き空気軸受を採用することにより、本実施形態の空気軸受のもつ、非常に高い静止安定性と、ロック時のスライダ等の幾何位置及び幾何姿勢の変化の大幅な低減効果を生かして、粗さや真円度などの精密表面性状の測定が可能となる。
したがって、本実施形態においては、例えばＣＭＭに粗さ計や真円度用に用いられる変位計を装着することにより、従来極めて困難であった、粗さ計や真円度測定機と同等の精度にて粗さや真円度の測定が行える。
【００４７】
また本発明はこれらの実施形態に限られることなく、さらに各種の変形が可能である。
すなわち、本実施形態におけるレギュレータは、チャンバの圧縮空気圧力を調整するもののみを示したが、浮上用給気管を介して浮上用圧縮空気圧力調整用レギュレータを設けてもよい。このレギュレータは浮上用と静止用の何れか一方、あるいは両方を備えても良い。要は、ロック指令の有無にかかわらずダイアフラム外壁の特定部位の基部からの高さが変わらない様に浮上用圧縮空気圧力または静止用圧縮空気圧力の調整が行えれば良い。このようにすれば、圧縮空気供給源の発生圧力の精度は必ずしも高くする必要がない。また、ダイアフラム外壁の特定部位の基部からの高さの調整精度が向上する。
【００４８】
また、これらのレギュレータや制御弁は、電磁弁やサーボ弁であっても良い。すなわち、要求精度に適した精度のレギュレータや制御弁を用いれば良い。
さらに本実施形態では圧縮空気を用いる例を示したが、より一般的に圧縮流体を用いることができる。たとえば、空気以外の気体や液体であっても良い。これによって必要な圧力に応じて適切な流体の選択が可能となる。
【００４９】
また、チャンバ内への静止用圧縮流体と浮上用圧縮流体は同一である必要はない。例えば、浮上用圧縮流体を空気として、静止用圧縮流体を油とすることができる。このようにすれば、高い圧力を容易に得ることができるので、剛性の高いダイアフラム構造とすることができる。
さらに、軸受支持高さＨについては、ロック指令の有無にかかわらず高さが変化しないように圧力調整のみによって調整したが、この高さＨを測定するセンサを設け、このセンサ出力が所定の値になるようにレギュレータで圧力調整を行う構成とすることが出来る。この場合のセンサは、静電容量式、光学式、電磁式、超音波式など各種のものを用いることが出来るが、非接触式のセンサが好ましい。このようにすれば、仮に圧力変動が生じても軸受支持高さＨが修正されるので、精度が高く安定な浮上・静止が可能となる。
【００５０】
また基部（案内面）と軸受本体側（軸受面）は、異なる材質を用いることが好ましい。例えば案内面としてアルミナセラミックスを用い、軸受面にはステンレス（例：SUS420J2）とする。このようにすれば、案内面の損傷を防ぐことができる。
さらに軸受本体側は、耐食性のある材質とすることが好ましい。具体的にはステンレスや銅合金を用いることが出来る。このようにすれば軸受内に圧縮空気を通しても腐食による損傷を防止することができる。
【００５１】
また本実施形態における空気軸受の軸受面の浮上用圧縮空気供給溝形状は、十字溝と円周溝を結合して十字溝の交差部分に圧縮空気出口を設ける構成としたが、この浮上用圧縮空気供給溝形状や圧縮空気出口は軸受の要求性能に応じて各種の形状とすることができる。
さらに本実施形態においては、図４に示すように圧縮空気供給溝３０ｄの外側に圧縮空気排気溝１０１ａと圧縮空気排気穴１０１ｂ（図４の例では４箇所）を設ける。そして、図５に示すように圧縮空気排気穴１０１ｂから排気管１０３を介してポンプなどの吸引手段１０４へ接続し、圧縮空気の供給量と排気量が略同一となるように吸引手段１０４の吸引量を制御する構成としても良い。この場合、前記浮上用圧縮空気給気管２８と図５に示す排気管１０３の各々に浮上用圧縮空気給気流量計と排気流量計（図示省略）を挿入し、両者が略同一となるように吸引手段の吸引量を制御する流量制御手段（図示省略）を設けた構成とすれば、制御精度は更に向上する。このようにすれば、浮上用圧縮空気の軸受外への流出と拡散を防止でき、その結果、測定機各部の不要な空気の対流を防止して各部の温度ばらつきの発生を防止できるので、測定精度が向上する。
【００５２】
また本実施形態においては、図４に示すように軸受面の圧縮空気排気溝１０１ａの外周に連続した外周抵抗部１０２を備えていることが好ましい。この外周抵抗部１０２は、軸受面と略同一面とする他、図５に示す空気軸受１６の断面図のように圧縮空気排気溝１０１ａの外側を始点とするテーパ形状（図５（Ｂ）参照）としたり、ラビリンスを形成して（図５（Ａ）参照）抵抗を増大させることができる。
このようにすれば、軸受を設置する環境が真空中であっても本発明を実施できる。特に軸受の浮上時には、前記チャンバ２２内の静止用圧縮空気は前記レギュレータ５３または前記制御弁５２から外部に排気され、浮上用圧縮空気は図５に示す排気管１０３から吸引され外部に排気される。またロック指令による軸受の静止時には、圧縮空気の放出は全く停止される。従って軸受を真空槽内で用いる場合に、真空槽内へ放出される圧縮空気の量を極めて少なくすることができるので、真空度への影響が少なく、極めて有用である。
【００５３】
【発明の効果】
以上説明したように本発明にかかる空気軸受によれば、ロック指令により、基部と可動部間への浮上用圧縮空気供給の解除と、静止用圧縮空気供給手段によるチャンバ内への静止用圧縮空気の供給を行い、該浮上用圧縮空気供給の解除により消失する基部と可動部間の空気膜の厚みと同じ量だけ、ダイアフラム外壁の特定部位を空気膜の厚み増大方向に変形させることとした。
この結果、本発明においては、基部に対する可動部の特定部位の位置及び姿勢を変えることなく、基部に対し可動部をしっかりとロックすることができる。
また本発明においては、前記ロック指令により、浮上用給気管による浮上用圧縮空気供給の解除と、静止用給気管による静止用圧縮空気の供給を行う制御弁を設けることにより、前記可動部のロックを、より簡易に行うことができる。
さらに本発明においては、前記ロック指令により、前記チャンバ内の静止用圧縮空気の圧力が、前記ロック指令により消失する基部と可動部間の空気膜の厚みに対応する静止用圧縮空気の圧力の値となるように、静止用圧縮空気の圧力調整を行うレギュレータを設けることにより、前記ロック時の基部に対する可動部の特定部位の位置及び姿勢の変化を、より大幅に低減することができる。
【図面の簡単な説明】
【図１】本実施形態にかかるロック機構付き空気軸受の浮上時の説明図である。
【図２】本実施形態にかかるロック機構付き空気軸受の静止（ロック）時の説明図である。
【図３】本実施形態にかかるロック機構付き空気軸受の機械への適用例である。
【図４】本実施形態にかかる他の実施形態における空気軸受の軸受面の説明図である。
【図５】本実施形態にかかる更に他の実施形態における空気軸受の断面図である。
【符号の説明】
１０ロック機構付き空気軸受（空気軸受）
１２案内面（基部）
１４スライダ（可動部）
１６空気軸受本体
２２チャンバ
２４ダイアフラム
２８空気軸受側圧縮空気供給配管（浮上用圧縮空気供給手段，浮上用圧縮空気給気管）
３２ロック機構側圧縮空気供給配管（静止用圧縮空気供給手段，静止用圧縮空気給気管）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of an air bearing, particularly a locking mechanism thereof.
[0002]
[Prior art]
Conventionally, static pressure thrust air bearings have been frequently used as guide mechanisms for measuring devices such as a three-dimensional measuring machine, and feeding devices such as ultra-precision processing machines such as aspherical processing machines and semiconductor manufacturing apparatuses.
This hydrostatic air bearing reduces the friction between the base and the movable part by floating the movable part from the base by the force of compressed air supplied from the other.
[0003]
[Problems to be solved by the invention]
By the way, for example, in a guide mechanism such as the above-described feeding device, extremely high positioning accuracy is required.
However, since the hydrostatic air bearing used for the guide mechanism is non-contact, no frictional force acts between the base and the movable part. For this reason, in a static pressure air bearing, a positioning error corresponding to at least a position detection unit is generated due to disturbances such as vibration, and it is difficult to stop at a position detection unit or less.
Therefore, there is an urgent need to improve positioning accuracy in hydrostatic air bearings. Conventionally, for example, a technique of providing a friction member on an air bearing (for example, Japanese Patent Laid-Open No. 60-45626), the supply of compressed air to the air bearing is shut off. It is conceivable to use a technique (for example, Japanese Patent Application Laid-Open No. 4-285809, Japanese Patent No. 2987517, etc.) for bringing the base portion into contact with the movable portion.
[0004]
However, the technique disclosed in Japanese Patent Laid-Open No. 60-45626 has not been adopted because the position of the movable part may fluctuate after a lock command due to disturbance such as vibration.
Further, JP-A-4-285809, Japanese Patent No. 2987517, and the like have been desired to further improve the reduction of the change in the position and posture of the movable portion with respect to the base portion.
The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide an air bearing capable of firmly locking a movable part with respect to the base without changing the position and posture of the specific part of the movable part with respect to the base. Is to provide.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, an air bearing according to the present invention is an air bearing comprising a base, a movable part, and a flying compressed air supply means, and includes a chamber and a stationary compressed air supply means. . Then, in response to a lock command for instructing the movable portion to be stationary with respect to the base portion, the floating compressed air supply means releases the floating compressed air supply between the base portion and the movable portion, and the stationary compressed air supply means supplies the inside of the chamber. Supply of compressed air for static
The diaphragm with respect to the base is deformed by deforming a specific part of the outer wall of the diaphragm in the direction of increasing the thickness of the air film by the same amount as the thickness of the air film between the base and the movable part that disappears when the supply of the compressed air for floating is released. The base portion and the movable portion are brought into contact with each other without changing the position and posture of a specific portion of the outer wall, and the movable portion is stationary with respect to the base portion by a frictional force generated by the contact.
[0006]
Here, the movable part is supported by the base part through an air film, and is movable relative to the base part.
The levitation compressed air supply means supplies levitation compressed air that forms the air film between the base portion and the movable portion.
The chamber is provided on the back surface of the movable part opposite to the surface in contact with the air film, and is configured by at least a diaphragm. When the compressed air for stationary is supplied, the thickness of the air film increases at a specific portion of the outer wall of the diaphragm. Deform in the direction.
The stationary compressed air supply means supplies the stationary compressed air into the chamber.
[0007]
The bearing here is not limited to a specific motion such as a rotational motion, but refers to a bearing that can be applied to a base that can move relative to a base such as a linear motion or a swing.
It is provided on the back surface of the movable part opposite to the surface in contact with the air film, and is composed of at least a diaphragm. That is, a chamber is composed of the back surface of the movable part and the diaphragm, and a chamber is already formed on the back surface of the movable part. This includes the provision of a configured diaphragm.
The specific part of the diaphragm outer wall referred to here includes the diaphragm outer wall itself and the part supported by the specific part of the diaphragm outer wall.
[0008]
In the present invention, the compressed air supply means for levitation includes a levitation air supply pipe that supplies compressed air from the compressed air supply source as the compressed air for levitation between the base portion and the movable portion, and The compressed air supply means preferably includes a static air supply pipe that supplies the compressed air from the compressed air supply source to the chamber as static compressed air, and further includes a control valve.
Here, the control valve is provided between the supply source and each of the air supply pipes, and according to the lock command, release of supply of the compressed air for levitation by the levitation air supply pipe, and stationary by the stationary air supply pipe Supply compressed air.
[0009]
The compressed air supply source mentioned here includes that the floating compressed air supply means and the stationary compressed air supply means use a common supply source, and use a separate supply source. In the present invention, provided in the latter stage of the control valve and supplied into the chamber via the stationary air supply pipe so that the pressure of the stationary compressed air in the chamber in the lock command becomes a predetermined value. A stationary regulator that adjusts the pressure of the compressed air for stationary use, or the floating air supply pipe through the floating air supply pipe so that the thickness of the air film when the lock command is released becomes a predetermined value. It is preferable to further include at least one of levitation regulators that adjust the pressure.
[0010]
Here, the regulator is not limited to supply / cancellation, and includes switching to the control valve as long as the pressure can be adjusted by controlling the opening of the valve.
The present invention further comprises a sensor for measuring the distance between the specific part of the outer wall of the diaphragm and the base, and a control circuit for controlling the regulator by the output of the sensor, regardless of whether the lock command is present or not. It is preferable to control the regulator so that the distance between the specific part and the base is always constant.
[0011]
Furthermore, in the present invention, it is preferable to include a stationary control memory, diaphragm control information acquisition means, and a regulator.
Here, the static control memory has a relationship between at least the pressure of the compressed air for static in the chamber obtained in advance and the amount of deformation in the thickness direction of the air film at a specific part of the outer wall of the diaphragm at the pressure. Is remembered.
[0012]
Further, the diaphragm control information acquisition means statically controls the pressure value of the stationary compressed air corresponding to the thickness of the air film between the base portion and the movable portion, which disappears by the release of the floating compressed air supply, according to the lock command. It is obtained from the memory.
The regulator is provided downstream of the control valve, and the pressure of the static compressed air in the chamber is set via the static air supply pipe so that the pressure obtained by the diaphragm control information acquisition unit is equal to the pressure value. The pressure of the stationary compressed air supplied into the chamber is adjusted.
[0013]
Furthermore, in the present invention, the compressed air supply means further includes a compressed air supply groove formed in a concave shape on a surface in contact with the air film of the movable part, and further includes a compressed air exhaust groove, a compressed air exhaust hole, And an exhaust pipe, and it is preferable to collect the compressed air for levitation.
Here, the compressed air exhaust groove is formed to be recessed outside the compressed air supply groove so as to collect the compressed air for levitation.
[0014]
The compressed air exhaust hole is opened in the wall surface of the compressed air exhaust groove and exhausts the recovered compressed air for levitation.
The exhaust pipe connects the compressed air exhaust hole and suction means for sucking the recovered compressed air for levitation.
In the present invention, it is preferable to further include an outer peripheral resistance portion that is continuously disposed on the outer peripheral side of the compressed air exhaust groove and is disposed on substantially the same surface as the surface of the movable portion that contacts the air film. It is.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings.
[0016]
FIG. 1A shows a schematic configuration of a guide mechanism of a feeding device using an air bearing according to an embodiment of the present invention, and FIG. 1B shows the air bearing body viewed from the bearing surface. FIG.
An air bearing with a lock mechanism (air bearing) 10 shown in the figure is an example of a static pressure thrust air bearing provided in each of the X-axis guide mechanism, the Y-axis guide mechanism, and the Z-axis guide mechanism of the coordinate measuring machine, A guide surface (base portion) 12, a slider (movable portion) 14, an air bearing body 16, a flying compressed air supply means 18, and a stationary compressed air supply means 20 are provided.
[0017]
The air bearing body 16 is provided with a diaphragm 24 constituting a chamber 22.
The floating compressed air supply means 18 includes a compressed air supply source 26, an air bearing side compressed air supply pipe (levitation supply pipe) 28, and an air bearing side compressed air supply passage 30 of the air bearing body 16.
The stationary compressed air supply means 20 includes the compressed air supply source 26, a lock mechanism side compressed air supply pipe (static air supply pipe) 32, and a lock mechanism side compressed air supply passage 34 of the air bearing body 16.
The guide surface 12 is provided on a table (not shown) of a coordinate measuring machine, and the air bearing body 16 is provided below a slider (movable part) 14 of the guide mechanism.
[0018]
In the present embodiment, the slider 14 is, for example, a Y-axis guide mechanism, and a driving force from a driving source 36 such as a motor is transmitted to the slider 14 via a feed mechanism 38 such as a ball screw. The movement of the slider 14 is defined by the guide surface 12 in a specific direction such as the Y-axis direction.
An air bearing body 16 is provided on the guide surface 12 via an air film 36, and a diaphragm 24 that constitutes the chamber 22 together with the back surface of the air bearing body 16 is provided on the back surface of the air bearing body 16. Holes 42 and 44 for providing the hard spheres 40 are provided in the approximate center of the upper part of the diaphragm 24 (on the central axis of the diaphragm) and the lower part of the slider 14, respectively. The lower part of the slider 14 is supported at the approximate center of the upper part of the diaphragm 24 via the rigid sphere 40.
[0019]
In the present embodiment, the central portion of the upper wall of the diaphragm 24 can be used as a specific portion of the outer wall of the diaphragm 24. However, since the approximate center of the hard sphere 40 is equivalent to the function of the central portion of the upper wall of the diaphragm 24, the hard sphere The approximate center of 40 is a specific part of the outer wall of the diaphragm 24.
On the central axis of the diaphragm 24 of the slider 14, a hole 48 for providing an adjusting screw 46 for adjusting a separation distance between the lower surface of the slider 14 and the upper surface of the diaphragm 24 is provided. 40 is in contact. A nut 50 is provided from the upper side of the slider 14 on the head side facing the tip of the adjustment screw 46, and the air bearing body 16 is firmly provided on the lower surface of the slider 14 via the rigid ball 40 by the nut 50. Yes. Along the central axis of the diaphragm 24, a weight W is applied to the slider 14 and a gate post (not shown) moved by the slider 14.
[0020]
In the air bearing body 16, the inlet 30a of the air bearing side compressed air supply passage 30 is opened from the side wall, and the outlet 30b is opened from the lower wall.
Further, the air bearing body 16 is provided with a lock mechanism side compressed air supply passage 34 that is independent of the air bearing side compressed air supply passage 30, and its inlet 34 a is opened from the side wall, and the diaphragm 24 and the air bearing body 16 are opened. An outlet 34b is opened from the back surface of the air bearing body 16 facing the chamber 22 that is airtight on the back surface.
The air bearing 10 with a lock mechanism includes a control valve 52, a regulator 53, and a computer 54.
[0021]
The control valve 52 includes at least three ports 56a, 56b, and 56c, and the compressed air supply source 26 and the third port 56c of the control valve 52 are connected by a main pipe 58.
An air bearing side compressed air supply pipe 28 is connected between the first port 56 a of the control valve 52 and the inlet 30 a of the air bearing side compressed air supply passage 30 of the air bearing body 16.
Between the second port 56b of the control valve 52 and the inlet 34a of the lock mechanism side compressed air supply passage 34 of the air bearing body 16, the lock mechanism side compressed air supply independent of the air bearing side compressed air supply pipe 28 is provided. They are connected by a pipe 32.
The control valve 52 and the computer 54 are connected by a signal line 60.
[0022]
When a control signal instructing ascent is sent from the computer 54 to the control valve 52, the control valve 52 opens the first port 56a and closes the second port 56b.
Then, the compressed air from the compressed air supply source 26 passes through the main pipe 58, the first port 56 a of the control valve 52, and the air bearing side compressed air supply pipe 28 from the inlet 30 a of the air bearing body 16 to the air bearing side. The compressed air is supplied to the compressed air supply passage 30 and is supplied toward the guide surface 12 from the outlet 30b opened from the bearing surface 16a of the air bearing body 16.
[0023]
The air bearing body 16 is lifted from the guide surface 12 by the force of compressed air supplied from the outlet 30 b of the bearing surface 16 a of the air bearing body 16.
In the figure, the bearing clearance from the guide surface 12 to the bearing surface 16a of the air bearing body 16 by the air film 36 is set to h, and the bearing support height from the guide surface 12 to the hard sphere center 40 is set to H.
By configuring the air bearing 10 in this manner, the starting friction or moving friction between the guide surface 12 and the bearing surface 16a of the air bearing body 16 is reduced, and the slider 14 is moved smoothly in the Y-axis direction, for example. Can do.
[0024]
By the way, for example, a measuring device such as a three-dimensional measuring machine, and a guide mechanism of a feeding device of an ultra-precision processing machine such as an aspherical surface processing machine or a semiconductor manufacturing apparatus, requires very high positioning accuracy.
For this reason, for example, in ball screw driving, it is generally considered that the motor shaft is mechanically fixed. However, a coupling, a ball screw, a ball nut, a joint portion with a slider, etc. from the motor shaft is a spring. It is an element and may be elastically deformed by disturbances such as vibrations, resulting in fluctuations in the position of the slider.
[0025]
Conventionally, it is conceivable that after the positioning is completed, the compressed air to the air bearing is shut off, the bearing surface of the slider is brought into contact with the guide surface, and friction is generated to obtain a completely stationary state of the slider. Although this method is very good in that the slider can be completely stationary, the geometric position and posture of the slider can be adjusted due to the disappearance of the air film formed before the supply of compressed air to the air bearing is interrupted. Since it collapsed greatly, there was still room for improvement in this respect.
Therefore, a characteristic feature of the present invention is that the bearing surface and the guide surface are brought into contact with each other without impairing the position and posture of the slider supported by the bearing, and the slider is caused by the frictional force generated by the contact between the bearing surface and the guide surface. Is completely stationary.
[0026]
For this purpose, in this embodiment, as shown in the figure, the air bearing body 16 is provided with a diaphragm 24 and a lock mechanism side compressed air supply passage 34. A lock mechanism side compressed air supply pipe 32 that is independent of the air bearing side compressed air supply pipe 28 is provided at the inlet 34 a of the lock mechanism side compressed air supply passage 34.
Then, as shown in FIG. 2, when a control signal (lock command) instructing the stop is sent from the computer 54 to the control valve 52, the control valve 52 closes the first port 56a and the second port 56b. Is in an open state.
[0027]
As a result, the compressed air supplied from the outlet 30b of the bearing surface 16a toward the guide surface 12 is released until immediately before the control signal (lock command) for instructing the stationary state, thereby forming the compressed air. The air film disappears. As a result, the bearing surface 16 a of the air bearing main body 16 comes into contact with the guide surface 12, and the slider 14 is stopped by the frictional force generated by the contact between the bearing surface 16 a and the guide surface 12.
Here, simultaneously with the release of the compressed air supply for levitation, the compressed air from the compressed air supply source 26 passes through the main pipe 58, the second port 56 b of the control valve 52, and the lock mechanism side compressed air supply pipe 32. The air is supplied to the lock mechanism side compressed air supply passage 34 from the inlet 34 a of the air bearing body 16, and is supplied into the chamber 22 from the outlet 34 b opened on the back surface of the air bearing body 16.
[0028]
The diaphragm 24 bends upward (arrow + Z direction in the figure) by the force of the compressed air supplied into the chamber 22.
In this figure, the amount of deflection δ of the diaphragm 24 is the same as the bearing clearance h shown in FIG. 1, and the bearing support height H from the guide surface 12 to the center of the rigid sphere 40 is as shown in FIG. The bearing support height H is the same height.
[0029]
As described above, in the present embodiment, the air supply to the bearing surface 16a is independent of the supply air to the bearing surface 16a on the back surface of the static pressure thrust air bearing 16 that originally has no binding force in the moving direction of the slider 14 (Y-axis direction). A chamber 22 constituted by a diaphragm 22 having a lock mechanism side compressed air supply pipe 32 which is an air piping system is provided.
In response to a positioning command from the control system such as the computer 54 for the slider 14, a stop command is issued to the drive source 36, and the compressed air supply to the chamber 22 and the compressed air supply to the air bearing body 16 are released. It is carried out.
[0030]
At this time, the air film formed between the bearing surface 16a of the static pressure thrust air bearing body 16 and the guide surface 12 disappears, while the compressed air is supplied to the chamber 22 to form the air film before disappearance. The diaphragm 24 is deformed by the same thickness as the air film.
Accordingly, the bearing surface 16a and the guide surface 12 are brought into contact with each other while maintaining the geometric position and the geometric posture of the slider 14 supported by the air bearing body 16, and the frictional force generated by the contact causes the Y of the slider 14 to the guide surface 12. Relative movement in the axial direction can be restricted.
[0031]
<Control valve>
By the way, in the air bearing, it is important to more easily realize the completely stationary state of the slider.
Therefore, a characteristic of the present invention is that the release of the compressed air supply to the bearing surface and the supply of the compressed air to the chamber are performed in the middle of the piping to the bearing in order to easily realize the completely stationary state of the slider. This is performed by a control command for the provided control valve.
For this purpose, the present embodiment includes the control valve 52 and the computer 54 as described above. Then, opening / closing control of the first port 56a and the second port 56b of the control valve 52 is performed by a control command from the computer 54, the supply of compressed air to the bearing surface 16a is canceled, and the supply of compressed air to the chamber 22 is performed. However, it can be done more easily. As a result, the slider 14 can be more easily stopped.
[0032]
<Regulator>
In order to further reduce the change in the geometric position and the geometric posture of the slider 14 supported by the bearing 16 at the stationary time, the deflection amount δ of the diaphragm 24 is an air film (bearing) formed by the supply of the floating compressed air. It is necessary to tune so that the thickness is the same as the clearance h).
Therefore, in the present embodiment, the tuning regulator 53 and the computer 54 are provided, and the deflection amount (deformation amount) δ of the diaphragm 24 is tuned by the shape of the diaphragm 24 and the pressure supplied to the chamber 22. .
[0033]
The tuning regulator 53 is provided between the second port 56 b of the control valve 52 and the lock mechanism side compressed air supply pipe 32. The tuning regulator 53 is connected to the control valve 52 through a signal line 62, and is connected to the computer 54 through a signal line 64.
The computer 54 includes a memory 66 and a CPU (diaphragm control information acquisition means) 68. The memory 66 includes a floating control memory 70 and a stationary control memory 72.
The levitation control memory 70 stores the pressure of the compressed air for levitation between the guide surface 12 and the bearing surface 16a, and the thickness of the air film between the guide surface 12 and the bearing surface 16a (bearing clearance). The relationship of h) is stored.
The static control memory 72 stores a relationship between the pressure of the static compressed air in the chamber 22 obtained in advance and the deflection amount δ of the diaphragm 24 at the pressure.
[0034]
The CPU 68 determines the thickness of the air film corresponding to the pressure of the compressed air for levitation supplied between the guide surface 12 and the bearing surface 16a immediately before the control signal of the stationary instruction by the control signal (lock command) instructing the stationary state. (Bearing clearance h) is obtained from the floating control memory 70. The value of the pressure of the compressed air for stationary corresponding to the obtained thickness of the air film is obtained from the stationary control memory 72.
Then, the CPU 68 instructs the tuning regulator 53 so that the static compressed air pressure supplied from the control valve 52 into the chamber 22 becomes the static compressed air pressure obtained from the static control memory 72.
The tuning regulator 53 adjusts the amount of compressed air supplied from the control valve 52 to the chamber 22 according to the opening degree of the flow path, etc., so that the pressure value of the stationary compressed air to the chamber 22 is instructed from the CPU 68. It is adjusted to be a value.
[0035]
As described above, in this embodiment, by providing the tuning regulator 53 in addition to the control valve 52, more detailed control of the pressure of the stationary compressed air to the chamber 22 can be performed. As a result, the amount of deflection δ of the diaphragm 24 can be controlled in more detail, so that the geometric position and the geometric posture of the slider 14 supported by the bearing 16 change at rest, that is, when the bearing surface 16a contacts the guide surface 12. Can be significantly reduced.
In this embodiment, in order to control the deflection amount δ of the diaphragm 24 in more detail, a pressure sensor (not shown) for monitoring the pressure of the compressed air in the chamber 22, and pressure information from the pressure sensor is used as a computer. It is more preferable to provide a signal line (not shown) or the like to be sent to, and grasp the pressure of the compressed air in the chamber 22 in more detail.
[0036]
<Timing>
In the above configuration, the example in which the release of the compressed air supply to the bearing surface 16a and the supply of the compressed air to the chamber 22 are performed simultaneously has been described. However, the air film 36 disappears due to the release of the compressed air supply to the bearing surface 16a. There is a slight deviation in the relationship between the deflection amount δ of the diaphragm 24 and the diaphragm 24. When it is desired to correct this, the air bearing body 16 is supported by the tuning regulator 53 by adjusting the opening and control timing. The change in the geometric position and the geometric posture of the slider 14 can be significantly reduced.
[0037]
Modified example
The present invention is not limited to the above-described configuration, and various modifications can be made within the scope of the gist of the invention.
[0038]
<Mechanical lock>
For example, in this embodiment, in addition to the air bearing 10 with a lock mechanism, the stationary stability of the slider 14 can be further obtained by mechanically restraining the movement of the driving actuator.
[0039]
<Exercise>
In the above configuration, an example of linear motion in the Y-axis direction and the like has been described. However, the air bearing with a lock mechanism of the present embodiment is not limited to this, and is within the scope of the gist of the invention. It is also preferable to apply to arbitrary movements such as rotational movement and swinging.
[0040]
<Application example to machine>
The air bearing 10 with a lock mechanism of the present embodiment can be used for any machine that uses an air bearing, but a machine that requires particularly high positioning accuracy, for example, a measuring instrument such as a three-dimensional measuring machine, an aspherical surface processing machine, etc. It is more preferable to use it for each guide mechanism of ultra-precision processing machines such as semiconductor manufacturing equipment. Thereby, compared with what was used for the general machine in which positioning accuracy is not requested | required very much, the effect which the air bearing with a lock mechanism of this embodiment as mentioned above has can be exhibited more notably.
An example is shown below.
[0041]
That is, as a probe attached to a recent CMM (hereinafter referred to as CMM), in addition to a general 3D type contact / non-contact probe, although it is 1D (one direction), the displacement resolution is CMM. There are those that are significantly higher than the position detection resolution, such as a displacement meter used for measuring roughness and roundness.
In this case, the positioning accuracy on the CMM side is sufficient to be about 1/10 of the detection stroke (measurement range) of the displacement meter, but what is important is the stationary stability. The stability is desirably equal to or less than the detection resolution of the displacement meter.
[0042]
However, until now, there has been no air bearing that can obtain a very high static stability and a significant reduction effect of changes in the geometric position and posture of a slider or the like when locked, as in the present invention. There was no example in which a displacement meter used for measuring roughness and roundness was mounted to measure roughness and roundness at a high level.
Therefore, in this embodiment, the air bearings such as the X-axis guide mechanism 76, the Y-axis guide mechanism 78, and the Z-axis guide mechanism 80 of the CMM 74 as shown in FIG. Air bearings are used.
[0043]
The CMM 74 is supported by a table 82, a gate pole 84 provided on the table 82, an X beam 86 supported by the gate pole 84 so as to be movable in the Y-axis direction, and supported by the X beam 86 so as to be movable in the X-axis direction. And a Z-axis spindle 90 supported by the slider 88 so as to be movable in the Z-axis direction.
A probe 92 is provided at the lower end of the Z-axis spindle 90. Then, based on input information from an input device (not shown), the probe 92 is brought into contact with the object 94 to be measured placed on the table 82, and position information detected by the contact signal generated at that time is detected by the computer. An arithmetic process is performed to obtain the dimensions of the object 94 to be measured.
[0044]
The air bearing with a lock mechanism according to the present embodiment is adopted as an air bearing for guiding the X-axis guide mechanism 76, the Y-axis guide mechanism 78, the Z-axis guide mechanism 80, and the like of such a coordinate measuring machine.
That is, as shown in FIG. 5B, the Y-axis guide mechanism 78 has the air bearing body 16 provided on the lower surface of the gate pole 84, and the gate pole 84 is connected to the table 22 via the air bearing body 16 and the air film 36. Move in the Y-axis direction.
[0045]
Further, as shown in FIG. 6C, the X-axis guide mechanism 76 has an air bearing body 16 provided on the lower surface and side surface of the slider 88, and the slider 88 passes through the air bearing body 16 and the air film 36. It moves in the X axis direction with respect to the beam 86.
As shown in FIG. 4D, in the Z-axis guide mechanism 80, the air bearing body 16 is provided on each side wall of the Z-axis spindle 90, and the Z-axis spindle is interposed through the air bearing body 16 and the air film 36. 90 moves in the Z-axis direction with respect to the slider 88.
The air bearing with a lock mechanism according to this embodiment can be applied to the guide mechanisms 76, 78, and 80 of the CMM 74 as described above.
[0046]
Therefore, instead of the general probe 92 of the CMM 74, for example, a displacement meter used for measuring roughness and roundness is mounted, and the CMM X-axis guide mechanism 76, Y-axis guide mechanism 78, Z, which moves the displacement meter, are moved. By adopting the air bearing with a lock mechanism according to the present embodiment for the air bearing such as the shaft guide mechanism 80, the air bearing of the present embodiment has a very high stationary stability and the geometry of the slider, etc. when locked. It is possible to measure precision surface properties such as roughness and roundness by making use of the effect of greatly reducing changes in position and geometric posture.
Therefore, in this embodiment, for example, by attaching a displacement meter used for a roughness meter or roundness to the CMM, for example, accuracy equivalent to that of a roughness meter and roundness measuring machine, which has been extremely difficult in the past, is achieved. Can measure roughness and roundness.
[0047]
The present invention is not limited to these embodiments, and various modifications can be made.
That is, the regulator in the present embodiment shows only the regulator that adjusts the compressed air pressure in the chamber, but a floating compressed air pressure adjusting regulator may be provided via the floating supply pipe. This regulator may be provided with either or both of levitating and stationary. In short, it is only necessary to adjust the floating compressed air pressure or the stationary compressed air pressure so that the height from the base of the specific portion of the outer wall of the diaphragm does not change regardless of the presence or absence of the lock command. In this way, it is not always necessary to increase the accuracy of the pressure generated by the compressed air supply source. Moreover, the adjustment accuracy of the height from the base part of the specific site | part of the diaphragm outer wall improves.
[0048]
These regulators and control valves may be electromagnetic valves or servo valves. That is, a regulator or a control valve having an accuracy suitable for the required accuracy may be used.
Furthermore, although the example which uses compressed air was shown in this embodiment, compressed fluid can be used more generally. For example, a gas or liquid other than air may be used. This makes it possible to select an appropriate fluid according to the required pressure.
[0049]
Also, the stationary compressed fluid into the chamber and the floating compressed fluid need not be the same. For example, the floating compressed fluid can be air and the stationary compressed fluid can be oil. In this way, since a high pressure can be easily obtained, a highly rigid diaphragm structure can be obtained.
Further, the bearing support height H is adjusted only by pressure adjustment so that the height does not change regardless of the presence or absence of a lock command. A sensor for measuring the height H is provided, and the sensor output is a predetermined value. Thus, the pressure can be adjusted with a regulator. In this case, various sensors such as a capacitance type, an optical type, an electromagnetic type, and an ultrasonic type can be used, but a non-contact type sensor is preferable. In this way, even if pressure fluctuation occurs, the bearing support height H is corrected, so that highly accurate and stable levitation and rest are possible.
[0050]
Moreover, it is preferable to use different materials for the base (guide surface) and the bearing body side (bearing surface). For example, alumina ceramic is used for the guide surface and stainless steel (eg, SUS420J2) is used for the bearing surface. In this way, the guide surface can be prevented from being damaged.
Further, the bearing body side is preferably made of a material having corrosion resistance. Specifically, stainless steel or copper alloy can be used. In this way, damage caused by corrosion can be prevented even if compressed air is passed through the bearing.
[0051]
In addition, the floating compressed air supply groove shape of the bearing surface of the air bearing in this embodiment is configured to connect the cross groove and the circumferential groove and provide the compressed air outlet at the crossing portion of the cross groove. The air supply groove shape and the compressed air outlet can have various shapes depending on the required performance of the bearing.
Furthermore, in this embodiment, as shown in FIG. 4, the compressed air exhaust groove 101a and the compressed air exhaust hole 101b (four places in the example of FIG. 4) are provided outside the compressed air supply groove 30d. Then, as shown in FIG. 5, the compressed air exhaust hole 101b is connected to the suction means 104 such as a pump through the exhaust pipe 103, and the suction of the suction means 104 so that the supply amount of compressed air and the exhaust amount are substantially the same. It is good also as a structure which controls quantity. In this case, a floating compressed air supply flow meter and an exhaust flow meter (not shown) are inserted into the floating compressed air supply pipe 28 and the exhaust pipe 103 shown in FIG. 5, respectively, so that both are substantially the same. If the flow rate control means (not shown) for controlling the suction amount of the suction means is provided, the control accuracy is further improved. In this way, it is possible to prevent the compressed air for levitation from flowing out and diffusing outside the bearing, and as a result, unnecessary air convection in each part of the measuring machine can be prevented, and temperature fluctuations in each part can be prevented. Accuracy is improved.
[0052]
Moreover, in this embodiment, it is preferable to provide the outer periphery resistance part 102 followed by the outer periphery of the compressed air exhaust groove 101a of a bearing surface as shown in FIG. The outer peripheral resistance portion 102 is substantially the same surface as the bearing surface, and has a tapered shape starting from the outside of the compressed air exhaust groove 101a as shown in the sectional view of the air bearing 16 shown in FIG. 5 (see FIG. 5B). Or a labyrinth (see FIG. 5A) to increase resistance.
In this way, the present invention can be implemented even when the environment in which the bearing is installed is in a vacuum. In particular, when the bearing floats, the stationary compressed air in the chamber 22 is exhausted to the outside from the regulator 53 or the control valve 52, and the compressed compressed air is sucked from the exhaust pipe 103 shown in FIG. 5 and exhausted to the outside. . Further, when the bearing is stationary by the lock command, the discharge of compressed air is completely stopped. Therefore, when the bearing is used in the vacuum chamber, the amount of compressed air released into the vacuum chamber can be extremely reduced, which is extremely useful with little influence on the degree of vacuum.
[0053]
【The invention's effect】
As described above, according to the air bearing of the present invention, the release of the floating compressed air supply between the base portion and the movable portion and the stationary compressed air into the chamber by the stationary compressed air supply means by the lock command. The specific portion of the outer wall of the diaphragm is deformed in the direction of increasing the thickness of the air film by the same amount as the thickness of the air film between the base and the movable part that disappears when the supply of the compressed air for floating is released.
As a result, in the present invention, the movable part can be securely locked to the base without changing the position and posture of the specific part of the movable part with respect to the base.
Further, in the present invention, the lock of the movable portion is provided by providing a control valve for releasing the supply of the compressed air for levitation by the levitation air supply pipe and supplying the compressed air for the stasis by the stationary air supply pipe in accordance with the lock command. Can be performed more easily.
Further, in the present invention, the value of the pressure of the stationary compressed air corresponding to the thickness of the air film between the base portion and the movable portion where the pressure of the stationary compressed air in the chamber disappears due to the locking command due to the locking command. As described above, by providing a regulator for adjusting the pressure of the compressed air for stationary use, the change in the position and posture of the specific part of the movable part with respect to the base part at the time of the lock can be greatly reduced.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram when an air bearing with a lock mechanism according to the present embodiment is levitated.
FIG. 2 is an explanatory diagram when the air bearing with a lock mechanism according to the present embodiment is stationary (locked).
FIG. 3 is an example of application of an air bearing with a lock mechanism according to the present embodiment to a machine.
FIG. 4 is an explanatory diagram of a bearing surface of an air bearing according to another embodiment of the present embodiment.
FIG. 5 is a cross-sectional view of an air bearing according to still another embodiment of the present embodiment.
[Explanation of symbols]
10 Air bearing with lock mechanism (air bearing)
12 Guide surface (base)
14 Slider (movable part)
16 Air bearing body
22 chambers
24 Diaphragm
28 Air Bearing Side Compressed Air Supply Pipe (Floating Compressed Air Supply Means, Floating Compressed Air Supply Pipe)
32 Lock mechanism side compressed air supply pipe (static compressed air supply means, static compressed air supply pipe)

Claims

A base, a movable part supported by the base via an air film and movable relative to the base, and a compressed air for levitation for supplying the compressed air for levitation forming the air film between the base and the movable part An air bearing comprising a supply means,
The movable portion is provided on the back surface opposite to the surface in contact with the air film, and is configured by at least a diaphragm. When compressed air for stationary is supplied, a specific portion of the outer wall of the diaphragm is deformed in the direction of increasing the thickness of the air film. A chamber;
A stationary compressed air supply means for supplying the stationary compressed air into the chamber;
And a release command of the floating compressed air supply between the base and the movable part by the floating compressed air supply means and a chamber by the stationary compressed air supply means by a lock command instructing the stationary of the movable part with respect to the base part Supply static compressed air to the inside,
The diaphragm with respect to the base is deformed by deforming a specific part of the outer wall of the diaphragm in the direction of increasing the thickness of the air film by the same amount as the thickness of the air film between the base and the movable part that disappears when the supply of the compressed air for floating is released. An air bearing characterized in that the base and the movable part are brought into contact with each other without changing the position and posture of a specific portion of the outer wall, and the movable part is stationary with respect to the base by a frictional force generated by the contact.

The air bearing according to claim 1,
The floating compressed air supply means includes a floating air supply pipe that supplies compressed air from the compressed air supply source as the floating compressed air between the base portion and the movable portion,
The stationary compressed air supply means includes a stationary air supply pipe that supplies compressed air from the compressed air supply source to the chamber as compressed compressed air.
Also, a control provided between the supply source and each of the air supply pipes, for releasing the floating compressed air supply by the floating air supply pipe and supplying the stationary compressed air by the stationary air supply pipe by the lock command. An air bearing comprising a valve.

3. The air bearing according to claim 2, wherein the chamber is provided after the control valve, and the chamber is provided via the stationary supply pipe so that the pressure of the stationary compressed air in the chamber in the lock command becomes a predetermined value. A static regulator that adjusts the pressure of the compressed air for static supply supplied to the inside, or the floating air via the floating air supply pipe so that the thickness of the air film when the lock command is released becomes a predetermined value An air bearing further comprising at least one of levitation regulators for adjusting the pressure of compressed air.

4. The air bearing according to claim 3, further comprising a sensor for measuring a distance between a specific portion of the outer wall of the diaphragm and the base, and a control circuit for controlling the regulator by an output of the sensor, regardless of whether the lock command is present. The air bearing is characterized in that the regulator is controlled so that the distance between the specific part and the base is always constant.

3. The air bearing according to claim 2, wherein a relationship between at least the pressure of the compressed air for stationary use in the chamber obtained in advance and the deformation amount in the thickness direction of the air film at a specific portion of the outer wall of the diaphragm at the pressure is stored. A stationary control memory, and
Diaphragm control information acquisition means for obtaining from the static control memory a value of the pressure of the static compressed air corresponding to the thickness of the air film between the base and the movable part that disappears when the floating compressed air supply is released by the lock command When,
The control valve is provided at a subsequent stage, and the pressure of the static compressed air in the chamber is set in the chamber via the static air supply pipe so that the pressure obtained by the diaphragm control information acquisition means becomes the pressure value. A regulator for adjusting the pressure of the supplied compressed air for stationary use;
An air bearing comprising:

The air bearing according to any one of claims 1 to 5, wherein the compressed air supply means further includes a compressed air supply groove formed in a concave shape on a surface in contact with the air film of the movable part,
A compressed air exhaust groove formed in a concave shape for collecting the floating compressed air outside the compressed air supply groove;
A compressed air exhaust hole that is opened in the wall surface of the compressed air exhaust groove and exhausts the recovered compressed air for levitation;
An exhaust pipe for connecting the compressed air exhaust hole and a suction means for sucking the recovered floating compressed air;
The air bearing is further characterized in that the compressed air for floating is recovered.

The air bearing according to claim 6, further comprising an outer peripheral resistance portion that is continuously disposed on an outer peripheral side of the compressed air exhaust groove and is disposed on substantially the same plane as a surface that contacts the air film of the movable portion. An air bearing characterized in that