JP3818881B2 - Contact type sensor - Google Patents

Description

【００１２】
ここでλは振動の次数により変化する係数、Ｉはスタイラスの断面２次モーメント、Ｅはスタイラス材料のヤング率、Ａはスタイラスの断面積、ρはスタイラスの密度、Ｌはスタイラスの長さを表している。
【００１３】
本発明の目的は、機械加工、化学工程で製作したスタイラスのアスペクト比の限界により生じる、深穴測定の限界を補い、深い穴や谷を有する表面形状の測定を可能にする接触型センサを提供することである。
【００１４】
【課題を解決するための手段】
本発明者は、上記の課題を解決するために、スタイラスの軸方向の共振周波数が形状的にスタイラス長さだけで決定されることを利用して、これまで困難とされた深穴の測定を、この深穴の形状に応じて、スタイラスの形状を加工することで深穴の三次元形状を測定することを考えた。ここで、スタイラスの軸方向の共振周波数ｆ_Lは以下の式で表現される。
【００１５】
【式（２）】

【００１６】
上記式（２）におけるパラメータは、式（１）と同様であり、スタイラスの形状に関係するパラメータは、スタイラスの長さＬだけであることがわかる。
【００１７】
具体的に、請求項１に記載の発明は、先端側に被測定物と接触する接触部を有するスタイラスと、このスタイラスを直接的あるいは間接的に支持し、一端が移動軸（スライダ）に結合されるホルダと、前記スタイラスを共振状態で振動させる加振手段と、前記接触部と前記被測定物との接触に際して生じる前記スタイラスの共振状態の変化から当該接触を検出する検出手段とを含んで構成される接触型センサにおいて、前記加振手段は、前記スタイラスをスタイラス軸方向の一軸方向のみに共振状態で振動させ、前記スタイラスは、略柱状の基端部と、断面積を小さくする加工が施されることにより前記基端部断面積よりも小さい断面積を有する略柱状の先端部と、前記基端部および前記先端部の間に位置し前記基端部側へ向うにしたがって次第に拡径するテーパ部とで構成され、サブミリオーダの内面形状を測定可能とし、前記先端部は、加工上、アスペクト比限界となる長さで形成されていることを特徴とするものである。
【００１８】
ここで、基端部断面積および先端部断面積は、スタイラス軸方向に直交した断面における断面積を表す。
本発明によれば、加振手段によってスタイラスをスタイラス軸方向に共振状態で振動させ、接触部と被測定物との接触の際に生じるスタイラスの共振状態の変化を検出手段によって検出することで、スタイラスと被測定物との接触を検出できる。
【００１９】
また、スタイラスは略柱状に形成されるとともに、ホルダに支持されるスタイラスの基端部断面積が先端部断面積よりも大きくなるように形成されているので、複雑な表面形状を持つ機械部品等のサブミリオーダの内面形状を測定するような場合、スタイラスのアスペクト比上、これまで困難とされた複雑な加工が施された深穴の測定も可能になる。
【００２０】
つまり、通常の加工において、比較的大きい断面積を有するスタイラスは容易に加工を行うことができ、このようなスタイラスは全長を長く形成することができる。ここで、その先端部に断面積を小さくする加工を施し、また、その長さをアスペクト比上限界となる長さになるように加工を施すことで、長い全長を有し、かつ被測定物近傍に位置される細い先端部を有するスタイラスを製作することができる。したがって、前述した接触型センサの測定範囲を示す、スタイラスのホルダから突出した長さを長くすることができ、深穴の最深部の三次元的な測定を可能にすることができる。
【００２１】
また、スタイラスは、該スタイラスの先端部と基端部とが、基端部側へ次第に拡径するテーパ部を介して一体的に形成されているので、被測定物の表面開口から内部に向けて、この方向に沿った断面における幅が次第に縮小するようなテーパ面を有する深穴、いわゆる皿状座ぐりを有する深穴の測定に対応できる。
【００２４】
また、請求項２に記載の発明は、前記接触部は、当該接触部の断面積が前記基端部の断面積より小さくなるように形成されていることを特徴とする。
ここで、接触部の断面積および基端部の断面積は、スタイラス軸方向に直交した断面における断面積を表す。
このような構成では、接触部は、当該接触部の断面積が基端部の断面積より小さくなるように形成されているので、測定対象である深穴の孔径によって決まる測定可能範囲が接触部によって制限されることはなく、先端部を極細に加工したスタイラスを用いて測定を行う場合でも、効果的に測定を行うことができる。
【００２５】
【発明の実施の形態】
以下、本発明の各実施形態を図面に基づいて説明する。
［第１実施形態］
図１に示すように、本発明の第１実施形態に係る接触型センサ１は、ホルダ１０と、スタイラス２０と、圧電素子３０とを備えている。
【００２６】
ホルダ１０は、図示しない三次元測定機等の移動軸に取り付けるための固定部１１と、この固定部１１から平行に延びた一対の腕部１２と、これら腕部１２と略直交して一対の腕部１２の先端側を結合する結合部１３とを備えている。結合部１３には、長手方向に沿って長孔１３Ａが形成され、これにより、長孔１３Ａの外周付近に細い棒状の平行な一対の圧電素子支持部１４が腕部１２と略直交して形成されている。つまり、一対の腕部１２で一対の圧電素子支持部１４が支持された状態となっている。
【００２７】
スタイラス２０は、略円柱状に形成され、その基端部２０Ｂの径は、先端部２０Ａの径よりも大きくなるように形成されており、先端部２０Ａと基端部２０Ｂとは基端部２０Ｂ側へ向かうにしたがって次第に拡径するようなテーパ２０Ｃを介して一体的に形成されている。また、先端部２０Ａには、被測定物と接触する球状の接触部２１が設けられており、接触部２１の径は、基端部２０Ｂの径よりも小さくなるように形成されている。なお、基端部２０Ｂには、必要に応じて図示しないカウンタバランスが設けられている。
【００２８】
圧電素子３０は、スタイラス２０を軸方向に共振状態で加振するとともに、接触部２１と被測定物との接触に際して生じるスタイラス２０の共振状態の変化を検出するためのものである。
この圧電素子３０は、一対の圧電素子支持部１４に跨った状態で、接着、はんだ付け等によりホルダ１０に装着されている。圧電素子３０のホルダ１０との装着面（図中下側の面）には、図示しない共通電極が形成され、装着面と反対側の面（図中上側の面）には、その中央で分割された２つの電極３１Ａ，３２Ａが形成されている。
【００２９】
スタイラス２０を軸方向に共振状態で加振する加振手段３１は、圧電素子３０に加振用電極３１Ａを形成し、この加振用電極３１Ａに所定周波数の電圧を印加するためのリード線（図示せず）を設けることで構成されている。
一方、接触部２１と被測定物との接触に際して生じるスタイラス２０の共振状態の変化を検出する検出手段３２は、圧電素子３０に検出用電極３２Ａを形成し、この検出用電極３２Ａに検出信号を取り出すためのリード線（図示せず）を設けることで構成されている。
【００３０】
このような圧電素子３０上面には、スタイラス２０が中心振り分けになるように、２つの電極３１Ａ，３２Ａ間に接着、はんだ付け等により装着されており、ホルダ１０とスタイラス２０とが互いに非接触の状態で、スタイラス２０と圧電素子３０とが互いに接触の状態で接触型センサ１が構成されている。
【００３１】
加振手段３１において、加振用電極３１Ａに所定周波数の電圧を印加すると、スタイラス２０がスタイラス軸方向に共振状態で振動する。このスタイラス２０の振動は、直接圧電素子３０に伝搬し、この圧電素子３０もスタイラス２０と同周波数で振動する。そして、この振動状態は、検出用電極３２Ａからの検出信号を観測することで検出可能となっている。つまり、検出手段３２によって、スタイラス２０の振動状態の検出が可能となっている。ここにおいて、スタイラス２０の振動は、直接圧電素子３０、すなわち検出手段３２に伝搬するようになっている。
【００３２】
このような構成を備えた接触型センサ１は、三次元測定機等のプローブとして用いられる。
具体的には、加振手段３１によってスタイラス２０が軸方向に沿って共振状態で振動する。この状態において、図２に示すような、入り口にテーパＷ１が施された有底の深穴を有する被測定物Ｗと接触型センサ１とを相対移動させ、接触部２１が被測定物Ｗに接触すると、スタイラス２０の振動が拘束され、スタイラス２０の共振状態（振動）に変化が生じる。この共振状態の変化を検出手段３２によって検出することで、スタイラス２０と被測定物Ｗとの接触を検出し、被測定物Ｗの三次元形状を測定できるようになる。
【００３３】
上述のような本実施形態によれば、次のような効果がある。
（１）本実施形態におけるスタイラス２０は、先端部２０Ａの径よりも基端部２０Ｂの径が大きくなるように形成され、また、該先端部２０Ａの長さはアスペクト比上限界となる長さとすれば、基端部の長さ分、スタイラス２０の全長を長くできる。例えば、図３（ｂ）の場合、スタイラス２０のアスペクト比上限界となる長さをＬｍとすると、スタイラス２０のホルダ１０から突出した長さはＬｍであるが、本実施形態の場合には、図３（ａ）のように、先端部２０Ａの長さに基端部２０Ｂの長さを付加できるので、スタイラス２０のホルダ１０から突出する長さＬを図３（ｂ）より長くできる。したがって、接触型センサ１の測定可能範囲を示すスタイラス２０のホルダ１０から突出する長さＬを、一様な径のスタイラス２０（図３（ｂ））に比べ、さらに長く形成することができるから、接触型センサ１の測定可能範囲を広げ、深穴の最深部における三次元形状測定を可能にすることができる。
【００３４】
（２）スタイラス２０は、先端部２０Ａと基端部２０Ｂとは基端部２０Ｂ側に拡径するテーパ２０Ｃを介して形成されているので、図２に示すような入り口にテーパＷ１が施された有底の深穴の測定を行う際に、テーパＷ１に対応したスタイラス２０のテーパ２０Ｃにより、スタイラス２０の基端部２０Ｂが被測定物Ｗに接触することなく、三次元形状測定が可能となる。
【００３５】
（３）スタイラスの形状が図３（ａ）に示す形状であっても、図３（ｂ）に示す円柱状の形状であっても、スタイラスの共振周波数は式（２）よりそれぞれＬ、Ｌｍで概ね決定する。つまり、本発明におけるスタイラス２０のような形状であっても、式（２）の単純な式で導くことができ、加振素子を加振する加振用回路や検出手段の出力信号を処理する信号処理回路の定数設定が簡易にできる。したがって、測定機の種類や測定対象の種類に合わせて、様々な形状のスタイラスを用いることで、接触型センサ１の使用範囲を広めることができる。
【００３６】
（４）スタイラス２０は、加振用電極３１Ａおよび検出用電極３２Ａが形成された圧電素子３０を介してホルダ１０に支持固定され、ホルダ１０とスタイラス２０とを互いに非接触の状態で接触型センサ１を構成しているので、ホルダ１０によるスタイラス２０の振動および状態変化（振動変化）の減衰を回避でき、検出手段３２によるスタイラス２０の振動および状態変化の検出を高感度にできる。したがって、スタイラス２０の接触部２１と被測定物Ｗとの接触に際して生じるスタイラス２０の状態変化を高感度にできるので、被測定物Ｗとの接触を高感度に検出できる。
【００３７】
（５）スタイラス２０は圧電素子３０上面に中心振り分けされるように接着、はんだ付け等されているので、スタイラス２０の振動の節が圧電素子上面に位置し、振動の効率がよくなる。
【００３８】
（６）スタイラス２０と圧電素子３０、すなわち検出手段３２とが互いに接触の状態にあるため、スタイラス２０の振動および状態変化が検出手段３２に直接伝搬される。これにより、スタイラス２０と被測定物との接触の際に生じるスタイラス２０の振動変化がわずかであったとしても、検出手段３２で確実に検出できる。したがって、スタイラス２０の接触部２１の形状による検出感度の劣化を防止できる。
【００３９】
（７）加振手段３１および検出手段３２は二つに分割された一つの圧電素子３０から構成されているから、少なくとも一つの圧電素子３０を設けることで、接触型センサ１に加振手段３１および検出手段３２を設けることができ、安価に構成できる。
【００４０】
［第２実施形態］
図４には本発明の第２実施形態に係る接触型センサ２が示されている。ここにおいて、本実施形態と前述の第１実施形態とは、加振手段および検出手段が一つの圧電素子で構成されるかそれぞれ別個の圧電素子で構成されるかが異なるのみで、その他の構成および作用は同一であるから、同一符号を付してそれらの説明を省略、または簡略する。
【００４１】
接触型センサ２は、加振手段３１を構成する加振用圧電素子４１と、検出手段３２を構成する検出用圧電素子４２とを備えており、二枚の圧電素子４１、４２の表裏面にはそれぞれ電極が形成されている。これら圧電素子４１、４２は、対向配置され、互いに圧電素子支持部１４を挟み込んだ状態で、かつ一対の圧電素子支持部１４にそれぞれ跨った状態でホルダ１０に装着されている。このうち、検出用圧電素子４２のホルダ１０への装着面と反対側の面には、スタイラス２０が装着されている。
【００４２】
このような構成では、加振手段３１において、加振用圧電素子４１に所定周波数の電圧を印加すると、ホルダ１０から検出手段３２へ、検出手段３２からスタイラス２０へと振動が伝搬し、スタイラス２０が軸方向に共振状態で振動する。つまり、加振手段３１は、間接的にスタイラス２０を振動させている。このスタイラス２０の振動は、直接検出用圧電素子４２に伝搬し、この検出用圧電素子４２もスタイラス２０と同周波数で振動する。そして、この振動状態は、検出用圧電素子４２の電極からの検出信号を観測することで検出可能となっている。つまり、検出手段３２によってスタイラス２０の振動状態の検出が可能となっている。
【００４３】
上述のような本実施形態によれば、前述の第１実施形態の効果（１）〜（７）に加えて、次のような効果がある。
（８）加振手段３１および検出手段３２は、それぞれ別個の圧電素子４１、４２から構成されているので、それらの電極構造を簡素化できる。
【００４４】
［第３実施形態］
図５には本発明の第３実施形態に係る接触型センサ３が示されている。ここにおいて、本実施形態と前述の第１実施形態とは、スタイラスが圧電素子に対して、中心振り分けとなって支持固定される構成であるか、スタイラスが圧電素子に対して、非対称に配置され支持固定される構成であるかが異なるのみで、その他の構成および作用は同一であるから、同一符号を付してそれらの説明を省略、または簡略する。
【００４５】
接触型センサ３は、圧電素子３０上面に、スタイラス２０の基端部２０Ｂが片側に突出しない状態で、２つの電極３１Ａ、３２Ａ間に接着、はんだ付け等により装着されており、ホルダ１０とスタイラス２０とが互いに非接触の状態で、かつ、スタイラス２０と圧電素子３０とが互いに接触の状態で接触型センサ３が構成されている。
【００４６】
このような構成では、加振手段３１において、加振用電極３１Ａに、式（２）に示されるスタイラス２０の長さによって決まる共振周波数に対応した所定の周波数の電圧を印加すると、スタイラス２０は軸方向に沿って共振状態で振動する。この状態において、被測定物と接触型センサ１とを相対移動させ、接触部２１が被測定物に接触すると、スタイラス２０の振動が拘束され、スタイラス２０の共振状態（振動）に変化が生じる。この共振状態の変化を検出手段３２によって検出することで、スタイラス２０と被測定物との接触を検出できるようになる。
【００４７】
上述のような本実施形態によれば、前述の第１実施形態の効果（１）〜（４）、（６）および（７）に加えて、次のような効果がある。
（９）スタイラス２０を圧電素子３０上面に、中心振り分けに固定するのではなく、非対称に固定することで、スタイラス２０の接触部２１からスタイラス２０が装着されている圧電素子３０までの突出している長さを長くすることができ、被測定物の最深部が深くなっても、三次元的な形状測定が可能になる。また、スタイラス２０自体を中心振り分けで使用されるスタイラス２０の長さより短くすることができることにより、スタイラス２０の製造加工を簡易にすることができる。
【００４８】
なお、本発明は、前記各実施形態に限定されるものではなく、本発明の目的を達成できる範囲での変形、改良等は本発明に含まれるものである。
たとえば、前記各実施形態では、スタイラス２０の接触部２１が球状に形成されていたが、本発明の接触部はこれに限定されるものではなく、本発明の接触型センサが用いられる測定機の測定対象に応じて接触部の形状を適宜決定すればよい。具体的に、たとえば、表面形状測定機に用いた場合には、図６（Ａ）に示すような針状の接触部２１Ａや、図６（Ｂ）に示すようなスタイラス２０の軸方向と略直交方向へ延びる突起状の接触部２１Ｂとすればよく、また、小穴測定機に用いた場合には、図６（Ｃ）に示すような算盤玉状の接触部２１Ｃとすればよい。
このように用いられる測定機の測定対象に応じて、スタイラスの接触部の形状を適宜決定することで、スタイラスと被測定物とが接触した際のスタイラスの振動の変化がより顕著となり、スタイラスと被測定物との接触をより高感度に検出できる。
【００４９】
前記各実施形態では、スタイラス２０は、略円柱状に形成され、スタイラス基端部２０Ｂの径が先端部２０Ａの径よりも大きく、先端部２０Ａと基端部２０Ｂとは、基端部２０Ｂ側に拡径するテーパ２０Ｃを介して一体的に形成されている構成としたが、これに限らず、たとえば、図７（ａ）に示すように、途中でテーパを介さず細い径の先端部２０Ａと太い径の基端部２０Ｂが段差を介して一体的に形成されてもよく、または、図７（ｂ）に示すように、先端部２０Ａが基端部２０Ｂから接触部２１に向かうにしたがって次第に縮径する略針状に形成されてもよい。本発明におけるスタイラス２０は、基端部２０Ｂの径が先端部２０Ａの径よりも大きく形成されていればよい。
【００５０】
ここで、図７（ａ）のような構成によれば、被測定物の表面側に径の大きな穴、内部に径の小さな穴を持った段付き穴の三次元形状測定に対応でき、また、スタイラス２０の製造加工を容易に行うことができる。また、図７（ｂ）のような構成によれば、被測定物の表面から内部に向けて縮径するように形成された深穴の三次元形状測定に対応でき、さらに、先端部を略針状に形成していることにより、一部に応力が集中的にかからないのでスタイラス２０の先端部２０Ａを長く形成でき、深穴の最深部の三次元形状測定を可能にする。このように、測定対象の形状に応じてスタイラスの形状を適宜決定すればよい。
この際、ホルダ１０から突出したスタイラスの長さＬを全て同一の長さに形成することにより、式（２）から、スタイラス２０の形状が異なっても、同一の共振周波数を有し、加振手段３１に与える加振周波数を変更せずに、測定を行うことができる。
【００５１】
前記各実施形態では、スタイラス２０を略円柱状に形成された構成を説明したが、これに限定されるものではなく、略角柱状に形成された構成であってもよく、式（２）より、スタイラス２０の共振周波数における形状パラメータは、スタイラス２０の長さのみであるので、スタイラス２０の断面形状はどのようなものであっても構わない。
【００５２】
前記各実施形態では、固体素子として圧電素子３０、４１、４２を用いたが、これに限定されるものではなく、磁歪素子、形状記憶素子等の固体素子であってもよい。
【００５３】
前記各実施形態では、ホルダ１０の形状がスタイラス２０に対し、左右対称な両持ち梁構造であったが、これに限定されるものではなく、片持ち梁の音叉構造であってもよい。
【００５４】
前記各実施形態では、スタイラス２０は、ホルダ１０に圧電素子３０を介して間接的に支持される構成を説明したが、スタイラス２０が、ホルダ１０に圧電素子３０を介さずに直接的に支持される構成でもよい。しかしながら、スタイラス２０の振動および状態変化の検出を高感度に行うには、スタイラス２０の振動および状態変化の減衰を回避することができる前者のような間接的な支持による構成が好ましい。
【００５５】
【発明の効果】
本発明によれば、機械加工、化学工程で製作したスタイラスのアスペクト比の限界により生じる、深穴測定の限界を補い、深い穴や谷を有する表面形状の測定を可能にすることができる。
【図面の簡単な説明】
【図１】本発明の第１実施形態に係る接触型センサを示す分解斜視図である。
【図２】本発明の測定例を示す図である。
【図３】本発明の要部を示す拡大図である。
【図４】本発明の第２実施形態に係る接触型センサを示す分解斜視図である。
【図５】本発明の第３実施形態に係る接触型センサを示す分解斜視図である。
【図６】本発明の変形例の要部を示す拡大斜視図である。
【図７】本発明の他の変形例を示す図である。
【図８】従来例を示す分解斜視図である。
【符号の説明】
１，２，３ 接触型センサ
１０ ホルダ
２０ スタイラス
２０Ａ 先端部
２０Ｂ 基端部
２０Ｃ テーパ
２１，２１Ａ，２１Ｂ，２１Ｃ 接触部
３１ 加振手段
３２ 検出手段
３０，４１，４２ 圧電素子[0001]
BACKGROUND OF THE INVENTION
The present invention is, for example, a contact type sensor that is used when measuring the fine surface shape of an object to be measured with a three-dimensional measuring machine or a surface texture measuring machine, or when measuring the inner surface shape of a hole with a small hole measuring machine. About.
[0002]
[Background]
Conventionally, height gauges (one-dimensional measuring machines), three-dimensional measuring machines have been used as measuring machines to measure the shape and dimensions of objects to be measured in research, development, and inspection at production sites in the field of precision machining or semiconductor manufacturing. Surface shape measuring machines, small hole measuring machines, and the like are known. In that case, in order to perform coordinate detection and position detection of a fine shape in the object to be measured, a contact type sensor that detects contact with the object to be measured is used for these measuring machines.
[0003]
For example, as a conventional example of such a contact type sensor, there is an excitation type contact detection sensor of Japanese Patent Application No. 2000-141469. As shown in FIG. 8, the vibration contact detection sensor 1 includes a holder 10, a stylus 20, and a piezoelectric element 30.
[0004]
The holder 10 includes a fixed portion 11 for attaching to a moving shaft such as a coordinate measuring machine (not shown), a pair of arm portions 12 extending in parallel from the fixed portion 11, and a pair of arms substantially orthogonal to the arm portions 12. And a coupling portion 13 for coupling the distal end side of the arm portion 12. A long hole 13A is formed in the coupling portion 13 along the longitudinal direction, whereby a pair of thin bar-like parallel piezoelectric element support portions 14 are formed substantially perpendicular to the arm portion 12 near the outer periphery of the long hole 13A. Has been.
The stylus 20 is formed in a substantially columnar shape, and a spherical contact portion 21 that comes into contact with an object to be measured is provided on the tip side thereof.
[0005]
The piezoelectric element 30 vibrates the stylus 20 in a resonance state in the axial direction, and detects a change in the resonance state of the stylus 20 that occurs when the contact portion 21 and the object to be measured are in contact with each other. The holder 10 is mounted in a state of straddling the element support portion 14.
In addition, a common electrode (not shown) is formed on the mounting surface with the holder 10, and a vibration electrode 31A and a detection electrode 32A are separately formed on the surface opposite to the mounting surface.
[0006]
In such a configuration, when a voltage having a predetermined frequency is applied to the excitation electrode 31A, the stylus 20 vibrates in a resonance state in the axial direction. In this state, when the contact portion 21 comes into contact with the object to be measured, a change occurs in the resonance state of the stylus 20, and this change is output by the detection electrode 32 </ b> A, thereby contacting the contact portion 21 with the object to be measured. It can be detected.
[0007]
[Problems to be solved by the invention]
By the way, when the shape of the object to be measured is a small hole, such as measuring the inner shape of the sub-millimeter order of the machine part, the depth of the small hole that can be measured by the sensor is determined by the piezoelectric element or the holder. Depth that does not interfere with the stylus, that is, the length from the stylus tip to the piezoelectric element on which the stylus is mounted. In order to measure a deeper hole or valley, a process for further extending the length protruding from the stylus holder is required, but this process is difficult.
[0008]
As a method of manufacturing and processing an ultrafine stylus, there is a processing method disclosed in Japanese Patent Application Laid-Open No. 11-271345, a fine surface shape measuring device and a stylus manufacturing method. Here, a fine electrical discharge machining method is used, and the material is processed using heat during discharge. In addition, since the process-affected layer is formed on the processed material in order to perform the processing using heat, further polishing is performed while pouring the slurry containing abrasive grains over the processed material. Yes.
[0009]
However, in order to further increase the protruding length of the stylus using the processing method as described above, the aspect ratio of the stylus becomes considerably large, and the formation of the work-modified layer of the stylus and the elimination thereof Because of the abrasive grain processing and the like, there was a processing limit.
[0010]
Furthermore, a general vibration vibration type sensor may use the bending vibration of a stylus, and the shape of the stylus cannot be changed unnecessarily. This is because the shape plane parameters that determine the resonance frequency of the bending vibration of the stylus include the stylus cross-sectional area and the stylus cross-sectional moment in addition to the stylus length, and change the stylus shape. This is because the resonance frequency of the stylus changes and it becomes difficult to estimate the resonance frequency of the stylus. In addition, when changing a complicated shape, the vibration mode is also complicated, and there is a possibility that stable sensor sensitivity cannot be obtained.
By the way, the resonance frequency f of the bending vibration of the stylus _B Is obtained by the following equation.
[0011]
[Formula (1)]

[0012]
Where λ is a coefficient that varies depending on the order of vibration, I is the moment of inertia of the cross section of the stylus, E is the Young's modulus of the stylus material, A is the cross sectional area of the stylus, ρ is the density of the stylus, and L is the length of the stylus. ing.
[0013]
An object of the present invention is to provide a contact sensor that compensates for the limitations of deep hole measurement caused by the limit of the aspect ratio of a stylus manufactured by machining and chemical processes, and enables measurement of a surface shape having deep holes and valleys. It is to be.
[0014]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventor has made measurement of deep holes, which has been difficult until now, by utilizing the fact that the axial resonance frequency of the stylus is determined solely by the stylus length. In consideration of the shape of the deep hole, the three-dimensional shape of the deep hole was measured by processing the shape of the stylus. Where the axial resonance frequency f of the stylus _L Is expressed by the following expression.
[0015]
[Formula (2)]

[0016]
It can be seen that the parameters in the above equation (2) are the same as those in the equation (1), and the only parameter related to the shape of the stylus is the stylus length L.
[0017]
Specifically, according to the first aspect of the present invention, the stylus having a contact portion that contacts the object to be measured on the tip side, and the stylus is directly or indirectly supported, and one end is coupled to the moving shaft (slider). A holder to which the stylus vibrates in a resonance state, and a detection means for detecting the contact from a change in the resonance state of the stylus that occurs upon contact between the contact portion and the object to be measured. In the configured contact sensor, the vibration means vibrates the stylus in a resonance state only in one axial direction of the stylus, and the stylus has a substantially columnar shape. The proximal end of By processing to reduce the cross-sectional area Said Than the base cross-sectional area It is composed of a substantially columnar tip portion having a small cross-sectional area, and a tapered portion that is located between the base end portion and the tip end portion and gradually increases in diameter toward the base end portion side, It is possible to measure the inner shape of the sub-millimeter order The tip portion is formed with a length that limits the aspect ratio in processing. It is characterized by this.
[0018]
Here, the cross-sectional area of the base end portion and the cross-sectional area of the distal end portion represent cross-sectional areas in a cross section orthogonal to the stylus axis direction.
According to the present invention, the vibrating means vibrates the stylus in the stylus axial direction in a resonance state, and the detection means detects the change in the resonance state of the stylus that occurs when the contact portion and the object to be measured are in contact. Contact between the stylus and the object to be measured can be detected.
[0019]
In addition, the stylus is formed in a substantially columnar shape, and the cross-sectional area of the base end portion of the stylus supported by the holder is larger than the cross-sectional area of the tip portion. In the case of measuring the inner surface shape of sub-millimeters, it is possible to measure deep holes that have been subjected to complicated processing that has been difficult until now due to the aspect ratio of the stylus.
[0020]
That is, in normal processing, a stylus having a relatively large cross-sectional area can be easily processed, and such a stylus can be formed to have a long overall length. Here, the tip part is processed to reduce the cross-sectional area, and the length is set to a length that is the upper limit of the aspect ratio, so that it has a long overall length and the object to be measured. A stylus with a narrow tip located in the vicinity can be made. Therefore, it is possible to increase the length protruding from the stylus holder, which indicates the measurement range of the contact-type sensor described above, and to enable three-dimensional measurement of the deepest part of the deep hole.
[0021]
Also , Su Since the stylus is integrally formed with the distal end portion and the proximal end portion of the stylus through a tapered portion that gradually expands in diameter toward the proximal end portion, from the surface opening of the object to be measured toward the inside, It is possible to cope with measurement of a deep hole having a tapered surface whose width in a cross section along this direction is gradually reduced, that is, a so-called countersunk deep hole.
[0024]
Claims 2 In the invention described in Item 1, the contact portion is formed such that a cross-sectional area of the contact portion is smaller than a cross-sectional area of the base end portion.
Here, the cross-sectional area of the contact portion and the cross-sectional area of the base end portion represent the cross-sectional area in a cross section orthogonal to the stylus axis direction.
In such a configuration, the contact part is formed such that the cross-sectional area of the contact part is smaller than the cross-sectional area of the base end part, and therefore the measurable range determined by the diameter of the deep hole to be measured is the contact part. However, the measurement can be effectively performed even when the measurement is performed using a stylus whose tip is finely processed.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, each embodiment of the present invention will be described with reference to the drawings.
[First Embodiment]
As shown in FIG. 1, the contact sensor 1 according to the first embodiment of the present invention includes a holder 10, a stylus 20, and a piezoelectric element 30.
[0026]
The holder 10 includes a fixed portion 11 for attaching to a moving shaft such as a coordinate measuring machine (not shown), a pair of arm portions 12 extending in parallel from the fixed portion 11, and a pair of arms substantially orthogonal to the arm portions 12. And a coupling portion 13 for coupling the distal end side of the arm portion 12. A long hole 13A is formed in the coupling portion 13 along the longitudinal direction, whereby a pair of thin bar-like parallel piezoelectric element support portions 14 are formed substantially perpendicular to the arm portion 12 near the outer periphery of the long hole 13A. Has been. That is, the pair of piezoelectric element support portions 14 are supported by the pair of arm portions 12.
[0027]
The stylus 20 is formed in a substantially cylindrical shape, and the diameter of the base end portion 20B is larger than the diameter of the tip end portion 20A. The tip end portion 20A and the base end portion 20B are the base end portion 20B. It is integrally formed through a taper 20C that gradually increases in diameter toward the side. In addition, a spherical contact portion 21 that comes into contact with the object to be measured is provided at the distal end portion 20A, and the diameter of the contact portion 21 is formed to be smaller than the diameter of the proximal end portion 20B. The base end 20B is provided with a counter balance (not shown) as necessary.
[0028]
The piezoelectric element 30 is used to vibrate the stylus 20 in the axial direction in a resonance state and to detect a change in the resonance state of the stylus 20 that occurs when the contact portion 21 contacts the object to be measured.
The piezoelectric element 30 is mounted on the holder 10 by bonding, soldering, or the like in a state of straddling the pair of piezoelectric element support portions 14. A common electrode (not shown) is formed on the mounting surface (lower surface in the drawing) of the piezoelectric element 30 with the holder 10, and the surface opposite to the mounting surface (upper surface in the drawing) is divided at the center. The two electrodes 31A and 32A thus formed are formed.
[0029]
A vibration means 31 for vibrating the stylus 20 in the axial direction in a resonance state forms a vibration electrode 31A on the piezoelectric element 30, and a lead wire for applying a voltage of a predetermined frequency to the vibration electrode 31A ( (Not shown).
On the other hand, the detection means 32 for detecting a change in the resonance state of the stylus 20 that occurs upon contact between the contact portion 21 and the object to be measured forms a detection electrode 32A on the piezoelectric element 30, and sends a detection signal to the detection electrode 32A. The lead wire (not shown) for taking out is provided.
[0030]
The upper surface of the piezoelectric element 30 is attached between the two electrodes 31A and 32A by bonding, soldering, or the like so that the stylus 20 is centered, and the holder 10 and the stylus 20 are not in contact with each other. In the state, the contact sensor 1 is configured with the stylus 20 and the piezoelectric element 30 in contact with each other.
[0031]
In the vibration means 31, when a voltage having a predetermined frequency is applied to the vibration electrode 31A, the stylus 20 vibrates in a resonance state in the stylus axis direction. The vibration of the stylus 20 propagates directly to the piezoelectric element 30, and the piezoelectric element 30 also vibrates at the same frequency as the stylus 20. This vibration state can be detected by observing a detection signal from the detection electrode 32A. That is, the detection unit 32 can detect the vibration state of the stylus 20. Here, the vibration of the stylus 20 propagates directly to the piezoelectric element 30, that is, the detection means 32.
[0032]
The contact sensor 1 having such a configuration is used as a probe for a coordinate measuring machine or the like.
Specifically, the stylus 20 vibrates in the resonance state along the axial direction by the vibration means 31. In this state, as shown in FIG. 2, the object to be measured W having a bottomed deep hole with a taper W1 at the entrance and the contact sensor 1 are moved relative to each other, and the contact portion 21 is moved to the object to be measured W. When contacted, the vibration of the stylus 20 is constrained, and a change occurs in the resonance state (vibration) of the stylus 20. By detecting the change in the resonance state by the detection means 32, the contact between the stylus 20 and the object to be measured W can be detected, and the three-dimensional shape of the object to be measured W can be measured.
[0033]
According to this embodiment as described above, the following effects are obtained.
(1) The stylus 20 in the present embodiment is formed so that the diameter of the base end portion 20B is larger than the diameter of the tip end portion 20A, and the length of the tip end portion 20A is a length that is the upper limit of the aspect ratio. By doing so, the total length of the stylus 20 can be increased by the length of the base end portion. For example, in the case of FIG. 3B, if the length that is the upper limit of the aspect ratio of the stylus 20 is Lm, the length of the stylus 20 protruding from the holder 10 is Lm. In the present embodiment, As shown in FIG. 3A, since the length of the base end portion 20B can be added to the length of the distal end portion 20A, the length L protruding from the holder 10 of the stylus 20 can be made longer than that in FIG. Therefore, the length L protruding from the holder 10 of the stylus 20 indicating the measurable range of the contact sensor 1 can be formed longer than the stylus 20 (FIG. 3B) having a uniform diameter. The measurable range of the contact sensor 1 can be expanded, and the three-dimensional shape measurement at the deepest part of the deep hole can be performed.
[0034]
(2) Since the tip 20A and the base end 20B of the stylus 20 are formed via a taper 20C that expands toward the base end 20B, a taper W1 is applied to the entrance as shown in FIG. When measuring the bottomed deep hole, the taper 20C of the stylus 20 corresponding to the taper W1 enables the three-dimensional shape measurement without the base end portion 20B of the stylus 20 contacting the workpiece W. Become.
[0035]
(3) Regardless of whether the shape of the stylus is the shape shown in FIG. 3A or the cylindrical shape shown in FIG. 3B, the resonance frequency of the stylus is L and Lm from equation (2), respectively. In general, decide. In other words, even the shape like the stylus 20 in the present invention can be derived by the simple expression of Expression (2), and the output signal of the excitation circuit and detection means for exciting the excitation element is processed. Constant setting of signal processing circuit can be simplified. Therefore, the use range of the contact sensor 1 can be widened by using styluses of various shapes according to the type of measuring instrument and the type of measurement object.
[0036]
(4) The stylus 20 is supported and fixed to the holder 10 via the piezoelectric element 30 on which the excitation electrode 31A and the detection electrode 32A are formed, and the holder 10 and the stylus 20 are in contact with each other in a non-contact state. 1 is configured, it is possible to avoid the vibration of the stylus 20 and the attenuation of the state change (vibration change) by the holder 10, and the detection means 32 can detect the vibration and the state change of the stylus 20 with high sensitivity. Therefore, since the state change of the stylus 20 that occurs when the contact portion 21 of the stylus 20 and the object to be measured W come into contact with each other can be made highly sensitive, the contact with the object to be measured W can be detected with high sensitivity.
[0037]
(5) Since the stylus 20 is bonded and soldered so as to be centered on the upper surface of the piezoelectric element 30, the vibration node of the stylus 20 is positioned on the upper surface of the piezoelectric element, and the vibration efficiency is improved.
[0038]
(6) Since the stylus 20 and the piezoelectric element 30, that is, the detection unit 32 are in contact with each other, the vibration and state change of the stylus 20 are directly propagated to the detection unit 32. Thereby, even if the vibration change of the stylus 20 generated when the stylus 20 and the object to be measured are in contact with each other is small, the detection unit 32 can reliably detect the vibration. Therefore, it is possible to prevent deterioration in detection sensitivity due to the shape of the contact portion 21 of the stylus 20.
[0039]
(7) Since the vibration means 31 and the detection means 32 are composed of one piezoelectric element 30 divided into two, the vibration means 31 is provided to the contact sensor 1 by providing at least one piezoelectric element 30. And the detection means 32 can be provided and it can comprise at low cost.
[0040]
[Second Embodiment]
FIG. 4 shows a contact sensor 2 according to a second embodiment of the present invention. Here, the present embodiment and the first embodiment described above differ only in whether the excitation means and the detection means are constituted by one piezoelectric element or separate piezoelectric elements. Since the operations are the same, the same reference numerals are used and the description thereof is omitted or simplified.
[0041]
The contact-type sensor 2 includes an excitation piezoelectric element 41 that constitutes the excitation means 31 and a detection piezoelectric element 42 that constitutes the detection means 32, and is provided on the front and back surfaces of the two piezoelectric elements 41 and 42. Each has an electrode. The piezoelectric elements 41 and 42 are arranged to face each other, and are attached to the holder 10 with the piezoelectric element support portions 14 sandwiched between each other and straddling the pair of piezoelectric element support portions 14. Among these, the stylus 20 is mounted on the surface opposite to the mounting surface of the detection piezoelectric element 42 to the holder 10.
[0042]
In such a configuration, when a voltage having a predetermined frequency is applied to the excitation piezoelectric element 41 in the excitation unit 31, vibration propagates from the holder 10 to the detection unit 32 and from the detection unit 32 to the stylus 20. Vibrates in a resonance state in the axial direction. In other words, the vibration means 31 indirectly vibrates the stylus 20. The vibration of the stylus 20 propagates directly to the detection piezoelectric element 42, and the detection piezoelectric element 42 also vibrates at the same frequency as the stylus 20. This vibration state can be detected by observing a detection signal from the electrode of the detection piezoelectric element 42. That is, the detection unit 32 can detect the vibration state of the stylus 20.
[0043]
According to the present embodiment as described above, the following effects can be obtained in addition to the effects (1) to (7) of the first embodiment.
(8) Since the excitation means 31 and the detection means 32 are each comprised from the separate piezoelectric elements 41 and 42, those electrode structures can be simplified.
[0044]
[Third Embodiment]
FIG. 5 shows a contact sensor 3 according to a third embodiment of the present invention. Here, the present embodiment and the first embodiment described above have a configuration in which the stylus is supported and fixed in a centrally distributed manner with respect to the piezoelectric element, or the stylus is disposed asymmetrically with respect to the piezoelectric element. Since only the configuration to be supported and fixed is different and the other configurations and operations are the same, the same reference numerals are given and the description thereof is omitted or simplified.
[0045]
The contact sensor 3 is mounted on the upper surface of the piezoelectric element 30 by bonding, soldering, or the like between the two electrodes 31A and 32A in a state where the base end portion 20B of the stylus 20 does not protrude to one side. The contact-type sensor 3 is configured in a state in which the stylus 20 and the piezoelectric element 30 are in contact with each other.
[0046]
In such a configuration, when the excitation means 31 applies a voltage having a predetermined frequency corresponding to the resonance frequency determined by the length of the stylus 20 shown in the expression (2) to the excitation electrode 31A, the stylus 20 It vibrates in a resonance state along the axial direction. In this state, when the object to be measured and the contact sensor 1 are relatively moved and the contact portion 21 comes into contact with the object to be measured, the vibration of the stylus 20 is constrained, and the resonance state (vibration) of the stylus 20 changes. By detecting the change in the resonance state by the detection means 32, the contact between the stylus 20 and the object to be measured can be detected.
[0047]
According to the present embodiment as described above, in addition to the effects (1) to (4), (6) and (7) of the first embodiment, the following effects are obtained.
(9) The stylus 20 protrudes from the contact portion 21 of the stylus 20 to the piezoelectric element 30 to which the stylus 20 is mounted by fixing the stylus 20 to the upper surface of the piezoelectric element 30 in an asymmetrical manner instead of fixing it to the center. The length can be increased, and three-dimensional shape measurement can be performed even when the deepest part of the object to be measured becomes deep. In addition, since the stylus 20 itself can be made shorter than the length of the stylus 20 used in the center distribution, the manufacturing process of the stylus 20 can be simplified.
[0048]
The present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
For example, in each of the above embodiments, the contact portion 21 of the stylus 20 is formed in a spherical shape. However, the contact portion of the present invention is not limited to this, and the measuring device using the contact type sensor of the present invention is not limited thereto. What is necessary is just to determine the shape of a contact part suitably according to a measuring object. Specifically, for example, when used in a surface shape measuring machine, the axial direction of the needle-shaped contact portion 21A as shown in FIG. 6A or the stylus 20 as shown in FIG. What is necessary is just to set it as the projection-shaped contact part 21B extended in an orthogonal direction, and when using for a small hole measuring machine, what is necessary is just to be the contact part 21C of the abacus ball shape as shown in FIG.6 (C).
By appropriately determining the shape of the contact portion of the stylus according to the measurement object of the measuring machine used in this way, the change in the vibration of the stylus when the stylus and the object to be measured come into contact becomes more prominent. Contact with the object to be measured can be detected with higher sensitivity.
[0049]
In each of the embodiments described above, the stylus 20 is formed in a substantially cylindrical shape, the diameter of the stylus base end 20B is larger than the diameter of the front end 20A, and the front end 20A and the base end 20B are on the base end 20B side. However, the present invention is not limited to this. For example, as shown in FIG. 7A, the tip portion 20A has a small diameter without going through a taper. The base end portion 20B having a large diameter may be integrally formed through a step, or as shown in FIG. 7B, the tip end portion 20A moves from the base end portion 20B toward the contact portion 21. It may be formed in a substantially needle shape that gradually decreases in diameter. The stylus 20 in the present invention only needs to be formed so that the diameter of the base end portion 20B is larger than the diameter of the tip end portion 20A.
[0050]
Here, according to the configuration as shown in FIG. 7 (a), it is possible to correspond to the three-dimensional shape measurement of a stepped hole having a hole having a large diameter on the surface side of the object to be measured and a hole having a small diameter inside. The stylus 20 can be easily manufactured and processed. Further, according to the configuration as shown in FIG. 7B, it is possible to cope with the three-dimensional shape measurement of the deep hole formed so as to reduce the diameter from the surface of the object to be measured toward the inside, and the tip portion is substantially omitted. By forming the needle shape, stress is not concentrated on a part of the needle, so that the tip portion 20A of the stylus 20 can be formed long, and the three-dimensional shape measurement of the deepest portion of the deep hole can be performed. In this way, the shape of the stylus may be appropriately determined according to the shape of the measurement target.
At this time, by forming all the lengths L of the stylus protruding from the holder 10 to be the same length, even if the shape of the stylus 20 is different from the equation (2), the stylus 20 has the same resonance frequency and is excited. Measurement can be performed without changing the excitation frequency applied to the means 31.
[0051]
In each of the above embodiments, the configuration in which the stylus 20 is formed in a substantially cylindrical shape has been described. However, the configuration is not limited thereto, and a configuration in which the stylus 20 is formed in a substantially prismatic shape may be used. Since the shape parameter at the resonance frequency of the stylus 20 is only the length of the stylus 20, the cross-sectional shape of the stylus 20 may be anything.
[0052]
In each of the embodiments, the piezoelectric elements 30, 41, and 42 are used as the solid elements, but the present invention is not limited to this, and solid elements such as magnetostrictive elements and shape memory elements may be used.
[0053]
In each of the above-described embodiments, the shape of the holder 10 is a both-side-supported beam structure that is symmetrical with respect to the stylus 20, but the present invention is not limited to this, and a cantilever tuning-fork structure may be used.
[0054]
In each of the embodiments described above, the configuration in which the stylus 20 is indirectly supported by the holder 10 via the piezoelectric element 30 has been described. However, the stylus 20 is directly supported by the holder 10 without the piezoelectric element 30 being interposed. It may be configured. However, in order to detect the vibration and state change of the stylus 20 with high sensitivity, a configuration based on indirect support such as the former that can avoid the vibration of the stylus 20 and attenuation of the state change is preferable.
[0055]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the limit of the deep hole measurement produced by the limit of the aspect ratio of the stylus manufactured by the machining process and the chemical process can be compensated, and the surface shape having deep holes and valleys can be measured.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing a contact sensor according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a measurement example of the present invention.
FIG. 3 is an enlarged view showing a main part of the present invention.
FIG. 4 is an exploded perspective view showing a contact sensor according to a second embodiment of the present invention.
FIG. 5 is an exploded perspective view showing a contact sensor according to a third embodiment of the present invention.
FIG. 6 is an enlarged perspective view showing a main part of a modification of the present invention.
FIG. 7 is a diagram showing another modification of the present invention.
FIG. 8 is an exploded perspective view showing a conventional example.
[Explanation of symbols]
1,2,3 Contact type sensor
10 Holder
20 Stylus
20A tip
20B Base end
20C taper
21, 21A, 21B, 21C Contact part
31 Excitation means
32 Detection means
30, 41, 42 Piezoelectric element

Claims (2)

A stylus having a contact portion in contact with the object to be measured on the distal end side;
A holder that directly or indirectly supports the stylus, one end of which is coupled to the moving shaft;
Vibration means for vibrating the stylus in a resonance state;
In a contact-type sensor configured to include detection means for detecting the contact from a change in the resonance state of the stylus that occurs when the contact portion and the object to be measured are in contact with each other,
The vibration means vibrates the stylus in a resonance state only in one axial direction of the stylus axis,
The stylus includes a substantially columnar base end portion, a substantially columnar tip having a smaller cross-sectional area than the proximal cross-sectional area by machining to reduce the cross-sectional area is performed, the base end and the It is composed of a tapered portion that is located between the distal end portions and gradually increases in diameter toward the proximal end portion side, and enables measurement of the inner surface shape of the submillimeter order ,
The contact-type sensor is characterized in that the tip is formed with a length that is an aspect ratio limit in processing . The contact sensor according to claim 1 ,
The contact portion is formed so that a cross-sectional area of the contact portion is smaller than a cross-sectional area of the base end portion.

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