JP3575264B2 - Flow velocity measuring method and device - Google Patents

Description

【０００６】
なお、磁場を用いて流速を測定する方法では、図２６の（ｂ）のように測定すべき速度起電力による信号磁場Ｂｖ の他に、励磁磁場が交流の場合には測定対象中に流れる−ｄＢ／ｄｔによる渦電流Ｊｅ が発生し、その渦電流による渦電流磁場Ｂｅ が検出される。
いま、測定しようとする鋳型内溶鋼流の流速は、０〜０．３ｍ／ｓｅｃ程度と小さいため、速度起電力による信号磁場Ｂｖ も小さく、励磁周波数が数十Ｈｚ以上と高い場合には渦電流磁場Ｂｅ に比べ大幅に小さくなってしまい、Ｂｅ が変動するとその変動の中にＢｖ が埋もれ、大きな測定誤差を生じてしまうという問題点がある。この渦電流磁場Ｂｅ は対象の流速と関係なく、流速信号のオフセット分の変動を引き起こす。
【０００７】
このような磁気を用いて非接触で速度を計測する装置として特開平２−３１１７６６号公報に示されるものがある。これは図２７の（ａ）のように溶鋼の流れ１１８と平行に１次コイル１１９、その水平方向両側に２つの２次コイル１２０ａ、１２０ｂを配置したものである。１次コイルに交流電流を印加して溶鋼面と平行な交流磁場１１７を溶鋼表面に印加し、２次コイルにより対象面と平行な磁場を検出する。導体が静止しているときには磁場は１次コイルを挟んで対称となり、２つの２次コイルの起電力に差はなく出力は零である。
導体が動いている場合には、図２７の（ｂ）のように速度効果により磁場は導体の速度方向に歪み、励磁コイルを挟んで対称でなくなるため、２つの２次コイルに生じる起電力に差が生じ、磁場の歪み量、即ち速度に対応した信号が２つの２次コイルの差分信号として得られる。
【０００８】
また磁気による方法では、装置と測定対象物体との距離（以下リフトオフと呼ぶ）により速度感度が変化するが、特開平２−３１１７６６号公報に示されたものでは、装置と測定対象物体との距離を、対象面と平行な磁場を検出する２次コイルの片方の出力電圧により測定し、補正を行っていた。
【０００９】
また磁気を用いて速度を計測する別の方法として特開平５−２９７０１２号公報に示されたものがある。これは図２８のように１次コイル１５１を測定対象１５２に対して垂直に配置し、１次コイル１５１に交流電流を印加し、磁界１５３を生じさせ、１次コイル１５１を挟んで両側に測定対象１５２に対して垂直に２次コイル１５４ａ、１５４ｂを配置し、１次コイル１５１、２次コイル１５４ａ、１５４ｂを巻いた鉄心１５５、１５６ａ、１５６ｂを備えたものである。そして流速は２次コイル１５４ａ、１５４ｂに生じた起電力の位相から検出するものであった。
【００１０】
また磁気を用いて速度を計測する別の方法として、本発明者らにより提案している特開平８−２１１０８４号公報によるものがある。これは図２９のように、中心の脚２０４ｂを中心として左右対称形のＥ型の形状をした磁心２０２に対し、中心の脚２０４ｂに励磁用の巻線２０３ｂを巻き、両端の脚２０４ａ、ｃに検出用の巻線２０３ａ，ｃをそれぞれが同じ向きの磁束を検出するように巻いたものである。これを移動する導電性の測定対象物体２０１の上に、脚の開いた面が対象面に向き、かつ各脚が対象面の移動方向に対し平行に並ぶように配置する。
【００１１】
そして励磁巻線に交流電流を流し、導体面に垂直な交流磁場を作り、２つの検出巻線の出力差を検出するものである。この時、図３０の（ａ）のように導体２０１が停止していれば、磁場は中心の脚を中心として左右対象であり、左右の検出巻線の出力は等しく、その差分は零となる。導体が動くと、図３０の（ｂ）のようにその流速に対応して磁場が歪み、両端の巻線の位置での磁束に差が出て、その差分信号が変化する。この変化量は対象の流速に対応しており、この変化量から、対象の流速を測定することができる。
またこの方法でも、リフトオフにより速度感度が変化するが、特開平８−２１１０８４号公報においては、このリフトオフを、図３１のように装置に併設した渦流距離計２５６を用いて検出し、補正を行っていた。
【００１２】
また磁気を用いて流速を計測する別の方法として、本発明者により提案している特願平８−２５５８６１号によるものがある。これは図３２のように、移動する導電性の測定対象物体の上に、対象面に対しその中心軸が垂直となるように、セラミックス製パイプ２に巻いた励磁巻線Ｐを配置し、その励磁巻線Ｐと対象面との間にセラミックス製の丸棒３に同じ向きに２つの検出巻線Ｓ_１ ，Ｓ_２ を巻いたものを、その中心軸が対象面および対象の移動方向と平行で、かつ２つの検出巻線Ｓ_１ ，Ｓ_２ の中間点が励磁巻線Ｐの中心軸上にくるように配置したものである。ここで励磁巻線Ｐに電流を流し、測定対象に磁場を励磁し、検出巻線Ｓ_１ ，Ｓ_２ で図２６の（ａ）に示した誘導磁場Ｂｖ を検出し流速を測定するものである。
またこの方法では、リフトオフの変化により、渦電流磁場Ｂｅ に起因するオフセット分が変化し、また流速感度が変化するが、前記特願平８−２５５８６１号では、図３２のように励磁装置上下に対象面に垂直な磁場成分を検出するように巻いた２つの検出巻線Ｓ_３ ，Ｓ_４ の出力電圧をもとにリフトオフを検出し、オフセットの変化、流速感度の変化を補正していた。
【００１３】
【発明が解決しようとする課題】
しかし、従来の特開平２−３１１７６６号公報、特開平５−２９７０１２号公報、特開平８−２１１０８４号公報及び特願平８−２５５８６１号のような磁場を励磁し、速度誘導磁場を検出し、検出した磁場から流速を算出するタイプの流速測定方法・装置では、先述のように励磁磁場として交流の磁場を用いた場合、検出装置で、対象より発生する渦電流磁場Ｂｅ を検出してしまい、流速信号のオフセットが変化してしまう。この変化は対象面が平坦であればリフトオフにより一意に決まるため、特願平８−２５５８６１号のように別途リフトオフを検出して補正することができる。
しかし対象面が平坦でなく波立ちがある場合には、図４のように局所的に見ると対象面が傾いており、この傾きにより渦電流磁場Ｂｅ が傾く。そのため特開平５−２９７０１２号公報及び特開平８−２１１０８４号公報のような垂直方向の磁場成分を検出する方法でも、特開平２−３１１７６６号公報及び特開平８−２５５８６１号のような水平方向の磁場成分を検出する方法でも、リフトオフが一定であっても、波の移動や変化に伴って装置下の対象面の傾きが変化するため、検出装置で検出してしまう渦電流磁場Ｂｅ の大きさが変化して、オフセット分が変化するので、リフトオフを検出して補正しても除去しきれないオフセット変化分が残り、測定誤差を生じてしまうという問題があった。
【００１４】
【課題を解決するための手段】
本発明の請求項１に係る流速測定方法は、移動する導電性の測定対象物の表面に対し垂直な磁場を励磁し、前記測定対象物の表面及びその移動方向と平行な方向の磁場を１箇所以上の範囲で検出し、該１箇所以上の範囲で検出した磁場信号に基づき前記測定対象物の流速を算出する流速測定方法において、前記励磁磁場の中心軸から前記測定対象物の移動方向と平行な方向に沿って、前記流速を測定するための磁場の検出範囲に対して、より離れた１箇所以上の範囲で、前記測定対象物の移動方向と平行な方向の磁場を検出し、該検出した磁場信号に基づき前記測定対象物の表面の傾きに係る情報を求め、該情報をもとに前記算出した測定対象物の流速を補正するものである。
【００１５】
本発明の請求項２に係る流速測定方法は、前記請求項１に係る流速測定方法において、前記測定対象物の移動方向に平行で測定対象物の表面に垂直な平面内で、前記励磁磁場が線対称となる測定対象面に対して垂直な軸を選択し、前記流速を算出するための磁場の検出範囲を、前記垂直な軸上の点を中心とした測定対象物の移動方向に平行な方向における所定長さの範囲とし、前記流速を補正するための磁場の検出範囲を、前記平面内で前記垂直な軸に対して励磁磁場が線対称となる第１及び第２の各点を中心とした、測定対象物の移動方向に平行な方向におけるそれぞれ等しい長さの範囲とし、かつ前記垂直な軸から前記第１及び第２の各点までの距離が、前記垂直な軸から前記流速を算出するための磁場の検出範囲を２等分した各々の範囲の中心位置までの距離よりもそれぞれ大きくするものである。
【００１６】
本発明の請求項３に係る流速測定方法は、前記請求項１に係る流速測定方法において、前記測定対象物の移動方向に平行で測定対象物の表面に垂直な平面内で、前記励磁磁場が線対称となる測定対象面に対して垂直な軸を選択し、前記流速を算出するための磁場の検出範囲を、前記平面内で前記垂直な軸に対して励磁磁場が線対称となる第１及び第２の各点を中心とした、測定対象物の移動方向に平行な方向におけるそれぞれ等しい長さの範囲とし、前記流速を補正するための磁場の検出範囲を、前記垂直な軸からの距離が前記第１及び第２の各点よりもそれぞれ遠方の、前記平面内で前記垂直な軸に対して励磁磁場が線対称となる第３及び第４の各点を中心とし、かつ測定対象物の移動方向に平行な方向におけるそれぞれ等しい長さの範囲とするものである。
【００１７】
本発明の請求項４に係る流速測定方法は、前記請求項１に係る流速測定方法において、前記測定対象物の移動方向に平行で測定対象物の表面に垂直な平面内で、前記励磁磁場が線対称となる測定対象面に対して垂直な軸を選択し、前記流速を算出するための磁場の検出範囲を、前記平面内で前記垂直な軸に対して励磁磁場が線対称となる第１及び第２の各点を中心とした、測定対象物の移動方向に平行な方向におけるそれぞれ等しい長さの範囲とし、前記流速を補正するための磁場の検出範囲を、前記垂直な軸上の点を中心とした測定対象物の移動方向に平行な方向における所定長さの範囲とし、かつ前記垂直な軸から前記流速を補正するための磁場の検出範囲を２等分した各々の範囲の中心位置までの距離が、前記垂直な軸から前記第１及び第２の各点までの距離よりも、それぞれ大きくするものである。
【００１８】
本発明の請求項５に係る流速測定方法は、前記請求項１に係る流速測定方法において、前記測定対象物の移動方向に平行で測定対象物の表面に垂直な平面内で、前記励磁磁場が線対称となる測定対象面に対して垂直な軸を選択し、前記流速を算出するための磁場の検出範囲を、前記垂直な軸上の点を中心とした測定対象物の移動方向に平行な方向における所定の長さの範囲とし、前記流速補正するための磁場の検出範囲を、前記垂直な軸上の点を中心とした、前記流速を算出するための磁場の検出範囲よりも、測定対象物の移動方向に平行な方向の長さが、長い範囲とするものである。
【００１９】
本発明の請求項６に係る流速測定方法は、前記請求項１から５までのいずれかの請求項に係る流速測定方法において、前記流速を算出するための磁場の検出範囲及び流速を補正するための磁場の検出範囲のすべてを、前記測定対象面に対して垂直な軸と交差し、かつ測定対象物の移動方向と平行な直線上に設けるようにしたものである。
【００２０】
本発明の請求項７に係る流速測定方法は、前記請求項１から６までのいずれかの請求項に係る流速測定方法において、前記流速を算出するための磁場の検出範囲を、前記励磁磁場の中心軸付近とし、前記流速を補正するための磁場の検出範囲を、前記測定対象物の流速に対する磁場変化量の最も小さくなる範囲とするようにしたものである。
【００２１】
本発明の請求項８に係る流速測定装置は、移動する導電性の測定対象物の表面に対し垂直な磁場を印加するように配置された励磁手段と、前記測定対象物の表面及びその移動方向と平行な方向の磁場を検出するように配置された１つ以上の磁場検出手段と、該１つ以上の磁場検出手段が検出した磁場信号に基づき前記測定対象物の流速を算出する測定手段とを有する流速測定装置において、前記測定対象物の移動方向と平行な方向上の、前記励磁磁場の中心軸から前記磁場検出手段の距離より離れた位置に配置され、前記測定対象物の移動方向と平行な方向の磁場を検出する１つ以上の副磁場検出手段と、前記１つ以上の副磁場検出手段が検出した磁場信号に基づき前記測定対象物の表面の傾きに係る情報を求め、該情報をもとに前記測定手段が算出した測定対象物の流速を補正する補正手段とを備えたものである。
【００２２】
本発明の請求項９に係る流速測定装置は、前記請求項８に係る流速測定装置において、前記測定対象物の移動方向に平行で測定対象物の表面に垂直な平面内で、前記励磁磁場が線対称となる測定対象面に対して垂直な軸を選択し、前記流速を算出するための磁場検出手段は、１つとして前記垂直な軸上に配置し、かつ測定対象物の移動方向に平行な方向における所定長さの範囲にもわたる磁場を検出するようにし、前記流速を補正するための副磁場検出手段は、２つとして前記平面内で前記垂直な軸に対して励磁磁場が線対称となる第１及び第２の各点上に配置し、さらに各副磁場検出手段は測定対象物の移動方向に平行な方向におけるそれぞれ等しい長さの範囲にわたる磁場を検出し、かつ前記垂直な軸から前記第１及び第２の各点までの距離が、前記垂直な軸から前記流速を算出するための磁場の検出範囲を２等分した各々の範囲の中心位置までの距離よりもそれぞれ大きくなるようにしたものである。
【００２３】
本発明の請求項１０に係る流速測定装置は、前記請求項８に係る流速測定装置において、前記測定対象物の移動方向に平行で測定対象物の表面に垂直な平面内で、前記励磁磁場が線対称となる測定対象面に対して垂直な軸を選択し、前記流速を算出するための磁場検出手段は、２つとしてそれぞれ前記平面内で前記垂直な軸に対して励磁磁場が線対称となる第１及び第２の各点上に配置し、かつ測定対象物の移動方向に平行な方向におけるそれぞれ等しい長さの範囲にわたる磁場を検出するようにし、前記流速を補正するための副磁場検出手段は、２つとして前記垂直な軸からの距離が前記第１及び第２の各点よりもそれぞれ遠方の、前記平面内で前記垂直な軸に対して励磁磁場が線対称となる第３及び第４の各点上に配置し、かつ各副磁場検出手段は測定対象物の移動方向に平行な方向におけるそれぞれ等しい長さの範囲にわたる磁場を検出するようにしたものである。
【００２４】
本発明の請求項１１に係る流速測定装置は、前記請求項８に係る流速測定装置において、前記測定対象物の移動方向に平行で測定対象物の表面に垂直な平面内で、前記励磁磁場が線対称となる測定対象面に対して垂直な軸を選択し、前記流速を算出するための磁場検出手段は、２つとしてそれぞれ前記平面内で前記垂直な軸に対して励磁磁場が線対称となる第１及び第２の各点上に配置し、かつ測定対象物の移動方向に平行な方向におけるそれぞれ等しい長さの範囲にわたる磁場を検出するようにし、前記流速を補正するための副磁場検出手段は、１つとして前記垂直な軸上に配置し、かつ測定対象物の移動方向に平行な方向における所定長さの範囲にわたる磁場を検出するようにし、さらに前記垂直な軸から前記流速を補正するための磁場の検出範囲を２等分した各々の範囲の中心位置までの距離が、前記垂直な軸から前記第１及び第２の各点までの距離よりも、それぞれ大きくなるようにしたものである。
【００２５】
本発明の請求項１２に係る流速測定装置は、前記請求項８に係る流速測定装置において、前記測定対象物の移動方向に平行で測定対象物の表面に垂直な平面内で、前記励磁磁場が線対称となる測定対象面に対して垂直な軸を選択し、前記流速を算出するための磁場検出手段は、１つとして前記垂直な軸上に配置し、かつ測定対象物の移動方向に平行な方向における所定長さの範囲にわたる磁場を検出するようにし、前記流速を補正するための副磁場検出手段は、１つとして前記垂直な軸上に配置し、かつ前記流速を算出するための磁場検出手段の検出範囲よりも、測定対象物の移動方向に平行な方向の長さが、長い範囲にわたる磁場を検出するようにしたものである。
【００２６】
本発明の請求項１３に係る流速測定装置は、前記請求項８から１２までのいずれかの請求項に係る流速測定装置において、前記磁場検出手段及び副磁場検出手段のすべてを、前記測定対象面に対して垂直な軸と交差し、かつ測定対象物の移動方向と平行な直線上に配置するようにしたものである。
【００２７】
本発明の請求項１４に係る流速測定装置は、前記請求項８から１３までのいずれかの請求項に係る流速測定装置において、前記磁場検出手段の検出範囲を、前記励磁磁場の中心軸付近とし、前記副磁場検出手段の検出範囲を、前記測定対象物の流速に対する磁場変化量の最も小さくなる範囲とするようにしたものである。
【００２８】
【発明の実施の形態】
本発明の実施の形態について説明する前に、まず本発明の流速測定方法および装置の動作原理について説明する。
（１）流速測定原理
ここでは元となる流速測定装置として図３のようなセンサヘッドを用いた場合について説明する。
このセンサヘッドは、図３のように、励磁装置として移動する導電性の測定対象体の上に、対象面に対しその中心軸が垂直となるように１つの励磁巻線Ｐを配置し、流速検出用の検出装置として、その励磁巻線Ｐと対象面の間に、２つの検出巻線Ｓ_１ ，Ｓ_２ を対象面および対象の移動方向にその中心軸が平行となり、かつ２つの検出巻線Ｓ_１ ，Ｓ_２ の中間点が励磁巻線Ｐの中心軸上にくるように配置したものである。このＳ_１ ，Ｓ_２ を以下、流速検出用の検出巻線と呼ぶ。
【００２９】
ここで、励磁巻線Ｐに交流の励磁電流を供給し、対象面に対し垂直な磁場を励磁する。すると、前述の速度効果による誘導磁場Ｂｖ が生じる。この誘導磁場Ｂｖ は図５のように励磁巻線Ｐの直下の検出巻線の位置では対象面に平行となっており、このＢｖ を、対象面に平行に配置した２つの検出巻線Ｓ_１ ，Ｓ_２ の和信号をとることで検出する。この検出したＢｖ は対象の流速に対応しているので、これから対象の流速を測定することができる。
実際には検出巻線Ｓ_１ ，Ｓ_２ の出力信号を、ロックインアンプ等を用いて励磁電流と−９０゜ずれた位相の成分を検波し、流速測定の元となる流速元信号とする（本来は励磁磁場即ち励磁電流と同位相の磁場成分を検波するが、ここでは磁場の検出に検出巻線を用いており、検出巻線で検出する磁場と検出巻線の検出電圧とに−９０゜の位相差があるため、−９０゜ずれた位相成分を検波する）。
【００３０】
（２）波立ちの影響対策
波立ちにより装置下の対象面が傾いていると、先述のようにこの流速検出用の検出巻線Ｓ_１ ，Ｓ_２ の出力信号である流速元信号のオフセットが変化し、正確な流速測定が不可能となる。
そこで図３の様に新たに検出巻線Ｓ_３ ，Ｓ_４ を、その中心軸が流速検出用の検出巻線Ｓ_１ ，Ｓ_２ の中心軸と同じとなるように、かつ励磁装置の中心軸を中心として対称の位置に、Ｓ_１ ，Ｓ_２ の外側に近接して配置する（請求項１〜６、８〜１３に対応）。
そしてこの検出巻線Ｓ_３ ，Ｓ_４ の和信号を、Ｓ_１ ，Ｓ_２ と同様に、ロックインアンプ等を用いて励磁電流と−９０゜ずれた位相の成分を検波する。
【００３１】
この新たな検出巻線Ｓ_３ ，Ｓ_４ は、流速検出用の検出巻線Ｓ_１ ，Ｓ_２ に近い位置で、Ｓ_１ ，Ｓ_２ と同じ方向の磁場を検出しているため、対象面の傾きによる渦電流磁場Ｂｅ の変化の影響をＳ_１ ，Ｓ_２ とほぼ同じように受ける。そのためこのＳ_３ ，Ｓ_４ の和信号からＳ_１ ，Ｓ_２ の和信号つまり流速元信号の傾きによるオフセット分の変化を演算することができ、傾きによるオフセット分の変化を補正することが可能となる（補正法は図８，９及び図１２，１３で説明する）。
以下このＳ_３ ，Ｓ_４ のことを流速検出用の検出巻線Ｓ_１ ，Ｓ_２ に対応して、傾き検出用の検出巻線、その和信号の検波後の信号を傾き元信号と呼ぶ。
【００３２】
図８に図３のセンサヘッドの対象面の傾きに対する流速元信号と傾き元信号の変化の様子を示す。
ここでは測定対象として、図６のようにＳＵＳ３１６製の板を用い、板を傾ける試験を行った。
試験の結果、図８の実線で示す流速元信号（Ｓ_１ ＋Ｓ_２ ）、破線で示す傾き元信号（Ｓ_３ ＋Ｓ_４ ）は、ともに傾きに対する変化はほぼ直線的であった。
【００３３】
そこで、図８の傾き−流速元信号特性直線の勾配（特性直線の傾き）をＡｆ 、傾き−傾き元信号特性直線の勾配（特性直線の傾き）をＡｓ とすると、次の（２）式で決まる係数αを用いて、（３）式のようにすれば、傾きの影響を補正できることが分かる。
α＝Ａｆ ／Ａｓ …（２）
（傾き補正後の信号）＝（流速元信号）−α・（傾き元信号） …（３）
なお、図８で傾き０でも各信号が０となっていないが、これは対象面の傾きが０であっても、対象から渦電流磁場Ｂｅ が生じており、これによるオフセット分である。この傾き０でのオフセット分は、対象面とのリフトオフにより一意に決まり、特願平８−２５５８６１号と同様に、何らかの方法でリフトオフを検出し補正することができる。
【００３４】
（３）傾き検出用の検出巻線の最適位置
前記（２）で説明したように、傾き検出用の検出巻線Ｓ_３ ，Ｓ_４ と流速検出用の検出巻線Ｓ_１ ，Ｓ_２ とは、渦電流磁場Ｂｅに対する特性がほぼ同じとなるが、同様に速度効果による誘導磁場Ｂｖ に対してもほぼ特性が同じとなり、流速元信号から適当な係数をかけて傾き元信号を引くと、対象面の傾きの影響を補正することができる反面、流速に対する信号の大きさもまた低減してしまうという問題がある。
図９に対象の流速に対する流速元信号と傾き元信号の変化の様子を示す。
ここでは図７のようにＳＵＳ３１６製の円板を回転させ、その上に本装置のセンサヘッドを配置して各信号を測定した。図７の（ａ）はこの試験装置を正面からみた図、（ｂ）は真上からみた図である。
図７の試験装置による試験の結果、図９の実線で示す流速元信号（Ｓ_１ ＋Ｓ_２ ）、破線で示す傾き元信号（Ｓ_３ ＋Ｓ_４ ）は、ともに対象の流速に対する変化はほぼ直線的で、両者の特性がほぼ等しいことが分かる。
【００３５】
そこで、図８の流速−流速元信号特性直線の勾配（特性直線の傾き）をＢｆ 、流速−傾き元信号特性直線の勾配（特性直線の傾き）をＢｓ とし、係数βを次の（４）式とおき、
β＝Ｂｆ ／Ｂｓ …（４）
また係数ｋを次の（５）、（６）式とおくと、

前記（３）式による（傾き補正後の流速に対する信号）の大きさは、補正前に比べ、１／ｋに低減する。たとえば図８，図９の特性を持つ装置の場合には、傾き補正後、流速に対する信号は、補正前に比べ約１／１５に減衰してしまうこととなる。
【００３６】
そこでここでは、傾き補正用の検出巻線と流速検出用の検出巻線との位置を変え、この流速信号の低減率を小さくすることを試みる。
いま、図１０のように１つの検出巻線の位置を、巻線の中心軸を対象の流速方向と平行に保ったまま、流速の方向と平行な方向（Ｘ方向、Ｘ＝０は励磁巻線中心軸上の点）に走査して、その検出巻線の出力信号における、流速特性直線の勾配（特性直線の傾き）Ｂ（Ｂｆ ，Ｂｓ に対応）および傾き特性直線の勾配（特性直線の傾き）Ａ（Ａｆ ，Ａｓ に対応）の変化の様子を調べ、その結果を図１１に示す（図１１ではＸ＝０ｍｍの値で正規化している）。
なお、図１０の測定対象は、傾き特性の場合はＳＵＳ板、流速特性の場合はＳＵＳ円板とした。
【００３７】
図１０及び図１１の結果から、以下のことが分かる。
（ａ）流速特性直線の勾配Ｂは励磁磁場中心軸付近が最大である。すなわち流速感度は中心軸付近が最大である。
（ｂ）流速特性直線の勾配Ｂ、傾き特性直線の勾配Ａ共に、励磁巻線の中心軸からの距離が離れると減少するが、流速特性直線の勾配Ｂの減衰率は傾き特性直線の勾配Ａの減衰率に比べ大きく、Ａよりも励磁巻線中心軸に近い点で０になる。よってＢ＝０となる点（即ち対象物の流速に対する磁場変化量の最も小さくなる位置）に、傾き検出巻線を配置すれば、（６）式からｋ＝１となり、流速感度を低下させることなく傾き補正を行うことができる。
【００３８】
以上から、各検出巻線の最適な位置が以下であることが分かった（請求項７、１４に対応）。
（ａ）流速検出用の検出巻線：可能な限り励磁磁場の中心軸に近い位置
（ｂ）傾き検出用の検出巻線：流速特性直線の勾配Ｂが０となる位置
この最適な検出巻線配置は例えば図２のようになるが、この場合の流速元信号と傾き元信号の、対象面の傾きに対する変化の様子及び対象の流速の対する変化の様子を、それぞれ図１２及び図１３に示す。
【００３９】
（４）リフトオフ変動の補正
本装置のセンサヘッドの流速検出位置と測定対象面との間の距離（即ちリフトオフ）が変化すると、傾きの影響補正後の信号に含まれる、傾き０でのリフトオフにより一意に決まるオフセット分が変化し、さらに本装置の流速感度が変化するが、後で説明する実施形態では、これらのリフトオフ変動の影響を、リフトオフを検出して補正する。ここでリフトオフの検出方法、リフトオフ変動の補正方法について簡単に説明する。
ここでは、特願平８−２５５８６１号と同様に、図２のように励磁巻線Ｐと対象面との間、およびそれと励磁巻線Ｐを中心に対称な位置に、励磁巻線Ｐと同軸に、対象面に対し垂直方向でそれぞれが同じ向きの磁場を検出するように２つの検出巻線Ｓ_５ ，Ｓ_６ を配置し、その差分信号からリフトオフの検出を行う。この検出巻線Ｓ_５ ，Ｓ_６ を以下リフトオフ検出用の検出巻線と呼ぶ。
【００４０】
このとき図５のように対象面に対し流速測定用の励磁巻線により垂直に磁場が励磁されているので、この磁場により対象中に流れる渦電流Ｊｅ によって、対象面に対し垂直な渦電流磁場Ｂｅが生じる。この渦電流磁場Ｂｅ は、対象面との距離によって変化するので、この渦電流磁場を検出巻線Ｓ_５ ，Ｓ_６ で検出すれば、対象面との距離すなわちリフトオフを検出することができる。
さらにリフトオフを変化させたときに、この傾き０でのリフトオフにより一意に決まるオフセット分がどう変化するかという、リフトオフ−オフセット特性、および流速感度がどう変化するかという、リフトオフ−流速感度特性をあらかじめ測定しておき、この特性を元に検出したリフトオフ信号を用いて、リフトオフ変動の影響を補正する。
以上で本発明の流速測定方法及び装置の動作原理についての説明が終了したので、次に本発明の実施形態について説明する。
【００４１】
実施形態１
図１は本発明の実施形態１に係る流速測定装置の構成図であり、図の装置は図２のような構成のセンサへッド１と、速測定回路３０、傾き検出回路４０、リフトオフ測定回路５０及び補正回路７０とからなる。
【００４２】
センサヘッド１は、図２のように、移動する導電性の測定対象物体の上に、対象面に対しその中心軸が垂直となるようにセラミックス製丸パイプ２に巻いた励磁巻線Ｐを配置し、その励磁巻線Ｐと対象面との間にセラミックス製の丸棒３を、その中心軸が対象面および対象の移動方向と平行となるように配置し、この丸棒３に励磁巻線Ｐの中心軸を中心として対称の位置に、２つの流速検出用の検出巻線Ｓ_１ ，Ｓ_２ を隣接して巻き、さらにセラミックス製の丸パイプ２より外側に、励磁巻線の中心軸を中心として対称の位置に、２つの傾き検出用の検出巻線Ｓ_３ ，Ｓ_４ を巻、さらに励磁巻線Ｐを巻いたセラミックス製丸パイプ２に対し、励磁巻線Ｐと対象との間に１つ、およびそれと励磁巻線Ｐを挟んで対称な位置に１つ、計２つのリフトオフ検出用の検出巻線Ｓ_５ ，Ｓ_６ を巻いたものである。
なおここで用いた装置の場合は、図２の傾き検出用の検出巻線の位置がほぼ最適な位置であり、このＳ_３ ，Ｓ_４ の位置で、流速特性直線の勾配Ｂはほぼ０となる。
【００４３】
流速測定回路３０は図１のように、励磁回路１０及び検出回路２０からなる。励磁回路１０は、発振器１１及び定電流アンプ１２からなる。また検出回路２０は、ブリッジ回路２１、バンドパスフィルタ２２及びロックインアンプ２３からなる。
励磁回路１０は、励磁巻線Ｐに電流を流し、測定対象に磁場を励磁する。このため、発振器１１により１Ｈｚ〜１ｋＨｚ の正弦波を発生させ、定電流アンプ１２を介して励磁巻線Ｐに励磁電流を供給する。ここでは励磁周波数は７０Ｈｚとした。
【００４４】
流速検出用の検出巻線Ｓ_１ ，Ｓ_２ からの出力信号は、検出回路２０に入る。ここで２つの検出巻線からの２信号はまずブリッジ回路２１で加算されて、その和信号が算出される。このブリッジ回路２１は、センサヘッド周囲に磁性あるいは導電性のもの、あるいは電磁場を発生するものがない状態で、その出力信号がゼロとなるようにあらかじめ調節しておく。このようにすることで、２つの検出巻線Ｓ_１ ，Ｓ_２ で検出してしまう不要な励磁磁場信号をキャンセルするようにブリッジ回路２１を調整できる。
その調整後の信号は、励磁回路１０の励磁電流の周波数を中心周波数とし、所定帯域幅のバンドパスフィルタ２２により、不要帯域のノイズ信号をあらかじめ除去した後に、ロックインアンプ２３によって、励磁回路１０の励磁電流に対し−９０°ずれた位相の成分が検波される。この検波用の基準位相信号（ｒｅｆ）が発振器１１からロックインアンプ２３に供給される。そしてロックインアンプ２３による検波後の信号が流速測定の元となる流速元信号である。
【００４５】
また傾き検出用の検出巻線Ｓ_３ ，Ｓ_４ からの出力信号は、傾き検出回路４０に入る。傾き検出回路４０はブリッジ回路４１、バンドパスフィルタ４２及びロックインアンプ４３からなる。
ここで２つの検出巻線Ｓ_３ ，Ｓ_４ からの２信号はまずブリッジ回路４１で加算され、その和信号が算出される。このブリッジ回路４１は、センサヘッドの周囲に磁性あるいは導電性のもの、あるは電磁場を発生するものがない状態で、その出力信号がゼロとなるようにあらかじめ調節しておく。
この調整後の信号は励磁回路１０の励磁電流の周波数を中心周波数とし、所定帯域幅のバンドパスフィルタ４２により、不要帯域のノイズ信号をあらかじめ除去した後に、ロックインアンプ４３によって、励磁回路１０の励磁電流に対し−９０°ずれた位相の成分が検波される。この検波用の基準位相信号が発振器１１からロックインアンプ４３に供給される。そしてロックインアンプ４３による検波後の信号が傾き補正の元となる傾き元信号である。
【００４６】
またリフトオフ検出用の検出巻線Ｓ_５ ，Ｓ_６ からの出力信号は、リフトオフ測定回路５０に入る。リフトオフ測定回路５０は、ブリッジ回路５１、バンドパスフィルタ５２及びロックインアンプ５３からなる。
ここで２つの検出巻線Ｓ_５ ，Ｓ_６ からの信号はまずブリッジ回路５１で減算され差分信号が算出される。このブリッジ回路５１は、センサヘッドの周囲に磁性あるいは導電性のもの、あるいは電磁場を発生するものがない状態で、その出力信号がゼロとなるようにあらかじめ調節しておく。
その調整後の信号は励磁回路１０の励磁電流の周波数を中心周波数とし、所定帯域幅のバンドパスフィルタ５２により、ノイズ信号をあらかじめ除去した後に、ロックインアンプ５３によって、励磁回路１０の励磁電流に対し−１８０°ずれた位相の成分が検波される（本来は励磁磁場即ち励磁電流と−９０°ずれた磁場成分を検波するが、ここでは磁場の検出に検出巻線を用いており、磁場と検出巻線の検出電圧とが−９０°の位相差があるため、−１８０°ずれた位相成分が検波される）。この検波用の基準位相信号が発振器１１からロックインアンプ５３に供給される。そしてロックインアンプ５３による検波後の信号がリフトオフ補正の元となるリフトオフ元信号である。
【００４７】
その後、流速測定回路３０の出力信号である流速元信号と、傾き検出回路４０の出力信号である傾き元信号と、リフトオフ測定回路５０の出力信号であるリフトオフ元信号とは補正回路７０に入る。
この補正回路７０は、Ａ／Ｄ変換器７１、コンピュータ７２及びＤ／Ａ変換器７３からなる。補正回路７０では、まずＡ／Ｄ変換器７１により流速元信号と、傾き元信号と、リフトオフ元信号とをそれぞれＡ／Ｄ変換し、コンピュータ７２に取り込む。そして以下の処理はコンピュータ７２上でソフトウェアにより行う。
（１）コンピュータ上では、まずリフトオフ元信号からリフトオフを演算する。ここではあらかじめリフトオフを変えたときのリフトオフ元信号の変化の様子を測定しておき、このリフトオフ−リフトオフ元信号特性曲線をもとにリフトオフ元信号からリフトオフを演算している。
【００４８】
（２）次に（３）式のように傾き元信号に係数αを掛け流速元信号から引いて、傾きの影響を補正する。ここでは係数αは一般にリフトオフにより変化するため、各リフトオフごとに図８，図１２のような傾き特性をあらかじめ取得しておき、それから（２）式を用いて求める。
（３）続いて傾きの影響除外後の信号のリフトオフ変動の補正を行う。ここではまず、先に演算したリフトオフを元に、渦電流磁場Ｂｅによるオフセット分を演算し、これを傾きの影響除外後の信号から引く。ここではあらかじめリフトオフを変えたときの傾き補正後の信号に含まれるオフセットの変化の様子を測定しておき、このリフトオフ−オフセット特性曲線をもとにリフトオフからオフセット分を演算している。
【００４９】
（４）次にオフセット分を差し引いた信号からリフトオフの変化に伴う流速感度変化分を補正し最終的な流速値を得る。ここではあらかじめリフトオフを変えたときの傾き補正後の信号の流速感度（対象の流速が０ｍ／ｓｅｃと、１ｍ／ｓｅｃの時での傾き補正後の信号の変化量）の様子を測定しておき、このリフトオフ−流速感度特性曲線をもとに、そのリフトオフでの流速感度を演算し、オフセット分を差し引いた後の信号をこの演算した流速感度で除算して、最終的な流速値を得る。
【００５０】
前記実施形態１では、流速測定用のセンサヘッドとして、図２，３のような構成のもの（即ち磁場検出巻線の素子数を、流速検出用巻線がＳ_１ ，Ｓ_２ の２つ、傾き検出用巻線がＳ_３ ，Ｓ_４ の２つとし、このＳ_１ 〜Ｓ_４ のすべてを測定対象物の移動方向と平行な同一直線上に配置した構成のもの）を用いて説明をしたが、他の構成による数多くのセンサヘッドを実現することができる。
本発明の本質は、対象の流速と平行な方向の磁場を検出する検出装置で流速を検出し、それとはまた別の位置の対象の流速と平行な方向の磁場を検出する検出装置で傾きを検出して補正をする点であり、この条件を満たす様々な形態を含むものである。
【００５１】
例えば、図１４〜１９の各々（ｂ），（ｃ），（ｄ）に示されるように流速検出用の検出巻線のみを１つ（図示のＳ_１ ）とする、あるいは傾き検出用の検出巻線のみを１つ（図示のＳ_３ ）とする、または流速検出用巻線と傾き検出用巻線の両方をそれぞれ１つとしても、実施形態１の場合と同様の機能を得ることができる（請求項２，４，５，９，１１，１２に対応）。
このように流速検出用巻線や傾き検出用巻線を１つのみとした場合は、ブリッジ回路を通すことなく、各検出巻線の出力信号をロックインアンプなどに直接入力して検波すればよい。
なお、例えば図１４の（ｃ）のように長い巻線を使用した場合、ほぼその全長にわたる磁場の平均値を検出するが、その検出巻線が励磁磁場中心軸をまたがない場合は、その巻線の出力は、ほぼその巻線の中心位置の磁場の大きさに相当する。また検出巻線が励磁磁場中心軸をまたぐ場合は、励磁磁場中心軸上でその検出巻線を２つに分け、おのおのの中心位置の磁場の大きさを足し合わせた値に相当する出力信号が得られる。
【００５２】
また、図１４の（ｃ），（ｄ）、図１５の（ｃ），（ｄ）のように、傾き検出用の検出巻線の上に流速検出用の検出巻線を巻いてもかまわない。
また流速検出用、傾き検出用の検出巻線が２つ以上あっても、それぞれの巻線の和信号をとれば構わない。
また図１５，１７，１９のように傾き検出用の検出巻線を、セラミックス丸パイプの外側でなく、内側に流速検出用の検出巻線と隣接して配置しても構わない。
また図１６〜１９のように流速検出用の検出巻線と傾き検出用の検出巻線とを同軸の丸棒に巻かずに、別々に巻いても構わない。そして両者の対象面からの高さが違っていても構わない。
またすべての場合において、流速検出用の検出巻線と傾き検出用の検出巻線とを逆に配置しても良いが、これは（３）式の補正式を見ても明らかなように、流速検出用の検出巻線を傾き検出用の検出巻線として、傾き検出用の検出巻線を流速検出用の検出巻線として用いるだけで本質的には元の場合と変わらない。
【００５３】
本発明のもう一つの本質は、傾き検出用の磁場の検出装置を、励磁磁場中心軸から対象の移動方向と平行な方向に沿って、流速検出用の磁場の検出装置よりも離すところにある（請求項７，１４に対応）。
これは例えば、図１４の（ａ）のように傾き検出用の検出巻線が２つ、流速検出用の検出巻線が２つの場合には、傾き検出用の検出巻線Ｓ_３ ，Ｓ_４ の中心位置は、励磁磁場中心軸からの距離が、流速検出用の検出巻線Ｓ_１ ，Ｓ_２ の中心位置よりも長くなるように、遠方に離せばよい。
また図１５の（ｄ）のように傾き検出用の検出巻線が１つ、流速検出用の検出巻線が１つの場合、傾き検出用の検出巻線Ｓ_３ の長さ（図の水平方向の長さ）を流速検出用の検出巻線Ｓ_１ よりも長くとればよい。
この場合、双方の検出巻線とも励磁磁場中心軸をまたいでいるため、先に説明したように、双方の検出巻線を励磁磁場中心軸で２つに分けて考えればよいが、すると図１５の（ｄ）の構成は、同図の（ｅ）とほぼ同じとなり、よって傾き検出用の磁場の検出装置は、流速検出用の磁場の検出装置よりも、励磁磁場中心軸より離れた位置となる。
また図１６〜図１９の構成は、流速検出用の検出巻線と傾き検出用の検出巻線とを、それぞれ別個のセラミックス製丸棒に巻いて、測定対象面からの高さが異なる位置に配置したが、各々のセラミックス製丸棒を測定対象面からの高さが同一で、各々の中心軸が流速の方向と平行になるように測定対象面に対して水平に並べて（図の前面と背面に水平に並べて）配置してもよい。
【００５４】
前記図１４〜１９に示した多くのセンサヘッドの構成例のうちから、磁場検出巻線の素子数とその配置により分類した実施形態を以下に示す。なおこのセンサヘッドの構成により分類した実施形態においては、前記説明と重複する部分も含まれる。
実施形態２
実施形態２は、例えば図１４の（ｂ）、図１５の（ｂ）、図１６の（ｂ）、図１７の（ｂ）、図１８の（ｂ）、または図１９の（ｂ）に示されるように、流速検出用巻線はＳ_１ の１つとし、傾き検出用巻線はＳ_１ の両側に設けたＳ_３ ，Ｓ_４ の２つとするセンサヘッドの構成である（請求項２，９に対応）。
本実施形態２における各検出巻線の配置及びその検出範囲は次の通りである。まず測定対象物の移動方向に平行で測定対象物の表面に垂直な平面内で、励磁巻線Ｐによる励磁磁場が線対称となる測定対象面に対して垂直な軸を選択し、単一の流速検出用巻線Ｓ_１ は、前記垂直な軸上に配置し、かつ測定対象物の移動方向に平行な方向における所定長さの範囲にわたる磁場を検出するようにし、２つの傾き検出用巻線Ｓ_３ ，Ｓ_４ は、前記平面内で前記垂直な軸に対して励磁磁場が線対称となる第１及び第２の各点上に配置し、さらに各傾き検出用巻線Ｓ_３ ，Ｓ_４ は測定対象物の移動方向に平行な方向におけるそれぞれ等しい長さの範囲にわたる磁場を検出し、かつ前記垂直な軸から前記第１及び第２の各点までの距離が、前記垂直な軸から前記流速を算出するための磁場の検出範囲を２等分した各々の範囲の中心位置までの距離よりもそれぞれ大きくなるようにする。
【００５５】
実施形態３
実施形態３は 例えば図２と重複する図１４の（ａ）、図３と重複する図１５の（ａ）、図１６の（ａ）、図１７の（ａ）、図１８の（ａ）、または図１９の（ａ）に示されるように、流速検出用巻線はＳ_１ ，Ｓ_２ の２つとし、傾き検出用巻線はＳ_１ ，Ｓ_２ の両側に設けたＳ_３ ，Ｓ_４ の２つとするセンサヘッドの構成である（請求項３，１０に対応）。
本実施形態３における各検出巻線の配置及びその検出範囲は次の通りである。
まず前記測定対象物の移動方向に平行で測定対象物の表面に垂直な平面内で、励磁巻線Ｐによる励磁磁場が線対称となる測定対象面に対して垂直な軸を選択し、２つの流速検出用巻線Ｓ_１ ，Ｓ_２ は、それぞれ前記平面内で前記垂直な軸に対して励磁磁場が線対称となる第１及び第２の各点上に配置し、かつ測定対象物の移動方向に平行な方向におけるそれぞれ等しい長さの範囲にわたる磁場を検出するようにし、２つの傾き検出用巻線Ｓ_３ ，Ｓ_４ は、前記垂直な軸からの距離が前記第１及び第２の各点よりもそれぞれ遠方の、前記平面内で前記垂直な軸に対して励磁磁場が線対称となる第３及び第４の各点上に配置し、かつ各傾き検出用巻線Ｓ_３ ，Ｓ_４ は測定対象物の移動方向に平行な方向におけるそれぞれ等しい長さの範囲にわたる磁場を検出するようにする。
【００５６】
実施形態４
実施形態４は 例えば図１４の（ｃ）、図１５の（ｃ）、図１６の（ｃ）、図１７の（ｃ）、図１８の（ｃ）、または図１９の（ｃ）に示されるように、流速検出用巻線はＳ_１ ，Ｓ_２ の２つとし、傾き検出用巻線は、Ｓ_１ ，Ｓ_２ を包含する検出範囲よりも測定対象物の移動方向と平行な方向に長い検出範囲をもつＳ_３ の１つとするセンサヘッドの構成である（請求項４，１１に対応）。
本実施形態４における各検出巻線の配置及びその検出範囲は次の通りである。
まず前記測定対象物の移動方向に平行で測定対象物の表面に垂直な平面内で、励磁巻線Ｐによる励磁磁場が線対称となる測定対象面に対して垂直な軸を選択し、２つの流速検出用巻線Ｓ_１ ，Ｓ_２ は、それぞれ前記平面内で前記垂直な軸に対して励磁磁場が線対称となる第１及び第２の各点上に配置し、かつ測定対象物の移動方向に平行な方向におけるそれぞれ等しい長さの範囲にわたる磁場を検出するようにし、単一の傾き検出用巻線のＳ_３ は、前記垂直な軸上に配置し、かつ測定対象物の移動方向に平行な方向における所定長さの範囲にわたる磁場を検出するようにし、さらに前記垂直な軸から前記傾き検出用巻線Ｓ_３ の磁場の検出範囲を２等分した各々の範囲の中心位置までの距離が、前記垂直な軸から前記第１及び第２の各点までの距離よりも、それぞれ大きくなるようにする。
【００５７】
実施形態５
実施形態５は 例えば図１４の（ｄ）、図１５の（ｄ）、図１６の（ｄ）、図１７の（ｄ）、図１８の（ｄ）、または図１９の（ｄ）に示されるように、流速検出用巻線はＳ_１ の１つとし、傾き検出用巻線は、Ｓ_１ の検出範囲よりも測定対象物の移動方向と平行な方向に長い検出範囲をもつＳ_３ の１つとするセンサヘッドの構成である（請求項５，１２に対応）。
本実施形態５における各検出巻線の配置及びその検出範囲は次の通りである。
まず前記測定対象物の移動方向に平行で測定対象物の表面に垂直な平面内で、励磁巻線Ｐによる励磁磁場が線対称となる測定対象面に対して垂直な軸を選択し、単一の流速検出用巻線Ｓ_１ は、前記垂直な軸上に配置し、かつ測定対象物の移動方向に平行な方向における所定長さの範囲にわたる磁場を検出するようにし、単一の傾き検出用巻線Ｓ_３ も、前記垂直な軸上に配置し、かつ流速検出用巻線Ｓ_１ の磁場検出範囲よりも、測定対象物の移動方向に平行な方向の長さが、長い範囲にわたる磁場を検出するようにする。
【００５８】
実施形態６
実施形態６は 例えば図２と重複する図１４の（ａ）及び図１４の（ｂ），（ｃ），（ｄ）、図３と重複する図１５の（ａ）及び図１５の（ｂ），（ｃ），（ｄ）に示すように、流速検出用巻線及び傾き検出用巻線のすべてを、前記測定対象面に対して垂直な軸と交差し、かつ測定対象物の移動方向と平行な直線上に配置するようにしたものである（請求項６，１３に対応）。
【００５９】
実施形態７
実施形態７は 図２と重複する図１４の（ａ）もしくは（ｂ）、図１６の（ａ）もしくは（ｂ）、または図１８の（ａ）もしくは（ｂ）に示されるように、また段落［００３７］及び［００３８］で説明したように、流検出用巻線Ｓ_１ 及びＳ_２ 、またはＳ_１ の磁場検出範囲を、励磁巻線Ｐによる励磁磁場の中心軸付近とし、傾き検出用巻線Ｓ_３ ，Ｓ_４ の磁場検出範囲を、前記測定対象物の流速に対する磁場変化量の最も小さくなる範囲とするようにしたものである（請求項７，１４に対応）。
【００６０】
その他の実施形態
実施形態１では、流速検出用巻線と、傾き検出用巻線の直径を同一としているが、両者が異なる直径であってもよい。
また実施形態１では、流速検出用、傾き検出用の検出装置は、いずれもセラミックス製のボビンに巻線を巻いた空心タイプのものを用いていたが、フェライト等の磁性体に巻線を巻いた磁心タイプのものを用いてもかまわない。
また磁気検出手段として、検出巻線でなくホール素子等の他の磁気センサを使用してもよい。
さらに、ここでは補正回路７０はコンピュータ上のソフトウェアで処理した例を示したが、ソフトウェアの代わりにハードウェア（例えば適当なアナログ回路等）を用いて処理してもかまわない。
また各検出巻線からの信号を検波するのに、ここではロックインアンプを用いた例で説明したが、各信号の求めたい位相の成分を検出できれば、ロックインアンプでなくてもよく、例えば代わりに同期検波器などを用いても良い。
【００６１】
次に、実施形態１の構成による本流速測定装置（図２の構成のセンサベッド１と、図１の流速測定回路３０、傾き検出回路４０、リフトオフ測定回路５０及び補正回路７０とからなる装置）を用いて、波立ち補正の確認試験を行った結果を示す。
試験装置としては、図２０のようにＳＵＳ３１６製の円板を斜めに回転軸に固定させ、その上に本装置のセンサヘッド１を配置して、波立ちを模擬した試験を行った。図２０の（ａ）はこの試験装置を正面からみた図、（ｂ）は真上からみた図である。
この試験では、まず本装置を周囲に磁性、導電性のもの、あるいは電磁場を発生するもののない場所に置き、流速測定回路３０、傾き検出回路４０及びリフトオフ測定回路５０中の各ブリッジ回路２１，４１及び５１を調節し、続いて停止したＳＵＳ円板上に配置する。
次に円板を回転させ、しばらくおいて円板を止め、再び装置をＳＵＳ円板上から外し、周囲に磁性、導電性のもの、あるいは電磁場を発生するもののない場所に置いた。
【００６２】
図２１は図２０の試験装置を用いた波立ち補正の確認試験結果例を示す図である。なお、図２１の横軸は時間（単位は秒）である。
図２１の（ａ）は円板回転速度から求めた測定対象の速度を示しており、（ｂ）はリフトオフを超音波距離計をもとに測定した値を示している。また同図の（ｃ）は流速検出用の検出巻線の出力信号に相当する流速元信号を示しており、（ｄ）は傾き検出コイルの出力信号である傾き元信号を示している。
そして図２１の（ｅ）が測定対象面の傾きおよびリフトオフ変動の補正後の本装置の最終出力である流速値であり、（ａ）と（ｅ）の両者の波形はほぼ同一である。
このように、傾き補正前は、波による対象面の傾きの変化により流速値が大きく変化しているが、傾き補正によりその変化が無くなり、対象の速度に対応した高精度の流速信号が得られ、かつ安定して速度の検出ができていることがわかる。
【００６３】
図２３は本流速測定装置の波立ち補正の確認試験を行ったもう一つの結果を示す図である。
ここでは低融点合金（ウッドメタル）を溶解し、図２２のような長細い容器に入れ、容器の長手方向に本装置センサベッド１の検出巻線の中心軸が平行となる（即ち本装置の流速検知方向と容器の長手方向が平行となる）ように、低融点合金の上に本装置を配置した。
ここで容器の片端に板を入れて動かし、低融点合金の湯面に波を発生させた。なお本試験では低融点合金の流速は零である。
この試験では、まず本装置を周囲に磁性、導電性のもの、あるいは電磁場を発生するもののない場所に置き、流速測定回路３０、傾き検出回路４０及びリフトオフ測定回路５０中の各ブリッジ回路２１，４１及び５１を調節し、続いて低融点合金上に本装置を配置し、板で波を生成した。なお図２３には既に本装置を低融点合金上に配置した状態からの信号の様子のみを記載している。
【００６４】
図２３の（ａ）はリフトオフを超音波距離計をもとに測定した値を示している。なお、各図の横軸はそれぞれ時間（単位は秒）を示している。
図２３の（ｂ）は流速検出用の検出巻線の出力信号に相当する流速元信号を示しており、（ｃ）は傾き検出コイルの出力信号である傾き元信号を示している。図２３（ｄ）は測定対象面の傾きおよびリフトオフ変動補正後の本装置の最終出力である流速値である。
このように、傾き補正前は、波による対象面の傾きの変化により流速値が大きく変化しているが、傾き補正によりその変化が無くなり、対象の速度に対応した流速信号が得られ、安定して速度の検出ができていることがわかる。
【００６５】
【発明の効果】
以上のように本発明によれば、移動する導電性の測定対象物の表面に対し垂直な磁場を印加するように配置された励磁手段と、前記測定対象物の表面及びその移動方向と平行な方向の磁場を検出するように配置された１つ以上の磁場検出手段と、該１つ以上の磁場検出手段が検出した磁場信号に基づき前記測定対象物の流速を算出する測定手段とを有する流速測定方法及び装置において、前記測定対象物の移動方向と平行な方向上の、前記励磁磁場の中心軸から前記磁場検出手段の距離より離れた位置に配置され、前記測定対象物の移動方向と平行な方向の磁場を検出する１つ以上の副磁場検出手段と、前記１つ以上の副磁場検出手段が検出した磁場信号に基づき前記測定対象物の表面の傾きに係る情報を求め、該情報をもとに前記測定手段が算出した測定対象物の流速を補正する補正手段とを備えるようにしたので、測定対象面に波立ちがあったり、対象面が傾いていても安定して流速の測定が可能となる。
【００６６】
また本発明によれば、流速を測定するための前記磁場検出手段の検出範囲を、前記励磁磁場の中心軸付近とし、傾きに係る情報を得るための前記副磁場検出手段の検出範囲を、前記測定対象物の流速に対する磁場変化量の最も小さくなる範囲とするようにしたので、傾きの補正精度が良く、その結果精度の高い流速値を得ることができる。
【００６７】
また本発明によれば、流速を測定するための前記磁場検出手段の素子数を１つ以上とし、また傾きに係る情報を得るための前記副磁場検出手段の素子数を１つ以上として、それぞれの素子数を組合せて多型式のセンサヘッドを構成することができるので、測定対象物の種類に応じて適当な型式のセンサヘッドを選択して測定することができ、本発明の適用範囲が拡大した。
【図面の簡単な説明】
【図１】本発明の実施形態１に係る流速測定装置の構成図である。
【図２】図１のセンサヘッドの構成図（最適化後）である。
【図３】本発明に係るセンサヘッドの別の構成図（最適化前）である。
【図４】測定対象の波立ち影響の説明図である。
【図５】流速およびリフトオフ検出の原理説明図である。
【図６】傾き特性の取得方法の説明図である。
【図７】流速特性の取得方法の説明図である。
【図８】傾き特性の例を示す図である。
【図９】流速特性の例を示す図である。
【図１０】検出装置の位置による傾き、流速特性の取得方法の説明図である。
【図１１】傾き特性直線の勾配および流速特性直線の勾配の説明図である。
【図１２】最適化後の傾き特性の例を示す図である。
【図１３】最適化後の流速特性の例を示す図である。
【図１４】本発明に係るセンサヘッドの別の構成図（１）である。
【図１５】本発明に係るセンサヘッドの別の構成図（２）である。
【図１６】本発明に係るセンサヘッドの別の構成図（３）である。
【図１７】本発明に係るセンサヘッドの別の構成図（４）である。
【図１８】本発明に係るセンサヘッドの別の構成図（５）である。
【図１９】本発明に係るセンサヘッドの別の構成図（６）である。
【図２０】波立ち補正の確認試験方法（その１）の説明図である。
【図２１】図２０の波立ち補正の確認試験結果例を示す図である。
【図２２】波立ち補正の確認試験方法（その２）の説明図である。
【図２３】図２２の波立ち補正の確認試験結果例を示す図である。
【図２４】連続鋳造の説明図である。
【図２５】接触式による従来の高温液体金属の流速測定装置の説明図である。
【図２６】磁場の速度効果及び渦電流の影響に関する説明図である。
【図２７】従来の磁気を用いた高温液体金属用非接触流速測定装置（その１）の説明図である。
【図２８】従来の磁気を用いた高温液体金属用非接触流速測定装置（その２）の説明図である。
【図２９】従来の磁気を用いた高温液体金属用非接触流速測定装置（その３）の説明図である。
【図３０】従来の磁気を用いた高温液体金属用非接触流速測定装置の測定原理説明図である。
【図３１】従来の磁気を用いた高温液体金属用非接触流速測定装置におけるリフトオフ検出方法の説明図である。
【図３２】従来の磁気を用いた高温液体金属用非接触流速測定装置のセンサヘッドの構成図である。
【符号の説明】
１ センサヘッド
２ セラミックス製丸パイプ
３ セラミックス製丸棒
Ｓ_１ ，Ｓ_２ 流速検出用検出巻線
Ｓ_３ ，Ｓ_４ 傾き検出用検出巻線
Ｓ_５ ，Ｓ_６ リフトオフ検出用検出巻線
１０ 励磁回路
１１ 発振器
１２ 定電流アンプ
２０ 検出回路
２１，４１，５１ ブリッジ回路
２２，４２，５２ バンドパスフィルタ
２３，４３，５３ ロックインアンプ
３０ 流速測定回路
４０ 傾き検出回路
５０ リフトオフ測定回路
７０ 補正回路
７１ Ａ／Ｄ変換器
７２ コンピュータ
７３ Ｄ／Ａ変換器[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to, for example, a flow velocity measuring method and apparatus for measuring a flow velocity and the like of a surface of a molten steel flow in a mold for casting molten steel in a continuous casting process.
[0002]
[Prior art]
In the continuous casting line, molten steel 103 is poured from a tundish 101 through a nozzle 102 into a copper mold 104 as shown in FIG. The molten steel poured into the mold hits the mold wall and is divided into an upflow 107 and a downflow 108. The ascending flow produces flows 109a and 109b on the surface. If the left and right balance of the molten steel flow on the surface is lost, a vortex is generated and the powder 105 spread on the molten steel surface is involved (111).
When the flow of molten steel on the surface becomes excessive, powder on the surface of molten steel is cut off (110). In any case, inclusions are trapped in the slab and cause product defects. For this reason, stabilizing the flow of molten steel in a mold is a very important task, and it is strongly required to continuously measure the flow velocity near the surface of molten steel.
[0003]
Conventionally, the flow rate of molten steel has been mainly measured by a contact type as disclosed in, for example, Japanese Patent Application Laid-Open No. 5-60774. As shown in FIG. 25, a rod 112 made of fine ceramics is immersed in molten steel 114, and the pressure received by the rod due to the flow of molten steel is detected by a pressure receiving sensor 113 to measure the flow velocity. In this method, a ceramic rod is immersed in high-temperature molten steel, so that long-term continuous measurement was impossible.
[0004]
On the other hand, it is known that the speed can be measured in a non-contact manner using magnetism. When the conductor 115 moves in a uniform magnetic field Bo as shown in FIG. 26A, a speed electromotive force Ev = v × Bo is generated in the conductor. Due to the speed electromotive force Ev, an induced current Jv is induced in the conductor, an induced magnetic field Bv is generated on the conductor, and the original magnetic field is distorted from Bo to B so as to be dragged in the direction of the speed of the conductor. Such an effect that the magnetic field is distorted by the movement of the conductor is hereinafter referred to as a speed effect of the magnetic field.
Since the degree of distortion due to the speed effect changes in accordance with the speed of the conductor, the speed of the target conductor can be known by measuring the amount of distortion. It is clear that measuring this distortion is nothing but measuring Bv because the source of the distortion is the induced magnetic field Bv due to the velocity effect. Bv can be expressed by the following equation (1).
[0005]
(Equation 1)

[0006]
In the method of measuring the flow velocity using a magnetic field, in addition to the signal magnetic field Bv due to the velocity electromotive force to be measured as shown in FIG. An eddy current Je due to dB / dt is generated, and an eddy current magnetic field Be due to the eddy current is detected.
Since the flow velocity of the molten steel flow in the mold to be measured is as small as about 0 to 0.3 m / sec, the signal magnetic field Bv due to the velocity electromotive force is small, and when the excitation frequency is as high as several tens Hz or more, the eddy current is increased. There is a problem that the magnetic field Be becomes much smaller than the magnetic field Be, and if Be changes, Bv is buried in the change and a large measurement error occurs. The eddy current magnetic field Be causes a fluctuation of the offset of the flow velocity signal regardless of the flow velocity of the target.
[0007]
Japanese Patent Application Laid-Open No. 2-31766 discloses a device for measuring the speed in a non-contact manner using such magnetism. As shown in FIG. 27 (a), a primary coil 119 is arranged parallel to the flow 118 of molten steel, and two secondary coils 120a and 120b are arranged on both sides in the horizontal direction. An alternating current is applied to the primary coil to apply an alternating magnetic field 117 parallel to the molten steel surface to the molten steel surface, and the secondary coil detects a magnetic field parallel to the target surface. When the conductor is stationary, the magnetic field becomes symmetrical with respect to the primary coil, and there is no difference between the electromotive forces of the two secondary coils and the output is zero.
When the conductor is moving, the magnetic field is distorted in the velocity direction of the conductor due to the velocity effect and is not symmetrical across the exciting coil as shown in FIG. 27B, so that the electromotive force generated in the two secondary coils is reduced. A difference is generated, and a signal corresponding to the distortion amount of the magnetic field, that is, the speed is obtained as a difference signal between the two secondary coils.
[0008]
In the method using magnetism, the speed sensitivity changes depending on the distance between the device and the object to be measured (hereinafter referred to as lift-off). In the method disclosed in Japanese Patent Laid-Open No. 2-311766, the distance between the device and the object to be measured is changed. Was measured by the output voltage of one of the secondary coils for detecting the magnetic field parallel to the target surface, and the correction was performed.
[0009]
Another method for measuring speed using magnetism is disclosed in Japanese Patent Application Laid-Open No. Hei 5-297012. In this method, as shown in FIG. 28, the primary coil 151 is arranged perpendicular to the measurement object 152, an alternating current is applied to the primary coil 151, a magnetic field 153 is generated, and the measurement is performed on both sides of the primary coil 151. The secondary coils 154a and 154b are arranged perpendicularly to the object 152, and include iron cores 155, 156a and 156b around which the primary coils 151 and the secondary coils 154a and 154b are wound. The flow velocity was detected from the phase of the electromotive force generated in the secondary coils 154a and 154b.
[0010]
Another method for measuring the speed using magnetism is disclosed in Japanese Patent Application Laid-Open No. Hei 8-2111084 proposed by the present inventors. As shown in FIG. 29, an exciting winding 203b is wound around the center leg 204b with respect to the E-shaped core 202 which is symmetrical about the center leg 204b as shown in FIG. Are wound so as to detect magnetic fluxes in the same direction. It is arranged on the moving conductive measurement object 201 so that the open surface of the leg faces the target surface and each leg is arranged in parallel to the moving direction of the target surface.
[0011]
Then, an alternating current is passed through the exciting winding to create an alternating magnetic field perpendicular to the conductor surface, and the output difference between the two detecting windings is detected. At this time, if the conductor 201 is stopped as shown in FIG. 30A, the magnetic field is symmetric with respect to the center leg, the outputs of the left and right detection windings are equal, and the difference is zero. . When the conductor moves, the magnetic field is distorted in accordance with the flow velocity as shown in FIG. 30 (b), a difference occurs in the magnetic flux at the positions of the windings at both ends, and the difference signal changes. The amount of change corresponds to the flow velocity of the target, and the flow velocity of the target can be measured from the amount of change.
Also in this method, the speed sensitivity changes due to the lift-off. In Japanese Patent Application Laid-Open No. Hei 8-211084, the lift-off is detected and corrected by using an eddy current distance meter 256 attached to the apparatus as shown in FIG. I was
[0012]
Another method for measuring the flow velocity using magnetism is disclosed in Japanese Patent Application No. 8-2555861 proposed by the present inventors. As shown in FIG. 32, an excitation winding P wound around a ceramic pipe 2 is arranged on a moving conductive measurement target object so that the central axis thereof is perpendicular to the target surface. The two detection windings S are arranged in the same direction on the ceramic round bar 3 between the excitation winding P and the target surface. ₁ , S ₂ , The center axis of which is parallel to the object plane and the moving direction of the object, and the two detection windings S ₁ , S ₂ Are arranged so that the intermediate point of the center line is on the central axis of the exciting winding P. Here, a current is applied to the excitation winding P to excite a magnetic field in the measurement object, and the detection winding S ₁ , S ₂ 26 detects the induction magnetic field Bv shown in FIG. 26A and measures the flow velocity.
Further, in this method, the offset due to the eddy current magnetic field Be changes due to the change in the lift-off, and the flow velocity sensitivity also changes. However, in the above-mentioned Japanese Patent Application No. 8-2555861, as shown in FIG. Two detection windings S wound to detect a magnetic field component perpendicular to the target surface ₃ , S ₄ The change in offset and the change in flow velocity sensitivity were corrected by detecting lift-off based on the output voltage.
[0013]
[Problems to be solved by the invention]
However, conventional magnetic fields such as JP-A-2-31766, JP-A-5-297012, JP-A-8-2111084 and Japanese Patent Application No. 8-2555861 are excited to detect a velocity-induced magnetic field, In a flow velocity measuring method / apparatus of a type that calculates a flow velocity from a detected magnetic field, when an AC magnetic field is used as an exciting magnetic field as described above, the detection apparatus detects an eddy current magnetic field Be generated from a target, The offset of the flow velocity signal changes. This change is uniquely determined by the lift-off if the target surface is flat, so that the lift-off can be separately detected and corrected as in Japanese Patent Application No. 8-2555861.
However, when the target surface is not flat and has a wavy shape, the target surface is tilted when viewed locally as shown in FIG. 4, and the eddy current magnetic field Be tilts due to this tilt. Therefore, even in a method for detecting a magnetic field component in a vertical direction as disclosed in JP-A-5-297012 and JP-A-8-2111084, a method for detecting a magnetic field component in a horizontal direction as disclosed in JP-A-2-31766 and JP-A-8-255581 is disclosed. Even in the method of detecting the magnetic field component, even if the lift-off is constant, the magnitude of the eddy current magnetic field Be detected by the detection device because the inclination of the target surface under the device changes with the movement or change of the wave. And the offset changes, so that even if the lift-off is detected and corrected, there remains an offset change that cannot be completely removed, causing a measurement error.
[0014]
[Means for Solving the Problems]
The flow velocity measuring method according to claim 1 of the present invention excites a magnetic field perpendicular to the surface of a moving conductive measuring object, and changes the magnetic field in a direction parallel to the surface of the measuring object and the moving direction thereof by one. In a flow velocity measuring method for detecting the flow velocity of the object to be measured based on the magnetic field signal detected in the one or more ranges, Along the direction parallel to the moving direction of the measurement object from the central axis of the excitation magnetic field, in a range of one or more places more distant from the magnetic field detection range for measuring the flow velocity, A magnetic field in a direction parallel to the moving direction of the measurement target is detected, information on the inclination of the surface of the measurement target is determined based on the detected magnetic field signal, and the measurement target is calculated based on the information. Is to correct the flow velocity.
[0015]
The flow velocity measuring method according to claim 2 of the present invention is the flow velocity measuring method according to claim 1, wherein the exciting magnetic field is in a plane parallel to a moving direction of the measurement target and perpendicular to a surface of the measurement target. Select an axis perpendicular to the measurement target surface to be line-symmetric, and set the detection range of the magnetic field for calculating the flow velocity to be parallel to the moving direction of the measurement target around the point on the vertical axis. And a detection range of the magnetic field for correcting the flow velocity is centered on the first and second points where the excitation magnetic field is line-symmetric with respect to the vertical axis in the plane. And the distances from the vertical axis to the first and second points are in the range of the same length in a direction parallel to the moving direction of the measurement object, and the flow rate is calculated from the vertical axis. Each range obtained by dividing the magnetic field detection range for calculation into two equal parts Than the distance to the center position of the one in which increased respectively.
[0016]
The flow velocity measuring method according to claim 3 of the present invention is the flow velocity measuring method according to claim 1, wherein the exciting magnetic field is in a plane parallel to a moving direction of the measurement target and perpendicular to a surface of the measurement target. An axis perpendicular to the measurement target plane that is line-symmetric is selected, and the detection range of the magnetic field for calculating the flow velocity is set to a first field in which the exciting magnetic field is line-symmetric with respect to the vertical axis in the plane. And the center of each of the second points, each having a range of equal length in a direction parallel to the moving direction of the measurement object, and a detection range of a magnetic field for correcting the flow velocity, a distance from the vertical axis. Are centered on third and fourth points, respectively, where the exciting magnetic field is line-symmetric with respect to the vertical axis in the plane, which are farther from the first and second points, respectively, and Range of equal length in the direction parallel to the movement direction of It is intended to.
[0017]
The flow velocity measuring method according to claim 4 of the present invention is the flow velocity measuring method according to claim 1, wherein the exciting magnetic field is in a plane parallel to a moving direction of the measurement target and perpendicular to a surface of the measurement target. An axis perpendicular to the measurement target plane that is line-symmetric is selected, and the detection range of the magnetic field for calculating the flow velocity is set to a first field in which the exciting magnetic field is line-symmetric with respect to the vertical axis in the plane. And the center of each of the second points, ranges of equal length in a direction parallel to the direction of movement of the measurement object, and the detection range of the magnetic field for correcting the flow velocity, the point on the vertical axis The center position of each range obtained by dividing the detection range of the magnetic field for correcting the flow velocity from the perpendicular axis into two equal parts in a range of a predetermined length in a direction parallel to the movement direction of the measurement object around the center Distance from the vertical axis to the first and Than the distance to the second points of, is to increase respectively.
[0018]
The flow velocity measuring method according to claim 5 of the present invention is the flow velocity measuring method according to claim 1, wherein the exciting magnetic field is in a plane parallel to a moving direction of the measurement target and perpendicular to a surface of the measurement target. Select an axis perpendicular to the measurement target surface to be line-symmetric, and set the detection range of the magnetic field for calculating the flow velocity to be parallel to the moving direction of the measurement target around the point on the vertical axis. The range of the predetermined length in the direction, the detection range of the magnetic field for correcting the flow velocity, the center of the point on the vertical axis, the detection range of the magnetic field for calculating the flow rate, the measurement target The length in the direction parallel to the moving direction of the object is a long range.
[0019]
A flow velocity measuring method according to claim 6 of the present invention is the flow velocity measuring method according to any one of claims 1 to 5, wherein the flow rate is calculated by correcting a magnetic field detection range and a flow velocity for calculating the flow velocity. All of the magnetic field detection ranges described above are provided on a straight line that intersects with an axis perpendicular to the surface to be measured and that is parallel to the moving direction of the object to be measured.
[0020]
A flow velocity measuring method according to a seventh aspect of the present invention is the flow velocity measuring method according to any one of the first to sixth aspects, wherein a detection range of a magnetic field for calculating the flow velocity is set to a range of the excitation magnetic field. The detection range of the magnetic field for correcting the flow velocity is set to be a range where the amount of change in the magnetic field with respect to the flow velocity of the measurement object is the smallest, near the central axis.
[0021]
The flow velocity measuring device according to claim 8 of the present invention is an exciting means arranged to apply a magnetic field perpendicular to the surface of the moving conductive measurement object, the surface of the measurement object and the moving direction thereof. One or more magnetic field detecting means arranged to detect a magnetic field in a direction parallel to the direction, and a measuring means for calculating a flow velocity of the object to be measured based on a magnetic field signal detected by the one or more magnetic field detecting means. In a flow velocity measuring device having A magnetic field in a direction parallel to the moving direction of the measurement object is disposed at a position in the direction parallel to the movement direction of the measurement object and away from the center axis of the excitation magnetic field by a distance of the magnetic field detection unit, and is detected. Do One or more sub-magnetic field detection means, and obtains information related to the inclination of the surface of the object to be measured based on the magnetic field signal detected by the one or more sub-magnetic field detection means, and based on the information, the measurement means Correction means for correcting the calculated flow velocity of the measurement object.
[0022]
The flow velocity measuring device according to claim 9 of the present invention is the flow velocity measuring device according to claim 8, wherein the exciting magnetic field is within a plane parallel to the moving direction of the measurement target and perpendicular to the surface of the measurement target. A magnetic field detecting means for selecting an axis perpendicular to the line to be measured, which is axisymmetric, and for calculating the flow velocity is disposed on the axis perpendicular to the axis, and is parallel to the moving direction of the object to be measured. The sub-magnetic field detecting means for detecting a magnetic field over a range of a predetermined length in various directions and correcting the flow velocity has two exciting magnetic fields that are line-symmetric with respect to the vertical axis in the plane. And each sub-magnetic field detecting means detects a magnetic field over a range of equal length in a direction parallel to the moving direction of the measurement object, and the vertical axis To the first and second points Away is what you respectively greater than the distance from the axis perpendicular to the center position of each range that bisects the detection range of the magnetic field to calculate the flow rate.
[0023]
The flow velocity measuring device according to claim 10 of the present invention is the flow velocity measuring device according to claim 8, wherein the exciting magnetic field is in a plane parallel to a moving direction of the measurement target and perpendicular to a surface of the measurement target. The magnetic field detecting means for selecting an axis perpendicular to the measurement target surface to be line-symmetric and calculating the flow velocity has two excitation magnetic fields with respect to the perpendicular axis in the plane, respectively. A sub-magnetic field detection for correcting the flow velocity is performed so as to detect a magnetic field disposed on each of the first and second points and extending over an equal length range in a direction parallel to the moving direction of the measurement object. Means are third and second in which the exciting magnetic field is line-symmetric with respect to the vertical axis in the plane, the distance from the vertical axis being farther than each of the first and second points, respectively. Placed on each of the fourth points, and each sub-field Detection means are those in which to detect the magnetic field ranging respectively equal length in a direction parallel to the moving direction of the object to be measured.
[0024]
The flow velocity measuring device according to claim 11 of the present invention is the flow velocity measuring device according to claim 8, wherein the exciting magnetic field is in a plane parallel to a moving direction of the measurement target and perpendicular to a surface of the measurement target. The magnetic field detecting means for selecting an axis perpendicular to the measurement target surface to be line-symmetric and calculating the flow velocity has two excitation magnetic fields with respect to the perpendicular axis in the plane, respectively. A sub-magnetic field detection for correcting the flow velocity is performed so as to detect a magnetic field disposed on each of the first and second points and extending over an equal length range in a direction parallel to the moving direction of the measurement object. The means is disposed on the vertical axis as one, and detects a magnetic field over a range of a predetermined length in a direction parallel to the moving direction of the measurement object, and further corrects the flow velocity from the vertical axis. Magnetic field for The distance to the center position of each range where the detection range is bisected is than the distance from the vertical axis to each point of the first and second, is obtained by the respectively larger.
[0025]
The flow velocity measuring device according to claim 12 of the present invention is the flow velocity measuring device according to claim 8, wherein the excitation magnetic field is within a plane parallel to the moving direction of the measurement target and perpendicular to the surface of the measurement target. A magnetic field detecting means for selecting an axis perpendicular to the line to be measured, which is axisymmetric, and for calculating the flow velocity is disposed on the axis perpendicular to the axis, and is parallel to the moving direction of the object to be measured. A magnetic field over a range of a predetermined length in a desired direction, and a sub-magnetic field detecting means for correcting the flow velocity is disposed on the vertical axis as one of the magnetic fields for calculating the flow velocity. The magnetic field is such that the length in the direction parallel to the moving direction of the measurement object is longer than the detection range of the detection means.
[0026]
The flow velocity measuring device according to claim 13 of the present invention is the flow velocity measuring device according to any one of claims 8 to 12, wherein all of the magnetic field detecting means and the sub magnetic field detecting means are provided on the surface to be measured. Are arranged on a straight line that intersects an axis perpendicular to the axis and is parallel to the moving direction of the measurement object.
[0027]
A flow velocity measuring device according to claim 14 of the present invention is the flow velocity measuring device according to any one of claims 8 to 13, wherein a detection range of the magnetic field detecting means is set to be near a central axis of the exciting magnetic field. The detection range of the sub-magnetic field detection means is set to a range in which the amount of change in the magnetic field with respect to the flow velocity of the measurement object is minimized.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
Before describing the embodiments of the present invention, the operating principle of the flow velocity measuring method and apparatus of the present invention will be described first.
(1) Flow velocity measurement principle
Here, a case where a sensor head as shown in FIG. 3 is used as a base flow velocity measuring device will be described.
In this sensor head, as shown in FIG. 3, one excitation winding P is arranged on a conductive measurement object moving as an excitation device so that its central axis is perpendicular to the object surface, As a detection device for detection, two detection windings S are provided between the excitation winding P and the target surface. ₁ , S ₂ And the center axis thereof is parallel to the object plane and the moving direction of the object, and the two detection windings S ₁ , S ₂ Are arranged so that the intermediate point of the center line is on the central axis of the exciting winding P. This S ₁ , S ₂ Is hereinafter referred to as a detection winding for flow velocity detection.
[0029]
Here, an AC exciting current is supplied to the exciting winding P to excite a magnetic field perpendicular to the target surface. Then, an induced magnetic field Bv due to the above-described speed effect is generated. The induction magnetic field Bv is parallel to the target surface at the position of the detection winding immediately below the excitation winding P as shown in FIG. 5, and this detection magnetic field Bv is divided into two detection windings S arranged in parallel to the target surface. ₁ , S ₂ Is detected by taking the sum signal of. Since the detected Bv corresponds to the flow velocity of the target, the flow velocity of the target can be measured from this.
Actually, the detection winding S ₁ , S ₂ The output signal is detected by using a lock-in amplifier or the like for a component having a phase shifted by -90 ° from the excitation current, and is used as a flow velocity original signal which is a source of the flow velocity measurement. The magnetic field component is detected. Here, a detection winding is used for detecting the magnetic field. Since the magnetic field detected by the detection winding and the detection voltage of the detection winding have a phase difference of −90 °, the phase difference is −90 °. The shifted phase component is detected).
[0030]
(2) Countermeasures for the effects of ripples
If the target surface under the device is tilted due to the undulation, the detection winding S ₁ , S ₂ The offset of the flow velocity original signal, which is the output signal of, changes, and accurate flow velocity measurement becomes impossible.
Therefore, as shown in FIG. ₃ , S ₄ And its central axis is a detection winding S for detecting the flow velocity. ₁ , S ₂ S at a position symmetrical with respect to the central axis of the excitation device so as to be the same as the central axis of ₁ , S ₂ (Corresponding to claims 1 to 6 and 8 to 13).
And this detection winding S ₃ , S ₄ The sum signal of ₁ , S ₂ Similarly to the above, a component having a phase shifted by -90 ° from the exciting current is detected by using a lock-in amplifier or the like.
[0031]
This new detection winding S ₃ , S ₄ Is a detection winding S for detecting a flow velocity. ₁ , S ₂ At a position close to ₁ , S ₂ , The influence of the change in the eddy current magnetic field Be due to the inclination of the target surface is represented by S ₁ , S ₂ And receive in much the same way. So this S ₃ , S ₄ From the sum signal of ₁ , S ₂ , That is, the change in the offset due to the gradient of the flow velocity original signal, and the change in the offset due to the gradient can be corrected (the correction method will be described with reference to FIGS. 8 and 9 and FIGS. 12 and 13). Do).
This S ₃ , S ₄ This is the detection winding S for detecting the flow velocity. ₁ , S ₂ Corresponding to the above, the detection winding for detecting the inclination and the signal after detection of the sum signal thereof are referred to as the inclination original signal.
[0032]
FIG. 8 shows how the flow velocity original signal and the inclination original signal change with respect to the inclination of the target surface of the sensor head of FIG.
Here, an SUS316 plate was used as a measurement target as shown in FIG. 6, and a test of tilting the plate was performed.
As a result of the test, the flow velocity original signal (S ₁ + S ₂ ), The slope original signal (S ₃ + S ₄ ), The change with respect to the slope was almost linear.
[0033]
Therefore, assuming that the gradient of the gradient-flow velocity original signal characteristic line (gradient of the characteristic line) in FIG. 8 is Af and the gradient of the gradient-gradient original signal characteristic line (gradient of the characteristic line) is As, the following equation (2) is used. It is understood that the influence of the inclination can be corrected by using the determined coefficient α as in equation (3).
α = Af / As (2)
(Signal after inclination correction) = (Flow velocity original signal) −α · (Slope original signal) (3)
In FIG. 8, each signal is not 0 even when the inclination is 0. However, even when the inclination of the target surface is 0, the eddy current magnetic field Be is generated from the target, and this is the offset component. The offset at the inclination of 0 is uniquely determined by the lift-off with respect to the target surface, and the lift-off can be detected and corrected by any method as in Japanese Patent Application No. 8-2555861.
[0034]
(3) Optimal position of detection winding for tilt detection
As described in the above (2), the detection winding S for detecting the inclination S ₃ , S ₄ And detection winding S for flow velocity detection ₁ , S ₂ This means that the characteristics with respect to the eddy current magnetic field Be are almost the same, but the characteristics are also substantially the same with respect to the induced magnetic field Bv due to the velocity effect, and when the gradient original signal is subtracted by multiplying the flow velocity original signal by an appropriate coefficient. Although the influence of the inclination of the target surface can be corrected, there is a problem that the magnitude of the signal with respect to the flow velocity also decreases.
FIG. 9 shows how the flow velocity original signal and the slope original signal change with respect to the target flow velocity.
Here, as shown in FIG. 7, a disk made of SUS316 was rotated, and the sensor head of the present apparatus was arranged thereon to measure each signal. FIG. 7A is a view of the test apparatus as viewed from the front, and FIG. 7B is a view of the test apparatus as viewed from directly above.
As a result of the test using the test apparatus shown in FIG. 7, the flow velocity original signal (S ₁ + S ₂ ), The slope original signal (S ₃ + S ₄ ) Indicates that the change with respect to the flow velocity of the object is almost linear, and the characteristics of both are almost equal.
[0035]
Then, the gradient of the flow velocity-flow velocity original signal characteristic straight line (gradient of the characteristic straight line) in FIG. Formula and
β = Bf / Bs (4)
When the coefficient k is given by the following equations (5) and (6),

The magnitude of (signal for the flow velocity after inclination correction) according to the above equation (3) is reduced to 1 / k as compared with before the correction. For example, in the case of the apparatus having the characteristics shown in FIGS. 8 and 9, the signal for the flow velocity after the inclination correction is attenuated to about 1/15 of that before the correction.
[0036]
Therefore, here, the positions of the detection winding for inclination correction and the detection winding for flow velocity detection are changed to try to reduce the reduction rate of the flow velocity signal.
Now, as shown in FIG. 10, the position of one detection winding is set in a direction parallel to the direction of the flow velocity (X direction, where X = 0 indicates the excitation winding, while the center axis of the winding is kept parallel to the flow velocity direction of the object). (The point on the center axis of the line) is scanned, and the gradient of the flow velocity characteristic line (the gradient of the characteristic line) B (corresponding to Bf and Bs) and the gradient of the gradient characteristic line (the characteristic line The state of change of the slope A (corresponding to Af and As) is examined, and the result is shown in FIG. 11 (in FIG. 11, normalized by the value of X = 0 mm).
Note that the measurement target in FIG. 10 was a SUS plate for the inclination characteristic and a SUS disk for the flow velocity characteristic.
[0037]
The following can be seen from the results of FIGS.
(A) The gradient B of the flow velocity characteristic line is maximum near the central axis of the exciting magnetic field. That is, the flow velocity sensitivity is maximum near the central axis.
(B) Both the gradient B of the flow-rate characteristic line and the gradient A of the gradient characteristic line decrease as the distance from the center axis of the exciting winding increases, but the attenuation rate of the gradient B of the flow-rate characteristic line becomes smaller. And becomes 0 at a point closer to the excitation winding center axis than A. Therefore, if the inclination detection winding is arranged at the point where B = 0 (that is, the position where the amount of change in the magnetic field with respect to the flow velocity of the object is the smallest), k = 1 from Equation (6), and the flow velocity sensitivity is reduced. The inclination can be corrected without any change.
[0038]
From the above, it has been found that the optimum position of each detection winding is as follows (corresponding to claims 7 and 14).
(A) Detection winding for flow velocity detection: Position as close as possible to the center axis of the excitation magnetic field
(B) Detection winding for detecting inclination: a position where the gradient B of the flow velocity characteristic line becomes 0
The optimum arrangement of the detection windings is, for example, as shown in FIG. 2. In this case, the change of the flow velocity original signal and the gradient original signal with respect to the inclination of the target surface and the change of the target flow velocity with respect to the inclination are shown in FIG. 12 and FIG.
[0039]
(4) Correction of lift-off fluctuation
When the distance (i.e., lift-off) between the flow velocity detection position of the sensor head of the present apparatus and the surface to be measured changes, the offset uniquely determined by the lift-off at the slope 0 included in the signal after the influence of the tilt changes. Further, the flow velocity sensitivity of the present apparatus changes. In the embodiment described later, the influence of these lift-off fluctuations is detected and corrected. Here, a lift-off detection method and a lift-off fluctuation correction method will be briefly described.
Here, similarly to Japanese Patent Application No. Hei 8-2555861, the excitation winding P and the excitation winding P are coaxially positioned between the excitation winding P and the target surface as shown in FIG. In the meantime, two detection windings S are provided so as to detect magnetic fields each having the same direction in the direction perpendicular to the target surface. ₅ , S ₆ And lift-off is detected from the difference signal. This detection winding S ₅ , S ₆ Is hereinafter referred to as a detection winding for detecting lift-off.
[0040]
At this time, since the magnetic field is excited perpendicularly to the target surface by the excitation winding for flow velocity measurement as shown in FIG. 5, the eddy current Je flowing through the target by the magnetic field causes the eddy current magnetic field perpendicular to the target surface. Be occurs. Since the eddy current magnetic field Be changes depending on the distance to the target surface, the eddy current magnetic field Be is detected by the detection winding S. ₅ , S ₆ In this case, the distance from the target surface, that is, the lift-off can be detected.
When the lift-off is further changed, the lift-off-flow characteristic, which is how the offset uniquely determined by the lift-off at the slope of 0, changes, and the lift-off-flow characteristic, how the flow velocity sensitivity changes, are determined in advance. The influence of the lift-off fluctuation is corrected by using a lift-off signal detected based on this characteristic beforehand measured.
Now that the description of the principle of operation of the flow velocity measuring method and apparatus of the present invention has been completed, an embodiment of the present invention will be described next.
[0041]
Embodiment 1
FIG. 1 is a configuration diagram of a flow velocity measuring device according to a first embodiment of the present invention. The illustrated device has a sensor head 1 configured as shown in FIG. 2, a speed measurement circuit 30, a tilt detection circuit 40, and a lift-off measurement. It comprises a circuit 50 and a correction circuit 70.
[0042]
As shown in FIG. 2, the sensor head 1 has an excitation winding P wound around a ceramic round pipe 2 on a moving conductive measurement target object such that the center axis thereof is perpendicular to the target surface. A ceramic round bar 3 is arranged between the exciting winding P and the target surface such that the center axis thereof is parallel to the target surface and the moving direction of the target. The two detection windings S for detecting the flow velocity are located symmetrically with respect to the center axis of P. ₁ , S ₂ Are wound adjacent to each other, and further outside the round pipe 2 made of ceramics, two detection windings S for detecting inclination are provided at positions symmetrical with respect to the center axis of the excitation winding. ₃ , S ₄ And a ceramic round pipe 2 wound with the exciting winding P, one between the exciting winding P and the target, and one at a position symmetrical to the exciting winding P and the exciting winding P. Detection windings S for detecting two lift-offs ₅ , S ₆ Is wound.
In the case of the device used here, the position of the detection winding for detecting the inclination in FIG. ₃ , S ₄ At the position, the gradient B of the flow velocity characteristic straight line becomes substantially zero.
[0043]
The flow velocity measurement circuit 30 includes the excitation circuit 10 and the detection circuit 20, as shown in FIG. The excitation circuit 10 includes an oscillator 11 and a constant current amplifier 12. The detection circuit 20 includes a bridge circuit 21, a band-pass filter 22, and a lock-in amplifier 23.
The excitation circuit 10 supplies a current to the excitation winding P to excite a magnetic field in the measurement target. For this reason, a sine wave of 1 Hz to 1 kHz is generated by the oscillator 11, and the exciting current is supplied to the exciting winding P via the constant current amplifier 12. Here, the excitation frequency was 70 Hz.
[0044]
Detection winding S for flow velocity detection ₁ , S ₂ Output from the control circuit 20 enters the detection circuit 20. Here, the two signals from the two detection windings are first added by the bridge circuit 21 and the sum signal is calculated. The bridge circuit 21 is adjusted in advance so that its output signal becomes zero in a state where there is no magnetic or conductive thing or anything that generates an electromagnetic field around the sensor head. By doing so, the two detection windings S ₁ , S ₂ The bridge circuit 21 can be adjusted so as to cancel the unnecessary excitation magnetic field signal detected by the above.
The signal after the adjustment has a frequency of the exciting current of the exciting circuit 10 as a center frequency, a noise signal in an unnecessary band is removed in advance by a band-pass filter 22 of a predetermined bandwidth, and then the lock-in amplifier 23 A component having a phase shifted by -90 ° with respect to the exciting current is detected. The reference phase signal (ref) for detection is supplied from the oscillator 11 to the lock-in amplifier 23. The signal after the detection by the lock-in amplifier 23 is the flow velocity original signal that is the basis of the flow velocity measurement.
[0045]
Also, a detection winding S for detecting the inclination ₃ , S ₄ Output from the controller enters the inclination detection circuit 40. The inclination detection circuit 40 includes a bridge circuit 41, a band-pass filter 42, and a lock-in amplifier 43.
Here, two detection windings S ₃ , S ₄ Are first added by the bridge circuit 41, and the sum signal is calculated. The bridge circuit 41 is adjusted in advance so that its output signal becomes zero in a state where there is no magnetic or conductive thing or a thing that generates an electromagnetic field around the sensor head.
The signal after this adjustment has the frequency of the exciting current of the exciting circuit 10 as a center frequency, and a noise signal of an unnecessary band is removed in advance by a band-pass filter 42 of a predetermined bandwidth. A component having a phase shifted by -90 ° with respect to the exciting current is detected. The reference phase signal for detection is supplied from the oscillator 11 to the lock-in amplifier 43. Then, the signal after detection by the lock-in amplifier 43 is a tilt original signal that is a source of tilt correction.
[0046]
The detection winding S for lift-off detection ₅ , S ₆ The output signal from the circuit enters the lift-off measuring circuit 50. The lift-off measurement circuit 50 includes a bridge circuit 51, a band-pass filter 52, and a lock-in amplifier 53.
Here, two detection windings S ₅ , S ₆ Are subtracted by the bridge circuit 51 to calculate a difference signal. The bridge circuit 51 is adjusted in advance so that its output signal becomes zero in a state where there is no magnetic or conductive thing or anything that generates an electromagnetic field around the sensor head.
The signal after the adjustment has the frequency of the exciting current of the exciting circuit 10 as a center frequency, and after removing a noise signal in advance by a band-pass filter 52 having a predetermined bandwidth, the lock-in amplifier 53 converts the signal into an exciting current of the exciting circuit 10. On the other hand, a component having a phase shifted by -180 ° is detected (originally, an exciting magnetic field, that is, a magnetic field component shifted by -90 ° from the exciting current is detected. Here, a detection winding is used for detecting the magnetic field. Since the detection voltage of the detection winding has a phase difference of −90 °, a phase component shifted by −180 ° is detected). The reference phase signal for detection is supplied from the oscillator 11 to the lock-in amplifier 53. The signal after detection by the lock-in amplifier 53 is a lift-off source signal that is a source of lift-off correction.
[0047]
Thereafter, the flow velocity original signal which is the output signal of the flow velocity measuring circuit 30, the inclination original signal which is the output signal of the inclination detecting circuit 40, and the lift-off original signal which is the output signal of the lift-off measuring circuit 50 enter the correction circuit 70.
The correction circuit 70 includes an A / D converter 71, a computer 72, and a D / A converter 73. In the correction circuit 70, first, the A / D converter 71 A / D converts the flow velocity original signal, the inclination original signal, and the lift-off original signal, and takes them into the computer 72. The following processing is performed by software on the computer 72.
(1) On the computer, first, the lift-off is calculated from the lift-off source signal. Here, the state of the change of the lift-off source signal when the lift-off is changed is measured in advance, and the lift-off is calculated from the lift-off source signal based on the lift-off-lift-off source signal characteristic curve.
[0048]
(2) Next, the slope original signal is multiplied by a coefficient α and subtracted from the flow velocity original signal as in equation (3) to correct the influence of the slope. Here, since the coefficient α generally changes due to lift-off, a slope characteristic as shown in FIGS. 8 and 12 is acquired in advance for each lift-off, and is then obtained using the equation (2).
(3) Subsequently, the lift-off fluctuation of the signal after the influence of the inclination is removed is corrected. Here, first, an offset by the eddy current magnetic field Be is calculated based on the previously calculated lift-off, and this is subtracted from the signal from which the influence of the inclination has been removed. Here, the state of the change in the offset included in the signal after the inclination correction when the lift-off is changed is measured in advance, and the offset is calculated from the lift-off based on the lift-off-offset characteristic curve.
[0049]
(4) Next, a flow velocity sensitivity change accompanying a change in lift-off is corrected from a signal from which the offset is subtracted to obtain a final flow velocity value. Here, the state of the flow velocity sensitivity of the signal after the inclination correction when the lift-off is changed (the amount of change in the signal after the inclination correction when the target flow velocity is 0 m / sec and 1 m / sec) is measured in advance. Based on the lift-off-flow velocity sensitivity characteristic curve, the flow velocity sensitivity at the lift-off is calculated, and the signal after the offset is subtracted is divided by the calculated flow velocity sensitivity to obtain a final flow velocity value.
[0050]
In the first embodiment, the sensor head for measuring the flow velocity has a configuration as shown in FIGS. ₁ , S ₂ The winding for detecting tilt is S ₃ , S ₄ And this S ₁ ~ S ₄ Are arranged on the same straight line parallel to the moving direction of the object to be measured), but many sensor heads with other configurations can be realized.
The essence of the present invention is to detect the flow velocity with a detection device that detects a magnetic field in a direction parallel to the flow velocity of the target, and to tilt the inclination with a detection device that detects a magnetic field in a direction parallel to the flow velocity of the target at another position. This is a point of detection and correction, and includes various forms that satisfy this condition.
[0051]
For example, as shown in each of (b), (c), and (d) of FIGS. ₁ ) Or only one detection winding for inclination detection (S ₃ ), Or the same function as that of the first embodiment can be obtained even if both the winding for detecting the flow velocity and the winding for detecting the inclination are each one. 11 and 12).
In the case where only one winding for flow velocity detection and one winding for inclination detection are used, the output signal of each detection winding can be directly input to a lock-in amplifier and detected without passing through a bridge circuit. Good.
When a long winding is used as shown in FIG. 14 (c), for example, the average value of the magnetic field over the entire length is detected. The output of the winding corresponds approximately to the magnitude of the magnetic field at the center of the winding. If the detection winding crosses the excitation magnetic field center axis, the detection winding is divided into two parts on the excitation magnetic field center axis, and an output signal corresponding to a value obtained by adding the magnitude of the magnetic field at each center position is obtained. can get.
[0052]
Further, as shown in FIGS. 14 (c) and (d) and FIGS. 15 (c) and (d), the detection winding for detecting the flow velocity may be wound on the detection winding for detecting the inclination. .
Even if there are two or more detection windings for flow velocity detection and inclination detection, the sum signal of each winding may be obtained.
Further, as shown in FIGS. 15, 17, and 19, the detection winding for detecting the inclination may be arranged adjacent to the detection winding for detecting the flow velocity inside, instead of outside the round ceramic pipe.
Further, as shown in FIGS. 16 to 19, the detection winding for detecting the flow velocity and the detection winding for detecting the inclination may be wound separately, instead of being wound around a coaxial round bar. The heights of the two from the target surface may be different.
In all cases, the detection winding for detecting the flow velocity and the detection winding for detecting the inclination may be arranged in reverse, but this is apparent from the correction expression of Expression (3). Only the detection winding for detecting the flow velocity is used as the detection winding for detecting the inclination, and the detection winding for detecting the inclination is used as the detection winding for detecting the flow velocity.
[0053]
Another essence of the present invention is that the magnetic field detection device for tilt detection is separated from the magnetic field detection device for flow velocity detection along the direction parallel to the moving direction of the target from the excitation magnetic field central axis. (Corresponding to claims 7 and 14).
For example, as shown in FIG. 14A, when there are two detection windings for detecting the inclination and two detection windings for detecting the flow velocity, the detection winding S for detecting the inclination is used. ₃ , S ₄ Is located at a distance from the central axis of the exciting magnetic field. ₁ , S ₂ It may be far away so that it is longer than the center position of.
In addition, as shown in FIG. 15D, when there is one detection winding for detecting inclination and one detection winding for detecting flow velocity, the detection winding S for detecting inclination is used. ₃ The detection winding S for detecting the flow velocity ₁ It should be longer than this.
In this case, since both detection windings cross the excitation magnetic field center axis, as described above, both detection windings may be divided into two by the excitation magnetic field center axis. (D) is almost the same as (e) in the same figure. Therefore, the magnetic field detecting device for detecting the inclination is located at a position farther from the center axis of the exciting magnetic field than the magnetic field detecting device for detecting the flow velocity. Become.
16 to 19, the detection winding for detecting the flow velocity and the detection winding for detecting the inclination are wound on separate ceramic rods, respectively, at different positions from the surface to be measured. The ceramic rods were arranged horizontally with respect to the surface to be measured so that their heights from the surface to be measured were the same and their central axes were parallel to the direction of the flow velocity. (Arranged horizontally on the back).
[0054]
Embodiments of the configuration examples of the sensor heads shown in FIGS. 14 to 19, which are classified according to the number of elements of the magnetic field detection winding and the arrangement thereof, will be described below. In addition, in the embodiment classified according to the configuration of the sensor head, a part overlapping with the above description is also included.
Embodiment 2
The second embodiment is shown in, for example, FIG. 14 (b), FIG. 15 (b), FIG. 16 (b), FIG. 17 (b), FIG. 18 (b), or FIG. 19 (b). As shown in FIG. ₁ And the inclination detecting winding is S ₁ S provided on both sides of ₃ , S ₄ (Corresponding to claims 2 and 9).
The arrangement of the detection windings and the detection range in the second embodiment are as follows. First, in a plane parallel to the moving direction of the measurement target and perpendicular to the surface of the measurement target, an axis perpendicular to the measurement target surface where the excitation magnetic field by the excitation winding P is line-symmetric is selected, and a single axis is selected. Flow velocity detection winding S ₁ Are arranged on the vertical axis and detect a magnetic field over a range of a predetermined length in a direction parallel to the moving direction of the measurement object, so that the two inclination detecting windings S ₃ , S ₄ Are arranged on the first and second points where the exciting magnetic field is axisymmetric with respect to the vertical axis in the plane, and furthermore, each of the inclination detecting windings S ₃ , S ₄ Detects a magnetic field over a range of equal length in a direction parallel to the direction of movement of the measurement object, and the distance from the vertical axis to each of the first and second points is greater than the distance from the vertical axis to the first and second points. The detection range of the magnetic field for calculating the flow velocity is set to be larger than the distance to the center position of each of the two divided ranges.
[0055]
Embodiment 3
Embodiment 3 includes, for example, (a) of FIG. 14 overlapping with FIG. 2, (a) of FIG. 15, (a) of FIG. 16, (a) of FIG. 17, (a) of FIG. Alternatively, as shown in FIG. ₁ , S ₂ And the inclination detecting winding is S ₁ , S ₂ S provided on both sides of ₃ , S ₄ (Corresponding to claims 3 and 10).
The arrangement of each detection winding and the detection range thereof in the third embodiment are as follows.
First, in a plane parallel to the moving direction of the measurement target and perpendicular to the surface of the measurement target, an axis perpendicular to the measurement target surface where the excitation magnetic field by the excitation winding P is line-symmetric is selected. Flow velocity detection winding S ₁ , S ₂ Are respectively arranged on the first and second points where the exciting magnetic field is line-symmetric with respect to the vertical axis in the plane, and have the same length in a direction parallel to the moving direction of the measuring object. To detect two magnetic fields S ₃ , S ₄ A third and a fourth each having a distance from the vertical axis farther than the first and second points, respectively, and the excitation magnetic field being line-symmetric with respect to the vertical axis in the plane; Placed on a point, and each winding S for detecting tilt ₃ , S ₄ Detects a magnetic field over a range of equal length in a direction parallel to the moving direction of the measurement object.
[0056]
Embodiment 4
Embodiment 4 is shown, for example, in FIG. 14 (c), FIG. 15 (c), FIG. 16 (c), FIG. 17 (c), FIG. 18 (c), or FIG. 19 (c). Thus, the flow rate detecting winding is S ₁ , S ₂ And the inclination detecting winding is S ₁ , S ₂ Having a detection range longer in the direction parallel to the moving direction of the measurement object than the detection range including ₃ (Corresponding to claims 4 and 11).
The arrangement of the detection windings and the detection range thereof in the fourth embodiment are as follows.
First, in a plane parallel to the moving direction of the measurement target and perpendicular to the surface of the measurement target, an axis perpendicular to the measurement target surface where the excitation magnetic field by the excitation winding P is line-symmetric is selected. Flow velocity detection winding S ₁ , S ₂ Are respectively arranged on the first and second points where the exciting magnetic field is line-symmetric with respect to the vertical axis in the plane, and have the same length in a direction parallel to the moving direction of the measuring object. To detect a magnetic field over a range of ₃ Is arranged on the vertical axis, and detects a magnetic field over a range of a predetermined length in a direction parallel to the moving direction of the measurement object, and further detects the tilt detection winding S from the vertical axis. ₃ The distance from the center of each of the ranges obtained by bisecting the magnetic field detection range is larger than the distance from the vertical axis to each of the first and second points.
[0057]
Embodiment 5
Embodiment 5 is shown, for example, in FIG. 14 (d), FIG. 15 (d), FIG. 16 (d), FIG. 17 (d), FIG. 18 (d), or FIG. 19 (d). Thus, the flow rate detecting winding is S ₁ And the winding for detecting inclination is S ₁ S having a detection range longer in the direction parallel to the moving direction of the measurement object than the detection range of ₃ (Corresponding to claims 5 and 12).
The arrangement of the detection windings and the detection range in the fifth embodiment are as follows.
First, in a plane parallel to the moving direction of the object to be measured and perpendicular to the surface of the object to be measured, an axis perpendicular to the surface of the object to be measured in which the exciting magnetic field generated by the exciting winding P is axisymmetric is selected. For detecting flow velocity S ₁ Are arranged on the vertical axis and detect a magnetic field over a range of a predetermined length in a direction parallel to the moving direction of the measurement object, and a single tilt detection winding S ₃ Are also arranged on the vertical axis and the flow rate detecting winding S ₁ The magnetic field is detected over a range in which the length in the direction parallel to the moving direction of the measurement target is longer than the magnetic field detection range of.
[0058]
Embodiment 6
In the sixth embodiment, for example, (a) of FIG. 14 and (b), (c), and (d) of FIG. 14 overlapping with FIG. 2 and (a) of FIG. 15 and (b) of FIG. , (C) and (d), all of the flow velocity detecting winding and the inclination detecting winding intersect with the axis perpendicular to the surface to be measured and the direction of movement of the object to be measured. It is arranged on a parallel straight line (corresponding to claims 6 and 13).
[0059]
Embodiment 7
As shown in (a) or (b) of FIG. 14, (a) or (b) of FIG. 16, or (a) or (b) of FIG. As described in [0037] and [0038], the flow detecting winding S ₁ And S ₂ Or S ₁ Is set near the center axis of the exciting magnetic field by the exciting winding P, and the inclination detecting winding S ₃ , S ₄ Is set to be a range in which the amount of change in the magnetic field with respect to the flow velocity of the measurement object is the smallest (corresponding to claims 7 and 14).
[0060]
Other embodiments
In the first embodiment, the diameter of the flow velocity detection winding and the diameter of the inclination detection winding are the same, but they may have different diameters.
Further, in the first embodiment, the air-core type in which the winding is wound on a ceramic bobbin is used as the detecting device for detecting the flow velocity and the inclination, but the winding is wound on a magnetic material such as ferrite. A magnetic core type may be used.
Further, other magnetic sensors such as a Hall element may be used as the magnetic detection means instead of the detection winding.
Further, here, an example in which the correction circuit 70 is processed by software on a computer has been described, but processing may be performed by using hardware (for example, an appropriate analog circuit or the like) instead of software.
In addition, here, an example using a lock-in amplifier to detect signals from the respective detection windings has been described. However, as long as a component of a desired phase of each signal can be detected, the component need not be a lock-in amplifier. Instead, a synchronous detector or the like may be used.
[0061]
Next, the present flow velocity measuring device having the configuration of the first embodiment (a device including the sensor bed 1 having the configuration of FIG. 2 and the flow velocity measuring circuit 30, the inclination detecting circuit 40, the lift-off measuring circuit 50, and the correction circuit 70 of FIG. 1) The results of conducting a verification test of wavy correction using are shown.
As a test device, as shown in FIG. 20, a disk made of SUS316 was fixed diagonally to a rotating shaft, and the sensor head 1 of the present device was arranged thereon to perform a test simulating waving. FIG. 20A is a view of the test apparatus as viewed from the front, and FIG. 20B is a view of the test apparatus as viewed from directly above.
In this test, the apparatus is first placed in a place where there is no magnetic, conductive or electromagnetic field around it, and each of the bridge circuits 21 and 41 in the flow velocity measurement circuit 30, the inclination detection circuit 40 and the lift-off measurement circuit 50 is set. And 51 are adjusted and then placed on the stopped SUS disk.
Next, the disk was rotated, the disk was stopped after a while, and the device was again removed from the SUS disk and placed in a place where there was no magnetic, conductive or electromagnetic field around.
[0062]
FIG. 21 is a diagram showing an example of a confirmation test result of waving correction using the test apparatus of FIG. Note that the horizontal axis in FIG. 21 is time (unit is seconds).
FIG. 21A shows the speed of the measurement target obtained from the disk rotation speed, and FIG. 21B shows the value obtained by measuring the lift-off based on the ultrasonic distance meter. Also, (c) of the figure shows the flow velocity original signal corresponding to the output signal of the detection winding for flow velocity detection, and (d) shows the inclination original signal which is the output signal of the inclination detection coil.
FIG. 21 (e) shows the flow velocity value which is the final output of the apparatus after correcting the inclination of the measurement target surface and the lift-off fluctuation, and the waveforms of both (a) and (e) are almost the same.
As described above, before the inclination correction, the flow velocity value largely changes due to the change in the inclination of the target surface due to the wave. However, the change is eliminated by the inclination correction, and a high-precision flow velocity signal corresponding to the target velocity is obtained. It can be seen that the speed can be detected stably.
[0063]
FIG. 23 is a diagram showing another result of a confirmation test of the wavy correction of the present flow velocity measuring device.
Here, a low melting point alloy (wood metal) is melted and put into a long and thin container as shown in FIG. 22, and the central axis of the detection winding of the sensor bed 1 of the present device becomes parallel to the longitudinal direction of the container (that is, of the present device). This device was arranged on the low melting point alloy such that the flow velocity detection direction and the longitudinal direction of the container were parallel.
Here, a plate was placed at one end of the container and moved to generate a wave on the surface of the low melting point alloy. In this test, the flow rate of the low melting point alloy is zero.
In this test, the apparatus is first placed in a place where there is no magnetic, conductive or electromagnetic field around it, and each of the bridge circuits 21 and 41 in the flow velocity measurement circuit 30, the inclination detection circuit 40 and the lift-off measurement circuit 50 is set. And 51 were adjusted, followed by placing the device on the low melting alloy and creating waves in the plate. FIG. 23 shows only the state of signals from a state where the present apparatus is already arranged on a low melting point alloy.
[0064]
FIG. 23A shows a value obtained by measuring lift-off based on an ultrasonic distance meter. Note that the horizontal axis in each drawing indicates time (unit is seconds).
FIG. 23 (b) shows a flow velocity original signal corresponding to an output signal of the detection winding for flow velocity detection, and FIG. 23 (c) shows a gradient original signal which is an output signal of the inclination detection coil. FIG. 23D shows the flow velocity value which is the final output of the apparatus after correcting the inclination of the measurement target surface and the lift-off fluctuation.
As described above, before the inclination correction, the flow velocity value largely changes due to the change in the inclination of the target surface due to the wave. It can be seen that the speed can be detected.
[0065]
【The invention's effect】
As described above, according to the present invention, exciting means arranged to apply a magnetic field perpendicular to the surface of a moving conductive measurement object, and a surface parallel to the surface of the measurement object and the moving direction thereof. A flow rate comprising: at least one magnetic field detecting means arranged to detect a magnetic field in a direction; and measuring means for calculating a flow rate of the object to be measured based on a magnetic field signal detected by the one or more magnetic field detecting means. In the measurement method and apparatus, A magnetic field in a direction parallel to the moving direction of the measurement object is disposed at a position in the direction parallel to the movement direction of the measurement object and away from the center axis of the excitation magnetic field by a distance of the magnetic field detection unit, and is detected. Do One or more sub-magnetic field detection means, and obtains information related to the inclination of the surface of the measurement object based on the magnetic field signal detected by the one or more sub-magnetic field detection means, and based on the information, the measurement means Since the correction means for correcting the calculated flow velocity of the object to be measured is provided, the flow velocity can be stably measured even if the surface to be measured is wavy or the surface is inclined.
[0066]
Further, according to the present invention, the detection range of the magnetic field detection means for measuring the flow velocity is near the center axis of the excitation magnetic field, the detection range of the sub-magnetic field detection means for obtaining information related to the inclination, Since the range of the change amount of the magnetic field with respect to the flow velocity of the measurement object is set to be the smallest, the inclination correction accuracy is good, and as a result, a flow velocity value with high accuracy can be obtained.
[0067]
According to the present invention, the number of elements of the magnetic field detecting means for measuring the flow velocity is one or more, and the number of elements of the sub-magnetic field detecting means for obtaining information related to the inclination is one or more, The number of elements can be combined to form a polymorphic sensor head, so that an appropriate type of sensor head can be selected and measured according to the type of the object to be measured, and the application range of the present invention is expanded. did.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a flow velocity measuring device according to a first embodiment of the present invention.
FIG. 2 is a configuration diagram (after optimization) of the sensor head of FIG. 1;
FIG. 3 is another configuration diagram (before optimization) of the sensor head according to the present invention.
FIG. 4 is an explanatory diagram of a ripple effect of a measurement target.
FIG. 5 is a diagram illustrating the principle of flow rate and lift-off detection.
FIG. 6 is an explanatory diagram of a method of acquiring a tilt characteristic.
FIG. 7 is an explanatory diagram of a method for acquiring flow velocity characteristics.
FIG. 8 is a diagram illustrating an example of a tilt characteristic.
FIG. 9 is a diagram illustrating an example of flow velocity characteristics.
FIG. 10 is an explanatory diagram of a method for acquiring inclination and flow velocity characteristics depending on the position of a detection device.
FIG. 11 is an explanatory diagram of a gradient of a gradient characteristic straight line and a gradient of a flow velocity characteristic straight line.
FIG. 12 is a diagram illustrating an example of a tilt characteristic after optimization.
FIG. 13 is a diagram illustrating an example of flow velocity characteristics after optimization.
FIG. 14 is another configuration diagram (1) of the sensor head according to the present invention.
FIG. 15 is another configuration diagram (2) of the sensor head according to the present invention.
FIG. 16 is another configuration diagram (3) of the sensor head according to the present invention.
FIG. 17 is another configuration diagram (4) of the sensor head according to the present invention.
FIG. 18 is another configuration diagram (5) of the sensor head according to the present invention.
FIG. 19 is another configuration diagram (6) of the sensor head according to the present invention.
FIG. 20 is an explanatory diagram of a confirmation test method (part 1) for correction of waviness.
21 is a diagram showing an example of a confirmation test result of the wavy correction of FIG. 20.
FIG. 22 is an explanatory diagram of a confirmation test method (part 2) for correction of ripples.
FIG. 23 is a diagram showing an example of a confirmation test result of wavy correction in FIG. 22.
FIG. 24 is an explanatory diagram of continuous casting.
FIG. 25 is an explanatory view of a conventional high-temperature liquid metal flow velocity measuring device using a contact method.
FIG. 26 is an explanatory diagram relating to a velocity effect of a magnetic field and an influence of an eddy current.
FIG. 27 is an explanatory diagram of a conventional non-contact flow velocity measuring device for high temperature liquid metal using magnetism (part 1).
FIG. 28 is an explanatory view of a conventional non-contact flow velocity measuring device for high-temperature liquid metal using magnetism (part 2).
FIG. 29 is an explanatory view of a conventional non-contact flow velocity measuring device for high temperature liquid metal using magnetism (part 3).
FIG. 30 is an explanatory view of the measurement principle of a conventional non-contact flow velocity measuring device for high-temperature liquid metal using magnetism.
FIG. 31 is an explanatory view of a lift-off detecting method in a conventional non-contact flow velocity measuring device for high-temperature liquid metal using magnetism.
FIG. 32 is a configuration diagram of a sensor head of a conventional non-contact flow velocity measuring device for high-temperature liquid metal using magnetism.
[Explanation of symbols]
1 Sensor head
2 Ceramic round pipe
3 Ceramic round bar
S ₁ , S ₂ Detection winding for flow velocity detection
S ₃ , S ₄ Detection winding for tilt detection
S ₅ , S ₆ Detection winding for lift-off detection
10 Excitation circuit
11 Oscillator
12 Constant current amplifier
20 Detection circuit
21,41,51 Bridge circuit
22, 42, 52 Bandpass filter
23, 43, 53 Lock-in amplifier
30 Flow velocity measurement circuit
40 Tilt detection circuit
50 Lift-off measurement circuit
70 Correction circuit
71 A / D converter
72 Computer
73 D / A converter

Claims (14)

A magnetic field perpendicular to the surface of the moving conductive measurement object is excited, and a magnetic field in a direction parallel to the surface of the measurement object and the direction of movement thereof is detected in one or more ranges. In the flow velocity measuring method for calculating the flow velocity of the measurement object based on the magnetic field signal detected in the range,
Along the direction parallel to the moving direction of the object to be measured from the central axis of the excitation magnetic field, the measurement object is located at one or more locations more distant from the magnetic field detection range for measuring the flow velocity. Detect a magnetic field in a direction parallel to the moving direction of the object, obtain information related to the inclination of the surface of the object to be measured based on the detected magnetic field signal, and calculate the calculated flow velocity of the object to be measured based on the information. A flow velocity measuring method characterized by correcting. In a plane parallel to the moving direction of the measurement target and perpendicular to the surface of the measurement target, an axis perpendicular to the measurement target surface where the exciting magnetic field is line-symmetric is selected.
The detection range of the magnetic field for calculating the flow velocity is a range of a predetermined length in a direction parallel to the moving direction of the measurement object around the point on the vertical axis,
The detection range of the magnetic field for correcting the flow velocity, the moving direction of the measurement object around the first and second points where the excitation magnetic field is line-symmetric with respect to the vertical axis in the plane. And the distance from the vertical axis to each of the first and second points is the detection range of the magnetic field for calculating the flow velocity from the vertical axis. 2. The flow velocity measuring method according to claim 1, wherein the distance is larger than a distance to a center position of each of the two divided ranges. In a plane parallel to the moving direction of the measurement target and perpendicular to the surface of the measurement target, an axis perpendicular to the measurement target surface where the exciting magnetic field is line-symmetric is selected.
The detection range of the magnetic field for calculating the flow velocity, the moving direction of the measurement object around the first and second points where the excitation magnetic field is line-symmetric with respect to the vertical axis in the plane Range of equal length in the direction parallel to
The magnetic field detection range for correcting the flow velocity, the distance from the vertical axis is farther than each of the first and second points, respectively, the excitation magnetic field with respect to the vertical axis in the plane in the plane. 2. The flow velocity measuring method according to claim 1, wherein the third and fourth points which are symmetrical with each other are centered and have equal lengths in directions parallel to the moving direction of the measurement object. In a plane parallel to the moving direction of the measurement target and perpendicular to the surface of the measurement target, an axis perpendicular to the measurement target surface where the exciting magnetic field is line-symmetric is selected.
The detection range of the magnetic field for calculating the flow velocity, the moving direction of the measurement object around the first and second points where the excitation magnetic field is line-symmetric with respect to the vertical axis in the plane Range of equal length in the direction parallel to
The detection range of the magnetic field for correcting the flow velocity is a range of a predetermined length in a direction parallel to a moving direction of the measurement object around a point on the vertical axis, and the flow velocity from the vertical axis. The distance to the center position of each range obtained by bisecting the detection range of the magnetic field for correcting the distance is larger than the distance from the vertical axis to each of the first and second points. The flow velocity measuring method according to claim 1, wherein In a plane parallel to the moving direction of the measurement target and perpendicular to the surface of the measurement target, an axis perpendicular to the measurement target surface where the exciting magnetic field is line-symmetric is selected.
The detection range of the magnetic field for calculating the flow velocity is a range of a predetermined length in a direction parallel to the moving direction of the measurement object around the point on the vertical axis,
The detection range of the magnetic field for correcting the flow velocity is centered on a point on the vertical axis, and the detection range of the magnetic field for calculating the flow velocity is in a direction parallel to the moving direction of the measurement target. The flow velocity measuring method according to claim 1, wherein the length is in a long range. All of the detection range of the magnetic field for correcting the flow rate and the detection range of the magnetic field for calculating the flow rate,
6. The apparatus according to claim 1, wherein the sensor is provided on a straight line that intersects an axis perpendicular to the measurement target surface and is parallel to a movement direction of the measurement target. 7. Flow velocity measurement method. The detection range of the magnetic field for calculating the flow velocity is near the center axis of the excitation magnetic field,
The detection range of the magnetic field for correcting the flow velocity is set to a range in which the amount of change in the magnetic field with respect to the flow velocity of the measurement object is the smallest. 3. The flow velocity measurement method according to 1. Exciting means arranged to apply a magnetic field perpendicular to the surface of the moving conductive measuring object, and arranged to detect a magnetic field in a direction parallel to the surface of the measuring object and its moving direction. One or more magnetic field detecting means, and a flow rate measuring device having a measuring means for calculating the flow rate of the object to be measured based on the magnetic field signal detected by the one or more magnetic field detecting means,
A magnetic field in a direction parallel to the moving direction of the measurement object is disposed at a position in the direction parallel to the movement direction of the measurement object and away from the center axis of the excitation magnetic field by a distance of the magnetic field detection unit, and is detected. and one or more sub-field detecting means for,
Based on the magnetic field signal detected by the one or more sub-magnetic field detecting means, information on the inclination of the surface of the measuring object is obtained, and based on the information, the flow rate of the measuring object calculated by the measuring means is corrected. A flow velocity measuring device comprising a correction means. In a plane parallel to the moving direction of the measurement target and perpendicular to the surface of the measurement target, an axis perpendicular to the measurement target surface where the exciting magnetic field is line-symmetric is selected.
The magnetic field detecting means for calculating the flow velocity is arranged on the vertical axis as one, and to detect a magnetic field over a range of a predetermined length in a direction parallel to the moving direction of the measurement target,
The sub-magnetic field detecting means for correcting the flow velocity is arranged at two points on the first and second points where the exciting magnetic field is line-symmetric with respect to the vertical axis in the plane. The magnetic field detecting means detects a magnetic field over an equal length range in a direction parallel to the moving direction of the measurement target, and a distance from the vertical axis to each of the first and second points is equal to the vertical direction. 9. The flow velocity measuring device according to claim 8, wherein a distance from a center to a center position of each of the bisected magnetic field detection ranges for calculating the flow velocity is set larger than an axis. In a plane parallel to the moving direction of the measurement target and perpendicular to the surface of the measurement target, an axis perpendicular to the measurement target surface where the exciting magnetic field is line-symmetric is selected.
The magnetic field detecting means for calculating the flow velocity is arranged on each of the first and second points where the exciting magnetic field is line-symmetric with respect to the vertical axis in the plane, and To detect magnetic fields over a range of equal length in a direction parallel to the direction of movement of the object,
The sub-magnetic field detecting means for correcting the flow velocity has two distances from the vertical axis farther than the first and second points, respectively, with respect to the vertical axis in the plane. The sub-magnetic field detecting means are arranged on the third and fourth points where the exciting magnetic field is axisymmetric, and each sub-magnetic field detecting means detects a magnetic field over a range of equal length in a direction parallel to the moving direction of the measurement object. 9. The measuring flow rate device according to claim 8, wherein: In a plane parallel to the moving direction of the measurement target and perpendicular to the surface of the measurement target, an axis perpendicular to the measurement target surface where the exciting magnetic field is line-symmetric is selected.
The magnetic field detecting means for calculating the flow velocity is arranged on each of the first and second points where the exciting magnetic field is line-symmetric with respect to the vertical axis in the plane, and To detect magnetic fields over a range of equal length in a direction parallel to the direction of movement of the object,
The auxiliary magnetic field detecting means for correcting the flow velocity is arranged on the vertical axis as one, and detects a magnetic field over a range of a predetermined length in a direction parallel to the moving direction of the measurement target, Further, the distance from the vertical axis to the center position of each of the two ranges of the magnetic field detection range for correcting the flow velocity is the distance from the vertical axis to each of the first and second points. 9. The flow velocity measuring apparatus according to claim 8, wherein each of the flow velocity measuring apparatuses is set to be larger than the above. In a plane parallel to the moving direction of the measurement target and perpendicular to the surface of the measurement target, an axis perpendicular to the measurement target surface where the exciting magnetic field is line-symmetric is selected.
The magnetic field detecting means for calculating the flow velocity is arranged on the vertical axis as one, and to detect a magnetic field over a range of a predetermined length in a direction parallel to the moving direction of the measurement target,
The auxiliary magnetic field detecting means for correcting the flow velocity is disposed on the vertical axis as one, and is more parallel to the moving direction of the measurement target than the detection range of the magnetic field detecting means for calculating the flow velocity. 9. The flow velocity measuring device according to claim 8, wherein a magnetic field over a long range is detected. All of the magnetic field detecting means and the sub magnetic field detecting means are arranged on a straight line which intersects with an axis perpendicular to the surface to be measured and which is parallel to the moving direction of the object to be measured. The flow velocity measuring device according to any one of claims 8 to 12. The detection range of the magnetic field detection means is near the central axis of the excitation magnetic field,
14. The apparatus according to claim 8, wherein a detection range of the sub-magnetic field detection unit is set to a range in which a variation amount of a magnetic field with respect to a flow velocity of the measurement object is the smallest. Flow velocity measuring device.

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