JP3664289B2 - Magnetic metal sensor - Google Patents

Description

以上のように被検出体１と磁性金属センサ２との配置関係を定めることによって、この被検出体１がａ₁，ａ₂方向に平行移動した場合、磁性金属センサ２の検出出力が以下の状態を繰り返すこととなる。すなわち、磁性金属センサ２の検出出力は、垂直部２２ａが１の金属片１１の影響により応答して垂直部２２ｂがいずれの金属片１１の影響によっても応答しない状態と、垂直部２２ｂが１の金属片１１の影響により応答して垂直部２２ａがいずれの金属片１１の影響によっても応答しない状態とを交互に繰り返すこととなる。
【００４９】
従って、この交互に繰り返される検出出力をカウントすることによって、被検出体１の移動位置を検出することができる。
【００５０】
つぎに、磁性金属センサ２の金属片１１の検出動作について説明する。
【００５１】
まず、１つの金属片１１を、この磁性金属センサ２のコイル２３からコイル２４にかけて通過させた場合の検出出力について図７を用いて説明する。なお、この図７は、横軸に、１つのみで構成される金属片１１のコイル２３，２４に対する位置を表し、縦軸に、図５に示す駆動検出回路３０において検出したコイル２３とコイル２４を直列接続した場合の中点Ｍの電圧を表している。また、縦軸のスレッショルドレベルは、上述したようにこの磁性金属センサ２に何等磁界や金属を近づけていない場合の中点Ｍの電圧を表している。
【００５２】
金属片１１がコイル２３及びコイル２４のいずれにも接近していない位置Ｐ₁にある場合には、コイル２３及びコイル２４を通る磁束の磁気回路の磁気抵抗は変化せず、磁石２５から与えられる磁束の本数に変化は生じていない。従って、コイル２３及びコイル２４のいずれのインピーダンスも変化しないので、中点Ｍの電位は、スレッショルドレベルにある。
【００５３】
続いて、金属片１１がコイル２３に接近していくと、金属片１１の透磁率が空気の透磁率よりも大きいことから、このコイル２３を通る磁束の磁気回路の磁気抵抗が小さくなっていき、磁石２５から与えられる磁束の本数が増加する。それに対し、コイル２４は金属片１１に応答しないため、コイル２４を通る磁束の磁気回路の磁気抵抗はコイル２３側の磁束が増加する分だけ減少する。そのため、コイル２３のインピーダンスが小さくなっていき、それに対して、コイル２４のインピーダンスは大きくなっていく。従って、金属片１１がコイル２３に接近するにつれて、中点Ｍの電位は、スレッショルドレベルから順次高くなっていく。そして、金属片１１がコイル２３に最も接近した位置Ｐ₂となる場合に、中点Ｍの電位が最も高くなる。
【００５４】
続いて、金属片１１がコイル２３に最も接近した位置Ｐ₂からコイル２４に接近していくと、コイル２３から金属片１１が離れていくため、コイル２３を通る磁束の磁気回路の磁気抵抗が大きくなっていき、磁石２５から与えられる磁束の本数が減少していく。それに対して、コイル２４に金属片１１が接近するため、コイル２４を通る磁束の磁気回路の磁気抵抗は小さくなっていく。そのため、コイル２３のインピーダンスが大きくなっていき、同時に、コイル２４のインピーダンスが小さくなっていく。従って、金属片１１がコイル２３からコイル２４に接近するにつれて、中点Ｍの電位は順次低くなっていく。そして、金属片１１がコイル２３とコイル２４の中間位置Ｐ₃に来ると中点Ｍの電位はスレッショルドレベルとなり、金属片１１がコイル２４に最も接近した位置Ｐ₄となると中点Ｍの電位が最も低くなる。
【００５５】
続いて、金属片１１がコイル２４に最も接近した位置Ｐ₄から、コイル２３及びコイル２４のいずれにも接近していない位置Ｐ₅に移動すると、コイル２３及びコイル２４を通る磁束の磁気回路の磁気抵抗がいずれも金属片１１に応答しなくなる。従って、コイル２３及びコイル２４のいずれのインピーダンスも変化しないので、中点Ｍの電位が、スレッショルドレベルとなる。
【００５６】
以上のように、磁性金属センサ２では、金属片１１がコイル２３からコイル２４にかけて通過すると、中点Ｍの電位が、金属片１１が接近していないときの電位をスレッショルドレベルとして、プラスマイナスに振れる。従って、この磁性金属センサ２では、このスレッショルドレベルを中心に検出出力を比較することによって、金属片１１の位置を容易かつ確実に検出することができる。
【００５７】
つぎに、コイル２３とコイル２４の間隔をλ／２にした磁性金属センサ２を、間隔λで並列に配置された複数の金属片１１に対して相対的に移動させた場合の検出出力について図８を用いて説明する。なお、この図８は、横軸に、複数の金属片１１に対する磁性金属センサ２の位置を表し、縦軸に、図５に示す駆動検出回路３０においてコイル２３とコイル２４を直列接続した場合の中点Ｍの電圧を表している。また、縦軸のスレッショルドレベルは、上述したようにこの磁性金属センサ２に何等磁界や金属を近づけていない場合の中点Ｍの電圧を表している。
【００５８】
この磁性金属センサ２では、コイル２３に１つの金属片１１が最も接近した位置にあるときには、コイル２４にはいずれの金属片１１も接近していない。そのため、コイル２３が金属片１１に応答している状態において、コイル２４が金属片１１に応答していない。従って、検出出力となる中点Ｍの電位は、スレッショルドレベルよりも大きくなっている。
【００５９】
また、この磁性金属センサ２では、コイル２４に１つの金属片１１が最も接近した位置にあるときには、コイル２３にはいずれの金属片１１も接近していない。そのため、コイル２４が金属片１１に応答している状態において、コイル２３が金属片１１に応答していない。従って、検出出力となる中点Ｍの電位は、スレッショルドレベルよりも小さくなる。
【００６０】
従って、この磁性金属センサ２では、間隔λで並列に配置された複数の金属片１１に対して相対的に移動させた場合、スレッショルドレベルを中心に上下に振れる信号を検出出力として得ることができる。
【００６１】
なお、図９に、一例として、上述した寸法の磁性金属センサ２と金属片１１を適用した場合の、磁性金属センサ２と金属片１１の相対移動位置に対する直列接続したコイル２３とコイル２４の中点Ｍの電位の関係を表した図を示す。
【００６２】
以上のように、磁性金属センサ２では、間隔λで並列に配置された複数の金属片１１に対して相対的に移動させた場合における検出出力を、金属片１１がコイル２３，２４のいずれにも接近していない位置の中点Ｍの電位をスレッショルドレベルとして比較することにより、１の金属片１１の数を容易かつ確実に検出することができる。
【００６３】
なお、この磁性金属センサ２を金属片カウンタに適用した場合、被検出体１が平行移動すると説明したが、本発明では、被検出体１とセンサ２との間で相対移動すればよいので、磁性金属センサ２側が平行移動しても良い。
【００６４】
また、更に別の磁性金属センサを上記磁性金属センサ２と（ｍ±１／４）λの距離をもって相対移動方向にずらして配置することで、上記図８に示した信号が９０゜の位相差を有する２相の信号として得ることができる（ｍは整数）。従って、この２相の信号に基づき相対的な移動量を出力する信号をつくることができるので、このように配置された磁性金属センサを用いて位置検出装置を構成することが可能となる。
【００６５】
また、被検出体を円形状に構成し、回転数や角度を測定するようにもできる。つぎに、上述した磁性金属センサ２を近接センサとして適用した場合について説明する。
【００６６】
この磁性金属センサ２を近接センサとして適用した場合には、例えば、ロボット等のアームが所定位置に近づいたかどうかを判断してそのアームの位置を制御するシステムや、被工作物に取り付けられるネジのゆるみや締め忘れ等を検出して作業工程のチェックを行うシステムに用いることが可能である。
【００６７】
このような磁性金属センサ２を金属の近接センサとして用いる場合には、コイル２３，２４の極性が互いに逆方向となるようにしてその差動出力を検出することによって、その感度を高くすることができる。
【００６８】
つまり、この磁性金属センサ２を近接センサとして用いる場合には、上述した図５に示す駆動検出回路３０の各スイッチを、例えば、スイッチＳ１，Ｓ１′をオフとし、スイッチＳ２，Ｓ２′をオンとして、コイル２３とコイル２４に流す励磁電流の位相を反転させる。このことにより、コイル２３とコイル２４との巻き線方向が同一である場合は互いに逆相の高周波パルス電流により励磁され、コイル２３とコイル２４との巻き線方向が逆である場合は同相の高周波パルス電流で励磁される。
【００６９】
そして、このように励磁したコイル２３，２４間の差分値を検出することによって、上記磁性金属センサ２の金属を高感度な近接センサとして用いることができる。
【００７０】
このように近接センサとして用いた場合の磁性金属センサ２の検出動作について、図１０を用いて説明する。
【００７１】
この図１０には、１つの金属片５１を、この磁性金属センサ２のコイル２３からコイル２４にかけて通過させた場合の検出出力を示している。なお、この図１０は、横軸に、１つのみで構成される金属片５１のコイル２３，２４に対する位置を表し、縦軸に、コイル２３とコイル２４の差動電圧を示している。
【００７２】
金属片５１がこの磁性金属センサ２の感磁部２１に接近していない場合には、コイル２３とコイル２４との電圧差は生じず、出力は、０となっている。そして、この感磁部２１に金属片５１が接近すると、コイル２３とコイル２４の極性が逆となっているため、コイル２３，２４のいずれか一方のインピーダンスが高くなり、他方のインピーダンスが低くなる。従って、その差動電圧は上昇する。
【００７３】
そして、金属片５１がコイル２３及びコイル２４の両者に対向する位置に来たときに、その差動電圧が最大レベルとなる。
【００７４】
従って、この磁性金属センサ２では、所定の電圧のスレッショルドレベルを設定し、検出した差動電圧をこの設定したスレッショルドレベルで２値化することにより、金属片５１が接近したかどうかを判断することができる。
【００７５】
以上のように磁性金属センサ２では、スイッチＳ１，Ｓ１′、スイッチＳ２，Ｓ２′によりコイル２４の極性を切り換えることにより、金属片カウンタ１１として適用することができるとともに、近接した磁性金属片の検出を行うことができる。そのため、この両者の機能を有する磁性金属センサ２を、安価に提供することができる。
【００７６】
なお、上述した駆動検出回路３０では、電圧比較部３７により発生されるスレッショルドレベルの電圧と、コイル２３，２４の中点Ｍの電圧とを比較し、その値を２値化している。従って、この磁性金属センサ２を、金属片カウンタに適用する場合と、近接センサとして用いる場合とでスレッショルドレベルが変わるときには、この電圧比較部３７の抵抗Ｒ₁，Ｒ₂の比率を変更すれば良い。この抵抗Ｒ₁，Ｒ₂の比率の変更は、例えば、トリマ等を用いて設定することが可能である。
【００７７】
また、この抵抗比率を変更することができない場合には、比較回路３８を差動増幅器に置き換え、差動電圧を直接システムコントローラ等に供給し、このシステムコントローラでＡ／Ｄ変換をしてデータを収集することにより、この磁性金属センサ２を金属片カウンタや近接センサの両者に適用することができる。
【００７８】
つぎに、磁性金属センサ２の感磁部２１に磁気インピーダンス効果素子を適用した場合について説明する。
【００７９】
これまで、略Ｕ字型のコア２２の垂直部２２ａ，２２ｂにコイル２３，２４を巻いた感磁部２１を備える磁性金属センサ２について説明したが、本発明に係る磁性金属センサでは、例えば、特開平６−２８１７１２号公報で提案されているようないわゆる磁気インピーダンス効果（ＭＩ）素子４１，４２を感磁部２１に適用することも可能である。
【００８０】
このＭＩ素子４１，４２は、材質がＦｅ、Ｓｉ、Ｃｏ、Ｂ等で構成されたアモルファス合金からなる。このＭＩ素子４１，４２は、図１１に示すように、略ワイヤ形状となっている。このＭＩ素子４１，４２は、長手方向（感磁方向）に対して高周波通電すると、この長手方向に入射する外部磁界に対してインピーダンス変化が生じる。
【００８１】
このＭＩ素子４１，４２を備えた磁性金属センサ２を、金属片カウンタに適用した場合の配置関係を図１２に示す。
【００８２】
このＭＩ素子４１，４２は、所定のギャップ幅ｇをもって長手方向が平行となるよう配置され、その配置位置が上述した垂直部２２ａ，２２ｂに対応する位置となっている。また、このＭＩ素子４１，４２は、磁石２５により長手方向に平行な磁界が与えられ、この方向に入射する外部磁界に対する感度が非常に高くなっている。また、このＭＩ素子４１，４２は、この方向の外部磁界に対してインピーダンス変化が生じ、その変化率が非常に大きくなっている。
【００８３】
また、ＭＩ素子４１，４２は、高周波のパルス電流で励磁される。ここで、ＭＩ素子４１，４２は、この磁性金属センサ２が金属片カウンタに適用される場合には、感磁方向が同一となるような同相の高周波パルス電流で励磁され、その極性が同一となっている。
【００８４】
なお、このＭＩ素子４１，４２を適用した磁性金属センサ２を近接センサとして用いる場合には、上述したコイル２３，２４をコア２２に巻回した場合と同様に、その極性が逆となる関係とする。この切り換えは、後述する駆動検出回路に設けられたスイッチにより行われる。
【００８５】
このようなＭＩ素子４１，４２は、信号線を介してこの磁性金属センサ２の外部に設けられた駆動検出回路と接続される。これらＭＩ素子４１，４２は、この駆動検出回路から励磁電流が供給され、この駆動検出回路により出力が検出される。
【００８６】
図１３にこのＭＩ素子４１，４２の駆動検出回路４０の回路図を示す。
【００８７】
駆動検出回路４０は、発振回路３４と、発振回路３４からのパルス信号に基づきＭＩ素子４１，４２の励磁電流をスイッチングするスイッチング回路３５と、ＭＩ素子４１の出力電圧を検出して平滑化する平滑回路３６ａと、ＭＩ素子４２の出力電圧を検出して平滑化する平滑回路３６ｂと、平滑化されたＭＩ素子４１，４２の出力どうしを比較する比較回路３８とを備えている。
【００８８】
また、この駆動検出回路４０はＭＩ素子４１の励磁電流の方向を切り換えるスイッチＳ３、スイッチＳ４とを備えている。
【００８９】
ＭＩ素子４２は、一端が抵抗Ｒ₂を介して電源電圧Ｖｃｃが供給され、他端がスイッチング回路３５を介して接地されている。
【００９０】
ＭＩ素子４１は、一端が上記抵抗Ｒ₂と同一の抵抗値の抵抗Ｒ₁に接続され、他端がスイッチＳ３と接続されている。このスイッチＳ３は、端子ａ側に切り換えられるとこのＭＩ素子４１の他端をスイッチング回路３５に接続し、端子ｂ側に切り換えられるとＭＩ素子４１の他端を電源に接続する。
【００９１】
また、抵抗Ｒ₁は、一端が上記ＭＩ素子４１と接続され、他端がスイッチＳ４と接続されている。このスイッチＳ４は、端子ａ側に切り換えられるとこの抵抗Ｒ₁の他端を電源Ｖｃｃに接続し、端子ｂ側に切り換えられるとこの抵抗Ｒの他端をスイッチング回路３５に接続する。
【００９２】
このようなスイッチＳ３、スイッチＳ４は、互いに連動して端子ａ側又は端子ｂ側に切り換えられる。
【００９３】
すなわち、磁性金属センサ２が金属片カウンタに適用され、金属片１１が並列に配置された被検出体１の移動位置の検出を行う場合には、スイッチＳ３，Ｓ４がともに端子ａ側に切り換えられ、ＭＩ素子４１とＭＩ素子４２との極性が同一とされ、また、抵抗Ｒ₁とＭＩ素子４１、抵抗Ｒ₂とＭＩ素子４２の接続が、電源Ｖｃｃとスイッチング回路３５との間で並列な関係となる。
【００９４】
また、磁性金属センサ２が近接した磁性金属片の検出を行う場合には、スイッチＳ３，Ｓ４がともに端子ｂ側に切り換えられ、ＭＩ素子４１とＭＩ素子４２との極性が反対にされ、また、抵抗Ｒ₁とＭＩ素子４１、抵抗Ｒ₂とＭＩ素子４２の接続が、電源Ｖｃｃとスイッチング回路３５との間で逆となるブリッジ回路が構成される。
【００９５】
発振回路３４は、例えば、周波数１ＭＨｚ，デューティ比１：１０のパルス信号を発生する。スイッチング回路３５は、このパルス信号に基づき、並列接続されたＭＩ素子４１，４２に流れる電流をスイッチングする。このことにより、これらＭＩ素子４１，４２は、高周波パルス電流で励磁される。
【００９６】
平滑回路３６ａは、ＭＩ素子４１と抵抗Ｒ₁との接続点の電圧を検出して平滑化する。平滑回路３６ｂは、ＭＩ素子４２と抵抗Ｒ₂との接続点の電圧を検出して平滑化する。
【００９７】
比較回路３８は、平滑回路３６ａにより平滑化されたＭＩ素子４１の出力電圧と、平滑回路３６ｂにより平滑化されたＭＩ素子４２の出力電圧とを比較し、その差動電圧を例えば図示しない制御回路等に供給する。
【００９８】
そして、この磁性金属センサ２が金属片カウンタに適用されていた場合には、この図示しない制御回路等が、この比較回路３８からの差動電圧を所定のスレッショルドレベルで２値化して、そのパルス数をカウントすることにより上記金属片１１の検出数を求めることができ、この検出数から磁性金属センサ２と被検出体１との相対移動位置を検出することができる。
【００９９】
また、この磁性金属センサ２が近接センサに適用されていた場合には、この図示しない制御回路等が、この比較回路３８からの差動電圧を検出してその差動電圧を所定のスレッショルドレベルと比較することにより、磁性金属片５１が近接したか否か検出することができる。
【０１００】
以上のような磁性金属センサ２では、スイッチＳ３、スイッチＳ４によりＭＩ素子４１の極性を切り換えることにより、金属片カウンタ１１として適用することができるとともに、近接した磁性金属片の検出を行うことができる。そのため、この両者の機能を有する磁性金属センサ２を、安価に提供することができる。また、この磁性金属センサ２では、ＭＩ素子を用いることができるため、コストが安くまた特性を良好にすることができる。
【０１０１】
【発明の効果】
本発明に係る磁性金属センサは、切換手段により磁電変換手段の極性を切り換えることにより、並列に配置された磁性金属片の検出、及び、近接した磁性金属片の検出を行うことができる。そのため、本発明では、この両者の機能を安価に提供することができる。
【図面の簡単な説明】
【図１】本発明の実施の形態の金属片カウンタの斜視図である。
【図２】上記金属片カウンタの被検出体の要部の平面図、及び、この被検出体の金属片の側面図である。
【図３】上記金属片カウンタの磁性金属センサの部分断面図である。
【図４】上記磁性金属センサに設けられた感磁部及びこの感磁部のコアを示す図である。
【図５】上記磁性金属センサの駆動検出回路を示す回路図である。
【図６】上記被検出体と上記磁性金属センサの配置関係を示す図である。
【図７】上記磁性金属センサの検出動作を説明する図である。
【図８】上記磁性金属センサの検出動作を説明する図である。
【図９】上記磁性金属センサと被検出体の相対移動位置に対する駆動検出回路の出力電圧を表す図である。
【図１０】上記磁性金属センサを近接センサとして用いた場合の検出動作を説明する図である。
【図１１】ＭＩ素子を説明する図である。
【図１２】上記ＭＩ素子を適用した場合の本発明の実施の形態の金属片カウンタの磁性金属センサの配置関係を説明する図である。
【図１３】上記ＭＩ素子を適用した磁性金属センサの駆動検出回路の回路図である。
【符号の説明】
１ 被検出体、２ 磁性金属センサ、３ センサ固定台、１１ 金属片、１１ａ 検出面、１２ 指示部、２１ 感磁部、２２ コア、２２ａ，２２ｂ 垂直部、２２ｃ 接続部、２３，２４ コイル、２５ 磁石、３０，４０ 駆動検出回路、３４ 発振回路、３５ スイッチング回路、３６，３６ａ，３６ｂ 平滑回路、３７ 基準電圧回路、３８ 比較回路、Ｓ１，Ｓ１′，Ｓ２，Ｓ２′，Ｓ３，Ｓ４ スイッチ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic metal sensor that detects the presence or absence of a magnetic metal piece.
[0002]
[Prior art]
Conventionally, a magnetic metal sensor for detecting the presence or absence of magnetic metal is known.
[0003]
[Problems to be solved by the invention]
Such a magnetic metal sensor is a metal counter that detects the number of metal pieces arranged in parallel, such as gear teeth or comb-like metal bars, and detects the movement position of the metal pieces. It is required to apply. Specifically, this magnetic metal sensor is a comb for knitting fibers with a system such as a machine tool that detects the number of gear teeth and controls the rotation speed and rotation angle of the gear, and a knitting machine such as cloth or chemical fiber. This is used in a system for detecting the number of sticks of a knitted bar and controlling the movement position.
[0004]
In addition, such a magnetic metal sensor detects an approaching metal and controls the operation and position of the metal. For example, this magnetic metal sensor detects whether the arm of a robot or the like has approached a predetermined position and controls the position of the arm, or detects whether a screw attached to the workpiece is loose or forgotten to tighten. Used in systems that check work processes.
[0005]
However, for example, a sensor designed for detecting gear teeth or comb-like metals is not suitable for forgetting to tighten screws or for detecting the position of a robot arm, and vice versa. The same can be said for. Therefore, in order to detect these conflicting metal pieces, individual sensors must be designed and prepared.
[0006]
This invention is made in view of such a situation, and it aims at providing the magnetic metal sensor which performs the detection of the magnetic metal piece arrange | positioned in parallel, and the detection of the adjacent magnetic metal piece. .
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, a magnetic metal sensor according to the present invention includes a pair of magnetoelectric conversion units that obtain detection output in response to a change in magnetic field, and a magnetic field generation unit that applies a magnetic field to the pair of magnetoelectric conversion units. And switching means for switching the polarity of one of the pair of magnetoelectric conversion means.
[0008]
In this magnetic metal sensor, in response to switching of the switching means, a plurality of metal pieces move relative to the detected parts arranged in parallel at a predetermined interval to detect the number of magnetic metal pieces, etc. It detects whether or not it is close to the magnetic metal piece. In this magnetic metal sensor, the polarity of the magnetoelectric conversion means is switched by the switching means, and the detection of the magnetic metal pieces arranged in parallel and the detection of the adjacent magnetic metal pieces are performed.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
First, a case where the magnetic metal sensor of the present invention is applied to a metal piece counter that detects a moving position of a detection object in which magnetic metal pieces are arranged in parallel at a predetermined interval will be described with reference to the drawings.
[0010]
FIG. 1 is a perspective view of a metal piece counter.
[0011]
This metal piece counter is composed of a detection object 1 and a magnetic metal sensor 2 fixed on a sensor fixing base 3.
[0012]
The detected object 1 has a plurality of metal pieces 11 arranged in parallel at a predetermined interval λ. The plurality of metal pieces 11 are made of a magnetic metal such as iron or cobalt and have, for example, a rectangular parallelepiped shape. Each of the plurality of metal pieces 11 has one end portion in the longitudinal direction attached to the instruction unit 12 and constitutes the detection target 1 as a whole.
[0013]
The dimension of the metal piece 11 is, for example, the length in the longitudinal direction, as shown in the plan view of FIG. 2A and the side view of FIG. 2B viewed from the A direction in FIG. l ₁ , width w ₁ , and height h ₁ are 5.0 mm, 0.5 mm, and 2.0 mm, respectively. Further, the interval λ of the parallel arrangement of the metal pieces 11 is 1.0 mm. The side surface of the metal piece 11 viewed from the direction A shown in FIG. 2A, that is, the side surface of the other end portion of the metal piece 11 to which the indication unit 12 in the longitudinal direction is not attached is hereinafter referred to as a detection surface 11a. Call.
[0014]
A drive shaft 13 is attached to the side surface of the instruction unit 12 of the detection target 1. The drive shaft 13 is connected to a drive mechanism (not shown). For example, the drive mechanism translates the detection target ₁ in the a ₁ direction and the a ₂ direction, which are directions in which the metal pieces 11 are arranged in parallel, based on control by a control circuit or the like.
[0015]
FIG. 3 shows the structure of the magnetic metal sensor 2.
[0016]
The magnetic metal sensor 2 includes a magnetic sensing part 21 in which a coil 23 and a coil 24 are wound around a substantially U-shaped open magnetic path type core 22, and a magnet 25 that applies a magnetic field to the magnetic sensing part 21. .
[0017]
As shown in FIG. 4A, the core 22 of the magnetic sensitive part 21 is arranged so that vertical parts 22a and 22b of a substantially rectangular parallelepiped are parallel to each other with a predetermined gap width g. The vertical portions 22a and 22b have one end portion in the longitudinal direction connected to the connection portion 22c, and a substantially U-shaped core 22 is integrally formed as a whole. The core 22 is made of a material exhibiting soft magnetism such as permalloy having a NiFe composition or an amorphous material composed of Fe, Co, Si, B, or the like.
[0018]
The dimensions of each part of the core 22 are, for example, the lengths l ₂ , widths w ₂ and heights h _{2 in} the longitudinal direction of the vertical portions 22a and 22b are 3.5 mm, 0.5 mm and 0.05 mm, respectively. ing. In addition, the gap width g between the vertical portions 22a and 22b is 1.0 mm, and the overall dimensions of the core 22 are the length l ₃ , width w ₃ and thickness h _{2 in} the longitudinal direction. It is 5.0 mm, 2.0 mm, and 0.05 mm.
[0019]
As shown in FIG. 4B, the core 22 having such a shape has coils 23 and 24 with respect to the vertical portion 22a and the vertical portion 22b, with the outer circumferences of the cylindrical bobbins 29a and 29b as guides, respectively. It is rolled up. The coils 23 and 24 are wound so that the central axes thereof are parallel to the longitudinal direction of the vertical portions 22a and 22b. Such coils 23 and 24 are configured, for example, by winding a copper wire having a diameter of 0.05 mm 50 times each.
[0020]
The magnetic sensing part 21 as described above has a very high sensitivity to an external magnetic field incident in parallel to the longitudinal direction (the x direction shown in FIG. 4) of the vertical parts 22a and 22b of the core 22. Further, the magnetosensitive portion 21 undergoes an impedance change with respect to the external magnetic field incident in parallel in the x direction, and the rate of change is very large. The longitudinal direction of the vertical portions 22a and 22b of the core 22, that is, the x direction shown in FIG.
[0021]
The coils 23 and 24 of the magnetic sensing unit 21 are excited with a high-frequency pulse current. Here, when the magnetic metal sensor 2 is applied to a metal piece counter, the relationship between the winding direction of the coils 23 and 24 and the current direction of the high frequency pulse current to be excited is the same in polarity. . That is, the magnetic field H1 generated in the coil 23 and the magnetic field H1 ′ generated in the coil 24 are in the same direction. For example, when the winding direction of the coil 23 and the coil 24 is the same, a high-frequency pulse current of the same phase is excited in each, and when the winding direction of the coil 23 and the coil 24 is opposite, they are opposite to each other. The high-frequency pulse current of the phase is excited.
[0022]
When the magnetic metal sensor 2 is used as a proximity sensor, the relationship between the winding direction of the coils 23 and 24 and the current direction of the high frequency pulse current to be excited is a relationship in which the polarity is reversed. That is, the magnetic field H1 generated in the coil 23 and the magnetic field H1 ′ generated in the coil 24 are in the opposite directions. For example, when the winding directions of the coil 23 and the coil 24 are the same, high-frequency pulse currents that are opposite to each other are excited, and when the winding directions of the coil 23 and the coil 24 are opposite, they are out of phase with each other. The high frequency pulse current is excited.
[0023]
Accordingly, one of the coils 24 of the magnetic sensing unit 21 is provided with a changeover switch in a drive detection circuit to be described later in order to reverse the polarity when the magnetic metal sensor 2 is applied as a proximity sensor. Yes. A detailed description of the case where the magnetic metal sensor 2 is used as a proximity sensor will be described later.
[0024]
Such coils 23 and 24 are connected to signal lines 31, 32 and 33 at the terminal block 26, and a drive detection circuit provided outside the magnetic metal sensor 2, for example, via the signal lines 31, 32 and 33. Connected. The coils 23 and 24 are supplied with an excitation current from the drive detection circuit, and the drive detection circuit detects the output.
[0025]
FIG. 5 shows a circuit diagram of this drive detection circuit.
[0026]
The drive detection circuit 30 is a smoothing circuit that detects and smoothes the oscillation circuit 34, the switching circuit 35 that switches the excitation current of the coils 23 and 24 based on the pulse signal from the oscillation circuit 34, and the output voltages of the coils 23 and 24. A circuit 36, a reference voltage circuit 37 that determines the threshold level of the coils 23 and 24, and a comparison circuit 38 that compares the output of the smoothed coils 23 and 24 with the threshold level are provided.
[0027]
Further, the drive detection circuit 30 includes switches S1, S1 ′ and switches S2, S2 ′ that switch the direction of the excitation current flowing through the coil 24 and reverse the polarity of the coil 24.
[0028]
The power source voltage Vcc is applied from one end of the coil 23 of the magnetic sensing unit 21, and the other end is connected to the midpoint M.
[0029]
One end of the coil 24 of the magnetic sensing unit 21 is connected to the midpoint M via the switch S1 and to the switching circuit 35 via the switch S2. The other end of the coil 24 of the magnetic sensing unit 21 is connected to the switching circuit 35 via the switch S1 ′ and to the midpoint M via the switch S2 ′.
Such switches S1, S1 ′ and switches S2, S2 ′ are turned on and off in conjunction with each other to switch the direction of the exciting current of the coil 24.
[0030]
Here, when the magnetic metal sensor 2 is applied to a metal piece counter, for example, the switches S1 and S1 ′ are turned on and the switches S2 and S2 ′ are turned off, and the coil 23 and the coil 24 are connected in series. Connected. At this time, the polarities of the coil 23 and the coil 24 are the same.
[0031]
When this magnetic metal sensor 2 is applied as a proximity sensor whose details will be described later, for example, the switches S1 and S1 ′ are turned off and the switches S2 and S2 ′ are turned on, and the coil 23 and the coil 24 are turned on. Are connected in series. At this time, the polarities of the coil 23 and the coil 24 are opposite.
[0032]
For example, the oscillation circuit 34 generates a pulse signal having a frequency of 1 MHz and a duty ratio of 1:10. Based on this pulse signal, the switching circuit 35 switches the current flowing through the coils 23 and 24 connected in series. As a result, the coils 23 and 24 are excited by a high-frequency pulse current.
[0033]
The smoothing circuit 36 detects and smoothes the voltage at the midpoint M of the coils 23 and 24 connected in series. For example, the reference voltage circuit 37 divides the power supply voltage with a resistor having a predetermined value to generate the reference voltage. This reference voltage is given to the comparison circuit 38 as a threshold level of the outputs of the coils 23 and 24.
[0034]
Here, as the value of the reference voltage, for example, the voltage at the midpoint M of the coils 23 and 24 connected in series in a state where no magnetic field or metal is close to the magnetic metal sensor 2 is set. Specifically, if the rate of change with respect to the applied magnetic field of the coils 23 and 24 and the resistance value when no magnetic field is applied are the same, the reference voltage is set to ½ of the power supply voltage Vcc. .
[0035]
The comparison circuit 38 compares the voltage at the midpoint M of the smoothed coils 23 and 24 supplied from the smoothing circuit 36 with the threshold level reference voltage supplied from the reference voltage circuit 37 and binarizes it. The binarized signal is supplied to, for example, a control circuit (not shown).
[0036]
The control circuit (not shown) can determine the number of detection of the metal piece 11 by counting the number of pulses of the signal binarized by the comparison circuit 38. From this detection number, the magnetic metal sensor 2 and the detected object are detected. The relative movement position with respect to the body 1 can be detected.
[0037]
As described above, the drive detection circuit 30 can excite a high-frequency pulse current in the coils 23 and 24 and can detect the outputs of the coils 23 and 24.
[0038]
Further, the magnet 25 is positioned and fixed at a predetermined interval from the magnetic sensing part 21 by the positioning part 25a so as to give a uniform magnetic field parallel to the magnetic sensing direction to the magnetic sensing part 21. The magnet 25 is provided at a position facing the connection portion 22 c of the magnetic sensing portion 21, and applies a magnetic field parallel to the magnetic sensing direction from the connection portion 22 c side of the core 22 to the magnetic sensing portion 21. For example, the magnet 25 is formed of a 1 × 1 × 2 mm rectangular ferrite magnet, and is disposed so that the surface of 1 × 2 mm faces the connection portion 22 c of the magnetic sensing portion 21. In this case, the magnet 25 is magnetized, for example, with a surface magnetic flux density of about 600 G so as to be perpendicular to the 1 × 2 mm surface.
[0039]
Further, the distance l _x between the magnetic sensing part 21 and the magnet 25 is determined according to the strength of the magnet 25 and the impedance characteristic of the magnetic sensing part 21 with respect to the magnetic field. Specifically, a magnetic field generated by the magnet 25 is applied to any one of the coils 23 and 24, and the maximum value of the output (that is, the output when saturated by the magnetic field applied from the magnet 25) and The minimum value of the output (that is, the output when the magnetic field from the magnet 25 does not reach) is detected. Then, a position that is an intermediate value between these detected values is obtained, and the distance between the magnetic sensing portion 21 and the magnet 25 at this time is determined as l _x . For example, in the case of the magnetic sensing part 21 and the magnet 25 described above, the distance l _x can be set to 2 mm.
[0040]
The magnet 25 is not limited to a ferrite magnet, and for example, an Sm-based or ZnMn-based permanent magnet, an electromagnet, or the like may be used. Further, when an electromagnet is used as the magnet 25, the magnetic field generated by the amount of current can be controlled, so that the adjustment of the distance l _x can be made dependent on this amount of current.
[0041]
The magnet 25 as described above can apply a bias magnetic field in the magnetic sensing direction to the magnetic sensing portion 21. Therefore, the impedance change is linear with respect to the external magnetic field, and the impedance change is steep. The magnetically sensitive portion 21 can be used within a range that exhibits excellent characteristics.
[0042]
And, a magnetic sensing part 21 in which a coil 23 and a coil 24 are wound around such a substantially U-shaped open magnetic path type core 22, a magnet 25 for giving a magnetic field in a magnetic sensing direction to the magnetic sensing part 21, etc. For example, for protection, the magnetic metal sensor 2 is configured as a whole by being accommodated in the aluminum case 27 in an epoxy resin sealed state.
[0043]
As described above, the magnetic metal sensor 2 has the magnetic sensing part 21 including the core 22 having an open magnetic path, and a magnetic field in the magnetic sensing direction is given to the magnetic sensing part 21 by the magnet 25. . Further, the core 22 of the magnetic sensing unit 21 is provided with a coil 23 and a coil 24 that are arranged in parallel and have the same polarity. Therefore, in the magnetic metal sensor 2, when the magnetic metal approaches one of the coils 23 and 24 wound around the core 22 provided in the magnetic sensing unit 21, the magnetic field applied by the magnet 25 changes. Therefore, in the magnetic metal sensor 2, it is possible to detect whether or not the magnetic metal is close by detecting a change in impedance caused by the change in the magnetic field by the detection circuit.
[0044]
Next, the arrangement relationship between the detected object 1 and the magnetic metal sensor 2 will be described.
[0045]
As described above, the detected object 1 is translated in the directions a ₁ and a ₂ shown in FIG. 1 by the driving mechanism (not shown), that is, the direction in which the metal pieces 11 are arranged in parallel. 2 is fixed and installed on the sensor fixing base 3. Further, the magnetic metal sensor 2 is configured such that the detected object 1 moves in parallel with the direction in which the metal pieces 11 are arranged in parallel to the detection surface 11 a of each metal piece 11. The U-shaped core 22 is installed so that the openings face each other. That is, in the magnetic metal sensor 2, the magnetic sensing direction (the x direction shown in FIG. 4) of the magnetic sensing unit 21 coincides with the longitudinal direction of the metal piece 11, and the moving direction a ₁ and a ₂ of the detected body 1 Arranged to be vertical.
[0046]
In addition, as shown in FIG. 6, the magnetic metal sensor 2 has the width g ′ of the vertical portion 22a and the vertical portion 22b of the core 22 in the moving directions a ₁ and a ₂ of the detected object 1 and the metal piece 11 in parallel. Is arranged at a predetermined angle so that it is (n + 1/2) λ (where n is an integer of 0 or more). That is, in the magnetic metal sensor 2, when the vertical portion 22a of the core 22 faces the detection surface 11a of one metal piece 11, the other vertical portion 22b is positioned so as not to face any detection surface 11a. In addition, the angle is set and arranged on the sensor fixing base 3.
[0047]
For example, in the case of the core 22 and the metal piece 11 having the dimensions described above, the angle θ between the straight line connecting the vertical portion 22a and the vertical portion 22b and the moving directions a ₁ and a ₂ of the detection target 1 is expressed as follows: It can be determined as follows.
[0048]

By determining the positional relationship between the detected object 1 and the magnetic metal sensor 2 as described above, when the detected object 1 is translated in the a ₁ and a ₂ directions, the detection output of the magnetic metal sensor 2 is as follows: The state will be repeated. That is, the detection output of the magnetic metal sensor 2 is a state in which the vertical portion 22a responds due to the influence of one metal piece 11 and the vertical portion 22b does not respond due to the influence of any metal piece 11, and the vertical portion 22b is one. In response to the influence of the metal pieces 11, the state in which the vertical portions 22 a do not respond to the influence of any of the metal pieces 11 is alternately repeated.
[0049]
Therefore, the movement position of the detected object 1 can be detected by counting the detection outputs that are alternately repeated.
[0050]
Next, the detection operation of the metal piece 11 of the magnetic metal sensor 2 will be described.
[0051]
First, the detection output when one metal piece 11 is passed from the coil 23 to the coil 24 of the magnetic metal sensor 2 will be described with reference to FIG. In FIG. 7, the horizontal axis represents the position of the metal piece 11 composed of only one piece with respect to the coils 23 and 24, and the vertical axis represents the coil 23 and the coil detected by the drive detection circuit 30 shown in FIG. The voltage at the middle point M when 24 is connected in series is shown. Further, the threshold level on the vertical axis represents the voltage at the midpoint M when no magnetic field or metal is brought close to the magnetic metal sensor 2 as described above.
[0052]
When the metal piece 11 is at a position P ₁ not approaching either the coil 23 or the coil 24, the magnetic resistance of the magnetic circuit of the magnetic flux passing through the coil 23 and the coil 24 does not change and is given from the magnet 25. There is no change in the number of magnetic fluxes. Therefore, since neither impedance of the coil 23 nor the coil 24 is changed, the potential of the midpoint M is at the threshold level.
[0053]
Subsequently, when the metal piece 11 approaches the coil 23, the magnetic resistance of the magnetic circuit of the magnetic flux passing through the coil 23 becomes smaller because the magnetic permeability of the metal piece 11 is larger than the magnetic permeability of air. The number of magnetic fluxes supplied from the magnet 25 increases. On the other hand, since the coil 24 does not respond to the metal piece 11, the reluctance of the magnetic circuit of the magnetic flux passing through the coil 24 is reduced by the increase of the magnetic flux on the coil 23 side. For this reason, the impedance of the coil 23 becomes smaller, while the impedance of the coil 24 becomes larger. Therefore, as the metal piece 11 approaches the coil 23, the potential at the midpoint M increases sequentially from the threshold level. When the metal piece 11 is at the position P ₂ closest to the coil 23, the potential at the midpoint M is the highest.
[0054]
Subsequently, when the metal piece 11 approaches the coil 24 from the position P ₂ closest to the coil 23, the metal piece 11 moves away from the coil 23, so that the magnetic resistance of the magnetic circuit of the magnetic flux passing through the coil 23 is reduced. The number of magnetic fluxes supplied from the magnet 25 decreases as the size increases. On the other hand, since the metal piece 11 approaches the coil 24, the magnetic resistance of the magnetic circuit of the magnetic flux passing through the coil 24 becomes smaller. For this reason, the impedance of the coil 23 increases, and at the same time, the impedance of the coil 24 decreases. Therefore, as the metal piece 11 approaches the coil 24 from the coil 23, the potential at the midpoint M decreases sequentially. The potential of come to the intermediate position P ₃ midpoint M of the metal piece 11 is coil 23 and the coil 24 becomes a threshold level, the metal piece 11 and the potential of the closest position P ₄ become the middle point M to the coil 24 The lowest.
[0055]
Subsequently, when the metal piece 11 moves from the position P ₄ closest to the coil 24 to the position P ₅ not close to either the coil 23 or the coil 24, the magnetic circuit of the magnetic flux passing through the coil 23 and the coil 24 is changed. None of the magnetic resistances respond to the metal piece 11. Accordingly, since neither the impedance of the coil 23 nor the coil 24 is changed, the potential at the midpoint M becomes the threshold level.
[0056]
As described above, in the magnetic metal sensor 2, when the metal piece 11 passes from the coil 23 to the coil 24, the potential at the midpoint M becomes plus or minus with the potential when the metal piece 11 is not approaching as a threshold level. Swing. Therefore, in the magnetic metal sensor 2, the position of the metal piece 11 can be detected easily and reliably by comparing the detection output around the threshold level.
[0057]
Next, the detection output when the magnetic metal sensor 2 with the interval between the coil 23 and the coil 24 set to λ / 2 is moved relative to the plurality of metal pieces 11 arranged in parallel at the interval λ is illustrated. 8 will be used for explanation. In FIG. 8, the horizontal axis represents the position of the magnetic metal sensor 2 relative to the plurality of metal pieces 11, and the vertical axis represents the case where the coil 23 and the coil 24 are connected in series in the drive detection circuit 30 shown in FIG. The voltage at the midpoint M is shown. Further, the threshold level on the vertical axis represents the voltage at the midpoint M when no magnetic field or metal is brought close to the magnetic metal sensor 2 as described above.
[0058]
In the magnetic metal sensor 2, when one metal piece 11 is closest to the coil 23, no metal piece 11 is close to the coil 24. Therefore, in a state where the coil 23 is responding to the metal piece 11, the coil 24 is not responding to the metal piece 11. Therefore, the potential at the midpoint M serving as the detection output is larger than the threshold level.
[0059]
Further, in the magnetic metal sensor 2, when one metal piece 11 is closest to the coil 24, no metal piece 11 is close to the coil 23. Therefore, in a state where the coil 24 is responding to the metal piece 11, the coil 23 is not responding to the metal piece 11. Therefore, the potential at the midpoint M serving as the detection output is smaller than the threshold level.
[0060]
Therefore, in the magnetic metal sensor 2, when the magnetic metal sensor 2 is moved relative to the plurality of metal pieces 11 arranged in parallel at the interval λ, a signal that swings up and down around the threshold level can be obtained as a detection output. .
[0061]
In FIG. 9, as an example, when the magnetic metal sensor 2 and the metal piece 11 having the dimensions described above are applied, the coil 23 and the coil 24 connected in series with respect to the relative movement positions of the magnetic metal sensor 2 and the metal piece 11 are shown. The figure showing the relationship of the electric potential of the point M is shown.
[0062]
As described above, in the magnetic metal sensor 2, when the metal piece 11 is moved relative to the plurality of metal pieces 11 arranged in parallel at the interval λ, the metal piece 11 is sent to any of the coils 23 and 24. The number of one metal piece 11 can be easily and reliably detected by comparing the potential at the midpoint M at a position that is not close as a threshold level.
[0063]
In addition, when this magnetic metal sensor 2 was applied to the metal piece counter, it has been described that the detected body 1 moves in parallel. However, in the present invention, the relative movement between the detected body 1 and the sensor 2 may be performed. The magnetic metal sensor 2 side may move in parallel.
[0064]
Further, by disposing another magnetic metal sensor with a distance of (m ± 1/4) λ from the magnetic metal sensor 2 in the relative movement direction, the signal shown in FIG. 8 has a phase difference of 90 °. Can be obtained as a two-phase signal having m (m is an integer). Therefore, since a signal for outputting a relative movement amount can be generated based on the two-phase signals, the position detection device can be configured using the magnetic metal sensors arranged in this way.
[0065]
Further, the object to be detected can be configured in a circular shape, and the rotation speed and angle can be measured. Next, a case where the above-described magnetic metal sensor 2 is applied as a proximity sensor will be described.
[0066]
When this magnetic metal sensor 2 is applied as a proximity sensor, for example, a system for determining whether an arm of a robot or the like has approached a predetermined position and controlling the position of the arm, or a screw attached to a workpiece. The present invention can be used in a system for checking a work process by detecting looseness or forgetting to tighten.
[0067]
When such a magnetic metal sensor 2 is used as a metal proximity sensor, the sensitivity can be increased by detecting the differential output so that the polarities of the coils 23 and 24 are opposite to each other. it can.
[0068]
That is, when the magnetic metal sensor 2 is used as a proximity sensor, the switches of the drive detection circuit 30 shown in FIG. 5 described above, for example, the switches S1 and S1 ′ are turned off and the switches S2 and S2 ′ are turned on. The phase of the excitation current flowing through the coil 23 and the coil 24 is reversed. As a result, when the winding direction of the coil 23 and the coil 24 is the same, the coil 23 and the coil 24 are excited by the high-frequency pulse currents of opposite phases, and when the winding direction of the coil 23 and the coil 24 is opposite, Excited with pulse current.
[0069]
And the metal of the said magnetic metal sensor 2 can be used as a highly sensitive proximity sensor by detecting the difference value between the coils 23 and 24 excited in this way.
[0070]
The detection operation of the magnetic metal sensor 2 when used as a proximity sensor in this way will be described with reference to FIG.
[0071]
FIG. 10 shows the detection output when one metal piece 51 is passed from the coil 23 to the coil 24 of the magnetic metal sensor 2. In FIG. 10, the horizontal axis represents the position of the single metal piece 51 composed of only one with respect to the coils 23 and 24, and the vertical axis represents the differential voltage between the coil 23 and the coil 24.
[0072]
When the metal piece 51 is not close to the magnetic sensing part 21 of the magnetic metal sensor 2, there is no voltage difference between the coil 23 and the coil 24, and the output is zero. When the metal piece 51 approaches the magnetic sensing part 21, since the polarity of the coil 23 and the coil 24 is reversed, the impedance of one of the coils 23 and 24 is increased and the impedance of the other is decreased. . Therefore, the differential voltage increases.
[0073]
When the metal piece 51 comes to a position facing both the coil 23 and the coil 24, the differential voltage becomes the maximum level.
[0074]
Therefore, in the magnetic metal sensor 2, a threshold level of a predetermined voltage is set, and the detected differential voltage is binarized at the set threshold level to determine whether the metal piece 51 has approached. Can do.
[0075]
As described above, the magnetic metal sensor 2 can be applied as the metal piece counter 11 by switching the polarity of the coil 24 by the switches S1, S1 'and the switches S2, S2', and can detect the adjacent magnetic metal pieces. It can be performed. Therefore, the magnetic metal sensor 2 having both functions can be provided at low cost.
[0076]
In the drive detection circuit 30 described above, the threshold level voltage generated by the voltage comparison unit 37 is compared with the voltage at the midpoint M of the coils 23 and 24, and the value is binarized. Therefore, when the threshold level changes between when the magnetic metal sensor 2 is applied to a metal piece counter and when it is used as a proximity sensor, the ratio of the resistors R ₁ and R ₂ of the voltage comparison unit 37 may be changed. . The ratio of the resistors R ₁ and R ₂ can be changed using, for example, a trimmer.
[0077]
If the resistance ratio cannot be changed, the comparison circuit 38 is replaced with a differential amplifier, the differential voltage is directly supplied to the system controller or the like, and A / D conversion is performed by the system controller. By collecting, this magnetic metal sensor 2 can be applied to both a metal piece counter and a proximity sensor.
[0078]
Next, a case where a magneto-impedance effect element is applied to the magnetic sensing part 21 of the magnetic metal sensor 2 will be described.
[0079]
Up to now, the magnetic metal sensor 2 including the magnetic sensing part 21 in which the coils 23 and 24 are wound around the vertical parts 22a and 22b of the substantially U-shaped core 22 has been described. However, in the magnetic metal sensor according to the present invention, for example, It is also possible to apply so-called magneto-impedance effect (MI) elements 41 and 42 as proposed in JP-A-6-281712 to the magnetic sensitive part 21.
[0080]
The MI elements 41 and 42 are made of an amorphous alloy made of Fe, Si, Co, B, or the like. The MI elements 41 and 42 have a substantially wire shape as shown in FIG. When high frequency current is applied to the MI elements 41 and 42 in the longitudinal direction (magnetic sensing direction), an impedance change occurs with respect to an external magnetic field incident in the longitudinal direction.
[0081]
FIG. 12 shows an arrangement relationship when the magnetic metal sensor 2 having the MI elements 41 and 42 is applied to a metal piece counter.
[0082]
The MI elements 41 and 42 are arranged so that the longitudinal directions thereof are parallel with a predetermined gap width g, and the arrangement positions thereof are positions corresponding to the above-described vertical portions 22a and 22b. Further, the MI elements 41 and 42 are given a magnetic field parallel to the longitudinal direction by the magnet 25, and the sensitivity to an external magnetic field incident in this direction is very high. Further, the MI elements 41 and 42 undergo impedance changes with respect to the external magnetic field in this direction, and the rate of change is very large.
[0083]
The MI elements 41 and 42 are excited with a high-frequency pulse current. Here, when the magnetic metal sensor 2 is applied to a metal piece counter, the MI elements 41 and 42 are excited by a high-frequency pulse current having the same phase so that the direction of magnetic sensitivity is the same, and the polarities thereof are the same. It has become.
[0084]
When the magnetic metal sensor 2 to which the MI elements 41 and 42 are applied is used as a proximity sensor, the polarity is reversed as in the case where the coils 23 and 24 are wound around the core 22. To do. This switching is performed by a switch provided in a drive detection circuit described later.
[0085]
Such MI elements 41 and 42 are connected to a drive detection circuit provided outside the magnetic metal sensor 2 through a signal line. The MI elements 41 and 42 are supplied with an excitation current from the drive detection circuit, and the output is detected by the drive detection circuit.
[0086]
FIG. 13 shows a circuit diagram of the drive detection circuit 40 for the MI elements 41 and 42.
[0087]
The drive detection circuit 40 is a smoothing circuit that detects and smoothes the output voltage of the MI element 41, the switching circuit 35 that switches the exciting current of the MI elements 41 and 42 based on the pulse signal from the oscillation circuit 34, and the pulse signal from the oscillation circuit 34. A circuit 36a, a smoothing circuit 36b for detecting and smoothing the output voltage of the MI element 42, and a comparison circuit 38 for comparing the outputs of the smoothed MI elements 41 and 42 are provided.
[0088]
The drive detection circuit 40 includes a switch S3 and a switch S4 that switch the direction of the excitation current of the MI element 41.
[0089]
One end of the MI element 42 is supplied with the power supply voltage Vcc via the resistor R ₂ , and the other end is grounded via the switching circuit 35.
[0090]
One end of the MI element 41 is connected to the resistor R ₁ having the same resistance value as the resistor R _2, and the other end is connected to the switch S 3. The switch S3 connects the other end of the MI element 41 to the switching circuit 35 when switched to the terminal a side, and connects the other end of the MI element 41 to the power source when switched to the terminal b side.
[0091]
The resistor R ₁ has one end connected to the MI element 41 and the other end connected to the switch S4. The switch S4, is switched to the terminal a connected to the other end of the resistor R ₁ to the power supply Vcc, it is switched to the terminal b side connecting the other end of the resistor R to the switching circuit 35.
[0092]
Such switches S3 and S4 are switched to the terminal a side or the terminal b side in conjunction with each other.
[0093]
That is, when the magnetic metal sensor 2 is applied to the metal piece counter and the movement position of the detected object 1 in which the metal piece 11 is arranged in parallel is detected, both the switches S3 and S4 are switched to the terminal a side. The polarities of the MI element 41 and the MI element 42 are the same, and the connection between the resistor R ₁ and the MI element 41 and the connection between the resistor R ₂ and the MI element 42 is parallel between the power supply Vcc and the switching circuit 35. It becomes.
[0094]
When the magnetic metal sensor 2 detects a magnetic metal piece that is close, the switches S3 and S4 are both switched to the terminal b side, and the polarities of the MI element 41 and the MI element 42 are reversed. A bridge circuit is formed in which the connection between the resistor R ₁ and the MI element 41 and the connection between the resistor R ₂ and the MI element 42 are reversed between the power supply Vcc and the switching circuit 35.
[0095]
For example, the oscillation circuit 34 generates a pulse signal having a frequency of 1 MHz and a duty ratio of 1:10. Based on this pulse signal, the switching circuit 35 switches the current flowing in the MI elements 41 and 42 connected in parallel. As a result, these MI elements 41 and 42 are excited by a high-frequency pulse current.
[0096]
Smoothing circuit 36a smoothes detects the voltage of the connection point between the MI device 41 and the resistor R _1. Smoothing circuit 36b smoothes detects the voltage of the connection point between the MI device 42 and the resistance R _2.
[0097]
The comparison circuit 38 compares the output voltage of the MI element 41 smoothed by the smoothing circuit 36a with the output voltage of the MI element 42 smoothed by the smoothing circuit 36b, and compares the differential voltage with, for example, a control circuit (not shown). Etc.
[0098]
When the magnetic metal sensor 2 is applied to the metal piece counter, the control circuit (not shown) binarizes the differential voltage from the comparison circuit 38 at a predetermined threshold level, and the pulse By counting the number, the detected number of the metal pieces 11 can be obtained, and the relative movement position between the magnetic metal sensor 2 and the detected object 1 can be detected from the detected number.
[0099]
When the magnetic metal sensor 2 is applied to a proximity sensor, a control circuit (not shown) detects a differential voltage from the comparison circuit 38 and sets the differential voltage to a predetermined threshold level. By comparing, it is possible to detect whether or not the magnetic metal pieces 51 are close to each other.
[0100]
The magnetic metal sensor 2 as described above can be applied as the metal piece counter 11 by switching the polarity of the MI element 41 by the switch S3 and the switch S4, and can detect a magnetic metal piece in the vicinity. . Therefore, the magnetic metal sensor 2 having both functions can be provided at low cost. Further, in this magnetic metal sensor 2, since an MI element can be used, the cost can be reduced and the characteristics can be improved.
[0101]
【The invention's effect】
The magnetic metal sensor according to the present invention can detect the magnetic metal pieces arranged in parallel and the adjacent magnetic metal pieces by switching the polarity of the magnetoelectric conversion means by the switching means. Therefore, in the present invention, both functions can be provided at low cost.
[Brief description of the drawings]
FIG. 1 is a perspective view of a metal piece counter according to an embodiment of the present invention.
FIG. 2 is a plan view of a main part of a detected object of the metal piece counter and a side view of the metal piece of the detected object.
FIG. 3 is a partial cross-sectional view of a magnetic metal sensor of the metal piece counter.
FIG. 4 is a diagram showing a magnetic sensing part provided in the magnetic metal sensor and a core of the magnetic sensing part.
FIG. 5 is a circuit diagram showing a drive detection circuit of the magnetic metal sensor.
FIG. 6 is a diagram showing an arrangement relationship between the detected object and the magnetic metal sensor.
FIG. 7 is a diagram illustrating a detection operation of the magnetic metal sensor.
FIG. 8 is a diagram for explaining a detection operation of the magnetic metal sensor.
FIG. 9 is a diagram illustrating an output voltage of a drive detection circuit with respect to a relative movement position of the magnetic metal sensor and a detection target.
FIG. 10 is a diagram for explaining a detection operation when the magnetic metal sensor is used as a proximity sensor.
FIG. 11 is a diagram illustrating an MI element.
FIG. 12 is a diagram for explaining the arrangement relationship of magnetic metal sensors of the metal piece counter according to the embodiment of the present invention when the MI element is applied.
FIG. 13 is a circuit diagram of a drive detection circuit of a magnetic metal sensor to which the MI element is applied.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 To-be-detected object, 2 Magnetic metal sensor, 3 Sensor fixing stand, 11 Metal piece, 11a Detection surface, 12 Indication part, 21 Magnetic sensing part, 22 Core, 22a, 22b Vertical part, 22c Connection part, 23, 24 Coil, 25 magnet, 30, 40 drive detection circuit, 34 oscillation circuit, 35 switching circuit, 36, 36a, 36b smoothing circuit, 37 reference voltage circuit, 38 comparison circuit, S1, S1 ', S2, S2', S3, S4 switch

Claims (1)

A pair of magnetoelectric conversion means for obtaining a detection output in response to a magnetic field change;
A magnetic field generating means for applying a magnetic field to the pair of magnetoelectric conversion means;
A magnetic metal sensor comprising switching means for switching the polarity of any one of the pair of magnetoelectric conversion means.

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