JP4389033B2 - Phase monitoring metal detector - Google Patents
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Description
本発明は、送信コイルと検出コイルと補償コイルとを有し、前記送信コイルが発生する交流磁界中における金属の移動を、検出コイルに発生する交流信号により検出する金属検出装置に係り、特に送信コイルに発生する電圧信号の位相の変化によって前記金属の検出を行えるように構成した位相監視型の金属検出装置に関するものである。 The present invention relates to a metal detection device that includes a transmission coil, a detection coil, and a compensation coil, and detects a movement of metal in an AC magnetic field generated by the transmission coil by an AC signal generated in the detection coil. The present invention relates to a phase monitoring type metal detecting device configured to detect the metal by a change in phase of a voltage signal generated in a coil.
従来の金属検出装置としては、送信コイルと補償コイルと検出コイルを有し、前記送信コイルが発生する交流磁界中の金属を、検出コイルに発生する交流信号の振幅の変化により検出するタイプのものが知られている。 As a conventional metal detection device, there is a type having a transmission coil, a compensation coil, and a detection coil, and detecting a metal in an AC magnetic field generated by the transmission coil by a change in amplitude of an AC signal generated in the detection coil. It has been known.
検出コイルに発生する交流信号の振幅の変化から磁界中の金属を検出する上記従来の金属検出装置によれば、金属を検出する感度が必ずしも十分でない場合があった。また、金属検出の態様によっては、検出コイルが出力する交流信号の振幅が大きく振れる場合があり、そのような場合に対応するために検出手段の検出レンジを任意に変更できるような構成にしておく必要があり、全体の機器構成が複雑になってしまうという問題があった。 According to the above-described conventional metal detection device that detects a metal in a magnetic field from a change in amplitude of an AC signal generated in the detection coil, the sensitivity for detecting the metal may not always be sufficient. In addition, depending on the metal detection mode, the amplitude of the AC signal output from the detection coil may fluctuate greatly, and in order to cope with such a case, the detection range of the detection means can be arbitrarily changed. There is a problem that the entire device configuration becomes complicated.
そこで、本発明は、このような課題を解決するためになされたものであり、より簡素な構成でありながら、安定した十分な感度で金属検出を行うことができる位相監視型の金属検出装置を提供することを目的としている。 Therefore, the present invention has been made to solve such problems, and a phase monitoring type metal detection device capable of performing metal detection with stable and sufficient sensitivity while having a simpler configuration. It is intended to provide.
請求項１に記載された位相監視型金属検出装置は、
送信コイルと、補償コイルと、交流信号が与えられた前記送信コイルが形成する交流磁界及び交流信号が与えられた前記補償コイルが形成する交流磁界によって交流信号が発生する検出コイルとを有し、前記送信コイルが発生する交流磁界中の金属を前記検出コイルに発生する交流信号により検出する金属検出装置であって、
前記送信コイルに所定周波数の交流電流を与えた場合に、前記検出コイルに発生する電圧信号が０になるように、前記補償コイルに与える交流電流を調整するとともに、
前記補償コイルに与える交流電流の位相を任意の調整量だけずらすことにより、
前記検出コイルに発生する電圧信号の位相の変化によって前記金属の検出を行うことを特徴としている。
The phase monitoring type metal detection device according to claim 1 is:
A transmission coil, a compensation coil, and an AC magnetic field formed by the transmission coil to which an AC signal is applied and a detection coil that generates an AC signal by an AC magnetic field formed by the compensation coil to which an AC signal is applied, A metal detection device for detecting a metal in an AC magnetic field generated by the transmission coil by an AC signal generated in the detection coil,
When an alternating current having a predetermined frequency is applied to the transmission coil, the alternating current applied to the compensation coil is adjusted so that a voltage signal generated in the detection coil becomes 0, and
By shifting the phase of the alternating current applied to the compensation coil by an arbitrary adjustment amount,
The metal is detected by a change in phase of a voltage signal generated in the detection coil.
請求項２に記載された位相監視型金属検出装置は、請求項１記載の位相監視型金属検出装置において、
前記補償コイルと前記検出コイルを、前記送信コイルが形成する交流磁界中に、前記送信コイルとは垂直な向きで配置したことを特徴としている。
The phase monitoring type metal detection device according to claim 2 is the phase monitoring type metal detection device according to claim 1,
The compensation coil and the detection coil are arranged in an AC magnetic field formed by the transmission coil in a direction perpendicular to the transmission coil.
請求項３に記載された位相監視型金属検出装置は、請求項２記載の位相監視型金属検出装置において、
前記検出コイルに発生する電圧信号の位相の変化の敏感さを、前記調整量を変化させて調整することにより、前記金属の検出の感度を調整する手段を備えたことを特徴としている。
The phase monitoring type metal detection device according to claim 3 is the phase monitoring type metal detection device according to claim 2,
It is characterized by comprising means for adjusting the sensitivity of detection of the metal by adjusting the sensitivity of the change in the phase of the voltage signal generated in the detection coil by changing the adjustment amount.
本発明によれば、例えばある周波数の正弦波で励磁した送信コイルの作り出す磁界中において、金属が近づいたり遠ざかったりした場合に、検出コイルから取り出される交流電圧信号の位相が変化するので、これを監視することにより金属の接近を検出することができ、また補償コイルに与える電流の位相の調整量を変えることで金属検出の感度を調整することもできる。 According to the present invention, for example, when a metal approaches or moves away in a magnetic field created by a transmission coil excited by a sine wave of a certain frequency, the phase of the AC voltage signal extracted from the detection coil changes. By monitoring, the approach of the metal can be detected, and the sensitivity of the metal detection can be adjusted by changing the adjustment amount of the phase of the current applied to the compensation coil.
図１は、本発明の実施の形態の一例である位相監視型金属検出装置の構成を、そのコイル配置も含めて示す図である。本位相監視型金属検出装置のコイルは、検出コイ１ルと補償コイル２と送信コイル３で構成される。検出コイル１は、送信コイル３が形成する交流磁界によって交流信号が発生するような配置となっており、補償コイル２は、検出コイル１に交流信号を発生させることができるような配置となっている。具体的には、図１に示すように、送信コイル３は図中横向きに配置され、検出コイル１と補償コイル２は送信コイル３とは垂直かつ互いに同軸となるように配置する。なお、検出コイル１と補償コイル２は同軸でなく、近接して平行に配置してもよい。 FIG. 1 is a diagram showing a configuration of a phase monitoring type metal detection device which is an example of an embodiment of the present invention, including its coil arrangement. The coil of this phase monitoring type metal detection apparatus is composed of a detection coil 1, a compensation coil 2 and a transmission coil 3. The detection coil 1 is arranged so that an AC signal is generated by the AC magnetic field formed by the transmission coil 3, and the compensation coil 2 is arranged so that the detection coil 1 can generate an AC signal. Yes. Specifically, as shown in FIG. 1, the transmission coil 3 is disposed sideways in the figure, and the detection coil 1 and the compensation coil 2 are disposed so that the transmission coil 3 is perpendicular and coaxial with each other. Note that the detection coil 1 and the compensation coil 2 are not coaxial and may be arranged close to each other in parallel.
送信コイル３には、直列接続されたコンデンサ１０を介してパワーアンプ１１が接続され、パワーアンプ１１には信号発生器１２が接続されている。また、検出コイル１には、並列接続のコンデンサ７とバンドパスフィルター４が接続され、さらにバンドパスフィルター４には増幅回路５を介してコックインアンプ等６が接続されている。そして、補償コイル２には、交流電源８を介して信号発生器９が接続されいる。
A
この状態で、送信コイル３に周波数Ｘの交流電流を流す。次に検出コイル１に誘起する電圧信号をロックインアンプ等６の電圧計で監視する。次に補償コイル２に送信コイル３と同じ周波数Ｘの交流電流を流し、補償コイル２に流れる交流電流の位相を、検出コイル１に発生する電圧信号がゼロになるように調整する。 In this state, an alternating current having a frequency X is passed through the transmission coil 3. Next, the voltage signal induced in the detection coil 1 is monitored by a voltmeter such as a lock-in amplifier 6. Next, an alternating current having the same frequency X as that of the transmission coil 3 is passed through the compensation coil 2, and the phase of the alternating current flowing through the compensation coil 2 is adjusted so that the voltage signal generated in the detection coil 1 becomes zero.
次に補償コイル２に流す電流の位相を、検出コイル１に発生する電圧信号がゼロになった位置から任意の調整量だけわずかにずらす。 Next, the phase of the current flowing through the compensation coil 2 is slightly shifted by an arbitrary adjustment amount from the position where the voltage signal generated in the detection coil 1 becomes zero.
以上の調整乃至設定を完了した本例の位相監視型金属検出装置によれば、金属を磁界内に近づけていくと、金属の位置に応じて検出コイル１に発生する電圧信号は周波数Ｘのままで様々な位相の状態が現れる。すなわち、金属が磁界内にあれば、金属の大きさを一定とすると、金属の接近・離反に伴い、検出コイル１と金属の距離に応じて検出コイル１に発生する電圧信号の位相が変化するので、この位相の変化の程度を監視すれば金属の接近（の程度）を検出できる。 According to the phase monitoring type metal detection apparatus of this example in which the above adjustment or setting is completed, when the metal is brought closer to the magnetic field, the voltage signal generated in the detection coil 1 according to the position of the metal remains at the frequency X. Various phase states appear. That is, if the metal is in the magnetic field, the phase of the voltage signal generated in the detection coil 1 changes according to the distance between the detection coil 1 and the metal as the metal approaches and separates if the size of the metal is constant. Therefore, if the degree of this phase change is monitored, the approach of the metal can be detected.
ここで、本例の位相監視型金属検出装置において、磁界に金属が接近することで検出コイル１の電圧信号の位相が変化する移相の原理について説明する。
始めに初期状態について説明する。送信コイル３に交流電流を流すと、周辺に交流磁界が形成される。このとき検出コイル１に発生する電圧信号を下記数式（１）とし、この時の位相を今後の基準として考える。
Here, the principle of phase shift in which the phase of the voltage signal of the detection coil 1 changes when the metal approaches the magnetic field in the phase monitoring type metal detection device of this example will be described.
First, the initial state will be described. When an alternating current is passed through the transmission coil 3, an alternating magnetic field is formed around it. The voltage signal generated in the detection coil 1 at this time is represented by the following formula (1), and the phase at this time is considered as a future reference.
この時に、補償コイル２には検出コイル１において下記数式（２）の信号が発生するような交流電流を流しその状態を保持する。 At this time, an alternating current that causes a signal of the following formula (2) to be generated in the detection coil 1 is passed through the compensation coil 2 to maintain the state.
この時、検出コイルに発生する電圧信号は送信コイル３の影響で発生する信号Vks(θ) と補償コイル２の影響で発生する信号Vkh(θ) の和であり下記数式（３）に示すとおりゼロとなる。 At this time, the voltage signal generated in the detection coil is the sum of the signal Vks (θ) generated due to the effect of the transmission coil 3 and the signal Vkh (θ) generated due to the effect of the compensation coil 2, as shown in the following formula (3). It becomes zero.
ここで、送信コイル３が形成する磁界内に金属が入ると、送信コイル３が作る磁界が金属を貫き、金属が誘導磁界を発生するために、結果として送信コイル３が作る磁界が歪む。その結果、検出コイル１を貫く磁束の量に変化が起こる。すると検出コイル１に発生する電圧も変化する。この時の送信コイル３の発生した磁界によって検出コイル１に発生する信号の振幅はＡからＢに変化し、下記数式（４）に示す信号になる。 Here, when a metal enters the magnetic field formed by the transmission coil 3, the magnetic field generated by the transmission coil 3 penetrates the metal, and the metal generates an induction magnetic field. As a result, the magnetic field generated by the transmission coil 3 is distorted. As a result, a change occurs in the amount of magnetic flux penetrating the detection coil 1. Then, the voltage generated in the detection coil 1 also changes. The amplitude of the signal generated in the detection coil 1 changes from A to B due to the magnetic field generated by the transmission coil 3 at this time, and becomes a signal represented by the following formula (4).
金属が近づいても補償コイル２に流す電流は保持されているため、補償コイル２が検出コイル１に発生する電圧は前記数式（２）のままである。このため、金属が近づいたときに検出コイル１に発生する信号は下記数式（５）に示す信号になる。 Since the current flowing through the compensation coil 2 is maintained even when the metal approaches, the voltage generated in the detection coil 1 by the compensation coil 2 remains the above formula (2). For this reason, the signal generated in the detection coil 1 when the metal approaches is a signal represented by the following mathematical formula (5).
ここで、本例の位相監視型金属検出装置では、補償コイル２が検出コイル１に発生する信号の位相をわずかにδだけずらしてある。すると検出コイル１に発生する電圧信号は、実際には前記数式（５）ではなく、下記数式（６）のようになっている。 Here, in the phase monitoring type metal detection device of this example, the phase of the signal generated by the compensation coil 2 in the detection coil 1 is slightly shifted by δ. Then, the voltage signal generated in the detection coil 1 is not actually the above formula (5) but the following formula (6).
数式（６）を計算していくと下記数式（７）に示すように周波数θは保存されるが位相αは数式（８）で表されるようにＡとＢとδの関係で決まることがわかる。 When calculating Equation (6), the frequency θ is preserved as shown in Equation (7) below, but the phase α is determined by the relationship between A, B, and δ as shown in Equation (8). Recognize.
数式（８）において、Ａとδは金属の接近に係わらず常に一定である。つまり金属の接近によって変化するのはＢのみであるため、金属の接近の具合によって位相αが連続的に変化した波形を得ることができる。従って、位相監視型金属検出装置の送信コイル３の磁界内で金属が移動すると、当該金属と送信コイル３との距離に応じて、検出コイル１が出力する電圧信号は波形はそのままで位相がずれていくこととなる。 In Equation (8), A and δ are always constant regardless of the approach of the metal. That is, since only B changes due to the approach of the metal, it is possible to obtain a waveform in which the phase α continuously changes depending on the approach of the metal. Therefore, when the metal moves in the magnetic field of the transmission coil 3 of the phase monitoring type metal detection device, the voltage signal output from the detection coil 1 is out of phase with the waveform unchanged, depending on the distance between the metal and the transmission coil 3. It will be followed.
以上説明した原理を用いることにより、本例の位相監視型金属検出装置によれば、検出コイル１に発生する電圧信号の位相を監視することで金属の接近を検出することができる。 By using the principle described above, according to the phase monitoring type metal detection device of this example, the approach of the metal can be detected by monitoring the phase of the voltage signal generated in the detection coil 1.
また本例の位相監視型金属検出装置によれば、金属の接近に係わらず常に一定であるδを任意に設定する手段を設けることにより、前述した位相の変化の敏感さを調整することができる。つまり、δを小さくしておくと、金属が遠方にあっても位相が敏感に変化する。またδを大きくしておくと、金属がごく近くに接近しないと位相は変化しない。これによって、金属検出の感度をδの調整具合で任意に設定することができる。究極の設定として、δを０にしておくと、金属の接近の具合によって位相が連続的に変化するのではなく、金属を検出した瞬間に位相が反転する、最も敏感な設定となる。 In addition, according to the phase monitoring type metal detection device of this example, by providing means for arbitrarily setting δ that is always constant regardless of the approach of the metal, it is possible to adjust the sensitivity of the phase change described above. . That is, if δ is kept small, the phase changes sensitively even if the metal is far away. If δ is increased, the phase will not change unless the metal is very close. As a result, the sensitivity of metal detection can be arbitrarily set by adjusting δ. As the ultimate setting, when δ is set to 0, the phase is not changed continuously depending on the approaching state of the metal, but is the most sensitive setting in which the phase is reversed at the moment when the metal is detected.
１ 検出コイル
２ 補償コイル
３ 送信コイル
４ バンドパスフィルター
５ 増幅回路
６ ロックインプ等
７ コンデンサ
８ 交流電源
９ 信号発生器
１０ コンデンサ
１１ パワーアンプ
１２ 信号発生器
DESCRIPTION OF SYMBOLS 1 Detection coil 2 Compensation coil 3 Transmission coil 4 Band pass filter 5 Amplifying circuit 6 Locking amplifier etc. 7 Capacitor 8 AC power supply 9 Signal generator 10
Claims (3)
前記送信コイルに所定周波数の交流電流を与えた場合に、前記検出コイルに発生する電圧信号が０になるように、前記補償コイルに与える交流電流を調整するとともに、
前記補償コイルに与える交流電流の位相を任意の調整量だけずらすことにより、
前記検出コイルに発生する電圧信号の位相の変化によって前記金属の検出を行うことを特徴とする位相監視型金属検出装置。 A transmission coil, a compensation coil, and an AC magnetic field formed by the transmission coil to which an AC signal is applied and a detection coil that generates an AC signal by an AC magnetic field formed by the compensation coil to which an AC signal is applied, A metal detection device for detecting a metal in an AC magnetic field generated by the transmission coil by an AC signal generated in the detection coil,
When an alternating current having a predetermined frequency is applied to the transmission coil, the alternating current applied to the compensation coil is adjusted so that a voltage signal generated in the detection coil becomes 0, and
By shifting the phase of the alternating current applied to the compensation coil by an arbitrary adjustment amount,
A phase monitoring type metal detecting apparatus, wherein the metal is detected by a change in a phase of a voltage signal generated in the detection coil.
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