JP2009300392A - Magnetic foreign object detector - Google Patents
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本発明は、例えば食品加工装置などにおいて加工食品に混入した磁性異物を検出する磁性異物検出装置に関するものである。 The present invention relates to a magnetic foreign matter detection device that detects magnetic foreign matter mixed in processed food in, for example, a food processing apparatus.
近年、食品加工技術の進歩や輸入食料品の増加にともない、食の安全性についての関心が高まっている。とりわけ加工食品の製造現場や食品包装などの生産課程で食品に異物が混入するおそれがあることから、特に人体への影響力が大きい金属異物（刃片や針、金属粉など）を検出して出荷する異物検出装置が用いられる。 In recent years, with the advance of food processing technology and the increase of imported food products, interest in food safety has increased. In particular, because foreign substances may be mixed into foods at the production site of processed foods and production processes such as food packaging, it is possible to detect metal foreign objects (blades, needles, metal powders, etc.) that have a particularly large impact on the human body. A foreign object detection device to be shipped is used.
食品異物検出の方式には、大きく分けて以下に述べる４タイプの検出原理が用いられる。第１の検出方式は、渦電流方式である。これは送信コイルに１ＭＨＺから３３３ｋＨｚの交流電流を流して交番磁界を発生させ、その交番磁界中を被検査物が通過したときに発生する渦電流による磁界分布変化を受信コイルで検出する方式である。この場合、発信コイルと受信コイルの共振現象を利用した検出方式であり、送受信コイルを含むブリッジ回路において所定の中心周波数で共振する検知回路を設け、被検出物が送受信コイルの間に形成される交番磁界内を通過する際に発生した渦電流による磁界分布変化を共振周波数の変化として検出する方式である（特許文献１参照）。 The four types of detection principles described below are broadly used for food foreign matter detection methods. The first detection method is an eddy current method. This is a system in which an alternating current of 1 MHZ to 333 kHz is caused to flow through a transmission coil to generate an alternating magnetic field, and a magnetic field distribution change due to an eddy current generated when an inspection object passes through the alternating magnetic field is detected by a receiving coil. . In this case, the detection method uses the resonance phenomenon of the transmission coil and the reception coil, and a detection circuit that resonates at a predetermined center frequency is provided in the bridge circuit including the transmission / reception coil, and the detection target is formed between the transmission / reception coils In this method, a change in magnetic field distribution due to an eddy current generated when passing through an alternating magnetic field is detected as a change in resonance frequency (see Patent Document 1).
第２の検出方式としては、被検査物をＣＣＤカメラを用いて撮像して行なわれる目視或いは画像処理による検査方式である。
第３の検出方式としては、被検査物に弱いＸ線を照射してその透過量を半導体センサで検出する方式である。
第４の検出方式としては、ＳＱＵＩＤ（超伝導量子干渉素子）磁気センサを用いた検出方式で、被検査物を予め磁化した後、続いて磁気シールドされた空間内でＳＱＵＩＤ磁気センサにより残留磁気の有無を検出する方式である。
The third detection method is a method in which weak X-rays are irradiated on the object to be inspected and the amount of transmission is detected by a semiconductor sensor.
As a fourth detection method, a detection method using a SQUID (superconducting quantum interference element) magnetic sensor is used. After inspecting an object to be inspected in advance, the SQUID magnetic sensor detects residual magnetism in a magnetically shielded space. This is a method for detecting the presence or absence.
上述した第１の検出方式においては、共振回路に流れる電流または印加電圧の周波数として１ＭＨＺから３３３ｋＨｚの高周波数が用いられており、被検出物の包装に導電材料である銅を使用すると、例えば１ｋＨｚにおける渦電流による表皮深さは２ｍｍ程度となるため、包装内の被検出物まで異物検出が十分に行なえない。また、被検出物に発生する渦電流が当該被検出物に含まれる水分、温度などの影響を受け易く検出感度が甘くなり易い。更には、異物の形状や大きさの限界を受け易く、例えば鉄粉であればφ０．５ｍｍ、ステンレス（ＳＵＳ３０４）製の小片であればφ０．７ｍｍが限界とされている。 In the first detection method described above, a high frequency of 1 MHZ to 333 kHz is used as the frequency of the current flowing through the resonance circuit or the applied voltage, and when copper as a conductive material is used for packaging the object to be detected, for example, 1 kHz Since the skin depth due to the eddy current is about 2 mm, foreign matter cannot be sufficiently detected up to the detected object in the package. In addition, eddy currents generated in the detected object are easily affected by moisture, temperature, etc. contained in the detected object, and the detection sensitivity is likely to be reduced. Furthermore, the shape and size of foreign matters are easily limited. For example, φ0.5 mm is the limit for iron powder, and φ0.7 mm is the limit for a small piece made of stainless steel (SUS304).
また、第２の検出方式においては、ＣＣＤカメラによる撮像であるため被検査物の表面の異常のみ検出できるが、内部の異常は検出できない。
また、第３の検出方式においては、Ｘ線照射装置が高価なうえに、定期的に消耗品（例えばＸ線管球やラインセンサ）を交換する必要があるためメンテナンスコストも派生する。
また、第４の検出方式においては、ＳＱＵＩＤ（超伝導量子干渉素子）磁気センサは高感度であり、被検出物の大きさに関する検出限界の精度も高い（例えば、ＳＵＳ３０４製の針であればφ０．１ｍｍまで検出可能）。しかしながら、超伝導素子を使用するため、液体窒素や液体ヘリウムなどを用いた大掛かりな冷却装置が必要となる。また、検出空間を磁気シールドする必要から環境磁界の影響を受けやすく、装置コストが高くなりやすい。
In the second detection method, since the image is taken by the CCD camera, only the abnormality of the surface of the inspection object can be detected, but the internal abnormality cannot be detected.
In the third detection method, the X-ray irradiation apparatus is expensive, and the consumables (for example, an X-ray tube and a line sensor) need to be replaced periodically, resulting in a maintenance cost.
In the fourth detection method, the SQUID (superconducting quantum interference element) magnetic sensor is highly sensitive and the detection limit accuracy with respect to the size of the object to be detected is high (for example, φ0 for a SUS304 needle). Detectable up to 1 mm). However, since a superconducting element is used, a large cooling device using liquid nitrogen or liquid helium is required. Further, since the detection space needs to be magnetically shielded, it is easily affected by an environmental magnetic field, and the apparatus cost is likely to increase.
本発明の目的は、上述した既存の検出方法に比べて、装置構成が簡易で低コストにもかかわらず、被検出物の内部まで異物検出が行なえる検出感度の高い磁性異物検出装置を提供することにある。 An object of the present invention is to provide a magnetic foreign object detection device with high detection sensitivity capable of detecting foreign objects up to the inside of an object to be detected, despite the simple structure and low cost of the apparatus as compared with the existing detection method described above. There is.
本発明は上記目的を達成するため、次の構成を備える。
被検出物に混入する磁性異物を検出する磁性異物検出装置であって、前記被検出物が通過する検査領域に磁界を発生させる磁界発生装置と、前記磁界発生装置により発生させた発生磁界に鎖交するよう配置され、前記被検出物が発生磁界中を通過する際にもたらす磁界分布変化を検出する空芯状の検出コイルと、前記検出コイルに誘導される誘導電流を増幅し電圧に変換する電流−電圧変換回路と、を具備したインダクション磁気センサと、前記インダクション磁気センサに具備した電流−電圧変換回路の出力信号を解析して前記磁性異物を特定する信号解析装置と、を備えたことを特徴とする。
In order to achieve the above object, the present invention comprises the following arrangement.
A magnetic foreign matter detection device for detecting a magnetic foreign matter mixed in a detection object, the magnetic field generation device generating a magnetic field in an inspection region through which the detection target passes, and the generated magnetic field generated by the magnetic field generation device. An air-core-shaped detection coil that is arranged to intersect and detects a magnetic field distribution change caused when the detected object passes through the generated magnetic field, and an induced current induced in the detection coil is amplified and converted into a voltage. An induction magnetic sensor provided with a current-voltage conversion circuit, and a signal analysis device for analyzing the output signal of the current-voltage conversion circuit provided in the induction magnetic sensor and identifying the magnetic foreign matter. Features.
この場合、インダクション磁気センサは、磁界分布変化を信号解析装置によって解析可能な出力信号の最小分解能から、前記検出コイルの導線材質、形状、巻数により決まるインダクタンス、抵抗、及び電流−電圧変換回路の構成が各々決定されるようになっている。
具体的には、磁束−電流換算係数について、検出コイルに鎖交する総磁束φ[Ｗｂ]とインダクタンスＬ[Ｈ]から誘導される誘導電流Ｉ＝φ／Ｌ[Ａ]となるが、インダクタンスＬを小さくすれば微弱な磁界でも大きな誘導電流が流れる。
一方、インダクタンスＬ[Ｈ]と抵抗Ｒ[Ω]により決まるカットオフ周波数ｆ＝Ｒ／２πＬ[Ｈｚ]以上の周波数では、上記磁束−電流変換係数により誘導電流により算出されるが、それ以下の周波数では誘導電流が２０ｄＢ／ｏｃｔで減衰する。即ち、上記磁束−電流換算係数とは反対にインダクタンスＬの値を大きくするのが好ましい。
以上より、インダクション磁気センサは、検出コイルのインダクタンスＬ[Ｈ]と抵抗Ｒ[Ω]により決まるカットオフ周波数ｆ＝Ｒ／２πＬ[Ｈｚ]以上の周波数で、検出コイルに鎖交する総磁束φ[Ｗｂ]に比例したとインダクタンスＬ[Ｈ]から誘導される誘導電流Ｉ＝φ／Ｌ[Ａ]を増幅して電圧信号として出力することが望ましい。
In this case, the induction magnetic sensor has an inductance, a resistance, and a current-voltage conversion circuit configuration determined by the conductive wire material, shape, and number of turns of the detection coil from the minimum resolution of the output signal that can analyze the change in the magnetic field distribution by the signal analyzer. Is determined.
Specifically, regarding the magnetic flux-current conversion coefficient, the induced current I = φ / L [A] derived from the total magnetic flux φ [Wb] and the inductance L [H] interlinked with the detection coil is obtained. If the value is reduced, a large induced current flows even in a weak magnetic field.
On the other hand, at a frequency equal to or higher than the cutoff frequency f = R / 2πL [Hz] determined by the inductance L [H] and the resistance R [Ω], it is calculated from the induced current by the magnetic flux-current conversion coefficient. Then, the induced current attenuates at 20 dB / oct. That is, it is preferable to increase the value of the inductance L contrary to the magnetic flux-current conversion coefficient.
As described above, the induction magnetic sensor has a total magnetic flux φ [interlinked with the detection coil at a frequency equal to or higher than the cutoff frequency f = R / 2πL [Hz] determined by the inductance L [H] and the resistance R [Ω] of the detection coil. It is desirable to amplify the induced current I = φ / L [A] induced from the inductance L [H] in proportion to Wb] and output it as a voltage signal.
また、前記磁界発生装置により発生する発生磁界の周波数の上限は、数十ｋＨｚ以下の低周波数であることを特徴とする。 The upper limit of the frequency of the generated magnetic field generated by the magnetic field generator is a low frequency of several tens of kHz or less.
また、前記電流−電圧変換回路において、前記被検出物による磁界分布変化によって前記検出コイルに誘導される誘導電流は、当該検出コイル両端を短絡した場合と同程度誘導される誘導電流の大きさに比例した電圧に変換されることを特徴とする。 In the current-voltage conversion circuit, the induced current induced in the detection coil due to a change in the magnetic field distribution by the detected object is the magnitude of the induced current induced to the same extent as when both ends of the detection coil are short-circuited. It is converted to a proportional voltage.
また、前記検出コイルの抵抗がゼロでない場合、当該検出コイルに直流磁界が鎖交しても誘導電流が流れないことを特徴とする。 Further, when the resistance of the detection coil is not zero, no induced current flows even if a DC magnetic field is linked to the detection coil.
また、前記検出コイルが前記磁界発生装置に発生する交番磁界を打ち消すように作動接続されていることを特徴とする。 The detection coil is operatively connected so as to cancel the alternating magnetic field generated in the magnetic field generator.
また、前記磁界発生装置は、交流電源と、該交流電源に接続された交番磁界を発生させる磁界発生コイルと、を具備し、前記検出コイルは、前記磁界発生コイル内に同芯状に設けられ、当該磁界発生コイルに通電して交番磁界を発生させた状態で被検出物が前記検出コイル内に置かれるか或いは前記検出コイル内を通過させる際に流れる誘導電流により磁界分布変化が検出されることを特徴とする。 The magnetic field generator includes an AC power source and a magnetic field generating coil that generates an alternating magnetic field connected to the AC power source, and the detection coil is provided concentrically within the magnetic field generating coil. A change in magnetic field distribution is detected by an induced current that flows when an object to be detected is placed in the detection coil in a state where an alternating magnetic field is generated by energizing the magnetic field generation coil. It is characterized by that.
或いは、前記磁界発生装置は、複数の永久磁石或いは直流電源に接続された磁界発生コイルのいずれかを具備し、前記検出コイルは前記永久磁石間若しくは前記磁界発生コイル内に同芯状に設けられ、前記磁界発生装置により直流磁界を発生させた状態で被検出物が前記検出コイル内を通過させる際に流れる誘導電流により磁界分布変化が検出されることを特徴とする。 Alternatively, the magnetic field generation device includes any of a plurality of permanent magnets or a magnetic field generation coil connected to a DC power source, and the detection coil is provided concentrically between the permanent magnets or within the magnetic field generation coil. A change in magnetic field distribution is detected by an induced current that flows when an object to be detected passes through the detection coil in a state where a DC magnetic field is generated by the magnetic field generator.
上述した磁性異物検出装置を用いれば、磁界発生装置により発生させた発生磁界に鎖交するよう同芯状に配置された検出コイル内を、被検出物が通過する際にもたらす磁界分布変化を前記検出コイルに誘導される誘導電流を増幅し電圧に変換するインダクション磁気センサにより検出して出力信号を解析して磁性異物を特定するようにしたので、装置構成が簡易で低コストにもかかわらず、被検出物の内部まで異物検出が行なえる検出感度の高い磁性異物検出装置を提供することができる。
特に、磁界発生装置により発生する発生磁界の周波数の上限は、数十ｋＨｚ以下の低周波数であることから、被検出物が導電材料で包装（例えばアルミホイル包装）されていても、表皮効果による渦電流は発生せず、当該被検出物の内部の異物まで検出することができる。
If the magnetic foreign matter detection device described above is used, the magnetic field distribution change caused when the object to be detected passes through the detection coil arranged concentrically so as to interlink with the generated magnetic field generated by the magnetic field generation device. The induction magnetic sensor that amplifies the induced current induced in the detection coil and converts it to a voltage is detected and the output signal is analyzed to identify the magnetic foreign matter. It is possible to provide a magnetic foreign matter detection device with high detection sensitivity capable of detecting foreign matter up to the inside of the detection object.
In particular, since the upper limit of the frequency of the generated magnetic field generated by the magnetic field generator is a low frequency of several tens of kHz or less, even if the object to be detected is packaged with a conductive material (for example, aluminum foil packaging), it is due to the skin effect. No eddy current is generated, and even foreign matter inside the detected object can be detected.
また、被検出物による磁界分布変化によって検出コイルに誘導される誘導電流は、当該検出コイル両端を短絡した場合と同程度誘導される誘導電流の大きさに比例した電圧に変換されることで検出感度を維持することができる。
また、検出コイルの抵抗値がゼロでない場合、当該検出コイルに直流磁界が鎖交しても誘導電流が流れないので、磁界発生装置により発生した一様な磁界中では検出感度を持たない。よって、被検出物に磁性異物が混入している場合のみ磁界分布に変動を生じて異常を検出することができる。
また、検出コイルが磁界発生装置に発生する交番磁界を打ち消すように作動接続されていると、磁界発生装置によって発生する交番磁界の変化だけでは検出感度を持たない。よって、被検出物に磁性異物が混入している場合のみ磁界分布に変動を生じて異常を検出することができる。
また、磁界発生コイルに通電して交番磁界を発生させた状態で被検出物が前記検出コイル内に置かれるか或いは前記検出コイル内を通過させる際に流れる誘導電流により磁界分布変化が検出されるか、或いは磁界発生装置により直流磁界を発生させた状態で被検出物が前記検出コイル内を通過させる際に流れる誘導電流により磁界分布変化が検出されるので、簡易な構成で高感度に磁性異物の検出が行なえる。
In addition, the induced current induced in the detection coil due to the change in magnetic field distribution due to the object to be detected is detected by being converted into a voltage proportional to the magnitude of the induced current induced to the same extent as when both ends of the detection coil are short-circuited. Sensitivity can be maintained.
In addition, when the resistance value of the detection coil is not zero, no induced current flows even if a DC magnetic field is linked to the detection coil, so that it does not have detection sensitivity in a uniform magnetic field generated by the magnetic field generator. Therefore, the abnormality can be detected by causing a variation in the magnetic field distribution only when a magnetic foreign matter is mixed in the object to be detected.
Further, when the detection coil is operatively connected so as to cancel the alternating magnetic field generated in the magnetic field generator, the detection sensitivity is not obtained only by the change of the alternating magnetic field generated by the magnetic field generator. Therefore, the abnormality can be detected by causing a variation in the magnetic field distribution only when a magnetic foreign matter is mixed in the object to be detected.
Further, a change in magnetic field distribution is detected by an induced current that flows when an object to be detected is placed in the detection coil in a state where an alternating magnetic field is generated by energizing the magnetic field generation coil or passes through the detection coil. Alternatively, since a magnetic field distribution change is detected by an induced current that flows when a detected object passes through the detection coil in a state where a DC magnetic field is generated by a magnetic field generator, magnetic foreign matter is detected with a simple configuration and high sensitivity. Can be detected.
以下、本発明に係る磁性異物検出装置の最良の実施形態について、添付図面を参照しながら説明する。本実施の形態は、一例として加工食品に混入する磁性異物（例えば、加工刃などに用いられるステンレススチール（ＳＵＳ３０４）小片、ステープラ針など）を検出する磁性異物検査装置について説明する。 Hereinafter, the best embodiment of a magnetic foreign object detection device according to the present invention will be described with reference to the accompanying drawings. In the present embodiment, as an example, a magnetic foreign matter inspection apparatus that detects magnetic foreign matters (for example, stainless steel (SUS304) small pieces, stapler needles, etc. used for processing blades) mixed in processed foods will be described.
尚、ＳＵＳ３０４は、本来非磁性のオーステナイト鋼であり磁化しないが、加工時の応力によってマルテンサイトに変態して磁性を帯びるようになることが知られている。したがって、加工食品に混入したステンレススチール製刃片や、ステンレス線が曲げ加工されたステープラ針などの小片は磁性異物として検出される。 It is known that SUS304 is originally a nonmagnetic austenitic steel and does not magnetize, but is transformed into martensite due to stress during processing and becomes magnetized. Accordingly, small pieces such as a stainless steel blade piece mixed with processed food and a stapler needle formed by bending a stainless steel wire are detected as magnetic foreign matters.
図１を参照して、磁性異物検出装置の概略構成について説明する。
磁界発生装置１は、被検出物（加工食品）２が通過する検査領域に均一な磁界を発生させる。被検出物２は、後述するように導電性包装材（アルミホイルなど）に包装されていてもよい。
With reference to FIG. 1, a schematic configuration of the magnetic foreign object detection device will be described.
The magnetic field generator 1 generates a uniform magnetic field in an inspection region through which an object to be detected (processed food) 2 passes. The detected object 2 may be packaged in a conductive packaging material (such as aluminum foil) as will be described later.
図１において、磁界発生装置１は、本実施形態では交番磁界を発生させる装置である。即ち、交流電源３と、該交流電源３に接続された空芯状コイル内に交番磁界を発生させる磁界発生コイル４を具備している。また、検出コイル５は、磁界発生コイル４内に形成される交番磁界内に同芯状に設けられている。磁界発生コイル４に通電して交番磁界を発生させた状態で被検出物２が検出コイル５内に置かれるか或いは当該検出コイル５内を通過させる際に誘導電流が流れることにより磁界分布変化が検出されるようになっている。 In FIG. 1, a magnetic field generator 1 is an apparatus that generates an alternating magnetic field in this embodiment. That is, an AC power source 3 and a magnetic field generating coil 4 that generates an alternating magnetic field in an air-core coil connected to the AC power source 3 are provided. The detection coil 5 is provided concentrically in an alternating magnetic field formed in the magnetic field generating coil 4. The detected magnetic field 2 is placed in the detection coil 5 in a state where the magnetic field generating coil 4 is energized to generate an alternating magnetic field, or an induced current flows when passing through the detection coil 5 to change the magnetic field distribution. It is to be detected.
尚、磁界発生装置１により発生する発生磁界の周波数の上限は、数十ｋＨｚ以下の低周波数である。それ以上の周波数を用いると、被検出物２に表皮効果により渦電流が発生するおそれがあり、被検出物２の内部に混入した磁性異物６（例えば、鉄粉、ステンレススチール小片、ステープラ針など）を検査できなくなるおそれがあるからである。 The upper limit of the frequency of the generated magnetic field generated by the magnetic field generator 1 is a low frequency of several tens of kHz or less. If a higher frequency is used, an eddy current may be generated in the detected object 2 due to the skin effect, and the magnetic foreign matter 6 (for example, iron powder, stainless steel piece, staple needle, etc.) mixed in the detected object 2 ) May not be inspected.
尚、磁界発生装置１は複数の永久磁石を対向配置するか或いは直流電源に接続された磁界発生コイルのいずれかを具備していてもよい。この場合、検出コイル５は、永久磁石間若しくは磁界発生コイル内に同芯状に設けられる。磁界発生装置１により発生する直流磁界中を被検出物２が検出コイル５内を通過させる際に流れる誘導電流により磁界分布変化が検出される。 The magnetic field generator 1 may be provided with either a plurality of permanent magnets facing each other or a magnetic field generating coil connected to a DC power source. In this case, the detection coil 5 is provided concentrically between the permanent magnets or in the magnetic field generating coil. A change in magnetic field distribution is detected by an induced current that flows when the detection object 2 passes through the detection coil 5 in a DC magnetic field generated by the magnetic field generator 1.
図２において、インダクション磁気センサ７は、磁界発生装置１により発生させた低周波発生磁界に鎖交するよう配置され、被検出物２が発生磁界中を通過する際にもたらす磁界分布変化を検出する空芯状の検出コイル５と、検出コイル５に誘導される誘導電流を増幅し、電圧に変換する電流−電圧変換回路８を具備している。検出コイル５は磁界発生装置１によって形成される均一磁界空間１０内に配置されている。この検出コイル５内に被検出物２が置かれるか或いは通過させることで、当該検出コイル５に誘導される誘導電流の値を電流−電圧変換回路８によって電圧値に変換して出力するようになっている。 In FIG. 2, the induction magnetic sensor 7 is arranged so as to be linked to the low-frequency generated magnetic field generated by the magnetic field generator 1, and detects a magnetic field distribution change caused when the detection object 2 passes through the generated magnetic field. An air-core detection coil 5 and a current-voltage conversion circuit 8 that amplifies the induced current induced in the detection coil 5 and converts it into a voltage are provided. The detection coil 5 is arranged in a uniform magnetic field space 10 formed by the magnetic field generator 1. The detected object 2 is placed in or passed through the detection coil 5 so that the value of the induced current induced in the detection coil 5 is converted into a voltage value by the current-voltage conversion circuit 8 and output. It has become.
電流−電圧変換回路８において被検出物２による磁界分布変化によって検出コイル５に誘導される誘導電流は、検出コイル５両端を短絡した場合と同程度に誘導される誘導電流に比例した電圧に変換されるようになっている。 In the current-voltage conversion circuit 8, the induced current induced in the detection coil 5 due to the change in the magnetic field distribution by the detected object 2 is converted into a voltage proportional to the induced current induced to the same extent as when both ends of the detection coil 5 are short-circuited. It has come to be.
また、インダクション磁気センサ７は、検出コイル５の抵抗がゼロでない場合、当該検出コイル５に直流磁界が鎖交しても誘導電流が流れないようになっている。磁界発生装置１により発生した一様な磁界では検出感度を持たない。よって、被検出物２に磁性異物６が混入している場合のみ磁界分布に変動を生じて異常を検出することができる。 Further, when the resistance of the detection coil 5 is not zero, the induction magnetic sensor 7 is configured such that no induced current flows even if a DC magnetic field is linked to the detection coil 5. The uniform magnetic field generated by the magnetic field generator 1 does not have detection sensitivity. Therefore, only when the magnetic foreign matter 6 is mixed in the object 2 to be detected, the magnetic field distribution is changed and an abnormality can be detected.
また、インダクション磁気センサ７は、検出コイル５が磁界発生装置１に発生する交番磁界を打ち消すように作動接続されている。磁界発生装置によって発生する交番磁界の変化だけでは検出感度を持たない。よって、被検出物２に磁性異物６が混入している場合のみ磁界分布に変動を生じて異常を検出することができる。 The induction magnetic sensor 7 is operatively connected so that the detection coil 5 cancels an alternating magnetic field generated in the magnetic field generator 1. Only the change of the alternating magnetic field generated by the magnetic field generator does not have detection sensitivity. Therefore, only when the magnetic foreign matter 6 is mixed in the object 2 to be detected, the magnetic field distribution is changed and an abnormality can be detected.
信号解析装置９は、インダクション磁気センサ７に具備した電流−電圧変換回路８の出力信号（電流−電圧変換値）を解析して磁性異物６を特定する。磁性異物６のうち例えば、鉄粉やステンレスなどに応じて電圧波形をサンプルとして記憶しておくことで、異物が何であるか特定することができる。 The signal analysis device 9 analyzes the output signal (current-voltage conversion value) of the current-voltage conversion circuit 8 provided in the induction magnetic sensor 7 and identifies the magnetic foreign matter 6. By storing a voltage waveform as a sample according to, for example, iron powder or stainless steel among the magnetic foreign substances 6, it is possible to identify what the foreign substances are.
図２において、インダクション磁気センサ７は、磁界分布変化を信号解析装置９によって解析可能な出力信号の最小分解能から、検出コイル５の導線材質、形状、巻数により決まるインダクタンス、抵抗、及び電流−電圧変換回路８の構成が各々決定されるようになっている。
具体的には、インダクション磁気センサ７は、検出コイル５のインダクタンスＬ[Ｈ]と抵抗Ｒ[Ω]により決まるカットオフ周波数ｆ＝Ｒ／２πＬ[Ｈｚ]以上の周波数とすることが望ましい。しかしながら、インダクションセンサの高感度さゆえ、検出コイル５のアンバランスが問題となるときには、それ以下の周波数が用いられる。本実施形態では一例として１０Ｈｚの周波数が用いられる。
In FIG. 2, the induction magnetic sensor 7 has an inductance, resistance, and current-voltage conversion determined by the conductive wire material, shape, and number of turns of the detection coil 5 from the minimum resolution of the output signal that can analyze the change in the magnetic field distribution by the signal analyzer 9. The configuration of each circuit 8 is determined.
Specifically, the induction magnetic sensor 7 preferably has a cut-off frequency f = R / 2πL [Hz] or higher determined by the inductance L [H] of the detection coil 5 and the resistance R [Ω]. However, due to the high sensitivity of the induction sensor, when the imbalance of the detection coil 5 becomes a problem, a lower frequency is used. In this embodiment, a frequency of 10 Hz is used as an example.
尚、検出コイル５に誘導される誘導電流は、電流−電圧変換回路８に用いられるオペアンプの帰還抵抗に比例した電圧として増幅される。この増幅電圧値をコイル抵抗の１００倍以上にしておけば、インダクション磁気センサ７の最小磁界感度は変わらない。インダクション磁気センサ７の最小磁界感度は、オペアンプの等価入力雑音電圧密度と等価雑音電流密度と磁束−電流換算係数により決まる。 The induced current induced in the detection coil 5 is amplified as a voltage proportional to the feedback resistance of the operational amplifier used in the current-voltage conversion circuit 8. If this amplified voltage value is set to 100 times or more of the coil resistance, the minimum magnetic field sensitivity of the induction magnetic sensor 7 does not change. The minimum magnetic field sensitivity of the induction magnetic sensor 7 is determined by the equivalent input noise voltage density, equivalent noise current density, and magnetic flux-current conversion coefficient of the operational amplifier.
次に、図３の多層ソレノイドコイル１１を用いて被検出物２に混入する異物検出を行なった検出実験結果の一例について説明する。以下に検出実験装置の構成例について説明する。多層ソレノイドコイル１１のうち外層コイル１１ａに発振装置１２から増幅回路１３を経て定電流モードで交流電流を流して交番磁界（低周波磁界）を発生させる。このときの、交番磁界の発振周波数は１０Ｈｚであり、入力電流ｉｍの大きさを、外層コイル１１ａに接続された電圧計１４によって電圧に換算して測定をおこなった。また、内層コイル（インダクショングラジオメータ）１１ｂには、誘導電流を電圧に変換する電流−電圧変換回路１５が接続されており、当該電流−電圧変換回路１５で出力された出力電圧を電圧計１６により測定を行った。
また、被検出物２は樹脂系試料台（非磁性）１７のＡ点及びＢ点に試料として各々固定され、該樹脂系試料台１７を多層ソレノイドコイル１１に挿入したときの出力電圧波形をオシロスコープにて観測を行なった。
Next, an example of a detection experiment result in which foreign matter mixed in the detection object 2 is detected using the multilayer solenoid coil 11 of FIG. A configuration example of the detection experiment apparatus will be described below. An alternating current (low frequency magnetic field) is generated by flowing an alternating current in the constant current mode from the oscillation device 12 through the amplifier circuit 13 to the outer layer coil 11a of the multilayer solenoid coil 11. In this case, the oscillation frequency of the alternating magnetic field is 10 Hz, the magnitude of the input current i m, was subjected to measurement in terms of voltage by the voltmeter 14 connected to the outer layer coils 11a. The inner coil (induction gradiometer) 11b is connected to a current-voltage conversion circuit 15 that converts an induced current into a voltage. The output voltage output from the current-voltage conversion circuit 15 is output by a voltmeter 16. Measurements were made.
The detected object 2 is fixed as a sample at points A and B of a resin sample stage (non-magnetic) 17 and the output voltage waveform when the resin type sample stage 17 is inserted into the multilayer solenoid coil 11 is an oscilloscope. Observed at.
図４（ａ）（ｂ）は、樹脂系試料台１７のＡ点及びＢ点に試料としてＰＣパーマロイ材を各々固定して多層ソレノイドコイル１１に挿入したときの出力電圧波形例を示す。図４（ａ）（ｂ）において、Ｅは入力電流波形、Ｆは入力電流に同期したトリガー電圧波形、Ｇはインダクション磁気センサの出力電圧波形を示す。
ＰＣパーマロイ材（78Permalloy, Nilaco社製）の場合、直径φ0.8ｍｍを共通で、長さをＡ点で5mm，10mmと変化させ、Ｂ点で長さを100mm，40mm，20mm，10mmと変化させて出力電圧波形を観測した。この結果、ＰＣパーマロイ材の場合、Ａ点で（φ0.8mm，長さ10mm）、Ｂ点で（φ0.8mm，長さ40mm）以上のサイズであれば出力電圧の変化が各々観測され、磁性異物を検出できることが確認できた。
4A and 4B show examples of output voltage waveforms when a PC permalloy material is fixed as a sample at points A and B of the resin sample stage 17 and inserted into the multilayer solenoid coil 11, respectively. 4A and 4B, E represents an input current waveform, F represents a trigger voltage waveform synchronized with the input current, and G represents an output voltage waveform of the induction magnetic sensor.
In the case of PC permalloy (78 Permalloy, Nilaco), the diameter is 0.8mm in common, the length is changed to 5mm and 10mm at point A, and the length is changed to 100mm, 40mm, 20mm and 10mm at point B. The output voltage waveform was observed. As a result, in the case of PC permalloy, if the size is larger than point A (φ0.8mm, length 10mm) and point B (φ0.8mm, length 40mm) or more, the change in output voltage is observed respectively It was confirmed that foreign matter could be detected.
図５（ａ）（ｂ）は、樹脂系試料台１７のＡ点に試料としてアルミ箔のみとアルミ箔で包装されたＰＣパーマロイ材（φ0.8ｍｍ，長さ20mm）を固定して多層ソレノイドコイル１１に挿入したときの出力電圧波形例を各々示す。図５（ａ）（ｂ）において、Ｅは入力電流波形、Ｆは入力電流に同期したトリガー電圧波形、Ｇはインダクション磁気センサの出力電圧波形を示す。
図５（ｂ）によれば、アルミ箔により包装されていても、ＰＣパーマロイ材による出力電圧の変化が観測され、磁性異物を検出できることが確認できた。
5 (a) and 5 (b) show a multilayer solenoid coil in which a PC permalloy material (φ0.8 mm, length 20 mm) wrapped with only aluminum foil and aluminum foil is fixed as a sample at point A of the resin sample stage 17. 11 shows an example of an output voltage waveform when inserted into 11, respectively. 5A and 5B, E indicates an input current waveform, F indicates a trigger voltage waveform synchronized with the input current, and G indicates an output voltage waveform of the induction magnetic sensor.
According to FIG.5 (b), even if it wrapped with the aluminum foil, the change of the output voltage by PC permalloy material was observed, and it has confirmed that the magnetic foreign material was detectable.
図６（ａ）（ｂ）は、樹脂系試料台１７のＡ点及びＢ点に試料としてステンレス材（SUS304, Nilaco社製）を各々固定して多層ソレノイドコイル１１に挿入したときの出力電圧波形例を示す。図６（ａ）（ｂ）において、Ｅは入力電流波形、Ｆは入力電流に同期したトリガー入力電圧波形、Ｇはインダクション磁気センサの出力電圧波形を示す。
本実施例は、樹脂系試料台１７のＡ点及びＢ点に試料であるステンレス材の長さ10mmを共通にして、直径をφ0.5mm，φ0.2mm，φ0.1mmと変化させた試料を各々固定して出力電圧波形を観測した。この結果、ステンレス材の場合には、φ0.2ｍｍ，長さ10mm以上のサイズであれば磁性異物を検出できることが確認できた。
6A and 6B show output voltage waveforms when stainless steel (SUS304, manufactured by Nilaco) is fixed to the A and B points of the resin sample stage 17 and inserted into the multilayer solenoid coil 11, respectively. An example is shown. 6A and 6B, E represents an input current waveform, F represents a trigger input voltage waveform synchronized with the input current, and G represents an output voltage waveform of the induction magnetic sensor.
In this example, a sample having a diameter of φ0.5 mm, φ0.2 mm, and φ0.1 mm with the same length of 10 mm of the stainless steel material as the sample at points A and B of the resin sample stage 17 is changed. The output voltage waveform was observed with each fixed. As a result, it was confirmed that in the case of stainless steel, magnetic foreign matter can be detected if the size is φ0.2 mm and the length is 10 mm or more.
図７（ａ）（ｂ）は、樹脂系試料台１７のＡ点に試料としてアルミ箔で包装されたステンレス材（SUS304, Nilaco社製;φ0.2ｍｍ，長さ10mm）を固定して多層ソレノイドコイル１１に挿入したときの出力電圧波形例を示す。図７（ａ）（ｂ）において、Ｅは入力電流波形、Ｆは入力電流に同期したトリガー入力電圧波形、Ｇはインダクション磁気センサの出力電圧波形を示す。
アルミ箔により包装されていても、出力電圧の変化が観測され、磁性異物が検出できることが確認できた。
7 (a) and 7 (b) show a multilayer solenoid by fixing a stainless steel (SUS304, manufactured by Nilaco; φ0.2mm, length 10mm) as a sample to a point A of the resin sample stage 17 as a sample. The example of an output voltage waveform when inserting in the coil 11 is shown. 7A and 7B, E indicates an input current waveform, F indicates a trigger input voltage waveform synchronized with the input current, and G indicates an output voltage waveform of the induction magnetic sensor.
Even when packaged with aluminum foil, changes in the output voltage were observed, confirming that magnetic foreign matter could be detected.
図８（ａ）（ｂ）及び図９（ａ）（ｂ）は、樹脂系試料台１７のＡ点及びＢ点に試料として鉄材（Fe99.5% ;Nilaco社製）を各々固定して多層ソレノイドコイル１１に挿入したときの出力電圧波形例を示す。図８（ａ）（ｂ）及び図９（ａ）（ｂ）において、Ｅは入力電流波形、Ｆは入力電流に同期したトリガー入力電圧波形、Ｇはインダクション磁気センサの出力電圧波形を示す。
図８（ａ）（ｂ）は、樹脂系試料台１７のＡ点及びＢ点に試料である鉄材の直径がφ0.5mmの場合、φ0.2mmの場合で長さを10mm，5mm，2mmと変化させたものを各々固定して得られた出力電圧波形示す。また、図９（ａ）（ｂ）は、直径がφ0.1mmの場合で長さを50mm，10mmと変化させたものを各々固定して得られた出力電圧波形を示す。この結果、鉄材の場合には、直径φ0.2ｍｍ，長さ5mm以上のサイズで磁性異物を検出できることが確認できた。また、直径φ0.1mmであれば、長さ50mm以上のサイズで磁性異物を検出できることも確認できた。
また、上記各サイズの鉄材はアルミ箔により包装されていても、出力電圧の変化が観測され、磁性異物が検出できることが確認できた。
FIGS. 8A, 8B and 9A, 9B show a multilayer structure in which an iron material (Fe99.5%; manufactured by Nilaco) is fixed as a sample at points A and B of the resin sample stage 17, respectively. The example of an output voltage waveform when it inserts in the solenoid coil 11 is shown. 8A, 8B, and 9A, 9B, E indicates an input current waveform, F indicates a trigger input voltage waveform synchronized with the input current, and G indicates an output voltage waveform of the induction magnetic sensor.
8 (a) and 8 (b) show the lengths of 10 mm, 5 mm, and 2 mm when the diameter of the iron material as a sample at points A and B of the resin-based sample stage 17 is φ0.5 mm and φ0.2 mm, respectively. The output voltage waveform obtained by fixing each changed one is shown. FIGS. 9A and 9B show output voltage waveforms obtained by fixing the diameters of 0.1 mm and changing the lengths to 50 mm and 10 mm, respectively. As a result, in the case of iron materials, it was confirmed that magnetic foreign matters could be detected with a diameter of φ0.2 mm and a length of 5 mm or more. It was also confirmed that a magnetic foreign object can be detected with a diameter of 50 mm or more when the diameter is 0.1 mm.
Moreover, even if the iron materials of the above sizes were packaged with aluminum foil, a change in output voltage was observed, and it was confirmed that magnetic foreign matters could be detected.
図１０は、樹脂系試料台１７のＡ点に試料としてチーズブロックの中にステープラ針を埋め込んだものを固定して多層ソレノイドコイル１１に挿入したときの出力電圧波形例を示す。これにより、食品中に混入した磁性異物を検出可能であることが確認できた。 FIG. 10 shows an example of an output voltage waveform when a sample in which a stapler needle is embedded in a cheese block as a sample is fixed and inserted into the multilayer solenoid coil 11 at a point A of the resin-based sample stage 17. Thereby, it was confirmed that the magnetic foreign matter mixed in the food could be detected.
以上の実験結果によれば、装置構成が簡易で低コストにもかかわらず、検出感度の高い磁性異物検出装置を提供することができることが分かる。また、磁界発生装置１により発生する発生磁界の周波数の上限は、数十ｋＨｚ以下の低周波数であることから、被検出物２が導電材料で包装（例えばアルミホイル包装）されていても、表皮効果による渦電流は発生せず、当該被検出物２の内部の磁性異物６まで検出することができる。 According to the above experimental results, it can be seen that a magnetic foreign object detection device with high detection sensitivity can be provided in spite of a simple device configuration and low cost. Further, since the upper limit of the frequency of the generated magnetic field generated by the magnetic field generator 1 is a low frequency of several tens of kHz or less, even if the detected object 2 is packaged with a conductive material (for example, aluminum foil package), the skin An eddy current due to the effect is not generated, and even the magnetic foreign matter 6 inside the detected object 2 can be detected.
尚、磁界発生装置１により発生する発生磁界の周波数を１０ｋＨｚ以上とし、電流−電圧変換回路８の代わりに検出コイル５の両端電圧をロックインアンプ等で検出することにより磁界分布変化を検出でき、渦電流方式による汎用の金属検出器としても使用できるので、装置の付加価値を高めた磁性異物検出装置を提供することができる。 The frequency of the magnetic field generated by the magnetic field generator 1 is set to 10 kHz or more, and the change in the magnetic field distribution can be detected by detecting the voltage across the detection coil 5 with a lock-in amplifier or the like instead of the current-voltage conversion circuit 8. Since it can also be used as a general-purpose metal detector by an eddy current method, it is possible to provide a magnetic foreign object detection device with increased added value of the device.
１ 磁界発生装置
２ 被検出物
３ 交流電源
４ 磁界発生コイル
５ 検出コイル
６ 磁性異物
７ インダクション磁気センサ
８，１５ 電流−電圧変換回路
９ 信号解析装置
１０ 均一磁界空間
１１ 多層ソレノイドコイル
１１ａ 外層コイル
１１ｂ 内層コイル
１２ 発振装置
１３ 増幅回路
１４，１６ 電圧計
１７ 樹脂系試料台
DESCRIPTION OF SYMBOLS 1 Magnetic field generator 2 Detected object 3 AC power supply 4 Magnetic field generating coil 5 Detection coil 6 Magnetic foreign substance 7 Induction magnetic sensor 8, 15 Current-voltage conversion circuit 9 Signal analysis device 10 Uniform magnetic field space 11 Multilayer solenoid coil 11a Outer coil 11b Inner layer Coil 12 Oscillator 13 Amplifying circuit 14, 16 Voltmeter 17 Resin sample stage
Claims (7)
前記被検出物が通過する検査領域に磁界を発生させる磁界発生装置と、
前記磁界発生装置により発生させた発生磁界に鎖交するよう配置され、前記被検出物が発生磁界中を通過する際にもたらす磁界分布変化を検出する空芯状の検出コイルと、前記検出コイルに誘導される誘導電流を増幅し電圧に変換する電流−電圧変換回路と、を具備したインダクション磁気センサと、
前記インダクション磁気センサに具備した電流−電圧変換回路の出力信号を解析して前記磁性異物を特定する信号解析装置と、を備えたことを特徴とする磁性異物検出装置。 A magnetic foreign matter detection device for detecting magnetic foreign matter mixed in an object to be detected,
A magnetic field generator for generating a magnetic field in an inspection region through which the detected object passes;
An air-core detection coil that is arranged so as to be linked to the generated magnetic field generated by the magnetic field generation device and detects a magnetic field distribution change caused when the detected object passes through the generated magnetic field, and the detection coil An induction magnetic sensor comprising: a current-voltage conversion circuit that amplifies an induced current that is induced and converts the current into a voltage;
A magnetic foreign matter detection device comprising: a signal analysis device that analyzes an output signal of a current-voltage conversion circuit provided in the induction magnetic sensor and identifies the magnetic foreign matter.
前記検出コイルは、前記磁界発生コイル内に同芯状に設けられ、当該磁界発生コイルに通電して交番磁界を発生させた状態で被検出物が前記検出コイル内に置かれるか或いは前記検出コイル内を通過させる際に流れる誘導電流により磁界分布変化が検出されることを特徴とする請求項１乃至５のいずれか１項記載の磁性異物検出装置。 The magnetic field generator includes an AC power source, and a magnetic field generating coil that generates an alternating magnetic field by energizing an air-core coil from the AC power source,
The detection coil is provided concentrically in the magnetic field generating coil, and an object to be detected is placed in the detection coil in a state where an alternating magnetic field is generated by energizing the magnetic field generating coil. 6. The magnetic foreign object detection device according to claim 1, wherein a change in the magnetic field distribution is detected by an induced current that flows when passing through the inside.
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| JP2012211824A (en) * | 2011-03-31 | 2012-11-01 | Central Nippon Expressway Co Ltd | Vehicle detector |
| JP2015059818A (en) * | 2013-09-18 | 2015-03-30 | トヨタ自動車株式会社 | Magnetic foreign matter detection method and magnetic foreign matter detection apparatus |
| JP2015210235A (en) * | 2014-04-30 | 2015-11-24 | マイクロマグネ有限会社 | Foreign matter detection device |
| CN108594315A (en) * | 2018-04-20 | 2018-09-28 | 江苏省地震局 | Electromagnetism of Earthquake disturbance observation system and observation procedure based on induction type magnetic sensor |
| CN110114957A (en) * | 2016-12-27 | 2019-08-09 | Tdk株式会社 | Wireless power supply, wireless receiving device and Wireless power transmission system |
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