JP3041026B2 - Metal detector - Google Patents
Metal detectorInfo
- Publication number
- JP3041026B2 JP3041026B2 JP23761590A JP23761590A JP3041026B2 JP 3041026 B2 JP3041026 B2 JP 3041026B2 JP 23761590 A JP23761590 A JP 23761590A JP 23761590 A JP23761590 A JP 23761590A JP 3041026 B2 JP3041026 B2 JP 3041026B2
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- Japan
- Prior art keywords
- coil
- metal
- metal detector
- transmission coil
- magnetic field
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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- Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
- Geophysics And Detection Of Objects (AREA)
Description
【発明の詳細な説明】 〔産業上の利用分野〕 本発明は、金属検出機に係り、特にベルトなどの搬送
手段により物品を搬送し、搬送中の物品内に混入してい
る金属を高感度で検出する金属検出機に関する。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal detector, and more particularly to a method for transporting an article by a transporting means such as a belt and detecting a metal mixed in the article being transported with high sensitivity. The present invention relates to a metal detector for detecting in the above.
食品や衣類などの製品を製造するに際し、様々な工程
を経るが、この間に製造装置の一部の欠落、製造装置の
洗浄に用いる金属ブラシの破片の製造装置への残留、あ
るいは、縫製用のミシン針の折れなどで製品に金属が混
入することがある。製品の安全性を保つには金属を取り
除いたり、金属の混入した製品を分類しなければならな
い。この金属を検出するには、通常、被測定物に磁界を
加え、金属の存在により、磁界が変化することを利用し
ている。磁界を加える方法としては、コイルに電流を加
え磁界を発生させる方法、磁界の変化を検出する方法と
しては、コイルに誘起される電圧変化を検出する方法を
用いている。通常、磁界を発生させるコイルを送信コイ
ル、磁界の変化を検出するコイルを受信コイルと呼び、
送信コイルと受信コイルを合わせて検出ヘッドと呼んで
いる。When manufacturing products such as food and clothing, it goes through various processes.During this time, some of the manufacturing equipment is missing, fragments of metal brushes used for cleaning the manufacturing equipment remain in the manufacturing equipment, or Metal may be mixed into the product due to broken sewing needles. To keep the product safe, the metal must be removed or the product containing the metal must be classified. To detect this metal, a magnetic field is usually applied to an object to be measured, and the fact that the magnetic field changes due to the presence of the metal is utilized. As a method of applying a magnetic field, a method of generating a magnetic field by applying a current to a coil is used. As a method of detecting a change in the magnetic field, a method of detecting a voltage change induced in the coil is used. Usually, a coil that generates a magnetic field is called a transmission coil, and a coil that detects a change in the magnetic field is called a reception coil.
The transmitting coil and the receiving coil are collectively called a detection head.
この種の金属検出機では、検出感度を向上させるため
に様々な検出ヘッド形状が提案されている。従来の代表
的な形状としては、特願昭58−34397号にあるように、
一つの送信コイルと二つの受信コイルを対向させて設
け、被測定物を送信コイルと受信コイルの間を通過させ
る対向形と呼ばれるもの（その基本構成を第２図に示
す）や、実願昭53−177263号にあるように、送信コイル
を二つの受信コイルで挟むようにし、しかも搬送手段で
あるベルトにたいして垂直になるように設け、被測定物
を三つのコイルの中を通過させる同軸形と呼ばれるもの
（その基本構成を第３図に示す）や、特願昭54−80542
号にあるように、一対の送受信コイルを磁気的に平衡状
態になるように垂直に設け、被測定物を送信コイルと受
信コイルの間を通過させる構成のＴ形と呼ばれるもの
（その基本構成を第４図に示す）などがある。In this type of metal detector, various detection head shapes have been proposed to improve detection sensitivity. As a conventional representative shape, as described in Japanese Patent Application No. 58-34397,
One transmission coil and two reception coils are provided so as to face each other, and an object to be measured is passed between the transmission coil and the reception coil, which is called an opposing type (the basic configuration is shown in Fig. 2). As described in No. 53-177263, a transmitting coil is sandwiched between two receiving coils, and is provided so as to be perpendicular to a belt as a conveying means, and a coaxial type in which an object to be measured passes through three coils. 3 (the basic configuration is shown in Fig. 3) and Japanese Patent Application No. 54-80542.
As shown in the figure, a pair of transmitting and receiving coils are provided vertically so as to be in a magnetically balanced state, and a device to be measured is passed between a transmitting coil and a receiving coil. FIG. 4).
このように構成された従来の金属検出機では、送信コ
イルで発生させた磁界をある距離をもうけて配置した受
信コイルで受け、送受信コイル間に磁界の帯を形成し、
その帯の中に被測定物を通過させるというように、あた
かも送受信コイル間に距離が必要であるがごとくの考え
に基づき設計が行なわれていた。このため、送信コイル
が持ち合わせている金属を磁化、あるいは金属に渦電流
を生ぜしめる能力の大きい領域と、受信コイルが持ち合
わせている検出感度の良好な領域を十分活用しておら
ず、金属検出機の検出感度に限界があり、微小な金属を
検出することが不可能であった。また、従来の金属検出
機においては、送信コイルと受信コイルをある距離をも
って配置するため、振動によりコイル間隔が変動し、雑
音の原因となっていた。In the conventional metal detector configured as described above, the magnetic field generated by the transmitting coil is received by the receiving coil arranged at a certain distance, and a magnetic field band is formed between the transmitting and receiving coils.
The design has been performed based on the idea that a distance between the transmitting and receiving coils is required, such as passing a device under test through the band. For this reason, the area where the transmission coil has a large ability to magnetize the metal or generate eddy currents in the metal and the area where the reception coil has a good detection sensitivity are not fully utilized. Has a limit in detection sensitivity, and it has been impossible to detect minute metals. Further, in the conventional metal detector, since the transmission coil and the reception coil are arranged at a certain distance, the coil interval fluctuates due to vibration, which causes noise.
本発明の目的は、送信コイルおよび受信コイルの検出
能力の良好な領域を使っていない、あるいは振動に弱い
といった従来の金属検出機の問題点を、数値計算に基づ
いた最適設計を行なうことにより解決し、検出感度が高
く、振動による雑音に強い特性を持つ金属検出機を提供
することである。An object of the present invention is to solve the problems of a conventional metal detector that does not use a region having good detection capabilities of a transmission coil and a reception coil or that the metal coil is vulnerable to vibration by performing an optimal design based on numerical calculations. It is another object of the present invention to provide a metal detector having a high detection sensitivity and a characteristic resistant to noise due to vibration.
前記課題を解決するために、本発明の金属検出機は、
金属の混入を検査したい被測定物を搬送する搬送手段
と、この搬送手段の搬送路の近くに、搬送手段の搬送方
向とほぼ平行な平面内にあり、電流を流すことにより磁
界を発生する送信コイル、および、前記平面と実質的に
同一平面内にあって、前記送信コイルが発生する磁束の
うちから、それぞれがほぼ等量を受けるような位置関係
で、しかも、前記搬送路の方向に対して、互いに前と後
の位置関係となるように配置されたほぼ同一形状の二つ
の受信コイルをそれぞれ有しており、かつ、前記送信コ
イルへ入力される信号の周波数が互いに異なる複数の検
出ヘッドとを備えて金属検出機を構成している。In order to solve the above problems, the metal detector of the present invention is:
A transport unit that transports the object to be measured for which metal contamination is to be inspected, and a transmission that is close to the transport path of the transport unit and that is in a plane that is substantially parallel to the transport direction of the transport unit and that generates a magnetic field by flowing an electric current. Coil, and, in the substantially same plane as the plane, of the magnetic flux generated by the transmission coil, in a positional relationship such that each receives an approximately equal amount, and further, with respect to the direction of the transport path A plurality of detection heads each having two reception coils of substantially the same shape arranged so as to have a front and rear positional relationship with each other, and having different frequencies of signals input to the transmission coils. And a metal detector.
次に本発明の金属検出機の作用について説明する。 Next, the operation of the metal detector of the present invention will be described.
被測定物に金属が混入していない場合は、二つの受信
コイルが受ける磁束は等しい。このため、二つの受信コ
イルの検出信号を差動増幅器に入力すれば、差動増幅器
の出力電圧はゼロボルトである。When no metal is mixed in the device under test, the magnetic fluxes received by the two receiving coils are equal. Therefore, if the detection signals of the two receiving coils are input to the differential amplifier, the output voltage of the differential amplifier is zero volt.
被測定物に鉄などの磁性金属が混入している場合は、
送信コイルより発生する磁界により、磁性金属が磁化さ
れる。磁性金属の磁化により新たに磁性金属による磁界
が発生し、二つの受信コイルは、送信コイルによる磁界
と磁性金属の磁化による磁界とが合成された磁束を検出
する。二つの受信コイルの信号を差動増幅器に入力する
と、送信コイルによる磁束は相殺され磁性金属による磁
束だけを検出することができる。このとき、差動増幅器
により出力される電圧は、金属の移動に伴って変化し、
移動速度に比例した周波数を有する特徴的な波形とな
る。If a magnetic metal such as iron is mixed in the DUT,
The magnetic metal is magnetized by the magnetic field generated by the transmission coil. A magnetic field is newly generated by the magnetic metal due to the magnetization of the magnetic metal, and the two receiving coils detect a magnetic flux in which the magnetic field of the transmitting coil and the magnetic field of the magnetic metal are combined. When the signals from the two receiving coils are input to the differential amplifier, the magnetic flux due to the transmitting coil is canceled and only the magnetic flux due to the magnetic metal can be detected. At this time, the voltage output by the differential amplifier changes with the movement of the metal,
A characteristic waveform having a frequency proportional to the moving speed is obtained.
被測定物に例えばSUS304ステンレス,SUS316ステンレ
スなどの非磁性体が混入している場合は、送信コイルが
発生する磁界により、混入した非磁性金属に渦電流が流
れる。この渦電流により新たに磁界が発生し、二つの受
信コイルは、送信コイルによる磁界と渦電流による磁界
の合成された磁束を検出する。二つの受信コイルの信号
を差動増幅器に入力すると、送信コイルによる磁束は相
殺され渦電流による磁束だけを検出することができる。
差動増幅器により出力される電圧は、金属の移動に伴っ
て変化し，移動速度に比例した周波数を有する特徴的な
波形となる。When a non-magnetic material such as SUS304 stainless steel or SUS316 stainless steel is mixed in the measured object, an eddy current flows through the mixed nonmagnetic metal due to a magnetic field generated by the transmission coil. A magnetic field is newly generated by the eddy current, and the two receiving coils detect a magnetic flux in which the magnetic field generated by the transmitting coil and the magnetic field generated by the eddy current are combined. When the signals of the two receiving coils are input to the differential amplifier, the magnetic flux due to the transmitting coil is cancelled, and only the magnetic flux due to the eddy current can be detected.
The voltage output by the differential amplifier changes with the movement of the metal and has a characteristic waveform having a frequency proportional to the moving speed.
このような原理による金属検出機において金属は、送
信コイルおよび受信コイルの向き、間隔、配置によら
ず、ただ磁界を発生する送信コイルに近いほど強く磁化
されたり、あるいは強い渦電流を流すことができる。ま
た、金属の磁化、あるいは渦電流による磁界は、検出さ
れる受信コイルに近いほど受信コイルに大きい起電力を
発生させることができる。このような点を考えると、従
来、あたかも送信コイル受信コイル間に距離が必要であ
るごとく考えられていた設計理念は再検討されるべき
で、検出原理に立ち返り数値的検討に基づいた最適コイ
ル形状、構成による設計をすべきことが明らかになる。
発明者等は電磁気理論に基づき数値的な検討を行ない、
送信コイルと受信コイルを同一の平面に構成し、これら
二つのコイル近傍に被測定物を通過させるという最適コ
イル形状、構成を見いだした。詳細な数値計算の結果、
本発明による金属検出機のコイル構成を取ることにより
従来にない高感度な金属検出機を構成することができる
ことが判明した。In a metal detector based on such a principle, regardless of the direction, spacing, and arrangement of the transmission coil and the reception coil, the metal can be strongly magnetized or flow a strong eddy current as it is closer to the transmission coil that generates a magnetic field. it can. In addition, the magnetic field due to the magnetization of the metal or the eddy current can generate a larger electromotive force in the receiving coil as it is closer to the receiving coil to be detected. Considering this point, the design philosophy that had been considered as if the distance between the transmitting coil and the receiving coil was necessary should be reconsidered, and the optimal coil shape based on the numerical principle and returning to the detection principle It becomes clear that a design based on the configuration should be performed.
The inventors conduct numerical studies based on electromagnetic theory,
The optimum coil shape and configuration were found in which the transmission coil and the reception coil were configured on the same plane, and the object to be measured was passed near these two coils. Detailed numerical calculation results,
It has been found that by adopting the coil configuration of the metal detector according to the present invention, it is possible to configure a metal detector with high sensitivity that has never existed before.
第５図に、被測定物の通過する開口部の寸法など条件
を同一にして、対向形、同軸形および本発明の金属検出
機それぞれの感度を、金属の通過高さ（下部のコイルか
ら測った高さ）ｚとの関係から求めた数値計算の一例を
示す。この計算においては、コイルの形状に沿って、コ
イル電流を線積分して空間の任意の点での磁界が求めら
れ、さらにその点に置かれている金属の透磁率あるいは
導電率より、金属の磁気双極子能率とそこから発生する
磁界分布が求められ、さらに、受信コイルの形状の中で
の面積分により受信コイルに誘起される起電力が求めら
れるという原理に基づいて発明者等が独自に導出した理
論式を用いた。図において、金属の通過高さ10mmにおい
て本発明の金属検出機（一面形）は、対向形に比べ約14
倍の、また同軸形に比べても約６倍の起電力がある。通
過高さ60mmにおいても同軸形には約1/3と劣るものの対
向形より約３倍も起電力が大きい。この比較により、対
向形は上部と下部で感度が高く、同軸形は比較的、通過
高さによらず均一な感度を有するのに対し、本発明の一
面形では、コイル近傍で、特に高感度を達成することが
明らかになった。FIG. 5 shows the sensitivity of each of the opposed type, the coaxial type, and the metal detector of the present invention measured under the same conditions such as the size of the opening through which the object passes and the metal passing height (measured from the lower coil). An example of a numerical calculation obtained from the relationship with the height (z) is shown below. In this calculation, the magnetic field at an arbitrary point in space is obtained by linearly integrating the coil current along the shape of the coil, and the magnetic permeability or conductivity of the metal placed at that point is calculated. Based on the principle that the magnetic dipole efficiency and the magnetic field distribution generated therefrom are determined, and the electromotive force induced in the receiving coil is determined by the area in the shape of the receiving coil, the inventors and others have made their own. The derived theoretical formula was used. In the figure, at a metal passing height of 10 mm, the metal detector of the present invention (one-sided) is about 14 times smaller than the opposed type.
There is twice as much electromotive force as that of the coaxial type. Even at a passage height of 60 mm, the coaxial type is inferior to approximately 1/3, but the electromotive force is approximately three times larger than the opposed type. According to this comparison, the opposing type has high sensitivity at the upper and lower parts, and the coaxial type has relatively uniform sensitivity regardless of the passage height, whereas the one-sided type of the present invention has a particularly high sensitivity near the coil. It is clear that this is achieved.
さらに詳しい数値計算の結果の一例として、本発明
と、従来の対向形と同軸形とについて数種類の通過高さ
ｚによる出力信号の時間変化（波形）をそれぞれ第６
図、第７図、第８図に示す。これより、本発明では、従
来形に比べコイル近傍で非常に高感度であることと、そ
の出力は移動速度に比例した周波数を有する特徴ある波
形を示すことがわかった。従って後段の信号処理で帯域
フィルタなどを用いてこの波形を選択的に取り出すこと
によりさらに高感度を達成できる。この結果が示すよう
に、本発明による金属検出機は、検出感度が非常に高い
装置である。As an example of the result of more detailed numerical calculation, the time change (waveform) of the output signal according to the present invention and the conventional opposed type and coaxial type according to several kinds of passing heights z is shown in FIG.
This is shown in FIGS. 7, 7 and 8. From this, it has been found that, in the present invention, the sensitivity is extremely high near the coil as compared with the conventional type, and that the output shows a characteristic waveform having a frequency proportional to the moving speed. Therefore, higher sensitivity can be achieved by selectively extracting this waveform using a band-pass filter or the like in the subsequent signal processing. As the results show, the metal detector according to the present invention is a device with very high detection sensitivity.
さらに、上記の数値検討により、送信コイルと受信コ
イルの間隔が出力信号に大きく影響することが明らかに
なり、送信コイルと受信コイルの相互位置の変化すなわ
ち振動が大きな雑音を発生することがわかった。一方、
本発明では送信コイルと受信コイルの間隔がほぼゼロで
あるので振動による雑音がほとんどない。In addition, the above numerical study revealed that the interval between the transmitting coil and the receiving coil had a large effect on the output signal, and that the change in the mutual position between the transmitting coil and the receiving coil, that is, the vibration generated large noise. . on the other hand,
In the present invention, since the interval between the transmission coil and the reception coil is almost zero, there is almost no noise due to vibration.
ところで、本発明の金属検出機と同様に、ほぼ同一平
面内に送信コイルと受信コイルを配置し、金属の磁化、
あるいは、金属に生じる渦電流を利用した装置に特願昭
59−139737号のような誘導性センサ装置がある。この種
の装置は、金属板や金属管の傷、あるいは、エッジの検
出を目的として発明されたものである。基本的には、受
信コイルに誘起される電圧が測定対象金属からの距離の
関数であるという点を利用しており、測定対象である金
属からの距離を計る距離計の一つである。この種の装置
では、常に測定対象である金属が装置近傍に存在し、そ
の表面のどの場所に突起や凹みがあるかという位置の情
報を知るために使われる。特に、高感度であるコイルの
領域を使うという理由ではなく、コイル間隔を一定に保
つことができ安定性が得られるという理由でコイルを固
定した形状にしている。また、被測定物を搬送する手段
を持ち合わせておらず、搬送手段の搬送速度を積極的に
利用し，搬送速度に比例した周波数を有する特徴的な波
形を出力して、直径1mm以下の微小金属を検出する金属
検出機とは、構成要素は共通な部分もあるものの全く違
う装置であると言える。By the way, similarly to the metal detector of the present invention, the transmission coil and the reception coil are arranged in substantially the same plane, and the magnetization of the metal,
Alternatively, a device using eddy current generated in metal
There is an inductive sensor device such as that of Japanese Patent No. 59-139737. This type of device has been invented for the purpose of detecting scratches or edges of a metal plate or a metal tube. Basically, it is one of the rangefinders that measures the distance from the metal to be measured by utilizing the fact that the voltage induced in the receiving coil is a function of the distance from the metal to be measured. In this type of device, the metal to be measured is always present near the device, and is used to know information on the position of the surface where the protrusion or dent exists. In particular, the coil has a fixed shape not because of using the coil area having high sensitivity but because the coil interval can be kept constant and stability can be obtained. In addition, it does not have a means for transporting the object to be measured, and actively uses the transport speed of the transport means, outputs a characteristic waveform having a frequency proportional to the transport speed, and outputs fine metal with a diameter of 1 mm or less. Can be said to be a completely different device, although there are some common elements in the metal detector.
本発明の一実施例を第１図を用いて説明する。図にお
いて１は、被測定物を搬送する手段であるベルトを示し
ている。ベルト１は、二つのローラ2,3により駆動さ
れ、被測定物４を一定速度で、左から右に搬送してい
る。このベルト１の下方近傍には、磁界を発生する送信
コイル５と、磁束を検出する二つの受信コイル6,7が形
成されている。送信コイルはほぼ長方形の形状をしてお
り、ベルト１の進行方向に長手方向がほぼ垂直になるよ
うに、かつ、ベルト面には平行になるように配置されて
いる。二つの長方形の受信コイル6,7は、送信コイル５
がおかれた面の近傍に、送信コイル５に囲まれた面の面
積を二分し、しかも、ベルト１の進行方向とは垂直であ
る送信コイル５の中心線21を対称軸とする様に設けられ
ている。また、二つの受信コイル6,7のそれぞれの前記
対称軸21側の長辺は、接近し、さらに、送信コイル５に
囲まれるように設けられている。このとき、それぞれ二
つの受信コイル6,7に囲まれた面を二分し、かつベルト
の進行方向には垂直である二つの受信コイル6,7の二つ
の中心線22,23の距離をＰとし、ベルトの速度をＶとす
ると、金属８が混入した被測定物４が通過すると、ほぼ
ｆ＝V/Pで表せる特異な周波数を持つ特徴的な波形の信
号を出力する装置を構成できる。尚、実施例では、対称
軸を持つように受信コイル6,7を配置したが必ずしも対
称軸を持つ必要はない。One embodiment of the present invention will be described with reference to FIG. In FIG. 1, reference numeral 1 denotes a belt as a means for transporting an object to be measured. The belt 1 is driven by two rollers 2 and 3, and conveys the workpiece 4 at a constant speed from left to right. A transmitting coil 5 for generating a magnetic field and two receiving coils 6 and 7 for detecting a magnetic flux are formed near the lower portion of the belt 1. The transmission coil has a substantially rectangular shape, and is disposed so that its longitudinal direction is substantially perpendicular to the traveling direction of the belt 1 and is parallel to the belt surface. The two rectangular receiving coils 6 and 7 are the transmitting coil 5
The area of the surface surrounded by the transmission coil 5 is bisected near the surface on which the transmission coil 5 is placed, and the center line 21 of the transmission coil 5 that is perpendicular to the traveling direction of the belt 1 is provided as a symmetric axis. Have been. The long sides of the two receiving coils 6 and 7 on the side of the symmetric axis 21 are provided so as to approach each other and are further surrounded by the transmitting coil 5. At this time, the distance between the two center lines 22 and 23 of the two receiving coils 6 and 7 that are perpendicular to the traveling direction of the belt is defined as P by dividing the surface surrounded by the two receiving coils 6 and 7 respectively. Assuming that the speed of the belt is V, a device that outputs a signal having a characteristic waveform having a peculiar frequency that can be substantially expressed by f = V / P when the DUT 4 mixed with the metal 8 passes can be configured. In the embodiment, the receiving coils 6 and 7 are arranged so as to have a symmetric axis, but it is not always necessary to have a symmetric axis.
上記実施例では、送信コイル５、受信コイル6,7の長
手方向が共にベルトの進行方向に対してほぼ垂直になる
ように設けたが、被測定物４そのものが検出感度に与え
る影響を低減するためにベルトの進行方向に対して斜め
に送信コイル５、受信コイル6,7を設けてもよい。第９
図にその実施例を示す。ここで、送信コイル５、受信コ
イル6,7の形状が共に長方形である必要はなく、第10図
のように平行四辺形の形状にしてもよい。平行四辺形の
形状の場合、検出ヘッドの搬送方向の長さが長くなるた
め第11図のようにくの字形にすれば搬送方向の長さが短
くて済む。また、二つの受信コイル6,7は、送信コイル
５に囲まれるように設ける必要はなく、第12図のように
受信コイル6,7が送信コイル５の面をはみ出して設けて
もよい。In the above embodiment, the transmission coil 5 and the reception coils 6, 7 are provided so that both longitudinal directions are substantially perpendicular to the traveling direction of the belt, but the influence of the measured object 4 itself on the detection sensitivity is reduced. For this purpose, the transmitting coil 5 and the receiving coils 6, 7 may be provided obliquely to the traveling direction of the belt. Ninth
FIG. Here, the shapes of the transmitting coil 5 and the receiving coils 6, 7 need not be rectangular, but may be parallelograms as shown in FIG. In the case of the shape of a parallelogram, the length of the detection head in the transport direction becomes long. Therefore, if the detection head is formed in a square shape as shown in FIG. 11, the length in the transport direction can be short. The two receiving coils 6, 7 do not need to be provided so as to be surrounded by the transmitting coil 5, and the receiving coils 6, 7 may be provided so as to protrude from the surface of the transmitting coil 5 as shown in FIG.
本発明の金属検出機は、送信コイル５、受信コイル6,
7近傍で検出感度が高いという点に着目すると第13図に
示す実施例も考えられる。被測定物４を搬送するベルト
１を２つのローラ2,3で駆動する。このベルト１により
挟まれる空間に、ベルト面に平行な一つの送信コイル５
と二つの受信コイル6,7をほぼ一面になるように設け
る。２つの受信コイル6,7は、ベルト１の被測定物４を
搬送する面の進行方向に並べてある。The metal detector of the present invention includes a transmitting coil 5, a receiving coil 6,
Focusing on the fact that the detection sensitivity is high near 7, an embodiment shown in FIG. 13 is also conceivable. The belt 1 that conveys the measured object 4 is driven by the two rollers 2 and 3. One transmitting coil 5 parallel to the belt surface is provided in the space sandwiched by the belt 1.
And the two receiving coils 6, 7 are provided so as to be substantially on one surface. The two receiving coils 6 and 7 are arranged in the traveling direction of the surface of the belt 1 that conveys the object 4 to be measured.
第14図は、本発明の金属検出機において振動などによ
り送信コイル５と受信コイル6,7との間隔が変動し雑音
の原因となることを防ぐ為に、送信コイル５と受信コイ
ル6,7を樹脂９により固定した実施例を示している。こ
の実施例では、樹脂９により固定したが、フォトリソグ
ラフィ技術を用い、絶縁板や、プリント基板に直接送信
コイル５と受信コイル6,7を形成することも考えられ
る。FIG. 14 is a view showing a structure of the metal detector of the present invention in order to prevent the distance between the transmitting coil 5 and the receiving coils 6, 7 from fluctuating due to vibration or the like and causing noise. Are fixed by a resin 9. In this embodiment, the transmission coil 5 and the reception coils 6, 7 may be formed directly on an insulating plate or a printed circuit board using a photolithography technique.
次に、本発明の金属検出機の信号処理の一例について
第17図を用いて説明する。Next, an example of signal processing of the metal detector of the present invention will be described with reference to FIG.
送信コイル５には、発信器10より交流信号を加える。
この交流信号により送信コイル５は、交番磁界を発生す
る。送信コイル５近傍におかれた二つの受信コイル6,7
は、送信コイル５により発生する磁界を受け取りそれぞ
れ起電力を発生する。二つの受信コイル6,7の起電力は
差動増幅器11に入力される。通常この差動増幅器11より
出力される電圧は、ゼロボルトに調整される。ここで、
金属８の混入した被測定物４が、送信コイル５および受
信コイル6,7の近傍に現われると、金属８の大きさとそ
の位置に応じた信号が差動増幅器11より出力される。差
動増幅器11より出力された信号は、送信コイル５に加え
た信号を用いて検波回路12で同期検波し、さらに移動速
度に比例した周波数の信号を取り出すための帯域フィル
タ13に入力する。この信号は、最後に表示器14に伝達さ
れる。An AC signal is applied to the transmission coil 5 from the transmitter 10.
The transmission coil 5 generates an alternating magnetic field by this AC signal. Two receiving coils 6, 7 placed near the transmitting coil 5
Receives the magnetic field generated by the transmission coil 5 and generates an electromotive force. The electromotive force of the two receiving coils 6, 7 is input to the differential amplifier 11. Usually, the voltage output from the differential amplifier 11 is adjusted to zero volt. here,
When the DUT 4 mixed with the metal 8 appears near the transmission coil 5 and the reception coils 6 and 7, a signal corresponding to the size and the position of the metal 8 is output from the differential amplifier 11. The signal output from the differential amplifier 11 is synchronously detected by a detection circuit 12 using the signal applied to the transmission coil 5, and further input to a bandpass filter 13 for extracting a signal having a frequency proportional to the moving speed. This signal is finally transmitted to the display 14.
実施例では交流を送信する場合について述べた。直流
でも同じ原理で検出可能である。In the embodiment, the case where the exchange is transmitted has been described. DC can be detected by the same principle.
本発明の金属検出機はコイル近傍で検出感度が高いと
いう点に着目すると、搬送手段であるベルト近傍に送信
コイルおよび受信コイルを配置せずに、検出感度を持た
せたい任意の場所に置くという使い方も考えられる。例
えば、第15図に示すように、ビンの栓の有無を調べるた
めに、搬送手段であるベルト近傍ではなく、検出ヘッド
をビンの口の近傍に置くといった使い方である。Paying attention to the fact that the metal detector of the present invention has high detection sensitivity near the coil, it is not necessary to arrange the transmission coil and the reception coil near the belt as the conveying means, but to place it at an arbitrary place where the detection sensitivity is desired. How to use is also conceivable. For example, as shown in FIG. 15, a method is used in which the detection head is placed near the mouth of the bottle, not near the belt as the transport means, in order to check for the presence or absence of the stopper of the bottle.
さらに、送信コイルと受信コイルより成る検出ヘッド
を複数配置し、検出する領域を分担させ、より一層の感
度の向上を達成することも可能である。この場合、磁気
ヘッドの相互干渉を防ぐため検出ヘッドごとに異なる周
波数の信号を送信コイルに入力する。第16図にその一例
を示す。第16図では４組の検出ヘッドを搬送方向に少し
ずつずらしているが，ずらさずに搬送路を囲むようにし
ても良い。Furthermore, it is possible to arrange a plurality of detection heads each including a transmission coil and a reception coil, share the detection area, and achieve further improvement in sensitivity. In this case, a signal of a different frequency is input to the transmission coil for each detection head in order to prevent mutual interference of the magnetic heads. Fig. 16 shows an example. In FIG. 16, the four sets of detection heads are slightly shifted in the transport direction, but the transport path may be surrounded without being shifted.
また、交流の周波数を変えて、いろいろな種類の信号
を取り出すことができるから、とくに、センサとなる送
信コイルと受信コイルの組の数を複数とすることによっ
て、金属の混入の位置とか、金属の大きさなどの情報を
得ることもできるようになる。In addition, since various types of signals can be extracted by changing the frequency of the alternating current, in particular, by setting the number of pairs of the transmitting coil and the receiving coil as a sensor to be plural, it is possible to determine the position of mixing of the metal or the metal. It will also be possible to obtain information such as the size of the object.
これまでの説明では，搬送手段は，例えばベルト上に
ある被測定物をのせて移動するが，送信コイルおよび受
信コイルは固定された位置に置いて考えてきた。しか
し，この発明の原理に従えば，搬送手段に沿って送信コ
イルおよび受信コイルを移動させることによっても検出
が可能である。In the description so far, the transporting means moves, for example, with an object to be measured placed on a belt, but the transmitting coil and the receiving coil are placed at fixed positions. However, according to the principle of the present invention, the detection can also be performed by moving the transmitting coil and the receiving coil along the transporting means.
このように、本発明の要旨を変更しない範囲での多く
の利用が考えられる。As described above, many uses are possible without changing the gist of the present invention.
以上説明したごとく本発明によれば、送信コイルと受
信コイルを，一つの送信コイルが作り出す磁束と二つの
受信コイルがそれぞれ受ける磁束との関係が最適になる
ように配置した検出ヘッドを複数備え、各送信コイルへ
入力される信号の周波数が互いに異なるようにしたた
め、検出ヘッド間の相互干渉が無く，従来にない検出感
度の高い金属検出機を実現できる。また、受信コイルと
送信コイルを一体化することが容易に行なえ、二つのコ
イルの間隔の変動を軽減できるため、安定性の良い金属
検出機を提供できる。As described above, according to the present invention, a plurality of detection heads are provided, in which the transmission coil and the reception coil are arranged so that the relationship between the magnetic flux generated by one transmission coil and the magnetic flux respectively received by the two reception coils is optimized. Since the frequencies of the signals input to the respective transmission coils are different from each other, there is no mutual interference between the detection heads, and it is possible to realize a metal detector with high detection sensitivity, which has not been achieved in the past. In addition, since the receiving coil and the transmitting coil can be easily integrated, and the fluctuation in the interval between the two coils can be reduced, a metal detector with good stability can be provided.
第１図は本発明による金属検出機の一実施例の概略説明
図、第２図は従来技術である対向形の概略説明図、第３
図は従来技術である同軸形の概略説明図、第４図は従来
技術であるＴ形の概略説明図、第５図は本発明の金属検
出機の検出感度と従来の金属検出機の検出感度を発明者
等が導出した理論式を用いて計算した計算値により比較
した図、第６図は発明者等が導出した理論式を用いて計
算した本発明の金属検出機の出力波形を示す図、第７図
は発明者等が導出した理論式を用いて計算した対向形の
出力波形を示す図、第８図は発明者等が導出した理論式
を用いて計算した同軸形の出力波形を示す図、第９図は
第１図において送信コイルと受信コイルに搬送方向に対
して傾きを持たせた実施例の概略説明図、第10図、第11
図および第12図は第１図において送信コイルと受信コイ
ルの形状を変えた実施例の概略説明図、第13図は第１図
において送信コイルと受信コイルの搬送手段への取付け
位置を変えた実施例の概略説明図、第14図は本発明によ
る金属検出機の送信コイルと受信コイルを固定する一実
施例を示す図、第15図はビンの栓の有無を検査する実施
例の概略説明図、第16図は本発明の金属検出機において
検出ヘッドを複数配置した実施例の概略説明図、第17図
は本発明による金属検出機の信号処理の一実施例を示す
図である。 １……搬送手段としてのベルト、 ２、３……ローラ、４……被測定物、 ５……送信コイル、６、７……受信コイル、 ８……金属、９……樹脂、 10……発信器、11……差動増幅器、 12……検波回路、13……帯域フィルタ、 14……表示器。FIG. 1 is a schematic explanatory view of an embodiment of a metal detector according to the present invention, FIG. 2 is a schematic explanatory view of a conventional opposed type, and FIG.
FIG. 4 is a schematic explanatory view of a conventional coaxial type, FIG. 4 is a schematic explanatory view of a conventional T type, and FIG. 5 is a detection sensitivity of the metal detector of the present invention and a detection sensitivity of the conventional metal detector. Fig. 6 is a diagram comparing the calculated values calculated using the theoretical formulas derived by the inventors, and Fig. 6 is a diagram showing the output waveform of the metal detector of the present invention calculated using the theoretical formulas derived by the inventors. FIG. 7 is a diagram showing the output waveform of the opposed type calculated using the theoretical formula derived by the inventors, and FIG. 8 is a diagram showing the output waveform of the coaxial type calculated using the theoretical formula derived by the inventors. FIG. 9 is a schematic explanatory view of an embodiment in which the transmitting coil and the receiving coil in FIG. 1 are inclined with respect to the transport direction, FIG. 10, FIG.
FIG. 12 and FIG. 12 are schematic explanatory views of an embodiment in which the shapes of the transmitting coil and the receiving coil are changed in FIG. 1, and FIG. 13 is a diagram in which the mounting position of the transmitting coil and the receiving coil to the conveying means is changed in FIG. FIG. 14 is a schematic view of an embodiment, FIG. 14 is a view showing one embodiment for fixing a transmission coil and a reception coil of a metal detector according to the present invention, and FIG. 15 is a schematic description of an embodiment for inspecting the presence or absence of a stopper of a bottle. FIG. 16 is a schematic explanatory view of an embodiment in which a plurality of detection heads are arranged in the metal detector of the present invention, and FIG. 17 is a diagram showing an embodiment of signal processing of the metal detector according to the present invention. 1 ... belt as a conveying means 2, 3 ... roller, 4 ... DUT, 5 ... transmission coil, 6, 7 ... reception coil, 8 ... metal, 9 ... resin, 10 ... Transmitter, 11: Differential amplifier, 12: Detection circuit, 13: Bandpass filter, 14: Display.
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平２−157682（ＪＰ，Ａ) 特開 平２−173591（ＪＰ，Ａ) 特開 昭60−253892（ＪＰ，Ａ) 特開 昭63−9883（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) G01V 3/10 G01N 27/72 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-157682 (JP, A) JP-A-2-1733591 (JP, A) JP-A-60-253892 (JP, A) JP-A-63-1988 9883 (JP, A) (58) Field surveyed (Int. Cl. 7 , DB name) G01V 3/10 G01N 27/72
Claims (1)
の方向とほぼ平行な平面内に配置された一つの送信コイ
ル（５）、および、前記平面と実質的に同一平面内にあ
って、前記送信コイルが発生する磁束のうちから、それ
ぞれがほぼ等量を受けるような位置関係で、かつ前記搬
送路の方向に対して、互いに前と後の位置関係となるよ
うに配置されたほぼ同一形状の二つの受信コイル（6,
7）をそれぞれ有しており、かつ、前記送信コイルへ入
力される信号の周波数が互いに異なる複数の検出ヘッド
とを含み、被測定物に含まれる金属を検出する金属検出
機。1. A transport means (1) for transporting an object to be measured, and one transmitting coil disposed near a transport path of the transport means and disposed in a plane substantially parallel to the direction of the transport path. (5) And, in a position substantially in the same plane as the plane, and in a positional relationship such that each of the magnetic fluxes generated by the transmission coil receives substantially the same amount, and in the direction of the transport path. On the other hand, two reception coils (6,
7. A metal detector for detecting a metal contained in an object to be measured, comprising: a plurality of detection heads each having 7) and having different frequencies of signals input to the transmission coil.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23761590A JP3041026B2 (en) | 1990-09-07 | 1990-09-07 | Metal detector |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23761590A JP3041026B2 (en) | 1990-09-07 | 1990-09-07 | Metal detector |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH04116493A JPH04116493A (en) | 1992-04-16 |
| JP3041026B2 true JP3041026B2 (en) | 2000-05-15 |
Family
ID=17017946
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP23761590A Expired - Lifetime JP3041026B2 (en) | 1990-09-07 | 1990-09-07 | Metal detector |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3041026B2 (en) |
Cited By (2)
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| JP2553453B2 (en) * | 1993-01-21 | 1996-11-13 | ニッカ電測株式会社 | Metal removal equipment |
| JP4511086B2 (en) * | 2001-09-14 | 2010-07-28 | アンリツ産機システム株式会社 | Metal detector |
| CN1306267C (en) | 2001-09-21 | 2007-03-21 | 德克工程株式会社 | Metal foreign matter detecting method and its device |
| JP2008039394A (en) * | 2004-11-29 | 2008-02-21 | Univ Nihon | Electromagnetic-induction sensor for metal detector |
| GB2441346B (en) * | 2006-09-01 | 2011-04-13 | Qinetiq Ltd | Metal object detecting apparatus |
| JP5069162B2 (en) * | 2008-03-28 | 2012-11-07 | アンリツ産機システム株式会社 | Metal detector |
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1990
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101865954A (en) * | 2010-06-21 | 2010-10-20 | 天津大学 | Device and method for measuring dangerous goods in envelops based on capacitance sensor |
| CN101865954B (en) * | 2010-06-21 | 2012-11-14 | 天津大学 | Device and method for measuring dangerous goods in envelops based on capacitance sensor |
| KR20210024692A (en) * | 2019-07-19 | 2021-03-08 | (주)나우시스템즈 | Metallic foreign components detecting apparatus and metallic foreign components detecting method |
| KR102233822B1 (en) | 2019-07-19 | 2021-03-30 | (주)나우시스템즈 | Metallic foreign components detecting apparatus and metallic foreign components detecting method |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04116493A (en) | 1992-04-16 |
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