JPH07198860A - Metal detector - Google Patents

Abstract

PURPOSE:To provide a metal detector wherein trace metal in an object to be inspected can be detected highly sensitively. CONSTITUTION:An electromagnetic generation source 2 generates an alternating field by means of an oscillation signal generated in an oscillator 1. A pair of receiving coils used as an electronagnetic sensor 3 receive an electromagnetic reaction of an object to be inspected W applied by the alternating field and a signal received by a phase detection means 4 is phase-detected. A phase operation means 154 calculates a phase from a detection result. The object to be inspectep W comes in the receiving coils and a trigger production means 153 outputs a trigger signal at the start and the end of passing a specified interval. A phase fluctuation quantity detection means 5 detects a quantity of phase fluctuation for showing a quantity of time fluctuation of a phase during a period when the object to be inspected W passes the interval. A judgement means 6 judges whether metal is mixed in the object to be inspected W from the size of the quantity of the phase fluctuation.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【産業上の利用分野】本発明は、食品、薬品を含む各種
の生活関連物資や、加工用原料などの被検査体中に混入
した金属片を検出する金属検出機に関るものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal detector for detecting various metal-related substances including foods and medicines, and metal fragments mixed in an object to be inspected such as raw materials for processing.

【０００２】[0002]

【従来の技術】ハム、味噌、菓子などの食品、あるいは
薬品、あるいはゴム、ビニール、ペイントなどの加工材
料などに金属異物が混入している場合、衛生上の大きな
問題となったり、製造機械に損傷を与えるおそれがある
ため、安全面、衛生面が重視される各種生活関連物資の
製造、商取引の現場では金属検出機が頻繁に用いられ
る。この種の金属検出機として、同一出願人による特開
平５−１０００４７（その基本構造を図１０に示す）の
ように、発振器１と、送信コイルと２、受信コイル３
と、第１の検波回路１２３と、第２の検波回路１２６
と、位相差算出手段１３２と、判定手段６とを備えてな
る金属検出機がある。2. Description of the Related Art When foreign substances such as ham, miso, and confectionery, chemicals, or processed materials such as rubber, vinyl, and paint are mixed with metal foreign matter, it causes a great hygiene problem and may cause a problem in manufacturing machines. Metal detectors are frequently used in the fields of manufacturing and commerce of various life-related goods where safety and hygiene are important because they may cause damage. As a metal detector of this type, as disclosed in Japanese Patent Application Laid-Open No. 5-100047 (the basic structure of which is shown in FIG. 10) by the same applicant, an oscillator 1, a transmitting coil and a receiving coil 3 are provided.
And a first detection circuit 123 and a second detection circuit 126.
There is a metal detector including the phase difference calculation means 132 and the determination means 6.

【０００３】この従来技術の金属検出機では、食品など
被検査体を搬送ベルトに載せるなどして、送信コイルで
発生させた交番磁界中を通過させる。このとき受信コイ
ルで受信される交流信号を用いて被検査体に金属片が混
入しているか否かを判定する。この金属検出機は、受信
コイルを２つ用いて両者を差動接続する構成で、被検査
体が何も到来しないときには搬送波の出力が相殺されて
ゼロになるよう工夫されている。ただし、被検査体自身
の影響と金属の検出信号が、ともに受信コイルに受信さ
れてしまうので、受信される交流信号の位相の中で、被
検査体影響の位相点と金属検出信号の位相点の違いに着
目して両者を区別している。被検査体影響が最も少ない
位相点は、その種別により異なるので、この従来技術の
金属検出機では、測定に先立つ初期条件設定が必要とな
る。すなわち、金属片を含まない被検査体を通過させ
て、その信号から位相差算出手段を用いて、被検査体自
身の影響が最も少ない検波位相を算出している。初期条
件設定後の実際の測定では、この位相点で位相検波する
ため、高感度で微小な金属を検出することができる。In this prior art metal detector, an object to be inspected such as food is placed on a conveyor belt and passed through an alternating magnetic field generated by a transmission coil. At this time, it is determined whether or not a metal piece is mixed in the inspected object by using the AC signal received by the receiving coil. This metal detector has a structure in which two receiving coils are differentially connected to each other, and is devised so that the output of the carrier wave is canceled and becomes zero when no inspection object arrives. However, since both the influence of the inspected object and the metal detection signal are received by the receiving coil, the phase point of the inspected object influence and the phase point of the metal detection signal are included in the phase of the received AC signal. The two are distinguished by focusing on the difference. Since the phase point having the least influence on the object to be inspected differs depending on its type, the metal detector of the conventional art requires initial condition setting prior to measurement. That is, an inspection object which does not include a metal piece is passed through, and the phase difference calculation means is used from the signal to calculate the detection phase that is least affected by the inspection object itself. In the actual measurement after setting the initial conditions, the phase detection is performed at this phase point, so that it is possible to detect a minute metal with high sensitivity.

【０００４】[0004]

【発明が解決しようとする課題】図１０に示す従来技術
の金属検出機は、雑音たる被検査体の影響に埋もれた、
信号たる金属の検出信号を取り出すために、被検査体の
影響が小さくなるある特定の位相を基準に受信信号を検
波していた。この装置には、前記の特定の位相を自動的
に決定する機能があり、わずらわしい初期条件設定作業
を容易なものとしていた。また、まだ公知とはなってい
ないが、同一出願人による特願平４−３３７９７５号の
ように、記憶手段を備えてなり被検査体の位相を記憶し
て、初期条件設定作業をさらに容易にしたものがある。The prior art metal detector shown in FIG. 10 is buried in the influence of a noisy object to be inspected.
In order to extract the detection signal of the metal that is the signal, the received signal is detected with reference to a certain specific phase in which the influence of the inspection object is small. This device has a function of automatically determining the above-mentioned specific phase, which facilitates troublesome initial condition setting work. Although not yet known, as in Japanese Patent Application No. 4-337975 filed by the same applicant, a storage means is provided to store the phase of the object to be inspected, thereby facilitating the initial condition setting work. There is something I did.

【０００５】これらの金属検出機によればかなり小さな
金属を検出することができるが、被検査体の影響をある
限界以下に低減することは困難であり、高感度に微小金
属を検出することはできなかった。本発明の目的は、以
上に述べたような問題を解決し、高感度に微小金属を検
出できる金属検出機を提供することである。These metal detectors can detect a considerably small metal, but it is difficult to reduce the influence of the object to be inspected to a certain limit or less, and it is difficult to detect a minute metal with high sensitivity. could not. An object of the present invention is to solve the above-mentioned problems and to provide a metal detector capable of detecting minute metals with high sensitivity.

【０００６】[0006]

【課題を解決するための手段】これまで述べたように、
従来技術では被検査体の影響が小さくなるある特定の位
相に着目していた。しかるに、後述するように発明者ら
の実験によれば、実際には被検査体の位相は固定したも
のではない。被検査体が金属検出機に到来し、通過する
に従って、被検査体の位相が変動するのである。だから
従来技術では被検査体の影響を完全には除去できず、微
小な金属が検出できなかったのである。そこで、本発明
の金属検出器は、位相の時間的変動を捉えるねらいで、
位相変動量検出手段、わずかに異なる複数の位相で広範
囲に位相検波する位相検波手段、あるいは位相を追尾す
るための追尾信号発生手段を備えてなり、高感度に微小
金属を検出できるのである。[Means for Solving the Problems] As described above,
In the prior art, attention was paid to a specific phase in which the influence of the inspection object is small. However, as will be described later, according to the experiments by the inventors, the phase of the object to be inspected is not actually fixed. The phase of the inspected object changes as the inspected object arrives at the metal detector and passes by. Therefore, the conventional technique cannot completely remove the influence of the object to be inspected and cannot detect the minute metal. Therefore, the metal detector of the present invention aims to capture the temporal variation of the phase,
The phase fluctuation amount detecting means, the phase detecting means for detecting the phase in a wide range with a plurality of slightly different phases, or the tracking signal generating means for tracking the phase is provided, and the minute metal can be detected with high sensitivity.

【０００７】請求項１に記載の金属検出機は、位相変動
量検知手段を備えてなり、時間的に変動する被検査体の
位相の変動量を検知して、変動量の大きさから、高感度
に微小金属を検出することとした。すなわち、前記の目
的を達成するために、請求項１に記載の金属検出機（図
１）は、発振器１と；該発振器の発振信号を受領して交
番磁界を発生する電磁気発生源２と；該交番磁界を印加
された被測定物の電磁気的反応を受信して、誘起される
受信信号を出力する電磁気センサ３と；前記受信信号を
位相検波する位相検波手段４と；該位相検波手段の検波
結果を受領して、前記受信信号の位相の時間的な変動量
を表す位相変動量を検知する位相変動量検知手段５と；
該位相変動量の大きさから、前記被測定物に金属が混入
しているか否かを判定する判定手段６とを備えている。A metal detector according to a first aspect of the present invention comprises a phase fluctuation amount detecting means, detects a phase fluctuation amount of the object to be inspected which fluctuates with time, and detects a high value from the magnitude of the fluctuation amount. It was decided to detect minute metals with high sensitivity. That is, to achieve the above object, the metal detector according to claim 1 (FIG. 1) is an oscillator 1; and an electromagnetic generation source 2 that receives an oscillation signal of the oscillator and generates an alternating magnetic field; An electromagnetic sensor 3 for receiving an electromagnetic response of an object to be measured to which the alternating magnetic field is applied and outputting a induced reception signal; a phase detection means 4 for phase-detecting the reception signal; and a phase detection means of the phase detection means. Phase fluctuation amount detection means 5 for receiving a detection result and detecting a phase fluctuation amount representing a temporal fluctuation amount of the phase of the received signal;
The determination means 6 determines whether or not a metal is mixed in the object to be measured based on the magnitude of the phase fluctuation amount.

【０００８】請求項２に記載の金属検出機は、わずかに
異なる複数の位相で位相検波する位相検波手段を備えて
なり、時間的に変動する被検査体の位相の変動を複数位
相を用い広範囲に捉えて、高感度に微小金属を検出する
こととした。すなわち、前記目的を達成するために、請
求項２に記載の金属検出機（図２）は、発振器１と；該
発振器の発振信号を受領して交番磁界を発生する電磁気
発生源２と；該交番磁界を印加された被測定物の電磁気
的反応を受信して、誘起される受信信号を出力する電磁
気センサ３と；わずかに異なる複数の位相を用いて、前
記受信信号を位相検波して、それぞれの位相に対応した
複数の位相検波結果を出力する複数の位相検波ユニット
７からなる位相検波手段４と；該複数の位相検波結果か
ら、前記被測定物に金属が混入しているか否かを判定す
る判定手段６とを備えている。A metal detector according to a second aspect of the present invention comprises a phase detection means for phase-detecting a plurality of phases which are slightly different from each other, and uses a plurality of phases for a time-dependent fluctuation of the phase of the object to be inspected. Therefore, we decided to detect minute metal with high sensitivity. That is, in order to achieve the above object, the metal detector according to claim 2 (FIG. 2) is an oscillator 1; an electromagnetic generation source 2 that receives an oscillation signal of the oscillator and generates an alternating magnetic field; An electromagnetic sensor 3 that receives an electromagnetic reaction of an object to be measured to which an alternating magnetic field is applied and outputs an induced reception signal; phase-detects the reception signal using a plurality of slightly different phases; Phase detection means 4 comprising a plurality of phase detection units 7 for outputting a plurality of phase detection results corresponding to respective phases; and whether or not metal is mixed in the DUT from the plurality of phase detection results. The determination means 6 for determining is provided.

【０００９】請求項３に記載の金属検出機は、追尾信号
発生手段を備えてなり、時間的に変動する被検査体の位
相を連続的に追尾して、常に被検査体の影響の小さい状
態で金属の検出信号を取ることとした。すなわち、前記
の目的を達成するために、請求項３に記載の金属検出機
（図３）は、発振器１と；該発振器の発振信号を受領し
て交番磁界を発生する電磁気発生源２と；該交番磁界を
印加された被測定物の電磁気的反応を受信して、誘起さ
れる受信信号を出力する電磁気センサ３と；前記被測定
物に金属が混入していないときの、該受信信号の位相の
時間的な変動を再現する追尾信号を、発生する追尾信号
発生手段８と；該追尾信号に基づいて時間的に変動する
基準位相を用いて、前記受信信号を位相検波する位相検
波手段４と；該位相検波手段の検波結果から、前記被測
定物に金属が混入しているか否かを判定する判定手段６
とを備えている。A metal detector according to a third aspect of the present invention comprises a tracking signal generating means for continuously tracking the phase of the object to be inspected which fluctuates with time so that the effect of the object to be inspected is always small. I decided to get the metal detection signal. That is, in order to achieve the above object, the metal detector according to claim 3 (Fig. 3) is an oscillator 1; an electromagnetic generation source 2 that receives an oscillation signal of the oscillator and generates an alternating magnetic field; An electromagnetic sensor 3 for receiving an electromagnetic reaction of an object to be measured to which the alternating magnetic field is applied and outputting an induced reception signal; a signal of the received signal when a metal is not mixed in the object to be measured. Tracking signal generating means 8 for generating a tracking signal that reproduces the temporal fluctuation of the phase; and phase detection means 4 for phase-detecting the received signal using a reference phase that temporally changes based on the tracking signal. And a judging means 6 for judging whether or not metal is mixed in the object to be measured from the detection result of the phase detecting means.
It has and.

【００１０】[0010]

【作用】次に、本発明の金属検出機の作用について説明
する。図４は、発明者らが本発明の金属検出機を用いて
実験により捉えた被検査体の食品の位相変動を示す図で
ある。食品に金属片は混入していない。実験に用いた金
属検出機は受信コイルを２つ用いて両者を差動接続する
構成で、被検査体が何も到来しないときには搬送波の出
力が相殺されてゼロになるよう工夫されている。図中、
（ａ）、（ｂ）、（ｃ）は、食品が金属検出機の第１受
信コイルに到来して順次通過する３つの位置ａ、ｂ、ｃ
での、（ｄ）、（ｅ）、（ｆ）は、食品がさらに第２受
信コイルに到来して順次通過する３つの位置ｄ、ｅ、ｆ
での受信信号を示している。横軸に検波位相を３６０度
にわたり示し、縦軸に検波出力の電圧の絶対値を示して
いる。なお、移相の変動は誇張して分かりやすく描いて
いる。従来技術の金属検出機では、図の位相範囲の中央
に示す位相点（ここでは０度と呼ぶ）で固定して位相検
波をしていた。その場合、ａからｆまでの各位置で、出
力電圧はあまり大きくない。つまり、検波位相を０度に
固定して測定すれば被検査体自身の影響はかなり低減さ
れている。Next, the operation of the metal detector of the present invention will be described. FIG. 4 is a diagram showing the phase variation of the food of the object to be inspected, which has been experimentally captured by the inventors using the metal detector of the present invention. No metal pieces are mixed in the food. The metal detector used in the experiment has a structure in which two receiving coils are used to differentially connect both of them, and is devised so that the output of the carrier wave is canceled out to zero when no object to be inspected arrives. In the figure,
(A), (b) and (c) are three positions a, b and c at which food comes to the first receiving coil of the metal detector and sequentially passes therethrough.
In (d), (e), and (f), three positions d, e, and f at which food further reaches the second receiving coil and sequentially passes therethrough.
The received signal at is shown. The horizontal axis shows the detection phase over 360 degrees, and the vertical axis shows the absolute value of the voltage of the detection output. The change in phase shift is exaggerated and drawn in an easy-to-understand manner. In the conventional metal detector, the phase detection is performed by fixing at the phase point (referred to as 0 degree here) shown in the center of the phase range in the figure. In that case, the output voltage is not so large at each position from a to f. That is, if the detection phase is fixed at 0 degree and the measurement is performed, the influence of the inspected object itself is considerably reduced.

【００１１】しかし、被検査体の食品の影響がゼロにな
る位相はａからｆまでの各位置で、固定したものではな
く、連続的に変動しているから、ある特定位相を基準に
して位相検波する限り食品影響を完全には除去できず、
微小な金属が検出できなかったのである。そこで、本発
明の金属検出機の主旨は、位相の時間的変動を逆に利用
して位相変動量の大小によって金属を検出したり、位相
変動を複数の位相を用い広範囲に捉えたり、あるいは変
動する位相を連続的に追尾して食品影響を完全に除去し
たりすることによって微小な金属片を検出することであ
る。However, the phase at which the influence of the food on the object to be inspected is zero is not fixed at each position from a to f but continuously fluctuates, so that the phase is based on a certain specific phase. As long as it is detected, food effects cannot be completely removed,
The minute metal could not be detected. Therefore, the purpose of the metal detector of the present invention is to detect the metal by the magnitude of the amount of phase fluctuation by utilizing the temporal fluctuation of the phase in reverse, to detect the phase fluctuation in a wide range using a plurality of phases, or to fluctuate. It is to detect minute metal pieces by continuously tracking the phase to be removed to completely remove the influence of food.

【００１２】食品の位相変動現象を、さらに詳しく解明
するねらいで、発明者らは食品の向きを斜めや横向きに
して実験をした。図５（ア）、（イ）、（ウ）にそれぞ
れ示すように、食品を正規の向きア、４５度斜め向き
イ、９０度横向きウにして測定した。なお、図５（ア）
に食品が順次通過する６つの位置をａ、ｂ、ｃ、ｄ、
ｅ、ｆで示す。位相変動量の測定結果を図６に示す。横
軸に食品が順次通過する位置を、縦軸に検出信号の出力
電圧が最小となる位相点（図４の谷の位相にあたる）を
規格値で示し、ア、イ、ウの実線に食品の向きの違い
を、一点鎖線エに金属片が混入した食品の測定結果を示
す。なお、図中で破線部分では、出力電圧がゼロボルト
直流となる位置であるから、位相の値は不定値となって
いる。この測定結果から分かるように、食品が金属検出
機を順次通過するにともない、食品の位相は連続的に変
動している。しかも、その変動量は食品の向きによら
ず、ほぼ一定であり、特にｄ位置とｅ位置の間では変動
量はわずかである。一方、金属片が混入した食品の位相
は、金属の検出信号が重畳するために大きく変動し、特
にｄ位置とｅ位置の間では変動量が食品の２倍以上あ
る。[0012] In order to elucidate the phase variation phenomenon of food in more detail, the inventors conducted an experiment with the food oriented obliquely or horizontally. As shown in FIGS. 5 (a), (a), and (c), the food was measured in the normal orientation a, 45 degrees obliquely a, and 90 degrees sideways. In addition, FIG.
The six positions where food sequentially passes through a, b, c, d,
Denote by e and f. The measurement result of the amount of phase fluctuation is shown in FIG. The horizontal axis indicates the position where food sequentially passes, and the vertical axis indicates the phase point at which the output voltage of the detection signal is the minimum (corresponding to the phase of the valley in Fig. 4) with the standard value. The difference in orientation is shown in the dash-dotted line d with the measurement results of the food product in which the metal pieces are mixed. It should be noted that in the broken line portion in the figure, the value of the phase is an indefinite value because it is the position where the output voltage is zero volt DC. As can be seen from this measurement result, the phase of the food continuously changes as the food sequentially passes through the metal detector. Moreover, the variation is almost constant regardless of the orientation of the food, and the variation is particularly small between the d position and the e position. On the other hand, the phase of the food containing the metal pieces fluctuates greatly because the detection signal of the metal is superposed, and in particular, the fluctuation amount between the d position and the e position is twice or more that of the food.

【００１３】従って、この実験結果に着目すれば、位相
の時間的変動を逆に利用して位相変動量の大小によって
金属を検出したり、位相変動を複数の位相を用いて広範
囲に捉えたり、あるいは変動する位相を連続的に追尾し
て食品影響を完全に除去したりすることによって微小な
金属片を検出することが可能となるのである。Therefore, paying attention to the results of this experiment, it is possible to detect the metal by the magnitude of the amount of phase fluctuation by conversely using the temporal fluctuation of the phase, or to detect the phase fluctuation in a wide range by using a plurality of phases. Alternatively, it is possible to detect minute metal fragments by continuously tracking the fluctuating phase and completely removing the food effect.

【００１４】[0014]

【実施例】以下、図７に基づいて本発明の特許請求の範
囲第１項に基づく第１実施例を説明する。本実施例の基
本は、従来技術の実施例（図１０）には無かった位相変
動量検知手段５を備えて被検査体と金属の位相変動量の
違いを捉えることにある。第１実施例では、位相変動量
検知手段の中で出力信号の振幅と位相を演算している。
さらに、作用の説明で述べたように被検査体がちょうど
金属検出機の中央を通過する瞬間に必ず出力信号がゼロ
ボルト直流になり、その直後に、ｄ位置、ｅ位置のよう
に特定位置で被検査体と金属の位相変動量に大きな差が
出るので、その特定位置のみで位相変動量を取るねらい
でトリガ生成手段を備えている。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment according to the first aspect of the present invention will be described below with reference to FIG. The basis of this embodiment is to detect the difference in the amount of phase fluctuation between the object to be inspected and the metal by providing the phase fluctuation amount detecting means 5 which is not present in the embodiment of the prior art (FIG. 10). In the first embodiment, the amplitude and phase of the output signal are calculated in the phase fluctuation amount detecting means.
Furthermore, as described in the explanation of the operation, the output signal always becomes zero volt DC at the moment when the object to be inspected just passes through the center of the metal detector, and immediately after that, at the specific position such as the position d or the position e. Since there is a large difference in the amount of phase fluctuation between the inspection object and the metal, a trigger generating means is provided in order to obtain the amount of phase fluctuation only at that specific position.

【００１５】位相変動量検知手段５は、振幅演算手段１
５１、位相演算手段１５４を具備しておりその出力をＡ
／Ｄ変換器１５２、１５６により、それぞれ振幅のデジ
タル値と位相のデジタル値に変換している。トリガ生成
手段１５３は、振幅のデジタル値が瞬間的にゼロになる
時点を見つけて、位相変動量を調べる特定時間の開始と
終了を知らせるトリガ信号を出力する。マスク手段１５
７はトリガ信号を受領して該特定時間の信号のみを通過
させて他はゼロとなるようマスクする。The phase fluctuation amount detecting means 5 is an amplitude calculating means 1
51, the phase calculation means 154 is provided and the output is A
The A / D converters 152 and 156 convert the amplitude digital value and the phase digital value, respectively. The trigger generation means 153 finds the moment when the digital value of the amplitude instantaneously becomes zero, and outputs a trigger signal that notifies the start and end of a specific time for examining the amount of phase fluctuation. Masking means 15
7 receives the trigger signal, passes only the signal of the specific time, and masks other signals to zero.

【００１６】発振器１が具備する基準信号発生器１０２
は所定周波数の基準パルス信号を出力する。該パルス信
号は移相回路１２０に基準位相を供給するとともに、フ
ィルタ１０３によって正弦波に変換され、電力増幅器１
０４によって増幅される。該正弦波は、励磁電流として
電磁気発生手段２としての送信コイルに入力される。送
信コイルから発生する交番磁界をちょうど等量受ける位
置に、電磁気センサ３としての１対の受信コイルが差動
接続されて配置されている。このため２つの受信コイル
には等しい大きさの誘起電圧が生じ、被検査体が何も到
来しないときには搬送波の出力が相殺されてゼロになる
よう工夫されている。この交番磁界中を、被検査体（ワ
ーク）Ｗがベルトなどで搬送されて到来する。Reference signal generator 102 included in the oscillator 1.
Outputs a reference pulse signal having a predetermined frequency. The pulse signal supplies a reference phase to the phase shift circuit 120 and is converted into a sine wave by the filter 103, and the power amplifier 1
Amplified by 04. The sine wave is input as an exciting current to the transmission coil as the electromagnetic generation means 2. A pair of receiving coils as the electromagnetic sensor 3 are arranged in a differential connection at positions where the alternating magnetic field generated from the transmitting coils is received in exactly the same amount. Therefore, induced voltages of equal magnitude are generated in the two receiving coils, and when the inspection object does not arrive, the output of the carrier wave is canceled to be zero. An object (work) W to be inspected is conveyed by a belt or the like and arrives in the alternating magnetic field.

【００１７】位相検波手段４の移相回路１２０は、互い
に９０度位相が異なる２つの基準位相を、第１の検波回
路１２３と第２の検波回路１２６に供給する。被検査体
や金属の電磁気的な反応は受信コイルから、まず差動増
幅器１０８で増幅され、該第１の検波回路および第２の
検波回路と２つのローパスフィルタ（ＬＰＦ）１２４、
１２７によって、位相検波されて、正弦（ｓｉｎ）と余
弦（ｃｏｓ）の２つの検波信号となる。The phase shift circuit 120 of the phase detection means 4 supplies two reference phases whose phases are different by 90 degrees to the first detection circuit 123 and the second detection circuit 126. The electromagnetic reaction of the object to be inspected or the metal is first amplified by the differential amplifier 108 from the receiving coil, and the first detection circuit and the second detection circuit and the two low pass filters (LPF) 124,
The phase detection is performed by 127 to obtain two detection signals of sine (sin) and cosine (cos).

【００１８】位相変動量検知手段５は、該正弦（ｓｉ
ｎ）と余弦（ｃｏｓ）の２つの信号を受領して、位相変
動量を調べるべき特定時間の間だけ、位相情報をデジタ
ル形式で出力して、他の時間はゼロとなるようマスクす
る。判定手段６は、該位相情報を受領して、該位相があ
らかじめ設定された被検査体の位相変動量より大きいか
小さいかにより、金属片の混入の有無を判定する。The phase fluctuation amount detecting means 5 detects the sine (si
n) and cosine (cos) are received, the phase information is output in digital form only during a specific time when the phase variation amount should be checked, and the other time is masked to be zero. The determination means 6 receives the phase information and determines whether or not the metal pieces are mixed depending on whether the phase is larger or smaller than the preset phase variation amount of the inspection object.

【００１９】つぎに、図８に基づいて本発明の特許請求
の範囲第２項に基づく第２実施例を説明する。本実施例
の基本は、わずかに異なる複数の位相を用いて、広範囲
に受信信号を検波して、被検査体と金属の位相変動量の
違いを捉えることにある。第２実施例では、位相検波手
段４が複数の位相検波ユニット７（その要部は位相検波
回路１２３、１２６、１６２、１６６）を具備してな
り、並列的に複数位相に基づいて位相検波している。作
用の説明で述べたように被検査体の位相変動量は比較的
小さいので、その小さな変動量にほぼ等しい位相差で複
数の位相検波回路１２３、１２６、１６２、１６６を動
作させると、常に、単一の位相検波回路が被検査体の位
相を捉えている。一方、金属の位相変動量は大きいの
で、混入金属の存在するときにのみ位相検波回路１２
３、１２６、１６２、１６６の他の位相検波回路が信号
を捉えるので、高感度に微小金属を検出することが可能
となる。Next, a second embodiment based on the second claim of the present invention will be described with reference to FIG. The basis of the present embodiment is to detect a received signal in a wide range by using a plurality of slightly different phases to detect the difference in the amount of phase fluctuation between the object to be inspected and the metal. In the second embodiment, the phase detection means 4 is provided with a plurality of phase detection units 7 (the main part of which is the phase detection circuits 123, 126, 162, 166) and performs phase detection based on a plurality of phases in parallel. ing. As described in the explanation of the operation, since the phase fluctuation amount of the object to be inspected is relatively small, when the plurality of phase detection circuits 123, 126, 162, 166 are operated with a phase difference substantially equal to the small fluctuation amount, A single phase detection circuit captures the phase of the DUT. On the other hand, since the phase fluctuation amount of the metal is large, the phase detection circuit 12 can be used only when the mixed metal is present.
Since the other phase detection circuits of 3, 126, 162, 166 capture the signal, it becomes possible to detect the minute metal with high sensitivity.

【００２０】発振器、電磁気発生源、電磁気センサは、
第１実施例と同様である。位相検波手段４は、複数の移
相回路１２０、１２１、１６１、１６５を具備してな
り、わずかに位相差がある複数の基準位相信号が生成さ
れる。受信コイル３の誘起電圧は差動増幅器１０８を介
して第１の検波回路に供給され、前記複数の基準位相信
号の一つを基準として、検波され、ローパスフィルタ
（ＬＰＦ）１２４で濾波され、Ａ／Ｄ変換器１２５でデ
ジタル信号に変換されて、判定手段６に供給される。同
時に、他の複数の検波回路、ローパスフィルタおよびＡ
／Ｄ変換機も並列的にわずかに異なった基準位相によっ
て同様に動作する。判定手段は、複数の広範囲の位相情
報を比較する。金属が無いときは、常に、単一の位相検
波回路が被検査体の位相を捉えているし、一方、混入金
属の存在するときにのみ他の位相検波回路が信号を捉え
るので、高感度に微小金属を検出することが可能とな
る。The oscillator, the electromagnetic source, and the electromagnetic sensor are
This is similar to the first embodiment. The phase detection means 4 includes a plurality of phase shift circuits 120, 121, 161, and 165, and generates a plurality of reference phase signals having a slight phase difference. The induced voltage of the receiving coil 3 is supplied to the first detection circuit via the differential amplifier 108, detected with reference to one of the plurality of reference phase signals, filtered by the low-pass filter (LPF) 124, and A The signal is converted into a digital signal by the / D converter 125 and supplied to the determination means 6. At the same time, other detection circuits, low-pass filters and A
The / D converter operates similarly in parallel with a slightly different reference phase. The determination means compares a plurality of wide range of phase information. When there is no metal, a single phase detection circuit always captures the phase of the object to be inspected, while on the other hand, the other phase detection circuit captures the signal only when mixed metal is present, so high sensitivity is achieved. It becomes possible to detect minute metals.

【００２１】つぎに、図９に基づいて本発明の特許請求
の範囲第３項に基づく第３実施例を説明する。本実施例
の基本は、位相変動を連続的に追尾する追尾信号発生手
段８を備えて、常に被検査体の影響の小さい位相を連続
的に追尾して、被検査体の影響を完全に除去して微小な
金属片を検出することである。Next, a third embodiment according to the third aspect of the present invention will be described with reference to FIG. The basis of this embodiment is that the tracking signal generating means 8 for continuously tracking the phase fluctuation is provided to continuously track the phase having a small influence of the inspection object to completely eliminate the influence of the inspection object. And to detect minute metal pieces.

【００２２】第３実施例では、追尾信号発生手段８の中
に記憶手段１７２を備えており、被検査体に特有な連続
的な位相変動特性の情報を格納している、さらに被検査
体の到来時点を正確に捉えるねらいでトリガ生成手段１
７１を備えている。作用の説明で述べたように被検査体
がちょうど金属検出機の中央を通過する瞬間に必ず出力
信号がゼロボルト直流になるので、振幅情報がゼロにな
った時点の直後から連続的に位相追尾することにより正
確な追尾が可能となる。制御手段１７３がトリガ信号に
よる正確な時間と、あらかじめ記憶格納してある連続的
な位相変動特性に従って追尾信号を生成し、Ｄ／Ａ変換
器１７４により電圧波形に変換されて移相回路１２０に
供給される。該移相回路１２０は、連続的に変化して且
つ常に互いに９０度異なる２つの基準位相信号を生成す
る。そのあとの検波回路の動作は第１、第２実施例と同
様である。In the third embodiment, the tracking signal generating means 8 is provided with a storage means 172 for storing information on the continuous phase fluctuation characteristic peculiar to the object to be inspected. Trigger generation means 1 with the aim of accurately grasping the arrival time
71 is provided. As described in the explanation of the action, the output signal is always zero volt DC at the moment when the DUT passes the center of the metal detector, so the phase is continuously tracked immediately after the time when the amplitude information becomes zero. This enables accurate tracking. The control means 173 generates a tracking signal according to the accurate time by the trigger signal and the continuous phase fluctuation characteristic stored and stored in advance, converted into a voltage waveform by the D / A converter 174 and supplied to the phase shift circuit 120. To be done. The phase shift circuit 120 generates two reference phase signals that continuously change and always differ from each other by 90 degrees. The subsequent operation of the detection circuit is the same as in the first and second embodiments.

【００２３】この実施例によれば、時間的に変動する被
検査体の位相を連続的に追尾して、常に被検査体の影響
の小さい状態で金属の検出信号を取ることができる。影
響の小さい位相の変動特性は被検査体の種別により異な
るので、初期条件設定作業として測定し記憶格納する必
要がある。初期条件設定作業の後の実際の測定では、金
属の混入していない被検査体の検出信号の電圧は極めて
小く、一方、金属混入の被検査体の検出信号の電圧は大
きい。この検出信号は位相情報および前記正弦（ｓｉ
ｎ）の検波信号にあらわれるので、いずれかを判定手段
に供給する。判定手段は、検出信号の電圧の大小を監視
して、従来は除去できなかった被検査体影響を完全に除
去して高感度に微小金属を検出する。According to this embodiment, it is possible to continuously track the time-varying phase of the object to be inspected and always obtain a metal detection signal with a small influence of the object to be inspected. Since the phase variation characteristic with a small influence differs depending on the type of the object to be inspected, it is necessary to measure, store and store it as an initial condition setting operation. In the actual measurement after the initial condition setting work, the voltage of the detection signal of the inspection object in which the metal is not mixed is extremely low, while the voltage of the detection signal of the inspection object in which the metal is mixed is large. This detection signal includes the phase information and the sine (si
Since it appears in the detection signal of n), either one is supplied to the determination means. The determination means monitors the magnitude of the voltage of the detection signal, completely removes the influence of the object to be inspected, which could not be conventionally removed, and detects the minute metal with high sensitivity.

【００２４】これまでに、３つの実施例を述べたが、本
発明の主旨はこれら３つに限定されるものではなく、前
記検波回路としてサンプルホールド回路を用いても良
く、また、前記受信コイルの誘起電圧を直接Ａ／Ｄ変換
した後にデジタル的な処理あるいはソフト的な処理によ
り位相検波、位相変動量検知、追尾信号発生を行っても
なんら差し支えない。あるいはまた、受信コイルは必ず
しも差動接続の１対のコイルでなく非差動コイルの使用
も可能であるし、電磁気センサとして受信コイル以外
に、ホール素子など他のセンサを用いても支障ない。Although three embodiments have been described so far, the gist of the present invention is not limited to these three, and a sample hold circuit may be used as the detection circuit, and the reception coil may be used. There is no problem in performing phase detection, phase fluctuation amount detection, and tracking signal generation by digital processing or software processing after the A / D conversion of the induced voltage is directly performed. Alternatively, the receiving coil need not necessarily be a pair of differentially connected coils but a non-differential coil can be used, and other sensors such as a Hall element may be used as the electromagnetic sensor in addition to the receiving coil.

【００２５】[0025]

【発明の効果】本発明の金属検出機は、位相の時間的変
動を捉えるねらいで、位相追尾手段、位相変動量検出手
段、あるいはわずかに異なる複数の位相で位相検波する
位相検波手段を備えているので、高感度に微小金属を検
出できる。The metal detector of the present invention is provided with a phase tracking means, a phase variation amount detecting means, or a phase detecting means for detecting a phase at a plurality of slightly different phases in order to capture the temporal variation of the phase. Therefore, it is possible to detect minute metal with high sensitivity.

【図面の簡単な説明】[Brief description of drawings]

【図１】請求項１に記載した本発明のブロック図であ
る。FIG. 1 is a block diagram of the present invention described in claim 1.

【図２】請求項２に記載した本発明のブロック図であ
る。FIG. 2 is a block diagram of the present invention described in claim 2.

【図３】請求項３に記載した本発明のブロック図であ
る。FIG. 3 is a block diagram of the present invention described in claim 3.

【図４】被検査体の位相の変動を示す図である。FIG. 4 is a diagram showing changes in the phase of the inspection object.

【図５】実験における被検査体の向きを示す図である。FIG. 5 is a diagram showing the orientation of a test object in an experiment.

【図６】被検査体および金属混入被検査体の位相の変動
の差異を示す図である。FIG. 6 is a diagram showing a difference in phase variation between the inspection object and the metal-containing inspection object.

【図７】本発明の第１実施例を示すブロック図である。FIG. 7 is a block diagram showing a first embodiment of the present invention.

【図８】本発明の第２実施例を示すブロック図である。FIG. 8 is a block diagram showing a second embodiment of the present invention.

【図９】本発明の第３実施例を示すブロック図である。FIG. 9 is a block diagram showing a third embodiment of the present invention.

【図１０】従来技術の金属検出機の装置構成を示すブロ
ック図である。FIG. 10 is a block diagram showing a device configuration of a conventional metal detector.

【符号の説明】[Explanation of symbols]

１ 発振器 ２ 電磁気発生源 ３ 電磁気センサ ４ 位相検波手段 ５ 位相変動量検出手段 ６ 判定手段 ７ 位相検波ユニット ８ 追尾信号発生手段 １０２ 基準信号発生器 １０３ フィルタ １０４ 電力増幅器 １０８ 差動増幅器 １２０ 移相回路 １２３ 第１の検波回路 １２４ ローパスフィルタ １２６ 第２の検波回路 １２７ ローパスフィルタ １５１ 振幅演算手段 １５２ Ａ／Ｄ変換器 １５３ トリガ生成手段 １５４ 位相演算手段 １５６ Ａ／Ｄ変換器 １５７ マスク手段 DESCRIPTION OF SYMBOLS 1 oscillator 2 electromagnetic generation source 3 electromagnetic sensor 4 phase detection means 5 phase fluctuation amount detection means 6 determination means 7 phase detection unit 8 tracking signal generation means 102 reference signal generator 103 filter 104 power amplifier 108 differential amplifier 120 phase shift circuit 123 First detection circuit 124 Low-pass filter 126 Second detection circuit 127 Low-pass filter 151 Amplitude calculation means 152 A / D converter 153 Trigger generation means 154 Phase calculation means 156 A / D converter 157 Mask means

Claims (3)

【特許請求の範囲】[Claims] 【請求項１】発振器（１）と；該発振器の発振信号を受
領して交番磁界を発生する電磁気発生源（２）と；該交
番磁界を印加された被検査体の電磁気的反応を受信し
て、誘起される受信信号を出力する電磁気センサ（３）
と；前記受信信号を位相検波する位相検波手段（４）
と；該位相検波手段の検波結果を受領して、前記受信信
号の位相の時間的な変動量を表す位相変動量を検知する
位相変動量検知手段（５）と；該位相変動量の大きさか
ら、前記被検査体に金属が混入しているか否かを判定す
る判定手段（６）とを備えたことを特徴とする金属検出
機。1. An oscillator (1); an electromagnetic generation source (2) which receives an oscillation signal of the oscillator and generates an alternating magnetic field; and receives an electromagnetic reaction of an object to be inspected to which the alternating magnetic field is applied. Electromagnetic sensor (3) that outputs the induced reception signal
And; phase detecting means (4) for phase detecting the received signal
A phase fluctuation amount detecting means (5) for receiving a detection result of the phase detecting means and detecting a phase fluctuation amount representing a temporal fluctuation amount of the phase of the received signal; and a magnitude of the phase fluctuation amount. From the above, a metal detector comprising: a determination means (6) for determining whether or not a metal is mixed in the inspection object. 【請求項２】発振器（１）と；該発振器の発振信号を受
領して交番磁界を発生する電磁気発生源（２）と；該交
番磁界を印加された被検査体の電磁気的反応を受信し
て、誘起される受信信号を出力する電磁気センサ（３）
と；わずかに異なる複数の位相を用いて、前記受信信号
を位相検波して、それぞれの位相に対応した複数の位相
検波結果を出力する複数の位相検波ユニット（７）を具
備する位相検波手段（４）と；該複数の位相検波結果か
ら、前記被検査体に金属が混入しているか否かを判定す
る判定手段（６）とを備えたことを特徴とする金属検出
機。2. An oscillator (1); an electromagnetic generation source (2) which receives an oscillation signal of the oscillator and generates an alternating magnetic field; and receives an electromagnetic reaction of an object to be inspected to which the alternating magnetic field is applied. Electromagnetic sensor (3) that outputs the induced reception signal
And; phase detection means comprising a plurality of phase detection units (7) for phase-detecting the reception signal using a plurality of slightly different phases and outputting a plurality of phase detection results corresponding to the respective phases ( 4); and a metal detector comprising: a judging means (6) for judging whether or not a metal is mixed in the object to be inspected, based on the plurality of phase detection results. 【請求項３】発振器（１）と；該発振器の発振信号を受
領して交番磁界を発生する電磁気発生源（２）と；該交
番磁界を印加された被検査体の電磁気的反応を受信し
て、誘起される受信信号を出力する電磁気センサ（３）
と；前記被検査体に金属が混入していないときの、該受
信信号の位相の時間的な変動を再現する追尾信号を、発
生する追尾信号発生手段（８）と；該追尾信号に基づい
て時間的に変動する基準位相を用いて、前記受信信号を
位相検波する位相検波手段（４）と；該位相検波手段の
検波結果から、前記被検査体に金属が混入しているか否
かを判定する判定手段（６）とを備えたことを特徴とす
る金属検出機。3. An oscillator (1); an electromagnetic generation source (2) for receiving an oscillation signal of the oscillator and generating an alternating magnetic field; receiving an electromagnetic reaction of an object to be inspected to which the alternating magnetic field is applied. Electromagnetic sensor (3) that outputs the induced reception signal
Tracking signal generating means (8) for generating a tracking signal that reproduces the temporal variation of the phase of the received signal when no metal is mixed in the object to be inspected; and based on the tracking signal Phase detection means (4) for phase-detecting the received signal using a reference phase that fluctuates with time; and it is determined whether or not metal is mixed in the inspected object based on the detection result of the phase detection means. A metal detector comprising: a determination means (6) for