JPH08105860A - Flaw detector for conductor - Google Patents
Flaw detector for conductorInfo
- Publication number
- JPH08105860A JPH08105860A JP6242947A JP24294794A JPH08105860A JP H08105860 A JPH08105860 A JP H08105860A JP 6242947 A JP6242947 A JP 6242947A JP 24294794 A JP24294794 A JP 24294794A JP H08105860 A JPH08105860 A JP H08105860A
- Authority
- JP
- Japan
- Prior art keywords
- exciting
- inspection object
- excitation
- flaw
- magnetic flux
- 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.)
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- Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、例えば棒鋼等の表面疵
の検出に利用しうる導電体の疵検出装置に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flaw detecting device for a conductor which can be used for detecting flaws on the surface of a steel bar or the like.
【０００２】[0002]
【従来の技術】例えば鉄鋼製品について表面疵を検出す
る場合、一般に渦流探傷方法や漏洩磁束探傷方法を用い
て検査が実施される。渦流探傷方法においては、励磁コ
イルで発生した磁界の中に検査対象物を通し、検査対象
物に渦電流を流す。そして、検査対象物の表面疵の有無
に応じて渦電流が変化するので、その変化によって生じ
る磁束を検知コイル等によって検出する。漏洩磁束探傷
方法においては、磁性体である検査対象物を磁化し、検
査対象物の疵によってその外側に漏れる漏洩磁束をセン
サを用いて検出する。2. Description of the Related Art For example, when detecting a surface flaw in a steel product, an inspection is generally carried out using an eddy current flaw detection method or a leakage magnetic flux flaw detection method. In the eddy current flaw detection method, an inspection target is passed through a magnetic field generated by an exciting coil, and an eddy current is passed through the inspection target. Then, since the eddy current changes depending on the presence or absence of the surface flaw of the inspection object, the magnetic flux generated by the change is detected by the detection coil or the like. In the leakage magnetic flux flaw detection method, a magnetic material to be inspected is magnetized, and a magnetic flux leaking to the outside due to a flaw in the inspection object is detected by using a sensor.
【０００３】渦流探傷法は、検出力が良い反面、被検材
の表面状態の磁気的不均一に誘発される疑似不要雑音信
号で妨げられる事が多く、このため一般にコイルを差動
巻にして両コイルの信号の差によって表面疵の検査を行
っている。Although the eddy current flaw detection method has a good detection power, it is often disturbed by a pseudo-unwanted noise signal induced by magnetic nonuniformity of the surface state of the material to be inspected. The surface flaw is inspected by the difference between the signals of both coils.
【０００４】図１５に、最も一般的に使用される自己励
磁方式の貫通型コイルで被検材を検査する様子を示す。
貫通型コイル３の励磁及び疵検知を行うコイル４ａ，４
ｂは各々巻線方向が逆で差動巻となっており、被検材１
にワレ疵２があり被検材１が貫通コイル３を矢印２０方
向に通過する場合、２１に示す疵信号が得られる。貫通
型コイル３によるワレ疵２の検知信号は、ワレ疵２が被
検材１の長手方向にどんなに長くても同様であり、これ
はコイル４ａ，４ｂの信号の差を検知信号としているた
めワレ疵２のフロントでの信号ａとテイルでの信号ｂの
２ケ所でしか信号が発生しない事による。また、検知信
号は、ワレ疵２のフロント及びテイル部の疵形状によっ
ても大きな影響を受け、疵が長手方向で急俊に変化すれ
ば検知信号も高くなるが緩やかであれば検知信号が低く
検出力が低下する等問題があり、貫通型コイル３による
ワレ疵２の検出は、疵深さの大きい疵のみにとどまって
いた。FIG. 15 shows how the most commonly used self-exciting feedthrough coil is used to inspect a material to be inspected.
Coil 4a, 4 for exciting the through-type coil 3 and detecting flaws
In b, the winding directions are opposite to each other and differential winding is performed.
When the crack 2 is present and the test material 1 passes through the penetrating coil 3 in the direction of the arrow 20, a flaw signal 21 is obtained. The detection signal of the crack 2 caused by the penetrating coil 3 is the same regardless of how long the crack 2 is in the longitudinal direction of the material to be inspected 1. This is because the difference between the signals of the coils 4a and 4b is the detection signal. This is because the signal is generated only at two points, the signal a at the front of the defect 2 and the signal b at the tail. The detection signal is also greatly affected by the flaw shapes of the front and tail portions of the crack 2, and the detection signal is high if the flaw changes rapidly in the longitudinal direction, but is low if it is gentle. There is a problem such as a decrease in force, and the detection of the crack 2 by the through-type coil 3 is limited to the flaw having a large flaw depth.
【０００５】この様な貫通型コイルの欠点を解消するた
めに、回転プロ−ブ型が考えられている。これは、図１
６に示す様に、励磁コイルと検知コイルを収納したプロ
−ブ５を矢印１９に示すように被検材１の断面周方向に
回転させて、被検材１のワレ疵２に対して直角に通過さ
せて、図１６に２２として示す様に、プロ−ブ５がワレ
疵横切る毎に疵信号を検知し、ワレ疵に対する検出力の
向上を図るものである。しかし、プロ−ブ５をワレ疵２
に対して何回も横断させるためには、プロ−ブ５を被検
材１の回りで高速回転させねばならず、回転機構が複雑
且つプロ−ブ５の被検材１に対する追従が難しく、また
ワレ疵２が短い場合見逃す危険性も高い等問題も多い。In order to eliminate such a drawback of the through type coil, a rotary probe type is considered. This is
As shown in FIG. 6, the probe 5 accommodating the exciting coil and the detection coil is rotated in the circumferential direction of the cross section of the test material 1 as shown by an arrow 19, and is perpendicular to the crack 2 of the test material 1. When the probe 5 crosses a crack, the flaw signal is detected every time the probe 5 crosses the crack, and the detection power for the crack is improved. However, the probe 5 is cracked 2
On the other hand, in order to traverse many times, the probe 5 must be rotated at high speed around the test material 1, the rotation mechanism is complicated, and it is difficult for the probe 5 to follow the test material 1. In addition, there are many problems such as a high risk of overlooking when the crack 2 is short.
【０００６】この様な問題点を解消するための従来技術
としては、例えば、特開昭６２−６１６２号公報，特開
昭６２−６１６３号公報，特開昭６２−１２３３５２号
公報，特開昭６２−１４５１６２号公報，特開昭６２−
１７２２５８号公報，及び特開昭６２−１７２２５９号
公報が公知である。As a conventional technique for solving such a problem, for example, Japanese Patent Laid-Open Nos. 62-6162, 62-6163, 62-123352, and 62-123352 are disclosed. No. 62-145162, JP-A-62-
Japanese Patent No. 172258 and Japanese Patent Laid-Open No. 62-172259 are known.
【０００７】特開昭６２−６１６２号公報では、励磁コ
イル及び検出コイルでなる検出ユニットを円周方向に多
数設置し、励磁コイルにより検査対象物の円周方向又は
断面方向の磁界を発生するとともに、多数の検出ユニッ
トをスイッチで順次に切換えることによって円周方向の
全体を検査可能にしている。In Japanese Patent Laid-Open No. 62-6162, a large number of detection units each composed of an exciting coil and a detecting coil are installed in the circumferential direction, and the exciting coil generates a magnetic field in the circumferential direction or the cross-sectional direction of an object to be inspected. By sequentially switching a large number of detection units with a switch, the entire circumference can be inspected.
【０００８】また特開昭６２−６１６３号公報および特
開昭６２−１２３３５２号公報では、励磁コイル及び検
出コイルでなる検出ユニットを円周方向に多数設置し、
励磁コイルにより検査対象物の円周方向又は断面方向の
磁界を発生するとともに、三相交流を用いて励磁コイル
を励磁し、スイッチを用いることなく、励磁位置を円周
方向に順次回転させるようにしている。Further, in Japanese Unexamined Patent Publication No. 62-6163 and Japanese Unexamined Patent Publication No. 62-123352, a large number of detection units each including an exciting coil and a detecting coil are installed in the circumferential direction,
The exciting coil generates a magnetic field in the circumferential or cross-sectional direction of the inspection object, and the exciting coil is excited using three-phase alternating current so that the exciting position is sequentially rotated in the circumferential direction without using a switch. ing.
【０００９】また特開昭６２−１４５１６２号公報で
は、円周方向に多数設置された検出ユニットを互いに機
械的に分離し、検出ユニット毎に検査対象物とのギャッ
プを一定に維持するようにしている。Further, in Japanese Laid-Open Patent Publication No. 62-145162, a large number of detection units installed in the circumferential direction are mechanically separated from each other, and a gap between the detection unit and the inspection object is kept constant. There is.
【００１０】特開昭６２−１７２２５８号公報および特
開昭６２−１７２２５９号公報では、検査対象物の円周
方向に順次に回転する磁界を発生するとともに、該円周
方向に多数のセンサを配設し、発生した磁界の回転に同
期して、多数のセンサの出力を順次にサンプリングする
技術を開示している。In Japanese Patent Laid-Open Nos. 62-172258 and 62-172259, a magnetic field that sequentially rotates in the circumferential direction of an inspection object is generated, and a large number of sensors are arranged in the circumferential direction. Disclosed is a technique for sequentially sampling the outputs of a large number of sensors in synchronization with the rotation of the generated magnetic field.
【００１１】[0011]
【発明が解決しようとする課題】これらの技術は、それ
ぞれに利点はあるにしても、以下の共通の欠点を内在し
ている。例えば、特開昭６２−６１６２号では、図１７
に示すような励磁コイルと検出コイルを用いるため、ま
た、特開昭６２−６１６３号及び特開昭６２−１２３３
５２号では図１８に示す励磁コイルを使用するため、更
に特開昭６２−１４５１６２号では図１９に示す励磁コ
イルを使用するために、励磁コイルからの磁束は被検査
材の半径方向に生ずる。これに対して、従来の図１５に
示す貫通型の励磁方式では、被検査材の長手（軸）方向
に磁束を発生させる。Although these techniques have their respective advantages, they have the following common drawbacks. For example, in Japanese Patent Laid-Open No. 62-6162, FIG.
Since an exciting coil and a detecting coil as shown in FIG. 1 are used, and also Japanese Patent Application Laid-Open No. 62-6163 and No. 62-1233.
No. 52 uses the exciting coil shown in FIG. 18, and in JP-A No. 62-145162 uses the exciting coil shown in FIG. 19, the magnetic flux from the exciting coil is generated in the radial direction of the material to be inspected. On the other hand, in the conventional through-type excitation method shown in FIG. 15, magnetic flux is generated in the longitudinal (axial) direction of the material to be inspected.
【００１２】ところで、自動探傷におけるＳ／Ｎ（きず
信号Ｓとベ−スノイズＮとの比率であり、きずの検出し
やすさを表す）は３倍以上必要と一般にいわれている
が、この信号のＳ／Ｎは、検出器と検査対象物のギャッ
プ変動により、検出器と検査対象物のギャップは小さい
程、Ｓ／Ｎは良くなるが、実際の検査工程は、例えば、
検査対象物である棒鋼を高速で搬送しながら検査を行う
ため、通材性との兼ね合いで極端にはギャップを狭くす
ることはできない。By the way, it is generally said that the S / N ratio (the ratio of the flaw signal S and the base noise N, which indicates the easiness of flaw detection) in automatic flaw detection is required to be three times or more. Due to fluctuations in the gap between the detector and the inspection target, the S / N becomes better as the gap between the detector and the inspection target becomes smaller, but the actual inspection process is, for example,
Since the inspection is performed while the steel bar to be inspected is transported at high speed, the gap cannot be extremely narrowed in consideration of the material permeability.
【００１３】また、搬送によって検査対象物は振動する
ので、検出器と被検査材とのギャップは常時変動する。
この際、励磁コイルからの磁束が被検査材の半径方向に
生ずるとギャップ変動により磁束密度が著しく変化する
ため、ベ−スノイズの変動が大きいばかりか、きず信号
の感度変化が極端に起こり、Ｓ／Ｎが著しく悪化する欠
点がある。Further, since the object to be inspected vibrates by the transportation, the gap between the detector and the material to be inspected constantly fluctuates.
At this time, when the magnetic flux from the exciting coil is generated in the radial direction of the material to be inspected, the magnetic flux density is remarkably changed due to the gap change. Therefore, not only the fluctuation of the base noise is large, but also the sensitivity change of the flaw signal occurs extremely. There is a drawback that / N is significantly deteriorated.
【００１４】しかし、図１５に示すように、励磁コイル
からの磁束を被検査材の軸方向に発生させた場合、ギャ
ップ変動による、被検査材の半径方向の磁束密度の変化
は比較的小さくなる利点がある。従って本発明は、前述
のプロ−ブ回転方式に代わって、被検査材の軸方向の磁
束を周方向に回転させながら発生させる事で、検査対象
物の疵に対して得られる信号のＳ／Ｎ比を改善し、疵検
出の信頼性を高めることを課題とする。However, as shown in FIG. 15, when the magnetic flux from the exciting coil is generated in the axial direction of the material to be inspected, the change in the magnetic flux density in the radial direction of the material to be inspected due to the gap variation is relatively small. There are advantages. Therefore, in the present invention, instead of the above-described probe rotation method, the magnetic flux in the axial direction of the material to be inspected is generated while rotating in the circumferential direction, so that the S / An object is to improve the N ratio and increase the reliability of flaw detection.
【００１５】[0015]
【課題を解決するための手段】上記課題を解決するた
め、請求項１の導電体の疵検出装置は、所定の軸方向に
搬送される検査対象物の外周を囲む形である、第１の励
磁手段（４）；前記検査対象物の外周を囲む形であり、
前記第１の励磁手段とは異なる位置に設置された、第２
の励磁手段（５）；前記第１の励磁手段と第２の励磁手
段との間の、前記検査対象物の表面と対向する位置に設
置された磁束検出手段（６，７）；および前記第１の励
磁手段と第２の励磁手段とが発生する磁界が、前記磁束
検出手段の位置にて、前記検査対象物の搬送方向に向い
ていて、かつ、前記検査対象物の円周方向に回転するよ
うに、磁界を発生させる、励磁制御手段（２Ａ，２
Ｂ）；を備える。In order to solve the above-mentioned problems, a flaw detection device for a conductor according to a first aspect of the present invention has a shape surrounding an outer circumference of an inspection object conveyed in a predetermined axial direction. Exciting means (4); a shape surrounding the outer periphery of the inspection object,
A second magnet, which is installed at a position different from that of the first magnetizing means,
Magnetic excitation means (5); magnetic flux detection means (6, 7) installed at a position facing the surface of the inspection object between the first excitation means and the second excitation means; The magnetic fields generated by the first excitation means and the second excitation means are oriented in the conveyance direction of the inspection object at the position of the magnetic flux detection means and rotate in the circumferential direction of the inspection object. So as to generate a magnetic field, the excitation control means (2A, 2
B);
【００１６】また、請求項２の導電体の疵検出装置は、
所定の軸方向に搬送される検査対象物（１）の外周を囲
む形でほぼ環状に配列された複数の励磁コイルを含む、
第１組の励磁手段（４）；前記検査対象物の外周を囲む
形でほぼ環状に配列された複数の励磁コイルを含み、前
記軸方向に対して前記第１組の励磁手段とは異なる位置
に設置された、第２組の励磁手段（５）；前記第１組の
励磁手段及び第２組の励磁手段が発生する磁界を、前記
検査対象物の円周方向に回転するとともに、第１組の励
磁手段と第２組の励磁手段の互いに前記軸方向に対向す
る励磁コイル対に、同一時点で互いに異なる磁極を形成
する、励磁制御手段（２Ａ，２Ｂ）；および前記第１組
の励磁手段と第２組の励磁手段との間の、前記検査対象
物の表面と対向する位置に設置された磁束検出手段
（６，７）；を備える。Further, the flaw detection device for a conductor according to claim 2 is
A plurality of exciting coils arranged in a substantially annular shape so as to surround the outer periphery of the inspection object (1) conveyed in a predetermined axial direction;
A first set of exciting means (4); including a plurality of exciting coils arranged in a substantially annular shape so as to surround the outer periphery of the inspection object, and at a position different from the first set of exciting means in the axial direction; A second set of exciting means (5) installed in the first set of exciting means; a magnetic field generated by the first set of exciting means and the second set of exciting means is rotated in the circumferential direction of the inspection object, and Excitation control means (2A, 2B) for forming different magnetic poles at the same time point on the pair of exciting coils of the pair of exciting means and the pair of exciting means that oppose each other in the axial direction; and the first set of exciting And a magnetic flux detecting means (6, 7) installed at a position facing the surface of the inspection object between the means and the second set of exciting means.
【００１７】また、請求項３においては、前記磁束検出
手段は、各々前記検査対象物の円周方向の一部分と対向
する複数の検出手段を、前記検査対象物を囲む形で環状
に配設してなり、更に前記複数の検出手段のうち互いに
隣接する２つの検出手段が出力する信号の差分を検出す
る差分検知手段（７１）を含む。According to a third aspect of the present invention, the magnetic flux detecting means includes a plurality of detecting means, each of which faces a part of the inspection object in the circumferential direction, and is annularly arranged so as to surround the inspection object. And further includes a difference detection means (71) for detecting a difference between signals output by two detection means adjacent to each other among the plurality of detection means.
【００１８】また、請求項４においては、前記励磁制御
手段は、３相以上の多相交流電源を含む。Further, in the present invention, the excitation control means includes a multi-phase AC power supply having three or more phases.
【００１９】なお上記括弧内に示した記号は、後述する
実施例中の対応する要素の符号を参考までに示したもの
であるが、本発明の各構成要素は実施例中の具体的な要
素のみに限定されるものではない。The symbols shown in the above parentheses are the reference numerals of the corresponding elements in the examples to be described later, but each component of the present invention is a specific element in the examples. It is not limited to only.
【００２０】[0020]
【作用】請求項１の発明においては、第１の励磁手段
（４）と第２の励磁手段（５）とがそれぞれ検査対象物
（１）の外周を囲む形で配置されており、第１の励磁手
段（４）と第２の励磁手段（５）とは検査対象物が搬送
される軸方向に対して互いにずれた位置に設置されてい
る。また、前記第１の励磁手段と第２の励磁手段との間
に、前記検査対象物の表面と対向するように、磁束検出
手段（６，７）が設置されている。そして、励磁制御手
段（２Ａ，２Ｂ）は、前記第１の励磁手段と第２の励磁
手段とが発生する磁界が、前記磁束検出手段の位置に
て、前記検査対象物の搬送方向に向いていて、かつ、前
記検査対象物の円周方向に回転するように磁界を制御す
る。According to the invention of claim 1, the first exciting means (4) and the second exciting means (5) are arranged so as to surround the outer periphery of the inspection object (1), respectively. The exciting means (4) and the second exciting means (5) are installed at positions displaced from each other with respect to the axial direction in which the inspection object is conveyed. Further, magnetic flux detecting means (6, 7) is installed between the first exciting means and the second exciting means so as to face the surface of the inspection object. In the excitation control means (2A, 2B), the magnetic fields generated by the first excitation means and the second excitation means are directed in the conveyance direction of the inspection object at the position of the magnetic flux detection means. In addition, the magnetic field is controlled so as to rotate in the circumferential direction of the inspection object.
【００２１】また請求項２においては、第１組の励磁手
段（４）と第２組の励磁手段（５）とがそれぞれ検査対
象物（１）の外周を囲む形でほぼ環状に配列された複数
の励磁コイルを含んでおり、第１組の励磁手段（４）と
第２組の励磁手段（５）とは検査対象物が搬送される軸
方向に対して互いにずれた位置に設置されている。そし
て、励磁制御手段（２Ａ，２Ｂ）は、第１組の励磁手段
及び第２組の励磁手段が発生する磁界を、前記検査対象
物の円周方向に回転するとともに、第１組の励磁手段と
第２組の励磁手段の互いに前記軸方向に対向する励磁コ
イル対に、同一時点で互いに異なる磁極を形成する。ま
た、磁束検出手段（６，７）は、第１組の励磁手段と第
２組の励磁手段との間に、前記検査対象物の表面と対向
するように設置される。In the second aspect, the first set of exciting means (4) and the second set of exciting means (5) are arranged in a substantially annular shape so as to surround the outer periphery of the inspection object (1). A plurality of exciting coils are included, and the first set of exciting means (4) and the second set of exciting means (5) are installed at positions displaced from each other with respect to the axial direction in which the inspection object is conveyed. There is. The excitation control means (2A, 2B) rotates the magnetic fields generated by the first set of excitation means and the second set of excitation means in the circumferential direction of the inspection object, and at the same time, the first set of excitation means. And different magnetic poles are formed at the same time point in the exciting coil pair of the second set of exciting means that face each other in the axial direction. The magnetic flux detecting means (6, 7) is installed between the first set of exciting means and the second set of exciting means so as to face the surface of the inspection object.
【００２２】このように構成すると、磁束検出手段が設
置される第１組の励磁手段と第２組の励磁手段との間の
空間における磁界は、前記軸方向の成分（Ｂｚ）が支配
的になる。つまり、第１組の励磁手段の１つの磁極から
第２組の励磁手段の１つの磁極へ（又はその反対に）向
かう磁路が形成される。この磁路は、検査対象物の表面
に隣接しているので、それを通る磁束によって、検査対
象物上に渦電流が流れる。渦電流の流れる方向は各励磁
手段によって生成された磁束の向きによって定まるが、
検査対象物の表面に疵がある場合には、疵を迂回するよ
うに渦電流が流れる。磁束検出手段（６，７）は、検査
対象物上の渦電流によって生じる磁束を検出する。従っ
て、検査対象物上の疵の有無によって渦電流が変化する
と、それが磁束検出手段で検出され、疵の有無が検出さ
れる。第１組の励磁手段及び第２組の励磁手段が発生す
る磁界は、検査対象物の円周方向に回転するので、円周
方向の各々の位置の疵が検出可能である。According to this structure, the magnetic field in the space between the first set of exciting means and the second set of exciting means in which the magnetic flux detecting means is installed is dominated by the axial component (Bz). Become. That is, a magnetic path is formed from one magnetic pole of the first set of exciting means to one magnetic pole of the second set of exciting means (or vice versa). Since this magnetic path is adjacent to the surface of the inspection object, the magnetic flux passing therethrough causes an eddy current to flow on the inspection object. The direction of eddy current flow is determined by the direction of the magnetic flux generated by each excitation means,
When the surface of the inspection object has a flaw, an eddy current flows so as to bypass the flaw. The magnetic flux detecting means (6, 7) detects the magnetic flux generated by the eddy current on the inspection object. Therefore, when the eddy current changes depending on the presence or absence of a flaw on the inspection object, the eddy current is detected by the magnetic flux detecting means, and the presence or absence of the flaw is detected. Since the magnetic fields generated by the first set of exciting means and the second set of exciting means rotate in the circumferential direction of the inspection object, flaws at respective positions in the circumferential direction can be detected.
【００２３】本発明では、検査対象物をその搬送方向
（Ｚ）に向かって平行に励磁させた状態で、疵の検出を
実施するが、従来の疵検出装置では、検査対象物をその
円周方向又は断面方向に励磁した状態で疵の検出を実施
している。実験によれば、疵によって得られる信号のＳ
／Ｎ比は、検査対象物が静止している状態、及び搬送に
よって検査対象物が振動している状態（磁束検出手段と
検査対象物とのギャップが変動している状態）のいずれ
においても、本発明の装置の方が従来の装置よりもはる
かに良い結果が得られた。従って、信頼性の高い疵検出
が実現する。In the present invention, the flaw is detected in a state where the inspection object is excited in parallel in the conveying direction (Z), but in the conventional flaw detection device, the inspection object is surrounded by the circumference thereof. The flaw is detected in the state of being excited in the direction of the cross section or the cross section. According to the experiment, S of the signal obtained by the flaw is
The / N ratio is in a state in which the inspection object is stationary and a state in which the inspection object vibrates due to conveyance (a state in which the gap between the magnetic flux detecting means and the inspection object changes). The device of the present invention gave much better results than the conventional device. Therefore, highly reliable flaw detection is realized.
【００２４】請求項３においては、磁束検出手段は、各
々前記検査対象物の円周方向の一部分と対向する複数の
検出手段を、前記検査対象物を囲む形で環状に配設して
なり、更に前記複数の検出手段のうち互いに隣接する２
つの検出手段が出力する信号の差分を検出する差分検知
手段（７１）を含む。即ち、検査対象物の円周方向に互
いに隣接する位置での磁束分布（渦電流によって生じる
磁束分布）の変化が、検査対象物上の疵として検出され
る。According to a third aspect of the present invention, the magnetic flux detecting means comprises a plurality of detecting means, each of which faces a part of the inspection object in the circumferential direction, is annularly arranged so as to surround the inspection object. Further, two of the plurality of detecting means that are adjacent to each other
It includes a difference detecting means (71) for detecting a difference between signals output by the one detecting means. That is, a change in the magnetic flux distribution (magnetic flux distribution generated by the eddy current) at positions adjacent to each other in the circumferential direction of the inspection target is detected as a flaw on the inspection target.
【００２５】請求項４においては、励磁制御手段は、３
相以上の多相交流電源を含む。即ち、多相交流電源を用
いて励磁磁界を回転させることによって、励磁磁界に生
じる空間高調波を低減することができ、磁界のむらが小
さくなり、より安定した疵検出が実現する。In the fourth aspect, the excitation control means is 3
Includes multi-phase AC power supplies with more than one phase. That is, by rotating the exciting magnetic field using the multi-phase AC power source, the spatial harmonics generated in the exciting magnetic field can be reduced, the unevenness of the magnetic field can be reduced, and more stable flaw detection can be realized.
【００２６】[0026]
【実施例】実施例の疵検出装置の構成を図１に示し、図
１のII−II線断面を図２に示し、図１のIII−III線断面
を図３に示す。まず図１を参照して説明する。検査対象
物である棒鋼１は、熱間圧延ラインで製造されるもので
あり、その軸方向（長手方向）に高速で搬送されながら
連続的に圧延される。この例では、仕上圧延工程の出側
において、棒鋼１の通路を囲むように疵検出装置が配置
されている。なお、疵検出装置の位置において、棒鋼１
の温度はキュ−リ点以上であるため、棒鋼１は非磁性体
である。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a flaw detecting apparatus of the embodiment is shown in FIG. 1, the II-II line cross section of FIG. 1 is shown in FIG. 2, and the III-III line cross section of FIG. 1 is shown in FIG. First, a description will be given with reference to FIG. The steel bar 1 to be inspected is manufactured on a hot rolling line, and is continuously rolled while being conveyed at a high speed in its axial direction (longitudinal direction). In this example, the flaw detection device is arranged so as to surround the passage of the steel bar 1 on the delivery side of the finish rolling process. At the position of the flaw detection device, the steel bar 1
Since the temperature is above the Curie point, the steel bar 1 is a non-magnetic material.
【００２７】疵検出装置の主要部は、３相交流電源２
Ａ，２Ｂ，信号発生器３，第１励磁ユニット４，第２励
磁ユニット５，検出ユニット６及び検出回路７で構成さ
れている。第１励磁ユニット４は、棒鋼１を囲むように
配置された環状の鉄心４０とそれに巻回された多数の励
磁コイル４７で構成されている。励磁コイル４７は、実
際には、図２に示すように円周方向に等間隔で配置され
た２４個のコイルでなっている。またこれらのコイルは
点線で示すように結線されるので、これらは４個ずつ６
組の励磁コイルグル−プ４１，４２，４３，４４，４５
及び４６に区分される。即ち、図４に示すように、励磁
コイルグル−プ４１，４２，４３，４４，４５及び４６
は、それぞれ＋Ｕ相，−Ｖ相，＋Ｗ相，−Ｕ相，＋Ｖ相
及び−Ｗ相の電源によって励磁される。The main part of the flaw detection device is a three-phase AC power supply 2
A, 2B, a signal generator 3, a first excitation unit 4, a second excitation unit 5, a detection unit 6 and a detection circuit 7. The first excitation unit 4 is composed of an annular iron core 40 arranged so as to surround the steel bar 1 and a large number of excitation coils 47 wound around the iron core 40. The exciting coil 47 is actually composed of 24 coils arranged at equal intervals in the circumferential direction as shown in FIG. Also, these coils are connected as shown by the dotted lines, so that these coils are 4 each
Excitation coil group 41, 42, 43, 44, 45
And 46. That is, as shown in FIG. 4, the exciting coil groups 41, 42, 43, 44, 45 and 46
Are excited by power sources of + U phase, −V phase, + W phase, −U phase, + V phase and −W phase, respectively.
【００２８】同様に、第２励磁ユニット５は、棒鋼１を
囲むように配置された環状の鉄心５０とそれに巻回され
た多数の励磁コイル５７で構成されている。励磁コイル
５７は、実際には、図３に示すように円周方向に等間隔
で配置された２４個のコイルでなっている。またこれら
のコイルは点線で示すように結線されるので、これらは
４個ずつ６組の励磁コイルグル−プ５１，５２，５３，
５４，５５及び５６に区分される。即ち、図４に示すよ
うに、励磁コイルグル−プ５１，５２，５３，５４，５
５及び５６は、それぞれ−Ｕ相，＋Ｖ相，−Ｗ相，＋Ｕ
相，−Ｖ相及び＋Ｗ相の電源によって励磁される。Similarly, the second exciting unit 5 is composed of an annular iron core 50 arranged so as to surround the steel bar 1 and a large number of exciting coils 57 wound around it. The exciting coil 57 is actually 24 coils arranged at equal intervals in the circumferential direction as shown in FIG. Further, since these coils are connected as shown by the dotted lines, these are four sets of four exciting coil groups 51, 52, 53,
It is divided into 54, 55 and 56. That is, as shown in FIG. 4, the exciting coil groups 51, 52, 53, 54, 5
5 and 56 are -U phase, + V phase, -W phase, and + U, respectively.
It is excited by the phase, -V, and + W phase power supplies.
【００２９】図１に示すように、第１励磁ユニット４に
供給する電力は、３相交流電源２Ａが生成し、第２励磁
ユニット５に供給する電力は、３相交流電源２Ｂが生成
する。３相交流電源２Ａ及び２Ｂは、信号発生器３が出
力する３相交流信号に同期して、それぞれ３相（Ｕ，
Ｖ，Ｗ）の交流電力を生成する。従って、３相交流電源
２Ａが出力する３相の交流電力と３相交流電源２Ｂが出
力する３相の交流電力との位相は互いに同期する。As shown in FIG. 1, the power supplied to the first excitation unit 4 is generated by the three-phase AC power supply 2A, and the power supplied to the second excitation unit 5 is generated by the three-phase AC power supply 2B. The three-phase AC power supplies 2A and 2B are synchronized with the three-phase AC signal output from the signal generator 3, and each of the three phases (U,
V, W) AC power is generated. Therefore, the phases of the three-phase AC power output by the three-phase AC power supply 2A and the three-phase AC power output by the three-phase AC power supply 2B are synchronized with each other.
【００３０】そして、図４に示すように、棒鋼１の軸方
向に対して、第１励磁ユニット４と第２励磁ユニット５
の互いに対向する位置にある励磁コイルグル−プに供給
される電力は互いに極性が逆になっている。つまり、例
えば励磁コイルグル−プ４１の通電によって発生する磁
極がＳ極の時には、励磁コイルグル−プ５１の通電によ
って発生する磁極はＮ極になる。また、励磁コイルグル
−プ４１の通電によって発生する磁極がＮ極の時には、
励磁コイルグル−プ５１の通電によって発生する磁極は
Ｓ極になる。このため、第１励磁ユニット４と第２励磁
ユニット５の互いに対向する方向、つまり棒鋼１の軸方
向に向かう磁界が発生する。Then, as shown in FIG. 4, the first exciting unit 4 and the second exciting unit 5 are arranged in the axial direction of the steel bar 1.
The polarities of the electric powers supplied to the exciting coil groups at the positions opposite to each other are opposite to each other. That is, for example, when the magnetic pole generated by energizing the exciting coil group 41 is the S pole, the magnetic pole generated by energizing the exciting coil group 51 is the N pole. Further, when the magnetic pole generated by energizing the exciting coil group 41 is the N pole,
The magnetic pole generated by energization of the exciting coil group 51 becomes the S pole. Therefore, a magnetic field is generated in which the first excitation unit 4 and the second excitation unit 5 face each other, that is, the magnetic field extends in the axial direction of the steel bar 1.
【００３１】検出ユニット６は、棒鋼１を囲むように環
状に構成されており、第１励磁ユニット４と第２励磁ユ
ニット５の中間の位置に配置されている。第１励磁ユニ
ット４と第２励磁ユニット５の励磁によって形成され
る、検出ユニット６の位置における棒鋼１の周囲の磁束
密度分布を、コンピュ−タシミュレ−ションによって計
算し求めた。その結果を図８に示す。なお、図８の上側
に示した実部と下側に示した虚部とは、互いに電源波形
の位相が９０度ずれた状態を示している。The detection unit 6 is formed in an annular shape so as to surround the steel bar 1, and is arranged at an intermediate position between the first excitation unit 4 and the second excitation unit 5. The magnetic flux density distribution around the steel bar 1 at the position of the detection unit 6 formed by the excitation of the first excitation unit 4 and the second excitation unit 5 was calculated and obtained by computer simulation. FIG. 8 shows the result. The real part shown on the upper side of FIG. 8 and the imaginary part shown on the lower side of FIG. 8 indicate a state where the phases of the power supply waveforms are deviated from each other by 90 degrees.
【００３２】更に、検出ユニット６の位置における棒鋼
１の周囲の磁束密度分布を各軸方向の成分に分解した結
果を、円周方向各位置での磁束密度として図９に示す。
図９において、Ｂｚ，Ｂｔ，及びＢｒが、それぞれＺ軸
方向（棒鋼の長手方向），棒鋼の径方向，および円周方
向の磁束密度を示している。つまり、検出ユニット６の
位置における磁束密度については、Ｚ軸方向の成分が支
配的であることが、図９から理解できる。Further, the result of decomposing the magnetic flux density distribution around the steel bar 1 at the position of the detection unit 6 into the components in each axial direction is shown in FIG. 9 as the magnetic flux density at each position in the circumferential direction.
In FIG. 9, Bz, Bt, and Br represent magnetic flux densities in the Z-axis direction (longitudinal direction of steel bar), the radial direction of steel bar, and the circumferential direction, respectively. That is, it can be understood from FIG. 9 that the component in the Z-axis direction is dominant in the magnetic flux density at the position of the detection unit 6.
【００３３】また、検出ユニット６の位置におけるＺ軸
方向の磁束密度分布の時間推移を図１０に示す。ここ
で、Ｔは信号発生器３が出力する信号の１周期（１／60
秒）である。図１０を参照すると、磁束密度の分布が、
時間とともに円周方向に移動することが理解できる。即
ち、検出ユニット６の位置に形成される磁界は、棒鋼１
の周囲を円周方向に回転する回転磁界になる。ある時点
においては、図１に示すように、第１励磁ユニット４上
に１つのＳ極と１つのＮ極とが形成され、第２励磁ユニ
ット５上に１つのＮ極と１つのＳ極とが形成され、第１
励磁ユニットのＳ極と第２励磁ユニットのＮ極との間、
ならびに第１励磁ユニットのＮ極と第２励磁ユニットの
Ｓ極との間の検出ユニット６の位置において、大きな磁
束密度が得られる。Further, FIG. 10 shows the time transition of the magnetic flux density distribution in the Z-axis direction at the position of the detection unit 6. Here, T is one cycle of the signal output from the signal generator 3 (1/60
Seconds). Referring to FIG. 10, the distribution of magnetic flux density is
It can be understood that it moves in the circumferential direction with time. That is, the magnetic field formed at the position of the detection unit 6 is
Becomes a rotating magnetic field that rotates around the circumference in the circumferential direction. At some point in time, as shown in FIG. 1, one S pole and one N pole are formed on the first excitation unit 4, and one N pole and one S pole are formed on the second excitation unit 5. Is formed, the first
Between the S pole of the excitation unit and the N pole of the second excitation unit,
A large magnetic flux density is obtained at the position of the detection unit 6 between the N pole of the first excitation unit and the S pole of the second excitation unit.
【００３４】次に、図１１を参照して説明する。上述の
ように、第１励磁ユニット４と第２励磁ユニット５を励
磁すると、Ｚ軸方向の磁界Ｈが棒鋼１の表面近傍に生じ
る。この磁界Ｈによって、導電体である棒鋼１の表面に
は、円周方向に向かって渦電流ｉが流れる。但し、棒鋼
１の表面に疵１ａが存在する場合、渦電流は疵１ａを迂
回するように流れるので、疵１ａの近傍では、渦電流に
Ｚ軸方向の成分ｉ" が生じる。この渦電流ｉ" によっ
て、円周方向の磁界Ｈ２が生じる。疵１ａが存在しない
時には、円周方向の磁界Ｈ２はほとんど生じない。従っ
て、円周方向の磁界Ｈ２を監視すれば、疵１ａの有無を
検出できる。Next, description will be made with reference to FIG. As described above, when the first excitation unit 4 and the second excitation unit 5 are excited, the magnetic field H in the Z-axis direction is generated near the surface of the steel bar 1. Due to this magnetic field H, an eddy current i flows in the circumferential direction on the surface of the steel bar 1 which is a conductor. However, when the flaw 1a exists on the surface of the steel bar 1, the eddy current flows so as to bypass the flaw 1a, so that a component i "in the Z-axis direction is generated in the eddy current near the flaw 1a. Causes a magnetic field H2 in the circumferential direction. When the flaw 1a does not exist, the magnetic field H2 in the circumferential direction hardly occurs. Therefore, the presence or absence of the flaw 1a can be detected by monitoring the magnetic field H2 in the circumferential direction.
【００３５】検出ユニット６は、円周方向の磁界Ｈ２を
検出するために設置されている。検出ユニット６の構成
を図１２に示す。図１２は、検出ユニット６の外観を円
周方向を縦方向に展開して示している。また、図１２の
Ｖ−Ｖ線断面を図５に示す。図１２を参照すると、検出
ユニット６はＺ軸方向に互いに近接した状態で並べた２
列の検出部６Ａ，６Ｂで構成されている。検出部６Ａ
は、円周方向に等間隔で並べた３０個のコイル板６Ａ
ａ，６Ａｂ，６Ａｃ，６Ａｄ，・・・・を備えている。
検出部６Ｂも同様である。これらのコイル板は、円周方
向に互いに隣接する２つずつが、それぞれ対になってい
る。The detection unit 6 is installed to detect the magnetic field H2 in the circumferential direction. The structure of the detection unit 6 is shown in FIG. FIG. 12 shows the appearance of the detection unit 6 with the circumferential direction developed in the vertical direction. Further, a cross section taken along line VV of FIG. 12 is shown in FIG. Referring to FIG. 12, the detection units 6 are arranged in a state of being close to each other in the Z-axis direction.
It is composed of detection units 6A and 6B for the columns. Detection unit 6A
Is 30 coil plates 6A arranged at equal intervals in the circumferential direction.
a, 6Ab, 6Ac, 6Ad, ...
The same applies to the detection unit 6B. Two of these coil plates, which are adjacent to each other in the circumferential direction, form a pair.
【００３６】１対のコイル板６Ａａ，６Ａｂの構成を図
６に示す。コイル板６Ａａ及び６Ａｂは、各々、樹脂基
板６１上にプリントされた箔状の導体によって形成され
る渦巻状のコイル６２を有している。コイル６２の外側
の一端には、リ−ド線６３ａ又は６３ｂが接続されてい
る。コイル板６Ａａのコイル６２の内側の一端と、コイ
ル板６Ａｂのコイル６２の内側の一端とは、導線６４に
よって互いに接続されている。他のコイル板６Ａｃ，６
Ａｄ，６Ａｅ，６Ａｆ，・・・についても同様である。The structure of the pair of coil plates 6Aa and 6Ab is shown in FIG. Each of the coil plates 6Aa and 6Ab has a spiral coil 62 formed by a foil-shaped conductor printed on the resin substrate 61. A lead wire 63a or 63b is connected to one end on the outside of the coil 62. The inner end of the coil 62 of the coil plate 6Aa and the inner end of the coil 62 of the coil plate 6Ab are connected to each other by a conductive wire 64. Other coil plates 6Ac, 6
The same applies to Ad, 6Ae, 6Af, ....
【００３７】磁界Ｈ２によって生じる磁束が、コイル６
２と鎖交し、コイル６２に電圧が誘起する。対のコイル
板（例えば６Ａａ，６Ａｂ）と対向する位置の棒鋼表面
に疵１ａが存在しない時には、２つのコイル６２に誘起
する電圧はほぼ等しくなるが、対のコイル板の一方と対
向する位置の棒鋼表面に疵１ａが存在し、他方の位置に
は疵が存在しない場合、２つのコイル６２に誘起する電
圧に差が生じる。従って、疵１ａがある時には、リ−ド
線６３ａ，６３ｂ間に現われる電位差が大きくなるの
で、その電位差を監視することにより、疵１ａを検出で
きる。The magnetic flux generated by the magnetic field H2 is generated by the coil 6
2 and the voltage is induced in the coil 62. When the flaw 1a does not exist on the surface of the steel bar at a position facing the pair of coil plates (for example, 6Aa, 6Ab), the voltages induced in the two coils 62 are almost equal, but at the position facing one of the pair of coil plates. When the flaw 1a is present on the surface of the steel bar and the flaw is not present at the other position, the voltage induced in the two coils 62 is different. Therefore, when the flaw 1a is present, the potential difference appearing between the lead lines 63a and 63b becomes large, so that the flaw 1a can be detected by monitoring the potential difference.
【００３８】検出回路７のうち、一対のコイル板６Ａ
ａ，６Ａｂに接続された部分の構成を図７に示す。ま
た、図７に示す回路の各部の信号例を図１３に示す。図
７を参照すると、差動増幅器７１は、コイル板６Ａａの
コイルが誘起する電圧ＳＡと、コイル板６Ａｂのコイル
が誘起する電圧ＳＢとの差分を増幅し、信号ＳＣとして
出力する。信号ＳＣは、シュミットトリガ７３に入力さ
れるとともに、反転増幅器７２を介してシュミットトリ
ガ７４に入力される。信号ＳＣの振幅が所定以上になる
と、シュミットトリガ７３及び／又は７４の出力が高レ
ベルＨになる。オアゲ−ト７５は、シュミットトリガ７
３，７４が出力する信号に基づいて、疵検出信号ＳＤを
生成する。他のコイル板（６Ａｃ，６Ａｄ，６Ａｅ，６
Ａｆ，・・・）の対についても、それぞれ図７に示すも
のと同一構成の検出回路が接続されている。Of the detection circuit 7, a pair of coil plates 6A
The structure of the portion connected to a and 6Ab is shown in FIG. In addition, FIG. 13 shows a signal example of each part of the circuit shown in FIG. Referring to FIG. 7, the differential amplifier 71 amplifies the difference between the voltage SA induced by the coil of the coil plate 6Aa and the voltage SB induced by the coil of the coil plate 6Ab, and outputs it as a signal SC. The signal SC is input to the Schmitt trigger 73 and the Schmitt trigger 74 via the inverting amplifier 72. When the amplitude of the signal SC exceeds a predetermined level, the output of the Schmitt trigger 73 and / or 74 becomes the high level H. Ogate 75 is a Schmitt trigger 7
The flaw detection signal SD is generated on the basis of the signals output from 3, 74. Other coil plates (6Ac, 6Ad, 6Ae, 6
The detection circuit having the same configuration as that shown in FIG. 7 is connected to each of the pairs Af, ...
【００３９】前述のように、第１励磁ユニット４と第２
励磁ユニット５の励磁によって生じる磁界Ｈは、回転磁
界であり、磁束密度の大きい部分が棒鋼１の円周方向に
一定の速度で回転する。そして、棒鋼１上の磁束密度の
大きい部分に渦電流が流れ、この渦電流を利用して疵の
有無が検出される。従って、磁界Ｈの回転に伴なって、
疵検出の対象になる位置も円周方向に移動する。棒鋼１
上の疵１ａは、それと対向する位置に存在する対のコイ
ル板（例えば６Ａａ，６Ａｂ）によって検出される。As described above, the first excitation unit 4 and the second excitation unit 4
The magnetic field H generated by the excitation of the excitation unit 5 is a rotating magnetic field, and a portion having a large magnetic flux density rotates in the circumferential direction of the steel bar 1 at a constant speed. Then, an eddy current flows in a portion of the steel bar 1 having a high magnetic flux density, and the presence or absence of a flaw is detected by using this eddy current. Therefore, as the magnetic field H rotates,
The target position for flaw detection also moves in the circumferential direction. Steel bar 1
The upper flaw 1a is detected by a pair of coil plates (for example, 6Aa, 6Ab) existing at a position facing the flaw 1a.
【００４０】この実施例では、Ｚ軸方向に並べた２列の
検出部６Ａ，６Ｂについて、コイル板の対が千鳥状にな
るように結線してある。即ち、図１２に示すように、１
列目の検出部６Ａについては、コイル板６Ａａ・６Ａ
ｂ，６Ａｃ・６Ａｄ，６Ａｅ・６Ａｆ，・・・がそれぞ
れ対をなしているが、２列目の検出部６Ｂについては、
コイル板６Ｂｂ・６Ｂｃ，６Ｂｄ・６Ｂｅ，６Ｂｆ・６
Ｂｇ，・・・がそれぞれ対をなしており、１列目の検出
部６Ａの互いに隣接するコイル板対とコイル板対との間
に、２列目の検出部６Ｂのコイル板対が位置している。In this embodiment, the two rows of detectors 6A and 6B arranged in the Z-axis direction are connected so that the pairs of coil plates are staggered. That is, as shown in FIG.
Regarding the detection unit 6A in the row, coil plates 6Aa and 6A
b, 6Ac · 6Ad, 6Ae · 6Af, ... Are paired, respectively, but regarding the detection unit 6B in the second row,
Coil plates 6Bb ・ 6Bc, 6Bd ・ 6Be, 6Bf ・ 6
Bg, ... form a pair, and the coil plate pair of the detection unit 6B in the second row is positioned between the coil plate pair and the coil plate pair adjacent to each other in the detection unit 6A in the first row. ing.
【００４１】例えば、円周方向のコイル板６Ａａ，６Ａ
ｂの近傍の位置では、それらによって疵が検出される
が、コイル板６Ａｂ，６Ａｃの近傍では、コイル板対６
Ａａ・６Ａｂ，又はコイル板対６Ａｃ・６Ａｄによって
疵を検出することは難しい。しかし、コイル板６Ａｂ，
６Ａｃの近傍では、２列目の検出部６Ｂのコイル板対６
Ｂｂ・６Ｂｃによって疵を検出することができる。従っ
て、円周方向のどの位置においても疵検出ができ、疵検
出が不可能な領域（不感帯）は生じない。For example, circumferential coil plates 6Aa, 6A
Defects are detected by them in the vicinity of b, but in the vicinity of the coil plates 6Ab and 6Ac, the coil plate pair 6 is detected.
It is difficult to detect flaws by Aa · 6Ab or coil plate pair 6Ac · 6Ad. However, the coil plate 6Ab,
In the vicinity of 6Ac, the coil plate pair 6 of the detection unit 6B in the second row is
Defects can be detected by Bb · 6Bc. Therefore, the flaw can be detected at any position in the circumferential direction, and a region (dead zone) where the flaw cannot be detected does not occur.
【００４２】図１の三相交流電源２Ａの構成を図１４に
示す。なお三相交流電源２Ｂの構成も図１４と同一であ
る。図１４を参照して説明する。３相電源２１から供給
される交流電力は、サイリスタブリッジ２２によって整
流され、インダクタ２５及びコンデンサ２６によって平
滑される。従って、コンデンサ２６の端子間には直流電
圧が現われる。コンデンサ２６の端子間に現われる電圧
は、サイリスタブリッジ２２がトリガされる位相に応じ
て変化する。位相角算出器２４に印加される電圧指令値
Ｖdcは、コンデンサ２６の端子間に現われる直流電圧の
調整に利用される。位相角算出器２４は、電圧指令値Ｖ
dcに対応するトリガ位相角αを算出する。ゲ−トドライ
バ２３は、位相角算出器２４が出力するトリガ位相角α
でサイリスタブリッジ２２の各々のサイリスタをトリガ
するように、それぞれのゲ−ト端子に印加するトリガ信
号を生成する。即ち、各々のサイリスタがスイッチング
する交流波形のゼロクロス点をそれぞれ検出し、ゼロク
ロス点を検出してから位相角αに相当する時間が経過し
た時に、トリガ信号を生成する。The structure of the three-phase AC power supply 2A shown in FIG. 1 is shown in FIG. The configuration of the three-phase AC power supply 2B is the same as that shown in FIG. This will be described with reference to FIG. The AC power supplied from the three-phase power supply 21 is rectified by the thyristor bridge 22 and smoothed by the inductor 25 and the capacitor 26. Therefore, a DC voltage appears between the terminals of the capacitor 26. The voltage appearing across the terminals of capacitor 26 varies depending on the phase at which thyristor bridge 22 is triggered. The voltage command value Vdc applied to the phase angle calculator 24 is used for adjusting the DC voltage appearing across the terminals of the capacitor 26. The phase angle calculator 24 determines the voltage command value V
Calculate the trigger phase angle α corresponding to dc. The gate driver 23 has a trigger phase angle α output from the phase angle calculator 24.
Then, a trigger signal to be applied to each gate terminal is generated so as to trigger each thyristor of the thyristor bridge 22. That is, a zero-cross point of an AC waveform that each thyristor switches is detected, and a trigger signal is generated when a time corresponding to the phase angle α has elapsed after the zero-cross point was detected.
【００４３】トランジスタブリッジ２７は、コンデンサ
２６の端子間に現われる直流電圧をスイッチングし、三
相交流電圧Ｕ，Ｖ，Ｗを生成する。トランジスタブリッ
ジ２７のスイッチングを制御する信号は、比較器２９に
よって生成され、ゲ−トドライバ２８を介して各トラン
ジスタのベ−ス端子に印加される。比較器２９の入力端
子には、信号発生器３の出力と三角波発生器３０の出力
が接続されている。信号発生器３は、周波数が６０Ｈｚ
の正弦波の三相交流電圧Ｕ１，Ｖ１，Ｗ１を出力する。
Ｕ１とＶ１およびＶ１とＷ１は、それぞれ１２０度の位
相差を有している。また三角波発生器３０は、繰り返し
周波数が３ＫＨｚの三角波信号を出力する。比較器２９
は、６個のアナログ比較器を内蔵しており、三相交流電
圧Ｕ１，Ｖ１，Ｗ１の正の半波及び負の半波の電圧を、
それぞれ独立したアナログ比較器で三角波発生器３０が
出力する三角波の電圧と比較し、それらの比較結果を６
つの二値信号として出力する。これらの二値信号が、ゲ
−トドライバ２８を介して、トランジスタブリッジ２７
に印加され、トランジスタブリッジ２７の出力に三相交
流電圧Ｕ，Ｖ，Ｗが現われる。The transistor bridge 27 switches the DC voltage appearing between the terminals of the capacitor 26 to generate three-phase AC voltages U, V, W. A signal for controlling the switching of the transistor bridge 27 is generated by the comparator 29 and applied to the base terminal of each transistor via the gate driver 28. The output of the signal generator 3 and the output of the triangular wave generator 30 are connected to the input terminal of the comparator 29. The frequency of the signal generator 3 is 60 Hz
The three-phase AC voltages U1, V1, and W1 of the sine wave are output.
U1 and V1 and V1 and W1 each have a phase difference of 120 degrees. Further, the triangular wave generator 30 outputs a triangular wave signal having a repetition frequency of 3 KHz. Comparator 29
Includes six analog comparators and outputs the positive half-wave voltage and the negative half-wave voltage of the three-phase AC voltage U1, V1, W1.
Each of the independent analog comparators compares the voltage of the triangular wave output from the triangular wave generator 30 with each other, and the comparison result is 6
Output as two binary signals. These binary signals pass through the gate driver 28 and the transistor bridge 27.
And three-phase AC voltages U, V, W appear at the output of the transistor bridge 27.
【００４４】この実施例の疵検出装置における疵検出信
号（ＳＣ）は、非常に大きなＳ／Ｎ比を有していること
が実験により確かめられた。また、検出ユニット６と棒
鋼１とのギャップの変動量が１ｍｍ程度の場合であって
も、深さが０．５ｍｍの疵に対して２．５程度のＳ／Ｎ
比が得られることが分かった。Experiments have confirmed that the flaw detection signal (SC) in the flaw detection apparatus of this embodiment has a very large S / N ratio. Further, even when the variation amount of the gap between the detection unit 6 and the steel bar 1 is about 1 mm, the S / N of about 2.5 for a flaw having a depth of 0.5 mm.
It was found that a ratio was obtained.
【００４５】なお上記実施例においては、検査対象物を
棒鋼として説明したが、導電体であれば、他の材質のも
のでも検査可能である。また実施例においては、励磁ユ
ニット４，５を付勢する電源として三相交流電源を用い
たが、三相を越える多相交流電源を用いてもよい。相数
が増えるに従って、励磁ユニット４，５によって生じる
磁界の空間高調波がより低減されるので、より安定した
疵検出が実現する。In the above embodiments, the object to be inspected is explained as a steel bar, but any other material can be inspected as long as it is a conductor. In the embodiment, the three-phase AC power supply is used as the power supply for energizing the excitation units 4 and 5, but a multi-phase AC power supply having more than three phases may be used. As the number of phases increases, the spatial harmonics of the magnetic field generated by the excitation units 4 and 5 are further reduced, so that more stable flaw detection is realized.
【００４６】また上記実施例においては、検出ユニット
６を円周方向に配設した多数のコイル板で構成したが、
従来より公知の様々な構成の磁界検出器を用いても、疵
を検出することが可能である。In the above embodiment, the detection unit 6 is composed of a large number of coil plates arranged in the circumferential direction.
It is possible to detect flaws by using magnetic field detectors of various conventionally known structures.
【００４７】[0047]
【発明の効果】本発明では、検査対象物をその搬送方向
（Ｚ）に向かって平行に励磁させた状態で疵の検出を実
施するので、疵によって得られる信号のＳ／Ｎ比が従来
と比べて大幅に改善され、信頼性の高い疵検出が実現す
る。また、励磁磁界を円周方向に回転するので、円周方
向の各々の位置で疵検出ができ、長手方向の疵も円周方
向の疵も共に検出可能である。According to the present invention, since the flaw is detected in a state where the inspection object is excited in parallel in the conveying direction (Z), the S / N ratio of the signal obtained by the flaw is different from the conventional one. Compared with the above, it is possible to realize flaw detection with high reliability and high reliability. Further, since the exciting magnetic field rotates in the circumferential direction, flaws can be detected at each position in the circumferential direction, and flaws in the longitudinal direction and flaws in the circumferential direction can both be detected.
【００４８】また請求項３においては、検査対象物の円
周方向に互いに隣接する位置での磁束分布（渦電流によ
って生じる磁束分布）の変化を、検査対象物上の疵とし
て検出するので、円周方向の小領域毎にそれぞれ疵の有
無を検出することができ、検出性能が向上する。例え
ば、深さが大きく異なる複数の疵が互いに近接した位置
に存在する検査対象物に対して両方の疵が検出可能であ
る。In the third aspect, the change in the magnetic flux distribution (the magnetic flux distribution generated by the eddy current) at the positions adjacent to each other in the circumferential direction of the inspection object is detected as a flaw on the inspection object. The presence or absence of flaws can be detected for each of the small areas in the circumferential direction, and the detection performance is improved. For example, both flaws can be detected with respect to an inspection object in which a plurality of flaws having greatly different depths are present in positions close to each other.
【００４９】また請求項４においては、多相交流電源を
用いて励磁磁界を回転させることによって、励磁磁界に
生じる空間高調波を低減することができ、磁界のむらが
小さくなり、より安定した疵検出が実現する。Further, according to the present invention, by rotating the exciting magnetic field using the polyphase AC power source, the spatial harmonics generated in the exciting magnetic field can be reduced, the unevenness of the magnetic field can be reduced, and the flaw detection can be more stable. Will be realized.
【図１】 実施例の疵検出装置の構成を示すブロック図
である。FIG. 1 is a block diagram showing a configuration of a flaw detection device according to an embodiment.
【図２】 図１のII−II線断面図である。FIG. 2 is a sectional view taken along line II-II of FIG.
【図３】 図１のIII−III線断面図である。3 is a sectional view taken along line III-III in FIG.
【図４】 励磁ユニット４，５の励磁位相の分布を示す
斜視図である。FIG. 4 is a perspective view showing a distribution of excitation phases of excitation units 4 and 5.
【図５】 検出ユニット６を示す図１２のＶ−Ｖ線断面
図である。5 is a cross-sectional view of the detection unit 6 taken along line VV of FIG.
【図６】 一対のコイル板６Ａａ，６Ａｂを示す斜視図
である。FIG. 6 is a perspective view showing a pair of coil plates 6Aa and 6Ab.
【図７】 検出ユニット６と検出回路７の一部分を示す
ブロック図である。7 is a block diagram showing a part of a detection unit 6 and a detection circuit 7. FIG.
【図８】 検出ユニット６の位置における磁束密度分布
を示すベクトル図である。FIG. 8 is a vector diagram showing a magnetic flux density distribution at the position of the detection unit 6.
【図９】 図８の磁束密度の各軸方向成分の円周方向分
布を示すグラフである。9 is a graph showing a circumferential direction distribution of each axial component of the magnetic flux density of FIG.
【図１０】 図９のＢｚの時間推移を示すグラフであ
る。FIG. 10 is a graph showing a time transition of Bz in FIG.
【図１１】 棒鋼上の磁界と渦電流との関係を示す斜視
図である。FIG. 11 is a perspective view showing a relationship between a magnetic field on a steel bar and an eddy current.
【図１２】 検出ユニット６の外観の周方向を縦に展開
して示す展開図である。FIG. 12 is a development view showing the appearance of the detection unit 6 with the circumferential direction vertically developed.
【図１３】 図７の回路の信号例を示すタイムチャ−ト
である。13 is a time chart showing a signal example of the circuit of FIG.
【図１４】 ３相交流電源２Ａの構成を示すブロック図
である。FIG. 14 is a block diagram showing a configuration of a three-phase AC power supply 2A.
【図１５】 従来例の構成を示す模式図である。FIG. 15 is a schematic diagram showing a configuration of a conventional example.
【図１６】 従来例の構成を示す模式図である。FIG. 16 is a schematic diagram showing a configuration of a conventional example.
【図１７】 従来例の構成を示す模式図である。FIG. 17 is a schematic diagram showing a configuration of a conventional example.
【図１８】 従来例の構成を示す模式図である。FIG. 18 is a schematic diagram showing a configuration of a conventional example.
【図１９】 従来例の構成を示す模式図である。FIG. 19 is a schematic diagram showing a configuration of a conventional example.
１：棒鋼 １ａ：疵 ２Ａ，２Ｂ：３相交流電源 ３：信号発生器 ４：第１励磁ユニット ５：第２励磁ユニッ
ト ６：検出ユニット ６Ａ，６Ｂ：検出部 ６Ａａ，６Ａｂ，６Ａｃ，６Ａｄ，・・・：コイル板 ６Ｂａ，６Ｂｂ，６Ｂｃ，６Ｂｄ，・・・：コイル板 ７：検出回路 ２１：三相交流電源 ２２：サイリスタブリッジ ２３，２８：ゲ−ト
ドライバ ２４：位相角算出器 ２５：インダクタ ２６：コンデンサ ２７：トランジスタ
ブリッジ ２９：比較器 ３０：三角波発生器 ４０，５０：鉄心 ４１〜４６，５１〜５６：励磁コイルグル−プ ４７，５７：励磁コイル ６１：樹脂基板 ６２：コイル ６３ａ，６３ｂ：リ
−ド線 ６４：導線1: Steel bar 1a: Defects 2A, 2B: 3-phase AC power supply 3: Signal generator 4: First excitation unit 5: Second excitation unit 6: Detection unit 6A, 6B: Detection unit 6Aa, 6Ab, 6Ac, 6Ad, ... ..: coil plate 6Ba, 6Bb, 6Bc, 6Bd, ...: coil plate 7: detection circuit 21: three-phase AC power supply 22: thyristor bridge 23, 28: gate driver 24: phase angle calculator 25: inductor 26: Capacitor 27: Transistor bridge 29: Comparator 30: Triangular wave generator 40, 50: Iron core 41-46, 51-56: Excitation coil group 47, 57: Excitation coil 61: Resin substrate 62: Coil 63a, 63b: Lead wire 64: Conductor wire
Claims (4)
外周を囲む形である、第１の励磁手段；前記検査対象物
の外周を囲む形であり、前記第１の励磁手段とは異なる
位置に設置された、第２の励磁手段；前記第１の励磁手
段と第２の励磁手段との間の、前記検査対象物の表面と
対向する位置に設置された磁束検出手段；および前記第
１の励磁手段と第２の励磁手段とが発生する磁界が、前
記磁束検出手段の位置にて、前記検査対象物の搬送方向
に向いていて、かつ、前記検査対象物の円周方向に回転
するように、磁界を発生させる、励磁制御手段；を備え
る導電体の疵検出装置。1. A first exciting means, which is a shape that surrounds an outer circumference of an inspection object that is conveyed in a predetermined axial direction; a shape that surrounds an outer circumference of the inspection object, and the first exciting means is the first exciting means. Second exciting means installed at different positions; magnetic flux detecting means installed between the first exciting means and the second exciting means at a position facing the surface of the inspection object; and The magnetic fields generated by the first excitation means and the second excitation means are oriented in the conveyance direction of the inspection object at the position of the magnetic flux detection means, and in the circumferential direction of the inspection object. A flaw detection device for an electric conductor, comprising an excitation control means for generating a magnetic field so as to rotate.
外周を囲む形でほぼ環状に配列された複数の励磁コイル
を含む、第１組の励磁手段；前記検査対象物の外周を囲
む形でほぼ環状に配列された複数の励磁コイルを含み、
前記軸方向に対して前記第１組の励磁手段とは異なる位
置に設置された、第２組の励磁手段；前記第１組の励磁
手段及び第２組の励磁手段が発生する磁界を、前記検査
対象物の円周方向に回転するとともに、第１組の励磁手
段と第２組の励磁手段の互いに前記軸方向に対向する励
磁コイル対に、同一時点で互いに異なる磁極を形成す
る、励磁制御手段；および前記第１組の励磁手段と第２
組の励磁手段との間の、前記検査対象物の表面と対向す
る位置に設置された磁束検出手段；を備える導電体の疵
検出装置。2. A first set of excitation means including a plurality of excitation coils arranged in a substantially annular shape so as to surround the outer periphery of an inspection object conveyed in a predetermined axial direction; and surrounds the outer periphery of the inspection object. A plurality of exciting coils arranged in a substantially circular shape,
A second set of exciting means installed at a position different from the first set of exciting means in the axial direction; a magnetic field generated by the first set of exciting means and the second set of exciting means, Excitation control in which different magnetic poles are formed at the same time point on the pair of exciting coils of the first set of exciting means and the second set of exciting means that face each other in the axial direction while rotating in the circumferential direction of the inspection object. Means; and said first set of excitation means and second
A flaw detection device for a conductor, comprising: a magnetic flux detection means installed at a position facing the surface of the inspection object between a pair of excitation means.
物の円周方向の一部分と対向する複数の検出手段を、前
記検査対象物を囲む形で環状に配設してなり、更に前記
複数の検出手段のうち互いに隣接する２つの検出手段が
出力する信号の差分を検出する差分検知手段を含む、前
記請求項２記載の導電体の疵検出装置。3. The magnetic flux detecting means comprises a plurality of detecting means, each of which faces a part of the inspection object in the circumferential direction, is annularly arranged so as to surround the inspection object. The flaw detection device for a conductor according to claim 2, further comprising a difference detection unit that detects a difference between signals output from two detection units adjacent to each other among the detection units.
流電源を含む、前記請求項２記載の導電体の疵検出装
置。4. The flaw detection device for a conductor according to claim 2, wherein the excitation control means includes a multi-phase AC power supply having three or more phases.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24294794A JP3327701B2 (en) | 1994-10-06 | 1994-10-06 | Conductor flaw detection device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24294794A JP3327701B2 (en) | 1994-10-06 | 1994-10-06 | Conductor flaw detection device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08105860A true JPH08105860A (en) | 1996-04-23 |
| JP3327701B2 JP3327701B2 (en) | 2002-09-24 |
Family
ID=17096597
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP24294794A Expired - Fee Related JP3327701B2 (en) | 1994-10-06 | 1994-10-06 | Conductor flaw detection device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3327701B2 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH09127063A (en) * | 1995-11-06 | 1997-05-16 | Nippon Steel Corp | Detector for flaw of conductor |
| JPH09127062A (en) * | 1995-11-02 | 1997-05-16 | Nippon Steel Corp | Detector for flaw of conductor |
| WO2003091655A1 (en) * | 2002-04-26 | 2003-11-06 | Azuma Systems Co., Ltd | Metal inspecting method and metal inspector |
| WO2004094939A1 (en) * | 2003-04-22 | 2004-11-04 | Azuma Systems Co., Ltd | Magnetic probe |
| JP2012198087A (en) * | 2011-03-22 | 2012-10-18 | Denshi Jiki Kogyo Kk | Magnetization device for inspection object, magnetic particle inspection device, and adjustment method of magnetization device for inspection object |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS626163A (en) * | 1985-07-03 | 1987-01-13 | Nippon Steel Corp | Rotary magnetic field type eddy current examination method |
| JPS626162A (en) * | 1985-07-03 | 1987-01-13 | Nippon Steel Corp | Eddy current examination method |
-
1994
- 1994-10-06 JP JP24294794A patent/JP3327701B2/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS626163A (en) * | 1985-07-03 | 1987-01-13 | Nippon Steel Corp | Rotary magnetic field type eddy current examination method |
| JPS626162A (en) * | 1985-07-03 | 1987-01-13 | Nippon Steel Corp | Eddy current examination method |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH09127062A (en) * | 1995-11-02 | 1997-05-16 | Nippon Steel Corp | Detector for flaw of conductor |
| JPH09127063A (en) * | 1995-11-06 | 1997-05-16 | Nippon Steel Corp | Detector for flaw of conductor |
| WO2003091655A1 (en) * | 2002-04-26 | 2003-11-06 | Azuma Systems Co., Ltd | Metal inspecting method and metal inspector |
| WO2003091657A1 (en) * | 2002-04-26 | 2003-11-06 | Azuma Systems Co., Ltd | Magnetic probe |
| WO2003091656A1 (en) * | 2002-04-26 | 2003-11-06 | Azuma Systems Co., Ltd | Coin shape detection method, coin identification sensor, and coin identification device |
| WO2004094939A1 (en) * | 2003-04-22 | 2004-11-04 | Azuma Systems Co., Ltd | Magnetic probe |
| JP2012198087A (en) * | 2011-03-22 | 2012-10-18 | Denshi Jiki Kogyo Kk | Magnetization device for inspection object, magnetic particle inspection device, and adjustment method of magnetization device for inspection object |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3327701B2 (en) | 2002-09-24 |
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