JP2015010902A - Magnetic inspection apparatus and magnetic inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic inspection device that can highly sensitively and highly accurately detect a foreign substance included in a food product, a medical product, industrial product, etc. and identify and recognize a printing medium using magnetic ink.SOLUTION: A magnetic inspection device comprises: inspection magnetic field sources m1 and m2 that generate an inspection magnetic field F1 to be applied to a detected object T which is included in an inspection object and is made of a magnetic material; and a magneto-impedance element E that includes a magnetism-sensitive body which extends in a specific axis direction in the inspection magnetic field and can change impedance in response to specific magnetism meaning magnetism in the specific axis direction. Since the inspection object is relatively displaced to the magneto-impedance element or the inspection magnetic field sources, the device can highly sensitively and highly accurately detect presence of the detected object in the inspection object, on the basis of a change in the specific magnetism to be induced by the detected object in the inspection magnetic field.

Description

  The present invention relates to a magnetic inspection apparatus or a magnetic inspection method thereof that can be used for detection of foreign matters contained in foods, pharmaceuticals, industrial products, etc., identification and recognition of print media using magnetic ink, and the like.

  Detection of foreign matters (for example, metal fine pieces and fine particles) contained in food, pharmaceuticals, industrial products, etc., and printing using special ink (magnetic ink) containing magnetic material, etc., using a magnetic inspection device equipped with a magnetic sensor In many cases, a medium (for example, a bill or a check) is recognized or identified. The description regarding such a magnetic inspection apparatus is, for example, in the following patent document.

Japanese Patent Laid-Open No. 11-96430 JP 2001-21631 A JP 2012-122983 A

  Patent Document 1 proposes a magnetic detection device using a magnetic sensor composed of a magneto-impedance element (referred to as “MI element” as appropriate). In this magnetic detection device, a detection target (metal foreign matter, etc.) included in the inspection object is sufficiently magnetized (further magnetized to saturation magnetization) in advance sufficiently away from the magnetic sensor, and the detection target By measuring the residual magnetism, foreign matter detection in the inspection object and recognition or identification of the inspection object (magnetic medium) are performed. However, when the object to be detected made of a soft magnetic material is separated from the applied magnetic field, the residual magnetism rapidly decreases, so that highly sensitive detection tends to be difficult. In particular, when the object to be detected is extremely small, the residual magnetism is very small, and it is difficult to detect with high accuracy by the magnetic detection device.

  In Patent Document 2 and Patent Document 3, an inspection object is inspected using a magnetic sensor composed of a magnetoresistive effect element (referred to as “MR element” as appropriate) while passing an inspection object through a strong magnetic field environment. A magnetic sensor device is proposed. Here, the MR element placed in a strong external magnetic field is strongly influenced by an external magnetic field that is not related to the magnetic field generated from the detected object. For this reason, it is necessary to use two MR elements and their differential amplifier circuits as in Patent Document 2, or to arrange the MR elements in the vicinity of where the magnetic field strength becomes zero as in Patent Document 3, Can be complicated and costly.

  Note that a magnetic sensor device including a Hall element is relatively low in sensitivity and has a small spatial resolution, and thus is not suitable for detecting a minute object to be detected or identifying a printed matter using magnetic ink. Magnetic sensor devices composed of fluxgate sensors are highly sensitive but difficult to miniaturize and have a small spatial resolution, similar to a Hall element, and are suitable for high-precision detection and identification of fine objects. No. Further, even if an attempt is made to measure the magnetic field generated from the detection object while passing the inspection object through the strong magnetic field environment, the core is always saturated in the strong magnetic field environment, so that the detection itself becomes difficult.

  The present invention has been made in view of such circumstances, and unlike conventional magnetic inspection apparatuses as described above, highly accurate detection, recognition, or identification can be performed even with an extremely fine object to be detected. It is an object of the present invention to provide a new magnetic inspection apparatus or magnetic inspection method that can be realized.

  As a result of extensive research and trial and error, the present inventor has conducted a trial and error, and as a result of using an external magnetic field source instead of a passive magnetic inspection device that detects the residual magnetism of the detected object as in the conventional magnetic inspection device. The inventors have come up with an active magnetic inspection apparatus that uses an MI element to detect magnetic fluctuations caused by the movement of an object to be detected in the generated strong magnetic field environment. By developing this result, the present invention described below has been completed.

《Magnetic inspection device》
(1) A magnetic inspection apparatus according to the present invention includes an inspection magnetic field source that generates an inspection magnetic field applied to a detection object made of a magnetic material included in an inspection object, and extends in a specific axial direction within the inspection magnetic field. A magneto-impedance element having a magnetosensitive element capable of changing impedance in response to specific magnetism that is magnetized in the specific axis direction, and the inspection object moves relative to the magneto-impedance element or the inspection magnetic field source. Thus, the presence state of the detected object in the inspection object can be grasped based on the change in the specific magnetism induced by the detected object in the inspection magnetic field.

(2) According to the magnetic inspection apparatus of the present invention, the inspection object is arranged in the inspection magnetic field which is a strong magnetic field environment, and the detected object (foreign matter, magnetic ink, etc.) contained in the inspection object is sufficiently provided. The magnetism emitted from the detected object can be detected in a magnetized state (and also in a saturated magnetization state). For this reason, it is possible to detect a soft magnetic material that has been difficult to detect by measurement using residual magnetism, and even a finer object to be detected can be subjected to magnetic inspection as compared with the conventional apparatus.

  Here, in the magnetic inspection apparatus of the present invention, an MI element having a much higher sensitivity and resolution than a conventional MR element or the like is used as a magnetic sensor, and the magnetic sensor is made of a magnetic sensitive body extending in a specific axis direction. The MI element does not detect the magnetic component in the direction perpendicular to the specific axis direction, but detects only the magnetic component in the specific axis direction. By using this MI element, even in a strong magnetic field environment, it is possible to detect only a change in a magnetic component (specific magnetism) in a specific direction induced by a detection object with high sensitivity, and detection with excellent spatial resolution is also possible. . Thus, according to the magnetic inspection apparatus of the present invention, it is possible to detect, recognize or identify the detected object with high accuracy.

《Magnetic inspection method》
The present invention can be grasped not only as the magnetic inspection apparatus described above but also as a magnetic inspection method. That is, the present invention is an inspection magnetic field source that generates an inspection magnetic field to be applied to an inspection object that can include an object to be detected made of a magnetic material, or a magnetism that extends in a specific axis direction in the inspection magnetic field and extends in the specific axis direction. A moving step capable of moving the inspection object relative to a magneto-impedance element having a magnetosensitive body capable of changing impedance in response to a specific magnetism, and the detected object within the inspection magnetic field during the moving step. A detection step of detecting the induced change in the specific magnetism by the magneto-impedance element, and the presence state of the detected object in the inspection object can be grasped based on the change in the specific magnetism. It can be grasped as a magnetic inspection method.

<Others>
(1) The inspection magnetic field referred to in this specification is a magnetic field formed by an inspection magnetic field source, and a specific axial direction component of the magnetism detected by the MI element when the detected object enters or leaves the magnetic field ( This is the range in which the specific magnetism) varies.

(2) “Means” and “Steps” which are constituent elements of the present invention can be read interchangeably. For example, the contents constituting the moving means and the determining means can be substantially the contents constituting the moving step and the determining step.

It is a schematic diagram of a magnetic inspection apparatus (Example 1). It is a graph which shows the variation | change_quantity of the specific magnetism detected by it. It is a schematic diagram of a magnetic inspection apparatus (Example 2). It is a graph which shows the variation | change_quantity of the specific magnetism detected by it. It is a schematic diagram of a magnetic inspection apparatus (Example 3). It is a graph which shows the variation | change_quantity of the specific magnetism detected by it. It is a schematic diagram of a magnetic inspection apparatus (Example 4). It is a graph which shows the variation | change_quantity of the specific magnetism detected by it. It is a schematic diagram of a magnetic inspection apparatus (Example 5). It is a graph which shows the variation | change_quantity of the specific magnetism detected by it. It is a schematic diagram of a magnetic inspection apparatus (Example 6). It is a graph which shows the variation | change_quantity of the specific magnetism detected by it. It is a schematic diagram of a magnetic inspection apparatus (Example 7). It is a graph which shows the variation | change_quantity of the specific magnetism detected by it. It is a schematic diagram of a magnetic inspection apparatus (Example 8). It is a graph which shows the variation | change_quantity of the specific magnetism detected by it.

  The contents described in this specification can be applied not only to the magnetic inspection apparatus of the present invention but also to the magnetic inspection method. One or two or more components arbitrarily selected from the present specification may be added to the above-described components of the present invention. Which embodiment is the best depends on the target, required performance, and the like.

<MI element>
The MI element is an element that uses a magneto-impedance effect (MI effect) in which the impedance of a magnetosensitive body under the supply of a high-frequency current changes according to an external magnetic field due to the skin effect. This magnetosensitive body is usually composed of a wire or a thin film made of a soft magnetic material such as a CoFeSiB alloy, but an amorphous wire having zero magnetostriction is particularly preferable in terms of sensitivity and cost.

  The impedance change according to the magnetic field change of the magnetosensitive body to which the high frequency (pulse) current is applied may be detected directly from the voltage across the magnetosensitive body, or a detection coil wound around the extending magnetosensitive body. You may detect indirectly as a change of an electromotive force via a (pickup coil). However, when a detection coil is used, the direction of specific magnetism can be detected, and detection with higher sensitivity is possible. In this case, the MI element according to the present invention includes a detection coil (detection means) in addition to the magnetic sensitive body (particularly, the magnetic sensitive wire).

  In addition to the MI element, a magnetic sensor composed of an MI element (referred to as “MI sensor” as appropriate) processes, for example, a pulse oscillation circuit that supplies a high-frequency (pulse) current to the MI element and a voltage generated in the pickup coil. A signal processing circuit and the like are provided. It is preferable that the circuit and the MI element are provided on the same substrate because the entire MI sensor is compact, and the magnetic inspection apparatus can be downsized. Many applications for such MI sensors have been filed, and are described in detail in, for example, WO 2005/19851 publication, WO 2009/119081 publication, and Japanese Patent 4655247 publication.

  Since one MI sensor is excellent in directivity, one MI sensor is basically provided for each magnetic detection direction (coordinate axis direction) that is a detection target. In the magnetic inspection apparatus of the present invention, it is sufficient to provide at least one MI element capable of detecting magnetism (specific magnetism) in a specific axis direction, but a plurality of MI elements may be provided corresponding to a plurality of detection directions. For example, two MI elements each having a specific axis direction in two directions perpendicular to the relative movement direction of the inspection object may be provided. As a result, even when the relative movement trajectory varies for each inspection object or becomes two-dimensional, the detection object can be detected more reliably for each inspection object. Note that a plurality (for example, a pair) of MI elements may be provided in the horizontal direction or the vertical direction along the same detection direction (specific axis direction). In the case where a plurality of MI elements are provided, it is preferable to integrate the pulse oscillation circuit on the input side and the signal processing circuit on the output side without providing each MI element so that the magnetic inspection apparatus can be reduced in size.

<Inspection magnetic field source>
The inspection magnetic field source may be a permanent magnet or an electromagnet. When a permanent magnet is used as the inspection magnetic field source, the magnetic inspection apparatus can be reduced in size and simplified, and generation of noise that affects detection by the MI element can be suppressed.

  As long as the generation of the inspection magnetic field and the detection of the specific magnetism or the amount of change in the inspection magnetic field are possible, the number of inspection magnetic field sources, the direction of the magnetic pole, etc. are not limited. However, it is preferable to adjust the arrangement of the inspection magnetic field source and the MI element so that the amount of change in the specific magnetism detected by the MI element increases when the detected object approaches or separates from the inspection magnetic field source or the MI element.

  Various arrangements of the inspection magnetic field source are conceivable. For example, the inspection magnetic field source may include at least a first inspection magnetic field source and a second inspection magnetic field source, and a magneto-impedance element may be disposed between the first inspection magnetic field source and the second inspection magnetic field source. One or a plurality of inspection magnetic field sources may be arranged along the specific axis direction, arranged perpendicular to the specific axis direction, or arranged obliquely or intersecting with the specific axis direction. May be. The plurality of inspection magnetic field sources may be arranged so that the same magnetic poles face each other (opposite each other) or different magnetic poles face each other (opposite each other).

"transportation"
The magnetic field state (distribution state of magnetic field lines) in the inspection magnetic field generated by the inspection magnetic field source can be disturbed and changed by the advancement / retraction or relative movement in the inspection magnetic field of the inspection object including the detection target. By detecting such a change state or change amount of the inspection magnetic field, the detection object can be detected and identified.

  Therefore, first, it is necessary that the inspection object including the detected object approaches (enters) or separates (withdraws) from the inspection magnetic field. At this time, any one of the inspection magnetic field source and / or the MI element and the inspection object needs to move. When inspecting many inspection objects efficiently, it is preferable that the magnetic inspection apparatus of the present invention further includes moving means that can move the inspection object relative to the inspection magnetic field source or the magneto-impedance element. This moving means is, for example, a transport means for transporting the inspection object into the inspection magnetic field. Conversely, if the magnetic inspection apparatus is a handy type in which the inspection magnetic field source and the MI element are packaged, the magnetic inspection apparatus may be automatically or manually approached or separated from the inspection object.

《Judgment means》
Next, in order to grasp the existence state of the detected object with high accuracy by the magnetic inspection apparatus of the present invention, the specific magnetism when the detected object is outside the inspection magnetic field (reference when not affected by the detected object) It is necessary to determine the presence / absence of the detected object, the distribution of the detected object, and the like by comparing the magnetism) with the specific magnetism when the detected object is in the inspection magnetic field.

  Therefore, it is preferable that the magnetic inspection apparatus of the present invention further includes a determination unit that can determine the presence state of the detected object based on the change amount or change state of the specific magnetism. In the case of detecting the presence or absence of a foreign object or the like that is the detection target, the determination unit may be a comparison unit that compares the amount of change in specific magnetism with a predetermined threshold, for example. On the other hand, in the case of grasping the position where such a foreign substance exists or performing recognition or identification of a printed matter using magnetic ink, the determination means, for example, the change state of specific magnetism (for example, the detection waveform of specific magnetism), It can be used as a comparison means for comparing with a reference state (for example, a reference waveform of specific magnetism) when the detection target does not exist.

<Inspection object and detected object>
The inspection object according to the present invention may be of any type or shape. For example, the inspection object is food, medicine, industrial product, special print medium (banknote, check, etc.), and the like. The object to be detected included in such an inspection object only needs to be made of a magnetic material that changes the specific magnetism detected in the inspection magnetic field. The object to be detected is a magnetic material or the like contained in a metal foreign object, printed matter, etc., depending on the inspection object and the inspection purpose. In the magnetic inspection apparatus of the present invention, residual magnetism is not detected as in the prior art, and an MI element that is more sensitive than an MR element can be used. Therefore, even if the object to be detected is extremely fine, highly accurate detection, identification, etc. Is possible. In addition, although it is preferable that the detection target is magnetized until it is saturated in the inspection magnetic field, the magnetization level of the detection target in the inspection magnetic field is not limited as long as the detection target can be detected.

  The “existing state of the object to be detected” as used in this specification differs depending on the form of the inspection object and the inspection purpose. For example, if the presence / absence of a foreign substance or the like is for the purpose of inspection, the presence state of the detected object is simply the presence / absence of the detected object. However, if the purpose of inspection is to identify the presence position of foreign matter, etc., the distribution status of magnetic materials contained in the print medium, and the identification and recognition of the inspection object, the presence status of the detection object The location and distribution are also included.

Example 1
(1) Configuration of Magnetic Inspection Device FIG. 1A shows an outline of a magnetic inspection device 1 which is an embodiment for more specifically explaining the present invention, and how the magnetic inspection device 1 detects the presence or absence of foreign matter T (steel balls). It was shown to. The magnetic inspection apparatus 1 includes a permanent magnet m11 (first inspection magnetic field source), a permanent magnet m12 (second inspection magnetic field source), an MI element E disposed in the center of the permanent magnets m11 and m12, and an MI element E. Drive circuit (not shown) and a determination circuit (not shown / determination means) for determining the presence or absence of the foreign matter T based on the output of the MI element E.

  The MI element E includes a magnetic sensing wire w disposed on the y-axis (specific axis) extending in the vertical direction in the drawing in the center of the permanent magnets m11 and m12, and a pickup surrounding the magnetic sensing wire w. It consists of a coil c. The magnetosensitive wire w is made of an amorphous wire having a substantially zero magnetostriction made of a CoFeSiB alloy.

  The permanent magnets m11 and m12 are made of plate-like rare earth magnets, and different poles (N pole of the permanent magnet m11 and S pole of the permanent magnet m12) are arranged facing each other along a direction perpendicular to the y axis (specific axis). ing. For reference, the inspection magnetic field F1 generated by these permanent magnets m11 and m12 is indicated by magnetic lines (broken lines).

  The MI element E (magnetic wire w and pickup coil c) and the drive circuit are formed on a silicon substrate, and these are the MI sensor (chip). The drive circuit includes a pulse oscillation circuit that is connected to both end electrodes of the magnetic sensing wire w and supplies a pulse current, and a signal processing circuit that samples, amplifies, and outputs the voltage generated in the pickup coil c at a predetermined timing. Become. The output obtained from the signal processing circuit is input to a determination circuit that determines the presence or absence of the foreign matter T.

(2) Foreign object detection by magnetic inspection apparatus As shown in FIG. 1A, a case where the foreign object T passes through the permanent magnets m11 and m12 and the MI element E (in the drawing) in the direction of the arrow (x-axis direction) is considered. . First, the y-axis direction component (specific magnetism) of the inspection magnetic field F1 when the foreign object T is sufficiently far away is measured by the MI element E arranged in the inspection magnetic field F1. The specific magnetism obtained at this time is set as a reference magnetic field (M0).

  Next, the foreign matter T is slowly moved from the far side on the left side (the negative side of the x axis) to the right side (the positive side of the x axis) by transport means such as a belt conveyor. This is a magnetic component in the y-axis direction of the inspection magnetic field F1 detected by the MI element E along with the change in the magnetization state (direction and strength) of the foreign matter T along with this movement. The specific magnetism (M) also changes.

  FIG. 1B shows how the specific magnetism (M) changes with respect to the reference magnetic field (M0) as the foreign object T moves (ΔM = M−M0). The waveform shown in FIG. 1B is a copy of the waveform of the output from the signal processing circuit of the MI element E observed with an oscilloscope. For reference, the magnetization state (direction) at each position of the foreign matter T is shown below FIG. 1B.

  As can be seen from FIG. 1B, when the foreign substance T passes through the inspection magnetic field F1, the specific magnetism detected by the MI element E is greatly increased from a negative peak (magnetic field downward) to a positive peak (magnetic field upward). You can see that it changes. Since the magnetic inspection apparatus 1 can determine the presence / absence of an object to be detected based on such a large amount of change in specific magnetism, inspection with very high sensitivity and high accuracy is possible.

  Incidentally, the inspection magnetic field F1 is a magnetic field formed by the permanent magnets m11 and m12, and is a magnetic field within a range in which the specific magnetism (y-axis component) detected by the MI element E due to the entry of the foreign matter T varies. . Most conveniently, it may be considered as a magnetic field that can be formed between the center of the permanent magnet m11 and the center of the permanent magnet m12 (section [-a, a] in the x-axis direction shown in FIG. 1A or FIG. 1B). The same applies to other embodiments.

Example 2
A magnetic inspection device 2 in which the shape and arrangement of the permanent magnet m11 and the permanent magnet m12 of the magnetic inspection device 1 are changed is shown in FIG. 2A. The permanent magnets m21 and m22 constituting the magnetic inspection apparatus 2 are rod-shaped rare earth magnets, and as shown in FIG. 2A, the same poles (N pole of the permanent magnet m21 and N pole of the permanent magnet m22) are connected to the y axis ( It is arranged facing each other along the direction perpendicular to the specific axis. For reference, the inspection magnetic field F2 generated by these permanent magnets m21 and m22 is indicated by magnetic lines of force (broken line). In addition, about the same component as the magnetic inspection apparatus 1, the same code | symbol was used also in the present Example. The same applies to other embodiments.

  FIG. 2B shows the amount of change (ΔM = M−M0) with respect to the reference magnetic field (M0) of the specific magnetism (M) detected by the MI element E of the magnetic inspection apparatus 2 as the foreign object T moves. When the magnetic inspection apparatus 1 and the magnetic inspection apparatus 2 are compared, the waveform relating to the change amount of the specific magnetism is different, but the presence / absence of the detected object can be determined with high sensitivity and high accuracy based on the large change amount of the specific magnetism It is the same.

Example 3
Unlike the magnetic inspection apparatus 1 or the like, the magnetic inspection apparatus 3 is formed by arranging one permanent magnet m3 made of a rod-shaped rare earth magnet along the y-axis (specific axis) as shown in FIG. 3A. For reference, the inspection magnetic field F3 generated by these permanent magnets m3 is indicated by magnetic lines (broken lines). Further, FIG. 3B shows the change amount (ΔM = M−M0) of the specific magnetism (M) with respect to the reference magnetic field (M0) detected by the MI element E of the magnetic inspection apparatus 3 as the foreign object T moves. In this case as well, the waveform related to the amount of change in the specific magnetism is different from that in the other embodiments. It is the same. In FIG. 3A, the N pole of the permanent magnet m3 is directed upward, but the S pole may be directed upward. By changing the magnetic pole toward the MI element E, the waveform shown in FIG.

Example 4
As shown in FIG. 4A, the magnetic inspection device 4 is formed by arranging a permanent magnet m41 and a permanent magnet m42 made of rod-shaped rare earth magnets in parallel so as to be along the y axis (specific axis) and sandwich the y axis at the center. . For reference, the inspection magnetic field F4 generated by these permanent magnets m41 and m42 is indicated by magnetic lines (broken lines). FIG. 4B shows the amount of change (ΔM = M−M0) with respect to the reference magnetic field (M0) of the specific magnetism (M) detected by the MI element E of the magnetic inspection apparatus 4 as the foreign object T moves. In this case as well, the waveform related to the amount of change in the specific magnetism is different from that of the other embodiments, but the other embodiment is that the presence / absence of the detected object can be determined with high sensitivity and high accuracy based on the large amount of change in the specific magnetism. It is the same. In FIG. 4A, the permanent magnet m41 and the permanent magnet m42 are arranged so as to be in contact with different poles, but the permanent magnet m41 and the permanent magnet m42 may be arranged so as to be in contact with each other with the same polarity.

Example 5
As shown in FIG. 5A, the magnetic inspection device 5 has a permanent magnet m <b> 51 and a permanent magnet m <b> 52 made of rod-shaped rare earth magnets arranged vertically so as to face each other with different polarities along the y-axis (specific axis). Become. For reference, the inspection magnetic field F5 generated by these permanent magnets m51 and m52 is indicated by magnetic lines (broken lines). In addition, FIG. 5B shows the amount of change (ΔM = M−M0) with respect to the reference magnetic field (M0) of the specific magnetism (M) detected by the MI element E of the magnetic inspection apparatus 5 as the foreign object T moves. In this case as well, the waveform related to the amount of change in the specific magnetism is different from that of the other embodiments, but the other embodiment is that the presence / absence of the detected object can be determined with high sensitivity and high accuracy based on the large amount of change in the specific magnetism. It is the same.

Example 6
The magnetic inspection apparatus 6 is obtained by changing the arrangement of the permanent magnets m51 and m52 and the arrangement of the MI element E of the magnetic inspection apparatus 5. That is, as shown in FIG. 6A, the permanent magnet m61 and the permanent magnet m62 made of rod-shaped rare earth magnets are arranged vertically so as to face each other with the same polarity along the y-axis (specific axis), and the MI element E Was placed closer to the lower permanent magnet m62 (side closer to the miracle of the foreign matter T). For reference, the inspection magnetic field F6 generated by these permanent magnets m61 and m62 is indicated by magnetic lines of force (broken line). FIG. 6B shows the amount of change (ΔM = M−M0) with respect to the reference magnetic field (M0) of the specific magnetism (M) detected by the MI element E of the magnetic inspection apparatus 6 as the foreign object T moves. In this case as well, the waveform related to the amount of change in the specific magnetism is different from that in the other embodiments. It is the same.

Example 7
As shown in FIG. 7A, the magnetic inspection apparatus 7 is configured by arranging a permanent magnet m71 and a permanent magnet m72 made of rod-shaped rare earth magnets to face each other with different polarities along an oblique direction of the y-axis (specific axis). For reference, the inspection magnetic field F7 generated by these permanent magnets m71 and m72 is indicated by magnetic lines of force (broken line). FIG. 7B shows the amount of change (ΔM = M−M0) with respect to the reference magnetic field (M0) of the specific magnetism (M) detected by the MI element E of the magnetic inspection apparatus 7 as the foreign object T moves. In this case as well, the waveform related to the amount of change in the specific magnetism is different from that of the other embodiments, but the other embodiment is that the presence / absence of the detected object can be determined with high sensitivity and high accuracy based on the large amount of change in the specific magnetism. It is the same.

Example 8
As shown in FIG. 8A, the magnetic inspection apparatus 8 is arranged in a cross shape (X shape) with four permanent magnets m81, m82, m83, and m84 made of rod-shaped rare earth magnets symmetrical with respect to the y axis (specific axis). Do it. In the present embodiment, the S poles of the permanent magnet m81 and the permanent magnet m82 are arranged inside, and the N poles of the permanent magnet m83 and the permanent magnet m84 are arranged inside. For reference, the inspection magnetic field F8 generated by these permanent magnets m81, m82, m83, and m84 is indicated by magnetic lines (broken lines). FIG. 8B shows the amount of change (ΔM = M−M0) with respect to the reference magnetic field (M0) of the specific magnetism (M) detected by the MI element E of the magnetic inspection apparatus 8 as the foreign object T moves. In this case as well, the waveform related to the amount of change in the specific magnetism is different from that in the other embodiments. It is the same.

  As described above, there can be various arrangements of inspection magnetic field sources and MI elements. In any case, according to the magnetic inspection apparatus of the present invention, detection and identification of a detection object with high sensitivity and high accuracy are possible. Etc. are possible.

1 Magnetic inspection device E MI element m1, m2 Permanent magnet (inspection magnetic field source)
F1 Inspection magnetic field T Foreign object (object to be detected)

Claims (5)

An inspection magnetic field source for generating an inspection magnetic field applied to a detection object made of a magnetic material included in the inspection object;
A magneto-impedance element having a magnetosensitive body that extends in a specific axis direction in the inspection magnetic field and can change impedance in response to specific magnetism that is magnetism in the specific axis direction;
The inspection object moves relative to the magneto-impedance element or the inspection magnetic field source, and based on the change in the specific magnetism induced by the detected object in the inspection magnetic field, A magnetic inspection apparatus capable of grasping the presence state of the detected object. The inspection magnetic field source comprises at least a first inspection magnetic field source and a second inspection magnetic field source,
The magnetic inspection apparatus according to claim 1, wherein the magneto-impedance element is disposed between the first inspection magnetic field source and the second inspection magnetic field source.   The magnetic inspection apparatus according to claim 1, wherein the inspection magnetic field source is disposed along the specific axis direction or a direction perpendicular to the specific axis direction.   Furthermore, the magnetic inspection apparatus in any one of Claims 1-3 provided with the moving means which can move the said test target object relatively with respect to the said test | inspection magnetic field source or the said magneto-impedance element. An inspection magnetic field source that generates an inspection magnetic field to be applied to an inspection object that can include an object to be detected made of a magnetic material, or a specific magnetic field that extends in a specific axis direction in the inspection magnetic field and is a magnetism in the specific axis direction. A moving step capable of moving the test object relative to a magneto-impedance element having a magnetosensitive element capable of changing impedance.
A detection step of detecting, by the magneto-impedance element, a change in the specific magnetism induced by the detected object in the inspection magnetic field during the moving step;
A magnetic inspection method characterized in that the presence state of the detected object in the inspection object can be grasped based on the change in the specific magnetism.

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