JP5693317B2 - Magnetic flaw detector - Google Patents

Description

  The present invention relates to a sheet-like or bag-like flexible magnetic flaw detection sheet enclosing a magnetic sensitive material that forms a pattern corresponding to the magnetic flux density, and a magnetic flaw detection sheet to be inspected by applying pressure to the magnetic flaw detection sheet. A magnetic pressure generating means and a magnetism generating mechanism are provided, and the magnetism generated by the magnetism generating mechanism is leaked from the object to be inspected by causing the magnetism generated by the magnetism generating mechanism to act on the object to be inspected in a state where the object is in contact with the magnetic flaw detection sheet. The present invention relates to a magnetic flaw detector configured to detect a magnetic flux to be detected by a magnetic sensor of a magnetic flaw detection sheet and perform a flaw detection on an inspection target based on a pattern created by the magnetic sensor.

As a technique related to the above-described magnetic flaw detection apparatus, for example, in Patent Document 1, a magnetic flaw detection sheet S, a pressing member 20, and a pressure plate 21 are placed in this order on the surface of the inspection object 1, and two rubber belts 25 are further provided. Is disposed so as to apply a biasing force to the pressure-bonding plate 21 over the surface of the pressure-bonding plate 21 placed and the surface of the object 1 to be inspected, and the two rubber belts 25 are inspected. It is disclosed that a permanent magnet 27 may be used as means for fixing to the surface of the object 1 (see FIGS. 7 and 8 of Patent Document 1). A magnetic flaw detection sheet S is disposed between the magnetic poles 30P and 30P in the U-shaped magnetism generation mechanism M, and power is supplied in a state where the magnetic poles 30P and 30P are in contact with the surface of the object 1 to be inspected. A pattern of the magnetic powder 13 is formed on the magnetic flaw detection sheet S by the generated magnetism, and the magnetic flaw detection is performed based on the pattern. In addition, the reference number quoted the thing in patent document 1. FIG.
Thus, the magnetic flaw detection sheet S is magnetically attached to the surface of the inspection object 1 to some extent by the weight of the pressing member 20 and the pressure plate 21, the urging force by the rubber belt 25, and the slight attraction force by the permanent magnet 27. It is thought that flaw detection can be performed.

As a technique related to the magnetic flaw detection apparatus, for example, Patent Document 2 discloses a U-shaped magnet in which a magnetic flaw detection sheet D and a pair of magnetic poles 3 and 3 are disposed with the magnetic flaw detection sheet D interposed therebetween. A generating mechanism A, a biasing mechanism B is attached to the magnetism generating mechanism A, and a pressure between the pressure-bonding body 4 biased by the biasing mechanism B and the magnetic flaw detection sheet D is flexible and freely deformable. A pressing member C capable of transmission is provided, and the magnetic flaw detection is performed based on the pattern of the magnetic powder 38 formed on the magnetic flaw detection sheet D. In addition, the permanent magnets 50 (three) of the pair of permanent magnets 50, 50 (three each) are provided at both locations of the crimped body 4 with the magnetic flaw detection sheet D sandwiched between the magnetic generation mechanisms A. Are arranged in parallel to the virtual straight line connecting the pair of magnetic poles 3 and 3 (see FIGS. 14 to 16 of Patent Document 2). In addition, the reference number quoted the thing in patent document 2. FIG.
As a result, the magnetic flaw detection sheet D is magnetically attached to the surface of the object 1 to be inspected to some extent by the urging force via the pressure-bonding body 4 and the pressing member C by the urging mechanism B and the attracting force by the permanent magnet 50. It is thought that flaw detection can be performed.

JP 2003-279545 A JP 2004-333484 A

  Here, as the magnetic flaw detection apparatus, the magnetic flaw detection sheet is uniformly and reliably adhered to the surface of the object to be inspected, and magnetism with a stronger magnetic flux density is applied to the object to be inspected, thereby By increasing the magnetic flux density that leaks from the magnetic particles in the magnetic flaw detection sheet and moving the magnetic particles appropriately to form a clear pattern, the detection accuracy of defects in the inspection target is further improved. Is desired.

In this regard, when the magnetic flaw detection apparatus of Patent Document 1 is examined, when the magnetic flaw detection sheet S is brought into close contact with the inspection object 1, the urging force mainly by the two rubber belts 25 is transmitted via the pressure plate 21 and the pressing member 20. Since the magnetic flaw detection sheet S is configured to be in close contact with the object 1 to be inspected, a sufficient urging force is not applied to a portion other than the portion where the rubber belt 25 and the crimping plate 21 are in contact with each other, and the magnetic flaw detection sheet S is made uniform. In addition, there is a problem that it is difficult to closely contact the object 1 to be inspected.
Further, each permanent magnet 27 in the pair of permanent magnets 27, 27 is disposed along a direction orthogonal to a virtual straight line connecting the magnetic poles 30P, 30P of the magnetism generating mechanism M in a top view. It is only used for fixing to the inspection object 1 and is not intended to increase the magnetic flux density leaking to the magnetic flaw detection sheet S. Further, as a result of the existence of each permanent magnet 27, the magnetic field generated by each permanent magnet 27 and the magnetic field generated by the magnetism generating mechanism M coexist and the both magnetic fields are complicated, and act on the object 1 to be inspected. The magnetic field (magnetic flux) and the magnetic field (magnetic flux) leaking to the magnetic flaw detection sheet S become complicated, and the pattern formed by the magnetic powder 13 may become unclear, and the magnetic field (magnetic flux) acting on the inspection object 1 cancels out. There is a problem that the magnetic flux density cannot be increased due to the matching, and it becomes difficult to improve the accuracy of detecting defects in the inspection object 1.

In the magnetic flaw detection apparatus disclosed in Patent Document 2, the magnetic flaw detection sheet D is pressed through the pressing member C by the urging force of the urging mechanism B attached to the magnetism generation mechanism A, so that the magnetic flaw detection sheet D is pressed. It is considered that D can be brought into close contact with the inspection object 1 to some extent.
Further, the magnetic flaw detection sheet D is brought into close contact with the inspection object 1 to some extent by the attraction force of a pair of permanent magnets 50 and 50 (each of which is three in total, six) arranged with the magnetic flaw detection sheet D sandwiched between them. It is thought that you can.
However, the longitudinal direction of the magnetic flaw detection sheet D is arranged in a direction orthogonal to a virtual straight line connecting the magnetic poles 3 and 3 of the magnetic generation mechanism A, and a pair is arranged so as to sandwich the magnetic flaw detection sheet D in the longitudinal direction. Even if the permanent magnets 50 and 50 are provided, it is difficult to make the magnetic flaw detection sheet D uniformly adhere to the inspection object 1. In addition, the pair of permanent magnets 50 and 50 are disposed on the pressure-bonding body 4, but are only used to attract the pressure-bonding body 4 to the object 1 to be inspected. It is not intended to increase the leakage flux density. Further, each of the permanent magnets 50 (three) in the pair of permanent magnets 50, 50 is between the magnetic poles 3, 3 in a direction along a virtual straight line connecting the magnetic poles 3, 3 of the magnetism generating mechanism A in a top view. In addition, the permanent magnets 50 on one side (b4, b5, b6 3 in FIG. 15 of Patent Document 2) are arranged at positions separated from the virtual line in a direction orthogonal to the virtual line. Are close to the short surface (the right end surface in FIG. 15) of the magnetic flaw detection sheet D. For this reason, as a result of the existence of each permanent magnet 50 on the one side, the magnetic field generated by each permanent magnet 50 is in the vicinity of a virtual straight line that connects the magnetic poles 3 and 3 of the magnetic generation mechanism A, which is the main magnetic flaw detection region. In addition, since the magnetic field generated by the magnetism generating mechanism A also acts on the inspected object 1 in the vicinity of the imaginary straight line, both magnetic fields are complicated and magnetic flaw detection in the vicinity of the imaginary straight line is performed. There is a problem that the magnetic field (magnetic flux) leaking to the sheet D becomes complicated, the pattern formed by the magnetic powder 38 may become unclear, and it becomes difficult to improve the detection accuracy of defects in the inspection target 1. . In some cases, the magnetic flux density leaking to the magnetic flaw detection sheet D in the vicinity of the virtual straight line may be reduced.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to adopt a configuration in which a permanent magnet is used in a magnetic flaw detection apparatus that uses a magnetic flaw detection sheet to perform magnetic flaw detection using the magnetism of a magnetic generation mechanism. However, while the magnetic flaw detection sheet is uniformly and reliably adhered to the surface of the inspection object, the magnetic flux density leaking from the inspection object to the magnetic detection body in the magnetic inspection sheet is further increased, and the magnetic detection body It is an object of the present invention to obtain a magnetic flaw detector capable of further improving the detection accuracy of a defect in an object to be inspected by forming a clear pattern by appropriately moving the pattern.

According to the present invention, a sheet-like or bag-like flexible magnetic flaw detection sheet enclosing a magnetic sensitive material forming a pattern corresponding to a magnetic flux density, and the magnetic flaw detection sheet by applying pressure to the magnetic flaw detection sheet A pressure applying means for contacting the object to be inspected, a permanent magnet that presses the magnetic flaw detection sheet from the surface side of the magnetic flaw detection sheet to the inspection object side by an attraction force that is magnetically attracted to the inspection object; And a magnetic flux leaking from the inspection target by causing the magnetism generated by the magnetic generation mechanism to act on the inspection target in a state where the magnetic flaw detection sheet is in contact with the inspection target. A magnetic flaw detector configured to be detected by a magnetic sensor of a magnetic flaw detection sheet and to perform the flaw detection of the inspection target based on a pattern created by the magnetic sensor. Features of the magnetic flaw detection apparatus according to claim 1 of the action and effects are as follows.

〔Feature〕
The magnetic generation mechanism for generating an alternating magnetic field includes a pair of parallel yoke portions each having a magnetic pole formed at one end thereof, and a connecting yoke portion connecting the other ends of the pair of parallel yoke portions. A U-shaped yoke made of a magnetic material and configured to generate a magnetic field in a direction along an imaginary straight line connecting the pair of magnetic poles by energizing a coil wound around the connecting yoke portion. ,
The magnetic flaw detection sheet is disposed in parallel with the plane including the virtual straight line between the pair of magnetic poles in a top view,
At least a pair of the permanent magnets is generated from the N pole to the S pole between the pair of permanent magnets in a state where the magnetic flaw detection sheet is sandwiched between the pair of permanent magnets and the pair of parallel yoke portions are not sandwiched. The DC magnetic field is arranged in parallel with the virtual straight line so as to overlap the AC magnetic field of the magnetism generating mechanism, and the permanent magnets are arranged so as to be positioned around the parallel yoke portions of the magnetism generating mechanism. There is in being.

[Action / Effect]
In the magnetic flaw detector having this configuration, a U-shaped magnetism generating mechanism having a pair of magnetic poles, a pair of permanent magnets, and a magnetic flaw detection sheet are arranged in an appropriate positional relationship, so that a magnetism generating an AC magnetic field is generated. By superimposing an AC magnetic field by a mechanism and a DC magnetic field by a pair of permanent magnets, a magnetic field having a stronger magnetic flux density can be formed, and the basic shape of the magnetic field is connected to the magnetic poles of the magnetic generation mechanism. A relatively simple and clear shape along the virtual straight line can be obtained. (Hereinafter, a magnetic generation mechanism that generates an alternating magnetic field is simply referred to as a magnetic generation mechanism. An alternating magnetic field generated by the magnetic generation mechanism may also be simply referred to as a magnetic field.)

In other words, when viewed from above, the pair of magnetic poles formed on the pair of parallel yoke portions in the magnetism generating mechanism are arranged with the magnetic flaw detection sheet sandwiched between the pair of magnetic poles, while the pair of permanent magnets Is arranged around the parallel yoke portion in parallel with the virtual straight line connecting the pair of magnetic poles with the magnetic flaw detection sheet sandwiched between the pair of permanent magnets but without the pair of parallel yoke portions (a pair of magnetic poles). It is arranged. In this case, the permanent magnets constituting the pair of permanent magnets are arranged to face each other via the magnetic flaw detection sheet in the direction along the virtual straight line. Therefore, in a top view, the DC magnetic field generated from the N pole to the S pole between the pair of permanent magnets is formed mainly in the direction along the virtual straight line, while the AC magnetic field generated between the pair of magnetic poles of the magnetism generating mechanism is , Mainly formed on the virtual straight line.
As a result, the AC magnetic field generated by the magnetism generating mechanism and the DC magnetic field generated by the pair of permanent magnets are superimposed on the object to be inspected (main magnetic flaw detection area) between the pair of magnetic poles and near the virtual straight line between the pair of permanent magnets. Thus, a magnetic field (magnetic flux) in a direction along the imaginary straight line when viewed from above can be applied. Therefore, the magnetic flux density acting on the inspection target near the virtual straight line is increased, and the magnetic flux density leaking from the inspection target to the magnetic flaw detection area of the magnetic flaw detection sheet can be increased. In addition, the magnetic field (magnetic flux) leaking to the magnetic flaw detection region mainly has a shape along the virtual straight line, and can have a relatively simple and clear shape.
The direction of the AC magnetic field is a direction along the virtual straight line, but the direction of the AC magnetic field is formed so as to be alternately reversed in the direction along the virtual straight line according to the frequency of the magnetic generation mechanism. When an AC magnetic field acts on a magnetic material, it is known that the higher the frequency, the stronger the magnetic field acts on the surface (skin effect). It is easy to find defects.
The magnetic flaw detection sheet is configured to be pressed against the object to be inspected by the pressure applying unit so that the magnetic flaw detection sheet and the surface of the object to be inspected are in close contact with each other. Since it is arranged in parallel with the virtual straight line with the flaw detection sheet in between and around the parallel yoke portion, the magnetic flaw detection sheet near the virtual straight line is attached by the attractive force that each permanent magnet attracts to the object to be inspected. In addition, it is possible to press from the surface side of the magnetic flaw detection sheet to the inspection object side at the positions on both sides across the region near the virtual straight line.

  Therefore, in a magnetic flaw detection apparatus that uses a magnetic flaw detection sheet to perform magnetic flaw detection by the magnetism of the magnetic generation mechanism, the magnetic flaw detection sheet is uniformly and reliably applied to the surface of the object to be inspected while adopting a configuration in which a permanent magnet is used. The structure to be in close contact with the object to be inspected is made stronger by increasing the magnetic flux density that leaks from the object to be inspected to the magnetic sensor in the magnetic flaw detection sheet, and the magnetic sensor is appropriately moved to form a clear pattern. Thus, it is possible to obtain a magnetic flaw detector capable of further improving the defect detection accuracy.

The features, functions and effects of the magnetic flaw detector according to claim 2 of the present invention are as follows.
〔Feature〕
The pressure applying means generates an urging force by a suction force that attracts the magnetic pole to the object to be inspected by magnetism generated by a pair of magnetic poles of the magnetic generation mechanism and a rigid plate-like pressure-bonded body made of a transparent resin. An urging mechanism, and a first pressure applying means disposed at one end of the plate-like pressure-bonded body and a second pressure applying means disposed at the other end in a direction orthogonal to the virtual straight line. Comprises pressing the plate-like pressure-bonded body by the first pressure applying means and the second pressure applying means to cause the magnetic flaw detection sheet to be pressed against the inspection object,
The first pressure applying means includes the urging mechanism, and one end portion of the plate-like pressure-bonding body receiving the urging force from the urging mechanism is movable in a direction approaching and separating from the object to be inspected. And configured to be supported by the magnetism generating mechanism disposed on one end side of the plate-like crimped body,
The first pressure applying means and the second pressure applying means are arranged in parallel to the virtual straight line when viewed from above, and the plate-like pressure-bonding body and the magnetic flaw detection sheet are the virtual straight line when viewed from above. Is disposed across the first pressure applying means and the second pressure applying means in a direction parallel to a plane including

[Action / Effect]
In the magnetic flaw detector having this configuration, in the direction orthogonal to the imaginary straight line connecting the pair of magnetic poles, the first pressure applying means disposed on one end side of the plate-like crimped body and the other end side are disposed in a top view. By providing the second pressure applying means, the entire surface of the magnetic flaw detection sheet can be pressed against the object to be inspected through the plate-like pressure-bonding body, and can be uniformly adhered to the surface of the object to be inspected.
Specifically, in a direction orthogonal to the imaginary straight line, the urging force by the urging mechanism of the first pressure applying means disposed at one end of the plate-like crimped body and supported by the magnetism generating mechanism in a top view, and The pressing force by the second pressure applying means disposed at the other end of the plate-like crimped body is parallel to the plane including the virtual straight line and parallel to the virtual straight line when viewed from above via the plate-like crimped body. A magnetic flaw detection sheet disposed in a direction orthogonal to the virtual straight line is applied across the first pressure application means and the second pressure application means, and the entire surface of the magnetic flaw detection sheet is applied to the surface of the inspection target. Uniform contact can be achieved.
In addition, as described above, in the direction along the virtual straight line, the magnetic flaw detection sheet in the vicinity of the virtual straight line is converted into an area in the vicinity of the virtual straight line by the attracting force that each permanent magnet attracts to the inspection target in the top view. It is possible to press from the surface side of the magnetic flaw detection sheet to the inspection object side at the positions on both sides of the sheet.
Note that, as described above, the magnetic flaw detection sheet is disposed extending in the direction perpendicular to the imaginary straight line from the first pressure applying unit and the region where the magnetic generation mechanism is present to the second pressure applying unit. When performing a magnetic flaw detection, the magnetism between a pair of magnetic poles of an extension region between the first pressure applying unit and the second pressure applying unit and a magnetism generating mechanism formed in a U shape through the extension region. The flaw detection area can be easily observed by the operator, and can be configured to be very easy to use.

The characteristics, operation and effect of the magnetic flaw detector according to claim 3 of the present invention are as follows.
〔Feature〕
The pressure applying means includes a transparent and deformable plate-shaped pressing member, and is disposed by stacking the plate-shaped pressure-bonding body, the plate-shaped pressing member, and the magnetic flaw detection sheet in this order, and presses the plate-shaped pressure-bonding body. Then, the magnetic flaw detection sheet is configured to be pressed against the inspection object.

[Action / Effect]
In the magnetic flaw detector having this configuration, the pressure applying means includes a plate-like pressing member that is transparent and deformable, and the plate-like pressure-bonding body, the plate-like pressing member, and the magnetic flaw detection sheet are arranged in this order to form a plate-like shape. The entire surface of the magnetic flaw detection sheet is pressed against the object to be inspected via the pressure-bonding body and the plate-like pressing member, so that the surface of the object to be inspected with unevenness can be satisfactorily inspected.

The characteristics, operation and effect of the magnetic flaw detector according to claim 4 of the present invention are as follows.
〔Feature〕
Two sets of the pair of permanent magnets are disposed on the plate-like crimped body, and each pair of permanent magnets is disposed on both sides of the pair of parallel yoke portions in a direction perpendicular to the virtual straight line when viewed from above. It is to be done.

[Action / Effect]
In the magnetic flaw detector having this configuration, the pair of parallel yoke portions (a pair of magnetic poles) of the magnetism generating mechanism are disposed with the magnetic flaw detection sheet sandwiched between the pair of parallel yoke portions in the plate-like crimped body when viewed from above. Since a pair of permanent magnets are disposed on both sides (one side and the other side in the direction perpendicular to the virtual straight line) with the magnetic flaw detection sheet sandwiched between them, the magnetic flux acting on the object to be inspected near the virtual straight line The density can be formed by a magnetic field in which a magnetic field by a pair of magnetic poles and a DC magnetic field by two pairs of permanent magnets are superimposed, and a stronger magnetic flux density can be obtained. In addition, the magnetic field generated by the pair of magnetic poles and the DC magnetic field generated by the two pairs of permanent magnets are formed along a virtual straight line when viewed from above, so that both magnetic fields do not become complicated and act on the object to be inspected ( The magnetic flux density of the magnetic flux (magnetic flux) can be enhanced well, and the magnetic field (magnetic flux) leaking from the object to be inspected to the magnetic flaw detection sheet has a shape mainly along the imaginary straight line, and has a relatively simple and clear shape. it can.
Further, due to the attractive force that each permanent magnet attracts to the object to be inspected, the magnetic flaw detection sheet in the vicinity of the virtual straight line in the direction along the virtual straight line when viewed from above (2 In addition, in the direction perpendicular to the virtual straight line, a total of four locations across the parallel yoke portion (two locations) are stably pressed from the surface side of the magnetic flaw detection sheet to the inspection target side. can do.

The features, operations and effects of the magnetic flaw detector according to claim 5 of the present invention are as follows.
〔Feature〕
The pair of permanent magnets is disposed on the plate-like crimped body, and the pair of permanent magnets is disposed on the virtual straight line when viewed from above.

[Action / Effect]
In the magnetic flaw detector having this configuration, the pair of parallel yoke portions (a pair of magnetic poles) of the magnetism generating mechanism are disposed with the magnetic flaw detection sheet sandwiched between the pair of parallel yoke portions in the plate-like crimped body in a top view. (Between a pair of magnetic poles) In other words, since a pair of permanent magnets are arranged on a virtual straight line connecting the pair of magnetic poles, the magnetic flux density acting on the object to be inspected near the virtual straight line is determined by the pair of magnetic poles. It can be formed by a magnetic field in which a magnetic field and a DC magnetic field by a pair of permanent magnets are superimposed, and a stronger magnetic flux density can be obtained. In addition, since the magnetic field generated by the pair of magnetic poles and the DC magnetic field generated by the pair of permanent magnets are formed along a virtual straight line when viewed from above, both magnetic fields are not complicated, and the magnetic field (magnetic flux) acting on the object to be inspected The magnetic flux density can be enhanced satisfactorily, and the magnetic field (magnetic flux) leaking from the object to be inspected to the magnetic flaw detection sheet has a shape mainly along the virtual line, and can be a relatively simple and clear shape.

The features, operations and effects of the magnetic flaw detector according to claim 6 of the present invention are as follows.
〔Feature〕
The pair of permanent magnets is constituted by a rectangular body or a plate member that is elongated along a direction along the virtual straight line.

[Action / Effect]
In the magnetic flaw detector with this configuration, the pair of permanent magnets is formed of a rectangular body or a plate member that is elongated along the direction along the virtual straight line, so the direction along the virtual line between the pair of permanent magnets A relatively stable shape of a DC magnetic field extending in the same direction can be formed, and even when superimposed with a magnetic field by a pair of magnetic poles formed in the same direction, a relatively stable shape of the magnetic field can be formed. Become.

The features, functions and effects of the magnetic flaw detector according to claim 7 of the present invention are as follows.
〔Feature〕
The connecting yoke portion of the magnetism generating mechanism constituting the first pressure applying means is configured as an intermediate gripping portion that can be gripped by an operator;
The second pressure applying means includes a gripping portion that is connected to both ends of the plate-like pressure-bonded body in a direction along the virtual straight line and is provided in a space on the plate-like pressure-bonded body.

[Action / Effect]
In the magnetic flaw detector having this configuration, in addition to the pressure by the first pressure applying unit, the operator presses the second pressure applying unit while holding the grip portion of the second pressure applying unit. In addition, it is possible to perform the magnetic flaw detection by pressing the plate-like pressure-bonded body, the plate-like pressing member, and the magnetic flaw detection sheet against the surface side of the inspection target to increase the degree of adhesion to the surface of the magnetic flaw detection sheet.

The features, operations and effects of the magnetic flaw detector according to claim 8 of the present invention are as follows.
〔Feature〕
The magnetic flaw detection is performed by applying pressure between the plate-shaped pressure-bonding body and the magnetic flaw detection sheet at a plurality of locations in the spreading direction of the plate-shaped pressure-bonding body by the first pressure applying means and the second pressure applying means. There is provided a pressure detecting means for detecting the pressure received by the plate-like crimped body from the inspection object side in a state where the sheet is in contact with the inspection object.

[Action / Effect]
In the magnetic flaw detector having this configuration, the pressure detection means is provided to detect the pressure generated between the object to be inspected and the plate-like crimped body, and accordingly, an appropriate pressure is applied based on the detection result. Check the condition and perform highly reliable inspection. In addition, for example, the magnetic flaw detection can be automated by configuring the apparatus to take a photograph of the pattern of the magnetic sensitive material appearing on the magnetic flaw detection sheet only when the pressure detection means detects a pressure of a predetermined value or more. it can.

Perspective view of magnetic flaw detector Exploded perspective view of magnetic flaw detector Partial cutaway side view of magnetic flaw detector Partial cutaway side view of the flaw detector Top view of magnetic flaw detector Block circuit diagram showing the control system of the magnetic flaw detector Schematic partial side view of a magnetic field formed by a magnetic flaw detector Top perspective view of magnetic flaw detection sheet Longitudinal section and transverse section of magnetic flaw detection sheet Top view of a magnetic flaw detector according to another embodiment FIG. 10 is a graph showing the relationship between magnetic flux density and time in the magnetic flaw detector of FIG.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
As shown in FIGS. 1 to 5, a magnetic flaw detector 100 according to the present invention is flexible in a sheet shape or a bag shape in which magnetic powder 38 (see FIG. 8) as a magnetic sensitive body forming a pattern corresponding to a magnetic flux density is enclosed. A magnetic flaw detection sheet D, a pressure applying means P for bringing the magnetic flaw detection sheet D into contact with the inspection object 1 by applying pressure to the magnetic flaw detection sheet D, and a magnetism generation mechanism A. Magnetic flux generated by the magnetic generation mechanism A in the state in which the magnetic flaw detection sheet D is in contact with the inspection target 1 to cause magnetic flux leaking from the inspection target 1 (magnetic flux turbulence) to be magnetic powder of the magnetic flaw detection sheet D The inspection object 1 is flaw-detected based on the pattern generated by the magnetic powder 38.

As described above, the magnetic flaw detection apparatus 100 is provided with the pressure applying means P that applies pressure to the magnetic flaw detection sheet D in order to increase the degree of adhesion of the magnetic flaw detection sheet D to the surface of the inspection object 1. As the pressure application means P, a first pressure application means P1 disposed on one end side of the magnetic flaw detection sheet D and a second pressure application means P2 disposed on the other end side are provided.
The first pressure applying means P1 presses the magnetic flaw detection sheet D against the inspection object 1 using the magnetic attraction force generated by the magnetism generating mechanism A. On the other hand, when the operator presses the second pressure applying unit P2, the magnetic flaw detection sheet D is similarly pressed against the inspection target 1.

  The magnetic flaw detection apparatus 100 is configured so as to be arranged and used in the order of the magnetic flaw detection sheet D, the plate-like pressing member C, and the plate-like pressure-bonding body 4 from the surface side of the object 1 to be inspected. The pressing of the body 4 toward the object 1 to be inspected is that, in the first pressure applying means P1, the magnetic attraction generated by the magnetism generating mechanism A is transmitted to the plate-like crimping body 4 via the biasing mechanism B. Further, in the second pressure applying means P2, the pressing force is transmitted as it is to the plate-like pressure-bonding body 4 when the operator performs a pressing operation.

  At the time of inspection, the magnetic flaw detection sheet D is in contact with the inspection object 1, the magnetism generation mechanism A is energized, and the magnetism generated from the magnetic generation mechanism A is applied to the inspection object 1 to be inspected. The magnetic flux that leaks from 1 is captured by the magnetic powder 38 of the magnetic flaw detection sheet D, and the test object 1 can be flawed based on the pattern that the magnetic powder 38 creates.

  By using the magnetic flaw detection apparatus 100 of the present invention, flaw detection can be performed on the inspection object 1 that is a magnetic material represented by iron. Specifically, as shown in FIG. 1 and FIG. 3, an operator is inspected for a defect (scratches such as cracks) in a surplus portion 1A of a welded portion of an iron plate material or a curved portion of an iron pipe. However, magnetic flaw detection can be performed by operating the magnetic flaw detection apparatus 100 with both hands. As the surplus portion 1A, for example, an inspection target having a general form having a width of about 10 mm and a rising height of about 4 mm from the surface of the inspection target 1 is used. Here, 1C indicates a defect existing in the surplus portion 1A. In addition, since the magnetic flaw detection apparatus 100 is relatively small and configured to be easy to handle, even the inspection object 1 having a vertical wall shape or a ceiling wall shape can be easily operated.

Hereinafter, each part of the magnetic flaw detector 100 will be described in more detail.
In the following description, for example, as illustrated in FIG. 1, the depth direction of the magnetic flaw detection apparatus 100 may be described as the X direction, the horizontal direction as the Y direction, and the height direction as the Z direction.

[Magnetic generation mechanism]
The magnetism generating mechanism A is an application of a hand magna (magnetization device to be inspected). As shown in FIGS. 1 to 4, a plate-like crimped body 4 and a plate-like pressing member C are attached to the hand magna. An urging mechanism B is provided for supporting and urging toward the inspection object 1 side.

  Specifically, as shown in FIG. 6, the magnetism generating mechanism A has a main body 2 having a yoke 2a made of a magnetic material. The yoke 2a has a pair of parallel yoke portions 2b each having a magnetic pole 3 formed at one end (the end on the side in contact with the object 1 to be inspected), and the other end of the pair of parallel yoke portions 2b. It is formed in a U-shape including a connecting yoke portion 2c that connects the end portions on the side separated from the object 1 to be inspected. Further, the main body 2 includes a coil 5 wound around the connecting yoke 2c of the yoke 2a and a cable 7 for supplying power to the coil 5.

  By winding a coil 5 made of a good conductor such as a copper alloy around a yoke 2a made of a magnetic material, the main body 2 functions as an electromagnet. Further, the main body 2 includes a cable 7 for supplying a current from the power supply unit 6 to the coil 5, a power switch 8 capable of turning on and off the current from the power supply unit 6, and a light emitting diode (an example of a light emitter). An illumination mechanism 9 is provided.

  Although FIG. 6 shows an illumination mechanism 9 made of a light emitting diode, it is possible to use a fluorescent lamp or a halogen lamp as the illumination mechanism 9, and for example, from a power source unit 6 or a light source disposed in the vicinity thereof. It is also possible to configure the illumination mechanism 9 with an optical fiber that guides the light beam to the site of the magnetic generation mechanism A. When an optical fiber is used as the illumination mechanism 9, it is not necessary to provide lamps in the vicinity of the magnetism generating mechanism A, and it is not necessary to form a power cable, so that the size of the apparatus can be suppressed.

  Further, the power switch 8 is disposed at a position where the operator can push and operate with the fingertip when operating the main body 2 while holding it. The illumination mechanism 9 is disposed at a position for illuminating the magnetic flaw detection sheet D by allowing light rays to pass through the transparent plate-like crimping plate 4. This makes it possible to clearly observe the pattern created by the magnetic powder 38 of the magnetic flaw detection sheet D even at night or indoors where there is no illumination. The schematic illumination area by the illumination mechanism 9 is a magnetic flaw detection sheet D at the position where the first pressure applying means P1 and the magnetism generation mechanism A are arranged in a top view of the magnetic flaw detection apparatus 100 shown in FIG. The upper surface (main magnetic flaw detection region).

  The power supply unit 6 includes an inverter circuit (not shown) to increase the frequency of the alternating current from the commercial power supply (about 180 Hz and 240 Hz is the upper limit) and supply the coil 5, and operates the power switch 8 to operate the coil 5. An alternating current is supplied to the lighting mechanism 9 and functions to supply a current to the illumination mechanism 9 simultaneously with the supply of the alternating current. As a result, in the magnetism generation mechanism A, the magnetism generated when the alternating current supplied from the power supply unit 6 flows through the coil 5 is transferred between the pair of parallel yoke portions 2b (between the pair of magnetic poles 3). An alternating magnetic field is formed along a virtual straight line L1 (Y direction) that connects the magnetic poles 3 of each other (see the broken line in FIG. 7), the pair of magnetic poles 3 are brought into contact with the surface of the object 1 to be inspected, and the alternating magnetic field is converted into a virtual straight line. It can be made to act on the surface of the inspection object 1 along L1. The direction of the AC magnetic field is a direction along the virtual straight line L1 (Y direction), but the direction of the AC magnetic field is formed so as to be alternately reversed in the Y direction according to the frequency of the AC current. The reason for increasing the frequency of alternating current is known to be that when an alternating (alternating) magnetic field acts on a magnetic material, the higher the frequency, the stronger the magnetic field acts near the surface (skin effect). This is to make it easier to find the defect 1C near the surface of the inspection object 1 by utilizing this phenomenon.

  If the power supply unit 6 supplies an alternating current having a frequency within the range of 240 Hz from the frequency of the commercial power supply at the frequency of the commercial power supply, there is no practical inconvenience, and the supplied voltage is 500 V or less. Is desirable.

[Plate-shaped crimped body]
As shown in FIGS. 1 to 5, the plate-like pressure-bonded body 4 is a plate-like rigid member having a predetermined thickness made of a transparent acrylic resin (see FIGS. 3 and 4), and is approximately T in top view. The first pressure applying means P1 (including the magnetism generating mechanism A) is disposed on one end side in the X direction (direction orthogonal to the virtual straight line L1) when viewed from above, and has the other end. On the side, second pressure applying means P2 are arranged in parallel. The detailed relationship between the plate-like crimped body 4 and the first pressure applying means P1 and the second pressure applying means P2 will be described later.

[First pressure applying means]
The first pressure applying means P1 is an urging mechanism that generates an urging force by an attraction force that attracts the magnetic pole 3 to the inspection target 1 by the magnetism generated by the magnetic generation mechanism A and the pair of magnetic poles 3 of the magnetic generation mechanism A. B, and is disposed on one end side of the plate-like crimped body 4 in the X direction.
Specifically, the other end of the pair of parallel yoke portions 2b of the magnetism generating mechanism A (the end on the side separated from the object 1 to be inspected in the Z direction) is connected to the one end (the magnetic pole 3 in the Z direction). A transparent acrylic resin support 20 from the side) is disposed in an insertion state in an insertion hole 20 a formed in the support 20. The support 20 includes a metal bracket 21 that covers the upper portion of the connecting yoke portion 2c and the upper surface of the support 20, and an engagement mechanism 22 that fixes and connects the bracket 21. The parallel yoke portion 2b of A is engaged and fixed. A plate-like pressure-bonded body made of acrylic resin that is transparent on one end side of the pair of parallel yoke portions 2b via the urging mechanism B with respect to the lower surface of the support body 20 (the magnetic pole side that contacts the object 1 to be inspected in the Z direction). 4 is disposed, and a plate-like pressing member C that is transparent and flexibly deformed on the lower surface side of the plate-like pressure-bonding body 4 and a magnetic flaw detection sheet D are supported in an overlapped state. The support 20 can be formed of metal. However, when a metal is used, an induced current is generated in the metal due to the action of an alternating magnetic field generated by the magnetic generation mechanism A, and heat can be generated. In the present embodiment, transparent acrylic resin is used in order to avoid this heat generation and to improve weight reduction and visibility.

  One end side (one end side in the X direction) of the plate-like crimped body 4 is supported by the urging mechanism B so as to be movable along the longitudinal direction (Z direction) of the parallel yoke portion 2b, and the parallel yoke portion 2b. The magnetic pole 3 is inserted into a through-hole 4a formed through the plate-like pressure-bonding body 4, and when not in use, as shown in FIG. 3, a virtual straight line L1 connecting the pair of magnetic poles 3 to each other, and the magnetic flaw detection sheet D The distance between the bottom surface in the Z direction is set to be the distance S.

  The urging mechanism B includes four through holes p formed in the support body 20, insertion bolts 25 inserted into the four through holes p formed in the plate-like crimp body 4, and the support body 20 and the plate-like crimp body. 4 and a compression coil spring 26 externally fitted to each insertion bolt 25. In a non-use state shown in FIG. 3, the plate-like crimped body 4 is suspended by the four insertion bolts 25. It becomes the form to support. In this urging mechanism B, not only the compression coil spring 26 but also a rubber that obtains an urging force by elastic deformation or a gas spring that uses gas pressure can be used.

Thus, the first pressure applying means P1 is configured to transmit the magnetic attraction force generated by the magnetism generating mechanism A to the plate-like crimping body 4 via the biasing mechanism B.
Further, as described above, the magnetism generating mechanism A of the first pressure applying means P1 includes the main body portion 2 including the generally U-shaped yoke 2a, so that the operator can connect the connecting yoke portion 2c of the yoke 2a. It is configured as an intermediate gripper (not shown) that can be gripped.

[Second pressure applying means]
As shown in FIGS. 1 to 5, the second pressure applying means P <b> 2 is a mechanism disposed on the other end side of the plate-like pressure-bonding body 4 in the X direction. A pair of substantially triangular support side plates 45 erected on the opposite side (upward in the Z direction in FIG. 1) from both side end portions in the Y direction, and between the pair of support side plates 45 And a gripping portion 46 that spans the entire area. Accordingly, the gripping portion 46 of the second pressure applying means P2 connects both side end portions in the Y direction on the other end side of the plate-like pressure-bonding body 4, and is disposed in a space on the plate-like pressure-bonding body 4. The gripper is configured as a gripper that can be gripped by the operator.

  And the intermediate | middle holding | grip part of the 1st pressure provision means P1, the virtual straight line L1 (Y direction) which connects a pair of magnetic poles 3 of the magnetic generation mechanism A of the said 1st provision means P1, and the holding part of the 2nd pressure provision means P2 46 is arranged in parallel.

(Plate-shaped pressing member)
The plate-like pressing member C is a flexible and transparent resin film in which polyvinyl alcohol and borax are mixed with a bag 30 in which a polyethylene film or polyvinyl film having a film thickness of about 0.1 to 0.5 mm is molded into a bag shape. A transparent gel-like (slime-like) material 31 (which may be water), or a material in which a network material obtained by copolymerizing polyethylene and styrene is gelled with oil, or a bag 30 The gelled material is directly affixed without being used, and is configured so as to be transparent and flexible as a whole. Even when the magnetic flaw detection sheet D is in a deformed state, It functions so that the acting pressure acts on the magnetic flaw detection sheet D with a uniform pressure. In the example shown in FIGS. 3 to 5, the plate-like pressing member C is disposed at a position below the plate-like pressure-bonding body 4 in the Z direction, and the second pressure applying means from the position of the first pressure applying means P <b> 1 in the X direction. It extends to the position of P2.

[Magnetic flaw detection sheet]
As shown in FIGS. 8 and 9, the magnetic flaw detection sheet D is obtained by superposing a top surface material 35 made of a flexible and transparent resin film and a back material 36 on the bottom surface side made of a flexible resin film, respectively. Are formed into a flexible sheet having a space d of about 20 to 30 μm by interposing a spacer 37 in which fibers are arranged in a mesh shape between the materials. A magnetic material having a particle size sufficiently smaller than the value of the gap d (about 20 to 30 μm) with a magnetic material of about 0.1 μm or more, and water or kerosene as a dispersion medium It has a sealing structure in which a fluid substance f (which may be a gas) is sealed and the outer peripheral portions of the front surface material 35 and the back surface material 36 are joined using a thermal welding technique or an adhesive.

  More specifically, the surface material 35 and the back material 36 have a film thickness of about 0.02 to 0.5 mm, and it is essential that the surface material 35 of the container is transparent. Some colored material may be used, and the back surface material 36 does not need to be transparent, and a colored resin can also be used. Polyethylene, polyvinyl, or PET (polyethylene terephthalate) resin can be used as the surface material 35 and the back surface material 36, and soft magnetic austenitic stainless steel foil is used as the back surface material 36 in place of the resin film. Is also possible. Further, not only iron and nickel but also magnetite and gamma-hectite can be used as the magnetic powder 38.

  Further, as the spacer 37, a particulate material having a particle diameter equal to the gap d is used in a form of being dispersed between the surface material 35 and the back material 36, or between the surface material 35 and the back material 36. It is also conceivable to use a plurality of columnar members that can form the gap d.

  Further, as shown in FIG. 5, the magnetic flaw detection sheet D is disposed in parallel with a plane including the virtual straight line L <b> 1 (a plane including the X direction and the Y direction) between the pair of magnetic poles 3 in a top view. It is formed in a width that can be disposed between the pair of magnetic poles 3, and is configured to have a depth width similar to that of the plate-like crimped body 4 in the X direction. That is, in the X direction, the magnetic flaw detection sheet D extends from the position of the first pressure applying means P1 (magnetism generating mechanism A) to the position of the second pressure applying means P2, and both ends of the magnetic flaw detection sheet D are connected to each other. Each is pulled in and fixed to the upper surface of the plate-like crimped body 4 (see FIGS. 1 and 8).

  Specifically, when the plate-like pressing member C and the magnetic flaw detection sheet D are supported on the plate-like pressing member 4, the plate-like pressing member C and the magnetic flaw detection sheet D are disposed on the lower surface side of the plate-like pressing member 4. And a pair of end portions in the X direction of the magnetic flaw detection sheet D are respectively drawn up to the upper surface of the plate-like pressure-bonding body 4, and the magnetic flaw detection sheet D is subjected to an appropriate tension in a state where the magnetic flaw detection sheet D is applied. A pair of end portions of the flaw detection sheet D are pressure-bonded with a fixing plate 40 and fixed with screws 41 (see FIG. 1).

  Therefore, in the magnetic flaw detector 100, the plate-like pressure-bonding body 4, the plate-like pressing member C, and the magnetic flaw detection sheet D are pressed from the first pressure applying means P1 and the second pressure applying means P2 to the inspection object 1 side, It is configured so that inspection can be performed satisfactorily.

  As shown in FIGS. 5 and 8, the magnetic flaw detection sheet D has a partition 39 that divides the inside of the magnetic flaw detection sheet D into a plurality of magnetosensitive body movement zones D1, D2, and D3 (three in the figure). It is arranged in parallel with the Y direction, and the movement of the magnetic powder 38 across the magnetosensitive body moving zones D1, D2, D3 is prevented. Specifically, in the top view, the magnetosensitive body moving zone D1 overlaps with the first pressure applying means P1, the magnetosensitive body moving zone D3 overlaps with the second pressure applying means P2, and the magnetosensitive body moving zone D2 is in the first position. The first pressure applying unit P1 and the second pressure applying unit P2 are disposed at positions that do not overlap. The partition 39 is zoned by fusing the front surface material 35 and the back surface material 36 together.

[Pressure detection means]
As shown in FIG. 5, the pressure detection means Se is provided between the plate-like pressure-bonding body 4 and the magnetic flaw detection sheet D in the Z direction (in the illustrated example, the plate-like pressing member C In between, the magnetic flaw detection sheet D is disposed on the inspection object 1 by applying pressure from the first pressure applying means P1 and the second pressure applying means P2. In this state, the pressure received by the plate-like crimped body 4 from the inspection object 1 side can be detected.
The pressure detecting means Se is configured to include a pressure sensitive element such as a piezoelectric element and a light emitting element that emits light by electric power generated in a state where the pressure sensitive element is pressure sensitive. It is configured to emit light while being generated at the position of Se. In FIG. 5, the pressure detection means Se is arranged at the four side end positions of the magnetosensitive body moving zone D2, and thus a predetermined pressing state can be achieved evenly around the magnetosensitive body moving zone D2. It is configured so that the detection means Se can shine evenly and it can be confirmed that a good pressing state can be realized.

[A pair of permanent magnets]
In the magnetic flaw detector 100 of the present invention, as shown in FIGS. 1 to 7, a pair of first permanent magnets 50 </ b> A, 50 </ b> A and a pair of second permanent magnets 50, 50 are attached to the plate-like crimped body 4. Permanent magnets 50B and 50B (two pairs of permanent magnets for a total of four permanent magnets) are arranged.

  Specifically, as shown in FIGS. 1 to 7, each permanent magnet of the pair of first permanent magnets 50 </ b> A and 50 </ b> A and the pair of second permanent magnets 50 </ b> B and 50 </ b> B is a neodymium made of a rectangular plate member in a top view. It is comprised with the magnet and the rectangular plane part is being fixed to the lower surface of the plate-shaped crimping | compression-bonding body 4 with the adhesive agent etc. (refer FIG.3 and FIG.4). In addition, as shown in FIG. 5, the pair of first permanent magnets 50 </ b> A and 50 </ b> A sandwiches the magnetic flaw detection sheet D between the pair of first permanent magnets 50 </ b> A and 50 </ b> A in a top view, and a pair of parallel Similarly, the pair of second permanent magnets 50B, 50B are arranged in parallel to the virtual straight line L1 (Y direction) without sandwiching the yoke portion 2b (the pair of magnetic poles 3). The magnetic flaw detection sheet D is sandwiched between the 50Bs, and the pair of parallel yoke portions 2b (the pair of magnetic poles 3) are not sandwiched, and are arranged in parallel with the virtual straight line L1 (Y direction). Each permanent magnet 50A, 50B made of a plate member has an insertion hole 51 through which the insertion bolt 25 of the urging mechanism B can be inserted in the Z direction in a rectangular plane portion (see FIG. 2). .

  Further, each permanent magnet 50A of the pair of first permanent magnets 50A, 50A is located on the second pressure applying means P2 side in the X direction with respect to each parallel yoke portion 2b of the magnetism generating mechanism A (other than the magnetic flaw detection sheet D). It arrange | positions so that it may be located in the site | part (an example of the circumference | surroundings of each parallel yoke part 2b) of an end side. Similarly, each of the permanent magnets 50B of the pair of second permanent magnets 50B, 50B is located on the opposite side to the second pressure applying means P2 in the X direction with respect to the parallel yoke portion 2b of the magnetism generating mechanism A (magnetic flaw detection sheet). It is arrange | positioned so that it may be located in the site | part (an example of the circumference | surroundings of each parallel yoke part 2b) of the one end side of D.

  Furthermore, each permanent magnet 50A, 50B made of a plate member formed in a rectangular shape in a top view has both long sides on the lower surface of the plate-like pressure-bonding body 4 along the virtual straight line L1 (Y direction). N poles and S poles are formed at both ends of each permanent magnet 50A, 50B in the Y direction, and the arrangement directions of the N poles and S poles in each permanent magnet 50A, 50B are the same. It has become. That is, as shown in FIG. 7, each permanent magnet 50A, 50B made of a plate member has long sides on the Y direction, and an N pole on the right side and an S pole on the left side in FIG. , Between the pair of first permanent magnets 50A and 50A and between the pair of second permanent magnets 50B and 50B, a DC magnetic field is disposed from the north pole to the south pole (from left to right) (solid line in FIG. 7). reference). In FIG. 7, for simplicity, the DC magnetic field between the pair of first permanent magnets 50A and 50A and between the pair of second permanent magnets 50B and 50B is lower than the permanent magnets 50A and 50B (in the Z direction). Only a part of what is formed on the lower side is shown.

  Thereby, between the pair of magnetic poles 3, and between the pair of first permanent magnets 50 </ b> A and 50 </ b> A and between the pair of second permanent magnets 50 </ b> B and 50 </ b> B, the inspection target 1 (main magnetic flaw detection region) in the vicinity of the virtual straight line L <b> 1. A direction along the imaginary straight line L1 in a top view in a state in which an AC magnetic field generated by the magnetic generation mechanism A and a DC magnetic field generated by two pairs of first permanent magnets 50A and 50A and a pair of second permanent magnets 50B and 50B are superimposed. A magnetic field (magnetic flux) in the (Y direction) can be applied. Therefore, the magnetic flux density acting on the inspection object 1 near the virtual straight line L1 is increased, and the magnetic flux density leaking from the inspection object 1 to the magnetic flaw detection area of the magnetic flaw detection sheet D can be increased. Further, the magnetic field (magnetic flux) leaking to the magnetic flaw detection region mainly has a shape along the virtual straight line L1, and can be a relatively simple and clear shape. In this case, it is possible to easily determine the magnetic flux (magnetic flux disturbance) leaking to the magnetic flaw detection sheet D due to the presence of the defect 1C in the inspection object 1.

  Further, the magnetic flaw detection sheet D is configured to be pressed against the inspection target 1 by the first pressure application unit P1 and the second pressure application unit P2 so that the magnetic inspection sheet D and the surface of the inspection target 1 are in close contact with each other. However, the magnetic flaw detection sheet D in the vicinity of the imaginary straight line L1 in the direction (Y direction) along the imaginary straight line L1 when viewed from the top due to the attractive force that each permanent magnet 50A, 50B attracts to the inspection object 1 In the places (two places) on both sides sandwiching the region in the vicinity of the virtual straight line L1, and in the direction (X direction) orthogonal to the virtual straight line L1, it covers the places (two places) on both sides of the parallel yoke portion 2b. It is possible to stably press from the surface side of the magnetic flaw detection sheet D to the inspection object 1 side at a total of four locations.

  Therefore, in the magnetic flaw detection apparatus 100 that uses the magnetic flaw detection sheet D and performs magnetic flaw detection by the magnetism of the magnetic generation mechanism A, the magnetic flaw detection sheet D is applied to the surface of the inspection object 1 while adopting a configuration in which the permanent magnet 50 is used together. The magnetic flux density leaking from the object 1 to be inspected to the magnetic powder 38 in the magnetic flaw detection sheet D is made stronger and the magnetic powder 38 is appropriately moved to make a clear pattern while ensuring a uniform and reliable contact with the magnetic inspection sheet D. By forming the magnetic flaw detection apparatus 100, the detection accuracy of the defect 1C in the inspection target 1 can be further improved.

[Magnetic flaw detection method using magnetic flaw detector]
In this magnetic flaw detector 100, the inspection object 1 is assumed to be a welded portion of a steel plate constituting a tank for storing oil or the like, or a welded portion of a steel plate constituting a bridge or the like. When performing, the work is performed as follows. For example, when flaw detection is performed on the surplus portion 1A of the welded portion, as shown in FIG. 3, a pair of magnetic poles 3 should be disposed at a position across the surplus portion 1A and flaw detection should be performed. By operating the power switch 8 in a state where the magnetic flaw detection sheet D is disposed at a position covering the part, the current from the power supply unit 6 is supplied to the coil 5, and the coil 5 generates magnetism. A pair of magnetic poles 3 are attracted to the inspection object 1.

  When the magnetic pole 3 is attracted to the inspection object 1 in this way, on the first pressure applying means P1 side, as shown in FIG. 4, a virtual straight line L1 connecting the pair of magnetic poles 3 and the bottom surface of the magnetic flaw detection sheet D The magnetic pole 3 moves relative to the plate-like crimped body 4 in the Z direction by an amount corresponding to the distance S between the two and the compression coil spring 26 of the urging mechanism B, and The urging force from the compression coil spring 26 is applied to the plate-like pressure-bonding body 4, and the pressing force from the plate-like pressure-bonding body 4 is applied to the magnetic flaw detection sheet D from the plate-like pressing member C. Is brought into close contact with the object 1 to be inspected.

On the other hand, on the second pressure applying means P2 side, when the operator presses, this pressing force is applied to the plate-like pressure-bonding body 4, and the pressing force from this plate-like pressure-bonding body 4 is further applied to the plate-like pressing member. The magnetic flaw detection sheet D is caused to act on the magnetic flaw detection sheet D from C, and the magnetic flaw detection sheet D is brought into close contact with the inspection object 1.
The degree of pressing force can be confirmed by the light emission state of the pressure detecting means Se described above.

  In addition, the attracting force of the permanent magnets 50 </ b> A and 50 </ b> B provided on the lower surface of the plate-like pressure-bonding body 4 to the object 1 to be inspected is applied to the plate-like pressure-bonding body 4. The pressing force C is applied to the magnetic flaw detection sheet D from the plate-like pressing member C, and the magnetic flaw detection sheet D is brought into close contact with the inspection object 1.

  In this close contact state, even if the surplus portion 1A exists in the welded portion, the magnetic flaw detection sheet D is deformed into a shape along the surplus portion 1A, and the plate-like pressing member C is deformed to follow this deformation, Since the pressure is applied to the magnetic flaw detection sheet D as a uniform pressure from the plate-shaped pressure-bonding body 4, the entire bottom surface of the magnetic flaw detection sheet D (the outer surface of the back surface material 36) is a gap with respect to the upper surface of the inspection object 1. It will be closely attached.

  Then, a magnetic circuit is formed between the pair of magnetic poles 3 and the test object 1 with the magnetic flaw detection sheet D in close contact with the test object 1 as described above. In this case, FIG. As shown in FIG. 3, an alternating magnetic field (lines of magnetic force) is formed in the direction (Y direction) connecting the pair of magnetic poles 3 by the magnetic generation mechanism A, and at the same time, the pair of first permanent magnets 50A and the pair of second permanent magnets 50B. A direct-current magnetic field (lines of magnetic force) is formed in the direction connecting them to each other (Y direction), and both magnetic fields (lines of magnetic force) are superimposed. Accordingly, a magnetic field having a strong magnetic flux density can be generated in the vicinity of the virtual straight line L1 connecting the magnetic poles 3, the magnetic field can be applied to the inspection target 1, and the extra portion 1 A of the inspection target 1 When the defect 1C exists in the part, a stronger magnetic flux leaks in the portion of the defect 1C and acts on the magnetic powder 38 of the magnetic flaw detection sheet D. As a result, the magnetic powder 38 lines up along the direction of the leaked magnetic flux. A pattern to be formed is created, and the defect 1C can be visually grasped. At this time, since the pattern of the magnetic powder 38 formed by the magnetic flux leaking from the inspection target 1 other than the defect 1C is formed in a relatively simple and clear shape along the virtual straight line L1, the pattern of the defect 1C The leakage magnetic flux pattern can be found more easily.

[Magnetic flux density near the virtual straight line]
In the above, the AC magnetic field (line of magnetic force) formed in the direction (Y direction) along the imaginary straight line L1 connecting the pair of magnetic poles 3 by the magnetic generation mechanism A, the pair of first permanent magnets 50A and 50A, and the pair of first magnets. 2 In the above description, the two magnetic fields (line of magnetic force) and the DC magnetic field (line of magnetic force) formed in the direction connecting the permanent magnets 50B and 50B (Y direction) are superimposed. The measured results are shown in FIG.
The magnetic flux density measurement result (Example) in FIG. 11 is a magnetic flaw detector having the configuration shown in FIG. 10, that is, a pair of third permanents on a virtual straight line L1 connecting the pair of magnetic poles 3 in a top view. The magnets 50C and 50C are arranged in a state where the magnetic flaw detection sheet D is sandwiched and the parallel yoke portion 2b is not sandwiched, and both long sides of each permanent magnet 50C made of a plate member are imaginary straight lines L1 ( The magnetic field flaw detector having a configuration arranged along the (Y direction) is used to apply a magnetic field along a virtual straight line L1 in which an alternating magnetic field by the pair of magnetic poles 3 and a direct magnetic field by the pair of third permanent magnets 50C and 50C are superimposed. It is a measurement result of the magnetic flux density which acts on the surface of the object 1 to be inspected. Further, the magnetic flux density measurement result (comparative example) in FIG. 11 is along the virtual straight line L1 with only the pair of magnetic poles 3 without providing the pair of third permanent magnets 50C, 50C in the magnetic flaw detector with the configuration of FIG. It is a measurement result of the magnetic flux density that acts on the surface of the inspection object 1 when an alternating magnetic field is generated. Note that the measurement position of the magnetic flux density was set to a substantially intermediate position between the pair of magnetic poles 3 on the virtual straight line L1 on the surface of the inspection object 1.

As a result, as can be seen from FIG. 11, in the comparative example, the range of the magnetic flux density is in the range of about −10 mT to 10 mT, whereas in the example in which the pair of third permanent magnets 50 </ b> C and 50 </ b> C is provided, The range of magnetic flux density has increased to the range of about 50 mT to about 70 mT. Therefore, by arranging the pair of third permanent magnets 50C, 50C at appropriate positions, the magnetic flux density acting on the inspection object 1 between the pair of magnetic poles 3 is compared with the magnetic flux density of only the pair of magnetic poles 3. We were able to confirm that we could be stronger. Therefore, the magnetic flux density acting on the inspection target 1 can be increased, the magnetic flux leaking from the inspection target 1 (including the defect 1C) can be increased, and the detection accuracy of the defect 1C can be improved. .
From this result, when the pair of first permanent magnets 50A, 50A and the pair of second permanent magnets 50B, 50B are disposed at appropriate positions as described above, the pair of third permanent magnets 50C, 50C. The magnetic flux density equal to or more than double that of the case of arranging the magnetic field can be applied to the inspection target 1, and the magnetic flux leaking from the inspection target 1 (including the defect 1C) is made stronger to detect the defect 1C. It is thought that accuracy can be improved.

[Another embodiment]
In addition to the above embodiment, the present invention can be configured as follows, for example. In this other embodiment, components having the same functions as those in the embodiment are given the same numbers and symbols as those in the embodiment.

(1) In the above embodiment, as the pair of permanent magnets 50, 50, a pair of first permanent magnets 50A, 50A and a pair of second permanent magnets 50B, 50B are provided, and a pair of third permanent magnets 50C, Although the configuration in which 50C is provided has been described, the combination when providing the pair of first to third permanent magnets can be selected as appropriate. For example, it is good also as a structure which arrange | positions all the 1st-3rd permanent magnets. Moreover, it is good also as a structure which provides a pair of 3 or more pairs of permanent magnets.

(2) In the above embodiment, a long plate member is used as each of the permanent magnets 50A, 50B, 50C of the pair of permanent magnets. However, a virtual straight line L1 connecting the magnetic poles 3 by the pair of magnetic poles 3 is used. The present invention is not limited to this configuration as long as the magnetic field in the vicinity can be strengthened and the pattern of the magnetic field generated in the vicinity of the virtual straight line L1 can be clarified. For example, each permanent magnet made of a long rectangular parallelepiped or a cube can be employed.

(3) In the embodiment described above, neodymium magnets are used as the permanent magnets 50A, 50B, and 50C of the pair of permanent magnets. However, any magnetic field can be generated between the permanent magnets in a natural state. For example, it can be used without particular limitation.

(4) In the above embodiment, the permanent magnets 50A, 50B, and 50C are fixed to the lower surface of the plate-like crimped body 4 with an adhesive, but the mounting method to the plate-like crimped body 4 is particularly limited. is not. For example, a configuration in which a pair of mounting recesses is formed on the lower surface of the plate-like crimped body 4, each permanent magnet made of a plate member or a rectangular body is fitted into the mounting recess and fixed by the insertion bolt 25 of the urging mechanism B It is good.

(5) In the above embodiment, the pressure detection means are arranged at the four corners in the peripheral portion of the magnetosensitive body moving zone D2 formed between the first pressure application means P1 and the second pressure application means P2 when viewed from above. Although the configuration is shown, the number and position thereof are not questioned, and further, they may be provided at positions corresponding to the four corners of the plate-like crimped body 4.

1 Inspected object 1A Extra portion 1C Defect 2 Body (Magnetic generation mechanism)
2a Yoke 2b Parallel yoke part 2c Connection yoke part 3 Magnetic pole 4 Plate-shaped crimping body 5 Coil 38 Magnetic powder (magnetic sensitive body)
46 Grasping part 50 A pair of permanent magnets 50A A pair of first permanent magnets 50B A pair of second permanent magnets 50C A pair of third permanent magnets 100 Magnetic flaw detection device A Magnetic generating mechanism B Energizing mechanism C Plate-like pressing member D Magnetic flaw detection sheet P pressure application means P1 first pressure application means P2 second pressure application means L1 virtual straight line Se pressure detection means

Claims (8)

A sheet-like or bag-like flexible magnetic flaw detection sheet enclosing a magnetic sensitive material that forms a pattern corresponding to the magnetic flux density, and the magnetic flaw detection sheet is brought into contact with an object to be inspected by applying pressure to the magnetic flaw detection sheet Pressure applying means, a permanent magnet that presses the magnetic flaw detection sheet from the surface side of the magnetic flaw detection sheet to the inspection target side by an attractive force that is magnetically attracted to the inspection target, and a magnetic generation mechanism When the magnetic flaw detection sheet is in contact with the inspection object, the magnetic force generated by the magnetism generating mechanism is applied to the inspection object, thereby causing magnetic flux leaking from the inspection object to be sensed by the magnetic inspection sheet. A magnetic flaw detector configured to perform flaw detection on the inspection target based on a pattern that is captured by a magnetic body and created by the magnetic sensitive body,
The magnetic generation mechanism for generating an alternating magnetic field includes a pair of parallel yoke portions each having a magnetic pole formed at one end thereof, and a connecting yoke portion connecting the other ends of the pair of parallel yoke portions. A U-shaped yoke made of a magnetic material and configured to generate a magnetic field in a direction along an imaginary straight line connecting the pair of magnetic poles by energizing a coil wound around the connecting yoke portion. ,
The magnetic flaw detection sheet is disposed in parallel with the plane including the virtual straight line between the pair of magnetic poles in a top view,
At least a pair of the permanent magnets is generated from the N pole to the S pole between the pair of permanent magnets in a state where the magnetic flaw detection sheet is sandwiched between the pair of permanent magnets and the pair of parallel yoke portions are not sandwiched. The DC magnetic field is arranged in parallel with the virtual straight line so as to overlap the AC magnetic field of the magnetism generating mechanism, and the permanent magnets are arranged so as to be positioned around the parallel yoke portions of the magnetism generating mechanism. Magnetic flaw detector. The pressure applying means generates an urging force by a suction force that attracts the magnetic pole to the object to be inspected by magnetism generated by a pair of magnetic poles of the magnetic generation mechanism and a rigid plate-like pressure-bonded body made of a transparent resin. An urging mechanism, and a first pressure applying means disposed at one end of the plate-like pressure-bonded body and a second pressure applying means disposed at the other end in a direction orthogonal to the virtual straight line. Comprises pressing the plate-like pressure-bonded body by the first pressure applying means and the second pressure applying means to cause the magnetic flaw detection sheet to be pressed against the inspection object,
The first pressure applying means includes the urging mechanism, and one end portion of the plate-like pressure-bonding body receiving the urging force from the urging mechanism is movable in a direction approaching and separating from the object to be inspected. And configured to be supported by the magnetism generating mechanism disposed on one end side of the plate-like crimped body,
The first pressure applying means and the second pressure applying means are arranged in parallel to the virtual straight line when viewed from above, and the plate-like pressure-bonding body and the magnetic flaw detection sheet are the virtual straight line when viewed from above. 2. The magnetic flaw detector according to claim 1, wherein the magnetic flaw detector is disposed across the first pressure applying unit and the second pressure applying unit in a direction parallel to a plane including the first straight line and in a direction perpendicular to the virtual straight line.   The pressure applying means includes a transparent and deformable plate-shaped pressing member, and is disposed by stacking the plate-shaped pressure-bonding body, the plate-shaped pressing member, and the magnetic flaw detection sheet in this order, and presses the plate-shaped pressure-bonding body. The magnetic flaw detection apparatus according to claim 2, wherein the magnetic flaw detection sheet is configured to press the magnetic inspection sheet against the inspection target.   Two sets of the pair of permanent magnets are disposed on the plate-like crimped body, and each pair of permanent magnets is disposed on both sides of the pair of parallel yoke portions in a direction perpendicular to the virtual straight line when viewed from above. The magnetic flaw detector according to claim 2 or 3 to be performed.   4. The magnetic flaw detector according to claim 2, wherein the pair of permanent magnets are disposed on the plate-like crimped body, and the pair of permanent magnets are disposed on the virtual straight line when viewed from above.   The magnetic flaw detection apparatus according to any one of claims 2 to 5, wherein the pair of permanent magnets is configured by a rectangular body or a plate member that is elongated along a direction along the virtual straight line. The connecting yoke portion of the magnetism generating mechanism constituting the first pressure applying means is configured as an intermediate gripping portion that can be gripped by an operator;
The second pressure applying means is provided with a grip portion that is connected to both ends of the plate-like pressure-bonded body in a direction along the virtual straight line and is provided in a space on the plate-like pressure-bonded body. The magnetic flaw detector according to any one of the above.   The magnetic flaw detection is performed by applying pressure between the plate-shaped pressure-bonding body and the magnetic flaw detection sheet at a plurality of locations in the spreading direction of the plate-shaped pressure-bonding body by the first pressure applying means and the second pressure applying means. The magnetic flaw detection as described in any one of Claims 2-7 which provided the pressure detection means which detects the pressure which the said plate-shaped crimping body receives from the said to-be-inspected object side in the state which contacted the said to-be-inspected object. apparatus.

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