Eddy current flaw detection device

Abstract

To increase the accuracy of detecting a defect and reduce the size of a device in detecting a defect in an eddy current.SOLUTION: In an eddy current detector having a thin film coil 13 with a conducting wire 15 provided as a current route in a substrate 14, the thin film 13 is formed into an arc shape in a cross section as a non-flat surface, such as a curved shape along the surface of a column or the surface of a sphere. A protruding top part 14A as a predetermined part is set in contact with or close to an inspection target surface 1A of an inspection target body 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to an eddy current flaw detector. [Background technology]

[0002] Eddy current testing targets conductive materials as the test object, and an AC current is supplied from an AC power source to a coil to induce eddy currents near the surface of the test object, and the coil detects the reactive magnetic field created by these eddy currents. If a defect is present near the surface of the test object, the defect will change the flow of the eddy current, which will change the strength and distribution of the reactive magnetic field created by the eddy current, making it possible to detect the defect. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-61561 [Patent Document 2] Japanese Patent Application Publication No. 9-33488 [Patent Document 3] Japanese Patent Application Publication No. 11-183441 [Patent Document 4] Japanese Patent Application Laid-Open No. 2015-105947 [Patent Document 5] Japanese Patent Application Laid-Open No. 2003-344360 Summary of the Invention [Problem to be solved by the invention]

[0004] In eddy current flaw detection, the magnetic field distribution generated by the coil may be controlled to maintain a high eddy current density by suppressing the spread of eddy currents and enable highly sensitive defect detection. For example, Patent Document 1 discloses an apparatus configuration in which the coil is surrounded by a magnetic flux focusing member (ferromagnetic body) made of a magnetic material to control the magnetic field distribution. However, with such an apparatus configuration, there is a concern that the apparatus will become larger due to the components installed around the coil.

[0005] The embodiments of the present invention have been made in consideration of the above circumstances, and have an object to provide an eddy current flaw detection device that can achieve both high sensitivity in defect detection and miniaturization of the device. [Means for solving the problem]

[0006] An eddy current flaw detector according to an embodiment of the present invention is an eddy current flaw detector including a thin film coil having a conductor wire provided on a substrate as a current path, the thin film coil being formed in a non-planar shape, and a predetermined part including a top part of the thin film coil being placed in contact with or close to the surface to be inspected of the object to be inspected. a portion other than the predetermined portion is disposed farther from the surface to be inspected than the predetermined portion; and is configured to induce an eddy current at a position corresponding to the predetermined portion in the vicinity of the surface to be inspected of the object to be inspected. [Effects of the Invention]

[0007] According to the embodiment of the present invention, it is possible to realize both high sensitivity in defect detection and miniaturization of the device. [Brief explanation of the drawings]

[0008] [Figure 1] 3 is a cross-sectional view taken along line II in FIG. 2, showing the thin-film coil and the like of the eddy current flaw detector according to the first embodiment. [Figure 2] 2 is a diagram showing the thin-film coil of FIG. 1 in an expanded plan view, and also showing the configuration of an eddy current flaw detector equipped with this thin-film coil. FIG. [Figure 3] FIG. 10 is a front cross-sectional view showing a thin film coil and the like of a comparative example. [Figure 4] FIG. 10 is a perspective view showing a substrate of a thin-film coil of an eddy current flaw detector according to a second embodiment. [Figure 5] FIG. 11 is a perspective view showing a substrate of a thin-film coil of an eddy current flaw detector according to a third embodiment. [Figure 6] FIG. 10 is a front cross-sectional view showing a substrate and the like of an eddy current flaw detector according to a fourth embodiment. [Figure 7] FIG. 11 is a perspective view showing a substrate of a thin-film coil of an eddy current flaw detector according to a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [A] First embodiment (Figs. 1 to 3) Fig. 1 shows a thin-film coil and other components of an eddy current flaw detector according to a first embodiment, and is a cross-sectional view taken along line II in Fig. 2. Fig. 2 also shows an expanded plan view of the thin-film coil of Fig. 1, as well as a configuration diagram of an eddy current flaw detector equipped with this thin-film coil. The eddy current flaw detector 10 shown in Figs. 1 and 2 induces eddy currents 2 near an inspection surface 1A of an inspection object 1 made of a conductive material, and detects defects in the inspection object 1 based on changes in the reaction magnetic field created by these eddy currents 2. The eddy current flaw detector 10 includes an eddy current flaw detector probe 11 equipped with a thin-film coil 13, and an eddy current flaw detector data collector 12 connected to the thin-film coil 13 of the eddy current flaw detector probe 11.

[0010] The eddy current flaw detection probe 11 normally includes a thin-film coil 13 at a position closest to the inspection surface 1A of the inspection object 1. This thin-film coil 13 is configured to include a flexible substrate 14 and a coil portion 16 in which a conductor 15 serving as a current path is provided, for example, in a helical (i.e., spiral or whorl) shape by printing or the like on, for example, an inner surface 14M of this substrate 14.

[0011] The substrate 14 of the thin-film coil 13 is formed to have a non-planar arc-shaped cross section, and has a convex top portion 14A as a predetermined portion. The thin-film coil 13 is placed so that the top portion 14A of the substrate 14 is in contact with or close to the surface 1A to be inspected of the object 1 to be inspected.

[0012] The eddy current flaw detection data collector 12 has a function of supplying an AC current to the coil portion 16 of the thin-film coil 13. When an AC current is supplied from the eddy current flaw detection data collector 12 to the coil portion 16 of the thin-film coil 13 in this manner, magnetic field lines A1 are generated around each of the individual conductor wires 15 through which current flows in the same direction (from the back to the front in FIG. 1) in a cross-sectional view of the coil portion 16 (FIG. 1). Then, a composite magnetic field line B1, which is a composite of these magnetic field lines A1, is formed across one entire side of the coil portion 16, with the top portion 14A of the substrate 14 as the boundary.

[0013] Similarly, when an AC current is supplied from the eddy current testing data collector 12 to the coil portion 16 of the thin-film coil 13, magnetic field lines A2 are generated around each of the individual conductor wires 15 through which the current flows in the same direction (from the front to the back in FIG. 1) in a cross-sectional view of the coil portion 16 (FIG. 1). Then, a composite magnetic field line B2, which is a combination of these magnetic field lines A2, is formed across the other entire side of the coil portion 16, with the top portion 14A of the substrate 14 as the boundary. These composite magnetic field lines B1 and B2 induce an eddy current 2 near the inspection surface 1A of the inspection object 1. The eddy current testing data collector 12 also has the function of detecting, as eddy current testing data, changes in the reaction magnetic field generated by this eddy current 2 and detected by the thin-film coil 13.

[0014] 3, a comparative example is assumed in which a thin-film coil 100 having a planar substrate 101 and a coil portion 103 in which conductor wires 102 are spirally provided on the substrate 101 by printing or the like is installed on the inspection surface 1A of the inspection object 1. In this case, too, when an alternating current is supplied from the eddy current flaw detection data collector 12, magnetic field lines A1 are generated around each of the individual conductor wires 102 through which current flows in the same direction (from the back to the front in FIG. 3) in a cross-sectional view of the coil portion 103. These magnetic field lines A1 are then combined to form a composite magnetic field line B1 across one side of the coil portion 103.

[0015] Similarly, when an alternating current is supplied from the eddy current flaw detection data collector 12, magnetic field lines A2 are generated around each of the individual conductor wires 102 through which the current flows in the same direction (from the front to the back in FIG. 3). Then, these magnetic field lines A2 are combined to form composite magnetic field lines B2 which are formed over the entire other side of the coil portion 103. In the thin-film coil 100 of this comparative embodiment, the thin-film coil 100 is installed in a planar shape on the inspection surface 1A of the inspection object 1, and therefore the region of eddy current 104 induced by the magnetic field lines B1 and B2 of this thin-film coil 100 near the inspection surface 1A of the inspection object 1 has a size equivalent to the size (dimensions) of the thin-film coil 100.

[0016] In contrast to this, in the first embodiment, the thin-film coil 13 is formed in an arc-shaped cross section, and the top portion 14A of the convex shape is placed in contact with or close to the inspection surface 1A of the inspection object 1. Therefore, the magnetic force distribution generated by the thin-film coil 13 is controlled so that the area where the magnetic field lines B1 and B2 generated by the entire coil portion 16 of the thin-film coil 13 contact the inspection surface 1A of the inspection object 1 is reduced. As a result, the area of ​​the eddy current 2 induced on the inspection surface 1A of the inspection object 1 by the magnetic field lines B1 and B2 of the thin-film coil 13 is significantly smaller than in the comparative embodiment.

[0017] As configured as above, the first embodiment provides the following effects (1) and (2). (1) The thin-film coil 13 is formed to have an arc-shaped cross section, and the top portion 14A of the convex shape is placed on the surface 1A to be inspected of the object 1. As a result, the area of ​​the eddy current 2 induced near the surface 1A to be inspected of the object 1 by the overall magnetic field lines B1 and B2 of the coil portion 16 of the thin-film coil 13 is small, and a high eddy current density can be ensured, thereby realizing high sensitivity in defect detection for small defects in the object 1 to be inspected.

[0018] (2) Since there is no need to place a ferromagnetic material around the thin-film coil 13 in order to control the magnetic field distribution generated by the thin-film coil 13, it is possible to miniaturize the eddy current flaw detection device 10, particularly the eddy current flaw detection probe 11 equipped with the thin-film coil 13.

[0019] The thin-film coil 13 may be arranged such that the substrate 14 is formed to have an arc-shaped cross section, and a predetermined portion thereof, i.e., a concave edge portion 14B, is in contact with or close to the surface 1A to be inspected of the object 1, as shown by the two-dot chain line in Fig. 1. In this case as well, the region of the eddy current 3 induced on the surface 1A to be inspected of the object 1 by the overall magnetic field lines B1 and B2 of the coil portion 16 of the thin-film coil 13 can be made smaller than in the comparative example.

[0020] [B] Second embodiment (Fig. 4) 4 is a perspective view showing a substrate of a thin-film coil of an eddy current flaw detector according to the second embodiment, etc. In this second embodiment, parts similar to those in the first embodiment are denoted by the same reference numerals as in the first embodiment, and the description thereof will be simplified or omitted.

[0021] The eddy current flaw detector 20 (Figure 2) of this second embodiment differs from the first embodiment in that the substrate 22 of the thin-film coil 21 is formed in a curved shape, for example a semi-cylindrical shape, that follows the surface of a cylinder as a non-planar shape, and the top portion 22A or edge portion 22B of this substrate 22 is placed in contact with or close to the test surface 1A of the test object 1.

[0022] Here, the semi-cylindrical shape of the substrate 22 is a shape obtained by cutting a cylinder along its axis, and the cross-sectional shape perpendicular to the axis is an arc shape similar to the substrate 14 in Fig. 1. Although not shown, the coil portion of the thin-film coil 21 is formed on, for example, the inner surface 22M of the substrate 22 in a curved shape that follows the surface of the cylinder similar to the substrate 22.

[0023] The magnetic field lines B1 and B2 (FIG. 1) created by the coil portion of this thin-film coil 21 induce narrow linear eddy currents 23 near the inspection surface 1A of the inspection object 1. The narrower the width of these eddy currents 23, the more improved the defect detection sensitivity for smaller defects, and therefore, the second embodiment also achieves the same effects as the effects (1) and (2) of the first embodiment.

[0024] [C] Third embodiment (Fig. 5) 5 is a perspective view showing a substrate of a thin-film coil of an eddy current flaw detector according to the third embodiment, etc. In this third embodiment, parts similar to those in the first embodiment are denoted by the same reference numerals as in the first embodiment, and the description thereof will be simplified or omitted.

[0025] The eddy current flaw detector 30 (Figure 2) of this third embodiment differs from the first embodiment in that the substrate 32 of the thin-film coil 31 is formed as a curved shape that follows the surface of a sphere as a non-planar shape, for example, the shape of the surface layer of a hemisphere, and the top portion 32A or peripheral portion 32B of this substrate 32 is placed in contact with or close to the test surface 1A of the test object 1.

[0026] Here, the longitudinal cross section of the substrate 32, which is the shape of the surface layer of the hemisphere, is an arc shape similar to the substrate 14 in Fig. 1. Although not shown, the coil portion of the thin-film coil 31 is formed on, for example, the inner surface 32M of the substrate 32 in a curved shape that follows the surface of a sphere similar to the substrate 32.

[0027] The magnetic field lines B1 and B2 (FIG. 1) created by the coil portion of this thin-film coil 31 induce small-area point-like eddy currents 33 near the inspection surface 1A of the inspection object 1. The smaller the area of ​​these point-like eddy currents 33, the more improved the defect detection sensitivity for smaller defects, and therefore the third embodiment also achieves the same effects as the effects (1) and (2) of the first embodiment.

[0028] [D] Fourth embodiment (Fig. 6) 6 is a front cross-sectional view showing a substrate and the like of an eddy current flaw detector according to a fourth embodiment. In this fourth embodiment, parts similar to those in the first embodiment are denoted by the same reference numerals as in the first embodiment, and descriptions thereof will be simplified or omitted.

[0029] The eddy current flaw detection device 40 (Figure 2) of this fourth embodiment differs from the first embodiment in that it is configured in a structure that allows the shape of the thin-film coil 41 to be arbitrarily changed so that the area of ​​the eddy current 44 induced near the test surface 1A of the test object 1 can be set to a desired size.

[0030] That is, the thin-film coil 41 is configured to include a flexible and pliable substrate 42 and a coil portion (not shown) provided on, for example, an inner surface 42M of the substrate 42. A mold 43 selected from a plurality of types is fitted, for example, inside the thin-film coil 41, to change the shape of the thin-film coil 41 to correspond to the mold 43. The thin-film coil 41 may be changed to an arbitrary radius of curvature without using the mold 43, and the shape may be maintained using a jig (not shown). Note that in FIG. 6, reference numeral 42A denotes the top portion of the substrate 42 having an arc-shaped cross section, and reference numeral 42B denotes the peripheral portion of the substrate 42.

[0031] As described above, by arbitrarily changing the shape of the thin-film coil 41, it is possible to induce a small area of ​​eddy current 44 near the test surface 1A of the test object 1, and therefore the fourth embodiment also achieves the same effects as the effects (1) and (2) of the first embodiment.

[0032] [E] Fifth embodiment (Fig. 7) 7 is a perspective view showing a substrate of a thin-film coil of an eddy current flaw detector according to the fifth embodiment. In the fifth embodiment, parts similar to those in the first embodiment are denoted by the same reference numerals as in the first embodiment, and the description thereof will be simplified or omitted.

[0033] The eddy current flaw detector 50 (FIG. 2) of the fifth embodiment differs from the first embodiment in that at least one of the substrate 52 of the exciting thin-film coil 51 and the substrate 56 of the detecting thin-film coil 55, and both in FIG. 7, are formed as spherical shapes that follow the surface of a sphere as a non-planar shape, for example, as the surface layer shape of a hemisphere, and top portions 52A, 56A or peripheral portions 52B, 56B of these substrates 52, 56 are placed in contact with or close to the inspected surface 1A of the inspected object 1. The exciting thin-film coil 51 and the detecting thin-film coil 55 are arranged, for example, overlapping each other.

[0034] Here, the exciting thin-film coil 51 is a thin-film coil that excites magnetic flux (magnetic lines of force) and causes this magnetic flux to act on the inspection surface 1A of the inspection object 1. The detecting thin-film coil 55 is a thin-film coil that detects a reaction magnetic field caused by an eddy current 58 induced near the inspection surface 1A of the inspection object 1.

[0035] Although not shown, the coil portion of the excitation thin-film coil 51 is formed in a curved shape that follows the surface of the sphere and is provided on, for example, the inner surface 52M of the substrate 52. Similarly, although not shown, the coil portion of the detection thin-film coil 55 is also formed in a curved shape that follows the surface of the sphere and is provided on, for example, the inner surface 56M of the substrate 56.

[0036] The exciting thin-film coil 51 and the detecting thin-film coil 55 do not necessarily have to have the same radius of curvature of the curved surface along the surface of the sphere. In addition, the winding configuration (diameter of the conductor, number of windings, etc.) of the conductor in each coil portion of the exciting thin-film coil 51 and the detecting thin-film coil 55 do not necessarily have to be the same.

[0037] In the fifth embodiment, by using both the exciting thin-film coil 51 and the detecting thin-film coil 55 in eddy current testing, it becomes possible to apply a coil section suitable for excitation to the exciting thin-film coil 51 and a coil section suitable for detection to the detecting thin-film coil 55. For example, by increasing (thickening) the diameter of the conductor wire of the coil section of the exciting thin-film coil 51, it becomes possible to supply a large AC current. Also, by decreasing (thinning) the diameter of the conductor wire of the coil section of the detecting thin-film coil 55 and increasing the number of windings, it becomes possible to increase the number of magnetic flux linkages with the reaction magnetic field created by the eddy current 58.

[0038] As described above, the excitation thin-film coil 51 and the detection thin-film coil 55 are formed in the shape of the surface layer of a hemisphere, and the top portions 52A, 56A or the peripheral portions 52B, 56B are installed so as to come into contact with the inspection surface 1A of the inspection object 1, thereby achieving the same effects as the effects (1) and (2) of the first embodiment, as well as the following effect (3).

[0039] (3) The coil portion of the excitation thin-film coil 51 is provided in a winding form suitable for excitation, and the coil portion of the detection thin-film coil 55 is provided in a winding form suitable for detection, thereby achieving even higher sensitivity in defect detection for small defects.

[0040] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, changes, and combinations can be made without departing from the spirit of the invention. Furthermore, such substitutions, changes, and combinations are included in the scope and spirit of the invention, and are also included in the inventions and their equivalents as set forth in the claims. [Explanation of symbols]

[0041] 1...object to be inspected, 1A...surface to be inspected, 2, 3...eddy current, 10...eddy current flaw detector, 14...substrate, 14A...top portion, 14B...edge portion, 15...conductor, 16...coil portion, 20...eddy current flaw detector, 21...thin film coil, 22...substrate, 22A...top portion, 22B...edge portion, 23...eddy current, 30...eddy current flaw detector, 31...thin film coil, 32...substrate, 32A...top portion, 32B...edge portion, 33...eddy current, 40...eddy current flaw detector, 41...thin film coil, 42...substrate, 43...mold, 44...eddy current, 50...eddy current flaw detector, 51...excitation thin film coil, 52...substrate, 52A...top portion, 52B...edge portion, 55...detection thin film coil, 56...substrate, 56A...top portion, 56B...edge portion

Claims

1. In an eddy current flaw detection device having a thin film coil in which a conductor wire is provided as a current path on a substrate, The thin-film coil is formed in a non-planar shape, a predetermined portion including its top portion is placed in contact with or close to the surface to be inspected of the object to be inspected, and portions other than the predetermined portion are placed farther away from the surface to be inspected than the predetermined portion, and the eddy current testing device is configured to induce an eddy current at a position corresponding to the predetermined portion in the vicinity of the surface to be inspected of the object to be inspected.

2. 2. The eddy current flaw detector according to claim 1, wherein the thin film coil is formed to have an arc-shaped cross section, and the top of the convex shape is configured to be placed on the surface of the object to be inspected.

3. The eddy current flaw detector according to claim 1 or 2, characterized in that the thin film coil is formed in a curved shape that follows the surface of a cylinder, and the convex top portion is configured to be placed on the surface to be inspected of the object to be inspected.

4. 3. An eddy current flaw detection device according to claim 1, wherein the thin film coil is formed in a curved shape that conforms to the surface of a sphere, and the convex top portion is configured to be placed on the surface to be inspected of the object to be inspected.

5. 5. The eddy current flaw detector according to claim 1, wherein the thin film coil is configured so that its shape can be arbitrarily changed.

6. An eddy current flaw detection device as described in any one of claims 1 to 5, characterized in that the thin film coil is at least one of an excitation thin film coil that excites magnetic flux and causes this magnetic flux to act on the object being inspected, and a detection thin film coil that detects the reaction magnetic field caused by eddy currents generated in the object being inspected.

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