Eddy current flaw detection device

Abstract

To increase the density of an eddy current which induces an inspection target body while ensuring the flexibility of a thin film coil.SOLUTION: An eddy current defect detector has a thin film coil 13 formed by spirally providing a conductive wire 15 as a current route in both surface of a flexible substrate 14 (a front surface 14A and a back surface 14B), in an eddy current defect probe. In the conductive wire 15, the number of winding per unit width of the thin film coil 13 is set to be different between around the center and around the outer periphery of the thin film coil 13. Also, the conductive wire 15 is set in the same position of both surfaces (the front surface 14A and the front surface 14B) of the substrate 14 when the thin film coil 13 is viewed in planer view.SELECTED DRAWING: Figure 2

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 presence or absence of the defect.

[0003] The coil used for this eddy current flaw detection is sometimes a thin-film coil, which is made by printing a coil pattern of conductive wires on a flexible substrate. Because this thin-film coil uses a highly flexible substrate, it can be flexibly fitted to the curved surface of the object being inspected, which has the advantage of enabling highly sensitive flaw detection. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-221273 [Patent Document 2] Japanese Patent Application Publication No. 11-51905 [Patent Document 3] Japanese Patent Application Publication No. 11-14600 [Patent Document 4] Japanese Patent Application Publication No. 9-89842 Summary of the Invention [Problem to be solved by the invention]

[0005] In eddy current flaw detection using a thin-film coil, the number of windings in the thin-film coil is smaller than that of conventional three-dimensional coils wound with conductor wire, which limits the eddy current density and poses the problem of a reduced signal-to-noise ratio (SN ratio) depending on the usage environment. To address this issue, Patent Document 1 discloses an apparatus configuration in which multiple thin-film coils are stacked to improve the detectability of eddy current density and reaction magnetic fields, but this apparatus configuration reduces the flexibility that is an advantage of thin-film coils.

[0006] An embodiment of the present invention has been made in consideration of the above circumstances, and aims to provide an eddy current flaw detection device that can increase the eddy current density of the eddy current induced in the object under test while ensuring the flexibility of the thin-film coil. [Means for solving the problem]

[0007] The eddy current flaw detection device according to an embodiment of the present invention is an eddy current flaw detection device having an eddy current flaw detection probe equipped with a thin film coil having conductors on both sides of a flexible substrate, the conductors being current paths, and the number of conductors per unit width of the thin film coil being set differently near the center and near the periphery of the thin film coil, and the thin film coil is set to have conductors on both sides of the substrate in a plan view. The same shape and The feature is that they are provided at the same position. [Effects of the Invention]

[0008] According to the embodiment of the present invention, it is possible to increase the eddy current density of the eddy current induced in the object under test while ensuring the flexibility of the thin-film coil. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a configuration diagram showing an eddy current flaw detector according to a first embodiment. [Figure 2] 2A and 2B show the thin-film coil of FIG. 1, where FIG. 2A is a plan view and FIG. 2B is a cross-sectional view taken along line II-II of FIG. 2A. [Figure 3]3A and 3B show a thin-film coil provided in an eddy current flaw detection probe of an eddy current flaw detection device according to a second embodiment, in which (A) is a plan view and (B) is a cross-sectional view taken along line III-III in FIG. [Figure 4] 4A and 4B show a thin-film coil provided in an eddy current flaw detection probe of an eddy current flaw detection device according to a third embodiment, in which (A) is a plan view and (B) is a cross-sectional view taken along line IV-IV in FIG. 4A. [Figure 5] 5A and 5B show a thin-film coil provided in an eddy current flaw detection probe of an eddy current flaw detection device according to a fourth embodiment, in which (A) is a plan view and (B) is a cross-sectional view taken along line VV in FIG. 5A. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [A] First embodiment (Figs. 1 and 2) Fig. 1 is a configuration diagram showing an eddy current flaw detector according to the first embodiment. The eddy current flaw detector 10 shown in Fig. 1 induces eddy currents near the surface of an object 1 to be inspected, which is made of a conductive material, and detects defects in the object 1 to be inspected based on changes in the reaction magnetic field created by the eddy currents. 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 eddy current flaw detector probe 11.

[0011] The eddy current testing probe 11 is placed on the surface of the object under test 1. Usually, a thin-film coil 13 is attached to the eddy current testing probe 11 at a position closest to the object under test 1. The eddy current testing data collector 12 supplies an AC current to the thin-film coil 13 in the eddy current testing probe 11 to induce an eddy current near the surface of the object under test 1, and also has the function of collecting, as eddy current testing data, changes in the reaction magnetic field generated by this eddy current and detected by the thin-film coil 13.

[0012] 2, the thin-film coil 13 is configured by providing a conductor 15, which serves as a current path, in a spiral (i.e., a spiral or whorl) shape, for example, by printing on both sides (front surface 14A and back surface 14B) of a flexible substrate 14. The conductors 15 provided on the front surface 14A and back surface 14B of the substrate 14 have the same shape. There are minimum manufacturing limits for the width of the conductor 15 itself and the conductor spacing 16, which is the gap between the conductors 15, and therefore the number of turns of the conductor 15 in the thin-film coil 13 is restricted.

[0013] Based on the above constraints, the number of turns of the conductor 15 per unit width of the thin-film coil 13 is set to be different between the center and the periphery of the thin-film coil 13. Note that the symbol W in Fig. 2 indicates the width direction of the thin-film coil 13. This causes variations in the conductor spacing 16 of the conductor 15 between the center and the periphery of the thin-film coil 13. The conductor spacing 16 is set depending on the application of eddy current flaw detection.

[0014] For example, when it is necessary to apply a high eddy current density to the object under test 1 from near the center to near the periphery of the thin-film coil 13, the conductor spacing 16 near the periphery of the thin-film coil 13 is made closer than the conductor spacing 16 near the center, as shown in Fig. 2. As a result, a magnetic flux with a high magnetic flux density is generated near the periphery of the thin-film coil 13 as the number of turns of the conductor 15 increases. This makes it possible to induce an eddy current with a high eddy current density at a position on the object under test 1 corresponding to the entire area from near the center to near the periphery of the thin-film coil 13.

[0015] Furthermore, when it is necessary to apply a high eddy current density concentrated near the center of the thin-film coil 13 to the object under test 1, the conductor spacing 16 near the center of the thin-film coil 13 is made closer than the conductor spacing 16 near the periphery. As a result, a magnetic flux with a high magnetic flux density is generated near the center of the thin-film coil 13 as the number of turns of the conductor 15 increases. This makes it possible to induce an eddy current with a high eddy current density concentrated at a position on the object under test 1 corresponding to the vicinity of the center of the thin-film coil 13.

[0016] Furthermore, the conductor 15 of the thin-film coil 13 is provided at the same position on both sides (front surface 14A and back surface 14B) of the substrate 14 in a plan view of the thin-film coil 13. This makes it possible to double the number of turns of the conductor 15 compared to one side (front surface 14A or back surface 14B) of the substrate 14 without stacking the thin-film coil as described in Patent Document 1. Therefore, the magnetic flux density of the magnetic flux generated by the thin-film coil 13 is also about twice as high as when the conductor 15 is provided on one side of the substrate 14.

[0017] As configured as above, the first embodiment provides the following effects (1) and (2). (1) The thin-film coil 13 of the eddy current testing probe 11 is formed by providing a conductor 15, which serves as a current path, in a spiral shape on both sides (front surface 14A and back surface 14B) of a flexible substrate 14. This allows the thin-film coil 13 to increase the magnetic flux density of the generated magnetic flux and increase the eddy current density of the eddy current induced in the test object 1 while ensuring flexibility with respect to the test object 1. As a result, eddy current testing can be achieved with a high signal-to-noise ratio (SN ratio) while taking advantage of the flexibility of the thin-film coil 13.

[0018] (2) The thin-film coil 13 has different numbers of windings of the conductor 15 per unit width of the thin-film coil 13 near its center and near its periphery, resulting in varying densities in the conductor spacing 16. In the region where the conductor spacing 16 is dense, a magnetic flux with high magnetic flux density is generated as the number of windings of the conductor 15 increases. As a result, the thin-film coil 13 can obtain a magnetic flux density distribution with an increased magnetic flux density at a desired position where the conductor spacing 16 is set dense, and can induce eddy currents with high eddy current density at a position on the object under test 1 corresponding to the desired position on the thin-film coil 13. As a result, eddy current testing can be achieved with a high signal-to-noise ratio (SN ratio) while taking advantage of the flexibility of the thin-film coil 13.

[0019] [B] Second embodiment (Fig. 3) 3A and 3B show a thin-film coil provided in an eddy current flaw detection probe of an eddy current flaw detection device according to a second embodiment, with (A) being a plan view and (B) being a cross-sectional view taken along line III-III in Fig. 3A. In this second embodiment, parts similar to those in the first embodiment are designated by the same reference numerals as in the first embodiment, and their explanations will be simplified or omitted.

[0020] The eddy current flaw detection device 20 (Figure 1) of this second embodiment differs from the first embodiment in that the thin-film coil 22 provided in the eddy current flaw detection probe 21 (Figure 1) has a conductor 23 of a partial length of the conductor 15 provided on one side (e.g., front surface 14A) of the substrate 14, which is provided on the other side (e.g., back surface 14B) of the substrate 14 by printing or the like.

[0021] That is, the conductor 23 has a shape in which a part of the central or outer periphery (central side in FIG. 3 ) of the conductor 15 provided on, for example, the surface 14A of the substrate 14 is removed, and is provided at the same position as the conductor 15 in a plan view of the thin-film coil 22. Furthermore, similar to the conductor 15, the number of windings of the conductor 23 may be set to be different near the center and near the periphery of the thin-film coil 22, and the conductor spacing 24 of the conductor 23 may be varied.

[0022] As configured as above, the second embodiment provides the following effect (3) in addition to the effects (1) and (2) of the first embodiment.

[0023] (3) In the thin-film coil 22, the conductor 23 has a length that is a part of the length of the conductor 15 provided on, for example, the front surface 14A of the substrate 14, and is provided on, for example, the back surface 14B of the substrate 14. Therefore, the number of turns of the conductors 15 and 23 per unit width of the thin-film coil 22 varies between near the center and near the periphery of the thin-film coil 22, over the entire front and back surfaces of the thin-film coil 22. As a result, magnetic flux with a high magnetic flux density can be generated in areas where the number of turns of the conductors 15 and 23 is large, over the entire front and back surfaces of the thin-film coil 22, thereby further enhancing the effect (2) of the first embodiment.

[0024] [C] Third embodiment (Fig. 4) 4A and 4B show a thin-film coil provided in an eddy current flaw detection probe of an eddy current flaw detection device according to a third embodiment, with (A) being a plan view and (B) being a cross-sectional view taken along line IV-IV in Fig. 4A. In this third embodiment, parts similar to those in the first embodiment are designated by the same reference numerals as in the first embodiment, and their explanations will be simplified or omitted.

[0025] The eddy current flaw detection device 30 (Figure 1) of this third embodiment differs from the first embodiment in that the thin-film coil 32 provided in the eddy current flaw detection probe 31 (Figure 1) has, in a plan view of the thin-film coil 32, a conductor 34 provided on one side (e.g., back side 14B) of the substrate 14 in correspondence with the gap (i.e., conductor spacing 35) between the conductors 33 provided on one side (e.g., front side 14A) of the substrate 14.

[0026] That is, the conductor 33 and the conductor 34 are provided at different positions on both surfaces (front surface 14A and back surface 14B) of the substrate 14 in a plan view of the thin-film coil 32. In the third embodiment, the conductor 33 is provided by printing or the like in a spiral shape on, for example, the front surface 14A of the substrate 14 with equal conductor spacing 35. Furthermore, the conductor 34 is provided by printing or the like on, for example, the back surface 14B of the substrate 14, in a manner that corresponds to the conductor spacing 35 of the conductor 33 near the center or near the periphery of the thin-film coil 32 (near the periphery in FIG. 4 ).

[0027] As a result, in the thin-film coil 32, the conductor spacing between the conductors 33 and 34 is set densely in the area where the conductor 34 is provided, as viewed from the front and back of the thin-film coil 32, and the conductor spacing between the conductors 33 and 34 is set sparsely in the area where the conductor 34 is not provided, as viewed from the front and back of the thin-film coil 32. The conductor spacing between the conductors 33 and 34 is set depending on the application of the thin-film coil 32.

[0028] For example, when it is necessary to apply a high eddy current density to the object under test 1 from near the center to near the periphery of the thin-film coil 32, as shown in FIG. 4, conductors 34 are provided on, for example, the back surface 14B of the substrate 14, corresponding to the conductor spacing 35 of the conductors 33 near the periphery of the thin-film coil 32. As a result, the conductor spacing between the conductors 33 and 34 near the periphery of the thin-film coil 32 is set closer overall on both the front and back surfaces of the thin-film coil 32 than the conductor spacing between the conductors 33 and 34 near the center. Therefore, a magnetic flux with a high magnetic flux density is generated near the periphery of the thin-film coil 32 as the number of turns of the conductors 33 and 34 increases. Therefore, it is possible to induce an eddy current with a high eddy current density at a position on the object under test 1 corresponding to the entire area from near the center to near the periphery of the thin-film coil 32.

[0029] Furthermore, when it is necessary to apply a high eddy current density concentrated near the center of the thin-film coil 32 to the device under test 1, conductors 34 are provided on, for example, the back surface 14B of the substrate 14, corresponding to the conductor spacing 35 of the conductors 33 near the center of the thin-film coil 32. As a result, the conductor spacing between the conductors 33 and 34 near the center of the thin-film coil 32 is set closer across the entire front and back surfaces of the thin-film coil 32 than the conductor spacing between the conductors 33 and 34 near the periphery. Therefore, a magnetic flux with a high magnetic flux density is generated near the center of the thin-film coil 32 as the number of turns of the conductors 33 and 34 increases. Therefore, it is possible to induce an eddy current with a high eddy current density concentrated at a position on the device under test 1 corresponding to the vicinity of the center of the thin-film coil 32.

[0030] As configured as above, the third embodiment provides the following effect (4) in addition to the effect (1) of the first embodiment.

[0031] (4) In the thin-film coil 32, in a plan view of the thin-film coil 32, the conductor wires 34 are provided on one side (e.g., the back side 14B) of the substrate 14, corresponding to the conductor wire spacing 35 of the conductor wires 33 provided on the other side (e.g., the front side 14A) of the substrate 14. Therefore, in the thin-film coil 32, in the region where the conductor wires 34 are provided, the conductor wire spacing between the conductor wires 33 and 34 is dense in the plan view of the thin-film coil 32, and in the region where the conductor wires 34 are not provided, the conductor wire spacing between the conductor wires 33 and 34 is sparse in the plan view of the thin-film coil 32. In other words, in the entire front and back of the thin-film coil 32, the number of windings of the conductor wires 33 and 34 per unit width of the thin-film coil 32 differs between near the center and near the periphery of the thin-film coil 32.

[0032] Therefore, a magnetic flux with a high magnetic flux density can be generated in the region where the number of windings of the conductors 33 and 34 is large (region where the conductor spacing of the conductors 33 and 34 is dense) on the entire front and back of the thin-film coil 32. As a result, similar to effect (2) of the first embodiment, it is possible to obtain a magnetic flux density distribution with an increased magnetic flux density at a desired position of the thin-film coil 32 where the conductor spacing of the conductors 33 and 34 is set densely, and it is also possible to induce an eddy current with a high eddy current density at a position of the object under test 1 corresponding to the desired position, thereby realizing eddy current testing with a high signal-to-noise ratio.

[0033] (D) Fourth embodiment (Fig. 5) 5A and 5B show a thin-film coil provided in an eddy current flaw detection probe of an eddy current flaw detection device according to a fourth embodiment, with (A) being a plan view and (B) being a cross-sectional view taken along line VV in Fig. 5A. In this fourth embodiment, parts similar to those in the first embodiment are given the same reference numerals as in the first embodiment, and their explanations will be simplified or omitted.

[0034] The eddy current flaw detection device 40 (Figure 1) of this fourth embodiment differs from the first embodiment in that the thin film coil 42 provided in the eddy current flaw detection probe 41 (Figure 1) has a magnetic layer 43 provided within the substrate 14 of the thin film coil 42.

[0035] The magnetic layer 43 is preferably a ferromagnetic layer made of a ferromagnetic material such as iron. The material forming the magnetic layer 43 is preferably, for example, a magnetic fluid or a magnetic powder, so as not to impair the flexibility of the substrate 14. The magnetic flux is concentrated in the magnetic layer 43 in the substrate 14, so that the thin-film coil 42 can generate magnetic flux with a high magnetic flux density.

[0036] As configured as above, the fourth embodiment also achieves the same effects as the effects (1) and (2) of the first embodiment, and also achieves the following effect (5).

[0037] (5) In the thin-film coil 42, the magnetic layer 43 is provided inside the flexible substrate 14, so that the magnetic flux generated in the thin-film coil 42 can be concentrated in the magnetic layer 43. Therefore, the thin-film coil 42 can increase the magnetic flux density and induce high-density eddy currents in the object under test 1 near the thin-film coil 42 while ensuring flexibility with respect to the object under test 1, thereby achieving eddy current testing with a high signal-to-noise ratio.

[0038] 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.

[0039] For example, in the first to fourth embodiments of the thin-film coils 13, 22, 32 and 42, the conductors 15, 23, 33 and 34 are spirally provided on the substrate 14, but these conductors 15, 23, 33 and 34 may be pulse-shaped. In this case, in the first, second and fourth embodiments, the number of conductors 15, 23 per unit width of the thin-film coils 13, 22 and 42 is set to be different near the center and near the periphery of the thin-film coils 13, 22 and 42. [Explanation of symbols]

[0040] 1...object to be inspected, 10...eddy current flaw detection device, 11...eddy current flaw detection probe, 13...thin film coil, 14...substrate, 14A...surface, 14B...back surface, 15...conductor, 16...conductor spacing, 20...eddy current flaw detection device, 21...eddy current flaw detection probe, 22...thin film coil, 23...conductor, 24...conductor spacing, 30...eddy current flaw detection device, 31...eddy current flaw detection probe, 32...thin film coil, 33, 34...conductor, 35...conductor spacing, 40...eddy current flaw detection device, 41...eddy current flaw detection probe, 42...thin film coil, 43...magnetic layer

Claims

1. An eddy current flaw detection device including an eddy current flaw detection probe having a thin film coil in which conductor wires serving as current paths are provided on both sides of a flexible substrate, An eddy current flaw detection device characterized in that the number of conductors per unit width of the thin-film coil is set differently near the center and near the periphery of the thin-film coil, and the conductors are arranged in the same shape and at the same position on both sides of the substrate when viewed in a plane.

2. An eddy current flaw detection device including an eddy current flaw detection probe having a thin film coil in which conductor wires serving as current paths are provided on both sides of a flexible substrate, The number of the conductors per unit width of the thin-film coil is set to be different between the vicinity of the center of the thin-film coil and the vicinity of the outer periphery of the thin-film coil, and An eddy current flaw detection device characterized in that the conductor of a partial length provided on one side of the substrate is provided on the other side of the substrate, and is provided in the same shape and at the same position as the partial length of the conductor provided on one side when viewed in a plane of the thin-film coil.

3. An eddy current flaw detection device including an eddy current flaw detection probe having a thin film coil in which conductor wires serving as current paths are provided on both sides of a flexible substrate, In a plan view of the thin-film coil, in a region where the conductors are provided on one side of the substrate, the gaps between the conductors on one side and the other side are dense, corresponding to the gaps between the conductors on the other side of the substrate, and in a region where the conductors are not provided on the other side, the gaps between the conductors on the one side and the other side are sparse, An eddy current flaw detection device characterized in that the number of wires per unit width of the thin film coil is set differently near the center and near the periphery of the thin film coil, across the entire one side and the other side of the substrate in the thin film coil.

4. 4. The eddy current flaw detector according to claim 1, wherein a magnetic layer is provided within the substrate.

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