JP7746203B2 - Eddy current flaw detection equipment - Google Patents

Description

An embodiment of the present invention relates to an eddy current flaw detector.

Eddy current testing targets conductive materials as the test object, and involves supplying an alternating current from an AC power source to a coil to induce eddy currents near the surface of the test object, which then detects the reactive magnetic field created by these eddy currents. If a defect is present near the surface of the test object, this defect will change the flow of eddy currents, which in turn will change the strength and distribution of the reactive magnetic field created by the eddy currents, making it possible to detect the presence or absence of a defect.

The coil used in this eddy current flaw detection is sometimes a thin-film coil, with a conductor coil pattern printed on a flexible substrate. Because this thin-film coil uses a highly flexible substrate, it can flexibly conform to the curved surface of the object being inspected, which has the advantage of enabling highly sensitive flaw detection.

Japanese Patent Application Laid-Open No. 2005-221273 Japanese Patent Application Publication No. 11-51905 Japanese Patent Application Publication No. 11-14600 Japanese Patent Application Publication No. 9-89842

In eddy current flaw detection using thin-film coils, the number of windings in the thin-film coil is smaller than in conventional three-dimensional coils made of wound conductor wire, which limits eddy current density and poses the issue of a reduced signal-to-noise ratio (S/N ratio) depending on the usage environment. To address this issue, Patent Document 1 discloses an equipment configuration that stacks multiple thin-film coils to improve the detectability of eddy current density and reaction magnetic fields, but this equipment configuration reduces the flexibility that is one of the advantages of thin-film coils.

Embodiments of the present invention have been made in consideration of the above circumstances, and aim to provide an eddy current flaw detector that can increase the eddy current density of eddy currents induced in an object under test while ensuring the flexibility of the thin-film coil.

An eddy current flaw detection device in 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 that serve as current paths on both sides of a flexible substrate, wherein the conductors are set so that the number of conductors per unit width of the thin film coil is different near the center and near the periphery of the thin film coil, and are arranged in the same shape and at the same position on both sides of the substrate when viewed in a plane.

According to an 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 maintaining the flexibility of the thin-film coil.

1 is a configuration diagram showing an eddy current flaw detection device according to a first embodiment. 2A and 2B show the thin-film coil of FIG. 1, in which FIG. 2A is a plan view and FIG. 2B is a cross-sectional view taken along line II-II of FIG. 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 FIG. 3A is a plan view and FIG. 3B is a cross-sectional view taken along line III-III in FIG. 3A. 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 FIG. 4A is a plan view and FIG. 4B is a cross-sectional view taken along line IV-IV in FIG. 4A. 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 V-V in FIG. 5A.

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 detection device according to the first embodiment. The eddy current flaw detection device 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 based on changes in the reaction magnetic field created by the eddy currents. The eddy current flaw detection device 10 includes an eddy current flaw detection probe 11 equipped with a thin-film coil 13, and an eddy current flaw detection data collector 12 connected to the eddy current flaw detection probe 11.

The eddy current testing probe 11 is placed on the surface of the object under test 1. Typically, 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 alternating current to the thin-film coil 13 in the eddy current testing probe 11 to induce eddy currents near the surface of the object under test 1, and collects the changes in the reaction magnetic field created by these eddy currents and detected by the thin-film coil 13 as eddy current testing data.

As shown in Figure 2, the thin-film coil 13 is constructed by providing conductor wires 15, which serve as current paths, on both sides (front surface 14A and back surface 14B) of a flexible substrate 14, for example, in a spiral (i.e., whorl) shape, by printing or the like. The conductor wires 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 wires 15 themselves and the conductor spacing 16, which is the gap between the conductor wires 15, so the number of turns of the conductor wire 15 in the thin-film coil 13 is limited.

Based on the above constraints, the number of turns of the conductor 15, which is the number of conductor wires per unit width of the thin-film coil 13, is set to be different near the center and the periphery of the thin-film coil 13. Note that the symbol W in Figure 2 indicates the width direction of the thin-film coil 13. This results in variations in the conductor spacing 16 of the conductor 15 near the center and the periphery of the thin-film coil 13. The conductor spacing 16 is set according to the application of eddy current flaw detection.

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 denser than the conductor spacing 16 near the center, as shown in Figure 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 eddy currents 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.

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 denser 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 eddy currents 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.

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 when viewed from above. 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.

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 (S/N ratio) while taking advantage of the flexibility of the thin-film coil 13.

(2) The thin-film coil 13 has different numbers of windings of the conductor 15 per unit width near its center and near its periphery, resulting in varying densities in the conductor spacing 16. In areas 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 increased magnetic flux density at the desired position where the conductor spacing 16 is set dense, and can induce eddy currents with high eddy current density at the 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 (S/N ratio) while taking advantage of the flexibility of the thin-film coil 13.

[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.

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.

In other words, the conductor 23 has a shape in which a portion 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 has been removed, and is provided in the same position as the conductor 15 in a plan view of the thin-film coil 22. Furthermore, like the conductor 15, the number of windings of the conductor 23 may be set differently near the center and the outer periphery of the thin-film coil 22, and the conductor spacing 24 of the conductor 23 may vary in density.

As configured as described above, the second embodiment achieves the same effects as effects (1) and (2) of the first embodiment, as well as the following effect (3).

(3) In the thin-film coil 22, a conductor 23 having a length equivalent to a portion of the conductor 15 provided on, for example, the front surface 14A of the substrate 14 is provided on, for example, the back surface 14B of the substrate 14. As a result, the number of turns of the conductors 15 and 23 per unit width of the thin-film coil 22 varies between the center and the periphery of the thin-film coil 22 across the entire front and back surfaces of the thin-film coil 22. As a result, a magnetic flux with a high magnetic flux density can be generated in the areas with a large number of turns of the conductors 15 and 23 across the entire front and back surfaces of the thin-film coil 22, further enhancing the effect (2) of the first embodiment.

[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.

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 a conductor 34 provided on one side (e.g., back side 14B) of the substrate 14 in a plan view of the thin-film coil 32, corresponding to the gap (i.e., conductor spacing 35) between the conductors 33 provided on one side (e.g., front side 14A) of the substrate 14.

In other words, the conductors 33 and 34 are provided at different positions on both surfaces (front surface 14A and back surface 14B) of the substrate 14 when viewed from above the thin-film coil 32. In the third embodiment, the conductors 33 are 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 conductors 34 are provided by printing or the like on, for example, the back surface 14B of the substrate 14, corresponding to the conductor spacing 35 of the conductors 33 near the center or periphery of the thin-film coil 32 (near the periphery in Figure 4).

As a result, in the area where the conductor 34 is provided on both the front and back sides of the thin-film coil 32, the conductor spacing between the conductors 33 and 34 is set densely in a planar view of the thin-film coil 32, and in the area where the conductor 34 is not provided, the conductor spacing between the conductors 33 and 34 is set sparsely in a planar view of the thin-film coil 32. The conductor spacing between the conductors 33 and 34 is set according to the application of the thin-film coil 32.

For example, when it is necessary to apply a high eddy current density to the device 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 across the entire front and back of the thin-film coil 32 than the conductor spacing between the conductors 33 and 34 near the center. Therefore, near the periphery of the thin-film coil 32, magnetic flux with a high magnetic flux density is generated as the number of turns of the conductors 33 and 34 increases. Therefore, it is possible to induce eddy currents with a high eddy current density at a position on the device under test 1 corresponding to the entire area from near the center to near the periphery of the thin-film coil 32.

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 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 periphery. Therefore, near the center of the thin-film coil 32, magnetic flux with a high magnetic flux density is generated as the number of turns of the conductors 33 and 34 increases. Therefore, it is possible to induce eddy currents 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.

As configured as described above, the third embodiment achieves the same effect as effect (1) of the first embodiment, as well as the following effect (4).

(4) In the thin-film coil 32, the conductors 34 are provided on one side (e.g., the back side 14B) of the substrate 14 in a plan view that corresponds to the conductor spacing 35 of the conductors 33 provided on one side (e.g., the front side 14A) of the substrate 14. Therefore, in the area where the conductors 34 are provided, the conductor spacing between the conductors 33 and 34 is dense in the plan view of the thin-film coil 32, while in the area where the conductors 34 are not provided, the conductor spacing between the conductors 33 and 34 is sparse in the plan view of the thin-film coil 32. In other words, in the area where the conductors 34 are provided, the number of windings of the conductors 33 and 34 per unit width of the thin-film coil 32 differs between the center and the periphery of the thin-film coil 32.

As a result, a magnetic flux with a high magnetic flux density can be generated in areas where the number of windings of the conductors 33 and 34 is large (areas where the conductor spacing of the conductors 33 and 34 is dense) on both the front and back of the thin-film coil 32 as a whole. As a result, similar to effect (2) of the first embodiment, a magnetic flux density distribution with an increased magnetic flux density can be obtained at the desired position of the thin-film coil 32 where the conductor spacing of the conductors 33 and 34 is set densely, and eddy currents with a high eddy current density can be induced at the position of the inspected object 1 corresponding to the desired position, thereby achieving eddy current testing with a high signal-to-noise ratio.

(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 V-V in Fig. 5A. In this fourth embodiment, parts that are the same as those in the first embodiment are given the same reference numerals as in the first embodiment, and descriptions thereof will be simplified or omitted.

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.

The magnetic layer 43 is preferably a ferromagnetic layer made of a ferromagnetic material such as iron. Furthermore, the material that makes up the magnetic layer 43 is preferably a magnetic fluid or magnetic powder, for example, so as not to impair the flexibility of the substrate 14. The thin-film coil 42 is able to generate magnetic flux with a high magnetic flux density by concentrating magnetic flux in the magnetic layer 43 within the substrate 14.

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

(5) In the thin-film coil 42, the magnetic layer 43 is provided within the flexible substrate 14, so the magnetic flux generated by the thin-film coil 42 can be concentrated in the magnetic layer 43. As a result, the thin-film coil 42 can increase the magnetic flux density and induce high-density eddy currents in the test object 1 near the thin-film coil 42 while maintaining flexibility relative to the test object 1, thereby achieving eddy current testing with a high signal-to-noise ratio.

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 a variety of 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 within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims.

For example, in the first to fourth embodiments, the thin-film coils 13, 22, 32, and 42 are described as having the conductors 15, 23, 33, and 34 spirally arranged on the substrate 14. However, these conductors 15, 23, 33, and 34 may also be arranged in a pulsed pattern. 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 differently near the center and near the periphery of the thin-film coils 13, 22, and 42.

1...Subject, 10...Eddy current flaw detection device, 11...Eddy current flaw detection probe, 13...Thin-film coil, 14...Substrate, 14A...Front surface, 14B...Back surface, 15...Conductor, 16...Wire spacing, 20...Eddy current flaw detection device, 21...Eddy current flaw detection probe, 22...Thin-film coil, 23...Conductor, 24...Wire spacing, 30...Eddy current flaw detection device, 31...Eddy current flaw detection probe, 32...Thin-film coil, 33, 34...Conductor, 35...Wire spacing, 40...Eddy current flaw detection device, 41...Eddy current flaw detection probe, 42...Thin-film coil, 43...Magnetic layer

Claims (4)

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