Probe head and eddy current testing probe

Abstract

It accurately detects defects in the object being inspected. [Solution] The probe head is a probe head for an eddy current testing probe that is inserted into a tubular object to be inspected and moves back and forth along the axis of the object to be inspected to inspect the inner surface of the object. The probe head comprises a coil section having an excitation coil that generates an alternating magnetic field and a detection coil that detects eddy currents generated on the inner surface by the alternating magnetic field; a coil holder that holds the coil section so as to face the inner surface; a probe body that supports the coil holder so as to be able to move back and forth in the radial direction about the axis; and a biasing member provided on the probe body that biases the coil holder toward the radially outward direction.

Description

[Technical Field]

[0001] The present disclosure relates to a probe head and an eddy current flaw detection probe. [Background Art]

[0002] Eddy Current Testing (ECT) is known as a method for non-destructively inspecting defects such as flaws and wall thinning in members made of metal materials such as pipes. In this eddy current testing method, an excitation coil generates an eddy current on the surface of an inspection object, and a voltage change (or impedance change) of a detection coil caused by the influence of the eddy current is observed. Thereby, defects occurring in the inspection object can be detected.

[0003] Patent Document 1 discloses an eddy current flaw detection probe (a so-called insertion-type ECT probe) that can detect defects inside a pipe by being inserted into the pipe. The eddy current flaw detection probe described in Patent Document 1 has a plurality of excitation coils and detection coils arranged in the circumferential direction on the outer surface of a cylindrical casing. This enables defect detection at a plurality of positions in the circumferential direction on the inner surface of the pipe. [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent No. 5959306 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] By the way, the eddy current testing probe described in Patent Document 1 is intended for piping with a constant inner diameter. For example, if one attempts to detect defects in an object to be inspected, such as a heat exchanger tube with a non-constant inner diameter, using the eddy current testing probe, there is a problem in that the distance between the excitation coil and detection coil and the inner surface of the object to be inspected (in other words, the lift-off) becomes large in areas where the inner diameter of the object to be inspected is large, making it difficult to detect defects accurately.

[0006] This disclosure is made in view of the above circumstances and aims to provide a probe head and an eddy current testing probe capable of accurately detecting defects in an object under inspection. [Means for solving the problem]

[0007] To address the above issues, the following configuration will be adopted. A probe head according to one aspect of the present disclosure is a probe head for an eddy current testing probe that is inserted into a tubular object to be inspected and moves back and forth along the axis of the object to be inspected to inspect the inner surface of the object, comprising: a coil section having an excitation coil for generating an alternating magnetic field and a detection coil for detecting eddy currents generated on the inner surface by the alternating magnetic field; a coil holder for holding the coil section so as to face the inner surface; and a probe body that supports the coil holder so as to be able to move back and forth in the radial direction about the axis.

[0008] An eddy current flaw detection probe according to one aspect of the present disclosure comprises a probe head, a cable-like member to which the probe head is attached and which can be bent and deformed according to the shape of the object to be inspected, and a flaw detector positioned outside the object to be inspected and detecting defects in the object based on the output signal of the coil. [Effects of the Invention]

[0009] The eddy current testing probe described herein can accurately detect defects in the object being inspected. [Brief explanation of the drawing]

[0010] [Figure 1] This is a perspective view of the probe head in an embodiment of the disclosure. [Figure 2] This is a cross-sectional view of the probe head in an embodiment of the disclosure. [Figure 3] This is a wiring diagram of the coil section in an embodiment of the present disclosure. [Figure 4] This is a front view of the probe head in the embodiment of the disclosure. [Figure 5] This is an explanatory diagram of the radius of curvature of the curved section. [Figure 6] This is an explanatory diagram of the lift-off between the object being inspected, which has the maximum radius of curvature, and the curved section. [Figure 7] This is an explanatory diagram of the lift-off between the object being inspected, which has the minimum radius of curvature, and the curved section. [Figure 8] This is a cross-sectional view showing the schematic arrangement of the switching circuit and flexible flat cable in an embodiment of the present disclosure. [Figure 9] This is a circuit diagram of the switching circuit. [Figure 10] This diagram shows an example of switching the coil section using a switching circuit. [Figure 11] This is a plan view of a flexible flat cable. [Figure 12] This is a side view of an eddy current testing probe in a modified embodiment of the present disclosure. [Figure 13] This diagram illustrates the mounting angles of multiple probe heads. [Figure 14] This diagram shows multiple probe heads stacked axially. [Modes for carrying out the invention]

[0011] Next, the probe head and eddy current testing probe in the embodiments of this disclosure will be described with reference to the drawings. The eddy current testing probe 100 of this embodiment is brought close to the inspection surface 81 of the object to be inspected 8 and detects changes in eddy currents generated in the object to be inspected 8 to perform flaw detection. The eddy current testing probe 100 performs flaw detection on the object to be inspected 8 using eddy current testing. woundand detects thickness reduction. Hereinafter, scratches and thickness reduction are collectively referred to as defects. The eddy current testing probe 100 of the present embodiment is a so-called multi-coil type probe. Examples of the inspection object 8 include boiler pipes of thermal power plants and metal cylindrical (in other words, tubular) pipes used as heat transfer tubes. The eddy current testing probe 100 of the present embodiment is inserted from an end of the inspection object 8 to detect the presence or absence of defects on the inner circumferential surface of the inspection object 8. Note that the contour of a cross section perpendicular to the axis a of the inspection object 8 is not limited to a perfect circle. In the following description, the direction in which the axis a extends is referred to as the axial direction Da, the direction in which the eddy current testing probe 100 is inserted into the inspection object 8 and advances is referred to as a first axial side Dai, and the direction in which the eddy current testing probe 100 retracts opposite to the first axial side Dai is referred to as a second axial side Dao. Further, the radial direction centered on the axis a is referred to as a radial direction Dr, and the circumferential direction is referred to as a circumferential direction Dc.

[0012] <Schematic Configuration of Eddy Current Testing Probe> Fig. 1 is a perspective view of a probe head according to an embodiment of the present disclosure. As shown in Fig. 1, the eddy current testing probe 100 of the present embodiment includes a probe head 1, a cord-like member 2, and a flaw detector 3. The cord-like member 2 is formed into a cord shape that can be bent and deformed according to the shape of the inspection object 8. Specifically, when the inspection object 8 is composed of a straight pipe and a bent pipe, the cord-like member 2 is formed into a cord shape that can be bent and deformed so as to be able to follow the bent pipe. The probe head 1 is attached to the cord-like member 2. The eddy current testing probe 100 is inserted into the tubular inspection object 8 and detects flaws on the inner circumferential surface of the inspection object 8 while advancing and retracting along the axis a of the inspection object 8. The flaw detector 3 displays, for example, the waveform of an output signal of the probe head 1 on a display (not shown) or the like. An operator determines the presence or absence of defects in the inspection object 8 based on the display on the display or the like.

[0013] <Configuration of Probe Head> Fig. 2 is a cross-sectional view of a probe head according to an embodiment of the present disclosure. Fig. 3 is a wiring diagram of a coil unit according to an embodiment of the present disclosure. As shown in FIGS. 1 and 2, the probe head 1 includes a coil section 10, a coil holder 20, and a probe body 30.

[0014] <Coil Section> As shown in FIG. 3, the coil section 10 includes an excitation coil 11 and a detection coil 12. The excitation coil 11 generates an alternating-current magnetic field. The detection coil 12 detects an eddy current generated on a surface to be inspected 81, which is the inner circumferential surface of the inspection object 8, by the alternating-current magnetic field generated by the excitation coil 11. The coil section 10 of the present embodiment is a so-called cross coil arranged such that one detection coil intersects with one excitation coil. In the present embodiment, one probe head 1 is provided with a plurality of coil sections 10. Each of the excitation coil 11 and the detection coil 12 includes a first end 13, which is a coil end, and a ground end 14.

[0015] <Coil Holder> FIG. 4 is a front view of the probe head according to the embodiment of the present disclosure. As shown in FIGS. 2 to 4, the coil holder 20 holds the coil section 10 so as to face the surface to be inspected 81, which is the inner circumferential surface of the inspection object 8. The probe head 1 of the present embodiment is provided with a plurality of coil holders 20. The plurality of coil holders 20 are arranged at intervals in a circumferential direction Dc centered on an axis a. In the present embodiment, a case where coil holders 20A and 20B are provided as two coil holders 20 for one probe head 1 will be described as an example. Note that, hereinafter, when it is not necessary to distinguish between the coil holders 20A and 20B, they may be simply referred to as the coil holder 20.

[0016] The two coil holders 20A and 20B are positioned symmetrically with respect to axis a in the cross-sectional view shown in Figure 2. In other words, in the circumferential direction Dc around axis a, coil holder 20A is positioned 180 degrees offset from coil holder 20B. To put it another way, coil holders 20A and 20B are positioned back to back. The coil holders 20A and 20B in this embodiment have the same shape.

[0017] The coil holder 20 holds multiple coil sections 10 arranged in the circumferential direction Dc centered on the axis a of the object to be inspected 8. In this embodiment, the coil holder 20 is shown as an example of holding eight coil sections 10 in a row. The number of coil sections 10 held by one coil holder 20 is not limited to eight. For example, the number of coil sections 10 held by one coil holder 20 may be seven or fewer, or nine or more. In Figure 4, the angular range of the circumferential direction Dc that can be inspected by one coil holder 20 is indicated by arrows.

[0018] As shown in Figure 2, the coil holder 20 of this embodiment comprises a coil holder body 21 and a tapered portion 22. The coil holder body 21 has a curved portion 25 extending in the circumferential direction Dc around axis a at its outermost radial point Dr.

[0019] <Curved section> The curved portion 25 is located on the outermost radial side Dr of the coil holder body 21 and extends in the circumferential direction Dc around axis a. The curved portion 25 is positioned along the inspection surface 81 and opposite to the inspection surface 81. The coil holder body 21 holds the above-mentioned coil portions 10 arranged in a single line along the curved portion 25 in the circumferential direction Dc. The multiple coil portions 10 do not protrude radially outward from the curved portion 25 and are positioned as close to the curved portion 25 as possible. The angle range in which the curved portion 25 is formed around axis a is 30 to 150 degrees, but as will be described later, it is preferable that the angle range not be too wide from the viewpoint of maintaining the lift-off of the coil portions 10 provided on the curved portion 25 within an inspectable range for different pipe diameters. Also, if the angle range is too narrow, it becomes necessary to devise measures such as connecting multiple probe heads 1 in series to ensure inspectionability for the entire inner diameter of the pipe, as will be described in the modified example later. For the reasons stated above, a preferred angular range for the formation of the curved portion 25 can be exemplified as a range of 45 to 75 degrees.

[0020] Figure 5 is an explanatory diagram of the radius of curvature of the curved section. Figure 6 is an explanatory diagram of the lift-off between the object being inspected with the maximum radius of curvature and the curved section. Figure 7 is an explanatory diagram of the lift-off between the object being inspected with the minimum radius of curvature and the curved section. The curved portion 25 has a radius of curvature between the maximum and minimum values ​​of the radius of curvature of the inspection target surface 81 (inner circumferential surface) that can be inspected. In other words, the curved portion 25 has a radius of curvature between the maximum and minimum values ​​of the radius of curvature of the inner circumferential surface of the inspection target object 8 inspected using the probe head 1 of this embodiment.

[0021] As shown in Figure 5, the radius of curvature R3 of the curved portion 25 in this embodiment is an intermediate value between the maximum value R1 of the radius of curvature on the inspection surface 81 and the minimum value R2 of the radius of curvature on the inspection surface 81. This prevents the lift-off, which is the radial distance Dr between the curved portion 25 and the inspection surface 81, from becoming larger in either the case of the maximum value R1 or the case of the minimum value R2. Specifically, the lift-off L2 at both ends of the circumferential direction Dc of the curved portion 25 in the case of the maximum value R1 shown in Figure 6 and the lift-off L1 at the center of the circumferential direction Dc of the curved portion 25 in the case of the minimum value R2 shown in Figure 7 can be made to be close in size. Therefore, it is possible to prevent only one of the lift-off L1 and lift-off L2 from becoming larger.

[0022] To give a more specific example, if the inspection surface 81 with the maximum radius of curvature R1 has an inner diameter of φ43.88, and the inspection surface 81 with the minimum radius of curvature R2 has an inner diameter of φ38.60, then if the radius of curvature R3 of the curved section 25 is set to 19.5 mm, the lift-off L1 of the coil section 10 located in the center of the circumferential direction Dc of the curved section 25 will vary between 0.51 mm and 0.72 mm, and the lift-off L2 of the coil sections 10 located at both ends of the circumferential direction Dc of the curved section 25 will vary between 0.57 mm and 0.77 mm. In general, the lift-off of the coil section in an eddy current flaw detection probe is set to be within 2 mm, but the smaller the lift-off, the better the detectability.

[0023] <Tapered section> As shown in Figures 1 and 2, the tapered portions 22 are located on the first axial side Dai and the second axial side Dao of the coil holder body 21, respectively. In this embodiment, two tapered portions 22 are provided on one coil holder 20. The two tapered portions 22 are arranged symmetrically with respect to the coil holder body 21 in the axial direction Da. The radial thickness Dr of the two tapered portions 22 gradually increases as they approach the coil holder body 21, up to the position of the curved portion 25 in the radial direction Dr.

[0024] <Probe body> The probe body 30 is fixed to the cable-like member 2 while supporting the coil holder 20. In this embodiment, the probe body 30 is fixed to the cable-like member 2 so as to cover its periphery. The probe body 30 in this embodiment has an insertion portion 31 through which the cable-like member 2 can be inserted in the axial direction Da. The probe body 30 is fastened to the cable-like member 2 with screws or the like.

[0025] The probe body 30 further includes a holder housing section 32, a biasing member 33, and a circuit housing section 34. <Holder storage section> The holder housing section 32 houses the coil holder 20 described above so that it can be displaced in the radial direction Dr. The holder housing section 32 opens outward in the radial direction Dr.

[0026] <Biasing member> The biasing member 33 biases the coil holder 20 outward in the radial direction Dr. In this embodiment, the biasing member 33 is positioned adjacent to the inside of the coil holder 20 in the radial direction Dr. Furthermore, in this embodiment, the biasing member 33 is positioned first axially on the Dai side of the coil holder body 21 and second axially on the Dao side of the coil holder body 21. In other words, in this embodiment, one coil holder 20 is biased by multiple biasing members 33. The biasing member 33 only needs to be configured to constantly press the coil holder 20 radially outward, and examples include coil springs and elastic members such as rubber. In this embodiment, the case where the biasing member 33 is a coil spring is illustrated as an example. In addition, although the case in which multiple biasing members 33 are provided at intervals in the axial direction Da has been described, multiple biasing members 33 may also be provided at intervals in the circumferential direction Dc. If the biasing member 33 is an elastic member, the biasing member 33 is installed inside the coil holder 20 in the radial direction Dr in a compressed and deformed state. In this embodiment, the probe body 30 supports the coil holder 20 so that it can move back and forth in the radial direction Dr around axis a.

[0027] <Circuit housing section> The circuit housing section 34 houses the switching circuit section 40, which will be described later. The circuit housing section 34 is located on the second axial side Dao of the probe body 30, relative to the holder housing section 32.

[0028] <Slope> The probe body 30 of this embodiment has inclined surfaces 36 and 37 that widen in diameter as they approach the coil holder 20, on the first axial side Dai and the second axial side Dao of the coil holder 20, respectively.

[0029] <Electrical Circuit Configuration> Figure 8 is a cross-sectional view showing a schematic arrangement of the switching circuit and flexible flat cable in an embodiment of the present disclosure. Figure 9 is a circuit diagram of the switching circuit. As shown in Figure 8, the probe head 1 further comprises a switching circuit section 40 and a flexible flat cable 50.

[0030] <Switching circuit section> The switching circuit 40 switches between using and not using the multiple coil units 10. However, if multiple coil units 10 are used simultaneously, their alternating magnetic fields may interfere with each other. Therefore, the switching circuit 40 switches between using and not using the multiple coil units 10 to prevent interference between their alternating magnetic fields.

[0031] A multiplexer can be used as the switching circuit section 40. As shown in Figure 9, the switching circuit section 40 is electrically connected to a plurality of coil sections 10 via a flexible flat cable 50. Furthermore, the switching circuit section 40 is electrically connected to the flaw detector 3 via a signal line such as a coaxial cable (not shown) routed inside the cable-like member 2. In this embodiment, the switching circuit section 40 selectively electrically connects only the excitation coil 11 and detection coil 12 of one coil section 10 from a plurality of coil sections 10 provided in a single coil holder 20 to the flaw detector 3.

[0032] As shown in Figure 8, in this embodiment, the switching circuit section 40 includes a switching circuit section 40A for the excitation coil 11 and a switching circuit section 40B for the detection coil.

[0033] Figure 10 shows an example of switching the coil section by the switching circuit section. In this embodiment, the switching circuit unit 40 simultaneously operates (uses) the coil unit 10 located at the furthest distance and point-symmetrical with respect to axis a, among the multiple coil units 10 provided on the two coil holders 20, so as not to interfere with the AC magnetic field. In other words, the switching circuit unit 40 in this embodiment connects the same number of coil units 10 as the number of coil holders 20 to the flaw detector 3. The switching of the circuit by the switching circuit unit 40 is controlled, for example, by the flaw detector 3.

[0034] As shown in Figure 10, the switching circuit 40, for example, when using the coil portion 10a closest to the first end 20a in the circumferential direction Dc of the coil holder 20A, uses the coil portion 10a of coil holder 20B which is point-symmetric to the position of coil portion 10a, and leaves the other coil portions 10 unused. Similarly, when using the coil portion 10b closest to the second end 20b in the circumferential direction Dc of the coil holder 20A, uses the coil portion 10b of coil holder 20B which is point-symmetric to the position of coil portion 10b, and leaves the other coil portions 10 unused. Note that the coil portion 10c in Figure 10 is an example of a coil portion 10 that is point-symmetric when the coil holders 20 (20A, 20B) are immersed in the probe body 30 (indicated by the dashed line).

[0035] <Flexible Flat Cable> The flexible flat cable 50 electrically connects the multiple coil sections 10 provided on the coil holder 20 to the switching circuit section 40. As shown in Figure 8, in this embodiment, the flexible flat cable 50 includes a flexible flat cable 50A that connects the excitation coil 11 to the switching circuit section 40, and a flexible flat cable 50B that connects the detection coil 12 to the switching circuit section 40. One of the flexible flat cables 50A and 50B extends inward in the radial direction Dr from a position adjacent to the first axial side Dai of the curved section 25, then changes direction in the axial direction Da, passes through the insertion section 31, and reaches the circuit housing section 34. Similarly, the other of the flexible flat cables 50A and 50B extends inward in the radial direction Dr from a position adjacent to the second axial side Dao of the curved section 25, then changes direction in the axial direction Da, passes through the insertion section 31, and reaches the circuit housing section 34. In the following explanation, when it is not necessary to distinguish between Flexible Flat Cable 50A and 50B, they may simply be referred to as Flexible Flat Cable 50.

[0036] Figure 11 is a plan view of a flexible flat cable. As shown in Figure 11, the flexible flat cable 50 is formed in a flexible sheet shape. The flexible flat cable 50 of this embodiment includes a first line 51 and a ground line 52. Since the flexible flat cable 50A and the flexible flat cable 50B in this embodiment have the same configuration, only the flexible flat cable 50A will be described below, and a detailed description of the flexible flat cable 50B will be omitted.

[0037] The first lines 51 of the flexible flat cable 50A are individually electrically connected to the first end 13 of the excitation coil 11. The number of first lines 51 of the flexible flat cable 50A is the same as the number of excitation coils 11. In this embodiment, the multiple first lines 51 provided on a single flexible flat cable 50A are arranged parallel to each other. On the other hand, the ground line 52 of the flexible flat cable 50A is provided as a single line, regardless of the number of excitation coils 11.

[0038] The flexible flat cable 50A has a coil-side electrode section 53 on the side closer to the excitation coil 11, and a cable end 50t connected to the switching circuit section 40 on the side opposite to the excitation coil 11. The coil-side electrode section 53 is provided with a plurality of first electrodes 54 individually electrically connected to a plurality of first lines 51, and a single ground electrode 55 connected to the ground line 52.

[0039] On the other hand, as shown in Figure 3, the extension portion 24 of this embodiment is provided with two aggregation electrodes 27: aggregation electrode 27A, to which the grounding end 14 of the excitation coil 11 is electrically aggregated, and aggregation electrode 27B, to which the grounding end 14 of the detection coil 12 is electrically aggregated. Aggregation electrode 27A is connected to the grounding electrode 55 of the flexible flat cable 50A, and aggregation electrode 27B is connected to the grounding electrode 55 of the flexible flat cable 50B. In other words, multiple grounding ends 14 are aggregated and electrically connected to the grounding line 52 of the flexible flat cable 50.

[0040] <Effects and Effects> The probe head 1 of the above embodiment comprises a coil section 10 having an excitation coil 11 and a detection coil 12, a coil holder 20 that holds the coil section 10 facing the inspection target surface 81, a probe body 30 that supports the coil holder 20 so that it can move back and forth in the radial direction Dr about axis a, and a biasing member 33 that biases the coil holder 20 toward the outside in the radial direction Dr.

[0041] This configuration allows the coil holder 20 to move forward and backward according to the inner diameter of the object being inspected 8. Therefore, even if the inner diameter of the object being inspected 8 changes during inspection, the coil holder 20 can be moved forward and backward to follow the change in inner diameter. This makes it possible to suppress an increase in the distance (lift-off) between the coil portion 10 held by the coil holder 20 and the inspection surface 81 of the object being inspected 8, even when using the same probe head 1, if the inner diameter of the object being inspected 8 changes during inspection. Consequently, defects in the object being inspected 8 can be detected with high accuracy.

[0042] Furthermore, the probe head 1 of the above embodiment is equipped with multiple coil sections 10. The coil holder 20 holds the multiple coil sections 10 arranged in the circumferential direction Dc around the axis a of the object to be inspected 8.

[0043] This configuration allows for inspection of a wider area of ​​the surface 81 in the circumferential direction Dc by multiple coil sections 10 arranged in the circumferential direction Dc without changing the orientation of the probe head 1. Therefore, the inspection time can be reduced compared to the case where the coil holder 20 has only one coil section 10. Furthermore, the complexity of the probe head 1's configuration can be suppressed compared to the case where one coil section 10 is provided in one coil holder.

[0044] Furthermore, the coil holder 20 of the above embodiment has a curved portion 25 extending in the circumferential direction Dc around axis a at its outermost radial point Dr. The curved portion 25 has a radius of curvature R3 between the maximum value R1 and minimum value R2 of the radius of curvature of the inspection target surface 81 that can be inspected, and multiple coil portions 10 are held along the curved portion 25.

[0045] This configuration prevents only one of the two lift-off values ​​from becoming larger: the lift-off L2 of the curved portion 25 that occurs with respect to the inspection surface 81 where the radius of curvature is the maximum value R1, and the lift-off L1 of the curved portion 25 that occurs with respect to the inspection surface 81 where the radius of curvature is the minimum value R2. Therefore, it is possible to prevent a decrease in defect detection accuracy due to increased lift-off values ​​L1 and L2.

[0046] Furthermore, the probe head 1 of the above embodiment is equipped with a plurality of coil holders 20 spaced apart in the circumferential direction Dc around axis a. In addition, the plurality of coil holders 20 are positioned symmetrically with respect to axis a.

[0047] This configuration allows a single probe head 1 to inspect a wider area in the circumferential direction Dc. Therefore, the time required for inspection can be further reduced. Furthermore, by arranging multiple coil holders 20 in symmetrical positions, the distance between the coil portions 10 provided on each coil holder 20 can be increased, thereby suppressing interference between the alternating magnetic fields of the coil portions 10 provided on each coil holder 20.

[0048] Furthermore, the probe head 1 of the above embodiment further includes a switching circuit 40 for switching between using and not using multiple coil sections 10, and a flexible flat cable 50 for electrically connecting the multiple coil sections 10 and the switching circuit 40.

[0049] This configuration allows for sequential switching between multiple coil sections 10, thereby suppressing interference that would occur if multiple adjacent coil sections 10 were used simultaneously. Consequently, the reliability of defect detection can be improved. Furthermore, the wiring connecting the multiple coil sections 10 and the switching circuit section 40 can be consolidated into a flexible flat cable 50. This reduces the space required for wiring within the probe head 1, allowing the probe head 1 to be made smaller. Consequently, it becomes possible to inspect smaller diameter objects 8.

[0050] Furthermore, the flexible flat cable 50 of the above embodiment has a plurality of first lines 51 to which a plurality of first ends 13 are individually electrically connected, and a ground line 52 to which a plurality of ground ends 14 are aggregated and electrically connected. This allows for a reduction in the number of flexible flat cables used for the grounding line 52 and miniaturization of the flexible flat cable 50, making it possible to further miniaturize the probe head 1.

[0051] Furthermore, the eddy current flaw detection probe 100 of the above embodiment comprises a probe head 1, a cable-like member 2, and a flaw detector 3. The switching circuit unit 40 simultaneously operates the coil units 10, which are located in point-symmetric positions with respect to axis a. By configuring the system in this way, multiple coil sections 10 located furthest apart from each other are used simultaneously on a single probe head 1, thereby suppressing interference between the alternating magnetic fields of the coil sections 10. Consequently, inspection time can be shortened while minimizing a decrease in inspection accuracy.

[0052] <Modified examples of embodiments> Next, a modified example of the above-described embodiment will be explained with reference to the drawings. The eddy current testing probe in this modified example differs from the above-described embodiment in that multiple probe heads are attached to a single cable-like member. Therefore, the same reference numerals are used for the same parts as in the above-described embodiment, and redundant explanations are omitted.

[0053] Figure 12 is a side view of an eddy current testing probe in a modified example of the embodiment of the present disclosure. As shown in Figure 12, the eddy current testing probe 200 in this modified example comprises a plurality of probe heads 1, a cable-like member 2, a flaw detector 3, and an alignment jig 60. The alignment jig 60 is a jig for positioning the cable-like member 2 on axis a, and can be omitted as appropriate.

[0054] The multiple probe heads 1 have the same configuration as the probe head 1 in the above embodiment and are equipped with multiple coil holders 20A, 20B spaced apart in the circumferential direction Dc around axis a. These multiple probe heads 1 are attached to the cable-like member 2 at intervals along its longitudinal direction. The longitudinal direction of the cable-like member 2 is also the axial direction Da.

[0055] In this modified example, the range extending in the circumferential direction Dc of one curved portion 25 is slightly greater than 60 degrees (60°+α) in terms of the angle of the circumferential direction Dc around axis a. In this modified example, three probe heads 1A, 1B, and 1C, each having a curved portion 25 within this angular range, are attached to the cable-like member 2. The +α angle can be exemplified as approximately 1 to 10 degrees. Note that the number of probe heads 1 attached to the cable-like member 2 is not limited to three, and the angular range of the curved portion 25 is not limited to 60°+α.

[0056] Figure 13 is a diagram illustrating the mounting angles of multiple probe heads. Figure 14 is a diagram showing multiple probe heads superimposed in the axial direction. As shown in Figure 13, the mounting angles of the probe heads 1A, 1B, and 1C with respect to the cable-like member 2, that is, the mounting angles in the circumferential direction Dc around axis a, are different from each other. In this modified example, the probe heads 1A, 1B, and 1C are arranged in the order of 1A, 1B, and 1C from the first axial side Dai to the second axial side Dao. The mounting angles of the probe heads 1A, 1B, and 1C are shifted by 60 degrees clockwise in that order. In other words, the mounting angle of probe head 1B is shifted by 60 degrees clockwise relative to probe head 1A, and the mounting angle of probe head 1C is shifted by 120 degrees clockwise relative to probe head 1A and by 60 degrees clockwise relative to probe head 1B.

[0057] In a modified version of the above embodiment, by attaching the multiple probe heads 1A, 1B, and 1C to the cable-like member 2 at different angles, different angular ranges of the inspection target surface 81 can be inspected simultaneously by each probe head 1A, 1B, and 1C. Furthermore, in the modified version of the above embodiment, as shown in Figure 14, the curved portions 25 of the multiple probe heads 1A, 1B, and 1C are arranged around the entire circumference (360°) when viewed from the axial direction Da, so that the entire circumference of the inspection target surface 81 can be inspected with a single eddy current testing probe 200. In addition, because the multiple probe heads 1A, 1B, and 1C are spaced apart in the axial direction Da, interference between the alternating magnetic fields of each probe head 1A, 1B, and 1C is suppressed, so that eddy current testing performed simultaneously by each probe head 1A, 1B, and 1C can be carried out with high accuracy. Furthermore, since inspection can be performed simultaneously using the three probe heads 1A, 1B, and 1C, the time required to inspect one full rotation of the inspection surface 81 can be reduced to one-third of the time required when switching between multiple coil sections. Therefore, it is possible to shorten the time required for eddy current testing and reduce the burden on the operator.

[0058] <Other Embodiments> This disclosure is not limited to the configuration of the embodiments described above, and design modifications are possible without departing from the spirit thereof. For example, in the embodiment described above, a case was described in which two coil holders 20 are provided for one probe body 30, but it is also possible to provide three or more coil holders 20 for one probe body 30. Furthermore, multiple coil holders 20 may be provided for one probe body 30 at intervals in the axial direction Da.

[0059] Furthermore, although the above embodiment describes a case where the coil section 10 has a cross coil, the excitation coil and detection coil in the coil section 10 are not limited to a cross coil.

[0060] <Note> The probe head and eddy current testing probe described in the embodiment can be understood, for example, as follows.

[0061] (1) According to the first embodiment, the probe heads 1, 1A, 1B, 1C are probe heads 1, 1A, 1B, 1C of an eddy current flaw detection probe that is inserted into a tubular object to be inspected 8 and moves back and forth along the axis a of the object to be inspected 8 to inspect the inner circumferential surface 81 of the object to be inspected 8, and include a coil section 10 having an excitation coil 11 that generates an alternating magnetic field and a detection coil 12 that detects eddy currents generated on the inner circumferential surface 81 by the alternating magnetic field; a coil holder 20 that holds the coil section 10 so as to face the inner circumferential surface 81; a probe body 30 that supports the coil holder 20 so as to be able to move back and forth in the radial direction Dr about the axis a; and a biasing member 33 provided on the probe body 30 that biases the coil holder 20 toward the outside in the radial direction Dr. An example of a coil section 10 is a cross coil.

[0062] This allows the coil holder 20 to move forward and backward in the radial direction Dr according to the inner diameter of the object being inspected 8. Therefore, even if the inner diameter of the object being inspected 8 changes during inspection, the coil holder 20 can move forward and backward in the radial direction Dr to follow the change in the inner diameter. This makes it possible to suppress an increase in the distance between the coil portion 10 held by the coil holder 20 and the inner circumferential surface 81 of the object being inspected 8, even when using the same probe heads 1, 1A, 1B, and 1C, when the inner diameter of the object being inspected 8 changes during inspection. Consequently, defects in the object being inspected 8 can be detected with high accuracy.

[0063] (2) According to the second embodiment, the probe heads 1, 1A, 1B, 1C are the probe heads 1, 1A, 1B, 1C of (1) and are equipped with a plurality of coil portions 10, and the coil holder 20 holds the plurality of coil portions 10 arranged in the circumferential direction Dc around the axis a of the object to be inspected 8.

[0064] This allows for inspection of a wider area of ​​the surface 81 in the circumferential direction Dc by multiple coil sections 10 arranged in the circumferential direction Dc without changing the orientation of the probe heads 1, 1A, 1B, and 1C. Therefore, the inspection time can be reduced compared to the case where the coil holder 20 has only one coil section 10. In addition, the complexity of the configuration of the probe heads 1, 1A, 1B, and 1C can be suppressed compared to the case where one coil section 10 is provided in one coil holder.

[0065] (3) According to the third embodiment, the probe heads 1, 1A, 1B, 1C are the probe heads 1, 1A, 1B, 1C of (2), wherein the coil holder 20 has a curved portion 25 extending in the circumferential direction Dc centered on the axis a at the outermost part in the radial direction Dr, the curved portion 25 has a radius of curvature R3 between the maximum value R1 and minimum value R2 of the radius of curvature of the inner circumferential surface 81 that can be inspected, and the plurality of coil portions 10 are held along the curved portion 25.

[0066] This prevents only one of the two lift-off values ​​from becoming larger: the lift-off L2 of the curved portion 25 that occurs with respect to the inspection surface 81 where the radius of curvature is the maximum value R1, and the lift-off L1 of the curved portion 25 that occurs with respect to the inspection surface 81 where the radius of curvature is the minimum value R2. Therefore, it is possible to prevent a decrease in defect detection accuracy due to an increase in lift-off values ​​L1 and L2.

[0067] (4) According to the fourth embodiment, the probe head 1, 1A, 1B, 1C is any one of the probe heads 1, 1A, 1B, 1C from (1) to (3), and comprises a plurality of coil holders 20 spaced apart in the circumferential direction Dc with respect to the axis a.

[0068] This allows a wider range of the circumferential direction Dc to be inspected with a single probe head 1, 1A, 1B, 1C. Therefore, the time required for inspection can be further reduced.

[0069] (5) According to the fifth embodiment, the probe heads 1, 1A, 1B, 1C are the probe heads 1, 1A, 1B, 1C of (4), and the plurality of coil holders 20 are provided in positions symmetrical with respect to the axis a.

[0070] This allows the distance between the coil sections 10 provided on each coil holder 20 to be increased, thereby suppressing interference between the alternating magnetic fields of the coil sections 10 provided on each coil holder 20.

[0071] (6) According to the sixth aspect, the probe heads 1, 1A, 1B, 1C are the probe heads 1, 1A, 1B, 1C of (2), further comprising a switching circuit unit 40 for switching the use of a plurality of coil units 10 and a flexible flat cable 50 for electrically connecting the plurality of coil units 10 and the switching circuit unit 40.

[0072] This allows multiple coil sections 10 to be switched sequentially, thereby suppressing interference that would occur if multiple adjacent coil sections 10 were used simultaneously. Consequently, the reliability of defect detection can be improved. In addition, the wiring connecting the multiple coil sections 10 and the switching circuit section 40 can be consolidated into a flexible flat cable 50. As a result, the space required for wiring within the probe heads 1, 1A, 1B, and 1C can be reduced, and the probe heads 1, 1A, 1B, and 1C can be made smaller. Consequently, it becomes possible to inspect objects 8 with smaller diameters.

[0073] (7) According to the seventh embodiment, the probe heads 1, 1A, 1B, 1C are the probe heads 1, 1A, 1B, 1C of (6), wherein the excitation coil 11 and the detection coil 12 each have a first end 13 electrically connected to the flexible flat cable 50 and a ground end 14, and the flexible flat cable 50 has a plurality of first lines 51 to which the plurality of first ends 13 are individually electrically connected and a ground line 52 to which the plurality of ground ends 14 are aggregated and electrically connected.

[0074] This allows for a reduction in the number of flexible flat cables used for grounding lines and miniaturization of the flexible flat cable 50, making it possible to further miniaturize the probe heads 1, 1A, 1B, and 1C.

[0075] (8) According to the eighth aspect, the eddy current testing probe 100,200 comprises one of the probe heads 1,1A,1B,1C from (1) to (7), a cable-like member 2 to which the probe head 1,1A,1B,1C is attached and which can be bent and deformed according to the shape of the object to be inspected 8, and a flaw detector 3 which is positioned outside the object to be inspected 8 and detects defects in the object to be inspected 8 based on the output signal of the coil section 10.

[0076] This allows for accurate and rapid defect detection using eddy current testing probes 100 and 200, thereby reducing the burden on workers.

[0077] (9) According to the ninth aspect, the eddy current testing probe 200 is (8) the eddy current testing probe 100, wherein the probe heads 1A, 1B, 1C are equipped with a plurality of coil holders 20 spaced apart in the circumferential direction Dc around the axis a, and a plurality of them are attached to the cable-like member 2 spaced apart in the longitudinal direction, and the mounting angles of the plurality of probe heads 1, 1A, 1B, 1C in the circumferential direction Dc around the axis a are different from each other.

[0078] This allows multiple probe heads 1A, 1B, and 1C to simultaneously inspect different angular ranges on the inspection surface 81. Furthermore, because the multiple probe heads 1A, 1B, and 1C are spaced apart in the axial direction Da, interference between the alternating magnetic fields of each probe head 1A, 1B, and 1C is suppressed, enabling accurate eddy current testing to be performed simultaneously by each probe head 1A, 1B, and 1C. Consequently, the time required for eddy current testing can be reduced, thereby alleviating the burden on the operator.

[0079] (10) According to the tenth embodiment, the eddy current testing probe 200 is the eddy current testing probe 100, 200 of (8) or (9), wherein the probe head 1, 1A, 1B, 1C further comprises a plurality of coil sections 10, a switching circuit section 40 for switching the use of the plurality of coil sections 10, and a flexible flat cable 50 for electrically connecting the plurality of coil sections 10 and the switching circuit section 40, wherein the coil holder 20 holds the plurality of coil sections 10 arranged in the circumferential direction Dc around the axis a of the object to be inspected 8, and the switching circuit section 40 simultaneously operates the coil sections 10 which are in point-symmetric positions around the axis a.

[0080] As a result, since the multiple coil sections 10 located furthest apart from each other are used simultaneously on a single probe head 1, 1A, 1B, 1C, interference between the alternating magnetic fields of the coil sections 10 can be suppressed. Therefore, it is possible to shorten the inspection time while suppressing a decrease in inspection accuracy. [Explanation of symbols]

[0081] 1, 1A, 1B, 1C… Probe heads 2… Cable-like member 3…Flaw detector 8…Items to be inspected 10... Coil section 11…Excitation coil 12…Detection coil 13...First end 14...Grounding end 20, 20A, 20B... Coil holders 21... Coil holder body 22... Tapered section 25…Curved section 27, 27A, 27B… Integrated electrodes 30…Probe body 31... Insertion part 32...Holder housing section 33… Biasing member 34...Circuit housing section 40…Switching circuit section 50... Flexible flat cable 51…First line 52...Ground line 53... Coil-side electrode section 81… Surface to be inspected 100, 200... eddy current testing probes a…Axis line

Claims

1. A probe head for an eddy current testing probe, which is inserted into a tubular object to be inspected and moves back and forth along the axis of the object to be inspected while inspecting the inner surface of the object, A coil section having an excitation coil for generating an alternating magnetic field, and a detection coil for detecting eddy currents generated on the inner surface by the alternating magnetic field, A coil holder that holds the coil portion so as to face the inner circumferential surface, A probe body supports the coil holder so that it can move back and forth in the radial direction about the axis, The probe body is provided with a biasing member that biases the coil holder toward the radially outward direction. Probe head.

2. The coil section comprises multiple such sections, The coil holder holds a plurality of the coil portions arranged in a circumferential direction around the axis of the object to be inspected. The probe head according to claim 1.

3. The coil holder has a curved portion extending circumferentially around the axis at its outermost radial end, The curved portion has a radius of curvature between the maximum and minimum values ​​of the radius of curvature of the inner circumferential surface that can be inspected. Multiple coil portions are held along the curved portion. The probe head according to claim 2.

4. Multiple coil holders are provided, spaced apart in the circumferential direction around the aforementioned axis. The probe head according to claim 1.

5. The multiple coil holders are positioned symmetrically with respect to the axis. The probe head according to claim 4.

6. A switching circuit unit that switches between using and not using multiple coil units, The system further comprises a flexible flat cable that electrically connects multiple coil sections and the switching circuit section. The probe head according to claim 2.

7. The excitation coil and the detection coil each have a first end that is electrically connected to the flexible flat cable and a ground end, The aforementioned flexible flat cable is Multiple first lines, each having a first end that is individually electrically connected, A grounding line comprising a plurality of grounding ends aggregated and electrically connected. The probe head according to claim 6.

8. The probe head according to claim 1, A cable-like member to which the probe head is attached, which can be bent and deformed according to the shape of the object to be inspected, The system includes a flaw detector positioned outside the object to be inspected, which detects defects in the object based on the output signal of the coil. Eddy current testing probe.

9. The probe head is equipped with a plurality of coil holders spaced apart in the circumferential direction around the axis, and a plurality of coil holders are attached to the cable-like member at intervals along its longitudinal direction. The mounting angles of the multiple probe heads in the circumferential direction around their respective axes are all different from each other. The eddy current testing probe according to claim 8.

10. The aforementioned probe head is Multiple coil sections, A switching circuit unit that switches between using and not using multiple coil units, The system further comprises a flexible flat cable that electrically connects multiple coil sections and the switching circuit section, The coil holder holds a plurality of the coil portions arranged in the circumferential direction around the axis of the object to be inspected, The switching circuit unit simultaneously operates the coil units which are located in point-symmetric positions with respect to the axis. The eddy current testing probe according to claim 8 or 9.

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