Eddy current flaw detection device and eddy current flaw detection method

Abstract

To reduce the trouble required for inspection by generating an eddy current in an inspection object by rotating a permanent magnet and hence dispensing with a coil excited by AC and miniaturizing a device and saving power.SOLUTION: An eddy current flaw detection device 1 for detecting a flaw by scanning an inspection object 2 while generating an eddy current in the inspection object includes: a rotating shaft 12 that is provided in a drive section 10 and is rotatable; a permanent magnet 13 rotated along with the rotating shaft while N and S poles are disposed in a direction orthogonal to an axis of the rotating shaft and sandwiching the rotating shaft; a detection coil 14 for detecting an eddy current occurring in the inspection object by rotation of the permanent magnet; and a holding section 30 that holds the permanent magnet in a predetermined position relative to the inspection object and holds the detection coil in a predetermined position relative to the permanent magnet and the inspection object.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an eddy current flaw detection device and an eddy current flaw detection method that rotate a permanent magnet to generate eddy currents in an object to be inspected and detect the eddy currents to detect defects such as scratches and cracks existing in the object to be inspected.

Background Art

[0002] Conventionally, in an eddy current flaw detection device or an eddy current flaw detection method in non-destructive inspection, an AC-excited coil has been used as a magnetic field source.

[0003] Also, for the purpose of accurately performing eddy current flaw detection on a portion having magnetic anisotropy such as a welded portion, Japanese Patent Application Laid-Open No. 11-295275 discloses a permanent magnet that applies a magnetic field to a detection region, an electric motor that changes the direction of the applied magnetic field, and a detection coil that detects a change in eddy current due to a defect in the detection region as a change in its impedance, and a technique of rotating the permanent magnet 90 degrees with an electric motor in accordance with the characteristics of the metal to be inspected is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in an apparatus or method using an AC-excited coil, the apparatus itself becomes large and heavy, and it is also necessary to secure an AC 100-volt power supply or the like. For this reason, a considerable amount of labor was required to use the apparatus or method at the site of non-destructive inspection. Further, the technique disclosed in Patent Document 1 is for dealing with a metal to be inspected having magnetic anisotropy, which is different from the present invention.

[0006] The present invention has been made in view of the above points, and by rotating a permanent magnet to generate eddy currents in an object to be inspected, an AC-excited coil becomes unnecessary, enabling miniaturization and power saving of the device and reducing the labor involved in inspection. An object of the present invention is to provide an eddy current flaw detection device and an eddy current flaw detection method that can achieve these objectives.

Means for Solving the Problems

[0007] The eddy current flaw detection device of the present invention is an eddy current flaw detection device that scans and inspects an object to be inspected while generating eddy currents in the object to be inspected, a rotatable rotating shaft provided in a drive unit, a permanent magnet with an N pole and an S pole arranged across the rotating shaft and rotating together with the rotating shaft, a detection coil that detects eddy currents generated in the object to be inspected by the rotation of the permanent magnet, a holding unit that holds the permanent magnet at a predetermined position with respect to the object to be inspected and holds the detection coil at a predetermined position with respect to the permanent magnet and the object to be inspected, and is characterized by comprising the above components.

[0008] According to the eddy current flaw detection device of the present invention, eddy currents are generated in the object to be inspected by rotating the permanent magnet. Therefore, the power required to generate eddy currents in the object to be inspected is only that for rotating the permanent magnet. As a result, miniaturization and power saving of the device can be achieved.

[0009] A preferred example of the eddy current flaw detection device of the present invention is wherein the object to be inspected is a pipe or a bar, there are two detection coils, a first detection coil and a second detection coil, the first detection coil and the second detection coil are differentially connected, the first detection coil is arranged on one side of the scanning direction from the permanent magnet, the second detection coil is arranged on the other side of the scanning direction from the permanent magnet, A first radial line connecting the axis of the object to be inspected and the first detection coil, and a second radial line connecting the axis of the object to be inspected and the second detection coil are arranged at the same angle when viewed from the axial direction of the object to be inspected.

[0010] A preferred example of the eddy current flaw detector of the present invention is A magnet radial line connecting the axis of the object to be inspected and the permanent magnet is arranged in the 3 o'clock direction of the clock face when viewed from the axial direction of the object to be inspected, The first radial line and the second radial line are arranged in the 9 o'clock direction when viewed from the axial direction of the object to be inspected.

[0011] A preferred example of the eddy current flaw detector of the present invention is The object to be inspected is a pipe or a bar, There are two detection coils, a first detection coil and a second detection coil, The first detection coil and the second detection coil are differentially connected, The first detection coil and the second detection coil are arranged on the same circumference of the object to be inspected, A first radial line connecting the axis of the object to be inspected and the first detection coil, and a second radial line connecting the axis of the object to be inspected and the second detection coil are arranged at different angles when viewed from the axial direction of the object to be inspected.

[0012] A preferred example of the eddy current flaw detector of the present invention is A magnet radial line connecting the axis of the object to be inspected and the permanent magnet is arranged in the 3 o'clock direction of the clock face when viewed from the axial direction of the object to be inspected, One of the first radial line or the second radial line is arranged in the 2 o'clock direction when viewed from the axial direction of the object to be inspected, The other of the first radial line or the second radial line is arranged in the 10 o'clock direction when viewed from the axial direction of the object to be inspected.

[0013] A preferred example of the eddy current flaw detector of the present invention is Among the detection coils, a shielding cover is provided to cover a portion other than the surface facing the object to be inspected and shield the magnetic field.

[0014] According to a preferred example of the eddy current flaw detector of the present invention, defects in an object to be inspected can be efficiently detected. Note that the expression "clock face" is used to specify the positions of the permanent magnet, the first detection coil, and the second detection coil. However, this clock face is virtual and there is no actual clock face there. Also, the clock face relatively shows the positional relationship among the permanent magnet, the first detection coil, and the second detection coil, and it is not necessary that 12 o'clock and 6 o'clock on the clock face are necessarily in the vertical direction.

[0015] The eddy current flaw detection method of the present invention is an eddy current flaw detection method using the above-described eddy current flaw detector, a preparation step of bringing the holding portion into contact with or attaching it to the object to be inspected to dispose the permanent magnet and the detection coil at predetermined positions and rotating the permanent magnet; a scanning step of relatively moving the holding portion along the object to be inspected to scan the object to be inspected; a detection step of detecting an eddy current generated in the object to be inspected by the detection coil; characterized by comprising

[0016] According to the eddy current flaw detection method of the present invention, the same operational effects as those of the above-described eddy current flaw detector can be achieved.

Effects of the Invention

[0017] As described above, according to the eddy current flaw detector and the eddy current flaw detection method of the present invention, miniaturization and power saving of the device can be achieved, and the labor required for inspection can be reduced.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the eddy current flaw detector 1 and the eddy current flaw detection method of the present invention will be described in detail with reference to the accompanying drawings. First, an embodiment of the eddy current flaw detector 1 will be described.

[0020] As shown in FIG. 1, the eddy current flaw detector 1 of the present embodiment includes a drive unit 10, a rotating shaft 12, a permanent magnet 13, a detection coil 14, a holding unit 30, a reference coil 15 or a magnetic measuring device 20, an oscilloscope 23, a lock-in amplifier 24, a personal computer (PC) as a display unit 25, and a shielding cover 40 (see FIG. 6). In addition, in the present embodiment, a pipe material or a bar material is used as the inspection object 2.

[0021] The drive unit 10 is configured using a known electric motor 10 or the like. As this electric motor 10, for example, a small DC motor with a power consumption of 10 watts or less is used. In the present embodiment, a DC motor with a power consumption of 7.5 watts is adopted.

[0022] The rotating shaft 12 extends from the output shaft 11 of the electric motor 10 (see FIG. 2(B)) and rotates the permanent magnet 13 by rotating itself. As this rotating shaft 12, the output shaft 11 of the electric motor 10 may be used as it is, or another member may be connected using a shaft coupling such as a coupling.

[0023] The permanent magnet 13 is mounted on the rotating shaft 12 such that its N and S poles are arranged in a direction perpendicular to the axis of the rotating shaft 12 and sandwiching the rotating shaft 12, and rotates together with the rotating shaft 12. By rotating this permanent magnet 13 close to the inspection object 2, a change in the magnetic field occurs and eddy currents are generated in the inspection object 2. In the present embodiment, a round neodymium magnet (magnetization radial direction) is used as this permanent magnet 13. Also, in the permanent magnet 13 of the present embodiment, there is one N pole and one S pole each, but for example, four or more N and S poles can be arranged along the circumferential direction of the permanent magnet 13, such as N pole, S pole, N pole, S pole, ···.

[0024] The detection coil 14 detects the reaction magnetic field from the eddy currents generated in the inspection object 2 as an induced electromotive force and outputs it as a measurement signal. In the present embodiment, an upper coil is adopted for the detection coil 14.

[0025] The holding unit 30 holds the permanent magnet 13 and the like at a predetermined position with respect to the inspection object 2, and in the present embodiment, includes a magnet holding unit 31, a detection coil holding unit 32, an inspection object holding unit 33, and a reference coil holding unit 35. The magnet holding unit 31 holds the electric motor 10, thereby also holding the rotating shaft 12 and the permanent magnet 13, and keeping the permanent magnet 13 at a predetermined position with respect to the inspection object 2. The detection coil holding unit 32 holds the detection coil 14 and keeps the detection coil 14 at a predetermined position with respect to the permanent magnet 13 and the inspection object 2. The inspection object holding unit 33 holds the inspection object 2 and keeps it at a predetermined position. In the present embodiment, since the pipe material 2 is used as the inspection object 2, the pipe material 2 is passed through a hole 34 (see Fig. 2(B)) provided in the inspection object holding unit 33. The reference coil holding unit 35 holds the reference coil 15 and keeps the reference coil 15 at a predetermined position with respect to the permanent magnet 13, the inspection object 2, and the detection coil 14. Although not shown, a probe holding unit 30 that holds the magnetic probe 21 to be described later at a predetermined position with respect to the permanent magnet 13 may be provided.

[0026] The reference coil 15 detects the eddy current generated in the object 2 to be inspected at a position different from that of the detection coil 14, and detects the degree of change in the magnetic field, that is, the rotation speed of the permanent magnet 13. The electrical signal detected by this reference coil 15 is input to a device such as an oscilloscope 23. In this embodiment, a through coil is employed as the reference coil 15.

[0027] Alternatively, a magnetic measuring instrument 20 may be used instead of the reference coil 15. The magnetic measuring instrument 20 includes a magnetic probe 21 and a gauss meter 22. Here, the magnetic probe 21 is arranged close to the permanent magnet 13. When the permanent magnet 13 rotates, the surrounding magnetic field changes. Therefore, this change can be detected by the magnetic probe 21 to observe the rotation speed of the permanent magnet 13. The output signal of this magnetic probe 21 is input to the gauss meter 22, and the output signal of the gauss meter 22 is input to a device such as an oscilloscope 23.

[0028] Generally, the oscilloscope 23 observes the waveform of the input signal, etc. Here, the waveform of the signal output from the reference coil 15 or the gauss meter 22 and input to the oscilloscope 23 is adjusted as necessary and output to the lock-in amplifier 24 as a reference signal. If the signal output from the reference coil 15 or the gauss meter 22 can be used as the reference signal as it is, the oscilloscope 23 is not necessary. If there is a device that can make the signal usable as the reference signal, that device may be used instead of the oscilloscope 23.

[0029] The lock-in amplifier 24 removes the noise contained in the measurement signal by using the measurement signal detected by the detection coil 14 and the reference signal output from the oscilloscope 23. If the lock-in amplifier 24 is not used and the defect of the object 2 to be inspected can be detected, the lock-in amplifier 24 is not necessary.

[0030] The PC as the display unit 25 displays the changes in voltage and phase on the screen from the signal output from the lock-in amplifier 24 by using display software (not shown), etc.

[0031] As shown in FIG. 6, the shielding cover 40 shields a magnetic field by covering portions of the detection coil 14 other than the surface 43 facing the object 2 to be inspected. In the present embodiment, a barrel-shaped object is adopted in which one opening of an iron pipe 41, which is a metal pipe, is closed with an iron plate to form a bottom surface 42. The detection coil 14 is fitted into this shielding cover 40, and the end of a winding (not shown) is drawn out from a hole (not shown) in the bottom surface 42 or near the bottom surface 42. Note that the material of the shielding cover 40 is not limited to iron, and other metals or other materials can be adopted as long as they can shield the magnetic field.

[0032] Next, with reference to FIGS. 2(A) to 2(C), an example of the positional relationship between the permanent magnet 13 and the detection coil 14 with respect to the object 2 to be inspected and the dimensions of the detection coil 14 will be described. These dimensions are used when explaining each of the embodiments described later. Note that the description of the reference coil 15 and the reference coil holding portion 35 is omitted in FIG. 2.

[0033] First, the positional relationship between the object 2 to be inspected and the permanent magnet 13 will be described. As shown in FIG. 2(A), the distance between the pipe material, which is the object 2 to be inspected, and the permanent magnet 13 is defined as dimension "B". If this dimension is large, sufficient eddy currents will not be generated in the object 2 to be inspected, and if it is small, the load on the electric motor 10 will increase. Further, as shown in FIG. 2(B), when viewed from the axial direction of the object 2 to be inspected, the deviation between the height of the axis of the object 2 to be inspected and the height of the center of the permanent magnet 13 is defined as dimension "A". In each of the embodiments described later, this dimension "A" is 0 mm in all cases.

[0034] Next, the positional relationship between the permanent magnet 13 and the detection coil 14 will be described. As shown in Fig. 2(A), in the axial direction of the inspection object 2, the distance between the axis (rotation axis 12) of the permanent magnet 13 and the inspection object holding part 33 is set as "C0". And the distance between the inspection object holding part 33 and the end of the detection coil 14 is set as "C". The distance between the permanent magnet 13 and the detection coil 14 in the scanning direction is the sum of these C0 and C. As the position of the detection coil 14, in addition to the distance along the axis of the inspection object 2 described above, there is an angle as viewed from the axial direction of the inspection object 2 which will be described later (see Fig. 3(B), Fig. 4(B), Fig. 5(B)). Also, the distance between the inspection object 2 and the surface 43 of the detection coil 14 facing the inspection object 2 is made as close as possible within a non-contact range, for example, it is 0.3 to 3 mm.

[0035] Next, with reference to Fig. 2(C), the dimensions of the detection coil 14 adopted in this embodiment will be described. As shown in this figure, for the bobbin of the detection coil 14, the distance between the flanges at both ends is "a", the distance between the outer sides of the flanges is "b", the diameter of the body is "c", and the outer diameter of the flange is "d". These dimensions are a = 10 mm, b = 14 mm, c = 10 mm, d = 18 mm. Also, the winding is made by winding an enameled wire with a wire diameter of 0.4 mm 200 times. Note that the dimensions of the detection coil 14, the wire diameter and the number of turns of the winding are examples and are not limited to these values, and are appropriately changed according to the size of the inspection object 2 and other conditions.

[0036] Next, with reference to Figs. 3 to 5 and Fig. 7, each embodiment of the eddy current flaw detector 1 will be described. The broken lines in the figures of each embodiment in Figs. 3 to 5 indicate the positions of the reference coils 15. Also, in Figs. 3 to 5, some configurations such as the electric motor 10 and the shielding cover 40 are omitted.

[0037] An explanation will be given for Fig. 7. In the table of Fig. 7(A), "○" indicates that the flaw waveform appears in both the voltage and the phase with respect to the flaw of the inspection object, "△" indicates that the flaw waveform appears in only one of the voltage or the phase, and "×" indicates that the flaw waveform cannot be discriminated in both the voltage and the phase. Fig. 7(B) shows the positional relationship between the inspection object 2, the permanent magnet 13, and the detection coil 14 described in Figs. 2(A) and (B).

[0038] [First Embodiment] As the first embodiment, the eddy current flaw detector 1 shown in FIGS. 3(A) and 3(B) will be described. In the table of FIGS. 7(A) and 7(B) for explaining the experimental results, this embodiment is No. 2.

[0039] In the eddy current flaw detector 1 of this embodiment, a steel pipe with an outer diameter of 14 mm and an inner diameter of 6 mm is used as the inspection object 2 (the same applies to other embodiments). The permanent magnet 13 is installed 10 mm away from the inspection object 2 (the distance B shown in FIG. 2), and is arranged at the 3 o'clock position of a virtual clock face when viewed from the axial direction of the inspection object 2 shown in FIG. 3(B). That is, the magnet radius line connecting the axis of the inspection object 2 and the permanent magnet 13 is arranged in the 3 o'clock direction of the clock face when viewed from the axial direction of the inspection object 2.

[0040] In this embodiment, one coil is adopted as the detection coil 14. This detection coil 14 is installed 30 mm away from the permanent magnet 13 in the direction along the axis of the inspection object 2 (scanning direction) shown in FIG. 3(A) (the distance C + C0 shown in FIG. 2), and is installed in the same 3 o'clock direction as the permanent magnet 13 when viewed from the axial direction of the inspection object 2 shown in FIG. 3(B). That is, the coil radius line connecting the axis of the inspection object 2 and the detection coil 14 is arranged in the 3 o'clock direction of the clock face when viewed from the axial direction of the inspection object 2. Note that the lines such as 2 o'clock, 3 o'clock, 6 o'clock, 9 o'clock, 10 o'clock, and 12 o'clock shown in FIGS. 3(B), 4(B), and 5(B) are for explaining the relative positional relationship between the permanent magnet 13 and the detection coil 14, and it is not necessary for 3 o'clock to be necessarily horizontal with respect to the inspection object 2.

[0041] Next, referring to Fig. 7(A), the experimental results in this embodiment will be described (No. 2). In this experiment, the inspection object 2 passed through the hole 34 of the inspection object holding part 33 is scanned by moving it relatively to the permanent magnet 13 along the axial direction of the inspection object 2. That is, the axial direction of the inspection object 2 becomes the scanning direction (the same applies to other embodiments). Also, in this embodiment, the rotation speeds of the permanent magnet 13 are two types, 83 Hz and 206 Hz. Since the permanent magnet 13 used in this embodiment has a pair of N poles and S poles arranged across the rotation axis 12, the rotation speed and frequency of the electric motor 10 are the same (the same applies to other embodiments).

[0042] As a result of scanning the inspection object 2 at these different frequencies, in the outer peripheral wounds of the inspection object 2 with a width of 3 mm and depths of 1.6 mm and 2.4 mm, a wound waveform appeared only in one of the voltage or the phase.

[0043] [Second Embodiment] Next, as a second embodiment, the eddy current flaw detector 1 shown in Figs. 4(A) and (B) will be described. In the table of Figs. 7(A) and (B) for explaining the experimental results, this embodiment is No. 4.

[0044] In this embodiment, the permanent magnet 13 is installed 10 mm away from the inspection object 2 (distance B shown in Fig. 2), and is arranged at the 3 o'clock position of a virtual clock face when viewed from the axial direction of the inspection object 2 shown in Fig. 4(B). That is, the magnet radius line connecting the axis of the inspection object 2 and the permanent magnet 13 is arranged in the 3 o'clock direction of the clock face when viewed from the axial direction of the inspection object 2.

[0045] In this embodiment, a first detection coil 14a and a second detection coil 14b connected in differential are employed as the detection coil 14. These two detection coils 14a and 14b are arranged such that the first detection coil 14a is disposed on one side of the scanning direction from the permanent magnet 13, and the second detection coil 14b is disposed on the other side of the scanning direction from the permanent magnet 13. Also, the first detection coil 14a and the second detection coil 14b are installed 16 mm apart from the permanent magnet 13 respectively in the direction (scanning direction) along the axis of the inspection object 2 shown in Fig. 4(A) (the distance of C + C0 shown in Fig. 2), and when viewed from the axial direction of the inspection object 2 shown in Fig. 4(B), they are installed in the 9 o'clock direction on the opposite side across the inspection object 2 from the permanent magnet 13. That is, the first radius line connecting the axis of the inspection object 2 and the first detection coil 14a and the second radius line connecting the axis of the inspection object 2 and the second detection coil 14b are arranged at the same angle when viewed from the axial direction of the inspection object 2.

[0046] Next, referring to Fig. 7(A), the experimental results in this embodiment will be described (No. 4). In this embodiment, at both rotation speeds of 83 Hz and 206 Hz of the permanent magnet 13, a flaw waveform appeared only in either the voltage or the phase for an outer peripheral flaw with a width of 3 mm and a depth of 0.8 mm in the inspection object 2. Also, for an outer peripheral flaw with a width of 3 mm and a depth of 2.4 mm in the inspection object 2, flaw waveforms appeared in both the voltage and the phase.

[0047] [Third Embodiment] Next, as the third embodiment, the eddy current flaw detector 1 shown in Figs. 5(A) and 5(B) will be described. In the tables of Figs. 7(A) and 7(B) for explaining the experimental results, this embodiment is No. 5.

[0048] In this embodiment, the permanent magnet 13 is installed 10 mm apart from the inspection object 2 (the distance of B shown in Fig. 2), and when viewed from the axial direction of the inspection object 2 shown in Fig. 5(B), it is disposed at the 3 o'clock position of a virtual clock face. That is, the magnet radius line connecting the axis of the inspection object 2 and the permanent magnet 13 is arranged in the 3 o'clock direction of the clock face when viewed from the axial direction of the inspection object 2.

[0049] In this embodiment, a first detection coil 14a and a second detection coil 14b that are differentially connected are employed as the detection coil 14. These two detection coils 14a and 14b are arranged such that the first detection coil 14a and the second detection coil 14b are disposed on the same circumference of the inspection object 2. Further, the first detection coil 14a and the second detection coil 14b are each installed 16 mm away from the permanent magnet 13 in the direction along the axis of the inspection object 2 (scanning direction) shown in Fig. 5(A) (the distance of C + C0 shown in Fig. 2), and are installed at the 2 o'clock direction and the 10 o'clock direction when viewed from the axial direction of the inspection object 2 shown in Fig. 5(B). That is, a first radius line connecting the axis of the inspection object 2 and the first detection coil 14a and a second radius line connecting the axis of the inspection object 2 and the second detection coil 14b are arranged at different angles when viewed from the axial direction of the inspection object 2. Also, one of the first radius line or the second radius line is arranged in the 2 o'clock direction when viewed from the axial direction of the inspection object 2, and the other of the first radius line or the second radius line is arranged in the 10 o'clock direction when viewed from the axial direction of the inspection object 2.

[0050] Next, referring to Fig. 7(A), the experimental results in this embodiment will be described (No. 5). In this embodiment, at both rotation speeds of 83 Hz and 206 Hz of the permanent magnet 13, damage waveforms appeared in both voltage and phase for outer peripheral damages with a width of 1 mm and depths of 0.6 mm, 1.0 mm, and 1.6 mm in the inspection object 2. Also, damage waveforms appeared in only one of voltage or phase for outer peripheral damages with a width of 3 mm and depths of 0.2 mm and 0.4 mm in the inspection object 2. Further, damage waveforms appeared in both voltage and phase for outer peripheral damages with a width of 3 mm and depths of 0.8 mm, 1.6 mm, and 2.4 mm in the inspection object 2.

[0051] Next, based on each configuration of the eddy current flaw detector 1 described above, an embodiment of an eddy current flaw detection method using the eddy current flaw detector 1 will be described. The eddy current flaw detection method of this embodiment includes a preparation step, a scanning step, and a detection step.

[0052] In the preparation step, first, the holding part 30 is brought into contact with or attached to the object to be inspected 2 to arrange the permanent magnet 13, the detection coil 14, and, if necessary, the reference coil 15 at predetermined positions. In this embodiment, the permanent magnet 13 is held by the magnet holding part 31, the detection coil 14 is held by the detection coil holding part 32, and the reference coil 15 is held by the reference coil holding part 35, and their respective positional relationships are determined. Therefore, by passing the object to be inspected 2 through the hole 34 of the object to be inspected holding part 33, the permanent magnet 13 and the like are arranged at predetermined positions. Next, the permanent magnet 13 may be rotated by energizing the electric motor 10. However, the permanent magnet 13 may be rotated before passing the object to be inspected 2 through the hole 34 of the object to be inspected holding part 33.

[0053] In the next scanning step, the holding part 30 is relatively moved along the object to be inspected 2 to scan the object to be inspected 2. Here, the object to be inspected holding part 33 may be moved along the object to be inspected 2, or the object to be inspected 2 may be moved relative to the object to be inspected holding part 33.

[0054] In the next detection step, the eddy current generated in the object to be inspected 2 is detected by the detection coil 14. Here, the measurement signal passed through the lock-in amplifier 24 is viewed on the PC screen as the display part 25. In this embodiment, since the signal passed through the lock-in amplifier 24 is viewed, a substantially flat or smooth waveform appears at a location without damage, and a characteristic damage waveform appears at a location with damage.

[0055] As described above, in the eddy current flaw detector 1 and the eddy current flaw detector 1 according to the present embodiment, the rotation of the permanent magnet 13 is used as a configuration for generating eddy currents in the inspection object 2. For this reason, an AC power supply flowing through a coil as in the prior art is unnecessary, and power saving and miniaturization can be achieved. For example, the electric motor 10 used in the eddy current flaw detector 1 of the present embodiment has a power consumption of about 7.5 W. Since the above-described eddy current flaw detector 1 is experimentally constructed, various devices using a commercial power supply are connected. However, if the necessary functions of these devices are made into dedicated circuits and incorporated into one housing, it is possible to obtain an eddy current flaw detector 1 that can be battery-driven, lightweight, and easy to carry.

[0056] Also, even when the reference coil 15 cannot be arranged, by arranging the magnetic probe 21 for detecting the rotation of the permanent magnet 13 and the gauss meter 22, it is possible to detect a flaw in the inspection object 2.

[0057] Note that the above-described eddy current flaw detector and eddy current flaw detection method are examples of the present invention, and the configuration can be appropriately changed without departing from the spirit of the invention.

Explanation of Reference Numerals

[0058] 1 ··· Eddy current flaw detector, 2 ··· Inspection object, 10 ··· Driving unit (electric motor), 11 ··· Output shaft, 12 ··· Rotating shaft, 13 ··· Permanent magnet, 14 ··· Detection coil, 14a ··· First detection coil, 14b ··· Second detection coil, 15 ··· Reference coil, 20 ··· Magnetic measuring instrument, 21 ··· Magnetic probe, 22 ··· Gauss meter, 23 ··· Oscilloscope, 24 ··· Lock-in amplifier, 25 ··· Display unit, 30 ··· Holding unit, 31 ··· Magnet holding unit, 32 ··· Detection coil holding unit, 33 ··· Inspection object holding unit, 34 ··· Hole, 35 ··· Reference coil holding unit, 40 ··· Shielding cover, 41 ··· Iron pipe, 42 ··· Bottom surface, 43 ··· Opposing surface,

Claims

1. An eddy current inspection device that scans an inspection object while generating an eddy current in the inspection object, A rotating shaft provided in the drive unit and capable of rotating; A permanent magnet having an N pole and an S pole disposed on either side of the rotating shaft and rotating together with the rotating shaft; a detection coil for detecting an eddy current generated in the inspection object by rotation of the permanent magnet; a holder that holds the permanent magnet at a predetermined position relative to the inspection object and holds the detection coil at a predetermined position relative to the permanent magnet and the inspection object; An eddy current flaw detector comprising:

2. The inspection object is a pipe or a rod, The detection coil includes a first detection coil and a second detection coil, the first detection coil and the second detection coil are differentially connected; the first detection coil is disposed on one side of the permanent magnet in a scanning direction, the second detection coil is disposed on the other side of the permanent magnet in the scanning direction, 2. The eddy current flaw detection device according to claim 1, wherein a first radial line connecting the axis of the object to be inspected and the first detection coil and a second radial line connecting the axis of the object to be inspected and the second detection coil are arranged at the same angle when viewed from the axial direction of the object to be inspected.

3. a magnet radius line connecting the axis of the inspection object and the permanent magnet is disposed in the direction of 3 o'clock on a clock face as viewed from the axial direction of the inspection object; 3. The eddy current flaw detector according to claim 2, wherein the first radial line and the second radial line are disposed at a 9 o'clock direction as viewed in the axial direction of the inspection object.

4. The inspection object is a pipe or a rod, The detection coil includes a first detection coil and a second detection coil, the first detection coil and the second detection coil are differentially connected; the first detection coil and the second detection coil are disposed on the same circumference of the inspection object; 2. The eddy current flaw detection device according to claim 1, wherein a first radial line connecting the axis of the object to be inspected and the first detection coil and a second radial line connecting the axis of the object to be inspected and the second detection coil are arranged at different angles when viewed from the axial direction of the object to be inspected.

5. a magnet radius line connecting the axis of the inspection object and the permanent magnet is disposed in the direction of 3 o'clock on a clock face as viewed from the axial direction of the inspection object; one of the first radial line and the second radial line is disposed at a 2 o'clock direction as viewed in an axial direction of the inspection object; 5. The eddy current flaw detector according to claim 4, wherein the other of the first radial line and the second radial line is disposed at a 10 o'clock direction as viewed in the axial direction of the inspection object.

6. 6. The eddy current flaw detector according to claim 1, further comprising a shielding cover for shielding a magnetic field by covering a portion of the detection coil other than a surface facing the inspection object.

7. An eddy current inspection method using the eddy current inspection device according to claim 6, a preparation step of abutting or attaching the holding unit to the inspection object to dispose the permanent magnet and the detection coil at predetermined positions and rotating the permanent magnet; a scanning step of scanning the inspection object by relatively moving the holding part along the inspection object; a detection step of detecting an eddy current generated in the inspection object by the detection coil; An eddy current flaw detection method comprising:

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