JP2002221514A - Eddy current flaw detection probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect a flaw in an eddy current flaw detection probe. SOLUTION: This probe for detecting the flaw in a test body 10 has plural excitation coils 22a-22h generating an AC magnetic field to generate an eddy current in the test body 10, and plural thin film-like detection coils 21a-21h overlapped in an upper-and-lower double-layer state and arranged in a line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eddy current inspection probe suitable for nondestructive inspection.

[0002]

2. Description of the Related Art Conventionally, eddy current flaw detection probes have been developed which are used for non-destructive inspection such as inspection at the time of manufacturing steel and non-ferrous materials and maintenance inspection at various plants such as a thin tube of a heat exchanger. The basic principle of flaw detection of a specimen using an eddy current flaw detection probe is to detect flaws by generating an eddy current on the specimen surface using an excitation coil and monitoring the impedance change of the detection coil due to the influence of the eddy current. is there. That is, if there is a flaw on the surface of the specimen, the flaw affects the eddy current generated on the surface of the specimen. This change in the eddy current also affects the impedance generated in the detection coil, and therefore, by monitoring the change in the impedance of the detection coil, a flaw in the test object can be detected.

FIGS. 4A to 4D are schematic views showing various configurations of a conventional eddy current inspection probe. Here, the eddy current flaw detection probes can be classified according to the method of detecting the impedance change and the configuration of the excitation coil and the detection coil. Focusing on the method of detecting the change in impedance of the detection coil, an absolute type in which a single detection coil detects a flaw in a test body as shown in FIGS. 4A and 4B, and FIGS. As shown in FIG. 4D, the detection coil can be divided into a differential type that detects a flaw of a test object by a differential component of impedance generated in each of the two detection coils.

[0004] Focusing on the configuration of the excitation coil and the detection coil, the self-induction type shown in FIGS. 4 (a) and 4 (c) and the configuration shown in FIGS. 4 (b) and 4 (d) are shown. It can be divided into the mutual induction type. What is self-guided?
One coil is a type that serves both as an excitation coil for generating an eddy current and a detection coil for detecting impedance. The mutual induction type refers to an excitation coil (primary coil) and a detection coil (secondary coil). Coil).

As described above, according to the method of detecting the impedance change of the detection coil and the configuration of the excitation coil and the detection coil, the detection coil can be classified into four types as shown in FIGS. 4 (a) to 4 (d). You can. Here, FIG.
The schematic configuration and operation of each eddy current flaw detection probe shown in FIG. 4D will be described.

FIG. 4A shows an absolute type and self-induction type eddy current flaw detection probe in which a single excitation / detection coil 59, which serves both as an excitation coil and a detection coil, is used as a test piece (plate-shaped test piece). (Inspection body) 10. The excitation and detection coil 59 is connected to an oscillator (not shown) and an instrument for monitoring impedance. The oscillator is for supplying an alternating current to the excitation and detection coil 59.

With this configuration, when detecting a flaw in the test body 10, first, an alternating current is supplied to the excitation / detection coil 59 by the oscillator, and an arrow F1,
An eddy current is generated on the surface of the specimen 10 by generating an alternating magnetic field as indicated by F2. An impedance corresponding to the eddy current is generated in the excitation / detection coil 59. Specimen 10
If the surface has a flaw, the eddy current changes, and the impedance of the exciting and detecting coil 59 also changes. Therefore, by monitoring the impedance of the exciting and detecting coil 59, the flaw of the test body 10 can be detected. .

FIG. 4B shows an absolute type and mutual induction type eddy current flaw detection probe.
The excitation coil 52 and the excitation coil 52 are set so as to face the specimen 10 and be adjacent to each other. An instrument (not shown) for monitoring impedance is connected to the detection coil 51, and an oscillator (not shown) is connected to the excitation coil 52.

With such a configuration, an alternating magnetic field is generated in the exciting coil 52 as shown by arrows F3 and F4, thereby generating an eddy current on the surface of the test body 10. Flaws are detected by monitoring the generated impedance. FIG. 4C shows a differential and self-induction type eddy current testing probe, which is installed at the same distance from the test piece 10.
The pair of excitation and detection coils 59a and 59b are set facing the test piece 10. The excitation and detection coils 59a and 59b include:
Oscillators (not shown) are connected to each other to supply an alternating current. Further, an unillustrated instrument for monitoring a differential component of impedance generated in each of the excitation and detection coils 59a and 59b is connected to the excitation and detection coils 59a and 59b.

With such a configuration, when detecting a flaw in the test piece 10, first, an alternating current is supplied by an oscillator to generate an alternating magnetic field in the excitation and detection coil 59a as indicated by arrows F5 and F6. Then, an alternating magnetic field is generated in the excitation and detection coil 59b as shown by arrows F7 and F8. At this time, the excitation and detection coils 59a and 59b respectively include
An impedance corresponding to the eddy current generated by the AC magnetic field is generated. If the surface of the test piece 10 is not damaged, the state of the surface of the test piece 10 is uniform, and the distribution of the eddy current generated on the surface of the test piece 10 is also uniform. The impedance generated at 59b is also equal. On the other hand, if there is a scratch on the surface of the test body 10, the distribution of the eddy current on the surface of the test body 10 becomes non-uniform in accordance with the scratch, so that the excitation and detection coils 59a, 59
A difference also occurs in the impedance generated in 9b. Therefore, a flaw can be detected by monitoring the differential component of the impedance generated in each of the excitation and detection coils 59a and 59b.

FIG. 4D shows a differential type and mutual induction type eddy current flaw detection probe in which an exciting coil 52 is installed facing a test piece 10.
Pair of detection coils 51a and 51b
Is placed facing the specimen 10. An oscillator (not shown) is connected to the excitation coil 52, and the detection coils 51a, 51b
Is connected to an instrument (not shown) for monitoring a differential component of impedance generated in each of the detection coils 51a and 51b. Here, the detection coils 51a and 51b are
The test piece 10 and the excitation coil 52 are disposed so as to be separated from the test piece 10 by the same distance, and are disposed line-symmetrically with respect to the center line of the excitation coil 52 in plan view when viewed toward the test piece 10. With respect to each other. As a result, the eddy current formed in the specimen 10 by the excitation coil 52 is
a and 51b have the same condition.

With such a configuration, an alternating magnetic field is generated in the exciting coil 52 as indicated by arrows F9 and F10.
An eddy current is generated on the surface of the test body 10, and a flaw can be detected by monitoring a difference in impedance between the detection coils 51a and 51b according to the eddy current. In order to perform flaw detection efficiently, there is a multi-coil type eddy current flaw detection probe configured by arranging a plurality of such detection coils and excitation / detection coils in the width direction of the test body 10 in a row. . FIG. 5 shows a self-induction type and absolute type multi-coil type eddy current inspection probe 20a constituted by arranging a plurality of (here, five) excitation and detection coils 59a to 59e, and FIG. 5 shows a mutual induction type and differential type multi-coil type eddy current inspection probe 20b configured by arranging (five) excitation coils 52a to 52e and a plurality of detection coils 51a to 51j (here, ten).

According to the multi-coil type eddy current inspection probes 20a and 20b in which each coil is arranged in a row in accordance with the width of the test piece 10, the wide flat test piece (test piece) 10 is provided. Also, by moving the test piece 10 as shown by the arrow A1 in FIG. 5 and the arrow B1 in FIG. 6, flaw detection can be performed in a relatively wide range at a time.

The above-described detection coil, excitation coil,
For example, a bobbin type or pancake type coil is often used as the excitation and detection coil.

[0015]

FIG. 7 is a diagram for explaining the detection sensitivity distribution of the multi-coil type eddy current testing probe 20a shown in FIG. 5, focusing on the excitation and detection coils 59a and 59b. FIG. 7A is a diagram showing a positional relationship between the excitation and detection coils 59a and 59b and the flaw 11, and FIG. 8B is a diagram showing the amplitude (signal level) of the detection signal detected by the excitation and detection coils 59a and 59b. FIG. The horizontal axis in FIG. 7B indicates a distance L from a reference line CL0 located between the axis of the excitation and detection coil 59a and the axis of the excitation and detection 59b, and the vertical axis indicates the horizontal axis. When there is a scratch at the position indicated by, the excitation and detection coils 59a and 59
b indicates the signal level detected. Each curve Lx, L
y indicates the detection sensitivity distribution of the excitation and detection coils 59a and 59b.

The exciting and detecting coil 59a is provided when the flaw 11 is directly below the exciting and detecting coil 59a, that is, when the flaw 11 is on the axis CLx of the exciting and detecting coil 59a.
The signal level is at its maximum. Therefore, the detection sensitivity distribution curve Lx of the excitation and detection coil 59a is maximum on the axis CLx, and similarly, the detection sensitivity distribution curve Ly of the excitation and detection coil 59b is the axis C of the excitation and detection coil 59b.
It becomes maximum on Ly.

Of course, the excitation and detection coils 59a, 59
Area with low detection level (low detection level area) between 9b
Exists. Accordingly, a single-stage multi-coil type eddy current flaw detection probe 20a, 20 having only one row of detection coils or excitation and detection coils as shown in FIGS.
In b, when the flaw 11 is located near the reference line CL0, the flaw 11 may not be detected accurately.

Such a low detection level region can be made smaller as the distance between adjacent excitation and detection coils or detection coils is reduced. Therefore, in order to reduce such a low detection level region (to flatten the detection level distribution of a flaw signal), a two-stage self-induction type multi-coil eddy current flaw detection probe 20c as shown in FIG. 8 is proposed. Have been. This multi-coil type eddy current testing probe 20c
A plurality (here, nine) of excitation / detection coils 59f to 59f
n are arranged in two rows (two stages) in the moving direction of the flaw detection probe 20c, and the first stage excitation and detection coils 59f to 59i in the front and the second stage excitation and detection coils 59j to 59j to the rear 59n are arranged in the width direction (the direction orthogonal to the moving direction of the multi-coil eddy current flaw detection probe 20c) so that the excitation and detection coils 59f to 59f are arranged.
The distance between each of the n in the width direction is shortened to make the detection level distribution of the flaw signal flat.

In order to intuitively and accurately evaluate the shape of a flaw, it is effective to create a bird's-eye view as shown in FIG. In FIG. 9, the X axis and the Y axis indicate the plane position of the test specimen 10, and the Z axis indicates
5 shows a level of a detection value detected by a multi-coil type eddy current inspection probe. However, it is very difficult to create such a bird's eye view based on the detection result of the multi-coil type eddy current inspection probe 20c.

That is, the two-stage multi-coil type eddy current flaw detection probe 20c has excitation and detection coils 59f to 59n.
Are arranged in two stages with respect to the moving direction of the multi-coil type eddy current testing probe 20c, so that the first stage excitation and detection coils 59f to 59i and the second stage excitation and detection coils 59j to 59n At the same time, different positions are detected in the moving direction (the detected positions are shifted). In order to create a bird's-eye view as shown in FIG. 9, the correspondence between the plane position of the test specimen 10 and the detected value at that plane position is important. It is necessary to correct, but since the movement speed of the flaw detection probe 20c also fluctuates, such a shift in the detection position also fluctuates, and it is very difficult to correct the position of the detection value accurately and to detect the flaw accurately. It becomes difficult.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an eddy current inspection probe capable of detecting a flaw accurately.

[0022]

Therefore, an eddy current flaw detection probe according to the present invention (Claim 1) includes a plurality of excitation coils for generating an eddy current in a test body by generating an AC magnetic field, and two upper and lower excitation coils. It is characterized in that it comprises a plurality of thin-film detection coils which are superposed and arranged in a line, and are configured to detect a flaw on the specimen.

Further, in the present eddy current flaw detection probe,
It is desirable that the plurality of thin-film detection coils be arranged so as to be shifted by about a half pitch between the upper layer and the lower layer (claim 2). Further, in the present eddy current inspection probe, it is desirable that a thin insulating layer is interposed between the upper layer and the lower layer between the upper and lower layers.

In the eddy current inspection probe of the present invention, it is preferable that the insulating layer is provided with a conduction hole for leading out a signal line of each detection coil in the lower layer (claim 4). Further, in the eddy current inspection probe of the present invention, each of the excitation coils is constituted by a circular coil having a short axial length arranged so as to stand substantially perpendicularly to the surface of the test piece. Are preferably arranged in a row above the plurality of thin film-shaped detection coils (claim 5).

Further, in the present eddy current probe,
It is preferable that each of the exciting coils is arranged obliquely with respect to the row direction of the plurality of exciting coils. Further, in the present eddy current flaw detection probe, it is preferable that a voltage is not simultaneously applied to the adjacent excitation coils among the plurality of excitation coils (claim 7).

It is desirable that the voltage is applied to each of the exciting coils in a pulsed manner. Further, in the present eddy current flaw detection probe, the eddy current flaw detection probe extends along the surface of the test piece in a direction perpendicular to the row direction of the plurality of thin film detection coils on the test piece. It is desirable that the test piece be moved to detect a flaw on the surface of the specimen (claim 9).

[0027]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show an eddy current inspection probe as one embodiment of the present invention.
FIGS. 1A to 1C are schematic diagrams showing the configuration, and FIG. 2 is a diagram showing the detection sensitivity distribution.
(B) is a figure which shows an example of the model of an exciting coil.

The eddy current flaw detection probe of this embodiment is a multi-coil type eddy current flaw detection probe, and is shown in FIGS.
As shown in (c), a plurality (eight in this case) of thin-film detection coils 21 which are stacked in two layers vertically and arranged in a line
1 to 21h, and a plurality (eight in this case) of excitation coils 22a to 22h arranged in a row above the detection coils 21a to 21h. By moving the test piece 10 in the direction indicated by the arrow A4 in (a), flaw detection (detection of a flaw) of the test piece 10 is performed.

The detection coils 21a to 21h and the excitation coils 22a to 22h do not need to be particularly distinguished from each other, and are hereinafter simply referred to as the detection coil 21 and the excitation coil 22. The excitation coil 22 will be described in more detail. Each of the exciting coils 22a to 22h is constituted by a circular coil having a short axial length (see FIG. 3A).
As shown in (b), the circle is set up on the specimen 10 so as to stand substantially vertically. In addition, each excitation coil 22a
As shown in FIG. 1 (a), each of the excitation coils 22a to 22h is rotated by an equal angle around an axis perpendicular to the test piece 10. The circular surface is arranged so as to be inclined. By arranging the excitation coils 22a to 22h such that their circles stand substantially vertically and obliquely on the test body 10, a spatially dense probe configuration can be realized,
Efficient excitation can be performed, and the size in the moving direction of the eddy current flaw detection probe is smaller than when the exciting coils 22a to 22h are arranged so that their circular surfaces are perpendicular to the row direction. It can be shortened to reduce the size.

Each of the exciting coils 22a to 22h has
An oscillator (not shown) is connected, and when a voltage is applied to each of the exciting coils 22a to 22h from the oscillator, the exciting coils 22a to 22h generate an eddy current in the test body 10. When the eddy currents 12 are simultaneously generated by the adjacent excitation coils 22, 22,
Since these eddy currents 12 affect each other, it is necessary to prevent the adjacent exciting coils 22 from generating the eddy current 12 at the same time. Here, it is set so that a voltage is applied to each of the excitation coils 22a to 22h in a pulsed manner, and a voltage is not applied to the adjacent excitation coils 22 at the same time.

Next, the detection coil 21 will be described.
When a voltage is applied to the exciting coil 22, an eddy current is generated on the specimen 10 by the action of the exciting coil 22. And
If there is a flaw on the test body 10, the state of the eddy current changes under the influence of the flaw, whereby a voltage is induced in the detection coil 21. The detection coil 21 is connected to a detection device (not shown) via a signal line 24a (only one side of the detection coil 21h is shown in FIG. 1C). Can be detected as a signal indicating the shape of.

The detection coils 21a to 21h are stacked in two layers, as described above. And FIG.
As shown in (b) and (c), the upper layer detection coils 21a to 21c
21d and the lower-layer detection coils 21e to 21h are close to each other.
1d and the lower detection coils 21e to 21h so that they do not affect each other.
An insulating film (thin film-like insulating layer) 23 is provided between the lower detecting coil 21e to 21h and the lower detecting coil 21e to 21h, and each detecting coil 21a to 21h is formed of a spiral thin film covered on the insulating film 23. It is made of metal. In addition,
Since the detection coils 21a to 21h and the insulating film 23 are extremely thin, it is difficult to show them with their actual thicknesses. Therefore, in FIG. 1B, the detection coils 21a to 21h are enlarged in the vertical direction (thickness direction). In the figure, the size is further enlarged in the vertical direction.

The signal generated in the detection coil 21 changes in accordance with the distance (lift-off) between the detection coil 21 and the flaw, but as described above, the upper detection coils 21a to 21a
d, lower detection coils 21e to 21h and insulating film 2
Since all 3 are formed in a thin film and overlapped,
Upper detection coil 21a to 21d, lower detection coil 21
The lift-off difference is hardly generated between e and 21h.

As shown in FIG. 1C, the insulating film 23 and the upper detection coils 21a to 21d are provided with a plurality of conduction holes 24 for extracting detection signals from the lower detection coils 21e to 21h. (Not shown in FIG. 1B). As described above, the detection coil 21 is made of a spiral thin-film metal, and the conduction holes 24 are arranged in the gaps between the spiral metals forming the upper detection coils 21a to 21d. The hole 24 is made of the insulating film 2
3 is formed by making a hole and attaching a conductive metal inside.

The upper detection coil 2 in the conduction hole 24
The portion extending to the side of 1a to 21d is previously formed at the conductive hole forming portion on the upper surface of the insulating film 23 in advance.
Pads (not shown) corresponding to the heights of a to 21d are provided, and are processed at the same time when the insulating film 23 is drilled and metal is adhered to the holes. Since the upper end of the conduction hole 24 reaches the upper surface of the upper detection coils 21a to 21d, the signal line 24a of each of the lower detection coils 21e to 21h.
One end of the detection coil 21h (only one side is shown) can be easily connected to the upper portions of the plurality of conduction holes 24. The other end of the signal line 24a is connected to a detection circuit (not shown) or the like. The metal is adhered to the inner peripheral surface of the conduction hole 24 by vacuum evaporation or plating.

Generally, each of the lower detection coils 21e to 21h
When the signal line 24a is pulled out downward, a space for this signal line is required below the lower detection coils 21e to 21h, but by drawing the signal line upward from the conduction hole 24, This space becomes unnecessary, and the detection coils 21a to 21h are accordingly
It can be made to approach.
In addition, since the conductive signal line 24a is not provided between the test body 10 and the lower detection coils 21e to 21h, the detection accuracy of the detection coil 21 is not reduced.

If the conductive hole 24 can be filled with a conductive metal, the conductive hole 24 is filled with a metal, and this metal is connected to the signal line 24a. May be configured such that it can be connected to the signal line 24a on the upper layer side to further enhance the conductivity. Further, the upper-layer detection coils 21a to 21d and the lower-layer detection coils 21e to 21h are arranged so as to be shifted by a half pitch. FIG. 2 is a diagram showing the detection sensitivity distribution of the detection coils 21a, 21e and 21f shown in FIGS. 1 (a) to 1 (c). The horizontal axis indicates the axis of the detection coil 21a. C
The vertical axis indicates the signal amplitude (signal level) LV detected by the detection coils 21a, 21e, and 21f when there is a flaw at the position indicated by the horizontal axis. Each of the curves La, Le, Lf corresponds to the detection coils 21a, 21e,
21 shows a detection sensitivity distribution of 21f. The signal level of the detection coil 21e is maximized when the flaw is directly below the detection coil 21e, that is, when there is a flaw on the axis CLe of the detection coil 21e. Le becomes maximum on the axis CLe. Similarly, the detection sensitivity distribution curve La of the detection coil 21a is maximum on the axis CLa of the detection coil 21a, and the detection sensitivity distribution curve Lf of the detection coil 21f is
On the axis CLf.

By superposing the detection coil 21a on the detection coils 21e and 21f with a half pitch shift, the valley between the detection sensitivity distribution curve Le of the lower detection coil 21e and the detection sensitivity distribution curve Lf of the detection coil 21f is reduced. The detection coil 21a in the upper layer covers the area as shown by the detection sensitivity distribution curve La to reduce the low detection level region as the eddy current inspection probe. That is, the lower detection coil 21
The low detection level region generated between e and 21f is detected by the high detection level region of the upper detection coil 21a, and the detection sensitivity distribution is flattened.

When the detection coils are arranged in the upper and lower layers as described above, it is advantageous to shift the upper and lower layers by a half pitch to uniformly increase the detection signal level. If you shift it, there is some effect. The eddy current flaw detection probe according to one embodiment of the present invention is configured as described above. Therefore, as shown in FIG. By moving in the direction indicated by
Perform surface flaw detection. A voltage is applied to each of the excitation coils 22a to 22h in a pulse form from an oscillator (not shown).
An eddy current is generated in the test body 10 according to the application of the voltage.
If there is a flaw on the test body 10, the state of the eddy current changes under the influence of the flaw and a voltage is induced in each of the detection coils 21a to 21h.
By monitoring with a detection device (not shown) connected to 〜21h, a flaw can be detected.

According to the present eddy current probe,
The detection coils 21a to 21h are superimposed on the upper and lower layers, and the upper detection coil 21a to 21d and the lower detection coil 21e to 21e
1h, the low detection level area generated between the lower detection coils 21e to 21h can be detected by the high detection level area of the upper detection coils 21a to 21d. Such flattening of the detection sensitivity distribution has an advantage that a flaw can be accurately detected.

Also, upper layer detection coils 21a to 21d,
The lower-layer detection coils 21e to 21h are arranged in a line in an overlapping manner without being displaced in the direction of movement of the probe, so that data (detection values) at the same position with respect to the direction of movement of the eddy current flaw detection probe are stored in the upper and lower layers. 9, the position correction is not required between the data of the upper detection coils 21a to 21d and the data of the lower detection coils 21e to 21h, and a bird's-eye view showing a flaw shape as shown in FIG. There is an advantage that creation can be performed easily.

Further, since the upper detection coils 21a to 21d, the lower detection coils 21e to 21h, and the insulating film 23 are all formed in a thin film and are superposed, the upper detection coils 21a to 21d and the lower detection coils 21e to 21d are superposed. 2
1h, there is almost no lift-off difference, and from such a viewpoint, there is an advantage that the position correction is unnecessary between the data of the upper detection coils 21a to 21d and the data of the lower detection coils 21e to 21h. There is.

Further, by drawing the signal line upward from the conduction hole 24, the lower layer detection coils 21e to 21e
Since there is no space for the signal line 24a below h, the detection coils 21a to 21h can be brought closer to the test object 10 (scratch) by that much. Detection coil 21
a to 21h and the wound, the longer the detection coil 21
Although the detection signals (scratch signals) detected by a to 21h are attenuated, the detection coils 21a to 21h can be brought close to the test piece 10 (scratch) as described above. There is an advantage that it can be suppressed. In addition, since the conductive signal line 24a is not located between the test body 10 and the lower detection coils 21e to 21h, there is an advantage that the detection accuracy of the detection coil 21 is not reduced.

Each of the excitation coils 22a to 22h has
A voltage is applied in a pulse form, and the adjacent exciting coil 2 is applied.
2 are not simultaneously applied. Therefore, it is possible to prevent the eddy currents from being generated close to each other and affecting each other. As a result, the flaw signal detected by the detection coil 21 in response to the change in the eddy currents may cause unnecessary disturbance. This is advantageous in that detection accuracy can be ensured.

By arranging the exciting coils 22a to 22h such that their circles stand substantially perpendicularly on the test piece 10 and are inclined obliquely to the column direction, a spatially dense probe is provided. Since the configuration can be realized, there is an advantage that efficient excitation can be performed. In addition, by arranging the excitation coils 22a to 22h in this manner, the size of the eddy current inspection probe can be reduced, so that there is an advantage that operability can be improved.

In the above embodiment, the detection coil 2
Although 1 is overlapped in two layers, the number of layers of the detection coil 21 is not limited to this, and may be, for example, three layers. In this case, it is most effective to displace the detection coils 21 by one-third pitch in each layer, but there is a certain effect even if the detection coils 21 are displaced by nearly one-third pitch. Further, in the above-described embodiment, the excitation coil 22 is configured by a circular coil, but may be configured by, for example, a rectangular coil or an elliptical coil as illustrated in FIG.

The eddy current inspection probe of the present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, the flaw detection of the test piece 10 having a flat plate shape is performed, but the flaw detection of a test piece having a cylindrical shape such as a pipe may be performed. In this case, for example, the peripheral surface of the test body may be flaw-detected by rotating the cylindrical test body about its axis under the eddy current detection probe.

[0048]

As described in detail above, according to the eddy current flaw detection probe of the present invention (claim 1), there are provided a plurality of thin-film detection coils which are arranged in two rows in an upper and lower two layers. Therefore, between the detection value of the detection coil of the upper layer and the detection value of the detection coil of the lower layer, the position correction is not required in the vertical direction and the moving direction of the eddy current flaw detection probe (row and vertical direction), There is an advantage that a flaw on the specimen can be detected accurately.

Further, if a plurality of thin-film detection coils are arranged so as to be displaced from each other by approximately a half pitch between the upper layer and the lower layer, the distance between the plurality of detection coils is narrowed, and the detection of the entire eddy current inspection probe is performed. There is an advantage that the sensitivity distribution can be flattened, whereby a flaw on the test body can be detected more accurately (claim 2). Furthermore, if a thin insulating layer is interposed between the upper and lower layers, it is possible to prevent the upper and lower detection coils from affecting each other, and to prevent damage to the test piece. Can be detected more accurately (claim 3).

Further, if the insulating layer is provided with a conduction hole for leading out the signal line of each detection coil in the lower layer, no space is required for the signal line below the detection coil, and the eddy current is reduced accordingly. Since the flaw detection probe can be brought close to the specimen, there is an advantage that the attenuation of the flaw signal is suppressed, and thereby the flaw on the specimen can be detected more accurately. Further, since a conductive signal line is not provided between the test body and the lower detection coil, there is an advantage that the detection accuracy of the detection coil is not reduced (claim 4).

Further, if each of the exciting coils is constituted by a circular coil having a short axial length and arranged so as to stand substantially perpendicularly to the surface of the test piece, the plurality of exciting coils become a plurality of thin films. Since the probes are spatially densely arranged above the detection coils in a rectangular shape, there is an advantage that the probe can be spatially densely formed and efficient excitation can be performed. Further, there is an advantage that the eddy current flaw detection probe can be reduced in size and operability can be improved (claim 5).

Furthermore, if each excitation coil is arranged obliquely with respect to the row direction of the plurality of excitation coils, the size of the eddy current inspection probe can be further reduced, and the operability can be further improved. There are advantages (claim 6).
In addition, by applying a pulse-like voltage to the mutually adjacent excitation coils of the plurality of excitation coils, for example, by applying a pulsed voltage to each of the excitation coils, it is possible to prevent the voltages from being simultaneously applied to these adjacent excitation coils. This has the advantage that it is possible to prevent eddy currents from being generated in close proximity at the same time and these eddy currents affecting each other, so that flaws on the specimen can be detected more accurately ( Claims 7 and 8).

Then, if the eddy current flaw detection probe is moved along the surface of the test piece in a direction perpendicular to the row direction of the plurality of thin film detection coils, flaw detection in a wide range is easily performed. (Claim 9).

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams showing a configuration of an eddy current flaw detection probe as one embodiment of the present invention, wherein FIG. 1A is a schematic plan view, and FIG. FIG. 3C is an enlarged view of the coil and the insulating film in the vertical direction, and FIG. 3C is a schematic cross-sectional view of a main part of the detection coil and the insulating film according to a front view thereof, which is greatly enlarged in the vertical direction. It is.

FIG. 2 is a diagram showing a detection sensitivity distribution of an eddy current flaw detection probe as one embodiment of the present invention.

3A and 3B are diagrams illustrating a configuration example of an excitation coil according to an embodiment of the present invention, wherein FIG. 3A is a circular excitation coil, and FIG.
FIG. 3 is a view showing a rectangular excitation coil.

4A and 4B are diagrams showing a configuration of a conventional eddy current flaw detection probe, wherein FIG. 4A is a schematic view showing an absolute type and self-induction type eddy current flaw detection probe, and FIG. Schematic diagram showing a current detection probe,
(C) is a schematic view showing a differential and self-induction type eddy current inspection probe, and (d) is a schematic view showing a differential and mutual induction eddy current inspection probe.

FIG. 5 is a schematic perspective view showing a configuration of a conventional self-induction type and single-stage multi-coil type eddy current testing probe.

FIG. 6 is a schematic perspective view showing a configuration of a conventional multi-coil type eddy current inspection probe of a mutual induction type and a single-stage type.

7A and 7B are views showing a conventional self-induction type and single-stage multi-coil type eddy current testing probe, in which FIG. 7A is a schematic plan view showing a positional relationship between the excitation and detection coil and the flaw, 4B is a diagram showing the amplitude (detection sensitivity distribution) of the detection signal detected by the excitation and detection coil.

FIG. 8 is a schematic perspective view showing a configuration of a conventional self-induction type two-stage multi-coil type eddy current testing probe.

FIG. 9 is a bird's-eye view showing a flaw shape of a test body created based on a detection value of an eddy current flaw detection probe.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Specimen 21, 21a-21h Detection coil 22, 22a-22h Excitation coil 23 Insulating film (thin film-like insulating layer) 24 Conducting hole 24a Signal line CLa, CLe, CLf Detection coil 21a, 21e,
21f axis center line LV Signal amplitude (signal level) La, Le, Lf Detection coils 21a, 21e, 21f
Detection sensitivity distribution

Claims (9)

[Claims] 1. A test apparatus comprising: a plurality of excitation coils for generating an eddy current in a test body by generating an alternating magnetic field; and a plurality of thin-film detection coils stacked in two rows in upper and lower layers. An eddy current flaw detection probe for detecting a flaw on a body. 2. The eddy current detection probe according to claim 1, wherein the plurality of thin-film detection coils are arranged so as to be shifted by approximately a half pitch between an upper layer and a lower layer. 3. The eddy current inspection probe according to claim 1, wherein a thin insulating layer is interposed between the upper layer and the lower layer. 4. The eddy current flaw detection probe according to claim 3, wherein a conduction hole for leading out a signal line of each of the lower detection coils is provided in the insulating layer. 5. Each of the above-mentioned exciting coils is constituted by a circular coil having a short axial length arranged so as to stand substantially perpendicularly to the surface of the test piece. Above the plurality of thin-film detection coils,
The eddy current inspection probe according to claim 1, wherein the probes are arranged in a row. 6. The eddy current inspection probe according to claim 5, wherein each of the excitation coils is arranged obliquely with respect to a row direction of the plurality of excitation coils. 7. The eddy current flaw detection probe according to claim 1, wherein a voltage is not applied to excitation coils adjacent to each other among the plurality of excitation coils at the same time. 8. The eddy current inspection probe according to claim 7, wherein a voltage is applied to each of the excitation coils in a pulsed manner. 9. The test piece is moved along the surface of the test piece in a direction perpendicular to the row direction of the plurality of thin-film detection coils along the surface of the test piece, thereby removing a scratch on the surface of the test piece. The eddy current flaw detection probe according to claim 1, wherein the detection is performed.