JP7299618B2 - Eddy current flaw detector and method for manufacturing eddy current flaw detector - Google Patents

Description

TECHNICAL FIELD The present application relates to an eddy current flaw detector and a method for manufacturing an eddy current flaw detector, which applies a current to a coil to generate a magnetic field, and relates to a technique of a device for detecting flaws or the like to be inspected and a method of manufacturing the same.

Eddy current testing is a type of non-destructive inspection, and is a technique for detecting damage such as corrosion and cracking in conductive materials such as metals. In eddy current testing, a current is applied to a coil to generate a magnetic field, which is brought close to a metal or the like to be inspected to generate an eddy current. The presence or absence of damage is determined by utilizing the property that this eddy current changes depending on the non-uniformity of the material near the surface of the inspection object.

Technologies related to eddy current flaw detection include an eddy current flaw detection sensor and an eddy current flaw detection method disclosed in Patent Document 1 described later. This eddy current flaw detection sensor 11A is configured with coils 1a, 1b, and 2 in a holding member 3 (Patent Document 1, paragraph number [0035] and FIG. 3). The coils 1a, 1b, and 2 are accommodated and attached to the concave portions 3a, 3b, and 3c formed in the holding member 3. It has been shown that it is possible to fix the coils 1a, 1b, 2 using potting resin or the like in order to retain them (Patent Document 1, paragraph number [0039]).

In potting resin treatment, a two-liquid urethane resin is poured into a case where electronic components are mounted and hardened to protect the electronic components from dirt and water, and to fix the electronic components within the case. be.

Japanese Patent Application Laid-Open No. 2007-263946

However, the technique disclosed in the aforementioned Patent Document 1 has the following problems. When the holding member 3 of the eddy current flaw detector is filled with potting resin and the coils 1a, 1b, 2 are buried and fixed, the coils 1a, 1b, 2 may be tilted or lifted due to the influence of the resin filling. . Such misalignment of the fixed positions of the coils 1a, 1b, 2 invites a problem of lowering the accuracy of eddy current flaw detection.

Therefore, in order to solve these problems, the eddy current flaw detector and the manufacturing method of the eddy current flaw detector according to the present application are an eddy current flaw detector that can perform highly accurate eddy current flaw detection by arranging and fixing the coil at an accurate position. And the object is to provide a method for manufacturing an eddy current flaw detector.

In the eddy current flaw detector according to the present application,
housing,
a shaft member positioned in contact with the shaft contact surface in the housing, the shaft member having a reference mark formed on the outer peripheral surface;
a coil member positioned in contact with a coil contact surface in the housing, the coil member being arranged such that the shaft member is positioned in a central space formed at the center;
an insulating member covering the coil member and the shaft member,
An eddy current flaw detector comprising
The upper end surface of the coil member corresponds to the level indicated by the reference mark provided on the outer peripheral surface of the shaft member.
It is characterized by

In addition, in the method for manufacturing an eddy current testing device according to the present application,
In the housing, a shaft member having a reference mark formed on the outer peripheral surface is arranged in contact with the shaft contact surface of the housing, and a coil member having a central space formed in the center is placed on the coil contact surface of the housing. contacting and arranging the shaft member so that it is located in the central space;
filling the housing with an insulating material, placing the upper end face of the coil member at a position corresponding to the reference mark, and burying the coil member in the insulating material;
curing the filled insulating material;
characterized by comprising

In the eddy current testing apparatus according to the present application, the upper end surface of the coil member corresponds to the level indicated by the reference markings provided on the outer peripheral surface of the shaft member. In addition, in the method for manufacturing an eddy current testing apparatus according to the present application, when filling the housing with the insulating material, the upper end face of the coil member is arranged at a position corresponding to the reference mark, and the coil member is buried in the insulating material.

Therefore, it is possible to obtain an eddy current flaw detection device and a method for manufacturing an eddy current flaw detection device that can accurately arrange and fix the coil member in the housing and perform highly accurate eddy current flaw detection.

1 is a plan view of a probe 1 showing a first embodiment of an eddy current flaw detection device and a method of manufacturing an eddy current flaw detection device according to the present application; FIG. FIG. 2 is a cross-sectional view of the probe 1 shown in FIG. 1 taken along the line II-II. 3 is a cross-sectional view showing details of indicator grooves 111 and 121 formed in cores 11 and 21 of probe 1 shown in FIG. 2. FIG. FIG. 2 is an exploded perspective view showing main components of the probe 1 shown in FIG. 1; FIG. 2 is a cross-sectional view taken along line II-II showing the manufacturing process of the probe 1 shown in FIG. 2 is a cross-sectional view taken along line II-II showing the manufacturing process of the probe 1 shown in FIG. 1, and is a cross-sectional view showing a state in which receiving coils 13 and 23 are further arranged in the case 50. FIG. 2 is a cross-sectional view in the direction of arrows II--II showing the manufacturing process of the probe 1 shown in FIG. 1, and is a cross-sectional view showing a state in which the case 50 is further filled with a lower resin 42. FIG. 2 is a cross-sectional view taken along line II-II showing the manufacturing process of the probe 1 shown in FIG. 1, and is a cross-sectional view showing a state in which transmission coils 15 and 25 are further arranged in a case 50. FIG.

[Explanation of terms in the embodiment]
The main terms used in the embodiments correspond to the following elements of the eddy current flaw detection device and the manufacturing method of the eddy current flaw detection device according to the present application, respectively.

Cores 11, 21... Shaft members Receiving coils 13, 23... Coil members Receiving coil upper surfaces 13a, 23a... Upper end faces of coil members Receiving coil shaft holes 13s, 23s, excitation coil shaft holes 15s, 25s...・Central space Exciting coils 15, 25 Upper coil member Lower resin 42 Insulating member, insulating material Filling end surface 49 Upper end surface of insulating material Case 50 Housing Positioning recesses 51, 52・・・・ Shaft contact surface Mounting surfaces 56, 57 ・・・ Coil contact surface Lower stepped parts 111a, 121a ・・・Reference display Upper stepped parts 111b, 121b ・・・ Upper reference display

[First embodiment]
A first embodiment of an eddy current flaw detector and a method for manufacturing an eddy current flaw detector according to the present application will be described. Eddy current testing includes pulsed eddy current (PEC). Pulsed eddy current testing is an inspection method in which eddy currents are generated on the surface of a metal to be inspected by applying a pulsed DC current to a coil to measure the thickness of the metal plate. By measuring the plate thickness, it is possible to inspect for damage due to corrosion, cracking, etc. of the inspected metal. In this embodiment, the probe 1 for performing this pulsed eddy current testing is taken as an example.

(Explanation of configuration and inspection operation of probe 1)
As shown in FIGS. 1 and 2, two cores 11 and 21 stand upright on the inner bottom surface of the case 50 of the probe 1 . The cores 11 and 21 are fixed by fitting into positioning recesses 51 and 52 (FIG. 2) formed at two locations on the inner bottom surface of the case 50, respectively. Display grooves 111 and 121 are formed on the outer peripheral surfaces of the cores 11 and 21 in the circumferential direction orthogonal to the central axis. The display grooves 111, 121 are annular recesses with a constant width.

FIG. 3 is a cross-sectional view showing the cores 11, 21 attached to the inner bottom surface of the case 50, showing details of the indicator grooves 111, 121 formed in the cores 11, 21. FIG. In FIG. 3, other members are omitted. The corner portions of the steps below the recesses of the display grooves 111 and 121 are configured as lower step portions 111a and 121a, and the corner portions of the upper steps are configured as upper step portions 111b and 121b.

Further, as shown in FIG. 2, the receiving coils 13 and 23 are positioned in the case 50 in contact with the inner bottom surface of the case 50 . The cores 11 and 21 are inserted and passed through the receiving coil shaft holes 13s and 23s (FIG. 4) of the receiving coils 13 and 23, respectively.

The top surfaces 13a and 23a of the receiving coils 13 and 23, which are flat surfaces at the top of the receiving coils 13 and 23, are at the level indicated by the lower steps 111a and 121a (FIG. 3) formed by the indicator grooves 111 and 121 of the cores 11 and 21. corresponds to In the present embodiment, the levels of the top surfaces 13a and 23a of the receiving coils and the levels of the lower stepped portions 111a and 121a match, and the top surfaces 13a and 23a of the receiving coils and the lower stepped portions 111a and 121a are on the same plane. positioned.

The receiving coils 13, 23 and the cores 11, 21 between the inner bottom surface of the case 50 and the upper stepped portions 111b, 121b are covered with the lower resin 42 inside the case 50. As shown in FIG. The lower resin 42 is made of potting resin. A filling end face 49, which is a flat upper surface of the lower resin 42, corresponds to the level indicated by the upper steps 111b, 121b formed by the indicator grooves 111, 121 of the cores 11, 21 (FIG. 3). In this embodiment, the level of the filling end face 49 and the level of the upper stepped portions 111b, 121b are aligned, and the filling end face 49 and the upper stepped portions 111b, 121b are positioned on the same plane.

Further, two exciting coils 15 and 25 are arranged in the case 50 so as to be in contact with the filling end surface 49 of the lower resin 42 . The cores 11 and 21 are inserted and passed through the exciting coil shaft holes 15s and 25s (FIG. 4) of the exciting coils 15 and 25, respectively. That is, the receiving coil 13 and the exciting coil 15 are arranged coaxially with respect to the core 11 and are insulated from each other by the lower resin 42 . Also, the receiving coil 23 and the exciting coil 25 are coaxially arranged with respect to the core 12 and are insulated from each other by the lower resin 42 .

The cores 11 and 21 above the exciting coils 15 and 25 and the upper step portions 111b and 121b are covered with an upper resin 44 in the case 50 . Like the lower resin 42, the upper resin 44 is also made of potting resin. Note that wiring of the probe 1 and other electronic components are omitted in the drawing.

Next, an inspection operation using this probe 1 will be described. In this embodiment, an example of inspecting damage inside a pipe used for vapor transfer using the probe 1 is shown. As shown in FIG. 2, the pipe 62 originally has a substantially uniform wall thickness L1, but the wall thickness is reduced at a damaged portion 70 due to corrosion, cracking, etc., and the probe 1 is located at such a damaged portion. Detect 70.

In some cases, a heat insulator 61 is attached to the pipe 62 in order to reduce the heat loss of the transferred steam. L1 can be detected. Therefore, the damaged portion 70 can be detected without removing the heat insulating material 61 from the pipe 62, and flaw detection can be performed easily and efficiently.

When performing inspection, first, the bottom surface of the probe 1 is brought into contact with the object to be detected as shown in FIG. Upon receipt of this command, the probe 1 applies a pulsed DC current to the excitation coils 15 and 25 for a predetermined excitation time (excitation mode) to form a magnetic field in the excitation coils 15 and 25 . As a result, eddy currents are generated in the metal surface of the pipe 62, and the eddy currents generate a magnetic field in the opposite direction.

After that, the probe 1 stops applying current to the excitation coils 15 and 25 for a predetermined reception time (reception mode). Here, the magnetic field caused by the eddy current generated on the metal surface of the pipe 62 passes through the receiving coils 13 and 23, and the induced current generated based on this is detected as a signal during the receiving mode, and is provided in the probe 1. stored in a memory (not shown).

The eddy currents are present on the metal surface of the pipe 62 at the beginning of the receive mode, but gradually penetrate inside the metal while attenuating. Therefore, the signals detected through the receiving coils 13 and 23 are also gradually attenuated. The penetrating eddy currents then reach the rear surface of the metal, but at this time the eddy currents are rapidly attenuated, and accordingly the signals detected through the receiving coils 13 and 23 are also rapidly reduced.

That is, the wall thickness of the pipe 62 can be detected by grasping temporal changes in the signals detected through the receiving coils 13 and 23 and finding the inflection point at which the detected signals begin to rapidly attenuate.

While performing the detection operation as described above, the probe 1 is scanned in the direction of the arrow 91 as shown in FIG. This makes it possible to detect the wall thickness L1 of the pipe 62 in the target range and detect the damaged portion 70 where the wall thickness L1 is thin.

(Description of the manufacturing method of probe 1)
Next, a method for manufacturing the probe 1 shown in FIGS. 1 and 2 will be described with reference to FIGS. 5 to 8. FIG. When manufacturing the probe 1, first, as shown in FIG. and hold it in an upright position.

After that, the receiver coils 13 and 23 are placed so as to be in contact with the mounting surfaces 56 and 57 on the inner bottom surface of the case 50, and the cores 11 and 21 are inserted through the receiver coil shaft holes 13s and 23s (FIG. 6). Since the thickness of the receiving coils 13 and 23 and the length of the lower stepped portions 111a and 121a (FIG. 3) formed by the display grooves 111 and 121 from the bottom surfaces of the cores 11 and 21 are formed to be the same, at this time The receiving coil upper surfaces 13a, 23a and the lower stepped portions 111a, 121a are positioned on the same plane.

Then, from the state shown in FIG. 6, the case 50 is filled with resin for forming the lower resin 42 (FIG. 7). The filling operation ends when the filling end surface 49, which moves in the increasing direction due to filling, reaches the level indicated by the upper steps 111b, 121b (FIG. 3) formed by the indicator grooves 111, 121 of the cores 11, 21. The filling amount of the resin is set in advance so that it does.

When the case 50 is filled with resin to form the lower resin 42, the receiver coils 13 and 23 may be tilted or lifted due to the effect of the resin filling. In such a case, the level of the receiving coil upper surfaces 13a, 23a (Fig. 6) of the receiving coils 13, 23 and the lower stepped portions 111a, 121a (Fig. 3) formed by the indicator grooves 111, 121 of the cores 11, 21 , the operator can easily visually recognize the positional deviation of the receiving coils 13 and 23. As shown in FIG.

When the positional deviation of the receiving coils 13 and 23 is visually recognized, the operator holds the receiving coils 13 and 23 using tools such as jigs and tweezers so that the level of the receiving coil upper surfaces 13a and 23a is lowered to the lower step portions 111a and 121a. Adjust the position to match the level of As a result, the receiving coils 13 and 23 can be arranged at accurate positions, and the probe 1 capable of highly accurate eddy current flaw detection can be obtained. After that, the filled resin is cured, and the positions of the receiving coils 13 and 23 are fixed by the lower resin 42 .

Next, as shown in FIG. 8, the exciting coils 15 and 25 are placed on the filled end face 49 of the hardened lower resin 42, and the cores 11 and 21 are inserted and arranged through the exciting coil shaft holes 15s and 25s. Then, from the state shown in FIG. 8, the case 50 is filled with resin for forming the upper resin 44, and the cores 11, 21 and the excitation coils 15, 25 are completely covered with the resin (FIG. 2). After that, the filled resin is cured, and the positions of the exciting coils 15 and 25 are fixed by the upper resin 44 .

Since the probe 1 is manufactured through the above steps, the width of the recesses of the display grooves 111 and 121 formed in the cores 11 and 21 is interposed between the receiving coils 13 and 23 and the exciting coils 15 and 25. It corresponds to the thickness of the insulating resin to be used.

As described above, when the case 50 is filled with the resin for forming the lower resin 42, the filling operation ends when the filling end surface 49 reaches the level indicated by the upper stepped portions 111b and 121b. Although the amount of resin to be filled is set in advance as shown in FIG. confirm. As a result, the excitation coils 15 and 25 placed on the lower resin 42 can be arranged and fixed at accurate positions within the kale 50, and the probe 1 capable of performing highly accurate eddy current testing can be obtained. can be done.

[Other embodiments]
In the above-described embodiment, the indicator grooves 111 and 121 are formed in the cores 11 and 21 (shaft members). (upper reference indication) is formed, but convex portions protruding outward from cores 11 and 21 are formed, and these convex portions form a lower step portion (reference indication) and an upper step portion (upper reference indication). good too.

In addition, the reference indication and the upper reference indication can be formed by providing indication lines on the outer peripheral surfaces of the cores 11 and 21 (shaft members) by printing or pasting a seal instead of the recesses or protrusions. In this case, a color different from the color of the outer peripheral surfaces of the cores 11 and 21 (shaft members) may be used to provide indication lines so as to facilitate visual recognition.

In addition, when the lower stepped portion (reference indication) and the upper stepped portion (upper reference indication) are formed by the concave portion or the convex portion, the operator can more easily and reliably perform the lower stepped portion (reference indication) and the upper stepped portion ( upper reference display) can be visually recognized. In particular, when the internal space of the case 50 (housing) is configured to be small in accordance with the miniaturization of the probe 1 (eddy current testing device), the lower stepped portion (reference indication) and the upper stepped portion formed by concave portions or convex portions If it is a part (upper reference display), it is easy to visually recognize.

Furthermore, in the above-described embodiment, the indicator grooves 111 and 121 are formed annularly on the outer peripheral surfaces of the cores 11 and 21, so that the lower stepped portions 111a and 121a (reference indicators) and Although the upper stepped portions 111b and 121b (upper reference indications) are shown, the reference indications and upper reference indications may be partially formed in the circumferential direction of the cores 11 and 21 (shaft members).

In the above-described embodiment, the lower stepped portions 111a and 121a (reference indications) and the upper stepped portions 111b and 121b (upper reference indications) are simultaneously formed by the display grooves 111 and 121 having a predetermined width. A lower stepped portion (reference indication) and an upper stepped portion (upper reference indication) may be formed separately.

Further, in the above-described embodiment, an example in which the pipe 62 is inspected by scanning with a single probe 1 (eddy current testing device) was shown, but a plurality of probes 1 (eddy current testing device) are arranged in the circumferential direction of the pipe to be inspected. device) can be fixedly provided, and a plurality of such probes 1 in the circumferential direction can be arranged anywhere in the axial direction of the pipe.

It is also possible to employ a system in which detection data is transmitted wirelessly or by wire from each probe 1 (eddy current flaw detector) to periodically inspect the pipe. In such a system, proper inspection cannot be performed if there is variation in detection accuracy among the plurality of probes 1 (eddy current flaw detectors) used. Therefore, it is more useful to use the probe 1 (eddy current flaw detection device) to which the eddy current flaw detection device and the method for manufacturing the eddy current flaw detection device according to the present application are applied to this system to perform highly accurate eddy current flaw detection.

11, 21: Cores 13, 23: Receiving coil 13a, 23a: Top of receiving coil
13s, 23s: Receiving coil shaft hole 15, 25: Exciting coil 15s, 25s: Exciting coil shaft hole
42: Lower resin 49: Filling end face 50: Case 51, 52: Positioning recess
56, 57: Mounting surface 111a, 121a: Lower step 111b, 121b: Upper step

Claims (3)

housing,
a shaft member positioned in contact with the shaft contact surface in the housing, the shaft member having a reference mark formed on the outer peripheral surface;
a coil member positioned in contact with a coil contact surface in the housing, the coil member being arranged such that the shaft member is positioned in a central space formed at the center;
an insulating member covering the coil member and the shaft member,
An eddy current flaw detector comprising
The upper end surface of the coil member corresponds to the level indicated by the reference mark provided on the outer peripheral surface of the shaft member.
An eddy current flaw detector characterized by: In the housing, a shaft member having a reference mark formed on the outer peripheral surface is arranged in contact with the shaft contact surface of the housing, and a coil member having a central space formed in the center is placed on the coil contact surface of the housing. contacting and arranging the shaft member so that it is located in the central space;
filling the housing with an insulating material, placing the upper end face of the coil member at a position corresponding to the reference mark, and burying the coil member in the insulating material;
curing the filled insulating material;
A method for manufacturing an eddy current flaw detector, comprising: A shaft member having a reference mark and an upper reference mark formed on the outer peripheral surface is arranged in the housing so as to be in contact with the shaft contact surface of the housing, and a coil member having a central space formed in the center is attached to the housing. contacting the coil contact surface and arranging the shaft member so that it is positioned in the central space;
A step of filling the housing with the insulating material, stopping the filling when the upper end surface of the insulating material, which fluctuates in an increasing direction due to the filling, reaches a position corresponding to the upper reference mark provided on the shaft member, placing the upper end surface of the coil member at a position corresponding to the reference mark and burying the coil member in the insulating material;
curing the filled insulating material;
placing an upper coil member having a central space formed in the center thereof in contact with the upper end surface of the hardened insulating material so that the shaft member is positioned in the central space;
A method for manufacturing an eddy current flaw detector, comprising:

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