JP2021063712A - Eddy current flaw detector and manufacturing method of eddy current flaw detector - Google Patents

Abstract

To provide an eddy current flaw detector and a manufacturing method of the eddy current flaw detector capable of performing eddy current flaw detection with high accuracy by arranging and fixing a coil in an accurate position.SOLUTION: First, cores 11 and 21 are erected and fixed in a case 50, and receiving coils 13 and 23 are placed so as to surround the cores 11 and 21. Then, resin for forming lower side resin 42 is filled in the case 50. At this time, since deviation occurs between a level of receiving coil upper surfaces 13a and 23a and a level of display grooves 111 and 121(lower steps 111a and 121a) of the cores 11 and 21 when positional deviation such as inclination or floating occurs in the receiving coils 13 and 23, an operator can easily visually recognize the positional deviation of the receiving coils 13 and 23 and can perform positioning of the receiving coils 13 and 23. Thereafter, the filled resin is hardened, exciting coils 15 and 25 are placed on a filled end surface 49, and the resin is filled to form an upper side resin 44.SELECTED DRAWING: Figure 2

Description

The method for manufacturing an eddy current flaw detector and a eddy current flaw detector according to the present application relates to an apparatus for detecting a scratch or the like to be inspected by applying an electric current to a coil to generate a magnetic field, and a technique for manufacturing the same.

Eddy current testing is a type of non-destructive inspection, and is a technique for detecting damage such as corrosion and cracks that occur in conductive materials such as metals. In eddy current flaw detection, a current is applied to the coil to generate a magnetic field, which is brought close to the metal 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 due to the non-uniformity of the material near the surface to be inspected.

As a technique related to eddy current flaw detection, there are an eddy current flaw detection sensor and an eddy current flaw detection method disclosed in Patent Document 1 described later. The eddy current flaw detection sensor 11A includes coils 1a, 1b, and 2 in the holding member 3 (Patent Document 1, paragraph number [0035], and FIG. 3). Then, the coils 1a, 1b, and 2 are housed and attached to the recesses 3a, 3b, and 3c formed in the holding member 3, and the coil shafts P1 and P2 of the coils 1a, 1b, and 2 are stably housed in the holding member 3. It has been shown that the coils 1a, 1b and 2 can be fixed using a potting resin or the like for holding (Patent Document 1, paragraph number [0039]).

The treatment with potting resin involves injecting a two-component urethane resin into a case on which electronic components are mounted and curing it to protect the electronic components from dirt and water and fixing the electronic components inside the case. is there.

JP-A-2007-263946

However, the technique disclosed in Patent Document 1 described above 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, and 2 are buried and fixed, the coils 1a, 1b, and 2 may be tilted or lifted due to the influence of the resin filling. .. Such a deviation of the fixed positions of the coils 1a, 1b, and 2 causes a problem that the accuracy of eddy current flaw detection is lowered.

Therefore, in the method of manufacturing the eddy current flaw detector and the eddy current flaw detector according to the present application, in order to solve these problems, the eddy current flaw detector can perform highly accurate eddy current flaw detection by arranging and fixing the coil at an accurate position. An object of the present invention 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 located in contact with the shaft contact surface in the housing and having a reference display formed on the outer peripheral surface.
A coil member that is located in contact with the coil contact surface in the housing and is arranged so that the shaft member is located in the central space formed in the center.
Insulating member covering the coil member and shaft member,
It is an eddy current flaw detector equipped with
The upper end face of the coil member corresponds to the level indicated by the reference display on the outer peripheral surface of the shaft member.
It is characterized by that.

In addition, in the method for manufacturing an eddy current flaw detector according to the present application,
A shaft member having a reference display formed on the outer peripheral surface is arranged in the housing 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. A step of contacting and arranging the shaft member so that it is located in the central space.
A step of filling the housing with an insulating material, arranging the upper end face of the coil member at a position corresponding to the reference display, and burying the coil member in the insulating material.
Steps to cure the filled insulating material,
It is characterized by being equipped with.

In the eddy current flaw detector according to the present application, the upper end surface of the coil member corresponds to the level indicated by the reference display provided on the outer peripheral surface of the shaft member. Further, in the method for manufacturing an eddy current flaw detector according to the present application, when the housing is filled with an insulating material, the upper end surface of the coil member is arranged at a position corresponding to the reference display, and the coil member is embedded in the insulating material.

Therefore, it is possible to accurately arrange and fix the coil member in the housing, and it is possible to obtain an eddy current flaw detector and a method for manufacturing an eddy current flaw detector capable of performing eddy current flaw detection with high accuracy.

It is a top view of the probe 1 which shows 1st Embodiment of the eddy current flaw detector and the manufacturing method of the eddy current flaw detector which concerns on this application. It is sectional drawing of the probe 1 shown in FIG. 1 in the II-II direction. FIG. 5 is a cross-sectional view showing details of display grooves 111 and 121 formed in the cores 11 and 21 of the probe 1 shown in FIG. It is an exploded perspective view which shows the main component of the probe 1 shown in FIG. FIG. 1 is a cross-sectional view taken along the 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 the cores 11 and 12 are arranged in the case 50. FIG. 1 is a cross-sectional view taken along the 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. 5 is a cross-sectional view taken along the 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 the lower resin 42 is further filled in the case 50. FIG. 5 is a cross-sectional view taken along the 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 the case 50.

[Terminology in the embodiment]
The main terms shown in the embodiments correspond to the following elements of the eddy current flaw detector and the method of manufacturing the eddy current flaw detector according to the present application, respectively.

Cores 11, 21 ... Shaft member Receiving coil 13, 23 ... Coil member Receiving coil upper surface 13a, 23a ... Upper end face of coil member Receiving coil shaft hole 13s, 23s, Exciting coil shaft hole 15s, 25s ...・ Central space Exciting coil 15, 25 ・ ・ ・ Upper coil member Lower resin 42 ・ ・ ・ Insulating member, insulating material Filled end face 49 ・ ・ ・ Upper end face of insulating material Case 50 ・ ・ ・ Housing positioning recess 51, 52 ・・ ・ Shaft contact surface Mounting surface 56, 57 ・ ・ ・ Coil contact surface Lower stage 111a, 121a ・ ・ ・ Reference display Upper stage 111b, 121b ・ ・ ・ Upper reference display

[First Embodiment]
The first embodiment of the eddy current flaw detector and the method of manufacturing the eddy current flaw detector according to the present application will be described. Eddy current testing includes pulsed eddy current testing (PEC). Pulse eddy current flaw detection is an inspection method in which a direct current is passed through a coil in a pulse shape to generate an eddy current on the surface of the metal to be inspected, and the thickness of the metal plate or the like is measured. By measuring the plate thickness, damage due to corrosion, cracks, etc. of the metal to be inspected can be inspected. In the present embodiment, the probe 1 for performing this pulse eddy current flaw detection is given as an example.

(Explanation of probe 1 configuration and inspection operation)
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 fitted and fixed to the 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 and 121 are annular recesses having a constant width.

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

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

The upper flat surfaces 13a and 23a of the receiving coils 13 and 23 are the levels indicated by the lower stage portions 111a and 121a (FIG. 3) formed by the display grooves 111 and 121 of the cores 11 and 21. It corresponds to. In the present embodiment, the levels of the upper surfaces 13a and 23a of the receiving coil and the levels of the lower stages 111a and 121a are the same, and the upper surfaces 13a and 23a of the receiving coil and the lower stages 111a and 121a are on the same plane. positioned.

The cores 11 and 21 between the inner bottom surfaces of the receiving coils 13 and 23 and the case 50 to the upper stages 111b and 121b are covered with the lower resin 42 in the case 50. The lower resin 42 is made of a potting resin. The filled end surface 49, which is the upper flat surface of the lower resin 42, corresponds to the level indicated by the upper step portions 111b and 121b (FIG. 3) formed by the display grooves 111 and 121 of the cores 11 and 21. In the present embodiment, the level of the filled end face 49 and the level of the upper step portions 111b and 121b are the same, and the filled end face 49 and the upper step portions 111b and 121b are located on the same plane.

Further, two exciting coils 15 and 25 are arranged in the case 50 in a state of being in contact with the filled end surface 49 of the lower resin 42. The cores 11 and 21 are inserted and penetrated into the exciting coil shaft holes 15s and 25s (FIG. 4) of the exciting coils 15 and 25. That is, the receiving coil 13 and the exciting coil 15 are coaxially arranged with respect to the core 11, and are insulated from each other by the lower resin 42. Further, 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 exciting coils 15 and 25 and the cores 11 and 21 on the upper side from the upper stage portions 111b and 121b are covered with the upper resin 44 in the case 50. Like the lower resin 42, the upper resin 44 is also made of a potting resin. Note that the wiring of probe 1 and other electronic components are omitted in the figure.

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

A heat insulating material 61 may be attached to the pipe 62 in order to reduce heat dissipation loss of the transferred steam. However, by bringing the probe 1 into contact with the outer surface of the heat insulating material 61, the wall thickness of the pipe 62 is increased. L1 can be detected. Therefore, the damaged portion 70 can be detected without removing the heat insulating material 61 from the pipe 62, and the flaw can be detected easily and efficiently.

When performing an inspection, first, the bottom surface of the probe 1 is brought into contact with the detection target as shown in FIG. 2, and the switch (not shown) of the probe 1 is turned on to give a command to start detection. In response to this command, the probe 1 applies a direct current in a pulse shape to the exciting coils 15 and 25 for a predetermined excitation time (excitation mode) to form a magnetic field in the exciting coils 15 and 25. As a result, an eddy current is generated on the metal surface of the pipe 62, and the eddy current generates a magnetic field in the opposite direction.

After that, the probe 1 stops applying the current to the exciting coils 15 and 25 for a predetermined reception time (reception mode). Here, the magnetic field due to the above-mentioned eddy current generated on the metal surface of the pipe 62 penetrates the receiving coils 13 and 23, and the induced current generated based on the magnetic field is detected as a signal during the receiving mode and is provided in the probe 1. It is recorded in the stored memory (not shown).

The eddy current is on the metal surface of the pipe 62 at the beginning of the reception mode, but gradually penetrates into the metal while being attenuated. Therefore, the signal detected through the receiving coils 13 and 23 is also gradually attenuated. Then, the permeated eddy current reaches the back surface of the metal, but at this time, the eddy current rapidly attenuates, and the signal detected through the receiving coils 13 and 23 also rapidly decreases accordingly.

That is, the wall thickness of the pipe 62 can be detected by grasping the change with time of the signal detected through the receiving coils 13 and 23 and finding the inflection point at which the rapid attenuation of the detected signal starts.

While performing the detection operation as described above, the probe 1 is scanned in the direction of arrow 91 as shown in FIG. As a result, it is 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.

(Explanation of manufacturing method of probe 1)
Next, the manufacturing method of the probe 1 shown in FIGS. 1 and 2 will be described with reference to FIGS. 5 to 8. When manufacturing the probe 1, first, as shown in FIG. 5, an adhesive is applied to the positioning recesses 51 and 52 formed on the inner bottom surface of the case 50, and the cores 11 and 21 are fitted into the positioning recesses 51 and 52, respectively. And fix it in an upright position.

After that, the receiving 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 and penetrated into the receiving coil shaft holes 13s and 23s (FIG. 6). At this time, the thickness of the receiving coils 13 and 23 and the lengths of the lower step 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 the same. The upper surfaces 13a and 23a of the receiving coil and the lower stage portions 111a and 121a are located on the same plane.

Then, from the state shown in FIG. 6, the case 50 is filled with the resin for forming the lower resin 42 (FIG. 7). The filling operation ends when the filling end face 49, which fluctuates in the increasing direction due to filling, reaches the level indicated by the upper steps 111b and 121b (FIG. 3) formed by the display grooves 111 and 121 of the cores 11 and 21. The filling amount of the resin is preset so as to be used.

When the case 50 is filled with resin to form the lower resin 42, the receiving coils 13 and 23 may be displaced due to the influence of the resin filling, such as tilting or lifting. In such a case, the levels of the receiving coil upper surfaces 13a and 23a (FIG. 6) of the receiving coils 13 and 23 and the lower step portions 111a and 121a (FIG. 3) formed by the display grooves 111 and 121 of the cores 11 and 21. Since the level of the receiving coils is deviated, the operator can easily visually recognize the misalignment of the receiving coils 13 and 23.

When the misalignment of the receiving coils 13 and 23 is visually recognized, the operator presses the receiving coils 13 and 23 using an instrument such as a jig or tweezers, and the level of the receiving coil upper surfaces 13a and 23a is lowered to the lower stages 111a and 121a. Adjust the position so that it matches the level of. As a result, the receiving coils 13 and 23 can be arranged at accurate positions, and a probe 1 capable of performing eddy current flaw detection with high accuracy 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 surface 49 of the cured lower resin 42, and the cores 11 and 21 are inserted and penetrated through the exciting coil shaft holes 15s and 25s. Then, from the state shown in FIG. 8, the case 50 is filled with a resin for forming the upper resin 44, and the cores 11 and 21 and the exciting coils 15 and 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.

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 step portions 111b and 121b. The filling amount of the resin is preset so that the resin is filled, but when the resin is filled, the operator visually confirms that the level of the filled end face 49 and the level of the upper step portions 111b and 121b match, just in case. Confirm. As a result, the exciting coils 15 and 25 placed on the lower resin 42 can be arranged and fixed at an accurate position in the kale 50, and a probe 1 capable of performing highly accurate eddy current flaw detection can be obtained. Can be done.

[Other Embodiments]
In the above-described embodiment, the display grooves 111 and 121 are formed in the cores 11 and 21 (shaft members), and the display grooves 111 and 121 form the lower step portions 111a and 121a (reference display) and the upper step portions 111b and 121b. (Upper reference display) was formed, but a convex portion protruding outward from the cores 11 and 21 was formed, and the lower step portion (reference display) and the upper step portion (upper reference display) were formed by this convex portion. May be good.

Further, it is also possible to form a reference display and an upper reference display by printing or attaching a sticker to the outer peripheral surfaces of the cores 11 and 21 (shaft members) instead of the concave or convex portions. In this case, the display line may be provided with a color different from the color of the outer peripheral surface of the cores 11 and 21 (shaft members) so that the display line can be easily recognized.

When the lower step portion (reference display) and the upper step portion (upper reference display) are formed by the concave portion or the convex portion, the operator can more easily and surely perform the lower step portion (reference display) and the upper step portion (reference display). The upper reference display) can be visually recognized. In particular, when the internal space of the case 50 (housing) is made smaller according to the miniaturization of the probe 1 (eddy current flaw detector), it is composed of concave or convex parts, and the lower stage (reference display) and the upper stage. If it is a part (upper reference display), it is easy to see.

Further, in the above-described embodiment, by forming the display grooves 111 and 121 in an annular shape on the outer peripheral surfaces of the cores 11 and 21, the lower step portions 111a and 121a (reference display) and the lower step portions 111a and 121a (reference display) and the entire circumference of the cores 11 and 21 are formed. Although the upper tiers 111b and 121b (upper reference display) are displayed, the reference display and the upper reference display may be partially formed in the circumferential direction of the cores 11 and 21 (shaft members).

Further, in the above-described embodiment, the lower step portions 111a and 121a (reference display) and the upper step portions 111b and 121b (upper reference display) are simultaneously formed by the display grooves 111 and 121 having a predetermined width, respectively. The lower step portion (reference display) and the upper step portion (upper reference display) may be individually formed.

Further, in the above-described embodiment, an example in which a single probe 1 (eddy current flaw detector) is scanned to inspect the pipe 62 has been shown, but a plurality of probes 1 (eddy current flaw detectors) in the circumferential direction of the pipe to be inspected have been shown. The device) can be fixedly provided, and a plurality of such probes 1 in the circumferential direction can be arranged everywhere in the axial direction of the pipe.

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

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

Claims (3)

Housing,
A shaft member located in contact with the shaft contact surface in the housing and having a reference display formed on the outer peripheral surface.
A coil member that is located in contact with the coil contact surface in the housing and is arranged so that the shaft member is located in the central space formed in the center.
Insulating member covering the coil member and shaft member,
It is an eddy current flaw detector equipped with
The upper end face of the coil member corresponds to the level indicated by the reference display on the outer peripheral surface of the shaft member.
An eddy current flaw detector characterized by this. A shaft member having a reference display formed on the outer peripheral surface is arranged in the housing 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. A step of contacting and arranging the shaft member so that it is located in the central space.
A step of filling the housing with an insulating material, arranging the upper end face of the coil member at a position corresponding to the reference display, and burying the coil member in the insulating material.
Steps to cure the filled insulating material,
A method of manufacturing an eddy current flaw detector, which is characterized by being equipped with. In the housing, a shaft member having a reference display and an upper reference display 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 in the housing. A step of contacting the coil contact surface and arranging the shaft member so as to be located in the central space.
It is a step of filling the housing with the insulating material, and when the upper end face of the insulating material, which fluctuates in the increasing direction due to filling, reaches the position corresponding to the upper reference display applied to the shaft member, the filling is stopped and the filling is stopped. A step in which the upper end face of the coil member is placed at a position corresponding to the reference display and the coil member is embedded in the insulating material.
Steps to cure the filled insulating material,
A step of bringing the upper coil member having a central space formed in the center into contact with the upper end face of the cured insulating material and arranging the shaft member so as to be located in the central space.
A method of manufacturing an eddy current flaw detector, which is characterized by being equipped with.

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