JP2004333330A - Sensor for eddy current flaw - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensor for eddy current flaw capable of inspecting the rust or damage of an object to be measured on the spot in a non-destructive manner, while reducing noise. <P>SOLUTION: This sensor for eddy current flaw has a flaw-detecting coil element 1, which has a wiring pattern 20 comprising a plurality of respectively independent wirings provided on a flexible board 10, the connection parts provided to both end parts of the flexible board and the connection terminals, respectively connected not only to both ends of a plurality of the wirings, but also to the connection parts, and a coil bobbin 50 which is formed into a hollow cylindrical shape using a non-magnetic material, has a coil winding part 51 on which the thickness of the bobbin is set to R/π or higher, when the outer diameter of the coil bobbin is set to 2R and can be divided lengthwise into two parts. After the coil bobbin 50 is mounted on an object 90 to be measured, the flaw-detecting coil element 1 is wound around the coil bobbin; and both connection parts thereof are connected by a connector 40, to constitute the sensor for eddy current flaw 5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an eddy current detection sensor for detecting the presence or absence of rust, breakage, disconnection, and the like in a steel wire (wire rope) supporting a bridge or the like.
[0002]
[Prior art]
As a method of detecting rust of a cable (steel wire), there is a method of detecting rust of a cable using a sensor including an eddy current flaw detector. This is a technology in which a sensor of an eddy current flaw detector is arranged on a steel wire pass line and electromagnetically detects rust or the like of the steel wire passing through the sensor (for example, see Patent Document 1).
[0003]
In addition, as an electric wire inspection device that non-destructively inspects the generation of rust on electric wires in an alive state that is overhead, a device that inspects by arranging coils that can be opened and closed so as to surround the periphery of the cable is proposed. (For example, see Patent Document 2).
[0004]
Further, the applicant has disclosed a connecting portion provided at both ends of a flexible substrate, a wiring pattern formed of a plurality of independent wires provided between the connecting portions, and a wiring pattern provided at both ends of the plurality of wires. It is proposed to form a flaw detection inspection coil by winding a flaw detection coil element comprising a flexible substrate provided with connection terminals respectively connected to the connected portions, around a pipe or a bobbin mounted on the pipe. (See Patent Document 3).
[0005]
[Patent Document 1]
JP-A-6-34608 [Patent Document 2]
JP 2001-128328 A [Patent Document 3]
Japanese Patent No. 3247666
[Problems to be solved by the invention]
In the method of inspecting a steel wire described in Patent Document 1, since the coil bobbin 50 around which the sensor coil 1 is wound is arranged so that the steel wire passes through the hollow hole 54, as shown in FIG. When the coil bobbin 50 is positioned at a predetermined distance d around the entire circumference of the steel wire bundle 90, the distance between the sensor coil 1 and the surface of the steel wire bundle 90 is equal to d + T. 7B, the inner diameter of the hollow hole 54 of the coil bobbin is set to be larger than the outer diameter of the steel wire bundle 90 because it is necessary to relatively move the coil bobbin and the steel wire bundle as shown in FIG. The distance between the outer circumference of the steel wire bundle and the inner circumference of the sensor coil fluctuates due to the eccentricity generated when moving the steel wire bundle, and the distance between the sensor coil 1 and the surface of the steel wire bundle 90 is 2d + T at the maximum and T at the minimum, It has a problem that affects the examination to generate a noise signal called backlash signal in so-called eddy current flaw detection method. Further, in a steel wire bundle whose surface is molded with a molding material, if the steel wire bundle is unevenly distributed inside the molding material, even if the surface of the molding material maintains a certain distance from the sensor coil, the sensor and the steel wire bundle are not removed. May change, and the above-mentioned noise signal may be generated to affect the inspection.
[0007]
Further, the electric wire inspection device described in Patent Document 2 has a problem that it is difficult to attach a sensor to a continuous steel wire, and a coil that is divided around even when it is not wound is used. The configuration in which a large number is arranged has a problem that the structure of the sensor is complicated.
[0008]
Similarly, when a coil using a flexible substrate described in Patent Literature 3 is wound around a bobbin, there is a problem that the gap between the tube and the bobbin is eccentric as in Patent Literature 1, causing an error.
[0009]
In view of the above problems, the present invention uses a coil element formed of a flexible substrate disclosed in Patent Literature 3 to remove, for example, rust or scratches on a magnetic linear body such as a steel wire supporting a bridge or the like. An object of the present invention is to provide an eddy current flaw detection sensor capable of performing non-destructive inspection while reducing noise on site.
[0010]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention is an eddy current flaw detection sensor for detecting rust or a flaw of a measurement object, and a coil bobbin that is relatively movably arranged outside the measurement object, and a coil bobbin on a surface of the coil bobbin. The coil bobbin has a hollow cylindrical shape using a non-magnetic material, and the difference between the outer diameter and the inner diameter when the outer diameter of the coil bobbin is 2R. At a rate of 2R / π or more, the inspection coil for flaw detection was wound around a coil bobbin mounted on a measurement object to form a sensor coil.
[0011]
Further, according to the present invention, in the eddy current flaw detection sensor, the eddy current flaw detection coil is provided on both ends of the wiring pattern formed of a plurality of independent wirings provided on the flexible substrate and the flexible substrate. The coil bobbin is formed as a coil element having connection terminals and connection terminals connected to both ends of the plurality of wirings and connected to the connection portions, respectively, so that the coil bobbin can be divided vertically.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
The configuration of the eddy current detection sensor according to the present invention will be described with reference to FIG. FIG. 1 is a conceptual diagram schematically showing a state in which an eddy current flaw detection sensor according to the present invention is mounted on a steel wire and inspected for rust, flaws, and the like. FIG. 2 is a cross-sectional view of the eddy current flaw detection sensor shown in FIG. 1 taken along a plane orthogonal to the longitudinal direction near the center of the coil bobbin.
[0013]
The eddy current flaw detection sensor 5 according to the present invention is configured by winding the eddy current flaw detection inspection coil 1 around a coil bobbin 50 mounted on a steel wire (measurement target) 90. Here, in order to facilitate the winding of the coil on site, the coil bobbin 50 may be provided with a coil winding portion including a groove portion 51, and furthermore, each of the coil bobbins 50 includes a plurality of independent wirings provided on a flexible substrate. A coil is formed by using a coil element having a wiring pattern and connection portions provided at both ends of the flexible substrate, and a coil element having connection terminals connected to both ends of the plurality of wires and connected to the connection portions, respectively. May be.
[0014]
A coil bobbin 50 made of a non-magnetic material such as a synthetic resin has a hollow hole 54, a hollow cylinder formed with a flange 57 at both ends and a groove 51 around which the coil element 1 for eddy current inspection is wound at an intermediate portion. It has a divided surface 52 which can be opened and closed by a hinge 56 provided on a flange 57, is divided into two in the axial direction, and is mounted so as to sandwich a steel wire 90. ing.
[0015]
Here, how the rattling noise is affected by the location where the measurement target 90 is located inside the coil will be discussed. It is considered that the eddy current flaw detection method used by the eddy current flaw detection sensor of the present invention utilizes the following two principles. That is, (a) a change in magnetic flux penetrating through the coil is measured, and (b) an eddy current is generated on the surface of the measurement object and the change is measured (eddy current flaw detection method). However, the method used by the present invention detects a change in the inductance of the coil based on a physical change (such as the occurrence of rust or a flaw) of the measurement object, but both principles change the inductance of the coil. However, the two principles are not clearly distinguished for flaw detection.
[0016]
In the method (A), a relatively similar signal can be obtained regardless of the position of the measurement target in the coil, whereas in the method (A), the coil and the measurement target are close (normally). Rust and flaws cannot be accurately measured unless the eddy current flaw detection method is about 1-2 mm). Therefore, the present invention provides an eddy current flaw detection sensor using the method (A) mainly by using the method of reducing the influence of the method (A).
[0017]
With reference to FIGS. 3 and 4, the position in the coil to which the effect of the method (a) (eddy current flaw detection) reaches is defined by the following equations (1) and (2). The range affected by the eddy current flaw detection method (a) is the range in which the magnetic field generated by the current flowing through the coil affects the measurement target. For that purpose, it is necessary to know the distribution of the magnetic field in the coil. It cannot generally simply indicate what magnetic field is formed by the current flowing through the coil (circular current) inside the coil. Therefore, the magnetic field inside the coil was determined by approximation as follows. As shown in FIG. 3A, assuming that the coil radius is R and the magnetic permeability is μ, the magnetic field B generated at the center of the coil by the circular current having the current value I is represented by the following equation (1). Further, as shown in FIG. 3B, a magnetic field B generated at a distance r from the electric wire by the linear current I flowing through the coil is represented by the following equation (2).
B = μI / 2R (1)
B = μI / 2πr (2)
[0019]
It is considered that the equation (2) in which the change in the magnetic field due to the change in distance is small at the center of the coil and the fluctuation in the magnetic field due to the change in the distance is large near the coil winding is dominant. FIG. 4 schematically shows how the magnetic field changes toward the center on the circular current line having the radius R as the origin 0. The change in the magnetic field inside the circular current is approximated according to the formula (2) in which the magnetic field greatly changes depending on the distance in the range of 0 to R / π, and in accordance with the formula (1) in which the magnetic field does not change with the distance in the range of R / π to R. it can. That is, in the range where the magnetic field according to the equation (1) is constant, the variation of the distance does not affect the method (a), whereas in the range where the magnetic field according to the equation (2) varies, the distance varies. Has a great effect on the above-mentioned method (a). Therefore, the effect of the above-mentioned method (a) is small, and the above-mentioned method (a) is dominant except for the diagonal lines apart from the coil line by R / π or more as shown in FIG. 3 (C). Part.
[0020]
That is, in the present invention, when the outer diameter of the coil winding portion of the coil bobbin is 2R, the thickness of the coil winding portion is set to R / π or more, and the influence of the above-mentioned method (a) is suppressed. The configuration of the sensor is such that the above method becomes dominant.
[0021]
Whether or not this condition is appropriate will be described with reference to actual measurement results shown in FIGS. FIG. 5 shows the output of the sensor as viewed through the eddy current flaw detector when an iron rod having a radius R of 8 mm was inserted into a coil having a radius R of 27 mm and the iron rod was moved from the inner wall of the coil toward the center of the coil. Is shown. When the iron bar is in contact with the inner wall of the coil, the distance is 0 mm. When the iron bar is moved 19 mm, the iron bar reaches the center of the coil. The output of the coil was 0.46 V when the iron bar was in contact with the inner wall of the coil, but was 0.23 V at a distance of 6 mm from the inner wall of the coil, 0.19 V at a distance of 8 mm and 10 mm at a distance of 10 mm. 0.16 V, 0.15 V at a distance of 12 mm, and 0.13 V when the iron bar was at the center of the coil. The output change when the iron bar moves from 6 mm to 8 mm is 0.04 V, whereas the output change when the iron bar moves from 10 mm to 12 mm is 0.01 V. When the radius R of the coil is 27 mm, R / π is 8.6 mm, and it can be seen that the amount of change in the sensor output due to the position of the iron bar at a distance of R / π or more from the coil wire becomes extremely small.
[0022]
An example in which a galvanized steel wire is actually measured by an eddy current flaw detection method using a coil will be described with reference to FIG. A galvanized steel wire having a diameter of 15 mm is inserted into a coil having a radius R of 27 mm, and the coil is moved in the longitudinal direction. Flaw detection was performed with the coil bobbin having three thicknesses of 1 mm, 10 mm, and 20 mm, and the influence of rattling was examined. The galvanized steel wire used had a galvanized portion removed at position A in the longitudinal direction. Curve BC00Y shows the case where the thickness of the coil bobbin shown in FIG. 2 is 1 mm, curve BC10Y shows the case where the thickness of the coil bobbin shown in FIG. 2 is 10 mm, and curve BC20Y shows the case where the thickness of the coil bobbin shown in FIG. . When the thickness of the coil bobbin is 1 mm, the signal strength is large, but noise due to rattling when the coil bobbin is moved is large, and it is difficult to easily find a change in output due to the presence or absence of galvanization of the galvanized steel wire. . When the thickness of the coil bobbin is 10 mm, the noise due to rattling when the coil bobbin is moved is smaller than that when the coil bobbin is moved to 1 mm, but the output change due to the presence or absence of zinc plating can be found. . Further, when the thickness of the coil bobbin is 20 mm, the signal intensity due to the zinc plating removal is reduced to about 70% of 1 mm, but the noise due to rattling when the coil bobbin is moved is extremely small, and the output due to the presence or absence of zinc plating is small. Changes can be easily found.
[0023]
In the above description, the case where the steel wire for the supporting steel cable of the bridge was measured was described. However, the measurement target is not limited to the above-mentioned steel wire, and the magnetic material may be used to cast steel pipes such as cast pipes, elevator cables and crane bulls. It can inspect rust, corrosion, etc. of a wire bundle and other linear materials made of a magnetic material.
[0024]
The method of increasing the thickness of the groove portion 51 of the coil bobbin 50 of the eddy current flaw detection sensor 5 is not limited to the method of integrally forming the coil bobbin with the thickness, but may be made of a non-magnetic material that can be attached to the groove portion 51. By separately providing a spacer and attaching it to the groove, the ratio between the gap d and the thickness T can be arbitrarily and easily changed.
[0025]
【The invention's effect】
As described above, according to the present invention, it is possible to reduce a noise signal due to the measurement object being eccentric in the hollow hole of the coil bobbin by keeping a fixed distance between the coil of the eddy current detection sensor and the measurement object. Can be. At this time, there is almost no decrease in the detection ability due to the distance between the coil of the eddy current detection sensor and the object to be measured, and the noise signal due to eccentricity can be greatly reduced.
[0026]
Furthermore, the coil of the eddy current flaw detection sensor is configured by connecting with a connector using a flexible printed circuit board having connection portions at both ends, so that the eddy current flaw detection sensor can be used for an unbroken measurement object that is continuous. The quick win can be quickly installed and inspected.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram illustrating an outline of a configuration of an eddy current flaw detection apparatus according to the present invention.
FIG. 2 is a cross-sectional view illustrating the measurement principle of the eddy current detection sensor of the eddy current inspection device according to the present invention.
FIG. 3 is a view for explaining the measurement principle of the eddy current flaw detector according to the present invention.
FIG. 4 is a characteristic diagram of equations (1) and (2) of FIG. 3;
FIG. 5 is an actual measurement diagram of an output depending on a position of a measurement target in an output coil of the eddy current sensor element according to the present invention.
FIG. 6 is an eddy current flaw detection measurement diagram of a steel wire bundle of the eddy current sensor element using the present invention.
FIG. 7 is a cross-sectional view illustrating a measurement principle of an eddy current detection sensor of a conventional eddy current inspection device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Eddy current flaw detection coil element 20 Wiring pattern 3 Eddy current flaw detection calculation part 40 Connector 5 Eddy current flaw detection sensor 50 Coil bobbin 51 Groove (coil winding part)
52 Division surface 54 Hollow hole 56 Hinge 57 Flange 90 Measurement target (steel wire)

Claims (3)

An eddy current flaw detection sensor that detects rust and scratches on the measurement object,
A coil bobbin arranged relatively movably outside the measurement object,
Having a flaw detection inspection coil wound on the surface of the coil bobbin,
The coil bobbin is formed in a hollow cylindrical shape using a non-magnetic material, and when the outer diameter of the coil bobbin is 2R, the difference between the outer diameter and the inner diameter is 2R / π or more,
An eddy current flaw detection sensor, wherein the flaw detection inspection coil is wound around a coil bobbin mounted on a measurement object. The inspection coil for flaw detection includes a wiring pattern formed of a plurality of independent wirings provided on a flexible substrate, connection portions provided at both ends of the flexible substrate, and connected to both ends of the plurality of wirings, respectively. The eddy current flaw detection sensor according to claim 1, wherein the flaw detection inspection coil element is provided and has a connection terminal connected to each of the connection portions. The eddy current flaw detection sensor according to claim 1 or 2, wherein the coil bobbin is configured to be vertically splittable.

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