JP2004212141A - Eddy current flaw detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an eddy current flaw detector which accurately detects the flaw of the surface layer part of a steel material having no magnetism such as a non-magnetic material, or a hot material. <P>SOLUTION: The eddy current flaw detector A is equipped with an exciting part 10, a detection part 20, a first signal processing part 30, a second signal processing part 40, and a differential amplifier 50. The first signal processing part 30 detects the signal related to a first exciting coil 11 in the detection signal detected by the detection part 20 to subject the same to signal processing. The second signal processing part 40 detecs the signal related to a second exciting coil 12 in the detection signal detected by the detection part 20 to subject the same to signal processing so that the intensity of the detected play noise signal j22 coincides with the intensity of a play noise signal j12 processed by the first signal processing part 30. The differential amplifier 50 is constituted so as to subject the flaw detecting pre-signal j1 from the first signal processing part 30, and the flaw detecting pre-signal j2 from the second signal processing part 40, both to subtraction processing. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an eddy current flaw detector. More specifically, the present invention relates to an eddy current flaw detection device capable of accurately detecting flaws on a surface layer of a non-magnetic steel material such as a non-magnetic material or a hot material.
[0002]
[Prior art]
2. Description of the Related Art An eddy current flaw detection of a mutual induction self-comparison method has been conventionally used for flaw detection of a surface flaw of a steel material. In the mutual induction self-comparison type eddy current flaw detection, phase detection is generally used to separate a flaw signal from noise caused by a change in distance between the flaw detection probe and the surface of the steel material, that is, to improve detection performance. ing.
[0003]
In the eddy current flaw detection of the magnetic material, since the phase difference between the flaw signal and the play noise signal is large, as shown in FIG. 15, the flaw signal and the play noise can be separated by the phase detection, and the detection accuracy is improved. On the other hand, a flaw detection signal in a steel material having no magnetism such as a non-magnetic material or a hot material has almost no phase difference between the flaw signal and the play noise. Therefore, even if phase detection is performed, as shown in FIG. It is difficult to separate it from play. For this reason, in eddy current flaw detection of a steel material having no magnetism such as a non-magnetic material or a hot material, even if phase detection is performed, the detection accuracy cannot be improved.
[0004]
In order to solve such a problem in the conventional eddy current flaw detection, an eddy current flaw detection using multiple frequencies has been proposed.
[0005]
For example, in Japanese Patent Application Laid-Open No. 9-80028, in eddy current flaw detection of steel using a flaw detection coil including an excitation coil and a detection coil, a current of a high frequency f1 'and a low frequency f2' are applied to a single excitation coil penetrated by a steel material. A first component having a first phase shift with respect to the high frequency f1 'current of the exciting coil is extracted from the voltage of the high frequency f1' induced in the detection coil, and the first component is extracted. From the components, at least one of the orthogonal two components and the length when it is represented by a vector is calculated, and when it is greater than or equal to a set value, it is detected as a flaw, and the low frequency f2 ′ induced in the detection coil is detected. A second component of the voltage having a second phase shift with respect to the current of the low frequency f2 ′ of the excitation coil is extracted, and the second component is used to extract the orthogonal two components and the length of the vector when it is represented by a vector. Calculate at least one To which it detects the flaws when the set value or more, multi-frequency eddy current flaw detection method according to the singular exciting coil system has been proposed.
[0006]
However, in the conventional eddy current flaw detection method using currents of a plurality of frequencies, currents having different frequencies are superimposed on a single excitation coil and excited, and the voltage induced in the detection coil is detected by the single detection coil. Then, the induced voltages at the respective frequencies are phase-detected to match the phases of the play noise (see FIGS. 17 (a) and 17 (b)). Then, the play noise is removed from the phase-detected signals by arithmetic processing. (See FIG. 17C), the detection accuracy of the flaw cannot be sufficiently improved.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the problems of the related art, and an object of the present invention is to provide an eddy current flaw detection device capable of accurately detecting a flaw on a surface portion of a steel material having no magnetism such as a nonmagnetic material or a hot material. And
[0008]
[Means for Solving the Problems]
An eddy current flaw detector of the present invention includes an exciting unit, a detecting unit, a first signal processing unit, a second signal processing unit, and a differential amplifier, and the exciting unit is supplied with an exciting current having a first frequency. A first exciting coil, and a second exciting coil to which an exciting current of a second frequency having a predetermined relationship with the first frequency is supplied, wherein the detecting unit includes the first exciting coil and the second exciting coil The first signal processing unit detects a signal relating to the first excitation coil among the detection signals detected by the detection unit, and performs signal processing on the detection coil. The second signal processing unit is configured to detect a signal related to the second excitation coil among detection signals detected by the detection unit, and to determine an amplitude and a phase of the detected play noise signal by the first signal processing. By department The differential amplifier is configured to perform signal processing so as to match the amplitude and the phase of the processed play noise signal, and the differential amplifier includes a signal before flaw detection from the first signal processing unit and a signal before flaw detection from the second signal processing unit. It is characterized in that it is configured to perform a subtraction process with a signal.
[0009]
In the eddy current flaw detector of the present invention, it is preferable that the phase of the flaw signal processed by the second signal processing unit is opposite to the phase of the flaw signal processed by the first signal processing unit.
[0010]
Further, in the eddy current flaw detector of the present invention, it is preferable that the exciting coil is a printed coil.
[0011]
Further, in the eddy current flaw detection device of the present invention, it is preferable that the first excitation current and the second excitation current are synchronized and one frequency is set to a predetermined multiple of the other frequency.
[0012]
[Action]
Since the eddy current flaw detector of the present invention is configured as described above, the S / N ratio is improved, and the flaw detection accuracy of a non-magnetic steel material such as a hot or non-magnetic material is improved.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described based on embodiments with reference to the accompanying drawings, but the present invention is not limited to only such embodiments.
[0014]
FIG. 1 is a block diagram showing a schematic configuration of an eddy current flaw detector according to an embodiment of the present invention. The eddy current flaw detection device (hereinafter simply referred to as a device) A is amplified by an excitation unit 10 having two sets of excitation coils 11 and 12 provided in a predetermined arrangement, a detection unit 20 having a detection coil 21, and an amplifier AMP. Two signal processing units to which the output signal a of the detection coil 21 is input, that is, a first signal processing unit 30 and a second signal processing unit 40, and an output signal of the first signal processing unit 30 and a second signal processing unit And a differential amplifier 50 for subtracting the output signal of the output signal 40 as a main component.
[0015]
The exciting section 10 is formed by applying a printed coil (coil element) formed by applying a predetermined pattern of printed wiring to an insulating thin film 13 (see FIG. 4) made of, for example, a polyimide resin having a thickness of about 100 μm (micrometer). ) Are provided with first and second excitation coils 11 and 12 each comprising a coil element pair connected to form a differential coil.
[0016]
The detection section 20 has a detection coil 21 composed of a printed coil (coil element) capable of detecting a portion excited by the first excitation coil 11 and the second excitation coil 12.
[0017]
Then, the excitation unit 10 and the detection unit 20 having the respective coils (coil elements) configured as described above are arranged on the surface Pa of the base material P made of a ferrite core constituting the flaw detection probe of the apparatus A facing the flaw detection material M. It is laminated via the insulating material thin film 13 (13C) (see FIG. 4), and faces the material to be inspected M.
[0018]
FIG. 2 shows the details of the arrangement pattern including the connection of the print coils constituting the first excitation coil 11 and the second excitation coil 12 of the excitation unit 10.
[0019]
As shown in the figure, the first excitation coil 11 and the second excitation coil 12 are, for example, print coils 14 and 15 formed on both surfaces of an insulating thin film 13 (13A) (see FIG. 4). The coils 14A, 14B, 14C, 14D and 15A, 15B, 15C, 15D are arranged so that their centers are located at the vertices of one square, and a pair of printed coils located at each diagonal is a differential coil. The winding pattern is set and the connection is made so that That is, the first excitation coil 11 and the second excitation coil 12 are set and connected in a winding pattern such that the print coil pairs 14A-14D, 14B-14C, 15A-15D, 15B-15C become differential coils. Is performed to form a two-layer structure.
[0020]
FIG. 2 shows a view of each print coil group viewed from the material to be inspected M side.
[0021]
Hereinafter, each layer of the print coil group is referred to as a layer closer to the surface Pa, that is, a first layer, a second layer,.
[0022]
More specifically, the first-layer printed coil group 14 is adjacent to a rectangular spiral first coil 14A whose winding pattern advances to the center, for example, clockwise when viewed from the material to be inspected M side. Coil 14B, which is arranged likewise and has a spiral wiring pattern similar to that of the first coil 14A, and a spiral pattern similar to that of the first coil 14A which is arranged at a diagonal position of the above-mentioned square with respect to the second coil 14B. And a fourth coil 14D which is disposed at a diagonal position of the above-mentioned square with respect to the first coil 14A and has a spiral wiring pattern similar to that of the first coil 14A. You.
[0023]
More specifically, the second-layer print coil group 15 is arranged so as to be adjacent to a rectangular spiral fifth coil 15A whose winding pattern advances to the center in the opposite direction to the first coil 14A. A sixth coil 15B composed of a spiral wiring pattern similar to that of the fifth coil 15A, and a spiral wiring pattern similar to that of the fifth coil 15A, which is disposed at the diagonal position of the square described above with respect to the sixth coil 15B. 7C and an eighth coil 15D which is arranged at a diagonal position of the above-mentioned square with respect to the fifth coil 15A and has a spiral wiring pattern similar to that of the fifth coil 15A.
[0024]
In the print coil groups 14 and 15, the coils of the corresponding layers, that is, the first coil 14A and the fifth coil 15A, the second coil 14B and the sixth coil 15B, the third coil 14C and the seventh coil 15C, The fourth coil 14D and the eighth coil 15D are provided with their centers and windings overlapped so as to reinforce the magnetic field, respectively (see FIG. 4).
[0025]
The connection of each coil pair 14A-14D and 15A-15D of the first excitation coil 11 as a differential coil is performed as follows. That is, the center line end of the first coil 14A is connected to the center line end of the fifth coil 15A via a through hole (not shown, the same applies hereinafter) formed in the insulating material thin film 13A, and the fifth coil An outer peripheral side wire end of 15A is connected to an outer peripheral side wire end of the eighth coil 15D, and a center side end of the eighth coil 15D is connected to a central side line of the fourth coil 14D through a through hole formed in the insulating thin film 13A. The coil pairs 14A to 14D and 15A to 15D are connected to the ends so that the coil pair is a differential coil.
[0026]
On the other hand, the connection using the coil pairs 14B-14C and 15B-15C of the second excitation coil 12 as differential coils is performed as follows. That is, the center line end of the fifth coil 15B is connected to the center line end of the second coil 14B via a through hole formed in the insulating thin film 13A, and the outer line end of the second coil 14B is connected to the third line end. The center side wire end of the third coil 14C is connected to the center side wire end of the seventh coil 15C through a through hole formed in the insulating thin film 13A, thereby connecting the center side wire end of the third coil 14C. The pairs 14B-14C and 15B-15C are differential coils.
[0027]
As described above, in the excitation unit 10, each of the print coil pairs arranged at one diagonal of the aforementioned square, that is, the pair of the first coil 14A and the fourth coil 14D and the fifth coil 15A A first excitation coil 11 is formed in which a pair with the eighth coil 15D is a differential coil, and each print coil pair arranged at one other diagonal, that is, a second coil 14B and a third coil A pair of 14C and a pair of the sixth coil 15B and the seventh coil 15C are formed as a differential coil, thereby forming a second excitation coil 12, whereby two sets of excitation coils, that is, the first excitation coil 11 and the second excitation coil 12 are formed. The exciting coils 12 are arranged orthogonally.
[0028]
Next, the detection unit 20 will be described with reference to FIG. As shown in the drawing, the detection unit 20 is composed of, for example, a detection coil 21 having a two-layer structure in which print coils 22 and 23 are provided on both surfaces of an insulating thin film 13 (13B) (see FIG. 4). It will be. FIG. 3 shows a view from the side of the material M to be inspected.
[0029]
Specifically, the print coils 22 and 23 are disposed on the upper layers of the print coil groups 14 and 15 constituting the excitation unit 10, that is, the third and fourth layers, respectively, and are formed concentrically with the square described above. The first and second excitation coils 11 and 12 are formed of rectangular spiral wiring patterns that can detect flaws at the excited portions.
[0030]
That is, the third-layer print coil 22 is composed of one coil (hereinafter, referred to as a ninth coil) 22 composed of a spiral wiring pattern that advances clockwise and inward, and the fourth-layer print coil 23 includes: A single coil (hereinafter, referred to as a tenth coil) 23 composed of a spiral wiring pattern that advances inward in the opposite direction is formed. The ninth coil 22 and the tenth coil 23 are formed such that the center and the wiring overlap each other. Have been.
[0031]
The detection coil 21 is connected to the center end of the ninth coil 22 via a through-hole (not shown, the same applies hereinafter) formed in the insulating thin film 13B. Thereby, the outer peripheral end of the ninth coil 22 is formed as one end and the outer peripheral end of the tenth coil 23 is formed as the other end.
[0032]
FIG. 4 schematically shows a lamination mode of the excitation unit 10 and the detection unit 20. As shown in the figure, the excitation unit 10 and the detection unit 20 are stacked via an insulating thin film 13C. In addition, the code | symbol W in FIG. 4 shows a flaw.
[0033]
Next, the signal processing unit will be described.
[0034]
The first signal processing unit 30 includes a detector 31, a phase shifter 32, and a band-pass filter 33. The first signal processing unit 30 detects a signal related to the exciting coil 11 from a detection signal of the detection unit 20, and detects the detected signal. Is phase-controlled by a phase shifter 32, and low-frequency noise and high-frequency noise are removed from the phase-controlled signal by a band-pass filter 33 to generate a first pre-flaw detection signal.
[0035]
Here, the phase shifter 32 controls the phase of the signal detected by the detector 31 so that, for example, the play noise signal is located on the Y axis shown in FIG.
[0036]
The band pass filter 33 removes the frequency of the flaw signal and other noise factors, for example, a gradual change due to a change in the temperature of the material to be inspected or electric noise such as white noise. The frequency is determined depending on the inspection environment.
[0037]
The second signal processing unit 40 includes a detector 41, a phase shifter 42, a bandpass filter 43, and an amplifier 44. The second signal processing unit 40 detects a signal related to the exciting coil 12 from a detection signal of the detection unit 20, The phase of the detected signal is controlled by a phase shifter 42, low-frequency noise and high-frequency noise are removed from the phase-controlled signal, and the amplitude (intensity) of the signal is adjusted by an amplifier 44. A second pre-flaw detection signal having the same amplitude (same intensity) as the first pre-flaw detection signal is generated. Note that the amplifier 44 may be provided in the first signal processing unit 30.
[0038]
Here, the phase shifter 42 controls the phase of the signal detected by the detector 41 similarly to the phase shifter 32, for example, the flaw signal has an opposite phase to the flaw signal whose phase is controlled by the phase shifter 32. The phase is controlled as described above, and the play noise signal is positioned on the Y axis shown in FIG.
[0039]
The bandpass filter 43 removes the frequency of the flaw signal and other noise factors, for example, a gradual change due to a change in the temperature of the material to be inspected or electric noise such as white noise. The frequency is determined depending on the inspection environment.
[0040]
The amplifier 44 adjusts the amplitude of the play noise signal whose phase is controlled by the phase shifter 42, that is, the strength of the play signal, so that the strength level of the play signal coincides with the strength level of the play noise signal whose phase is controlled by the phase shifter 32 ( See FIG. 8).
[0041]
Next, the principle of the eddy current flaw detection in the device A having such a configuration will be described with reference to FIG.
[0042]
As shown in FIG. 5, the frequency f1 of the first exciting current b1 and the frequency f2 of the second exciting current b2 are such that the frequency f1 of one (eg, the first exciting current b1) is equal to that of the other (eg, the second exciting current b2). When the first exciting current b1 is represented by cos {2π · f1 · (t)} (t: t is a variable representing time), the second exciting current b2 Are synchronized as represented by cos {2π · f2 · (t)}.
[0043]
At this time, the output signal a of the detection unit 20 has the same frequencies f1 and f2 as the first excitation current b1 and the second excitation current b2, and the phases are shifted by α and β, respectively, as shown in Expression 1 below. It becomes a signal in which each component is superimposed.
[0044]
a = k1 · cos {2π · f1 · (t) + α} + k2 · cos {2π · f2 · (t) + β} (1)
[0045]
Here, k1 and k2 are coefficients representing the amplitude of each component.
[0046]
As described above, the output signal a of the detection unit 20 is processed by the first and second signal processing units 30 and 40 to be the first and second pre-flaw detection signals. It is done like this.
[0047]
The output signal a of the detection unit 20 input to the first signal processing unit 30 is a signal c1 (= cos ｛2π · f1 · (= cos ｛2π · f1 · () having the same period and the same phase as the first excitation current b1 separately input to the detector 31. t)｝) and a signal d1 (= sin {2π · f1 · (t)｝) whose phase is delayed by 90 degrees with respect to the frequency f1, and a detection signal e1 (= (k1 / 2) · cos α); It is output as g1 (= (k1 / 2) · sin (−α)).
[0048]
The detected signals e1 and g1 obtained by detecting the output signal a of the detection unit 20 by the detector 31 are phase-controlled by the phase shifter 32 and converted into signals h1 and i1, and then the signal h1 (or i1) is converted into a band. The signal is filtered by the pass filter 33 and becomes a first pre-flaw detection signal j1.
[0049]
The output signal a of the detection unit 20 input to the second signal processing unit 40 is detected by a signal separately input to the detector 41 so that the flaw signal has the opposite phase to the flaw signal detected by the detector 31. It is output as detection signals e2 and g2. Specifically, the detection is performed by a signal c2 (= cos {2π · f2 · (t)}) having the same period and the same phase as the second excitation current b2 and a signal d2 (= sin {2π · f2 · (t)}) is detected for the frequency f2 and output as a detected signal e2 (= (k2 / 2) · cosα) and g2 (= (k2 / 2) · sin (−α)). You.
[0050]
The detection signals e2 and g2 obtained by detecting the output signal a of the detection unit 20 by the detector 41 are phase-controlled by the phase shifter 42 and converted into signals h2 and i2, and then the signal h2 (or i2) is converted into a band. After being filtered by the pass filter 43, the amplitude (intensity) is adjusted by the amplifier 44 to obtain the second pre-flaw detection signal j2.
[0051]
The first pre-flaw detection signal j1 obtained by the first signal processing unit 30 and the second pre-flaw detection signal j2 obtained by the second signal processing unit 40 are subjected to subtraction processing by the differential amplifier 50, whereby the flaw signal is amplified. In addition, a flaw detection signal m from which the play noise signal has been removed is obtained.
[0052]
Hereinafter, the eddy current flaw detection by the device A will be described more specifically with reference to FIGS.
[0053]
FIG. 6 schematically shows a relative positional relationship between the first and second exciting coils 11 and 12 of the exciting unit 10 and various flaws W1, W2 and W3. In the figure, white arrows V1, V2, V3 indicate the directions in which the flaws W1, W2, W3 move with respect to the first and second excitation coils (differential coils) 11, 12.
[0054]
FIG. 7 shows flaw signals j11 and j21 of the first and second pre-flaw detection signals j1 and j2 corresponding to the flaws W1, W2 and W3. 2A shows a flaw signal j11 of the first signal processing unit 30, and FIG. 2B shows a flaw signal j21 of the second signal processing unit 40. FIG. 8 shows play noise signals j12 and j22 of the first and second pre-flaw detection signals j1 and j2. FIG. 6A shows the play noise signal j12 of the first signal processing unit 30, and FIG. 6B shows the play noise signal j22 of the second signal processing unit 40.
[0055]
When the first and second exciting coils 11 and 12 are excited by the exciting currents of the frequencies f1 and f2, that is, the first and second exciting currents b1 and b2, respectively, at a position where there is no flaw, the detection coil 21 is balanced as a whole. The output signal a is stabilized. Therefore, when there is no flaw, the pre-flaw detection signals j1 and j2 become flat.
[0056]
Conversely, when the flaw sequentially passes through the opposing positions of the coil pairs (14A and 14D, 14B and 14C) constituting the first and second excitation coils 11 and 12, the pre-flaw detection signals of the corresponding frequencies f1 and f2. Since changes appear in the flaw signals j11 and j21 of j1 and j2, flaw detection can be performed. This will be specifically described below.
[0057]
(1) As shown in FIG. 6, the coils on one end of the first excitation coil 11 (first coil 14A, fifth coil 15A) and the coil on the other end of second excitation coil 12 (third coil 14C, 7C, the flaw W1 connecting the center of the above-mentioned square parallel to the side of the square moves in the direction of the arrow V1 and sequentially passes through the first and second exciting coils 11 and 12. As shown in FIG. 7, a signal W1a appears as a flaw signal j11 in the first pre-flaw detection signal j1, and a signal W1b having an opposite phase to the signal W1a appears as a flaw signal j21 in the second pre-flaw detection signal j2. As shown in FIG. 8, the signal G1 appears as the play noise signal j12 in the first pre-flaw detection signal j1, and the signal G2 having the same phase and the same strength as the play G1 appears as the play noise signal j22 in the second pre-flaw detection signal j2. .
[0058]
When the first pre-flaw detection signal j1 including the signal W1a and the signal G1 and the second pre-flaw detection signal j2 including the signal W1b and the signal G2 are subtracted by the differential amplifier 50, a flaw signal obtained by amplifying the signals W1a and W1b. Is obtained, the play noise signal becomes zero, and the play noise is removed. In other words, a flaw detection signal m free of backlash noise and in which the flaw signal is emphasized is obtained. Therefore, the flaw detection accuracy is improved.
[0059]
(2) A flaw W2 that is orthogonal to the diagonal line of the first excitation coil 11 and extends in a direction parallel to the diagonal line of the second excitation coil 12 moves in the direction of the arrow V2, and sequentially passes through each coil of the first excitation coil 11. In the case where the signal passes through each coil of the second excitation coil 12 at the same time, a signal W2a having the same waveform as the signal W1a appears as a flaw signal j11 in the first pre-flaw detection signal j1, as shown in FIG. The flaw signal j21 does not appear in the pre-flaw detection signal j2. As shown in FIG. 8, the signal G1 appears as the play noise signal j12 in the first pre-flaw detection signal j1, and the signal G2 having the same phase and the same strength as the play G1 appears as the play noise signal j22 in the second pre-flaw detection signal j2. .
[0060]
When the first pre-flaw detection signal j1 including the signal W2a and the signal G1 and the second pre-flaw detection signal j2 including the signal G2 are subtracted by the differential amplifier 50, the signal W2a is obtained, and the play noise is removed. . In other words, a flaw detection signal m free of backlash noise and in which the flaw signal is emphasized is obtained. Therefore, the flaw detection accuracy is improved.
[0061]
(3) Conversely, a flaw W3 that is orthogonal to the diagonal line of the second excitation coil 12 and extends in a direction parallel to the diagonal line of the first excitation coil 11 moves in the direction of the arrow V3, and causes each coil of the second excitation coil 12 to move. When passing sequentially and simultaneously passing through the coils of the first excitation coil 1A, as shown in FIG. 7, a signal W3b having the same waveform as the signal W1b appears as a flaw signal j21 in the second signal f2 before flaw detection. The flaw signal j11 does not appear in the first pre-flaw detection signal j1. As shown in FIG. 8, the signal G1 appears as the play noise signal j12 in the first pre-flaw detection signal j1, and the signal G2 having the same phase and the same strength as the play G1 appears as the play noise signal j22 in the second pre-flaw detection signal j2. .
[0062]
When the second pre-flaw detection signal j2 including the signal W3b and the signal G2 and the first pre-flaw detection signal j1 including the signal G1 are subtracted by the differential amplifier 50, the signal W3b is obtained, and the play noise is removed. . In other words, a flaw detection signal m free of backlash noise and in which the flaw signal is emphasized is obtained. Therefore, the flaw detection accuracy is improved.
[0063]
【Example】
The eddy current flaw detection of the non-magnetic material (SUS316) was performed using the device A of the embodiment with the frequencies of the exciting currents of the first and second exciting coils 11 and 12 set to 200 kHz and 400 kHz, respectively.
[0064]
FIG. 9 shows the result of detecting the obtained detection signal by the detectors 31 and 41. FIG. 7A shows the result of detection by the detector 31 of the first signal processing unit 30, and FIG. 7B shows the result of detection by the detector 41 of the second signal processing unit 40. In order to simplify the drawing, the in-phase component (X) (or e1, e2) and the 90 ° phase delay component (Y) (or g1, g2) are shown on the same axis.
[0065]
The phase of the detection signal detected by the detector 31 is shifted by the phase shifter 32 so that the play noise signal coincides with the X-axis direction. The signal after the phase shift is shown in a vector diagram in FIG. 10A, and the flaw signal is shown in FIG. 11A. FIG. 12 shows the play noise signal.
[0066]
The detection signal detected by the detector 41 was phase-shifted in the X-axis direction by a phase shifter 42 in the form of a play noise signal. The signal after the phase shift is shown in a vector diagram in FIG. 10B, the flaw signal after the intensity adjustment is shown in FIG. 11B, and the play noise signal is also shown in FIG.
[0067]
FIGS. 13 and 14 show the results obtained by subtracting the first and second pre-flaw detection signals obtained in this manner by the differential amplifier 50. FIG. FIG. 13 shows that the flaw signal is amplified and the flaw signal is emphasized. FIG. 14 shows that the backlash noise has been removed.
[0068]
Therefore, according to the apparatus A of the embodiment, it is understood that the rattling noise is removed and the flaw detection signal in which the flaw signal is emphasized can be obtained. That is, according to the apparatus A of the embodiment, it can be understood that the eddy current flaw detection of a hot material or a non-magnetic material can be accurately performed.
[0069]
As described above, the present invention has been described based on the embodiments, but the present invention is not limited to only such embodiments, and various modifications are possible. For example, in the embodiment, the excitation coil and the detection coil are print coils, but the excitation coil and the detection coil are not limited to the print coils, but may be various coils. In the embodiment, the print coil has two layers, but may have three or more layers. Further, a plurality of coils can be arranged to efficiently detect a flaw in a wide range.
[0070]
【The invention's effect】
As described above in detail, according to the eddy current flaw detection device of the present invention, the S / N ratio is improved, and an eddy current flaw detection of a steel material having no magnetism such as a hot material or a non-magnetic material can be accurately performed. The effect is obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an eddy current flaw detector according to one embodiment of the present invention.
FIG. 2 is a schematic diagram showing details of a differential coil of an exciting unit.
FIG. 3 is a schematic diagram illustrating details of a detection coil of a detection unit.
FIG. 4 is a schematic diagram illustrating a lamination mode of an excitation unit and a detection unit.
FIG. 5 is a graph showing a waveform of an exciting current supplied to a differential coil of an exciting unit of the eddy current flaw detector, wherein FIG. 5 (a) shows a current of a first exciting coil, and FIG. 3 shows a second excitation current.
FIG. 6 is a schematic diagram showing a relative positional relationship between an exciting coil and various flaws.
7A and 7B are graphs showing flaw signals corresponding to various flaws shown in FIG. 6, wherein FIG. 7A shows a signal of a first signal processing unit and FIG. 7B shows a signal of a second signal processing unit; Is shown.
8A and 8B are graphs showing play noise signals corresponding to various flaws shown in FIG. 6, wherein FIG. 8A shows a signal of a first signal processing unit, and FIG. 8B shows a signal of a second signal processing unit. Is shown.
9A and 9B show detection signals of the first signal processing unit, and FIG. 9B shows a detection signal of the second signal processing unit according to the embodiment.
10A and 10B are vector diagrams of a play noise signal after phase control by the phase shifter of the embodiment, wherein FIG. 10A shows the signal of the first signal processing unit, and FIG. Here's what.
FIGS. 11A and 11B are graphs of flaw signals after phase control by the phase shifter of the embodiment, wherein FIG. 11A shows the signal of the first signal processing unit, and FIG. Here's what.
FIG. 12 is a graph of a play noise signal after phase control by the phase shifter of the embodiment.
FIG. 13 is a graph of a flaw signal according to the embodiment.
FIG. 14 is a graph of a play noise signal of the example.
15A and 15B are schematic diagrams of a flaw signal and a play noise signal of phase detection in a conventional eddy current flaw detection of a magnetic material, wherein FIG. 15A is a vector diagram and FIG. 15B is a graph diagram of a flaw signal.
16A and 16B are schematic diagrams of a flaw signal and a play noise signal of phase detection in a conventional non-magnetic material eddy current flaw detection, wherein FIG. 16A is a vector diagram, and FIG. 16B is a graph diagram of a flaw signal. .
17A and 17B are schematic diagrams of a flaw signal and a play noise signal of eddy current flaw detection of a nonmagnetic material according to a conventional two-frequency method, in which FIG. 17A shows a vector diagram of a first frequency, and FIG. A vector diagram of the frequency is shown, and (c) shows a vector diagram after the subtraction processing.
[Explanation of symbols]
A Eddy current flaw detector
W flaw
M Material to be inspected
10 Exciting part
11 1st excitation coil
12 Second excitation coil
20 Detector
21 Detection coil
30 first signal processing unit
31 detector
32 phase shifter
33 Bandpass Filter
40 second signal processing unit
41 Detector
42 phase shifter
43 Bandpass Filter
44 Amplifier
50 differential amplifier

Claims (4)

An excitation unit, a detection unit, a first signal processing unit, a second signal processing unit, and a differential amplifier;
The excitation unit has a first excitation coil to which an excitation current of a first frequency is supplied, and a second excitation coil to which an excitation current of a second frequency having a predetermined relationship with the first frequency is supplied. And
The detection unit has a detection coil capable of detecting a portion excited by the first excitation coil and the second excitation coil,
The first signal processing unit is configured to detect a signal related to the first excitation coil among the detection signals detected by the detection unit and perform signal processing,
The second signal processing unit detects a signal related to the second excitation coil among detection signals detected by the detection unit, and an amplitude and a phase of the detected play noise signal are processed by the first signal processing unit. It is configured to perform signal processing to match the amplitude and phase of the play noise signal,
The eddy current flaw detection device, wherein the differential amplifier is configured to subtract a signal before flaw detection from the first signal processing unit and a signal before flaw detection from the second signal processing unit. 2. The eddy current flaw detector according to claim 1, wherein a phase of the flaw signal processed by the second signal processing unit is opposite to a phase of the flaw signal processed by the first signal processing unit. 2. The eddy current flaw detector according to claim 1, wherein the exciting coil is a printed coil. 2. The eddy current flaw detection device according to claim 1, wherein the first excitation current and the second excitation current are synchronized, and one frequency is set to a predetermined multiple of the other frequency.

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