JPH064664U - Device for detecting disconnection of probe coil in eddy current testing - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a probe coil disconnection detecting device capable of easily detecting disconnection of a probe coil in a mutual induction flaw detection test in an eddy current flaw detection test. [Configuration] Mutual induction flaw detection test Detects the detection voltage of the probe coil as a distance measurement index voltage between the probe coil and the material to be inspected, detects, rectifies and integrates the voltage, compares it with the reference voltage and compares it with the comparison output. Detects disconnection. [Effect] The presence or absence of disconnection of the exciting coil of the mutual induction flaw detection test probe coil or the coil for distance measurement, or the coil windings of both of them can be accurately and reliably constantly monitored and detected during operation of the eddy current flaw detection test apparatus. Becomes possible,
The quality assurance system of the inspected material can be made more reliable.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a rotary flaw detector applying electromagnetic induction (eddy current), and more particularly, to a self-diagnosis of a plurality of probe coils for flaw detection used for flaw detection test, and more particularly to a mutual induction flaw detection test probe coil disconnection detection device. Is.

[0002]

[Prior art]

 Conventionally, in the mutual induction flaw detection test probe coil, a method of directly or indirectly measuring an exciting current has been carried out as a method of constantly monitoring the disconnection detection of the exciting coil. A principle diagram of the conventional example is shown in FIG. 5 of the accompanying drawings.

In FIG. 5, the oscillator 1 generates a flaw detection test AC frequency. The output of the oscillator 1 is applied to the power amplifier 2. When the output of the power amplifier 2 is the load 3, that is, the test coil for electromagnetic induction (eddy current) flaw detection, in the mutual induction coil structure, the excitation coil is used. 3A is applied. A low resistance 4 (r) is connected between the ground side terminal of the exciting coil 3A and the ground. When the power from the power amplifier 2 is applied to the load 3A, the current i 2 flows, and the resistance r causes the voltage e = ir. This voltage e is amplified by the first amplifier 5 and then converted into a DC voltage by the rectifier 6. This DC voltage is amplified by the second amplifier 8 and then applied to one input of the voltage comparator 9. The reference reference voltage E for comparison is applied to the other input of the voltage comparator 9 from the terminal 10.

In such a circuit configuration, if the exciting coil 3A is disconnected, the power from the power amplifier 2 is cut off. As a result, the value of the voltage e obtained by i × r becomes zero, and the outputs of the rectifier 6 and the amplifier 8 also become zero, so that the output to the terminal 11 of the voltage comparator 9 changes. In this way, it was possible in principle to detect the disconnection of the exciting coil for the eddy current flaw detection test simply and reliably. In FIG. 5, reference numeral 3B indicates a flaw detection (pickup) coil.

Further, as another method for detecting the disconnection of the flaw detection test probe coil, when the flaw detection test coil detects a sound portion of the inspection material, it is not a harmful defect (scratch), but the physical property of the metal surface of the inspection material. It is possible to judge that the probe coil is normal or that it is disconnected by knowing whether the noise voltage is "absent" depending on the "presence" of the noise voltage caused by the non-uniformity of the noise voltage. Such noise gives an instruction output of background noise which is about 1/2 to 1/10 of the flaw signal. Conventionally, it has been attempted to determine whether the flaw detection test coil is normal or whether the flaw detection test coil is abnormal, depending on whether or not such a noise signal is detected.

[0006]

[Problems to be solved by the device]

 However, the conventional method as described above with reference to FIG. 5 has a problem that it is technically difficult to detect the voltage drop e calculated by i × r when the exciting current is very small. It was In order to solve such a problem, it is considered that the resistance r should be increased in principle in order to obtain the large voltage drop e. In this case, for example, a normal load, that is, a mutual induction coil If the resistance r is chosen to be a value that is several times that of the impedance of the exciting coil, the disadvantage is that the resistor r consumes most of the energy generated from the power amplifier.

Further, when the flaw detection test frequency is a high frequency (for example, 512 KHz, 1024 KHz, etc.), a high amplification degree is required similarly to the signal amplification of the eddy current flaw detection test, and a high load impedance causes a capacitance due to capacitance generated by wiring. Due to the reactive reactance, the inconvenience that precious applied power is shunted to the ground will occur.

Further, regarding the presence / absence of disconnection of the exciting coil of the coil winding wound around the flaw detection test probe coil, a reliable judgment output can be obtained, but other coil windings, that is, flaw detection test probe coil and The distance measurement (AGC) coil and the flaw detection coil are used to correct the distance-sensitivity characteristics of the flaw detection (pickup) coil combined with the flaw detection test probe coil by measuring the distance from the inspection material. There is also the inconvenience that it is not possible to output the information as to the presence or absence of disconnection of each coil wound independently as an electric signal.

Furthermore, the conventional method of detecting disconnection depending on the presence or absence of noise voltage due to the probe coil described above also has the following problems. That is, when the inspected material is the same material, has the same outer diameter, and the inspected material is different even within the same lot, the noise indication height obtained by flaw detection on a sound part is It is known to have changed several times or more. As described above, it is practically difficult to accurately grasp the presence / absence of a disconnection of the probe coil in a situation where the noise voltage indication height changes significantly, and the frequency of malfunction of the disconnection detection circuit increases. Was there.

An object of the present invention is to provide a probe coil disconnection detection device in an eddy current flaw detection test that can solve the problems of the prior art.

[0011]

[Means for Solving the Problems]

 According to one feature of the present invention, in the device for detecting disconnection of a probe coil in an eddy current flaw detection test using a mutual induction flaw detection test probe coil including an exciting coil and a distance measuring coil electromagnetically coupled to the exciting coil, The detection rectification means for detecting and rectifying the voltage induced by the measuring coil, the integration means for integrating the output voltage from the detection and rectification means, and the output voltage from the integration means and the reference reference voltage are compared. And a comparison means for the purpose of outputting the warning of the disconnection of the probe coil by the output of the comparison means.

According to another feature of the present invention, a probe coil breakage detection device in an eddy current flaw detection test using a mutual induction flaw detection test probe coil including an excitation coil and a distance measuring coil electromagnetically coupled to the excitation coil. In, the detection rectification means for detecting and rectifying the voltage induced by the distance measuring coil, the integration means for integrating the output voltage from the detection rectification means, the output voltage from the integration means and the reference reference voltage And a comparison means for comparing the output of the comparison means and a terminal control signal used for flaw detection control of the standard length inspection material to obtain a logical product and output a probe coil disconnection alarm. .

[0013]

【Example】

 Next, the present invention will be described in more detail with reference to FIGS. 1 to 4 of the accompanying drawings.

First, an embodiment of the present invention will be described in detail taking one channel as an example. FIG. 2 shows an example of connection of the mutual induction flaw test probe coil used in the rotary flaw detector. This mutual induction flaw detection test probe coil 20 is composed of three coils: an excitation coil 20A, a distance measurement index output AGC coil 20B, and a flaw detection (pickup) coil 20C. , Is directly or indirectly electromagnetically coupled through the magnetic field lines. The exciting coil 20A is connected to a power amplifier 24 through a rotary transformer utilizing electromagnetic coupling or a suitable slip ring 21 (T ₁ ), and an input of the power amplifier 24 is an alternating current, for example, this embodiment. In this case, a high frequency voltage of 512 KHz or 1024 KHz is applied. The high frequency flows in through the rotary transformer 21 as shown by an arrow in the figure, is applied to the exciting coil 20A, and a magnetic field line for generating an eddy current is generated on the surface of the material to be inspected.

The distance measuring coil 20B detects a magnetic line of force coupled to the exciting coil 20A directly and via the material to be inspected, and generates a distance measuring index voltage. The distance measurement index voltage is passed through the rotary transformer 22 (T ₂ ) and the amplifier 25, and then the distance correction control voltage is generated.

The flaw detection test detection coil 20C detects a change in eddy current on the surface of the material to be inspected as a change in voltage, and amplifies it by an amplifier 26 via a rotary transformer 23 (T ₃ ). An AC bridge may be used between the amplifier 26 and the rotary transformer 23.

FIG. 1 illustrates one embodiment of the present invention which receives amplified output from a mutual induction flaw test probe coil as described with respect to FIG. 2 to form a flaw detection signal and also forms a break alarm output. It is a schematic block diagram which shows the circuit structure as an example.

In FIG. 1, the distance measurement index voltage between the probe coil and the material to be inspected is amplified by the amplifier 25 of FIG. 2 and then amplified from the terminal A to a phase (synchronous) detector or a linear detector 27. It is input, detected and rectified, and further input to the low-pass filter 28 to remove the residual voltage at the flaw detection test frequency. The present invention utilizes this filter output. The output of the low-pass filter 28, after being amplified by the DC amplifier 29, becomes a positive DC voltage in the rectifying circuit composed of the feedback amplifier 30 and the diode 31. This DC voltage is input to the integrator 32. The integrator 32 is composed of a resistor R ₁ , a capacitor C ₁ and a resistor R _2, and these resistors and the capacitor function to smooth the fluctuation of the distance measurement index voltage.

The fluctuation of the distance measurement index voltage referred to here is (a) the fluctuation of the distance between the flaw detection test probe and the material to be detected, especially the movement of the center of rotation of the rotating probe coil and the movement of the material to be inspected. There are two types of mixture: distance variation due to the difference from the center (eccentricity), and (b) distance variation that causes the aforementioned eccentricity momentarily due to mechanical vibration while the inspected material is passing. ing. Therefore, in order to detect the distance measurement index voltage in a stable and reliable manner, it is necessary to smooth and average these voltage fluctuations. This purpose is fulfilled by the integrator 32 as described above.

The output waveform of the amplifier 29 through the low pass filter 28 is shown in FIG. 4A, the output waveforms of the rectifying circuits 30 and 31 are shown in FIG. 4B, and the output waveform of the integrator 32 is shown. Is shown in FIG. 4 (C). In FIG. 4, when one or both of the exciting coil 20A and / or the distance measuring AGC coil 20B is disconnected at an arbitrary time, when the time t after the time constant τ seconds of the integrator 32 passes, the AGC Since it becomes impossible to integrate and hold the voltage, the output voltage waveform of the integrator 32 (see (C) in FIG. 4) is attenuated.

In FIG. 1, the output of the integrator 32 is input to the voltage comparator 33. The reference comparison voltage e is applied to the other input of the voltage comparator 33. Input from the integrator 32 to the voltage comparator 33, the voltage represented by + margin (margin) voltage e _m of the reference comparison voltage e has a value in the normal operation. An AND circuit (AND circuit) 34 is connected to the output of the voltage comparator 33. To the other one input terminal 35 of the AND circuit 34, a terminal-controlled positive voltage f which is used as a conventional means at the time of flaw detection of a standard length inspection material is applied.

When one or both coil windings of the exciting coil 20A or the AGC coil 20B are broken, the output of the integrator 32 reaches the judgment level e after t seconds shown in (D) of FIG. . At this time, the voltage comparator 33 of FIG. 1 generates the output voltage d saturated at the positive electrode, as shown in FIG. Since the AND circuit 34 of FIG. 1 is applied with the two-input co-positive voltage, it generates an alarm output voltage for notifying the disconnection of the probe coil winding at the output terminal 36.

In this embodiment, the AND circuit 34 is used to prevent malfunctions when the terminal control flaw detection is not ON, and such an AND circuit is always necessary. is not.

Next, the functional operation as described above will be described in more detail with reference to FIG.

In FIG. 4, the uppermost waveform (A) indicates an analog recording instruction normally obtained at the time of flaw detection through the rotary transformer 23 and the amplifier 26 by the flaw detection detection coil 20C of the probe coil 20 of FIG. Shows an example of. FIG. 4B shows a waveform of the terminal control positive voltage f applied to the other input terminal 35 of the AND circuit 34 in the circuit of FIG. It shows that the flaw detection net time such as the recording instruction signal and noise is turned ON and OFF for each of the standard length materials. 4C corresponds to the integrated waveform of FIG. 3C and is obtained by the present invention. In this example, the probe coil 20 is normal until the n + 1th and n + 2th coils. Yes, it shows the situation when the coil winding breaks in the first half of the (n + 3) th coil. That is, the output d 1 of the voltage comparator 33 is generated after t seconds, and (D) of FIG. 4 shows this waveform, which corresponds to the signal of (D) of FIG. FIG. 4E shows the waveform of the output of the AND circuit 34 of FIG. 1, and this output is the signal f of FIG. 4B and the signal d of FIG. 4D. The alarm output is a logical product and is generated at the terminal 36 in FIG.

For the flaw detection test probe coil of a plurality of channels, each channel may be provided with the integrator, the voltage comparator, and the AND circuit as described above.

Next, the signal processing for obtaining the flaw detection signal by the circuit configuration of FIGS. 1 and 2 will be described.

In FIG. 1, the input terminal B receives a signal amplified by the flaw detection coil 20C shown in FIG. 2 through the rotating transformer 23 and the amplifier 26 through the AC bridge. This signal is further passed to the phase detector 38, where the flaw signal is demodulated, the S / N ratio of the flaw signal is improved by the filter 39, and the flaw signal with the improved S / N ratio is divided. It is applied to one input of the calculator 40. As described above, the other input of the divider 40 is input from the distance measurement index output AGC coil 20B of FIG. 2 through the rotary transformer 22 and the amplifier 25 to the terminal A of FIG. Then, a distance measuring index voltage between the probe and the surface of the material to be inspected, which is obtained through the low pass filter 28, is applied. Therefore, the divider 40 automatically corrects the amplitude of the flaw signal obtained from the flaw detection coil according to the variation in the distance between the probe and the surface of the material to be inspected. This is called the AGC function here.

The switch 41 is for turning on, turning off, and switching the above-mentioned AGC function. A bandpass filter 42 is connected to the output side of the switch 41, and the output thereof is further sent to the next signal output terminal 43.

[0030]

[Effect of device]

 According to the configuration of the probe coil disconnection detecting device of the present invention as described above, the following special effects can be obtained.

First of all, even in the existing eddy current flaw detector, the disconnection detecting device including the integrator, voltage comparator, AND circuit of the present invention is added to each signal channel (system). In the probe coil for high-frequency low-power excitation, the presence or absence of disconnection in the coil winding of either the excitation coil or the AGC coil is monitored accurately and reliably during operation of the test equipment. It becomes possible to do.

Secondly, if any of the probe coils is broken during flaw detection at a predetermined scanning interval by a plurality of flaw detection test probe coils, only the defective specific probe channel does not leak at a predetermined interval to cover the entire circumference. Since it is impossible to detect flaws, as a result, it is not possible to inform the operator that the flaws are missed due to the scanning failure of the flaw detection, and there is a risk that the test will be completed with defective materials mixed as good materials. In contrast to the conventional structure, according to the device configuration of the present invention, the alarm circuit functions, and it is possible to immediately force the worker to replace the defective probe. It is possible to make the quality assurance system for the entire circumference and the entire surface more reliable.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing a configuration of a signal processing circuit in a flaw detection test including a disconnection detection device according to an embodiment of the present invention.

FIG. 2 is a schematic circuit diagram showing a connection example of a mutual induction flaw detection test probe coil used in a rotary flaw detection device.

FIG. 3 is a diagram showing signal waveforms at various portions in the circuit configuration of FIG.

FIG. 4 is a diagram for explaining the relationship between flaw detection timing and wire breakage detection of each standard length material in the circuit configuration of FIG. 1 in more detail.

FIG. 5 is a diagram showing a principle of a conventional example of a method for constantly monitoring the detection of disconnection of an exciting coil in a mutual induction flaw detection test probe coil.

[Explanation of symbols]

 20 Mutual induction test probe coil 20A Excitation coil 20B AGC coil for distance measurement index output 20C Detection coil for flaw detection 21 Rotation transformer 22 Rotation transformer 23 Rotation transformer 24 Amplifier 25 Amplifier 26 Amplifier 27 Linear detector 28 Low-pass filter 29 DC amplifier 30 Feedback amplifier 31 Diode 32 Integrator 32 33 Voltage comparator 34 AND circuit 35 Input terminal 36 Output terminal 38 Phase detector 39 Filter 40 Divider 41 Switch 42 Bandpass filter 43 Signal output terminal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Isobe 1-5-7 Sakuragawa, Itabashi-ku, Tokyo Inside Hara Denshi Sokki Co., Ltd. (72) Inventor Eiichiro Chikamatsu 1-5-7 Sakuragawa, Itabashi-ku, Tokyo Within Hara Denshi Sokki Co., Ltd.

Claims (2)

[Scope of utility model registration request] 1. A disconnection detecting device for a probe coil in an eddy current flaw detection test, which uses a mutual induction flaw detection test probe coil including an exciting coil and a distance measuring coil electromagnetically coupled to the exciting coil, and is induced by the distance measuring coil. Detection rectification means for detecting and rectifying the voltage to be detected,
Integrating means for integrating the output voltage from the detecting and rectifying means,
The probe coil is characterized in that it comprises a comparing means for comparing the output voltage from the integrating means and a reference voltage, and a probe coil disconnection alarm is output by the output of the comparing means. Disconnection detection device. 2. A probe coil disconnection detection device in an eddy current flaw detection test using a mutual induction flaw detection test probe coil including an exciting coil and a distance measuring coil electromagnetically coupled to the exciting coil, which is induced by the distance measuring coil. Detection rectification means for detecting and rectifying the voltage to be detected,
Integrating means for integrating the output voltage from the detecting and rectifying means,
A comparing means for comparing the output voltage from the integrating means with a reference voltage, and the output of the comparing means;
A probe coil disconnection detection device, which is configured to output a probe coil disconnection alarm by obtaining a logical product with a terminal control signal used for flaw detection control of a standard length inspection material.