JPH10185877A - Apparatus and method for probe rotation-type flaw detection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an apparatus and a method that can be easily made to be of multichannel and that can perform a signal transmission in a compact manner, by converting a transmission signal into a digital signal, and transmitting it optically. SOLUTION: The outer side of a transparent material 16 such as glass or the like is plated 17 so as to exclude the input part and the output part of light, a reflecting mirror is formed, and a light conductor 11 for signal transmission is formed. Then, a light-emitting device 13 is installed at the outside of the light conductor 11, light is made to enter the light conductor 11, the light is multiple-reflected at the inside, and the light is detected by a light-receiving device 14 for an output part. In addition, the light conductor 11 is of an airtight structure, and its shape is preferably a ring shape. In this case, in order to transmit many probe signals by one transmission line, the frequency band of the probe signals is lowered, and an analog signal is converted into a digital signal so as to be transmitted. Then, a light-emitting diode, a laser diode or the like is used as the light-emitting device 13, and a phototransistor, a photodiode or the like is used as the light-receiving device 14. Thereby, the signal can be transmitted with high reliability, and the performance of a flaw detection can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary probe type flaw detector for detecting magnetic flux leakage, eddy current flaw detection, and the like for detecting surface flaws on metal rods, metal pipes, and the like, particularly surface flaws on steel bars and steel pipes. About.

[0002]

2. Description of the Related Art Eddy current flaw detection is a non-destructive inspection method in which an eddy current is generated in a material to be inspected by passing an alternating current through a coil, and the eddy current disturbed by a flaw or the like is detected as a change in impedance of the coil. Leakage magnetic flux inspection is a nondestructive inspection method in which a DC or AC magnetic field is applied to a material to be inspected to magnetize the material and a magnetic field leaking from the wound is detected by a magnetic sensor.

In any of the methods, in order to inspect a minute flaw, a coil or a magnetic sensor (hereinafter, collectively referred to as a probe) is miniaturized in order to detect a change in an eddy current or a leakage magnetic field in a minute area. There is a tendency for the inspection range of one probe to be narrow. For this reason, in order to efficiently inspect the entire surface of the material to be inspected, it is necessary to scan a plurality of probes at high speed along the material to be inspected.

As one of the scanning methods, a plurality of probes are rotated around a straight-moving axis along a material while moving the material to be inspected in the form of a rod, particularly a round bar or a tube, so that the surface of the material to be inspected is formed in a spiral shape. There is a method called a probe rotation method for performing scanning. This method is widely used for flaw detection lines where flaw detection speed and flaw detection precision are required, because even when the straight traveling speed of the material to be inspected increases, the entire surface of the material to be inspected can be inspected by rotating the probe at a high speed. I have. A flaw detector using this scanning method is called a probe rotary flaw detector.

In the probe rotating type flaw detector, signals from a plurality of probes attached to a rotor rotating at a high speed need to be taken out of the rotor. As a device for extracting a signal from the rotor, there are a contact type slip ring and a non-contact type rotary transformer. In the case of a slip ring, a contact transformer jumps during high-speed rotation or requires maintenance due to wear. Therefore, in most cases, a rotary transformer is used.

FIG. 9 is a schematic sectional view of a rotary transformer used for extracting a signal from a rotor. The rotary transformer has a structure having a pair of concentric coils 71 having a rotation axis as a central axis and a magnetic core made of ferrite 72. The electric signal is converted to a magnetic field by a coil attached to the rotor, and the magnetic field is converted to an electric signal by the coil attached to the stator, so that the signal is transmitted.

The feature of the rotary transformer is that it has a simple structure and is non-contact, so that it can be applied to high-speed rotation.

In recent years, an air-core rotary transformer has been proposed as an apparatus that avoids the difficulty of manufacturing a rotary transformer using the ferrite and solves the problem of signal waveform distortion due to the non-linear magnetic characteristics of the ferrite ( Mizuno et al .: Iron and Steel, 74 (1988), p. This air core rotary transformer has a simple structure in which a coil is wound around a resin plate, and is easy to manufacture and inexpensive. Furthermore, it has the feature of not generating waveform distortion because it does not use ferrite, and has sufficient performance as a rotary transformer of an eddy current flaw detector.

The above-mentioned rotary transformer and air-core rotary transformer are non-contact and therefore can be applied to high-speed rotation.
Increase in the number of probes (hereinafter referred to as "multi-channel")
The following problems can be raised in the application to the system.

A) In the case of a rotary transformer In a rotary transformer using ferrite, in order to transmit a multi-channel signal, a coil wound around a plurality of grooves is applied. In order to reduce the distance, it is necessary to provide a certain interval between the coils. As a result, when a plurality of coils are arranged, the diameter of the rotary transformer increases. The ferrite that forms the rotary transformer is manufactured by sintering, but large ones are difficult to homogenize,
Problems with ferrite quality. If the ferrite is inhomogeneous, the transmission efficiency fluctuates due to the fluctuation of the air gap during rotation, causing noise. The specific gravity of ferrite is 4.
Since it is as large as 95, there is a problem of vibration during rotation. Furthermore, it takes a long time to manufacture ferrites having a large diameter, so that it becomes very expensive, which causes a great increase in the price of the entire apparatus. For the above reasons, it is difficult to increase the number of channels by using a rotary transformer using ferrite.

B) Air-core rotary transformer When an air-core rotary transformer is used, since a closed magnetic path is not formed unlike a rotary transformer using ferrite, leakage magnetic flux is large in principle. Therefore, in order to reduce the influence between adjacent coils, it is necessary to install a magnetic shield coil between adjacent coils. Therefore, the distance in the radial direction of the rotary transformer required for one signal transmission is larger than that using a ferrite, which is not suitable for multi-channel.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rotary probe type flaw detector equipped with a compact signal transmission device capable of easily increasing the number of channels, and a method thereof.

[0013]

The present inventor paid attention to the following items in order to achieve the above-mentioned object.

A transmission method using optical transmission is used instead of signal transmission based on magnetic flux change using a rotary transformer.

FIG. 1 is a schematic cross-sectional view of a rotary probe type flaw detector of the present invention when transmission by an optical signal is in one direction. This figure shows a case where a signal is transmitted from the rotor side to the stator side.
Introduced in 1. The light guide is provided with a portion without plating in a circumferential shape, and the light emitting device 13 is installed at a position facing the circumferential portion without plating. The emitter can always send a certain amount of light into the light guide from this position, even when the probe is rotating. The outside of the light guide is coated with plating 17 so that light does not leak to the outside of the ring except for the light introduction part and the output part and is reflected inside, and light from the light emitter is reflected inside the light guide. To propagate. By installing the light receiver 14 at a position opposite to the stator output side of the light guide,
It is possible to receive a part of the light reflected and emitted in the light guide.

FIG. 2 is a schematic cross-sectional view of the rotary probe type flaw detector of the present invention when signal transmission by light is bidirectional. This figure shows a case in which a light emitter and a light receiver are attached to a rotor and a stator, and signals are transmitted bidirectionally. The transmission method is as described above.

The signal is converted into a digital signal. The digital signal does not suffer from deterioration due to transmission, and a plurality of probe signals can be transmitted in a time-division manner, so that only a single signal path is required. Therefore, it is possible to avoid an increase in size due to the increase in the number of channels as in the case of using a rotary transformer. Further, by using digital transmission, signal fluctuation due to mechanical vibration of the rotating unit can be suppressed.

Therefore, digitization of a signal has great utility in digitization itself, and can be used not only for optical transmission but also for a conventional rotary transformer.

If the analog value of the probe signal is simply digitized and transmitted, the signal (oscillation frequency) applied to the probe is as high as several tens of kHz to 1 MHz.
A high signal bandwidth is required. In order to avoid this, a low signal band (処理 10 kHz) after detecting the probe signal
z). In addition, an electronic circuit including a CPU is mounted on the rotor for time-division transmission processing of a plurality of probe signals. Hereinafter, the “electric component” refers to an oscillator, an electronic circuit, or the like provided in these rotors.

If a generator is provided as a power supply source for these electrical components, the problem of the power supply path, particularly the contact point to the rotor, is eliminated.

The present invention has been completed by repeating tests based on the above matters, and has the following gist of a rotary probe type flaw detector (see FIGS. 1 and 2).

(1) A flaw detector comprising a rotor and a stator including a flaw detection probe, wherein the rotor has a light emitter and a stator and a light receiver, or the rotor has a light receiver and a stator and a light emitter or a rotary. A probe rotary flaw detection device that includes a light emitter and a light receiver on a stator, a light receiver and a light emitter on a stator, and a light guide for guiding light from the light emitter to the light receiver on one or both of the stator and the rotor ( [Invention 1]).

(2) A method in which a rotor including a flaw detection probe is rotated along a surface of a bar-shaped inspection material to detect a flaw, wherein signals between the rotor and the stator are transmitted and received by optical transmission. Probe type flaw detection method (referred to as [Invention 2]).

(3) A flaw detection device including a rotor and a stator including a flaw detection probe, wherein the rotator includes an AD converter and a signal processor (referred to as [invention 3]).

(4) A flaw detection apparatus provided with a rotor and a stator including a flaw detection probe, wherein the rotor and the stator constitute a generator, and a probe rotary type for supplying electric power to electric components provided in the rotor. Flaw detector (referred to as [Invention 4]).

[Invention 1] includes not only one-way optical transmission from the rotor side but also two-way optical transmission in which optical signals are exchanged with the stator. The signal includes a probe signal from the rotor side, a control signal for the probe from the stator side, and the like. The probe signal may be a single probe signal or a multi-channel probe signal.
Throughout [Invention 1] to [Invention 4], the term "flaw detection probe" refers to one or a plurality of flaw detection probes.

Even when bidirectional transmission is performed, one light guide may be used, or two light guides may be used as shown in FIG.

The term "bar-shaped material to be inspected" refers to a bar-shaped material, which is a material to be inspected, having a cross section perpendicular to the straight traveling direction or a circle or a shape similar thereto.

The AD converter according to the second aspect of the invention converts the analog signal of the flaw detection probe into a digital signal, and is applicable not only to optical transmission but also to signal transmission using a conventional rotary transformer. Similarly, the probe rotary flaw detector according to [Invention 3] is applicable not only to a device having an optical waveguide in a signal transmission unit but also to a device which transmits a signal by a conventional rotary transformer.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the reasons for limiting the present invention will be described.

1. Apparatus and method provided with optical transmission section (in the case of [Invention 1] and [Invention 2]) The optical conductor 11 is used as a signal transmission component. This is a reflection mirror in which plating 17 is partially applied to the outside of a transparent material 16 such as glass or transparent acryl except for a light introduction part and an output part. Plating is usually performed by vapor deposition or chemical treatment of aluminum or the like. A light emitting device is installed outside the light guide, light is introduced into the light guide, the light is caused to travel by multiple internal reflection, and the light is output from the output unit to the outside of the light guide and detected by the light receiver. The shape of the light guide is preferably a ring shape. The ring-shaped light guide is called a light guide ring.

If dust or the like adheres to the light guide, a sufficient signal intensity may not be obtained in some cases. Therefore, it is desirable to adopt a sealed structure that can prevent the dust from adhering. The use of the sealed structure makes it possible to prevent disturbance light from entering. However, it is necessary that the rotating part rotates smoothly even in a closed structure.

When the signal speed is low, a light emitting diode or the like can be used as the light emitting device. When a high speed is required, a laser diode may be used. In addition, a phototransistor can be used as a light receiving device if the speed is low, and a photodiode or a photo diode is required if high speed is required.
A photomultiplier or the like may be used.

Although only one light-emitting device and one light-receiving device may be used, a plurality of light-emitting devices and light-receiving devices should be installed outside the light guide for stable transmission in consideration of a decrease in output when the light-emitting device and the light-receiving device are separated. Is desirable. It is preferable that these elements are further arranged at equal intervals in order to secure a balance during rotation.

When bidirectional transmission is performed, light emitted from the light emitter on the rotor side passes through the light guide and is received not only by the light receiver on the stator side but also multiple reflections inside the light guide on the rotor side. The light is also received by the photodetector on the rotor side.

Such a signal collision can be determined by determining the transmission direction according to the transmission time zone or incorporating information for distinguishing between transmission from the stator side and transmission from the rotor side into the transmission contents. Can be avoided.

In addition to the above-mentioned method, as a method for avoiding the physical superposition of the signals, the light wavelength of the light emitting element is made different between the stator side and the rotor side, What is necessary is just to apply a filter to the light receiver attached to the child to cut off the wavelength from the light emitter attached to the same side.

The transmission speed depends on the responsiveness of the light emitting device and the light receiving device. When a light emitting diode capable of high-speed response is used, signal transmission of about 30 MHz is possible. As information to be transmitted, analog transfer or digital transfer using a change in light intensity can be considered, but digitization is simpler because gap adjustment between light guide rings is not required. However, to transmit a digital signal, it is necessary to digitize the signal in advance as described below.

2. Digitization of Signals (In the case of [Invention 3]) In order to transmit a large number of probe signals through one transmission line, signals of a large number of probes may be transmitted in a time-division manner. Although this method can directly transmit a raw signal of a probe signal in a time-division manner, it is not practical because a frequency band to be handled becomes high. Therefore, after detecting the probe signal and lowering the frequency band, the computer may convert the analog signal into a digital signal, convert the signal into a series of signals including probe number information, and transmit the signal. As these detectors and signal processors, those generally used can be used.

As described above, the rotator provided with the electrical component for digitizing the probe signal may be applied not only to optical transmission but also to a device using a conventional rotary transformer.

3. Power supply by generator (in the case of [Invention 4]) In order to digitize the signal from the probe, it is necessary to incorporate electric components in the rotor. Power supply is required for the electrical components. As described above, when a slip ring is used for a contact portion with the rotor, when the rotation speed is increased, the contact jumps and cannot be applied. Therefore,
A generator is built in the rotor as a means for supplying electric power to the electrical components. Although various types of generators are conceivable, it is generally appropriate to use an electromagnetic induction type generator.

FIG. 3 is a schematic cross-sectional view illustrating an electromagnetic induction type generator. The rotor has a magnetic pole and a coil, and the stator has a permanent magnet and a magnetic pole. The rotor rotates to generate an electromotive force in the coil. This electromotive force becomes an AC voltage that is four times the number of revolutions, so it is rectified, adjusted to a constant voltage, and then supplied to electrical components.

FIG. 4 schematically shows a device for keeping the voltage of the electric power from the generator constant. As these devices and the like, those commonly used can be used.

Such a generator supplies power not only to electrical components for digitizing a signal by optical transmission but also to electrical components of a rotor for digitizing a signal in a conventional transmission type device using a rotary transformer. May be used.

[0045]

Next, an embodiment in which the present invention is applied to a multi-channel rotary probe type eddy current flaw detector using eight probes will be described.

FIGS. 5 and 6 are schematic sectional views showing the outline of the apparatus. The main configuration of the device includes a probe 44 and electrical components 45 (oscillator 6
1), a generator 46 (including the permanent magnet 21 and the like) and a part of the light guide ring 11. There is a rotation driving motor 41, a rotation transmission pulley, and a belt 42 for driving these together. On the stator side, one of the light guide rings 11 and a flaw detection controller 47 for processing a signal obtained therefrom are incorporated.

FIG. 7 shows the configuration of the present apparatus from the probe to the signal display.

FIG. 8 is a diagram for explaining the contents of signals. Next, the flow of signals will be described with reference to FIGS. 7 and 8, focusing on signal conversion.

<Rotor side> An AC voltage having a frequency of 8 to 1024 kHz is generated by an oscillator mounted on the rotor.
An electric current was applied to each of the probes 1 to 8 of the probe 44. Since each probe output has the frequency component of the oscillator 51 added as a carrier wave, it is sent to the numbers 1 to 8 of the detectors 52 corresponding to the probes of numbers 1 to 8 in order to remove the carrier signal. The detector needs a reference wave (oscillation wave) for detection.
Sent from. The detector 52 multiplies the probe signal by the reference signal in order to simplify the configuration of the device, and
The configuration is such that integration is performed by a low-pass filter of Hz. Since the frequency of 10 kHz is merely adapted to the signal component to be extracted, it may be other than 10 kHz. The outputs of the detector numbers 1 to 8 become flaw detection signals and are sequentially sent to the AD converter 54 by the switch 53. The speed required for AD conversion requires a conversion speed of 8 × 10 kHz = 80 kHz or more because eight flaw detection signals are handled in a frequency band of 10 kHz. , A converter having a conversion speed of about 400 kHz was selected, and the switching speed of the switch was set to 100 kHz. The conversion resolution was 12 bits (4096 division). Here, “speed” refers to the number of times that the operation can be repeated in one second, that is, the frequency.

The output value of No. 1 of the detector 52 after the AD conversion is sent to No. 1 of the signal processor 55 and converted into a 1-bit serial signal. This serial signal is composed of a probe number of 3 bits (= 8), an AD conversion value of 12 bits, and a spare 1 bit of 16 bits, and a total of 18 bits of 2 bits indicating the start and end of communication. . Therefore, since 18 bits are transmitted at a speed of 100 kHz, the transfer frequency per bit is 1.8 MHz. Therefore, the carrier frequency needs to be 1.8 MHz or more, but here, 3 MHz is set to allow a margin.

The converted serial signal is supplied to the light emission controller 12
To drive the light emitting device 13. As the light emitting device 13, a laser diode having a fast rising and falling light emission speed was used in order to secure a transport speed of 3 MHz.

A power generator 46 utilizing the rotational energy of the rotor was used to supply power to the above electrical components. Voltage regulator 5 to make the AC voltage of the generator constant
9 (rectifier 32, constant voltage regulator 33), the output was converted to the voltages ± 15 V and 5 V required by the electrical component 45 (such as the oscillator 51).

<Stator Side> Next, the stator side will be described. The light reflected and propagated in the light guide ring 11 is detected by the light receiver 14. A photomultiplexer was used for the light receiving device in order to ensure a sufficient response.

The output of the photodetector 14 is sent to the photodetector amplifier 15 and is level-amplified and binarized (for example, 0 level 0.6 V or less, 1 level 2.8 V or more). Then, this binarized signal is sent to the signal processor 56. The serial signal data sent here is decoded into a probe number and a flaw detection signal value. When the decoding is completed, the data is sent to the DA converter 57 of the number corresponding to each probe number and becomes an analog value. Then, the data is sent to the flaw detector and the display 58, and the presence or absence of a flaw is displayed and used for the subsequent processing.

<Light Guide Ring> In this embodiment, a one-way signal is transmitted from the rotor to the stator.

As shown in FIG. 6, the light guide ring has an outer diameter of 10 mm.
It is made of acrylic resin having a diameter of 0 mm and an inner diameter of 80 mm, and is aluminum-plated except for a surface where the light guide rings face each other and a portion where the light emitting device and the light receiving device are attached. It goes without saying that the materials of the light guide ring and the plating are not limited to those described above. The two light guide rings were configured to rotate with a gap of 1 mm. The periphery of the light guide ring was hermetically sealed so that dust and the like did not adhere to the surface of the light guide ring.

According to the above configuration, signals from a plurality of probes can be transmitted by a compact device such as a single optical transmission line, which is easier to adjust than conventional rotary transformers, and enables stable signal transmission. It has become possible.

[0058]

According to the present invention, highly reliable signal transmission becomes possible, and the flaw detection performance is improved. As a result, it is possible to improve product quality and yield.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of one-way optical transmission using a light guide.

FIG. 2 is an explanatory diagram of bidirectional optical transmission using a light guide.

FIG. 3 is a schematic cross-sectional view of a generator.

FIG. 4 is a schematic diagram of an apparatus for controlling a power generation output to a constant voltage.

FIG. 5 is a longitudinal sectional view of a rotary probe type flaw detector of the present invention used in Examples.

FIG. 6 is a schematic longitudinal sectional view of a rotation mechanism of the probe rotary flaw detector used in the example.

FIG. 7 is a configuration diagram of an apparatus relating to signals from a probe to a signal display.

FIG. 8 is an explanatory diagram of signal contents.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Light guide (light guide ring) 12 ... Light emission controller 13 ... Light emitting device 14 ... Light receiver 15 ... Light receiving amplifier 16 ... Transparent material 17 ... Plating 18 ... Signal 21 ... Permanent magnet 22 ... Magnetic pole 23 ... Rotating body magnetic pole 31 ... Electric power generation Machine 32 ... Rectifier 33 ... Constant voltage regulator 41 ... Rotation drive motor 42 ... Rotation transmission pulley, belt 43 ... Material to be inspected 44 ... Probe 45 ... Electrical components (such as the oscillator 51) 46 ... Generator (such as the permanent magnet 21) 47 ... flaw detection controller 51 ... oscillator 52 ... detector 53 ... switch 54 ... AD converter 55 ... rotor side signal processor 56 ... stator side signal processor 57 ... DA converter 58 ... flaw detector, display 59: voltage regulator (rectifier 32, constant voltage device 33) 61: flaw detection signal 62: output signal of AD converter 63: output of signal processor on stator side 64: contents of output of probe number 1 71 ... coils 72 ... ferrite

[Procedure amendment]

[Submission date] February 21, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Fig. 9

[Correction method] Added

[Correction contents]

FIG. 9 is a schematic sectional view of a conventional rotary transformer.

Claims (4)

[Claims] 1. A flaw detector comprising a rotor and a stator including a flaw detection probe, wherein the rotor has a light emitter and a stator and a light receiver, or the rotor has a light receiver and a stator and a light emitter or a rotor. A light emitting device, a light receiving device, a light receiving device and a light emitting device on a stator, and a light guide for guiding light from the light emitting device to the light receiving device on one or both of the stator and the rotor. Type flaw detector. 2. A method for detecting a flaw by rotating a rotor including a flaw detection probe along a surface of a rod-shaped material to be inspected, wherein signals between the rotor and the stator are transmitted and received by optical transmission. A rotary probe type flaw detection method, characterized in that: 3. A flaw detection apparatus including a rotor including a flaw detection probe and a stator, wherein the rotator includes an AD converter and a signal processor. 4. A flaw detector comprising a rotor and a stator including a flaw detection probe, wherein the rotor and the stator constitute a generator, and supply power to electrical components provided in the rotor. Probe rotating type flaw detector.