JP2002039965A - Method for detecting break of steel strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable and highly accurate method for detecting breaks of steel strips by surely detecting breaks of steel strips irrespective of materials of the steel strips. SOLUTION: Two electrodes 13 and 14 are set on the steel strip 11. Pseudo random signals are propagated between the electrodes. Transmission signals and reception signals are correlated. The break of the steel strip is detected from a change of a correlation waveform. Even when original reception signals cannot be distinguished due to pseudo random signals propagating a path other than inside the steel strip 11, the presence/absence of the break in the steel strip 11 is detected by obtaining a difference from the measured result of a steel strip without breaks.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a break in a steel strip, and more particularly to a technique for detecting a break in a steel strip in a manufacturing process of a lined steel material.

[0002]

2. Description of the Related Art Conventionally, as a method for detecting breakage of a steel strip, a method of detecting a breakage from an abnormal tension of a steel strip as disclosed in Japanese Patent Application Laid-Open No. 7-109919 has been widely known. A method and an apparatus for detecting breakage of a steel strip described in the above publication will be described with reference to FIG. FIG. 13 is a schematic configuration diagram of a steel strip breakage detection device.

[0003] As shown in the figure, a steel strip rupture detecting device 50 is provided.
Is provided with a pay-off reel 52 for winding one end of a steel strip 51, a photoelectric switch 53 for detecting the presence or absence of the steel strip 51, a continuous processing facility 54 for processing the steel strip 51, A tension meter 55 for measuring the tension of the strip 51, a bridle roll 56a for applying tension to the steel strip 51,
56b. A drive motor 57 is connected to the payoff reel 52, and a motor drive control device 58 is connected to the drive motor 57. A tension control device 59 is connected to the motor drive control device 58, and the actual tension Tm and the tension command value Tref measured by the tension meter 55 are input to the tension control device 59, and the actual tension Tm
The tension control device 59 sends a control signal output based on the difference between the tension command value Tref and the tension command value Tref to the motor drive control device 58 so that the tension of the steel strip 51 is kept constant. Further, the bridle rolls 56a and 56b are also provided with drive motors 60a and 6b.
0b are connected to each other, and a motor drive control device 61 is connected to the drive motors 60a and 60b. A speed control device 62 is connected to the motor drive control device 61, and the actual speed Vm and the speed command value Vref measured by a pulse oscillator 63 attached to the drive motor 60b are input to the speed control device 62. Then, the speed controller 62 sends a control signal based on these deviations to the motor drive controller 61, so that the transport speed of the steel strip 51 is kept constant. Then, the actual tension Tm measured by the tension meter 55, the signal from the photoelectric switch 53, and the tension command value Vr
ef is input to the arithmetic processing unit 64, and the arithmetic processing unit 64 detects whether or not the steel strip 51 is broken based on these values.

A method of detecting a steel strip break by the steel strip break detection device will be described. First, a signal indicating the presence or absence of light transmission from the photoelectric switch 53 is sent to the arithmetic processing unit 64 and the steel strip 5
1 is detected. If the photoelectric switch 53 outputs an off signal without transmitting light, it is determined that “steel strip is present” and it is recognized that the steel strip 51 is not broken. Conversely, the photoelectric switch 53
When it transmits light and outputs an ON signal, it is determined that there is no steel strip. In this case, the arithmetic processing unit 64 determines the magnitude of the tension lower limit value α · Tref of the steel strip 51 calculated based on a preset constant α (<1.0) and the tension command value Tref, and the actual tension value Tm. The comparison of the relationship is performed. And as a result,
When the actual tension value Tm decreases and the relationship of Tm ≦ α · Tref is reached, it is recognized that a break has occurred in the steel strip 51, and a steel strip break alarm signal is output.

However, according to the above-mentioned method, since the fracture is detected by applying tension to the steel strip, when the material is very brittle and cannot withstand a slight tension, almost no tension is applied. There is a problem that it is difficult to detect the breakage of the steel strip because it cannot be applied.

[0006] In addition to the method of detecting breakage from abnormal steel strip tension as described above, a steel strip breakage detecting method and apparatus for electrically detecting breakage is disclosed in, for example, Japanese Patent Application Laid-Open No. 3-287.
No. 058 and JP-A-3-287059.

A method and an apparatus for detecting breakage of a steel strip described in the above publication will be described with reference to FIGS. 14 (a) and 14 (b). FIG. 14A is a schematic configuration diagram of a steel strip breakage detection device in an apparatus for electroplating a steel strip,
(B) is an equivalent circuit of FIG. As shown
In the steel strip breakage detecting device 70, a dam roll 73 is provided at the entrance and exit of a plating tank 72 for electroplating the steel strip 71, and conductor rolls 74 are provided before and after the dam roll 73. The steel strip 71 is conveyed through these rolls under a certain tension. An anode 75 is provided in the plating tank 72 as means for detecting the breakage of the steel strip 71, and a rectifier 76 for supplying a voltage is connected to the anode 75. Further, the other terminal of the rectifier 76 is connected to the conductor roll 74, a voltmeter 77 is connected between the anode 75 and the conductor roll 74, and an ammeter 78 is connected between the rectifier 76 and the anode 75, respectively. In the equivalent circuit of FIG. 14B, R ₁ is a circuit resistance, R ₀ is a plating resistance, and R
Is the resistance of the steel strip 71. The outputs of the voltmeter 77 and the ammeter 78 are respectively input to comparators (not shown). Normally, a set voltage and a set current to be supplied to the steel strip 71 are input to the comparator, and the measured values of the current and the voltage are compared with the set values. Then, the comparison result is input to a judgment circuit, and the output of the judgment circuit is input to a break recognition relay.

The plating current flowing when the voltage is supplied from the rectifier 76 passes through the plating solution from the anode 75 and enters the steel strip 71, and then returns from the conductor roll 74 to the rectifier 76. The plating voltage is measured as a potential difference between both ends of the plating resistance R ₀ and the steel strip resistance R. When the steel strip 71 breaks, the resistance R increases infinitely. At this time, the plating current becomes infinitely small, and the plating voltage increases to the rated voltage of the rectifier 76 in an attempt to secure a predetermined plating current.
Thus, the breakage of the steel strip 71 can be detected by the decrease in the plating current and the increase in the plating voltage.

However, in this method, since the breakage of the steel strip is electrically detected, if a grounded metal portion exists in the production line and it is in contact with the steel strip, However, there is a problem that a signal propagated through the metal portion is generated, and the reliability of detection of breakage of the steel strip is extremely reduced.

[0010]

As described above, in the conventional method for detecting the breakage of a steel strip by detecting the breakage of the steel strip due to abnormal tension in the steel strip, the material is very brittle and cannot withstand even a slight tension. In the case of such a steel type, there is a problem that it is difficult to detect breakage of the steel strip because almost no tension can be applied.

Further, in the method of electrically detecting the breakage of the steel strip, in the case where there is an electrically grounded metal part in the production line and it is in contact with the steel strip,
A signal that propagates through this metal part is generated,
There has been a problem that the reliability of detection of breakage of a steel strip is extremely reduced.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a reliable and highly accurate steel strip by reliably detecting breakage of the steel strip regardless of the material of the steel strip. An object of the present invention is to provide a fracture detection method.

[0013]

According to a first aspect of the present invention, there is provided a method for detecting breakage of a steel strip, which changes with time between any two points of a steel strip passed through a production line. A first step of transmitting a signal, and a second step of detecting breakage of the steel strip based on a change in a waveform on a time axis of the signal propagated in the steel strip. Features.

According to a second aspect of the present invention, in the method for detecting breakage of a steel strip according to the first aspect, the signal is a pulse-like or sinusoidal electric signal.

According to a third aspect of the present invention, in the method for detecting breakage of a steel strip according to the first aspect, the signal is an ultrasonic signal.

Further, in the fracture detecting method according to a fourth aspect of the present invention, a first step of transmitting a pseudo-random signal between any two points of a steel strip passed in a production line; A second step of performing a correlation process between the reception signal and the transmission signal of the pseudo-random signal, and a change in the correlation waveform on the time axis obtained by the correlation process in the second step, And a third step of detecting breakage.

According to the method for detecting breakage of a steel strip, a signal is propagated between two points on the steel strip. When the steel strip breaks between the two points, the signal cannot pass through the steel strip, so that the waveform of the received signal changes as compared with the transmission signal. The break of the steel strip can be detected from the change in the waveform. In addition, in detecting the break of a steel strip, it is not determined by applying a physical force to the steel strip, but by the presence or absence of signal transmission between two points. Can be detected. Note that a pulse-like or sine-wave-like electric signal or an ultrasonic signal can be used as a signal to be propagated to the steel strip.

Further, according to the method for detecting breakage of a steel strip, a pseudo random signal is propagated between two points on the steel strip. Then, correlation processing between the transmission signal and the reception signal of the pseudo random signal is performed. Therefore, it is possible to stably detect a received signal having a good S / N ratio by suppressing a noise component. Also, by using a pseudo-random signal, sufficient power can be provided during one cycle, so that a received signal can be detected even when signal attenuation is large. Then, the signal subjected to the correlation processing is observed by a recording and display device, and the break of the steel strip can be reliably detected by a change in the correlation waveform near the time when the break of the steel strip occurs. Performance and accuracy can be improved. In addition, the detection of steel strip breakage is not performed by applying a physical force to the steel strip, but by transmitting a pseudo-random signal between two points. Breakage can be detected.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. For this explanation,
Common parts are denoted by common reference symbols.

A method for detecting breakage of a steel strip according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a conceptual configuration diagram of a steel strip breakage detection device. As shown in the drawing, a steel strip rupture detecting device 10 includes an oscillator 15 that generates an electric signal to flow through the steel strip 11 on the transport roller 12, and a steel strip 11 to flow the electric signal generated by the oscillator 15 to the steel strip 11.
In order to receive an electric signal propagating in the steel strip 11 from the electrode 13 provided to be in contact with the upper side, the electrode 13,
Electrode 1 also provided on steel strip 11 to be in contact
4, a recording and display device 17 that receives the electric signal received by the electrode 14 and displays the waveform thereof.

Next, the operation of the steel strip rupture detecting device 10 will be described. First, the oscillator 15 outputs a time-varying electric signal such as a pulse wave or a sine wave. This electric signal is placed on the transport roller 12 from the electrode 13,
The electric signal introduced into the steel strip 11 being conveyed and propagated inside the steel strip 11 is received by the electrode 14. The electric signal received by the electrode 14 is sent to the recording and display device 17 to record and display the waveform.

FIG. 2 shows the flow of the steel strip rupture detection processing after the record display device 17. First, the received signal is input to the recording and display device 17 (step S10), and based on the received signal, the recording and display device 17 displays the waveform of the received signal (step S10).
11). Then, a change in the waveform of the received signal is observed (step S12). If a change in the waveform of the received signal with respect to the transmitted signal is observed, it is determined that the steel strip 11 is broken (step S13). If not, it is determined that it has not broken (step S13 '). This is electrode 1
If the steel strip 11 is broken between 3 and 14, the electric signal cannot pass through the steel strip 11 and the waveform of the received signal changes.

The higher the frequency of the electric signal generated by the oscillator 15 is, the shorter the wavelength is and the time resolution is improved. However, when a high-frequency signal of about several GHz flows through a metal, the signal becomes a surface wave and the It propagates in the air, not in the zone. Conversely, if the frequency is low (less than 1 MHz), sufficient time resolution cannot be obtained. Therefore, depending on the type of steel strip, 1M
It is preferable to use an electric signal in a frequency band of not less than 1 Hz and less than 1 GHz.

According to the method for detecting the breakage of the steel strip, the steel strip 1
Electrodes 13 and 14 are provided at two points on
An electric signal is propagated between the four. If the steel strip 11 is broken between the electrodes 13 and 14, the electric signal cannot pass through the steel strip 11, and the waveform of the received signal changes as compared with the transmission signal. The break of the steel strip 11 can be reliably detected from the change in the waveform. In addition, when a break is detected, no physical force is applied to the steel strip, so that a break can be reliably detected even in a steel strip of a very brittle material.

Next, a method for detecting breakage of a steel strip according to a second embodiment of the present invention will be described. FIG. 3 is a conceptual configuration diagram of a steel strip breakage detection device. As shown in the drawing, the steel strip breakage detecting device 10 has a configuration in which the signal processing device 16 is provided between the electrode 14 and the recording and displaying device 17 in the configuration described in the first embodiment. The signal processing device 16
, The output from the oscillator 15 is also directly input.

Next, the operation of the above-described steel strip fracture detecting device 10 will be described. First, the oscillator 15 outputs a pseudo random signal. The electric signal is introduced from the electrode 13 into the steel strip 11 placed and conveyed on the conveying roller 12 and also input as a reference signal to the signal processing device 17. Then, the electric signal introduced from the electrode 13 into the steel strip 11 and propagated inside the steel strip 11 is received by the electrode 14. The electric signal received at the electrode 14 is converted into a signal
And a correlation process with the reference signal is performed. The result of this correlation processing is output to the recording and display device 17, and the correlation waveform is recorded and displayed.

FIG. 4 shows the flow of the steel strip break detection processing after the signal processing device 16. F (t) for the received signal and g for the reference signal
Assuming (t), first, these two signals are input to the signal processing device 16 (step S20). Next, the signal processing device 16 performs a correlation process based on f (t) and g (t) (step S21). This correlation processing is performed by the following equation.

[0028]

(Equation 1)

Here, Φ (τ) is the correlation at time τ, and T is the time for one period of the pseudo random signal. Received signal f
(t) is a signal in which noise is superimposed on the pseudo random signal transmitted and propagated from the electrode 13. Therefore, the received signal f (t) to be subjected to the correlation process is considered separately into a pseudo random signal component and a noise component. First, since there is no correlation between the pseudo random signal used as the reference signal g (t) and the noise component, the correlation result of the noise component is zero. On the other hand, the correlation between the pseudo-random signal included in the received signal f (t) and the reference signal g (t) is an autocorrelation function of the pseudo-random signal. Assuming that a path length passing through the inside of the steel strip 11 is L ₁ and a propagation speed of a signal in the steel strip 11 is v ₁ , a time t ₁ corresponding to the path length is:

[0030]

(Equation 2)

Is as follows. From Equation ₁ , it can be seen that at this time t1, the correlation waveform has a pulse-shaped peak. Therefore, it is possible to discriminate the noise signal from other noise signals.

Then, the recording and display device 17 displays the waveform of the correlation signal obtained by the correlation processing (step S2).
2). Then to observe the change in the waveform of the correlation signal at the time t ₁ (step S23) by, when a change in the correlation waveform is observed, it is determined that the steel strip 11 is broken (step S24), and changes If there is no, it is determined that there is no break (step S24 ').

When the distance between the electrode 13 and the electrode 14 on the steel strip 11 is very long, if a pulse wave or a sine wave is used for the electric signal propagating in the steel strip 11, the signal is attenuated and the intensity is reduced. In some cases, it may be difficult to detect breakage. However, according to the steel strip rupture detection method as described above, the pseudo-random signal is used as the electric signal, the correlation processing is performed between the transmission signal and the reception signal, and the rupture of the steel strip is detected based on a change in the correlation waveform. ing. Since the pseudo random signal can have sufficient power during one cycle, the received signal can be detected even when the signal attenuation is large. Further, by performing the correlation processing, a noise component can be suppressed, and a received signal having a good S / N ratio can be stably detected. Therefore, the breakage of the steel strip can be reliably detected, and the reliability and accuracy of the method for detecting the breakage of the steel strip can be improved. In addition, when a break is detected, no physical force is applied to the steel strip, so that a break can be reliably detected even in a steel strip of a very brittle material.

Next, a method for detecting breakage of a steel strip according to a third embodiment of the present invention will be described. Since the fracture detecting device for a steel strip according to the present embodiment and its operation are substantially the same as the configuration described in the second embodiment, the description is omitted, and the fracture detecting process after the signal processing device 16 will be described with reference to FIG. explain.

Assuming that the received signal is f (t) and the reference signal is g (t), these two signals are first input to the signal processing device 16 (step S30). Next, the signal processing device 16
Perform correlation processing based on (t) and g (t) (step S3
1). This correlation processing is the same as the processing described in the second embodiment. Then, the recording and display device 17 displays the waveform of the correlation signal obtained by the correlation processing (step S3).
2). Then the correlation waveform is observed whether significant changes in the waveform at the time t ₁ corresponding to the path length is observed (step S
33).

In the steel strip production line, there are many metal parts such as a transport roller, a gantry thereof, and a roller for winding the steel strip into a coil. Steel strip 11
When these are in contact with these metal parts, there are a plurality of paths through which electric signals propagate between the electrodes 13 and 14. In general, the electric signal propagating from the electrode 13 to the electrode 14 has different path lengths when passing through the inside of the steel strip 11 and when passing through other paths, and the correlation waveform corresponds to the path length of each signal transmission path. It will have a peak at the time. That is, the electric signal passing through the inside of the steel strip 11 and the electric signal passing through other paths due to the difference in the path length are:
The correlation waveform can be distinguished by the peak time. However, when the path length of the signal transmission path other than the steel strip 11 is almost the same as the path length of the signal transmission path passing through the inside of the steel strip 11, even if the fracture occurs in the steel strip 11, the correlation waveform corresponding thereto is obtained. In some cases, the change in the magnitude or intensity of the peak does not appear remarkably. This is because the peak (background) of the correlation waveform at the time corresponding to each of the signal transmission path passing through the inside of the steel strip 11 and the other signal transmission paths overlaps.

[0037] Accordingly, recorded beforehand the correlation waveform when generating no breaks, when significant changes in the waveform at time t ₁ is not observed, the signal processing device 16 or the recording display device 17 is correlated at any time Take the difference between the waveforms (step S
34) to remove the background. The recording and display device 17 displays the correlation waveform from which the background has been removed, that is, the amount of change between the two correlation waveforms (step S3).
5), by observing changes in the waveform in the vicinity of the time t ₁ (step S36), determines that the steel band 11 is greater than the predetermined amount the amount of change waveform is predetermined is broken (step S3
7) If it is smaller than the predetermined amount, it is determined that no break has occurred (step S37 '). Note that at time S33, the time t
Also in the case where the change in the peak or the intensity is sufficiently observed in No. ₁ , it is determined that the steel strip 11 is broken (step S37).

According to the above-described method for detecting breakage of a steel strip, even if an original electric signal cannot be detected by an electric signal propagating through a path other than the inside of the steel strip, the steel strip having no breakage can be detected. By taking the difference from the measurement result of
Since the presence or absence of breakage of the steel strip can be reliably detected, the reliability and accuracy of the method for detecting breakage of the steel strip can be improved.

Next, a method for detecting breakage of a steel strip according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 6 is a conceptual configuration diagram of a steel strip breakage detection device. As shown in the drawing, a steel strip breakage detecting device 20 generates an ultrasonic signal to be passed through a steel strip 21 on a transport roller 22 by an ultrasonic oscillator 2.
5. The ultrasonic signal generated by the ultrasonic oscillator 25 is
In order to receive the ultrasonic signal transmitted through the steel strip 21 from the transmission ultrasonic probe 23 provided to be in contact with the steel strip 21 to flow to the steel strip 21, the transmission ultrasonic probe 23. ,
Similarly, a receiving ultrasonic probe 24 provided to be in contact with the steel strip 21, an ultrasonic signal processing device 26 for receiving an ultrasonic signal received by the receiving ultrasonic probe 24, An ultrasonic recording and display device 27 that records and displays the waveform of an ultrasonic signal in response to the output of the processing device 26 is provided.

Next, the operation of the steel strip rupture detecting device 20 will be described. First, the ultrasonic oscillator 25 outputs an ultrasonic signal. This ultrasonic signal is introduced from the transmitting ultrasonic probe 23 into the steel strip 21 placed and conveyed on the conveying roller 22, and the ultrasonic signal propagated inside the steel strip 21 is the receiving ultrasonic wave. It is received by the probe 24. The ultrasonic signal received by the receiving ultrasonic probe 24 is sent to the ultrasonic signal processing device 26, where processing such as frequency decomposition is performed. This processing result is output to the ultrasonic signal recording and display device 27, and the waveform of the ultrasonic signal is recorded and displayed.

The flow of the processing after the signal processing device 26 is exactly the same as that in the first embodiment in which the electric signal is replaced by the ultrasonic signal, and the description is omitted.

As described above, the ultrasonic probes 23, 24 are provided at two points on the steel strip 21, and the ultrasonic probes 23, 24 are provided.
The same effect as in the first embodiment can be obtained by transmitting an ultrasonic signal between them.

When the wavelength of the ultrasonic signal is substantially equal to or shorter than the size of the grain boundary existing in the steel strip, the signal is scattered and attenuated by the grain boundary.
Care must be taken to use frequencies at wavelengths sufficiently longer than the size of the grain boundaries.

[0044]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for detecting breakage of a steel strip according to a first embodiment of the present invention will be described with reference to FIG. FIG. 7 is a conceptual configuration diagram of a steel strip breakage detection device.

As shown in FIG.
Are electrodes 33, 34 provided to contact the steel strip 31 on a transport roller (not shown), an oscillator 35 for generating and outputting an electric signal to be transmitted to the electrode 33, an electric signal received by the electrode 34, and an oscillator. A signal processing device 36 receives an electric signal output from the signal processing device 35, and a recording and display device 37 receives an output from the signal processing device 36.

The electrodes 33 and 34 are of a roller type so as not to hinder the conveyance of the steel strip 31, and an electric signal is supplied via a shoe to a metal roll which is electrically insulated from a metal part in the production line. Is done. The electrodes 33 and 34, the oscillator 35, and the signal processing device 36 are coaxial cables 3 respectively.
8 and 38, the covering of the coaxial cable 38 is used as a ground in order to prevent signal attenuation, and the covering of the coaxial cable 38 on the transmitting side and the receiving side is short-circuited. Further, the oscillator 35 and the signal processing device 36
Are housed in metal boxes, which are electrically grounded. Further, an A / D converter and a personal computer are used for the recording and display device 37. The calculation of the difference between the correlation waveforms is also performed by this computer.

Next, the steel strip rupture detecting device 30 having the above-described structure is used.
The operation of the steel strip and the method of detecting the breakage of the steel strip will be described.

First, an M-sequence signal (pseudo-random signal) with a frequency of 10 MHz output from the oscillator 35 from the electrode 33
Is transmitted to a steel strip 31 that is placed and transported on a transport roller (not shown). This M-sequence signal propagates inside the steel strip 31 and is received by the electrode 34. The signal processing device 3 receives the received signal received by the electrode 34 and a signal output from the oscillator 36 and having the same form and the same phase as the M-sequence signal as a reference signal.
Reference numeral 6 performs a correlation process and the like, and the result is sent to the record display device 37 to perform record display.

Next, FIGS. 8 to 10 show actual measurement examples.
This will be described with reference to FIG. FIG. 8 shows a correlation waveform between a transmission signal and a reception signal in a normal steel strip. As shown
A large peak is observed around t = 0.48 s, and judging from the path length, it can be seen that this peak is a signal passing through the inside of the steel strip 31.

FIG. 9 shows a correlation waveform between the transmission signal and the reception signal in the broken steel strip. However, there is no significant difference between the two even when compared with the correlation waveform before the steel strip breakage in FIG. Therefore, it cannot be determined from the correlation waveforms in FIGS. 8 and 9 whether or not the steel strip has broken.

FIG. 10 shows the difference between the correlation waveforms shown in FIGS. 8 and 9. That is, FIG. 10 corresponds to FIGS.
, And it can be seen that there is a large waveform change between the two as shown.

By taking the difference between the two, it is possible to clearly determine the breakage of the steel strip. Note that a chirp pulse signal or the like may be used as the pseudo random signal in addition to the M-sequence signal.

Next, a method for detecting breakage of a steel strip according to a second embodiment of the present invention will be described. The configuration of the steel strip break detection device is the same as the configuration described in the second embodiment,
The electrodes 33 and 34 are connected to a tire-type ultrasonic probe and the oscillator 3
5 is replaced with an ultrasonic oscillator 35, a signal processing device 36 is replaced with an ultrasonic signal signal processing device, and the recording / display device 37 is replaced with an ultrasonic signal recording / display device.

FIGS. 11 and 12 show the detection results obtained by the steel strip rupture detecting device having the above-described structure. 11 and 1
Reference numeral 2 denotes an ultrasonic signal, which is propagated through a steel strip using a 20 kHz burst wave, and the F of the received signal received by the receiving probe.
FIG. 11 shows waveforms obtained from a steel strip before rupture, and FIG. 12 shows waveforms obtained from a steel strip after FT (Fast Fourier Transmission) processing. As shown in FIG. 11, a signal of 20 kHz was received in the steel strip before breaking, and it can be seen that the ultrasonic signal has propagated in the steel strip. However, after breaking, 2
The signal of 0 kHz was not received, and it can be clearly determined that the steel strip was broken.

In this embodiment, 20 k
Although a burst wave of Hz is used, it is a matter of course that the present invention is not limited to this signal and frequency, and a chirp pulse signal or the like may be used. Further, although the FFT analyzer is used in the ultrasonic signal processing apparatus, an FFT process may be performed on a signal directly taken into a computer by a spectrum analyzer or an A / D converter.

It should be noted that various modifications can be made in each of the above-described embodiments and examples without departing from the gist thereof. The above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed components. For example, even if some components are deleted from all the components shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved and the effects described in the column of the effect of the invention can be solved. Is obtained, a configuration from which this configuration requirement is deleted can be extracted as an invention.

[0057]

As described above, according to the present invention, a high reliability and high accuracy steel strip breakage detection method can be realized by reliably detecting the breakage of the steel strip regardless of the material of the steel strip. Can be provided.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an apparatus configuration of a steel strip break detection device for describing a steel strip break detection method according to a first embodiment of the present invention.

FIG. 2 is a flowchart for explaining a method of detecting breakage of a steel strip according to the first embodiment of the present invention, and is a flowchart of the method of detecting breakage of a steel strip.

FIG. 3 is a conceptual diagram of an apparatus configuration of a steel strip breakage detection device for describing a steel strip breakage detection method according to second and third embodiments of the present invention.

FIG. 4 is a flowchart for explaining a method for detecting breakage of a steel strip according to a second embodiment of the present invention, and is a flowchart of the method for detecting breakage of a steel strip.

FIG. 5 is a flowchart for explaining a method for detecting breakage of a steel strip according to a third embodiment of the present invention.

FIG. 6 is a conceptual diagram of an apparatus configuration of a steel strip rupture detection device for explaining a steel strip rupture detection method according to a fourth embodiment of the present invention.

FIG. 7 is a conceptual diagram of an apparatus configuration of a steel strip break detection device for describing a steel strip break detection device and a steel strip break detection method according to a first embodiment of the present invention.

FIG. 8 is a diagram for explaining a steel strip breakage detecting method according to the first embodiment of the present invention, and shows a correlation waveform between a transmission signal and a reception signal in the steel strip before the breakage.

FIG. 9 is a view for explaining a method for detecting breakage of a steel strip according to the first embodiment of the present invention, and shows a correlation waveform between a transmission signal and a reception signal in the steel strip after the breakage.

FIG. 10 is a diagram for explaining a method for detecting breakage of a steel strip according to the first embodiment of the present invention, and is a waveform showing a difference between correlation waveforms of FIGS. 8 and 9;

FIG. 11 is a view for explaining a method of detecting breakage of a steel strip according to a modification of the second embodiment of the present invention, and shows a waveform of a transmission signal.

FIG. 12 is a view for explaining a method of detecting a break in a steel strip according to a modification of the second embodiment of the present invention, and shows a waveform of a received signal.

FIG. 13 is a conceptual diagram of an apparatus configuration of a steel strip breakage detection device for explaining a conventional steel strip breakage detection method.

FIG. 14 is a conceptual diagram of a device configuration of a steel strip breakage detection device for describing a conventional steel strip breakage detection method.

[Explanation of symbols]

 10, 20, 30, 50, 70 ... Steel strip breakage detection device 11, 21, 31, 51, 71 ... Steel strip 12, 22 ... Transport roller 13, 14, 33, 34 ... Electrode 15, 35 ... Oscillator 16, 36 ... Signal processing device 17, 37 ... Recording display device 23, 24 ... Ultrasonic probe 25 ... Ultrasonic oscillator 26 ... Ultrasonic signal processing device 27 ... Ultrasonic signal recording display device 38 ... Coaxial cable 52 ... Pay-off reel 53 ... Optical switch 54 ... Continuous processing equipment 55 ... Tension meter 56a, 56b ... Bride roll 57, 60a, 60b ... Drive motor 58, 61 ... Motor drive control device 59 ... Tension control device 62 ... Speed control device 63 ... Pulse oscillator 64 arithmetic processing unit 72 plating tank 73 dam roll 74 conductor roll 75 anode 76 rectifier 77 voltmeter 8 ... ammeter

Claims (4)

[Claims] 1. A first method for transmitting a time-varying signal between any two points of a steel strip passed through a production line.
And a second step of detecting breakage of the steel strip based on a change in the waveform on the time axis of the signal that has propagated in the steel strip. Break detection method. 2. The method according to claim 1, wherein the signal is a pulse-like or sine-wave-like electric signal. 3. The method according to claim 1, wherein the signal is an ultrasonic signal. 4. A first step of propagating a pseudo-random signal between any two points of a steel strip passed in a production line, and a correlation process between a reception signal and a transmission signal of the pseudo-random signal. And a third step of detecting breakage of the steel strip based on a change in the correlation waveform on the time axis obtained by the correlation processing in the second step. Characteristic method of detecting steel strip breakage.