JP3098069B2 - Defect detection device in metal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect detecting device for detecting a defect mixed in a metal material.

[0002]

2. Description of the Related Art In a manufacturing process of a copper wire or the like, if a non-magnetic foreign material such as an iron piece is mixed in the copper wire, this causes a disconnection in each drawing process or the like. Therefore, it is necessary to inspect the presence or absence of a magnetic foreign substance before starting each wire drawing step. Conventionally, the following method has been adopted for inspection of this magnetic foreign matter. That is, high speed copper wire 1 in a DC high a magnetic field H _o, as shown in FIG. 3, for example, V = 900
Run at m / mm. Also, along the travel path of the copper wire 1 in the DC high magnetic field H _o, placing the detection coil 2. When the magnetic foreign object 3 in the copper wire 1 is mixed, when the magnetic foreign object 3 passes through the magnetic field H _o, the magnetic flux φ is varied in the detection coil 2, as a result, in the detection coil 2 , The following number 1
Generates an electromotive force represented by.

(Equation 1) Here, in the above, N is the number of turns of the detection coil 2. The detection of the magnetic foreign substance 3 is performed based on the electromotive force generated in the detection coil 2.

A problem in the above-described method for detecting a magnetic foreign matter is noise caused by vibration of the copper wire 1.
That is, when the copper wire 1 in a magnetic field H _o vibrates, eddy current is generated in the copper wire 1, the magnetic flux of the eddy current in the detection coil 2 phi is changed, the noise voltage is generated in the detection coil 2.
Such noise is roughly classified into the following two types.
No. 1 is noise generated by the copper wire 1 oscillating with a relatively long wavelength (hereinafter, referred to as long wavelength noise), and the long wavelength noise is noise of a relatively low frequency.
No. 2 is noise (hereinafter, referred to as traveling wave noise) generated when a traveling wave having a short wavelength is generated in the copper wire 1, and this traveling wave noise becomes relatively high frequency noise.
The frequency components of the two types of noise and the iron piece 3
FIG. 4 shows frequency components of the detection signal generated by the above.
In this figure, the curve A shows the frequency component of the long wavelength noise, and the curve B shows the frequency component of the detection signal. Also,
Actual noise is a complex combination of the above two types of noise. Since these two kinds of noise are detected together with the detection signal, the magnetic foreign matter detection method using one detection coil shown in FIG. 3 has a practically sufficient detection capability, in other words, a satisfactory S / N (signal component to noise). Component ratio) cannot be obtained.

Therefore, conventionally, various configurations have been considered to remove these noises. For example, FIG.
The two detection coils 2 are displaced along the travel path of
a and 2b are arranged, and these detection coils 2a and 2b are differentially coupled. With this configuration, it is possible to remove long-wavelength noise. That is, the copper wire 1 vibrates, and the vibration causes the detection coil 2a to have, for example, the state shown in FIG.
It is assumed that the noise signal shown in FIG. In this case, assuming that the wavelength of the vibration of the copper wire 1 is relatively long, the detection coil 2
As shown in FIG. 6B, a noise signal having the same phase as that of the noise signal generated in the detection coil 2a is generated substantially simultaneously in b. Since these noise signals are differentially coupled to the detection coils 2a and 2b, they are mutually canceled in the detection coils 2a and 2b and are not output to the outside. By adopting such a configuration, it is possible to reduce long-wavelength noise to 1/10 to 1/20 of the case of the configuration in FIG.

However, it is impossible to remove traveling wave noise by the above-mentioned configuration. That is, when a traveling wave having a short wavelength is generated in the copper wire 1, the noise signal generated in each of the detection coils 2a and 2b due to the traveling wave has a phase shift as illustrated in FIGS. 7A and 7B. It will be. Therefore, it is impossible to cancel these noise signals by differential coupling.

In order to solve the above-mentioned problems, the applicant of the present application has filed Japanese Patent Application No. 55-136105 (Japanese Patent Publication No.
No. 864) has come to propose a magnetic foreign matter detection device having the configuration shown in FIG. In this figure, three detection coils 12a, 12b, and 3a are displaced from each other along a traveling path of a copper wire 11 (non-magnetic material) traveling in a DC high magnetic field H.
12c are arranged at equal intervals. Then, the output of the detection coil 12a is sent to the in-phase amplifier 14 of the arithmetic circuit 13.
The output of the detection coil 12b is the inverting amplifier 1 of the arithmetic circuit 13.
5 and the output of the detection coil 12c are supplied to the inverting amplifier 17 of the arithmetic circuit 16 and the in-phase amplifier 18 of the arithmetic circuit 16, respectively. The output of the in-phase amplifier 14 and the output of the inverting amplifier 15 are respectively supplied to an adding circuit 19, and the output of the inverting amplifier 17 and the output of the in-phase amplifier 18 are each supplied to an adding circuit 20. The adding circuit 19 adds the output of the in-phase amplifier 14 and the output of the inverting amplifier 15, and the output is supplied to the adding circuit 33. Addition circuit 2
0 adds the output of the inverting amplifier 17 and the output of the in-phase amplifier 18, and the output is supplied to the adding circuit 33. The addition circuit 33 adds the outputs of the addition circuits 19 and 20, and outputs the addition result to a signal processing circuit (not shown).

In the above configuration, the detection coils 12a,
12b, arithmetic circuit 13 and detection coils 12b, 12
c and the arithmetic circuit 16 each constitute a differential bridge circuit, and it is possible to remove long-wavelength noise by this circuit configuration. That is, when the copper wire 11 oscillates at a relatively long wavelength, thereby generating in-phase noise signals shown in FIGS. 9A and 9B in the detection coils 12a and 12b, these noise signals are The signal is amplified by the in-phase amplifier 14 and the inverting amplifier 15 and becomes a signal shown in FIGS. That is, the outputs of the in-phase amplifier 14 and the inverting amplifier 15 have phases opposite to each other. Then, when these outputs are added by the adding circuit 19, the output of the adding circuit 19 becomes substantially zero as shown in FIG. Thus, the detection coils 12a, 12b
Does not appear at the output terminal of the adder circuit 19. Similarly, the long-wavelength noise generated in the detection coils 12b and 12c is canceled by the addition circuit 20, and does not appear at the output terminal of the addition circuit 20.

That is, the in-phase long-wavelength noise generated in the detection coils 12 a to 12 c is removed by the arithmetic circuits 13 and 16. Next, the case of detecting the iron piece 23 (magnetic foreign matter) mixed in the copper wire 11 will be described. When the iron piece 23 sequentially passes through the detection coils 12a to 12c, the detection coils 12a to 12c are respectively applied to the detection coils 12a to 12c as shown in FIG.
(C) The detection signals whose phases are shifted by 180 ° are generated. These detection signals are amplified by a common mode amplifier 14, inverting amplifiers 15, 17 and a common mode amplifier 18, respectively.
The signals shown in FIGS. Note that FIG.
(E) shows the outputs of the inverting amplifiers 15 and 17 together. Then, when the signal shown in FIG. 10D and the signal shown in FIG.
The signal shown in (g) is output from the addition circuit 19, and
When the signal shown in FIG. 10E and the signal shown in FIG. 10F are added by the adding circuit 20, the signal shown in FIG. 10H is output from the adding circuit 20. These adders 19,
20 (FIGS. 10 (G) and 10 (H)) are added to an adder circuit 33.
Accordingly, the addition is performed, and a magnetic foreign matter detection signal shown in FIG.

Here, the amplitude of the magnetic foreign matter detection signal will be considered. For example, in the configuration shown in FIG. 5, it is assumed that when the iron piece 3 sequentially passes through the detection coils 2a and 2b, the detection signals shown in FIGS. 10A and 10B are obtained in the detection coils 2a and 2b, respectively. These detection signals are inverted and added because the detection coils 2a and 2b are differentially coupled, and a signal shown in FIG. 10G is obtained between the terminals T1 and T2 (FIG. 5). The signal shown in FIG.
As is clear from comparison with the magnetic foreign matter detection signal shown in (i), the magnetic foreign matter detection signal shown in (i) of FIG. 10 can obtain twice the amplitude of the detection output by the configuration shown in FIG. .

Next, a configuration for removing traveling wave noise will be described. In FIG. 8, reference numerals 26 and 27 denote addition / inversion circuits each having the same configuration. The addition / inversion circuit 26 includes high-pass filters (hereinafter abbreviated as HPFs) 28a and 29
a, an adding circuit 30a for adding the outputs of the HPFs 28a and 29a, and an inverting circuit 31a for inverting and outputting the output of the adding circuit 30a. The cutoff frequency of the HPFs 28a and 29a is It is the frequency at the intersection of curves B and C shown in FIG. The outputs of the in-phase amplifier 14 and the inverting amplifier 15 are supplied to the HPFs 28a and 29a, respectively, and the output of the inverting circuit 31a is supplied to the adding circuit 33. The HPFs 28b and 29b of the inverting / adding circuit 27 have inverting amplifiers 1 respectively.
7. Each output of the common mode amplifier 18 is supplied to the inverting circuit 31
The output of b is supplied to the addition circuit 33. The addition circuit 33 adds together the outputs of the inversion circuits 31a and 31b and the outputs of the addition circuits 19 and 20, and the output is supplied to a signal processing circuit (not shown).

In the above configuration, a traveling wave having a short wavelength of the copper wire 11 is generated, whereby the detection coils 12a to 1a are generated.
The case where the traveling wave noise signals shown in FIGS. 11A to 11C are generated in FIG. 2C will be described. These noise signals are amplified by the in-phase amplifier 14, the inverting amplifiers 15, 17 and the in-phase amplifier 18, respectively, and then supplied to the input terminals of the adders 19 and 20, and the HPFs 28a, 29a, 28b and 29b. The addition circuit 19 adds the output terminals of the in-phase amplifier 14 and the inverting amplifier 15 and outputs the result to the addition circuit 33 as a signal shown in FIG. The addition circuit 21 adds the outputs of the inverting amplifier 17 and the in-phase amplifier 18,
The signal is output to the addition circuit 33 as a signal shown in FIG. On the other hand, the signals supplied to the respective input terminals of the HPFs 28a and 29a have the frequencies of these signals, respectively.
Since the cutoff frequency is higher than the cutoff frequency of the adder circuit 29a (see FIG. 2), it is supplied to the adder circuit 30a via the HPFs 28a and 29a.
A signal substantially the same as the signal shown in FIG. Then, this signal is inverted by the inverting circuit 31a, and the first
The signal shown in FIG. Similarly, the signals applied to the respective input terminals of the HPFs 28b and 29b are added by an adding circuit 30b and then added to the inverting circuit 3
The signal is inverted by 1b and applied to the adder circuit 33 as a signal shown in FIG. The outputs of the adders 19 and 20 and the outputs of the inverting circuits 31a and 31b (the signals shown in FIGS.
When they are added by 3, the output of the adding circuit 33 becomes zero. That is, when traveling wave noise signals are generated in each of the detection coils 12a to 12c, these noise signals are all canceled by the addition circuit 33 and do not appear at the output terminal of the addition circuit 33. The signal generated when the iron piece 23 mixed in the copper wire 11 passes through the detection coils 12a, 12b, 12c is output from the HPFs 28a, 29a,
28b, 29b.
Since the cutoff frequency of b is set higher than the frequency of the signal generated by the iron piece 23, the cutoff frequency is cut off there.

[0012]

As described above,
According to the configuration shown in FIG. 8, the amplitude of the magnetic foreign matter detection signal is
In addition to being twice as large as the configuration shown in FIG. 5, it is possible to remove both long-wave noise and traveling-wave noise. However, the in-phase amplifier 14 and the inverting amplifier 15, etc., themselves include delay elements. For this reason, when each signal generated from each detection coil due to the passage of the magnetic foreign matter is amplified by the in-phase amplifier 14 and the inverting amplifier 15, etc., a phase rotation occurs, and the amount of this phase rotation is determined by each detection. It depends on the frequency of the signal obtained from the coil. Therefore, it is difficult to input the signals obtained from the respective detection coils to the adder circuit 19 in a state where the signals are 180 ° out of phase with each other, and in many cases, a magnetic foreign matter detection signal having a large amplitude cannot be obtained. Also, depending on the traveling state of the copper wire 11, an extremely large level of noise may be detected by the detection coil. In such a case, even with the configuration of FIG. 8, a sufficiently large magnetic foreign matter detection signal cannot be obtained, and the magnetic foreign matter detection signal is buried in the noise signal remaining without being removed. There has been a problem that detection may not be possible. The present invention has been made in view of the above circumstances, and has as its object to provide a defect detection device capable of obtaining a detection signal having a larger amplitude.

[0013]

According to a first aspect of the present invention, there is provided a defect detecting apparatus for driving a metal material in a direct current magnetic field to detect a defect mixed in the metal material with the direct current magnetic field generated by the defect. (A) a plurality of detection coils which are arranged at positions shifted from each other along a traveling path of the metal material in the DC magnetic field; A circuit that inverts the output of one of the two detection coils, shifts the phase of one of the inverted output and the output of the other detection coil, adds the two, and outputs the result. And at least one first arithmetic circuit configured to adjust a shift amount when the phase is shifted. A defect detection device according to a second aspect of the present invention is the defect detection device according to the first aspect, wherein the output of one of the two detection coils adjacent to each other is inverted, and the output of the other detection coil is inverted. It is characterized by comprising at least one second arithmetic circuit for adding to the output of the detection coil, and an adding circuit for adding each output of the first and second arithmetic circuits. A defect detecting device according to a third aspect of the present invention is the defect detecting device according to the second aspect of the present invention, wherein the defect detecting device includes at least three detection coils and detects two adjacent detection coils among these detection coils. A plurality of sets of the first and second arithmetic circuits connected to each set of coils, and an adder circuit for adding each output of the first and second arithmetic circuits in each set. It is characterized by.

[0014]

According to each of the above arrangements, the signals obtained from the respective detection coils are shifted by 180 ° from each other with the passage of the defect by adjusting the amount of phase shift in the first arithmetic circuit. Can be added. Therefore,
A large amplitude detection signal is obtained.

[0015]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a magnetic foreign matter detection device according to one embodiment of the present invention. As shown in this figure, four detection coils 12a, 12b, 12c, 1 are displaced from each other along the path along which copper wire 11 travels.
2d are arranged. Here, the distance between the detection coils 12a and 12b and the distance between the detection coils 12c and 12d are substantially equal and shorter than the distance between the detection coils 12b and 12c. The detection coils 12a and 12b and the detection coils 12c and 12d are each differentially coupled. Then, the differentially coupled detection coil 12
A detection unit 100 is connected to a and 12b, and a detection unit 200 having exactly the same configuration as the detection unit 100 is connected to the differentially coupled detection coils 12c and 12d.

Next, the configuration of the detection unit 100 will be described. The output of the detection coil 12a is supplied to the in-phase amplifier 101, and the output of the detection coil 12b is supplied to the inverting amplifier 102. Further, the in-phase amplifier 101 supplies output signals C and D, which are in phase with respect to the input signal, to first input terminals of the phase shift addition circuit 103 and the addition circuit 104, respectively. The inverting amplifier 102 outputs the output signals E and F, each having a phase opposite to that of the input signal, to the phase shift addition
3 and the second input terminal of each of the adders 104. Here, the phase shift addition circuit 103 shifts the input signal to the first input terminal on the time axis, adds the input signal to the second input terminal, and outputs the resultant signal. It is configured to be able to be adjusted by the above. The outputs of the phase shift addition circuit 103 and the addition circuit 104 are added by an addition circuit 105, and the addition result is used as a magnetic foreign matter detection signal by the detection unit 10.
Output from 0. Each detection unit 100 and 200
Are differentially amplified by the differential amplifier 300 and output.

The operation of the magnetic foreign matter detecting device will be described below. When vibration of a relatively long wavelength occurs in the copper wire 11, signals A and B having substantially the same phase are output from the detection coils 12a and 12b, respectively. In this case, the phase shift addition circuit 103 adds the signal A in phase with the signal A by a predetermined amount and the signal E in phase opposite to the signal B. Here, since the wavelength of the signal C is long, the shift operation of the signal C may be neglected at all, and it may be considered that the phase shift addition circuit 103 adds two signals having substantially opposite phases. Therefore, the addition result in the phase shift addition circuit 103 becomes 0, and the long wavelength noise does not propagate to the subsequent stage from the phase shift addition circuit 103.
In addition, in the adder circuit 104, the signal D having the same phase as the signal A and the signal F having the opposite phase with respect to the signal B are added, so that the addition result becomes zero. Therefore, the long-wavelength noise does not propagate to a stage subsequent to the phase shift adding circuit 104. As described above, the long wavelength noise is removed in the detection unit 100 and is not output from the detection unit 100.

Next, the operation of detecting the iron piece 23 will be described with reference to FIG. The iron piece 23 is the detection coil 12a-1.
It is assumed that 2d passes sequentially. As a result, the detection coil 12
The signal A shown in FIG. 2 (a) is output from FIG.
As shown in (b), the signal B having a phase delayed from the signal A
Is output from the detection coil 12b. Amplified outputs C and D in phase with respect to signal A are output from in-phase amplifier 101 (FIG. 2C), and amplified outputs E and F in phase opposite to signal B are output from inverting amplifier 102. (FIG. 2 (d)). Then, the signal C is shifted by the phase angle φ by the phase shift addition circuit C and then added to the signal E. Here, the phase angle φ when shifting the signal C is adjusted by volume adjustment so that the phase difference between the waveform obtained as a result of shifting the signal C and the signal E becomes 180 degrees. By performing such adjustment, the output signal G having a large amplitude is supplied to the phase shift addition circuit 1 as shown in FIG.
03. On the other hand, the signals D and F are added in the adding circuit 104. Here, when the phase delay of the signal F with respect to the signal D is larger than 180 degrees, the amplitude of the output signal H of the adder 104 is equal to the amplitude of the output signal G of the phase shift addition circuit 103, as shown in FIG. It is smaller than that. Then, the signals G and H are added by the adding circuit 105, and the magnetic foreign matter detection signal K shown in FIG. As described above, when the signals C and E are obtained by the passage of the magnetic foreign matter, the phase of the signal C is shifted so that the phase difference between the signal C and the signal E becomes 180 degrees. Is added, a magnetic foreign matter detection signal having a large amplitude can be obtained.

Further, according to the magnetic foreign matter detecting device, even when high-frequency traveling wave noise is input via the detection coils 12a to 12d, these noises can be reduced. That is, the traveling wave noise input via the detection coil 12a passes through the in-phase amplifier 101, then passes through separate paths such as the phase shift addition circuit 103 and the addition circuit 104, and is delayed by different delay times. And input to the addition circuit 105. Therefore, the addition circuit 105 adds the traveling wave noise and the traveling wave noise whose input timing is slightly shifted from the traveling wave noise. The traveling wave noise includes various frequency components, and among these frequency components, a considerable number of components having the input timing shift amount substantially equal to the half cycle are included. Therefore, a considerable number of the frequency components constituting the traveling wave noise are added in an anti-phase relationship and cancel each other. Similarly to the above, traveling wave noise input via the detection coil 12b is also reduced by being added after passing through the phase shift addition circuit 103 and the addition circuit 104, respectively. The operation of the detection unit 100 has been described above.
At 00, the same operation as described above is performed. Each magnetic foreign matter detection signal output from the detection units 100 and 200 is differentially amplified by the differential amplifier 300. In this case, since the magnetic foreign matter detection signals of the detection units 100 and 200 are 180 ° or more out of phase, they are output without being canceled by the differential amplifier 300. Also,
Each detection coil 12a to 12d arranged at uneven intervals
When traveling wave noise is detected in step (1), each traveling wave noise propagates through a plurality of different paths and is input to the differential amplifier 300. As a result, some frequency components in the traveling wave noise cancel each other out and are removed. Is done. As described above, the case where the magnetic foreign substance in the copper wire is detected has been described as an example. However, according to the present invention, it is possible to detect a cavity existing in a metal material, a portion having a locally different magnetic permeability, and the like. Needless to say, there is.

[0020]

As described above, according to the present invention, it is possible to obtain a detection signal having a large amplitude, and to reliably detect a defect in a traveling metal material. The effect is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a magnetic foreign matter detection device according to one embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of the embodiment.

FIG. 3 is a diagram illustrating a principle of detecting a magnetic foreign substance.

FIG. 4 is a diagram illustrating a relationship between each frequency of a magnetic foreign matter detection signal and various noise signals.

FIG. 5 illustrates a differentially coupled detection coil that can cancel long wavelength noise.

FIG. 6 is a waveform chart for explaining the operation of the configuration shown in FIG.

7 is a waveform diagram exemplifying traveling wave noise generated in each detection coil shown in FIG. 5;

FIG. 8 is a block diagram showing a configuration of a conventional magnetic foreign matter detection device.

FIG. 9 is a waveform diagram illustrating an operation of the magnetic foreign matter detection device.

FIG. 10 is a waveform chart for explaining the operation of the magnetic foreign matter detection device.

FIG. 11 is a waveform chart for explaining the operation of the magnetic foreign matter detection device.

[Explanation of symbols]

12a to 12d: detection coil, 101: common-mode amplifier, 102: inverting amplifier, 103: phase shift addition circuit, 104: addition circuit, 105: addition circuit.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akio Ueno 1-15-7 Shimokamo, Kawanishi-shi, Hyogo Japan S-Tech Co., Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 27 / 72-27/90

Claims (3)

(57) [Claims] 1. A defect detection apparatus for running a metal material in a DC magnetic field and detecting a defect in the metal material based on a change in the DC magnetic field caused by the defect. A plurality of detection coils that are arranged at different positions along the travel path of the metal material; and (b) among two detection coils adjacent to each other,
A circuit for inverting the output of one of the detection coils, shifting one of the inverted output and the output of the other detection coil, adding the two, and outputting the result. An apparatus for detecting a defect in a metal, comprising: at least one first arithmetic circuit configured to adjust an amount. 2. An at least one second arithmetic circuit for inverting the output of one of the two detection coils adjacent to each other and adding the output of the other detection coil to the output of the other detection coil; 2. The defect detection device according to claim 1, further comprising an addition circuit that adds each output of the first and second arithmetic circuits. 3. A plurality of sets of the first and second coils having at least three detection coils and connected to each set of two detection coils adjacent to each other among the detection coils. 3. The defect detection device according to claim 2, further comprising: an arithmetic circuit for adding the outputs of the first and second arithmetic circuits in each set.