JP2606043Y2 - Eddy current flaw detector - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an orthogonal magnetic field type eddy current flaw detector used for checking the soundness of a metal object such as a flat metal plate.

[0002]

2. Description of the Related Art A conventional structure of an eddy current flaw detection device for flaw detection of a metal flat plate or the like will be described with reference to FIGS. As shown in FIG. 5, the eddy current flaw detector used to determine the presence or absence of a defect in a metal object and to confirm its soundness includes an excitation coil 101, a detection coil 102, and a magnetic core 103.
And the like, a flaw detector 120 having a screen 121, a connection cable 130 for connecting between the flaw detector 100 and the flaw detector 120, and the like.

This type of flaw detector 1 in an eddy current flaw detector
FIG. 6 shows an electrical connection state and a magnetic field state of the flaw detector 120. In FIGS. 5 and 6, reference numeral 110 denotes a metal to be inspected, and 111 denotes a defect in the metal to be inspected. 131 denotes a magnetic field generated by the exciting coil 101, 1
Numeral 32 denotes an eddy current flowing in the metal body caused by a magnetic field generated by the exciting coil, and 133 denotes a magnetic field generated by the eddy current 132. 141 is an oscillator built in the flaw detector 120.

[0004] An alternating current having a constant magnitude (amplitude) and a constant frequency is supplied to the exciting coil 101 of the flaw detector 100 from the oscillator 141 incorporated in the flaw detector 120 via the connection cable 130.

When an alternating current flows through the exciting coil 101, a magnetic field 131 is generated from the exciting coil 101. Since the magnetic field 131 links with the detection coil 102 and the test object metal 110, the eddy current 1
32 occurs.

The eddy current 132 is generated concentrically with the exciting coil 101 when the test object metal 110 is healthy (that is, when there is no defect). The eddy current 132 also generates a magnetic field 133, and this magnetic field 133 also links with the exciting coil 101.

These alternating magnetic fields 131 and 133
However, an AC voltage is induced in the exciting coil 101 by interlinking with the exciting coil 101. Test metal 110
When the defect 111 occurs, the flow of the eddy current 132 changes compared to the case where there is no defect. At this time, an eddy current 132 is generated. Since the magnetic field 133 also changes as compared with the case where there is no defect, the voltage induced in the exciting coil 101 also changes, and this change in voltage is observed on the screen 121 of the flaw detector 120 to determine whether there is a defect.

When actually applied, the induced voltage waveform 123 of the detection coil 102 on the screen 121 of the flaw detector 120 at this time is observed while moving the flaw detector 100 along the subject metal 110.

Further, the flaw detector 120 is provided with the flaw detector 100.
Has a function of compensating for reducing the induced voltage when placed on a healthy portion (the portion having no defect 111) of the test metal 110. In the portion having no defect 111, the flaw detector 12
The waveform of each part of the screen 121 of 0 is as shown in FIG.

In FIG. 7, reference numerals 121 and 122 denote the same as those in FIG. 5, respectively. Reference numeral 124 denotes an induced voltage of the detection coil 102 in the case where there is no defect, with the above-described correction. In the case where there is no defect, the detection coil 1
The induced voltage of 02 is represented by a small amplitude.

FIG. 8 shows waveforms when there is a defect. Reference numerals 121 and 122 in FIG. 8 are the same as those in FIGS. 5 and 7, respectively. Reference numeral 125 in FIG. 8 denotes an induced voltage of the detection coil 102 in the case where there is a defect. This voltage is subjected to the above-described correction for reducing the swing width when there is no defect. It appears as the swing width.

Therefore, the flaw detector 100 is connected to the object metal 110.
By observing the screen 121 of the flaw detector 120 while moving, the presence or absence of a defect can be determined, and the soundness of the test object metal can be known.

[0013]

However, in the above-described conventional flaw detector, since the eddy current in the test object metal flows concentrically with the exciting coil of the flaw detector, the flaw is generated irrespective of the direction of the defect. However, there is a problem that the direction of the defect cannot be determined.

The present invention has been made in view of the above circumstances,
Using a certain relationship between the direction of the magnetic field and the direction of the defect,
It is an object of the present invention to provide an orthogonal magnetic field type eddy current inspection device capable of determining the direction of a defect.

[0015]

SUMMARY OF THE INVENTION The present invention relates to an eddy current flaw detection device, which corresponds to a magnetic core having a cross-shaped body and four legs, and corresponding to each of the four legs of the magnetic core. and four excitation coils provided in the barrel of the cruciform, and four detection coils which are provided in each leg of the present 4 above magnetic core, each excitation
Means for supplying alternating current for detecting the magnetic coil, of the respective exciting coils, and means for applying a direct current to alternating each set of exciting coils and a pair of excitation coils opposed to the pair, the DC Due to the magnetic field generated when current flows,
The magnetic core is magnetically saturated to increase the direction of the magnetic field for defect detection.
The magnetic permeability of the core by the direct current
Of the magnetic field is used to control the direction of the AC magnetic field.
It is characterized in that the direction is further limited.

[0016]

Since the eddy current flaw detector according to the present invention is configured as described above, a magnetic field interlinking with the test object metal is generated in a direction orthogonal to each period by a switch operation and a power supply operation. I do. The voltage induced in the detection coil depends on the degree to which the eddy current in the metal is hindered by the defect, and the degree to which the eddy current is hindered by the defect varies depending on the direction of the magnetic field (the direction of the eddy current) and the direction of the defect.
That is , if an alternating current for detection is applied to each of the four excitation coils,
Moni, among the respective exciting coils, a pair of exciting coils which face each other with a set a direct current flows alternately in each set of the excitation coils, by a magnetic field generated when a direct current flows, the
The magnetic core around which the coil is wound is magnetically saturated,
By forcibly switching the direction of the
The decrease in the magnetic permeability of the core due to the DC current
To control the direction of the magnetic field so that the direction of the magnetic field can be further limited.
To better understand the direction of detected defects
It was made.

Therefore, the direction of the defect can be sensed by generating an orthogonal magnetic field in each period, observing the total voltage induced in the detection coil in each period, and comparing the induced voltage in each period. become.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. In the figure, reference numeral 1 denotes a magnetic core of the flaw detector in a cross shape.
The magnetic core 1 is made of a material having high magnetic permeability in order to efficiently generate a magnetic field and to detect the magnetic field efficiently. The exciting coils 21 to 24 and the detecting coils 31 to 34 are wound around the cross-shaped magnetic core 1.

Reference numerals 11, 12, 13, and 14 denote legs of a cross-shaped magnetic core (legs forming a part of the cross-shaped magnetic core), and the legs (legs) 11, 12, 13, and 14 correspond to the object metal. Used in the closest position.

Reference numerals 21, 22, 23, and 24 denote excitation coils, respectively. An alternating current is always supplied from the flaw detector 50, and a DC current is supplied to the excitation coil (-a) 2 by a switch.
1, and the excitation coil (-c) 23 or the excitation coil (-b) 22 and the excitation coil (-d) 24 are supplied as a set for each period. When a DC current is applied, the magnetic permeability of the portion of the magnetic core 1 decreases, and therefore, the legs (legs) 11-13, 12- of the magnetic core 1 connected to the portion.
The magnetic field emanating from 14 is attenuated.

An AC magnetic field is generated from the legs of the magnetic core connected to the portion where no DC current flows, and this magnetic field acts on the test object metal. Reference numerals 31, 32, 33, and 34 denote detection coils, respectively.
33, 34 are legs (legs) 11, 12, 13, 1 of the magnetic core 1;
4, and induces a voltage by a magnetic field inside the magnetic core 1 (inside the detection coil).

Reference numeral 41 denotes an exciting current generated by the flaw detector 50. Reference numeral 50 denotes a flaw detector, and the excitation coils 21, 22, 2
An AC voltage for exciting the coils 3 and 24 is generated.
It has necessary functions such as passing an alternating current to 1, 2, 23, and 24, and taking in the voltage induced in the detection coils 31, 32, 33, and 34, amplifying it as necessary, and displaying it on a screen. I have.

Reference numeral 51 denotes a screen of the flaw detector 50, which includes an exciting current of the exciting coils 21, 22, 23, 24, and a detecting coil 3;
The induced voltages of 1, 32, 33, and 34 and the operating state of the switch 61 are displayed.

Reference numeral 53 denotes an induced voltage waveform of the detection coil displayed on the screen 51 of the flaw detector 50, and reference numeral 54 similarly denotes a voltage waveform indicating the operation state of the switch 61. Reference numeral 61 denotes a switch, which has two operation states, and has a single (first) operation state, and the excitation coils (−) arranged in a line (to face each other).
a) 21, DC power is supplied to the exciting coil (-c) 23, and in another (second) operating state, the remaining one set of aligned (opposing) exciting coils (-b) 22, It has a function of supplying a direct current to the exciting coil (-d) 24.

Reference numeral 62 denotes a DC power supply for supplying a DC current to the exciting coils 21, 22, 23, 24 through the switch 61. Reference numerals 91, 91 denote lead wires, respectively, and the excitation coils 21, 22, 23, 24 and the detection coils 3
1, 32, 33 and 34 are connected to the switch 61 and to the flaw detector 50 via the connection cable 130.
Reference numeral 130 denotes a connection cable, and the flaw detector 50 and the switch 6
1, and the detection coils 31, 32, 33, 34 are connected.

FIGS. 2 and 3 show the direction of the magnetic field in each operation state of the switch 61. FIG. 2 shows that the direct current is supplied to the exciting coil (-b) 22 and the exciting coil (-d) 24. FIG. 3 shows the excitation coil (−a) 2
1, and a case where a direct current is applied to the exciting coil (-c) 23. Reference numerals 97 and 99 in these figures indicate the directions of the magnetic field acting on the test object metal, respectively.

As shown in FIGS. 2 and 3, in each operating state of the switch 61, the magnetic permeability of the core 1 where the DC current is applied is reduced, so that both sides of the core 1 where the DC current is not applied. A magnetic field is generated only between the legs of the magnetic core 1 of FIG. For this reason, a magnetic field is generated in the directions 97 and 99 in each drawing.

The four detection coils 31, 32, 33, 34
Are connected in series, and these four detection coils 3
Observe the sum of the voltages induced at 1,32,33,34. FIG. 4 shows the relationship between the direction of the defect and the waveform displayed by the flaw detector.

The flow of the eddy current generated in the test object metal is prevented by the defect, and is most affected by the presence of the defect when the direction of the defect matches the direction of the magnetic field.

FIG. 4 shows an example in which the direction of the defect coincides with the direction 97 of the magnetic field. During the period in which the direction of the magnetic field is 97, the voltage induced in the detection coil is most affected by the defect, It changes greatly compared to the case without.

On the other hand, during the period when the direction of the magnetic field is 99,
The effect of the defect becomes extremely small, and the induced voltage of the detection coil hardly changes from the case without the defect. This state is shown in the form of a display screen 51 of the flaw detector 50 in FIG.

In the flaw detector display screen, a period Ta is a period during which the direction of the magnetic field is indicated by an arrow 97, and a period Tb is a period during which the direction of the magnetic field is indicated by an arrow 99. Since the induced voltage of the detection coil is adjusted and displayed so as to minimize the case where no defect is present, the direction of the defect and the direction of the magnetic field are adjusted as shown in FIG.
In the case of (a), on the display screen 51 of the flaw detector 50, the amplitude of the induced voltage increases in the period Ta and decreases in the period Tb. Therefore, the direction of the defect can be sensed by comparing the amplitudes Aa and Ab of the induced voltage of the detection coil for each period.

[0033]

[Effects of the Invention] As described in detail above, the orthogonal magnetic field type eddy current flaw detector according to the present invention makes it possible to detect the direction of a defect existing in a metal to be inspected, and to perform repair necessary in the next step. Therefore, the amount of information is increased, and the accuracy of repair and the time period are greatly improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an orthogonal magnetic field type eddy current inspection device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a magnetic field direction (-1) for explaining the operation of the embodiment.

FIG. 3 is a diagram showing a direction (-2) of a magnetic field for explaining the operation of the embodiment.

FIG. 4 is a diagram showing a relationship between a defect direction and a flaw detector display waveform for explaining the operation of the embodiment.

FIG. 5 is a diagram showing a configuration of a conventional flaw detector.

FIG. 6 is a diagram showing an electrical connection state of a conventional flaw detector.

FIG. 7 is a diagram showing waveforms in the case where there is no defect in the conventional device.

FIG. 8 is a diagram showing waveforms in a case where there is a defect in the conventional device.

[Explanation of symbols]

1 ... magnetic core (cross-shaped magnetic core), 11 ... foot (leg) of magnetic core-a,
12: Magnetic core feet (legs)-b, 13: Magnetic core feet (legs)-
c, 14: magnetic core feet (d)-d, 21: excitation coil-
a, 22 ... exciting coil-b, 23 ... exciting coil-c, 2
4: Excitation coil-d, 31: Detection coil-a, 32: Detection coil-b, 33: Detection coil-c, 34: Detection coil-d, 41: Excitation current of the coil, 53: Induction voltage of the detection coil, 54: voltage indicating the operation state of the switch, 61
... Switch, 62 ... DC power supply, 97 ... Direction of magnetic field-1
99 ... magnetic field direction-2.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01N 27/72-27/90

Claims (1)

(57) [Scope of request for utility model registration] 1. A magnet having a cruciform body and four legs.
A core and a cross-shaped body corresponding to each of the four legs of the magnetic core
Four excitation coils, and four detection coils provided on each of the four legs of the magnetic core.
An output coil, means for passing an alternating current for detection to each of the exciting coils, and a pair of opposed exciting coils among the respective exciting coils.
DC current is alternately applied to each set of excitation coils.do it,
thenThe magnetic field is magnetically saturated with the magnetic field generated,
Force the direction of the magnetic field for defect detectionMake it turn
Means,  At each point when a DC current is applied to the excitation coil
Of the above four detection coilsInductionObserve voltageDisplay as possible
MeansOrthogonal magnetic field type
Eddy current flaw detector.