JPH0543066U - Eddy current flaw detector - Google Patents

Abstract

(57) [Summary] [Purpose] Not only the presence or absence of a defect existing in the metal to be inspected but also the direction in which the defect is generated can be sensed, so that the defective portion can be repaired accurately and in a short period of time. [Structure] A magnetic core 1 is formed in a square frame shape, foot portions 11 to 14 projecting in one direction are provided at four corners, and excitation coils 21 to 24 are wound around each side portion of the frame-shaped portion. Parts 11-14
The detection coils 31 to 34 are wound around. Then, by the switch circuit 61, the exciting coils 21, which are located opposite to each other,
23, 22, and 24 are paired and alternately switched at a constant interval to supply an exciting current to alternately generate orthogonal magnetic fields. The generated magnetic field is interlinked with the object metal via the legs 11 to 14 of the magnetic core 1, the magnetic field generated from the object metal is detected by the detection coils 31 to 34, and the detection signal is switched by the switch circuit 61. Depending on the condition, flaw detector 5
0 is displayed on the screen 51, and the direction of the defect is determined by comparing the signal levels for each period in which the magnetic fields are orthogonal.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an eddy current flaw detector used for determining the presence or absence of a defect in a metal object such as a metal flat plate and confirming its soundness.

[0002]

[Prior Art]

 In general, an eddy current flaw detector is used to determine the presence or absence of a defect in a metal object such as a metal flat plate and confirm its soundness. As shown in FIG. 5, a conventional eddy current flaw detector comprises a flaw detector 100 including an excitation coil 101, a detection coil 102, and a magnetic core 103, and a flaw detector 120 having a display screen 121. The connection cable 130 is connected to 120. FIG. 6 shows an electrical connection state of the eddy current flaw detector.

In FIG. 5 and FIG. 6, 110 is a target metal to be inspected, 111 is a defect in the metal to be inspected, 131 is a magnetic field generated in the exciting coil 101, and 132 is a metal generated by a magnetic field generated by the exciting coil. Eddy current 133 flowing in the body is a magnetic field generated by the eddy current 132, and 141 is an oscillator built in the flaw detector 120.

An alternating current having a constant magnitude (amplitude) and a constant frequency flows from the oscillator 141 to the exciting coil 101 through the connection cable 130. A magnetic field 131 is generated by an alternating current flowing through the exciting coil 101, and the magnetic field 131 is interlinked with the detection coil 102 and the metal 110 to be inspected, so that an eddy current 132 is generated in the metal 110 to be inspected. The eddy current 132 is generated concentrically with the exciting coil 101 when the object metal 110 is sound. A magnetic field 133 is also generated by this eddy current 132 and interlinks with the detection coil 102. The AC voltage is induced in the detection coil 102 by interlinking the AC magnetic fields 131 and 133 with the detection coil 102.

When a defect 111 is present in the object metal 110, the flow method of the eddy current 132 changes as compared with the case where there is no defect. At this time, the magnetic field 133 generated by the eddy current 132 also changes as compared with the case where there is no defect, so the voltage induced in the detection coil 101 also changes, and this change in voltage is observed on the display screen 121 of the flaw detector 120. , Determine the presence of defects.

When actually applied, the current waveform 122 of the exciting coil 101 and the detection coil displayed on the screen 121 of the flaw detector 120 at this time while the flaw detector 100 is moved along the metal 110 to be inspected. Observe the induced voltage waveform 123 of 102.

Further, the flaw detector 120 has a correction function of reducing the induced voltage when the flaw detector 100 is placed on a sound portion of the object metal 110 (a portion without the defect 111), and In the portion without 111, the induced voltage waveform 124 of the detection coil 102 is displayed with a small swing width as shown in FIG.

FIG. 8 shows each waveform when there is a defect. If there is a defect, the process of reducing the induced voltage is not performed, so the induced voltage waveform 125 of the detection coil 102 is displayed with a large fluctuation range.

Therefore, the presence or absence of a defect can be determined by observing the screen 121 of the flaw detector 120 while moving the flaw detector 100 on the subject metal 110, and the soundness of the subject metal 110 can be known.

[0010]

[Problems to be solved by the device]

 However, in the above-mentioned conventional eddy current flaw detector, since the eddy current in the object metal 110 flows concentrically with the exciting coil 101 of the flaw detector 100, an induced voltage is generated irrespective of the defect direction, and the defect direction is generated. There was a problem that I did not understand.

The present invention has been made in view of the above circumstances, and not only can detect a defect existing in a metal to be inspected but also can reliably determine the direction in which the defect is generated, and repair the defective portion. It is an object of the present invention to provide an eddy current flaw detector that is accurate and can be performed in a short period of time.

[0012]

[Means for Solving the Problems]

 The eddy-current flaw detector according to the present invention is formed in a square frame shape, and has a magnetic core provided with foot portions projecting in one direction at each corner, and wound around each side of the frame-shaped portion of the magnetic core. The four exciting coils installed, the four detecting coils wound around each leg of the magnetic core, and the two exciting coils facing each other out of the four exciting coils are respectively paired. And a switching circuit that alternately connects to the excitation signal source at regular intervals to alternately generate orthogonal magnetic fields, and the magnetic field generated by the excitation coil is linked to the metal to be inspected through the foot of the magnetic core. Means for detecting the magnetic field generated from the subject metal by the detection coil, and display means for displaying the signal detected by this means on the screen in correspondence with the switching state of the switch circuit. It is characterized by having it.

[0013]

[Action]

 The exciting current output from the exciting signal source is switched by the switch circuit at regular intervals, and is alternately applied to the two sets of exciting coils provided on opposite sides of each side of the frame-shaped portion of the magnetic core. Supplied. As a result, orthogonal magnetic fields are alternately generated from the two sets of exciting coils and interlink with the metal to be inspected through the legs of the magnetic core. As a result, an eddy current is generated in the object metal, and a magnetic field is generated by this eddy current. This magnetic field is detected by the detection coil and displayed on the screen corresponding to the switching state of the switch circuit.

The voltage induced in the detection coil depends on the degree to which the eddy current in the metal to be inspected is impeded by the defect. The degree to which the eddy current is obstructed by the defect is in the direction of the magnetic field (the direction of the eddy current). And it depends on the direction of the defect. Therefore, the direction of the defect can be sensed by displaying the signal detected by the detection coil on the screen corresponding to the switching state of the switch circuit and comparing the signal levels in each period in which the magnetic fields are orthogonal.

[0015]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an eddy current flaw detector according to an embodiment of the present invention. In the figure, reference numeral 1 is a magnetic core, which is formed, for example, in the shape of a square frame, and foot portions 11 to 14 projecting to one surface are integrally provided at four corners thereof. As a material forming the magnetic core 1, a high magnetic permeability material is used in order to improve the efficiency of generating and detecting a magnetic field. Then, the magnetic core 1 is wound with the exciting coils 21 to 24 on each side and the detection coils 31 to 34 are wound on the legs 11 to 14. The exciting current sent from the flaw detector 50 is selectively supplied to the exciting coils 21 to 24 through the switch circuit 61 and the lead wire 91. Further, the detection coils 31 to 34 are connected to the flaw detector 50 via a lead wire 92.

On the other hand, the flaw detector 50 has an exciting signal source (not shown) for supplying an exciting current to the exciting coils 21 to 24 inside and a display screen 51 at the front part. An excitation current waveform 41 with respect to the excitation coils 21 to 24, an induced voltage waveform 53 of the detection coils 31 to 34, and a voltage waveform 54 showing the operating state of the switch circuit 61 are displayed on 51. In this case, the coil induced voltage waveform 53 on the screen 51 displays the total voltage induced in each of the detection coils 31 to 34.

The switch circuit 61 is switched to two operating states by, for example, a switching signal from the flaw detector 50, and supplies an exciting current to the pair of exciting coils 21 and 23 facing each other in the first operating state. Then, the switching operation of the lead wire 91 is performed so as to supply the exciting current to the other set of the exciting coils 22 and 24 facing each other in the second operating state. The switching operation of the switch circuit 61 is performed at regular time intervals.

Next, the operation of the above embodiment will be described. When performing flaw detection on the object metal, the legs 11 to 14 of the magnetic core 1 are moved along the object metal. At the time of this flaw detection, the coil exciting current output from the flaw detector 50 is switched at regular intervals by the switch circuit 61, and is alternately supplied to the exciting coils 21 and 22 and the exciting coils 22 and 24. As a result, magnetic fields are alternately generated from the exciting coils 21 and 22 and the exciting coils 22 and 24, and the magnetic fields interlink with the metal to be examined and the detecting coils 31 to 34.

2 and 3 show the directions of the magnetic fields generated in the respective operating states of the switch circuit 61. In FIG. 2, when the exciting coils 21 and 23 are energized, FIG. 3 shows the exciting coils 22 and 24. This is the case when electricity is applied. Reference numerals 96 and 98 in these figures show the generation of magnetic fields in a simulated manner, and arrows 97 and 99 show the directions of magnetic fields near the centers of the legs 11 to 14 of the magnetic core 1.

In each operating state of the switch circuit 61 as shown in FIGS. 2 and 3, energization is performed so that a magnetic field is generated only between the legs on both sides of the exciting coils 21, 23 or 22, 24 during energization. Therefore, a magnetic field is generated near the centers of the legs 11 to 14 of the magnetic core 1 in the directions of arrows 97 and 99 in each operation state.

FIGS. 4A and 4B show the relationship between the direction of the defect 111 generated in the metal 110 to be inspected and the display waveform on the flaw detector screen 51. The flow of the eddy current generated in the object metal 110 is blocked by the defect 111, and is most affected when the direction of the defect 111 and the direction of the magnetic field match. FIG. 4 shows an example in which the direction of the defect 111 coincides with the direction 97 of the magnetic field. In the period in which the direction of the magnetic field is the arrow 97, that is, the period in which the exciting coils 21 and 23 are energized, the detection coil 31 The voltages induced in ˜34 are most affected by the defect 111 and greatly change as compared with the case where there is no defect.

On the other hand, in the period in which the direction of the magnetic field is the arrow 99, that is, in the period in which the excitation coils 22 and 24 are being energized, the influence of the defect 111 is extremely small, and the induced voltage in the detection coils 31 to 34 is small. Almost no change from the case without defects.

As a result, the signal waveform as shown in FIG. 4B is displayed on the display screen 51 of the flaw detector 50. In this display screen 51, a period Ta is a period in which the direction of the magnetic field is the arrow 97 (a period during which the exciting coils 21 and 23 are energized), and a period Tb is a period in which the direction of the magnetic field is the arrow 99 (exciting coil 22). , 24 is energized).

Since the induced voltages of the detection coils 31 to 34 are corrected and displayed so as to minimize the case where there is no defect, the direction of the defect 111 and the direction of the magnetic field are as shown in FIG. 4A. At this time, on the display screen 51 of the flaw detector 50, the induced voltage of the detection coils 31 to 34 has a large amplitude in the period Ta and a small amplitude in the period Tb. Therefore, by comparing the amplitudes Aa and Ab of the induced voltages of the detection coils 31 to 34 for each period, it is possible to detect the direction of the defect 111 generated in the object metal 110.

[0026]

[Effect of the device]

 As described above, according to the present invention, it is possible to detect not only the defect existing in the metal to be inspected but also the direction in which the defect is occurring reliably, and it is possible to perform repairs required in the next step. Since the amount of information on the defect information becomes large, it becomes possible to repair the defective portion accurately and in a short period of time.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an eddy current flaw detector according to an embodiment of the present invention.

FIG. 2 is a diagram showing directions of magnetic fields generated by a pair of exciting coils.

FIG. 3 is a diagram showing directions of magnetic fields generated by another pair of exciting coils.

FIG. 4 is a diagram showing the relationship between the direction of a defect of a metal to be inspected and a flaw detector display waveform in the present invention.

FIG. 5 is a configuration diagram of a conventional eddy current flaw detector.

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

FIG. 7 is a diagram showing each signal waveform in the conventional device when there is no defect.

FIG. 8 is a diagram showing each signal waveform when a conventional device has a defect.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic core, 11-14 ... Foot part of magnetic core, 21-24 ... Excitation coil, 31-34 ... Detection coil, 41 ... Excitation current waveform of coil, 53 ... Induction voltage waveform of detection coil, 54 ... Operation of switch circuit Voltage waveform indicating the state, 61 ... Switch circuit, 97, 99 ... Direction of magnetic field near the center of the magnetic core.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoya Shimizu 1-1-1, Wadasaki-cho, Hyogo-ku, Kobe-shi, Hyogo Mitsubishi Heavy Industries Ltd. Kobe Shipyard

Claims (1)

[Scope of utility model registration request] 1. A magnetic core, which is formed in a square frame shape and has foot portions projecting in one direction at each corner, and four magnetic cores wound around each side of the frame-shaped portion of the magnetic core. An exciting coil; four detection coils wound around each foot of the magnetic core;
Of the two exciting coils, two exciting coils located opposite to each other are paired and alternately switched and connected to the exciting signal source at regular intervals to alternately generate orthogonal magnetic fields, and the exciting coil. A magnetic field generated from the magnetic core is interlinked with the metal to be inspected through the foot portion of the magnetic core, a means for detecting the magnetic field generated from the metal to be detected by the detection coil, and a signal detected by this means of the switch circuit. An eddy current flaw detector comprising: a display unit for displaying on a screen in accordance with a switching state.