JP2006053053A - Probe device for eddy current flaw detection - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an inspection of high precision using a resonance coil in an eddy current flaw detector due to a stationary probe. <P>SOLUTION: This probe device for eddy current flaw detection has a pair of probe coils arranged in a mutually parallel state and attaining the same phase of a generated magnetic field, a bridge circuit having a pair of the probe coils as two sides and emitting a detection signal when the impedances of the probe coils do not coincide with each other, a resonance coil arranged across a pair of the probe coils at a position where the magnetic fields generated from the probe coils are set off in a state parallel to the probe coils and not producing a detection signal by the bridge circuit and the resonance circuit connected to the resonance coil. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a probe device that inspects a scratch or the like inside a metal material using eddy current.

Conventionally, a stationary probe device has a structure as shown in FIG. That is, a pair of probe coils L1 and L2 that generate magnetic fields arranged in parallel to each other and the pair of probe coils have two sides, and a bridge circuit 10 that generates a detection signal when the impedances of these probe coils do not match. And consist of In the inspection, the metal material surface is scanned with the probe so that the distance between the tips of the probe coils L1 and L2 is parallel to the metal material surface to be inspected. As a result, an eddy current is generated in the metal material. However, if there is no abnormality in the metal material, the impedances of both probe coils L1 and L2 are the same, so no inspection signal is output from the bridge circuit 10. On the other hand, when there are scratches or foreign matter in the metal material, the magnitude of the eddy current generated in that portion changes, and as a result, the impedance balance of both probe coils L1 and L2 is lost, and the inspection signal from the bridge circuit 10 is lost. Occurs. By detecting this inspection signal, it is possible to inspect the presence or absence of scratches on the metal material.
In addition to such a stationary probe, there is an apparatus that directly passes a coil through a thin and long conductor such as an electric wire as such a deep wound survey apparatus using eddy current. In this type of deep flaw detection apparatus, as shown in Patent Document 1 below, when the impedance balance is lost using a resonance coil, this is amplified to perform a more accurate inspection. Has been done.
Japanese Patent No. 28882856

As described in Patent Document 1, it is desirable for a stationary probe apparatus to perform a highly accurate inspection using a resonance coil. However, when the coil is directly passed through the conductor to be inspected, it is easy to install the resonance coil because the coils to be detected are arranged in a line, but in the case of a stationary probe, the coils to be detected are parallel. Therefore, the resonance coil cannot be provided as it is.
Therefore, an object of the present invention is to realize a highly accurate inspection using a resonance coil in an eddy current flaw detector using a stationary probe.

In order to solve the above problems, the present invention has the following configuration.
The invention according to claim 1 is a pair of probe coils arranged in parallel to each other and having a magnetic field generated in reverse phase,
The pair of probe coils has two sides, a bridge circuit that generates a detection signal when the impedances of the probe coils do not match, and a bridge circuit between the pair of probe coils that is in parallel with the detection signal. In a state where the magnetic field generated from the probe coil is canceled,
It is a probe device for eddy current deep wound having a resonance circuit connected to the resonance coil.

  According to the first aspect of the present invention, the magnetic field of the probe coil is reversed, and the resonant coil is installed in a position where the magnetic field is just canceled in parallel between them. The magnetic flux becomes zero. On the other hand, if there is a scratch on the metal, the balance between the probes is lost. As a result, a change in magnetic flux occurs in the resonance coil. When the resonance coil resonates by the resonance circuit, the Q value of the probe coil increases, The difference in inductance becomes larger. That is, a large output can be obtained even with a small change, and a more accurate inspection can be performed with a stationary probe.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a circuit diagram of a probe device X for eddy current flaw detection according to an embodiment of the present invention. The eddy current flaw detection probe apparatus X includes probe coils 11 and 12, a bridge circuit 10, a resonance coil 21, and a resonance circuit 22.
The probe coils 11 and 12 and the resonance coil 21 are formed by winding the tips provided on the E-shaped ferrite core 30 around three shafts 31, 32 and 33 arranged in a straight line. The probe coils 31 and 32 are wound around the shafts 31 and 32 at both ends, and the resonance coil 21 is wound around the middle shaft 33. The probe coils 11 and 12 are the same, and the distances between the probe coils 11 and 12 and the resonance coil 21 are equal.
The bridge circuit 10 is formed with probe coils 11 and 12, a resistor 13, a resistor 14, and an AC power supply 15. At this time, the magnetic fluxes generated in the probe coils 11 and 12 are connected so as to have opposite phases. As a result, the magnetic flux passing through the resonance coil 21 cancels out the magnetic flux from the probe coil 11 and the magnetic flux from the probe coil 12 as shown in FIG. . In the bridge circuit 10, when the impedances of both probe coils 11 and 12 are equal, the output from the output terminal 16 is 0, and the impedances 11 and 12 of both probe coils are
When the balance of 12 is lost, an output signal is generated from the output terminal 16.
The resonance circuit 22 is a known circuit, and causes resonance with respect to a current generated by a change in magnetic flux of the resonance coil 21 together with the resonance coil 21 by a capacitor.

Next, the usage method and operation | movement of the probe apparatus X for eddy current test which has the above structures are demonstrated.
First, the metal material surface to be inspected is scanned so that the lines connecting the tips of the axes 31, 32, and 33 of the iron core 30 are parallel. As a result, an eddy current is generated in the metal material, but if there is no abnormality in the metal material, the impedances of the probe coils 11 and 12 are the same, so that no inspection signal is output from the bridge circuit, and the resonance coil 21 The magnetic flux passing through is also zero. On the other hand, when a flaw or a foreign substance exists in the metal material, the magnitude of the eddy current generated in the portion changes, and as a result, the balance between the impedances 11 and 12 of both probe coils is lost. As a result, the magnetic flux passing through the resonance coil 21 changes, and when the induced current flows, the resonance coil 21 resonates. As a result, the Q value of the probe coil 11 (12) increases due to the change in magnetic flux generated, and the difference in impedance between the probe coils 11 and 12 increases. That is, a larger detection signal is generated from the output terminal 16 of the bridge circuit 10 than in the case where the resonance coil 21 is not provided, and a test with higher sensitivity can be performed with a stationary probe.

It is a circuit diagram of the probe apparatus for eddy current flaw detection. It is a conceptual diagram which shows the magnetic flux which passes along a resonance coil. It is a circuit diagram of a conventional stationary eddy current flaw detection probe apparatus.

Explanation of symbols

X Probe device for eddy current flaw detection 10 Bridge circuit 11, 12 Probe coil 21 Resonant coil 22 Resonant circuit

Claims (1)

A pair of probe coils arranged in parallel to each other and having opposite phases of the generated magnetic field;
A bridge circuit for generating a detection signal when the pair of probe coils has two sides and impedances of these probe coils do not match;
A resonance coil arranged between the pair of probe coils in parallel with them and in a state in which the magnetic field generated from the probe coil is canceled in a state where the bridge circuit does not generate a detection signal;
A probe device for eddy current damage having a resonance circuit connected to the resonance coil.

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