JPS609718Y2 - Flaw detection coil device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a flaw detection coil device for detecting flaws, particularly longitudinal flaws, in a material to be inspected.

There are various types of flaw detection coil devices, such as a penetrating type and a probe type.

The penetrating type, for example, is equipped with two annular coils, the coils are passed through the material to be inspected, and the coils are connected to two sides of a bridge, and the bridge detects changes in impedance of the coil due to flaws in the material to be inspected. However, with this method, if a flaw straddles both coils, the bridge becomes balanced, making it difficult to detect longitudinal flaws.

Probe types include adjacent comparison type and standard comparison type.Longitudinal flaws can be detected not only in the standard comparison type but also in the adjacent comparison type as long as the flaws do not extend over both coils. A bridge is required, and if a large number of probes are arranged in the circumferential direction or surface direction of the material to be inspected for wide range flaw detection, the equipment becomes complicated and expensive.

The present invention aims to improve these points and provide a coil device that can accurately detect longitudinal flaws and that does not make the flaw detection device so complicated even when flaw detection is performed over a wide range.

This will now be described in detail with reference to embodiments shown in the drawings.

FIG. 1 shows a first embodiment of the present invention, in which 1 is a short cylindrical yoke, and magnetic cores 2 made of ferrite are attached to the yoke at equal intervals and radially.

In this example, eight magnetic cores 2 are provided by dividing the cylinder into eight equal parts, and the tip thereof is located at the circumference 4 of the hole through which the round bar-shaped or cylindrical test material passes.
are made to line up at the top.

A bobbin 3 wound with an excitation coil 5 and a detection coil 6 is fitted and fixed onto each rod-shaped or plate-shaped magnetic core 2 .

As shown in FIG. 2, the excitation coils 5 of each magnetic core are all connected in series and energized by an AC excitation power source 7, forming alternately N and S poles on the magnetic pole faces facing the circumference 4 of each magnetic core.

The detection coils 6 of each magnetic core are all connected in series with alternately opposite polarities, and both ends 8 thereof serve as detection output terminals.

FIG. 3 shows a second embodiment of the present invention. In FIG. 1, a coil unit consisting of a magnetic core 2, a pobbin 3, an excitation coil 5, and a detection coil 6 is arranged in a circular shape, that is, centered at the hole through which the test material passes. In contrast to the coil units arranged in a radial manner, in this example an even number of these coil units are arranged in a straight line.

That is, 1 is a yoke, 2 is a magnetic core, one magnetic pole surface of each magnetic core 2 is aligned on a plane parallel to the surface of the test material 10, and the other magnetic pole surface is connected to each other by a straight yoke 1. be done.

It is convenient to manufacture the yoke 1 and the magnetic core 2 as a comb-shaped integral piece.

An excitation coil 5 and a detection coil 6 are wound around each magnetic core via a bobbin 3, and these excitation coils and detection coils are connected in the same manner as in FIGS. 1 and 2.

Next, the flaw detection operation of the coil device shown in FIG. 3 will be explained with reference to FIGS. 4 and 5, but the flaw detection operation of the device shown in FIG. 1 is the same as that of FIG. 3.

When the coil device 100 is arranged parallel to the test material 10 with a gap as shown in FIG. 3 and the coil 5 is energized, the coil units A, B, C...N are shown by arrows. A magnetic flux φ is generated as shown in FIG.

Due to this alternating magnetic flux, each of the detection coils 6 has a voltage ea,
eb...en are generated, but since these voltages have opposite polarities alternately and there are an even number, the output voltage eo, which is the sum of these voltages, is O if there is no flaw.

Next, as shown in FIG.
1 is located between coil units A and B, the magnetic flux changes its path as shown in the figure, possibly reducing its strength, so that the induced voltage e in the detection coils of both units is
eb becomes small.

However, since both decrease and have opposite polarities, there is no change in the output voltage eO.

Next, if the flaw 11 is under the magnetic pole surface of the coil unit C as shown in the figure, the magnetic flux changes its path as shown in the figure, and in some cases its strength decreases, and the induced voltage ec in the detection coil of the coil unit C decreases. However, the induced voltages of the detection coils of the coil units on both sides do not change much.

Therefore, the output voltage eO changes greatly.

If the flaw is located between these positions, the output will take an intermediate value, and depending on whether the flaw deviates to the left or right from the position between the coil units, the increase or decrease in the output voltage eo will be reversed as shown in Figure 5. .

In this manner, flaws can be detected, and by moving the specimen 10 in the direction of the longitudinal flaw, that is, in the right angle direction in FIG. 3, it is possible to accurately detect the longitudinal flaw extending in that direction.

Since this device does not use a bridge and only requires the addition of coil units, wide-area flaw detection can be carried out easily and inexpensively.

It is preferable to provide two sets of coil devices to ensure that no flaws are detected, and to stagger each magnetic core.

FIG. 6 shows the embodiment, and 100A and 100B are the third
In the coil device 100 shown in the figure, these magnetic cores 2 are arranged in a staggered manner with a half pitch shift between the coil devices as shown by dotted lines.

According to this arrangement, the undetectable portion between the coil units of the first coil device 100A is transferred to the second coil device 100B.
Flaws can be detected at the most sensitive part on the magnetic core, and leak-free flaw detection is possible.

The same thing can be done with the circular arrangement shown in FIG.

7 and 8 show a third modification of the invention, in which the excitation coil 5 is wound around the yoke 1 at a distance from the detection coil 6.

As shown in FIG. 9, the coils 5 are alternately connected in series with opposite polarities and excited, thereby causing the magnetic core 2 to alternately N.

It is possible to create a magnetic pole of S.

As explained in detail above, according to the present invention, an AC bridge is not required and a wide range can be detected with a simple device.

There is no problem of bridge unbalance caused by changes in coil winding resistance due to temperature rise, so stability is good, and the coil arrangement can be changed to linear, circular, or any other shape, making it easy to adapt to the shape of the material being tested. It has advantages such as being able to be used as a flaw detection coil device.

[Brief explanation of the drawing]

FIG. 1 is a schematic end view showing the first embodiment of the present invention;
3 is a partial side view showing the second embodiment of the present invention; FIGS. 4 and 5 are operation explanatory diagrams of FIG. 3; 6, 7, and 8 are explanatory diagrams showing other modified examples of the present invention, and FIG. 9 is a wiring diagram of the coil in these examples. In the drawing, 2 and 5 are the magnetic core and excitation coil for generating a magnetic field, and 6
1 is a detection coil, 10 is a test material, 1 is a yoke, A. B...N is a coil unit, 100°00A. 100B is a coil device.

Claims (5)

[Scope of utility model registration request] (1) A flaw detection system consisting of a magnetic field generator that alternately generates an even number of N and S magnetic poles, and a group of detection coils that are fitted in each of the N and S magnetic poles and connected in series with opposite polarities. coil device. (2) An even number of coil units consisting of excitation coils and detection coils wound around a magnetic core are arranged radially on the circumference through which the test material penetrates, with one magnetic pole surface aligned and the other magnetic pole surface used as a yoke. The flaw detection coil device according to claim 1, characterized in that they are connected to each other by. (3) An even number of coil units consisting of excitation coils and detection coils wound around a magnetic core are arranged in a straight line with one magnetic pole surface aligned on the same plane, and the other magnetic pole surface is connected to each other by a yoke. A flaw detection coil device according to claim 1 of the utility model registration claim. (4) Two coil devices consisting of an even number of coil units
3. The flaw detection coil device according to claim 2 or 3, wherein the magnetic pole surfaces facing the test material are staggered and arranged side by side in a staggered manner. (5) Practical use characterized in that the magnetic field generating device includes a yoke portion and an even number of magnetic pole portions protruding from the yoke portion, and an excitation coil is wound around the yoke portion and a detection coil is wound around the magnetic pole portion. A flaw detection coil device according to claim 1 of the patent registration claim.