JP2011007570A - Leakage flux flaw detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a leakage flux flaw detector facilitating the elimination from a specimen and capable of evaluating the healthiness of the specimen without requiring large power.SOLUTION: In the leakage flux flaw detector equipped with a magnetizer for magnetizing the specimen and a magnetism sensor for detecting the leakage flux from the specimen magnetized by the magnetizer, the magnetizer is constituted by combining a permanent magnet with an electromagnet and is variable in its magnetization properties.

Description

  The present invention relates to a leakage flux testing apparatus, and more particularly, to a leakage flux testing apparatus having a magnetizer whose magnetization performance can be varied.

  Conventionally, a leakage magnetic flux flaw detection method is known as a method for flaw detection of a subject's soundness (internal defect and surface defect of the subject). This method includes a magnetizer and a magnetic sensor, and magnetizes the subject. 2. Description of the Related Art Leakage magnetic flux flaw detectors that can flaw detect the health of a subject by detecting the magnetic flux leaking from the subject with a magnetic sensor after being magnetized (excited) by a detector are widely used. In addition, as a method of magnetizing a subject with a magnetizer, a permanent magnet method (for example, Patent Document 1) in which a subject is magnetized using a permanent magnet as a magnetizer, or a subject is magnetized using an electromagnet as a magnetizer. The electromagnet system (for example, patent document 2) to be made is mentioned.

  The permanent magnet system can be suitably used in an environment where an external power source or the like cannot be used because the subject can be magnetized by the magnetization performance of the permanent magnet without using an external power source or the like. However, since the permanent magnet cannot adjust the magnetization performance, a large-scale desorption device is required for desorption from the subject when a permanent magnet with strong magnetization performance is used. Although it is conceivable to use a permanent magnet with weak magnetizing performance in order to facilitate the desorption, if the thickness of the subject is thick, there arises a problem that the soundness of the subject cannot be accurately evaluated.

  On the other hand, for example, in an electromagnet magnetizer that can magnetize a subject by energizing a coil wound around a core of a magnetic material, the number of turns of the coil and the current flowing through the coil are adjusted as appropriate. Thus, even when the subject is thick, the subject can be easily magnetized. Furthermore, since the magnetic force can be adjusted by stopping energization according to the electromagnet system, it is possible to easily desorb from the subject without using a desorption device as in the permanent magnet system.

  However, although the electromagnet system is easily turned on and off, desorption is easy, and a large amount of electric power is required to magnetize the subject, which is not suitable for an environment (local measurement) where large electric power cannot be supplied.

JP 2002-156363 A JP 2004-279245 A

  The present invention has been made in view of such a situation, and leakage magnetic flux flaw detection that can be easily detached from the subject and can evaluate the health of the subject without requiring large electric power. The main object is to provide a device.

  The present invention for solving the above problems is a leakage flux testing apparatus comprising a magnetizer for magnetizing a subject, and a magnetic sensor for detecting leakage flux from the subject magnetized by the magnetizer, The magnetizer is a magnetizer in which a magnetizing performance is variable by combining a permanent magnet and an electromagnet.

  The magnetizer may include the permanent magnet and an electromagnet obtained by winding the permanent magnet with a coil, and the magnetizer may connect the pair of permanent magnets to the pair of permanent magnets. It may consist of the electromagnet provided in the.

  According to the present invention, it is easy to desorb from the subject, and the soundness of the subject can be evaluated without requiring large electric power.

It is a schematic diagram which shows an example of the leakage magnetic flux detection apparatus of this invention. It is a schematic diagram which shows an example of the leakage magnetic flux detection apparatus of this invention.

  Hereinafter, the leakage magnetic flux detection apparatus of the present invention will be specifically described with reference to the drawings. FIG. 1 is a schematic diagram illustrating an example of a leakage magnetic flux detection device according to an embodiment of the present invention.

  As shown in FIG. 1, a leakage magnetic flux detection apparatus 10 of the present invention includes a magnetizer 20 that magnetizes a subject, and a magnetic sensor 40 that detects leakage flux from the subject 30 magnetized by the magnetizer. Is done. In particular, the magnetizer 20 constituting the leakage magnetic flux flaw detector 10 of the present invention is a magnetizer in which a permanent magnet 21 and an electromagnet 23 are combined to change the magnetization performance for magnetizing a subject. Have The leakage magnetic flux flaw detector 10 of the present invention is not particularly limited as long as it has this requirement, and can be applied to any subject 30 that can be magnetized by the magnetizer 20.

(Magnetizer)
The magnetizer 20 is an essential component in the leakage magnetic flux flaw detector 10 of the present invention, and is configured by combining a permanent magnet 21 and an electromagnet 23 connected to a power source 32. First, the measurement operation for magnetizing the subject 30 by the magnetizer 20 and the operation for detaching the magnetizer 20 from the subject 30 after the measurement will be specifically described.

(1) Operation at the time of measurement When the power source 32 is off at the time of measurement, no magnetic force (magnetic flux) is generated in the electromagnet 23. Magnetic flux corresponding to the magnetization performance possessed is input to the subject 30, and the subject 30 is magnetized. The flow of magnetic flux at this time is “N pole of permanent magnet → subject → S pole of permanent magnet → N pole of permanent magnet” (hereinafter, the flow of the magnetic flux by the permanent magnet 21 is changed to the positive magnetic flux. (It may be referred to as a flow (symbol X).)
Here, assuming that the magnetization performance (the strength of the magnetic force) that the permanent magnet 21 has in advance is A, depending on the magnetization performance of the permanent magnet 21 and the thickness of the subject 30, the permanent magnet 21 having the magnetization performance A has the subject 30. In some cases, it cannot be sufficiently magnetized. That is, the subject 30 may not be magnetized to a magnetization level necessary for detection. According to the leakage magnetic flux flaw detector 10 characterized by the magnetizer 20 as a result of intensive studies on such a problem, the excitation direction of the electromagnet 23 is the same direction as the flow of positive magnetic flux by the permanent magnet 21 (positive direction). It is possible to improve the magnetization performance for magnetizing the subject 30 by flowing a current from the power supply 32 so that the magnetic flux flows (Y).

  Specifically, assuming that the magnetizing performance of the electromagnet 23 is B, the magnetizing performance for magnetizing the subject 30 by flowing a current so that the excitation direction of the electromagnet 23 is a positive direction magnetic flux flow (symbol Y). Is “magnetization performance of permanent magnet” + “magnetization performance of electromagnet” = A + B. The magnetizing performance B of the electromagnet 23 is proportional to the number of turns of the coil and the current passed through the coil, and the magnetizing performance of the magnetizer 20 for magnetizing the subject 30 can be varied by appropriately adjusting the magnetizing performance B of the electromagnet 23. Can be possible. That is, according to the magnetizer 20, the magnetizing performance A of the permanent magnet 21 for magnetizing the subject 30 is appropriately supplemented by the magnetizing performance B of the electromagnet 23 without requiring a large amount of electric power. Can do.

(2) Operation at Desorption When the magnetizer 20 is desorbed from the subject 30 and the power source 32 is off, the subject 30 and the magnetizer 20 are magnetized by the magnetic force according to the magnetization performance A of the permanent magnet 21. If the permanent magnet 21 having strong magnetization performance A is used, it may be difficult to detach the magnetizer 20 from the subject 30.

  Even in this case, the current is supplied from the power source 32 so that the excitation direction of the electromagnet 23 is the flow in the direction opposite to the flow of the magnetic flux in the positive direction by the permanent magnet (the flow of the magnetic flux in the reverse direction (symbol Z)). The magnetization performance of the magnetizer 20 can be reduced.

  Specifically, when the magnetizing performance of the electromagnet 23 is B, the magnetizing performance for magnetizing the subject 30 by flowing an electric current so that the excitation direction of the electromagnet 23 is the flow of magnetic flux in the opposite direction (sign Z). Is “magnetization performance of permanent magnet” − “magnetization performance of electromagnet” = A−B. As described above, the magnetization performance B of the electromagnet 23 is proportional to the number of turns of the coil and the current flowing through the coil, and the magnetizer 20 is detached from the subject 30 by appropriately adjusting the magnetization performance B of the electromagnet 23. Therefore, the magnetization performance of the magnetizer 20 can be made variable. That is, in order to desorb the magnetizer 20 from the subject 30, the magnetizing performance A of the permanent magnet 21 is weakened by the magnetization performance B of the electromagnet 23, so that the magnetizer 20 can be easily removed from the subject 30. Can be desorbed.

  That is, according to the magnetizer 20 constituting the leakage magnetic flux flaw detector 10 of the present invention, when the magnetization performance of the permanent magnet 21 constituting the magnetizer 20 is A and the magnetization performance of the electromagnet 23 is B, the magnetizer 20 The overall magnetization performance can be varied in the range of (A−B) to (A + B). Furthermore, since the magnetizing performance B of the electromagnet 23 can be set as described above, the subject 30 can be made sufficiently even when the magnetizing performance of the permanent magnet 21 is insufficient to sufficiently magnetize the subject 30. In addition, the permanent magnet 21 can be easily desorbed even when the magnetization performance of the permanent magnet 21 is difficult to desorb the magnetizer 20 from the subject 30.

  The configuration of the magnetizer 20 is not particularly limited as long as it is a magnetizer 20 in which the permanent magnet 21 and the electromagnet 23 are combined as described above and the magnetization performance thereof is variable. For example, FIG. As shown in FIG. 2, the magnetizer 20 includes a substantially U-shaped one permanent magnet 21 formed by a pair of magnetic pole portions (21a, 21b), and an electromagnet 22 in which the permanent magnet 21 is directly wound by a coil. It may be configured to be combined. In FIG. 1, one magnetic pole portion 21 a has an N pole and the other magnetic pole portion 21 b has an S pole, and the coil is connected to a power source 32.

  In addition, as shown in FIG. 2, the magnetizer 20 is provided so as to connect the two permanent magnets 21 formed of a pair of magnetic pole portions (21 a, 21 b) and the two permanent magnets 21. It is good also as a structure which consists of the electromagnet 23. FIG. The electromagnet 23 having the configuration can be formed by, for example, winding a yoke or the like with a coil, and the coil is connected to the power source 32.

  Further, the shape of the magnetizer 20 is not limited to the gate shape shown in FIGS. 1 and 2, and the shape of the magnetizer 20 is not particularly limited as long as it has a pair of magnetic poles.

  The permanent magnet 21 may be a permanent magnet 21 made of any material as long as it has a function having magnetic performance in advance. Examples thereof include an alnico magnet, a ferrite magnet, a neodymium magnet, and a samarium cobalt magnet. .

  The electromagnet 23 is not particularly limited as long as the electromagnet 23 has a function capable of changing the excitation direction in the same direction and the reverse direction as the flow of the magnetic flux in the positive direction by the permanent magnet 21 depending on the direction of the current flowing in the coil. As shown in FIG. 2, it may be formed by winding a coil around a permanent magnet, or as shown in FIG. 2 by winding a coil around a yoke or the like that is a magnetic material. Note that the number of turns of the coil, the coil wire diameter, and the like can be appropriately set depending on the shape of the magnetizer 20, the necessary magnetizing force, and the like, and the number of turns of the coil and the coil wire diameter are not limited. Moreover, there is no limitation in particular also about the power supply 32 which sends an electric current to a coil, A conventionally well-known DC power supply etc. (for example, Kikusui Electronics Co., Ltd. product: DC stabilization power supply) can be used suitably.

  There is no particular limitation on the material of the yoke, but it is preferably made of a material having a high magnetic saturation value and high magnetic permeability that can obtain a large magnetic flux with a small current. For example, pure iron or the like can be suitably used. Further, there is no particular limitation on the mechanism for changing the direction of the current flowing through the coil, and a conventionally known switch or the like can be suitably used.

(Magnetic sensor)
As shown in FIG. 1, a magnetic sensor 40 is provided near the center of the magnetizer 20. The magnetic sensor 40 is provided for detecting leakage magnetic flux from the subject 30, and a conventionally known magnetic sensor can be appropriately selected and used as long as it has a function of detecting leakage magnetic flux. The installation position of the magnetic sensor 40 is not particularly limited, and may be provided on the magnetizer 20 side as shown in FIG. 1 or may be provided at a position facing the magnetizer 20 with the subject interposed therebetween. A plurality of magnetic sensors 40 may be provided.

(Conveyance roller)
Further, as shown in FIG. 1, a conveyance roller 50 may be provided between the magnetic poles 21 a and 21 b and the subject 30 for facilitating the conveyance of the leakage magnetic flux flaw detector 10 along the subject 30. . The conveyance roller 50 is an arbitrary configuration in the leakage magnetic flux flaw detector 10 of the present invention.

DESCRIPTION OF SYMBOLS 10 ... Magnetic flux flaw detector 20 ... Magnetizer 21 ... Permanent magnet 23 ... Electromagnet 30 ... Subject 40 ... Magnetic sensor

Claims (3)

A leakage magnetic flux flaw detector comprising a magnetizer for magnetizing a subject, and a magnetic sensor for detecting leakage magnetic flux from the subject magnetized by the magnetizer,
The leakage magnetic flux flaw detector as described above, wherein the magnetizer is a magnetizer in which a permanent magnet and an electromagnet are combined to change the magnetization performance.   The leakage magnetic flux flaw detector according to claim 1, wherein the magnetizer includes the permanent magnet and an electromagnet obtained by winding the permanent magnet with a coil.   The leakage magnetic flux flaw detector according to claim 1, wherein the magnetizer includes a pair of permanent magnets and an electromagnet provided so as to connect the pair of permanent magnets.

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