JP2016090393A - Magnetic flaw detection device and excitation coil for magnetic flaw detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic flaw detection device that employs an excitation coil capable of forming an almost uniform magnetic field without using an electric connection connector capable of dividing and connecting the excitation coil in a peripheral direction, and to provide the excitation coil.SOLUTION: A magnetic flaw detection device M of the present invention comprises: one pair of excitation coils 1 (1-1 and 1-2) that is arranged apart from each other on an outer face of, for one example, a metal pipe SPa of an inspected object S; a power source unit 2 that supplies power to at least one of the one pair of excitation coils and thereby causes a pulse-like magnetic field to be generated; a magnetic field detection unit 3 that is arranged between the one pair of excitation coils 1 on the outer face of the metal pipe SPa and detects the magnetic field; and a determination unit 42 that determines presence or absence of a defect of the metal pipe SPa on the basis of a detection result of the magnetic detection unit 3. The one pair of excitation coils 1 respectively comprises: curved tabular magnetic shield units 11-1 and 11-2 for shielding the magnetic field; and elongated electric conduct members 12-1 and 12-2 that are wound around the magnetic filed shield units 11-1 and 11-2 via an insulation material.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a magnetic flaw detection apparatus that detects a predetermined defect (abnormality) in an inspection object by applying pulsed magnetism. And this invention relates to the exciting coil for magnetic flaw detectors used for such a magnetic flaw detector.

  The method of inspecting the presence or absence of defects (abnormalities) such as scratches and thinning (thinning) of metal pipes such as steel pipes, iron pipes and aluminum pipes is mainly ultrasonic using ultrasonic waves in addition to visual observation. There are a flaw detection method and a magnetic flaw detection method using magnetism. This magnetic flaw detection method includes a leakage magnetic flux flaw detection method in which a DC magnetic field or an AC magnetic field is applied to an object to be detected, and a magnetic flux generated by a defect (defect leakage magnetic flux) is detected. There are eddy current flaw detection methods that detect changes due to defects in current. One of them is a magnetic flaw detector using a Helmholtz coil that generates a spatially homogeneous magnetic field, which is disclosed in, for example, Patent Document 1.

  The non-destructive inspection apparatus using pulse magnetism disclosed in Patent Document 1 is a non-destructive inspection apparatus using pulse magnetism that non-destructively inspects a defect of a pipe to be inspected, and is inserted through the pipe to be inspected. A pair of exciting coils (Helmholtz coils) that can be arranged at an arbitrary position with respect to the pipe to be inspected, a pulse power source that applies a pulse voltage to at least one of the pair of exciting coils, and an outer periphery of the pipe to be inspected A magnetic sensor that is disposed between the pair of excitation coils on the surface and detects a magnetic field parallel to the central axis direction of the pipe to be inspected, and at least one of the pair of excitation coils is driven by the pulse power source. A nondestructive inspection apparatus using pulsed magnetism, comprising: means for detecting a pulsed magnetic field generated by the magnetic sensor and analyzing the response of the pulsed magnetic field detected by the magnetic sensor. . According to the said patent document 1, it is described that the nondestructive inspection apparatus of such a structure can test | inspect the defect of to-be-inspected piping as follows. That is, a magnetic field in the central axis direction of the pipe to be inspected can be applied to a predetermined location of the pipe to be inspected by a pair of exciting coils inserted through the pipe to be inspected. By providing a magnetic sensor disposed between the pair of exciting coils on the outer peripheral surface of the pipe to be inspected, a magnetic field parallel to the central axis direction of the pipe to be inspected can be detected. The magnetic field generated by the exciting coil is transmitted to the magnetic sensor through the piping to be inspected. In the middle, the magnetic field in the direction of the central axis of the pipe to be inspected leaks to the outside, but the magnetic field propagated by corrosion and defects differs. Here, the magnetic field generated by driving the excitation coil with a pulsed power supply is a pulsed magnetic field, so that the rising magnetic signal detected by the magnetic sensor is timed at the time of rising of the pulsed magnetic field and the time zone during which a constant magnetic field is applied thereafter. Attenuates with. By analyzing the peak value and attenuation characteristics of the detected pulse magnetic signal, it is possible to detect defects such as corrosion and cracks in the pipe with higher accuracy. The non-destructive inspection apparatus disclosed in Patent Document 1 inspects a double-structured insulated pipe in which the periphery of the pipe is kept warm by a heat insulating material and is further covered with an outer sheet metal such as a thin steel plate on the outside of the heat insulating material. Suitable for

JP 2014-44087 A

  By the way, when the nondestructive inspection apparatus disclosed in Patent Document 1 is to inspect a pipe as an object to be inspected, the pipe must be inserted into the pair of exciting coils. Generally, piping is relatively long, and if the inspection location is near the center of the piping, the pair of exciting coils must be moved from the end of the piping to the inspection location, which is cumbersome and troublesome. Further, when inspecting a pipe that is actually disposed, it may occur that the pair of exciting coils cannot be moved to an inspection location by a pipe fixing tool or a support tool. For this reason, in Patent Document 1, an electrical connection connector capable of dividing and connecting the exciting coil at a predetermined position in the circumferential direction is provided in the exciting coil.

  However, such an electrical connection connector causes an initial failure, breaks during use, or causes a failure. In addition, since the electrical connection connector wears due to its use, the current-carrying state in the electrical connection connector is not always the same for each inspection, and the current value changes for each inspection, resulting in a stable inspection result. It can happen that there is nothing. In particular, in order to generate pulsed magnetism (pulse magnetism), when a dynamic current such as a pulsed current (pulse current) is applied, the change is expected to increase. . Furthermore, the excitation coil is generally formed by winding a conductor member for several tens of turns. However, when an electrical connection connector is used, an electrical connection connector is provided for each turn. For this reason, the division | segmentation and connection by an electrical connection connector are troublesome, and it takes an effort. In addition, if even one of these becomes a poor connection, the exciting coil cannot be energized.

  The present invention has been made in view of the above circumstances, and its object is to provide a substantially uniform magnetic field without using the electrical connection connector capable of dividing and connecting the exciting coil at a predetermined position in the circumferential direction. The present invention provides a magnetic flaw detector using an exciting coil capable of forming a magnetic field and the exciting coil.

  As a result of various studies, the present inventor has found that the above object is achieved by the present invention described below. That is, the magnetic flaw detector according to one aspect of the present invention provides a pulse by supplying power to at least one of the pair of excitation coils and the pair of excitation coils that are spaced apart from each other on the outer surface of the inspection object. On the outer surface of the object to be inspected, disposed between the pair of excitation coils and detecting the magnetism, and on the basis of the detection result of the magnetic detection unit. A determination unit for determining the presence or absence of a predetermined defect in the inspection object, and each of the pair of exciting coils includes a curved plate-shaped magnetic shielding unit for shielding magnetism and an insulating material for the magnetic shielding unit. And a long conductor member wound therethrough.

  Such a magnetic flaw detector includes a pair of exciting coils formed by winding a long conductor member around a curved plate-shaped magnetic shielding portion via an insulating material. For this reason, each cross-sectional shape in each of the pair of exciting coils is arcuate. Therefore, for inspection, for example, a pair of exciting coils can be arranged on the outer surface of an object to be inspected, such as a tube, along the concave curved surfaces of the exciting coils. For this reason, the magnetic flaw detection apparatus can form a substantially uniform magnetic field by the pair of excitation coils without using the electrical connection connector capable of dividing and connecting the excitation coils at predetermined positions in the circumferential direction.

  According to another aspect, the magnetic flaw detector described above includes a plurality of sets of the pair of exciting coils.

  Since such a magnetic flaw detection apparatus includes a plurality of pairs of excitation coils, a plurality of pairs of excitation coils can be arranged along the length direction of the object to be inspected, thereby inspecting in the length direction. Can detect a wider range of objects. In the magnetic flaw detection apparatus, a plurality of pairs of exciting coils can be arranged along the circumferential direction of the object to be inspected, whereby a wider range of the object to be inspected can be detected in the circumferential direction.

  According to another aspect, in the above-described magnetic flaw detector, the plurality of sets of a pair of exciting coils are arranged in a cylindrical shape.

  Since such a magnetic flaw detector includes a plurality of pairs of exciting coils arranged adjacent to each other in the circumferential direction so as to form a cylindrical shape, the magnetic flaw detector includes a pair of the plurality of pairs of excitation coils. A substantially Helmholtz coil can be constituted by the exciting coil, and a more uniform magnetic field can be formed across the entire circumferential direction between the pair of exciting coils like the Helmholtz coil.

  In another aspect, in these above-described magnetic flaw detectors, adjacent portions of the respective conductor members in the exciting coils adjacent to each other in the circumferential direction are arranged to be parallel to each other along the radial direction. It is characterized by.

  In such a magnetic flaw detector, by passing currents flowing in opposite directions to the respective conductor members in the exciting coils adjacent to each other in the circumferential direction, adjacent portions of these respective conductor members are parallel to each other along the radial direction. Therefore, the magnetic fields of the adjacent portions induced by the current are opposite to each other and cancel each other (cancelled). Therefore, the magnetic flaw detector can form a more uniform magnetic field using the plurality of sets of a pair of exciting coils.

  An excitation coil for a magnetic flaw detector according to the present invention is an excitation coil for a magnetic flaw detector used for a magnetic flaw detector that detects a predetermined defect in an inspection object by applying magnetism, and shields magnetism. And a long conductor member wound around the magnetic shielding part with an insulating material interposed between the magnetic shielding part and the magnetic shielding part.

  Such an excitation coil for a magnetic flaw detector can be used without using the electrical connection connector capable of dividing and connecting the excitation coil at a predetermined position in the circumferential direction even when inspecting an inspection object such as a tube. A substantially uniform magnetic field can be formed by using a pair of coils.

  The magnetic flaw detector and the coil for a magnetic flaw detector according to the present invention can form a substantially uniform magnetic field without using an electrical connection connector that can divide and connect the exciting coil at a predetermined position in the circumferential direction.

It is a figure which shows the structure of the magnetic flaw detector in embodiment. It is a figure which shows the to-be-inspected object of the other aspect test | inspected with the magnetic flaw detector of embodiment. It is a figure which shows the exciting coil of the other aspect in the magnetic flaw detector of embodiment.

  Hereinafter, an embodiment according to the present invention will be described with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted suitably. In this specification, when referring generically, it shows with the reference symbol which abbreviate | omitted the suffix, and when referring to an individual structure, it shows with the reference symbol which attached the suffix.

  FIG. 1 is a diagram illustrating a configuration of a magnetic flaw detector according to an embodiment. 1A shows the overall configuration, and FIG. 1B is a cross-sectional view around the exciting coil. FIG. 2 is a diagram showing another aspect of the inspection object to be inspected by the magnetic flaw detector according to the embodiment.

  In the magnetic flaw detector according to the embodiment, a pulsed magnetic field is applied to an inspection object to be inspected by a pair of excitation coils arranged apart from each other, and a change in the magnetic field is detected to detect a predetermined inspection object. This is a device for detecting defects (abnormalities). For example, as shown in FIG. 1, the magnetic flaw detector M in such an embodiment includes a pair of first and second excitation coils 1-1 and 1-2, a power supply unit 2, and a magnetic detection unit 3. The control processing unit 4 includes a determination unit 42. In the example illustrated in FIG. 1, the control unit 4 further includes an input unit 5, an output unit 6, and an interface unit (IF unit) 7.

  The pair of first and second exciting coils 1-1 and 1-2 are devices that are arranged apart from each other on the inspection object SP to be inspected and generate a magnetic field by receiving power supply. . The inspection object SP is preferably a metal pipe SPa such as a steel pipe, an iron pipe, and an aluminum pipe, and in the example shown in FIG. 1, it is a single-layer structure pipe. The inspection object SP may be a double-structured tube SPb shown in FIG. This double-structured pipe SPb includes, for example, a steel pipe SPb1 positioned inside, a heat insulating material SPb2 covering the outer periphery of the steel pipe SPb1 with a predetermined thickness, and an exterior positioned covering the outer periphery of the heat insulating material SPb2. It is a heat insulation pipe provided with the molten zinc iron plate SPb3 which is a sheet metal. The first and second exciting coils are arranged at a predetermined interval along the axial direction of the metal tube SPa that is an example of the inspection object SPa. The predetermined interval is preferably a length substantially equal to the radius of the first and second exciting coils 1-1 and 1-2 so as to have a form similar to a Helmholtz coil.

  The first and second exciting coils 1-1 and 1-2 include magnetic shielding portions 11-1 and 11-2 and conductor members 12-1 and 12-2, respectively. Since the first and second exciting coils 1-1 and 1-2 have the same shape, the magnetic shielding portion 11, the conductor member 12 and the exciting coil 1 will be collectively described below.

  The magnetic shielding part 11 is a member for shielding magnetism, and is formed in a curved plate shape. The magnetic shielding part 11 is preferably curved according to the shape of the metal pipe SPa. More specifically, the magnetic shielding part 11 is, for example, a part of a cylinder (hollow column) cut along the axial direction, and its cross section orthogonal to the axial direction is arcuate (partial shape of the ring). It has become. The arc-shaped cross section of the magnetic shielding part 11 is similar to a part of the cross section of the metal pipe SPa so as to follow the outer peripheral surface of the metal pipe SPa. The central angle of the magnetic shielding part 11 is 180 degrees or less so that it can be placed on the outer peripheral surface of the metal tube SPa (including directly above (abutting on the outer peripheral surface) and above (including spaced from the outer peripheral surface)). Preferably there is. In addition, since it can arrange | position by the elastic deformation, the central angle of the magnetic shielding part 11 can also exceed 180 degree | times slightly. In the example shown in FIG. 1, it is 180 degrees so that the outer periphery of the metal pipe SPa can be covered to the maximum without difficulty. In addition, the central angle of the magnetic shielding part 11 may be any of 120 degrees, 90 degrees, and 60 degrees. The magnetic shielding part 11 having such a central angle includes a plurality of exciting coils 1 having the same shape when surrounding the entire circumference of the metal pipe SPa or the double-structured pipe SPb as will be described later, including the case of 180 degrees. It can be executed with. Therefore, it is only necessary to mass-produce the exciting coil 1 having the same shape, so that the cost of the exciting coil 1 can be reduced due to the mass production effect.

  Such a magnetic shielding part 11 is formed of, for example, an electromagnetic steel plate, preferably a plurality of laminated electromagnetic steel plates. For example, the magnetic shielding part 11 is formed by compressing soft magnetic powder having an insulating film.

  The conductor member 12 is a wire having a long electrical conductivity such as a round cross-section or a square cross-section, and is wound along the outer peripheral surface of the magnetic shield 11 via an insulating material such as resin or oil paper, A coil is formed. The conductor member 12 is a conductor wire having a relatively high conductivity such as copper or aluminum and insulated and coated with a resin.

  The number of turns of the excitation coil 1 having such a configuration is appropriately set according to the intensity of a desired magnetic field to be generated by the excitation coil 1.

  Since such a first exciting coil 1-1 is formed by winding a long first conductor member 12-1 around a curved plate-like first magnetic shielding portion 11-1, the first conductor member 12- A part of 1 has an overlapping portion that overlaps in the radial direction via the first magnetic shielding portion 11-1. Similarly, since the second exciting coil 1-2 is formed by winding the long second conductor member 12-2 around the second magnetic shielding portion 11-2 having a curved plate shape, the second conductor member 12- 1 has a superposed portion that overlaps in part in the radial direction through the second magnetic shielding portion 11-2.

  One end of the first conductor member 12-1 in the first excitation coil 1-1 is connected to the power supply unit 2, and the other end of the first conductor member 12-1 is the second conductor member 12 in the second excitation coil. -2 is connected to one end, and the other end of the second conductor member 12-2 is connected to the power supply unit 2. Thus, the 1st and 2nd exciting coils 1-1 and 1-2 are connected in series. The first and second excitation coils 1-1, 1-2 are made to be able to pass currents in opposite directions (currents of opposite phases) to the first and second excitation coils 1-1, 1-2. -2, in order to allow current to flow through only one of them, as shown by a broken line in FIG. 1, the one end and the other end of the first conductor member 12-1 in the first exciting coil 1-1 are respectively The one end and the other end of the second conductor member 12-2 in the second excitation coil 1-2 may be connected to the power supply unit 2, respectively.

  The power supply unit 2 is connected to the control processing unit 4, and according to the control of the control processing unit 4, a pulsed current (pulse current) is applied to at least one of the pair of first and second exciting coils 1-1 and 1-2. Is a device for generating pulsed magnetism (pulse magnetism) by supplying power. In the example shown in FIG. 1, since the first and second exciting coils 1-1 and 1-2 are connected in series as described above, the power supply unit 2 includes the first and second exciting coils 1-1. Pulse magnetism is generated by supplying a pulsed current to both 1-2. Note that, as described above, the power supply unit 2 appropriately switches the respective energization paths to the first and second exciting coils 1-1 and 1-2 in order to supply a reverse-phase current or only one current. A switching circuit may be provided.

  The magnetic detection unit 3 is disposed between the pair of exciting coils 1-1 and 1-2 on the outer surface (including directly above and above) of the inspection object SP, and is connected to the control processing unit 4. Then, the magnetic detection unit 3 detects magnetism and outputs the detection result to the control processing unit 4. Various magnetic sensors can be used as the magnetic detection unit 3. More specifically, the magnetic detection unit 3 includes a magnetic sensor using a magnetoresistive element (MR element) that uses a magnetoresistive effect in which an electric resistance changes according to the magnetic field, and a skin effect of a high permeability alloy magnetic material. Magnetic sensor using magneto-impedance element using the magneto-impedance effect that changes the impedance due to magnetic field, magnetic sensor using hall element using the Hall effect, and flux gate using the magnetic saturation of high permeability material A magnetic sensor, a magnetic sensor element using a superconducting quantum interference device (SQUID), or a superconducting quantum interference device using a superconductor ring having a Josephson junction at two locations, or the like is used.

  The input unit 5 is connected to the control processing unit 4. For example, various commands such as a command for instructing the measurement of the inspection object SP, and an identifier (for example, an identification number of the inspection object) in the inspection object SP, for example. A device that inputs various data necessary for measuring input or the like to the magnetic flaw detector M, such as a plurality of input switches assigned with predetermined functions, a keyboard, a mouse, and the like. The output unit 6 is connected to the control processing unit 4, and under the control of the control processing unit 4, commands and data input from the input unit 5, and measurement results of the inspection object SP measured by the magnetic flaw detector M ( For example, a device that outputs measurement data of the magnetic detection unit 3 and the presence or absence of defects), for example, a display device such as a CRT display, an LCD (liquid crystal display) and an organic EL display, or a printing device such as a printer.

  A touch panel may be configured from the input unit 5 and the output unit 6. In the case of configuring this touch panel, the input unit 5 is a position input device that detects and inputs an operation position such as a resistive film method or a capacitance method, and the output unit 6 is a display device. In this touch panel, a position input device is provided on the display surface of the display device, one or more input content candidates that can be input to the display device are displayed, and the user touches the display position where the input content to be input is displayed. Then, the position is detected by the position input device, and the display content displayed at the detected position is input to the magnetic flaw detector M as the operation input content of the user. In such a touch panel, since the user can easily understand the input operation intuitively, the magnetic flaw detector M that is easy for the user to handle is provided.

  The IF unit 7 is a circuit that is connected to the control processing unit 4 and inputs / outputs data to / from an external device according to the control of the control processing unit 4. For example, an interface circuit of RS-232C that is a serial communication system , An interface circuit using the Bluetooth (registered trademark) standard, an interface circuit performing infrared communication such as an IrDA (Infrared Data Association) standard, and an interface circuit using the USB (Universal Serial Bus) standard.

  The control processing unit 4 is a circuit for controlling each part of the magnetic flaw detector M according to the function of each part. The control processing unit 4 includes, for example, a microcomputer including a CPU (Central Processing Unit), a memory, and peripheral circuits thereof. In the control processing unit 4, a control unit 41 and a determination unit 42 are functionally configured by executing a program.

  The controller 41 is for controlling each part of the magnetic flaw detector M according to the function of each part.

  The determination unit 42 determines the presence or absence of a predetermined defect (abnormality) in the inspection object SP based on the detection result of the magnetic detection unit 3. Examples of the predetermined defect include wrinkles, cracks, and thinness (thinning). For example, the determination unit 42 determines the presence or absence of the predetermined defect by the determination method disclosed in Patent Document 1. In Patent Document 1, the presence / absence of a defect is determined by analyzing a peak value and an attenuation characteristic in a detection result obtained by the magnetic detection unit 3 by applying a pulse magnetic field. More specifically, the determination unit 42 may determine the presence / absence of the defect by changing the pulse response characteristics according to the presence / absence of the defect. More specifically, the pulse response, which is the intensity of the magnetic field with respect to the passage of time starting from the timing at which the pulse magnetic field is applied, is applied to the pair of first and second exciting coils 1-1 and 1-2 in the same direction. When a pulse magnetic field is applied by flowing a current (in-phase pulse current), if there is a defect, attenuation is faster than when the metal tube SPa is normal. For this reason, the time constant T0 of the pulse response characteristic in the normal metal tube SPa is measured in advance as the determination threshold value th1 and stored in the control processing unit 4 in advance, and the determination unit 42 controls the power supply unit 2 according to the control of the control unit 41. By passing the in-phase pulse current through the pair of first and second exciting coils 1-1 and 1-2 by comparing the time constant Tm in the detection result of the magnetic detection unit 3 with the determination threshold th1 The presence or absence of a defect in the pipe SPa can be determined.

  In addition, for example, when the negative-phase pulse current is configured to be energized as described above, the determination unit 42 is a pair of the first and second exciting coils 1 by the power source unit 2 according to the control of the control unit 41. -1, 1-2 may be applied to a pulsed magnetic field by applying a pulse current having a reverse phase, and the presence / absence of the defect may be determined based on the presence / absence of a rise or fall in the pulse response. When a pulse current of the reverse phase is passed through the pair of first and second exciting coils 1-1 and 1-2, the normal metal tube SPa has a rise or fall in the pulse response, but the defective metal In the tube SPa, these rise and fall hardly occur in the pulse response. For this reason, the determination part can determine as mentioned above.

  Note that the double-structured pipe SPb such as a heat insulating pipe shown in FIG. 2 is also determined in the same manner as the metal pipe SPa.

  In such a magnetic flaw detector M, when a test object SP such as a metal pipe SPa or a double-structured pipe SPb is flawed, first, a user (operator) forms a pair of first on the outer peripheral surface of the test object SP. The first and second exciting coils 1-1 and 1-2 are arranged at a predetermined interval. When the power switch (not shown) is turned on by the user, the control processing unit 4 executes initialization of each necessary unit, and the control processing unit 4 includes the control unit 41 and the determination unit 42 by executing the program. Is functionally configured.

  When receiving an instruction to start flaw detection by the user via the input unit 5, the control unit 41 causes the power supply unit 2 to supply, for example, the in-phase pulse current to the pair of first and second exciting coils 1-1 and 1-2. Shed. As a result, the pair of first and second exciting coils 1-1 and 1-2 generate a pulse magnetic field and apply it to the object SP. This pulse magnetic field is detected by the magnetic detection unit 3 along the inspection object SP, and the magnetic detection unit 3 outputs the detection result to the control processing unit 4. The determination unit 42 determines the presence or absence of a predetermined defect in the inspection object SP based on the detection result of the magnetic detection unit 3, and the control unit 41 detects the detection result of the magnetic detection unit 3 and the determination result of the determination unit 42. Is output to the output unit 6. The control unit 41 may output the detection result of the magnetic detection unit 3 and the determination result of the determination unit 42 to an external device (not shown) via the IF unit 7 as necessary.

  As described above, the magnetic flaw detector M according to the present embodiment has the long conductor member 12 (12-1) interposed between the curved plate-shaped magnetic shield 11 (11-1, 11-2) via the insulating material. , 12-2) is provided with a pair of exciting coils 1 (1-1, 1-2). For this reason, each cross-sectional shape in each of the pair of first and second exciting coils 1-1 and 1-2 is an arc shape that is a partial shape of the ring. Therefore, for inspection, for example, the first and second exciting coils 1-1 and 1-2 are recessed at an arbitrary position on the outer surface of the object SP to be inspected, such as a metal tube SPa or a double-structured tube SPb. A pair of first and second exciting coils 1-1 and 1-2 can be arranged along each curved surface. Further, even when the inspection object SP is engaged with a fixture or a support, it is possible to move on the outer surface of the inspection object SP. For this reason, the magnetic flaw detector M according to the present embodiment uses a pair of first and second excitation coils 1-1 without using the electrical connection connector that can divide and connect the excitation coils at predetermined positions in the circumferential direction. A substantially uniform magnetic field can be formed by 1-2. And since the magnetic flaw detector M in this embodiment is not provided with the said electrical connection connector, initial failure, the damage in use, the change of the energization state for every inspection, disconnection, etc. resulting from the said electrical connection connector The trouble can be avoided.

  In the magnetic flaw detector M according to the above-described embodiment, the exciting coil 1 is formed by winding the conductor member 12 around the curved plate-shaped magnetic shielding portion 11. However, the magnetic shielding portion 11 is a sheet-like shape that can be bent. It may be. Such a sheet-like magnetic shielding part 11 is used by being curved along the outer periphery of the inspection object SP. Since it can be curved according to the outer periphery curvature of the inspection object SP if it is a sheet shape, it can be applied to a wide range of inspection objects SP, and the storage space when not in use can be saved.

  Moreover, although the magnetic flaw detector M in the above-described embodiment is configured to include one pair of excitation coils 1, it is not limited thereto, and may be configured to include a plurality of pairs of excitation coils 1. good. Since such a magnetic flaw detector M includes a plurality of pairs of excitation coils 1, a plurality of pairs of excitation coils 1 can be arranged along the length direction of the inspection object SP. A wider range of the inspection object SP can be detected in the direction. In the magnetic flaw detector M, a plurality of pairs of exciting coils 1 can be arranged along the circumferential direction of the inspection object SP, thereby detecting a wider range of the inspection object SP in the circumferential direction.

  When the magnetic flaw detection apparatus M is configured to include a plurality of pairs of excitation coils 1, the plurality of pairs of excitation coils 1 are preferably arranged so as to be cylindrical. Since such a magnetic flaw detector M includes a plurality of pairs of exciting coils 1 arranged sequentially adjacent to each other in the circumferential direction so as to have a cylindrical shape, the magnetic flaw detector includes the plurality of sets of 1 A substantially Helmholtz coil can be constituted by the pair of excitation coils 1, and a more uniform magnetic field can be formed across the entire circumferential direction between the pair of excitation coils 1 like the Helmholtz coil.

  FIG. 3 is a diagram illustrating an exciting coil according to another aspect of the magnetic flaw detector according to the embodiment. In one example, as shown in FIG. 3, the magnetic flaw detector M includes a pair of first and second excitation coils 1-1, 1-2 and a pair of third and fourth excitation coils 1-3, 1- Two pairs of exciting coils 1 each having four pairs are provided. FIG. 3 shows a peripheral portion of two pairs of exciting coils 1. In the example shown in FIG. 3, the pair of first and second exciting coils 1-1 and 1-2 are connected in series and connected to the power supply unit 2. Similarly, the pair of third and fourth exciting coils 1-3 and 1-4 are connected in series and connected to the power supply unit 2. And the adjacent part of each conductor member 12 in the exciting coils 1 adjacent to each other in the circumferential direction is preferably arranged so as to be parallel to each other along the radial direction. In the example shown in FIG. 3, the adjacent portions P1 and P2 of the conductor members 12-1 and 12-3 in the first exciting coil 1-1 and the third exciting coil 1-3 adjacent to each other in the circumferential direction are in the radial direction. Are arranged so as to be parallel to each other. Similarly, unillustrated adjacent portions P3 and P4 of the conductor members 12-2 and 12-4 in the second exciting coil 1-2 and the fourth exciting coil 1-4 adjacent to each other in the circumferential direction are along the radial direction. Are arranged parallel to each other. More specifically, the end surfaces parallel to the axial direction in the first and third magnetic shielding portions 11-1 and 11-3 having a semi-cylindrical shape with a central angle of 180 degrees are formed flat so as to follow the radial direction. Is done. By winding the first and third conductor members 12-1 and 12-3 around the first and third magnetic shielding portions 11-1 and 11-3 having such a shape, the adjacent portions P1 and P2 The first and third conductor members 12-1 and 12-3 are substantially parallel to each other. Similarly, each end surface parallel to the axial direction in the second and fourth magnetic shielding materials 11-2 and 11-4 having a semi-cylindrical shape with a central angle of 180 degrees is formed flat so as to be along the radial direction. By winding the second and fourth conductor members 12-2 and 12-4 around the second and fourth magnetic shielding portions 11-2 and 11-4 having such shapes, the adjacent portions P3 and P4 The second and fourth conductor members 12-2 and 12-4 are substantially parallel to each other. In such a magnetic flaw detector M, the respective conductor members 12-1, 12-3; 12-2, 12 in the exciting coils 1-1, 1-3; 1-2, 1-4 adjacent to each other in the circumferential direction. -4 are energized with currents flowing in opposite directions, so that adjacent portions P1, P2; P3, P4 of the conductor members 12-1, 12-3; 12-2, 12-4 are aligned along the radial direction. Since they are arranged so as to be parallel to each other, the magnetic fields of the adjacent portions P1, P2; P3, P4 induced by the currents are opposite to each other and cancel (cancel). Therefore, the magnetic flaw detector M can form a more uniform magnetic field using the two pairs of exciting coils 1-1, 1-2; 1-3, 1-4.

  In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Therefore, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not covered by the claims. To be construed as inclusive.

M Magnetic flaw detector SP Inspected object SPa Metal tube SPb Double structure tube 1, 1-1 to 1-4 Excitation coil 2 Power supply unit 3 Magnetic detection unit 11, 11-1 to 11-4 Conductive member 12, 12- 1-12-4 Magnetic shielding part 42 determination part

Claims (5)

A pair of exciting coils that are spaced apart from each other on the outer surface of the object to be inspected;
A power supply unit that generates pulsed magnetism by supplying power to at least one of the pair of exciting coils;
A magnetic detection unit that is disposed between the pair of excitation coils on the outer surface of the inspection object and detects magnetism;
A determination unit that determines presence or absence of a predetermined defect in the inspection object based on a detection result of the magnetic detection unit;
Each of the pair of exciting coils includes a curved plate-shaped magnetic shielding portion for shielding magnetism, and a long conductor member wound around the magnetic shielding portion with an insulating material interposed therebetween. Magnetic flaw detector. The magnetic flaw detector according to claim 1, comprising a plurality of pairs of the pair of exciting coils. The magnetic flaw detector according to claim 2, wherein the plurality of pairs of excitation coils are arranged in a cylindrical shape. 4. The magnetic flaw detection according to claim 2, wherein adjacent portions of the conductor members in the exciting coils adjacent to each other in the circumferential direction are arranged so as to be parallel to each other along the radial direction. apparatus. An excitation coil for a magnetic flaw detector used in a magnetic flaw detector that detects a predetermined defect in an inspection object by applying magnetism,
An excitation coil for a magnetic flaw detector, comprising: a magnetic shielding part for shielding magnetism; and a long conductor member wound around the magnetic shielding part via an insulating material.

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