Electromagnetic ultrasonic sensor and ultrasonic flaw detection apparatus

Abstract

To provide an electromagnetic ultrasonic sensor and an ultrasonic flaw detector capable of further increasing signal intensity.SOLUTION: The electromagnetic ultrasonic sensor TSa includes a magnet group TMG and a coil so as to surround a space in which the test object WK is arranged, the magnet group TMG includes a plurality of first permanent magnets PM1 (PM11 to PM14) sequentially arranged in a circumferential direction so that S-poles and N-poles alternately face the space in the circumferential direction, the coil includes one or a plurality of unit coils, and the unit coil connects two first inter-conductor wires PM1 to SC14 adjacent in the circumferential direction so that, in each of the plurality of first permanent magnets SC11, first conductor wires SC11 to along the axial direction between the first permanent magnets and the test object WK, a current direction of the first conductor wires and SC13 at the S-pole, and a current direction of the first conductor wires and at the N-pole are opposite to each other, SC12 PM1 SC14 SC14 SC11, and second conductive wires RC11 to RC14 along the circumferential direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electromagnetic ultrasonic sensor capable of transmitting and receiving ultrasonic waves, and an ultrasonic flaw detector equipped with the same for detecting defects in a test object. [Background technology]

[0002] Ultrasonic flaw detectors that use ultrasonic waves to detect defects in a test object, such as cracks, cavities, inclusions, recesses, thinning, etc., are used in a variety of cases because they can inspect the test object nondestructively. One known example is an ultrasonic flaw detector that uses guided waves, and an electromagnetic ultrasonic sensor that is provided in this ultrasonic flaw detector is disclosed in, for example, Patent Document 1.

[0003] The electromagnetic ultrasonic sensor disclosed in Patent Document 1 is an electromagnetic ultrasonic sensor that transmits and receives guided waves, which are ultrasonic waves that travel inside a pipe wall, and includes: a permanent magnet arranged so that a first magnetic pole faces a portion of the pipe wall surface of the pipe and a second magnetic pole faces in a direction away from the portion of the pipe wall surface, a first coil wound around the permanent magnet around a first coil axis perpendicular to a line connecting the first magnetic pole and the second magnetic pole, and a second coil wound around the permanent magnet around a second coil axis perpendicular to the line connecting the first magnetic pole and the second magnetic pole and perpendicular to the first coil axis. The electromagnetic ultrasonic sensor is a plurality of sensors, and the plurality of sensors are arranged at intervals from each other in the circumferential direction of the pipe. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-098226 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the electromagnetic ultrasonic sensor disclosed in Patent Document 1, the permanent magnet is arranged so that its first magnetic pole faces a portion of the pipe wall surface, making it difficult to apply the electromagnetic ultrasonic sensor disclosed in Patent Document 1 to an object with a small diameter. If an attempt is made to apply the electromagnetic ultrasonic sensor to an object with a small diameter, the permanent magnet must be made smaller according to the diameter of the object, resulting in a decrease in ultrasonic signal strength. Furthermore, in Patent Document 1, multiple electromagnetic ultrasonic sensors arranged circumferentially face the pipe wall surface with the same pole, so the magnetic fields of the permanent magnets cancel each other out. As a result, the magnetic field applied to the surface of the object is reduced, resulting in a decrease in ultrasonic signal strength.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electromagnetic ultrasonic sensor capable of increasing the signal strength of ultrasonic waves, and an ultrasonic flaw detection device including the same. [Means for solving the problem]

[0007] After various studies, the inventors of the present invention found that the above object can be achieved by the following invention. That is, an electromagnetic ultrasonic sensor according to one aspect of the present invention is an electromagnetic ultrasonic sensor comprising a magnet group and a coil so as to surround a space for placing a test object, the magnet group comprising a plurality of first permanent magnets which are sequentially arranged along the circumferential direction so that their south poles and north poles face the space alternately in the circumferential direction, the coil comprising one or a plurality of predetermined unit coils, the unit coils being arranged such that, for each of the plurality of first permanent magnets, when the test object is placed in the space, a magnetic field is formed between the first permanent magnet and the test object along an axial direction relative to the circumferential direction. and a second conductor wire that connects two adjacent first conductor wires in the circumferential direction and extends along the circumferential direction so that a first direction of current flowing in the first conductor wire, which is arranged between the first permanent magnet facing the space at its S pole and the subject, and a second direction of current flowing in the first conductor wire, which is arranged between the first permanent magnet facing the space at its N pole and the subject, are opposite to each other, and each first conductor wire and each second conductor wire are formed of a single conductor wire that makes one or more turns around the space in the axial direction. Preferably, in the above-mentioned electromagnetic ultrasonic sensor, when the coil includes a plurality of unit coils, the plurality of unit coils are connected in series. Preferably, in the above-mentioned electromagnetic ultrasonic sensor, when the coil includes a plurality of unit coils, the plurality of unit coils are connected in parallel.

[0008] In such an electromagnetic ultrasonic sensor, multiple first permanent magnets are sequentially arranged along the circumferential direction so that their south and north poles alternate in the circumferential direction and face the space, so the first permanent magnets do not necessarily need to be arranged so that they face each other at a portion of the object surface, and the magnetic fields of the first permanent magnets do not cancel each other out and the magnetic fields around each first permanent magnet are amplified. As a result, the electromagnetic ultrasonic sensor can further increase the signal strength of the ultrasonic waves.

[0009] In another aspect, in the above-mentioned electromagnetic ultrasonic sensor, the magnet group is a plurality of first permanent magnets, each of which faces the space with its south pole and north pole alternating in the axial direction, and which are sequentially arranged in the axial direction at intervals of half the wavelength of the ultrasonic waves transmitted to and received from the subject.

[0010] Such an electromagnetic ultrasonic sensor has a plurality of magnet groups arranged in the axial direction with alternating magnetic poles, and can therefore enhance ultrasonic waves with frequency components of specific wavelengths.

[0011] In another aspect, in the electromagnetic ultrasonic sensor described above, each of the plurality of first permanent magnets is one of a plurality of second permanent magnets that form a Halbach structure in a tangential direction relative to the circumferential direction.

[0012] Such an electromagnetic ultrasonic sensor uses one of the multiple second permanent magnets forming the Halbach structure as the first permanent magnet, which makes it possible to make the magnetic field of the first permanent magnet stronger, thereby further increasing the ultrasonic signal strength.

[0013] In another aspect, in the above-described electromagnetic ultrasonic sensor, the plurality of first permanent magnets are two third permanent magnets, one of which is arranged in the axial direction and one of which forms a Halbach structure in the tangential direction to the circumferential direction and the other in the axial direction, and which face the space with its S pole and the other of which is arranged in the axial direction and faces the space with its N pole, and the magnet group is a plurality of first permanent magnets, each of which faces the space with its S pole and N pole alternately in the axial direction, and which are arranged sequentially in the axial direction at intervals of half the wavelength of the ultrasonic waves transmitted to and received from the subject.

[0014] Such an electromagnetic ultrasonic sensor has a plurality of magnet groups in the axial direction, and of the plurality of third permanent magnets that form Halbach structures in the tangential direction and the axial direction, two third permanent magnets that face the space and are arranged in the axial direction are used as first permanent magnets. This makes it possible to make the magnetic field of the first permanent magnets stronger, thereby further increasing the ultrasonic signal strength.

[0015] In another aspect, in the above-mentioned electromagnetic ultrasonic sensor, the plurality of first permanent magnets include four first permanent magnets arranged sequentially along the circumferential direction at 90° intervals, and are arranged at a position rotated 45° circumferentially from the case where the first conductor wire is arranged at the circumferential center position of the first permanent magnet.

[0016] When ultrasonic waves are transmitted and received between the first permanent magnet and the first conductor wire, they can be transmitted and received in so-called T-mode ultrasonic waves, and when the first permanent magnet is moved to the position of the second conductor wire and ultrasonic waves are transmitted and received between the first permanent magnet and the second conductor wire, they can be transmitted and received in so-called L-mode ultrasonic waves.In the above-mentioned electromagnetic ultrasonic sensor, the first conductor wire is disposed at a position rotated 45° circumferentially from the case where it is disposed at the central position of the first permanent magnet in the circumferential direction, so that ultrasonic waves can be transmitted and received between the first permanent magnet and each of the first and second conductor wires, and ultrasonic waves in both T-mode and L-mode can be transmitted and received.

[0017] Note that T-mode (Torsional mode) ultrasound is ultrasound that propagates through the subject while vibrating in a twisting manner, and L-mode (Longitudinal mode) ultrasound is ultrasound that propagates through the subject while vibrating in the propagation direction.

[0018] An ultrasonic flaw detection device according to another aspect of the present invention includes any one of these electromagnetic ultrasonic sensors for transmission and reception.

[0019] This makes it possible to provide an ultrasonic flaw detector equipped with either of these electromagnetic ultrasonic sensors for transmission and reception, and the ultrasonic flaw detector can transmit ultrasonic waves with a higher signal strength to the test object. [Effects of the Invention]

[0020] The electromagnetic ultrasonic sensor according to the present invention can increase the signal strength of ultrasonic waves, and the present invention can provide an ultrasonic flaw detection device equipped with this electromagnetic ultrasonic sensor. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a block diagram showing the configuration of an ultrasonic flaw detection device according to an embodiment. [Figure 2] 3 is a diagram for explaining the configuration of an electromagnetic ultrasonic sensor provided in the ultrasonic flaw detection device. FIG. [Figure 3] 10 is a diagram for explaining a coil of another aspect (a coil of a second aspect) in the electromagnetic ultrasonic sensor. FIG. [Figure 4] 10 is a diagram for explaining a coil of another aspect (a coil of a third aspect) in the electromagnetic ultrasonic sensor. FIG. [Figure 5] 10A and 10B are diagrams for explaining the effects of the electromagnetic ultrasonic sensor of the embodiment, as an example. [Figure 6] 10A and 10B are diagrams for explaining the effects of an electromagnetic ultrasonic sensor of a comparative example, as an example. [Figure 7] FIG. 1 is a diagram showing an example of a received ultrasonic signal. [Figure 8] 4 is a flowchart showing an operation of the ultrasonic flaw detection device. [Figure 9] 10A and 10B are diagrams for explaining an electromagnetic ultrasonic sensor in a first modified embodiment. [Figure 10] FIG. 10 is a perspective view for explaining an electromagnetic ultrasonic sensor in a second modified embodiment. [Figure 11] FIG. 10 is a plan view seen from the axial direction for explaining the electromagnetic ultrasonic sensor in the second modified embodiment. [Figure 12] 10A and 10B are diagrams for explaining the effects of the electromagnetic ultrasonic sensor according to the second modified embodiment of the embodiment, as an example. [Figure 13] 10A and 10B are diagrams for explaining an electromagnetic ultrasonic sensor in a third modified embodiment. [Figure 14] 14 is a plan view seen from the left side of the paper in the axial direction in FIG. 13 for explaining the magnet group in the electromagnetic ultrasonic sensor of the third modified embodiment. FIG. [Figure 15] 17A and 17B are cross-sectional views taken along the line II shown in FIGS. 14 and 16, respectively. [Figure 16] 14 is a plan view illustrating the magnet group in the electromagnetic ultrasonic sensor of the third modified embodiment, as viewed from the right side of the paper in the axial direction in FIG. 13. FIG. [Figure 17] 10A and 10B are diagrams for explaining an electromagnetic ultrasonic sensor in a fourth modified embodiment. [Figure 18] FIG. 10 is a diagram for explaining a coil (fourth mode coil) in the electromagnetic ultrasonic sensor of the fourth modified embodiment. [Figure 19] 10 is a diagram for explaining a coil of another embodiment (a coil of a fifth embodiment) in the electromagnetic ultrasonic sensor of the fourth modified embodiment. FIG. [Figure 20] 10 is a diagram for explaining a coil of another embodiment (a coil of a sixth embodiment) in the electromagnetic ultrasonic sensor of the fourth modified embodiment. FIG. [Figure 21] 10 is a diagram for explaining the positional relationship between a first permanent magnet and a first conductor wire of a coil in the electromagnetic ultrasonic sensor of the fourth modified embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments. In addition, components with the same reference numerals in each drawing indicate the same components, and their description will be omitted as appropriate. In this specification, when referring to a general term, a reference numeral without a subscript is used, and when referring to an individual component, a reference numeral with a subscript is used.

[0023] FIG. 1 is a block diagram showing the configuration of an ultrasonic flaw detector according to an embodiment. FIG. 2 is a diagram illustrating the configuration of an electromagnetic ultrasonic sensor provided in the ultrasonic flaw detector. FIG. 2A is a perspective view, and FIG. 2B is a plan view viewed from the axial direction. FIGS. 3 and 4 are diagrams illustrating coils of other aspects (second and third aspect coils) in the electromagnetic ultrasonic sensor. In FIGS. 3 and 4, the coils are illustrated expanded on a plane, and the first permanent magnets PM11 to PM14 (PM21 to PM24) are illustrated by dashed lines. FIG. 5 is a diagram illustrating the effects of an electromagnetic ultrasonic sensor of an example, as an example. FIG. 5A is a plan view viewed from the axial direction to illustrate the arrangement of four first permanent magnets PM11 to PM14 (PM21 to PM24) relative to an object WK used in a simulation as the example, and FIG. 5B shows the results of magnetic field analysis. FIG. 6 is a diagram illustrating the effects of an electromagnetic ultrasonic sensor of a comparative example, as an example. Fig. 6A is a plan view seen from the axial direction to explain the arrangement of four first permanent magnets PM11-PM14 (PM21-PM24) relative to the subject WK used in the simulation as the comparative example, and Fig. 6B shows the results of magnetic field analysis. In each of Figs. 5B and 6B, arrows (→) indicate magnetic field lines and their directions, and the shading indicates the magnitude of magnetic flux density, with lighter shading indicating greater magnetic flux density. Fig. 7 is a diagram showing an example of a received ultrasonic signal. The horizontal axis of Fig. 7 is time (ms) and the vertical axis is the magnitude of the received signal (signal value, Received signal) (mV).

[0024] The ultrasonic flaw detection device 1000 in the embodiment includes, for example, an ultrasonic wave generating unit UG, a transmitting electromagnetic ultrasonic sensor TSa, a receiving electromagnetic ultrasonic sensor RSa, a control processing unit 1, and a memory unit 5, as shown in Figures 1 and 2, and in the example shown in Figures 1 and 2, further includes an input unit 2, a display unit 3, and an interface unit (IF unit) 4.

[0025] The transmitting electromagnetic ultrasonic sensor TSa is an electromagnetic ultrasonic sensor that includes a magnet group TMG and a coil CO1 (reference symbol not shown) so as to surround a space in which the test object WK is to be placed, and is a device that is connected to an ultrasonic wave generator UG and transmits ultrasonic waves of a guided wave to the test object WK using the ultrasonic wave generator UG. The receiving electromagnetic ultrasonic sensor RSa is an electromagnetic ultrasonic sensor that includes a magnet group RMG and a coil CO2 (reference symbol not shown) so as to surround a space in which the test object WK is to be placed, and is a device that receives ultrasonic waves that propagate through the test object WK, and is connected to a control processing unit 1 and outputs a received ultrasonic wave signal to the control processing unit 1.

[0026] An electromagnetic acoustic sensor (hereinafter abbreviated as "EMAT") is a probe that uses electromagnetic action to generate a sound source directly inside a subject and transmit and receive ultrasonic waves. EMATs do not require a couplant to transmit and receive ultrasonic waves, allowing for contactless measurement. There are two types of EMATs: Lorentz type and magnetostrictive type, both of which are composed of a magnet and a coil. A Lorentz type EMAT has a magnet that forms a static magnetic field in a metal and a coil that generates eddy currents in the metal using high-frequency current. The interaction between the static magnetic field and the eddy current generates a Lorentz force in the metal, generating ultrasonic waves, and receives the ultrasonic waves propagating through the metal through the inverse action. On the other hand, a magnetostrictive EMAT is applicable only to magnetic materials and transmits and receives ultrasonic waves by utilizing the magnetostrictive effect of the magnetic material. In this embodiment, a Lorentz type EMAT is used.

[0027] The transmitting electromagnetic ultrasonic sensor TSa and the receiving electromagnetic ultrasonic sensor RSa have the same structure, so the following mainly describes the transmitting electromagnetic ultrasonic sensor TSa, and by listing the reference signs in the configuration of the receiving electromagnetic ultrasonic sensor RSa in parentheses after the reference signs in the configuration of the transmitting electromagnetic ultrasonic sensor TSa that correspond to the configuration of the receiving electromagnetic ultrasonic sensor RSa, the description of the receiving electromagnetic ultrasonic sensor RSa will be omitted in lieu of the description of the receiving electromagnetic ultrasonic sensor RSa.

[0028] The magnet group TMG (RMG) includes a plurality of first permanent magnets PM1 (PM2) sequentially arranged along the circumferential direction so that their south and north poles alternate in the circumferential direction and face the space. The number of first permanent magnets PM1 (PM2) may be any number, preferably four. In the example shown in FIG. 2, the magnet group TMG (RMG) includes four first permanent magnets PM11-PM14 (PM21-PM24) sequentially arranged along the circumferential direction at 90° intervals. Each of these four first permanent magnets PM11-PM14 (PM21-PM24) has a quadrangular prism shape (e.g., a cube or rectangular parallelepiped shape). The space for placing the subject WK is, for example, a columnar shape with a polygonal cross section having the same number of sides as the number of first permanent magnets PM1 (PM2). In the example shown in FIG. 2, the space is a rectangular prism or cube large enough to accommodate the subject WK. The first permanent magnets PM11, PM13 (PM21, PM23) are arranged to face each other across the space with their south poles facing the space. That is, the first permanent magnet PM11 (PM21) is arranged so that the magnetic pole plane of its south pole is located on a side surface (first side surface) of a rectangular parallelepiped (or cube) that forms the space, and the first permanent magnet PM13 (PM23) is arranged so that the magnetic pole plane of its south pole is located on a side surface (second side surface) of the rectangular parallelepiped (or cube) that forms the space that faces the first side surface. The first permanent magnets PM12, PM14 (PM22, PM24) are arranged so that they face each other across the space with their north poles facing the space. That is, the first permanent magnet PM12 (PM22) is arranged so that the magnetic pole plane of its N pole is located on the side (third side) sandwiched between the first and second side faces of the rectangular parallelepiped (or cube) that forms the space, and the first permanent magnet PM14 (PM24) is arranged so that the magnetic pole plane of its N pole is located on the side (fourth side) facing the third side face of the rectangular parallelepiped (or cube) that forms the space. Therefore, the normal (first normal) to the magnetic pole plane of the S pole of the first permanent magnets PM11, PM13 (PM21, PM23) and the normal (second normal) to the magnetic pole plane of the N pole of the first permanent magnets PM12, PM14 (PM22, PM24) are perpendicular to each other.

[0029] The coil CO1 (CO2) includes one or more predetermined unit coils. The unit coil of the coil CO1 (CO2) includes, for each of a plurality of first permanent magnets PM1 (PM2), a first conductor wire SC1 (SC2) that is arranged along the axial direction with respect to the circumferential direction between the first permanent magnet PM1 (PM2) and the test subject WK when the test subject WK is placed in the space, and a second conductor wire RC1 (RC2) that connects two first conductor wires SC1 (SC2) adjacent to each other in the circumferential direction and that is arranged along the circumferential direction so that a first direction of current flowing in the first conductor wire SC1 (SC2) that is arranged between the first permanent magnet PM1 (PM2) that faces the space with its south pole and the test subject WK and a second direction of current flowing in the first conductor wire SC1 (SC2) that is arranged between the first permanent magnet PM1 (PM2) that faces the space with its north pole and the test subject WK are opposite to each other. Each of the first conductor wires SC1 (SC2) and each of the second conductor wires RC1 (RC2) is formed of a single conductor wire that makes one or more turns around the space in the axial direction.

[0030] 2, the coil CO1 (CO2) is a coil COa1 (COa2) (reference symbol not shown in FIG. 2, see FIG. 9, etc.) (a first-mode coil) that includes one unit coil COa (reference symbol not shown in FIG. 2) that makes one turn, and the unit coil COa (COa) in the first-mode coil COa1 (COa2) includes four first conductor wires SCa11 to SCa14 (SCa21 to SCa24) and four second conductor wires RCa11 to RCa14 (RCa21 to RCa24). When a test object WK is placed in the space, the first conductor wire SCa11 (SCa21) is arranged between the first permanent magnet PM11 (PM21) and the test object WK along the axial direction. The first conductor wire SCa12 (SCa22) is arranged between the first permanent magnet PM12 (PM22) and the test subject WK along the axial direction. The first conductor wire SCa13 (SCa23) is arranged between the first permanent magnet PM13 (PM23) and the test subject WK along the axial direction. The first conductor wire SCa14 (SCa24) is arranged between the first permanent magnet PM14 (PM24) and the test subject WK along the axial direction. These first conductor wires SCa11 to SCa14 (SCa21 to SCa24) are arranged sequentially in the circumferential direction in this order. These four second conductor wires RCa11 to RCa14 (RCa21 to RCa24) are configured as follows so that the first current direction and the second current direction are opposite to each other. The second conductor wire RCa11 (RCa21) connects one axial end of the first conductor wire SCa11 (SCa21) to one axial end of the first conductor wire SCa12 (SCa22), thereby connecting the first conductor wires SCa11 (SCa21) and SCa12 (SCa22), which are adjacent to each other in the circumferential direction, and is arranged along the circumferential direction. The second conductor wire RCa12 (RCa22) connects the other axial end of the first conductor wire SCa12 (SCa22) to the other axial end of the first conductor wire SCa13 (SCa23), thereby connecting the first conductor wires SCa12 (SCa22) and SCa13 (SCa23), which are adjacent to each other in the circumferential direction, and is arranged along the circumferential direction.The second conductor wire RCa13 (RCa23) connects one axial end of the first conductor wire SCa13 (SCa23) to one axial end of the first conductor wire SCa14 (SCa24), thereby connecting the first conductor wires SCa13 (SCa23) and SCa14 (SCa24), which are adjacent to each other in the circumferential direction, and is arranged along the circumferential direction. The second conductor wire RCa14 (RCa24) connects the other axial end of the first conductor wire SCa14 (SCa24) to the other axial end of the first conductor wire SCa11 (SCa21), thereby connecting the first conductor wires SCa14 (SCa24) and SCa11 (SCa21), which are adjacent to each other in the circumferential direction, and is arranged along the circumferential direction. Therefore, the first conductor wire SCa11 (SCa21), the second conductor wire RCa11 (RCa21), the first conductor wire SCa12 (SCa22), the second conductor wire RCa12 (RCa22), the first conductor wire SCa13 (SCa23), the second conductor wire RCa13 (RCa23), the first conductor wire SCa14 (SCa24), and the second conductor wire RCa14 (RCa24) are sequentially connected in this order in a so-called zigzag pattern to form a unit coil COa (COa) in the first mode coil COa1 (COa2) that makes one circuit around the axial direction in the space. Note that an axial line along the axial direction is perpendicular to each of the first and second normal lines that are perpendicular to each other.

[0031] In the transmitting electromagnetic ultrasonic sensor TSa, lead conductors (first lead conductors, not shown) are connected to the respective ends of the first conductor wire SCa11 and the second conductor wire RCa14, and each of the first lead conductors is connected to the ultrasonic generator UG, and the coil COa1 is fed with power from the ultrasonic generator UG. In the receiving electromagnetic ultrasonic sensor RSa, lead conductors (second lead conductors, not shown) are connected to the respective ends of the first conductor wire SCa21 and the second conductor wire RCa24, and each of the second lead conductors is connected to the control processor 1, and the coil COa2 outputs an ultrasonic reception signal to the control processor 1.

[0032] For the coil CO1 (CO2), instead of the coil COa1 (COa2) of the first embodiment shown in Fig. 2, any one of the coils COb1 (COb2) and COc1 (COc2) of the following second and third embodiments may be used. Alternatively, for the coil CO1 (CO2), instead of the coil COa1 (COa2) of the first embodiment shown in Fig. 2, any one of the coils COd1 (COd2) to CO1f (COf2) of the fourth to sixth embodiments shown in Figs. 18 to 20 described below may be used. These coils COd1 (COd2) to COf1 (COf2) of the fourth to sixth embodiments will be described later.

[0033] The coil COb1 (COb2) of the second embodiment has one unit coil COb with two turns, and the unit coil COb (COb) in the coil COb1 (COb2) of the second embodiment is configured, for example, as shown in Figure 3, with seven first conductor wires SCb11 to SCb17 (SCb21 to SCb27) and eight second conductor wires RCb11 to RCb18 (RCb21 to RCb28).

[0034] When the test object WK is placed in the space, the first conductor wires SCb11 (SCb21) and SCb17 (SCb27) are arranged between the first permanent magnet PM11 (PM21) and the test object WK along the axial direction, and are arranged with a circumferential offset as shown in FIG. 3. The first conductor wires SCb11 (SC21) and SCb17 (SCb27) may be arranged to overlap in the radial direction with an insulator interposed between them. The same applies below. The first conductor wires SCb12 (SCb22) and SCb16 (SCb26) are arranged between the first permanent magnet PM12 (PM22) and the test object WK along the axial direction, and the first conductor wires SCb12 (SCb22) and SCb16 (SCb26) are arranged with a circumferential offset as shown in FIG. 3. The first conductor wires SCb13 (SCb23) and SCb15 (SCb25) are arranged between the first permanent magnet PM13 (PM23) and the test object WK along the axial direction, and the first conductor wires SCb13 (SCb23) and SCb15 (SCb25) are arranged with a circumferential offset, as shown in Fig. 3. The first conductor wire SCb14 (SCb24) is arranged between the first permanent magnet PM14 (PM24) and the test object WK along the axial direction. These first conductor wires SCb11, SCb17; SCb12, SCb16; SCb13, SCb15; SCb14 (SCb21, SCb27; SCb22, SCb26; SCb23, SCb25; SCb24) are arranged sequentially in the circumferential direction in this order.

[0035] These eight second conductor wires RCb11 to RCb18 (RCb21 to RCb28) are configured as follows so that the first current direction and the second current direction are opposite to each other. The second conductor wire RCb11 (RCb21) is connected to one axial end of the first conductor wire SCb11 (SCb21) and is arranged along the circumferential direction. The second conductor wire RCb12 (RCb22) connects the other axial end of the first conductor wire SCb11 (SCb21) to the other axial end of the first conductor wire SCb12 (SCb22), thereby connecting the first conductor wires SCb11 (SCb21) and SCb12 (SCb22) that are adjacent to each other in the circumferential direction and is arranged along the circumferential direction. The second conductor wire RCb13 (RCb23) connects one axial end of the first conductor wire SCb12 (SCb22) to one axial end of the first conductor wire SCb13 (SCb23), thereby connecting the first conductor wires SCb12 (SCb22) and SCb13 (SCb23), which are adjacent in the circumferential direction, and is arranged along the circumferential direction. The second conductor wire RCb14 (RCb24) connects the other axial end of the first conductor wire SCb13 (SCb23) to the other axial end of the first conductor wire SCb14 (SCb24), thereby connecting the first conductor wires SCb13 (SCb23) and SCb14 (SCb24), which are adjacent in the circumferential direction, and is arranged along the circumferential direction. The second conductor wire RCb15 (RCb25) connects one axial end of the first conductor wire SCb14 (SCb24) to one axial end of the first conductor wire SCb15 (SCb25), thereby connecting the first conductor wires SCb14 (SCb24) and SCb15 (SCb25), which are adjacent in the circumferential direction, and is arranged along the circumferential direction. The second conductor wire RCb16 (RCb26) connects the other axial end of the first conductor wire SCb15 (SCb25) to the other axial end of the first conductor wire SCb16 (SCb26), thereby connecting the first conductor wires SCb15 (SCb25) and SCb16 (SCb26), which are adjacent in the circumferential direction, and is arranged along the circumferential direction.The second conductor wire RCb17 (RCb27) connects one axial end of the first conductor wire SCb16 (SCb26) to one axial end of the first conductor wire SCb17 (SCb27), thereby connecting the first conductor wires SCb16 (SCb26) and SCb17 (SCb27) that are adjacent to each other in the circumferential direction, and is arranged along the circumferential direction. The second conductor wire RCb18 (RCb28) is connected to the other axial end of the first conductor wire SCb17 (SCb27) and is arranged along the circumferential direction.

[0036] Therefore, the second conductor wire RCb11 (RCb21), the first conductor wire SCb11 (SCb21), the second conductor wire RCb12 (RCb22), the first conductor wire SCb12 (SCb22), the second conductor wire RCb13 (RCb23), the first conductor wire SCb13 (SCb23), the second conductor wire RCb14 (RCb24), the first conductor wire SCb14 (SCb24), the second conductor wire RCb15 (RCb25), and the first conductor wire SCb15 (SCb25) The second conductor wire RCb16 (RCb26), the first conductor wire SCb16 (SCb26), the second conductor wire RCb17 (RCb27), the first conductor wire SCb17 (SCb27), and the second conductor wire RCb18 (RCb28) are sequentially connected in this order in a so-called zigzag pattern, thereby forming a unit coil COb (COb) in the second embodiment of the coil COb1 (COb2) that wraps around the space twice around the axial direction.

[0037] In the transmitting electromagnetic ultrasonic sensor TSa, first lead conductors are connected to the respective ends of the second conductor wires RCb11 and RCb18, and the first lead conductors are connected to the ultrasonic generator UG, and the coil COb1 is fed with power from the ultrasonic generator UG. In the receiving electromagnetic ultrasonic sensor RSa, second lead conductors are connected to the respective ends of the second conductor wires RCb21 and RCb28, and the second lead conductors are connected to the control processor 1, and the coil COb2 outputs an ultrasonic reception signal to the control processor 1.

[0038] The coil COc1 (COc2) of the third embodiment includes, for example, three unit coils COb-1, COb-2, and COb-3 of two turns shown in Fig. 3 that are connected in series in sequence as shown in Fig. 4, and these three unit coils COb-1, COb-2, and COb-3 are arranged with a circumferential offset as shown in Fig. 4. These three unit coils COb-1, COb-2, and COb-3 may be arranged overlapping in the radial direction with an insulator interposed therebetween.

[0039] In the transmitting electromagnetic ultrasonic sensor TSa, first lead conductor wires are connected to the start end of the first unit coil COb-1 and the end end of the third unit coil COb-3, and each of the first lead conductor wires is connected to the ultrasonic generator UG, and power is supplied to the coil COc1 from the ultrasonic generator UG. In the receiving electromagnetic ultrasonic sensor RSa, second lead conductor wires are connected to the start end of the first unit coil COb-1 and the end end of the third unit coil COb-3, and each of the second lead conductor wires is connected to the control processing unit 1, and the coil COc2 outputs an ultrasonic reception signal to the control processing unit 1.

[0040] In the example shown in Fig. 4, the three unit coils COb-1, COb-2, and COb-3 are connected in series, but they may also be connected in parallel. Also, in the example shown in Fig. 4, the number of unit coils COb is three, but this is not limited to this and may be any number, and multiple unit coils COb may be connected in series or in parallel.

[0041] In the transmitting electromagnetic ultrasonic sensor TSa configured as described above, the plurality of first permanent magnets PM1 are arranged sequentially along the circumferential direction so that the south poles and north poles alternate in the circumferential direction and face the space, so it is not necessary to arrange the first permanent magnets PM1 so that they face each other at a portion of the surface of the object to be inspected, and the magnetic fields of the first permanent magnets PM1 do not cancel each other out and the magnetic fields around each first permanent magnet are amplified. Therefore, the electromagnetic ultrasonic sensor TSa can increase the signal strength of the ultrasonic waves, and the ultrasonic flaw detection device 1000 can ultrasonically inspect a linear body (rod-shaped body, columnar body) with a relatively small cross section as the object to be inspected WK.

[0042] Fig. 5B shows the results of a simulated magnetic field analysis as an example, and Fig. 6B shows the results of a simulated magnetic field analysis as a comparative example. In the simulation, the magnetic field was assumed to be uniformly distributed in the axial direction of the space, and the magnetic field in the cross section of the space was analyzed.

[0043] In this example (first example) and comparative example, as shown in FIGS. 5A and 6A, four first permanent magnets PM11 to PM14 (PM21 to PM24) are used, each having a width of 12 mm and a height of 21 mm. The magnetic pole plane of each permanent magnet PM11 to PM14 (PM21 to PM24) is 12 mm. The space for arranging the subject WK is a square with a cross section of 14 mm x 14 mm. In the comparative example, the four permanent magnets PM11 to PM14 (PM21 to PM24) are arranged with the same pole (e.g., south pole) facing the square space. In contrast, in the first example, as in the above-described embodiment, the four permanent magnets PM11 to PM14 (PM21 to PM24) are arranged with south and north poles facing the square space alternately in the circumferential direction. The subject WK is a wire rod with a diameter of 12 mm made of a non-magnetic material. When the object WK is placed in the square space, the distance (Lift off) between the object WK and each of the permanent magnets PM11 to PM14 (PM21 to PM24) is set to 1 mm. For the simulation, Ansoft's Maxwell, a general-purpose finite element method magnetic field analysis tool, was used.

[0044] In the comparative example, the maximum surface magnetic flux density of the magnetic field formed on the test object WK by the permanent magnets PM11 to PM14 (PM21 to PM24) was 0.15 [T]. In contrast, in the first example, the maximum surface magnetic flux density of the magnetic field formed on the test object WK by the permanent magnets PM11 to PM14 (PM21 to PM24) was 0.63 [T], which is larger than the comparative example, being 0.63 / 0.15 (=4.2) times larger. Therefore, the electromagnetic ultrasonic sensor TSa can increase the signal strength of the ultrasonic waves.

[0045] Furthermore, the electromagnetic ultrasonic sensor TSa transmits ultrasonic waves using the first permanent magnet PM1 and the first conductor wire SC1, so that it can transmit ultrasonic waves in a so-called T-mode. Therefore, the ultrasonic flaw detector 1000 has high sensitivity to elongated defects extending along the axial direction.

[0046] The ultrasonic wave generating unit UG is connected to the control processing unit 1 and is a device that causes the electromagnetic ultrasonic sensor TSa for transmission to generate ultrasonic waves of guided waves under the control of the control processing unit 1. The ultrasonic wave generating unit UG is configured to include, for example, an oscillation pulser.

[0047] The input unit 2 is connected to the control processing unit 1 and is a device that inputs various commands, such as a command to start flaw detection, and various data required to operate the ultrasonic flaw detection device 1000, such as the name of the test object, to the ultrasonic flaw detection device 1000, and is, for example, a keyboard, a mouse, and a plurality of input switches to which predetermined functions are assigned. The display unit 3 is connected to the control processing unit 1 and is a device that displays the commands and data input from the input unit 2 and the results of ultrasonic flaw detection under the control of the control processing unit 1, and is, for example, a display device such as a CRT display, an LCD (liquid crystal display), or an organic EL display.

[0048] The input unit 2 and the display unit 3 may be configured with a touch panel. In the case where the input unit 2 is configured with this touch panel, the input unit 2 is, for example, a resistive or capacitive position input device that detects and inputs an operation position. In this touch panel, a position input device is provided on the display surface of the display unit 3, and one or more input content candidates that can be input are displayed on the display unit 3. When a user touches the display position displaying the input content they want to input, the position is detected by the position input device, and the display content displayed at the detected position is input to the ultrasonic flaw detection device 1000 as the user's operation input content. With such a touch panel, the user can easily intuitively understand the input operation, and therefore, an ultrasonic flaw detection device 1000 that is easy for the user to use is provided.

[0049] The IF unit 4 is connected to the control processing unit 1 and is a circuit that inputs and outputs data to and from, for example, an external device under the control of the control processing unit 1, and is, for example, an interface circuit for RS-232C, which is a serial communication method, an interface circuit using the Bluetooth (registered trademark) standard, an interface circuit using the USB standard, etc. The IF unit 4 may also be, for example, a communication interface circuit that transmits and receives communication signals to and from an external device, such as a data communication card or a communication interface circuit conforming to the IEEE802.11 standard, etc.

[0050] The storage unit 5 is connected to the control processing unit 1 and is a circuit that stores various predetermined programs and various predetermined data under the control of the control processing unit 1.

[0051] The various predetermined programs include, for example, a control processing program, and the control processing program includes, for example, a control program and a defect detection processing program, etc. The control program is a program that controls each of the units UG, TSa, RSa, 2 to 5 of the ultrasonic flaw detector 1000 according to the function of each unit. The defect detection processing program is a program that transmits guided wave ultrasonic waves to the test object WK using the transmitting electromagnetic ultrasonic sensor TSa, and detects defects in the test object WK based on the ultrasonic waves received by the receiving electromagnetic ultrasonic sensor RSa.

[0052] The various predetermined data include data necessary for executing each of these programs, such as the name of the object, the received ultrasonic signal, the ultrasonic sound speed Vs, a threshold (direct determination threshold) Thd for detecting direct ultrasonic waves received directly by the receiving electromagnetic ultrasonic sensor RSa from the transmitting electromagnetic ultrasonic sensor TSa, and a threshold (defect determination threshold) The for detecting ultrasonic waves (echoes) from defects. Since the intensity of the direct ultrasonic waves is relatively greater than the intensity of ultrasonic waves from defects, the direct determination threshold Thd is set to a relatively greater value than the defect determination threshold The (Thd>>The).

[0053] The storage unit 5 includes, for example, a ROM (Read Only Memory), which is a nonvolatile storage element, and an EEPROM (Electrically Erasable Programmable Read Only Memory), which is a rewritable nonvolatile storage element. The storage unit 5 also includes a RAM (Random Access Memory), which serves as a working memory for the control processing unit 1 and stores data generated during execution of the predetermined program. The storage unit 5 may also be configured with a hard disk drive or solid state drive (SSD) with a relatively large storage capacity.

[0054] The control processing unit 1 is a circuit for controlling each of the units UG, TSa, RSa, 2 to 5 of the ultrasonic flaw detection device 1000 in accordance with the function of each unit, and for performing ultrasonic flaw detection. The control processing unit 1 is configured to include, for example, a CPU (Central Processing Unit) and its peripheral circuits. In the control processing unit 1, a control unit 11 and a defect detection processing unit 12 are functionally configured by executing the control processing program.

[0055] The control unit 11 controls each of the units UG, TSa, RSa, 2 to 5 of the ultrasonic flaw detector 1000 in accordance with the function of each unit, and is in charge of overall control of the ultrasonic flaw detector 1000.

[0056] The defect detection processing unit 12 transmits guided wave ultrasonic waves to the inspection object WK using the transmitting electromagnetic ultrasonic sensor TSa and detects defects in the inspection object WK based on the ultrasonic waves received by the receiving electromagnetic ultrasonic sensor RSa. The defect detection processing unit 12 calculates the distance L (=(Δt / 2)×Vs) from the receiving electromagnetic ultrasonic sensor RSa to the defect by multiplying Δt / 2, which is half the propagation time Δt (=tr2−tr1) from the first reception time tr1 at which the guided wave ultrasonic waves transmitted to the inspection object WK by the transmitting electromagnetic ultrasonic sensor TSa are received by the receiving electromagnetic ultrasonic sensor RSa directly (without passing through a defect) to the second reception time tr2 at which the ultrasonic waves reflected by the defect are received by the receiving electromagnetic ultrasonic sensor RSa. The defect detection processing unit 12 calculates the distance L (=(Δt / 2)×Vs) from the receiving electromagnetic ultrasonic sensor RSa to the defect, for example, by multiplying Δt / 2, which is half the propagation time Δt (=tr2−tr1), by the sound speed Vs. Note that the distance L to the defect is defined as the length from the center position of the receiving electromagnetic ultrasonic sensor RSa (for example, the center position in the axial direction of the first permanent magnet PM2) to the defect.

[0057] More specifically, the defect detection processing unit 12 detects signals equal to or greater than the direct determination threshold Thd as direct ultrasonic signals from the ultrasonic reception signals received by the receiving electromagnetic ultrasonic sensor RSa to detect a first reception time point tr1. Then, the defect detection processing unit 12 detects signals equal to or greater than the defect determination threshold The from the ultrasonic reception signals received by the receiving electromagnetic ultrasonic sensor RSa as ultrasonic signals (echo signals) reflected from defects. The defect detection processing unit 12 detects peaks from the detected signals equal to or greater than the defect determination threshold The, determines the time of the detected peak as a second reception time point tr2, and calculates the distance L to the defect. The defect determination threshold The is appropriately set in advance, for example, from multiple samples. When multiple signals equal to or greater than the defect determination threshold The are detected, the peaks and distances L are calculated for each of the detected signals equal to or greater than the defect determination threshold The as ultrasonic signals reflected from each of the multiple defects, and multiple defects are detected.

[0058] FIG. 7 shows an example of a received signal of an ultrasonic wave received by the receiving electromagnetic ultrasonic sensor RSa.

[0059] The four first permanent magnets PM11-PM14 and PM21-PM24 in the transmitting electromagnetic ultrasonic sensor TSa and receiving electromagnetic ultrasonic sensor RSa were each 7 mm wide, 18 mm high, and 30 mm long in the axial direction. The distance between the transmitting electromagnetic ultrasonic sensor TSa and the receiving electromagnetic ultrasonic sensor RSa was 500 mm. The test piece WK was a stainless steel wire rod with a diameter of 7 mm and a length of 2000 mm. The transmitting electromagnetic ultrasonic sensor TSa was positioned 500 mm axially from one end of the test piece WK, and the receiving electromagnetic ultrasonic sensor RSa was positioned 1000 mm axially from the one end.

[0060] The ultrasonic flaw detector 1000 configured as described above can transmit and receive ultrasonic waves in T mode to and from the test object WK, which is a φ7 mm stainless steel wire, as shown in FIG. 7. The signal DRW shown in FIG. 7 immediately after the start of transmission is a signal (a received signal of a direct ultrasonic wave (rectangular wave)) directly received by the receiving electromagnetic ultrasonic sensor RSa from the transmitting electromagnetic ultrasonic sensor TSa. The signal pW1 following the signal DRW is a signal received by the receiving electromagnetic ultrasonic sensor RSa of an ultrasonic wave (echo) that was transmitted from the transmitting electromagnetic ultrasonic sensor TSa and reflected at one end of the test object WK. The signal pW2 following the signal pW1 is a signal received by the receiving electromagnetic ultrasonic sensor RSa of an ultrasonic wave (echo) that was transmitted from the transmitting electromagnetic ultrasonic sensor TSa and reflected at the other end of the test object WK. No defects were detected in this test object WK. Note that, since ultrasonic waves can be transmitted and received in T mode as shown in FIG. 7, if there is a defect in the test object WK, the ultrasonic waves reflected by this defect can be received.

[0061] The number of first permanent magnets PM1, PM2, the number of unit coils in coils CO1, CO2, and the frequency of the ultrasonic waves are set appropriately depending on the material, shape, and size of the test object WK, as well as flaw detection conditions such as spatial resolution, etc. 2 and 7 show a so-called two-sensing method in which separate electromagnetic ultrasonic sensors are used for transmission and reception, but a one-sensing method in which one electromagnetic ultrasonic sensor transmits and receives ultrasonic waves may also be used.

[0062] The control processing unit 1, input unit 2, display unit 3, IF unit 4 and storage unit 5 in such an ultrasonic flaw detector 1000 can be configured by, for example, a desktop or notebook computer.

[0063] Next, the operation of this embodiment will be described with reference to a flowchart shown in FIG.

[0064] When the ultrasonic flaw detection device 1000 having such a configuration is powered on, it initializes the necessary parts and starts its operation. The control processing unit 1 is functionally configured with a control unit 11 and a defect detection processing unit 12 by executing a control processing program. The transmitting electromagnetic ultrasonic sensor TSa and the receiving electromagnetic ultrasonic sensor RSa are set so that the test object WK is placed in the space.

[0065] In FIG. 8, first, the ultrasonic flaw detection device 1000 causes the defect detection processing unit 12 of the control processing unit 1 to cause the transmitting electromagnetic ultrasonic sensor TSa to transmit guided wave ultrasonic waves to the test object WK via the ultrasonic wave generating unit UG (S1), and then receives ultrasonic waves from the test object WK with the receiving electromagnetic ultrasonic sensor RSa (S2).

[0066] Next, the ultrasonic flaw detector 1000 detects the first and second reception times tr1 and tr2 based on the received signal of the ultrasonic wave received by the receiving electromagnetic ultrasonic sensor RSa using the defect detection processing unit 12, and calculates the distance L from the receiving electromagnetic ultrasonic sensor RSa to the defect (S3).

[0067] Then, the ultrasonic flaw detection device 1000 causes the defect detection processing unit 12 to display the distance L to the flaw calculated in step S3 on the display unit 3 (S4), and ends this processing. Note that the display unit 3 may display, for example, an ultrasonic reception signal as shown in Fig. 7, and the defect detection processing unit 12 may output the flaw detection results (distance L, ultrasonic reception signal) to an external device via the IF unit 4 as necessary.

[0068] As described above, the ultrasonic flaw detector 1000 in the embodiment includes the transmitting electromagnetic ultrasonic sensor TSa configured as described above, so that ultrasonic waves with a greater signal strength can be transmitted to the test object WK in T mode, and the electromagnetic ultrasonic sensor RSa configured as described above can suitably receive the T mode ultrasonic waves propagating through the test object WK. The ultrasonic flaw detector 1000 does not necessarily need to arrange the first permanent magnets PM1 and PM2 so that they face each other at a portion of the test object surface; this eliminates the cancellation of the magnetic fields of the first permanent magnets PM1 and PM2 and amplifies the magnetic fields around each first permanent magnet. The ultrasonic flaw detector 1000 can also ultrasonically test linear objects (rod-shaped objects, columnar objects) with a relatively small cross section as the test object WK.

[0069] In the above-described embodiment, the transmitting electromagnetic ultrasonic sensor TSa is configured with one magnet group TMG, and the receiving electromagnetic ultrasonic sensor RSa is configured with one magnet group RMG, but the magnet group of the electromagnetic ultrasonic sensor may be multiple, with each of the multiple first permanent magnets facing the space with its south pole and north pole alternating in the axial direction and sequentially arranged in the axial direction at intervals λ / 2, which is half the wavelength λ of the ultrasonic waves transmitted to and received from the subject (first modified embodiment).

[0070] Fig. 9 is a diagram for explaining an electromagnetic ultrasonic sensor in a first modified embodiment. In the example shown in Fig. 9, the electromagnetic ultrasonic sensor includes four magnet groups.

[0071] More specifically, the transmitting electromagnetic ultrasonic sensor TSb includes four first to fourth magnet groups TMG1 to TMG4 and a coil COa1 similar to that of the above-described embodiment. Each of the first to fourth magnet groups TMG1 to TMG4 includes four first permanent magnets PM111 to PM141, PM112 to PM142, PM113 to PM143, and PM114 to PM144 (PM141, PM142, PM143, and PM144 are not shown) that are sequentially arranged along the circumferential direction at 90° intervals so that their south and north poles alternate in the circumferential direction and face the space, similar to the magnet group TMG shown in Fig. 2. The first permanent magnet PM111 of the first magnet group TMG1 is arranged so that the magnetic pole plane of the S pole faces the space, and the first permanent magnet PM112 of the second magnet group TMG2, which is adjacent to the first permanent magnet PM111 of the first magnet group TMG1 in the axial direction, faces the magnetic pole plane of the N pole into the space and is arranged so that the distance λ / 2 is between the first permanent magnet PM111 and the first permanent magnet PM112 of the second magnet group TMG2 in the axial direction. The first permanent magnet PM113 of the third magnet group TMG3 adjacent to the first permanent magnet PM112 faces its magnetic pole plane into the space and is arranged so as to be spaced axially apart by the distance λ / 2 from the first permanent magnet PM112, and the first permanent magnet PM114 of the fourth magnet group TMG4 adjacent to the first permanent magnet PM113 of the third magnet group TMG3 faces its magnetic pole plane into the space and is arranged so as to be spaced axially apart by the distance λ / 2 from the first permanent magnet PM113. As a result, the four first to fourth magnet groups TMG1 to TMG4 in the transmitting electromagnetic acoustic sensor TSb, each of the first permanent magnets PM111 to PM114, PM121 to PM124, PM131 to PM134, and PM141 to PM144, face their south and north poles alternately in the axial direction into the space and are arranged sequentially in the axial direction with respect to the test object WK at the distance λ / 2. Therefore, the distance between the first permanent magnets of the same polarity is the wavelength λ (=(the distance λ / 2)×2).

[0072] Similarly, the receiving electromagnetic ultrasonic sensor RSb includes four first to fourth magnet groups RMG1 to RMG4 and a coil COa2 similar to that in the above-described embodiment. Each of the first to fourth magnet groups RMG1 to RMG4 includes four first permanent magnets PM211 to PM241, PM212 to PM242, PM213 to PM243, and PM214 to PM244 (PM241, PM242, PM243, and PM244 are not shown) that are sequentially arranged along the circumferential direction at 90° intervals so that their south and north poles alternate in the circumferential direction and face the space, similar to the magnet group RMG shown in Fig. 2. The first permanent magnet PM211 of the first magnet group RMG1 is arranged so that the magnetic pole plane of the S pole faces the space, and the first permanent magnet PM212 of the second magnet group RMG2, which is adjacent to the first permanent magnet PM211 of the first magnet group RMG1 in the axial direction, faces the magnetic pole plane of the N pole into the space and is arranged so that the distance λ / 2 is between the first permanent magnet PM211 and the second permanent magnet group RMG2. The first permanent magnet PM213 of the third magnet group RMG3 adjacent to the first permanent magnet PM212 faces its magnetic pole plane into the space and is arranged so as to be spaced axially apart by the distance λ / 2 from the first permanent magnet PM212, and the first permanent magnet PM214 of the fourth magnet group RMG4 adjacent to the first permanent magnet PM213 of the third magnet group RMG3 faces its magnetic pole plane into the space and is arranged so as to be spaced axially apart by the distance λ / 2 from the first permanent magnet PM213. As a result, the four first to fourth magnet groups RMG1 to RMG4 in the receiving electromagnetic acoustic sensor RSb, each of the first permanent magnets PM211 to PM214, PM221 to PM224, PM231 to PM234, and PM241 to PM244, face their south and north poles alternately in the axial direction into the space and are arranged sequentially in the axial direction with respect to the test object WK at the distance λ / 2. Therefore, the distance between the first permanent magnets of the same polarity is the wavelength λ (=(the distance λ / 2)×2).

[0073] The ultrasonic flaw detector 1000 is configured to include the electromagnetic ultrasonic sensors TSb and RSb for transmission and reception, respectively, in the first modified embodiment, instead of the electromagnetic ultrasonic sensors TSa and RSa for transmission and reception, respectively, in the embodiment.

[0074] Due to so-called velocity dispersion and superposition, ultrasonic waves of guided waves may generate ultrasonic waves of multiple modes in T mode even when an attempt is made to generate ultrasonic waves of one mode in T mode. The transmitting and receiving electromagnetic ultrasonic sensors TSb, RSb, and the ultrasonic flaw detection device 1000 equipped with them in the first modified embodiment can emphasize ultrasonic waves having a frequency component of wavelength λ corresponding to the spacing λ between the first permanent magnets of the same pole. Therefore, the transmitting electromagnetic ultrasonic sensor TSb and the ultrasonic flaw detection device 1000 can increase the signal strength of the frequency component, and the receiving electromagnetic ultrasonic sensor RSb and the ultrasonic flaw detection device 1000 can increase the reception sensitivity of ultrasonic waves of the frequency component.

[0075] In the above-described embodiment, each of the plurality of first permanent magnets PM1 and PM2 in the transmitting and receiving electromagnetic ultrasonic sensors TSa and RSa may be one of the plurality of second permanent magnets that form a Halbach structure (Halbach array) in a tangential direction to the circumferential direction (second modified embodiment). In the example shown in Figures 10 and 11, the plurality of first permanent magnets PM1 and PM2 are first magnets HM111 (PM11), HM211 (PM21); first magnets HM112 (PM12), HM212 (PM22); first magnets HM113 (PM13), HM213 (PM23); and first magnets HM114 (PM14), HM214 (PM24).

[0076] Fig. 10 is a perspective view for explaining an electromagnetic ultrasonic sensor in a second modified embodiment. Fig. 11 is a plan view seen from the axial direction for explaining an electromagnetic ultrasonic sensor in the second modified embodiment. In the examples shown in Figs. 10 and 11, the electromagnetic ultrasonic sensor includes four Halbach structure magnets (Halbach structure magnet bodies).

[0077] More specifically, the transmitting electromagnetic ultrasonic sensor TSc comprises four first to fourth Halbach structure magnet bodies THM1 to THM4 arranged sequentially along the circumferential direction at 90° intervals, and a coil COa1 similar to that in the above-described embodiment, and the receiving electromagnetic ultrasonic sensor RSc comprises four first to fourth Halbach structure magnet bodies RHM1 to RHM4 arranged sequentially along the circumferential direction at 90° intervals, and a coil COa2 similar to that in the above-described embodiment. The four first through fourth Halbach structure magnet bodies THM1 through THM4 in the transmitting electromagnetic ultrasonic sensor TSc and the four first through fourth Halbach structure magnet bodies RHM1 through RHM4 in the receiving electromagnetic ultrasonic sensor RSc have the same structure, and therefore, hereinafter, the first through fourth Halbach structure magnet bodies THM1 through THM4 will be mainly described, and the reference signs in the configurations of the first through fourth Halbach structure magnet bodies RHM1 through RHM4 that correspond to the configurations of the first through fourth Halbach structure magnet bodies TM1 through THM4 will be written in parentheses after the reference signs in the configurations of the first through fourth Halbach structure magnet bodies TM1 through THM4 that correspond to the configurations of the first through fourth Halbach structure magnet bodies RHM1 through RHM4, and the description of the first through fourth Halbach structure magnet bodies RHM1 through RHM4 will be omitted.

[0078] The first Halbach structure magnet body THM1 (RHM1) includes three first to third magnets HM111 to HM131 (HM211 to HM231) each having a rectangular prism shape (e.g., a cube or a rectangular parallelepiped shape) that form a Halbach structure in a tangential direction (first tangential direction) to the circumferential direction. More specifically, the first magnet HM111 (HM211) is disposed with its south pole facing the space, and is used as the first permanent magnet PM11 (PM21). The second magnet HM121 (HM221) is arranged with the magnetic pole face of the south pole of the second magnet HM121 (HM221) abutting against one side surface of the first magnet HM111 (HM211) so that the 21st direction of the magnetic field (magnetic field) from the north pole to the south pole of the second magnet HM121 (HM221) is perpendicular to the 11th direction of the magnetic field (magnetic field) from the north pole to the south pole of the first magnet HM111 (HM211). The side surface is perpendicular to the magnetic pole face. The third magnet HM131 (HM231) is disposed with the other side of the third magnet HM131 (HM231) abutting against the magnetic pole face of the north pole of the second magnet HM121 (HM221) so that the 31st direction of the magnetic field in the third magnet HM131 (HM231), which is directed from the north pole to the south pole, is perpendicular to the 21st direction of the magnetic field in the second magnet HM121 (HM221). The 11th direction of the magnetic field in the first magnet HM111 (HM211) and the 31st direction of the magnetic field in the third magnet HM131 (HM231) are parallel to each other and opposite to each other. These three first to third magnets HM111 to HM131 (HM211 to HM231) are sequentially connected by being attached at their contact surfaces with, for example, an adhesive or the like. The first Halbach structure magnet body THM1 (RHM1) has a rectangular prism shape as a whole due to the first to third magnets HM111 to HM131 (HM211 to HM231) configured as described above.

[0079] Similarly, the second Halbach structure magnet body THM2 (RHM2) includes three first to third magnets HM112 to HM132 (HM212 to HM232) each having a rectangular prism shape (e.g., a cube or a rectangular parallelepiped shape) that form a Halbach structure in a tangential direction (second tangential direction) to the circumferential direction. More specifically, the first magnet HM112 (HM212) is disposed with its north pole facing the space and is used as the first permanent magnet PM12 (PM22). The second magnet HM122 (HM222) is positioned with the magnetic pole face of the N pole of the second magnet HM122 (HM222) abutting against one side of the first magnet HM112 (HM212) so that the 22nd direction of the magnetic field (magnetic field) from the N pole to the S pole of the second magnet HM122 (HM222) is perpendicular to the 12th direction of the magnetic field from the N pole to the S pole of the first magnet HM112 (HM212). The third magnet HM132 (HM232) is disposed with the other side of the third magnet HM132 (HM232) abutting against the magnetic pole face of the south pole of the second magnet HM122 (HM222) so that the 32nd direction of the magnetic field in the third magnet HM132 (HM232), which runs from the north pole to the south pole, is perpendicular to the 22nd direction of the magnetic field in the second magnet HM122 (HM222). The 12th direction of the magnetic field in the first magnet HM112 (HM212) and the 32nd direction of the magnetic field in the third magnet HM132 (HM232) are parallel to each other but in opposite directions. These three first through third magnets HM112-HM132 (HM212-HM232) are sequentially connected by being attached at their contact surfaces with, for example, an adhesive or the like. The second Halbach structure magnet body THM2 (RHM2) has a rectangular prism shape as a whole due to the first to third magnets HM112 to HM132 (HM212 to HM232) configured as described above.

[0080] Similarly, the third Halbach structure magnet body THM3 (RHM3) includes three first to third magnets HM113 to HM133 (HM213 to HM233) each having a rectangular prism shape (e.g., a cube or a rectangular parallelepiped shape) that form a Halbach structure in a tangential direction (third tangential direction) to the circumferential direction. More specifically, the first magnet HM113 (HM213) is disposed with its south pole facing the space, and is used as the first permanent magnet PM13 (PM23). The second magnet HM123 (HM223) is positioned with the magnetic pole face of the S pole of the second magnet HM123 (HM223) abutting against the other side of the first magnet HM113 (HM213) so that the 23rd direction of the magnetic field (magnetic field) from the N pole to the S pole of the second magnet HM123 (HM223) is perpendicular to the 13th direction of the magnetic field from the N pole to the S pole of the first magnet HM113 (HM213). The third magnet HM133 (HM233) is arranged with one side of the third magnet HM133 (HM233) abutting against the magnetic pole face of the north pole of the second magnet HM123 (HM223) so that the 33rd direction of the magnetic field in the third magnet HM133 (HM233), which runs from the north pole to the south pole, is perpendicular to the 23rd direction of the magnetic field in the second magnet HM123 (HM223). The 13th direction of the magnetic field in the first magnet HM113 (HM213) and the 33rd direction of the magnetic field in the third magnet HM133 (HM233) are parallel to each other but in opposite directions. These three first through third magnets HM113-HM133 (HM213-HM233) are sequentially connected by being attached at their contact surfaces with, for example, an adhesive or the like. The third Halbach structure magnet body THM3 (RHM3) has a rectangular prism shape as a whole due to the first to third magnets HM113 to HM133 (HM213 to HM233) configured as described above.

[0081] Similarly, the fourth Halbach structure magnet body THM4 (RHM4) includes three first to third magnets HM114 to HM134 (HM214 to HM234) each having a quadrangular prism shape (e.g., a cube or a rectangular parallelepiped shape) that form a Halbach structure in a tangential direction (fourth tangential direction) to the circumferential direction. More specifically, the first magnet HM114 (HM214) is disposed with its north pole facing the space, and is used as the first permanent magnet PM14 (PM24). The second magnet HM124 (HM224) is positioned with the magnetic pole face of the N pole of the second magnet HM124 (HM224) abutting against the other side of the first magnet HM114 (HM214) so ​​that the 24th direction of the magnetic field (magnetic field) from the N pole to the S pole of the second magnet HM124 (HM224) is perpendicular to the 14th direction of the magnetic field from the N pole to the S pole of the first magnet HM114 (HM214). The third magnet HM134 (HM234) is arranged with one side of the third magnet HM134 (HM234) abutting against the magnetic pole face of the south pole of the second magnet HM124 (HM224) so ​​that the 34th direction of the magnetic field in the third magnet HM134 (HM234), which is directed from the north pole to the south pole, is perpendicular to the 24th direction of the magnetic field in the second magnet HM124 (HM224). The 14th direction of the magnetic field in the first magnet HM114 (HM214) and the 34th direction of the magnetic field in the third magnet HM134 (HM234) are parallel to each other and opposite to each other. These three first through third magnets HM114-HM134 (HM214-HM234) are sequentially connected by being attached at their contact surfaces with, for example, an adhesive or the like. The fourth Halbach structure magnet body THM4 (RHM4) has a rectangular prism shape as a whole due to the first to third magnets HM114 to HM134 (HM214 to HM234) configured as described above.

[0082] The first and third tangential directions are parallel to each other, the second and fourth tangential directions are parallel to each other, the first and second tangential directions (third and fourth tangential directions) are perpendicular to each other, the 11th, 33rd and 24th directions are the same direction, the 21st, 12th and 34th directions are the same direction, the 31st, 22nd and 13th directions are the same direction, and the 32nd, 23rd and 14th directions are the same direction.

[0083] Fig. 12 is a diagram illustrating, as an example, the effects of an electromagnetic ultrasonic sensor according to a second modified embodiment of the embodiment. Fig. 12A is a plan view, viewed from the axial direction, illustrating the arrangement of four first through fourth Halbach structure magnet bodies THM1 through THM4 (RHM1 through RHM4) relative to a test object WK used in a simulation as the embodiment, and Fig. 12B shows the results of magnetic field analysis. In Fig. 12B, arrows (→) indicate magnetic field lines and their directions, and the shading indicates the magnitude of magnetic flux density, with lighter shades indicating greater magnetic flux density.

[0084] 12A, the first magnets HM111-HM114 (HM211-HM214) and the third magnets HM131-HM134 (HM231-HM234) are magnets measuring 12 mm wide x 21 mm high, and the magnetic pole planes of the first magnets HM111-HM114 (HM211-HM214) used as the first permanent magnets PM11-PM14 (PM21-PM24) are 12 mm. That is, the first magnets HM111-HM114 (HM211-HM214) and the third magnets HM131-HM134 (HM231-HM234) are magnets similar to those used in FIGS. 5 and 6. The second magnets HM121-HM124 (HM221-HM224) are magnets measuring 10 mm wide x 21 mm high. The space for placing the subject WK is a square with a cross section of 14 mm x 14 mm, similar to the case of FIGS. 5 and 6 described above. The subject WK is a wire rod with a diameter of 12 mm made of a non-magnetic material, similar to the case of FIGS. 5 and 6 described above. When the subject WK is placed in the square space, the distance (lift off) between the subject WK and each of the first magnets HM111-HM114 (HM211-HM214) is 1 mm, similar to the case of FIGS. 5 and 6 described above.

[0085] In the first example of the embodiment shown in FIG. 5, the maximum surface magnetic flux density of the magnetic field formed on the test object WK by the permanent magnets PM11-PM14 (PM21-PM24) was 0.63 [T] as described above. However, in the second example of the second modified embodiment shown in FIG. 12, the maximum surface magnetic flux density of the magnetic field formed on the test object WK by the first to fourth Halbach structure magnet bodies THM1-THM4 (RHM1-RHM4) is 1.0 [T], which is even larger, 1.0 / 0.63 (≒ 1.59) times. Compared with the comparative example, in the second example, the maximum surface magnetic flux density is 1.0 / 0.15 (≒ 6.67) times. Therefore, the electromagnetic ultrasonic sensor TSc can further increase the ultrasonic signal strength.

[0086] The ultrasonic flaw detector 1000 is configured to include the electromagnetic ultrasonic sensors TSc and RSc for transmission and reception in the second modified embodiment, instead of the electromagnetic ultrasonic sensors TSa and RSa for transmission and reception in the embodiment.

[0087] The transmitting electromagnetic ultrasonic sensor TSc in the second modified form and the ultrasonic flaw detection device 1000 equipped with it can increase the signal strength of the ultrasonic waves transmitted to the test object WK, and the receiving electromagnetic ultrasonic sensor RSc in the second modified form and the ultrasonic flaw detection device 1000 equipped with it can increase the receiving sensitivity of the ultrasonic waves.

[0088] Furthermore, in the above-described embodiment, the plurality of first permanent magnets PM1, PM2 in the transmitting and receiving electromagnetic ultrasonic sensors TSa, RSa are two third permanent magnets arranged in the axial direction among a plurality of third permanent magnets that form a Halbach structure in the tangential direction to the circumferential direction and in the axial direction, with the third permanent magnet facing the space with its S pole and the third permanent magnet facing the space with its N pole. The magnet group may be a plurality of first permanent magnets, each of which alternates between facing the space with its S pole and N pole in the axial direction and which are arranged sequentially in the axial direction at intervals of half the wavelength of the ultrasonic waves transmitted to and received from the subject (third modified embodiment). In the examples shown in the following FIGS. 13 to 16, in the magnet group HHG shown representatively, for transmission, the plurality of first permanent magnets PM1 are: first magnet HHM311 (third magnet HHM231), first magnet HHM211 (HHM111); first magnet HHM312 (third magnet HHM232 (not shown), first magnet HHM212 (not shown) (HHM112); first magnet HHM313 (third magnet HHM233), first magnet HHM213 (HHM113); first magnet HHM314 (third magnet HHM234 (not shown), first magnet HHM214 (not shown) (HHM114). The same applies to the plurality of first permanent magnets PM2 for reception.

[0089] FIG. 13 is a perspective view illustrating an electromagnetic ultrasonic sensor in a third modified embodiment. FIG. 14 is a plan view illustrating the magnet group in the electromagnetic ultrasonic sensor in the third modified embodiment, viewed from the left side of the paper in the axial direction in FIG. 13. FIG. 15 is a cross-sectional view taken along the line II in each of FIGS. 14 and 16. FIG. 16 is a plan view illustrating the magnet group in the electromagnetic ultrasonic sensor in the third modified embodiment, viewed from the right side of the paper in the axial direction in FIG. 13. The magnet group THG1 includes first to fourth Halbach structure magnet bodies THM111 to THM141 (not shown). The magnet group THG2 includes first to fourth Halbach structure magnet bodies THM112 to THM142 (not shown). The magnet group THG3 includes first to fourth Halbach structure magnet bodies THM113 to THM143 (not shown). The magnet group THG4 includes first through fourth Halbach structure magnet bodies THM114-THM144 (not shown). The magnet group RHG1 includes first through fourth Halbach structure magnet bodies RHM111-RHM141 (not shown). The magnet group RHG2 includes first through fourth Halbach structure magnet bodies RHM112-RHM142 (not shown). The magnet group RHG3 includes first through fourth Halbach structure magnet bodies RHM113-RHM143 (not shown). The magnet group RHG4 includes first through fourth Halbach structure magnet bodies RHM114-RHM144 (not shown). The four magnet groups THG1 to THG4 and RHG1 to RHG4 arranged sequentially in the axial direction in the transmitting and receiving electromagnetic ultrasonic sensors TSd and RSd shown in Fig. 13 have the same structure, and therefore one of these magnet groups THG1 to THG4 and RHG1 to RHG4 is representatively shown as the magnet group HHG in Fig. 14 to Fig. 16. Note that the coil COa is not shown in Fig. 14 to Fig. 16.

[0090] More specifically, in FIG. 15, the magnet group HHG includes three first to third sub-magnet groups SHG1 to SHG3 that are arranged sequentially in the axial direction.

[0091] The first sub-magnet group SHG1 includes four first to fourth Halbach structure magnet bodies TAH11 to TAH14 that are sequentially arranged along the circumferential direction at intervals of 90°.

[0092] The first Halbach structure magnet body TAH11 includes three square prism-shaped magnets, first through third, HHM111-HHM131, that form a Halbach structure in the first tangential direction. The second Halbach structure magnet body TAH12 includes three square prism-shaped magnets, first through third, HHM112-HHM132, that form a Halbach structure in the second tangential direction. The third Halbach structure magnet body TAH13 includes three square prism-shaped magnets, first through third, HHM113-HHM133, that form a Halbach structure in the third tangential direction. The fourth Halbach structure magnet body TAH14 includes three square prism-shaped magnets, first through third, HHM114-HHM134, that form a Halbach structure in the fourth tangential direction. Here, although the south and north poles are reversed, the first to third magnets HHM111 to HHM131 correspond to the first to third HM111 to HM131 shown in FIG. 11, the first Halbach structure magnet body TAH11 corresponds to the first Halbach structure magnet body THM1, the first to third magnets HHM112 to HHM132 correspond to the first to third HM112 to HM132 shown in FIG. 11, the second Halbach structure magnet body TAH12 corresponds to the second Halbach structure magnet body THM2, and the first to third magnets HHM113 to HHM133 correspond to the first to third HM111 to HM132 shown in FIG. 11. The first through third magnets HHM113 through HHM133 correspond to the first through third Halbach structure magnet body THM3, the third Halbach structure magnet body TAH13 corresponds to the third Halbach structure magnet body THM3, the first through third magnets HHM114 through HHM134 correspond to the first through third HM114 through HM134 shown in FIG. 11, and the fourth Halbach structure magnet body TAH14 corresponds to the fourth Halbach structure magnet body THM4. The first through fourth Halbach structure magnet bodies TAH11 through TAH14 have the same structure as the first through fourth Halbach structure magnet bodies THM1 through THM4, respectively, and therefore description thereof will be omitted.

[0093] The third sub-magnet group SHG3 includes four first to fourth Halbach structure magnet bodies TAH31 to TAH34 that are sequentially arranged along the circumferential direction at intervals of 90°.

[0094] The first Halbach structure magnet body TAH31 includes three square prism-shaped magnets, first through third, HHM311-HHM331, that form a Halbach structure in the first tangential direction. The second Halbach structure magnet body TAH32 includes three square prism-shaped magnets, first through third, HHM312-HHM332, that form a Halbach structure in the second tangential direction. The third Halbach structure magnet body TAH33 includes three square prism-shaped magnets, first through third, HHM313-HHM333, that form a Halbach structure in the third tangential direction. The fourth Halbach structure magnet body TAH34 includes three square prism-shaped magnets, first through third, HHM314-HHM334, that form a Halbach structure in the fourth tangential direction. Here, the first to third magnets HHM311 to HHM331 correspond to the first to third HM111 to HM131 shown in FIG. 11, the first Halbach structure magnet body TAH31 corresponds to the first Halbach structure magnet body THM1, the first to third magnets HHM312 to HHM332 correspond to the first to third HM112 to HM132 shown in FIG. 11, the second Halbach structure magnet body TAH32 corresponds to the second Halbach structure magnet body THM2, and the first to third magnets HHM313 to HHM333 correspond to the first to third HM112 to HM132 shown in FIG. 11, the first through third magnets HHM314 through HHM334 correspond to the first through third HM114 through HM134 shown in FIG. 11, the fourth Halbach structure magnet body TAH34 corresponds to the fourth Halbach structure magnet body THM4, and the first through fourth Halbach structure magnet bodies TAH31 through TAH34 have the same structure as the first through fourth Halbach structure magnet bodies THM1 through THM4, respectively, and therefore description thereof will be omitted.

[0095] The second sub-magnet group SHG2 includes four Halbach structure magnet bodies TAH21 to TAH24 that are sequentially arranged in the circumferential direction at 90° intervals. Fig. 15 shows the first and third Halbach structure magnet bodies TAH21 and TAH23, but does not show the second and fourth Halbach structure magnet bodies TAH22 and TAH24.

[0096] The first Halbach structure magnet body TAH21 includes three rectangular prism-shaped first to third magnets HHM211 to HHM231 that form a Halbach structure in the axial direction. More specifically, the first magnet HHM211 is disposed with its north pole facing the space and is used as a first permanent magnet. The first magnet HHM211 is also the first magnet HHM111 of the first Halbach structure magnet body TAH11 and is also a part of the first Halbach structure magnet body TAH11. In other words, the first magnet HHM211 and the first magnet HHM111 share a single magnet. The second magnet HHM221 is arranged with the magnetic pole face of the N pole of the second magnet HHM221 abutting one side of the first magnet HHM211 so that the 25th direction of the magnetic field (magnetic field) from the N pole to the S pole of the second magnet HHM221 is perpendicular to the 15th direction of the magnetic field from the N pole to the S pole of the first magnet HHM211. The third magnet HHM231 is arranged with its S pole facing the space and is used as a first permanent magnet. That is, the first magnet HHM211 and the third magnet HHM231 are used as the first permanent magnet. The first magnet HHM211 and the third magnet HHM231 are arranged sequentially in the axial direction at an interval λ / 2, which is half the wavelength λ of the ultrasound transmitted to and received from the subject WK, by adjusting the size of the magnets. The third magnet HHM231 is also the first magnet HHM311 of the first Halbach structure magnet body TAH31 and is also a part of the first Halbach structure magnet body TAH31. In other words, the third magnet HHM231 and the first magnet HHM311 share a single magnet. The second magnet HHM221 is arranged with the south pole magnetic pole face of the second magnet HHM221 abutting against the other side of the third magnet HHM231 so that the 25th direction of the second magnet HHM221 is perpendicular to the 35th direction of the magnetic field from the north pole to the south pole of the third magnet HHM231. The 15th direction of the magnetic field in the first magnet HHM211 and the 35th direction of the magnetic field in the third magnet HHM231 are parallel to each other and in opposite directions. These three first through third magnets HHM211 to HHM231 are sequentially connected by being attached at their contact surfaces with, for example, an adhesive, etc. The first Halbach structure magnet body TAH21 has a rectangular prism shape as a whole due to the first through third magnets HHM211 to HHM231 configured in this way.

[0097] Similarly, the second Halbach-structure magnet body TAH22 (not shown) includes three rectangular prism-shaped first to third magnets HHM212 to HHM232 that form a Halbach structure in the axial direction. More specifically, the first magnet HHM212 is disposed with its south pole facing the space and is used as a first permanent magnet. The first magnet HHM212 is also the first magnet HHM112 of the second Halbach-structure magnet body TAH12 and is also part of the second Halbach-structure magnet body TAH12. In other words, the first magnet HHM212 and the first magnet HHM112 share a single magnet. The second magnet HHM222 is arranged with the magnetic pole face of the south pole of the second magnet HHM222 abutting one side of the first magnet HHM212 so that the 26th direction of the magnetic field (magnetic field) from the north pole to the south pole of the second magnet HHM222 is perpendicular to the 16th direction of the magnetic field from the north pole to the south pole of the first magnet HHM212. The third magnet HHM232 is arranged with its north pole facing the space and is used as a first permanent magnet. That is, the first magnet HHM212 and the third magnet HHM232 are used as the first permanent magnet. The first magnet HHM212 and the third magnet HHM232 are arranged sequentially in the axial direction at the interval λ / 2 by adjusting the size of the magnets. The third magnet HHM232 is also the first magnet HHM312 of the second Halbach structure magnet body TAH32 and is also a part of the second Halbach structure magnet body TAH32. In other words, the third magnet HHM232 and the first magnet HHM312 share a single magnet. The second magnet HHM222 is arranged with the N pole face of the second magnet HHM222 abutting against the other side of the third magnet HHM232 so that the 26th direction of the second magnet HHM222 is perpendicular to the 36th direction of the magnetic field in the third magnet HHM232, which is directed from the N pole to the S pole. The 16th direction of the magnetic field in the first magnet HHM212 and the 36th direction of the magnetic field in the third magnet HHM232 are parallel to each other and in opposite directions. These three first to third magnets HHM212 to HHM232 are sequentially connected by being attached at their contact surfaces with, for example, an adhesive, etc. The second Halbach structure magnet body TAH22 has a rectangular prism shape as a whole due to the first to third magnets HHM212 to HHM232 configured in this way.

[0098] Similarly, the third Halbach-structure magnet body TAH23 includes three rectangular prism-shaped first through third magnets HHM213 to HHM233 that form a Halbach structure in the axial direction. More specifically, the first magnet HHM213 is disposed with its north pole facing the space and is used as a first permanent magnet. The first magnet HHM213 is also the first magnet HHM113 of the third Halbach-structure magnet body TAH13 and is also a part of the third Halbach-structure magnet body TAH13. In other words, the first magnet HHM213 and the first magnet HHM113 share a single magnet. The second magnet HHM223 is arranged with the magnetic pole face of the N pole of the second magnet HHM223 abutting one side of the first magnet HHM213 so that the 27th direction of the magnetic field (magnetic field) from the N pole to the S pole of the second magnet HHM223 is perpendicular to the 17th direction of the magnetic field from the N pole to the S pole of the first magnet HHM213. The third magnet HHM233 is arranged with its S pole facing the space and is used as a first permanent magnet. That is, the first magnet HHM213 and the third magnet HHM233 are used as the first permanent magnet. The first magnet HHM213 and the third magnet HHM233 are arranged sequentially in the axial direction at the interval λ / 2 by adjusting the size of the magnets. The third magnet HHM233 is also the first magnet HHM313 of the third Halbach structure magnet body TAH33 and is also a part of the third Halbach structure magnet body TAH33. In other words, the third magnet HHM233 and the first magnet HHM313 share a single magnet. The second magnet HM223 is arranged with the south pole magnetic pole face of the second magnet HHM223 abutting against the other side of the third magnet HHM233 so that the 27th direction of the second magnet HHM223 is perpendicular to the 37th direction of the magnetic field in the third magnet HHM233, which is directed from the north pole to the south pole. The 17th direction of the magnetic field in the first magnet HHM213 and the 37th direction of the magnetic field in the third magnet HHM233 are parallel to each other and in opposite directions. These three first through third magnets HHM213-HHM233 are sequentially connected by being attached at their contact surfaces with, for example, an adhesive, etc. The third Halbach structure magnet body TAH23 has a rectangular prism shape as a whole due to the first through third magnets HHM213-HHM233 configured in this way.

[0099] Similarly, the fourth Halbach-structure magnet body TAH24 (not shown) includes three rectangular prism-shaped first to third magnets HHM214 to HHM234 that form a Halbach structure in the axial direction. More specifically, the first magnet HHM214 is disposed with its south pole facing the space and is used as a first permanent magnet. The first magnet HHM214 is also the first magnet HHM114 of the fourth Halbach-structure magnet body TAH14 and is also a part of the fourth Halbach-structure magnet body TAH14. In other words, the first magnet HHM214 and the first magnet HHM114 share a single magnet. The second magnet HHM224 is arranged with the magnetic pole face of the south pole of the second magnet HHM224 abutting one side of the first magnet HHM214 so that the 28th direction of the magnetic field (magnetic field) from the north pole to the south pole of the second magnet HHM224 is perpendicular to the 18th direction of the magnetic field from the north pole to the south pole of the first magnet HHM214. The third magnet HHM234 is arranged with its north pole facing the space and is used as a first permanent magnet. That is, the first magnet HHM214 and the third magnet HHM234 are used as the first permanent magnet. The first magnet HHM214 and the third magnet HHM234 are arranged sequentially in the axial direction at the interval λ / 2 by adjusting the size of the magnets. The third magnet HHM234 is also the first magnet HHM314 of the fourth Halbach structure magnet body TAH34 and is also a part of the fourth Halbach structure magnet body TAH34. In other words, the third magnet HHM234 and the first magnet HHM314 share a single magnet. The second magnet HHM224 is arranged with the N pole face of the second magnet HHM224 abutting against the other side of the third magnet HHM234 so that the 28th direction of the second magnet HHM224 is perpendicular to the 38th direction of the magnetic field in the third magnet HHM234, which is directed from the N pole to the S pole. The 18th direction of the magnetic field in the first magnet HHM214 and the 38th direction of the magnetic field in the third magnet HHM234 are parallel to each other and in opposite directions. These three first through third magnets HHM214-HHM234 are sequentially connected by being attached at their contact surfaces with, for example, an adhesive, etc. The fourth Halbach structure magnet body TAH24 has a rectangular prism shape as a whole due to the first through third magnets HHM214-HHM234 configured in this way.

[0100] In the transmitting electromagnetic ultrasonic sensor TSd, the four first to fourth magnet groups THG1 to THG4 configured as described above are arranged sequentially in the axial direction with the directions of the axial Halbach structure aligned so that the spacing between like poles is the wavelength λ of the ultrasonic waves transmitted to and received from the test object WK.In the receiving electromagnetic ultrasonic sensor RSd, the four first to fourth magnet groups RHG1 to RHG4 configured as described above are arranged sequentially in the axial direction with the directions of the axial Halbach structure aligned so that the spacing between like poles is the wavelength λ of the ultrasonic waves transmitted to and received from the test object WK. As described above, one magnet group HHG has two third permanent magnets as first permanent magnets arranged with the axial spacing of λ / 2 and opposite magnetic poles facing the space, so that the four first to fourth magnet groups THG1 to THG4, RHG1 to RHG4 are arranged so that each of the multiple first permanent magnets alternates between the south pole and north pole facing the space in the axial direction, and are arranged sequentially in the axial direction at intervals of half the wavelength of the ultrasound transmitted to and received from the subject.

[0101] Such a transmitting electromagnetic ultrasonic sensor TSd has a plurality of magnet groups THG in the axial direction, and of the plurality of third permanent magnets that form Halbach structures in the tangential direction and the axial direction, two third permanent magnets that face the space and are arranged in the axial direction are used as first permanent magnets, so the magnetic field of the first permanent magnets can be made stronger, thereby further increasing the ultrasonic signal strength.

[0102] The ultrasonic flaw detector 1000 is configured to include electromagnetic ultrasonic sensors TSd and RSd for transmission and reception, respectively, in the third modified embodiment, instead of the electromagnetic ultrasonic sensors TSa and RSa for transmission and reception, respectively, in the embodiment.

[0103] The transmitting electromagnetic ultrasonic sensor TSd in the third modified embodiment and the ultrasonic flaw detection device 1000 equipped with the same can increase the signal strength of the ultrasonic waves transmitted to the test object WK, and the receiving electromagnetic ultrasonic sensor RSd in the third modified embodiment and the ultrasonic flaw detection device 1000 equipped with the same can increase the receiving sensitivity of the ultrasonic waves.

[0104] Furthermore, in the above-described embodiment, the plurality of first permanent magnets PM1, PM2 in the transmitting and receiving electromagnetic ultrasonic sensors TSa, RSa may each comprise four first permanent magnets arranged sequentially along the circumferential direction at intervals of 90°, and may be arranged at a position rotated 45° circumferentially from the case where the first conductor wire is arranged at the circumferential center position of the first permanent magnet (fourth variant).

[0105] Fig. 17 is a diagram for explaining an electromagnetic ultrasonic sensor in a fourth modified embodiment. Fig. 18 is a diagram for explaining a coil (a coil of a fourth embodiment) in the electromagnetic ultrasonic sensor in the fourth modified embodiment. Fig. 19 is a diagram for explaining a coil of another embodiment (a coil of a fifth embodiment) in the electromagnetic ultrasonic sensor in the fourth modified embodiment. Fig. 20 is a diagram for explaining a coil of another embodiment (a coil of a sixth embodiment) in the electromagnetic ultrasonic sensor in the fourth modified embodiment. Fig. 21 is a diagram for explaining the positional relationship between a first permanent magnet and a first conductor wire of the coil in the electromagnetic ultrasonic sensor in the fourth modified embodiment. Fig. 21A shows the positional relationship between the first permanent magnet and the first conductor wire of the coil in the electromagnetic ultrasonic sensor in the fourth modified embodiment, Fig. 21B shows the reference position and also shows the positional relationship between the first permanent magnet and the first conductor wire of the coil in the case of T mode, and Fig. 21C shows the positional relationship between the first permanent magnet and the first conductor wire of the coil in the case of L mode.

[0106] More specifically, the transmitting electromagnetic ultrasonic sensor TSe comprises four first permanent magnets PM11 to PM14 arranged sequentially along the circumferential direction at 90° intervals, and a coil COd1, and the receiving electromagnetic ultrasonic sensor RSe comprises four first permanent magnets PM21 to PM24 arranged sequentially along the circumferential direction at 90° intervals, and a coil COd2.

[0107] The coils COd1 and COd2 of the electromagnetic ultrasonic sensors TSe and RSe for transmission and reception, respectively, are provided with, for example, a plurality k (k≧2) of unit coils COb-1, COb-2, ..., COb-k of two turns as shown in FIG. 3 above, as shown in FIG. 18, and these k unit coils COb-1, COb-2, ..., COb-k are sequentially connected in series and sequentially arranged side by side in the axial direction.

[0108] In the transmitting electromagnetic ultrasonic sensor TSe, first lead conductor wires are connected to the start end of the first unit coil COb-1 and the end end of the k-th unit coil COb-k, and each first lead conductor wire is connected to the ultrasonic generator UG, and power is supplied to coil COd1 from the ultrasonic generator UG. In the receiving electromagnetic ultrasonic sensor RSe, second lead conductor wires are connected to the start end of the first unit coil COb-1 and the end end of the k-th unit coil COb-k, and each second lead conductor wire is connected to the control processor 1, and coil COd2 outputs an ultrasonic reception signal to the control processor 1.

[0109] In the transmitting and receiving electromagnetic ultrasonic sensors TSe and RSe, the coils COe1 and COe2 shown in FIG. 19 or the coils COf1 and COf2 shown in FIG. 20 may be used instead of the coils COd1 and COd2.

[0110] The coil COe1 (COe2) shown in Fig. 19 includes three unit coils, COd-1, COd-2, and COd-3 shown in Fig. 18, which are connected in series in sequence, and these three unit coils COd-1, COd-2, and COd-3 are arranged circumferentially offset as shown in Fig. 19. Note that these three unit coils COd-1, COd-2, and COd-3 may be arranged overlapping in the radial direction with an insulator interposed therebetween.

[0111] In this case, in the transmitting electromagnetic ultrasonic sensor TSe, first lead conductor wires are connected to the start end of the first unit coil COd-1 and the end end of the third unit coil COd-3, and each first lead conductor wire is connected to the ultrasonic generator UG, and power is supplied to the coil COe1 from the ultrasonic generator UG. In the receiving electromagnetic ultrasonic sensor RSe, second lead conductor wires are connected to the start end of the first unit coil COd-1 and the end end of the third unit coil COd-3, and each second lead conductor wire is connected to the control processor 1, and the coil COe2 outputs an ultrasonic reception signal to the control processor 1.

[0112] The coil COf1 (COf2) shown in Fig. 20 includes three unit coils, COd-1, COd-2, and COd-3 shown in Fig. 18, connected in parallel, and these three unit coils COd-1, COd-2, and COd-3 are arranged circumferentially offset as shown in Fig. 20. Note that these three unit coils COd-1, COd-2, and COd-3 may be arranged overlapping in the radial direction with an insulator interposed therebetween.

[0113] In this case, in the transmitting electromagnetic ultrasonic sensor TSe, first lead conductor wires are connected to the respective starting ends and terminal ends of the unit coils COd-1 to COd-3, and each of the first lead conductor wires is connected to the ultrasonic generator UG, and power is supplied to the coil COf1 from the ultrasonic generator UG. In the receiving electromagnetic ultrasonic sensor RSe, second lead conductor wires are connected to the respective starting ends and terminal ends of the unit coils COd-1 to COd-3, and each of the second lead conductor wires is connected to the control processor 1, and the coil COf2 outputs an ultrasonic reception signal to the control processor 1.

[0114] In coils COd1, COd2 configured as described above, when the four first permanent magnets PM1, PM2 are arranged with the first conductor wires SC1, SC2 at the circumferential center of the first permanent magnets PM1, PM2 as shown in Fig. 21B and the first conductor wires SC1, SC2 arranged along the axial direction, the electromagnetic interaction between the first conductor wires SC1, SC2 and the first permanent magnets PM1, PM2 causes the transmitting electromagnetic ultrasonic sensor TSe to transmit ultrasonic waves in T mode and the receiving electromagnetic ultrasonic sensor RSe to receive ultrasonic waves in T mode. On the other hand, in coils COd1, COd2 configured as described above, when the four first permanent magnets PM1, PM2 are arranged with the second conductor wires RC1, RC2 arranged along the circumferential direction as shown in Fig. 21C, the electromagnetic interaction between the second conductor wires RC1, RC2 and the first permanent magnets PM1, PM2 causes the transmitting electromagnetic ultrasonic sensor TSe to transmit ultrasonic waves in L mode and the receiving electromagnetic ultrasonic sensor RSe to receive ultrasonic waves in L mode.

[0115] Therefore, in the fourth modified embodiment, the four first permanent magnets PM1 and PM2 are positioned at positions rotated 45° circumferentially from the case where the first conductor wire SC11 is positioned at the circumferential center position of the first permanent magnet PM11, as shown in Figure 21A.

[0116] In this fourth modified embodiment, ultrasonic waves can be transmitted and received between the first permanent magnet and each of the first and second conductor wires, and ultrasonic waves in both T mode and L mode can be transmitted and received.

[0117] In order to express the present invention, the present invention has been properly and sufficiently described above through the embodiments with reference to the drawings, but it should be recognized that those skilled in the art can easily change and / or improve the above-mentioned embodiments. Therefore, unless the changes or improvements made by those skilled in the art are at a level that causes departure from the scope of the claims described in the claims, such changes or improvements are interpreted as being included in the scope of the claims. [Explanation of symbols]

[0118] WK Subject TSa~TSe transmitting electromagnetic ultrasonic sensor RSa~RSe receiving electromagnetic ultrasonic sensor TMG (TMG1 to TMG4), RMG (RMG1 to RMG4), HHG magnet group PM1 (PM11 (PM111~PM114)~PM14 (PM141~PM144), PM2 (PM21 (PM211~PM214)~PM24 (PM241~PM244)) First permanent magnet CO1 (COa1~COf1), CO2 (COa2~COf2) coil SC1 (SCa11-SCa14, SCb11-SCb17), SC2 (SCa21-SCa24, SCb21-SCb27) First conductor wire RC1 (RCa11-RCa14, RCb11-RCb18), RC2 (RCa21-RCa24, RCb21-RCb28) Second conductor wire THM1 (THM111-THM114)-THM4 (THM141-THM144), RHM1 (RHM111-RHM114)-RHM4 (RHM141-RHM144), TAH1 (TAH11-TAH41)-TAH4 (TAH14-TAH44) Halbach structure magnet SHG1 to SHG3 sub-magnet group UG ultrasonic generator 1000 Ultrasonic flaw detection equipment 1 Control processing section 2 Input section 3 Display section 4 Interface section (IF section) 5 Storage section 11 Control section 12 Defect detection processing section

Claims

1. An electromagnetic ultrasonic sensor including a magnet group and a coil surrounding a space for placing a subject, the magnet group includes a plurality of first permanent magnets sequentially arranged along the circumferential direction so that south poles and north poles alternate in the circumferential direction and face the space, the coil includes one or more predetermined unit coils, The unit coil is a first conductor wire disposed between each of the first permanent magnets and the subject when the subject is disposed in the space, the first conductor wire extending along an axial direction relative to the circumferential direction; a second conductor wire that connects two first conductor wires that are adjacent to each other in the circumferential direction and that extends along the circumferential direction such that a first direction of current flowing in the first conductor wire that is disposed between the first permanent magnet, whose south pole faces the space, and the subject, and a second direction of current flowing in the first conductor wire that is disposed between the first permanent magnet, whose north pole faces the space, and the subject, are opposite to each other; Each of the first conductor wires and each of the second conductor wires is formed by a single conductor wire that makes one or more turns around the space in the axial direction. Electromagnetic ultrasonic sensor.

2. the magnet group is a plurality of first permanent magnets, each of which has its south pole and its north pole alternately facing the space in the axial direction and is sequentially arranged in the axial direction at intervals of half the wavelength of ultrasound waves transmitted to and received from the subject; 2. The electromagnetic ultrasonic sensor according to claim 1.

3. Each of the plurality of first permanent magnets is one of a plurality of second permanent magnets that form a Halbach structure in a tangential direction to the circumferential direction.

2. The electromagnetic ultrasonic sensor according to claim 1.

4. the plurality of first permanent magnets are two third permanent magnets, one of which is disposed in the axial direction and the other of which is disposed in the axial direction and has its south pole facing the space, among a plurality of third permanent magnets which form a Halbach structure in a tangential direction with respect to the circumferential direction and in the axial direction, and the other of which is disposed in the axial direction and has its south pole facing the space, the magnet group is a plurality of first permanent magnets, each of which has its south pole and its north pole alternately facing the space in the axial direction and is sequentially arranged in the axial direction at intervals of half the wavelength of ultrasound waves transmitted to and received from the subject; 2. The electromagnetic ultrasonic sensor according to claim 1.

5. The plurality of first permanent magnets include four first permanent magnets arranged sequentially along the circumferential direction at 90° intervals, and the first conductor wires are arranged at positions rotated 45° in the circumferential direction from a position where the first conductor wires are arranged at the central position of the first permanent magnets in the circumferential direction.

2. The electromagnetic ultrasonic sensor according to claim 1.

6. The electromagnetic ultrasonic sensor according to any one of claims 1 to 5 is provided for both transmission and reception. Ultrasonic flaw detection equipment.

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