Defect detection device and method for manufacturing defect detection device

Abstract

Provided is a defect detection device for detecting a defect in a rotor core having a columnar shape centered around an axis and having a plurality of slots arranged at intervals in the circumferential direction, each of the slots including: a neck part that is open toward the outer peripheral side and is defined by a pair of first surfaces extending in the radial direction when viewed in the axial direction; a dovetail part that is in communication with the neck part and is defined by a pair of inclined surfaces of which the circumferential spacing gradually increases toward the inner peripheral side; and a body part in communication with the dovetail part and defined by a pair of second surfaces that extend in the radial direction. The defect detection device comprises: a device body having a first inspection surface that comes into contact with the first surfaces, an inclination inspection surface that comes into contact with the inclined surfaces, and a second inspection surface that comes into contact with the second surfaces; a plurality of array coils respectively embedded inside the first inspection surface, the inclination inspection surface, and the second inspection surface; and a plurality of permanent magnets provided alongside the array coils.

Description

Defect detection device and method for manufacturing the defect detection device

[0001] The present disclosure relates to a defect detection device and a method for manufacturing a defect detection device.

[0002] To ensure stable operation of large generators (electric motors) used in power plants and other facilities, it is necessary to detect defects in each part that occur over time with high accuracy. In particular, the rotor core, which is a rotating body, is subjected to loads due to centrifugal force. As a result, defects such as cracks due to stress concentration are likely to occur in each part of the rotor core. Here, a component called a wedge is inserted into a slot formed on the outer surface of the rotor core to accommodate the coil and prevent the coil from popping out. The wedge fits from the inner periphery into a dovetail portion formed on the inner surface of the slot. Because centrifugal force is applied to the wedge, the dovetail portion is particularly susceptible to load.

[0003] A known technique for detecting defects in a dovetail portion is described in Patent Document 1. The device disclosed in Patent Document 1 mainly includes a jig that can contact the inner surface of a slot including the dovetail portion, and a pressing mechanism that presses the jig against the slot.

[0004] Patent No. 6121711

[0005] However, when the jig is pressed against the inner surface of the slot using only a pressing mechanism as described above, the jig may lift off when moved along the slot, potentially affecting the accuracy of defect detection. Furthermore, because the rotor core of an electric motor is generally made of a magnetic material, there is also the disadvantage that detection accuracy may be reduced by magnetic noise.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a defect detection device that is capable of stably performing highly accurate defect detection, and a method for manufacturing a defect detection device.

[0007] In order to solve the above-described problems, a defect detection device according to the present disclosure is a defect detection device that detects defects in a rotor core that is cylindrical about its axis, has a plurality of slots that are recessed radially inward from the outer peripheral surface and are arranged at intervals in the circumferential direction, and each slot has, when viewed from the axial direction, a neck portion that opens toward the outer peripheral side and is formed by a pair of first surfaces that extend radially, a dovetail portion that communicates with the neck portion and is formed by a pair of inclined surfaces that gradually increase the circumferential spacing toward the inner peripheral side, and a body portion that communicates with the dovetail portion and is formed by a pair of second surfaces that extend radially, and the defect detection device has a device main body that has a first inspection surface abutting the first surfaces, an inclined inspection surface abutting the inclined surfaces, and a second inspection surface abutting the second surface, a plurality of array coils that are embedded inside the first inspection surface, the inclined inspection surface, and the second inspection surface, respectively, and a plurality of permanent magnets that are arranged alongside the array coils.

[0008] The manufacturing method of a defect detection device according to the present disclosure is a manufacturing method of the above-mentioned defect inspection device, and includes the steps of obtaining dimensions of each part related to the shape of the slot, forming the device body by three-dimensional additive manufacturing based on the dimensions, and attaching the array coil and the permanent magnet.

[0009] According to the present disclosure, it is possible to provide a defect detection device capable of stably performing highly accurate defect detection, and a method for manufacturing a defect detection device.

[0010] Fig. 1 is a cross-sectional view showing the configuration of a rotor core of an electric motor; Fig. 2 is an enlarged view of a main part of the rotor core, and a cross-sectional view showing the configuration of a defect detection device according to an embodiment of the present disclosure; Fig. 3 is a front view showing the configuration of a defect detection device according to an embodiment of the present disclosure; Fig. 4 is an explanatory view showing the arrangement of an array coil according to an embodiment of the present disclosure, which is a development view of each surface of the device main body; Fig. 5 is a flowchart showing each step of a manufacturing method of a defect detection device according to an embodiment of the present disclosure;

[0011] A defect detection device 1 according to an embodiment of the present disclosure and a manufacturing method thereof will be described below with reference to FIGS. 1 to 5. FIG.

[0012] The defect detection device 1 according to this embodiment is preferably used to detect defects inside slots 94 formed in a rotor 90 of an electric motor.

[0013] (Rotor Configuration) As shown in Fig. 1, the rotor 90 includes a rotor core 91, coils 92, and wedges 93. The rotor core 91 has a cylindrical shape centered on the axis X. A plurality of slots 94 are formed in the outer peripheral surface of the rotor core 91, recessed radially inward and arranged at intervals in the circumferential direction. A coil 92 is housed inside each slot 94. The openings on the outer peripheral side of the slots 94 are closed by wedges 93 to prevent the coils 92 from popping out due to centrifugal force.

[0014] More specifically, as shown in FIG. 2 , the slot 94 has a neck portion 101, a dovetail portion 102, and a body portion 103. The neck portion 101 is formed by a pair of first surfaces 201 that open toward the outer periphery and extend radially when viewed from the direction of the axis X. The dovetail portion 102 is located radially inward of the neck portion 101. The dovetail portion 102 is formed by a pair of inclined surfaces 202 that communicate with the neck portion 101 and whose circumferential spacing gradually increases toward the inner periphery. The body portion 103 is formed by a pair of second surfaces 203 that communicate with the dovetail portion 102 and extend radially.

[0015] The wedge 93 is inserted from the direction of the axis X into the slot 94 having the neck portion 101, the dovetail portion 102, and the body portion 103. The wedge 93 engages with the inclined surface of the dovetail portion 102, thereby preventing the wedge 93 from jumping outward in the radial direction.

[0016] (Configuration of Defect Detection Apparatus) As shown in FIG. 2 , the defect detection apparatus 1 includes an apparatus main body 10 , a wear-resistant member 11 , an array coil 12 , and a permanent magnet 13 .

[0017] (Device Main Body) The device main body 10 has a first inspection surface 21, an inclined inspection surface 22, and a second inspection surface 23. The first inspection surface 21 can abut against a first surface 201 of the slot 94. The inclined inspection surface 22 can abut against an inclined surface 202 of the slot 94. The second inspection surface 23 can abut against a second surface 203 of the slot 94. In other words, the dimensions of each part of the device main body 10 are determined so that when the device main body 10 is inserted into the slot 94, the first surface 201 and the first inspection surface 21, the inclined surface and the inclined inspection surface 22, and the second surface 203 and the second inspection surface 23 abut simultaneously. Note that when a wear-resistant member 11, which will be described later, is provided, the above-mentioned surfaces do not come into direct contact with each other, but the term "abutting" herein also includes a state in which the surfaces face each other via the wear-resistant member 11.

[0018] 3, a pair of gripping portions 31 that protrude radially outward are formed on the radially outer end surface of the device body 10. The gripping portions 31 are used when manually scanning the device body 10 along the slot 94. A wiring housing portion 32 is formed between the gripping portions 31 to route various wirings to the outside. A manufacturing method for this device body 10 will be described later.

[0019] (Wear-Resistant Member) The first inspection surface 21, the inclined inspection surface 22, and the second inspection surface 23 of the device body 10 are covered with a wear-resistant member 11. The wear-resistant member 11 is provided to prevent wear and damage to these surfaces when the device body 10 is scanned along the slot 94. The wear-resistant member 11 is a thin film made of so-called engineering plastic. Specifically, polyacetal or PEEK (polyether ether ketone) is preferably used as the wear-resistant member 11.

[0020] (Array Coils) A plurality of array coils 12 are embedded inside the device main body 10. Specifically, the array coils 12 are embedded inside the first inspection surface 21, the inclined inspection surface 22, and the second inspection surface 23. As shown in FIGS. 2 to 4 , the array coils 12 are located at different radial positions when viewed from the direction of the axis X, and partially overlap each other. Specifically, the radial positions of the array coils 12 gradually change radially inward as they move from one side to the other side along the axis X. Furthermore, pairs of array coils 12 are arranged at the ends on one side and the other side along the axis X, spaced apart from each other in the radial direction. The array coils 12 arranged at these ends are arranged so as to cover the corners between the first inspection surface 21 and the inclined inspection surface 22 and the corners between the inclined inspection surface 22 and the second inspection surface 23. In other words, the axes of the array coils 12 are oriented toward the respective corners.

[0021] Although not shown in detail, the array coil 12 has an excitation coil and a detection coil. The excitation coil generates eddy currents near each surface of the slot 94. When this eddy current is disturbed by a defect, the detection coil detects the disturbance component. The excitation coil and the detection coil have their central axes intersecting. In other words, this array coil 12 is a cross coil. It is also possible for each coil to serve as both the excitation coil and the detection coil.

[0022] When the maximum outer diameter of the array coil 12, which is a cross coil, is D, it is desirable that adjacent array coils 12 overlap each other by D / 2 or more in the radial direction.

[0023] (Permanent Magnets) Each of the array coils 12 is surrounded by a pair of permanent magnets 13 in the axial direction X. These permanent magnets 13 serve to bring the device body 10 into close contact with the inner surface of the slot 94 by magnetic force. In addition, since the rotor 90 is mainly formed of a magnetic material, it is possible to maintain a state as close to magnetic saturation as possible by the magnetic force of the permanent magnets 13 in order to reduce magnetic noise during defect detection.

[0024] (Method for Manufacturing Defect Detection Device) Next, a method for manufacturing the above-mentioned defect detection device 1 will be described with reference to Fig. 5. As shown in Fig. 5, first, the dimensions of each part of the slot 94 are obtained (step S1). The dimensions of each part here refer to, for example, the lengths of the first surface 201, the inclined surface, and the second surface 203 when viewed from the direction of the axis X, and the intersection angle between these surfaces.

[0025] Next, based on the above dimensions, the device main body 10 is formed by three-dimensional additive manufacturing (step S2). After that, the array coil 12 and permanent magnets 13 are attached to the device main body 10 (step S3), and wiring for each part is performed (step S4). Finally, the wear-resistant member 11 is attached, completing the defect detection device 1 (step S5).

[0026] (Effects) To ensure stable operation of large generators (electric motors) used in power plants and the like, it is necessary to detect defects in each part due to long-term operation with high accuracy. In particular, the rotor 90, which is a rotating body, is subjected to loads due to centrifugal force. As a result, defects such as cracks due to stress concentration are likely to occur in each part of the rotor core 91. Here, a member called a wedge 93 is inserted into a slot 94 formed on the outer peripheral surface of the rotor core 91 to accommodate the coil 92, in order to prevent the coil 92 from protruding. The wedge 93 is fitted from the inner peripheral side into a dovetail portion 102 formed on the inner surface of the slot 94. Because centrifugal force is applied to the wedge 93, the dovetail portion 102 is particularly likely to be subjected to load.

[0027] Conventionally, a technique proposed for detecting defects in the dovetail portion 102 mainly includes a jig that can contact the inner surface of the slot 94, including the dovetail portion 102, and a pressing mechanism for pressing the jig against the slot 94.

[0028] However, when the jig is pressed against the inner surface of the slot 94 using only the pressing mechanism as described above, the jig may lift off when moved along the slot 94, potentially affecting the accuracy of defect detection. Furthermore, because the rotor core 91 of an electric motor is generally made of a magnetic material, there is also the drawback that detection accuracy may be reduced by magnetic noise. To overcome these drawbacks, the present embodiment employs the above-described configurations.

[0029] With the above configuration, the shape of the device body 10 itself corresponds to the shape of the slot 94, allowing the array coil 12 to be positioned close to each side of the slot 94. This further improves defect detection accuracy. Conversely, if a device body 10 that does not correspond to the shape of the slot 94 is used, the distance between the array coil 12 and each side increases, potentially resulting in lift-off noise. The above configuration significantly reduces this possibility. Furthermore, the provision of the permanent magnet 13 allows magnetic saturation to eliminate magnetic noise from the rotor core 91, which is made of a magnetic material. This allows for an accurate inspection waveform with noise removed, further improving defect detection accuracy. In other words, the provision of the permanent magnet 13 simultaneously achieves two effects: ensuring close contact between the device body 10 and the slot 94 and canceling magnetic noise.

[0030] According to the above configuration, the multiple array coils 12 are positioned at different radial positions and partially overlap each other in the radial direction, so that when the device main body 10 is moved in the direction of the axis X, defect inspection using eddy currents can be performed without omission over the entire radial area of ​​each surface. This significantly reduces the possibility of overlooking defects, thereby further improving the reliability of the defect detection device 1.

[0031] Here, stress concentration occurs at the corners between the first surface 201 and the inclined surface 202 and the corners between the inclined surface 202 and the second surface 203, which tend to cause defects such as cracks. With the above configuration, the array coils 12 are arranged corresponding to these corners, making it possible to more actively and precisely detect defects at these corners. In particular, since the axes of the array coils 12 are oriented toward the corners, defects can be detected with high accuracy.

[0032] According to the above configuration, a pair of permanent magnets 13 are arranged in the vicinity of the array coil 12, sandwiching the array coil 12 therebetween, thereby achieving a high level of both magnetic saturation by the permanent magnets 13 and prevention of lift-off of the array coil 12.

[0033] According to the above configuration, by holding the gripping portion 31 and moving the device body 10 in the direction of the axis X, the operator can stably and smoothly scan each surface along the slot 94 without causing lift-off, which further improves the accuracy of defect detection.

[0034] According to the above configuration, the provision of the wear-resistant member 11 makes it difficult for the device body 10 itself to wear out or be damaged, even when multiple inspections are performed, which allows the defect inspection device to be used repeatedly over a long period of time.

[0035] According to the above method, the device body 10 is custom-made by three-dimensional additive manufacturing. This makes it possible to absorb individual differences in the dimensions of the slots 94 between rotor cores 91. This further improves adhesion between the array coil 12 and each surface, making it possible to further increase the accuracy of defect detection. In particular, the use of three-dimensional additive manufacturing makes it possible to inexpensively produce multiple device bodies 10, thereby maintaining a high level of balance between ensuring inspection accuracy and reducing costs. Ultimately, this contributes to the stable operation of electric motors and further improves plant availability.

[0036] (Other Embodiments) Although the embodiments of the present disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like within the scope that does not deviate from the gist of the present disclosure are also included.

[0037] For example, the number of array coils 12 described in the above embodiment is merely an example, and can be changed as appropriate depending on the design and specifications.

[0038] Furthermore, the application of the defect detection device 1 is not limited to electric motors used for power generation in plants, but the defect detection device 1 can be applied to any electric motor that has slots 94.

[0039] Furthermore, in the above embodiment, an example has been described in which the device body 10 is produced by three-dimensional additive manufacturing. However, as long as cost and time permit, the device body 10 can also be produced by other methods. For example, a method of producing the device body 10 by injection molding a synthetic resin is conceivable.

[0040] Furthermore, the position and shape of the grip portion 31 are merely examples and can be changed as appropriate according to the design and specifications.

[0041] It is also possible to adopt a configuration in which no wear-resistant member 11 is provided. In this case, the amount of lift-off is reduced by the amount of the wear-resistant member 11, thereby further improving the defect detection accuracy.

[0042] <Additional Notes> The defect detection device 1 and the manufacturing method of the defect inspection device described in each embodiment can be understood, for example, as follows.

[0043] (1) A defect detection device 1 according to a first aspect is a defect detection device 1 for detecting defects in a rotor core 91 having a cylindrical shape centered on an axis X, a plurality of slots 94 recessed radially inward from an outer peripheral surface, and arranged at intervals in the circumferential direction, wherein the slots 94 have a neck portion 101 formed by a pair of first surfaces 201 that open toward the outer peripheral side and extend in the radial direction, as viewed from the direction of the axis X, and a pair of inclined surfaces 202 that communicate with the neck portion 101 and whose circumferential interval gradually increases toward the inner peripheral side. The defect detection device 1 has a dovetail portion 102 and a body portion 103 formed by a pair of second surfaces 203 that are connected to the dovetail portion 102 and extend radially, and the defect detection device 1 has a device main body 10 having a first inspection surface 21 abutting the first surface 201, an inclined inspection surface 22 abutting the inclined surface 202, and a second inspection surface 23 abutting the second surface 203, a plurality of array coils 12 embedded inside the first inspection surface 21, the inclined inspection surface 22, and the second inspection surface 23, respectively, and a plurality of permanent magnets 13 installed alongside the array coils 12.

[0044] According to the above configuration, since the shape of the device body 10 itself corresponds to the shape of the slot 94, the array coil 12 can be placed close to each side of the slot 94. This further improves the defect detection accuracy. Furthermore, since the device body 10 is provided with the permanent magnets 13, magnetic noise caused by the rotor core 91 made of a magnetic material can be eliminated by magnetic saturation based on the magnetic force of the permanent magnets 13. This makes it possible to further improve the defect detection accuracy.

[0045] (2) The defect detection device 1 according to the second aspect is the defect detection device 1 of (1), in which the multiple array coils 12 are positioned at different radial positions when viewed from the direction of the axis X, and portions of the array coils 12 overlap with each other in the radial direction.

[0046] According to the above configuration, the radial positions of the multiple array coils 12 are different and some of them overlap with each other in the radial direction, so that by moving the device main body 10 in the direction of the axis X, it is possible to inspect the entire radial area of ​​each surface without omission.

[0047] (3) The defect detection device 1 according to the third aspect is the defect detection device 1 of (1) or (2), in which some of the plurality of array coils 12 are respectively arranged at the corner between the first inspection surface 21 and the inclined inspection surface 22, and at the corner between the inclined inspection surface 22 and the second inspection surface 23.

[0048] Here, stress concentration occurs at the corners, which tend to cause defects such as cracks. According to the above configuration, the array coils 12 are arranged corresponding to the respective corners, so that defects at the corners can be detected more proactively and precisely.

[0049] (4) The defect detection device 1 according to the fourth aspect is a defect detection device 1 according to any one of aspects (1) to (3), in which the permanent magnets 13 are arranged in pairs so as to sandwich the array coil 12 on both sides in the direction of the axis X.

[0050] According to the above configuration, a pair of permanent magnets 13 are arranged in the vicinity of the array coil 12 on either side thereof, thereby achieving two effects: magnetic saturation by the permanent magnets 13 and prevention of lift-off of the array coil 12.

[0051] (5) The defect detection device 1 according to the fifth aspect is a defect detection device 1 according to any one of aspects (1) to (4), and further has a gripping portion 31 provided at each end of the device main body 10 on both sides in the direction of the axis X.

[0052] According to the above configuration, by holding the gripping portion 31 and moving the device body 10 in the direction of the axis X, the operator can stably and smoothly scan each surface along the slot 94 without causing lift-off, which further improves the accuracy of defect detection.

[0053] (6) The defect detection device 1 of the sixth aspect is a defect detection device 1 of any one of aspects (1) to (5), further having a film-like wear-resistant member 11 covering the first inspection surface 21, the inclined inspection surface 22, and the second inspection surface 23.

[0054] According to the above configuration, the provision of the wear-resistant member 11 makes it difficult for the device body 10 itself to wear out or be damaged, even when multiple inspections are performed, which allows the defect inspection device to be used repeatedly over a long period of time.

[0055] (7) The defect detection device 1 according to the seventh aspect is a manufacturing method for the defect detection device 1 according to any one of aspects (1) to (6), and includes the steps of acquiring dimensions of each part related to the shape of the slot 94, forming the device main body 10 by three-dimensional additive manufacturing based on the dimensions, and attaching the array coil 92 and the permanent magnet 13.

[0056] According to the above method, customization by three-dimensional additive manufacturing can absorb individual differences in the dimensions of the slot 94. This further improves the adhesion between the array coil 12 and each surface, making it possible to further increase the accuracy of defect detection.

[0057] According to the above-described defect detection device 1 and the manufacturing method of the defect detection device 1, it is possible to perform stable and highly accurate defect detection.

[0058] DESCRIPTION OF SYMBOLS 1... Defect detection device 10... Device body 11... Wear-resistant member 12... Array coil 13... Permanent magnet 21... First inspection surface 22... Inclined inspection surface 23... Second inspection surface 31... Grip portion 32... Wiring accommodating portion 90... Rotor 91... Rotor core 92... Array coil 93... Wedge 94... Slot 101... Neck portion 102... Dovetail portion 103... Body portion 201... First surface 202... Inclined surface 203... Second surface X... Axis

Claims

1. A defect detection device for detecting defects in a rotor core which is cylindrical about its axis, has a plurality of slots which are recessed radially inward from the outer circumferential surface and are arranged at intervals in the circumferential direction, wherein each of the slots has, when viewed from the axial direction, a neck portion formed by a pair of first surfaces which open toward the outer circumferential side and extend in the radial direction, a dovetail portion formed by a pair of inclined surfaces which communicate with the neck portion and whose circumferential spacing gradually increases toward the inner circumferential side, and a body portion formed by a pair of second surfaces which communicate with the dovetail portion and extend in the radial direction, wherein the defect detection device has: a device main body having a first inspection surface abutting the first surfaces, an inclined inspection surface abutting the inclined surfaces, and a second inspection surface abutting the second surface; a plurality of array coils respectively embedded inside the first inspection surface, the inclined inspection surface, and the second inspection surface; and a plurality of permanent magnets provided in conjunction with the array coils.

2. A defect detection device as described in claim 1, wherein the multiple array coils are positioned at different radial positions when viewed from the axial direction, and partially overlap each other in the radial direction.

3. A defect detection device as described in claim 1 or 2, wherein a portion of the plurality of array coils are respectively arranged at a corner between the first inspection surface and the inclined inspection surface, and at a corner between the inclined inspection surface and the second inspection surface.

4. A defect detection device as claimed in claim 1 or 2, wherein the permanent magnets are provided in pairs, sandwiching the array coil on both sides in the axial direction.

5. A defect detection device according to claim 1 or 2, further comprising gripping portions provided at both ends of said device body in the axial direction.

6. A defect detection device according to claim 1 or 2, further comprising a film-like wear-resistant member covering said first inspection surface, said inclined inspection surface, and said second inspection surface.

7. A method for manufacturing a defect detection device as described in claim 1 or 2, comprising the steps of: acquiring dimensions of each part related to the shape of the slot; forming the device body by three-dimensional additive manufacturing based on the dimensions; and attaching the array coil and the permanent magnet.

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