Wound core, method for manufacturing wound core, and wound core manufacturing device

Abstract

The present invention relates to a wound core, a manufacturing method of a wound core, and a wound core manufacturing apparatus. The wound core (10) is a wound core having a hollow portion (15) of a rectangular shape in the center, including a portion in which direction electromagnetic steel sheets (1) in which planar portions (4) and curved portions (5) are continuously alternated in a length direction are stacked in a sheet thickness direction, characterized in that a plurality of direction electromagnetic steel sheets are connected to each other via at least one joint portion (6) in each roll by stacking the direction electromagnetic steel sheets (1) individually bent processed in a layered manner and assembled in a wound shape, and an average Vickers hardness of a cross section of the curved portion (5) of the above-mentioned direction electromagnetic steel sheet (1) along a thickness direction of the direction electromagnetic steel sheet (1), that is, an L cross section along the above-mentioned length direction, is 190-250 HV.

Description

Technical Field

[0001] This invention relates to wound iron cores, a method for manufacturing wound iron cores, and an apparatus for manufacturing wound iron cores. This application is based on and claims priority to Japanese Patent Application No. 2020-178562, filed on October 26, 2020, the contents of which are incorporated herein by reference. Background Technology

[0002] The core of a transformer includes laminated cores and wound cores. Wound cores are generally manufactured as follows: directional electromagnetic steel sheets are laminated and wound into a ring (wound shape), and then the wound is pressurized to form a roughly square shape (in this specification, wound cores manufactured in this way are sometimes referred to as box-type cores). Due to this forming process, the directional electromagnetic steel sheets undergo mechanical processing strain (plastic deformation strain), which is the main cause of significant deterioration in the iron loss of the directional electromagnetic steel sheets; therefore, strain-relief annealing is required.

[0003] On the other hand, as another manufacturing method for wound iron cores, patent documents 1 to 3 disclose techniques such as: pre-bending a portion of the steel plate that will become the corner of the wound iron core to form a relatively small bending area with a radius of curvature of 3 mm or less, and then stacking the bent steel plate to form a wound iron core (in this specification, a wound iron core manufactured in this way is sometimes referred to as a single core (registered trademark)). According to this manufacturing method, the large-scale forming process as in the past is not required, the steel plate is precisely bent to maintain the shape of the iron core, and the processing strain is concentrated only in the bending portion (corner). Therefore, the strain removal based on the above-mentioned annealing process can also be omitted, which has greater industrial advantages and is being promoted for application.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2005-286169

[0007] Patent Document 2: Japanese Patent No. 6224468

[0008] Patent Document 3: Japanese Patent Application Publication No. 2018-148036 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] However, when bending the corner portion of the steel plate to form a single core through a steel plate bending process, strain is introduced into the bent portion. Due to this strain, when using the magnetic core in its unannealed state, there is a problem that the core iron loss becomes inferior. Furthermore, even when the magnetic core is annealed, depending on the annealing conditions, the introduced strain may not be completely released, and there is still a possibility that the core iron loss will become inferior. For example, in Patent Document 3, the amount of plastic strain introduced is not sufficiently controlled. Therefore, the iron loss may deteriorate in the method described in Patent Document 3.

[0011] The present invention was made in view of the above circumstances, and its purpose is to provide a wound iron core, a method for manufacturing a wound iron core, and an apparatus for manufacturing a wound iron core, which can achieve low iron loss regardless of whether annealing is performed.

[0012] Methods for solving problems

[0013] To achieve the above objectives, the present invention provides a wound core having a rectangular hollow portion at its center and comprising a portion of directional electromagnetic steel sheets, which are continuously stacked in the thickness direction along the length direction and alternately have planar portions and curved portions. This core is formed by stacking individually bent directional electromagnetic steel sheets into layers and assembling them into a wound shape. In each roll, multiple directional electromagnetic steel sheets are interconnected via at least one joint. The invention is characterized in that any of the curved portions of any one or more of the stacked directional electromagnetic steel sheets has an average Vickers hardness of 190-250 HV in the cross-section along the thickness direction of the directional electromagnetic steel sheet, i.e., the L-section along the length direction.

[0014] In view of the actual situation in single-core wound iron cores where strain is introduced into the bent portion during the bending process of the steel plate at the corner of the single core, resulting in a disadvantage in core iron loss due to this strain, the inventors have focused on the possibility that a low-iron-loss wound iron core can be obtained by controlling the amount of plastic strain introduced into the bent portion within a specified range when bending the steel plate to form the bent portion. The inventors have obtained the following insight: if the average Vickers hardness in the L-section of the bent portion after bending is in the range of 190-250 HV, the amount of plastic strain introduced into the bent portion is suppressed within a specified range, and a low-iron-loss wound iron core can be achieved regardless of whether annealing is performed.

[0015] To achieve an average Vickers hardness in the bent portion within the range of 190-250 HV after bending, controlling two parameters—the tensile stress during steel sheet processing and the coefficient of kinetic friction between the steel sheet and the bending tool—is effective in steel sheet bending processes using bending tools. Specifically, for example, when performing bending on the bent portion of a stacked directional electromagnetic steel sheet, combining both of the following conditions simultaneously...

[0016] (1) The tensile stress applied in the length direction (L direction) of the steel plate during processing is set to be between 0.8 MPa and 6.8 MPa (for example, the directional electromagnetic steel plate is bent while being subjected to a tensile stress in the length direction of 0.8 MPa and 6.8 MPa).

[0017] (2) Set the coefficient of dynamic friction between the steel plate and the bending tool to be above 0.10 and below 0.74.

[0018] It can effectively, easily and reliably achieve an average Vickers hardness in the range of 190-250HV. Thus, even when using the core in the unannealed state, it is possible to obtain a core with less iron loss degradation. Furthermore, when the core is annealed, it is possible to obtain a core with less residual strain.

[0019] In the above configuration, the positions in the L-section of the bent portion where the Vickers hardness is to be measured can be any 10 points, for example. Preferably, the positions in the L-section of the bent portion where the Vickers hardness is to be measured are located at a predetermined distance from the surface of the steel plate in the thickness direction. More preferably, the positions in the L-section of the bent portion where the Vickers hardness is to be measured are approximately at the center in the thickness direction of the steel plate. Furthermore, each measuring point is also preferably separated from each other by a predetermined distance in the length direction of the steel plate.

[0020] Furthermore, the present invention also provides a method and apparatus for manufacturing a wound iron core having the above-mentioned features.

[0021] The effects of the invention

[0022] According to the present invention, the average Vickers hardness in the L-section of the bent portion after bending is in the range of 190-250 HV. Therefore, the amount of plastic strain introduced into the bent portion is suppressed within a specified range. Regardless of whether annealing is performed, a low-iron-loss wound core, a method for manufacturing a wound core, and an apparatus for manufacturing a wound core can be achieved. Attached Figure Description

[0023] Figure 1 This is a perspective view schematically illustrating a wound iron core according to one embodiment of the present invention.

[0024] Figure 2 yes Figure 1 The side view of the wound iron core shown in the embodiment.

[0025] Figure 3 This is a side view schematically illustrating another embodiment of the present invention, showing a wound iron core.

[0026] Figure 4 This is a side view schematically showing an example of a single layer of directional electromagnetic steel sheet that constitutes a wound iron core.

[0027] Figure 5 This is a side view schematically showing another example of a single layer of directional electromagnetic steel sheet that constitutes a wound iron core.

[0028] Figure 6 This is a side view schematically showing an example of a bent portion of the directional electromagnetic steel plate constituting the wound core of the present invention.

[0029] Figure 7 This is a schematic perspective view of an example of a bending process device used to apply tensile stress to the end face of a steel plate that is bent along its length direction while bending the plate.

[0030] Figure 8 This is a diagram illustrating an example of a method for measuring Vickers hardness at any 10 points in the L-section of a curved section.

[0031] Figure 9 It is a block diagram that schematically illustrates the structure of a winding iron core manufacturing apparatus in a single-core manner.

[0032] Figure 10 This is a schematic diagram showing the dimensions of the wound iron core manufactured during the performance evaluation. Detailed Implementation

[0033] The wound iron core according to one embodiment of the present invention will now be described in detail. However, the present invention is not limited to the configuration disclosed in this embodiment, and various modifications can be made without departing from the spirit of the invention. Furthermore, in the numerical ranges described below, both the lower and upper limits are included. Values ​​expressed as "more than" or "less than" are not included in the numerical range. Additionally, "%" related to chemical composition, unless otherwise specified, refers to "mass %".

[0034] Furthermore, the terms used in this specification to define shapes, geometric conditions, and their degrees, such as "parallel," "perpendicular," "identical," "right angle," etc., as well as the values ​​of lengths and angles, are not limited to their strict meanings but are interpreted to include the range of degrees to which the same function can be expected.

[0035] In addition, in this specification, "directional electromagnetic steel plate" is sometimes simply referred to as "steel plate" or "electromagnetic steel plate", and "wound iron core" is simply referred to as "iron core".

[0036] One embodiment of the present invention provides a wound core having a generally rectangular core body in side view. This core body has a stacked structure comprising directional electromagnetic steel sheets, which alternately consist of planar portions and curved portions in the length direction, and are stacked in the thickness direction, and are generally polygonal in side view. Here, the planar portion refers to the straight portion other than the curved portion. The inner surface radius of curvature r of the curved portion in side view is, for example, 1.0 mm or more and 5.0 mm or less. As an example, the directional electromagnetic steel sheet has a chemical composition containing 2.0 to 7.0% Si by mass, with the remainder consisting of Fe and impurities, and has an aggregate structure oriented according to the Goss orientation. For example, directional electromagnetic steel strip as described in JIS C 2553:2019 can be used as the directional electromagnetic steel sheet.

[0037] Next, the shapes of the wound core and the directional electromagnetic steel plate according to one embodiment of the present invention will be specifically described. The shapes of the wound core and the directional electromagnetic steel plate described herein are not particularly novel, and are based on known shapes of wound cores and directional electromagnetic steel plates.

[0038] Figure 1 This is a perspective view schematically illustrating one embodiment of a wound iron core. Figure 2 yes Figure 1 The side view of the wound iron core shown in the embodiment. Furthermore, Figure 3 This is a side view schematically illustrating another embodiment of the wound iron core.

[0039] Furthermore, in this invention, side view refers to the view along the width of the elongated directional electromagnetic steel plate 1 constituting the wound iron core. Figure 1 Viewed along the Y-axis. A side view is a diagram showing the shape as seen from the side. Figure 1 (Graph of the Y-axis direction).

[0040] One embodiment of the present invention provides a wound core 10 comprising a wound core body that is generally polygonal in shape when viewed from the side. The wound core body 10 has a stacked structure of directional electromagnetic steel plates 1 stacked in the thickness direction, which is generally rectangular in shape when viewed from the side. The wound core body 10 can be used directly as a wound core, or, as needed, can be equipped with known fasteners such as cable ties to fix the stacked directional electromagnetic steel plates together.

[0041] In this embodiment, the core length of the wound core body 10 is not particularly limited. As long as the number of bends 5 is the same, even if the core length changes in the wound core 10, the volume of the bends 5 remains constant, and therefore the iron loss generated in the bends 5 is constant. The longer the core length, the smaller the volume fraction of the bends 5 relative to the wound core body 10, and therefore the smaller the impact on iron loss degradation. Therefore, the core length of the wound core body 10 is preferably relatively long. The core length of the wound core body 10 is preferably 1.5 m or more, more preferably 1.7 m or more. In addition, in this invention, the core length of the wound core body 10 refers to the circumference at the center point of the stacking direction of the wound core body 10 when viewed from the side.

[0042] This type of wound iron core can be used well for any previously known application.

[0043] The core of this embodiment is characterized by being approximately polygonal in side view. In the following description using the accompanying drawings, a generally rectangular (quadrilateral) core, which is also of a general shape, will be used for simplification. However, depending on the angle and number of the bent portions 5 and the length of the flat portions 4, cores of various shapes can be manufactured. For example, if all the bent portions 5 have an angle of 45° and the lengths of the flat portions are equal, it becomes an octagon in side view. Furthermore, if the angle is 60°, there are six bent portions 5, and the lengths of the flat portions 4 are equal, it becomes a hexagon in side view.

[0044] like Figure 1 as well as Figure 2 As shown, the wound core body 10 has a generally rectangular stacked structure 2 comprising alternating planar portions 4, 4a and curved portions 5 of directional electromagnetic steel plates 1 stacked in the thickness direction, and having a hollow portion 15 when viewed from the side. The corner portion 3, including the curved portions 5, has two or more curved portions 5 in a curved shape when viewed from the side, and the total value of the curvature angle of each curved portion 5 present in one corner portion 3 is, for example, 90°. The corner portion 3 has a planar portion 4a shorter than the planar portion 4 between adjacent curved portions 5, 5. Therefore, the corner portion 3 is configured to have two or more curved portions 5 and one or more planar portions 4a. Furthermore, in Figure 2 In one embodiment, the bend 5 is 45°. Figure 3 In one embodiment, the bend 5 is 30°.

[0045] As these examples illustrate, the wound core of this embodiment can be constructed from bends with various angles, but from the viewpoint of suppressing strain caused by deformation during processing and thus suppressing iron loss, the bending angle of the bend 5 is... Preferably, the angle is 60° or less, more preferably 45° or less. The bending angle of the bent portion of a core. It can be constructed arbitrarily. For example, it can be set as... and From a production efficiency perspective, it is preferable to have equal bending angles. If the deformation area is reduced to a certain extent, the iron loss of the manufactured iron core can be reduced by the iron loss of the steel plate used. In this case, different combinations of angles can also be processed. The design can be arbitrarily selected based on the priorities in iron core processing.

[0046] Reference Figure 6 A more detailed explanation of the curved section 5 is provided. Figure 6 This diagram schematically illustrates an example of a curved portion (curved section) 5 of a directional electromagnetic steel sheet 1. The bending angle of the curved portion 5 refers to the angle difference between the straight section on the rear side and the straight section on the front side in the bending direction within the curved portion of the directional electromagnetic steel sheet. It is represented as the supplementary angle between two imaginary lines Lb-elongation1 and Lb-elongation2, obtained by extending the straight sections of the plane portions 4 and 4a that sandwich the curved portion 5 on the outer surface of the directional electromagnetic steel sheet 1. At this point, the point where the extended straight line separates from the surface of the steel plate is the boundary between the flat portion 4 and the curved portion 5 on the outer surface side of the steel plate. Figure 6 Points F and G are in the middle.

[0047] Furthermore, straight lines perpendicular to the outer surface of the steel plate are extended from points F and G respectively, and their intersections with the inner surface of the steel plate are designated as points E and D respectively. Points E and D are the boundaries between the flat portion 4 and the curved portion 5 on the inner surface of the steel plate.

[0048] Furthermore, in this invention, the curved portion 5 is the part of the directional electromagnetic steel plate 1 surrounded by the aforementioned points D, E, F, and G when viewed from the side. Figure 6 In the diagram, the inner surface of the steel plate between point D and point E, i.e., the curved part 5, is denoted as La, and the outer surface of the steel plate between point F and point G, i.e., the curved part 5, is denoted as Lb.

[0049] Furthermore, the figure shows the radius of curvature r of the inner surface of the curved portion 5 in a side view. The radius of curvature r of the curved portion 5 is obtained by approximating La with an arc passing through points E and D. A smaller radius of curvature r results in a more abrupt curvature of the curved portion 5, while a larger radius of curvature r results in a gentler curvature of the curved portion 5.

[0050] In the wound core of the present invention, the radius of curvature r of each bent portion 5 of each directional electromagnetic steel plate 1 stacked in the thickness direction can vary to a certain extent. This variation is sometimes due to variations caused by forming accuracy, and can also be considered due to unexpected variations caused by processing during stacking, etc. In current conventional industrial manufacturing, such unexpected errors can be suppressed to about 0.2 mm or less. In the case of such large variations, the radius of curvature can be measured on a sufficient number of steel plates and averaged to obtain a representative value. In addition, it is also possible to intentionally change it for some reason, and the present invention does not exclude this method. The radius of curvature r of the bent portion 5 (the radius of curvature of the inner surface of the bent portion 5 when viewed from the side) is preferably 1 mm or more and 5 mm or less. By setting the radius of curvature r to 1 mm or more and 5 mm or less, the process factor (BF) can be further suppressed.

[0051] Furthermore, there are no particular limitations on the method for measuring the radius of curvature r of the bend 5. For example, it can be measured by observing it at 200x magnification using a commercially available microscope (Nikon ECLIPSE LV150). Specifically, the curvature center point A is determined based on the observation results. For example, if the intersection point obtained by extending line segment EF and line segment DG inwards to the opposite side of point B is defined as A, then the radius of curvature r is equivalent to the length of line segment AC. Here, when connecting point A and point B with a straight line, the intersection point on the arc DE on the inner side of the bend of the steel plate is set as C.

[0052] Figure 4 as well as Figure 5 This is a schematic diagram illustrating an example of a single layer of directional electromagnetic steel sheet 1 wound into a core body. Figure 4 as well as Figure 5 The directional electromagnetic steel plate 1 used in the example is a steel plate that has been bent to realize a single-core wound iron core. It has two or more bent portions 5 and a flat portion 4. It forms a ring that is roughly polygonal when viewed from the side through the end face of one or more directional electromagnetic steel plates 1 in the longitudinal direction, i.e., the joint portion 6 (gap).

[0053] In this embodiment, the wound core body 10 only needs to have a generally polygonal layered structure when viewed from the side. It can be as follows: Figure 4 As shown in the example, a directional electromagnet sheet is formed by a joint 6 to constitute one layer of the wound core body (each roll is connected by one joint 6 to form a directional electromagnet sheet), or as... Figure 5 As shown in the example, one directional electromagnet 1 constitutes about half a turn of the wound core, and two directional electromagnets 1 constitute one layer of the wound core body via two joints 6 (each roll connects two directional electromagnets 1 to each other via two joints 6).

[0054] The thickness of the directional electromagnetic steel plate 1 used in this embodiment is not particularly limited, and can be appropriately selected according to the application, but it is usually in the range of 0.15mm to 0.35mm, preferably in the range of 0.18mm to 0.27mm.

[0055] Furthermore, there are no particular limitations on the method for manufacturing directional electromagnetic steel sheets, and conventionally known methods for manufacturing directional electromagnetic steel sheets can be appropriately selected. As a preferred specific example of the manufacturing method, the following method can be cited: After hot rolling a slab with a C content of 0.04 to 0.1% by mass and other chemical compositions as described above for directional electromagnetic steel sheets, the slab is heated to 1000°C or higher and then annealed as needed. Next, a cold-rolled steel sheet is formed by cold rolling once or twice or more, with intermediate annealing. This cold-rolled steel sheet is then decarburized and annealed, for example, in a wet hydrogen-inactive gas environment to 700 to 900°C. Further nitriding annealing is performed as needed. After applying an annealing separating agent, a final annealing is performed at approximately 1000°C, and an insulating film is formed at approximately 900°C. Furthermore, coating for adjusting the coefficient of kinetic friction can then be performed.

[0056] Furthermore, the effects of the present invention can be achieved even in steel plates that have undergone a process known as "magnetic domain control" using strain, grooves, etc., during the steel plate manufacturing process.

[0057] Furthermore, in this embodiment, the wound core composed of directional electromagnetic steel plates 1 having the above-described manner is formed by stacking individually bent directional electromagnetic steel plates 1 into layers and assembling them into a wound shape. In each roll, multiple directional electromagnetic steel plates 1 are interconnected via at least one joint 6, and the cross-section of the bent portion 5 of the stacked directional electromagnetic steel plates 1 along the thickness direction (Z-axis direction in the figure), i.e., the L-section along the length direction (to match the thickness direction of the directional electromagnetic steel plate 1), is... Figure 6 A plane parallel to the plane cuts through the plane. Figure 6 The average Vickers hardness of the cross-section of the directional electromagnetic steel plate 1 (enclosed by points D, E, F, and G) is 190-250 HV. The deviation in Vickers hardness is small among the bent portions 5 of the directional electromagnetic steel plates 1. Therefore, when measuring the average Vickers hardness, any one of the directional electromagnetic steel plates can be selected for measurement, or for example, three directional electromagnetic steel plates can be selected for measurement to obtain the average value of these measurements. Furthermore, the deviation in the bent portions 5 of the directional electromagnetic steel plates is also small, so any bent portion 5 can be selected and its average value taken as the average Vickers hardness, or the average value of multiple bent portions 5 can be obtained. The Vickers hardness was measured according to JIS Z 2244 (2009). The measurement load was 25 gf.

[0058] Furthermore, the average Vickers hardness of the flat portion 4 and the average Vickers hardness of the curved portion 5 are preferably 200 HV to 225 HV. Regarding the average Vickers hardness of the flat portion 4, in the Vickers hardness measurement of the curved portion 5 described above, "curved portion" is replaced with "flat portion".

[0059] The absolute value of the difference between the average Vickers hardness of the flat portion 4 and the average Vickers hardness of the bent portion 5 is preferably 50 HV or less. More preferably, the absolute value of the difference between the average Vickers hardness of the flat portion 4 and the average Vickers hardness of the bent portion 5 is 40 HV or less. If the absolute value of the difference between the average Vickers hardness of the flat portion 4 and the average Vickers hardness of the bent portion 5 is 50 HV or less, the process factor (BF) can be further suppressed.

[0060] To achieve an average Vickers hardness of 190-250 HV in the bent portion 5 after bending, in this embodiment, during the bending of the steel sheet using a bending tool (punch), both the tensile stress during steel sheet processing and the coefficient of kinetic friction between the steel sheet 1 and the bending tool are controlled within specified ranges. Specifically, in this embodiment, regarding the bending of any bent portion 5 formed from any one or more of the stacked directional electromagnetic steel sheets 1, the bending process is controlled so that the tensile stress during steel sheet processing is in the range of 0.8 MPa to 6.8 MPa, and the coefficient of kinetic friction between the directional electromagnetic steel sheet 1 and the bending tool is in the range of 0.10 to 0.74. More preferably, the tensile stress is 2.2 MPa to 4.3 MPa. More preferably, the coefficient of kinetic friction is 0.3 to 0.44. Hereinafter, the apparatus for achieving this bending process will be briefly described. In addition, regarding the coefficient of dynamic friction, two samples, a plate and a steel plate, made of the same material roughness as the surface of the punch, are brought into contact and left to stand. A counterweight is placed on the sample to serve as the test load. A rope is attached to the upper sample and it is allowed to slide. The resistance (friction) generated at this time is measured by a load sensor.

[0061] A bending process in which a tensile stress ranging from 0.8 MPa to 6.8 MPa is applied to the end face (section C) perpendicular to the length direction of the steel plate to be bent, along the entire length direction L. This bending process is achieved, for example, by using a... Figure 7 The bending process is performed by the bending processing section 71 of the device (bending tool) 50 shown. Figure 7The device 50 shown includes: a steel plate pressing part 52, which presses and fixes one side portion 1a of the directional electromagnetic steel plate 1, for example, in a clamping state; and a bending mechanism 54, which holds the other side end 1b of the directional electromagnetic steel plate 1 that is being bent, and applies tensile stress to the end face of the other side end 1b in the length direction L while bending it in a direction Z orthogonal to the length direction L and the width direction C. Specifically, the bending mechanism 54 includes: a holding portion 62, which clamps and holds the other end 1b of the directional electromagnetic steel plate 1 from a direction Z orthogonal to the length direction L and the width direction C; a tensile stress applying portion 63, which is provided on one side of the holding portion 62 in the length direction L and applies a tensile stress of 0.8 MPa to 6.8 MPa to the other end 1b of the directional electromagnetic steel plate 1 held by the holding portion 62 in the length direction L; and a bending portion forming portion 59, which forms a bending portion 5 by pressing the holding portion 62 down along the Z direction, thereby bending the other end 1b of the directional electromagnetic steel plate 1 held by the holding portion 62 at a processing speed of 20 mm / sec to 80 mm / sec. By appropriately controlling the coefficient of dynamic friction and the tensile stress and setting the processing speed to 20 mm / sec to 80 mm / sec, the absolute value of the difference between the Vickers hardness of the flat portion 4 and the Vickers hardness of the bending portion 5 can be made to be 50 HV or less. The tensile stress application section 63 can control the tensile stress using a load cell 56 with a spring 55, and the load can be set using a handle 57. Furthermore, the bending section forming section 59 includes a servo motor 58, a pump 60 driven by the servo motor 58, and a lifting section 61 connected to the upper end of the holding section 62. By using the pressure generated by the pump 60 to raise and lower the lifting section 61, the holding section 62 can be moved along the Z direction.

[0062] Furthermore, in bending processes using this device 50, to ensure that the coefficient of dynamic friction between the steel plate 1 and the device 50 (bending tool) is in the range of 0.10 to 0.74, for example, the surface roughness of the upper die 52a and the lower die 52b, which constitute the steel plate pressing part 52 and clamp the directional electromagnetic steel plate 1 from above and below, can be set to make the coefficient of dynamic friction in the range of 0.10 to 0.74. Alternatively, a layer formed of oil or the like can be adhered to the surfaces of the upper die 52a and the lower die 52b (changing the thickness of the oil film) to make the coefficient of dynamic friction in the range of 0.10 to 0.74. Additionally, the coefficient of dynamic friction between the directional electromagnetic steel plate 1 and the bending tool is typically 0.03 or less.

[0063] Next, refer to Figure 8 This describes an example of measuring the Vickers hardness in the L-section of the bent portion 5 of the directional electromagnetic steel plate 1 obtained using the device 50 described above.

[0064] In the determination of Vickers hardness of the bent portion 5 of the directional electromagnetic steel plate 1, such as Figure 8 As shown in (a), Vickers hardness is measured at 10 arbitrary points in the cross-section along the thickness direction of the directional electromagnetic steel plate 1, i.e., along the length direction L as illustrated in the diagram. Specifically, during the measurement, 10 approximately square indentations (hardness evaluation points; arbitrary points) 90 are formed along the length direction of the bend 5, into which a rigid indenter is pressed into the cross-section of the directional electromagnetic steel plate 1, and the hardness is measured. Figure 8 The lengths D1 and D2 of the two diagonals of the approximately square indentation 90 shown in (b) are averaged as the length D of the diagonal of the indentation 90. The Vickers hardness of the indentation 90 is calculated based on this diagonal length D using a known method. For example, in this embodiment, a Mitutoyo HM-221 is used as a hardness evaluation device to measure the Vickers hardness. Here, it is preferable that the load of the indenter, i.e., the test force, is set to 25 gf, and the position of the indentation 90, which serves as the hardness evaluation point, is a predetermined distance away from the steel plate surface in the thickness direction of the steel plate (at least 2.5D away from the steel plate surface inward). Furthermore, the position of the indentation 90 is more preferably at the center in the thickness direction of the steel plate. In addition, each indentation 90 is preferably separated from each other by a predetermined distance (at least 2.5D) along the length direction of the steel plate. Furthermore, in this embodiment, the average Vickers hardness of these 10 indentations 90 needs to be 190-250 HV.

[0065] In addition, in the evaluation of the diagonal lengths D1 and D2, which were analyzed using a Mitutoyo HM-221 analyzer after drawing 10 indentations at 90°, such as... Figure 8 As shown in (c), the indentation 90 is connected to the inside of the evaluation line 92. That is, unlike... Figure 8 As shown in (d), a portion of the indentation 90 is exposed outside the evaluation line 92, or not as shown in (d). Figure 8 As shown in (e), the indentation 90 transitions inward from the evaluation line 92.

[0066] Here, the method for preparing a sample for measuring the cross-section of the bent portion 5 will be described using the wound iron core 10 of this embodiment as an example.

[0067] From near the corner 3 of the directional electromagnetic steel plate 1 that constitutes the wound iron core 10 ( Figure 2The sample for measuring the cross-section of the bent portion 5 is collected in area A. A shearing machine is used to collect a sample including the bent portion 5 from area A. At this time, the gap from the shearing blade is set to approximately 0.1–2 mm, and shearing is performed so that the shearing surface does not cut across the bent portion 5. Furthermore, it is difficult to cut the overlapping bent workpiece, i.e., the directional electromagnetic steel plate 1, in one go; therefore, it is cut one sheet at a time. Next, with the parts after each sheet cut overlapping, epoxy resin is embedded on one side of the plate width, and the embedded surface is ground. During grinding, the SiC polishing paper is changed from #80 (JIS R 6010 grit) to #220, #600, #1000, and #1500, and then ground with 6μm, 3μm, and 1μm diamond polishing and finished to a mirror surface. Finally, to cause tissue corrosion, the tissue was immersed in a solution obtained by adding 2-3 drops of picric acid and hydrochloric acid to 3% nitric acid ethanol for less than 20 seconds to cause tissue corrosion, thereby serving as a sample for measuring the cross-section of the curved section 5.

[0068] In addition, Figure 9 The diagram below provides a schematic representation of an apparatus capable of manufacturing a wound iron core that involves bending steel plates as described above. Figure 9 A manufacturing apparatus 70 for a single-core wound iron core is shown in summary. The manufacturing apparatus 70 includes a bending processing section 71 for bending directional electromagnetic steel plates 1 individually. In addition, it may also include an assembly section 72 for forming a wound iron core by stacking the bent directional electromagnetic steel plates 1 into layers and assembling them into a wound shape. This forms a wound iron core with a wound shape that includes a portion of directional electromagnetic steel plates 1 stacked in the thickness direction, where the planar portion 4 and the curved portion 5 are continuously stacked in the length direction.

[0069] The directional electromagnetic steel sheet 1 is fed to the bending section 71 at a predetermined conveying speed from the steel sheet supply section 75, which holds the annular strip formed by winding the directional electromagnetic steel sheet 1 into a roll. The directional electromagnetic steel sheet 1 thus supplied is appropriately cut to suitable dimensions in the bending section 71, and is individually bent one sheet at a time, with each few sheets undergoing a bending process. In the directional electromagnetic steel sheet 1 thus obtained, the radius of curvature of the bend 5 generated during the bending process becomes extremely small, and therefore the processing strain applied to the directional electromagnetic steel sheet 1 due to the bending process becomes extremely small. Thus, if it is assumed that the density of processing strain increases and the volume where processing strain has an effect can be reduced, the annealing process can be omitted.

[0070] Furthermore, the bending processing unit 71 includes the aforementioned device 50, which controls the bending process so that the tensile stress during steel plate processing is in the range of 0.8 MPa to 6.8 MPa and the coefficient of dynamic friction between the steel plate 1 and the bending tool is in the range of 0.10 to 0.74, thereby forming any one or more of the stacked directional electromagnetic steel plates 1 with arbitrary bending portions 5.

[0071] Next, the following presents data on actual verification of the case where iron loss is suppressed by the wound iron core 10 of this embodiment with the above configuration.

[0072] In obtaining actual verification data, the inventors used various steel plates as raw materials to manufacture products having the properties shown in Table 1 and... Figure 10 Iron cores a to f with the shapes shown.

[0073] Additionally, L1 is the distance between the innermost parallel directional electromagnetic steel plates 1 of the wound core in a plane section parallel to the X-axis and including the center CL (distance between planar portions on the inner surface side). L2 is the distance between the innermost parallel directional electromagnetic steel plates 1 of the wound core in a longitudinal section parallel to the Z-axis and including the center CL (distance between planar portions on the inner surface side). L3 is the stacking thickness of the wound core in a plane section parallel to the X-axis and including the center CL (thickness in the stacking direction). L4 is the width of the stacked steel plates of the wound core in a plane section parallel to the X-axis and including the center CL. L5 is the distance between the innermost adjacent planar portions of the wound core, arranged at right angles (distance between curved portions). In other words, L5 is the length of the shortest planar portion 4a among the planar portions 4 and 4a of the innermost circumference directional electromagnetic steel plates in the length direction. R is the radius of curvature of the curved portion 5 on the innermost circumference side of the wound core. This refers to the bending angle of the bent portion 5 of the wound iron core. The roughly rectangular iron cores No. a to f in Table 1 are constructed by dividing the inner surface side planar portions at approximately the center of a distance L1, and then joining two iron cores with a roughly "U" shape. The radius of curvature of iron core e increases towards the outer edge. Otherwise, the inner and outer radii of curvature of the cores are the same. Furthermore, the bending angle of iron core e is 90 degrees.

[0074] Here, the core of core No. e is a so-called box-type wound core, which has always been used as a general wound core. It is manufactured by stamping a generally rectangular shape after shearing a steel sheet, winding it into a cylindrical shape, and maintaining the cylindrical stacked state. Therefore, the radius of curvature of the bent portion 5 of the wound core of core No. e varies considerably depending on the stacking position of the steel sheet. Regarding the core of core No. e, in Table 1, * indicates that r increases with the direction of outward, with r = 5 mm at the innermost circumference and r = 60 mm at the outermost circumference. Furthermore, the core of core No. c is a single-core wound core with a larger radius of curvature r than the cores of cores No. a, b, d, and f (single-core wound cores) (radius of curvature r exceeds 5 mm), and the core of core No. d is a single-core wound core with three bent portions 5 at one corner 3.

[0075] Table 1

[0076]

[0077] Tables 2 through 10 show the various magnetic core shapes described above, for which target bending angles have been set. The Vickers hardness (HV) of the bent portion 5 was obtained by measuring 204 examples of raw materials, including the steel plate thickness (mm), the tensile stress (MPa) applied along the length L of the steel plate 1, and the coefficient of dynamic friction between the steel plate 1 and the bending tool (the dies 52a and 52b of the device 50). Furthermore, the process factor (BF) was evaluated based on the iron loss of the core (W / kg) and the iron loss of the steel plate (W / kg). Additionally, the Vickers hardness was measured at the center of the plate thickness direction, with each indentation spaced equidistantly from each other along the length of the steel plate by a specified distance (2.5D). The load was 25 gf. The Vickers hardness of the core e was determined by measuring the Vickers hardness of each bent portion 5 collected from the outermost and innermost circumferences of the core e, and obtaining their average value. Similarly, regarding the Vickers hardness of the planar portion of the iron core e, the Vickers hardness is measured on the planar portion sampled from the outermost and innermost circumferences, just as it is on the curved portion, and the average value is obtained. The absolute value of the difference between the Vickers hardness of the curved portion and the planar portion is calculated based on the difference between the average Vickers hardness of the curved portion and the average Vickers hardness of the planar portion.

[0078] In the determination of the process coefficient, for the wound iron cores No. a to No. f in Table 1, the excitation current method as described in JIS C 2550-1 was used under the conditions of a frequency of 50 Hz and a magnetic flux density of 1.7 T to determine the iron loss value (core iron loss) W of the wound iron core. A. Further, a specimen with a width of 100 mm × a length of 500 mm is collected from a strip (sheet width of 152.4 mm) of a grain-oriented electrical steel sheet used for an iron core, and the specimen is measured under the conditions of a frequency of 50 Hz and a magnetic flux density of 1.7 T through a single-sheet magnetic property test of the electrical steel sheet using the H-coil method described in JIS C 2556, so that the iron loss value of the raw material steel sheet (iron loss of the steel sheet) W B . Then, by dividing the iron loss value W A by the iron loss value W B , a process factor (BF) is obtained. A case where BF is 1.15 or higher is defined as evaluation D. A case where BF is 1.13 or higher and less than 1.15 is defined as evaluation C. A case where BF is 1.05 or higher and less than 1.13 is defined as evaluation B. A case where BF is less than 1.05 is defined as evaluation A. A case of evaluation A or evaluation B is defined as acceptable.

[0079] Table 2

[0080]

[0081] Table 3

[0082]

[0083] Table 4

[0084]

[0085] Table 5

[0086]

[0087] Table 6

[0088]

[0089] Table 7

[0090]

[0091] Table 8

[0092]

[0093] Table 9

[0094]

[0095] Table 10

[0096]

[0097] As can be seen from Tables 2 to 10, for the cores No. a, b, d, and f that are single-core magnetic cores with a small radius of curvature r (less than 5 mm) in the bending section 5, regardless of their plate thickness, as long as the average Vickers hardness of any 10 points in the L section of the steel plate 1 is 190-250 HV, that is, by setting the tensile stress applied to the steel plate during steel plate processing to 0.8 MPa or more and 6.8 MPa or less, and setting the coefficient of dynamic friction between the steel plate and the punches 52a and 52b (bending tools) to 0.10 or more and 0.74 or less, the process factor (BF) can be suppressed to less than 1.13 (which can suppress the iron loss of the wound core). On the other hand, in the case of a single-core magnetic core No. c with a curvature radius of 6 mm in the bent portion and a box-type magnetic core No. e, even if the tensile stress applied to the steel plate during steel plate processing is set to 0.8 MPa or more and 6.8 MPa or less, and the coefficient of dynamic friction between the steel plate and the punches 52a and 52b (bending tools) is set to 0.10 or more and 0.74 or less, the average Vickers hardness in the L section of the steel plate 1 does not converge within the range of 190-250 HV, and the process factor (BF) cannot be sufficiently suppressed.

[0098] Based on the above results, it is clear that the wound iron core of the present invention, including this embodiment, is a single core, and the average Vickers hardness of any 10 points in the L section of the directional electromagnetic steel plate 1 is 190-250 HV, thereby reducing the iron loss degradation.

[0099] (Postscript)

[0100] The wound iron core, the method for manufacturing the wound iron core, and the apparatus for manufacturing the wound iron core according to the above embodiments can be mastered as follows.

[0101] The wound core of the present invention is a wound shape comprising a rectangular hollow portion at the center, and a portion of directional electromagnetic steel sheets, which are continuously stacked in the thickness direction and alternately have planar portions and curved portions in the length direction. It is formed by stacking individually bent directional electromagnetic steel sheets into layers and assembling them into a wound shape. In each roll, multiple directional electromagnetic steel sheets are interconnected via at least one joint. The wound core is characterized in that…

[0102] The average Vickers hardness of any 10 points in any one or more of the stacked directional electromagnetic steel plates, along the thickness direction of the directional electromagnetic steel plate (i.e., along the length direction L section), is 190-250 HV.

[0103] The method for manufacturing the wound core of the present invention comprises a wound shape having a rectangular hollow portion at the center, including a portion of directional electromagnetic steel plates that are continuously stacked in the thickness direction with alternating planar portions and curved portions in the length direction. The wound core is formed by stacking individually bent directional electromagnetic steel plates into layers and assembling them into a wound shape. In each roll, multiple directional electromagnetic steel plates are interconnected via at least one joint. The method for manufacturing this wound core is characterized by...

[0104] By applying a tensile stress of 0.8 MPa to 6.8 MPa to the directional electromagnetic steel sheet along its length direction while bending the directional electromagnetic steel sheet, and / or by setting the coefficient of friction between the bending tool used to bend the directional electromagnetic steel sheet and the directional electromagnetic steel sheet to 0.10 to 0.74, any of the aforementioned bent portions of any one or more of the stacked directional electromagnetic steel sheets are formed.

[0105] The winding core manufacturing apparatus of the present invention is characterized by comprising: a bending processing section for individually bending directional electromagnetic steel sheets; and an assembly section for stacking and assembling the directional electromagnetic steel sheets individually bent by the bending processing section into a winding shape, thereby forming a winding core with a rectangular hollow portion at the center. In each roll, multiple directional electromagnetic steel sheets are interconnected via at least one joint, and the directional electromagnetic steel sheets, which alternately consist of planar portions and curved portions in the length direction, are continuous in the thickness direction. In the overlapping portion, the bending processing unit applies a tensile stress of 0.8 MPa to 6.8 MPa to the directional electromagnetic steel sheet in the length direction while bending the directional electromagnetic steel sheet, and / or sets the coefficient of friction between the bending tool for bending the directional electromagnetic steel sheet and the directional electromagnetic steel sheet to 0.10 to 0.74 to bend the directional electromagnetic steel sheet, thereby forming any of the bent portions of any one or more of the stacked directional electromagnetic steel sheets.

[0106] Explanation of symbols

[0107] 1: Directional electromagnetic steel plate; 4: Flat part; 5: Bending part; 6: Joint part; 10: Winded iron core (winded iron core body).

Claims

1. A wound iron core having a rectangular hollow portion at its center, comprising a wound shape of directional electromagnetic steel sheets, with alternating planar and curved portions along its length, stacked in the thickness direction, formed by stacking individually bent directional electromagnetic steel sheets into layers and assembling them into a wound shape, wherein multiple directional electromagnetic steel sheets are interconnected in each roll via at least one joint, characterized in that... The curved portion of the stacked directional electromagnetic steel sheet has an average Vickers hardness of 190-250 HV in a cross section along the thickness direction and in the L-section along the length direction of the directional electromagnetic steel sheet.

2. A method for manufacturing a wound iron core, the wound iron core having a rectangular hollow portion at its center, comprising a portion of directional electromagnetic steel sheets, which are continuously stacked in the thickness direction with alternating planar portions and curved portions in the length direction, and formed by stacking individually bent directional electromagnetic steel sheets into layers and assembling them into a wound shape, wherein multiple directional electromagnetic steel sheets are interconnected in each roll via at least one joint, characterized in that... The directional electromagnetic steel sheet is bent while being subjected to a tensile stress ranging from 0.8 MPa to 6.8 MPa along its length. The directional electromagnetic steel sheet is bent by setting the coefficient of dynamic friction between the bending tool and the directional electromagnetic steel sheet to be between 0.10 and 0.

74. This forms the aforementioned curved portion of the stacked directional electromagnetic steel sheets.

3. A winding iron core manufacturing apparatus, characterized in that, have: The bending processing department separately bends the directional electromagnetic steel sheet; and The assembly section stacks the directional electromagnetic steel sheets, which have been individually bent by the bending section, into layers and assembles them into a coiled shape, thereby forming a coiled iron core with a rectangular hollow portion at the center. In each coil, multiple directional electromagnetic steel sheets are interconnected via at least one joint, and the coiled iron core includes portions in the thickness direction where planar portions and curved portions alternately and continuously. The bending process described above involves applying a tensile stress of 0.8 MPa to 6.8 MPa to the directional electromagnetic steel sheet along its length direction while bending the sheet. The coefficient of dynamic friction between the bending tool and the directional electromagnetic steel sheet is set to 0.10 to 0.74, thereby forming the bent portion of the stacked directional electromagnetic steel sheet.

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