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

Abstract

The wound core (10) includes a portion in which the direction electromagnetic steel sheets (1) in which the flat portions (4) and the bent portions (5) are alternately continuous in the long side direction are stacked in the sheet thickness direction, is formed by stacking the direction electromagnetic steel sheets (1) individually bent processed into layers and assembled into a wound shape, and when an average height of a roughness curve element in a width direction intersecting the long side direction of a surface forming the bent portion (5) of the direction electromagnetic steel sheet (1) is Ra(b), and an average height of a roughness curve element in the width direction of a surface forming the flat portion (4) of the direction electromagnetic steel sheet (1) is Ra(s), a relation of 1.00 < Ra(b) / Ra(s) ≤ 5.00 is satisfied.

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 claims priority based on Japanese Patent Application No. 2020-178561, filed on October 26, 2020, the contents of which are incorporated herein by reference. Background Technology

[0002] Transformer cores can be laminated or wound. Wound cores are generally manufactured as follows: directional electromagnetic steel sheets are laminated and wound into a ring (wound shape), 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). This forming process causes mechanical strain (plastic deformation strain) on the directional electromagnetic steel sheets as a whole. This strain 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 at 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 stamping 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), so the strain removal based on the above-mentioned annealing process can also be omitted. It has significant 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, in the manufacture of a single core, although the range affected by the plastic deformation strain (processing strain) introduced along with bending in the steel plate is limited, with bending (introduction of plastic strain), the surface shape of the bent portion also becomes roughened with undulating changes and the like, and as a result, it is undeniable that the frictional force between the overlapping steel plates becomes larger, and the noise associated with the vibration during excitation becomes larger (the noise characteristics deteriorate significantly).

[0011] The present invention has been made in view of the above circumstances, and an object thereof is to provide a wound core, a method for manufacturing a wound core, and a wound core manufacturing apparatus that can reduce the noise caused by the plastic deformation strain introduced along with bending in the steel plate.

[0012] Means for solving the problem

[0013] To achieve the above object, the present invention is a wound core including a portion where directionality electromagnetic steel plates having flat portions and bent portions alternately continuous in the long side direction are laminated in the plate thickness direction, and is formed by laminating the directionality electromagnetic steel plates that have been individually bent and processed into a layered structure and assembling them into a wound shape. The wound core is characterized in that when the average height of the roughness curve elements in the width direction intersecting the long side direction of the surface of the bent portion of the directionality electromagnetic steel plate is set as Ra(b), and the average height of the roughness curve elements in the width direction of the surface of the flat portion of the directionality electromagnetic steel plate is set as Ra(s), the relationship 1.00 < Ra(b) / Ra(s) ≤ 5.00 is satisfied.

[0014] The wound core of the present invention having the above structure is formed by laminating the individually bent and processed directionality electromagnetic steel plates into a layered structure and assembling them into a wound shape (a so-called single core that can omit stress relief annealing). By applying a tensile stress in the long side (rolling) direction (L direction) to the entire end surface (C cross-section) of the steel plate to be bent and performing bending processing simultaneously, when the average height of the roughness curve elements in the width direction intersecting the long side direction of the surface (profile) of the bent portion of the directionality electromagnetic steel plate is set as Ra(b), and the average height of the roughness curve elements in the width direction of the surface (profile) of the flat portion of the directionality electromagnetic steel plate is set as Ra(s), the relationship 1.00 < Ra(b) / Ra(s) ≤ 5.00 is satisfied. Here, the surface of the bent portion and the surface of the flat portion refer to the outer surfaces facing the outside of the wound core (the outer surfaces of the bent portion and the flat portion). Ra(b) and Ra(s) are the average height Rc of the roughness curve elements defined by Japanese Industrial Standard JIS B 0601 (2013).

[0015] As described above, in the manufacture of a single core, due to the plastic strain introduced by bending in the directionality electromagnetic steel sheet, the frictional force between the mutually laminated steel sheets becomes large, and thus there is a problem that the noise accompanying the vibration during excitation becomes large. Therefore, the inventors of the present application focused on the fact that if a tensile stress is applied in the longitudinal direction (rolling direction) while bending the directionality electromagnetic steel sheet, the roughness on the outside of the bending region (bending portion) of the directionality electromagnetic steel sheet decreases (smoothing), and obtained the following recognition: When bending the steel sheet, a tensile stress is applied to the steel sheet in the longitudinal direction while bending, so that the relationship of 1.00 < Ra(b) / Ra(s) ≤ 5.00 is satisfied (or, the average height Ra of the roughness curve elements on the inner and outer sides of the above-mentioned bending region of the directionality electromagnetic steel sheet is controlled). As a result, the noise caused by the plastic deformation strain is reduced. This is considered because, by applying a tensile force in the longitudinal direction while bending the directionality electromagnetic steel sheet, the proportion of the plastic strain brought by the tensile force in the deformation strain introduced into the bending region becomes large (the ratio of the compressive strain relative to the tensile strain becomes small), and the average height (Ra(b)) of the roughness curve elements on the outside of the bending region of the directionality electromagnetic steel sheet decreases (smoothing), so that the frictional force between the steel sheets laminated in a laminated state becomes small, and the noise accompanying the vibration during excitation (especially in the bending region) decreases.

[0016] In addition, the average height of the roughness curve elements is determined according to Japanese Industrial Standard JIS B 0601 (2013). Further, in the above structure, the radius of curvature of the bending portion of the directionality electromagnetic steel sheet is preferably 1 mm or more and 5 mm or less. Here, the radius of curvature of the bending portion refers to the inner surface side radius of curvature in the side view of the bending portion.

[0017] Furthermore, the present invention also provides a method for manufacturing a wound core, including: a bending process of bending the directionality electromagnetic steel sheet alone; and an assembling process of laminating the bent directionality electromagnetic steel sheets in a layered manner and assembling them into a wound shape, thereby forming a wound core having a wound shape including a portion where the directionality electromagnetic steel sheets in which the flat portions and the bending portions are alternately continuous in the long side direction are laminated in the plate thickness direction; in the bending process, a tensile stress in the range of 4 MPa or more and 16 MPa or less is applied to the directionality electromagnetic steel sheet in the long side direction while bending the above-mentioned directionality electromagnetic steel sheet.

[0018] In addition, the present invention also provides a winding core manufacturing device, which includes: a bending processing unit that individually bends a directional electromagnetic steel sheet; and an assembling unit that stacks the bent directional electromagnetic steel sheets in layers and assembles them into a wound shape, thereby forming a wound core having a wound shape including a portion where the directional electromagnetic steel sheets in which flat portions and bent portions are alternately continuous in the long side direction are stacked in the plate thickness direction; the bending processing unit applies a tensile stress within a range of 4 MPa or more and 16 MPa or less to the directional electromagnetic steel sheet in the long side direction, and at the same time bends the directional electromagnetic steel sheet.

[0019] In the manufacturing method and manufacturing device having the above structure, when individually bending each directional electromagnetic steel sheet, a tensile stress within a range of 4 MPa or more and 16 MPa or less is applied to the directional electromagnetic steel sheet in the long side direction (rolling direction) of the steel sheet, and at the same time the directional electromagnetic steel sheet is bent. By applying a tensile stress under such conditions while bending the steel sheet, as a result, the relationship of 1.00 < Ra(b) / Ra(s) ≤ 5.00 is satisfied, and the same effect as that of the above-mentioned wound core can be obtained. That is, due to the influence of the tensile stress applied in the long side direction, after bending processing, the average height (Ra(b)) of the roughness curve elements on the outer side of the bent area of the directional electromagnetic steel sheet decreases (smoothens), whereby the frictional force between the steel sheets overlapping each other in the stacked state becomes smaller, and the noise accompanying the vibration during excitation (especially in the bent area) decreases (the noise characteristics are improved). In addition, in the manufacturing method and manufacturing device having the above structure, preferably, during the bending processing, a tensile stress within a range of 4 MPa or more and 16 MPa or less is applied to the directional electromagnetic steel sheet in the longer direction, and at the same time the directional electromagnetic steel sheet is bent at a strain rate of 5 mm / second or more and 100 mm / second or less. In addition, preferably, during the bending processing, the directional electromagnetic steel sheet is bent such that the radius of curvature of the bent portion of the directional electromagnetic steel sheet becomes 1 mm or more and 5 mm or less.

[0020] Advantages of the Invention

[0021] According to the present invention, since a tensile force is applied to the directional electromagnetic steel sheet in the longer direction while performing bending processing, the relationship of 1.00 < Ra(b) / Ra(s) ≤ 5.00 is satisfied, so after bending processing, the roughness on the outer side of the bent area (bent portion) of the directional electromagnetic steel sheet decreases. Thereby, the frictional force between the steel sheets overlapping each other in the stacked state becomes smaller, and the noise accompanying the vibration during excitation decreases. Description of the Drawings

[0022] Figure 1 It is a perspective view schematically showing a wound core according to an embodiment of the present invention.

[0023] Figure 2 yes Figure 1 The side view of the wound iron core shown in the embodiment.

[0024] Figure 3 This is a side view schematically illustrating another embodiment of the present invention of a wound iron core.

[0025] 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.

[0026] 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.

[0027] Figure 6 This is a side view schematically showing an example of the curved portion of the directional electromagnetic steel plate constituting the wound core of the present invention.

[0028] Figure 7 This is a diagram illustrating an example of a method for measuring the average height Ra(b) of the roughness curve elements in the width direction of the surface forming the curved portion and the average height Ra(s) of the roughness curve elements in the width direction of the surface forming the flat portion.

[0029] Figure 8 This is a schematic perspective view of an example of a device used to perform a bending process, which applies tensile stress to the portion of the steel plate to be bent in the long direction while bending the steel plate.

[0030] Figure 9 This is a block diagram that schematically represents the structure of a manufacturing apparatus for a wound iron core, which is a single core comprising a directional electromagnetic steel plate with elastic deformation in a planar portion.

[0031] Figure 10 This is a schematic diagram showing the dimensions of the wound iron core manufactured during the performance evaluation. Detailed Implementation

[0032] 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 within the range. 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 %".

[0033] 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.

[0034] 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".

[0035] One embodiment of the present invention provides a wound core comprising a generally rectangular core body in side view. This core body has a stacked structure comprising alternating planar and curved portions of directional electromagnetic steel sheets stacked in the thickness direction, and is generally polygonal in side view. The inner surface radius of curvature r of the curved portions in side view is, for example, 1.0 mm to 5.0 mm. As an example, the directional electromagnetic steel sheets have a chemical composition containing 2.0 to 7.0% Si by mass, with the remainder consisting of Fe and impurities, and have an aggregate structure oriented according to the Goss orientation. For example, directional electromagnetic steel strips as described in JIS C2553:2019 can be used as the directional electromagnetic steel sheets.

[0036] 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, but are based on known shapes of wound cores and directional electromagnetic steel plates.

[0037] 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.

[0038] Furthermore, in this invention, side view refers to the view along the width of the elongated directional electromagnetic steel plate constituting the wound 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).

[0039] 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.

[0040] 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.

[0041] This type of wound iron core can be used well for any previously known application.

[0042] The core of this embodiment is characterized by being approximately polygonal in side view. In the following description using the accompanying drawings, for the sake of simplicity, a generally rectangular (quadrilateral) core, which is also of a general shape, will be used. 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.

[0043] like Figure 1 as well as Figure 2 As shown, the wound core body 10 has a generally rectangular stacked structure 2, which includes a portion of directional electromagnetic steel plates 1 stacked continuously in the thickness direction, with alternating planar portions 4 and curved portions 5 along the long side. The stacked structure 2 has 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. The sum of the curvature angles of the curved portions 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 has a shape with 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°.

[0044] As these examples illustrate, the wound core of this embodiment can be constructed from bends with various angles. However, from the viewpoint of suppressing strain caused by deformation during processing and thus suppressing iron loss, the bending angles φ (φ1, φ2, φ3) of the bends 5 are preferably 60° or less, more preferably 45° or less. The bending angles φ of the bends in a single core can be arbitrarily configured. For example, φ1 can be set to 60° and φ2 to 30°. From the viewpoint of production efficiency, it is preferable that the bending angles are equal.

[0045] 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 of the curved portion 5 of the directional electromagnetic steel sheet 1. It is represented as the supplementary angle φ formed by extending two imaginary lines, Lb-elongation 1 and Lb-elongation 2, from the straight sections of the surfaces 4 and 4a on both sides of 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 detaches from the steel sheet surface is the boundary between the flat section 4 and the curved portion 5 on the outer surface side of the steel sheet. Figure 6 Points F and G are in the middle.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] For the wound core 10 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 may vary to some 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 0.3 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 a representative value can be obtained by averaging. Furthermore, it is also possible to intentionally change it for some reason, and the present invention does not exclude this method.

[0050] 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.

[0051] 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 In the example, the directional electromagnetic steel plate 1 used is bent to achieve a single-core wound iron core, and has two or more bent portions 5 and flat portions 4. It forms a ring that is roughly polygonal when viewed from the side through the end face of the long side direction of one or more directional electromagnetic steel plates 1, i.e., the joint portion 6 (gap).

[0052] 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 10 (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 approximately half a circumference 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 via two joints 6).

[0053] The thickness of the grain-oriented electrical steel sheet 1 used in this embodiment is not particularly limited and can be appropriately selected according to the use and the like. Generally, it is in the range of 0.15 mm to 0.35 mm, and preferably in the range of 0.18 mm to 0.23 mm.

[0054] In addition, the method for manufacturing the grain-oriented electrical steel sheet 1 is not particularly limited, and a conventionally known method for manufacturing a grain-oriented electrical steel sheet can be appropriately selected. As a preferred specific example of the manufacturing method, for example, the following method can be cited: After heating a slab having a chemical composition of 0.04 to 0.1% by mass of C and other components of the above-mentioned grain-oriented electrical steel sheet to 1000 °C or higher and performing hot rolling, hot rolling annealing is performed as needed. Then, a cold-rolled steel sheet is formed by one or two or more cold rolling operations with intermediate annealing interposed therebetween. The cold-rolled steel sheet is decarburized annealed by heating it to 700 to 900 °C in a wet hydrogen-inert gas atmosphere, and nitriding annealing is further performed as needed. Based on the application of an annealing separating agent, final annealing is performed at around 1000 °C, and an insulating film is formed at around 900 °C. And thereafter, painting or the like for adjusting the dynamic friction coefficient can also be performed.

[0055] In addition, even for a steel sheet in which a process called "magnetic domain control" that generally uses strain, grooves, etc. is performed by a known method in the manufacturing process of the steel sheet, the effects of the present invention can be achieved.

[0056] In addition, in this embodiment, the wound core 10 composed of the grain-oriented electrical steel sheet 1 having the above-described configuration is formed by laminating the grain-oriented electrical steel sheets 1 obtained by being individually bent and processed into a layered shape and assembling them into a wound shape. In each roll, a plurality of grain-oriented electrical steel sheets 1 are connected to each other via at least one joint portion 6. When performing the bending process individually, a tensile stress is applied to the entire end face (C cross-section) of the steel sheet to be bent in the longitudinal direction, and bending processing is performed simultaneously. Thus, when the average height of the roughness curve elements in the width direction ( Figure 7 the Y-axis direction) intersecting the longitudinal direction ( Figure 1 the rolling direction L) of the surface (profile) of the bent portion 5 of the grain-oriented electrical steel sheet is Ra(b), and the average height of the roughness curve elements in the width direction of the surface (profile) of the flat portion 4 (4a) of the grain-oriented electrical steel sheet 1 is Ra(s), the relationship of 1.00 < Ra(b) / Ra(s) ≤ 5.00 is satisfied. In addition, in this case, the above-mentioned radius of curvature (the inner surface side radius of curvature in the side view of the bent portion 5) r of the bent portion 5 is preferably 1 mm or more and 5 mm or less. By making the radius of curvature r 1 mm or more and 5 mm or less, the noise associated with vibration during excitation can be further reduced.

[0057] Here, the average height Ra(b) of the roughness curve elements in the width direction of the surface forming the curved portion 5 and the average height Ra(s) of the roughness curve elements in the width direction of the surface forming the flat portion 4 (4a) are, for example, set as the average values ​​obtained by measuring 10 fields of view on the curved portion 5 and the flat portion 4 (4a) respectively using a digital microscope (KEYENCE VHX-7000). Specifically, for example, as Figure 7 As shown by the dashed line in (a), a portion of the directional electromagnet 1 constituting the wound iron core is cut off to obtain... Figure 7 The cut steel plate 1A shown in (b) includes a corner portion 3 and two flat portions 4 on both sides. During cutting, it is desirable to cut the flat portion 4 (4a) in a manner that does not crush the bent portion 5. Next, using the aforementioned digital microscope, the outer surface of the flat portion 4 (4a) and the outer surface (Lb) of the bent portion 5 of the directional electromagnetic steel plate 1 facing outwards from the wound core are measured with respect to the cut steel plate 1A. As the measurement location, it is desirable to measure at the center of the steel plate width, which is farther from the end face of the steel plate 1A (see reference). Figure 7 Measurements are taken at locations P and Q in (b). Here, as shown... Figure 7 As shown in (c), the bent part 5, i.e. Figure 6 The portion of the directional electromagnetic steel plate 1 enclosed by points D, E, F, and G, that is, the plane extending in the width direction C and the long side direction L. Figure 7 The outer surface (Lb) of the portion surrounded by points F, F', G, and G' in section (c) is scanned from above along the width direction C as shown by the dashed arrow using the aforementioned digital microscope, and Ra(b) is measured. Here, if necessary, the curved portion 5 to be measured can be marked beforehand using a marker or similar object. Similarly, regarding the flat portion 4 (4a), the outer surface portion of the flat portion 4 (4a) is scanned from above along the width direction C as shown by the dashed arrow using the aforementioned digital microscope, and Ra(s) is measured. This flat portion 4 (4a) can be taken either separately from the flat portion 4 (4a) of the same iron core or from the remaining strip (hoop) from the iron core manufacturing process. In any case, any steel plate that does not undergo plastic deformation is acceptable. Regarding the measurement field of view, for example, the magnification is set to 200x to allow for... Figure 7The size of one visual field shown in (c) is 500 μm × 500 μm. The average heights Ra(s) and Ra(b) of the roughness curve elements are measured in accordance with JIS B 0601 (2013). When measuring the average height of the roughness curve elements with a digital microscope, vibration correction can also be performed by setting the cutoff value λs = 0 μm and the cutoff value λc = 0 mm. The measurement magnification is preferably 100 times or more, and more preferably 500 times to 700 times. And, for example, such measurements are performed on 10 cut steel plates 1A, and their average values are set as Ra(b) and Ra(s). In addition, Ra(b) is preferably 0.5 μm to 4.0 μm. Ra(b) is more preferably 0.6 to 3.9 μm. Further, Ra(s) is preferably 0.5 μm to 1.0 μm. Ra(s) is more preferably 0.6 μm to 0.8 μm.

[0058] In addition, bending processing is performed to satisfy the relationship of 1.00 < Ra(b) / Ra(s) ≤ 5.00, that is, bending processing in which tensile stress is applied in the long side direction L to the entire end face (C section) of the steel plate to be bent. For example, it is performed by the bending processing unit 71 of the device 50 shown in Figure 8 the device 50 shown. Figure 8 The device 50 shown in has: a steel plate pressing portion 52 that presses and fixes, for example, one side portion 1a of the anisotropic electromagnetic steel plate 1 in a clamped state; and a bending mechanism 54 that bends the other end portion 1b of the anisotropic electromagnetic steel plate 1 to be bent in a direction Z orthogonal to the long side direction L and the width direction C while applying tensile stress to the end face of the other end portion 1b in the long side direction L. Specifically, the bending mechanism 54 has: a holding portion 62 that clamps and holds, for example, the other end portion 1b of the anisotropic electromagnetic steel plate 1 from the direction Z orthogonal to the long side direction L and the width direction C; a tensile stress applying portion 63 that is provided on one side of the holding portion 62 in the long side direction L and applies a tensile stress in the range of 4 MPa or more and 16 MPa or less to the other end portion 1b of the anisotropic electromagnetic steel plate 1 held by the holding portion 62 in the long side direction L; and a bending portion forming portion 59 that bends the other end portion 1b of the anisotropic electromagnetic steel plate 1 held by the holding portion 62, for example, at a strain rate of 5 mm / second or more and 100 mm / second or less by pushing down the holding portion 62 in the Z direction to form a bending portion 5. The tensile stress applying portion 63 can control the tensile stress by using a load gauge 56 with a spring 55, and can set the load by a handle 57. In addition, the bending portion forming portion 59 has a servo motor 58, a pump 60 driven by the servo motor 58, and a lifting portion 61 coupled to the upper end of the holding portion 62, and can move the holding portion 62 in the Z direction by using the pressure generated by the pump 60 to lift and lower the lifting portion 61.

[0059] Figure 9 Roughly showing a manufacturing apparatus 70 for a wound iron core formed in a single-core form, the manufacturing apparatus 70 includes a bending processing section 71 including the above-described apparatus 50 that bends the oriented electromagnetic steel sheet 1 individually, and the bent oriented electromagnetic steel sheet 1 is laminated in layers and assembled into a wound shape, thereby forming a wound iron core including a portion where the oriented electromagnetic steel sheets 1 in which the flat portions 4 and the bent portions 5 are alternately continuous in the long side direction are laminated in the plate thickness direction. In this case, it may also include an assembling section 72 that laminates the bent oriented electromagnetic steel sheets 1 in layers and assembles them into a wound shape.

[0060] The oriented electromagnetic steel sheet 1 is discharged from a steel sheet supply section 90 that holds a strip (hoop) formed by winding the oriented electromagnetic steel sheet 1 into a roll shape at a predetermined conveying speed and supplied to the bending processing section 71. The thus-supplied oriented electromagnetic steel sheet 1 is appropriately cut into a suitable size in the bending processing section 71, and is subjected to a bending process (bending processing step) of being bent individually at a time in such a manner that each time a few sheets are taken. In this bending process, as described above, a tensile stress in the range of 4 MPa or more and 16 MPa or less is applied to the oriented electromagnetic steel sheet 1 in the long side direction L, and at the same time, the oriented electromagnetic steel sheet 1 is bent at a strain rate of, for example, 5 mm / second or more and 100 mm / second or less to form the bent portion 5. By applying a tensile stress in the range of 4 MPa or more and 16 MPa or less to the oriented electromagnetic steel sheet 1, it is possible to satisfy 1.00 < Ra(b) / Ra(s) ≤ 5.00. In addition, in the bending processing step, it is preferable to bend the oriented electromagnetic steel sheet 1 in such a manner that the radius of curvature of the bent portion becomes 1 mm or more and 5 mm or less. The thus-obtained oriented electromagnetic steel sheet 1 has a very small radius of curvature of the bent portion 5 generated by the bending process, so the processing strain applied to the oriented electromagnetic steel sheet 1 by the bending process becomes very small. In this way, it can be considered that the density of the processing strain becomes large. On the other hand, if the volume affected by the processing strain can be reduced, the annealing process can be omitted. In addition, the cut and bent oriented electromagnetic steel sheets 1 are laminated in layers, for example, by an assembling section 72 and assembled into a wound shape, thereby constituting a wound iron core (assembling step).

[0061] Next, the data for actually verifying the case of suppressing iron loss in the wound iron core 10 of the present embodiment with the above-described configuration is shown below.

[0062] When obtaining the actual verification data, the inventors of the present application used each steel sheet as a raw material to manufacture iron cores a to f having the shapes shown in Table 1 and Figure 10 shown.

[0063] 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 the inner surface side planar portions). 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 the inner surface side planar portions). 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 when added together (distance between curved portions). In other words, L5 is the length in the long side direction of the shortest planar portion 4a among the planar portions 4 and 4a of the innermost circumferential directional electromagnetic steel plates. r is the radius of curvature of the bend 5 on the inner surface side of the wound iron core, and φ is the bending angle of the bend 5 on the inner surface side of the wound iron core. The roughly rectangular iron cores No. a to f in Table 1 are structures formed by dividing the planar portions on the inner surface side at a distance of L1 at approximately the center and joining two iron cores with a roughly "コ" shape.

[0064] Here, the core of core No. e is a so-called box-shaped wound core manufactured by the following method: As a conventional wound core, it is formed by cutting and rolling a steel sheet into a cylindrical shape, then stamping it in a cylindrical laminated state so that the corners have a certain curvature to create a roughly rectangular shape. Therefore, the radius of curvature of the bend 5 varies considerably depending on the lamination position of the steel sheet. Regarding the core of core No. e, in Table 1, ※ indicates that r increases with the outer edge, 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 bends 5 at one corner 3.

[0065] [Table 1]

[0066] Table 1

[0067]

[0068] Tables 2 to 5 show the measurements obtained from 85 examples of raw materials with various core shapes as described above, for which target bending angle φ (°), steel plate thickness (mm), and tensile stress (MPa) applied in the long side direction L were set respectively. The measurements included the average value (μm) of Ra(b) at 10 locations (10 field-of-view measurements) for the bent portion 5, the average value (μm) of Ra(s) at 10 locations (10 field-of-view measurements) for the flat portion 4 (4a), and the ratio Ra(b) / Ra(s). Furthermore, core noise (dBA) was measured and evaluated. The 10 measurements referred to, for the bent portion 5, randomly selecting 10 steel plates from the integral wound core, taking one location of each bent portion as one field of view, and measuring Ra(b) and the measured bending angle. The average heights Ra(b) and Ra(s) of the roughness curve elements were measured using a digital microscope (Keyence VHX-7000). The average height Rc of the roughness curve elements was measured based on JIS B 0601 (2013). The critical values ​​were set to λs = 0 and λc = 0, and vibration correction was applied during the measurement. The measurement magnification was set to 500–700 times.

[0069] In the evaluation of core noise, the aforementioned wound core was prepared, energized, and noise measurements were performed. The noise measurement was conducted in an anechoic chamber with a dark noise level of 16 dBA. The noise meter was positioned 0.3 m above the core surface, and the A-characteristic was used as a correction for perceived noise. Furthermore, the excitation frequency was set to 50 Hz, and the magnetic flux density was set to 1.7 T. A core noise level below 44 dBA was considered acceptable.

[0070] [Table 2]

[0071] Table 2

[0072]

[0073] [Table 3]

[0074] Table 3

[0075]

[0076] [Table 4]

[0077] Table 4

[0078]

[0079] [Table 5]

[0080] Table 5

[0081]

[0082] As can be seen from Tables 2 to 5, for the iron cores of core No. a, b, c, d, and f in the single-core form, as long as the steel plate thickness is within the range of 0.15 mm to 0.35 mm, regardless of the plate thickness, by applying a tensile stress (tension) within the range of 4 MPa or more and 16 MPa or less in the long side direction L, a ratio Ra(b) / Ra(s) that satisfies the relationship of 1.00 < Ra(b) / Ra(s) ≤ 5.00 can be obtained. Thus, the core noise is suppressed to 44 dBA or less. In contrast, if the tensile stress is too strong, the surface roughness becomes smaller, but due to the addition of strain, etc., there is a tendency for noise deterioration this time. In addition, the iron cores of core No. a, b, c with a smaller radius of curvature r (5 mm or less) of the bending part can suppress the core noise compared with the iron core of core No. c with a radius of curvature of 6 mm. In addition, in the case of the iron core of core No. e in the form of a box-type core, even if a tensile stress within the range of 4 MPa or more and 16 MPa or less is applied in the long side direction L to satisfy the relationship of 1.00 < Ra(b) / Ra(s) ≤ 5.00, the core noise cannot be sufficiently suppressed.

[0083] From the above results, it can be seen that the wound core of the present invention applies a tensile stress in the long side direction to the entire end face (C section) of the steel plate to be bent while performing bending processing to satisfy the relationship of 1.00 < Ra(b) / Ra(s) ≤ 5.00, so the noise caused by plastic deformation strain is reduced.

[0084] Reference Signs Explanation

[0085] 1 Directional electromagnetic steel plate; 4, 4a Plane part; 5 Bending part; 10 Wound core (wound core main body); 50 Device; 70 Manufacturing device; 71 Bending processing part; 72 Assembly part.

Claims

1. A wound core is formed by laminating in the plate thickness direction a portion where flat portions and bent portions of the grain-oriented electromagnetic steel sheet are continuously alternated in the longitudinal direction of the grain-oriented electromagnetic steel sheet, and is formed by laminating the grain-oriented electromagnetic steel sheet that has been individually bent and processed into a layered structure and assembling it into a wound shape. The wound core is characterized in that when the average height of the roughness curve elements in the width direction intersecting the longitudinal direction of the surface forming the bent portion of the grain-oriented electromagnetic steel sheet is Ra(b), and the average height of the roughness curve elements in the width direction of the surface forming the flat portion of the grain-oriented electromagnetic steel sheet is Ra(s), the relationship 1.00 < Ra(b) / Ra(s) ≤ 5.00 is satisfied.

2. The wound core according to claim 1, characterized in that the radius of curvature of the bent portion is 1 mm or more and 5 mm or less.

3. A method for manufacturing a wound core, characterized in that it includes: a bending process for individually bending a grain-oriented electromagnetic steel sheet; and an assembling process for laminating the grain-oriented electromagnetic steel sheet after the bending process into a layered structure and assembling it into a wound shape, thereby forming a wound core having a wound shape including a portion where flat portions and bent portions of the grain-oriented electromagnetic steel sheet are continuously alternated in the longitudinal direction of the grain-oriented electromagnetic steel sheet and laminated in the plate thickness direction, in the bending process, a tensile stress in the range of 4 MPa or more and 16 MPa or less is applied to the grain-oriented electromagnetic steel sheet in the longitudinal direction, and the grain-oriented electromagnetic steel sheet is bent simultaneously so that when the average height of the roughness curve elements in the width direction intersecting the longitudinal direction of the surface forming the bent portion of the grain-oriented electromagnetic steel sheet is Ra(b), and the average height of the roughness curve elements in the width direction of the surface forming the flat portion of the grain-oriented electromagnetic steel sheet is Ra(s), the relationship 1.00 < Ra(b) / Ra(s) ≤ 5.00 is satisfied.

4. The method for manufacturing a wound core according to claim 3, characterized in that in the bending process, the grain-oriented electromagnetic steel sheet is bent so that the radius of curvature of the bent portion of the grain-oriented electromagnetic steel sheet becomes 1 mm or more and 5 mm or less.

5. A wound core manufacturing apparatus, characterized in that it comprises: a bending processing section for individually bending a grain-oriented electromagnetic steel sheet; and an assembling section for laminating the grain-oriented electromagnetic steel sheet after the bending process into a layered structure and assembling it into a wound shape, thereby forming a wound core having a wound shape including a portion where flat portions and bent portions of the grain-oriented electromagnetic steel sheet are continuously alternated in the longitudinal direction of the grain-oriented electromagnetic steel sheet and laminated in the plate thickness direction, The above bending processing section applies a tensile stress within the range of 4 MPa or more and 16 MPa or less to the above-oriented electrical steel sheet in the above long side direction, and simultaneously bends the above-oriented electrical steel sheet such that when the average height of the roughness curve elements in the width direction intersecting the above long side direction of the surface forming the above bending portion of the above-oriented electrical steel sheet is Ra(b), and the average height of the roughness curve elements in the above width direction of the surface forming the above flat portion of the above-oriented electrical steel sheet is Ra(s), the relationship 1.00 < Ra(b) / Ra(s) ≤ 5.00 is satisfied.

6. The winding core manufacturing apparatus according to claim 5, wherein the above bending processing section bends the above-oriented electrical steel sheet such that the radius of curvature of the above bending portion of the above-oriented electrical steel sheet becomes 1 mm or more and 5 mm or less.

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