Stator core, electric motor, and generator

Abstract

This stator core has a spiral shape in which the distance from the central axis is constant, and comprises: a core wire part composed of a wire made of electromagnetic soft iron; and an insulating film covering the outer peripheral surface of the core wire part. The half width of the peak corresponding to the iron (220) plane in an X-ray diffraction analysis of the core wire part is 0.31 degrees or less.

Description

Stator cores, electric motors and generators

[0001] This disclosure relates to a stator core, an electric motor, and a generator. This application claims priority to Japanese Application No. 2023-199294, filed November 24, 2023, and incorporates by reference all of the contents of said Japanese application.

[0002] Stator cores for electric motors or generators are generally manufactured by punching electromagnetic steel sheets. However, such stator cores have a problem in that a large portion of the electromagnetic steel sheets used as raw materials is discarded, resulting in low manufacturing yields. In addition, such stator cores are manufactured by stacking punched electromagnetic steel sheets. Therefore, there is also the problem that it is difficult to manufacture stator cores with large heights.

[0003] As a stator core that can solve such problems, a stator core in which a thin plate strip is wound in a spiral shape has been proposed (see, for example, Patent Document 1).

[0004] International Publication No. 2010 / 105866

[0005] The stator core according to the present disclosure has a spiral shape with a constant distance from a central axis, and includes a core portion made of soft electromagnetic iron or silicon steel wire, and an insulating film covering the outer surface of the core portion. X-ray diffraction analysis of the core portion shows that the half-width of the peak corresponding to the iron (220) plane is 0.31 degrees or less.

[0006] FIG. 1 is a schematic perspective view showing the structure of a stator core according to the present embodiment. FIG. 2 is a view corresponding to a cross section including the central axis A of FIG. 1 (a cross section taken along line II-II in FIG. 1). FIG. 3 is a schematic cross-sectional view showing the structure of a core portion and an insulating film constituting the stator core. FIG. 4 is a flowchart showing an outline of a method for manufacturing a stator core. FIG. 5A is an enlarged cross-sectional view of a portion of a stator core according to a first modified example. FIG. 5B is an enlarged cross-sectional view of a portion of a stator core according to a further modified example of the first modified example. FIG. 5C is an enlarged cross-sectional view of a portion of a stator core according to a second modified example. FIG. 5D is an enlarged cross-sectional view of a portion of a stator core according to a third modified example. FIG. 5E is an enlarged cross-sectional view of a portion of a stator core according to a further modified example of the third modified example. FIG. 5F is an enlarged cross-sectional view of a portion of a stator core according to a fourth modified example. FIG. 5G is an enlarged cross-sectional view of a portion of a stator core according to a fifth modified example. FIG. 6 is a perspective view of an electric motor and a generator according to the present embodiment. FIG. 7 is a cross-sectional view taken along line XX in FIG. 6. FIG. 8 is a graph showing the relationship between the half-width of a peak corresponding to the iron (220) plane and the maximum magnetic permeability.

[0007] [Problem to be Solved by the Present Disclosure] The spiral stator core disclosed in the above-mentioned Patent Document 1 improves the problems of yield and difficulty in manufacturing. However, according to the investigations of the present inventors, such a stator core has a problem in that the maximum magnetic permeability, which is an important characteristic of the stator core, is insufficient.

[0008] Therefore, one of the objects of the present disclosure is to provide a stator core that can reduce the reduction in yield and the difficulty of manufacturing, and can achieve a high maximum magnetic permeability.

[0009] According to the above stator core, it is possible to provide a stator core that can improve yield reduction and manufacturing difficulty and achieve a high maximum magnetic permeability.

[0010] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. The stator core of the present disclosure includes: (1) a core portion having a spiral shape with a constant distance from a central axis, the core portion being made of a wire made of soft magnetic iron or silicon steel, and an insulating film covering the outer surface of the core portion. In an X-ray diffraction analysis of the core portion, the half-width of the peak corresponding to the iron (220) plane is 0.31 degrees or less.

[0011] The present inventors investigated the reason why the maximum magnetic permeability is not sufficiently improved in a spiral stator core having an insulating film. As a result, they obtained the following findings and came up with the configuration of the stator core disclosed herein. When forming a soft iron or silicon steel wire into a spiral shape, typically, a raw wire material made of soft iron or silicon steel is first prepared and then formed to obtain a wire having a desired cross-sectional area and shape. During this forming process, a large amount of strain is introduced into the wire due to the large amount of processing required. To remove this strain, the wire is annealed to reduce the strain, and then the wire is formed into a spiral shape (coiled). However, a stator core including a core portion manufactured in this manner does not have a sufficient maximum magnetic permeability. In response to this, the present inventors discovered that the maximum magnetic permeability can be significantly improved by performing annealing after coiling. This is thought to be because coiling involves a smaller amount of processing than molding, and therefore introduces smaller strain, but this small strain prevents an improvement in maximum magnetic permeability. The inventors have discovered that a significant improvement in maximum magnetic permeability can be achieved by reducing the strain after coiling to an extremely low level, specifically to a level where the half-width of the peak corresponding to the iron (220) plane in X-ray diffraction analysis is 0.31 degrees or less. Note that small strain in the iron (220) plane (half-width of 0.31 degrees or less) means that the strain in the iron crystal lattice, including other crystal planes, is small as a whole.

[0012] In the stator core of the present disclosure, the half-width of the peak corresponding to the iron (220) plane in X-ray diffraction analysis of the core wire is set to 0.31 degrees or less, thereby achieving a high maximum magnetic permeability. Furthermore, by adopting a structure including a spiral-shaped core wire made of soft magnetic iron or silicon steel wire and an insulating film covering the outer surface of the core wire, reduced yields and manufacturing difficulties are alleviated. Thus, the stator core of the present disclosure can achieve a high maximum magnetic permeability while reducing reduced yields and manufacturing difficulties.

[0013] (2) In the above (1), the half-width of the peak corresponding to the iron (220) plane in an X-ray diffraction analysis of the core wire may be 0.30 degrees or less. This configuration makes it possible to more reliably achieve a high maximum magnetic permeability.

[0014] (3) In the above (1) or (2), in a cross section including the central axis, insulating films covering adjacent core portions in a direction parallel to the central axis may be in contact with each other. This configuration can achieve a further improvement in maximum magnetic permeability.

[0015] (4) In the above (1) or (2), the stator core may further include a resin portion covering the insulating film, and in a cross section including the central axis, the resin portion may include at least one selected from the group consisting of a first portion covering the insulating film located on the opposite side of the central axis as viewed from the core portion, a second portion covering the insulating film located between the core portion and the central axis, and a third portion located between the insulating films covering adjacent core portions in a direction parallel to the central axis. This configuration can improve the insulation of the core portion.

[0016] (5) In the above (4), the resin portion may be a hardened body that bonds the insulating film that covers the adjacent core wire portions in a direction parallel to the central axis. This configuration can improve the stability of the shape of the insulating-coated iron wire including the first portion, the second portion, and the insulating film.

[0017] (6) In any one of (1) to (5) above, the cross section of the core wire portion perpendicular to the longitudinal direction may be rectangular. This configuration reduces the space between adjacent core wire portions in the direction parallel to the central axis. As a result, further improvement in maximum magnetic permeability can be achieved.

[0018] (7) In any one of (1) to (6) above, a height of the core portion in a direction parallel to the central axis of a cross section perpendicular to the longitudinal direction of the core portion may be 0.6 mm or less. With this configuration, eddy current loss is reduced, and as a result, iron loss can be reduced.

[0019] (8) In any one of the above (1) to (7), the insulating film may be made of an inorganic material. Inorganic materials are suitable as materials for the insulating film covering the core portion.

[0020] (9) In the above (8), the inorganic material may be a phosphate. Phosphate is particularly suitable as a material for the insulating film covering the core wire from the viewpoints of insulating properties, cost, ease of forming the insulating film, etc.

[0021] (10) In any one of (1) to (9) above, the thickness of the insulating film may be 0.1 μm or more and 30 μm or less. If the thickness of the insulating film is less than 0.1 μm, there is a risk of insufficient insulation between adjacent core wires in a direction parallel to the central axis. On the other hand, if the thickness of the insulating film exceeds 30 μm, there is a risk of insufficient maximum magnetic permeability. Therefore, it is preferable that the thickness of the insulating film be within the above range. From the viewpoint of ensuring a higher maximum magnetic permeability, it is more preferable that the thickness of the insulating film be 5 μm or less.

[0022] (11) In any one of (1) to (10) above, the aspect ratio, which is the ratio of the length of the stator core in a direction parallel to the central axis thereof to the outer diameter thereof, may be equal to or greater than 3. This configuration can increase the torque of an electric motor equipped with the stator core, or can increase the power generation performance of a generator equipped with the stator core while miniaturizing the electric motor or generator.

[0023] (12) An electric motor according to the present disclosure includes a stator core according to any one of (1) to (11) above. This electric motor has a stator core with a high maximum magnetic permeability, and therefore has high torque.

[0024] (13) A generator according to the present disclosure includes a stator core according to any one of (1) to (11) above. Since the generator includes a stator core having a high maximum magnetic permeability, the generator has high power generation efficiency.

[0025] [Details of the embodiment of the present disclosure] Next, an embodiment of the stator core of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0026] Fig. 1 is a schematic perspective view showing the structure of a stator core in this embodiment. Fig. 2 is a view corresponding to a cross section including the central axis A of Fig. 1 (a cross section taken along line II-II in Fig. 1). Fig. 3 is a schematic cross section showing the structure of the core wire portion and insulating film that constitute the stator core.

[0027] 1, stator core 1 in this embodiment has a structure in which insulating coated iron wire 10 is wound in a spiral shape at a constant distance from central axis A. Referring to Fig. 1 and Fig. 2, stator core 1 includes core wire portion 11 and insulating film 12. Core wire portion 11 and insulating film 12 constitute insulating coated iron wire 10.

[0028] The core wire portion 11 has a spiral shape with a constant distance r from the central axis A. The core wire portion 11 is composed of a wire made of electromagnetic soft iron or silicon steel. In this disclosure, electromagnetic soft iron refers to electromagnetic soft iron as defined in JIS standard C2504. In this disclosure, silicon steel is steel containing 1.0 to 5.0% by mass of silicon and 0.1% or less by mass of carbon, with the remainder being iron and unavoidable impurities. The silicon steel may further contain at least one of 0.01 to 1.2% by mass of manganese and 0.01 to 1.2% by mass of aluminum. The cross-sectional shape of the core wire portion 11 perpendicular to the longitudinal direction (cross-sectional shape of the core wire portion 11) is not particularly limited, but may be rectangular, as in the present embodiment. In this disclosure, rectangle also includes a square. The cross-sectional shape of the core wire portion 11 does not necessarily mean that the outer peripheral surfaces are strictly perpendicular to each other at each vertex. For example, chamfered portions may be formed in the regions of the outer peripheral surface corresponding to each vertex. The regions of the outer peripheral surface corresponding to each vertex may also have curved surface portions with an arc-like shape. The cross-sectional shape of the core wire portion 11 means that (1) the proportion of the chamfered portions and curved surface portions formed at the corners of each side is 20% or less (preferably small), (2) the angle between opposite sides is 2° or less (preferably 0.3° or less), and (3) the length of one side relative to the other side is 60% to 140% of the length of the other side (preferably close to 100%).

[0029] 2 and 3, the height h of the core wire portion 11 in a cross section perpendicular to the longitudinal direction, in a direction parallel to the central axis A, is preferably 0.6 mm or less. Reducing the height h to this level reduces eddy current loss in the stator core 1. As a result, iron loss in the stator core 1 can be reduced. The width w of the core wire portion 11 in a cross section perpendicular to the longitudinal direction, in a direction perpendicular to the central axis A, can be appropriately determined depending on the characteristics required of the stator core 1. The width w may be greater or smaller than the height h. The width w may be the same as the height h. In other words, the cross section perpendicular to the longitudinal direction of the core wire portion 11 may be square.

[0030] The insulating film 12 is disposed so as to cover the outer peripheral surface of the core wire portion 11. The insulating film 12 may cover the end surfaces of the core wire portion 11 in addition to the outer peripheral surface. The material constituting the insulating film 12 is not particularly limited as long as it has insulating properties, but may be, for example, an inorganic material. From the viewpoints of insulating properties, cost, ease of insulating film formation, etc., the material constituting the insulating film 12 is preferably a phosphate. The phosphate is at least one selected from the group consisting of iron phosphate, zinc phosphate, and manganese phosphate. The material constituting the insulating film 12 may be an oxide of the soft magnetic iron or silicon steel constituting the core wire portion 11. In other words, the insulating film 12 may be an oxide film.

[0031] 1 and 2 , in a cross section including the central axis A, the insulating films 12 covering adjacent core wire portions 11 in a direction parallel to the central axis A are in contact with each other. From another perspective, in a cross section including the central axis A, the outer circumferential surfaces of adjacent insulating-coated iron wires 10 are in contact with each other. Even if, in a cross section including the central axis A, the insulating films 12 covering adjacent core wire portions 11 in a direction parallel to the central axis A are separated from each other, the stator core 1 still functions. However, by bringing the insulating films 12 covering the core wire portions 11 into contact with each other, the maximum magnetic permeability of the stator core 1 can be improved.

[0032] 3, the thickness t of insulating film 12 can be set appropriately depending on the characteristics required of stator core 1. However, from the viewpoint of ensuring both sufficient insulation and high maximum magnetic permeability, it is preferable to set the thickness to 0.1 μm or more and 30 μm or less, and further 0.1 μm or more and 5 μm or less. As described above, stator core 1 of the present embodiment employs a structure including core portion 11 having a spiral shape and made of a wire made of electromagnetic soft iron or silicon steel, and insulating film 12 covering the outer surface of core portion 11, thereby providing a stator core in which reduced yields and difficulty in manufacturing are improved.

[0033] Referring to FIG. 2 , the length L of the stator core 1 in a direction parallel to the central axis A is 50 mm or more, further 100 mm or more, and further 130 mm or more. If the length L of the stator core 1 in a direction parallel to the central axis A is within the above-mentioned range, the torque of an electric motor 2 (described later, see FIG. 7 ) including the stator core 1 can be increased. There is no upper limit to the length L of the stator core 1 in a direction parallel to the central axis A. The length L of the stator core 1 in a direction parallel to the central axis A is the average ((L1 + L2) / 2) of lengths L1 and L2 at two locations 180 degrees apart in the circumferential direction around the central axis A. The outer diameter D of the stator core 1 is 30 mm or less, further 20 mm or less. If the outer diameter D of the stator core 1 is within the above-mentioned range, the electric motor 2 or generator 3 including the stator core 1 can be made smaller. The aspect ratio (L / D), which is the ratio of the length L of the stator core 1 in a direction parallel to the central axis A to the outer diameter D of the stator core 1, is 3 or more, preferably 5 or more, further 10 or more, or even 15 or more. If the aspect ratio is within the above range, it is possible to achieve both high torque and compactness in the electric motor 2 equipped with the stator core 1. There is no upper limit to the aspect ratio.

[0034] In the stator core 1 of the present embodiment, the half-width of the peak corresponding to the iron (220) plane in the X-ray diffraction analysis of the core wire portion 11 is 0.31 degrees or less. In this way, the distortion of the core wire portion 11 is reduced to an extremely low level, and therefore the stator core 1 is a stator core with improved maximum magnetic permeability. From the viewpoint of further improving the maximum magnetic permeability, it is preferable that the half-width of the peak corresponding to the iron (220) plane in the X-ray diffraction analysis of the core wire portion 11 is 0.30 degrees or less. As described above, the stator core 1 of the present disclosure is a stator core that can achieve high maximum magnetic permeability while improving yield reduction and manufacturing difficulty.

[0035] Next, an example of a method for manufacturing the stator core 1 according to the present embodiment will be described. FIG. 4 is a flowchart showing an outline of the method for manufacturing the stator core 1 according to the present embodiment. Referring to FIG. 4, in the method for manufacturing the stator core 1 according to the present embodiment, a raw material wire preparation step is first carried out as step S10. In step S10, a raw material wire made of soft magnetic iron or silicon steel to become the core portion 11 is prepared. The wire diameter of the raw material wire can be appropriately selected taking into consideration the cross-sectional area of ​​the desired core portion 11 in a cross section perpendicular to the longitudinal direction, etc.

[0036] Next, a forming step is performed as step S20. The raw wire prepared in step S10 is formed. The forming step is not limited. Examples of forming steps include wire drawing and rolling. Wire drawing and rolling may be performed independently or in combination. For example, wire drawing is performed by passing the raw wire through a through hole formed in a die. Wire drawing may be performed multiple times using multiple dies. In this embodiment, the cross section of the core wire portion 11 in the longitudinal direction is rectangular. Therefore, for example, a raw wire having a circular cross section perpendicular to the longitudinal direction is first prepared, and then the raw wire is drawn once or multiple times to form a wire having a circular cross section whose cross-sectional area perpendicular to the longitudinal direction is smaller than that of the raw wire. Then, wire drawing is performed using a die having a through hole with a rectangular cross section (deformed shape processing) to obtain a wire having a rectangular cross section perpendicular to the longitudinal direction. This wire becomes the core wire portion 11. For example, the rolling process is performed by passing the raw wire through rollers. The area reduction rate in the forming process can be, for example, 20% to 95%. In step S20, magnetic annealing may be performed after the forming process.

[0037] Next, an insulating film forming step is performed as step S30. In step S30, an insulating film 12 is formed on the outer surface of the wire obtained in step S20, which has a rectangular cross section perpendicular to the longitudinal direction. If the material constituting the insulating film 12 is phosphate, a phosphate coating treatment is performed in step S30. If the material constituting the insulating film 12 is oxide, in step S30, the core wire portion 11 after step S20 is left in the air at room temperature (25°C). The insulating film 12 may be an oxide film that is naturally (unintentionally) formed immediately after step S20. As a result, the insulating film 12 is formed on the outer surface of the soft magnetic iron or silicon steel wire obtained in step S20. For example, a phosphate coating or an oxide film can be used as the insulating film forming the insulating film 12. The soft magnetic iron or silicon steel wire obtained in step S20 becomes the core wire portion 11. As a result, an iron wire 10 with an insulating coating is obtained, which includes the core wire portion 11 and the insulating film 12.

[0038] Next, a coiling step is carried out as step S40. In this step S40, the iron wire 10 with the insulating coating obtained in step S30 is processed into a spiral (coil) shape (coiling process). The coiling process can be carried out, for example, by bending the iron wire 10 with a pin (processing using a coiling machine) or by winding the iron wire 10 with the insulating coating around a shaft.

[0039] Next, an annealing step is performed as step S50. In step S50, the spirally formed iron wire 10 with the insulating coating is annealed. The annealing step can be performed, for example, by heating the spirally formed iron wire 10 with the insulating coating to a temperature range of 600°C to 900°C in an inert gas atmosphere such as a nitrogen atmosphere. From the viewpoint of characteristic stability, it is preferable to hold the iron wire 10 in this temperature range for 5 minutes to 60 minutes. While the holding time in this temperature range may be less than 5 minutes, it is preferable to hold the iron wire 1 in this temperature range for 5 minutes or more because the characteristics of the stator core 1 tend to become unstable. Although the holding time in this temperature range may exceed 60 minutes, it is preferable to hold the iron wire 1 in this temperature range for 60 minutes or less from the viewpoint of productivity. The stator core 1 of the present embodiment can be manufactured by the above procedure.

[0040] In the manufacturing method of the stator core 1 of the present embodiment, an annealing treatment is performed after completion of the coiling process. As a result, the strain of the core wire portion 11 constituting the stator core 1 is reduced to a level where the half-width of the peak corresponding to the iron (220) plane in X-ray diffraction analysis is 0.31 degrees or less. As a result, the manufacturing method of the stator core of the present embodiment allows the manufacturing of a stator core 1 having a high maximum magnetic permeability. Furthermore, in the manufacturing method of the stator core of the present embodiment, after completion of the coiling process, the stator core 1 is heated to the above temperature range in an inert gas atmosphere and held for the above preferred time period while in a free-form state, rather than being in a state where it is wound around a core material or otherwise constrained by other members, and an annealing treatment is performed. As a result, the stator core 1 of the present embodiment has uniform strain throughout its entire region and reduced variation in grain size.

[0041] [Manufacturing Method of Modified Example] The position of step S30 is not limited to that of the above embodiment. Step S30 may be performed in parallel with step S20, step S40, or step S50. For example, when step S30 is performed in parallel with step S50, an insulating film 12, which is a naturally formed oxide film, is formed on the outer peripheral surface of the core wire portion 11 when the core wire portion 11 is heated after step S40. Although not shown, step S30 may be performed after step S10 and before step S20. Although not shown, step S30 may be performed after step S40 and before step S50. Step S30 may be performed after step S50.

[0042] [Modified Stator Cores] Stator cores according to first to fifth modified examples will be described with reference to Figures 5A to 5G. As shown in Figures 5A to 5G, the stator core 1 includes a resin portion 13 in addition to the core portion 11 and the insulating film 12. The resin portion 13 covers the insulating film 12 that covers the core portion 11.

[0043] [First Modification] A stator core of a first modification will be described with reference to Fig. 5A. Fig. 5A is an enlarged cross-sectional view of a portion of the stator core in the first modification. As shown in Fig. 5A, in the first modification, the resin portion 13 includes a first portion 131 and a third portion 133.

[0044] In a cross section including the central axis A, the first portion 131 is located on the opposite side of the central axis A from the core portion 11. In a cross section including the central axis A, the first portion 131 is located on the surface of the insulating film 12 that contacts the outer surface SA. The outer surface SA is the surface of the core portion 11 that is located on the opposite side of the central axis A. The first portion 131 has a cylindrical shape that extends in a direction parallel to the central axis A.

[0045] The third portion 133 is continuous with the first portion 131. In a cross section including the central axis A, the third portion 133 is located between the insulating films 12 that cover adjacent core portions 11 in a direction parallel to the central axis A. In a cross section including the central axis A, the third portion 133 is located between the insulating films 12 that contact each of the two opposing surfaces S1. In a cross section including the central axis A, the two opposing surfaces S1 are two surfaces where adjacent core portions 11 in a direction parallel to the central axis A face each other. The third portion 133 is filled between the insulating films 12 that contact each of the two opposing surfaces S1. In a cross section including the central axis A, the third portion 133 faces the entire opposing surface S1 in the radial direction.

[0046] The resin portion 13 is composed of a cured body 130. The cured body 130 bonds the insulating films 12 that cover the core portions 11 that are adjacent to each other in a direction parallel to the central axis A. The cured body 130 is a cured product of an adhesive or a cured product of a paint, and more specifically, a cured product of an epoxy resin adhesive or a cured product of an epoxy resin paint.

[0047] The thickness (length in the radial direction) of the first portion 131 is 10 μm to 40 μm, and the thickness (length in the direction parallel to the central axis A) of the third portion 133 is 10 μm to 40 μm.

[0048] The resin portion 13 is formed between step S40 and step S50. After step S40, adhesive or paint is applied to the insulating coated iron wire 10 processed into a spiral shape, and then the adhesive or paint is cured to form a cured body 130.

[0049] [Further Modification of First Modification] A stator core according to a further modification of the first modification will be described with reference to Fig. 5B. Fig. 5B is an enlarged cross-sectional view of a portion of the stator core according to the further modification of the first modification. As shown in Fig. 5B, in this further modification of the first modification, the third portion 133 faces a radial portion of each of the two opposing surfaces S1 in a cross section including the central axis A.

[0050] The opposing surface S1 includes a first end S2 and a second end S3. In a cross section including the central axis A, the first end S2 is an end of the opposing surface S1 that is far from the central axis A. In a cross section including the central axis A, the second end S3 is an end of the opposing surface S1 that is close to the central axis A.

[0051] In this modified example, the third portion 133 faces the first end S2 in a cross section including the central axis A. On the other hand, when viewed in a direction parallel to the central axis A, the third portion 133 is misaligned with the second end S3.

[0052] [Second Modification] A stator core according to a second modification will be described with reference to Fig. 5C. Fig. 5C is an enlarged cross-sectional view of a portion of the stator core according to the second modification. As shown in Fig. 5C, in the second modification, the resin portion 13 includes a first portion 131 (see Fig. 5A). On the other hand, the resin portion 13 does not include a second portion 132 (described later, see Fig. 5D) or a third portion 133 (see Fig. 5A).

[0053] [Third Modification] A stator core according to a third modification will be described with reference to FIG. 5D . FIG. 5D is an enlarged cross-sectional view of a portion of the stator core according to the third modification. As shown in FIG. 5D , in the third modification, the resin portion 13 includes a second portion 132. In a cross section including the central axis A, the second portion 132 is located between the core portion 11 and the central axis A. Specifically, the second portion 132 is located on the surface of the insulating film 12 that contacts the inner surface SB. The inner surface SB is the surface of the core portion 11 that faces the central axis A. The second portion 132 has a cylindrical shape that extends in a direction parallel to the central axis A. The thickness (radial length) of the second portion 132 is 10 μm to 40 μm. Meanwhile, the resin portion 13 does not include the first portion 131 (see FIG. 5A ) or the third portion 133 (see FIG. 5A ).

[0054] [Further Modification of the Third Modification] A stator core according to a further modification of the third modification will be described with reference to Fig. 5E. Fig. 5E is an enlarged cross-sectional view of a portion of a stator core according to the further modification of the third modification. As shown in Fig. 5E, in this modification, the resin portion 13 includes a third portion 133 in addition to the second portion 132. In this modification, the third portion 133 is continuous with the second portion 132. In a cross section including the central axis A, the third portion 133 faces the second end S3. On the other hand, when viewed in a direction parallel to the central axis A, the third portion 133 is misaligned with the first end S2.

[0055] [Fourth Modification] A stator core according to a fourth modification will be described with reference to Fig. 5F. Fig. 5F is an enlarged cross-sectional view of a portion of the stator core according to the fourth modification. As shown in Fig. 5F, the resin portion 13 includes the third portion 133 (see Fig. 5A). On the other hand, the resin portion 13 does not include the first portion 131 (see Fig. 5A) or the second portion 132 (see Fig. 5E).

[0056] [Fifth Modification] A stator core according to a fifth modification will be described with reference to Fig. 5G. Fig. 5G is an enlarged cross-sectional view of a portion of the stator core according to the fifth modification. As shown in Fig. 5G, the resin portion 13 includes a first portion 131, a second portion 132, and a third portion 133. The third portion 133 is continuous with both the first portion 131 and the second portion 132.

[0057] As can be seen from the first to fifth modified examples described above, the resin part 13 may include at least one selected from the group consisting of a first part 131, a second part 132, and a third part 133.

[0058] [Motor and Generator] An embodiment of the motor of the present disclosure will be described with reference to Fig. 6 and Fig. 7. Fig. 6 is a perspective view of the motor and generator in this embodiment. Fig. 7 is a cross-sectional view taken along line XX in Fig. 1.

[0059] 6 and 7 , the electric motor 2 includes a case 21, a shaft 22, a rotor 23, a stator core 1, and coils 24. The case 21 has a cylindrical shape having an axis B. The case 21 houses a portion of the shaft 22, the rotor 23, the stator core 1, and the coils 24. The shaft 22 shares the axis B with the case 21. The shaft 22 rotates about the axis B relative to the case 21. An end 221 of the shaft 22 in a direction parallel to the axis B is located outside the case 21.

[0060] The rotor 23 is fixed to a portion of the shaft 22. The rotor 23 has a common axis B with the shaft 22. The rotor 23 rotates about the axis B together with the shaft 22. The rotor 23 is composed of a permanent magnet. The stator core 1 is fixed to the inner surface of the case 21. The stator core 1 is located radially outside the rotor 23. The stator core 1 is located away from the outer circumferential surface of the rotor 23. The rotor 23 rotates relative to the stator core 1. The central axis A of the stator core 1 coincides with the axis B of the rotor 23. The coil 24 is located between the rotor 23 and the stator core 1. The coil 24 is located away from the outer circumferential surface of the rotor 23. The coil 24 is fixed to the inner surface 111 of the stator core 1.

[0061] The generator 3 has the same configuration as the electric motor 2. That is, the generator 3 includes a case 21, a shaft 22, a rotor 23, a stator core 1, and coils 24.

[0062] A stator core according to the present disclosure was fabricated and an experiment was conducted to confirm that a high maximum magnetic permeability could be obtained. The experimental procedure was as follows.

[0063] First, a stator core was fabricated using the same procedure as in the above embodiment, including steps S10 to S50 (Process A). For comparison, a stator core was fabricated using the stator core manufacturing method of the above embodiment, but with steps S40 and S50 swapped (Process B). The width w of the core wire was 1.0 mm, the height h was 1.7 mm, the thickness t of the insulating layer was 1 to 3 μm, the outer diameter D of the stator core was 19.6 mm, and the inner diameter was 17.6 mm. The annealing temperature was varied between 400°C and 800°C, and samples were fabricated with different magnitudes of strain in the core wire (the half-width of the peak corresponding to the iron (220) plane in X-ray diffraction analysis).

[0064] The core wire of the obtained sample was subjected to X-ray diffraction analysis to measure the half-width of the peak corresponding to the iron (220) plane. The X-ray diffraction analysis was performed under the following conditions: X-ray used: Cu—Ka, excitation conditions: 45 kV 200 mA, incident optical system: CB-f, slit size: 0.8 mm, mask: 0.5 mm, receiving optical system: Hypix-3000, scanning method: 2θ-θ, measurement range: 2θ = 20 to 140°.

[0065] The magnetization curves of the samples were also measured, and the maximum magnetic permeability was calculated from the measured magnetization curves. The magnetization curves were measured using the secondary winding method, with a 108-turn primary winding and a 30-turn secondary winding wound around the ring. Iron loss was measured at room temperature (25°C) using an AC BH analyzer (manufactured by Metron Giken Co., Ltd.) until an excitation magnetic flux density Bm of 2.2 T (22 kG) was reached.

[0066] Figure 8 shows the relationship between the half-value width and maximum magnetic permeability of the samples obtained as a result of the above experiment. In Figure 8, the horizontal axis corresponds to the half-value width of the peak corresponding to the iron (220) plane in the X-ray diffraction analysis of the core wire. The vertical axis corresponds to the maximum magnetic permeability of the sample. The maximum magnetic permeability is expressed as relative magnetic permeability (unitless).

[0067] 8, the measurement points corresponding to the samples of Process A and Process B are located on a common curve. It can be seen that the maximum permeability increases sharply in the region where the half-width of the peak corresponding to the iron (220) plane is 0.31 degrees or less, and further in the region where it is 0.30 degrees or less, resulting in an excellent maximum permeability. The above experimental results confirm that the stator core of the present disclosure can improve yield reduction and manufacturing difficulties while achieving a high maximum permeability.

[0068] Among the measurement points in Process B, the measurement point with the smaller half-width corresponds to the sample annealed at 700°C. Meanwhile, among the measurement points in Process A, the measurement points corresponding to the samples annealed at 600°C, 700°C, and 800°C correspond to three measurement points with half-widths of less than 0.30°C. From this, it is considered that in Process B, a sufficiently small amount of strain was achieved during annealing, resulting in a half-width of less than 0.30°C, but strain was introduced by the subsequent coiling process, exceeding the strain required to achieve a high maximum magnetic permeability. From another perspective, in a process in which coiling is performed after annealing, as in Process B, even if strain is sufficiently reduced during annealing, strain is again introduced during coiling, making it difficult to manufacture a stator core capable of achieving a high maximum magnetic permeability.

[0069] It should be understood that the embodiments and examples disclosed herein are illustrative in all respects and are not limiting in any respect. The scope of the present invention is defined not by the above description but by the claims, and it is intended to include all modifications within the meaning and scope of the claims.

[0070] 1 stator core, 2 electric motor, 3 generator, 10 insulating coated iron wire, 11 core wire portion, 12 insulating film, 13 resin portion, 21 case, 22 shaft, 23 rotor, 24 coil, 111 inner surface, 130 hardened body, 131 first part, 132 second part, 133 third part, 221 end, A central axis, B axis, L length in a direction parallel to the central axis of the stator core, L1, L2 lengths at two points 180 degrees apart in the circumferential direction around the central axis, D outer diameter, S1 opposing surface, S2 first end, S3 second end, SA outer surface, SB inner surface, h height, r distance, t thickness, w width.

Claims

1. a core portion having a spiral shape with a constant distance from a central axis and made of a wire made of electromagnetic soft iron or silicon steel; an insulating film covering an outer circumferential surface of the core portion, A stator core, wherein the half width of a peak corresponding to an iron (220) plane in an X-ray diffraction analysis of the core wire portion is 0.31 degrees or less.

2. 2. The stator core according to claim 1, wherein a half width of a peak corresponding to an iron (220) plane in an X-ray diffraction analysis of the core wire portion is 0.30 degrees or less.

3. The stator core according to claim 1 , wherein, in a cross section including the central axis, the insulating films covering the core wire portions adjacent to each other in a direction parallel to the central axis are in contact with each other.

4. The stator core further includes a resin portion covering the insulating film, In a cross section including the central axis, the resin portion a first portion covering the insulating film, the first portion being located on the opposite side of the core wire portion from the central axis; a second portion covering the insulating film located between the core portion and the central axis; and a third portion located between the insulating films covering the adjacent core portions in a direction parallel to the central axis; The stator core according to claim 1 , comprising at least one selected from the group consisting of:

5. The stator core according to claim 4 , wherein the resin portion is a hardened body that bonds the insulating films that cover the core wire portions adjacent to each other in a direction parallel to the central axis.

6. The stator core according to claim 1 , wherein a cross section perpendicular to the longitudinal direction of the core wire portion is rectangular.

7. 2. The stator core according to claim 1, wherein a cross section of said core portion perpendicular to a longitudinal direction thereof has a height of 0.6 mm or less in a direction parallel to said central axis.

8. The stator core according to claim 1 , wherein the insulating film is made of an inorganic material.

9. The stator core of claim 8 , wherein the inorganic material is a phosphate.

10. The stator core according to claim 1 , wherein the insulating film has a thickness of 0.1 μm or more and 30 μm or less.

11. The stator core according to claim 1 , wherein an aspect ratio, which is a ratio of a length of the stator core in a direction parallel to the central axis to an outer diameter of the stator core, is 3 or more.

12. An electric motor comprising the stator core according to any one of claims 1 to 11.

13. A generator comprising the stator core according to any one of claims 1 to 11.