Stator cores, electric motors, and generators

Abstract

This provides a stator core that improves yield and manufacturing difficulties while achieving a high maximum magnetic permeability. [Solution] The stator core has a helical shape with a constant distance from the central axis and comprises a core wire portion made of electromagnetic soft iron wire and an insulating film covering the outer surface of the core wire portion. The half-width of the peak corresponding to the iron(220) plane in X-ray diffraction analysis of the core wire portion is 0.31 degrees or less.

Description

Technical Field

[0001] The present disclosure relates to a stator core, an electric motor, and a generator. This application claims priority based on Japanese Application No. 2023-199294 filed on November 24, 2023, and incorporates all the descriptions set forth in the said Japanese application.

Background Art

[0002] A stator core provided in an electric motor or a generator is generally manufactured by performing punching on an electromagnetic steel sheet. However, such a stator core has a problem that there are many parts discarded in the electromagnetic steel sheet as a raw material, and the yield during manufacturing is low. Further, such a stator core is manufactured by stacking punched electromagnetic steel sheets. Therefore, there is also a problem that it is difficult to manufacture a stator core having a large height.

[0003] As a stator core capable of coping with such problems, a stator core in which a thin strip is wound in a spiral shape has been proposed (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

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

Brief Description of the Drawings

[0006] [Figure 1]Figure 1 is a schematic perspective view showing the structure of the stator core in this embodiment. [Figure 2] Figure 2 is a cross-sectional view corresponding to the section containing the central axis A in Figure 1 (a cross-sectional view along the line segment II-II in Figure 1). [Figure 3] Figure 3 is a schematic cross-sectional view showing the structure of the core wire portion and insulating film that constitute the stator core. [Figure 4] Figure 4 is a schematic flowchart of the manufacturing method for a stator core. [Figure 5A] Figure 5A is an enlarged cross-sectional view of a portion of the stator core in the first modified example. [Figure 5B] Figure 5B is an enlarged cross-sectional view of a portion of the stator core in a further modification of the first modification. [Figure 5C] Figure 5C is an enlarged cross-sectional view of a portion of the stator core in the second modified example. [Figure 5D] Figure 5D is an enlarged cross-sectional view of a portion of the stator core in the third modified example. [Figure 5E] Figure 5E is an enlarged cross-sectional view of a portion of the stator core in a further modification of the third modification. [Figure 5F] Figure 5F is an enlarged cross-sectional view of a portion of the stator core in the fourth modified example. [Figure 5G] Figure 5G is an enlarged cross-sectional view of a portion of the stator core in the fifth modified example. [Figure 6] Figure 6 is a perspective view of the electric motor and generator in this embodiment. [Figure 7] Figure 7 is a cross-sectional view along line XX in Figure 6. [Figure 8] Figure 8 shows the relationship between the half-width of the peak corresponding to the iron (220) surface and the maximum permeability. [Modes for carrying out the invention]

[0007] [Issues this disclosure aims to address] A helical stator core, such as the one disclosed in Patent Document 1, improves yield and manufacturing difficulties. However, according to the inventors' research, such a stator core has the problem that the maximum magnetic permeability, which is an important characteristic of the stator core, is not sufficient.

[0008] Therefore, one of the objectives of this disclosure is to provide a stator core that improves yield and manufacturing difficulties while achieving a high maximum magnetic permeability. [Effects of this disclosure]

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

[0010] [Description of Embodiments in this Disclosure] First, the embodiments of this disclosure will be listed and described. The stator core of this disclosure is (1) It has a helical shape with a constant distance from the central axis and comprises a core wire made of electromagnetic soft iron or silicon steel, and an insulating film covering the outer surface of the core wire. The full width at half maximum of the peak corresponding to the iron (220) plane in X-ray diffraction analysis of the core wire is 0.31 degrees or less.

[0011] The inventors investigated the reasons why the maximum magnetic permeability is not sufficiently improved in helical stator cores having an insulating film. As a result, they obtained the following findings and arrived at the configuration of the stator core of this disclosure. When forming a wire made of soft iron or silicon steel into a helical shape, generally, a raw wire made of soft iron or silicon steel is prepared first, and a wire having the desired cross-sectional area and cross-sectional shape is obtained by performing a forming process on this raw wire. At this time, because the amount of processing in the forming process is large, a large strain is introduced into the wire. From the viewpoint of removing this strain, the wire is subjected to an annealing treatment to reduce the strain, and then the wire is processed into a helical shape (coiling). However, in stator cores including the core wire portion manufactured in this way, the maximum magnetic permeability is not sufficiently improved. In contrast, the inventors have found that the maximum magnetic permeability is significantly improved by performing the annealing treatment after coiling. This is thought to be because coiling involves less processing than forming, resulting in less strain being introduced, but this small strain hinders the improvement of maximum magnetic permeability. The inventors have found that by reducing the strain after coiling to an extremely low level, specifically to a level where the full width at half maximum of the peak corresponding to the iron(220) plane in X-ray diffraction analysis is 0.31 degrees or less, a significant improvement in maximum magnetic permeability can be achieved. It should be noted that small strain on the iron(220) plane (full width at half maximum of 0.31 degrees or less) means that the overall strain of the iron crystal lattice, including other crystal planes, is small.

[0012] In the stator core of this disclosure, a high maximum magnetic permeability can be achieved by setting the half-width of the peak corresponding to the iron(220) plane in the X-ray diffraction analysis of the core wire portion to 0.31 degrees or less. Furthermore, by adopting a structure that includes a core wire portion having a helical shape and composed of electromagnetic soft iron or silicon steel wire, and an insulating film covering the outer surface of the core wire portion, yield reduction and manufacturing difficulties are improved. Thus, the stator core of this disclosure improves yield reduction and manufacturing difficulties while achieving a high maximum magnetic permeability.

[0013] (2) In the above (1), the half-value width of the peak corresponding to the iron (220) plane in the X-ray diffraction analysis of the core wire portion may be 0.30 degrees or less. With this configuration, a high maximum magnetic permeability can be more reliably achieved.

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

[0015] (4) In the above (1) or (2), the stator core further includes a resin portion covering the insulating film. In the cross-section including the central axis, the resin portion includes at least any 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 wire portion, a second portion covering the insulating film located between the core wire portion and the central axis, and a third portion located between the insulating films covering the core wire portions adjacent to each other in the direction parallel to the central axis. With this configuration, the insulation property of the core wire portion can be enhanced.

[0016] (5) In the above (4), the resin portion may be a cured body that adheres the insulating films covering the core wire portions adjacent to each other in the direction parallel to the central axis. With this configuration, the shape stability of the iron wire with an insulating film including the first portion, the second portion, and the insulating film can be enhanced.

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

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

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

[0020] (9) In (8) above, the inorganic material may be a phosphate. Phosphates are particularly suitable as insulating film materials covering the core wire portion from the viewpoint of insulating properties, cost, and ease of insulating film formation.

[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 that the insulation will be insufficient between adjacent core wire portions in the direction parallel to the central axis. On the other hand, if the thickness of the insulating film exceeds 30 μm, there is a risk that the maximum magnetic permeability will be insufficient. 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 even 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 the direction parallel to the central axis to the outer diameter of the stator core, may be 3 or more. This configuration makes it possible to increase the torque of the electric motor equipped with the stator core, or to increase the power generation performance of the generator equipped with the stator core, while making the electric motor or generator smaller.

[0023] (12) The electric motor of this disclosure comprises any one of the stator cores described in (1) to (11) above. Since this electric motor is equipped with a stator core having a high maximum magnetic permeability, the motor has high torque.

[0024] (13) The generator of this disclosure comprises any one of the stator cores described in (1) to (11) above. Since this generator is equipped with a stator core having a high maximum magnetic permeability, the generator has high power generation efficiency.

[0025] [Details of the embodiments of this disclosure] Next, embodiments of the stator core of this disclosure will be described with reference to the drawings. In the following drawings, identical or corresponding parts will be given the same reference numerals, and their descriptions will not be repeated.

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

[0027] Referring to Figure 1, the stator core 1 in this embodiment has a structure in which an insulated iron wire 10 is wound in a spiral shape at a constant distance from the central axis A. Referring to Figures 1 and 2, the stator core 1 comprises a core wire portion 11 and an insulating film 12. The core wire portion 11 and the insulating film 12 constitute the insulated iron wire 10.

[0028] The core wire portion 11 has a helical shape such that the distance r from the central axis A is constant. 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 shape of the cross-section perpendicular to the longitudinal direction of the core wire portion 11 (the cross-sectional shape of the core wire portion 11) is not particularly limited, but may be rectangular, for example, as in this embodiment. In this disclosure, a rectangle includes a square. The state in which the cross-sectional shape of the core wire portion 11 is rectangular does not necessarily mean that, for example, the outer surfaces at each vertex are perpendicular in a strict sense. For example, a chamfered portion may be formed in the area of ​​the outer surface corresponding to each vertex. A curved surface having an arc shape may be formed in the area of ​​the outer surface corresponding to each vertex. The state in which the cross-sectional shape of the core wire portion 11 is rectangular means that (1) the proportion occupied by the chamfered portion and curved surface formed at the corners of each side is 20% or less (smaller is more preferable), (2) the angle between opposite sides is 2° or less (preferably 0.3° or less), and (3) with respect to one side, the length of the other side opposite to that side is 60% to 140% of the length of that side (closer to 100% is preferable).

[0029] Referring to Figures 2 and 3, the height h of the cross-section of the core wire portion 11 perpendicular to the longitudinal direction, in the direction parallel to the central axis A, is preferably 0.6 mm or less. By reducing the height h to this level, the eddy current loss of the stator core 1 is reduced. As a result, the iron loss of the stator core 1 can be reduced. The width w of the cross-section of the core wire portion 11 perpendicular to the longitudinal direction, in the direction perpendicular to the central axis A, can be appropriately determined according to the characteristics required of the stator core 1. The width w may be greater than or less than the height h. The width w may also be the same as the height h. That is, the cross-section of the core wire portion 11 perpendicular to the longitudinal direction may be a square.

[0030] The insulating film 12 is arranged to cover the outer circumferential surface of the core wire portion 11. In addition to the outer circumferential surface of the core wire portion 11, the insulating film 12 may also cover the end face. The material constituting the insulating film 12 is not particularly limited as long as it has insulating properties, but may be an inorganic material, for example. From the viewpoint of insulating properties, cost, and ease of insulating film formation, 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 electromagnetic soft iron or silicon steel that constitutes the core wire portion 11. In other words, the insulating film 12 may be an oxide film.

[0031] Referring to Figures 1 and 2, in a cross-section including the central axis A, the insulating films 12 covering adjacent core wire portions 11 are in contact with each other in a direction parallel to the central axis A. From another perspective, in a cross-section including the central axis A, the outer surfaces of adjacent insulated iron wires 10 are in contact with each other. The stator core 1 will function even if the insulating films 12 covering adjacent core wire portions 11 are separated in a cross-section including the central axis A in a direction parallel to the central axis A. However, the maximum magnetic permeability of the stator core 1 can be improved by the contact between the insulating films 12 covering the core wire portions 11.

[0032] Referring to Figure 3, the thickness t of the insulating film 12 can be appropriately set according to the characteristics required for the stator core 1. However, from the viewpoint of ensuring sufficient insulation and achieving a high maximum magnetic permeability, it is preferable to set it to 0.1 μm or more and 30 μm or less, and more preferably 0.1 μm or more and 5 μm or less. As described above, the stator core 1 of this embodiment has a helical shape and employs a structure that includes a core wire portion 11 made of electromagnetic soft iron or silicon steel wire and an insulating film 12 covering the outer surface of the core wire portion 11, thereby improving yield reduction and manufacturing difficulties.

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

[0034] Furthermore, in the stator core 1 of this 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, because the strain of the core wire portion 11 is reduced to an extremely low level, 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 this disclosure is a stator core that improves yield reduction and manufacturing difficulties, and is capable of achieving high maximum magnetic permeability.

[0035] Next, an example of a method for manufacturing the stator core 1 in this embodiment will be described. Figure 4 is a schematic flowchart of the method for manufacturing the stator core 1 in this embodiment. Referring to Figure 4, in the method for manufacturing the stator core 1 in this embodiment, first, a raw wire preparation step is carried out as step S10. In this step S10, a raw wire made of electromagnetic soft iron or silicon steel, which will become the core wire portion 11, is prepared. The wire diameter of the raw wire can be appropriately selected considering the cross-sectional area of ​​the section perpendicular to the longitudinal direction of the desired core wire portion 11.

[0036] Next, a molding process is carried out as process S20. Molding is performed on the raw wire prepared in process S10. The molding process is not limited. Examples of molding processes include wire drawing and rolling. Wire drawing and rolling may be carried out individually or in combination. For example, wire drawing is carried out by passing the raw wire through a through hole formed in a die. Wire drawing may be carried out in multiple processes using multiple dies. In this embodiment, the cross-sectional shape of the core wire portion 11 in the longitudinal direction is rectangular. Therefore, for example, first a raw wire with a circular cross-section perpendicular to the longitudinal direction is prepared, and by one or more wire drawing processes, it is processed into a wire with a circular cross-section and a smaller cross-sectional area perpendicular to the longitudinal direction compared to the raw wire. After that, wire drawing is carried out using a die with a rectangular through hole (shape processing), and a wire with a rectangular cross-section perpendicular to the longitudinal direction is obtained. This wire becomes the core wire portion 11. For example, rolling is performed by passing the raw wire through rollers. The reduction ratio in the above forming process can be, for example, 20% to 95%. In addition, magnetic annealing may be performed after the forming process in step S20.

[0037] Next, an insulating film formation process is carried out as step S30. In this 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 a phosphate, a phosphate coating treatment is carried out in step S30. If the material constituting the insulating film 12 is an 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 also be an oxide film that is naturally (unintentionally) formed immediately after step S20. As a result, an insulating film 12 is formed on the outer surface of the electromagnetic soft iron or silicon steel wire obtained in step S20. As the insulating film that forms the insulating film 12, for example, a phosphate coating or an oxide film can be used. The electromagnetic soft iron or silicon steel wire obtained in step S20 becomes the core wire portion 11. As a result, an insulated iron wire 10 including the core wire portion 11 and the insulating film 12 is obtained.

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

[0039] Next, an annealing process is carried out as step S50. In this step S50, an annealing treatment is performed on the insulated iron wire 10 that has been processed into a helical shape. The annealing treatment can be carried out, for example, by heating the insulated iron wire 10 that has been processed into a helical shape to a temperature range of 600°C to 900°C in an inert gas atmosphere such as a nitrogen atmosphere. From the viewpoint of stability of properties, it is preferable to hold it in this temperature range for a time of 5 minutes to 60 minutes. The holding time in this temperature range may be less than 5 minutes, but it is preferable to hold it for 5 minutes or more because the properties of the stator core 1 tend to become unstable. The holding time in this temperature range may exceed 60 minutes, but from the viewpoint of productivity, it is preferable to hold it for 60 minutes or less. The stator core 1 of this embodiment can be manufactured by following the above procedure.

[0040] In the manufacturing method of the stator core 1 of this embodiment, annealing is performed after the coiling process is completed. This reduces the strain in the core wire portion 11 constituting the stator core 1 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 this embodiment makes it possible to manufacture a stator core 1 having a high maximum magnetic permeability. Furthermore, in the manufacturing method of the stator core of this embodiment, after the coiling process is completed, the stator core 1 is heated to the above temperature range in an inert gas atmosphere in a free-form state, rather than being constrained by other members such as being wound around a core material, and is held for the above preferred time to perform the annealing process. As a result, the strain in the stator core 1 of this embodiment is made uniform throughout, and the variation in crystal grain size is also reduced.

[0041] [Manufacturing method for modified form] The location of step S30 is not limited to the above embodiment. Step S30 may be performed in parallel with steps S20, S40, or S50. For example, if step S30 is performed in parallel with step S50, an insulating film 12, which is an oxide film that is naturally formed when the core wire portion 11 is heated after step S40, is formed on the outer circumferential surface of the core wire portion 11. Although not shown in the diagram, process S30 may be performed after process S10 and before process S20. Although not shown in the diagram, process S30 may be performed after process S40 and before process S50. Process S30 may also be performed after process S50.

[0042] [A modified stator core] The stator cores of the 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 further comprises a resin part 13 in addition to the core wire portion 11 and the insulating film 12. The resin part 13 covers the insulating film 12 that covers the core wire portion 11.

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

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

[0045] The third part 133 is continuous with the first part 131. In a cross-section including the central axis A, the third part 133 is located between insulating films 12 covering adjacent core wire portions 11 in a direction parallel to the central axis A. In a cross-section including the central axis A, the third part 133 is located between insulating films 12 in contact with 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 wire portions 11 face each other in a direction parallel to the central axis A. The third part 133 fills the space between the insulating films 12 in contact with each of the two opposing surfaces S1. In a cross-section including the central axis A, the third part 133 faces the entire area of ​​the opposing surfaces S1 in the radial direction.

[0046] The resin part 13 is composed of a cured body 130. The cured body 130 adheres an insulating film 12 to the adjacent core wire parts 11 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, 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 Part 1, 131 is 10 μm to 40 μm. The thickness (length in the direction parallel to the central axis A) of Part 3, 133 is 10 μm to 40 μm.

[0048] The resin part 13 is formed between steps S40 and S50. After step S40, an adhesive or paint is applied to the insulated iron wire 10 which has been processed into a helical shape, and then the adhesive or paint is cured to form the cured body 130.

[0049] [Further variations of the first variation] A stator core of a further modification of the first modification will be described with reference to Figure 5B. Figure 5B is an enlarged cross-sectional view of a portion of the stator core in a further modification of the first modification. As shown in Figure 5B, in the further modification of the first modification, the third portion 133 faces a portion of the radial direction 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 the end on the opposing surface S1 that is farther from the central axis A. In a cross-section including the central axis A, the second end S3 is the end on the opposing surface S1 that is closer to the central axis A.

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

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

[0053] [Third variation] A third modified stator core will be described with reference to Figure 5D. Figure 5D is an enlarged cross-sectional view of a part of the stator core in the third modified example. As shown in Figure 5D, in the third modified example, 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 wire portion 11 and the central axis A. Specifically, the second portion 132 is located on the surface of the insulating film 12 that is in contact with the inner surface SB. The inner surface SB is the surface of the core wire portion 11 that faces the central axis A. The second portion 132 has a cylindrical shape that extends along a direction parallel to the central axis A. The thickness (length in the radial direction) of the second portion 132 is 10 μm to 40 μm. On the other hand, the resin portion 13 does not include the first portion 131 (see Figure 5A) and the third portion 133 (see Figure 5A).

[0054] [Further variations of the third variation] A stator core of a further modification of the third modification will be described with reference to Figure 5E. Figure 5E is an enlarged cross-sectional view of a portion of the stator core in a further modification of the third modification. As shown in Figure 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 portion S3. On the other hand, when viewed in a direction parallel to the central axis A, the third portion 133 is offset from the first end portion S2.

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

[0056] [Fifth variation] A fifth modified example of the stator core will be described with reference to Figure 5G. Figure 5G is an enlarged cross-sectional view of a portion of the stator core in the fifth modified example. As shown in Figure 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 the first portion 131 and the second portion 132, respectively.

[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] [Electric motors and generators] Embodiments of the electric motor of this disclosure will be described with reference to Figures 6 and 7. Figure 6 is a perspective view of the electric motor and generator in this embodiment. Figure 7 is a cross-sectional view along line XX in Figure 6.

[0059] As shown in Figures 6 and 7, the electric motor 2 comprises a case 21, a shaft 22, a rotor 23, a stator core 1, and a coil 24. The case 21 has a cylindrical shape with an axis B. The case 21 houses a portion of the shaft 22, the rotor 23, the stator core 1, and the coil 24. The shaft 22 shares an axis B with the case 21. The shaft 22 rotates about axis B relative to the case 21. The end 221 of the shaft 22 in a direction parallel to 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 together with the shaft 22 about axis B. The rotor 23 is made up of permanent magnets. The stator core 1 is fixed to the inner surface of the case 21. The stator core 1 is located radially outward of 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 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 comprises a case 21, a shaft 22, a rotor 23, a stator core 1, and a coil 24. [Examples]

[0062] We fabricated the stator core described herein and conducted experiments 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 also fabricated using the same method as in the above embodiment, but with steps S40 and S50 swapped (Process B). The width w of the core wire portion was 1.0 mm, the height h was 1.7 mm, the thickness t of the insulating film 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. Samples were prepared by varying the annealing temperature in the range of 400°C to 800°C to change the magnitude of strain in the core wire portion (the full width at half maximum of the peak corresponding to the iron (220) plane in X-ray diffraction analysis).

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

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

[0066] Figure 8 shows the relationship between the full width at half maximum (FWHM) and the maximum permeability in the sample obtained from the above experiment. In Figure 8, the horizontal axis corresponds to the FWHM 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 permeability of the sample. The maximum permeability is expressed as relative permeability (dimensionless).

[0067] Referring to Figure 8, the measurement points corresponding to each sample from Process A and Process B are located on a common curve. Furthermore, 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) surface is 0.31 degrees or less, and even further in the region where it is 0.30 degrees or less, indicating that excellent maximum permeability can be obtained. From these experimental results, it is confirmed that the stator core of this disclosure improves yield reduction and manufacturing difficulties, while also enabling the achievement of high maximum permeability.

[0068] Of the measurement points in Process B, the one with the smallest full width at half maximum (FWHM) corresponds to the sample heated at 700°C during annealing. On the other hand, of the measurement points in Process A, the measurement points corresponding to the samples heated at 600°C, 700°C, and 800°C during annealing correspond to the three measurement points with a FWHM of less than 0.30 degrees. From this, it can be concluded that in Process B, although a sufficiently small amount of strain resulting in a FWHM of less than 0.30 degrees was achieved during annealing, strain was introduced during the subsequent coiling process, exceeding the strain required to achieve a high maximum magnetic permeability. To explain from another perspective, in processes like Process B, where coiling is performed after annealing, even if the strain is sufficiently reduced during annealing, strain is introduced again during coiling, making it difficult to manufacture a stator core capable of achieving a high maximum magnetic permeability.

[0069] The embodiments and examples disclosed herein are illustrative in all respects and should be understood not to be restrictive in any way. The scope of the present invention is defined by the claims rather than the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended. [Explanation of symbols]

[0070] 1 Stator core, 2 Motor, 3 Generator, 10 Insulated iron wire, 11 Core wire section, 12 Insulating film, 13 Resin section, 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 the direction parallel to the central axis of the stator core, L1, L2 Lengths of 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. It has a spiral shape with a constant distance from the central axis, and consists of a core wire made of electromagnetic soft iron or silicon steel, The core wire portion comprises an insulating film covering the outer surface of the core wire portion, A stator core in which the full width at half maximum of the peak corresponding to the iron (220) plane in the X-ray diffraction analysis of the core wire portion is 0.31 degrees or less.

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

3. The stator core according to claim 1 or claim 2, wherein in a cross-section including the central axis, the insulating films covering adjacent core wire portions in a direction parallel to the central axis are in contact with each other.

4. The stator core further comprises a resin portion covering the insulating film, In the cross-section including the central axis, the resin portion is The first part covering the insulating film, located on the opposite side of the central axis when viewed from the core wire portion, A second part covering the insulating film located between the core wire portion and the central axis, A third part located between the insulating film covering the adjacent core wire portions in a direction parallel to the central axis A stator core according to claim 1 or claim 2, comprising at least one selected from the group consisting of the following.

5. The stator core according to claim 4, wherein the resin portion is a cured body that adheres the insulating film covering the core wire portions adjacent to each other in a direction parallel to the central axis.

6. The stator core according to any one of claims 1 to 5, wherein the cross-section perpendicular to the longitudinal direction of the core wire portion is rectangular.

7. The stator core according to any one of claims 1 to 6, wherein the height of the cross section perpendicular to the longitudinal direction of the core wire portion in the direction parallel to the central axis is 0.6 mm or less.

8. The stator core according to any one of claims 1 to 7, wherein the insulating film is made of an inorganic material.

9. The stator core according to claim 8, wherein the inorganic material is a phosphate salt.

10. The stator core according to any one of claims 1 to 9, wherein the thickness of the insulating film is 0.1 μm or more and 30 μm or less.

11. The stator core according to any one of claims 1 to 10, wherein the aspect ratio, which is the ratio of the length of the stator core in the direction parallel to the central axis to the outer diameter of the stator core, is 3 or more.

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

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

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