Stator manufacturing method, stator core, and stator

Abstract

To provide a stator manufacturing method, a stator core, and a stator that can be manufactured with high precision and can improve assembly workability.SOLUTION: A stator manufacturing method includes a punching step, a cutting step, a cutting and raising back step, a laminating step, a developing step, a winding step, and a developing and returning step. In the punching step, a stator core plate 13 is punched out from an electromagnetic steel sheet. In the cutting step, a back yoke plate 18 is sheared to form a cut-off portion 16 at only one location and a notch portion 15. In the cutting and raising step, the cut and raised portion of the back yoke plate 18 is pushed back and made flat. In the lamination step, a plurality of stator core plates 13 are laminated. The developing step develops the stator core plate 13. After the winding step, the back yoke plate 18 is returned to the annular shape.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a stator manufacturing method, a stator core, and a stator. [Background technology]

[0002] For example, an inner rotor brushless motor includes a cylindrical stator and a cylindrical rotor rotatably mounted radially inside the stator. The stator includes a stator core having a cylindrical back yoke and a plurality of teeth protruding radially inward from the back yoke, and coils wound around the teeth. When current is applied to the coil, magnetic flux linkage is formed in the teeth. Magnetic attraction and repulsion are generated between this magnetic flux linkage and magnets mounted on the rotor, causing the rotor to rotate.

[0003] Stator cores are often formed by laminating electromagnetic steel sheets to reduce iron loss. To increase the coil space factor, the stator core may be divided circumferentially for each tooth to form split cores (split laminated cores). By winding a coil on each split core, the coil winding process is less subject to restrictions. This allows for an improvement in the coil space factor.

[0004] The method for manufacturing the split core involves first punching out a plurality of split core plates (blanks, core pieces) that will become the split cores from an electromagnetic steel sheet, and then stacking these split core plates to form the split cores. After forming the split cores, a coil is wound around each split core, and then the circumferential ends of the back yoke of each split core are joined together in an annular shape to form a stator (see, for example, Patent Document 1).

[0005] To easily connect the split cores, grooves are sometimes formed on both circumferential ends of the back yoke, and protrusions are sometimes provided in these grooves. With this configuration, the circumferential end of a circumferentially adjacent back yoke is inserted into the groove of any back yoke. The two circumferentially adjacent back yokes are then connected by the protrusions (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2020 / 194787 [Patent Document 2] Japanese Patent Publication No. 2020-174507 Summary of the Invention [Problem to be solved by the invention]

[0007] In the above-mentioned Patent Document 1, a small gap may be formed between the connected back yokes due to manufacturing errors at both circumferential ends of the back yokes. In this case, there is a possibility that the stator core may be deformed due to magnetic attraction and repulsion forces with the rotor that are generated when current is applied to the coil. Furthermore, excessive pressure may be applied locally to the connected back yoke, which may cause deformation of the back yoke when the split cores are connected.

[0008] In the above-mentioned Patent Document 2, due to the rigidity of the back yoke, there is a possibility that another back yoke inserted into the groove will hit the protrusion and be unable to overcome this protrusion. This could result in deformation of the protrusion when trying to connect them forcibly, or the assembly work itself could become cumbersome.

[0009] The present invention provides a stator manufacturing method, a stator core, and a stator that can be manufactured with high precision and that can improve assembly workability. [Means for solving the problem]

[0010] In order to solve the above problems, the stator manufacturing method of the present invention includes a punching step of punching out from an electromagnetic steel sheet a stator core plate having an annular back yoke plate and a plurality of tooth plates protruding radially inward from the inner peripheral edge of the back yoke plate; a cutting step of, after the punching step, shearing between adjacent tooth plates in the circumferential direction of the back yoke plate to form a separation portion in only one location of the back yoke plate and forming notches in locations other than the separation portion so that the back yoke plate will not separate; and a cutting step of, after the cutting step, pushing back and flattening the raised portions of the back yoke plate caused by forming the notches. a stacking process of stacking a plurality of the stator core plates after the cutting and raising process to form a stator core having a back yoke made up of a plurality of stacked back yoke plates and teeth made up of a plurality of stacked tooth plates; an unfolding process of unfolding the stator core plates after the cutting and raising process or after the stacking process, by opening the separation portions to separate them and opening the notches, and unfolding the stator core plates so that adjacent tooth plates in the circumferential direction are lined up in a direction intersecting the protruding direction of the tooth plates; a winding process of winding coils around the teeth after the unfolding process; and an unfolding process of unfolding the back yoke back into a ring shape after the winding process. [Effects of the Invention]

[0011] According to the present invention, the stator core and the stator can be manufactured with high precision, and the workability of assembling the stator core and the stator can be improved. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view taken along the radial direction of a brushless motor according to a first embodiment of the present invention. [Figure 2]FIG. 2 is a plan view of a stator core plate in the first embodiment of the present invention. [Figure 3] FIG. 3 is an enlarged view of part III in FIG. 2. [Figure 4] FIG. 3 is an enlarged view of part IV in FIG. 2. [Figure 5] FIG. 2 is a development view of the stator core according to the first embodiment of the present invention. [Figure 6] FIG. 10 is a side view of a stator core according to a second embodiment of the present invention. [Figure 7] 10A and 10B show a first stator core plate according to a second embodiment of the present invention, where FIG. 10A is a plan view and FIG. [Figure 8] 10A and 10B show a second stator core plate according to a second embodiment of the present invention, where FIG. 10A is a plan view and FIG. [Figure 9] FIG. 10 is a side view of the stator core after a lamination process in the second embodiment of the present invention. [Figure 10] FIG. 10 is an enlarged cross-sectional view of a portion of a boss in a modified example of the second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Next, an embodiment of the present invention will be described with reference to the drawings.

[0014] [First embodiment] <Brushless motor> FIG. 1 is a cross-sectional view taken along the radial direction of a brushless motor 1 to which a stator 2 according to a first embodiment of the present invention is applied. The brushless motor 1 is a drive source for electrical equipment (for example, power windows, sunroofs, power seats, etc.) mounted on a vehicle, for example.

[0015] As shown in Figure 1, the brushless motor 1 includes an annular stator 2 and a rotor 3 that is disposed radially inside the stator 2 and supported rotatably relative to the stator 2. In the following description, the direction parallel to the rotation axis C of the rotor 3 will be referred to simply as the axial direction. The rotation direction of the rotor 3 will be referred to as the circumferential direction. The radial direction of the rotor 3, which is perpendicular to the axial and circumferential directions, coincides with the radial direction of the stator 2.

[0016] <Rotor> The rotor 3 includes a shaft 4 and a cylindrical rotor core 5 fitted and fixed to the shaft 4. A magnet 5a is provided on the outer peripheral surface of the rotor core 5. The magnet 5a forms a surface magnetic flux on the outer peripheral surface of the rotor core 5. Note that the magnet 5a is not limited to being provided on the outer peripheral surface of the rotor core 5, and may be embedded near the outer peripheral surface of the rotor core 5, for example.

[0017] <Stator> The stator 2 includes a stator case 6 that forms the outer shell of the stator 2, a stator core 7 that is fitted into the stator case 6, and a coil 8 that is wound around the stator core 7. The stator case 6 is made of a metal material and has a cylindrical portion 6a having a cross section along the radial direction that is a rounded regular hexagon. One end of the shaft 4, for example, is rotatably supported by the stator case 6.

[0018] The stator core 7 is formed by stacking a plurality of stator core plates 13 (see FIG. 2) that are punched by pressing electromagnetic steel sheets. The stator core 7 is formed by integrally molding a back yoke 11 formed in a cylindrical shape with rounded corners and a regular hexagon to correspond to the shape of the stator case 6, and a plurality of teeth 12 (six in this embodiment) that protrude radially inward from the back yoke 11. A coil 8 is wound around each tooth 12 from above an insulator 9, for example, by a concentrated winding method.

[0019] Here, the stator core 7 is formed by connecting a plurality of (six in this embodiment) split cores 10, each divided into teeth 12, in an annular shape. The split cores 10 are divided in the circumferential direction by cutouts 15 and cutouts 16 formed in each corner 11a of the back yoke 11. The cutouts 15 are formed on the radially inner side of each corner 11a of the back yoke 11. The cutouts 16 are formed across the entire radial direction of each corner 11a of the back yoke 11. The cutouts 15 and cutouts 16 will be described in detail later.

[0020] The split core 10 is composed of a split back yoke 14 that extends linearly in the axial direction along the inner surface of the stator case 6, and one tooth 12 that protrudes radially inward from the circumferential center of the split back yoke 14. When viewed in the axial direction, the extension direction of the tooth 12 is perpendicular to the extension direction of the split back yoke 14. Of the circumferential ends of each split back yoke 14, the radially outer side of the location where the cutout portion 15 is formed functions as a connecting portion 17 that connects adjacent split cores 10 in the circumferential direction.

[0021] <Stator manufacturing method> Next, a method for manufacturing the stator 2 will be described. First, a method for manufacturing the stator core 7 will be described. Fig. 2 is a plan view of the stator core plate 13. Fig. 3 is an enlarged view of part III in Fig. 2. Fig. 4 is an enlarged view of part IV in Fig. 2.

[0022] 2 to 4, first, a press is applied to an electromagnetic steel sheet P to punch out the stator core plate 13 (punching process). The punching is performed by applying a shearing process using a press. The stator core plate 13 in the punching process is formed by integrating an annular back yoke plate 18 in the shape of a rounded regular hexagon with a plurality of (six in this embodiment) tooth plates 19 that protrude radially inward from the inner peripheral edge of the back yoke plate 18.

[0023] In the punching process, a plurality of bosses 21 are formed on the stator core plate 13 by protruding a portion of the stator core plate 13 in the thickness direction. The plurality of bosses 21 are formed by drawing using a press. The bosses 21 are arranged on, for example, the tooth plate 19. The bosses 21 of each stator core plate 13 are fitted together in the thickness direction when the stator core plates 13 are stacked. This integrates the stacked stator core plates 13.

[0024] In the punching process, void holes 22 are formed in all but one of the multiple (six in this embodiment) corners 18a of the back yoke plate 18 (i.e., between adjacent tooth plates 19 in the circumferential direction). The void holes 22 are formed by shearing using a press. The void holes 22 are disposed at approximately the center of the corners 18a in the circumferential direction and at approximately the center in the radial direction. The void holes 22 are used in the cutting process, which will be described later.

[0025] Next, the cutout portions 15 are formed by pressing the portions of the back yoke plate 18 where the waste holes 22 are formed, and the corner portions 18a where the waste holes 22 are not formed are also pressed to form the cutout portions 16 (cutting process). The cutout portions 15 and the cutout portions 16 are formed by shearing the plate using press working. The notch 15 is formed along the radial direction from the circumferential center of the inner peripheral edge of the corner 18a to the waste hole 22. The formation of the waste hole 22 prevents cracks from forming along the entire radial direction of the corner 18a due to the notch 15. The cut-off portion 16 is formed at the circumferential center of the corner 18a and along the entire radial direction of the corner 18a.

[0026] By forming the cutout portions 15 and the cut-off portions 16, split back yoke plates 23 are formed by splitting the back yoke plate 18 in the circumferential direction. One tooth plate 19 is formed in the circumferential center of each split back yoke plate 23, protruding radially inward from the inner peripheral edge. The split back yoke plates 23 and the tooth plates 19 form split core plates 20. Circumferentially adjacent split core plates 20 are connected via the radially outer sides of the discard holes 22. The radially outer portions of the discard holes 22 function as connecting portions 17 that connect circumferentially adjacent split core plates 20. Meanwhile, at the cut-off portions 16, the split core plates 20 on either side of the cut-off portion 16 are completely separated from each other.

[0027] The cut-out portions 15 and the cut-off portions 16 are formed by shearing, so that the split back yoke plates 23 on both sides of the cut-out portions 15 and the cut-off portions 16 are cut and raised in opposite directions. For this reason, after the cutting process, a press process is performed to push back the cut-and-raised portions and flatten the split back yoke plates 23 (cut-and-raise return process). Next, the plurality of stator core plates 13 are stacked (stacking step). The stacked plurality of divided core plates 20 form a plurality of divided cores 10 (see FIG. 1). The stator core 7 is formed from these divided cores 10.

[0028] FIG. 5 is a development view of the stator core 7. As shown in FIG. As shown in Fig. 5, after the lamination process, the separation portions 16 are opened to separate the stator core 7, and the cut portions 15 are opened to unfold the stator core 7 (unfolding process). In the unfolding process, the split back yokes 14 are unfolded so that they are aligned in a straight line. As a result, the teeth 12 are aligned in a direction perpendicular to the direction in which the teeth 12 protrude from the split back yokes 14.

[0029] Here, because the split back yokes 14 extend linearly when viewed in the axial direction, it is easy to unfold the stator core 7 in the unfolding process. By arranging the split back yokes 14 linearly after unfolding, it is also easy to align the teeth 12 in one direction. By unfolding stator core 7, the intervals between teeth 12 can be made wider than when split cores 10 are connected in an annular shape.

[0030] Next, with the stator core 7 unfolded, the coil 8 is wound around each tooth 12 from above the insulator 9 (see Figure 1) using a concentrated winding method (winding process). Since the spacing between each tooth 12 is wider than when the split cores 10 are connected in an annular shape, the coil 8 can be easily wound around each tooth 12.

[0031] Next, the split core 10 (back yoke 11) is returned to its annular shape (expanding back process). That is, the cut-off portions 16, which are both ends of the back yoke 11 in the circumferential direction, are butted against each other. Here, the cut portions 15 and cut-off portions 16 formed in the back yoke 11 are formed when the back yoke 11 was originally in a ring-shaped state, so when the back yoke 11 is returned to its ring-shaped state by the unfolding and returning process, no gaps are formed between the divided back yokes 14.

[0032] After the back yoke 11 is returned to its annular shape, the stator core 7 is inserted or press-fitted into the stator case 6. By inserting the stator core 7 into the stator case 6 and bonding or press-fitting it, the annular state of the back yoke 11 is maintained. This completes the manufacture of the stator 2.

[0033] As described above, in the first embodiment, the manufacturing process of the stator 2 includes a punching process, a cutting process, a cutting and raising process, a stacking process, an unfolding process, a winding process, and an unfolding and returning process. After punching out the annular back yoke plate 18, the cut portions 15 and the cut-off portions 16 are formed in the back yoke plate 18, and the back yoke 11 is unfolded. This prevents gaps from being formed between adjacent split back yokes 14 in the circumferential direction due to manufacturing errors, and prevents excessive localized pressure from being applied to the split back yokes 14, when the back yoke 11 is returned to its annular shape. Moreover, because the cut portions 15 and the cut-off portions 16 are formed by shearing, no cutting allowance is required when forming the cut portions 15 and the cut-off portions 16. This allows the stator core 7 to be manufactured with high precision.

[0034] Furthermore, since the stator core 7 is expanded by forming the cut portions 15, the back yoke 11 is not completely divided into individual teeth 12. In addition, since the stator core 7 can be manufactured with high precision, the stator core 7 can be easily assembled in the expansion and return process. While improving the manufacturing precision of the stator core 7, it is also possible to improve the assembly of the stator core 7 (stator 2), which will make it possible to contribute to Goal 7 of the Sustainable Development Goals (SDGs) led by the United Nations, which is to "Ensure access to affordable, reliable, sustainable and modern energy for all," and Goal 9, which is to "Build resilient infrastructure, promote inclusive and sustainable industrialization, and foster innovation."

[0035] The stator case 6 and the stator core 7 are formed in a cylindrical shape with rounded corners, a regular hexagon, when viewed from the axial direction. This allows the radial width of the brushless motor 1 to be made as small as possible compared to when the stator case 6 and the stator core 7 are cylindrical. This allows the brushless motor 1 to be made flat. Furthermore, because the split back yokes 14 extend linearly when viewed in the axial direction, the stator core 7 can be easily unfolded during the unfolding process. By arranging the split back yokes 14 linearly after unfolding, the teeth 12 can also be easily aligned in one direction. This improves the manufacturing efficiency of the stator 2.

[0036] In the above-described first embodiment, the annular state of the back yoke 11 is maintained by inserting or press-fitting the stator core 7 into the stator case 6. However, this is not limited to this, and after the detached portions 16 that are both circumferential ends of the back yoke 11 are butted together in the unfolding and returning process, the detached portions 16 may be welded to maintain the annular state of the back yoke 11.

[0037] In the first embodiment described above, the expanding process is performed after the laminating process in the method for manufacturing the stator 2. However, the present invention is not limited to this, and the expanding process may be performed first to expand each stator core plate 13, and then the laminating process may be performed.

[0038] [Second embodiment] Next, a second embodiment of the present invention will be described with reference to Figures 6 to 9, with reference to Figure 1. In the following figures, the same aspects as those of the first embodiment described above will be given the same reference numerals, and the description thereof will be omitted. FIG. 6 is a side view of a stator core 207 according to the second embodiment. In the second embodiment, the basic configuration of the brushless motor 1 is the same as that of the first embodiment described above, in that it comprises an annular stator 202, a rotor 3 arranged radially inside the stator 202 and supported rotatably relative to the stator 202, and the stator 202 comprises a stator core 207 and a coil 8 wound around the stator core 207.

[0039] As shown in Figure 6, the difference between the first embodiment and the second embodiment is that the stator core 7 of the first embodiment is formed by stacking multiple stator core plates 13 of one type, while the stator core 207 of the second embodiment is formed by stacking multiple stator core plates 213a, 213b of two types (first stator core plate 213a, second stator core plate 213b) one by one in a staggered manner.

[0040] Fig. 7 shows the first stator core plate 213a, with (a) being a plan view and (b) being a development view. Fig. 8 shows the second stator core plate 213b, with (a) being a plan view and (b) being a development view. Figs. 7(a) and 8(a) correspond to the above-mentioned Fig. 2. Figs. 7(b) and 8(b) correspond to the above-mentioned Fig. 5. 7(a) and 7(b), in the first stator core plate 213a, a plurality of (six in this embodiment) first separate core plates 220a are connected to each other via connecting portions 17. On the other hand, the two first separate core plates 220a having the first separation portion 216a are completely separated from each other.

[0041] Here, the difference between the stator core plate 13 in the first embodiment described above and the first stator core plate 213a in this second embodiment is that the formation positions of the cut-off portions 16 in the first embodiment and the formation positions of the first cut-off portions 216a in the second embodiment are different. That is, in the first stator core plate 213a, the first cut-off portions 216a are not formed along the radial direction at the circumferential center of the corners 18a. The first cut-off portions 216a of the first stator core plate 213a extend obliquely in the radial direction from the circumferential center of the inner peripheral edge of the corners 18a, and reach the outer peripheral edge of the corners 18a.

[0042] More specifically, first cut-off portion 216a is formed along the extending direction of the inner peripheral edge of one of two first separate back yoke plates 223a located on either side of first cut-off portion 216a. As a result, the two first separate back yoke plates 223a having first cut-off portion 216a each have a long first separate back yoke plate 24a and a short first separate back yoke plate 24b that protrude from the corresponding teeth plate 19 toward each other and have different circumferential lengths.

[0043] The length La from the corresponding tooth plate 19 to the first cut-off portion 216a in the long first separate back yoke plate 24a (hereinafter simply referred to as the length La of the long first separate back yoke plate 24a) is longer than the length Lb from the corresponding tooth plate 19 to the first cut-off portion 216a in the short first separate back yoke plate 24b (hereinafter simply referred to as the length Lb of the short first separate back yoke plate 24b). A connecting boss 221 is formed on the circumferential end of the long first separate back yoke plate 24a near the first cut-off portion 216a.

[0044] 8(a) and 8(b), the basic configuration of the second stator core plate 213b is the same as that of the first stator core plate 213a. That is, in the second stator core plate 213b, a plurality of (six in this embodiment) second separate core plates 220b are connected to each other via connecting portions 17. On the other hand, the two second separate core plates 220b having the second separation portions 216b are completely separated from each other.

[0045] Here, similar to the first cut-off portions 216a of the first stator core plate 213a, the second cut-off portions 216b of the second stator core plate 213b also extend obliquely in the radial direction from the circumferential center of the inner peripheral edge of the corner 18a and reach the outer peripheral edge of the corner 18a. However, when viewed from the same direction as the first stator core plate 213a, the orientation of the second cut-off portions 216b of the second stator core plate 213b is symmetrical to the orientation of the first cut-off portions 216a of the first stator core plate 213a, with the circumferential center of the corner 18a as the center.

[0046] For this reason, when the second stator core plate 213b is viewed from the same direction as the first stator core plate 213a, the short second separate back yoke plate 25b is formed on the side of the first stator core plate 213a where the long first separate back yoke plate 24a is formed. The long second separate back yoke plate 25a is formed on the side of the first stator core plate 213a where the short first separate back yoke plate 24b is formed.

[0047] The length Lc from the corresponding tooth plate 19 in the long second separate back yoke plate 25a to the second separation portion 216b (hereinafter simply referred to as the length Lc of the long second separate back yoke plate 25a) is the same as the length La of the long first separate back yoke plate 24a. The length Ld from the corresponding tooth plate 19 in the short second separate back yoke plate 25b to the second separation portion 216b (hereinafter simply referred to as the length Ld of the short second separate back yoke plate 25b) is the same as the length Lb of the short second separate back yoke plate 25b. A connecting boss 221 is formed on the circumferential end of the long second separate back yoke plate 25a near the second separation portion 216b.

[0048] <Stator manufacturing method> Next, a method for manufacturing the stator 202 in the second embodiment will be described. In the second embodiment, the method of manufacturing the stator 202 is similar to that of the first embodiment in that it includes a punching step, a cutting step, a cutting and restoring step, a stacking step, an unfolding step, a winding step, and an unfolding and restoring step. Here, in the second embodiment, the unfolding step is performed before the stacking step. In the stacking step, the first stator core plates 213a and the second stator core plates 213b are stacked one by one in a staggered manner.

[0049] FIG. 9 is a side view of stator core 207 after the lamination process. As shown in FIG. 9, in the stator core 207 after the stacking process but before the unfolding / restoring process (hereinafter simply referred to as before the unfolding / restoring process), at one longitudinal end (the left end in FIG. 9) having the second cut-off portion 216b, one long first divided back yoke plate 24a and one short second divided back yoke plate 25b are stacked one on top of the other. In the stator core 207 before the unfolding and returning process, at the other longitudinal end portion (the right end portion in Figure 9) having the second cut-off portion 216b, the short first divided back yoke plate 24b and the long second divided back yoke plate 25a are stacked one by one in a staggered manner.

[0050] Therefore, before the unfolding / returning process, a first recess 26a is formed between the axially aligned long first divided back yoke plates 24a at one longitudinal end of the stator core 207. Before the unfolding / returning process, a second recess 26b is formed between the axially aligned long second divided back yoke plates 25a at the other longitudinal end of the stator core 207.

[0051] In the unfolding / returning process, the long second separate back yoke plate 25a is inserted into the first recess 26a, and the second cut-off portion 216b of this long second separate back yoke plate 25a is brought into contact with the second cut-off portion 216b of the short second separate back yoke plate 25b. At the same time, the long first separate back yoke plate 24a is inserted into the second recess 26b, and the first cut-off portion 216a of this long first separate back yoke plate 24a is brought into contact with the first cut-off portion 216a of the short first separate back yoke plate 24b.

[0052] At this time, the long first separate back yoke plate 24a and the long second separate back yoke plate 25a are inserted into the corresponding recesses 26a, 26b while undergoing slight elastic deformation so as to ride up onto each other's connecting bosses 221. Then, when the respective cut-off portions 216a, 216b abut against each other, the connecting bosses 221 of the long first separate back yoke plate 24a and the connecting bosses 221 of the long second separate back yoke plate 25a overlap in the axial direction (thickness direction) and are fitted together. This completes the manufacture of the stator 2.

[0053] Here, the cut-off portions 216a, 216b of each stator core plate 213a, 213b extend obliquely in the radial direction from the circumferential center of the inner peripheral edge of the corner 18a to the outer peripheral edge of the corner 18a. The cut-off portions 216a, 216b are formed along the extending direction of the inner peripheral edge of one of the two separate back yoke plates 223a, 223b. Therefore, when the first cut-off portions 216a butt against each other in the unfolding / returning process, the long first separate back yoke plate 24a restricts the radially outward movement of the short first separate back yoke plate 24b (see FIG. 7(a)). Furthermore, in the unfolding and returning process, when the second detached portions 216b butt against each other, the long second separate back yoke plates 25a restrict the radially outward movement of the short second separate back yoke plates 25b (see FIG. 8(a)).

[0054] Therefore, the second embodiment described above achieves the same effects as the first embodiment. In addition, the long first separate back yoke plates 24a and the short second separate back yoke plates 25b are stacked alternately, one by one. The short first separate back yoke plates 24b and the long second separate back yoke plates 25a are stacked alternately, one by one. Furthermore, connecting bosses 221 are formed on the long first separate back yoke plates 24a and the long second separate back yoke plates 25a, respectively, and these connecting bosses 221 are overlapped in the axial direction to connect the ends including the separation portions 216a, 216b. Therefore, without using the stator case 6 as in the first embodiment, the stator core 207 can be maintained in an annular shape, improving the manufacturing efficiency of the stator 202.

[0055] Furthermore, recesses 26a, 26b are formed in every other one of the stator core plates 213a, 213b, and the long first separate back yoke plate 24a and the long second separate back yoke plate 25a are inserted into these recesses 26a, 26b. Because the separate back yoke plates 24a, 25a are arranged one at a time, the separate back yoke plates 24a, 25a can be easily elastically deformed during the unfolding and returning process. Therefore, the long first separate back yoke plate 24a and the long second separate back yoke plate 25a can be inserted into the corresponding recesses 26a, 26b while undergoing slight elastic deformation so as to ride over each other's connecting bosses 221. This allows the ends of the stator core plates 213a, 213b, including the cut-off portions 216a, 216b, to be easily connected together, further improving the workability of manufacturing the stator 202.

[0056] The connecting bosses 221 are used as a means for easily connecting the ends of the stator core plates 213a, 213b, including the cut-off portions 216a, 216b. This makes it possible to inexpensively and reliably connect the ends of the stator core plates 213a, 213b, including the cut-off portions 216a, 216b. The use of the connecting bosses 221 makes it easier for the long first separate back yoke plate 24a and the long second separate back yoke plate 25a to ride over each other's connecting bosses 221.

[0057] [Modification of the second embodiment] FIG. 10 is a partially enlarged cross-sectional view of the boss 21 in a modified example of the second embodiment. 10, the connecting bosses 221 formed on the long first separate back yoke plate 24a and the long second separate back yoke plate 25a may be formed so that the protruding height H gradually decreases toward the insertion direction of the recesses 26a, 26b. In other words, the protruding height H of the connecting bosses 221 is lower on the side that receives the long first separate back yoke plate 24a or the long second separate back yoke plate 25a than on the opposite side.

[0058] This configuration makes it easier to insert the long first divided back yoke plate 24a and the long second divided back yoke plate 25a into the recesses 26a, 26b. It also makes it easier for the long first divided back yoke plate 24a and the long second divided back yoke plate 25a to ride over each other's connecting bosses 221.

[0059] In the second embodiment described above, the connecting boss 221 is used as a means for connecting the ends of the stator core plates 213a, 213b including the cut-off portions 216a, 216b. However, this is not limiting, and any configuration may be used as long as it can engage the ends of the stator core plates 213a, 213b including the cut-off portions 216a, 216b. For example, a hook-shaped claw may be formed to engage the ends of the stator core plates 213a, 213b including the cut-off portions 216a, 216b.

[0060] In the second embodiment described above, the length Lc of the long second separate back yoke plate 25a is the same as the length La of the long first separate back yoke plate 24a. The length Ld of the short second separate back yoke plate 25b is the same as the length Lb of the short first separate back yoke plate 24b. However, this is not limited to this, and the lengths La and Lc may be different. The lengths Lb and Ld may be different. It is sufficient that the length La of the long first separate back yoke plate 24a and the length Lb of the short first separate back yoke plate 24b are different. It is sufficient that the length Lc of the long second separate back yoke plate 25a and the length Ld of the short second separate back yoke plate 25b are different.

[0061] The present invention is not limited to the above-described embodiment, and includes various modifications to the above-described embodiment without departing from the spirit of the present invention. For example, in the above embodiment, the brushless motor 1 is described as a drive source for electrical equipment (such as power windows, sunroofs, and power seats) mounted on a vehicle. However, the present invention is not limited to this, and the brushless motor 1 can be used as a drive source for various electrically powered devices.

[0062] In the above-described embodiment, the brushless motor 1 has been described as having six teeth 12. The stator case 6 has been described as having a cylindrical portion 6a whose radial cross section is a rounded regular hexagon. The stator core 7, 207 has been described as having a back yoke 11 formed in a cylindrical shape with a rounded regular hexagon to match the shape of the stator case 6. However, this is not limited to this, and the back yoke 11 of the stator case 6 or the stator core 7, 207 may be cylindrical. The back yoke 11 of the stator case 6 or the stator core 7, 207 may also be cylindrical. The number of teeth 12 is also not limited to six. The cylindrical polygonal shape may be changed depending on the number of teeth 12. [Explanation of symbols]

[0063] 1...brushless motor, 2...stator, 3...rotor, 4...shaft, 5...rotor core, 6...stator case, 6a...tubular portion, 7...stator core, 8...coil, 10...split core, 11...back yoke, 11a...each corner portion, 12...teeth, 13...stator core plate, 14...split back yoke, 15...notch portion, 16...separation portion, 17...connection portion, 18...back yoke plate, 18a...corner portion, 19...teeth plate, 20...split core plate, 21...boss, 22...empty hole, 23...split back yoke plate, 24a...long first split back yoke plate Plate, 24b...short first divided back yoke plate, 25a...long second divided back yoke plate, 25b...short second divided back yoke plate, 26a...first recess, 26b...second recess, 202...stator, 207...stator core, 213a...first stator core plate, 213b...second stator core plate, 216a...first separation portion, 216b...second separation portion, 220a...first divided core plate, 220b...second divided core plate, 221...connecting boss, 223a...first divided back yoke plate, 223b...second divided back yoke plate

Claims

1. A punching process for punching out from an electromagnetic steel sheet a polygonal stator core plate having an annular back yoke plate made of polygonal, linear split back yoke plates with the same number of corners as the number of squares, and a plurality of tooth plates protruding radially inward from the inner peripheral edge of each split back yoke plate; a cutting step of, after the punching step, performing a shearing process between the teeth plates adjacent to each other in the circumferential direction of the back yoke plate to form a cut-off portion at only one location of the back yoke plate, and forming cut-off portions at locations other than the cut-off portion so that the back yoke plate will not be cut off; a cut-and-raise returning step of pushing back and flattening portions of the back yoke plate that have been cut and raised due to the formation of the cut portions after the cut-and-raise step; a lamination step of laminating the plurality of stator core plates after the cutting-and-raising step to form a polygonal cylindrical stator core having a back yoke made up of the plurality of stacked back yoke plates and teeth made up of the plurality of stacked tooth plates; an unfolding step of unfolding the stator core plate after the cutting and restoring step or the stacking step, by unfolding the separation portions and opening the cut portions so that the tooth plates are aligned in a direction intersecting the protruding direction of the tooth plates and the back yoke plate is linear; a winding step of winding a coil around the teeth after the expanding step; a rolling-back process for rolling the back yoke back into a polygonal cylindrical shape after the rolling-back process; have A stator manufacturing method comprising:

2. In the cutting step, the separation portion is formed at a position shifted from the center between the adjacent tooth plates in the circumferential direction, thereby making the lengths from the two tooth plates located on either side of the separation portion to the separation portion different from each other, thereby forming a long back yoke plate having a long length from one of the two tooth plates to the separation portion, and a short back yoke plate having a shorter length from the other of the two tooth plates to the separation portion than the long back yoke plate, In any one of the punching step, the cutting step, and the cutting and restoring step, an engagement portion is formed in the vicinity of the cut-off portion at a location that will become the long back yoke plate, The lamination step is performed after the spreading step, In the stacking step, the stator core plates are stacked such that the long back yoke plates and the short back yoke plates are alternately arranged one by one, In the unfolding / returning step, the engaging portions that overlap in the axial direction are engaged with each other, thereby connecting the end portions of the stacked back yoke plates where the separation portions are formed.

2. The method for manufacturing a stator according to claim 1.

3. The engaging portion is a boss formed by protruding a part of the back yoke plate in the thickness direction.

3. The method for manufacturing a stator according to claim 2.

4. a first stator core plate formed by connecting a plurality of first divided core plates in an annular shape; a second stator core plate formed by connecting a plurality of second divided core plates in an annular shape; Equipped with A polygonal cylindrical stator core having a plurality of corners, formed by alternately stacking the first stator core plates and the second stator core plates one by one, The first separate core plate is a first separate back yoke plate extending linearly in the circumferential direction; a first teeth plate protruding radially inward from the first separate back yoke plate; and the first stator core plate is formed by connecting circumferential end portions of the first separate back yoke plates that are adjacent in the circumferential direction, The second separate core plate is a second separate back yoke plate extending linearly in the circumferential direction; a second teeth plate protruding radially inward from the second split back yoke plate; and the second stator core plate is formed by connecting circumferential end portions of the second divided back yoke plates adjacent to each other in the circumferential direction, any two of the first divided back yoke plates adjacent to each other in the circumferential direction among the plurality of first divided back yoke plates have a long first divided back yoke plate and a short first divided back yoke plate that protrude from the corresponding first teeth plate toward each other and have different circumferential lengths, the long first separate back yoke plate and the short first separate back yoke plate each have a first cut-off portion extending obliquely with respect to the radial direction from a circumferential center of an inner peripheral edge of the corner portion to an outer peripheral edge of the corner portion, Among the plurality of second divided back yoke plates, a portion that overlaps with the long first divided back yoke plate in the axial direction is defined as a short second divided back yoke plate formed with the same circumferential length as the short first divided back yoke plate, Among the plurality of second divided back yoke plates, a portion that overlaps with the short first divided back yoke plate in the axial direction is defined as a long second divided back yoke plate formed with the same circumferential length as the long first divided back yoke plate, the long second separate back yoke plate and the short second separate back yoke plate each have a second cut-off portion extending obliquely with respect to the radial direction from a circumferential center of an inner peripheral edge of the corner portion to an outer peripheral edge of the corner portion, the long first separate back yoke plate and the long second separate back yoke plate each have an engaging portion formed at a location where they overlap in the axial direction, and are engaged with each other; the first cut-off portion of the long first separate back yoke plate and the first cut-off portion of the short first separate back yoke plate are butted against each other, The second cut-off portion of the long second separate back yoke plate and the second cut-off portion of the short second separate back yoke plate are butted against each other. A stator core characterized by:

5. The engaging portions are bosses formed by protruding portions of the long first separate back yoke plate and the long second separate back yoke plate in the thickness direction.

5. The stator core according to claim 4.

6. The stator core according to claim 4 or 5; a coil wound around the first tooth plate and the second tooth plate of the stator core; a cylindrical case into which the outer peripheral surface of the stator core is fitted, A stator characterized by:

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