Stator core material and method for manufacturing stator core

Abstract

This stator core material includes: a plurality of plate-like core pieces each including an arc-like yoke section and a teeth section extending from the inner circumferential surface of the corresponding yoke section; and belt-like joining pieces each joining the yoke sections of the adjacent core pieces. The longitudinal length of the inner circumferential surface, of each of the joining pieces, adjacent to the yoke section is set to be a length that is shorter than the circumferential length of the outer circumferential surface of the yoke section facing the inner circumferential surface, of the joining piece, adjacent to the yoke section, and that allows at least a portion of the inner circumferential surface of the joining piece to come into surface contact with the outer circumferential surface of the yoke section when the plurality of core pieces are wound and contact surfaces formed at the circumferential ends are brought into contact with each other.

Description

Stator Core Material and Method for Manufacturing Stator Core

[0001] The technology of the present disclosure relates to a stator core material and a method for manufacturing a stator core.

[0002] As a method for manufacturing a stator core that constitutes a rotating electrical machine, for example, an inner rotor type motor, a method of manufacturing an annular stator core by combining a plurality of substantially arc-shaped core pieces is known. Such a method of combining core pieces to manufacture an annular stator core is advantageous from the perspective of material yield compared to a method of punching and forming an annular stator core.

[0003] For example, Japanese Patent Application Laid-Open No. 2007-143257 describes a laminated core in which adjacent segment core pieces mutually connected by a connecting portion formed on the outer peripheral portion are spirally wound and laminated while bending the connecting portion and aligning the side end portions of the segment core pieces.

[0004] The laminated core (in other words, the stator core) manufactured by the method as described in Japanese Patent Application Laid-Open No. 2007-143257 is used as a part of the stator through a process of attaching a coil to the teeth portion, etc. However, the laminated core manufactured by the above method is formed into an annular shape simply by bending the connecting portion. Therefore, an elastic recovery phenomenon, so-called springback, may occur in the connecting portion. Since the springback acts in a direction to release the contact state between the core pieces of the laminated core formed into an annular shape, it has been difficult to convey the laminated core to the next process or the like while maintaining the desired shape.

[0005] The present disclosure provides a stator core material and a method for manufacturing a stator core that can easily maintain the shape of the stator core as a desired shape.

[0006] A stator core material according to a first aspect of the present disclosure includes a plurality of plate-shaped core pieces, each containing an arc-shaped yoke portion and teeth portions extending from the inner circumferential surface of the yoke portion, and a strip-shaped connecting piece connecting the yoke portions of adjacent core pieces, wherein the longitudinal length of the inner circumferential surface of the connecting piece adjacent to the yoke portion is shorter than the circumferential length of the outer circumferential surface of the yoke portion facing the inner circumferential surface of the connecting piece adjacent to the yoke portion, and the length is set such that at least a portion of the inner circumferential surface of the connecting piece makes surface contact with the outer circumferential surface of the yoke portion when the plurality of core pieces are wound together and the contact surfaces formed at the circumferential ends of the yoke portions of adjacent core pieces are brought into contact with each other.

[0007] In such a stator core material, by making the longitudinal length of the connecting piece shorter than the circumferential length of the outer surface of the yoke portion facing the connecting piece, circumferential stress can be generated between the yoke portions when the core pieces are wound. In addition, when the stator core material is in contact with the contact surfaces of the yoke portions of adjacent core pieces, the longitudinal length of the connecting piece is set to a length that allows for surface contact with the outer surface of the yoke portion, thereby applying a circumferential compressive force between the core pieces. Therefore, the molded state of the stator core material can be maintained without using other components such as housings.

[0008] A stator core material according to a second aspect of the present disclosure is a stator core material according to a first aspect of the present disclosure, wherein one end of the connecting piece is connected to the circumferential center of the outer surface of the yoke portion of one of the adjacent core pieces, and the other end is connected to at least one of the end of the outer surface of the yoke portion of the other adjacent core piece and the outer surface end of the contact surface.

[0009] In such a stator core material, a compressive stress of a desired magnitude along the circumferential direction can be applied between the wound core pieces.

[0010] A stator core material according to a third aspect of the present disclosure is a stator core material according to the first aspect of the present disclosure, wherein one end and the other end of the connecting piece are connected to the circumferential center of the outer peripheral surface of the yoke portion of an adjacent core piece.

[0011] In such a stator core material, a compressive stress of a desired magnitude along the circumferential direction can be applied between the wound core pieces.

[0012] A stator core material according to a fourth aspect of the present disclosure is a stator core material according to a second or third aspect of the present disclosure, wherein a bulge is formed on the outer circumferential surface of the yoke portion facing the connecting piece, which bulges radially beyond an arc-shaped reference line connecting the outer circumferential end of the contact surface and the inner circumferential end of the end of the connecting piece connected to the circumferential center on the outer circumferential side of the yoke portion.

[0013] In such a stator core material, the position where the connecting piece and the yoke portion are in surface contact can be adjusted, thereby allowing the pressing force from the connecting piece to be adjusted.

[0014] A stator core material according to a fifth aspect of the present disclosure is a stator core material according to any of the first to fourth aspects of the present disclosure, wherein the connecting piece has a relief groove formed between the inner circumferential end of the end connected to the circumferential center on the outer circumference of the yoke portion and the outer circumferential surface of the yoke portion.

[0015] Such stator core materials facilitate stamping and forming using a die.

[0016] A stator core material according to a sixth aspect of the present disclosure is a stator core material according to any of the first to fifth aspects of the present disclosure, wherein, of the adjacent contact surfaces, one contact surface has a recess that is circumferentially recessed, and the other contact surface has a protrusion that circumferentially protrudes and fits into the recess when a plurality of core pieces are wound around it.

[0017] In such a stator core material, the positioning between adjacent core pieces is stable, and the contact state between contact surfaces can be firmly maintained.

[0018] A method for manufacturing a stator core according to a seventh aspect of the present disclosure includes the steps of: preparing a stator core material comprising a plurality of plate-shaped core pieces including an arc-shaped yoke portion and teeth portions extending from the inner circumferential surface of the yoke portion, and a strip-shaped connecting piece connecting the yoke portions of adjacent core pieces, wherein the longitudinal length of the inner circumferential surface of the connecting piece adjacent to the yoke portion is shorter than the circumferential length of the outer circumferential surface of the yoke portion facing the inner circumferential surface of the connecting piece adjacent to the yoke portion; and winding the stator core material around the plurality of core pieces to bring the contact surfaces formed at the circumferential ends of the yoke portions of adjacent core pieces into contact with each other, thereby bringing at least a portion of the inner circumferential surface of the connecting piece into surface contact with the outer circumferential surface of the yoke portion.

[0019] In this method of manufacturing stator cores, the longitudinal length of the connecting piece is shorter than the circumferential length of the outer surface of the yoke portion facing the connecting piece, thereby generating circumferential stress between the yoke portions when the core pieces are wound. In addition, the contact surfaces of the yoke portions of adjacent core pieces of the stator core material are brought into contact with each other, and the connecting piece is brought into surface contact with the outer surface of the yoke portion. As a result, a circumferential compressive force can be applied between the core pieces. Consequently, the molded state of the stator core material can be maintained without using other components such as housings.

[0020] According to the stator core material and stator core manufacturing method described above, it is possible to easily maintain the shape of the stator core in a desired shape.

[0021] This is a schematic plan view showing an example of a stator core material according to the first embodiment. This is an enlarged view of part A in Figure 1. This is a schematic plan view showing an example of a stator core formed using the stator core material shown in Figure 1. This is an enlarged view of part B in Figure 3. This is an enlarged view corresponding to Figure 2 showing one modified example of the stator core material shown in Figure 1. This is an enlarged view corresponding to Figure 2 showing another modified example of the stator core material shown in Figure 1. This is an enlarged view of Figure 2 showing yet another modified example of the stator core material shown in Figure 1. This is an enlarged view of a key part a flowchart showing an example of a method for manufacturing a stator core according to the first embodiment. This is a perspective view showing an example of a bending jig used for forming the stator core material shown in Figure 1. This is a schematic plan view showing an example of a stator core material according to the second embodiment. This is an enlarged view of part C in Figure 10. This is a schematic plan view showing an example of a stator core formed using the stator core material shown in Figure 10. This is an enlarged view corresponding to Figure 11 showing one modified example of the stator core material shown in Figure 10. This is an enlarged view of a key part showing another modified example of the stator core material shown in Figure 10. Figure 10 is an enlarged view of a key part showing another modified example of the stator core material.

[0022] This application is based on Japanese Patent Application No. 2024-172728, filed in Japan on 1 October 2024, and Japanese Patent Application No. 2025-006390, filed in Japan on 16 January 2025, the contents of which form part of the content of this application. The disclosure can be understood more fully by the following detailed description. Further applications of this application will become clear from the following detailed description. However, the detailed description and specific examples are preferred embodiments of the disclosure and are described for illustrative purposes only, for various changes and modifications will be obvious to those skilled in the art within the spirit and scope of the disclosure from this detailed description. The applicant has no intention of dedicating any of the described embodiments to the public, and any disclosed modifications and alternatives, even those not literally included in the claims, are also part of the invention under the doctrine of equivalents. Similar reference numbers and names in various drawings indicate similar elements.

[0023] The following describes various embodiments for implementing this disclosure with reference to the drawings. In the following, only the necessary parts for explaining the objectives of this disclosure are schematically shown, and the explanation will primarily focus on the parts necessary for explaining the relevant sections of this disclosure. Any parts omitted from the explanation will be considered to be based on prior art. Furthermore, identical or equivalent components in the drawings are denoted by the same or similar reference numerals, and redundant explanations are omitted. Additionally, if multiple identical or equivalent components are included in the drawings, reference numerals may be assigned to only some of them for clarity.

[0024] <First Embodiment> Figure 1 is a schematic plan view showing an example of a stator core material according to the first embodiment. Note that Figure 1 shows the state of the stator core material 1 before molding, and only a part of it is shown. In this embodiment, the stator core material 1 that constitutes the stator core as a component of the stator that constitutes an inner rotor type motor will be described exemplarily. As shown in Figure 1, the stator core material 1 according to this embodiment includes a plurality of core pieces 2 and connecting pieces 5 that connect adjacent core pieces 2.

[0025] The stator core material 1 described above can be formed by punching out a strip of electromagnetic steel sheet, for example, with a thickness of about 0.1 to 1.0 mm, using a die (not shown). The number of core pieces 2 included in the stator core material 1 and their circumferential lengths can be adjusted as appropriate according to the size of the stator core to be manufactured.

[0026] The core piece 2 may include a yoke portion 3 formed in an arc shape and a plurality of teeth portions 4 (six in Figure 1) extending inward from the inner circumferential surface of the yoke portion 3 at predetermined intervals. The spaces between adjacent teeth portions 4 function as slots around which a coil (not shown) is wound. The number of teeth portions 4 formed on a single core piece 2 is not particularly limited and can be changed as appropriate. Furthermore, the above-mentioned yoke portion 3 being "arc-shaped" means that the overall shape of the yoke portion 3 is substantially arc-shaped, and for example, it includes cases where a part of the yoke portion 3 is not arc-shaped.

[0027] Furthermore, the outer circumferential surface 3A of the yoke portion 3 of the core piece 2, which includes the configuration described above, may be provided with a projection 6 for connecting the connecting piece 5. In this embodiment, the projection 6 is exemplified as being located at the circumferential center of the outer circumferential surface 3A of the yoke portion 3 of the core piece 2. The circumferential center here refers to the arc length center position of the outer circumferential surface 3A of the yoke portion 3. In addition, both longitudinal ends of the yoke portion 3 constitute contact surfaces 7 that come into contact with similar portions of the yoke portion 3 of other adjacent core pieces 2 during molding, as described later. Moreover, notches (not shown) may be provided at appropriate locations on the outer circumferential side of the yoke portion 3 or the connecting piece 5 for positioning the stator core manufactured by molding the stator core material 1 described above, or for use as a welding part when welding stator cores together.

[0028] Figure 2 is an enlarged view of section A in Figure 1. The connecting piece 5 is composed of a strip-shaped member that connects adjacent core pieces 2. The longitudinal ends 5E, 5E of the connecting piece 5 may be connected to protrusions 6 formed on the yoke portion 3 of the adjacent core piece 2, as shown in Figure 2. In this embodiment, the connecting piece 5 is exemplified as a strip-shaped member with a uniform width and thickness, but the shape of the connecting piece 5 may be partially modified. For example, the connecting piece 5 may be made thinner or narrower in one or more places so that it can be easily bent when forming the stator core, which will be described later. In Figure 2, in order to distinguish between the left and right core pieces 2, for the sake of explanation, the left core piece 2 in Figure 2 is shown as "core piece 2-1" and the right core piece 2 is shown as "core piece 2-2". In addition, the components of each core piece 2-1 and 2-2 are distinguished by being assigned similar sub-numbers as appropriate. The two ends 5E, 5E described above are examples of "one end" and "the other end".

[0029] Furthermore, it is preferable that a relief groove 8 is formed between the end 5E of the connecting piece 5 and the outer circumferential surface 3A of the yoke portion 3, specifically between the inner circumferential end P1 of the end 5E connected to the yoke portion 3 and the outer circumferential surface 3A of the yoke portion 3. The relief groove 8 can be composed of a groove having a predetermined width that extends in the circumferential direction. By providing such a relief groove 8, the molding of the stator core material 1 can be facilitated. Note that the reference numeral VL shown in Figure 2 indicates a reference line showing the position of the inner circumferential surface 5A of the connecting piece 5 when the stator core material 1 is molded into an annular shape.

[0030] Figure 3 is a schematic plan view showing an example of a stator core formed using the stator core material shown in Figure 1. The stator core material 1, which includes the above-described configuration, can be formed into an annular shape in plan view as shown in Figure 3 by bending the connecting piece 5 and winding a plurality of core pieces 2 to bring adjacent contact surfaces 7 of the plurality of core pieces 2 into contact with each other. In Figure 3, an example is shown in which an annular shape is formed by arranging 8 × n pieces (n = 1, 2, 3...) of core pieces 2 in concentric circles. When the number of core pieces 2 included in the stator core material 1 is 8 × 2 or more, the stator core material 1 is formed by bending the connecting piece 5 and winding a plurality of core pieces 2 in a spiral shape and stacking them. The stator core material 1A formed into an annular shape in this way can be used as a stator core or as one of the components constituting a stator core.

[0031] In addition, for example, when the core pieces 2 described above are wound spirally and laminated, crimped portions may be formed at appropriate locations on the core pieces 2, or an adhesive may be interposed between the layers, in order to connect the core pieces 2 of each layer. Alternatively, grooves for welding may be provided at appropriate locations on the core pieces 2.

[0032] In this embodiment, the stator core material 1 adjusts the longitudinal length of the connecting piece 5 in order to prevent the molded core pieces 2 from separating due to the springback described above. Specifically, in this embodiment, the stator core material 1 adjusts the longitudinal length L1 of the inner circumferential surface 5A of the connecting piece 5, which is adjacent to the yoke portion 3, to be shorter than the circumferential length L2 of the outer circumferential surface 3A of the yoke portion 3 that faces the connecting piece 5.

[0033] The circumferential length L2 of the outer surface 3A of the yoke portion 3 facing the aforementioned connecting piece 5 will be explained with reference to Figure 2. In this embodiment, the aforementioned circumferential length L2 refers to the sum of the circumferential length L2-1 from the outer surface 3A-1 of the yoke portion 3-1 of one core piece, for example, core piece 2-1, which is connected to the yoke portion 3-1 of the connecting piece 5, to the contact surface 7-1 that contacts another core piece 2-2 adjacent to core piece 2-1, and the circumferential length L2-2 from the outer surface 3A-2 of the yoke portion 3-2 of core piece 2-2, which is connected to the yoke portion 3-2 of the connecting piece 5, to the contact surface 7-2 that contacts core piece 2-1, in a state where multiple core pieces 2 are wound together as shown in Figure 3 and the contact surfaces 7 of the multiple core pieces 2 are in contact with each other. By adjusting the longitudinal length L1 of the inner circumferential surface 5A of the connecting piece 5 or the circumferential length L2 of the outer circumferential surface 3A of the yoke portion 3 as described above, when the stator core material 1 is formed into an annular shape, circumferential compressive stress can be generated in the yoke portion 3 of the core piece 2. Therefore, the contact state between the contact surfaces 7 of adjacent yoke portions 3 can be maintained. Note that the circumferential lengths L2-1 and L2-2 may be the same length. Furthermore, the adjustment of the longitudinal length L1 of the inner circumferential surface 5A of the connecting piece 5 or the circumferential length L2 of the outer circumferential surface 3A of the yoke portion 3 may be achieved by devising the shape of the inner circumferential surface 5A of the connecting piece 5 or the outer circumferential surface 3A of the yoke portion 3.

[0034] Figure 4 is an enlarged view of section B in Figure 3. In addition to the above-described configuration, the stator core material 1 according to this embodiment has a longitudinal length L1 of the inner circumferential surface 5A of the connecting piece 5 such that when multiple core pieces 2 connected by the connecting piece 5 are wound around it and the contact surfaces 7 of the yoke portions 3 of each core piece 2 are brought into contact with each other, at least a portion of the inner circumferential surface 5A of the connecting piece 5 makes surface contact with the outer circumferential surface of the yoke portion 3. By adjusting the longitudinal length L1 of the connecting piece 5 in this way, and bringing at least a portion of its inner circumferential surface 5A into surface contact with the outer circumferential surface 3A of the yoke portion 3, a pressing force P, shown by the arrow in Figure 4, acts on the yoke portion 3 from the connecting piece 5 toward the contact surface 7. This pressing force P also acts as a compressive stress along the circumferential direction between the contact surfaces 7 of adjacent core pieces 2. This pressing force P acts on the molded stator core material 1A as a stress that resists the springback described above. Therefore, it is possible to suppress the separation of the core pieces 2 of the molded stator core material 1A due to springback after molding. Note that the term "surface contact" here includes surface contact where a small gap is formed, as long as it is substantial surface contact considering manufacturing tolerances.

[0035] As described above, according to the stator core material 1 of this embodiment, when formed into an annular shape, a compressive stress along the circumferential direction and a pressing force P that presses the yoke portion 3 act from the connecting piece 5 to the yoke portion 3. Therefore, these forces prevent the formation of gaps between the contact surfaces 7 of adjacent core pieces 2 due to the action of springback. Thus, the shape of the stator core can be easily maintained in the desired shape.

[0036] Figure 5 is an enlarged view corresponding to Figure 2, showing a modified example of the stator core material shown in Figure 1. In the first embodiment described above, a relief groove 8 is formed between the end 5E of the connecting piece 5 and the outer circumferential surface 3A of the yoke portion 3, but this relief groove 8 can be omitted. Specifically, as shown in the modified example in Figure 5, the inner circumferential end P1 of the connecting piece 5 and the base of the protrusion 6 on the outer circumferential surface 3A of the yoke portion 3 may coincide. In this case, when the stator core material 1 is formed into an annular shape, the inner circumferential surface 5A of the connecting piece 5 and the outer circumferential surface 3A of the yoke portion 3 are in substantially total surface contact.

[0037] Figures 6A and 6B are enlarged views corresponding to Figure 2, showing other modified examples of the stator core material shown in Figure 1. In the first embodiment described above, the outer circumferential surface 3A of the yoke portion 3 extends along an arc-shaped reference line VL connecting the outer circumferential end of the contact surface 7 and the inner circumferential end P1 of the end 5E of the connecting piece 5 connected to the yoke portion 3, except for the portion in which the relief groove 8 is formed. However, the shape of the outer circumferential surface 3A can be changed as appropriate. Specifically, a bulge 9 that bulges radially beyond the reference line VL may be formed on the outer circumferential surface 3A of the yoke portion 3 facing the connecting piece 5.

[0038] The bulge 9 may be formed on the entire outer circumferential surface 3A of the yoke portion, or it may be formed on only a part of the outer circumferential surface 3A. Specifically, for example as shown in Figure 6A, one or more bulges 9A can be provided on the outer circumferential surface 3A at a position adjacent to the inner circumferential end P1 of the end 5E of the connecting piece 5 connected to the yoke portion 3. Alternatively, for example as shown in Figure 6B, one or more bulges 9B can be provided at a position adjacent to the outer circumferential end of the contact surface 7.

[0039] By adopting the bulging portion 9 described above, the circumferential length of the outer surface 3A of the yoke portion 3 is substantially extended, making it easier to bring the inner surface 5A of the connecting piece 5 and the outer surface 3A of the yoke portion 3 into surface contact when the stator core material 1 is formed into an annular shape.

[0040] Figures 7A and 7B show yet another modification of the stator core material shown in Figure 1, and are enlarged views of the main parts where the contact surfaces of adjacent core pieces are located. In the first embodiment described above, the contact surface 7 is exemplified as being composed of a plane extending along the radial direction when the stator core material 1 is formed into an annular shape, but the shape of the contact surface 7 can be changed. Specifically, as shown in Figures 7A and 7B, it is preferable that one of the adjacent contact surfaces includes a recess that is indented in the circumferential direction, and the other contact surface includes a convex portion that protrudes in the circumferential direction and fits into the recess when multiple core pieces are wound around it. In the example shown in Figure 7A, the contact surface 7A of the core piece 2 on the left side of the figure constitutes one contact surface including the recess, and the contact surface 7B of the core piece 2 on the right side of the figure constitutes the other contact surface including the convex portion. Furthermore, in the example shown in Figure 7B, the contact surface 7C of the core piece 2 on the left side of the figure constitutes the other contact surface including the convex portion, and the contact surface 7D of the core piece 2 on the right side of the figure constitutes the other contact surface including the concave portion.

[0041] As described above, by employing recesses and protrusions that interlock with each other when the core pieces 2 are wound around the contact surfaces 7A and 7B, the positioning of the core pieces 2 can be stably performed, and the contact state between the contact surfaces 7A and 7B can be firmly maintained. The number, arrangement, and specific shape of the recesses and protrusions can be appropriately changed within the range that maintains their function.

[0042] Figure 8 is a flowchart showing an example of a method for manufacturing a stator core according to the first embodiment. Below, an example of a method for manufacturing a stator core using the stator core material 1 described above will be explained, mainly with reference to Figure 8.

[0043] The manufacturing method of the stator core according to the present embodiment includes at least a plurality of plate-shaped core pieces 2 including an arc-shaped yoke portion 3 and teeth portions 4 extending from the inner peripheral surface of the yoke portion 3, and a strip-shaped connecting piece 5 that connects the yoke portions 3 of adjacent core pieces 2. The longitudinal length L1 of the inner peripheral surface 5A adjacent to the yoke portion 3 of the connecting piece 5 is shorter than the circumferential length L2 (= [L2-1] + [L2-2]) of the outer peripheral surface 3A of the yoke portion 3 facing the inner peripheral surface 5A adjacent to the yoke portion 3 of the connecting piece 5. A step of preparing the stator core material 1 (corresponding to step S01 described later), and a step of winding the stator core material 1 around a plurality of core pieces 2 to bring into contact the contact surfaces 7 formed at the circumferential ends of the yoke portions 3 of adjacent core pieces 2, and bringing at least a part of the inner peripheral surface 5A of the connecting piece 5 into surface contact with the outer peripheral surface 3A of the yoke portion 3 (corresponding to step S02 described later). Hereinafter, it will be described in detail.

[0044] As shown in FIG. 8, the manufacturing method of the stator core according to the present embodiment first prepares the above-described stator core material 1 (step S01). Next, the prepared stator core material 1 is wound in a ring shape to form the stator core (step S02).

[0045] FIG. 9 is a perspective view showing an example of a bending jig used for forming the stator core material shown in FIG. 1. The above-described forming of the stator core can be carried out using, for example, a bending jig 10 as shown in FIG. 9. As shown in FIG. 9, the bending jig 10 may be composed of a base 11, a column 12 erected at the central portion of the base 11, and a peripheral wall 14 that partially surrounds the periphery of the column 12 with a predetermined gap 13.

[0046] It is preferable that the dimensions of the outer diameter of the column 12 and the inner diameter of the peripheral wall 14 are adjusted to match the size of the stator core to be manufactured. Further, the peripheral wall 14 is formed in a substantially C shape in a plan view, and a gap formed between the ends of the peripheral wall 14 functions as an inlet 15 into which the stator core material 1, which is the core material before forming, is inserted.

[0047] The forming process in step S02 is carried out by sequentially inserting core pieces 2 that are linearly connected to the stator core material 1 into the inlet 15 of the bending jig 10 having the above-described configuration. The core piece 2 inserted into the inlet 15 advances along the gap 13 and is wound around the support column 12. When the pre-formed stator core material 1 is inserted into the bending jig 10 and the core piece 2 advances along the gap 13, the connecting piece 5 connected to the core piece 2 is bent so as to follow the inner wall of the peripheral wall 14. By this bending, the contact surfaces 7 of adjacent core pieces 2 come into contact with each other, and at least a part of the inner peripheral surface 5A of the connecting piece 5 and the outer peripheral surface 3A of the yoke portion 3 are in surface contact. As a result, the adjacent core pieces 2 are changed from a linearly connected state to a concentrically connected state.

[0048] Further, as described above, the stator core material 1 according to the present embodiment has the longitudinal length of the connecting piece 5 adjusted, and by the above-described forming, the inner peripheral surface 5A of the connecting piece 5 is in surface contact with the outer peripheral surface 3A of the yoke portion 3 to apply the pressing force P. Since this pressing force P acts in a direction to bring the contact surfaces 7 of adjacent core pieces 2 closer to each other, even when springback acts on the formed stator core material 1A taken out from the bending jig 10, the contact state of the contact surfaces 7 can be maintained. Then, the annular stator core manufactured through the above-described steps is used alone or in a state where a plurality of sheets are stacked as a component constituting a stator.

[0049] The stator core manufactured by the above-described process can maintain its formed state without using other members such as a housing due to the pressing force P acting along the circumferential direction from the connecting piece 5.

[0050] <Second Embodiment> In the first embodiment described above, an example was shown in which both ends 5E, 5E of the connecting piece 5 are connected to the circumferential center of the outer peripheral surface 3A of adjacent yoke portions 3. However, the connection structure between the core piece and the connecting piece is not limited to this. Therefore, an example in which the connection structure between the connecting piece and the core piece differs from that of the stator core material 1 according to the first embodiment will be described below as the stator core material 101 according to the second embodiment (see Figure 10). In the following description, the focus will be on the configuration of the stator core material 101 according to this embodiment that differs from that of the first embodiment. Among the various components of the stator core material 101 of the second embodiment, those components that are the same as those of the first embodiment will be given the same names as those of the first embodiment, and their descriptions will be appropriately adapted from those of the first embodiment.

[0051] Figure 10 is a schematic plan view showing an example of a stator core material according to the second embodiment. Figure 11 is an enlarged view of section C in Figure 10. Figure 10 also shows a part of the stator core material 101 before molding, similar to Figure 1. The stator core material 101 according to this embodiment is similar to that of the first embodiment in that it includes a plurality of core pieces 102 and connecting pieces 105 that connect adjacent core pieces 102, as shown in Figures 10 and 11. On the other hand, the connection structure between the core pieces 102 and the connecting pieces 105 in the stator core material 101 according to this embodiment differs from that of the first embodiment.

[0052] The core piece 102 may include a yoke portion 103 formed in an arc shape and a plurality of teeth portions 104 extending inward from the inner circumferential surface of the yoke portion 103 at a predetermined interval. Preferably, the radial width of the yoke portion 103 is adjusted considering the arrangement of the connecting piece 105. Specifically, as shown in Figure 11, it is preferable that the radial width D2 of the portion where the connecting piece 105 is located opposite the outer circumferential surface 103A is adjusted to be smaller (for example, by about the same amount as the width of the connecting piece 105) than the radial width D1 of the portion where the connecting piece 105 is not located opposite the outer circumferential surface 103A. When the width of the yoke portion 103 is adjusted as described above, it becomes difficult for steps to be formed on the outer circumferential surface of the stator core material 101A (see Figure 13), which is formed by shaping the stator core material 101 into an annular form.

[0053] Furthermore, contact surfaces 107A and 107B are provided at both circumferential ends of the yoke portion 103, respectively. In this embodiment, one contact surface 107A includes a recess that is indented in the circumferential direction, and the other contact surface 107B includes a protrusion that is circumferentially projecting and fits into the aforementioned recess when the core piece 102 is wound around it.

[0054] The connecting piece 105 is composed of a strip-shaped member that connects adjacent core pieces 102. In this embodiment, one end 105E1 in the longitudinal direction of the connecting piece 105 is connected to the circumferential center of the outer peripheral surface 103A of one yoke portion 103 of the adjacent core piece 102 (in Figure 11, the yoke portion 103 of the right core piece 102). On the other hand, the other end 105E2 in the longitudinal direction of the connecting piece 105 is connected to the point where the end of the outer peripheral surface 103A of the other yoke portion 103 of the adjacent core piece 102 (in Figure 11, the yoke portion 103 of the left core piece 102) intersects with the outer peripheral end of the contact surface 107A. In other words, in this embodiment, the connection position of the other end 105E2 of the connecting piece 105 is different from that of the connecting piece 5 in the first embodiment.

[0055] A relief groove 108 may be formed between the inner circumferential surface 105A side of one end 105E1 of the connecting piece 105 in this embodiment and the outer circumferential surface 103A of the yoke portion 103. This relief groove 108 can be omitted. In addition, a shape similar to the bulge portion 9 described in the first embodiment may be adopted at an appropriate location on the outer circumferential surface 103A of the yoke portion 103 facing the inner circumferential surface 105A.

[0056] In this embodiment, the other end 105E2 of the connecting piece 105 is connected to the point where the end of the outer peripheral surface 103A of the yoke portion 103 intersects with the outer peripheral end of the contact surface 107A. However, the connection position of the other end 105E2 is not limited to this. For example, the other end 105E2 may be connected to a suitable location adjacent to the contact surface 107A on the outer peripheral surface 103A of the yoke portion 103, or to a suitable location on the outer peripheral side of the contact surface 107A. It is preferable to select a connection position for the other end 105E2 that does not cause irregularities to form on the outer peripheral surface when the stator core material 101 is formed into an annular shape.

[0057] Figure 12 is a schematic plan view showing an example of a stator core formed using the stator core material shown in Figure 10. The stator core material 101, which includes the above-described configuration, can be formed into an annular shape in plan view as shown in Figure 12 by bending the connecting piece 105 and winding a plurality of core pieces 102, thereby bringing the adjacent contact surfaces 107 of the plurality of core pieces 102 into contact with each other. The stator core material 101A formed into an annular shape in this way can be used as a stator core or as one of the components constituting a stator core.

[0058] In the stator core material 101 according to this embodiment, similar to the stator core material 1 described above, the longitudinal length of the connecting piece 105 is adjusted to prevent the molded core pieces 102 from separating due to springback. Specifically, in the stator core material 101 according to this embodiment, the longitudinal length of the inner circumferential surface 105A of the connecting piece 105 adjacent to the yoke portion 103 is adjusted to be shorter than the circumferential length of the outer circumferential surface 103A of the yoke portion 103 facing the connecting piece 105. The circumferential length of the outer circumferential surface 103A of the yoke portion 103 facing the connecting piece 105 refers to the circumferential length from the relief groove 108 portion to the contact surface 107B in Figure 11.

[0059] By adjusting the longitudinal length of the inner circumferential surface 105A of the connecting piece 105, or the circumferential length of the outer circumferential surface 103A of the yoke portion 103 facing the inner circumferential surface 105A, as described above, when the stator core material 101 is formed into an annular shape, circumferential compressive stress can be generated in the yoke portion 103 of the core piece 102. Therefore, the contact state between the contact surfaces 107A and 107B of adjacent yoke portions 103 can be maintained.

[0060] In addition, in this embodiment as well, it is preferable to further adjust the longitudinal length of the inner circumferential surface 105A of the connecting piece 105 or the circumferential length of the outer circumferential surface 103A of the yoke portion 103 facing the inner circumferential surface 105A so that at least a portion of the inner circumferential surface 105A of the connecting piece 105 makes surface contact with the outer circumferential surface 103A of the yoke portion 103 when the stator core material 101 is formed into an annular shape. In the stator core material 101 of this embodiment as well, if the inner circumferential surface 105A of the connecting piece 105 and the outer circumferential surface 103A of the yoke portion 103 make surface contact, the pressing force P illustrated in Figure 4 in the first embodiment will be generated. Therefore, it is possible to further suppress the separation of the core pieces 102 of the molded stator core material 101A due to springback after molding.

[0061] As described above, the stator core material 101 according to this embodiment can also obtain the same effects as those described in the first embodiment. In addition, compared to the stator core material 1 according to the first embodiment, the stator core material 101 according to this embodiment makes it easier to reduce the area in which the inner circumferential surface 105A of the connecting piece 105 contacts the outer circumferential surface 103A of the yoke portion 103. Therefore, it is possible to selectively use the stator core material 1 and the stator core material 101 depending on the material and shape of the stator core, the magnitude of the compressive stress to be generated between the core pieces, etc.

[0062] Furthermore, the stator core material 101 described above can be formed into an annular shape by performing the same process as the method for manufacturing the stator core described in the first embodiment. That is, by performing the steps of preparing the stator core material 101 described above, and winding a plurality of core pieces 102 around the stator core material 101 to bring the contact surfaces 107A and 107B formed at the circumferential ends of the yoke portion 103 of a plurality of adjacent core pieces 102 into contact with each other, and bringing at least a portion of the inner circumferential surface 105A of the connecting piece 105 into surface contact with the outer circumferential surface 103A of the yoke portion 103, a formed stator core material 101A as shown in Figure 12 can be provided.

[0063] Next, some modifications of the second embodiment described above will be explained. First, when forming the stator core material 101 of the above structure into an annular shape, the amount of bending is greatest at the point where the other end 105E2 of the connecting piece 105 is connected to the core piece 102 during the forming process. The magnitude of the aforementioned amount of bending is proportional to the bending angle θ1 (see Figure 11) between the connecting piece 105 and the core piece 102. Here, in the bending process of metal materials, stress tends to concentrate at points with a large amount of bending, and generally, a large springback force is likely to occur. Therefore, distributing the amount of bending can be expected to have a great effect in avoiding separation of the core pieces 102 due to springback.

[0064] Figure 13 is an enlarged view corresponding to Figure 11, showing a modified example of the stator core material shown in Figure 10. Based on the above, the stator core material 201 according to this modified example employs connecting pieces 205 whose connecting angle is adjusted so that the bending angle θ2 of the core piece 102 is small, as shown in Figure 13. The aforementioned bending angles θ1 and θ2 refer to the angle between a straight line along the extending direction of the connecting pieces 105 and 205 and a tangent line passing through the outer peripheral surface 103A of the yoke portion 103 of the core piece 102 where the other ends 105E2 and 205E2 of the connecting pieces 105 and 205 are connected. Furthermore, for the stator core material 201 of this modified example, components with the same configuration as the stator core material 101 according to the second embodiment are denoted by the same reference numerals as those used for the stator core material 101 according to the second embodiment, and their descriptions are omitted.

[0065] Preferably, the other end 205E2 of the connecting piece 205 is adjusted to a connection angle such that the bending angle θ2 is in the range of 10 to 20°. If the bending angle θ2 is in the range of 10 to 20°, the amount of bending at the position where the other end 205E2 of the connecting piece 205 is connected becomes sufficiently small, and large springback forces are less likely to occur in that part. Note that if the bending angle θ2 becomes small, the amount of bending of other parts of the connecting piece 205, for example, one end 205E1 side, may increase, but even in this case, the amount of bending of the connecting piece 205 required when winding the core piece 102 is distributed to each part of the connecting piece 205, so the occurrence of large springback forces can be avoided.

[0066] Figures 14A and 14B show other modified examples of the stator core material shown in Figure 10, and are enlarged views of the main parts showing the portion where the contact surfaces of adjacent core pieces are located. In the second embodiment described above, for example, one contact surface 107A located on the right side in Figure 11 includes a recess, and the other contact surface 107B located on the left side in Figure 11 includes a convex portion, but the shapes of the contact surfaces 107A and 107B can be changed. Specifically, as shown in Figure 14A, one of the adjacent contact surfaces 107C located on the right side may include a convex portion, and the other contact surface 107D located on the left side may include a recess. Also, as shown in Figure 14B, both adjacent contact surfaces 107, 107 can be composed of planes extending in the radial direction.

[0067] This disclosure is not limited to the embodiments described above, and can be implemented with various modifications without departing from the spirit of this disclosure. All such modifications are included in the technical concept of this disclosure. Furthermore, unless otherwise specified in the specification, each component of this disclosure is not limited to one, but may exist in multiple forms.

[0068] All documents cited herein, including publications, patent applications, and patents, are incorporated here by reference to the same extent as each document is specifically identified and referred to, and all of its contents are described herein.

[0069] The use of nouns and similar demonstrative pronouns in connection with the description of this disclosure (particularly in connection with the following claims) shall be construed as both singular and plural unless otherwise specifically noted herein or if it is clearly inconsistent with the context. The words “equip,” “have,” “include,” and “incorporate” shall be construed as open-ended terms (i.e., “include, but not limited to”) unless otherwise specifically noted herein. The numerical ranges described herein are intended solely as abbreviations for referring individually to each value that falls within that range, unless otherwise specifically noted herein, and each value is incorporated into the specification as if it were individually enumerated herein. All methods described herein can be performed in any appropriate order unless otherwise specifically noted herein or if it is clearly inconsistent with the context. Any examples or illustrative phrases used herein (e.g., “etc.”) are intended solely to better illustrate this disclosure and not to impose any limitations on the scope of this disclosure unless otherwise specifically asserted. Nothing in the specification shall be construed as indicating that any element not described in the claims is essential to the implementation of this disclosure.

[0070] This specification describes preferred embodiments of the Disclosure, including the best mode known to the inventors for carrying out the Disclosure. Those skilled in the art will see, upon reading the above description, that variations of these preferred embodiments will become apparent. The inventors expect that skilled individuals will appropriately apply such variations and that the Disclosure will be carried out in ways other than those specifically described herein. Therefore, this Disclosure includes all modifications and equivalents of the claims appended to this Specification, as permitted by applicable law. Furthermore, any combination of the above elements in all variations is incorporated into this Disclosure unless specifically noted herein or is obviously inconsistent with the context.

Claims

1. A stator core material comprising: a plurality of plate-shaped core pieces including an arc-shaped yoke portion and a tooth portion extending from the inner circumferential surface of the yoke portion; and a strip-shaped connecting piece connecting the yoke portions of adjacent core pieces, wherein the longitudinal length of the inner circumferential surface of the connecting piece adjacent to the yoke portion is shorter than the circumferential length of the outer circumferential surface of the yoke portion facing the inner circumferential surface of the connecting piece adjacent to the yoke portion; and the length of the connecting piece is set such that at least a portion of the inner circumferential surface of the connecting piece makes surface contact with the outer circumferential surface of the yoke portion when the plurality of core pieces are wound together and the contact surfaces formed at the circumferential ends of the yoke portions of adjacent core pieces are brought into contact with each other.

2. The stator core material according to claim 1, wherein one end of the connecting piece is connected to the circumferential center of the outer surface of the yoke portion of one of the adjacent core pieces, and the other end is connected to at least one of the end of the outer surface of the yoke portion of the other adjacent core piece and the outer surface end of the contact surface.

3. The stator core material according to claim 1, wherein one end and the other end of the connecting piece are connected to the circumferential center of the outer surface of the yoke portion of an adjacent core piece.

4. The stator core material according to claim 2 or 3, wherein a bulge is formed on the outer circumferential surface of the yoke portion facing the connecting piece, the bulge being radially larger than the arc-shaped reference line connecting the outer circumferential end of the contact surface and the inner circumferential end of the end of the connecting piece connected to the circumferential center of the outer circumferential side of the yoke portion.

5. The stator core material according to claim 2 or 3, wherein a relief groove is formed between the inner circumferential end of the end connected to the circumferential center on the outer circumference of the yoke portion and the outer circumferential surface of the yoke portion.

6. The stator core material according to claim 1, wherein one of the adjacent contact surfaces has a recess that is circumferentially recessed, and the other contact surface has a protrusion that is circumferentially protruding and fits into the recess when a plurality of core pieces are wound around it.

7. A method for manufacturing a stator core, comprising: a step of preparing a stator core material comprising a plurality of plate-shaped core pieces including an arc-shaped yoke portion and teeth portions extending from the inner circumferential surface of the yoke portion, and a strip-shaped connecting piece connecting the yoke portions of adjacent core pieces, wherein the longitudinal length of the inner circumferential surface of the connecting piece adjacent to the yoke portion is shorter than the circumferential length of the outer circumferential surface of the yoke portion facing the inner circumferential surface of the connecting piece adjacent to the yoke portion; and a step of winding the stator core material around the plurality of core pieces to bring the contact surfaces formed at the circumferential ends of the yoke portions of adjacent core pieces into contact with each other, thereby bringing at least a portion of the inner circumferential surface of the connecting piece into surface contact with the outer circumferential surface of the yoke portion.

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