Stator core manufacturing method and stator core

Abstract

This stator core manufacturing method includes: a step for preparing a core material which includes a plurality of core pieces including yoke parts and tooth parts, and in which some of the yoke parts of the adjacent core pieces are connected by connection parts; a step for temporarily shaping the core material into an annular shape by winding the plurality of core pieces while bending the core pieces at the connection parts; and a step for pressing one or more of the connection parts of the core material temporarily shaped into the annular shape to apply a circumferential compressive stress to the plurality of core pieces.

Description

Stator core manufacturing method and stator core

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

[0002] A method for manufacturing a stator core for a rotating electrical machine, such as an inner rotor type motor, is known in which a ring-shaped stator core is manufactured by combining a plurality of core pieces having a substantially arc-shaped configuration. This method for manufacturing a ring-shaped stator core by combining core pieces is advantageous in terms of material yield compared to a method for manufacturing a ring-shaped stator core by stamping.

[0003] For example, Japanese Patent Application Laid-Open No. 2007-143257 describes the use of a laminated core in a stator core, in which adjacent segment core pieces are connected to each other by connecting portions formed on the outer periphery, the connecting portions are bent to align the side ends of the segment core pieces, and multiple consecutive segment core pieces are spirally wound and stacked.

[0004] A stator core manufactured by the method disclosed in JP 2007-143257 A is used as part of a stator after undergoing a process of attaching coils to the teeth of the stator core, but because the stator core manufactured by the above method is formed into an annular shape by bending the connecting portions, an elastic recovery phenomenon, known as springback, can occur in the connecting portions. This makes it difficult to transport the stator core to the next process while maintaining the desired shape.

[0005] In view of the above-mentioned problems, the present disclosure provides a stator core manufacturing method that allows the shape of the stator core to be maintained as a desired shape, and the stator core.

[0006] A method for manufacturing a stator core according to a first aspect of the present disclosure includes the steps of preparing a core material including a plurality of core pieces each including a yoke portion and a tooth portion, with portions of the yoke portions of adjacent core pieces connected by connecting portions; winding the plurality of core pieces while bending them at the connecting portions to pre-shape the core material into a ring; and pressing one or more of the connecting portions of the pre-shaped core material into a ring to impart circumferential compressive stress to the plurality of core pieces.

[0007] In this method of manufacturing a stator core, a circumferential compressive stress is applied to the core material after it has been preformed into an annular shape, and this compressive stress acts to maintain the contact state between the core pieces, thereby maintaining the shape of the preformed annular core material. Therefore, the stator core can be maintained in the desired shape without using a separate member such as a housing.

[0008] A method for manufacturing a stator core according to a second aspect of the present disclosure is the same as the method for manufacturing a stator core according to the first aspect of the present disclosure, in which the step of applying circumferential compressive stress to the plurality of core pieces includes a step of pressing one or more of the connecting portions of the annularly molded core material toward the outside of the core material to plastically deform it.

[0009] In such a method for manufacturing a stator core, a circumferential compressive stress can be applied to the core material preliminarily formed into an annular shape through a relatively simple process of plastically deforming one or more connecting portions.

[0010] A method for manufacturing a stator core according to a third aspect of the present disclosure is the method for manufacturing a stator core according to the first aspect of the present disclosure, wherein the step of applying circumferential compressive stress to the plurality of core pieces includes a step of pressing a press-in member into a space surrounded by the yoke portions and the connecting portions of adjacent core pieces.

[0011] In such a method for manufacturing a stator core, a circumferential compressive stress can be applied to the core material preliminarily formed into an annular shape through a relatively simple process of press-fitting a press-fit member.

[0012] A method for manufacturing a stator core according to a fourth aspect of the present disclosure is a method for manufacturing a stator core according to any one of the first to third aspects of the present disclosure, wherein the step of pre-molding the core material into a ring shape includes a step of spirally winding and stacking the multiple core pieces while bending them at the connecting portions.

[0013] In such a method for manufacturing a stator core, it is easy to manufacture a stator core that is configured by stacking annular cores.

[0014] A method for manufacturing a stator core according to a fifth aspect of the present disclosure is a method for manufacturing a stator core according to any one of the first to fourth aspects of the present disclosure, further including a step of stacking a plurality of the core materials pre-formed into an annular shape before a step of applying circumferential compressive stress to the plurality of core pieces.

[0015] In this method of manufacturing a stator core, the axial length of the stator core can be easily adjusted.

[0016] A stator core according to a sixth aspect of the present disclosure includes the core material manufactured by the stator core manufacturing method according to any one of the first to sixth aspects of the present disclosure.

[0017] In such a stator core, the connecting portion is plastically deformed in the radial direction to impart circumferential compressive stress to the core material, making it less likely for the core material to spring back in the opening direction (in other words, to its shape before molding).

[0018] According to the above-described method for manufacturing a stator core and the stator core, the shape of the stator core can be maintained as desired.

[0019] FIG. 3 is a schematic plan view showing an example of a core material used in a manufacturing method for a stator core according to an embodiment. FIG. 4 is a flowchart showing an example of a manufacturing method for a stator core according to an embodiment. FIG. 5 is a perspective view showing an example of a bending jig used for temporary forming in the manufacturing method for the stator core shown in FIG. 2. FIG. 6 is a schematic plan view showing an example of a temporarily formed core material. FIG. 7 is a perspective view showing another example of a bending jig used for final forming in the manufacturing method for the stator core shown in FIG. 2. FIG. 8 is an explanatory view showing an overview of an example of final forming in FIG. 2. FIG. 9 is an explanatory view showing an overview of another example of final forming.

[0020] This application is based on Japanese Patent Application No. 2024-149871, filed on August 30, 2024, in Japan, the contents of which are incorporated herein by reference. The present disclosure will become more fully understood from the following detailed description. Further scope of application of the present application will become apparent from the following detailed description. However, the detailed description and specific examples are preferred embodiments of the present disclosure and are set forth for illustrative purposes only. From this detailed description, various changes and modifications will be apparent to those skilled in the art within the spirit and scope of the present disclosure. The applicant does not intend to dedicate any of the described embodiments to the public, and the applicants also consider disclosed modifications and alternatives, even if not literally included within the scope of the claims, to be part of the invention under the doctrine of equivalents. Like reference numbers and names in the various drawings indicate like elements.

[0021] Hereinafter, each embodiment for carrying out the present disclosure will be described with reference to the drawings. Note that the scope necessary for the explanation to achieve the object of the present disclosure will be schematically shown below, and the scope necessary for explaining the relevant parts of the present disclosure will be mainly explained, and the parts for which explanation is omitted will be referred to as publicly known technologies. Furthermore, identical or similar reference numerals will be used for identical or corresponding components in the drawings, and duplicate explanations will be omitted. Furthermore, when a plurality of identical or corresponding components are included in the drawings, only some of them may be referenced to make the drawings easier to understand.

[0022] Fig. 1 is a schematic plan view showing an example of a core material used in a manufacturing method for a stator core according to one embodiment. Note that Fig. 1 shows only a portion of the tip side of the core material 1 before molding. In the manufacturing method for a stator core according to this embodiment, a method for manufacturing a stator core as one component of a stator that makes up an inner rotor type motor will be described as an example. In the manufacturing method for a stator core according to this embodiment, a core material 1 before molding, in which a plurality of core pieces 2 are connected via connecting portions 5, as shown in Fig. 1, is used.

[0023] To explain the pre-forming core material 1 in more detail, the pre-forming core material 1 is configured by connecting a portion of the yoke portion 3 of adjacent core pieces 2, each including a yoke portion 3 and a tooth portion 4, with a connecting portion 5. This pre-forming core material 1 may be formed by punching out a strip-shaped electromagnetic steel sheet having a thickness of, for example, about 0.1 to 1.0 mm using a die. The number of core pieces 2 included in the pre-forming core material 1 can be adjusted as appropriate to suit the size of the stator core to be manufactured, etc.

[0024] The core laminations 2 may be composed of a yoke portion 3 formed in a substantially arcuate shape and a plurality of teeth 4 (six in FIG. 1 ) extending at predetermined intervals from the inner surface of the yoke portion 3. The spaces between adjacent teeth 4 function as slots around which coils (not shown) are wound. The number of teeth 4 formed on one core lamination 2 is not particularly limited and can be changed as appropriate.

[0025] A notch 6 may be provided at the outer peripheral end of each of both longitudinal ends of the yoke portion 3. A connecting portion 5 may be connected to the portion of this notch 6. Of the two ends described above, the portion without the notch 6 forms a contact surface 7 that abuts against a similar portion of another adjacent yoke portion 3 during pre-forming, which will be described later. In addition, a notch different from the notch 6 described above may be provided at an appropriate location on the outer peripheral side of the yoke portion 3 for positioning the manufactured stator core or for use as a weld.

[0026] The connecting portion 5 is made of a strip-shaped member that can connect adjacent core laminations 2 together. Both longitudinal ends of the connecting portion 5 are connected to the outer peripheral portions of the notches 6 formed in the yoke portions 3 of adjacent core laminations 2. This connecting portion 5 is the portion that is bent during pre-molding, which will be described later. In this regard, one or more portions of the connecting portion 5 can also be molded to be thin-walled or narrow. Furthermore, the specific shape of the connecting portion 5 is not limited to a strip shape and can be changed as appropriate.

[0027] 2 is a flowchart showing an example of a method for manufacturing a stator core according to an embodiment. The method for manufacturing a stator core according to this embodiment using the above-described pre-molded core material 1 will be described below mainly with reference to FIG.

[0028] The method for manufacturing a stator core according to this embodiment includes the steps of: preparing a core material 1 including a plurality of core pieces 2, each including a yoke portion 3 and a tooth portion 4, with the yoke portions 3 of adjacent core pieces 2 being connected together at portions of a connecting portion 5 (corresponding to step S01, described later); winding the plurality of core pieces 2 while bending them at the connecting portions 5 to provisionally form the core material 1 into an annular shape (corresponding to step S02, described later); and pressing one or more connecting portions 5 of the core material 1A provisionally formed into an annular shape to impart a circumferential compressive stress to the plurality of core pieces 2 (corresponding to step S03, described later). These steps will be described in detail below.

[0029] 2, in the method for manufacturing a stator core according to this embodiment, first, a pre-formed core material 1 having the above-described configuration is prepared (step S01). Next, the prepared pre-formed core material 1 is wound into a ring shape to perform a preliminary forming of the stator core (step S02). This preliminary forming can be performed using a bending jig, which will be described later.

[0030] Fig. 3 is a perspective view showing an example of a bending jig used for temporary shaping in the manufacturing method of the stator core shown in Fig. 2. The temporary shaping described above can be performed using, for example, a bending jig 10 as shown in Fig. 3. The bending jig 10 may be composed of a base 11, a support 12 erected in the center of the base 11, and a peripheral wall 14 that partially surrounds the periphery of the support 12 with a predetermined gap 13 therebetween.

[0031] The outer diameter of the support 12 and the inner diameter of the peripheral wall 14 are preferably adjusted to fit the size of the stator core to be manufactured. The peripheral wall 14 is formed in a roughly C-shape in plan view, and a gap formed between the ends of the peripheral wall 14 functions as an inlet 15 through which the core material 1 before molding is inserted.

[0032] The pre-forming in step S02 described above is performed by sequentially inserting linearly connected core pieces 2 of the pre-formed core material 1 into the inlet 15 of the bending jig 10 having the configuration described above. The core pieces 2 inserted into the inlet 15 proceed along the gap 13 and are wound around the support 12. When the pre-formed core material 1 is inserted into the bending jig 10 and the core pieces 2 proceed along the gap 13, the connecting portions 5 connected to the core pieces 2 are bent so as to fit along the inner wall of the peripheral wall 14. This bending brings the contact surfaces 7 of adjacent core pieces 2 into contact with each other, thereby changing the state in which the adjacent core pieces 2 are connected linearly to a state in which they are connected concentrically.

[0033] 4 is a schematic plan view showing an example of a pre-molded core material. As shown in FIG. 4, the pre-molded core material 1A described above is pre-molded into a circular shape by concentrically arranging a predetermined number of core pieces 2, for example, eight core pieces 2. In this regard, the number of core pieces 2 included in the pre-molded core material 1 prepared in step S01 may be 8×n (n=1, 2, 3, ...). When the number of core pieces 2 included in the pre-molded core material 1 is 8×2 or more, the above-mentioned step S02 includes a step of spirally winding and stacking the multiple core pieces 2 while folding the pre-molded core material 1 at the connecting portions 5.

[0034] In addition, when the core pieces 2 are spirally wound and stacked, in order to connect the core pieces 2 of each layer, crimped portions may be formed at appropriate positions on the core pieces 2, or adhesive may be interposed between the layers. Alternatively, grooves for welding may be formed at appropriate positions on the core pieces 2.

[0035] Fig. 5 is a perspective view showing another example of a bending jig used in the main forming in the manufacturing method of the stator core shown in Fig. 2. In the above-described embodiment, the bending jig 10 shown in Fig. 3 is used to temporarily form the core material 1 before forming, but the configuration of the bending jig is not limited to this. For example, the same temporary forming as described above can also be performed using a bending jig 20 shown in Fig. 5.

[0036] As shown in Figure 5, the bending jig 20 comprises a mounting table 21, a guide 22 formed on the mounting table 21 and having an arc-shaped wall surface adjusted to the same diameter as the outer diameter of the core piece 2, and a movable part 24 having a pin 23 and moving the pin 23 in a direction toward or away from the guide 22.

[0037] When provisionally forming the core material 1 before molding using the bending jig 20 having the above-described configuration, the following procedure may be performed. That is, first, at least a portion of the core material 1 before molding is placed on the mounting table 21, and the core material 1 before molding is slid while the outer diameter of the core piece 2 on the mounting table 21 is aligned with the arc-shaped wall surface of the guide 22. Then, when the connecting portion 5 is positioned within the movable range of the pin 23, the movable portion 24 is moved in the direction of arrow M1, pressing the pin 23 against the connecting portion 5 and bending the core piece 2 toward the outer diameter. By repeating the above-described operation each time the connecting portion 5 is positioned within the movable range of the pin 23, the multiple core pieces 2 connected in a linear fashion are formed into a circular shape, and the core material 1 is provisionally formed.

[0038] 4, the pre-formed core material 1A is formed into an annular shape by abutting the contact surfaces 7 of adjacent core pieces 2, and does not have a fixing structure or the like for maintaining the annular shape. Therefore, for example, when the pre-formed core material 1 is removed from the bending jig 10, springback occurs in the bent connecting portions 5, making it difficult to maintain the annular shape of the pre-formed core material 1A. Therefore, in this embodiment, after the pre-formation, actual forming is performed to maintain the annular shape (step S03).

[0039] The above-mentioned main molding includes pressing one or more connecting portions 5 of the provisionally molded core material 1A, specifically, pressing the provisionally molded core material 1A radially outward, thereby applying circumferential compressive stress to the multiple core pieces 2. Various methods for pressing one or more connecting portions 5 are conceivable, and the following method, for example, can be adopted.

[0040] FIG. 6 is an explanatory diagram outlining an example of the final forming shown in FIG. 2, showing an enlarged view of portion A in FIG. 4. In this embodiment, the final forming can be performed by pressing one or more connecting portions 5 of an annularly formed core material 1A radially outward to plastically deform the core material 1A, as shown in FIG. 6. Specifically, a pin-shaped pressing jig 30 is first inserted into the space 8 surrounded by adjacent yoke portions 3 and connecting portions 5 of the preliminarily formed core material 1A. Next, the pressing jig 30 is moved radially outward (in the direction of arrow M2 in FIG. 6) of the preliminarily formed core material 1A, plastically deforming the connecting portions 5 so that they bulge radially outward from the preliminarily formed core material 1A. When the connecting portions 5 are plastically deformed in this manner, a compressive stress P1 is applied along the circumferential direction between adjacent contact surfaces 7 that are in contact with each other.

[0041] The compressive stress P1 applied by the final molding acts to maintain the contact state between the contact surfaces 7, and therefore acts to maintain the annular shape of the pre-molded core material 1A. Therefore, after the final molding, the core material can maintain the desired shape, specifically the annular state, without using a separate member such as a housing.

[0042] Although the pressing jig 30 described above is exemplified as being configured as a pin-shaped member, the shape and number of the pressing jig 30 can be changed as appropriate. For example, the pressing jig 30 can be configured as a rectangular prism-shaped member such as a square prism, rather than a pin-shaped member. Also, multiple pressing jigs 30 may be inserted into one space 8 to press multiple locations on the connecting portion 5. Furthermore, if the pressing jig 30 is inserted into each of the multiple spaces 8 and then moved radially outward of the pre-molded core material 1A, the multiple connecting portions 5 arranged in an annular shape can be plastically deformed simultaneously.

[0043] Furthermore, the above-described final forming can be performed simultaneously on multiple connecting portions 5 arranged in the axial direction. In relation to this, for example, when manufacturing a stator core by combining multiple provisionally formed core materials 1A, a step of stacking multiple core materials 1A provisionally formed into an annular shape may be performed before the above-described final forming. If the final forming is performed after stacking multiple provisionally formed core materials 1A, the process for manufacturing the stator core can be simplified.

[0044] In the above-described embodiment, the case where the final molding is performed using the pressing jig 30 has been exemplified, but the present disclosure is not limited to this. Below, several other examples of the final molding will be described as illustrative examples.

[0045] FIG. 7 is an explanatory diagram showing an overview of another example of the permanent molding. Similar to FIG. 6, FIG. 7 is an enlarged view of portion A shown in FIG. 4. Another example of the permanent molding, as shown in FIG. 7, can be performed by pressing a press-fit member 40 made of resin or the like into one or more spaces 8 of a core material 1A that has been preliminarily molded into an annular shape. The press-fit member 40 to be pressed into the space 8 may be adjusted in size so as to cause the connecting portion 5 to bulge radially outward from the preliminarily molded core material 1A when pressed into the space 8. When the press-fit member 40 is pressed into the space 8, the connecting portion 5 is pressed radially outward from the preliminarily molded core material 1A, thereby compressing the notch 6 in the direction indicated by arrow M3. The pressing force indicated by arrow M3 acts on the adjacent contact surface 7 as a compressive stress similar to the compressive stress P1 described above.

[0046] In the above-described example of the final molding, the press-fit member 40 pressed into the space 8 may be removed after the final molding, or may remain as part of the stator core without being removed. However, if the press-fit member 40 is removed after the final molding, it is preferable to plastically deform the connecting portion 5 by pressing the press-fit member 40 into the space 8. On the other hand, if the press-fit member 40 pressed into the space 8 is left in the space 8 to form part of the stator core, the connecting portion 5 does not need to be plastically deformed as long as it is elastically deformed. Furthermore, the space 8 into which the press-fit member 40 is pressed may be all of the space 8 of the pre-molded core material 1A, or only a portion of the space 8. Furthermore, although the above-described press-fit member 40 is exemplified as being pre-molded, the same effect as the press-fit member 40 may be obtained by filling the space 8 with resin and hardening it. Furthermore, when the press-fit member 40 is press-fitted, a portion of the yoke portion 3 that defines the space 8 may be pressurized to crimp the core pieces 2 stacked in the axial direction together.

[0047] Although some of the above-described final forming methods use components such as the pressing jig 30 and the press-fitting member 40, a similar effect can be achieved by adjusting the dimensions of the core material. Specifically, when connecting multiple core pieces (e.g., eight core pieces) 2 from a pre-formed core material 1 to manufacture a circular stator core, the total circumferential length of the yoke portions 3 of the eight connected core pieces 2 is made slightly longer than the circumference of the yoke of the finished stator core. When the pre-formed core material 1 including the core pieces 2 whose dimensions have been adjusted in this way is wound into a circular shape by pre-forming, when the contact surface 7 of the core piece 2 located at the leading end of the core material 1 contacts the contact surface 7 of the core piece 2 located at the trailing end, the connected core pieces 2 are temporarily spread apart in the circumferential direction, causing the contact surfaces 7 to contact each other. This assembly process can impart a circumferential compressive stress to the pre-formed core material 1. The circumferential dimension of the yoke portions 3 of the eight connected core pieces 2 may be increased for only one piece or for multiple pieces. Furthermore, when increasing the circumferential dimension of the yoke portion 3, the entire yoke portion 3 can be enlarged uniformly, or at least one of the inner diameter side and the outer diameter side can be enlarged selectively.

[0048] Furthermore, when carrying out the various types of final molding described above, it is preferable to press the core material 1A, which has been provisionally molded into a ring shape, in the axial direction using a pressing jig (not shown) to prevent the core piece 2 from deforming and bulging in the axial direction during the process of applying circumferential compressive stress.

[0049] The core material that has undergone the above-described series of forming processes is transported to another manufacturing device as a stator core, for example, a device for attaching coils to the stator core.

[0050] As described above, with the stator core manufacturing method and stator core according to this embodiment, by pressing the connecting portion 5, specifically by pressing it radially outward of the stator core, a circumferential stress can be applied to the core material 1A pre-formed into an annular shape. This prevents gaps from forming between the contact surfaces 7 of adjacent core pieces 2 due to springback. This allows the stator core to maintain the desired shape, i.e., the annular shape, without using a separate member such as a housing. In addition, because a circumferential compressive stress acts on each core piece 2, the core pieces 2 are less likely to separate from each other even when an external force is applied, and this also prevents problems such as partial vibration of the stator core when used as a motor.

[0051] The present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present disclosure. All of these modifications are included in the technical concept of the present disclosure. Furthermore, unless otherwise specified in the specification, each component of the present disclosure is not limited to one, and may be present in multiple forms.

[0052] All references, including publications, patent applications, and patents, cited in this specification are herein incorporated by reference to the same extent as if each reference was individually and specifically indicated to be incorporated by reference and set forth herein in its entirety.

[0053] The use of nouns and similar referents in connection with the description of this disclosure (particularly in connection with the claims that follow) shall be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The words "comprises," "has," "includes," and "comprises" shall be construed as open-ended terms (i.e., meaning "including, but not limited to"), unless otherwise noted. The recitation of numerical ranges herein is merely intended to serve as a shorthand method for referring individually to each value falling within the range, unless otherwise indicated herein, and each value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or clearly contradicted by context. Any example or exemplary language used herein (e.g., "such as"), unless otherwise claimed, is intended merely to better illustrate the disclosure and does not pose a limitation on the scope of the disclosure. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the present disclosure.

[0054] Preferred embodiments of the disclosure are described herein, including the best mode known to the inventors for carrying out the disclosure. Variations of these preferred embodiments will become apparent to those skilled in the art upon reading the foregoing description. The inventor expects that skilled persons will apply such variations as appropriate, and intends to practice the disclosure otherwise than as specifically described herein. Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, this disclosure includes any combination of the above-described elements in all variations thereof unless otherwise indicated herein or otherwise clearly contradicted by context.

Claims

1. A method for manufacturing a stator core, comprising the steps of: preparing a core material including a plurality of core pieces each having a yoke portion and a tooth portion, with portions of the yoke portions of adjacent core pieces connected by connecting portions; winding the plurality of core pieces while bending them at the connecting portions to pre-shape the core material into an annular shape; and pressing one or more of the connecting portions of the pre-shape core material into an annular shape to impart circumferential compressive stress to the plurality of core pieces.

2. A method for manufacturing a stator core as described in claim 1, wherein the step of applying circumferential compressive stress to the plurality of core pieces includes a step of pressing one or more of the connecting portions of the annularly formed core material toward the outside of the core material to plastically deform it.

3. A method for manufacturing a stator core as described in claim 1, wherein the step of applying circumferential compressive stress to the plurality of core pieces includes a step of press-fitting a press-fit member into a space surrounded by the yoke portions and the connecting portions of adjacent core pieces.

4. A method for manufacturing a stator core according to claim 1, wherein the step of pre-forming the core material into an annular shape includes a step of spirally winding and stacking the multiple core pieces while bending them at the connecting portions.

5. A method for manufacturing a stator core according to claim 1, further comprising a step of stacking a plurality of the core materials preliminarily formed into an annular shape before the step of applying circumferential compressive stress to the plurality of core pieces.

6. A stator core comprising the core material manufactured by the method for manufacturing a stator core according to any one of claims 1 to 5.

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