Method for manufacturing a stator and apparatus for manufacturing a stator

Abstract

In a method for manufacturing a stator according to the present invention, carried out is a stress removal step for supplying an electric current to an induction heating coil disposed in a plurality of slots so that a laminated core generates heat, thereby removing a residual stress in the laminated core which is caused by pressing.

Description

Technical Field

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[0001] The present invention relates to a method for manufacturing a stator and a manufacturing apparatus for a stator.

Background Art

[0002] Conventionally, a method for manufacturing a stator is known in which a laminated core is heated by passing an electric current through an induction heating coil to remove residual stress in the laminated core caused by press working. Such a method for manufacturing a stator is disclosed, for example, in Japanese Patent No. 6645163.

[0003] Japanese Patent No. 6645163 discloses a method for annealing a motor core (laminated core) by induction heating. In the method for annealing a motor core described in Japanese Patent No. 6645163, a motor core including a plurality of slots formed by laminating electromagnetic steel sheets after punching (press working) is prepared. Then, annular heating induction coils (induction heating coils) are respectively disposed outside and inside the motor core. Then, by passing an electric current through the heating induction coils disposed outside and inside the motor core, the entire motor core is heated, and distortion (residual stress) in the motor core caused by punching is removed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the annealing method for laminated cores described in Japanese Patent Publication No. 6645163, the entire laminated core is heated when residual stress caused by press working is removed. In this case, since the entire laminated core is heated and then slowly cooled after heating, the time required to remove residual stress becomes relatively long. In other words, productivity is low. Also, since the entire laminated core is heated, the temperature change in each part of the laminated core becomes large, and the amount of deformation of the laminated core becomes large. In other words, a jig is required to suppress the large amount of deformation of the laminated core. For this reason, there is a need for a stator manufacturing method and manufacturing apparatus that can shorten the time required to remove residual stress and suppress the large amount of deformation of the laminated core when removing residual stress.

[0006] This invention was made to solve the above-mentioned problems, and one objective of this invention is to provide a method for manufacturing a stator and a stator manufacturing apparatus that can shorten the time required to remove residual stress and suppress the amount of deformation of the laminated core when removing residual stress. [Means for solving the problem]

[0007] To achieve the above objective, the method for manufacturing a stator in the first aspect of this invention comprises a core forming step of forming a laminated core by press working, in which electromagnetic steel sheets are laminated and a plurality of teeth protruding in the radial direction and a plurality of slots formed between the plurality of teeth are formed, and a stress relief step after the core forming step of heating the laminated core by passing an electric current through induction heating coils placed in each of the plurality of slots to remove residual stress in the laminated core caused by press working, wherein the stress relief step is A slot arrangement portion is provided within a slot, which includes a base as a tip portion extending along the radial direction of the laminated core, and folded portions in which both radial ends of the tip portion are folded back toward the axial side of the laminated core. Arranged within multiple slots, From the folded part The process includes passing an electric current through an induction heating coil having a plurality of axial extensions extending in the axial direction and a connecting portion that connects the plurality of axial extensions arranged in a plurality of circumferentially adjacent slots.

[0008] The first aspect of this invention relates to a method for manufacturing a stator, which includes a stress relief step in which the laminated core is heated by passing an electric current through induction heating coils placed in each of the multiple slots, thereby removing residual stress in the laminated core caused by press working. This allows for the localized heating of the portion of the laminated core surrounding multiple slots during the stress relief step, thereby locally removing residual stress in the laminated core caused by press working in that portion. This reduces the heating time and cooling time of the laminated core, as well as the amount of deformation of the laminated core, compared to heating the entire laminated core. As a result, the time required to remove residual stress can be shortened, and the amount of deformation of the laminated core during residual stress removal can be suppressed. In a laminated core formed by press working, the portion of the shear cut surface of the laminated core where residual stress occurs is the portion surrounding multiple slots through which a large amount of magnetic flux flows when the stator is used as part of a rotating electric machine, and it is necessary to remove the residual stress from this portion. In this invention, the localized heating of the portion of the laminated core surrounding multiple slots is achieved by focusing on this point.

[0009] Furthermore, in order to achieve the above objective, the stator manufacturing apparatus in the second aspect of this invention includes an induction heating coil for heating the laminated core by passing an electric current through it, in which the laminated core is arranged in each of the multiple slots of the laminated core, which includes a plurality of teeth that protrude radially and a plurality of slots formed between the plurality of teeth, and the induction heating coil is provided to remove residual stress in the laminated core, and the induction heating coil is provided A slot arrangement portion is provided within a slot, which includes a base as a tip portion extending along the radial direction of the laminated core, and folded portions in which both radial ends of the tip portion are folded back toward the axial side of the laminated core. Arranged within multiple slots, From the folded part It includes a plurality of axial extensions extending in the axial direction and a connecting portion that connects the plurality of axial extensions, which are arranged in a plurality of adjacent slots in the circumferential direction.

[0010] The stator manufacturing apparatus in the second aspect of this invention includes an induction heating coil that, when positioned in each of the multiple slots of the laminated core, heats the laminated core by passing an electric current through it to remove residual stress in the laminated core. By using the induction heating coil, the portions surrounding the multiple slots of the laminated core are heated locally, thereby removing residual stress in the laminated core locally in those portions. As a result, similar to the stator manufacturing method in the first aspect, the time for heating and slowly cooling the laminated core is relatively shorter compared to the case where the entire laminated core is heated, and the amount of deformation of the laminated core is reduced. Consequently, similar to the stator manufacturing method in the first aspect, the time required to remove residual stress can be shortened, and the amount of deformation of the laminated core when removing residual stress can be suppressed. [Effects of the Invention]

[0011] According to the present invention, as described above, it is possible to provide a method for manufacturing a stator and a manufacturing apparatus that can shorten the time required to remove residual stress and suppress the amount of deformation of the laminated core when removing residual stress. [Brief explanation of the drawing]

[0012] [Figure 1] This is a perspective view showing a stator according to the first to fourth embodiments of the present invention. [Figure 2] This figure shows the manufacturing flow of a stator according to the first embodiment of the present invention. [Figure 3] This is a perspective view showing the laminated core in the manufacturing flow of a stator according to the first embodiment of the present invention. [Figure 4] This is a perspective view showing a stator manufacturing apparatus according to a first embodiment of the present invention. [Figure 5] This is a partially enlarged perspective view of a stator manufacturing apparatus according to the first embodiment of the present invention. [Figure 6]It is a perspective view showing an induction heating coil of a stator manufacturing apparatus according to a first embodiment of the present invention. [Figure 7] It is a cross-sectional view along a plane orthogonal to the axial direction of the tip portion of the induction heating coil of the stator manufacturing apparatus according to the first embodiment of the present invention. [Figure 8] It is a perspective view for explaining the movement of the laminated core in the stator manufacturing flow according to the first embodiment of the present invention. [Figure 9] It is a diagram showing a stator manufacturing flow according to a second embodiment of the present invention. [Figure 10] It is a perspective view showing a stator manufacturing apparatus according to a second embodiment of the present invention. [Figure 11] It is a diagram showing a stator manufacturing flow according to a third embodiment of the present invention. [Figure 12] It is a perspective view showing a stator manufacturing apparatus according to a third embodiment of the present invention. [Figure 13] It is a diagram showing a stator manufacturing flow according to a fourth embodiment of the present invention. [Figure 14] It is a perspective view showing a stator manufacturing apparatus according to a fourth embodiment of the present invention. [Figure 15] It is a perspective view showing a stator manufacturing apparatus according to a modified example of the second embodiment of the present invention. [[ID=二十九]] [Figure 16] It is a side view showing an induction heating coil of a stator manufacturing apparatus according to a first modified example of the first to fourth embodiments of the present invention. [Figure 17] It is a side view showing an induction heating coil of a stator manufacturing apparatus according to a second modified example of the first to fourth embodiments of the present invention.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0014] [Configuration of Stator According to the First to Fourth Embodiments] Referring to FIG. 1, the configuration of the stator 10 according to the first to fourth embodiments of the present invention will be described.

[0015] In the following description, the axial, radial, and circumferential directions of the stator core 11 (laminated core 10A (see Figure 3)) of the stator 10 will be referred to as the Z direction, R direction, and C direction, respectively. Furthermore, one side and the other side in the axial direction (Z direction) will be referred to as the Z1 side and the Z2 side, respectively. Also, the inner and outer sides in the radial direction (R direction) will be referred to as the R1 side and the R2 side, respectively.

[0016] As shown in Figure 1, the stator 10, together with a rotor (not shown) positioned on the R1 side of the stator 10 opposite the stator 10, constitutes part of an inner-rotor type rotating electric machine (not shown). The rotating electric machine is, for example, a motor, a generator, or a motor-generator.

[0017] The stator 10 comprises a stator core 11 and a coil section (not shown).

[0018] The stator core 11 has a cylindrical shape with a central axis (not shown) along the Z direction. The stator core 11 is formed by laminating multiple electrical steel sheets (for example, silicon steel sheets) in the Z direction.

[0019] The stator core 11 includes an annular back yoke 11a and a plurality of teeth 11b protruding from the back yoke 11a toward R1. A slot 11c is formed between each adjacent tooth 11b in the C direction. In other words, the stator core 11 includes a plurality of slots 11c.

[0020] Each of the multiple slots 11c is provided to extend in the Z direction. Each of the multiple slots 11c is formed so that both sides in the Z direction are open in the stator core 11. Furthermore, each of the multiple slots 11c is formed so that the R1 side is open in the stator core 11.

[0021] The coil section includes multiple slot housings, each housed in one of the multiple slots 11c. The coil section also includes multiple coil end sections connecting the slot housings housed in different slots 11c. The coil section is made of copper wire. The coil section is configured to generate magnetic flux when supplied with three-phase alternating current power from a power supply unit (not shown).

[0022] [Method for manufacturing a stator and apparatus for manufacturing a stator according to the first embodiment] Referring to Figures 2 to 8, the method for manufacturing the stator 10 and the manufacturing apparatus 100 for the stator 10 according to the first embodiment of the present invention will be described in accordance with the manufacturing flow of the stator 10 according to the first embodiment.

[0023] (Core formation process) First, as shown in Figure 2, a core formation process is performed in step S110. As shown in Figure 3, the core formation process (S110) is a process in which electrical steel sheets are laminated and a laminated core 10A is formed by press working (punching), which includes a plurality of teeth 11b protruding in the radial direction (R direction) and a plurality of slots 11c formed between the plurality of teeth 11b. Specifically, the laminated core 10A is formed by punching out a plurality of electrical steel sheets and then laminating the plurality of electrical steel sheets.

[0024] In the core formation process (S110), residual stress is generated in the shear cut portion of the laminated core 10A formed by punching. The area around the multiple slots 11c in the shear cut portion is where a large amount of magnetic flux flows when the stator 10 is used as part of a rotating electric machine. The area around the multiple slots 11c in the shear cut portion refers to the area around each of the multiple slots 11c (inner wall surface 11d (see Figure 7)) and the tip of each of the multiple teeth 11b. On the other hand, the R2 side end of the back yoke 11a in the shear cut portion is where almost no magnetic flux flows when the stator 10 is used as part of a rotating electric machine. Therefore, the area of ​​the laminated core 10A where residual stress needs to be removed is the area around the multiple slots 11c in the shear cut portion.

[0025] (Stress relief process) Next, as shown in Figure 2, a stress relief process is performed in step S120. As shown in Figure 4, the stress relief process (S120) is a process in which the laminated core 10A is heated by passing an electric current through induction heating coils 110 placed in each of the multiple slots 11c, thereby removing residual stress in the laminated core 10A caused by press working (punching). In other words, the stress relief process (S120) is a process in which the laminated core 10A is annealed in order to remove residual stress generated at the shear cut portion of the laminated core 10A. The stress relief process (S120) is performed using the manufacturing apparatus 100 for the stator 10. The manufacturing apparatus 100 for the stator 10 is equipped with induction heating coils 110. The induction heating coils 110 are coils that are placed in each of the multiple slots 11c of the laminated core 10A, and by passing an electric current through them, heat the laminated core 10A to remove residual stress in the laminated core 10A caused by press working. Note that Figure 4 omits the illustration of the inert gas injection unit 130, which will be described later.

[0026] As a result, in the stress relief process (S120), by using the induction heating coil 110, the areas around multiple slots 11c in the laminated core 10A are locally heated, thereby locally removing residual stress in the laminated core 10A caused by the press working (punching) in the areas around multiple slots 11c in the laminated core 10A. Compared to heating the entire laminated core 10A, this shortens the heating time and slow cooling time of the laminated core 10A, and also reduces the amount of deformation of the laminated core 10A. As a result, the time required to remove residual stress can be shortened, and the amount of deformation of the laminated core 10A when removing residual stress can be suppressed.

[0027] As shown in Figure 5, the stress relief step (S120) is a step in which the laminated core 10A is heated by passing an electric current through an induction heating coil 110, which includes a tip portion 111 that expands radially (R direction) and folded portions 112 in which both radial ends of the tip portion 111 are folded back toward the axial direction (Z direction). Specifically, the induction heating coil 110 includes a tip portion 111, folded portions 112, an axial extension portion 113, and a connecting portion 114 (see Figure 4). As shown in Figure 6, the tip portion 111 extends along the R direction. The folded portions 112 are folded back toward the Z1 side from each of the radial ends of the tip portion 111. The Z1 side ends of the folded portions 112 are connected to the axial extension portion 113 that extends in the Z direction. As shown in Figure 4, the connecting portion 114 extends along the C direction to connect adjacent axial extension portions 113 in the C direction.

[0028] As a result, as shown in Figure 6, when viewed from the circumferential direction (direction C), a portion surrounded by the induction heating coil 110 can be formed by the tip portion 111 and the pair of folded portions 112. Consequently, magnetic flux is more easily concentrated in the vicinity of the portion surrounded by the induction heating coil 110 compared to the vicinity of the portion not surrounded by the induction heating coil 110, so the laminated core 10A can be efficiently heated using the portion surrounded by the induction heating coil 110.

[0029] The stress relief step (S120) is a step in which the laminated core 10A is heated by passing an electric current through an induction heating coil 110 which includes a slot arrangement section 115 having a triangular shape, which, when viewed from the circumferential direction (C direction), includes a base 111a extending along the radial direction (R direction) as the tip portion 111 and a hypotenuse 112a extending axially (Z direction) from the base 111a as the folded portion 112. Specifically, when viewed from the C direction, the slot arrangement section 115 has an isosceles triangular shape formed by the base 111a extending along the R direction and a pair of folded portions 112.

[0030] As a result, in the axial direction (Z direction), a pair of opposing portions (a pair of axial extensions 113) are formed on the side opposite to the base 111a of the triangular slot arrangement portion 115 of the induction heating coil 110, facing each other and with current flowing in opposite directions. In the pair of opposing portions, the magnetic fluxes generated by the currents flowing in opposite directions cancel each other out. That is, a pair of opposing portions that do not heat the laminated core 10A are formed adjacent to the triangular slot arrangement portion 115 that can heat the laminated core 10A. As a result, as shown in Figure 5, by flowing current through the induction heating coil 110 with the pair of opposing portions (a pair of axial extensions 113) positioned near the laminated core 10A in the axial direction (Z direction), it is possible to prevent excessive heating of the area near the axial end face 10a of the laminated core 10A. Furthermore, since thermal deformation is likely to occur near the end face 10a in the axial direction of the laminated core 10A due to the fact that the laminated core 10A is made up of multiple relatively thin electrical steel sheets laminated together, it is undesirable to generate excessive heat in that area.

[0031] As shown in Figure 6, the stress relief step (S120) is a step in which the laminated core 10A is heated by passing an electric current through the induction heating coil 110, in which the ferrite core 120 is arranged in the inner portion surrounded by the induction heating coil 110 when viewed from the circumferential direction (direction C). Specifically, the manufacturing apparatus 100 for the stator 10 is equipped with a ferrite core 120. The ferrite core 120 is arranged inside the slot arrangement portion 115, which has an isosceles triangular shape when viewed from direction C.

[0032] As a result, the ferrite core 120 allows the magnetic flux generated by the current flowing through the portion of the induction heating coil 110 surrounding the ferrite core 120 (slot arrangement portion 115) to be concentrated near the portion of the induction heating coil 110 surrounding the ferrite core 120 (slot arrangement portion 115). Consequently, the laminated core 10A can be heated more efficiently compared to the case where current is passed through the induction heating coil 110 in which the ferrite core 120 is not placed in the inner portion surrounded by the induction heating coil 110.

[0033] The ferrite core 120 has a shape that conforms to the shape of the inner space of the slot arrangement portion 115 when viewed from direction C. That is, the ferrite core 120 has an isosceles triangular shape when viewed from direction C. The ferrite core 120 is formed in a plate shape so that it does not protrude from the induction heating coil 110 on either side in the C direction when viewed from direction Z. The ferrite core 120 is fixed to the induction heating coil 110 (slot arrangement portion 115) using an adhesive (for example, an epoxy resin adhesive) with an attachment sandwiched between the ferrite core 120 and the induction heating coil 110. That is, when the laminated core 10A is moved in the Z direction relative to the induction heating coil 110 (described later), the ferrite core 120 moves in the Z direction together with the laminated core 10A.

[0034] As shown in Figure 7, the stress relief step (S120) is a step in which the laminated core 10A is heated by passing an electric current through the induction heating coil 110, in which, when viewed from the axial direction (Z direction), the portion of the induction heating coil 110 that is arranged in each of the slots 11c (slot arrangement portion 115) has a shape that conforms to the shape of the inner wall surface 11d of the slot 11c.

[0035] As a result, when the laminated core 10A is heated by passing current through the induction heating coil 110, it is possible to suppress the large differences in the distance L between the portion of the induction heating coil 110 located in each of at least several slots 11c (slot arrangement portion 115) and the inner wall surface 11d of the slot 11c for each portion of the induction heating coil 110. As a result, compared to the case where the portion of the induction heating coil 110 located in each of at least several slots 11c (slot arrangement portion 115) does not have a shape that conforms to the shape of the inner wall surface 11d of the slot 11c when viewed from the axial direction (Z direction), it is possible to heat the laminated core 10A while suppressing uneven heating of the laminated core 10A in the peripheral portions of the multiple slots 11c that are heated locally.

[0036] As shown in Figure 8, the stress relief step (S120) is a step in which the laminated core 10A is heated by passing an electric current through the induction heating coil 110 while changing the relative position between the laminated core 10A and the induction heating coil 110 in the axial direction (Z direction). Specifically, the manufacturing apparatus 100 of the stator 10 is equipped with a core moving mechanism (not shown). The core moving mechanism is configured to move the laminated core 10A in the Z direction. Then, in the stress relief step (S120), the laminated core 10A is heated by passing an electric current through the induction heating coil 110 while moving the laminated core 10A in the Z direction relative to the induction heating coil 110 using the core moving mechanism.

[0037] This allows the laminated core 10A to be heated by passing current through the induction heating coil 110, while changing the area in the laminated core 10A that generates a large amount of heat in the axial direction (Z direction). As a result, compared to the case where the relative position between the laminated core 10A and the induction heating coil 110 is fixed and current is passed through the induction heating coil 110, it is possible to heat the laminated core 10A while suppressing uneven heating in the area around the multiple slots 11c that generate localized heat within the laminated core 10A.

[0038] The stress relief step (S120) is a step in which the laminated core 10A is heated by passing an electric current through the induction heating coil 110 while inert gas is ejected from an inert gas injection unit 130, which is provided separately from the induction heating coil 110 and is configured to change its relative position to the laminated core 10A together with the induction heating coil 110. Specifically, the manufacturing apparatus 100 for the stator 10 includes an inert gas injection unit 130. The inert gas injection unit 130 is configured to be supplied with inert gas. The inert gas injection unit 130 has ejection holes 131 formed therein for ejecting inert gas from the inside out. The inert gas injection unit 130 is formed in a plate shape so as not to protrude from the induction heating coil 110 on either side in the C direction when viewed from the Z direction. The ejection holes 131 are provided on both sides in the C direction of the plate-shaped inert gas injection unit 130. The inert gas injection unit 130 is fixed to the induction heating coil 110 (slot arrangement unit 115) using an adhesive (for example, an epoxy resin adhesive) with an attachment sandwiched between the inert gas injection unit 130 and the induction heating coil 110 (slot arrangement unit 115). In other words, when the laminated core 10A is moved in the Z direction relative to the induction heating coil 110, the inert gas injection unit 130 moves together with the laminated core 10A in the Z direction.

[0039] As a result, the inert gas ejected from the inert gas injection unit 130 reduces the oxygen concentration around the parts of the laminated core 10A that are to be locally heated, allowing the laminated core 10A to be heated. Consequently, oxidation of the laminated core 10A can be prevented when the laminated core 10A is heated. Furthermore, by providing the inert gas injection unit 130, which changes its relative position to the laminated core 10A and ejects inert gas together with the induction heating coil 110, there is no need to provide a device (such as a vacuum chamber) to cover the entire laminated core 10A and reduce the oxygen concentration inside. In addition, since the inert gas injection unit 130 is provided separately from the induction heating coil 110, a flow path (for example, a cooling water flow path 116, which will be described later) can be provided inside the induction heating coil 110 for circulating fluids other than inert gas.

[0040] A cooling water channel 116 is formed inside the induction heating coil 110 for circulating cooling water. Then, in the stress relief process (S120), the laminated core 10A is heated by passing an electric current through the induction heating coil 110 while circulating cooling water through the cooling water channel 116. As a result, the induction heating coil 110, which becomes hot when an electric current is passed through it, is prevented from degrading due to excessive heat by circulating cooling water through the cooling water channel 116 provided inside the induction heating coil 110.

[0041] The stress relief step (S120) is a step in which the laminated core 10A is heated by passing current through an induction heating coil 110, which is placed in each of the slots 11c. Specifically, the induction heating coil 110 includes a plurality of slot arrangement sections 115 corresponding to all of the slots 11c of the laminated core 10A. The plurality of slot arrangement sections 115 are connected in series with each other. Then, with a slot arrangement section 115 placed in each of the slots 11c of the laminated core 10A, current is passed through the induction heating coil 110.

[0042] By the above method, in the stress relief step (S120), residual stress is removed from the peripheral portions of the multiple slots 11c in the shear cut portion, and the stator core 11 (see Figure 1) in which the coil portion is arranged is formed.

[0043] (Coil placement process) Next, as shown in Figure 2, the coil placement process is performed in step S130. The coil placement process (S130) is the process of placing the coil section relative to the stator core 11 (see Figure 1).

[0044] [Method for manufacturing a stator and apparatus for manufacturing a stator according to the second embodiment] Referring to Figures 9 and 10, a method for manufacturing a stator 10 and a manufacturing apparatus 200 for manufacturing a stator 10 according to a second embodiment of the present invention will be described in accordance with the manufacturing flow of the stator 10 according to the second embodiment. In the figures, the same reference numerals are used for parts that are the same as those in the first embodiment described above.

[0045] (Stress relief process) As shown in Figure 9, a stress relief process is performed in step S220. The stress relief process (S220), as shown in Figure 10, is a process that removes residual stress in the laminated core 10A caused by press working (punching) by passing an electric current through induction heating coils 210 placed in each of the multiple slots 11c, similar to the stress relief process (S120) of the first embodiment. Furthermore, the stress relief process (S220) is performed using the stator 10 manufacturing apparatus 200, similar to the stress relief process (S120) of the first embodiment. The stator 10 manufacturing apparatus 200 is equipped with induction heating coils 210.

[0046] In the stress relief process (S220), the first stress relief process (S221) and the second stress relief process (S222) are performed in this order. The first stress relief process (S221) is a process of heating the laminated core 10A by passing an electric current through induction heating coils 210 located in each of every other slot 11c among the multiple slots 11c in the C direction when viewed from the Z direction. The second stress relief process (S222) is a process of heating the laminated core 10A by passing an electric current through induction heating coils 210 located in each of the multiple slots 11c in the C direction where no induction heating coils 210 that were heated in the first stress relief process (S221) are located. In other words, the stress relief process (S220) is a process in which, when viewed from the axial direction (Z direction), current is passed through the induction heating coils 210 located in each of the N slots 11c among the multiple slots 11c in the circumferential direction (C direction), and this process is repeated (N+1) times while sequentially changing the multiple slots 11c in the circumferential direction (C direction) where the induction heating coils 210 are located, and N=1.

[0047] Specifically, the induction heating coil 210 includes multiple slot arrangement sections 115 corresponding to half of the slots 11c of the laminated core 10A, such that each of the multiple slot arrangement sections 115 is positioned in every other slot 11c of the multiple slots 11c in the C direction. Then, in the first stress relief step (S221), with the induction heating coil 110 (slot arrangement section 115) positioned in half of the multiple slots 11c, the laminated core 10A is heated by passing current through the induction heating coil 210. Then, in the second stress relief step (S222), with the induction heating coil 210 (slot arrangement section 115) positioned in the remaining half of the multiple slots 11c, the laminated core 10A is heated by passing current through the induction heating coil 110. Furthermore, after the first stress relief process (S221), the laminated core 10A is moved to change the slot 11c in which the induction heating coil 210 (slot arrangement section 115) is located, in order to perform the second stress relief process (S222).

[0048] As a result, in both the first stress relief step (S221) and the second stress relief step (S222), when current is passed through the induction heating coils 210 located in every N slots 11c among the multiple slots 11c in the circumferential direction (C direction), the slots 11c in which the induction heating coils 210 through which current is passed are located at every N slots in the circumferential direction (C direction). Therefore, it is possible to suppress the close proximity in the circumferential direction (C direction) between induction heating coils 210 that are adjacent to each other in the circumferential direction (C direction) and through which current is passed. Consequently, unlike the case in which current is passed through the induction heating coils 210 located in every slot 11c of the laminated core 10A, it is possible to suppress the cancellation of the magnetic flux generated by each of the induction heating coils 210 that are adjacent to each other in the circumferential direction (C direction) and through which current is passed. Furthermore, in the stress relief step (S120) of the first embodiment described above, if current is passed through the induction heating coils 210 located in each of the slots 11c of the laminated core 10A, the overall heating time is shortened, but the size of the induction heating coils 210 increases, leading to increased equipment costs. In contrast, by passing current through the induction heating coils 210 located in every N slots 11c among the multiple slots 11c in the circumferential direction (C direction), the size of the induction heating coils 210 can be reduced, thereby suppressing the increase in equipment costs.

[0049] Furthermore, the manufacturing method for the stator 10 and the other configurations of the manufacturing apparatus 200 for the stator 10 according to the second embodiment are substantially the same as those of the manufacturing method for the stator 10 and the manufacturing apparatus 100 according to the first embodiment.

[0050] [Method for manufacturing a stator and apparatus for manufacturing a stator according to the third embodiment] Referring to Figures 11 and 12, a method for manufacturing a stator 10 and a manufacturing apparatus 300 for the stator 10 according to a third embodiment of the present invention will be described in accordance with the manufacturing flow of the stator 10 according to the third embodiment. In the figures, the same reference numerals are used for parts that are the same as those in the first embodiment described above.

[0051] (Stress relief process) As shown in Figure 11, a stress relief process is performed in step S320. The stress relief process (S320), as shown in Figure 12, is a process that removes residual stress in the laminated core 10A caused by press working (punching) by passing an electric current through induction heating coils 310 placed in each of the multiple slots 11c, similar to the stress relief process (S120) of the first embodiment. Furthermore, the stress relief process (S320) is performed using the manufacturing apparatus 300 for the stator 10, similar to the stress relief process (S120) of the first embodiment. The manufacturing apparatus 300 for the stator 10 is equipped with induction heating coils 310.

[0052] The stress relief step (S320) is a step in which the laminated core 10A is heated by passing an electric current through an induction heating coil 310, which includes a slot arrangement portion 315 having a triangular shape when viewed from the circumferential direction (C direction), including a base 311a extending along the radial direction (R direction) as the tip portion 311 and a hypotenuse 312a extending axially (Z direction) from the base 311a as the folded portion 312. Specifically, the induction heating coil 310 includes a tip portion 311, a folded portion 312, and an axial extension portion 313. Unlike the induction heating coil 110 of the first embodiment, in which an isosceles triangular slot arrangement portion 115 was formed, the induction heating coil 310 has a slot arrangement portion 315 having a right-angled triangular shape when viewed from the C direction, formed by a base 311a extending along the R direction and a pair of folded portions 312.

[0053] The stator 10 manufacturing apparatus 300 includes a ferrite core 320, similar to the induction heating coil 110 in the first embodiment. The ferrite core 320 is located inside the slot arrangement section 315, which has a right-angled triangular shape when viewed from direction C. The stator 10 manufacturing apparatus 300 also includes an inert gas injection section 330, similar to the induction heating coil 110 in the first embodiment.

[0054] Furthermore, the manufacturing method for the stator 10 and the other configurations of the manufacturing apparatus 300 for the stator 10 according to the third embodiment are substantially the same as those of the manufacturing method for the stator 10 and the manufacturing apparatus 100 for the stator 10 according to the first embodiment.

[0055] [Method for manufacturing a stator and apparatus for manufacturing a stator according to the fourth embodiment] Referring to Figures 13 and 14, the method for manufacturing the stator 10 and the manufacturing apparatus 400 for the stator 10 according to the fourth embodiment of the present invention will be described in accordance with the manufacturing flow of the stator 10 according to the fourth embodiment. In the figures, the same reference numerals are used for parts that are the same as those in the first embodiment described above.

[0056] (Stress relief process) As shown in Figure 13, a stress relief process is performed in step S420. The stress relief process (S420), as shown in Figure 14, is a process that removes residual stress in the laminated core 10A caused by press working (punching) by passing an electric current through induction heating coils 410 placed in each of the multiple slots 11c, similar to the stress relief process (S120) of the first embodiment. Furthermore, the stress relief process (S420) is performed using the stator 10 manufacturing apparatus 400, similar to the stress relief process (S120) of the first embodiment. The stator 10 manufacturing apparatus 400 is equipped with induction heating coils 410.

[0057] The stress relief step (S420) is a step in which an inert gas is circulated through a gas channel 416 provided inside the induction heating coil 410, and an inert gas is ejected from a gas nozzle 416a of the induction heating coil 410, while an electric current is passed through the induction heating coil 410 to generate heat in the laminated core 10A. Specifically, a gas channel 416 for circulating inert gas is formed inside the induction heating coil 410. The gas channel 416 is configured to be supplied with inert gas. The induction heating coil 410 has a gas nozzle 416a formed therein for ejecting inert gas from the gas channel 416 inside the induction heating coil 410 toward the outside. The gas nozzle 416a is formed in the slot arrangement section 115. Although Figure 14 shows an example where the gas nozzle 416a is formed in the tip section 111, the gas nozzle 416a may also be formed in the folded section 112. Unlike the manufacturing apparatus 100 of the first embodiment described above, the stator 10 manufacturing apparatus 400 does not include an inert gas injection unit 130 that is provided separately from the induction heating coil 110.

[0058] This allows the laminated core 10A to be heated while the oxygen concentration around the localized heat-generating slots 11c of the laminated core 10A is reduced by the inert gas ejected from the gas nozzle 416a of the induction heating coil 410. As a result, oxidation of the laminated core 10A can be prevented when heating the laminated core 10A.

[0059] Furthermore, the manufacturing method for the stator 10 and the other configurations of the stator manufacturing apparatus 400 according to the fourth embodiment are substantially the same as those of the manufacturing method for the stator 10 and the stator manufacturing apparatus 100 according to the first embodiment.

[0060] [Differentiation] It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims rather than by the description of the embodiments above, and further includes all modifications (exceptions) within the meaning and scope of the claims.

[0061] For example, in the first to third embodiments described above, an example was shown in which a cooling water channel 116 for circulating cooling water is formed inside the induction heating coil 110, but the present invention is not limited thereto. In the present invention, a cooling water channel for circulating cooling water may not be formed inside the induction heating coil.

[0062] Furthermore, in the first to fourth embodiments described above, examples were shown in which, when viewed from the axial direction (Z direction), the portion of the induction heating coil 110 that is arranged in each of at least a plurality of slots 11c (slot arrangement portion 115) has a shape that conforms to the shape of the inner wall surface 11d of the slot 11c, but the present invention is not limited thereto. In the present invention, when viewed from the axial direction, the portion of the induction heating coil that is arranged in each of at least a plurality of slots (slot arrangement portion) may have a shape that does not conform to the shape of the inner wall surface of the slot.

[0063] Furthermore, in the second embodiment described above, an example was shown in which, after the first stress relief step (S221), the laminated core 10A is moved to change the slot 11c in which the induction heating coil 210 (slot arrangement section 115) is located in order to perform the second stress relief step (S222). However, the present invention is not limited to this. In the present invention, as shown in the modified example in Figure 15, the manufacturing apparatus 500 of the stator 10 equipped with two sets of induction heating coils 210 may be used so that, after the first stress relief step (S221), the laminated core 10A is not moved to change the slot 11c in which the induction heating coil 210 (slot arrangement section 115) is located in order to perform the second stress relief step (S222).

[0064] Furthermore, in the second embodiment described above, an example was shown in which current is passed through the induction heating coils 210, which are arranged in each of the N slots 11c among the plurality of slots 11c in the circumferential direction (C direction) when viewed from the axial direction (Z direction), and this is repeated (N+1) times while sequentially changing the plurality of slots 11c in the circumferential direction (C direction) where the induction heating coils 210 are arranged, with N=1. However, the present invention is not limited to this. In the present invention, N may be 2 or more. Note that N can be arbitrarily set considering the number of slots in the laminated core, the size of the laminated core, etc. For example, if the number of slots in the laminated core is small and the radial length of the laminated core is small, or the thickness (axial size) of the laminated core is small, N can be increased.

[0065] Furthermore, in the fourth embodiment described above, an example was shown in which a gas passage 416 for circulating an inert gas is formed inside the induction heating coil 410, and the stator manufacturing apparatus 400 does not have an inert gas injection unit 130 provided separately from the induction heating coil 110, but the present invention is not limited thereto. In the present invention, a gas passage for circulating an inert gas may not be formed inside the induction heating coil, and the stator manufacturing apparatus may have an inert gas injection unit provided separately from the induction heating coil, or a gas passage for circulating an inert gas may be formed inside the induction heating coil, and the stator manufacturing apparatus may have an inert gas injection unit provided separately from the induction heating coil.

[0066] Furthermore, in the first to third embodiments described above, an example was shown in which the laminated core 10A is heated by passing an electric current through the induction heating coils 110 (210, 310) while ejecting an inert gas from an inert gas injection unit 130 (330), which is provided separately from the induction heating coils 110 (210, 310) and is provided in such a way that its relative position to the laminated core 10A can be changed together with the induction heating coils 110 (210, 310). However, the present invention is not limited to this. In the present invention, the laminated core may also be heated by passing an electric current through the induction heating coils while ejecting an inert gas from an inert gas injection unit, which is provided separately from the induction heating coils and whose relative position to the laminated core does not change relative to the induction heating coils.

[0067] Furthermore, in the first to fourth embodiments described above, an example was shown in which the laminated core 10A is heated by passing a current through the induction heating coils 110 (210, 310, 410) while moving the laminated core 10A in the Z direction (axial direction) relative to the induction heating coils 110 (210, 310, 410) using a core moving mechanism, but the present invention is not limited thereto. In the present invention, the laminated core may be heated by passing a current through the induction heating coils while moving the induction heating coils axially relative to the laminated core, or the laminated core may be heated by passing a current through the induction heating coils while moving both the induction heating coils and the laminated core axially relative to each other.

[0068] Furthermore, while the first to fourth embodiments described above show an example in which a ferrite core 120 (320) is arranged in the inner portion surrounded by the induction heating coils 110 (210, 310, 410), the present invention is not limited to this. In the present invention, a ferrite core may not be arranged in the inner portion surrounded by the induction heating coils.

[0069] Furthermore, in the first to fourth embodiments described above, examples were shown in which the induction heating coil 110 (210, 310, 410) includes a slot arrangement portion 115 having a triangular shape when viewed from the circumferential direction (direction C), but the present invention is not limited thereto. In the present invention, the induction heating coil may be configured so as not to include a slot arrangement portion having a triangular shape when viewed from the circumferential direction, as shown in the first modified example in Figure 16 and the second modified example in Figure 17. For example, as shown in Figure 16, the manufacturing apparatus 600 for the stator 10 includes an induction heating coil 610. The induction heating coil 610 includes a slot arrangement portion 615 having a U-shape when viewed from the circumferential direction. Also, as shown in Figure 17, the manufacturing apparatus 700 for the stator 10 includes an induction heating coil 710. The induction heating coil 710 includes a slot arrangement portion 715 having a zigzag shape that folds back multiple times in the radial direction when viewed from the circumferential direction. In addition, in the configurations of the first modified example shown in Figure 16 and the second modified example shown in Figure 17, a gas flow path for circulating inert gas may be formed inside the induction heating coil, or the stator manufacturing apparatus may be equipped with an inert gas injection unit separate from the induction heating coil. [Explanation of Symbols]

[0070] 10…Stator, 10A…Laminated core, 11b…Teeth, 11c…Slot, 11d…Inner wall (of slot), 100, 200, 300, 400, 500, 600, 700…Manufacturing equipment (for stator), 110, 210, 310, 410, 610, 710…Induction heating coil, 111, 311…Tip, 111a, 311a…Base, 112, 312…Folded section, 112a, 312a…Hypotenuse, 115, 315, 615, 715…Slot arrangement section, 120, 320,…Ferrite core, 130, 330…Inert gas injection section, 416…Gas flow path, 416a…Gas nozzle

Claims

1. A core forming step involves forming a laminated core by press working, in which electrical steel sheets are laminated and a laminated core is formed including a plurality of teeth protruding in the radial direction and a plurality of slots formed between the plurality of teeth, The system includes a stress relief step, which, after the core formation step, generates heat in the laminated core by passing an electric current through induction heating coils placed in each of the plurality of slots, thereby removing residual stress in the laminated core caused by the press work. A method for manufacturing a stator, comprising the stress relief step of passing an electric current through an induction heating coil having a slot arrangement portion disposed within the slot, which includes a base as a tip portion extending along the radial direction of the laminated core and folded portions in which both radial ends of the tip portion are folded back toward the axial side of the laminated core; a plurality of axial extension portions disposed within the plurality of slots and each extending axially from the folded portion; and a connecting portion that connects the plurality of axial extension portions disposed within the plurality of adjacent slots in the circumferential direction.

2. The method for manufacturing a stator according to claim 1, wherein the stress relief step is a step of heating the laminated core by passing an electric current through the induction heating coil, which includes the slot arrangement portion having a triangular shape, as viewed from the circumferential direction of the laminated core, including a base extending along the radial direction as the tip portion and a hypotenuse extending in the axial direction from the base portion as the folded portion.

3. The method for manufacturing a stator according to claim 1, wherein the stress relief step is a step of heating the laminated core by passing an electric current through the induction heating coil, in which a ferrite core is arranged in the inner portion surrounded by the induction heating coil when viewed from the circumferential direction of the laminated core.

4. The method for manufacturing a stator according to claim 1, wherein the stress relief step is a step of heating the laminated core by passing an electric current through the induction heating coil while changing the relative position between the laminated core and the induction heating coil in the axial direction of the laminated core.

5. The method for manufacturing a stator according to claim 1, wherein the stress relief step is a step of generating heat in the laminated core by passing an electric current through the induction heating coil while ejecting an inert gas from an inert gas injection unit provided separately from the induction heating coil.

6. The method for manufacturing a stator according to claim 4, wherein the stress relief step is a step of generating heat in the laminated core by passing an electric current through the induction heating coil while ejecting an inert gas from an inert gas injection unit which is provided separately from the induction heating coil and which is provided so as to be able to change its relative position to the laminated core together with the induction heating coil.

7. The method for manufacturing a stator according to claim 1, wherein the stress relief step is a step of heating the laminated core by passing an electric current through the induction heating coil while circulating an inert gas through a gas channel provided inside the induction heating coil and ejecting the inert gas from a gas nozzle of the induction heating coil.

8. The method for manufacturing a stator according to claim 1, wherein the stress relief step is a step of passing a current through the induction heating coils, which are arranged in each of the N slots among the plurality of slots in the circumferential direction of the laminated core, when viewed from the axial direction of the laminated core, and repeating this process (N+1) times while sequentially changing the plurality of slots in the circumferential direction in which the induction heating coils are arranged.

9. The method for manufacturing a stator according to claim 1, wherein the stress relief step is a step of heating the laminated core by passing an electric current through the induction heating coil, in which, when viewed from the axial direction of the laminated core, at least the portion of the induction heating coil that is arranged in each of the plurality of slots has a shape that conforms to the shape of the inner wall surface of the slot.

10. A laminated core is provided, which includes a plurality of teeth that protrude radially and a plurality of slots formed between the plurality of teeth, and is positioned in each of the plurality of slots of the laminated core, wherein an induction heating coil is provided to heat the laminated core by passing an electric current through it to remove residual stress in the laminated core. A stator manufacturing apparatus comprising an induction heating coil having a base as a tip portion extending along the radial direction of the laminated core, and folded portions in which both radial ends of the tip portion are folded back toward the axial side of the laminated core, a slot arrangement portion disposed within the slot, a plurality of axial extension portions disposed within the plurality of slots and each extending axially from the folded portion, and a connecting portion that connects the plurality of axial extension portions disposed within the plurality of adjacent slots in the circumferential direction.

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