Stator core

Abstract

To provide a stator core capable of achieving both processability of stacking belt-shaped steel plates into a spiral shape and a magnetic characteristic of the stator core.SOLUTION: A stator core includes: a back yoke formed by stacking belt-shaped steel plates (20) into a spiral shape about a center axis and extending in a circumferential direction about the center axis; and a plurality of teeth extending from the back yoke toward the center axis. Slots (23) are formed between the adjacent teeth. In a back yoke forming portion (21a) of the belt-shaped steel plates forming the back yoke, an inclined portion (30) that becomes thinner toward an outer diameter direction of the stator core is partially formed. At positions in the back yoke forming portion corresponding to the slots in the circumferential direction of the stator core, slits (25) that are open toward the slots and extend in the outer diameter direction while having a width narrower than the width of the slots in the circumferential direction are formed.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a stator core applied to a rotating electric machine. [Background technology]

[0002] For example, there is a method for manufacturing a helical stator core in which a strip-shaped steel plate is processed into a punched piece having a shape in which an edge portion in the sheet width direction serves as a core back portion, and a plurality of teeth are arranged parallel to the sheet width direction inside the core back portion, and the punched piece is bent into a spiral shape around a cylindrical winding shaft so that the core back portion is on the radially outer side, and stacked while being wound up, to form a laminate into the stator core shape (see Patent Document 1).In the method for manufacturing a helical stator core described in Patent Document 1, the portion of the strip-shaped steel plate that will become the core back portion is crushed with a tapered rolling surface that slopes down toward the outer diameter side, making it easier to bend the strip-shaped steel plate into a spiral shape. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-188962 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in the helical stator core (stator core) described in Patent Document 1, the core back portion (back yoke portion) is rolled to have a tapered shape, which reduces the cross-sectional area of ​​the magnetic path in the core back portion, which may reduce the amount of magnetic flux or increase iron loss, resulting in a deterioration in the magnetic properties of the stator core.

[0005] The present invention has been made to solve the above-mentioned problems, and its main object is to provide a stator core that can achieve both the workability of spirally stacking strip-shaped steel plates and the magnetic properties of the stator core. [Means for solving the problem]

[0006] The first means for solving the above problem is: A stator core (11) is formed by laminating strip-shaped steel plates (20) in a spiral shape around a central axis (C1), and includes a back yoke (21) extending in a circumferential direction around the central axis (C1), and a plurality of teeth (22) extending from the back yoke toward the central axis, with slots (23) formed between each of the adjacent teeth, a back yoke forming portion (21a) of the strip-shaped steel plate that forms the back yoke is partially formed with an inclined portion (30) that becomes thinner in an outer radial direction of the stator core, At a position in the circumferential direction of the stator core corresponding to the slot in the back yoke forming portion, a slit (25) is formed that opens toward the slot and extends in the outer radial direction with a width narrower than the width of the slot in the circumferential direction.

[0007] According to the above configuration, the back yoke forming portion of the strip-shaped steel sheet has a sloped portion formed in part thereof that becomes thinner in the radial direction of the stator core. Therefore, the portion of the back yoke forming portion where the sloped portion is formed can be easily bent into a spiral shape. Because the sloped portion is formed in part of the back yoke forming portion, a reduction in the cross-sectional area of ​​the magnetic path of the back yoke can be suppressed compared to when the sloped portion is formed over the entire back yoke forming portion, and a deterioration in the magnetic properties of the stator core can be suppressed.

[0008] Furthermore, at positions in the circumferential direction of the stator core corresponding to the slots in the back yoke forming portion, slits are formed that open toward the slots and extend in the outer radial direction with a width narrower than the width of the slots in the circumferential direction. Therefore, when stacking the strip-shaped steel plate in a spiral shape, the strip-shaped steel plate can be easily deformed so that opposing side surfaces of the slits (hereinafter referred to as "slit mating surfaces") approach each other. Therefore, even if the back yoke forming portion is partially formed with an inclined portion, the strip-shaped steel plate can be easily bent into a spiral shape. As described above, the above-mentioned stator core (helical stator core) can achieve both the ease of stacking the strip-shaped steel plate in a spiral shape and the magnetic characteristics of the stator core. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 4 is a perspective view showing a manufacturing method of the stator core. [Figure 2] FIG. [Figure 3] FIG. [Figure 4] A partially enlarged view of a strip of steel plate. [Figure 5] FIG. 4 is a partially enlarged view showing an inclined portion of a strip-shaped steel plate according to a comparative example. [Figure 6] FIG. 4 is a partially enlarged view showing an inclined portion of a strip-shaped steel plate. [Figure 7] FIG. 10 is a partially enlarged view showing a modified example of the inclined portion. [Figure 8] FIG. 10 is a partially enlarged view showing another modified example of the inclined portion. [Figure 9] FIG. 10 is a partially enlarged view showing another modified example of the inclined portion. [Figure 10] FIG. 10 is a partially enlarged view showing another modified example of the inclined portion. [Figure 11] FIG. 10 is a partially enlarged view showing another modified example of the inclined portion. [Figure 12] FIG. 10 is a partially enlarged view showing another modified example of the inclined portion. [Figure 13] FIG. 10 is a partially enlarged view showing another modified example of the inclined portion. [Figure 14] FIG. 10 is a partially enlarged view showing another modified example of the inclined portion. [Figure 15] FIG. 10 is a partially enlarged view showing another modified example of the inclined portion. [Figure 16] FIG. 10 is a partially enlarged view showing a modified example of the slit. [Figure 17] FIG. 10 is a partially enlarged view showing another modified example of the slit. [Figure 18] FIG. 10 is a partially enlarged view showing another modified example of the slit. [Figure 19] FIG. [Figure 20] FIG. 10 is a partially enlarged view showing another modified example of the inclined portion. [Figure 21] FIG. [Figure 22] FIG. 10 is a partially enlarged view showing another modified example of the slit. [Figure 23] FIG. 10 is a partially enlarged view showing another modified example of the slit. [Figure 24] FIG. 10 is a partially enlarged view showing a circumferential slit at the end of the slit. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment embodied in a stator core of a rotating electric machine mounted on a vehicle (for example, a hybrid vehicle or an electric vehicle) will be described with reference to the drawings. In the following embodiments and modifications, identical or equivalent parts are designated by the same reference numerals in the drawings, and the explanations of the identical reference numerals will be used to refer to the same parts. The rotating electric machine is, for example, an electric motor (motor), a generator, or an MG (Motor Generator).

[0011] The rotating electric machine of this embodiment is applicable to permanent magnet synchronous motors, wound field motors, and induction motors, and is a rotating electric machine with three-phase windings. The rotating electric machine includes a cylindrical stator core 11 shown in Fig. 2. Hereinafter, the axial direction refers to the direction of the central axis C1 of the stator core 11, the radial direction refers to the radial direction of the stator core 11, i.e., the direction perpendicular to the central axis C1, and the circumferential direction refers to the circumferential direction of the stator core 11, i.e., the direction around the central axis C1.

[0012] FIG. 3 is a partially enlarged view of the stator core 11. The stator core 11 has an annular back yoke 21. The back yoke 21 extends circumferentially around a central axis C1 (not shown). The stator core 11 has a plurality of teeth 22 that protrude radially inward (toward the central axis C1) from the back yoke 21 and are arranged at predetermined distances in the circumferential direction. Slots 23 are formed between adjacent teeth 22. The slots 23 have an opening shape that extends radially and are provided at equal intervals in the circumferential direction in the stator core 11. The number of slots 23 in the stator core 11 is, for example, 48 (48 or more). The slots 23 open to the inner circumferential side of the stator core 11. The stator is configured by having stator windings wound around the slots 23. The stator core 11 has, for example, one slit 25 (more specifically, a series of slits 25 overlapping in the axial direction) corresponding to each slot 23. That is, stator core 11 has 48 (or more) slits 25 formed at equal intervals in the circumferential direction.

[0013] As shown in FIG. 1 , the stator core 11 is formed by stacking a strip-shaped steel sheet 20 while winding it around a winding shaft 61. The strip-shaped steel sheet 20 is formed of, for example, an electromagnetic steel sheet, which is a magnetic material. The strip-shaped steel sheet 20 extends linearly before being bent into a spiral shape. The winding shaft 61 is formed in a cylindrical shape, and the center axis of the winding shaft 61 is the center axis C1. At this time, the back yoke forming portion 21a of the strip-shaped steel sheet 20 is positioned radially outward of the winding shaft 61, and the strip-shaped steel sheet 20 is wound while being bent into a spiral shape, thereby forming the stator core 11 in which the strip-shaped steel sheet 20 is stacked in a spiral shape. The back yoke forming portion 21a is a portion that forms the back yoke 21 of the stator core 11 when stacked. The tooth forming portions 22a are portions that form the teeth 22 of the stator core 11 when stacked. During the bending process, the back yoke forming portion 21a is stretched in the circumferential direction.

[0014] Here, a roll pair consisting of an upper roll 63 and a lower roll 64 is arranged in front of the winding shaft 61. The roll pair clamps and compresses a part of the back yoke forming portion 21a of the strip-shaped steel sheet 20 fed between the upper and lower rolls 63, 64. Specifically, the upper and lower rolls 63, 64 partially crush the back yoke forming portion 21a with tapered rolling surfaces that slope downward toward the outer diameter side, making it easier to bend the back yoke forming portion 21a into a spiral shape.

[0015] 4 is a partially enlarged view of the strip-shaped steel plate 20. This figure shows the state of the strip-shaped steel plate 20 before it is bent into a spiral shape.

[0016] In the back yoke forming portion 21a of the strip-shaped steel plate 20, one slit 25 is formed at each position corresponding to the 48 (plurality of) slots 23, so that each slit 25 opens toward the slot 23. That is, the slits 25 are formed in a row in the longitudinal direction (the circumferential direction after bending) in the back yoke forming portion 21a. The slits 25 extend in the radially outward direction with a width narrower than the width of the slots 23 in the circumferential direction. The slits 25 are formed in a V-shape in the back yoke forming portion 21a, widening from a predetermined position in the radial direction of the stator core 11 toward the inner diameter side. Opposing side surfaces 25a of the slits 25 (hereinafter also referred to as "slit mating surfaces 25a") are formed flat. When the strip-shaped steel plate 20 is bent into a spiral shape, the strip-shaped steel plate 20 is deformed so that the slit mating surfaces 25a approach each other. Then, the slit mating surfaces 25a come into contact with or approach each other.

[0017] Fig. 5 is a partially enlarged view showing an inclined portion 90 of a strip-shaped steel plate 80 of a comparative example. In Fig. 5, the right figure shows a cross section taken along line AA of the left figure. Note that in the strip-shaped steel plate 80 of the comparative example, the same parts as those in this embodiment are given the same reference numerals and their explanations will be incorporated herein.

[0018] The slits 25 are not formed in the back yoke forming portion 81a of the strip-shaped steel plate 80. The entire back yoke forming portion 81a forms an inclined portion 90 that becomes thinner toward the outer diameter of the stator core 11. The inclined portion 90 is a portion that is rolled by a pair of rolls, and is extended in the circumferential direction toward the outer diameter side of the back yoke forming portion 81a. This makes it easier to bend the strip-shaped steel plate 80 into a spiral shape.

[0019] However, when the entire back yoke forming portion 81a is rolled to form the inclined portion 90, the cross-sectional area of ​​the magnetic path of the back yoke forming portion 81a (and therefore the back yoke) decreases, which may result in a decrease in the amount of magnetic flux or an increase in iron loss, thereby deteriorating the magnetic characteristics of the stator core 11.

[0020] Fig. 6 is a partially enlarged view showing the inclined portion 30 of the strip-shaped steel plate 20 of this embodiment. In Fig. 6, the right side shows a cross section taken along line AA of the left side.

[0021] The outer peripheral edge of back yoke forming portion 21a forms inclined portions 30 that become thinner in the outer radial direction of stator core 11. Inclined portions 30 are formed around the entire circumference in a range of back yoke forming portion 21a in the radial direction where slits 25 are not formed. In other words, inclined portions 30 are formed around the entire circumference in a range on the outer radial side of back yoke forming portion 21a than slits 25. In other words, inclined portions 30 that become thinner in the outer radial direction of stator core 11 are partially formed in back yoke forming portion 21a.

[0022] The inclined portion 30 (rolled portion) is a portion that has been rolled by the upper and lower rolls 63, 64, and is extended in the circumferential direction toward the outer diameter side of the back yoke forming portion 21a. The inclined portion 30 is formed, for example, so that a portion of one of the two plate surfaces (the surface with the largest area) of the strip-shaped steel plate 20 is inclined with respect to the other plate surface. Note that the inclined portion 30 can also be formed so that a portion of both of the two plate surfaces of the strip-shaped steel plate 20 is inclined with respect to the plate surface in the portion where the inclined portion 30 is not formed.

[0023] The range in which inclined portions 30 are formed in back yoke forming portion 21a is narrower than the range in which inclined portions 90 are formed in back yoke forming portion 81a of the comparative example. Therefore, the reduction in the cross-sectional area of ​​the magnetic path due to the formation of inclined portions 30 in back yoke forming portion 21a is less than the reduction in the cross-sectional area of ​​the magnetic path due to the formation of inclined portions 90 in back yoke forming portion 81a. Furthermore, in the range in back yoke forming portion 21a where inclined portions 30 are not formed, multiple slits 25 are formed aligned in the circumferential direction. This makes it easier to bend strip-shaped steel plate 20 into a spiral shape, even if the range in which inclined portions 30 are formed in back yoke forming portion 21a is narrower than the range in which inclined portions 90 are formed in back yoke forming portion 81a.

[0024] The present embodiment described above in detail has the following advantages.

[0025] The back yoke forming portion 21a of the strip-shaped steel sheet 20 is partially formed with an inclined portion 30 that becomes thinner toward the outer diameter of the stator core 11. Therefore, the portion of the back yoke forming portion 21a where the inclined portion 30 is formed can be easily bent into a spiral shape. Because the inclined portion 30 is partially formed in the back yoke forming portion 21a, a reduction in the cross-sectional area of ​​the magnetic path of the back yoke 21 can be suppressed compared to a comparative example strip-shaped steel sheet 80 in which the inclined portion 30 is formed over the entire back yoke forming portion 21a, and a deterioration in the magnetic characteristics of the stator core 11 can be suppressed. In particular, in the stator core 11 of a rotating electric machine mounted on a vehicle, the radial width of the back yoke 21 is increased to increase the output of the rotating electric machine. Therefore, by suppressing a reduction in the cross-sectional area of ​​the magnetic path of the back yoke 21, a significant deterioration in the performance of the rotating electric machine can be suppressed.

[0026] At positions in the circumferential direction of the stator core 11 corresponding to the slots 23 in the back yoke forming portion 21a, slits 25 are formed. The slits 25 open toward the slots 23 and extend radially outward with a width narrower than the width of the slots 23 in the circumferential direction. Therefore, when the strip-shaped steel plate 20 is spirally stacked, the strip-shaped steel plate 20 can be easily deformed so that the slit mating surfaces 25a approach each other. Therefore, even if the back yoke forming portion 21a has a configuration in which the inclined portion 30 is partially formed, the strip-shaped steel plate 20 can be easily bent into a spiral shape. In particular, in the stator core 11 of a rotating electric machine mounted on a vehicle, the radial width of the back yoke 21 is wide. This facilitates bending the strip-shaped steel plate 20, thereby improving processing accuracy and reducing the scale of the processing equipment. As described above, the above-described stator core 11 (helical stator core) can achieve both the ease of spirally stacking the strip-shaped steel plate 20 and the magnetic characteristics of the stator core 11.

[0027] The inclined portion 30 is formed around the entire periphery of the back yoke forming portion 21a in an area where no slits 25 are formed. With this configuration, the inclined portion 30 formed around the entire periphery of the stator core 11 in the back yoke forming portion 21a makes it easier to bend the strip-shaped steel plate 20 into a spiral shape. As a result, the workability of stacking the strip-shaped steel plate 20 into a spiral shape can be improved.

[0028] The above embodiment can be modified as follows: The same parts as those in the above embodiment are denoted by the same reference numerals and the description thereof will be incorporated herein.

[0029] As shown in FIG. 7 , a configuration may be adopted in which a radius R1 from the central axis C1 (not shown) to an end 30a of the inclined portion 30 on the central axis C1 side is shorter than a radius R2 from the central axis C1 to an end 25n of the slit 25 on the opposite side of the central axis C1. That is, the inclined portion 30 is formed in the back yoke forming portion 21a from an outer radial end 21b to a predetermined position on the inner radial side of the outer radial end 25n of the slit 25. With this configuration, a portion of the area where the inclined portion 30 is formed can overlap a portion of the area where the slit 25 is formed in the radial direction of the stator core 11. Therefore, the inclined portion 30 or the slit 25 can form a portion in the radial direction of the stator core 11 that is easy to bend the strip-shaped steel plate 20 into a spiral. This improves the workability of spirally stacking the strip-shaped steel plate 20. Furthermore, compared to the comparative example of a strip-shaped steel plate 80 in which an inclined portion 30 is formed over the entire back yoke forming portion 21a, the cross-sectional area of ​​the magnetic path of the back yoke 21 can be prevented from decreasing, and the magnetic properties of the stator core 11 can be prevented from deteriorating.

[0030] As shown in FIG. 8 , a configuration may be employed in which a radius R1 from the center axis C1 (not shown) to an end 30a of the inclined portion 30 on the side of the center axis C1 is longer than a radius R2 from the center axis C1 to an end 25n of the slit 25 on the opposite side of the center axis C1. That is, the inclined portion 30 is formed in the back yoke forming portion 21a from an outer radial end 21b to a predetermined position on the outer radial side of the outer radial end 25n of the slit 25. With this configuration, a range B where the inclined portion 30 is not formed can be provided in the radial direction of the stator core 11 between the range where the inclined portion 30 is formed and the range where the slit 25 is formed. Therefore, even if the back yoke forming portion 21a is extended in the circumferential direction by forming the inclined portion 30, the slit 25 can be prevented from widening. This prevents the magnetic path in the back yoke 21 from being cut by the slit 25, thereby preventing a deterioration in the magnetic properties of the stator core 11. Furthermore, since the slits 25 are formed, even if the inclined portion 30 is partially formed in the back yoke forming portion 21a, the belt-shaped steel plate 20 can be easily bent into a spiral shape.

[0031] As shown in FIGS. 9 and 10 , the inclined portions 30 may be formed intermittently in the circumferential direction of the stator core 11 in the back yoke forming portion 21a. This configuration can suppress a reduction in the cross-sectional area of ​​the magnetic path due to the inclined portions 30 being formed in the back yoke forming portion 21a, compared to when the inclined portions 30 are formed around the entire circumference of the stator core 11 in the back yoke forming portion 21a. As a result, deterioration in the magnetic characteristics of the stator core 11 can be suppressed. Furthermore, because the slits 25 are formed, even when the inclined portions 30 are partially formed in the back yoke forming portion 21a, the belt-shaped steel sheet 20 can be easily bent into a spiral shape. The inclined portions 30 may be formed in the back yoke forming portion 21a from the outer radial end 21b to a predetermined position on the outer radial side of the outer radial end 25n of the slit 25, or may be formed to a predetermined position on the inner radial side of the outer radial end 25n of the slit 25. The inclined portions 30 formed intermittently in the circumferential direction of the stator core 11 in the back yoke forming portion 21a can be formed, for example, by eccentrically displacing the rotation axis of the upper roll 63 upward (away from the lower roll 64) with respect to the central axis of the upper roll 63. Also, the inclined portions 30 can be formed intermittently in the circumferential direction of the stator core 11 in the back yoke forming portion 21a by varying the force with which the upper roll 63 presses the strip-shaped steel sheet 20 and increasing the force with which the upper roll 63 presses the strip-shaped steel sheet 20 at the timing when the inclined portions 30 are formed.

[0032] Specifically, as shown in FIG. 9 , a configuration can be employed in which the inclined portions 30 are formed in positions of the back yoke forming portion 21a corresponding to the slits 25 in the circumferential direction of the stator core 11. That is, the inclined portions 30 are formed in a range of the back yoke forming portion 21a that includes the slits 25 (a range that overlaps the slits 25) in the circumferential direction of the stator core 11. With this configuration, the portions of the back yoke forming portion 21a that are extended in the circumferential direction of the stator core 11 by forming the inclined portions 30 can be limited to positions corresponding to the slits 25. Furthermore, by extending the positions of the back yoke forming portion 21a corresponding to the slits 25 in the circumferential direction of the stator core 11, the slit mating surfaces 25a can be made to approach each other more easily. Therefore, the range in which the inclined portions 30 are formed in the back yoke forming portion 21a can be narrowed to suppress a deterioration in the magnetic properties of the stator core 11, while improving the workability of spirally stacking the strip-shaped steel plate 20.

[0033] 11 , in the circumferential direction of the stator core 11, a radius R11 from the central axis C1 to the end of the inclined portion 30 on the central axis C1 side in a first portion P1 of the back yoke forming portion 21a is longer than a predetermined radius, and in a second portion P2 of the back yoke forming portion 21a other than the first portion P1, a radius R12 from the central axis C1 to the end of the inclined portion 30 on the central axis C1 side is shorter than a predetermined radius. That is, the inclined portion 30 is formed in the back yoke forming portion 21a around the entire circumference of the stator core 11, and its radial width varies depending on the circumferential position. With this configuration, the area in which the inclined portion 30 is formed can be narrower in the circumferential direction of the stator core 11 in the first portion P1 of the back yoke forming portion 21a than in the second portion P2. Therefore, it is possible to suppress a reduction in the cross-sectional area of ​​the magnetic path caused by forming the inclined portion 30 in the back yoke forming portion 21a, compared to when the radius from the central axis C1 to the end of the inclined portion 30 on the central axis C1 side is shorter than a predetermined radius over the entire circumference of the stator core 11. As a result, it is possible to suppress a deterioration in the magnetic characteristics of the stator core 11.

[0034] As shown in FIG. 12 , a configuration can be adopted in which the second portion P2 is a portion of the back yoke forming portion 21a that corresponds to the tooth forming portion 22a (teeth 22) in the circumferential direction of the stator core 11. That is, the second portion P2 is formed in a range of the back yoke forming portion 21a that overlaps with the tooth forming portion 22a in the circumferential direction of the stator core 11. With this configuration, the inclined portion 30 formed in the portion of the back yoke forming portion 21a that corresponds to the tooth forming portion 22a in the circumferential direction of the stator core 11 can be made wider in the radial direction than the inclined portion 30 formed in the portion corresponding to the slit 25. That is, the longer the length of the strip-shaped steel plate 20 in the radial direction of the stator core 11, the wider the inclined portion 30 can be. Therefore, the ratio of the formed portion to the non-formed portion of the inclined portion 30 can be made nearly constant around the entire circumference of the stator core 11, and the occurrence of variations in plate thickness and wrinkles due to the formation of the inclined portion 30 by rolling can be suppressed.

[0035] Note that by forming convex portions corresponding to the first portion P1 and the second portion P2, respectively, on at least one of the upper roll 63 and the lower roll 64, it is possible to form an inclined portion 30 whose radial width varies depending on the circumferential position. Also, the first portion P1 and the second portion P2 may be discontinuously switched as shown in Fig. 12, or may be continuously switched as shown in Fig. 13.

[0036] As shown in FIGS. 14 and 15 , a configuration may be adopted in which the inclination of the inclined portions 30 varies in the circumferential direction of the stator core 11. That is, in FIG. 14 , the inclination of the inclined portions 30 in the cross section taken along line E-E corresponding to the slits 25 is gentler than the inclination of the inclined portions 30 in the cross section taken along line A-A corresponding to the tooth forming portions 22a (teeth 22). Also, in FIG. 15 , the inclination of the inclined portions 30 in the cross section taken along line A-A corresponding to the tooth forming portions 22a (teeth 22) is gentler than the inclination of the inclined portions 30 in the cross section taken along line E-E corresponding to the slits 25. This configuration can suppress a reduction in the cross-sectional area of ​​the magnetic path due to the formation of the inclined portions 30 in the back yoke forming portion 21a in the portion with a gentler inclination, compared to when the inclination of the inclined portions 30 is constant around the entire circumference of the stator core 11. As a result, it is possible to improve the processability of spirally stacking the strip-shaped steel plate 20 while suppressing a deterioration in the magnetic properties of the stator core 11.

[0037] As shown in FIGS. 16 to 18, a configuration can be adopted in which, when the strip-shaped steel plates 20 are stacked in a spiral shape, a predetermined gap G is formed between the opposing side surfaces 25a of the slits 25. With this configuration, as shown in FIG. 19, when the strip-shaped steel plates 20 are stacked in a spiral shape, that is, when the stator (stator core 11) is completed, a cooling fluid can easily circulate inside the stator core 11 through the gaps formed by the inclined portions 30 in the stator core 11 and the predetermined gaps G formed by the slits 25. This can improve the cooling performance of the stator. The cooling fluid may be liquid or gas.

[0038] As shown in Figure 20, the inclined portion 30 (rolled portion) may be formed so that a portion of both of the two plate surfaces (the surface with the largest area) of the strip-shaped steel plate 20 is inclined relative to the plate surface in the portion where the inclined portion 30 is not formed.

[0039] As shown in Fig. 21, a circular hole 25b (hole) may be formed at the end (base) of the slit 25 on the opposite side (outer diameter side) from the slot 23. With this configuration, when bending the strip-shaped steel sheet 20 into a spiral, the strip-shaped steel sheet 20 can be deformed so that the slit mating surfaces 25a approach each other, with the circular hole 25b as a fulcrum. Therefore, when bending the strip-shaped steel sheet 20 into a spiral, it is possible to further improve the workability.

[0040] 22, the back yoke forming portion 21a of the strip-shaped steel plate 20 may be formed with two (or more) slits 25 at positions corresponding to the slots 23, each slit opening toward the slot 23. That is, in combination with the above embodiment, the back yoke forming portion 21a of the strip-shaped steel plate 20 may be formed with at least one slit 25 at a position corresponding to the slot 23, each slit opening toward the slot 23.

[0041] 23, the back yoke forming portion 21a of the strip-shaped steel plate 20 may be formed with one slit 25 for each of the plurality of slots 23, so that the slit 25 opens toward the slot 23. Note that the back yoke forming portion 21a of the strip-shaped steel plate 20 may be formed with multiple slits 25 for each of the plurality of slots 23, so that the slits 25 open toward the slot 23.

[0042] As shown in FIG. 24 , the strip-shaped steel sheet 20 may have circumferential slits 40 formed therein, extending from the end of the slit 25 opposite the slot 23 to both sides in the circumferential direction of the stator core 11. The circumferential slits 40 are formed in an oval, elliptical, rectangular, or inverted triangular shape. With this configuration, the range in which stress is concentrated due to bending of the strip-shaped steel sheet 20 can be expanded from the back yoke forming portion 21a corresponding to the end of the slit 25 opposite the slot 23 to the length of the circumferential slit 40 in the circumferential direction of the stator core 11. This reduces stress concentration in the back yoke forming portion 21a, and suppresses the occurrence of variations in sheet thickness and wrinkles due to uneven residual strain in the back yoke forming portion 21a.

[0043] The above modifications may be implemented in combination.

[0044] Characteristic configurations extracted from the above-described embodiment and modified examples will be described below. [Configuration 1] A stator core (11) is formed by laminating strip-shaped steel plates (20) in a spiral shape around a central axis (C1), and includes a back yoke (21) extending in a circumferential direction around the central axis (C1), and a plurality of teeth (22) extending from the back yoke toward the central axis, with slots (23) formed between each of the adjacent teeth, a back yoke forming portion (21a) of the strip-shaped steel plate that forms the back yoke is partially formed with an inclined portion (30) that becomes thinner in an outer radial direction of the stator core, A stator core, wherein a slit (25) is formed at a position in the circumferential direction of the stator core corresponding to the slot in the back yoke forming portion, the slit opening toward the slot and extending in the outer radial direction with a width narrower than the width of the slot in the circumferential direction. [Configuration 2] A stator core as described in configuration 1, wherein a radius (R1) from the central axis to an end (30a) of the inclined portion on the central axis side is shorter than a radius (R2) from the central axis to an end (25n) of the slit opposite to the central axis. [Configuration 3] A stator core as described in configuration 1, wherein a radius (R1) from the central axis to an end (30a) of the inclined portion on the central axis side is longer than a radius (R2) from the central axis to an end (25n) of the slit opposite to the central axis. [Configuration 4] 4. The stator core according to any one of configurations 1 to 3, wherein the inclined portion is formed on the back yoke forming portion over the entire circumference of the stator core. [Configuration 5] 4. The stator core according to any one of configurations 1 to 3, wherein the inclined portions are formed discontinuously in the circumferential direction of the stator core in the back yoke forming portion. [Configuration 6] 6. The stator core according to configuration 5, wherein the inclined portion is formed at a position in the back yoke forming portion corresponding to the slit in the circumferential direction of the stator core. [Configuration 7] A stator core according to any one of configurations 1 to 4, wherein, in the circumferential direction of the stator core, in a first portion (P1) of the back yoke forming portion, a radius (R11) from the central axis to the end of the inclined portion on the central axis side is longer than a predetermined radius, and in a second portion (P2) of the back yoke forming portion that is a portion other than the first portion, a radius (R12) from the central axis to the end of the inclined portion on the central axis side is shorter than the predetermined radius. [Configuration 8] 8. The stator core according to configuration 7, wherein the second portion is a portion of the back yoke forming portion that corresponds to the teeth in the circumferential direction of the stator core. [Configuration 9] The stator core according to any one of configurations 1 to 4 and 7, wherein the inclination of the inclined portion varies in the circumferential direction of the stator core. [Configuration 10] A stator core according to any one of configurations 1 to 9, wherein when the strip-shaped steel plates are stacked in a spiral shape, a predetermined gap (G) is formed between the opposing side surfaces (25a) of the slits. [Configuration 11] The stator of any one of configurations 1 to 10, wherein the back yoke forming portion is formed with circumferential slits (40) extending from the end of the slit opposite the slot to both sides in the circumferential direction of the stator core. [Explanation of symbols]

[0045] 11... stator core, 20... steel plate, 21... back yoke, 21a... back yoke forming portion, 22... teeth, 23... slot, 25... slit, 30... inclined portion.

Claims

1. A stator core (11) is formed by stacking strip-shaped steel plates (20) in a spiral shape around a central axis (C1), and includes a back yoke (21) extending in a circumferential direction around the central axis (C1), and a plurality of teeth (22) extending from the back yoke toward the central axis, with slots (23) formed between each of the adjacent teeth, a back yoke forming portion (21a) of the strip-shaped steel plate that forms the back yoke is partially formed with an inclined portion (30) that becomes thinner in the outer radial direction of the stator core; A stator core, wherein a slit (25) is formed at a position in the circumferential direction of the stator core corresponding to the slot in the back yoke forming portion, the slit opening toward the slot and extending in the outer radial direction with a width narrower than the width of the slot in the circumferential direction.

2. 2. The stator core of claim 1, wherein a radius (R1) from the central axis to an end (30a) of the inclined portion on the central axis side is shorter than a radius (R2) from the central axis to an end (25n) of the slit opposite the central axis.

3. 2. The stator core of claim 1, wherein a radius (R1) from the central axis to an end (30a) of the inclined portion on the central axis side is longer than a radius (R2) from the central axis to an end (25n) of the slit opposite the central axis.

4. 4. The stator core according to claim 1, wherein the inclined portion is formed on the back yoke forming portion over the entire circumference of the stator core.

5. 4. The stator core according to claim 1, wherein the inclined portion is formed intermittently in the circumferential direction of the stator core at the back yoke forming portion.

6. The stator core according to claim 5 , wherein the inclined portion is formed in a position of the back yoke forming portion corresponding to the slit in the circumferential direction of the stator core.

7. A stator core as described in any one of claims 1 to 3, wherein, in the circumferential direction of the stator core, in a first portion (P1) of the back yoke forming portion, a radius (R11) from the central axis to the end of the inclined portion on the central axis side is longer than a predetermined radius, and in a second portion (P2) of the back yoke forming portion that is a portion other than the first portion, a radius (R12) from the central axis to the end of the inclined portion on the central axis side is shorter than the predetermined radius.

8. The stator core according to claim 7 , wherein the second portion is a portion of the back yoke forming portion that corresponds to the teeth in the circumferential direction of the stator core.

9. 4. The stator core according to claim 1, wherein the inclination of the inclined portion varies in the circumferential direction of the stator core.

10. A stator core according to any one of claims 1 to 3, wherein when the strip-shaped steel plates are stacked in a spiral shape, a predetermined gap (G) is formed between the opposing side surfaces (25a) of the slits.

11. The stator core according to any one of claims 1 to 3, wherein a circumferential slit (40) is formed in the back yoke forming portion, the slit extending from an end of the slit opposite the slot to both sides in the circumferential direction of the stator core.

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