Method for producing stator core

Abstract

To provide a method for producing a stator core capable of suppressing a decrease in space factor.SOLUTION: The method for producing a cylindrical stator core, which is formed by bending and laminating a steel sheet (20) into a ring shape, comprises a step of preliminarily forming a recess 40 in a portion of the steel sheet that deforms in the thickness direction when bent into the ring shape.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] For example, there is a straight core constructed by laminating steel plates with multiple teeth protruding from one long side of a strip-shaped back yoke and V-shaped notches provided between adjacent teeth on the back yoke on the side from which the teeth protrude (see Patent Document 1).In Patent Document 1, after windings are wound around the teeth of the straight core, the back yoke is bent at the notches to form a ring-shaped stator. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3681487 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the portion where a compressive force is applied when the back yoke is bent, the steel plate may be deformed in the plate thickness direction, forming a protrusion. If a protrusion that protrudes in the plate thickness direction is formed on the steel plate, gaps may occur between the stacked steel plates, and the space factor of the stator core may decrease. Note that this situation is not limited to stator cores manufactured by bending a straight core, but is generally common also in stator cores manufactured by stacking strip-shaped steel plates in a spiral shape.

[0005] The present invention has been made to solve the above-mentioned problems, and a main object of the present invention is to provide a manufacturing method for a stator core that can suppress a decrease in the space factor. [Means for solving the problem]

[0006] The first means for solving the above problem is: A method for manufacturing a cylindrical stator core (11) formed by bending and laminating steel plates (20) into an annular shape, comprising: The method includes a step of forming a recess (40) in advance in a portion of the steel plate that will deform in the plate thickness direction when bent into an annular shape.

[0007] The cylindrical stator core manufactured by the above manufacturing method is constructed by bending steel plates into an annular shape and stacking them. The manufacturing method includes a step of forming recesses in advance in the steel plates at portions that will deform in the plate thickness direction when bent into an annular shape. Therefore, even if the steel plates deform in the plate thickness direction when bent into an annular shape, the recesses can suppress the amount of protrusion of the steel plates in the plate thickness direction. This suppresses the generation of gaps between the stacked steel plates and the reduction in the space factor of the stator core. As a result, it is possible to suppress a reduction in the output of a rotating electric machine equipped with the stator core and an increase in the size of the rotating electric machine to compensate for the output of the rotating electric machine. [Brief explanation of the drawings]

[0008] [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] Cross-sectional view of line VV in Figure 4. [Figure 6] An enlarged view of a portion of steel plates that have been bent into a ring shape and stacked. [Figure 7] Cross-sectional view taken along line VII-VII in Figure 6. [Figure 8] FIG. 10 is a partially enlarged cross-sectional view showing a modified example of the detour portion. [Figure 9] FIG. 10 is a partially enlarged view of a modified example of the recessed portion. [Figure 10] Cross-sectional view taken along line XX in Figure 9. [Figure 11] FIG. 10 is a partial enlarged view of another modified example of the recess. [Figure 12] FIG. 10 is a partial enlarged view of another modified example of the recess. [Figure 13] Cross-sectional view taken along line XIII-XIII in Figure 12. [Figure 14] Cross-sectional view taken along line XIV-XIV in Figure 12. [Figure 15] 10A and 10B are enlarged partial cross-sectional views showing examples of changes in the depth of the recessed portion. [Figure 16] An enlarged view of a portion of steel plates that have been bent into a ring shape and stacked. [Figure 17] Cross-sectional view taken along line XVII-XVII in Figure 16. [Figure 18] FIG. 10 is a partial cross-sectional view showing a modified example of the plate thickness increasing portion. [Figure 19] FIG. 10 is a partially enlarged cross-sectional view of another modified example of the recess. [Figure 20] FIG. 10 is a partial enlarged view of another modified example of the recess. [Figure 21] FIG. 10 is a partial enlarged view of another modified example of the recess. [Figure 22] FIG. 10 is a partial enlarged view of another modified example of the recess. [Figure 23] FIG. 10 is a partial enlarged view of another modified example of the recess. [Figure 24] FIG. 10 is a partial enlarged view of another modified example of the recess. [Figure 25] FIG. 10 is a partially enlarged view showing a modified example of the strip-shaped steel plate. [Figure 26] FIG. 10 is a plan view showing a modified example of the manufacturing method of the stator core. DETAILED DESCRIPTION OF THE INVENTION

[0009] 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).

[0010] 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.

[0011] 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, 48 ​​(or more) slits 25 are formed at equal intervals in the circumferential direction in the stator core 11. Circular holes 25b (holes) are formed at the ends (bases) of the slits 25 on the opposite side (outer diameter side) from the slots 23.

[0012] 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 (not shown). 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 is formed in a cylindrical shape, and the center axis of the winding shaft 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, 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. That is, the stator core 11 (helical stator core) is formed by bending and stacking the steel sheet 20 into an annular shape. The back yoke forming portion 21a is a portion that forms the back yoke 21 of the stator core 11 by being stacked. The tooth forming portion 22a is a portion that forms the teeth 22 of the stator core 11 by being stacked. During bending, the portion of the back yoke forming portion 21a on the outer diameter side of a neutral line (not shown) is stretched in the circumferential direction, and the portion on the inner diameter side of the neutral line is compressed in the circumferential direction.

[0013] Fig. 4 is a partially enlarged view of the strip-shaped steel sheet 20. This figure shows the state of the strip-shaped steel sheet 20 before it is bent into a spiral shape. Fig. 5 is a cross-sectional view taken along line VV in Fig. 4. The strip-shaped steel sheet 20 shown in Figs. 4 and 5 is formed by press working before the winding shown in Fig. 1 is performed.

[0014] 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 with the circular holes 25b as fulcrums so that the slit mating surfaces 25a approach each other. Then, the slit mating surfaces 25a come into contact with or approach each other.

[0015] Here, the manufacturing method of the stator core 11 of this embodiment includes a step of forming recesses 40 in advance in portions of the steel sheet 20 that will deform in the plate thickness direction when bent into an annular shape. That is, before the winding shown in FIG. 1 is performed, the steel sheet 20 is formed with the tooth forming portions 22a, the back yoke forming portion 21a, the circular holes 25b, and the recesses 40 by press working. As described above, when the strip-shaped steel sheet 20 is bent into a spiral shape, the strip-shaped steel sheet 20 is deformed so that the slit mating surfaces 25a approach each other, with the circular holes 25b as the fulcrum. Therefore, the portion that deforms in the plate thickness direction is a portion of the back yoke forming portion 21a that corresponds to the slits 25 and the circular holes 25b in the longitudinal direction of the steel sheet 20 (the circumferential direction when bent into an annular shape). Specifically, the portion that deforms in the plate thickness direction is a portion of the back yoke forming portion 21a that is located on the outer diameter side of the slits 25 and the circular holes 25b. In other words, the slits 25 are formed by the above press working at positions corresponding to the recesses 40 (portions that deform in the plate thickness direction) in the circumferential direction when the steel plate 20 is bent into an annular shape.

[0016] As shown in FIG. 4, the recesses 40 are formed in a rectangular shape in a plan view of the steel plate 20. In the longitudinal direction of the steel plate 20, the width of the recesses 40 is, for example, wider than the width of the slits 25 and the circular holes 25b and narrower than the width of the slots 23. In the lateral direction of the steel plate 20 (the radial direction when bending into an annular shape), the recesses 40 are formed, for example, from the end of the circular holes 25b to the outer edge of the steel plate 20. As shown in FIG. 5, the recesses 40 are formed to a certain depth, for example, on one plate surface (main surface, the surface with the largest area) of the steel plate 20. The depth of the recesses 40 is set so that the amount of deformation in the plate thickness direction when the steel plate 20 is bent into an annular shape is smaller than the depth of the recesses 40. In other words, the recesses 40 are formed in the press working so that the amount of deformation in the plate thickness direction when the steel plate 20 is bent into an annular shape is smaller than the depth of the recesses 40. The depth of the recess 40 can be set based on the results of calculations (simulations) or prototyping, depending on the radius (curvature) of the back yoke forming portion 21a (stator core 11), the thickness of the steel plate 20, the number of slits 25, the width of the slot 23, etc.

[0017] Fig. 6 is a partially enlarged view of steel sheets 20 that have been bent into an annular shape and laminated. Fig. 7 is a cross-sectional view taken along line VII-VII in Fig. 6. For ease of explanation, Fig. 7 shows only three layers of the spirally laminated multi-layer steel sheets 20.

[0018] 7, a detour portion 41 is formed in a portion that deforms in the thickness direction when the strip-shaped steel plate 20 is bent into a spiral shape. That is, in the manufacturing method of the stator core 11, the portion that deforms in the thickness direction when the steel plate 20 is bent into a ring shape is detoured in the thickness direction. The detour portion 41 is contained within the recess 40, and does not protrude from the surface of the portion of the back yoke forming portion 21a where the recess 40 is not formed.

[0019] Specifically, in the portion of the back yoke forming portion 21a where the recess 40 is formed, the amount of deformation of the detour portion 41 in the plate thickness direction increases toward the inner diameter side of the stator core 11. The portion of the detour portion 41 where the amount of deformation in the plate thickness direction is greatest is also contained within the recess 40 and does not protrude from the surface of the portion of the back yoke forming portion 21a where the recess 40 is not formed. Therefore, the stacked steel sheets 20 are not pushed up by the detour portions 41 of the steel sheets 20 in adjacent layers. Therefore, no force is acting to create gaps between the stacked steel sheets 20. Furthermore, the detour portion 41 is easily deformed in a direction that causes it to further bend or return to its original shape. The thickness of the detour portion 41 (the portion that deforms in the plate thickness direction) may or may not increase when the steel sheet 20 is bent into an annular shape.

[0020] The present embodiment described above in detail has the following advantages.

[0021] The cylindrical stator core 11 manufactured by the above manufacturing method is configured by bending steel plates 20 into an annular shape and stacking them. Here, the above manufacturing method includes a step of forming recesses 40 in advance in the portions of the steel plates 20 that will deform in the plate thickness direction when bent into an annular shape. Therefore, even if the steel plates 20 deform in the plate thickness direction when bent into an annular shape, the recesses 40 can suppress the amount of protrusion of the steel plates 20 in the plate thickness direction. Therefore, it is possible to suppress the generation of gaps between the stacked steel plates 20, and to suppress a decrease in the space factor of the stator core 11. As a result, it is possible to suppress a decrease in the output of a rotating electric machine including the stator core 11 and an increase in the physical size required to compensate for the output of the rotating electric machine.

[0022] In the above manufacturing method, the recesses 40 are formed so that the amount of deformation in the thickness direction of the steel sheet 20 when it is bent into an annular shape is smaller than the depth of the recesses 40. This process makes it possible to ensure that even if the steel sheet 20 is deformed in the thickness direction when it is bent into an annular shape, the deformed portion fits within the recesses 40. This further prevents gaps from being formed between the stacked steel sheets 20.

[0023] In the above manufacturing method, the portion of the steel plate 20 that would deform in the thickness direction when the steel plate 20 is bent into a ring shape is bent in the thickness direction. This process allows the portion of the steel plate 20 that would deform in the thickness direction when the steel plate 20 is bent into a ring shape to be bent in the thickness direction, while making the amount of deformation in the thickness direction smaller than the depth of the recess 40. Therefore, for example, when correcting the roundness of the steel plate 20 after bending it into a ring shape, the bent portion 41 makes it easier to deform the steel plate 20.

[0024] The above manufacturing method includes a step of forming slits 25 in advance at positions corresponding to the recesses 40 in the circumferential direction when the steel plate 20 is bent into an annular shape. This step allows the recesses 40 to be formed at positions corresponding to the slits 25, thereby limiting the range in which the recesses 40 are formed. This reduces the force required to form the recesses 40, allowing, for example, the size of processing equipment to be reduced. Furthermore, because the range in which the recesses 40 are formed can be limited, deterioration of the magnetic properties of the stator core 11 due to work hardening can be suppressed.

[0025] In the above manufacturing method, the steel plates 20 are stacked in a spiral shape to form the stator core 11 (helical stator core). This process can prevent gaps from being generated between the stacked steel plates 20 in the helical stator core, and can prevent a decrease in the space factor of the stator core 11.

[0026] 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.

[0027] As shown in FIG. 8 , the detour portions 41 of the stacked steel sheets 20 may overlap each other. Specifically, the convex side of one of the adjacent detour portions 41 may be recessed into the concave side of the other. A gap is formed between the adjacent detour portions 41 in the stacking direction of the steel sheets 20. Therefore, the stacked steel sheets 20 are not pushed up by the detour portions 41 of the steel sheets 20 of the adjacent layers. In this case, the detour portions 41 may not be contained within the recesses 40, but may protrude from the surface of the back yoke forming portion 21a where the recesses 40 are not formed. With this configuration, the overlapping detour portions 41 can suppress circumferential misalignment between the steel sheets 20, thereby improving the roundness of the stator core 11.

[0028] When the steel plate 20 is bent into a ring shape, the deformation of the steel plate 20 in the plate thickness direction increases toward the inner diameter side of the back yoke forming portion 21a. In this regard, as shown in Figures 9 and 10, the recesses 40 may be formed so that the depth of the recesses 40 increases toward the inner diameter side of the back yoke forming portion 21a when the steel plate 20 is bent into a ring. In the short direction of the steel plate 20 (the radial direction when bending into a ring), the recesses 40 are formed, for example, from the end of the circular hole 25b to the outer edge of the steel plate 20.

[0029] Here, when the recesses 40 are formed so that the depth of the recesses 40 is deeper toward the inner diameter side when the steel sheet 20 is bent into a ring shape, the amount of elongation of the steel sheet 20 in the longitudinal direction (the circumferential direction when bending) becomes greater toward the inner diameter side. Therefore, when the recesses 40 are pre-formed in the steel sheet 20, the amount of elongation of the steel sheet 20 in the longitudinal direction (the circumferential direction when bending) becomes non-uniform, which may cause variations in the shape of the steel sheet 20. In this regard, as shown in FIG. 11 , the recesses 40 may be formed so that the width of the recesses 40 in the circumferential direction becomes wider toward the outer diameter side when the steel sheet 20 is bent into a ring shape. That is, the depth of the recesses 40 becomes deeper toward the inner diameter side when the steel sheet 20 is bent into a ring shape, and the width of the recesses 40 in the circumferential direction becomes wider toward the outer diameter side when the steel sheet 20 is bent into a ring shape. With this configuration, the amount of elongation of the steel sheet 20 in the longitudinal direction when the recesses 40 are pre-formed in the steel sheet 20 can be made more uniform, thereby stabilizing the shape of the steel sheet 20.

[0030] Furthermore, the recesses 40 may be formed so that the cross-sectional area of ​​the recesses 40 in a cross section perpendicular to the radial direction when the steel sheet 20 is bent into an annular shape is constant regardless of the radial position. FIG. 12 is an enlarged view of one recess 40. FIG. 13 is a cross-sectional view taken along line XIII-XIII in FIG. 12, and FIG. 14 is a cross-sectional view taken along line XIV-XIV in FIG. 12. The cross-sectional area of ​​the recess 40 in FIG. 13 is equal to the cross-sectional area of ​​the recess 40 in FIG. 14. With this configuration, the area of ​​the steel sheet 20 processed when the recesses 40 are pre-formed in the steel sheet 20 can be kept constant regardless of the radial position when the steel sheet 20 is bent into an annular shape. Therefore, the amount of longitudinal elongation of the steel sheet 20 when the recesses 40 are pre-formed in the steel sheet 20 can be kept constant regardless of the radial position, thereby further stabilizing the shape of the steel sheet 20.

[0031] The depth of the recess 40 in Figures 9 and 11 may be continuously deeper toward the inner diameter side when the steel plate 20 is bent into a ring shape, as shown in Figure 10, or may be stepwise deeper toward the inner diameter side when the steel plate 20 is bent into a ring shape, as shown in Figure 15.

[0032] Fig. 16 is a partially enlarged view showing a state in which the steel sheets 20 shown in Figs. 9 to 14, for example, are bent into an annular shape and stacked. Fig. 17 is a cross-sectional view taken along line XVII-XVII in Fig. 16. For ease of explanation, Fig. 17 shows only three layers of the spirally stacked multi-layer steel sheets 20.

[0033] 17, an increased thickness portion 42 is formed in a portion that deforms in the thickness direction when the strip-shaped steel plate 20 is bent into a spiral shape. That is, in the manufacturing method of the stator core 11, the thickness of the portion that deforms in the thickness direction when the steel plate 20 is bent into an annular shape is increased. The increased thickness portion 42 is contained within the recess 40 and does not protrude from the surface of the portion of the back yoke forming portion 21a where the recess 40 is not formed.

[0034] Specifically, the portion of the increased thickness portion 42 that deforms the most in the thickness direction is contained within the recess 40 and does not protrude beyond the surface of the portion of the back yoke forming portion 21a where the recess 40 is not formed. The thickness t1 of the increased thickness portion 42 is thinner than the thickness t0 of the portion that is not deformed in the thickness direction. Therefore, the stacked steel sheets 20 are not pushed up by the increased thickness portions 42 of the steel sheets 20 in adjacent layers. Therefore, no force that creates gaps between the stacked steel sheets 20 acts. Furthermore, with this configuration, the thickness of the portion that deforms in the thickness direction when the steel sheets 20 are bent into an annular shape can be increased while the deformation in the thickness direction can be made smaller than the depth of the recess 40. Therefore, increasing the thickness hardens the deformed portion, thereby increasing the fixing force when, for example, shrink-fitting a case to the stator core 11.

[0035] 18, the thickness t2 of the thickness-increasing portion 42 may be slightly thicker than the thickness t0 of the portion that is not deformed in the thickness direction. Even in this case, even if the steel plate 20 is deformed in the thickness direction when bent into an annular shape, the amount of protrusion of the steel plate 20 in the thickness direction can be suppressed by the recess 40. Therefore, it is possible to suppress the generation of large gaps between the stacked steel plates 20, and to suppress a decrease in the space factor of the stator core 11.

[0036] The width of the recess 40 in the longitudinal direction of the steel plate 20 (the circumferential direction when bent into a ring) may be continuously wider as it approaches the outer diameter side when the steel plate 20 is bent into a ring, as shown in FIG. 11 , or may be gradually wider as it approaches the outer diameter side when the steel plate 20 is bent into a ring.

[0037] As shown in FIG. 19, recesses 40 may be formed on both plate surfaces (main surfaces, surfaces with the largest area) of the steel plate 20.

[0038] 20, two (or more) recesses 40 may be formed in the back yoke forming portion 21a of the strip-shaped steel plate 20 at positions corresponding to the slits 25 and the circular holes 25b. In this case, too, the recesses 40 may be formed so that the depth of the recesses 40 increases toward the inner diameter side when the steel plate 20 is bent into an annular shape, or the depth of the recesses 40 may be constant.

[0039] 21, one recess 40 may be formed for each of a plurality of slits 25 and circular holes 25b in the back yoke forming portion 21a of the strip-shaped steel plate 20. Note that, in the back yoke forming portion 21a of the strip-shaped steel plate 20, a plurality of recesses 40 may be formed for each of a plurality of slits 25 and circular holes 25b.

[0040] 22, recesses 40 may be formed continuously in the longitudinal direction of the steel plate 20 (the circumferential direction when bent into an annular shape). Even in this case, the manufacturing method of the stator core 11 includes a step of forming recesses 40 in advance in portions of the steel plate 20 that will deform in the plate thickness direction when bent into an annular shape. Note that even in this case, the recesses 40 may be formed so that the depth of the recesses 40 increases toward the inner diameter side when the steel plate 20 is bent into an annular shape, or so that the depth of the recesses 40 is constant.

[0041] 23, the recesses 40 may be formed in the short direction of the steel plate 20, for example, from the end of the circular hole 25b to just before the outer edge of the steel plate 20. Also, as shown in Fig. 24, the recesses 40 that are continuous in the longitudinal direction of the steel plate 20 may be formed from the end of the circular hole 25b to just before the outer edge of the steel plate 20. Even in these cases, the manufacturing method of the stator core 11 includes a step of forming the recesses 40 in advance in the portions of the steel plate 20 that will deform in the plate thickness direction when bent into an annular shape.

[0042] As shown in Fig. 25, the circular hole 25b may be omitted from the back yoke forming portion 21a of the steel plate 20. That is, the step of forming the circular hole 25b may be omitted from the manufacturing method of the stator core 11. The same applies to the steel plates 20 shown in Figs. 4, 9, 11, 12, and 20 to 24.

[0043] As shown in FIG. 26 , the above-described embodiment and its modifications can also be applied to a manufacturing method for a stator core 11 (stator) in which a base iron core 11p formed by stacking a predetermined number of steel plates 20 is rolled into a C-shape and its both circumferential ends are joined. The base iron core 11p is formed by stacking a predetermined number of rectangular steel plates 20 (magnetic members) in which teeth 22 and slots 23 are formed at a predetermined pitch. Then, after winding the stator winding 12 around the teeth 22 of the base iron core 11p, the base iron core 11p is rolled into a C-shape and its both circumferential ends are welded (joined), thereby forming a stator. Even in this case, the manufacturing method for the stator core 11 only needs to include a step of forming recesses 40 in advance in the portions of the steel plates 20 that will deform in the plate thickness direction when bent into an annular shape. In addition, after forming the stator core 11 by rolling the bare iron core 11p into a "C" shape and joining both circumferential ends thereof, the stator winding can be wound around the teeth 22 or the stator winding formed by the conductor segments can be inserted into the slots 23.

[0044] The above modifications may be implemented in combination.

[0045] Characteristic methods extracted from the above-described embodiments and modifications will be described below. [Method 1] A method for manufacturing a cylindrical stator core (11) formed by bending and laminating steel plates (20) into an annular shape, comprising: The method for manufacturing a stator core includes a step of forming a recess (40) in advance in a portion of the steel plate that will deform in the plate thickness direction when bent into an annular shape. [Method 2] The method for manufacturing a stator core according to method 1, wherein the recesses are formed so that the depth of the recesses increases toward the inner diameter side when the steel plate is bent into a ring shape. [Method 3] The method for manufacturing a stator core according to method 2, wherein the recesses are formed so that the width of the recesses in the circumferential direction increases toward the outer diameter side when the steel plate is bent into an annular shape. [Method 4] A method for manufacturing a stator core according to method 3, wherein the recess is formed so that the cross-sectional area of ​​the recess in a cross section perpendicular to the radial direction when the steel plate is bent into a ring shape is constant regardless of the radial position. [Method 5] The method for manufacturing a stator core according to any one of methods 1 to 4, wherein the recesses are formed so that the amount of deformation in the plate thickness direction when the steel plate is bent into an annular shape is smaller than the depth of the recesses. [Method 6] Method 6. A method for manufacturing a stator core according to method 5, wherein the thickness of the portion of the steel plate that deforms in the thickness direction when the steel plate is bent into an annular shape is increased. [Method 7] The method for manufacturing a stator core according to method 5 or 6, wherein the portion (42) that deforms in the thickness direction when the steel plate is bent into an annular shape is bent in the thickness direction. [Method 8] The method for manufacturing a stator core according to Method 7, wherein the bent portions (41) of the stacked steel plates are overlapped with each other. [Method 9] The method for manufacturing a stator core according to any one of methods 1 to 8, further comprising the step of forming slits (25) in advance at positions corresponding to the recesses in the circumferential direction when the steel plate is bent into an annular shape. [Method 10] 10. The method for manufacturing a stator core according to any one of methods 1 to 9, wherein the steel plates are stacked in a spiral to form a helical stator core. [Explanation of symbols]

[0046] 11... stator core, 20... steel plate, 25... slit, 40... recess.

Claims

1. A method for manufacturing a cylindrical stator core (11) formed by bending and laminating steel plates (20) into an annular shape, comprising: The method for manufacturing a stator core includes a step of forming a recess (40) in advance in a portion of the steel plate that will deform in the plate thickness direction when bent into an annular shape.

2. The method for manufacturing a stator core according to claim 1 , wherein the recesses are formed so that the depth of the recesses increases toward an inner diameter side when the steel plate is bent into an annular shape.

3. The method for manufacturing a stator core according to claim 2 , wherein the recesses are formed so that the width of the recesses in the circumferential direction increases toward an outer diameter side when the steel plate is bent into an annular shape.

4. 4. The method for manufacturing a stator core according to claim 3, wherein the recesses are formed so that a cross-sectional area of ​​the recesses in a cross section perpendicular to the radial direction when the steel plate is bent into an annular shape is constant regardless of the position in the radial direction.

5. The method for manufacturing a stator core according to any one of claims 1 to 4, wherein the recesses are formed so that an amount of deformation in a plate thickness direction when the steel plate is bent into an annular shape is smaller than a depth of the recesses.

6. The method for manufacturing a stator core according to claim 5 , wherein the thickness of the steel plate is increased in a portion that deforms in the thickness direction when the steel plate is bent into an annular shape.

7. The method for manufacturing a stator core according to claim 5, wherein the portion (42) that deforms in the thickness direction when the steel plate is bent into an annular shape is bent in the thickness direction.

8. 8. The method for manufacturing a stator core according to claim 7, wherein the bent portions (41) of the stacked steel plates overlap each other.

9. The method for manufacturing a stator core according to any one of claims 1 to 4, further comprising a step of forming a slit (25) in advance at a position corresponding to the recess in the circumferential direction when the steel plate is bent into an annular shape.

10. The method for manufacturing a stator core according to any one of claims 1 to 4, wherein the steel plates are stacked in a spiral to form a helical stator core.

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