Method for manufacturing laminated core

Abstract

To prevent or suppress undulation of an annular iron core piece in a mold without forming a plurality of recesses or protrusions on an outer circumferential surface of a laminated iron core.SOLUTION: In a method for manufacturing a laminated iron core, a plurality of annular iron core pieces 12 each formed into an annular shape by punching a thin strip with a punch and a die are laminated in a lamination mold 30 to manufacture a laminated iron core 10. In the manufacturing method, a plurality of protrusions 32 formed on an inner circumferential surface of the lamination mold 30 is brought into contact with an outer circumferential surface of the annular iron core piece 12, and at least one slit 20 that extends in a circumferential direction of the annular iron core piece 12 is formed in the annular iron core piece. A length in the circumferential direction in the slit 20 is set longer than a length in the circumferential direction of the protrusion 32. When viewed from a center of the annular iron core piece 12, the whole area in the circumferential direction of the protrusion 32 is overlapped with the slit 20.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a laminated core.

Background Art

[0002] In the method for manufacturing a laminated core described in Patent Document 1 below, a plurality of annular core pieces punched from a thin strip material with a punch and a die are laminated and formed in a mold. In this manufacturing method, a plurality of concave portions or convex portions are formed around each annular core piece, and the concave portions or convex portions are engaged with linear convex portions or linear concave portions provided inside the die, thereby applying a radial tensile force to the annular core piece. As a result, it is possible to prevent a large-diameter annular core piece from being held in a state with undulation in the die. A similar technique is also disclosed in Patent Document 2 below.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above prior art, a plurality of linear concave portions or linear convex portions are formed on the outer peripheral surface of the manufactured laminated core. For this reason, when the laminated core is fitted into the casing of a rotating electric machine by shrink fitting or the like, the contact area between the laminated core and the casing decreases. As a result, for example, the holding force of the casing for holding the laminated core decreases. Further, when the laminated core is a rotor core, if a plurality of linear concave portions or linear convex portions are formed on its outer peripheral surface, the magnetic characteristics deteriorate.

[0005] In view of the above facts, an object of the present invention is to obtain a method for manufacturing a laminated core that can prevent or suppress the undulation of annular core pieces in a mold without forming a plurality of concave or convex portions on the outer peripheral surface of the laminated core.

Means for Solving the Problems

[0006] A method for manufacturing a laminated core according to a first aspect is a method for manufacturing a laminated core in which a plurality of annular core pieces formed in an annular shape by punching a thin plate strip with a punch and a die are laminated in a mold. A plurality of convex portions formed on the inner peripheral surface of the mold are brought into contact with the outer peripheral surface of the annular core piece, and at least one slit extending in the circumferential direction is formed in the annular core piece. The length of the slit in the circumferential direction is set to be longer than the length of the convex portion in the circumferential direction, and the entire circumferential region of the convex portion as viewed from the center of the annular core piece is overlapped with the slit.

[0007] Note that "extending" in the first aspect means existing so as to continuously extend along the circumferential direction of the annular core piece, and the longitudinal direction of the slit is along the circumferential direction of the annular core piece. This "extending" includes, for example, a configuration in which the slit is inclined with respect to the circumferential direction of the annular core piece, or a configuration in which the slit is bent such that one end side in the longitudinal direction is displaced in the radial direction of the annular core piece with respect to the other end side in the longitudinal direction.

[0008] In the method for manufacturing a laminated core according to the first aspect, a plurality of annular core pieces formed by punching a thin strip material with a punch and a die are laminated in a mold to manufacture a laminated core. In this manufacturing method, a plurality of convex portions formed on the inner peripheral surface of the mold are brought into contact with the outer peripheral surface of the annular core piece. At least one slit extending in the circumferential direction is formed in the annular core piece. The length of the slit in the circumferential direction is set to be longer than the length of the convex portion in the circumferential direction. And, when viewed from the center of the annular core piece, the entire region of the convex portion in the circumferential direction overlaps with the slit. Thereby, when excessive side pressure is applied from the convex portion of the mold to the outer peripheral surface of the annular core piece, the portion of the annular core piece located between the slit and the convex portion elastically deforms. As a result, since the above side pressure is absorbed, it is possible to prevent or suppress the annular core piece in the mold from deforming in a wavy manner due to the side pressure. Moreover, it is not necessary to form a plurality of concave portions and convex portions on the outer peripheral surface of the annular core piece.

[0009] In the method for manufacturing a laminated core according to the second aspect, in the first aspect, the same number of slits as the convex portions are formed in the annular core piece.

[0010] According to the method for manufacturing a laminated core according to the second aspect, the same number of slits as the convex portions formed in the mold are formed in the annular core piece. Thereby, the side pressure applied to the outer peripheral surface of the annular core piece from the plurality of convex portions can be absorbed respectively by the deformation of the portions of the annular core piece located between the plurality of slits and the plurality of convex portions. As a result, it is possible to more effectively prevent or suppress the waviness of the annular core piece in the mold.

[0011] In the method for manufacturing a laminated core according to the third aspect, in the first aspect or the second aspect, in at least a part of the region overlapping with the convex portion when viewed from the center of the annular core piece, the width from the outer periphery of the annular core piece to the slit is set to be smaller than the width of the slit in the radial direction of the annular core piece.

[0012] According to the method for manufacturing a laminated core of the third aspect, in at least a part of the region overlapping the convex portion of the mold when viewed from the center of the annular core piece, the width from the outer periphery of the annular core piece to the slit is set to be smaller than the width of the slit in the radial direction of the annular core piece. Thereby, in the annular core piece, the portion between the outer periphery and the slit is likely to be elastically deformed by the lateral pressure from the convex portion.

[0013] The method for manufacturing a laminated core of the fourth aspect is, in the third aspect, in the entire region overlapping the convex portion when viewed from the center of the annular core piece, the width from the outer periphery of the annular core piece to the slit is set to be smaller than the width of the slit in the radial direction of the annular core piece.

[0014] According to the method for manufacturing a laminated core of the fourth aspect, in the entire region overlapping the convex portion of the mold when viewed from the center of the annular core piece, the width from the outer periphery of the annular core piece to the slit is set to be smaller than the width of the slit in the radial direction of the annular core piece. Thereby, in the annular core piece, the portion between the outer periphery and the slit is more likely to be elastically deformed by the lateral pressure from the convex portion.

[0015] The method for manufacturing a laminated core of the fifth aspect is, in any one of the first aspect to the fourth aspect, a magnet insertion hole for inserting a permanent magnet is formed separately from the slit in the annular core piece.

[0016] According to the method for manufacturing a laminated core of the fifth aspect, a magnet insertion hole for inserting a permanent magnet is formed separately from the slit in the annular core piece. Thereby, compared with the case where the magnet insertion hole is also used as the slit, for example, the degree of freedom in the shape of the magnet insertion hole and the slit is improved.

Effects of the Invention

[0017] As described above, in the method for manufacturing a laminated core according to the present invention, it is possible to prevent or suppress the undulation of the annular core piece in the mold without forming a plurality of concave portions or convex portions on the outer peripheral surface of the laminated core.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Embodiment for Carrying Out the Invention

[0019] Hereinafter, a method for manufacturing a laminated iron core according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3. In the method for manufacturing a laminated iron core according to the present embodiment, a plurality of annular iron core pieces formed in an annular shape by punching a thin plate strip with a punch and a die are laminated in a mold to manufacture a laminated iron core. This laminated iron core is a motor core for rotating electrical machines for automobiles, home appliances, and other industrial fields. In FIG. 1, as an example, a case where the laminated iron core manufactured by the method for manufacturing a laminated iron core according to the present embodiment is a rotor core 10 is illustrated. This rotor core 10 is configured by laminating a plurality (for example, several hundred) of annular iron core pieces 12. Note that FIG. 2 schematically shows a cross section of the rotor core 10.

[0020] In the present embodiment, as an example, the annular iron core piece 12 is formed with a central opening 14, a plurality of perforations 16, a plurality of caulking portions 18, and a plurality of slits 20. The central opening 14 is formed in the central portion of the annular iron core piece 12. A rotating shaft of the rotor is inserted into this central opening 14. The plurality of perforations 16 are arranged at equal intervals in the circumferential direction of the annular iron core piece 12 on the inner circumferential side of the annular iron core piece 12. The plurality of caulking portions 18 are arranged at equal intervals in the circumferential direction of the annular iron core piece 12 slightly on the outer circumferential side of the annular iron core piece 12 compared to the plurality of perforations 16. The plurality of slits 20 are arranged at equal intervals in the circumferential direction of the annular iron core piece 12 at the outer peripheral portion of the annular iron core piece 12. Hereinafter, the circumferential direction of the annular iron core piece 12 may be simply referred to as the "circumferential direction", and the radial direction of the annular iron core piece 12 may be simply referred to as the "radial direction".

[0021] In the method for manufacturing a laminated iron core according to the present embodiment, a progressive die device (not shown) is used. In this progressive die device, a first half punching process, an outer diameter punching process, and a lamination process are performed on a thin plate strip in which pilot holes are formed in a previous process. The above-mentioned thin plate strip is, for example, an electromagnetic steel sheet having a thickness of 0.25 to 0.35 millimeters.

[0022] In the first half punching process, various punching operations are sequentially performed on the thin plate strip material to form the basic shape excluding the outer shape of the annular core piece 12. At this time, while the thin plate strip material is intermittently transferred in the forward feed die device, the punching process is sequentially performed by a plurality of punches provided on the upper die (not shown) that moves in the vertical direction and a plurality of dies provided on the lower die. In this embodiment, the central opening 14, the plurality of punched holes 16, the plurality of caulking portions 18, and the plurality of slits 20 shown in FIG. 1 are formed by this first half punching process.

[0023] In the outer shape punching process, the outer shape of the annular core piece 12 is punched by an outer shape punching punch provided on the upper die and an outer shape punching die provided on the lower die. When the annular core piece 12 is obtained by this outer shape punching process, a stacking process is performed. In the stacking process, the annular core pieces 12 punched by the outer shape punching process are sequentially stacked in a stacking die (squeezing ring) 30 provided on the lower die below the outer shape punching die. At this time, the annular core pieces 12 stacked vertically are caulked and fitted to each other at the caulking portions 18. Thereby, the laminated core 10 is manufactured.

[0024] The above-mentioned stacking die 30 corresponds to the "die" in the present invention. This stacking die 30 has a cylindrical inner peripheral surface facing the outer peripheral surface of the laminated core 10, and a plurality of convex portions 32 are formed on the inner peripheral surface. The plurality of convex portions 32 are arranged at equal intervals in the circumferential direction of the inner peripheral surface of the stacking die 30 and extend in the stacking direction of the annular core pieces 12. The plurality of convex portions 32 are configured to contact the outer peripheral surface of the laminated core 10 (that is, the outer peripheral surfaces of the plurality of annular core pieces 12).

[0025] In this embodiment, as an example, the same number of convex portions 32 as the number of slits 20 are formed in the annular core piece 12. In FIG. 1, an example in which both the convex portions 32 and the slits 20 are eight in number is illustrated. The slit 20 has a substantially oval shape extending in the circumferential direction of the annular core piece 12 as an example. The circumferential length of the slit 20 is set to be longer than the circumferential length of the convex portion 32. When a plurality of annular core pieces 12 are laminated in the lamination die 30, the circumferential positions of the plurality of slits 20 and the circumferential positions of the plurality of convex portions 32 are aligned. Each annular core piece 12 in the lamination die 30 is arranged such that the entire circumferential region of each convex portion 32 overlaps with each slit 20 when viewed from the center of each annular core piece 12. Note that a configuration may be adopted in which the number of slits 20 formed in the annular core piece 12 is equal to or greater than the number of convex portions 32.

[0026] (Operation and Effect) Next, the operation and effect of this embodiment will be described.

[0027] In the method for manufacturing a laminated core according to this embodiment, a plurality of annular core pieces 12 formed in an annular shape by punching a thin strip material with a punch and a die are laminated in a lamination die 30 to manufacture a laminated core 10. In this manufacturing method, a plurality of convex portions 32 formed on the inner peripheral surface of the lamination die 30 come into contact with the outer peripheral surface of the annular core piece 12. A plurality of slits 20 extending in the circumferential direction are formed in the annular core piece 12. The circumferential length of the slit 20 is set to be longer than the circumferential length of the convex portion 32. Then, when viewed from the center of the annular core piece 12, the entire circumferential region of the convex portion 32 overlaps with the slit 20. Thereby, when excessive side pressure is applied from the convex portion 32 of the lamination die 30 to the outer peripheral surface of the annular core piece 12, a portion 12A located between the slit 20 and the convex portion 32 in the annular core piece 12 elastically deforms (see the two-dot chain line in FIG. 3). As a result, since the above side pressure is absorbed, it is possible to prevent or suppress the annular core piece 12 in the lamination die 30 from deforming in a wavy manner due to the side pressure. Moreover, since it is not necessary to form a plurality of concave portions and convex portions on the outer peripheral surface of the annular core piece 12, it is possible to suppress a decrease in magnetic characteristics.

[0028] Also, in the present embodiment, the same number of slits 20 as the convex portions 32 formed in the laminated mold 30 are formed in the annular core piece 12. As a result, the side pressure applied to the outer peripheral surface of the annular core piece 12 from the plurality of convex portions 32 can be absorbed by the deformation of the portion 12A located between the plurality of slits 20 and the plurality of convex portions 32 in the annular core piece 12. As a result, the undulation of the annular core piece 12 in the laminated mold 30 can be more effectively prevented or suppressed.

[0029] (Modification example) Next, various modification examples of the above embodiment will be described with reference to FIGS. 4 to 7 and FIGS. 11 to 18. These modification examples are included in the present invention. In FIGS. 4 to 7, the alternate long and short dash line L1 is a virtual straight line passing through one circumferential end of the convex portion 32 and the center of the annular core piece 12, and the alternate long and short dash line L2 is a virtual straight line passing through the other circumferential end of the convex portion 32 and the center of the annular core piece 12. The circumferential region between the virtual straight lines L1 and L2 is a region overlapping the convex portion 32 when viewed from the center of the annular core piece 12.

[0030] In the first modification example shown in FIG. 4, a hole 22 different from the slit 20 is formed in the vicinity of the slit 20 in the annular core piece 12. This hole 22 is arranged on the inner circumferential side of the annular core piece 12 with respect to the slit 20. Similar to the above embodiment, the circumferential length of the slit 20 is set to be longer than the circumferential length of the convex portion 32, but the circumferential length of the hole 22 is set to be shorter than the circumferential length of the convex portion 32. Both circumferential ends of the slit 20 are arranged outside the circumferential region between the virtual straight line L1 and the virtual straight line L2. The annular core piece 12 in the laminated mold 30 is arranged such that the entire circumferential region of each convex portion 32 overlaps with each slit 20 when viewed from its center.

[0031] Also in this first modified example, the same operations and effects as those of the above-described embodiment can be obtained. Moreover, in this first modified example, in the region overlapping with the convex portion 32 when viewed from the center of the annular core piece 12, the width W1 from the outer periphery of the annular core piece 12 to the slit 20 is set to be smaller than the width W2 of the slit 20 in the radial direction of the annular core piece 12. Thereby, in the annular core piece 12, the portion 12A between the outer periphery and the slit 20 is more likely to be elastically deformed by the lateral pressure from the convex portion 32. In FIG. 4, the case where the above widths W1 and W2 are constant in the circumferential direction of the annular core piece 12 is illustrated, but the above widths W1 and W2 may vary in the circumferential direction of the annular core piece 12. Further, the width W1 may be set smaller than the width W2 only in a part of the circumferential region between the virtual straight line L1 and the virtual straight line L2.

[0032] In the second modified example shown in FIG. 5, similarly to the above fourth modified example, a hole 22 different from the slit 20 is formed in the vicinity of the slit 20 in the annular core piece 12, and this hole 22 is disposed on the outer peripheral side of the annular core piece 12 with respect to the slit 20. Also in this second modified example, the same operations and effects as those of the above-described embodiment can be obtained.

[0033] In the third modified example shown in FIG. 6, the annular core piece 12 has two protruding portions 12B protruding into the slit 20. The two convex portions 12B extend radially outward from the radially inner edge portion of the slit 20. A gap is formed between the tip portions of the two convex portions 12B and the radially outer edge portion of the slit 20. Thereby, elastic deformation of the portion 12A located between the slit 20 and the convex portion 32 in the annular core piece 12 is allowed. Also in this third modified example, the same operations and effects as those of the above-described embodiment can be obtained.

[0034] In the fourth modification example shown in FIG. 7, the annular core piece 12 has one protruding portion 12C protruding into the slit 20. This convex portion 12C extends from the edge on one side in the circumferential direction in the slit 20 to the other side in the circumferential direction. A gap is formed between this convex portion 12C and the radially outer edge of the slit 20. Thereby, elastic deformation of the portion 12A of the annular core piece 12 located between the slit 20 and the convex portion 32 is allowed. Also in this fourth modification example, the same operations and effects as those in the above-described embodiment can be obtained.

[0035] Note that the first to third comparative examples shown in FIGS. 8 to 10 are not included in the present invention. In the first comparative example shown in FIG. 8, the entire circumferential region of the convex portion 32 does not overlap the slit 20 when viewed from the center of the annular core piece 12. In the second comparative example shown in FIG. 9, the annular core piece 12 has a portion 12D connecting the radially outer edge and the radially inner edge of the slit 20. In this second comparative example, the entire circumferential region of the convex portion 32 does not overlap the slit 20 when viewed from the center of the annular core piece 12. In the third comparative example shown in FIG. 10, the slit 20 is formed in a zigzag shape. The slit 20 of this third modification example does not exist so as to extend along the circumferential direction of the annular core piece 12.

[0036] In the fifth to seventh modification examples shown in FIGS. 11 to 13, magnet insertion holes 24 for inserting permanent magnets are formed separately from the slit 20 in the annular core piece 12. In FIGS. 11 to 13, only one slit 20 is shown for ease of viewing the drawing, but a plurality of slits 20 are formed side by side in the circumferential direction of the annular core piece 12, and a plurality of magnet insertion holes 24 are formed adjacent to each slit 20.

[0037] In the fifth modification example shown in FIG. 11, a pair of magnet insertion holes 24 are formed side by side in the circumferential direction on the outer peripheral side of the annular core piece 12. The pair of magnet insertion holes 24 are arranged radially inside with respect to the slit 20. Also in this fifth modification example, the same operations and effects as those in the above-described embodiment can be obtained.

[0038] In the sixth modification example shown in FIG. 12, a plurality of sets (for example, eight sets) of a pair of magnet insertion holes 24 are formed side by side in the circumferential direction on the outer peripheral side of the annular iron core piece 12. In FIG. 12, only two sets of the pair of magnet insertion holes 24 are shown. These magnet insertion holes 24 are arranged on the radially outer side with respect to the slit 20. The slit 20 and the convex portion 32 are arranged side by side in the radial direction, and a portion where the magnet insertion hole 24 is not formed between the slit 20 and the convex portion 32 is arranged on the radially inner side with respect to the convex portion 32. Also in this sixth modification example, the same operations and effects as those of the above-described embodiment can be obtained.

[0039] In the seventh modification example shown in FIG. 13, a plurality of (for example, eight) magnet insertion holes 24 are formed side by side in the circumferential direction on the outer peripheral side of the annular iron core piece 12. In FIG. 13, only two of the magnet insertion holes 24 are shown. A slit 20 is formed between the magnet insertion holes 24 arranged in the circumferential direction. Also in this seventh modification example, the same operations and effects as those of the above-described embodiment can be obtained.

[0040] In the eighth to tenth modification examples shown in FIGS. 14 to 16, a plurality of teeth portions 12T are formed on the annular iron core piece 12. By laminating this annular iron core piece 12, a wound rotor is manufactured. In FIGS. 14 to 16, for ease of viewing the drawing, only one slit 20 is shown, but a plurality of slits 20 are formed side by side in the circumferential direction of the annular iron core piece 12.

[0041] In the eighth modification example shown in FIG. 14, a slit 20 is formed at the tip of the tooth 12T that contacts the convex portion 32. In the ninth modification example shown in FIG. 15, a slit 20 is formed on the radially inner side with respect to the tooth 12T that contacts the convex portion 32. In the tenth modification example shown in FIG. 16, a portion between the teeth 12T adjacent to each other in the circumferential direction on the annular iron core piece 12 contacts the convex portion 32, and a slit 20 is formed on the radially inner side with respect to this convex portion 32. Also in these eighth to tenth modification examples, the same operations and effects as those of the above-described embodiment can be obtained.

[0042] In the 11th modification example shown in Fig. 17, a plurality (for example, eight sets) of magnet insertion holes 24 are formed in the circumferential direction on the inner side in the radial direction of the annular iron core piece 12, and slits 20 are formed on the outer side in the radial direction with respect to each set of magnet insertion holes 24. By laminating this annular iron core piece 12, a magnet type stator is manufactured. In Fig. 17, only one slit 20 is shown for ease of viewing the drawing, and only one set of a pair of magnet insertion holes 24 is shown. Also in this 11th modification example, the same operations and effects as those in the above embodiment can be obtained.

[0043] In the 12th modification example shown in Fig. 18, a plurality of teeth portions 12T are formed on the inner side in the radial direction of the annular iron core piece 12. By laminating this annular iron core piece 12, a wound type stator is manufactured. In this annular iron core piece 12, a slit 20 is formed on the outer peripheral side of the portion located on the outer side in the radial direction with respect to the teeth portion 12T, and the outer peripheral surface of the portion contacts the convex portion 32. In Fig. 18, only one slit 20 is shown for ease of viewing the drawing. Also in this 12th modification example, the same operations and effects as those in the above embodiment can be obtained.

[0044] As described above, the present invention has been described with some embodiments, but the present invention can be variously modified and implemented without departing from the gist thereof. Needless to say, the scope of rights of the present invention is not limited to the above embodiments and modification examples.

Explanation of reference numerals

[0045] 10 Stacked iron core 12 Annular iron core piece 20 Slit 24 Magnet insertion hole 30 Stacking die (die) 32 Convex portion

Claims

1. In a method for manufacturing a laminated core by laminating a plurality of annular core pieces formed in an annular shape by punching a thin plate strip with a punch and a die in a mold, a plurality of convex portions formed on the inner peripheral surface of the mold are brought into contact with the outer peripheral surface of the annular core piece, and at least one slit extending in the circumferential direction is formed in the annular core piece, and the length of the slit in the circumferential direction is set to be longer than the length of the convex portion in the circumferential direction, and a method for manufacturing a laminated core in which the entire region of the convex portion in the circumferential direction as viewed from the center of the annular core piece overlaps with the slit.

2. The method for manufacturing a laminated core according to claim 1, wherein the same number of slits as the convex portions are formed in the annular core piece.

3. The method for manufacturing a laminated core according to claim 1 or claim 2, wherein in at least a part of a region overlapping the convex portion as viewed from the center of the annular core piece, the width from the outer periphery of the annular core piece to the slit is set to be smaller than the width of the slit in the radial direction of the annular core piece.

4. The method for manufacturing a laminated core according to claim 3, wherein in the entire region overlapping the convex portion as viewed from the center of the annular core piece, the width from the outer periphery of the annular core piece to the slit is set to be smaller than the width of the slit in the radial direction of the annular core piece.

5. The method for manufacturing a laminated core according to any one of claims 1 to 4, wherein a magnet insertion hole for inserting a permanent magnet is formed in the annular core piece separately from the slit.

Images