Stator core piece punching method

Abstract

To provide a punching method capable of improving the accuracy of punched stator core pieces while suppressing floating of scrap.SOLUTION: A punching method for a stator core piece 3 having a second inner diameter edge 13 punched radially outward from a first inner diameter edge 67 of a steel plate W punched out of a rotor core piece 1, and a plurality of slots 17 arranged at intervals along the second inner diameter edge 13 and open radially inward, includes inner peripheral punching, which punches out the second inner diameter edge 13 and a plurality of protrusions 5b protruding radially outward from the second inner diameter edge 13 into a steel plate W having the first inner diameter edge 67, slot punching, which punches out the plurality of slots 17 into the steel plate W so that they overlap and encompass the punched portions of the plurality of protrusions 5b, and outer peripheral punching, which punches out an outer diameter edge 15 of the stator core piece 3.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for punching out stator core pieces used in the stators of rotating electrical machines. [Background technology]

[0002] A conventional method for punching out stator core pieces is disclosed in Patent Document 1, in which disk-shaped rotor core pieces are punched out of a steel plate, and then annular disk-shaped stator core pieces are punched out from the radially outer side thereof.

[0003] When punching out the stator core pieces, first, a plurality of slots for the stator core pieces are punched out of the steel sheet prior to punching out the rotor core pieces. Then, the rotor core pieces are punched out of the steel sheet radially inward from the slots, leaving first inner diameter edges, which are the inner edges of the punched portions, in the steel sheet.

[0004] The second inner diameter edge that defines the inner periphery of the stator core piece is punched out from the steel plate radially outside the first inner diameter edge to form an inner opening of the slot in the radial direction, whereby the area between the first and second inner diameter edges is punched out into the die as annular scrap including the portion where the slot opening has been punched out.

[0005] The scrap has a protrusion corresponding to the opening of the slot, which improves its bite into the die and prevents it from floating up.

[0006] However, in this method, the slots in the stator core pieces are punched out first, and then the rotor core pieces are punched out. Therefore, when the rotor core pieces are punched out, the rigidity around the slots in the areas of the stator core pieces to be punched is reduced, and the punching of the rotor core pieces is likely to affect the areas of the stator core pieces to be punched out. As a result, there is a risk of a decrease in the accuracy of the punched stator core pieces. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 61-39132 Summary of the Invention [Problem to be solved by the invention]

[0008] The problem to be solved is that when the floating of scrap is suppressed, there is a risk that the accuracy of the punched stator core pieces may be reduced. [Means for solving the problem]

[0009] The present invention provides a method for punching out a stator core piece, which includes a second inner diameter edge punched radially outward from a first inner diameter edge of a steel plate from which a rotor core piece is punched, and a plurality of slots arranged at intervals along the second inner diameter edge and open radially inward.

[0010] A first aspect of the present invention includes inner peripheral punching for punching the second inner peripheral edge and a plurality of recesses extending radially outward from the second inner peripheral edge into the steel plate having the first inner peripheral edge, slot punching for punching the plurality of slots into the steel plate so as to overlap and enclose the plurality of recesses, and outer peripheral punching for punching the outer peripheral edge of the stator core piece into the steel plate.

[0011] A second aspect of the present invention includes slot punching for punching the plurality of slots into the steel plate having the first inner diameter edge, inner peripheral punching for punching the second inner diameter edge into the steel plate and a plurality of openings extending from the second inner diameter edge radially outward to the plurality of slots, and outer peripheral punching for punching the outer diameter edge of the stator core piece into the steel plate. [Effects of the Invention]

[0012] According to the present invention, it is possible to improve the accuracy of punched stator core pieces while suppressing floating of scrap. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a plan view showing the relationship between the stator core pieces and the rotor core pieces and the scrap in a fitted state according to the first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic plan view showing an example of the scrap of FIG. [Figure 3] FIG. 3 is a schematic side view of a punching device according to the first embodiment, with a part thereof in cross section. [Figure 4] FIG. 4 is a schematic development view of a part of a steel plate showing the punching of rotor core pieces according to the first embodiment. [Figure 5] FIG. 5 is a schematic development view showing inner peripheral punching for the steel plate of FIG. [Figure 6] FIG. 6 is a schematic development view showing slot punching for the steel plate after inner peripheral punching in FIG. [Figure 7] FIG. 7 is a schematic development view showing outer periphery punching of the steel plate after slot punching in FIG. [Figure 8] FIG. 8 is a cross-sectional view showing the bite of the scrap into the die in Example 1. [Figure 9] FIG. 9 is a schematic development view of a part of a steel sheet when punching a narrow portion of a slot in a slot punching process according to a modified example of the first embodiment. [Figure 10] FIG. 10 is a schematic development view of a part of a steel sheet when punching a main body of a slot in slot punching according to a modified example of the first embodiment. [Figure 11] FIG. 11 is a schematic development view of a part of a steel plate showing inner peripheral punching according to another modification of the first embodiment. [Figure 12] FIG. 12 is a schematic development view of a part of a steel plate showing inner peripheral punching according to still another modification of the first embodiment. [Figure 13] FIG. 13 is a schematic development view showing the slot punching after punching the inner periphery of FIG. [Figure 14] FIG. 14 is a schematic side view, partly in section, of a punching device according to a second embodiment of the present invention. [Figure 15] FIG. 15 is a schematic development view of a part of a steel plate showing slot punching according to Example 2. As shown in FIG. [Figure 16] FIG. 16 is a schematic development view of a part of the steel plate showing the inner peripheral punching after the slot punching in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] The objective of improving the accuracy of punched stator core pieces while suppressing scrap floating has been achieved by a punching method in which annular scrap having slots and protrusions is punched out of the steel plate from which the rotor core pieces have been punched.

[0015] One embodiment of the punching method is a method for punching out a stator core piece 3 having a second inner diameter edge 13 punched radially outward from a first inner diameter edge 67 of a steel plate W from which a rotor core piece 1 has been punched, and a plurality of slots 17 arranged at intervals along the second inner diameter edge 13 and open radially inward.

[0016] This punching method involves inner peripheral punching, slot punching, and outer peripheral punching, in that order. Inner peripheral punching involves punching a second inner peripheral edge 13 and multiple recesses 69a extending radially outward from the second inner peripheral edge 13 into a steel sheet W having a first inner peripheral edge 67. In slot punching, multiple slots 17 are punched into the steel sheet W, stacked so as to contain the multiple recesses 69a. In outer peripheral punching, the outer peripheral edge 15 of the stator core piece 3 is punched into the steel sheet W.

[0017] The recesses 69a can be provided for some or all of the plurality of slots 17. Here, some of the plurality of slots 17 have a number of recesses 69a that is less than the number of the plurality of slots 17, and here, all of the plurality of slots 17 have the same number of recesses 69a as the number of the plurality of slots 17.

[0018] The slot 17 may include a main body portion 68 and a narrow width portion 69 that is narrower in the circumferential direction than the main body portion 68 and opens the main body portion 68 radially inward. In this case, the inner peripheral cutout is such that the recess 69a is included in the slot 17 as part or all of the narrow width portion 69 in the slot 17 that overlaps with the recess 69a.

[0019] The scrap punched out by the inner peripheral punching has a radial protrusion 5b corresponding to the recess 69a, and the radial tip edge of the protrusion 5b can have any suitable shape, but may be, for example, linear.

[0020] In another embodiment, the punching method may be to perform slot punching, inner peripheral punching, and outer peripheral punching in this order. Slot punching involves punching a plurality of slots 17 into a steel sheet W having a first inner diameter edge 67. In inner peripheral punching, a second inner diameter edge 13 and a plurality of openings 69 extending radially outward from the second inner diameter edge 13 to the plurality of slots 17 are punched into the steel sheet W. Outer peripheral punching involves punching an outer diameter edge 15 of the stator core piece 3 into the steel sheet W. [Example]

[0021] [Punching equipment, etc.] Fig. 1 is a plan view showing the relationship between the stator core pieces and rotor core pieces and scrap according to Example 1. Fig. 2 is a schematic plan view showing an example of the scrap in Fig. 1. In the following description, the Z direction refers to the up-down direction, the X direction refers to the feed direction of the steel plate or the longitudinal direction of the punching device, and the Y direction refers to the width direction of the steel plate or the width direction of the punching device.

[0022] The rotor core pieces 1, stator core pieces 3, and scrap 5 in Fig. 1 are punched out from a steel plate W by the punching device in Fig. 3. Note that, although Fig. 1 shows the rotor core pieces 1, stator core pieces 3, and scrap 5 in a fitted state, these are actually discharged separately by the punching device in Fig. 3.

[0023] The rotor core pieces 1 and the stator core pieces 3 in FIG. 1 are each in the form of a plate, with a plurality of pieces stacked to form the rotor and stator of a rotating electrical machine.

[0024] The rotor core piece 1 includes a first outer diameter edge 7, a shaft hole 9, and a magnet hole 11. The first outer diameter edge 7 defines the outer peripheral shape of the rotor core piece 1. The outer peripheral shape is circular, but may have welding protrusions or the like (not shown) as needed. Therefore, the first outer diameter edge 7 is also circular, but may have radial irregularities corresponding to the welding protrusions or the like. The shaft hole 9 fits onto the rotating shaft of an electric motor. A permanent magnet (not shown) is attached to the magnet hole 11.

[0025] The stator core piece 3 is configured in an annular shape and includes a second inner diameter edge 13, a second outer diameter edge 15, a plurality of slots 17, and the like.

[0026] The second inner diameter edge 13 defines the inner peripheral shape of the stator core piece 3. The inner peripheral shape here refers to the arc-shaped edge portion located between adjacent slots 17 in the circumferential direction, and the second inner diameter edge 13 refers to the arc-shaped portion or a virtual circle connecting the arc-shaped portions.

[0027] The second outer diameter edge 15 defines the outer peripheral shape of the stator core sheet 3. The outer periphery of the stator core sheet 3 is formed into a circular shape, and has welding projections, key grooves, and the like, as needed, although not shown.

[0028] The slots 17 are arranged at intervals along the second inner diameter edge 13 and are open radially inward. In this embodiment, the slots 17 are arranged at predetermined intervals in the circumferential direction. Each slot 17 has a main portion 68 and a narrow portion 69 (see FIG. 7).

[0029] The main body portion 68 has a rectangular shape extending in the radial direction in a plan view, and is a hole that penetrates the stator core segment 3 in the plate thickness direction. The main body portion 68 opens radially inward via a narrow width portion 69. The narrow width portion 69 is a hole in the plate thickness direction that is formed to have a narrower width in the circumferential direction than the main body portion 68. Note that the slot 17 may not have the narrow width portion 69, and the main body portion 68 may open radially inward with its width unchanged.

[0030] 1 and 2, scrap 5 is generated by punching out the first outer diameter edge 7 of the rotor core piece 1 and the second inner diameter edge 13 of the stator core piece 3. This scrap 5 is annular, and a plurality of radially extending protrusions 5b are attached to the outer diameter edge 5a. In FIG. 2, the number of protrusions 5b (slots 17) is simplified for the convenience of explaining the protrusions 5b, and does not match that in FIG. 1.

[0031] FIG. 3 is a schematic side view of a punching device according to the first embodiment, with a part thereof in cross section.

[0032] 3, in the punching device, a rotor die 19 and a stator die 21 are arranged in this order along the X direction, which is the feeding direction of the steel sheet W. The steel sheet W is a strip-shaped electromagnetic steel sheet.

[0033] The rotor die 19 and the stator die 21 respectively include upper dies 23 and 25 and lower dies 27 and 29. The upper dies 23 and 25 are attached to a press ram 31, and the lower dies 27 and 29 are attached to a bolster 33.

[0034] The rotor die 19 includes a first stage 35 , a second stage 37 , and a third stage 39 , and the stator die 21 includes a first stage 41 , a second stage 43 , and a third stage 45 .

[0035] The first to third stages 35 to 39 of the rotor die 19 are respectively equipped with punches 47, 49, and 51. The first to third stages 41 to 45 of the stator die 21 are respectively equipped with punches 53, 55, and 57.

[0036] The punches 47 , 49 , and 51 of the rotor die 19 are supported by the upper die 23 of the rotor die 19 , and the punches 53 , 55 , and 57 of the stator die 21 are supported by the upper die 25 of the stator die 21 .

[0037] In the rotor die 19, for example, the punch 47 punches out the magnet holes 11 of the rotor core pieces 1, the punch 49 punches out the shaft holes 9, and the punch 51 punches out the rotor core pieces 1 themselves.

[0038] In the stator die 21, for example, a punch 53 punches out the second inner diameter edge 13 of the stator core piece 3, including the recess 69a (see FIG. 5). A punch 55 simultaneously punches out the main body 68 and narrow width portion 69 of the slot 17 (see FIG. 6). A punch 57 punches out the second outer diameter edge 15 of the stator core piece 3 (see FIG. 7).

[0039] Additionally, the upper die 23 of the rotor mold 19 is provided with a punch 59 that punches pilot holes in the steel sheet W in correspondence with punching on the rotor core piece 1 side. The upper die 25 on the stator core piece 3 side is provided with a punch 61 that punches pilot holes in the steel sheet W in correspondence with punching on the stator core piece 3 side.

[0040] The punching device also includes strippers 63 and 65 for the rotor die 19 and the stator die 21, respectively.

[0041] The lower mold 27 of the rotor mold 19 is provided with a die 27a for punching out the rotor core pieces 1. This die 27a is provided with a squeeze 27b continuous with it in the punching direction. The lower mold 29 of the stator mold 21 is provided with a die 29a for punching out the stator core pieces 3 and a squeeze 29b continuous with it in the punching direction.

[0042] During punching, the steel sheet W is sequentially fed in the X direction in this punching device, and the upper dies 23 and 25 are raised and lowered in the Z direction in conjunction with this. As a result, the punches 47, 49, and 51 of the first to third stages 35 to 39 of the rotor die 19 and the punches 53, 55, and 57 of the first to third stages 41 to 45 of the stator die 21 are all lowered and raised in the Z direction.

[0043] When the upper dies 23 and 25 are lowered, the steel sheet W is pressed down by the strippers 63 and 65, and then the punches 59, 47, 49, 51, 61, 53, 55, and 57 start to function. This allows the rotor core pieces 1 and the stator core pieces 3 to be punched out from the strip-shaped steel sheet W in a so-called parent-child punching process.

[0044] [Method of punching out stator core pieces] Fig. 4 is a schematic development of a portion of a steel plate W showing punching of a rotor core piece 1 according to Example 1. Fig. 5 is a schematic development showing inner peripheral punching of the steel plate W of Fig. 4. Fig. 6 is a schematic development showing slot punching of the steel plate W after inner peripheral punching of Fig. 5. Fig. 7 is a schematic development showing outer peripheral punching of the steel plate W after slot punching of Fig. 6. Fig. 8 is a cross-sectional view showing the bite of scrap 5 into die 29. In Figs. 4 to 7, punches are indicated by hatching, and planned punching locations are indicated by dashed lines.

[0045] The rotor core pieces 1 are punched out by the punch 51 of the rotor die 19 of the punching device in Fig. 3. When the rotor core pieces 1 are punched out, the slots 17 of the stator core pieces 3 are not punched out, and a decrease in rigidity of the portions of the stator core pieces 3 to be punched around the rotor core pieces 1 is suppressed. This prevents the effects of punching the rotor core pieces 1 from extending to the portions of the stator core pieces 3 to be punched out. When the punching of the rotor core pieces 1 is completed, a first inner diameter edge 67 is formed in the steel plate W from which the circular rotor core pieces 1 have been punched out, as shown in Figs. 1 and 4.

[0046] The first inner diameter edge 67 is the edge of the hole remaining after punching out the rotor core piece 1, and therefore has a circular shape corresponding to the first outer diameter edge 7 of the rotor core piece 1. Therefore, if the rotor core piece 1 has welding protrusions or the like on its outer periphery, the first inner diameter edge 67 will have a shape with corresponding radial irregularities or the like. The first inner diameter edge 67 may also be formed by further punching out the radial outer side of the edge of the hole remaining after punching out the rotor core piece 1.

[0047] The steel sheet W having the first inner diameter edge 67 thus formed is then punched in order at the first stage 41 to the third stage 45 by the stator die 21 shown in Fig. 3. Prior to these punching steps, a pilot hole (not shown) for punching out the stator core pieces 3 is punched by the punch 61.

[0048] In the first stage 35, inner peripheral punching is performed as shown in Fig. 5. That is, a steel sheet W having a first inner diameter edge 67 is punched outward in the radial direction of the first inner diameter edge 67 by a punch 53. As a result, a second inner diameter edge 13 and a plurality of recesses 69a extending radially outward from the second inner diameter edge 13 are punched out.

[0049] As described above, the second inner diameter edge 13 refers to the arc-shaped portion located between adjacent slots 17 in the circumferential direction or its imaginary circle, but before punching out the slots 17, it refers to the arc-shaped portion located between adjacent recesses 69a in the circumferential direction or its imaginary circle.

[0050] In this embodiment, the second inner diameter edge 13 is concentric with the first inner diameter edge 7. However, the first and second inner diameter edges 7 and 13 do not need to be concentric, and their centers may be offset from each other as long as the second inner diameter edge 13 is located outside the first inner diameter edge 7.

[0051] The recesses 69a are radial recesses that penetrate the steel sheet W in the thickness direction. The recesses 69a are provided to correspond to all of the slots 17. However, the recesses 69a may also be provided to correspond to some of the slots 17.

[0052] Each recess 69a has a rectangular shape in plan view, and is smaller in circumferential width and radial length than the narrow width portions 69 of the slot 17. The planar shape of the recess 69a can be set as appropriate. The circumferential width of the recess 69a may be set within the range of the circumferential width of the narrow width portions 69. The radial length of the recess 69a may be set within the range of the radial length of the slot 17 including the main body portion 68 and the narrow width portions 69.

[0053] By this inner peripheral punching, the portion between the first inner diameter edge 7 and the second inner diameter edge 13 is punched out as an annular scrap 5 including a plurality of protrusions 5b as shown in FIGS.

[0054] The multiple protrusions 5b correspond to the recesses 69a and are therefore provided to correspond to all of the multiple slots 17. However, it is also possible to provide the protrusions 5b to correspond to some of the multiple slots 17 in accordance with the recesses 69a, such as by forming the protrusions 5b on every other slot 17.

[0055] The planar shape of each protrusion 5b corresponds to the recess 69a. Therefore, in this embodiment, each protrusion 5b has a rectangular planar shape. The leading edge of the protrusion 5b is formed in a straight line. The leading edge of the protrusion 5b may have other shapes, such as an arc shape. Both circumferential edges of the protrusion 5b are oriented in the radial direction and are parallel to each other. Both circumferential edges of the protrusion 5b may also have a shape that follows the radial direction.

[0056] The scrap 5 punched out in this manner is stuck to the die 70 for punching the inner periphery of the lower mold 29, as shown in Fig. 8, and is prevented from floating up. That is, the entire outer periphery of the outer diameter edge 5a and the protrusions 5b of the scrap 5 engage with the inner periphery of the die 70, improving the sticking of the scrap 5 to the die 70, i.e., increasing the resistance in the punching direction, and preventing the scrap 5 from floating up. Note that, although the leading edge of the protrusions 5b engages with the inner surface of the die 70 in the radial direction, the protrusions 5b may be formed short so that they do not engage with the inner surface of the die 70 in the radial direction.

[0057] Furthermore, the protrusions 5b can be easily formed into the intended shape by suppressing the influence of punching the rotor core pieces 1, and the scrap 5 can be more easily bitten into the die 70.

[0058] Once this inner peripheral punching is completed, slot punching is performed in the second stage 37 as shown in Figure 6. In slot punching, a punch 55 is used to punch multiple slots 17 into the steel sheet W, stacking them so that multiple recesses 69a are included therein. The punch 55 is integrally provided with a slot punch portion 55a and a narrow width portion punch portion 55b. The radial inner edge of the narrow width portion punch portion 55b protrudes radially inward beyond the second inner diameter edge 13.

[0059] This punch 55 simultaneously punches out the main body portion 68 and the narrow width portion 69 in each slot 17. At this time, the slot 17 is overlapped with the recess 69a so that the narrow width portion 69 contains the recess 69a. Therefore, the portion to be punched of the stator core piece 3 has the slot 17 while eliminating the recess 69a. Furthermore, since the slot 17 simultaneously punches out the main body portion 68 and the narrow width portion 69, the positional accuracy between them is improved. Furthermore, the pilot holes improve the positional accuracy between the slot 17 and each portion of the stator core piece 3.

[0060] When the slot punching is completed, outer peripheral punching is performed in the third stage 39 as shown in Fig. 7. In the outer peripheral punching, the outer peripheral edge 15 of the stator core piece 3 is punched out. As a result, the stator core piece 3 is dropped into the die 29a of the third stage 45.

[0061] As described above, in this embodiment, annular scraps 5 having slots 17 and protrusions 5b are punched out of the steel plate W from which the rotor core pieces 1 have been punched. Therefore, punching of the rotor core pieces 1 is performed without the slots 17, which reduces the impact of punching of the rotor core pieces 1 on the portions of the stator core pieces 3 to be punched. Therefore, in this embodiment, the precision of the punched stator core pieces 3 can be improved while preventing the scraps 5 having the protrusions 5b from floating up.

[0062] Moreover, in this embodiment, the precision of the punched scrap 5 can be improved, so that the scrap 5 can be easily formed into the intended shape, and the scrap 5 can be more reliably prevented from floating up.

[0063] In addition, in this embodiment, after punching out the annular scrap 5 having multiple protrusions 5b, that is, after punching out the second inner diameter edge 13 of the stator core piece 3 and multiple recesses 69a, multiple slots 17 are formed to encompass the multiple recesses 69a.

[0064] Therefore, the radial length of the protrusion 5b of the scrap 5 can be adjusted within the range in which the slot 17 is formed, and the scrap 5 can be more reliably prevented from floating up.

[0065] Furthermore, the protrusions 5b of this embodiment are engaged (hooked) into the die 70 not only on both circumferential sides but also at the radial leading edge, so that the scrap 5 can be more reliably prevented from floating up.

[0066] In addition, in this embodiment, the main body 68 and narrow width portion 69 of the slot 17 are punched out simultaneously, so that the positional accuracy between them can be improved.

[0067] Furthermore, in this embodiment, the upper die 23 of the rotor die 19 and the upper die 25 of the stator die 21 are separated, so that the precision of the punched stator core segments 3 can be further improved.

[0068] Furthermore, since the upper die 25 of the stator die 21 is provided with a punch 61 for forming pilot holes used to punch out the stator core segments 3, the precision of the stator core segments 3 can be further improved.

[0069] [Variations] 9 and 10 are schematic developments of a portion of a steel plate when punching a slot according to a modified example of Example 1, where FIG. 9 shows the state when punching the narrow portion of the slot, and FIG. 10 shows the state when punching the main body of the slot.

[0070] In this modification, the narrow portion 69 and the main body portion 68 of the slot 17 are punched out in this order in the second stage 37. The order in which the narrow portion 69 and the main body portion 68 are punched out may be reversed.

[0071] In this slot punching, the punch 55 in the second stage 37 is changed. In the punch 55, a narrow width punching portion 55b in FIG. 9 and a slot punching portion 55a in FIG. 10 are arranged side by side on the upper die 25 in the X direction, which is the feed direction of the steel sheet W.

[0072] As a result, the narrow portions 69 of the slots 17 are punched out by punching at the narrow portion punching portions 55b, and then the main bodies 68 of the slots 17 are punched out by punching at the slot punching portions 55a. This makes it possible to distribute the load when punching out the slots 17, thereby further improving the precision of the stator core segments 3.

[0073] FIG. 11 is a schematic development view of a part of a steel plate showing inner peripheral punching according to another modification of the first embodiment.

[0074] In this modification, the radial length of the recess 69 a at the portion to be punched of the stator core piece 3 is increased so that it reaches the main body 68 of the slot 17 .

[0075] As a result, the protrusions 5b of the scrap 5 become longer in the radial direction, and the scrap 5 can be more easily attached to the inside of the die.

[0076] Fig. 12 is a schematic development of a part of a steel plate showing inner peripheral punching according to yet another modified example of Example 1. Fig. 13 is a schematic development of a part of the steel plate showing slot punching after inner peripheral punching in Fig. 12.

[0077] In this modification, the circumferential width and radial length of the recess 69a are longer than those of Example 1. The circumferential width of the recess 69a matches the narrow portion 69 of the slot 17. The radial length of the recess 69a almost reaches the main body 68 of the slot 17.

[0078] In this modification, the punch 55 is modified so as to punch out the main body 68 of the slot 17 in the same manner as the slot punching portion 55a of FIG.

[0079] In this modification, the narrow width portion 69 of the slot 17 can be punched out by punching the inner periphery, so that the configuration of the slot punching punch 55 can be simplified. [Example]

[0080] [Punching device] 14 is a schematic side view of a punching device according to Example 2, with a portion thereof cut away. Since Example 2 has a basic configuration in common with Example 1, the same reference numerals are used to designate corresponding components, and redundant explanations will be omitted.

[0081] In the punching device of this embodiment, the stator die 21 is changed from that of the punching device of embodiment 1, and the order of inner peripheral punching and slot punching is changed.

[0082] That is, in this embodiment, a punch 71 for punching a slot is provided on the first stage 41 of the stator die 21, and a punch 73 for punching an inner periphery is provided on the second stage 43.

[0083] The punch 71 punches out the main body 68 of the slot 17, similar to the slot punching portion 55a in Figure 10, and the punch 73 punches out the second inner diameter edge 13 including the narrow portion 69, similar to the punch 53 in Figure 12.

[0084] [Stator punching method] Fig. 15 is a schematic development of a part of a steel plate showing slot punching. Fig. 16 is a schematic development of a part of the steel plate showing inner peripheral punching after slot punching in Fig. 15.

[0085] In the punching method of this embodiment, punching of the rotor core pieces 1 is completed, and the steel plate W having the first inner diameter edge 67 is punched in order in the first stage 41 to the third stage 45 of the stator die 21. Before the first stage 41, a pilot hole (not shown) for punching the stator is punched by the punch 61.

[0086] In the first stage 41, as shown in FIG. 15, the main body 68 of the slot 17 is punched out by punching the slot with a punch 71.

[0087] In the second stage 43, as shown in Fig. 16, the second inner diameter edge 13 and the narrow portion 69 of the slot 17 are punched out as an opening by punching the inner circumference with a punch 73. The opening here refers to the portion where the slot 17 opens radially to the second inner diameter edge 13.

[0088] The second inner diameter edge 13, including the narrow portion 69, is punched out radially outside the first inner diameter edge 67, and the area between the first inner diameter edge 67 and the second inner diameter edge 13, including the narrow portion 69, is punched out as an annular scrap 5 having a convex portion 5b.

[0089] In this embodiment, the slot punching, which is subject to a relatively high load, is positioned in the center of the press ram 31, thereby making it possible to uniformize the load as a whole. Furthermore, in the second embodiment, the same effects as in the first embodiment can be achieved. [Explanation of symbols]

[0090] 1 Rotor core piece 3 Stator core pieces 5. Scrap 5a Outer diameter edge (scrap) 5b Convex part (scrap) 13 Second bore edge (stator) 15 Second outer edge (stator) 17 slots 67 First inner edge 69 Narrow part 69a Recess W steel plate

Claims

1. A method for punching a stator core piece, the method comprising: punching a second inner diameter edge of a steel plate from which a rotor core piece is punched, the second inner diameter edge being punched radially outward relative to a first inner diameter edge; and forming a plurality of slots arranged at intervals along the second inner diameter edge and open radially inward, the method comprising: Inner peripheral punching is performed by punching the second inner peripheral edge and a plurality of recesses extending radially outward from the second inner peripheral edge into the steel plate having the first inner peripheral edge; Slot punching is performed by punching the plurality of slots into the steel plate while overlapping the plurality of slots so as to include the plurality of recesses therein; outer periphery punching to punch out outer diameter edges of the stator core pieces from the steel plate; A method for punching a stator core piece comprising:

2. 2. The method for punching stator core pieces according to claim 1, The recesses are provided for some or all of the plurality of slots. Stator core piece punching method.

3. 3. The method for punching stator core pieces according to claim 1 or 2, The slot includes a main body portion and a narrow portion that is narrower in width than the main body portion in the circumferential direction and opens the main body portion on the inside in the radial direction, The inner peripheral cutout is a slot that overlaps with the cutout portion of the recess, and the cutout portion of the recess is included in the slot as part or all of the narrow width portion. Stator core piece punching method.

4. 3. The method for punching stator core pieces according to claim 1 or 2, The scrap punched out by the inner peripheral punching has a radial convex portion corresponding to the concave portion, The radial tip edge of the protrusion is linear. Stator core piece punching method.

5. A method for punching a stator core piece, the method comprising: punching a second inner diameter edge of a steel plate from which a rotor core piece is punched, the second inner diameter edge being punched radially outward relative to a first inner diameter edge; and forming a plurality of slots arranged at intervals along the second inner diameter edge and open radially inward, the method comprising: punching the plurality of slots into the steel plate having the first inner diameter edge; an inner peripheral punching that punches the second inner diameter edge and a plurality of openings extending from the second inner diameter edge toward the outer side in the radial direction and reaching the plurality of slots in the steel plate; outer periphery punching to punch out outer diameter edges of the stator core pieces from the steel plate; A method for punching a stator core piece comprising:

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