Method for manufacturing a stator core and apparatus for manufacturing a stator core

Abstract

To provide a manufacturing method of a stator core and a manufacturing apparatus of a stator core, capable of suppressing scrap rising.SOLUTION: A manufacturing method of a stator core includes: a first punching step of forming a first through hole constituting a central hole by punching a central hole piece from a workpiece W by cooperation of a first punch and a first die 161 having a first die hole 161a; and a second punching step of forming a plurality of second through holes constituting a plurality of slots respectively by punching a plurality of slot pieces from the workpiece formed with the first through hole. The first punching step includes deformation processing of increasing friction force between the inner face of the first die hole 161a and the central hole piece by sliding the central hole piece to a scrap rising suppressing part 190 disposed at the inner face of the first die hole 161a so as to plastically deform it. The deformation processing is performed only on the inner face of a support part 161c for supporting a planned part Wp to be formed with the second through hole in the workpiece W of the first die 161 of the inner face of the first die hole 161a.SELECTED DRAWING: Figure 5

Description

Technical Field

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

Background Art

[0002] A stator core used in a rotating electric machine has an annular yoke having a central hole and a plurality of teeth extending radially inward from the yoke. Slots communicating with the central hole are formed between adjacent teeth.

[0003] Patent Document 1 discloses a method for manufacturing a stator core by laminating a plurality of core pieces punched from a workpiece using a punch and a die. In this method, first, a plurality of slot pieces are punched from the workpiece, thereby forming a plurality of slot spaces constituting the plurality of slots. Thereafter, a through hole constituting the central hole is formed so as to communicate with the plurality of slot spaces by punching a central hole piece from the workpiece. Thereafter, after punching core pieces from the workpiece, the stator core is manufactured by laminating the plurality of core pieces.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the method described in Patent Document 1, a central hole piece is punched out from a workpiece after multiple slot pieces have been punched out from the workpiece. In other words, when the central hole piece is punched out, multiple slot spaces have already been formed in the workpiece. For this reason, the portion of the outer edge of the central hole piece that faces each slot space does not come into contact with the inside of the die. In this case, the contact area between the central hole piece and the die is smaller compared to the case where the entire outer edge of the central hole piece comes into contact with the inside of the die, making it difficult for the central hole piece to be retained inside the die. This can cause so-called sludge lifting, where the central hole piece lifts up from inside the die as the punch rises. The main causes of sludge lifting include, for example, burrs formed on the central hole piece sticking to the punch, or the central hole piece being attracted to the punch due to the magnetic force of the workpiece or the processing oil. Since sludge lifting hinders the smooth manufacturing of stator cores, it is desirable to suppress sludge lifting. [Means for solving the problem]

[0006] A method for manufacturing a stator core to solve the above problems is a method for manufacturing a stator core which is formed by stacking a plurality of iron core pieces punched out from a workpiece, each having a central hole and a plurality of slots that communicate with the central hole and are formed at intervals in the circumferential direction of the central hole, comprising: a first punching step in which a first through hole constituting the central hole is formed by punching out a central hole piece from the workpiece through the cooperation of a punch and a die having a die hole through which the punch moves back and forth; and a second punching step in which a plurality of slot pieces are punched out from the workpiece in which the first through hole is formed to form a plurality of second through holes which each constitute the plurality of slots, wherein the first punching step includes a deformation process that increases the frictional force between the inner surface of the die hole and the central hole piece by sliding the central hole piece on a sludge suppression part provided on the inner surface of the die hole to cause plastic deformation, and the deformation process is performed only on the inner surface of the die hole, on the inner surface of a support part that supports the portion of the workpiece in which the second through holes are formed.

[0007] According to this method, in the first punching step, a central hole piece is punched out of the workpiece, and then in the second punching step, multiple slot pieces are punched out of the workpiece. In other words, at the time the central hole piece is punched out of the workpiece, the slot pieces have not yet been punched out. Therefore, compared to the case where multiple slot pieces are punched out of the workpiece before the central hole piece is punched out, the contact area between the inner surface of the die hole and the central hole piece increases. In addition, in the first punching step, a deformation process is performed in which the central hole piece is slid against a sludge suppression section to undergo plastic deformation. This increases the frictional force generated between the inner surface of the die hole and the central hole piece. Therefore, sludge from the central hole piece can be suppressed.

[0008] Furthermore, because a sludge-up suppression section is provided on the inner surface of the die hole, deformation marks corresponding to the plastic deformation of the central hole piece occur on the edge of the first through hole that corresponds to the sludge-up suppression section. If such deformation marks occur on the iron core piece, the product accuracy of the stator core may decrease.

[0009] In this respect, according to the above method, the deformation process is performed only on the inner surface of the die hole, specifically on the inner surface of the support portion that supports the part of the die in which the second through-hole is formed in the workpiece. Therefore, the deformation marks formed on the edge of the first through-hole are punched out together with the slot piece when the second through-hole is formed in the workpiece. This prevents the formation of deformation marks on the edge of the first through-hole. Consequently, a decrease in the product accuracy of the stator core can be suppressed.

[0010] A stator core manufacturing apparatus for solving the above problems is a stator core manufacturing apparatus that has a central hole and a plurality of slots connected to the central hole and formed at intervals in the circumferential direction of the central hole, and is made by stacking a plurality of iron core pieces punched out from a workpiece, comprising: a first punching station that forms a first through hole constituting the central hole by punching out a central hole piece from the workpiece through the cooperation of a punch and a die having a die hole through which the punch moves back and forth; and a second punching station that forms a plurality of second through holes constituting the plurality of slots by punching out a plurality of slot pieces from the workpiece in which the first through hole has been formed, wherein the inner surface of the die hole is provided with a debris suppression part that increases the frictional force between the inner surface of the die hole and the central hole piece by plastically deforming the central hole piece by sliding with the central hole piece, and the debris suppression part is provided only on the inner surface of the die hole and on the inner surface of a support part that supports the portion of the die in the workpiece in which the second through holes are formed.

[0011] In this configuration, after the central hole piece is punched out of the workpiece by the first punching station, multiple slot pieces are punched out of the workpiece by the second punching station. In other words, at the time the central hole piece is punched out of the workpiece, the slot pieces have not yet been punched out. Therefore, compared to the case where punching by the first punching station is performed after punching by the second punching station, the contact area between the inner surface of the die hole and the central hole piece increases. In addition, since a sludge-up suppression part is provided on the inner surface of the die hole, the central hole piece undergoes plastic deformation as it slides against the sludge-up suppression part. This increases the frictional force generated between the inner surface of the die hole and the central hole piece. Therefore, sludge-up of the central hole piece can be suppressed.

[0012] Furthermore, because a sludge-up suppression section is provided on the inner surface of the die hole, deformation marks corresponding to the plastic deformation of the central hole piece occur on the edge of the first through hole that corresponds to the sludge-up suppression section. If such deformation marks occur on the iron core piece, the product accuracy of the stator core may decrease.

[0013] In this regard, according to the above configuration, the sludge suppression portion is provided only on the inner surface of the die hole, specifically on the inner surface of the portion of the die that supports the part of the workpiece in which the second through-hole is formed. Therefore, the deformation marks formed on the edge of the first through-hole are punched out together with the slot piece when the second through-hole is formed in the workpiece. This prevents the formation of deformation marks on the edge of the first through-hole. Consequently, a decrease in the product accuracy of the stator core can be suppressed. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a plan view showing a schematic configuration of a rotating electric machine equipped with a stator core according to one embodiment. [Figure 2] Figure 2 is a cross-sectional view showing the schematic configuration of a press apparatus according to one embodiment. [Figure 3] Figure 3 is a plan view showing the workpiece processed by the press machine shown in Figure 2. [Figure 4] Figure 4 is a plan view showing the first die of Figure 2. [Figure 5] Figure 5 is a perspective view showing the first die of Figure 2. [Figure 6] Figure 6 is a plan view showing a central hole piece on which a protrusion has been formed. [Figure 7] Figure 7 is a cross-sectional view showing the first die of the first modification example. [Figure 8] Figure 8 is a schematic front view showing the first die of the second modification example. [Modes for carrying out the invention]

[0015] An embodiment of a method for manufacturing a stator core and an apparatus for manufacturing a stator core will be described below with reference to Figures 1 to 6. (Rotating Electric Machine M) As shown in Figure 1, the rotating electric machine M comprises a rotor 10 and a stator 40 surrounding the rotor 10. The rotor 10 and the stator 40 are each substantially cylindrical in shape. The rotor 10 is configured to be rotatable inside the stator 40.

[0016] (Rotor 10) The rotor 10 includes a rotor core 11 and a plurality of magnets 30 fixed to the rotor core 11 via a resin material.

[0017] The rotor core 11 has an insertion hole 12, a plurality of magnet accommodation holes 13, and a plurality of cooling channels 14. A shaft is inserted into the insertion hole 12. The magnet 30 is accommodated in each magnet accommodation hole 13 together with the resin material. A cooling medium for cooling the rotor 10 flows through the cooling channels 14.

[0018] The rotor core 11 is formed by laminating a plurality of rotor core pieces 20. The rotor core pieces 20 are punched out from a workpiece W such as an electromagnetic steel sheet (see FIG. 2). (Stator 40) The stator 40 includes a stator core 41 and a plurality of coils 60 wound around the stator core 41.

[0019] The stator core 41 has a yoke 42, a plurality of teeth 43, and a plurality of slots 44. The yoke 42 is annular. The plurality of teeth 43 project inward in the radial direction from the yoke 42 and are provided at intervals from each other in the circumferential direction. One slot 44 is formed between adjacent teeth 43 in the circumferential direction. The slot 44 penetrates the stator core 41 in the axial direction.

[0020] The stator core 41 has a center hole 45. The center hole 45 penetrates the stator core 41 in the axial direction. The center hole 45 is substantially circular in plan view. Each slot 44 communicates with the center hole 45.

[0021] The stator core 41 has three fixing portions 46 that project outward in the radial direction from the yoke 42. Each fixing portion 46 has a fixing hole 47 into which a bolt for fixing the stator core 41 to a housing (not shown) is inserted. The fixing hole 47 penetrates the fixing portion 46 in the axial direction.

[0022] The stator core 41 is constructed by stacking multiple stator core pieces 50. The stator core pieces 50 are punched out from a workpiece W such as an electrical steel sheet (see Figure 2). The stator core piece 50 has a first through hole 55, a plurality of second through holes 54, and a plurality of third through holes 57. The first through hole 55 is substantially circular in shape. The plurality of second through holes 54 are formed at intervals from each other along the outer peripheral edge of the first through hole 55. Each second through hole 54 communicates with the first through hole 55. The plurality of third through holes 57 are formed at intervals from each other along the outer peripheral edge of the first through hole 55 on the outer peripheral side of the second through holes 54.

[0023] The central hole 45 is formed by multiple first through holes 55 communicating in the stacking direction. The multiple slots 44 are formed by multiple second through holes 54 communicating in the stacking direction. The multiple fixing holes 47 are formed by multiple third through holes 57 communicating in the stacking direction.

[0024] (Pressing device 100) Next, we will describe the press machine 100 used to manufacture the rotor core 11 and the stator core 41.

[0025] As shown in Figure 2, the press device 100 is a device in which a rotor punching device 110 and a stator punching device 150 are arranged in series. The stator punching device 150 is an example of a "stator core manufacturing device".

[0026] The rotor punching device 110 is equipped with a die device that performs multiple processing operations, such as punching holes, on a workpiece W that is conveyed intermittently. The rotor punching device 110 manufactures a rotor core 11 by punching out rotor core pieces 20 from the workpiece W and stacking them.

[0027] The stator punching device 150 is equipped with a die device that performs multiple processing operations, such as punching holes, on a workpiece W that is conveyed intermittently. The stator punching device 150 manufactures a stator core 41 by punching out stator core pieces 50 from the workpiece W and stacking them. The workpiece W processed in the rotor punching device 110 is conveyed to the stator punching device 150.

[0028] (Rotor punching machine 110) The rotor punching machine 110 comprises a lower die 120 and an upper die 130 configured to move forward and backward relative to the lower die 120. The lower die 120 is provided with a die 121. The upper die 130 is provided with a punch 131 at a position corresponding to the die 121.

[0029] The upper die 130 is provided with a stripper plate 140 that holds the workpiece W in place when punching out the workpiece W. The stripper plate 140 is biased toward the lower die 120 by a biasing member (not shown). The stripper plate 140 has a punch insertion hole 140a into which the punch 131 is inserted.

[0030] The die 121 has a die hole 121a through which the punch 131 moves forward and backward. In a plan view, the die hole 121a has a substantially circular shape corresponding to the outer circumference shape of the rotor core 11. The rotor punching device 110 punches out rotor core pieces 20 from the workpiece W through the cooperation of the punch 131 and the die 121. The rotor core pieces 20 are held inside the die hole 121a and are joined with the next rotor core piece 20 punched out. A rotor core 11 is manufactured by sequentially stacking and joining a predetermined number of rotor core pieces 20 inside the die hole 121a.

[0031] The rotor punching device 110 is configured to perform various processes on the workpiece W, such as punching holes that constitute the insertion hole 12, the magnet housing hole 13, and the cooling channel 14, prior to punching out the rotor core piece 20.

[0032] (Stator punching machine 150) The stator punching machine 150 comprises a lower die 160 and an upper die 170 configured to move back and forth relative to the lower die 160.

[0033] The lower die 160 is provided with a first die 161, a second die 162, and a third die 163 in order from the upstream side in the conveying direction of the workpiece W. The upper die 170 is provided with a first punch 171, a plurality of second punches 172, and a third punch 173 at positions corresponding to the first die 161, the second die 162, and the third die 163, respectively. The first punch 171 and the first die 161 are examples of a "punch" and a "die," respectively.

[0034] The upper die 170 is provided with a stripper plate 180 that holds the workpiece W in place when punching out the workpiece W. The stripper plate 180 is biased toward the lower die 160 by a biasing member (not shown). The stripper plate 180 has a first punch insertion hole 181a, a second punch insertion hole 182a, and a third punch insertion hole 183a into which the first punch 171, second punch 172, and third punch 173 are inserted, respectively.

[0035] The first die 161 has a first die hole 161a through which the first punch 171 moves forward and backward. In a plan view, the first die hole 161a has a substantially circular shape corresponding to the shape of the first through hole 55. The first die hole 161a is an example of a "die hole".

[0036] The second die 162 has multiple second die holes 162a through which multiple second punches 172 move forward and backward. In Figure 2, for convenience, one second punch 172 and one second die hole 162a are shown. In a plan view, each second die hole 162a has a roughly rectangular shape corresponding to the shape of the second through hole 54.

[0037] The third die 163 has a third die hole 163a through which the third punch 173 moves forward and backward. In a plan view, the third die hole 163a has a shape that corresponds to the outer circumference shape of the stator core 41.

[0038] The stator punching machine 150 comprises a first punching station S1, a second punching station S2, and a third punching station S3. The first punching station S1 includes a first die 161 and a first punch 171. The second punching station S2 includes a second die 162 and a second punch 172. The third punching station S3 includes a third die 163 and a third punch 173.

[0039] In the stator punching machine 150, the workpiece W is transported in the order of the first punching station S1, the second punching station S2, and the third punching station S3. Processing stations, such as doweling, may be provided between each punching station S1, S2, and S3 to perform various processing operations on the workpiece W.

[0040] The first punching station S1 forms a first through hole 55 in the workpiece W by punching out a central hole piece W1 from the workpiece W through the cooperation of the first die 161 and the first punch 171. The second punching station S2 forms multiple second through holes 54 in the workpiece W by punching out multiple slot pieces W2 from the workpiece W through the cooperation of the second die 162 and the second punch 172. In Figure 2, the cross-sectional view of the second punching station S2 shows a different cross-section from that of the first punching station S1 and the third punching station S3.

[0041] As shown in Figure 3, the second punching station S2 forms multiple third through holes 57 in the workpiece W by punching out multiple fixing hole pieces W3 from the workpiece W through the cooperation of a die and a punch (not shown). The formation of the third through holes 57 in the workpiece W may also be performed at the first punching station S1.

[0042] As shown in Figure 2, the third punching station S3 punches out stator core pieces 50 from the workpiece W through the cooperation of the third die 163 and the third punch 173. The stator core pieces 50 are held inside the third die hole 163a and are joined with the next punched stator core piece 50. A predetermined number of stator core pieces 50 are sequentially stacked and joined together inside the third die hole 163a to manufacture the stator core 41.

[0043] (Scrap-removal suppression unit 190) As shown in Figure 4, a plurality of sludge-reducing portions 190 are provided on the inner surface of the first die hole 161a at intervals from each other in the circumferential direction of the first die hole 161a. The sludge-reducing portions 190 have the function of increasing the frictional force between the inner surface of the first die hole 161a and the central hole piece W1 by causing plastic deformation of the central hole piece W1 through sliding with the central hole piece W1 when the central hole piece W1 is punched out from the workpiece W.

[0044] As shown in Figure 5, the first die 161 has a support surface 161b that supports the lower surface of the workpiece W. As shown by dot hatching in Figure 5, the support surface 161b has a plurality of support portions 161c. The plurality of support portions 161c are spaced apart from each other in the circumferential direction of the first die hole 161a. The support portions 161c support the lower surface of the planned portion Wp, which is the part of the workpiece W in which the second through hole 54 is to be formed. Therefore, the support portions 161c are located directly below the planned portion Wp.

[0045] As shown in Figure 4, the sludge suppression portion 190 is provided only on the inner surface of the support portion 161c, which is shown by the dashed line in the figure, on the inner surface of the first die hole 161a. The sludge suppression portion 190 is provided on the inner surface of at least two of the multiple support portions 161c. In this embodiment, the sludge suppression portion 190 is provided on the inner surface of each of the three support portions 161c, which are provided at 120° intervals in the circumferential direction of the first die hole 161a. That is, the sludge suppression portion 190 is provided on the inner surface of the first die hole 161a at equal intervals in the circumferential direction of the first die hole 161a.

[0046] As shown in Figure 5, the sludge suppression section 190 is composed of an inclined groove 191 that extends inclined with respect to the axial direction of the first die hole 161a on the inner surface of the support section 161c. The cross-sectional shape of the inclined groove 191 perpendicular to the longitudinal direction is, for example, a square shape.

[0047] The inclined groove 191 extends from the edge of the first die hole 161a inward in the axial direction of the first die hole 161a. In other words, the inclined groove 191 is formed to straddle the cutting edge of the first die hole 161a.

[0048] (Manufacturing method for the rotor core 11) Next, the manufacturing method of the rotor core 11 will be described. The manufacturing method for the rotor core 11 comprises multiple processing steps and a rotor outer shape cutting step. In the multiple processing steps, a progressive die (not shown) is used to cut various holes in the workpiece W, such as insertion holes 12, magnet housing holes 13, and cooling channel 14.

[0049] As shown in Figure 2, in the rotor outer shape punching process, first, the upper die 130 descends, pressing the workpiece W against the lower die 120 by the stripper plate 140. Then, as the upper die 130 descends further, the punch 131 enters the inside of the die hole 121a. As a result, the rotor core piece 20 is punched out of the workpiece W by the punch 131 and the die 121. A rotor through hole Hr corresponding to the outer circumference shape of the rotor core piece 20 is formed in the workpiece W from which the rotor core piece 20 has been punched out.

[0050] Inside the die bore 121a, multiple rotor core pieces 20 are stacked and bonded to one another. By stacking a predetermined number of rotor core pieces 20 inside the die bore 121a, a rotor core 11 is manufactured.

[0051] (Method for manufacturing the stator core 41) Next, we will explain how to manufacture the stator core 41. The manufacturing method for the stator core 41 comprises a first punching step, a second punching step, and a third punching step. The manufacturing method for the stator core 41 may also include various processing steps for the workpiece W, such as punching holes and forming dowels.

[0052] Prior to the first punching process, the portion of the workpiece W in which the rotor through-hole Hr has been formed is transported to the first punching station S1 by a feeding device (not shown). In the first punching process, the upper die 170 first descends, pressing the workpiece W against the lower die 160 by the stripper plate 180. Then, as the upper die 170 descends further, the first punch 171 enters the interior of the first die hole 161a. As a result, the first punch 171 and the first die 161 punch out the central hole piece W1 from the workpiece W. A first through hole 55 is formed in the workpiece W from which the central hole piece W1 has been punched out.

[0053] In the first punching process, the outer periphery of the rotor through-hole Hr is punched out from the workpiece W as a central hole piece W1, thereby forming the first through-hole 55. The central hole piece W1 is the portion of the outer periphery of the rotor through-hole Hr that is punched out coaxially with the rotor through-hole Hr. Therefore, the central hole piece W1 is annular in shape.

[0054] The first punching process includes a deformation treatment that increases the frictional force between the inner surface of the first die hole 161a and the central hole piece W1 by sliding the central hole piece W1 against the sludge suppression part 190 and causing plastic deformation. The deformation treatment is performed only on the inner surface of the support part 161c of the inner surface of the first die hole 161a. More specifically, the deformation treatment is performed only on the inner surface of the support part 161c where the sludge suppression part 190 is provided, among the inner surfaces of the multiple support parts 161c.

[0055] As shown in Figure 6, in the portion of the inner surface of the first die hole 161a where the inclined groove 191 is formed, the clearance between the outer surface of the first punch 171 and the inner surface of the first die hole 161a is larger than in other portions. Therefore, in the initial stage of punching out the central hole piece W1, a projection P is formed on the portion of the central hole piece W1 facing the inclined groove 191, protruding into the inclined groove 191. In this state, as the central hole piece W1 is pushed into the first die hole 161a in the axial direction by the first punch 171, the projection P is crushed against the wall surface of the inclined groove 191 and overcomes the inclined groove 191. As a result, the projection P reaches the portion of the inner surface of the first die hole 161a where the inclined groove 191 is not formed. At this time, since the projection P is pressed strongly against the inner surface of the first die hole 161a, the frictional force between the inner surface of the first die hole 161a and the central hole piece W1 increases. As a result, the central hole piece W1 is held inside the first die hole 161a.

[0056] Although not shown in the illustration, as a projection P is formed on the central hole piece W1, a deformation mark corresponding to the projection P is generated on the edge of the first through hole 55 in the workpiece W.

[0057] As shown in Figure 2, next, prior to the second punching process, as the upper die 170 rises, the stripper plate 180 and the first punch 171 separate from the workpiece W, and the portion of the workpiece W in which the first through hole 55 is formed is transported to the second punching station S2.

[0058] In the second punching process, first, the upper die 170 descends, pressing the workpiece W against the lower die 160 by the stripper plate 180. Then, as the upper die 170 descends further, the second punch 172 enters the interior of the second die hole 162a. As a result, the second punch 172 and the second die 162 punch out multiple slot pieces W2 from the workpiece W. Multiple second through holes 54, which communicate with the first through hole 55, are formed in the workpiece W from which the multiple slot pieces W2 have been punched out.

[0059] Furthermore, in the second punching process, multiple fixed hole pieces W3 are punched out by a punch and die (not shown), thereby forming multiple third through holes 57 in the workpiece W. Next, prior to the third punching process, as the upper die 170 rises, the stripper plate 180 and the second punch 172 separate from the workpiece W, and the portion of the workpiece W in which the first through hole 55 has been formed is transported to the third punching station S3.

[0060] In the third punching step, first, the upper die 170 descends, pressing the workpiece W against the lower die 160 by the stripper plate 180. Then, as the upper die 170 descends further, the third punch 173 enters the interior of the third die hole 163a. ​​As a result, the stator core piece 50 is punched out of the workpiece W by the third punch 173 and the third die 163. A stator through hole Hs corresponding to the outer circumference shape of the stator core piece 50 is formed in the workpiece W from which the stator core piece 50 has been punched out.

[0061] Inside the third die bore 163a, multiple stator core pieces 50 are stacked and bonded to one another. By stacking a predetermined number of stator core pieces 50 inside the third die bore 163a, a stator core 41 is manufactured.

[0062] The operation and effects of this embodiment will now be described. (1) In the first punching step, a central hole piece W1 is punched out from the workpiece W to form a first through hole 55. In the second punching step, a plurality of slot pieces W2 are punched out from the workpiece W in which the first through hole 55 is formed to form a plurality of second through holes 54. The first punching step includes a deformation process that increases the frictional force between the inner surface of the first die hole 161a and the central hole piece W1 by sliding the central hole piece W1 against a sludge suppression part 190 provided on the inner surface of the first die hole 161a and causing plastic deformation. The deformation process is performed only on the inner surface of the support part 161c.

[0063] According to the above method, in the first punching step, a central hole piece W1 is punched out from the workpiece W, and then in the second punching step, multiple slot pieces W2 are punched out from the workpiece W. In other words, at the time the central hole piece W1 is punched out from the workpiece W, the slot pieces W2 have not yet been punched out from the workpiece W. Therefore, compared to the case where the central hole piece W1 is punched out after multiple slot pieces W2 have been punched out from the workpiece W, the contact area between the inner surface of the first die hole 161a and the central hole piece W1 is increased. In addition, in the first punching step, a deformation process is performed in which the central hole piece W1 is slid against the sludge suppression section 190 to undergo plastic deformation. This increases the frictional force generated between the inner surface of the first die hole 161a and the central hole piece W1. Therefore, sludge rising of the central hole piece W1 can be suppressed.

[0064] Furthermore, since the sludge suppression portion 190 is provided on the inner surface of the first die hole 161a, deformation marks corresponding to the plastic deformation of the central hole piece W1 are formed on the edge of the first through hole 55 in the portion corresponding to the sludge suppression portion 190. If such deformation marks occur on the stator core piece 50, the product accuracy of the stator core 41 may decrease.

[0065] In this regard, according to the above method, the deformation process is performed only on the inner surface of the first die hole 161a, specifically on the inner surface of the support portion 161c that supports the portion of the first die 161 in which the second through hole 54 in the workpiece W is formed. Therefore, the deformation marks formed on the edge of the first through hole 55 are punched out together with the slot piece W2 when the second through hole 54 is formed in the workpiece W. This prevents the formation of deformation marks on the edge of the first through hole 55. Consequently, a decrease in the product accuracy of the stator core 41 can be suppressed.

[0066] (2) In the first punching process, the first die 161 is one in which the waste-removal suppression section 190 is composed of an inclined groove 191. According to the above method, a projection P is formed on the portion of the central hole piece W1 that faces the inclined groove 191. As the central hole piece W1 is pushed into the first die hole 161a, the projection P is crushed against the wall surface of the inclined groove 191 and then strongly pressed against the inner surface of the first die hole 161a. As a result, the projection P is held inside the first die hole 161a, and the removal of debris from the central hole piece W1 can be suppressed. Therefore, the removal of debris from the central hole piece W1 can be suppressed by a simple method.

[0067] (3) In the first punching process, the first die 161 used is one in which the waste-removing suppression section 190 is provided on the inner surface of at least two of the multiple support sections 161c.

[0068] According to the above method, at least two sludge-reducing portions 190 are provided at intervals on the inner surface of the first die hole 161a. As a result, plastic deformation occurs at at least two locations on the central hole piece W1 due to the deformation process. This increases the frictional force between the inner surface of the first die hole 161a and the central hole piece W1. Therefore, sludge-reducing of the central hole piece W1 can be suppressed.

[0069] (4) In the first punching process, the outer circumference of the portion of the workpiece W from which the rotor core piece 20 has been punched out is punched out as a central hole piece W1, thereby forming the first through hole 55. According to the above method, the outer periphery of the portion of the rotor core piece 20 punched out in the workpiece W is punched out as a central hole piece W1. This makes it possible to punch out the stator core piece 50 from the outer periphery of the rotor core piece 20 in a single workpiece W. Therefore, in manufacturing the stator core 41, the portion of the workpiece W that would otherwise be scrap can be effectively utilized.

[0070] (5) The stator punching device 150 includes a first punching station S1 that forms a first through hole 55 in the workpiece W, and a second punching station S2 that forms a plurality of second through holes 54 in the workpiece W. A sludge lifting suppression part 190 is provided on the inner surface of the first die hole 161a in the first punching station S1. The sludge lifting suppression part 190 is provided only on the inner surface of the support part 161c.

[0071] According to the above configuration, the effects and benefits described above (1) can be achieved. <Example of changes> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0072] In the first punching process, a central hole piece W1 may be punched out from a workpiece W in which no rotor through hole Hr has been formed, thereby forming the first through hole 55. In this case, the central hole piece W1 is circular in shape.

[0073] The inner surface of the first die hole 161a may be provided with one crumb lifting suppression portion 190, or with multiple crumb lifting suppression portions 190. The multiple crumb lifting suppression portions 190 may be provided at unequal intervals in the circumferential direction of the first die hole 161a.

[0074] The cross-sectional shape of the inclined groove 191 perpendicular to the longitudinal direction is not limited to a rectangular shape, but may also be, for example, semicircular. As shown in Figure 7, the sludge-up suppression portion 190 may be composed of an inclined surface 192 formed on the inner surface of the support portion 161c, specifically on the portion that constitutes the edge of the first die hole 161a. With this configuration, the sagging of the central hole piece W1 tends to be greater in the portion that contacts the inclined surface 192 than in other portions. As a result, the sagging of the central hole piece W1 is strongly pressed against the inner surface of the first die hole 161a, making it easier for the central hole piece W1 to be held against the inner surface of the first die hole 161a. Therefore, sludge-up of the central hole piece W1 can be suppressed by a simple method.

[0075] As shown in Figure 8, two inclined surfaces 192 and 193, which have different shapes, may be formed adjacent to each other in the circumferential direction of the first die hole 161a on the edge of the first die hole 161a. Inclined surface 192 is the same as in the modified example described above. Inclined surface 193 is formed on the inner surface of the portion of the first die 161 adjacent to the support portion 161c in the circumferential direction. The distance from the upper edge to the lower edge of inclined surface 193 is smaller than the distance from the upper edge to the lower edge of inclined surface 192. The inclination angle of inclined surface 192 with respect to the support surface 161b and the inclination angle of inclined surface 193 with respect to the support surface 161b may be the same or different. With this configuration, the central hole piece W1 is more prone to deformation in the portions of the central hole piece W1 that are in contact with inclined surfaces 192 and 193, respectively. As a result, the central hole piece W1 is more easily held against the inner surface of the first die hole 161a. Furthermore, since the distance from the upper edge to the lower edge of the inclined surface 193 is smaller than the distance from the upper edge to the lower edge of the inclined surface 192, the deformation of the central hole piece W1 caused by contact with the inclined surface 193 can be made smaller than the deformation caused by contact with the inclined surface 192. As a result, the deformation marks corresponding to the deformation of the central hole piece W1 can be made smaller at the edge of the first through hole 55 formed in the stator core piece 50. Therefore, the deterioration of the product accuracy of the stator core 41 can be suppressed while preventing the central hole piece W1 from rising.

[0076] The above embodiment includes the configuration described in the following appendix. [Note 1] A method for manufacturing a stator core, comprising stacking a plurality of iron core pieces punched out from a workpiece, each having a central hole and a plurality of slots that communicate with the central hole and are formed at intervals in the circumferential direction of the central hole, the method comprising: a first punching step of forming a first through hole constituting the central hole by punching out a central hole piece from the workpiece through the cooperation of a punch and a die having a die hole through which the punch moves forward and backward; and a second punching step of forming a plurality of second through holes constituting the plurality of slots by punching out a plurality of slot pieces from the workpiece in which the first through hole has been formed, wherein the first punching step includes a deformation process that increases the frictional force between the inner surface of the die hole and the central hole piece by sliding the central hole piece on a sludge suppression portion provided on the inner surface of the die hole to cause plastic deformation, and the deformation process is performed only on the inner surface of the die hole, on the inner surface of a support portion that supports the portion of the workpiece in which the second through holes are formed.

[0077] [Note 2] The method for manufacturing a stator core according to [Note 1], wherein the die is configured such that the sludge suppression portion is made up of inclined grooves that extend inclined with respect to the axial direction of the die hole on the inner surface of the support portion.

[0078] [Note 3] The method for manufacturing a stator core according to [Note 1], wherein the die is configured such that the sludge suppression portion is formed by an inclined surface formed on the inner surface of the support portion that constitutes the opening edge of the die hole.

[0079] [Note 4] The method for manufacturing a stator core according to any one of [Note 1] to [Note 3], wherein the die is such that the sludge suppression portion is provided on the inner surface of at least two of the support portions which are spaced apart in the circumferential direction of the die hole.

[0080] [Note 5] When the iron core piece is a stator iron core piece, in the first punching step, the outer circumference of the portion of the workpiece from which the rotor iron core piece has been punched out is punched out as the central hole piece to form the first through hole, the method for manufacturing a stator core according to any one of [Note 1] to [Note 4]. [Explanation of Symbols]

[0081] S1...First Hitting Station S2... Second Hitting Station W...work W1…Center hole piece W2... Slot piece Wp... Planned section 10…Rota 11…Rotor core 20…Rotor core pieces 40…Status 41… Stator core 44... Slot 45...Center hole 50… Stator core piece 54…Second through hole 55…First through hole 150... Stator punching machine 161...First Die 161a...First die hole 161b…support surface 161c...Support part 171...First punch 190...Scrap-removal suppression unit 191...Slanted groove 192…Slope surface 193…Slope surface

Claims

1. A method for manufacturing a stator core, comprising stacking multiple iron core pieces punched out from a workpiece, each having a central hole and a plurality of slots that communicate with the central hole and are formed at intervals in the circumferential direction of the central hole, A first punching step in which a punch and a die having a die hole through which the punch moves back and forth punch out a central hole piece from the workpiece to form a first through hole constituting the central hole, The process includes a second punching step of punching out a plurality of slot pieces from the workpiece in which the first through hole is formed, thereby forming a plurality of second through holes that each constitute the plurality of slots, The first punching step includes a deformation process that increases the frictional force between the inner surface of the die hole and the central hole piece by sliding the central hole piece against a sludge suppression portion provided on the inner surface of the die hole and causing plastic deformation. The deformation process is performed only on the inner surface of the die hole, specifically on the inner surface of the support portion that supports the portion of the die in which the second through hole in the workpiece is formed. A method for manufacturing a stator core.

2. As the die, the sludge suppression portion is made up of inclined grooves that extend inclined with respect to the axial direction of the die hole on the inner surface of the support portion. A method for manufacturing a stator core according to claim 1.

3. As the die, the sludge suppression portion is made up of an inclined surface formed on the inner surface of the support portion that constitutes the edge of the die hole. A method for manufacturing a stator core according to claim 1.

4. As the die, the sludge suppression portion is provided on the inner surface of at least two of the support portions, which are spaced apart in the circumferential direction of the die hole. A method for manufacturing a stator core according to claim 1.

5. As the workpiece, a rotor core piece that constitutes the rotor core, which is positioned inside the central hole, is punched out. In the first punching step, the outer circumference of the portion of the workpiece from which the rotor core piece has been punched out is punched out as the central hole piece to form the first through hole. A method for manufacturing a stator core according to any one of claims 1 to 4.

6. A stator core manufacturing apparatus comprising a central hole and a plurality of slots connected to the central hole and formed at intervals in the circumferential direction of the central hole, wherein a plurality of iron core pieces punched out from a workpiece are stacked, A first punching station that forms a first through-hole constituting the central hole by punching out a central hole piece from the workpiece through the cooperation of a punch and a die having a die hole through which the punch moves forward and backward, The system comprises a second punching station that punches out a plurality of slot pieces from the workpiece in which the first through hole is formed, thereby forming a plurality of second through holes that each constitute the plurality of slots, The inner surface of the die hole is provided with a sludge suppression portion that increases the frictional force between the inner surface of the die hole and the central hole piece by plastically deforming the central hole piece through sliding with the central hole piece. The aforementioned sludge suppression portion is provided only on the inner surface of the die hole, specifically on the inner surface of the support portion that supports the portion of the die in which the second through hole is formed in the workpiece. A manufacturing device for stator cores.

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