Method for manufacturing a laminated stator core and laminated stator core manufactured according to the method

Abstract

A method for manufacturing a laminated stator core, comprising: forming stator core laminations in one or more rows from a strip material, wherein the stator core laminations each have an annular yoke and chevron-shaped tabs, the tabs being arranged circumferentially at equal intervals around the annular yoke, the tabs projecting radially outward from the annular yoke, and each tab having a through-hole; and laminating the multiple stator core laminations to form the laminated stator core, wherein the laminated stator core has an annular yoke formed by laminating the annular yokes and tabs formed by laminating the tabs, the tabs being arranged circumferentially around the annular yoke, each tab having a bolt hole formed by the through-holes; comprising: Forming a recess over one or both of the following sections: (a) a lateral section of at least one tab piece C of the stator core sheet A, which is to be formed adjacent to the stator core sheet B, and (b) an edge section of the annular yoke piece D, which transitions into the lateral section, the edge section next to the tab piece C; Shaping the stator core lamination B such that a tab section E of the stator core lamination B is fitted into the recess of the stator core lamination A with a gap; and thereby improving material yield when forming the stator core laminations from the strip material; Forming the laminated stator core, which is formed from several laminated stator core blocks, wherein each stator core lamination or several stator core laminations are rotated and laminated over each other in such a way that the tab pieces C are vertically aligned to form each of the stator core blocks, wherein cutouts formed by laminating the recesses of each of the laminated stator core blocks are arranged in different parts of the laminated stator core, thereby visually confirming an interface between the laminated stator core blocks.

Description

TECHNICAL FIELD

[0001] The invention relates to a method for producing a laminated stator core from a strip material in high yield (e.g. with a low waste content) and to a laminated stator core produced by the method. TECHNICAL BACKGROUND

[0002] A laminated stator core for an inner-rotor rotating machine, such as a motor and a power generator installed in a hybrid vehicle, is fixed to a housing by bolts. The bolts are inserted into bolt holes formed in a plurality of protrusions (hereinafter referred to as ears) located in a circumferential direction of a yoke of the laminated stator core and projecting radially outward from an outer periphery of the yoke (see, for example, Patent Document 1).

[0003] For example, in order to manufacture the laminated stator core having the plurality of lugs in the outer periphery of the yoke from a strip material at a high yield (ie, with little waste), Patent Document 2 discloses a method of forming (punching out) a plurality of rows of stator core sheets having a plurality of lug pieces from the strip material, wherein the stator core sheets are laminated to form the lugs, in a circumferential direction of an annular yoke piece. PRIOR ART PATENT DOCUMENTS [Patent Document 1]: Japanese Unexamined Published Patent Application JP 2007 - 159 300 A [Patent Document 2]: Japanese Patent JP 2 840 268 B2 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] In order to effectively produce the stator core laminations from the strip material, an arrangement (positioning) of the tab pieces in the strip material is important when forming the stator core laminations from the strip material.

[0005] For example in Fig. 10(A), a stator core sheet 102 has three tab pieces 100 arranged at equal intervals in the circumferential direction of an annular yoke piece 101. When the stator core sheets 102 are formed in a row from a strip material 103 using a punching tool, the following known arrangement of the adjacent stator core sheets 102 improves the material yield: a tip of the tab piece 100 of one stator core sheet 102 faces a connecting portion between the tab piece 100 and the annular yoke piece 101 of the other stator core sheet 102. When the stator core sheets 102, as shown in Fig. 10(B), are formed in two rows from a strip material 104 with the punching tool, the following known arrangement improves the material yield: the tab piece 100 of the stator core lamination 102 lying on one side in the width direction of the strip material 104 is arranged in a space between the longitudinally adjacent (ie row-symmetrical) stator core laminations 102 lying on the other side in the width direction of the strip material 104.

[0006] If, as in Fig. 11, a gap Δ between the adjacent stator core laminations 102 in the longitudinal direction of the strip material is reduced too much for further improving the material yield of the stator core laminations 102, the tab pieces 100 of the adjacent stator core laminations 102 in the longitudinal direction of the strip material 104 are superimposed (i.e., overlapped) on each other, and therefore, a minimum value of the gap Δ is limited (i.e., the gap between the stator core laminations 102 cannot be narrowed). Therefore, the material yield cannot be improved beyond a certain degree (i.e., the waste ratio cannot be reduced).

[0007] The present invention has been made in view of the above circumstances and has an object to provide a method for producing a laminated stator core from a strip material in high yield and a laminated stator core produced by the method. MEANS FOR SOLVING THE TASKS

[0008] To achieve the above object, a first aspect of the present invention provides a method for manufacturing a laminated stator core, which includes: forming stator core sheets in one or more rows from a strip material, wherein the stator core sheets each have an annular yoke piece and chevron-shaped or angular-shaped or arrow-shaped or serrated-shaped orV-shaped ear pieces (chevron-shaped ear pieces), the ear pieces being arranged around the inner yoke piece at equal intervals in the circumferential direction, the ear pieces protruding radially outward from the annular yoke piece, the ear pieces each having a through-hole; and laminating the plurality of stator core sheets to form the laminated stator core, the laminated stator core comprising an annular yoke formed by laminating the annular yoke pieces and ear pieces formed by laminating the ear pieces, the ear pieces being arranged in the circumferential direction of the annular yoke, each ear piece having a bolt hole formed by the through-holes; the method comprising: forming a recess over one or both of the following portions: (a) a lateral portion of at least one ear piece C of the stator core sheet A which is adjacent to or on the outside of the stator core sheet.to be formed onto the stator core lamination B, and (b) an edge portion of the annular yoke piece D which merges into the side portion, the edge portion adjacent to the tab piece C; forming the stator core lamination B such that a tab piece E of the stator core lamination B is fitted into the recess of the stator core lamination A with a gap; and thereby improving a material yield when forming the stator core laminations from the strip material.

[0009] To achieve the above object, a second aspect of the present invention provides a method for manufacturing a laminated stator core, which includes: forming stator core sheets in one or more rows from a strip material, the stator core sheets each having an annular yoke piece and V-shaped tab pieces, the tab pieces being arranged around the annular yoke piece at equal intervals in the circumferential direction, the tab pieces projecting radially outward from the annular yoke piece, the tab pieces each having a through hole;and laminating the plurality of stator core sheets to form the laminated stator core, the laminated stator core comprising an annular yoke formed by laminating the annular yoke pieces and tabs formed by laminating the tab pieces, the tabs being arranged in a circumferential direction in the circumferential direction of the annular yoke, each tab having a bolt hole formed through the through-holes; the method comprising: forming a recess over one or both of the following portions: (a) a lateral portion of at least one tab piece C of the stator core sheet A to be formed adjacent to the stator core sheet B, and (b) an edge portion of the annular yoke piece D that merges into the lateral portion, the edge portion adjacent to the tab piece C;Forming the stator core lamination B such that a tab piece E of the stator core lamination B is fitted into the recess of the stator core lamination A with a gap; reducing a width of the gap by removing a tip of the tab piece E; and thereby improving a material yield when forming the stator core laminations from the strip material.;

[0010] In the method for manufacturing the laminated stator core according to the first and second aspects of the present invention, it is preferable that the recess has a circular arc shape.

[0011] In the method for manufacturing the laminated stator core according to the first and second aspects of the present invention, it is preferable that the width of the gap is equal to two to twenty times a thickness of the strip material.

[0012] If the gap width is less than twice the thickness of the strip material, positioning accuracy deteriorates, and feeding the strip material becomes difficult when the stator core laminations are formed by punching. If the gap width is greater than 20 times the thickness of the strip material, the adjacent stator core laminations are formed with a wider gap than necessary, which prevents the material yield from being improved.

[0013] In the method for manufacturing the laminated stator core according to the first and second aspects of the present invention, it is preferable that a width of an area between the through hole and the recess formed in the tab piece C is greater than or equal to a difference between a flange radius of a bolt to be inserted into the bolt hole and a radius of the through hole.

[0014] To achieve the above object, a third aspect of the present invention provides a laminated stator core manufactured by the manufacturing method of the laminated stator core according to the first aspect of the present invention, comprising: a cutout formed in a part of the tab or the annular yoke or both in a lamination direction.

[0015] To achieve the above object, a fourth aspect of the present invention provides a laminated stator core manufactured by the manufacturing method of the laminated stator core according to the second aspect of the present invention, comprising: a cutout formed in a part of the tab or the annular yoke or both in a lamination direction; and a flat cutout formed in a part of a tip of the tab other than the tab having the cutout in the lamination direction. EFFECT OF THE INVENTION

[0016] In the method for manufacturing the laminated stator core according to the first aspect of the present invention and the laminated stator core according to the third aspect of the present invention, when the stator core sheets are formed from the strip material and the strip material having a smaller width than that of the conventional material is used, the material yield is improved. Thus, the consumption of strip material and the material cost can be reduced. To form the adjacent stator core sheets A, B in the strip material, a tab piece E of the stator core sheet B is fitted into the recess formed in the stator core sheet A, and the width of the gap between the stator core sheets A, B is narrowed. This can reduce the consumption of strip material and the material cost.When forming the stator core laminations A and B with a punching die, the punching die can be small, thus reducing the cost of the punching die. The small punching die allows for a downsizing of the press, thus reducing the cost of the press. As a result, the manufacturing cost of the laminated stator core can be further reduced.

[0017] According to the invention, to form the stator core block, each stator core lamination or a plurality of stator core laminations are rotated and stacked or laminated on top of each other such that the tab pieces C are vertically aligned. In this way, when forming the laminated stator core with the plurality of laminated stator core blocks, the cutouts of the laminated stator core blocks are arranged in different parts of the laminated stator core. Therefore, an interface between the laminated stator core blocks can be easily confirmed visually.

[0018] In the method for manufacturing the laminated stator core according to the second aspect of the present invention and the laminated stator core according to the fourth aspect of the present invention, when the stator core sheets are formed from the strip material and the strip material having a smaller width than that of the conventional material is used, the material yield is further improved. Thus, the consumption of strip material and the material cost can be further reduced. To form the adjacent stator core sheets A, B in the strip material, a tab piece E excluding the tip of the stator core sheet B is fitted into the recess formed in the stator core sheet A, and the width of the gap between the stator core sheets A, B is reduced. Thus, the consumption of strip material and the material cost can be further reduced.When the stator core laminations A and B are formed by the punching die, the punching die can be small in size, thus reducing the cost of the punching die. The small punching die allows for a downsizing of the press, thus reducing the cost of the press. Furthermore, the existing press does not need to be replaced with a new one that corresponds to the larger punching die. As a result, the manufacturing cost of the laminated stator core can be further reduced.

[0019] According to the present invention, when the laminated stator core is formed by rotating and laminating the plurality of laminated stator core blocks so that the tab pieces are vertically aligned, the cutouts and flat cutouts of the laminated stator core blocks are located in different parts of the laminated stator core. Therefore, an interface between the laminated stator core blocks can be easily confirmed visually.

[0020] In the method for manufacturing the laminated stator core according to the first and second aspects of the present invention, when the recess has the circular arc shape, interference between the recess and the tab piece E is prevented, and therefore the gap therebetween can have a small width.

[0021] In the method for manufacturing the laminated stator core according to the first and second aspects of the present invention, when the width of the gap is equal to two to twenty times a thickness of the strip material, the stator core sheets can be accurately formed with the improved material yield.

[0022] In the method for manufacturing the laminated stator core according to the first and second aspects of the present invention, when the width of the area between the through hole and the recess, both formed in the tab piece C, is greater than or equal to the difference between the flange radius of the bolt to be inserted into the bolt hole and the radius of the through hole, the deformation of the tab pieces can be prevented and the deterioration of the strength of the tabs formed with the tab pieces can be avoided. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows how stator core sheets are to be formed from a strip material in a method for producing a laminated stator core according to a first embodiment of the present invention. Fig. 2 shows a plan view of a stator core sheet formed according to the method for producing the laminated stator core. Fig. 3 shows a perspective view of a stator core formed by the method for manufacturing the laminated stator core. Fig. 4 is an enlarged partial view illustrating how to form stator core sheets from a strip material in a method for manufacturing a laminated stator core according to a second embodiment of the present invention. Fig. 5 shows a perspective view of a laminated stator core formed by the method for manufacturing the laminated stator core. Fig. 6 is an enlarged partial view illustrating how to form stator core sheets from a strip material in a method for manufacturing a laminated stator core according to a third embodiment of the present invention. Fig. 7 shows a perspective view of a laminated stator core formed by the method for manufacturing the laminated stator core. Fig. 8 is an enlarged partial view illustrating how to form stator core sheets from a strip material in a method for manufacturing a laminated stator core according to a fourth embodiment of the present invention. Fig. 9 shows a perspective view of a laminated stator core formed by the method for manufacturing the laminated stator core. Fig. 10 (A) is an explanatory view showing how to form stator core sheets according to a conventional example. Fig. 10 (B) is an explanatory view showing how to form stator core sheets according to a conventional example. Fig. 11 is an explanatory view of problems in the method of forming stator core sheets according to the conventional examples. MODE FOR CARRYING OUT THE INVENTION

[0023] With reference to the accompanying drawings, embodiments of the present invention will be described below for a better understanding of the invention.

[0024] As in the Fig. 1 to 3, in a method for manufacturing a laminated stator core according to a first embodiment of the present invention, stator core sheets 13 are punched out in two rows (one example of a plurality of rows) from a strip material 14, that is, for example, an electrical steel sheet having a thickness of 0.2-0.5 mm (that is, in an exemplary method for forming outlines of the stator core sheets), and the plurality of stator core sheets 13 are stacked one on top of another to form a laminated stator core 18. The stator core sheet 13 has tab pieces 11 formed at equal intervals in the circumferential direction of an annular yoke piece 12. Viewed from above, the tab piece 11 is chevron-shaped (inverted V-shape) and protrudes radially outward from the annular yoke piece 12. The tab piece 11 has a through-hole 10 at its center.The laminated stator core 18 includes an annular yoke 17 formed by laminating the annular yoke pieces 12. In a circumferential direction of the annular yoke 17, tabs 16, 16a, and 16b are formed by laminating the tab pieces 11. Each of the tabs 16, 16a, and 16b has a bolt hole 15 formed through the through holes 10. In the figures, reference numeral 19 indicates a locking portion for connecting the vertically adjacent stator core sheets 13. Reference numeral 20 indicates a slot of the laminated stator core 18. A detailed description will be given below.

[0025] Fig. 1 shows an arrangement of the stator core sheets 13 in the strip material 14 in the method for manufacturing the laminated stator core according to the first embodiment of the present invention. The stator core sheets 13 are arranged adjacently in the longitudinal direction of the strip material 104 before punching. One of the adjacent stator core sheets 13 (hereinafter referred to as stator core sheet A) includes a recess 21 formed in a lateral portion of at least one tab piece 11 (hereinafter referred to as tab piece C). The other stator core sheet 13 (hereinafter referred to as stator core sheet B) is shaped such that a tab piece 11 (hereinafter referred to as tab piece E) of the stator core sheet B is fitted into the recess 21 of the stator core sheet A with a gap. With this arrangement, the stator core sheets A, B can be formed with the narrow gap therebetween in the strip material 14.

[0026] A width W1 of a region between the through hole 10 formed in the tab piece C and the recess 21 formed in the lateral portion of the tab piece C is equal to (or may be larger than) a difference between a flange radius of a bolt to be inserted into the bolt hole 15 and a radius of the through hole 10. This setting prevents excessive increase in the width W1 and deformation of the tab piece C, which may be caused, for example, by upsetting when screwing the tab piece C. Now, the recess 21 of the stator core sheet A has a circular arc shape, which prevents interference between the recess 21 of the stator core sheet A and the tab piece E of the stator core sheet B when the tab piece E is fitted into the recess 21 with the clearance. A width δ1 of the clearance can also be reduced.In addition, the width δ1 of the gap between the recess 21 of the stator core sheet A and the tab piece E of the stator core sheet B is equal to two to twenty times the thickness of the strip material 14. Therefore, the stator core sheet B can be punched out without deteriorating the positioning accuracy and feeding of the strip material 14, while preventing an unnecessary gap width. As a result, the stator core sheets 13 can be punched out of the strip material 14 with a high yield, thereby reducing the consumption of the strip material 14 and material costs.

[0027] When punching out the adjacent stator core sheets 13, the tab piece E of the stator core sheet B is fitted into the recess 21 of the stator core sheet A, and therefore, the width δ1 of the gap between the stator core sheets A, B can be narrowed. Accordingly, the punching die for the stator core sheets 13 can be small, thereby reducing the cost of the punching die. Furthermore, when the dimensions of the punching die are increased, an existing press must be replaced with a new press corresponding to the larger punching die, but this need no longer exists here. As a result, the manufacturing cost of the laminated stator core can be further reduced.

[0028] A description will be given below of the laminated stator core 18 manufactured by the method for manufacturing the laminated stator core according to the first embodiment of the present invention.

[0029] The laminated stator core 18 is manufactured by laminating the stator core sheets 13, which are punched from the strip material 14 with high yield. Therefore, the material costs and the manufacturing costs of the laminated stator core 18 can be reduced.

[0030] As in Fig. 3, the laminated stator core 18 is provided with the plurality (three in Fig. 3) Laminated stator core blocks 22 are formed. Each of the laminated stator core blocks 22 is formed by laminating the plurality of stator core sheets 13 such that the tab pieces C are vertically aligned. The laminated stator core block 22 is rotated on the underlying laminated stator core block 22 before laminating. Thus, cutouts 23 of the laminated stator core blocks 22 formed by laminating the recesses 21 are arranged in different parts of the laminated stator core 18. Therefore, an interface between the laminated stator core blocks 22 of the laminated stator core 18 can be easily confirmed visually.

[0031] The width W1 of the area between the through hole 10 of the tab piece C and the recess 21 is the difference between the flange radius of the bolt to be inserted into the bolt hole 15 and the radius of the through hole 10. Therefore, even if the tab piece C has the recess 21, the deformation of the tab piece C is prevented. For this reason, in the laminated stator core block 22, the strength of a tab block 24 formed by laminating the tab pieces C is prevented from being lower than that of a tab block 25 formed by laminating the tab pieces 11 without the recess 21. As a result, the deterioration of the strength of the tabs 16, 16a, and 16b in the laminated stator core 18 manufactured from the plurality of laminated stator core blocks 22 can be prevented.

[0032] Compared with the method for manufacturing the laminated stator core according to the first embodiment of the present invention, a method for manufacturing the laminated stator core according to a second embodiment of the present invention has the features described below.

[0033] As in Fig. 4, when forming the stator core laminations from the strip material, the stator core laminations are arranged adjacent to each other in the longitudinal direction of the strip material before punching. Specifically, one of the adjacent stator core laminations, i.e., the stator core lamination A, has a recess 26 disposed over both (a) a lateral portion of the tab piece C of the stator core lamination A and (b) an outer periphery of an annular yoke piece D adjacent to the lateral portion of the tab piece C. The stator core lamination B is formed such that the tab piece E of the stator core lamination B is fitted into the recess 26 of the stator core lamination A with a gap of width δ2. In the figures, the common components are represented by the same reference numerals, and their descriptions are omitted.

[0034] Hereinafter, descriptions of functions common to the methods for manufacturing the laminated stator cores according to the first and second embodiments will be omitted. In short, descriptions will be given only of functions unique to the method for manufacturing the laminated stator core according to the second embodiment.

[0035] In the method for manufacturing the laminated stator core according to the second embodiment, the recess 26 is provided over both (a) the lateral portion of the tab piece C and (b) the outer periphery of the annular yoke piece D adjacent to the lateral portion of the tab piece C. In other words, the recess 26 extends from a lower end of the lateral portion of the chevron-shaped or V-shaped tab piece C to the annular yoke piece D adjacent to the tab piece C. And the tab piece E of the stator core sheet B is fitted into the recess 26 of the stator core sheet A with the clearance. Then, a distance between the tab pieces C, E of the stator core sheets A, B is wider than that in the method for manufacturing the laminated stator core according to the first embodiment.Therefore, even if the depth of the recess 26 is small, the tab piece E of the stator core sheet B is fitted into the recess 26 with a gap of a smaller width δ2 than the width δ1 in the first embodiment.

[0036] Considering the above facts, the stator core sheets can be punched out from the strip material in high yield, and the strip material consumption and material cost can be reduced.

[0037] Furthermore, the recess 26 can be shallower than that in the method for manufacturing the laminated stator core according to the first embodiment. Therefore, a width W2 of the area between the through-hole 10 formed in the tab piece C and the recess 26 formed in the lateral portion of the tab piece C is larger than the width W1 in the first embodiment. Therefore, deformation of the tab piece C can be further prevented.

[0038] With reference to Fig. 5, a description will be given below of a laminated stator core 27 manufactured by the method for manufacturing the laminated stator core according to the second embodiment of the present invention. The common components with the laminated stator core 18 manufactured by the method for manufacturing the laminated stator core according to the first embodiment are represented by the same reference numerals, and their descriptions will be omitted.

[0039] The laminated stator core 27 is formed by laminating stator core sheets punched from a strip material at high yield. Therefore, the material costs and manufacturing costs of the laminated stator core 27 can be reduced.

[0040] As in Fig. 5, the laminated stator core 27 is formed from the plurality (three in Fig. 5) laminated stator core blocks 28 are formed. Each of the laminated stator core blocks 28 is formed by laminating the plurality of stator core sheets so that the tab pieces C are vertically aligned. Now, (a) a distance between the bolt hole 15 of the laminated stator core 27 and a cutout 29 of the laminated stator core block 28 formed by laminating the recesses 28 is larger than (b) a distance between the bolt hole 15 of the laminated stator core 18 and the cutout 23 of the laminated stator core block 22 formed by laminating the recesses 21 in the first embodiment. For this reason, in the laminated stator core 27, the strength of a tab block 30 formed by laminating the tab pieces C with the recesses 26 is prevented from being lower than that of a tab block 31 formed by laminating the tab pieces 11 without the recesses 26.As a result, the deterioration of the strength of the tabs 32, 32a and 32b in the laminated stator core 27 consisting of the plurality of laminated stator core blocks 28 can be prevented.

[0041] Compared with the method for manufacturing the laminated stator core according to the first embodiment of the present invention, a method for manufacturing the laminated stator core according to a third embodiment of the present invention has the features described below.

[0042] As in Fig. 6, when forming the stator core laminations from the strip material, the stator core laminations are arranged adjacent to each other in the longitudinal direction of the strip material before punching. Specifically, one of the adjacent stator core laminations, i.e., the stator core lamination A, has a recess 33 disposed over both (a) a lateral portion of the tab piece C of the stator core lamination A and (b) an outer periphery of an annular yoke piece D adjacent to the lateral portion of the tab piece C. The stator core lamination B is formed such that the tab piece E of the stator core lamination B is fitted into the recess 33 of the stator core lamination A with a gap of width δ3. A tip of the tab piece E is removed and flattened. In the figures, the common components are represented by the same reference numerals, and their descriptions are omitted.

[0043] Hereinafter, descriptions of functions common to the methods for manufacturing the laminated stator cores according to the first and third embodiments will be omitted. In short, descriptions will be given only of functions unique to the method for manufacturing the laminated stator core according to the third embodiment.

[0044] In the method for manufacturing the laminated stator core according to the third embodiment, the recess 33 is provided over both (a) the lateral portion of the tab piece C and (b) the outer periphery of the annular yoke piece D adjacent to the lateral portion of the tab piece C. In other words, the recess 33 extends from a lower end of the lateral portion of the chevron-shaped or V-shaped tab piece C to the annular yoke piece D on the tab piece C side. And the tab piece E of the stator core sheet B is fitted into the recess 33 of the stator core sheet A with the clearance. Then, a distance between the tab pieces C, E of the stator core sheets A, B is wider than that in the method for manufacturing the laminated stator core according to the first embodiment. Further, the tip of the tab piece E of the stator core sheet B is removed and flattened.Therefore, even when the depth of the recess 33 is small, the tab piece E of the stator core sheet B is fitted into the recess 33 with the gap of a smaller width δ3 than the width δ1 in the first embodiment. Now, a width U of a portion between the tip of the tab piece E of the stator core sheet B and the through-hole 10 formed in the tab piece E is the difference between the flange radius of the bolt to be inserted into the bolt hole 15 and the radius of the through-hole 10, thereby preventing deformation of the tab piece E.

[0045] In the case of removing the tip of the tab piece E, the tip of the tab piece E may be flattened or rounded to have a large curvature, as long as the tab piece E without the tip has a sufficient contact area for a flange surface of the bolt to be inserted into the bolt hole 15. Preferably, the tip of the tab piece E is rounded to have a large curvature.

[0046] Considering the above facts, the gap between the stator core sheet A and the tab piece E of the stator core sheet B can be further reduced. As a result, the stator core sheets can be punched out of the strip material with higher yield, and the strip material consumption and material cost can be reduced.

[0047] In addition, the recess 33 can be shallower than the recess 21 in the first embodiment. Consequently, a width W3 of the area between the through-hole 10 formed in the tab piece C and the recess 33 formed in the lateral portion of the tab piece C is larger than the width W1 in the first embodiment. Therefore, deformation of the tab piece C can be further prevented.

[0048] With reference to Fig. 7, a description will be given below of a laminated stator core 34 manufactured according to the method for manufacturing the laminated stator core according to the third embodiment of the present invention. The components common to the laminated stator core 18 manufactured according to the method for manufacturing the laminated stator core according to the first embodiment are represented by the same reference numerals, and their descriptions will be omitted.

[0049] The laminated stator core 34 is formed from laminated stator core sheets that are punched from a strip material with higher yield. Consequently, the material costs and the manufacturing costs of the laminated stator core 34 can be further reduced.

[0050] As in Fig. 7, the laminated stator core 34 is provided with the plurality (three in Fig. 7) laminated stator core blocks 35 are formed. Each of the laminated stator core blocks 35 is formed by laminating the plurality of stator core sheets 13 so that the tab pieces C are vertically aligned. Now, (a) a distance between the bolt hole 15 of the laminated stator core 34 and a cutout 36 of the laminated stator core block 35 formed by laminating the recesses 33 is larger than (b) a distance between the bolt hole 15 of the laminated stator core 18 and the cutout 23 of the laminated stator core block 22 formed by laminating the recesses 21 in the first embodiment. In addition, the width U of the area between the tip of the tab piece E of the stator core sheet B and the through hole 10 formed in the tab piece E is the difference between the flange radius of the bolt to be inserted into the bolt hole 15 and the radius of the through hole 10.For these reasons, the strength of a tab block 37 formed by laminating the tab pieces C and a tab block 38 formed by laminating the tab pieces E is prevented from being lower than the strength of a tab block 39 formed by laminating the tab pieces excluding the tab pieces C, E. Here, since the tab block 38 is formed by laminating the tab pieces E without the tips, one end of the tab block 38 includes a shallow cutout in the lamination direction. As a result, the deterioration of the strength of the tab blocks 40, 40a, and 40b in the laminated stator core 34 manufactured from the plurality of laminated stator core blocks 35 can be prevented.

[0051] As in the Fig. 8 and Fig. As shown in Fig. 9, in a method for manufacturing a laminated stator core according to a fourth embodiment of the present invention, stator core sheets 44 (the adjacent stator core sheets 44 are referred to as stator core sheets A, B) are punched out in a row from a strip material 45, which is, for example, an electrical steel sheet having a thickness of 0.2-0.5 mm (that is, in an exemplary method for forming outlines of the stator core sheets), and the plurality of stator core sheets 44 are stacked one on top of another to form a laminated stator core 49. The stator core sheet 44 has tab pieces 42 formed at equal intervals in the circumferential direction of an annular yoke piece 43. When viewed from above, the tab piece 42 is chevron-shaped (inverted V-shaped) and protrudes radially outward from the annular yoke piece 43. The tab piece 42 has a through hole 41 in its center.The laminated stator core 49 includes an annular yoke 48 formed by laminating the annular yoke pieces 43. The annular yoke 48 has tabs 47 formed in its circumferential direction by laminating the tab pieces 42. Each of the tabs 47 has a bolt hole 46 formed through the through holes 41. In the figures, reference numeral 50 indicates a locking portion for connecting the vertically adjacent stator core sheets 44. Reference numeral 51 indicates a slot of the laminated stator core 49. A detailed description will be given below.

[0052] Fig. 8 shows an arrangement of the stator core sheets A, B in the strip material 45 in the method for manufacturing the laminated stator core according to the fourth embodiment of the present invention. The stator core sheets A, B adjacent in the longitudinal direction of the strip material 45 are punched out of the strip material 45. One of the adjacent stator core sheets A, B, i.e., the stator core sheet A, has a recess 52 formed in an edge portion of an annular yoke piece D located on the side of a tab piece C, which yoke piece D merges into the lateral portion of the tab piece C (an example of at least one of the tab pieces 42). The stator core sheet B is shaped such that the tab piece E (an example of a tab piece 42 of the stator core sheet B) of the stator core sheet B is fitted into the recess 52 of the stator core sheet A with a gap of the width δ4.With this arrangement, the gap between the stator core sheet A and the tab piece E of the stator core sheet B can be reduced.

[0053] Now, the recess 52 of the stator core sheet A is circular arc-shaped, preventing interference between the recess 52 of the stator core sheet A and the tab piece E of the stator core sheet B when the tab piece E is fitted into the recess 52 with the gap. A width δ4 of the gap can also be reduced. Furthermore, the width δ4 of the gap between the recess 52 of the stator core sheet A and the tab piece E of the stator core sheet B is equal to two to twenty times the thickness of the strip material 45. Therefore, the stator core sheet B can be punched out without deteriorating the positioning accuracy and feeding of the strip material 45, while preventing an unnecessarily wide gap.

[0054] As a result, the stator core sheets 44 can be punched out of the strip material 45 in high yield, and thereby the consumption of the strip material 45 and the material cost can be reduced.

[0055] When punching out the adjacent stator core sheets A, B, the tab piece E is fitted into the recess 52 of the stator core sheet A, and therefore, the width δ4 of the gap between the stator core sheets A, B can be reduced. Therefore, the punching die for the stator core sheets A, B can be small, and the cost of the punching die can be reduced. Furthermore, when the dimensions of the punching die are increased, an existing press must be replaced with a new press corresponding to the larger size of the punching die, but this need no longer exists here.

[0056] A description will now be given of the laminated stator core 49 manufactured by the method for manufacturing the laminated stator core according to the fourth embodiment.

[0057] The laminated stator core 49 is manufactured by laminating the stator core sheets 44, which are punched out of the strip material 45 at high yield. Therefore, the material costs and manufacturing costs of the laminated stator core 49 can be reduced.

[0058] As in Fig. 9, the laminated stator core 49 is provided with the plurality (three in Fig. 9) laminated stator core blocks 53 are formed. Each of the laminated stator core blocks 53 is formed by laminating the plurality of stator core sheets 44 such that the tab pieces C are vertically aligned. The laminated stator core block 53 is rotated on the underlying laminated stator core block 53 before laminating. Thus, cutouts 55 formed by laminating the recesses 52 are arranged in various parts of the laminated stator core 49. Therefore, an interface between the laminated stator core blocks 53 can be easily confirmed visually.

[0059] As in Fig.8, the recess 52 is formed in the edge portion of the annular yoke piece D located on the side of the link piece C, which is continuous with the lateral portion of the link piece C. Therefore, (a) a width of a region between the through-hole 41 formed in the link piece C and an outer periphery of the link piece C becomes identical to (b) a width of a region between the through-hole 41 formed in a link piece not located near the recess 52 and an outer periphery of that link piece. Accordingly, the strength of the link block formed by laminating the link pieces becomes identical to the strength of the link block formed by laminating the link pieces not located near the recess 52. In the laminated stator core 49, all the link blocks 47 have approximately the same strength.When a width of the annular yoke 48 becomes smaller, the strength of the link blocks 47 is reduced a little.

[0060] In the first to fourth embodiments, the yield of the strip material from which the stator core laminations are punched can be improved, for example, by 2-20% compared to conventional methods. Furthermore, the consumption of strip material can be reduced, for example, by 5-25% compared to conventional methods. As a result, material costs can be reduced, for example, by 5-25% compared to conventional methods.

[0061] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and other embodiments and various modifications can be realized without departing from the scope of the claims.

[0062] Furthermore, the present invention includes combinations of elements of the embodiments of the present invention and the other embodiments and modifications. For example, in the method for manufacturing the laminated stator core according to the third and fourth embodiments, the tip of the tab piece of one of the adjacent stator core sheets, which is fitted into the recess of the other stator core sheet, may be removed and flattened to further reduce the width of the gap therebetween. In the case of removing the tip of the tab piece, the tip of the tab piece may be flattened or rounded to have the large curvature, as long as the tab piece without the tip has the sufficient contact area with the flange surface of the bolt to be inserted into the bolt hole 15. Preferably, the tip of the tab piece is rounded to have the large curvature.

[0063] The method for manufacturing the laminated stator core according to the present invention has been described using the example case where the stator core laminations are punched out of the strip material using a punching tool. However, the present invention can also be applied to the case where the stator core laminations are formed from the strip material by electrical discharge machining or laser cutting.

[0064] In the present invention, several stator core laminations are rotated at a time, but each stator core lamination can also be rotated before the laminations are stacked or laminated on top of each other. DESCRIPTION OF REFERENCE SYMBOLS

[0065] 10: Through hole; 11: Tab piece; 12: Annular yoke piece; 13: Stator core sheet; 14: Strip material; 15: Bolt hole; 16, 16a, 16b: Tab; 17: Annular yoke; 18: Laminated stator core; 19: Locking portion; 20: Slot; 21: Recess; 22: Laminated stator core block; 23: Cutout; 24, 25: Tab block; 26: Recess; 27: Laminated stator core; 28: Laminated stator core block; 29: Cutout; 30, 31: Tab block; 32, 32a, 32b: Tab; 33: Recess; 34: Laminated stator core; 35: Laminated stator core block; 36: Cutout; 37, 38, 39: Tab block; 40, 40a, 40b: Tab; 41: Through hole; 42: Tab piece; 43: Annular yoke piece; 44: Stator core sheet; 45: Strip material; 46: Bolt hole; 47: Tab; 48: Annular yoke; 49: Laminated stator core; 50: Locking portion; 51: Slot; 52: Recess; 53: Laminated stator core block; 55: Cutout.

Claims

[1] A method of manufacturing a laminated stator core, the method comprising: forming stator core laminations in one or more rows from a strip material, the stator core laminations each having an annular yoke piece and chevron-shaped tab pieces, the tab pieces being arranged around the annular yoke piece at equal intervals in the circumferential direction, the tab pieces projecting radially outward from the annular yoke piece, and each of the tab pieces having a through-hole; and laminating the plurality of stator core laminations to form the laminated stator core, the laminated stator core comprising an annular yoke formed by laminating the annular yoke pieces and tabs formed by laminating the tab pieces, the tabs being arranged in the circumferential direction of the annular yoke, the tabs each having a bolt hole formed through the through-holes; the method comprising: Forming a recess over one or both of the following portions: (a) a lateral portion of at least one tab piece C of the stator core sheet A to be formed adjacent to the stator core sheet B, and (b) an edge portion of the annular yoke piece D which merges into the lateral portion, the edge portion adjacent to the tab piece C; Forming the stator core sheet B so that a tab piece E of the stator core sheet B is fitted into the recess of the stator core sheet A with a gap; and thereby improving material yield when forming the stator core laminations from the strip material; Forming the laminated stator core formed from a plurality of laminated stator core blocks, wherein each stator core sheet or a plurality of stator core sheets are rotated and laminated one on top of the other so that the tab pieces C are vertically aligned to form each of the stator core blocks, wherein cutouts formed by laminating the recesses of each of the laminated stator core blocks are arranged in different parts of the laminated stator core, thereby visually confirming an interface between the laminated stator core blocks. [2] A method of manufacturing a laminated stator core, the method comprising: forming stator core laminations in one or more rows from a strip material, the stator core laminations each having an annular yoke piece and chevron-shaped tab pieces, the tab pieces being arranged around the annular yoke piece at equal intervals in the circumferential direction, the tab pieces projecting radially outward from the annular yoke piece, and each of the tab pieces having a through-hole; and laminating the plurality of stator core laminations to form the laminated stator core, the laminated stator core comprising an annular yoke formed by laminating the annular yoke pieces and tabs formed by laminating the tab pieces, the tabs being arranged in the circumferential direction of the annular yoke, the tabs each having a bolt hole formed through the through-holes; the method comprising: Forming a recess over one or both of the following portions: (a) a lateral portion of at least one tab piece C of the stator core sheet A to be formed adjacent to the stator core sheet B, and (b) an edge portion of the annular yoke piece D which merges into the lateral portion, the edge portion adjacent to the tab piece C; Forming the stator core sheet B such that a tab piece E of the stator core sheet B is fitted into a space in the recess of the stator core sheet A; Reducing the width of the gap by removing a tip of the tab piece E; and thereby improving material yield when forming the stator core laminations from the strip material; Forming the laminated stator core formed from a plurality of laminated stator core blocks, wherein each stator core sheet or a plurality of stator core sheets are rotated and laminated one on top of the other so that the tab pieces C are vertically aligned to form each of the stator core blocks, wherein cutouts formed by laminating the recesses of each of the laminated stator core blocks are arranged in different parts of the laminated stator core, thereby visually confirming an interface between the laminated stator core blocks. [3] A method for manufacturing the laminated stator core according to claim 1 or 2, wherein the recess is circular arc-shaped. [4] A method for manufacturing the laminated stator core according to any one of claims 1 to 3, wherein the width of the gap is equal to two to twenty times a thickness of the strip material. [5] A method for manufacturing the laminated stator core according to any one of claims 1 to 4, wherein a width of a portion between the through hole formed in the tab piece C and the recess formed in the tab piece C is greater than or equal to a difference between a flange radius of a bolt to be inserted into the bolt hole and a radius of the through hole. [6] A laminated stator core manufactured by the method for manufacturing the laminated stator core according to claim 1, wherein the cutout is formed in a part of the tab or the annular yoke or both in the lamination direction. [7] A laminated stator core manufactured by the method for manufacturing the laminated stator core according to claim 2, wherein the cutout is formed in a part of the tab or the annular yoke or both in the lamination direction; the stator core comprises: a shallow cutout formed in a part of a tip of the tab other than the tab having the cutout in the siping direction.

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