阅读说明：本技术 铁芯、定子及旋转电机 (Iron core, stator and rotating electrical machine ) 是由 斋藤达哉 上野友之 于 2019-10-17 设计创作，主要内容包括：一种铁芯,其在轴向间隙型旋转电机中使用,所述铁芯为环状,具有将所述铁芯在周向分割的多个铁芯片,所述铁芯片具有：轭部；以及齿部,其与所述轭部一体地成型,从所述轭部在轴向凸出,所述轭部包含：多个凸部,它们设置于与相邻的一个铁芯片的轭部连结的一个侧面；以及多个凹部,它们与所述凸部相对应,设置于与相邻的另一个铁芯片的轭部连结的另一个侧面,所述凸部间的间隔小于或等于由所述轭部的外周和内周之间的直线距离决定的所述轭部的侧面的长度的80％。(A core for use in an axial gap type rotating electrical machine, the core having an annular shape and comprising a plurality of core pieces that divide the core in a circumferential direction, the core pieces comprising: a yoke portion; and a tooth portion integrally molded with the yoke portion and protruding in an axial direction from the yoke portion, the yoke portion including: a plurality of projections provided on one side surface coupled to the yoke portion of an adjacent core segment; and a plurality of concave portions provided on the other side surface coupled to the yoke portion of the adjacent other core segment, corresponding to the convex portions, wherein the interval between the convex portions is less than or equal to 80% of the length of the side surface of the yoke portion determined by the linear distance between the outer circumference and the inner circumference of the yoke portion.)

1. An iron core used in an axial gap type rotating electrical machine,

the iron core is annular and is provided with a plurality of iron core pieces which divide the iron core in the circumferential direction,

the iron core sheet has:

a yoke portion; and

a tooth portion integrally molded with the yoke portion and protruding in an axial direction from the yoke portion,

the yoke includes:

a plurality of projections provided on one side surface coupled to the yoke portion of an adjacent core segment; and

a plurality of concave portions provided on the other side surface coupled to the yoke portion of the other core segment adjacent to the concave portions, corresponding to the convex portions,

the interval between the convex portions is less than or equal to 80% of the length of the side surface of the yoke determined by the straight-line distance between the outer circumference and the inner circumference of the yoke.

2. The core of claim 1,

when the yoke is viewed from a plane view from the tooth projecting side, a center line between mutually facing side surfaces of the tooth and a tooth of another adjacent core segment is defined as a reference line, and a distance from the recess to a root of the tooth is 20% or more of a distance from the reference line to the root of the tooth.

3. The iron core of claim 1 or 2,

the size of the convex part is greater than or equal to 1mm and less than or equal to 10 mm.

4. The iron core of any of claims 1-3,

a minimum radius of curvature of the convex portion and the concave portion when the yoke is viewed from a side of the tooth portion in a plan view is 1.0mm or more.

5. The iron core of any of claims 1-4,

the adjacent convex parts are symmetrical relative to the central line between the convex parts.

6. The iron core of any of claims 1-5,

the thickness of the yoke is greater than or equal to 1.0mm and less than or equal to 10 mm.

7. The iron core of any of claims 1-6,

the core pieces are formed of dust cores,

the dust core is composed of an aggregate of a plurality of coated soft magnetic particles having an insulating coating on the surface of the soft magnetic particles,

the soft magnetic particles are iron-based particles composed of at least one of pure iron and an iron-based alloy,

the iron-based alloy is at least one selected from the group consisting of Fe-Si based alloys, Fe-Al based alloys, Fe-Cr-Al based alloys, and Fe-Cr-Si based alloys.

8. The core of claim 7,

the insulating coating comprises a phosphate coating.

9. The core of claim 7 or 8,

the relative density of the dust core is 90% or more.

10. The iron core of any of claims 1-9,

has an annular member fitted to the outer peripheral surface of the yoke of the plurality of core segments,

the ring-shaped member is fixed to the plurality of core pieces by a contraction force in an inner diameter direction thereof.

11. The iron core of any of claims 1-10,

the side surfaces of the yoke portions of the adjacent core pieces are bonded to each other, or,

the core segment has a plate-like member disposed on the side of the yoke portion of the adjacent core segment opposite to the side on which the tooth portions project, and the surface of the yoke portion opposite to the side is bonded to the plate-like member.

12. The iron core of any of claims 1-11,

the difference between the position of the end face of the highest tooth and the position of the end face of the lowest tooth among the teeth of the plurality of core pieces is less than or equal to 0.15 mm.

13. The iron core of any of claims 1-12,

in a state where the plurality of iron pieces are combined into a ring shape, a circularity of an outer circumferential surface of the yoke portion is 0.1mm or less.

14. The iron core of any of claims 1-13,

the flatness of the end face of the tooth part is less than or equal to 0.2 mm.

15. A stator of an axial gap type rotating electrical machine,

the stator has:

the iron core of any one of claims 1 to 14; and

and coils arranged in the teeth of the core pieces constituting the core.

16. A rotating electrical machine of an axial gap type, which has a rotor and a stator and is disposed so that the rotor and the stator are axially opposed to each other,

in the case of the rotary electric machine, the rotor is,

the stator is the stator of claim 15.

Technical Field

The invention relates to an iron core, a stator and a rotating electric machine.

The present application claims priority based on japanese application No. 2018-228584, 12/5/2018, and the entire contents of the disclosure in the above japanese application are cited.

Background

Patent document 1 discloses an axial gap type rotating electrical machine in which a rotor and a stator are arranged to face each other in an axial direction. The stator used in such a rotating electrical machine has: an annular yoke; a core having a plurality of teeth protruding in an axial direction from a yoke portion; and a coil disposed on each tooth. Patent document 1 describes that a core is divided in a circumferential direction to form a plurality of core pieces, and the core pieces are formed by a dust core in which a yoke portion and a tooth portion are integrally molded.

Patent document 1: japanese patent laid-open publication No. 2017-229191

Disclosure of Invention

The iron core of the present invention is used in an axial gap type rotating electrical machine,

the iron core is annular and is provided with a plurality of iron core pieces which divide the iron core in the circumferential direction,

the iron core sheet has:

a yoke portion; and

a tooth portion integrally molded with the yoke portion and protruding in an axial direction from the yoke portion,

the yoke includes:

a plurality of projections provided on one side surface coupled to the yoke portion of an adjacent core segment; and

a plurality of concave portions provided on the other side surface coupled to the yoke portion of the other core segment adjacent to the concave portions, corresponding to the convex portions,

the interval between the convex portions is less than or equal to 80% of the length of the side surface of the yoke determined by the straight-line distance between the outer circumference and the inner circumference of the yoke.

The stator of the present invention is a stator of an axial gap type rotating electric machine, and includes:

the iron core of the invention; and

and coils arranged in the teeth of the core pieces constituting the core.

The rotating electric machine of the present invention is an axial gap type rotating electric machine having a rotor and a stator, the rotor and the stator being disposed so as to face each other in an axial direction,

in the case of the rotary electric machine, the rotor is,

the stator is the stator of the present invention.

Drawings

Fig. 1 is a schematic perspective view of an iron core according to an embodiment.

Fig. 2 is a schematic plan view of the core according to the embodiment.

Fig. 3 is a schematic sectional view of the core taken along line III-III of fig. 2.

Fig. 4 is a schematic perspective view of the core piece.

Fig. 5 is a schematic plan view of the core piece.

Fig. 6 is a schematic cross-sectional view showing an example of a mold for molding a core piece.

Fig. 7 is a schematic plan view of the die.

Fig. 8 is an enlarged plan view of a key portion of the die.

Fig. 9 is a schematic side view of a core having a plate-like member.

Fig. 10 is a schematic plan view of a core having a ring member.

Fig. 11 is a schematic perspective view of a stator according to the embodiment.

Fig. 12 is a schematic cross-sectional view of a rotary electric machine according to an embodiment.

Detailed Description

[ problems to be solved by the invention ]

In order to improve productivity of the axial gap rotating electric machine, it is desirable to improve assembling property of the core.

In the case where the core is configured by a plurality of core segments, the plurality of core segments need to be annularly combined, and the side surfaces of the yoke portions of the adjacent core segments need to be butted and connected to each other. As in patent document 1, if the side surface of the yoke portion of each core segment is formed linearly in the radial direction, it is difficult to position the yoke portions of adjacent core segments with respect to each other. For example, when a plurality of iron core pieces are combined into a ring shape, adjacent iron core pieces may be radially offset.

An object of the present invention is to provide an iron core having excellent assemblability. Another object of the present invention is to provide a stator having the above-described core. Another object of the present invention is to provide a rotating electric machine including the stator.

[ Effect of the invention ]

The iron core of the present invention has excellent assembling performance. The stator of the present invention has excellent assembling performance of the iron core. The rotating electric machine of the present invention has high productivity.

[ description of embodiments of the invention ]

The present inventors considered that the yoke portions of adjacent core segments are positioned with respect to each other by fitting the convex portions and the concave portions by providing the convex portions on one side surface of the yoke portions of the core segments and providing the concave portions corresponding to the convex portions on the other side surface. In this process, the present inventors have conducted intensive studies and found that, when a core piece made of a powder magnetic core is molded by a die in the case where a convex portion is provided on a side surface of a yoke portion, stress acting on a portion where the side surface of the yoke portion is molded becomes large in the die for molding the circumferential surface of the yoke portion. If excessive stress is applied to the die, the die may be damaged. Therefore, it is important to design the convex portion provided on the side surface of the yoke so that the load to the die can be reduced as much as possible. As a result of intensive studies, the present inventors have found that stress acting on a die can be reduced as described later by providing a plurality of convex portions on the side surface of a yoke and setting the interval between the convex portions to be less than or equal to 80% of the length of the side surface of the yoke.

The present invention has been made based on the above findings. First, embodiments of the present invention will be described.

(1) The iron core according to the embodiment of the present invention is used for an axial gap type rotating electrical machine,

the iron core is annular and is provided with a plurality of iron core pieces which divide the iron core in the circumferential direction,

the iron core sheet has:

a yoke portion; and

a tooth portion integrally molded with the yoke portion and protruding in an axial direction from the yoke portion,

the yoke includes:

a plurality of projections provided on one side surface coupled to the yoke portion of an adjacent core segment; and

a plurality of concave portions provided on the other side surface coupled to the yoke portion of the other core segment adjacent to the concave portions, corresponding to the convex portions,

the interval between the convex portions is less than or equal to 80% of the length of the side surface of the yoke determined by the straight-line distance between the outer circumference and the inner circumference of the yoke.

The iron core of the present invention has the advantages of easy alignment of adjacent iron core pieces and excellent assembling performance. The reason for this is that the yoke portions of adjacent core segments can be positioned by fitting the convex portions and the concave portions together by having a plurality of convex portions on one side surface of the yoke portion of the core segment and a plurality of concave portions corresponding to the convex portions on the other side surface. Therefore, according to the iron core of the present invention, when the plurality of iron core pieces are combined into a ring shape, the adjacent iron core pieces can be suppressed from being displaced in the radial direction.

In the case where the core pieces are dust cores, the core pieces made of the dust cores are obtained by compression molding soft magnetic powder that is an aggregate of a plurality of soft magnetic particles. When the core segment is molded by the mold, the interval between the convex portions of the side surface of the yoke portion is 80% or less of the length of the side surface of the yoke portion, and thus the stress acting on the side surface of the die for molding the side surface of the yoke portion can be reduced. This also expects an effect of reducing the load on the die, and can suppress damage to the die. The significance of the distance between the projections and the reason why the stress acting on the die can be reduced are described later.

(2) As an embodiment of the above-described iron core,

mention is made of: when the yoke is viewed from a plane view from the tooth projecting side, a center line between mutually facing side surfaces of the tooth and a tooth of another adjacent core segment is defined as a reference line, and a distance from the recess to a root of the tooth is 20% or more of a distance from the reference line to the root of the tooth.

In the above aspect, the distance from the recess to the root of the tooth is 20% or more of the distance from the reference line to the root of the tooth, and thus the distance between the recess and the root of the tooth in the surface of the yoke on the tooth projecting side can be secured to a certain extent in the core segment. Thus, when the core segment is a dust core, it is possible to suppress a decrease in the strength of the punch due to a decrease in the thickness of the punch for molding the tooth-protruded side surface of the yoke portion when the core segment is molded by the die.

(3) As an embodiment of the above-described iron core,

mention is made of: the size of the convex part is greater than or equal to 1mm and less than or equal to 10 mm.

In the above aspect, the size of the convex portion is 1mm or larger, and thus the yoke portions of the adjacent core pieces are easily positioned. When the core piece is a dust core, the size of the projection is 10mm or less, and thus molding is easy. The significance of the size of the projection is described later.

(4) As an embodiment of the above-described iron core,

mention is made of: a minimum radius of curvature of the convex portion and the concave portion when the yoke is viewed from a side of the tooth portion in a plan view is 1.0mm or more.

In the above-described aspect, when the core piece is a dust core, damage to the die can be suppressed. The reason for this is that the minimum radius of curvature of the convex portion and the concave portion is 1.0mm or more, and thus stress concentration on the die for molding the yoke portion side surface can be alleviated when the core piece is molded by the die.

(5) As an embodiment of the above-described iron core,

mention is made of: the adjacent convex parts are symmetrical relative to the central line between the convex parts.

In the above-described aspect, when the core piece is a dust core, damage to the die can be more effectively suppressed. The reason for this is that the adjacent projections have symmetrical shapes, and therefore, when the core piece is molded by the die, the stress acting on the die can be effectively reduced.

(6) As an embodiment of the above-described iron core,

mention is made of: the thickness of the yoke is greater than or equal to 1.0mm and less than or equal to 10 mm.

In the above-described core, the plurality of core segments may be fastened by fitting and fixing an annular member to an outer peripheral surface of the yoke portion in a state where the plurality of core segments are combined in an annular shape. If the thickness of the yoke portion is 1.0mm or more, the ring-shaped member is easily fixed, and fastening force is easily secured. If the yoke is too thick, the load to the die increases, and therefore the thickness of the yoke is set to 10mm or less.

(7) As an embodiment of the above-described iron core,

mention is made of: the core pieces are formed of dust cores,

the dust core is composed of an aggregate of a plurality of coated soft magnetic particles having an insulating coating on the surface of the soft magnetic particles,

the soft magnetic particles are iron-based particles composed of at least one of pure iron and an iron-based alloy,

the iron-based alloy is at least one selected from the group consisting of Fe-Si based alloys, Fe-Al based alloys, Fe-Cr-Al based alloys, and Fe-Cr-Si based alloys.

Pure iron or the iron-based alloy is a relatively soft material. Therefore, the soft magnetic particles constituting the dust core are iron-based particles composed of pure iron or the above iron-based alloy, and thus the soft magnetic particles are easily deformed at the time of molding the dust core. Thus, the above-described method can obtain a powder magnetic core having high density and high dimensional accuracy. By increasing the density of the dust core, the mechanical strength and magnetic properties of the core sheet can be improved. In addition, by having an insulating coating on the surface of the soft magnetic particles, the electrical insulation between the soft magnetic particles can be improved. Therefore, the core loss of the core piece due to the eddy current loss can be reduced.

(8) As an embodiment of the iron core described in the above (7),

mention is made of: the insulating coating comprises a phosphate coating.

The phosphate coating has high adhesion to the iron-based particles and excellent deformability. Therefore, the insulating coating contains a phosphate coating, and thus easily follows the deformation of the iron-based particles when molding the powder magnetic core. Thus, the insulating coating of the above-described embodiment is less likely to be damaged, and the iron loss of the core piece 10 can be reduced.

(9) As an embodiment of the iron core according to the above (7) or (8),

mention is made of: the relative density of the dust core is 90% or more.

The relative density of the powder magnetic core is 90% or more, whereby the density of the powder magnetic core is high. In the above-described aspect, the mechanical strength and magnetic properties of the core sheet can be improved by increasing the density of the dust core.

(10) As an embodiment of the above-described iron core,

mention is made of: has an annular member fitted to the outer peripheral surface of the yoke of the plurality of core segments,

the ring-shaped member fixes the plurality of core pieces by a contraction force in an inner diameter direction thereof.

The core includes the annular member fitted to the outer peripheral surface of the yoke portion, and thus a plurality of core pieces combined in an annular shape can be integrated. Further, the outer periphery of the yoke portion can be fastened by the contraction force in the inner diameter direction of the annular member, and the plurality of core pieces can be firmly fastened.

(11) As an embodiment of the above-described iron core,

mention is made of: the side surfaces of the yoke portions of the adjacent core pieces are bonded to each other, or,

the core segment has a plate-like member disposed on the side of the yoke portion of the adjacent core segment opposite to the side on which the tooth portions project, and the surface of the yoke portion opposite to the side is bonded to the plate-like member.

The side surfaces of the yoke portions of the adjacent core segments are bonded to each other, or the surface of the yoke portion opposite to the tooth portion projecting side is bonded to the plate-like member, whereby the plurality of core segments can be integrated in a ring-like combination.

(12) As an embodiment of the above-described iron core,

mention is made of: the difference between the position of the end face of the highest tooth and the position of the end face of the lowest tooth among the teeth of the plurality of core pieces is less than or equal to 0.15 mm.

When the surface of the yoke opposite to the convex side of the tooth is placed on a plane, the difference between the position of the end face of the highest tooth and the position of the end face of the lowest tooth is less than or equal to 0.15mm, and thus the fluctuation of the height of each end face of the tooth is small. In the case where the rotating electric machine is configured using the iron core, each end face of the tooth portion is disposed to face the magnet of the rotor. The fluctuation in the height of each end face of the tooth portion is small, whereby in the rotary electric machine, the fluctuation in the interval between each end face of the tooth portion and the rotor can be reduced. This can reduce cogging and the like, and suppress a reduction in characteristics of the rotating electric machine.

(13) As an embodiment of the above-described iron core,

mention is made of: in a state where the plurality of iron pieces are combined into a ring shape, a circularity of an outer circumferential surface of the yoke portion is 0.1mm or less.

The roundness of the outer peripheral surface of the yoke portion is 0.1mm or less, whereby the dimensional accuracy of the core is high.

(14) As an embodiment of the above-described iron core,

mention is made of: the flatness of the end face of the tooth part is less than or equal to 0.2 mm.

The flatness of the end faces of the teeth is less than or equal to 0.2mm, whereby in the rotary electric machine, the end faces of the teeth can be brought into close facing relation with the rotor. This can suppress a reduction in the characteristics of the rotating electric machine.

(15) A stator according to an embodiment of the present invention is a stator of an axial gap type rotating electrical machine, the stator including:

the iron core according to any one of (1) to (14) above; and

and coils arranged in the teeth of the core pieces constituting the core.

The stator of the present invention has excellent assembling performance of the iron core. This is because the core is easy to align adjacent core pieces, and has excellent assemblability.

(16) A rotating electrical machine according to an embodiment of the present invention includes a rotor and a stator, and is an axial gap type rotating electrical machine in which the rotor and the stator are arranged to face each other in an axial direction,

in the rotating electric machine, the stator is the stator described in (15) above.

The rotating electric machine of the present invention has high productivity. This is because the stator is provided, and thus the assembling property of the core is excellent.

[ details of embodiments of the present invention ]

Specific examples of the core, the stator, and the rotating electrical machine according to the embodiment of the present invention will be described below with reference to the drawings. The same reference numerals in the drawings denote the same items. The present invention is not limited to these examples, but is defined by the claims, and includes all modifications within the meaning and range equivalent to the claims.

< iron core >

The iron core 1 according to the embodiment and the core segments 10 constituting the iron core 1 will be described with reference to fig. 1 to 10. The core 1 is used in an axial gap type rotating electrical machine. More specifically, the core 1 can be used as a stator core. As shown in fig. 1 and 2, the core 1 is annular and includes a plurality of core pieces 10 dividing the core 1 in the circumferential direction. That is, the core 1 is formed by combining a plurality of core pieces 10 into a ring shape. In this example, the number of the iron core pieces 10 is 6. The core segment 10 includes a yoke portion 11 and tooth portions 12 projecting from the yoke portion 11 in the axial direction (see also fig. 4 and 5). In the following description, when the core 1 and the core segment 10 are described, the projecting side of the tooth 12 is set to be upper and the opposite side is set to be lower.

In this example, as shown in fig. 1 and 2, the core 1 has an annular shape. Specifically, in the core 1, the yoke portion 11 has a circular plate shape, and the plurality of tooth portions 12 are provided at equal intervals in the circumferential direction. In this example, the number of the teeth 12 is 12. In this example, the core 1 is divided into 6 equal parts, and has 6 core pieces 10, specifically, core pieces 10a to 10 f. The core pieces 10a to 10f have the same shape. The core 1 is configured by combining 6 core segments 10a to 10f in an annular shape, and connecting side surfaces 20 and 30 (see fig. 4 and 5) of yoke portions 11 of adjacent core segments 10 in a butt joint manner. The number of segments of the core 1, in other words, the number of core segments 10 can be selected as appropriate. The number of teeth 12 in the core 1 can also be set as appropriate.

(iron core plate)

As shown in fig. 4 and 5, the core segment 10 includes a yoke portion 11 and a tooth portion 12. The core sheet 10 is formed by a dust core. The yoke 11 and the teeth 12 are integrally molded.

(yoke)

The yoke 11 is a fan-plate-shaped portion constituting the core piece 10. The yoke 11 has a fan-shaped plane, and a tooth 12 projects from one plane. That is, one plane refers to the upper surface. The yoke 11 has arc-shaped inner and outer circumferential surfaces and side surfaces 20 and 30. The inner peripheral surface and the outer peripheral surface are formed in concentric circular arc shapes.

(tooth part)

The tooth 12 is a portion that is integrally molded with the yoke 11 and protrudes in the axial direction from one plane, i.e., the upper surface of the yoke 11. The axial direction is a direction perpendicular to the circumferential direction and the radial direction of the core 1, and specifically, a direction perpendicular to the upper surface of the yoke 11. The tooth portion 12 is a columnar body, and examples of the columnar body include a prismatic body, a cylindrical body, and an elliptic cylindrical body. Examples of the prism include a triangular prism and a trapezoidal prism. In this example, the teeth 12 are triangular prisms, and the end faces 41 of the teeth 12 are triangular, more specifically, isosceles triangular. The tooth portion 12 may be a trapezoidal column, and the end surface 41 may be trapezoidal. The "triangular shape" and the "trapezoidal shape" may include shapes having a chamfer at a corner, rather than a triangle and a trapezoid in a strict geometrical sense, and include a range that can be substantially regarded as a triangle and a trapezoid.

The number of teeth 12 in the core piece 10 may be 1 or more. In this example, there are 2 teeth 12(12a, 12 b). The tooth 12 located on the side surface 20 side of the yoke 11 is denoted by 12a, and the tooth 12 located on the side surface 30 side is denoted by 12 b.

One of the characteristic points of the core 1 is that, as shown in fig. 4 and 5, a plurality of convex portions 21 and 22 are provided on one side surface 20 of the yoke portion 11 of the core segment 10, and a plurality of concave portions 31 and 32 corresponding to the convex portions 21 and 22 are provided on the other side surface 30. Another characteristic point of the core 1 is that the interval between the convex portions 21, 22 is less than or equal to 80% of the length of the side surface 20 of the yoke portion 11.

Convex and concave

The yoke 11 includes a plurality of protrusions 21 and 22 provided on one side surface 20 and a plurality of recesses 31 and 32 provided on the other side surface 30. The convex portions 21, 22 of the side surface 20 and the concave portions 31, 32 of the side surface 30 are formed in shapes corresponding to each other. A concave portion 23 is present between the convex portions 21, 22, and a convex portion 33 is present between the concave portions 31, 32. In this example, the convex portions 21 and 22 and the concave portions 31 and 32 have the same arc shape and the same size. Here, as shown in fig. 5, one side surface 20 of the yoke portion 11 in the core piece 10a is coupled to the other side surface 30 of the yoke portion 11 in the adjacent one core piece 10 b. The other side surface 30 of the yoke portion 11 of the core segment 10a is coupled to the one side surface 20 of the yoke portion 11 of the adjacent other core segment 10 f. Therefore, the convex portions 21 and 22 provided on the side surface 20 of the yoke portion 11 in the core segment 10a and the concave portions 31 and 32 provided on the side surface 30 of the yoke portion 11 in the adjacent core segment 10b are fitted to each other. The concave portions 31 and 32 provided on the side surface 30 of the yoke portion 11 in the core segment 10a and the convex portions 21 and 22 provided on the side surface 20 of the yoke portion 11 in the adjacent core segment 10f are fitted to each other. The yoke portions 11 of the core segment 10a and the adjacent core segments 10b and 10f can be positioned with respect to each other by fitting the convex portions 21 and 22 and the concave portions 31 and 32. Therefore, when a plurality of core segments 10 are combined in a ring shape, the adjacent core segments 10 can be prevented from shifting in the radial direction.

In this example, the number of the convex portions 21 and 22 and the number of the concave portions 31 and 32 are 2, respectively. The number of the convex portions 21 and 22 and the concave portions 31 and 32 may be changed as appropriate, and may be 3 or more. The shapes of the convex portions 21 and 22 and the concave portions 31 and 32 may be appropriately changed, and may be, for example, a rectangular shape or a triangular shape. In this example, the shape of each of the convex portions 21 and 22 is the same, but the shape of each of the convex portions 21 and 22 may be different.

Interval between projections

The distance between the projections 21 and 22 is less than or equal to 80% of the length of the side surface 20 of the yoke 11. The interval between the projections 21 and 22 is defined as follows. In this example, as shown in fig. 5, an intermediate line L passing through an intermediate point between the tooth portion 12a of the core piece 10a and the tooth portion 12b of the adjacent one of the core pieces 10b is taken_A. Specifically, a line passing through a midpoint between the side surfaces of the core piece 10a and the tooth 12b of the core piece 10b facing each other is defined as an intermediate line L_A. Middle line L_AIs a straight line along the radial direction of the annular core 1. Next, a line L is drawn between the two_AStraight lines L parallel to each other and passing through the apexes of the projections 21, 22₁. In addition, a line L is drawn between the drawing and the middle_AStraight lines L parallel to each other and passing through the apexes of the recesses 23 between the adjacent projections 21 and 22₂. The straight line L is formed in the sides of the adjacent convex portions 21 and 22 facing each other₁And a straight line L₂Points 2 intersecting the center line La are set as points a and b, respectively. The distance between the 2 points ab is defined as the distance between the convex portions 21 and 22. In this example, the middle line L_AAnd is coincident with the centerline La. The length of the side surface 20 of the yoke 11 is set to be a linear distance between the outer circumference and the inner circumference of the yoke 11. In other words, the length of the side surface 20 of the yoke 11 is the length in the radial direction between the outer circumference and the inner circumference of the yoke 11. Hereinafter, the length of the side surface 20 of the yoke 11 may be simply referred to as "yoke side surface length".

In fig. 5, when the distance between the convex portions 21 and 22, which is represented by the distance ab, is less than or equal to 80% of the length of the side surface of the yoke portion, as will be described later, stress acting on the side surface 52 (see fig. 7 and 8) of the die 50 for molding the side surface 20 of the yoke portion 11 can be reduced when the core segment 10 is molded by the die 5 (see fig. 6). The reason for this will be described later with reference to fig. 8.

The ratio of the interval between the convex portions 21 and 22 to the length of the side surface of the yoke portion is 70% or less and 50% or less. The distance between the projections 21, 22 is, for example, 40mm or less, and further 30mm or less. If the distance between the projections 21 and 22 is too small, molding becomes difficult, and therefore the lower limit of the distance between the projections 21 and 22 is, for example, about 1.0 mm.

Adjacent convex parts in symmetrical shape

In this example, the adjacent projections 21 and 22 are symmetrical with respect to the center line between the projections 21 and 22. Here, as shown in fig. 5, the center line between the convex portions 21 and 22 is a straight line Lc which is perpendicular to the center line La and passes through the midpoint of the line ab. When the projections 21 and 22 have a symmetrical shape, the stress acting on the side surface 52 (see fig. 7 and 8) of the die 50 can be effectively reduced.

< distance from recess to root of tooth >

In this example, the distance from the recesses 31, 32 to the root of the tooth 12(12b) is greater than or equal to L in FIG. 5_BThe indicated reference line is 20% of the distance from the root of the tooth 12(12 b). The reference line is a middle line between the tooth portions 12 of the adjacent core segments 10 when the yoke portion 11 is viewed in plan from above, which is a side on which the tooth portions 12 protrude. In this example, as shown in fig. 5, a middle line L passing through a middle point between the tooth 12b of the core piece 10a and the tooth 12a of another adjacent core piece 10f_BSet as the reference line. Specifically, a line passing through a midpoint between the side surfaces of the core piece 10a and the tooth 12b of the core piece 10f facing each other is defined as an intermediate line L_B. Middle line L_BIs a straight line along the radial direction of the annular core 1. Next, a line L is drawn between the two_BOrthogonally passing through the recesses 31, 32Straight line L at each vertex₃. Each straight line L₃The vertexes of the upper concave portions 31 and 32 are represented by L, and the straight lines L₃The intersection with the peripheral edge of the tooth 12b is m. The distance between the 2 points lm is set to the distance from the recesses 31 and 32 to the root of the tooth 12 b. In addition, each straight line L₃And a middle line L_BThe intersection of (A) is n. The distance between 2 points nm is set as the distance from the reference line to the root of the tooth 12 b. Here, a straight line L is drawn₃In this case, the apexes of the concave portions 31 and 32 are set to be farthest from the intermediate line L in the concave portions 31 and 32_BPoint (2) of (c). In other words, the apexes of the recesses 31 and 32 are the closest points to the roots of the teeth 12b in the recesses 31 and 32.

The above-mentioned intermediate line L_BThe ratio of the distance from the recess 31, 32 to the root of the tooth 12(12b) to the distance from the reference line to the root of the tooth 12(12b) is 20% or more as a reference line. In fig. 5, the distance from the reference line to the root of the tooth portion 12b is represented by the distance between nm. The distance from the recesses 31 and 32 to the root of the tooth 12b is represented by the distance lm. The ratio (%) of the distances can be set to [ (lm distance/nm distance) × 100]And then the result is obtained. The ratio of the above-described distances is 20% or more, and thus in the core segment 10, the gap between the concave portions 31 and 32 on the surface of the yoke 11 on the side where the tooth 12 protrudes, that is, the upper surface, and the root of the tooth 12(12b) can be secured to some extent. In this case, when the core segment 10 is molded by the die 5 (see fig. 6), a decrease in strength of the 1 st lower punch 71 due to a decrease in thickness of the 1 st lower punch 71 that molds the upper surface of the yoke 11 can be suppressed.

The ratio of the distance from the recesses 31 and 32 to the root of the tooth 12(12b) to the distance from the reference line to the root of the tooth 12(12b) is further 30% or more. The upper limit of the ratio of the distance from the recesses 31, 32 to the root of the tooth 12(12b) is not particularly set, and is, for example, 90%. The distance from the recesses 31 and 32 to the root of the tooth 12(12b) is, for example, 1mm or more and 9mm or less, and further 2mm or more and 8mm or less.

Size of convex part

In this example, the size of the projections 21, 22 is 1mm or more and 10mm or less. The sizes of the projections 21 and 22 are defined as follows. In this example, as shown in fig. 5, a straight line L passing through the apexes of the convex portions 21 and 22 is drawn₁And a straight line L passing through the apex of the concave portion 23 between the adjacent convex portions 21, 22₂The distance therebetween is set to the size of the convex portions 21, 22.

When the size of the protruding portions 21 and 22 is 1mm or larger, the yoke portions 11 of the adjacent core pieces 10 are easily positioned. The size of the projections 21, 22 is 10mm or less, and thus molding is easy. The size of the projections 21 and 22 is more than or equal to 2mm and less than or equal to 8 mm.

Minimum radius of curvature of convex and concave portions

In this example, the minimum radius of curvature of the convex portions 21 and 22 and the concave portions 31 and 32 in a plan view of the yoke portion 11 from the side of the tooth portion 12, that is, from the upper side is 1.0mm or more. When the shape of the convex portions 21 and 22 and the concave portions 31 and 32 is a shape having a corner portion with a small radius of curvature, the corner portion is formed on the side surface 52 (see fig. 7) of the die 50 for molding the side surfaces 20 and 30 of the yoke portion 11 in accordance with the shape. Stress is easily concentrated on the corner portion having a small radius of curvature. When the minimum radius of curvature of the convex portions 21 and 22 and the concave portions 31 and 32 is 1.0mm or more, stress concentration on the die 50 can be alleviated when the core segment 10 is molded by the die 5 (see fig. 6).

The minimum radius of curvature of the convex portions 21 and 22 and the concave portions 31 and 32 is more than or equal to 2.0 mm. The upper limit of the minimum radius of curvature of the convex portions 21 and 22 and the concave portions 31 and 32 is not particularly set, and is, for example, 20 mm.

Thickness of yoke

The yoke 11 has a thickness of, for example, 1.0mm or more and 10mm or less, and further 2mm or more and 8mm or less. The thickness of the yoke portion 11 refers to the size of the yoke portion 11 in the axial direction of the core 1. In fig. 3, the thickness of the yoke 11 is denoted by Ty. As described later, in a state where a plurality of core segments 10 are combined into an annular core 1, an annular member 90 (see fig. 10) may be fitted and fixed to the outer circumferential surface of the yoke portion 11. If the thickness of the yoke 11 is 1.0mm or more, the ring member 90 is easily fixed. If the yoke 11 is too thick, the load on the die 50 increases when the core segment 10 is molded by the die 5 (see fig. 6). Therefore, the thickness of the yoke 11 is set to 10mm or less.

Roundness of yoke

In a state where the plurality of core segments 10 are combined into the annular core 1, the circularity of the outer circumferential surface of the yoke portion 11 is preferably 0.1mm or less. The roundness of the outer peripheral surface of the yoke 11 is 0.1mm or less, whereby the dimensional accuracy of the core 1 is high. Therefore, when the annular member 90 (see fig. 10) is fitted and fixed to the outer peripheral surface of the yoke 11, the annular member is easily fixed to the outer peripheral surface of the yoke 11. In addition, in the core 1, if the circularity of the outer peripheral surface of the yoke portion 11 is 0.1mm or less, the outer peripheral surfaces of the yoke portions 11 of the core pieces 10 constituting the core 1 are aligned in the circumferential direction. That is, the radial positional deviation of each core segment 10 is small, and the positions of the teeth 12 of each core segment 10 are aligned in the circumferential direction. As described later, when the rotating electrical machine 300 (see fig. 12) is configured using the core 1, each end face 41 of the tooth 12 is disposed to face the magnet 220 of the rotor 200. Since the radial positional deviation of each core segment 10 is small, the relative areas of the end surfaces 41 of the respective tooth portions 12 and the magnets 220 of the rotor 200 in the rotating electrical machine 300 are uniform. This can reduce cogging and the like, and suppress a reduction in the characteristics of the rotating electrical machine 300. When the circularity of the outer peripheral surface of the yoke portion 11 is measured, the circularity is evaluated by point measurement so as not to include a recess formed at a connecting portion between the side surfaces 20 and 30 (see fig. 4 and 5) of the yoke portions 11 of the adjacent core segments 10.

Height of end faces of tooth

In the core 1, the difference between the position of the end face 41 of the highest tooth 12 and the position of the end face 41 of the lowest tooth 12 among the teeth 12 of the plurality of core pieces 10 is preferably 0.15mm or less. As shown in fig. 3, the position of the end surface 41 of the tooth 12 is an axial height position from a surface of the yoke 11 opposite to the side where the tooth 12 protrudes, that is, a lower surface thereof, to the end surface 41 in a state of being placed on a plane. In fig. 3, the height position of the end surface 41 of the tooth 12 is denoted by Ht. The difference between the position of the end face 41 of the highest tooth 12 and the position of the end face 41 of the lowest tooth 12 is less than or equal to 0.15mm, whereby the fluctuation in height of each end face 41 of the teeth 12 is small. As described later, when the rotating electrical machine 300 (see fig. 12) is configured using the core 1, each end face 41 of the tooth 12 is disposed to face the magnet 220 of the rotor 200. The fluctuation in the height of each end face 41 of the tooth portion 12 is small, whereby in the rotary electric machine 300, the fluctuation in the interval between each end face 41 of the tooth portion 12 and the rotor 200 can be reduced. This can reduce cogging and the like, and suppress a reduction in the characteristics of the rotating electrical machine 300.

Flatness of end faces of teeth

The flatness of the end face 41 of the tooth 12 is preferably less than or equal to 0.2 mm. In this case, in the rotary electric machine 300 (see fig. 12), the end faces 41 of the tooth portions 12 can be brought close to the rotor 200 so as to face each other. This can suppress a decrease in the characteristics of the rotating electric machine 300.

In this example, the side surfaces of the yoke portions 11 of the adjacent core segments 10 are bonded to each other, and thereby the plurality of core segments 10 combined in a ring shape are integrated. For example, as illustrated in fig. 9, when the plate-like member 80 is disposed on the lower side of the yoke portion 11 of the adjacent core segment 10 opposite to the side where the tooth portion 12 protrudes, the lower surface opposite to the yoke portion 11 may be bonded to the plate-like member 80. In this case, the plurality of core segments 10 are fixed to and integrated with the plate-like member 80 in a ring-like combination.

As illustrated in fig. 10, the core 1 may include an annular member 90, and the annular member 90 may be fitted to the outer peripheral surface of the yoke portion 11 of the plurality of core segments 10 combined in an annular shape. The annular member 90 is fixed to the plurality of core pieces 10 constituting the core 1 by a contraction force in the inner diameter direction thereof. In this example, the annular member 90 is thermally attached to the outer peripheral surface of the yoke 11. The annular member 90 is formed of a material and a size such that the inner diameter thereof before hot charging at normal temperature is smaller than the outer diameter of the yoke portion 11 of the core 1, and the inner diameter thereof is larger than the outer diameter of the yoke portion 11 of the core 1 by heating during hot charging. In fig. 2, the outer diameter of the yoke 11 is denoted by Do. In fig. 2, Di represents the inner diameter of the yoke 11. The order of the shrink-fitting of the ring-shaped member 90 and the plurality of core pieces 10 combined in a ring shape is as follows. The annular member 90 is heated to a predetermined temperature and expanded, thereby making the inner diameter thereof larger than the outer diameter of the yoke portion 11 of the core 1. The annular member 90 having an enlarged inner diameter by heating is fitted to the outer peripheral surface of the yoke portion 11 of the core 1. The annular member 90 is cooled and contracted, and thereby the outer periphery of the core 1 is fastened by the annular member 90.

When the ring member 90 is provided, the plurality of core pieces 10 can be integrated. Further, the outer periphery of the yoke portion 11 can be fastened by the contraction force in the inner diameter direction of the annular member 90, and the plurality of core pieces 10 can be firmly fastened. Either one of the plate member 80 and the ring member 90 described above may be used, or both may be used.

Powder magnetic core

The core sheet 10 is formed by a dust core. The dust core is obtained by compression molding soft magnetic powder. The soft magnetic powder is an aggregate of a plurality of coated soft magnetic particles having an insulating coating on the surface of the soft magnetic particles. That is, the dust core is composed of an aggregate of a plurality of coated soft magnetic particles. The soft magnetic particles are preferably iron-based particles composed of at least one of pure iron and an iron-based alloy. Pure iron means iron having a purity of 99 mass% or more. The iron-based alloy includes at least one selected from the group consisting of an Fe (iron) -Si (silicon) -based alloy, an Fe (iron) -Al (aluminum) -based alloy, an Fe (iron) -Cr (chromium) -Al (aluminum) -based alloy, and an Fe (iron) -Cr (chromium) -Si (silicon) -based alloy. The soft magnetic particles constituting the dust core may be particles composed of only pure iron, particles composed of only an iron-based alloy, or mixed particles of particles composed of pure iron and particles composed of an iron-based alloy. Examples of the insulating coating include a phosphate coating and a silica coating.

Pure iron or the iron-based alloy is a relatively soft material. Therefore, the soft magnetic particles are iron-based particles composed of pure iron or the above-described iron-based alloy, and thus the soft magnetic particles are easily deformed when the powder magnetic core is molded. Thus, a high-density and high-dimensional-accuracy dust core is obtained. By increasing the density of the dust core, the mechanical strength and the magnetic characteristics of the core sheet 10 can be improved. In addition, by having an insulating coating on the surface of the soft magnetic particles, the electrical insulation between the soft magnetic particles can be improved. Therefore, the core loss of the core segment 10 due to the eddy current loss can be reduced.

In addition, the insulating coating preferably comprises a phosphate coating. The phosphate coating has high adhesion to the iron-based particles and excellent deformability. Therefore, the insulating coating contains a phosphate coating, and thus easily follows the deformation of the iron-based particles when molding the powder magnetic core. This makes the insulating coating less likely to be damaged, and can reduce the iron loss of the core piece 10.

The relative density of the dust core is preferably 90% or more. By increasing the density of the dust core, the mechanical strength and the magnetic characteristics of the core sheet 10 can be improved. More preferably, the relative density is greater than or equal to 93%. The relative density refers to a ratio (%) of the density of the actual dust core to the true density of the dust core. The true density is a theoretical density when no void is included in the interior. The true density of the dust core can also be determined from the true density of the soft magnetic powder used. The relative density of the powder magnetic core is determined, for example, as [ (molding density of powder magnetic core/true density of powder magnetic core) × 100 ]. The molding density of the powder magnetic core can be determined by immersing the powder magnetic core in oil to impregnate the powder magnetic core with the oil, and then determining the density [ oil-containing density × (mass of powder magnetic core before oil-containing/mass of powder magnetic core after oil-containing) ]. The oil density is a value obtained by dividing the mass of the powder magnetic core after oil inclusion by the volume. The volume of the powder magnetic core can be typically measured by a liquid displacement method.

The core segment 10 made of the dust core can be molded by the mold 5 as illustrated in fig. 6, for example. The mold 5 has: a die 50 having a die hole 51; and an upper punch 60 and a lower punch 70 which are fitted into the die hole 51 of the die 50. The die 50 molds the circumferential surface of the yoke 11. The upper punch 60 molds the lower surface of the yoke 11, i.e., the surface on the side opposite to the projecting side of the tooth 12. The lower punch 70 has a 1 st lower punch 71 and a 2 nd lower punch 72. The 1 st lower punch 71 molds the upper surface of the yoke 11, that is, the surface on the convex side of the tooth 12, and molds the circumferential surface of the tooth 12. The 1 st lower punch 71 is axially formed with a through hole through which the 2 nd lower punch 72 is inserted. The 2 nd lower punch 72 is inserted through the 1 st lower punch 71 to mold the end face 41 of the tooth 12.

When the core piece 10 is molded using the die 5, the lower punch 70 is fitted into the die hole 51 of the die 50, and the soft magnetic powder is filled in the die hole 51. Then, the soft magnetic powder is compressed by the upper punch 60 and the lower punch 70, and the iron core piece 10 is molded.

The average particle diameter of the soft magnetic powder is, for example, 20 μm or more and 300 μm or less, and further 40 μm or more and 250 μm or less. By setting the average particle diameter of the soft magnetic powder within the above range, handling and compression molding are facilitated. The average particle diameter of the soft magnetic powder is a particle diameter in which the cumulative mass is 50% of the mass of all particles, measured by a laser diffraction/scattering particle diameter/particle size distribution measuring apparatus.

By increasing the molding pressure at the time of compressing the soft magnetic powder, the iron core piece 10 can be densified. The molding pressure is, for example, 700MPa or more, and further 2000MPa or more.

As shown in fig. 7, the die hole 51 of the die 50 is formed in a shape corresponding to the circumferential surface of the yoke 11 (see fig. 5). One side surface 52 of the die hole 51 is a portion for molding the side surface 20 of the yoke 11. The side surface 52 is formed with concave portions 521 and 522 and convex portions 523 (see also fig. 8) for molding the convex portions 21 and 22 and the concave portions 23, corresponding to the shape of the side surface 20 of the yoke 11. The other side surface 53 of the die hole 51 is a portion for molding the side surface 30 of the yoke 11. The side surface 53 is formed with convex portions 531, 532, and concave portions 533 which mold the concave portions 31, 32, and the convex portion 33, corresponding to the shape of the side surface 30 of the yoke 11.

When the core piece 10 is molded, the raw material powder is compressed, so that stress acts on the die 50 in a direction in which the die hole 51 is pressed and expanded. As shown in fig. 8, stress acts on the side surface 52 of the die 50 from both sides on the convex portion 523 of the die 50 sandwiched between the convex portions 21 and 22 of the yoke 11. In fig. 8, the stress to be applied to the convex portion 523 is indicated by an open arrow. In this example, as described with reference to fig. 3, the distance between the adjacent protrusions 21 and 22 is less than or equal to 80% of the length of the side surface of the yoke portion, for example, approximately less than or equal to 40mm, and therefore the stresses acting on the protrusions 523 cancel each other out and decrease. Therefore, the stress acting on the side surface 52 of the die 50 can be reduced, and the damage of the die 50 can be suppressed. In this example, since the adjacent convex portions 21 and 22 have symmetrical shapes, the magnitudes of the stresses applied from both sides of the convex portion 523 are substantially equal. This cancels out the stress acting on the convex portion 523, thereby more effectively suppressing the damage of the die 50.

On the other hand, on the side surface 53 of the die 50, the concave portion 533 is pressed to expand from the raw material powder at the time of molding. Since the concave portion 533 is sandwiched between the convex portions 531 and 532 having a large distance to the outer peripheral edge of the die 50, the die is less likely to be damaged by stress.

< stator >

A stator 100 according to an embodiment will be described with reference to fig. 11. The stator 100 is used in an axial gap type rotating electrical machine. The stator 100 includes a core 1 and coils 110 arranged in the teeth 12 of core pieces 10 constituting the core 1. The coil 110 is a cylindrical coil in which a winding is wound in a spiral shape. In this example, the coil 110 is a triangular-tube-shaped edgewise wound coil in which an enameled flat wire is used as a winding.

< rotating electric machine >

A rotating electric machine 300 according to an embodiment will be described with reference to fig. 12. The rotating electrical machine 300 may be a motor or a generator. Rotating electric machine 300 has rotor 200 and stator 100. The rotating electrical machine 300 is an axial gap type rotating electrical machine in which the rotor 200 and the stator 100 are disposed to face each other in the rotation axis direction.

The stator 100 and the rotor 200 are housed in a cylindrical case 310. Disc-shaped plates 320 are attached to both ends of the housing 310, respectively. A through hole is formed in the center of the two plates 320, and the rotating shaft 330 penetrates the housing 310.

(rotor)

The rotor 200 includes a plurality of flat plate-shaped magnets 220 and an annular holding plate 210 that supports the magnets 220. The planar shape of the magnet 220 is a shape substantially corresponding to the end face 41 of the tooth 12. When the end surfaces 41 of the tooth portions 12 have a triangular shape, the planar shape of the magnet 220 includes a triangular shape and a trapezoidal shape. The holding plate 210 is fixed to the rotation shaft 330 and rotates together with the rotation shaft 330. Each magnet 220 is embedded in the holding plate 210. The magnets 220 are arranged at equal intervals in the circumferential direction of the rotating shaft 330. The magnet 220 is magnetized in the axial direction of the rotating shaft 330. The magnetization directions of the circumferentially adjacent magnets 220 are opposite to each other.

(stator)

The stator 100 is disposed such that the end face 41 of the tooth 12 faces the magnet 220 of the rotor 200. The stator 100 is fixed to the housing 310 by fitting the outer circumferential surface of the yoke portion 11 of the core 1 to the inner circumferential surface of the housing 310. An annular bearing 340 for rotatably supporting the rotary shaft 330 is attached to the inner circumferential surface of the yoke 11.

{ Effect of embodiment }

The core 1, the stator 100, and the rotating electrical machine 300 according to the above-described embodiments have the following effects.

In the core segment 10 constituting the core 1, the yoke 11 has a plurality of projections 21 and 22 on one side surface 20 and a plurality of recesses 31 and 32 corresponding to the projections 21 and 22 on the other side surface 30. Therefore, when a plurality of core segments 10 are combined into a ring shape, the yoke portions 11 of the adjacent core segments 10 can be positioned by fitting the convex portions 21 and 22 and the concave portions 31 and 32. This can suppress the adjacent core segments 10 from shifting in the radial direction. Therefore, the core 1 is easily aligned with the adjacent core pieces 10, and is excellent in assemblability.

The stator 100 has the core 1, and thus has excellent assembly properties. The rotating electric machine 300 has the stator 100 excellent in assemblability, and thus has high productivity.

[ Experimental example 1]

The distribution of stress acting on the die 50 when the iron core piece 10 described in the embodiment is molded by the die 5 is analyzed by cae (computer air engineering).

For stress analysis, "NX nanostran" manufactured by siemens is used. The analysis conditions were set as follows. The molding pressure was set at 980 MPa. The physical property values of the die 50 were young's modulus: 206000MPa, Poisson ratio: 0.3.

the size of the designed core piece 10 is set in the following manner.

Thickness of yoke 11 (Ty in fig. 3): 5mm

Length of side 20 of yoke 11: 40mm

Size of the convex portions 21, 22: 3mm

Ratio of distances from the recesses 31, 32 to the roots of the teeth 12: 70 percent of

Minimum radius of curvature of the convex portions 21, 22 and the concave portions 31, 32: 3.0mm

From the result of the stress analysis obtained by CAE, the maximum stress generated by the convex portion 523 in the side surface 52 of the die 50 is obtained. In test example 1, the maximum stress in each case was obtained by changing the interval between the convex portions 21 and 22 and changing the ratio of the interval between the convex portions to the length of the side surface of the yoke portion. The results are shown in table 1.

[ Table 1]

As is clear from table 1, the smaller the interval between the convex portions, the smaller the maximum stress at the convex portions of the die at the time of molding can be. In particular, it was found that when the interval between the convex portions was less than or equal to 80% of the length of the side surface of the yoke portion, the maximum stress generated at the convex portions could be reduced to 1500MPa or less.

[ test example 1]

An iron core piece having the same structure as the iron core piece 10 described in the embodiment was produced and evaluated.

The size of the core piece 10 is set in the following manner.

Thickness of yoke 11 (Ty in fig. 3): 5mm

Outer diameter (Do in fig. 2) of yoke 11: 120mm

Inner diameter of yoke 11 (Di in fig. 2): 40mm

Height of end surface 41 of tooth 12 (Ht in fig. 3): 18mm

Length of side 20 of yoke 11: 40mm

Ratio of interval between the convex portions 21, 22: 57 percent

Size of the convex portions 21, 22: 3mm

Ratio of distances from the recesses 31, 32 to the roots of the teeth 12: 70 percent of

Minimum radius of curvature of the convex portions 21, 22 and the concave portions 31, 32: 3.0mm

As the soft magnetic powder used as the raw material, a powder having phosphate-coated soft magnetic particles on the surface of a pure iron powder was used. The average particle diameter of the soft magnetic powder was 50 μm. The molding pressure was set at 980 MPa. The relative density of the core sheet 10 constituted by the obtained dust core was 92%.

6 iron core pieces 10 were produced under the same conditions, and the iron core 1 was produced by combining the iron core pieces 10 in a ring shape. The core piece 10 has 2 teeth 12 in 1 piece. The total number of teeth 12 is 12. The following evaluations were performed on the obtained iron core 1.

Roundness of yoke

The circularity of the outer peripheral surface of the yoke was measured using a commercially available 3D shape measuring machine. Specifically, the circularity was measured by point measurement using "VR-3200" manufactured by Keyence. As a result, the roundness of the outer peripheral surface of the yoke portion is 0.1mm or less.

Flatness of end faces of teeth

The flatness of the end faces of the teeth was measured using a commercially available 3D shape measuring machine, specifically "VR-3200" manufactured by KEYENCE corporation. As a result, the flatness of each end face of each of the 12 teeth portions was 0.1mm or less.

Height of end face of tooth

The height position of each end face of 12 teeth in total was measured using a commercially available 3D shape measuring machine, specifically "VR-3200" manufactured by KEYENCE corporation, in a state where the lower surface of the yoke was placed on a plane. Then, the difference between the position of the end face of the highest tooth and the position of the end face of the lowest tooth was obtained, and the difference was 0.15 mm.

Description of the reference numerals

1 iron core

10. 10a, 10b, 10c, 10d, 10e, 10f iron core sheet

11 yoke part

12. 12a, 12b teeth

20. 30 side surface

21. 22 convex part

23 recess

31. 32 concave part

33 convex part

41 end face

5 mould

50-die

51 die hole

52. Side surface 53

521. 522 recess

523 convex part

531. 532 convex part

533 recess

60 upper punch

70 lower punch

71 1 st lower punch 72 2 nd lower punch

80 plate-like member

90 annular member

100 stator

110 coil

200 rotor

210 holding plate 220 magnet

300 rotating electric machine

310 case 320 plate

330 rotating shaft 340 bearing

L_A、L_BMiddle line

L₁、L₂Lc straight line La center line

a. b point l vertex m, n intersection point

Ty thickness Ht height position

Do outer diameter Di inner diameter