Iron core and rotating electric machine

Abstract

The iron core is an iron core for an axial gap type rotary electric machine, and includes a ring-shaped yoke and a plurality of columnar teeth arranged at intervals around the axis of the yoke. The yoke and the plurality of teeth are formed of an integrated powder compact. The yoke includes a first surface having boundaries with the plurality of teeth, a second surface opposite the first surface, and an outer peripheral surface and an inner peripheral surface connecting the first surface and the second surface. When the iron core is viewed from a first direction parallel to the axis, the plurality of teeth each include an outer region located further outward than a first envelope circle formed by the outer peripheral surface.

Description

Technical Field

[0001] This disclosure relates to iron cores and rotating electric machines.

[0002] This application claims priority based on Japanese Patent Application No. 2023-219625 dated December 26, 2023, and invokes all the contents set forth in the said Japanese application. Background Technology

[0003] Patent Document 1 discloses a core for an axially backlash type rotary electric motor. This core has an annular magnetic yoke and multiple columnar teeth protruding from the surface of the yoke. The yoke and each of the teeth are formed from a single, integrally pressed powder molded body. In Patent Document 1, after pressing soft magnetic powder to form the pressed powder molded body with the yoke and multiple teeth, the end faces of each tooth in the pressed powder molded body are ground. By grinding the end faces of each tooth, the height deviation from the back of the yoke to the end faces of each tooth is reduced.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2021-100329 Summary of the Invention

[0007] The disclosed core is for use in an axially spaced rotary electric motor and includes: an annular magnetic yoke; and a plurality of columnar teeth spaced apart around the axis of the magnetic yoke. The magnetic yoke and the plurality of teeth are integrally formed from a pressed powder molded body. The magnetic yoke includes: a first surface having a boundary with the plurality of teeth; a second surface opposite to the first surface; and an outer peripheral surface and an inner peripheral surface connecting the first surface and the second surface. When the core is viewed from a first direction parallel to the axis, each of the plurality of teeth has an outer region located further outward than the first envelope circle formed by the outer peripheral surface. Attached Figure Description

[0008] Figure 1 This is a schematic perspective view showing an example of an iron core according to an embodiment.

[0009] Figure 2 yes Figure 1 A rough bottom view of the iron core.

[0010] Figure 3 yes Figure 1 A rough top view of the iron core.

[0011] Figure 4 It is shown Figure 1 An enlarged view of one of the teeth in the iron core.

[0012] Figure 5 yes Figure 4 VV cross-sectional diagram.

[0013] Figure 6 yes Figure 1 VI-VI cross-sectional view.

[0014] Figure 7 This is a schematic perspective view of the die used to manufacture the iron core in the embodiment.

[0015] Figure 8 This is a schematic perspective view of the punch used in manufacturing the iron core of the embodiment.

[0016] Figure 9 This is a schematic perspective view of the upper punch used in the manufacturing implementation of the iron core.

[0017] Figure 10 It is by Figure 7 Dies and Figure 8 A schematic top view of the cavity formed by the lower punch, filled with powder.

[0018] Figure 11 It shows that Figure 7 Stamping dies, Figure 8 The lower punch and Figure 9 A schematic cross-sectional view of a portion of the state after the upper punch is assembled.

[0019] Figure 12 It shows that it has Figure 1 A schematic three-dimensional diagram of an example of a stator with an iron core.

[0020] Figure 13 It shows that it has Figure 12 A schematic perspective view of an example of a rotating electric motor with a stator. Detailed Implementation

[0021] [The technical problem this disclosure aims to solve]

[0022] A pressed powder molded body is produced by filling a cavity formed in a mold with powder and then pressing the powder under pressure. Powder is supplied to the cavity using a powder hopper with an opening at the bottom. The powder hopper moves linearly back and forth on the mold. As the powder hopper moves onto the cavity, the powder inside falls into the cavity from the opening due to gravity. With the reciprocating movement of the powder hopper, the bottom surface of the hopper drags a portion of the powder filled into the cavity. Therefore, there is a tendency for the area near the powder supply start point from the powder hopper in the cavity to contain more powder than the area near the powder supply return point. If the powder filling amount is unbalanced, the length from the back of the yoke to the end faces of the individual teeth in the pressed powder molded body obtained after pressure forming may deviate.

[0023] In the technology of Patent Document 1, after manufacturing the powder pressing body with the aforementioned length deviation, the end faces of each tooth in the powder pressing body are ground. In the technology of Patent Document 1, the grinding process is required, involves a large number of steps, and there is a desire to improve productivity.

[0024] One of the purposes of this disclosure is to provide a core with small deviations in length from the reference plane of the yoke to the end faces of the individual teeth and excellent productivity.

[0025] [The Effects of This Disclosure]

[0026] The disclosed core exhibits small deviations in length from the reference plane of the yoke to the end faces of the individual teeth, and boasts excellent productivity.

[0027] [Description of embodiments of this disclosure]

[0028] First, the implementation plan of this disclosure will be presented for illustration.

[0029] (1) The core disclosed herein is for an axially spaced rotary electric motor and comprises: an annular magnetic yoke; and a plurality of columnar teeth spaced apart around the axis of the magnetic yoke. The magnetic yoke and the plurality of teeth are integrally formed from a powder-pressed material. The magnetic yoke comprises: a first surface having a boundary with the plurality of teeth; a second surface opposite to the first surface; and an outer peripheral surface and an inner peripheral surface connecting the first surface and the second surface. When the core is viewed from a first direction parallel to the axis, each of the plurality of teeth has an outer region located further outward than the first envelope circle formed by the outer peripheral surface.

[0030] The axis of the magnetic yoke is the axis of rotational symmetry of the annular magnetic yoke. That is, the axis of the magnetic yoke is a straight line passing through the center of the annular circle and perpendicular to the first face of the magnetic yoke.

[0031] As described above, a powder-pressed body is produced by filling powder into a cavity formed in a mold and then pressing the powder. The cavity has a shape corresponding to the iron core. For example, the cavity has a shape with the first side of the yoke facing down and the second side facing up. The second side of the yoke is, for example, a plane. A powder box that supplies powder to the cavity reciprocates on the powder constituting the second side of the yoke.

[0032] In the conventional iron core described in Patent Document 1, when the iron core is viewed from a first direction, each tooth does not have a region located further outward than the first envelope circle formed by the outer peripheral surface of the yoke. In the conventional iron core, the opening shape of the cavity is the shape of the yoke, that is, it is annular. If the opening is annular, the outline of the powder group disposed on the opening surface of the cavity is circular. When the outline of the powder group disposed on the opening surface of the cavity is circular, a portion of the powder is easily dragged by the powder box as the powder box reciprocates.

[0033] In the iron core according to the embodiments of this disclosure, when the iron core is viewed from a first direction, each tooth has an outer region located further outward than the first envelope circle formed by the outer peripheral surface of the yoke. In the iron core according to the embodiments of this disclosure, the opening shape of the cavity is such that it combines the yoke and the outer region, having a concave-convex profile. If the opening has a concave-convex profile, the powder group disposed on the opening surface of the cavity has a discontinuous portion around the axis of the yoke. If there is a discontinuous portion, the powder is not easily dragged by the powder box even when the powder box moves back and forth. If the powder is not easily dragged when the powder box moves back and forth, the filling amount of powder filling the cavity is less likely to become unbalanced. If the filling amount of powder is less likely to become unbalanced, the length from the reference surface of the yoke to the end face of each of the multiple teeth is less likely to deviate in the pressed powder molded body obtained after pressure molding. Therefore, in the iron core according to the embodiments of this disclosure, the deviation of the length from the reference surface of the yoke to the end face of each of the multiple teeth is small.

[0034] In the iron core according to the embodiments of this disclosure, the deviation in length from the reference surface of the yoke to the end face of each of the multiple teeth is small at the time when the powder is press-formed into a pressed powder body. Therefore, after the pressed powder body is manufactured, it is not necessary to perform grinding on the end face of each tooth. Therefore, the iron core according to the embodiments of this disclosure has excellent productivity.

[0035] (2) In the iron core of (1) above, the plurality of teeth may each have a first end face located at a front end protruding from the first face in a direction parallel to the axis, and the deviation of the length from the second face to the first end face of each of the plurality of teeth is less than 0.05 mm.

[0036] A rotary motor is constructed by housing a stator and a rotor together, with coils arranged on each tooth of the iron core. In this case, the second face of the magnetic yoke is in contact with the inner surface of the housing. If the deviation in length from the second face to the first end face of each tooth is less than 0.05 mm, then when the stator and rotor are housed in the housing, the end face of each tooth is positioned at a substantially uniform interval from any part of the magnet. Therefore, the rotary motor constructed using the aforementioned iron core not only has excellent assemblability but also exhibits reduced torque ripple. Due to the low torque ripple of the rotary motor, noise and vibration are less likely to increase. Furthermore, the low torque ripple of the rotary motor makes it less prone to rotor shaft wobbling. In other words, the frictional force between the rotor shaft and the bearings is less likely to change. Consequently, mechanical energy loss in the rotary motor is less likely to increase.

[0037] (3) In the iron core of (1) or (2) above, the plurality of teeth may each have a first end face located at a front end protruding from the first face in a direction parallel to the axis, and the outer region has a second end face as a face opposite to the first end face. The second end face is disposed between the extension surface of the second face and the first end face, and is spaced apart from the extension surface of the second face.

[0038] By having a gap between the second end face and the extended surface of the second face, wiring space corresponding to that gap can be ensured. If each tooth has an outer region, the core becomes larger in the second direction orthogonal to the first direction compared to existing cores. However, by utilizing the outer region to ensure the aforementioned wiring space, the overall size of the stator formed by arranging coils on each tooth of the core can be suppressed.

[0039] (4) In the iron core of (3) above, the second end face may also have: a proximal surface, located between the extension surface of the first surface and the extension surface of the second surface in a manner connected to the second surface or the outer peripheral surface; and a distal surface, which is further away from the outer peripheral surface than the proximal surface and located away from the extension surface of the second surface.

[0040] As will be described below, the die for pressing and forming the iron core with the outer region of each tooth includes a die, a lower punch, and an upper punch. The yoke is formed by supporting the first surface with the die and pressing the second surface with the upper punch. Each tooth is pressed by the lower punch and the upper punch. The second end face is formed by transferring the shape of a protrusion formed on the upper punch. If a protrusion exists on the upper punch, relatively large stress is generated at the corner of the die that forms the first corner formed by the first surface and the outer peripheral surface of the yoke. If a step formed by a proximal surface and a distal surface is formed on the second end face, the aforementioned stress generated in the die is easily reduced.

[0041] (5) In the core of any one of (1) to (4) above, each of the plurality of teeth may have a first end face located at a front end protruding from the first face in a direction parallel to the axis, and the ratio of the second length of the outer region to the first length of each of the plurality of teeth is 60% or more and 90% or less. The first length is the length from the second face to the first end face. The second length is the length of the portion of the outer region located at the position farthest from the axis along the first direction.

[0042] The stress generated at the corner of the die forming the first corner of the yoke is due to the difference between the forming pressure applied to the outer region of each tooth and the forming pressure applied to the region outside the outer region. If the ratio is 60% or more and 90% or less, the stress can be easily reduced. If the ratio is 90% or less, there is a gap between the second end face, which is the face opposite to the first end face in the outer region, and the extended face of the second face, which easily ensures wiring space corresponding to the gap. If the ratio is 60% or more, the magnetic flux flowing from the rotor magnet into the outer region of the tooth can easily and efficiently flow into the yoke.

[0043] (6) In any of the iron cores described in (1) to (5) above, when the iron core is viewed from the first direction, the angle between the first tangent and the second tangent at the first intersection point is 90° or less. The first intersection point is the intersection of the side surface of the outer region and the first envelope circle. The first tangent is a tangent to the first envelope circle passing through the first intersection point. The second tangent is a tangent to the side surface of the outer region passing through the first intersection point.

[0044] If the angle is below 90°, it is easier to reduce the stress generated at the corner of the die that forms the first corner of the yoke.

[0045] (7) In any of the above (1) to (6), the first corner formed by the first surface and the outer peripheral surface, and the second corner formed by the first surface and the inner peripheral surface may be rounded.

[0046] If the first corner is rounded, it is easier to reduce the stress generated at the corner of the die that forms the first corner. If the second corner is rounded, it is easier to reduce the stress generated at the corner of the die that forms the second corner.

[0047] (8) In the iron core of (7) above, the radius of curvature of the first corner is larger than the radius of curvature of the second corner.

[0048] During pressure forming, a relatively large stress is generated at the corner of the die forming the first corner. If the radius of curvature of the first corner is larger than the radius of curvature of the second corner, it is easier to reduce the stress generated at the corner of the die forming the first corner.

[0049] (9) In any of the above (1) to (8) iron cores, the diameter of the second envelope circle surrounding the plurality of teeth may be more than 15% larger than the diameter of the first envelope circle.

[0050] The ratio of the diameter of the second envelope circle to the diameter of the first envelope circle is related to the amount of protrusion of the outer region along a second direction, with the outer circumference of the yoke as a reference. The second direction is orthogonal to the first direction and is along the diameter of the yoke. If the diameter of the second envelope circle is more than 15% larger than the diameter of the first envelope circle, that is, the aforementioned ratio is more than 115%, then the opening shape of the cavity of the mold for making the iron core has a profile with a large unevenness. The larger the unevenness, the less likely the powder will be dragged by the powder box even if the powder box moves back and forth. The larger the unevenness, the smaller the deviation in length from the second surface of the yoke to the end face of each of the multiple teeth.

[0051] (10) The rotary electric machine according to the embodiments of the present disclosure includes: a rotor; and a stator, which is opposed to the rotor in a direction along the rotation axis of the rotor. The stator includes: an iron core of any one of (1) to (9) above; and a coil, which is disposed in each of the plurality of teeth in the iron core.

[0052] Because the rotary electric motor according to the embodiments of this disclosure has the aforementioned iron core, it exhibits excellent assemblability. As described above, the deviation in length of the iron core from the second face of the yoke to the end faces of each of the plurality of teeth is small. This is because, for this reason, the iron core, coils, and rotor can be precisely configured when the stator and rotor are housed in the housing. Furthermore, because the rotary electric motor according to the embodiments of this disclosure has the aforementioned iron core, torque pulsation can be reduced, and noise and vibration are minimized.

[0053] [Details of the embodiments of this disclosure]

[0054] Specific examples of the iron core and rotating electric machine of this disclosure are described with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or equivalent parts. In the drawings, for ease of explanation, parts of the structure are sometimes shown in an exaggerated or simplified manner. The dimensional proportions of the parts in the drawings may also differ from actual dimensions. It should be noted that the invention is not limited to these examples, but is shown by the claims and is intended to include all modifications within the meaning and scope of the claims.

[0055] Iron Core

[0056] Reference Figures 1 to 6and appropriate reference Figure 12 , Figure 13 The iron core 1 of the embodiment will be described below. The iron core 1 is used for Figure 13 The rotary motor 8 shown is of the axial clearance type. Typically, the iron core 1 is used for... Figure 12 The stator 7 shown is composed of an iron core 1.

[0057] The iron core 1 has a circular magnetic yoke 2 and a plurality of columnar teeth 4. The teeth 4 are spaced apart around the axis of the magnetic yoke 2. The magnetic yoke 2 and the plurality of teeth 4 are formed by a single powder-pressed molding. One characteristic of the iron core 1 in this embodiment is that each tooth 4 has an outer region 40. Figure 2 As shown, when viewing the core 1 from the first direction D1, the outer region 40 is a region located further outward than the first envelope circle 61 formed by the outer peripheral surface of the yoke 2. The first direction D1 is a direction parallel to the axis of the yoke 2. Hereinafter, Figure 1 Both the upward and downward directions are referred to as the first direction D1. Furthermore, the direction orthogonal to the first direction D1 is referred to as the second direction D2. For example... Figure 4 As shown, the second direction D2 is along the diameter of the yoke 2.

[0058] <Magnetic yoke>

[0059] like Figures 1 to 3 As shown, the magnetic yoke 2 is a plate component with a planar annular shape. The magnetic yoke 2 has a first surface 21, a second surface 22, an outer peripheral surface 23, and an inner peripheral surface 24. The first surface 21 has a boundary with a plurality of teeth 4 and is a surface where the plurality of teeth 4 protrude in a direction parallel to the axis of the magnetic yoke 2. The second surface 22 is the surface opposite to the first surface 21. The first surface 21 and the second surface 22 are planar. A shaft hole 25 is provided at the center of the magnetic yoke 2, penetrating the first surface 21 and the second surface 22. The outer peripheral surface 23 and the inner peripheral surface 24 are the surfaces connecting the first surface 21 and the second surface 22. Adjacent teeth 4 of the plurality of teeth 4 arranged at intervals around the axis of the magnetic yoke 2 are magnetically coupled to each other.

[0060] like Figure 2 As shown, when viewing the core 1 from the first direction D1, the yoke 2 is the portion of the first envelope circle 61 formed by the outer circumferential surface 23 that is a true circle. In other words, the yoke 2 is the portion of the space A2 between the outer circumferential surface 23 and the inner circumferential surface 24 that is fixed around the axis of the yoke 2. The portion of the core 1 located outside the first envelope circle 61 is entirely part of the tooth 4, which will be described below.

[0061] like Figure 3 As shown, the first corner 31, formed by the first surface 21 and the outer peripheral surface 23, and the second corner 32, formed by the first surface 21 and the inner peripheral surface 24, can also be rounded. If the first corner 31 is rounded, it is easier to reduce the... Figure 7The stress generated at the corner portion forming the first corner portion 31 in the die 91 shown. If the second corner portion 32 is rounded, it is easier to reduce the stress generated at the corner portion forming the second corner portion 32 in the die 91. The radius of curvature of the first corner portion 31 can also be larger than the radius of curvature of the second corner portion 32. During pressure forming, the corner portion forming the first corner portion 31 in the die 91 generates relatively large stress. If the radius of curvature of the first corner portion 31 is larger than the radius of curvature of the second corner portion 32, it is easier to reduce the stress generated at the corner portion forming the first corner portion 31 in the die 91. The radius of curvature of the first corner portion 31 and the radius of curvature of the second corner portion 32 can also be the same. It is also possible that only the first corner portion 31 is rounded. It is also possible that none of the corners in the first corner portion 31 and the second corner portion 32 are rounded.

[0062] <teeth>

[0063] like Figure 1 As shown, each tooth 4 is a columnar component. Each tooth 4 is spaced apart around the axis of the yoke 2. Typically, each tooth 4 is arranged at equal intervals around the axis of the yoke 2. The number of teeth 4 can be appropriately selected as long as it is two or more. The number of teeth 4 can also be three or more, or six or more. When the core 1 is used in a three-phase AC rotating device, the number of teeth 4 is, for example, a multiple of three. In the accompanying drawings, a core 1 with 12 teeth 4 is illustrated.

[0064] [Basic structure of teeth]

[0065] Each tooth 4 has a main region protruding from the first surface 21 of the yoke 2 in a direction parallel to the axis of the yoke 2. Each tooth 4 also has a secondary region protruding outward from the main region in a direction orthogonal to the axis of the yoke. The outer direction is away from the axis of the yoke 2. Figure 2 As shown, when observing the core 1 from the first direction D1, the sub-region is the outer region 40 located further outward than the first envelope circle 61. Figure 5 As shown, the outer region 40 in this example has a portion located between the first extended surface 51 obtained by extending the first surface 21 and the second extended surface 52 obtained by extending the second surface 22. In other words, as Figure 4 and Figure 5 As shown, the outer region 40 in this example has a portion that protrudes outward from the outer peripheral surface 23 of the yoke 2.

[0066] Each tooth 4 has a first end face 41 protruding from the first surface 21 in a direction parallel to the axis of the yoke 2. In this example, the first end face 41 is a surface parallel to the first surface 21. The first end face 41 can also be an inclined surface with a certain angle relative to the first surface 21. The shape of the first end face 41 is, for example, trapezoidal. In this example, the edge of the trapezoidal first end face 41 located further from the axis of the yoke 2 is formed by a curve. The region between the first end face 41 and the first extended surface 51 of each tooth 4 has the same shape in the first direction D1 parallel to the axis of the yoke 2. The tooth 4 with the trapezoidal first end face 41 is a quadrangular prism. The tooth 4 with the trapezoidal first end face 41 easily ensures a large cross-sectional area of ​​the tooth 4. The tooth 4 with the trapezoidal first end face 41 easily ensures a large space between adjacent teeth 4. As long as the space between adjacent teeth 4 can be ensured to be large, it is easy to ensure Figure 12 The coil 70 shown has a large configuration space, making it easy to construct a stator 7 with a high footprint. Figure 12 , Figure 13 The shape of the first end face 41 can also be an isosceles triangle, a rectangle, or a circle. The area between the first end face 41 and the first extended surface 51 in each tooth 4 can also be formed into a cone shape as it moves from the first extended surface 51 toward the first end face 41.

[0067] The terms "trapezoidal shape" and "triangular shape" here include not only geometric trapezoids and triangles, but also shapes with rounded corners, as in this example, including areas that are substantially considered trapezoids or triangles. For example, when the outline includes a straight line, the shape of the polygon's vertices includes the intersection of the extensions of that straight line. For example, when the outline includes both a curve and a straight line, the shape of the polygon's vertices includes the intersection of the tangent of the curve and the straight line or its extension.

[0068] Representatively, each of the four teeth has the same shape and size.

[0069] [External Area]

[0070] like Figure 2 , Figure 4 and Figure 5 As shown, the outer region 40 has a second end face 42, which is a surface opposite to the first end face 41. The second end face 42 is a surface that extends from the outer peripheral surface 23 of the magnetic yoke 2 in a direction intersecting the first direction D1. In this example, the second end face 42 is along the second direction D2. Figure 4 and Figure 5 As shown, in this example, the second end face 42 is disposed between the first end face 41 and the second extended face 52, and is spaced apart from the second extended face 52.

[0071] like Figure 4 and Figure 5As shown, the second end face 42 in this example has a proximal surface 421 and a distal surface 422. The proximal surface 421 is located between the first extended surface 51 and the second extended surface 52, connected to the second surface 22 or the outer peripheral surface 23 of the magnetic yoke 2. In this example, the proximal surface 421 is located near the second extended surface 52. The distal surface 422 is located further away from the outer peripheral surface 23 than the proximal surface and is located away from the second extended surface 52. In this example, the distal surface 422 is located between the first extended surface 51 and the second extended surface 52, connected to the side surface 43 of the outer region 40.

[0072] In this example, the second end face 42 is mostly formed by the distal end face 422. By having a gap A1 between the distal end face 422 and the second extended face 52, it is possible to ensure, according to the gap A1, the conditions for... Figure 12 The wiring space of the coil 70 is shown. If each tooth 4 has an outer region 40, the core 1 is larger in the second direction D2 compared to the existing core. However, by utilizing the outer region 40 to ensure the aforementioned wiring space, the stator 7 (which is formed by arranging the coil 70 on each tooth 4 of the core 1) can be prevented from being too large. Figure 12 The overall size is increased.

[0073] The interval A1 is the interval furthest from the outer peripheral surface 23 in the interval between the second end face 42 and the second extended surface 52. A larger interval A1 ensures a larger wiring space. For example, the interval A1 is 10% or more of the first length L1 from the second surface 22 to the first end face 41. The method for measuring the first length L1 of each tooth 4 will be described below. The interval A1 is related to the second length L2 of the outer region 40. The second length L2 is the length along the first direction D1 of the portion of the outer region 40 located at the position furthest from the axis of the yoke 2. In other words, the second length L2 is the length along the first direction D1 of the portion of the side surface 43 of the outer region 40 that protrudes outward from the main region of the tooth 4 along the second direction D2. If the interval A1 increases, the second length L2 decreases. Considering the second length L2, the interval A1 is, for example, less than 40% of the first length L1. The interval A1 is, for example, more than 10% and less than 40% of the first length L1. The interval A1 can also be more than 15% and less than 35% of the first length L1, or more than 20% and less than 30%.

[0074] In this example, a step is formed on the second end face 42 by the proximal face 421 and the distal face 422. (See reference...) Figure 11As will be described below, the die 9 for pressing and forming the iron core 1, which has an outer region 40 for each tooth 4, includes a die 91, a lower punch 92, and an upper punch 93. The magnetic yoke 2 is formed by supporting the first surface 21 with the die 91 and pressing the second surface 22 with the upper punch 93. Each tooth 4 is pressed by the lower punch 92 and the upper punch 93. The second end face 42 is formed by transferring the shape of the protrusion 934 of the upper punch 93. If the protrusion 934 exists in the upper punch 93, a relatively large stress is generated at the corner portion in the die 91 where the first corner portion 31 is formed. By forming the aforementioned step on the second end face 42, the stress generated in the die 91 is easily reduced.

[0075] In this example, the outer peripheral surface 23 connecting the second surface 22 and the proximal surface 421 is formed by an inclined surface that is closer to the first surface 21 the further towards the outer periphery of the magnetic yoke 2. Similarly, the connecting surface connecting the proximal surface 421 and the distal surface 422 is also formed by an inclined surface that is closer to the first surface 21 the further towards the outer periphery of the magnetic yoke 2. If the outer peripheral surface 23 connecting the second surface 22 and the proximal surface 421, as well as the aforementioned connecting surface, are inclined surfaces, the upper punch 93 can be easily removed from the powder-pressed body after pressure forming.

[0076] The second end face 42 can also be composed of a single surface. The second end face 42 composed of a single surface can also be an inclined surface that is closer to the first surface 21 as it moves towards the outer periphery of the magnetic yoke 2. If the second end face 42 is an inclined surface, the upper punch 93 can be easily removed from the powder-forming body after pressure forming.

[0077] like Figure 3 As shown, when observing the core 1 from the first direction D1, the angle θ between the first tangent T1 and the second tangent T2 at the first intersection point T0 is, for example, 90° or less. The first intersection point T0 is the intersection of the side surface 43 of the outer region 40 and the first envelope circle 61. When observing the core 1 from the first direction D1, the side surface 43 of the outer region 40 is a plane coplanar with the side surface of the main region in each tooth 4. In this example, the side surface 43 is a plane coplanar with the side surface of the main region. The side surface 43 of the outer region 40 is not limited to the plane in this example; it can also be a surface with monotonic curvature or a surface with varying curvature. The first tangent T1 is a tangent to the first envelope circle 61 passing through the first intersection point T0. The second tangent T2 is a tangent to the side surface 43 of the outer region 40 at the first intersection point T0. If the angle θ is 90° or less, it is easier to reduce the stress generated at the corner portion forming the first corner portion 31 in the die 91 of the mold 9 that pressurizes the core 1. The angle θ can also be less than 90°, below 80°, or below 70°.

[0078] [Size of the outer region]

[0079] like Figure 2As shown, when viewing the core 1 from the first direction D1, the diameter of the second envelope circle 62 surrounding the plurality of teeth 4 is, for example, more than 15% larger than the diameter of the first envelope circle 61. The ratio of the diameter of the second envelope circle 62 to the diameter of the first envelope circle 61 is related to the amount of protrusion of the outer region 40 along the second direction D2, with the outer peripheral surface 23 of the yoke 2 as a reference. If the diameter of the second envelope circle 62 is more than 15% larger than the diameter of the first envelope circle 61, that is, the ratio is more than 115%, then the opening shape of the cavity of the mold 9 for making the core 1 has a profile with a large unevenness. As will be described below, the larger the unevenness, the smaller the deviation in length from the second surface 22 of the yoke 2 to the first end face 41 of each of the plurality of teeth 4. The larger the unevenness, the easier it is to reduce the stress generated at the corner portion forming the first corner portion 31 in the punch 91 of the mold 9 for pressurizing the core 1.

[0080] If the above ratio is too high, the magnetic properties of the entire iron core 1 may become uneven. If the above ratio is below 130%, the iron core 1 is more likely to have uniform magnetic properties overall. The above ratio can also be above 115% and below 130%, above 118% and below 127%, or above 120% and below 125%.

[0081] like Figure 4 and Figure 5 As shown, in each tooth 4, the ratio of the second length L2 to the first length L1 is, for example, 60% or more and 90% or less. As described above, the ratio of the second length L2 to the first length L1 is related to the distance between the second end face 42 and the second extended face 52, which in this example is the distance A1 between the distal face 422 and the second extended face 52. The die 91 of the mold 9 that pressurizes the core 1 ( Figure 7 The first corner portion 31 in ) Figure 3 The stress generated at the corner during forming is due to the difference between the forming pressure applied to the outer region 40 of each tooth 4 and the forming pressure applied to the region outside the outer region 40. The upper punch 93 of the die 9 is positioned such that the second end face 42 is spaced apart from the second extended surface 52. Figure 9 The forming pressure on the outer region 40 increases. If the ratio of the second length L2 to the first length L1 is 60% or more and 90% or less, the aforementioned stress is easily reduced. If the ratio of the second length L2 to the first length L1 is 90% or less, a spacing A1 can be provided, ensuring wiring space corresponding to that spacing A1. If the ratio is 60% or more, the magnetic flux flowing from the magnet 84 of the rotor 80 (described below) into the outer region 40 can easily and efficiently flow into the yoke 2. The ratio of the second length L2 to the first length L1 can also be 65% or more and 85% or less, or 70% or more and 80% or less.

[0082] [Deviation in the length of multiple teeth]

[0083] Using the second surface 22 of the yoke 2 as a reference surface, the deviation in length from this reference surface to the first end face 41 of each of the plurality of teeth 4 is small. For example, the deviation of the first length L1 from the second surface 22 to the first end face 41 of each tooth 4 is less than 0.05 mm. For example, assuming it is used in... Figure 2 After moving upwards from the bottom of the attached image, from Figure 2 The powder box (not shown) folded downwards from above to form the iron core 1. In this case, as... Figure 6 As shown, the deviation of the first length L1 of the multiple teeth 4 is less than 0.05 mm.

[0084] Figure 13 The rotary motor 8 shown is constructed by housing a stator 7, which is formed by arranging coils 70 on each tooth 4 of the iron core 1, together with a rotor 80 within a housing 82. At this time, the second surface 22 of the magnetic yoke 2 is in contact with the inner surface of the housing 82. If the deviation of the first length L1 from the second surface 22 to the first end face 41 of each tooth 4 is less than 0.05 mm, then when the stator 7 and rotor 80 are housed in the housing 82, the first end face 41 of each tooth 4 is positioned at a substantially uniform interval from any part of the magnet 84. Therefore, the rotary motor 8 constructed using the aforementioned iron core 1 not only has excellent assemblability but also exhibits reduced torque ripple. Due to the low torque ripple of the rotary motor 8, noise and vibration are less likely to increase. Because of the low torque ripple of the rotary motor 8, the rotation shaft 81 of the rotor 80 is less likely to wobble. In other words, the frictional force between the rotation shaft 81 of the rotor 80 and the bearing 83 is less likely to change. Therefore, mechanical energy loss in the rotary motor 8 is less likely to increase.

[0085] The deviation of the first length L1 of the multiple teeth 4 is calculated as follows. First, for each tooth 4, the first length L1 from the second surface 22 of the yoke 2 to the first end face 41 of the tooth 4 is measured. The iron core 1 is placed on the inspection plate with the first end face 41 of the tooth 4 facing upwards using a height gauge equipped with a grade 0 inspection plate. Multiple measurement points are selected on the first end face 41 of each tooth 4. The measurement points are set on a straight line drawn through the centroid of the tooth 4 and the axis of the yoke 2. Three or more measurement points are selected on this straight line. The measurement points on this straight line include the centroid of the tooth 4, the edge portion of the tooth 4 located near the axis of the yoke 2, and the edge portion of the tooth 4 located away from the axis of the yoke 2. The length from the inspection plate to each measurement point is measured, and the average value of the measured lengths is taken as the first length L1 of each tooth 4. Next, the maximum and minimum lengths are selected from the first lengths L1 of the multiple teeth 4. The deviation of the first length L1 of the multiple teeth 4 can be calculated by calculating the difference between the maximum and minimum lengths. The smaller the deviation of the first length L1 of the multiple teeth 4, the better. For example, the deviation of the first length L1 of the multiple teeth 4 is less than 0.04 mm or less than 0.03 mm.

[0086] <Constructing Materials>

[0087] The iron core 1 is composed of a pressed powder body containing soft magnetic powder. The soft magnetic powder, for example, comprises multiple iron-based particles composed of pure iron or iron-based alloys. Pure iron is iron with a purity of 99% or higher, meaning it contains 99% or more iron (Fe) by mass. Pure iron provides advantages such as high saturation magnetic flux density, excellent formability, and ease of densification through press forming. Therefore, by including iron-based particles composed of pure iron, it is possible to form an iron core 1 with high saturation magnetic flux density, a relatively high and dense iron core 1, and an iron core 1 that is easy to form and has excellent manufacturability during manufacturing. Furthermore, due to its density, it is possible to form an iron core 1 that not only easily increases the saturation magnetic flux density but also possesses excellent mechanical properties such as strength. Iron-based alloys are alloys containing additive elements, with the balance being Fe and unavoidable impurities. Iron-based alloys contain one or more additive elements. Examples of additive elements include silicon (Si), aluminum (Al), and chromium (Cr). Iron-based alloys have a higher electrical resistance than pure iron. Therefore, if the core contains iron-based particles made of iron-based alloys, iron losses such as eddy current losses can be reduced, and a low-loss core 1 can be formed. Alternatively, the core 1 can be configured to contain both iron-based particles made of pure iron and iron-based particles made of iron-based alloys.

[0088] Soft magnetic powder generally comprises coated particles with an insulating film on the surface of powder particles made of soft magnetic materials. The inclusion of coated particles reduces iron losses such as eddy current losses, enabling the formation of a low-loss iron core 1. In particular, if the powder particles are composed of pure iron and coated with an insulating film, an iron core 1 with not only high saturation magnetic flux density and excellent magnetic properties but also low losses can be formed. The insulating film is composed of oxides such as phosphates, silicon dioxide, magnesium oxide, and aluminum oxide.

[0089] Relative density

[0090] The relative density of core 1 is, for example, 90% or higher. Core 1 with a relative density of 90% or higher exhibits high saturation magnetic flux density and excellent strength. The relative density of core 1 can also be 93% or higher, or 95% or higher. Here, relative density is the ratio (%) of the measured density of the pressed powder molded body to the theoretical density of the pressed powder molded body constituting core 1. The aforementioned theoretical density can be used as an equivalent value for the true density of the soft magnetic powder constituting the pressed powder molded body.

[0091] In the iron core 1 where each tooth 4 has an outer region 40, the relative density of the outer region 40 is higher than the relative density of the parts outside the outer region 40. The relative density of the outer region 40 is, for example, 93% or more, 95% or more, or 96% or more.

[0092] Methods for Manufacturing Iron Cores

[0093] The iron core 1 of the embodiment can be used Figures 7 to 11 It is manufactured using the mold 9 shown. Mold 9 has... Figure 7 The die 91 shown Figure 8 The lower punch 92 shown, and Figure 9 The upper punch 93 is shown.

[0094] The die 91 is a cylindrical component. The die 91 has a central portion 911 and an outer peripheral portion 912. The central portion 911 forms the central region of the shaft including the die 91 and is a solid body extending to both end faces of the die 91. The central portion 911 serves to form the shaft hole 25 of the yoke 2 in the iron core 1. The outer peripheral portion 912 is located on the outer periphery of the central portion 911. The outer peripheral portion 912 has a recess 913 and a through hole 917 opening on the upper surface of the die 91. The recess 913 and the through hole 917 are alternately arranged around the shaft of the die 91. The recess 913 has a bottom 914, an inner side 915, and an outer side 916. The inner side 915 is also a side of the central portion 911. The outer side 916 is provided opposite to the inner side 915. The bottom 914 connects the inner side 915 and the outer side 916. The recess 913 forms most of the yoke 2 in the iron core 1. The bottom 914 forms the first surface 21 of the yoke 2. The outer surface 916 forms the outer peripheral surface 23 of the yoke 2. The inner surface 915 forms the inner peripheral surface 24 of the yoke 2. The through hole 917 passes through the upper and lower parts of the die 91. The through hole 917 forms the tooth 4 in the iron core 1. The through hole 917 has the same cross-sectional shape and size as the first end face 41 of the tooth 4. The envelope circle surrounding the multiple through holes 917 is larger than the envelope circle surrounding the multiple recesses 913. The envelope circle surrounding the multiple recesses 913 is formed by the outer surface 916 of the recesses 913. The contour forming the outer peripheral portion 912 is concave and convex. The lower punch 92 is inserted into and passes through the through hole 917.

[0095] The lower punch 92 has a base 921 and a plurality of cylindrical portions 922. The base 921 is a cylindrical component. The plurality of cylindrical portions 922 are spaced apart around the axis of the base 921. Each cylindrical portion 922 is inserted into and passes through a through hole 917 in the die 91. The end face 923 of each cylindrical portion 922 has the same shape and size as the first end face 41 of the tooth 4. The end face 923 constitutes the first end face 41 of the tooth 4.

[0096] The upper punch 93 is a cylindrical component. The upper punch 93 has an annular first end face 931. The first end face 931 forms the second surface 22 of the magnetic yoke 2. The upper punch 93 has multiple protrusions 932 on its outer peripheral surface. The multiple protrusions 932 are spaced apart around the axis of the upper punch 93. Each protrusion 932 extends vertically along the upper punch 93. A protrusion 934 is provided at the front end of each protrusion 932. The protrusion 934 is located at the part of the protrusion 932 furthest from the axis of the upper punch 93. The protrusion 932, through the protrusion 934, has a second end face 933 having two surfaces forming a step. The second end face 933 forms the second end face 42 of the outer region 40 of the tooth 4. The face that is closer to the first end face 931 constitutes the proximal face 421, and the face that is farther from the first end face 931 constitutes the distal face 422.

[0097] A cavity for filling powder 95 is formed by inserting the cylindrical portion 922 of the lower punch 92 into the through hole 917 of the die 91. Powder is supplied to the cavity using a powder box (not shown). The powder box has an opening at the bottom. The powder box moves linearly back and forth on the die 91. When the powder box moves onto the cavity, the powder inside falls into the cavity from the opening due to gravity. Figure 10 The image shows a mold cavity filled with powder 95. After the powder 95 is filled into the mold cavity, the powder box is folded back. During this folding back, there is a tendency for the bottom surface of the powder box to drag a portion of the powder 95 filled into the mold cavity.

[0098] In mold 9 of this example, as Figure 10 As shown, the opening shape of the cavity has a concave-convex profile corresponding to the contour of the outer periphery 912 of the die 91. If the opening has a concave-convex profile, the powder 95 group disposed on the opening surface of the cavity has discontinuous portions around the axis of the die 91. If discontinuous portions exist, the powder 95 is less likely to be dragged by the powder box even when the powder box reciprocates. If the powder 95 is less likely to be dragged during the reciprocating movement of the powder box, the filling amount of powder 95 filling the cavity is less likely to become unbalanced.

[0099] After filling the cavity with 95% powder, as Figure 11 As shown, the powder 95 is pressurized by the lower punch 92 and the upper punch 93. If the amount of powder 95 filling the cavity is not easily unbalanced, the length from the second surface 22 of the magnetic yoke 2 to the first end face 41 of each of the multiple teeth 4 in the pressed powder molded body obtained after press molding is not easily deviated.

[0100] The second end face 42 of each tooth 4 is formed by transferring the shape of the protrusion 934 provided on the upper punch 93. If the protrusion 934 exists on the upper punch 93, relatively large stress is generated at the corner between the bottom 914 and the outer side 916 of the recess 913 provided on the die 91. The first corner 31 of the magnetic yoke 2 is formed by this corner. If there is a step formed by two surfaces on the second end face 933, the aforementioned stress generated in the die 91 can be easily reduced.

[0101] The corners of the bottom 914 and the outer side 916 of the recess 913 in the die 91, as well as the corners of the bottom 914 and the inner side 915, can also be rounded. In this case, the radius of curvature of the corners of the bottom 914 and the outer side 916 can also be larger than the radius of curvature of the corners of the bottom 914 and the inner side 915.

[0102] The iron core 1 obtained by the above-described mold 9 has a small deviation in length from the second surface 22 of the magnetic yoke 2 to the first end face 41 of each of the plurality of teeth 4 at the time when the powder 95 is pressed and formed into a pressed powder body. Therefore, after the pressed powder body is made, it is not necessary to perform grinding on the first end face 41 of each tooth 4. Therefore, the iron core 1 obtained by the above-described mold 9 has excellent productivity.

[0103] Rotating Electrical Machines

[0104] Reference Figure 12 and Figure 13 The rotary motor 8 according to the embodiment will be described below. The rotary motor 8 includes a rotor 80 and a stator 7. The stator 7 is positioned opposite the rotor 80 in the direction along the rotation axis of the rotor 80. The rotary motor 8 can be used as a motor or a generator. Figure 13 This is a cross-sectional view taken along a plane parallel to the rotation axis 81 of the rotary motor 8. Figure 13 The example shown is a single-rotor, double-stator type rotary electric machine assembled in such a way that one rotor 80 is sandwiched between two stators 7. In addition, the rotary electric machine 8 may also be assembled in such a way that it has one rotor 80 and one stator 7, or in such a way that one stator 7 is sandwiched between two rotors 80.

[0105] like Figure 12 As shown, the stator 7 includes an iron core 1 and a coil 70. The coil 70 is disposed in each tooth 4 of the iron core 1. The coil 70 has a cylindrical portion formed by winding the wire into a spiral shape. In this example, the coil 70 is a flat, upright wound coil with the winding wire set as a four-cornered cylindrical shape covering the flat corner wire. The wiring group 71 of the coil 70 is disposed in the space formed by the interval A1 between the second end face 42 and the second extended surface 52 of the outer region 40 of each tooth 4.

[0106] like Figure 13 As shown, the stator 7 and rotor 80 are housed in a housing 82 having a cylindrical internal space. The housing 82 has a cylindrical portion and two plate portions. The cylindrical portion surrounds the outer periphery of the stator 7 and rotor 80. Plate portions are respectively arranged at both ends of the cylindrical portion. The stator 7 and rotor 80 are housed in the housing 82 by being sandwiched between the two plate portions. The stator 7 is fixed to the housing 82 by embedding a portion of the magnetic yoke 2 of the iron core 1 into the plate portions of the housing 82. Both plate portions have through holes at their center. A bearing 83 is provided in the through hole, and a rotating shaft 81 is inserted into and passes through the bearing 83. A bearing (not shown) is also provided in the shaft hole 25 of the magnetic yoke 2, and the rotating shaft 81 is inserted into and passes through this bearing. The rotating shaft 81 extends through the housing 82.

[0107] The rotor 80 is a flat plate component comprising a plurality of magnets 84 and a rotor body supporting the magnets 84. Each magnet 84 is, for example, a flat plate with a planar shape corresponding to the shape of the first end face 41 of the tooth 4. The rotor body is an annular component supported by a rotating shaft 81 in a manner rotatable relative to the housing 82. The magnets 84 are arranged at equal intervals around the shaft of the rotor body. Each magnet 84 is magnetized in the direction along the axis of the rotating shaft 81. The magnetization directions of adjacent magnets 84 around the shaft of the rotor body are opposite to each other. When the rotor body rotates, the magnets 84 also rotate with the rotor body.

[0108] The stator 7 is configured such that the first end face 41 of the tooth 4 is opposite to the magnet 84 of the rotor 80. The coil 70 of the stator 7 is energized to generate a rotating magnetic field, and the rotor 80 rotates relative to the stator 7 by the attractive or repulsive force caused by the rotating magnetic field. When the rotor 80 rotates, the first end face 41 of the tooth 4 is subjected to magnetic flux from the rotating magnet 84.

[0109] Because the rotary motor 8 of this embodiment has the iron core 1 of this embodiment, it has excellent assemblability. As described above, the deviation in length of the iron core 1 from the second surface 22 of the magnetic yoke 2 to the first end face 41 of each of the plurality of teeth 4 is small. This is because, for this reason, when the stator 7 and the rotor 80 are housed in the housing 82, the iron core 1, the coil 70 and the rotor 80 are arranged with high precision. In addition, because the rotary motor 8 of this embodiment has the iron core 1 of this embodiment, torque pulsation can be reduced, and noise and vibration are low.

[0110] [Experimental Example 1]

[0111] In Experiment 1, iron cores with external regions for each tooth and existing iron cores without external regions for each tooth were fabricated, and the deviation in length from the second face of the yoke to the first end face of each tooth was measured. Specimen No. 1-1 is an iron core with external regions for each tooth. Specimen No. 1-2 is an existing iron core without external regions for each tooth.

[0112] Sample Description

[0113] In sample No. 1-1, using Figures 7 to 11The mold 9 shown is used to press-form a powder containing soft magnetic powder into a pressed powder body. The annular magnetic yoke of the iron core formed by this pressed powder body is integrally formed with 12 teeth. When the iron core is viewed from a first direction parallel to the axis of the magnetic yoke, each tooth has an outer region located further outward than the first envelope circle formed by the outer circumferential surface of the magnetic yoke. The envelope circle surrounding the teeth is called the second envelope circle. The diameter of the second envelope circle is 17% larger than the diameter of the first envelope circle, based on the diameter of the first envelope circle. The ratio of the diameter of the second envelope circle to the diameter of the first envelope circle is related to the amount of protrusion of the outer region along a second direction based on the outer circumferential surface of the magnetic yoke. The second direction is orthogonal to the first direction and is along the diameter of the magnetic yoke.

[0114] In specimen No. 1-1, each tooth has a first end face located at a front end protruding from a first surface of the yoke in a direction parallel to the axis of the yoke, and an outer region having a second end face as a surface opposite to the first end face. The second end face is disposed between an extension surface of the second surface of the yoke and the first end face, and is spaced apart from the extension surface of the second surface. This space is 25% of a first length from the second surface of the yoke to the first end face of each tooth. That is, the ratio of the length of the portion in the outer region located at the position farthest from the axis of the yoke along the first direction to the first length is 75%.

[0115] In Sample No. 1-2, the same powder as in Sample No. 1-1 was press-formed to create a pressed powder body. The annular magnetic yoke of the iron core formed by this pressed powder body is integrated with 12 teeth. When the iron core is viewed from the first direction, each tooth does not have a region located further outward than the first envelope circle formed by the outer circumference of the magnetic yoke.

[0116] Deviation in length from the second face of the magnetic yoke to the first end face of each of the multiple teeth

[0117] For the cores of each obtained sample, the deviation of the length from the second face of the yoke to the first end face of each of the multiple teeth was investigated as follows. First, for each tooth, the first length L1 from the second face of the yoke to the first end face of the tooth was measured. The core was placed on the inspection plate with the first end face of the tooth facing upwards using a height gauge equipped with a grade 0 inspection plate. At least three measurement points were selected on the first end face of each tooth. In this example, measurement points were selected on a straight line drawn through the centroid of the tooth and the center of the yoke, including the centroid of the tooth, the edge of the tooth near the axis of the yoke, and the edge of the tooth away from the axis of the yoke. The length from the inspection plate to each measurement point was measured, and the average of the measured lengths was taken as the first length L1 of each tooth. Next, the maximum and minimum lengths were selected from the first lengths L1 of the multiple teeth, and the difference between the maximum and minimum lengths was calculated. This difference was taken as the deviation of the length from the second face of the yoke to the first end face of each of the multiple teeth. In sample No. 1-1, the deviation of the above length was 0.047 mm. In specimens No. 1-2, the deviation of the above length was 0.099 mm.

[0118] The results of the aforementioned length deviations indicate that if the core has an outer region for each tooth, the deviation in length from the second surface of the yoke to the first end face of each tooth can be reduced. In a core where each tooth has an outer region, the opening shape of the cavity of the mold for making the core is such that the yoke and the outer region are joined together, and it has a concave-convex profile. If the opening has a concave-convex profile, the powder group disposed on the opening surface of the cavity has a discontinuous portion around the axis of the yoke. It is believed that if there is a discontinuous portion, even if the powder box moves back and forth, the powder is not easily dragged by the powder box, and the filling amount of powder filling the cavity is less likely to become unbalanced. It is believed that because the filling amount of powder is less likely to become unbalanced, the length from the second surface of the yoke to the first end face of each tooth is less likely to deviate in the pressed powder molded body obtained after pressure forming.

[0119] In existing iron cores where each tooth lacks an external region, the opening shape of the cavity of the mold used to make the iron core is the shape of a yoke, that is, an annular shape. It is believed that if the opening is an annular shape, the outline of the powder group disposed on the opening surface of the cavity is circular, and as the powder box moves back and forth, a portion of the powder is dragged by the powder box.

[0120] [Experimental Example 2]

[0121] In Test Example 2, iron cores were fabricated where each tooth had an outer region and the ratio of the second length to the first length was different. The maximum stress generated in the die during pressure forming was measured. The first length is the length from the second face of the yoke to the first end face of each tooth. The second length is the length along the first direction of the portion of the outer region located at the position furthest from the axis of the yoke. Sample No. 2-1 is an iron core with the aforementioned ratio of 92%. Sample No. 2-2 is an iron core with the aforementioned ratio of 85%. All conditions except for the aforementioned ratios for Sample No. 2-1 and Sample No. 2-2 are the same as those for Sample No. 1-1.

[0122] The stress distribution acting on the die during the manufacture of the iron cores of specimen No. 2-1 and specimen No. 2-2 was analyzed using CAE (Computer Aided Engineering). Based on the CAE analysis results, the maximum stress value (MPa) generated in the die was calculated.

[0123] The above analysis shows that the maximum stress acts on the corner of the die that forms the first corner, which is composed of the first surface and the outer peripheral surface of the yoke. In specimen No. 2-1, the maximum stress is 1096 MPa. In specimen No. 2-2, the maximum stress is 1074 MPa.

[0124] The above analysis shows that if the ratio is below 90%, the stress generated at the corner of the die forming the first corner of the yoke can be reduced. On the other hand, if the ratio is less than 60% and too small, the magnetic flux flowing from the rotor magnet into the outer region of the teeth will not flow into the yoke efficiently.

[0125] [Experimental Example 3]

[0126] In Test Example 3, iron cores were fabricated in which each tooth had an outer region and the ratio of the diameter of the second envelope circle to the diameter of the first envelope circle was different. The maximum stress generated in the upper punch during pressure forming was measured. In Specimen No. 3-1, the diameter of the second envelope circle was 6% larger than the diameter of the first envelope circle, based on the diameter of the first envelope circle. In Specimen No. 3-2, the diameter of the second envelope circle was 13% larger than the diameter of the first envelope circle, based on the diameter of the first envelope circle. All conditions except for the aforementioned ratios in Specimen No. 3-1 and Specimen No. 3-2 were the same as those in Specimen No. 1-1.

[0127] CAE was used to analyze the stress distribution acting on the upper punch during the manufacturing of the iron cores of specimens No. 3-1 and No. 3-2. Based on the CAE analysis results, the maximum stress value (MPa) generated in the upper punch was calculated.

[0128] The above analysis results show that the maximum stress acts at the root of the protrusion in the upper punch. In specimen No. 3-1, the maximum stress is 2241 MPa. In specimen No. 3-2, the maximum stress is 1153 MPa.

[0129] The above analysis shows that if the diameter of the second envelope circle is more than 10% larger than the diameter of the first envelope circle, the stress generated at the root of the protrusion in the upper punch can be reduced. It is believed that if the ratio is small, the contact area between the upper punch and the powder constituting the outer region becomes smaller, and a relatively large stress will be generated at the root of the protrusion in the upper punch.

[0130] [Experimental Example 4]

[0131] In Test Example 4, an iron core was fabricated in which each tooth has an outer region, and the first corner formed by the first surface and outer peripheral surface of the yoke, and the second corner formed by the first surface and inner peripheral surface, are respectively rounded. The maximum stress generated in the die during pressure forming was measured. Specimen No. 4-1 is an iron core with a radius of curvature of 2.5 mm for both the first and second corners. Specimen No. 4-2 is an iron core with a radius of curvature of 2.5 mm for the first corner and 2.0 mm for the second corner. All conditions of Specimen No. 4-1 and Specimen No. 4-2, except for the aforementioned radius of curvature, are the same as those of Specimen No. 1-1.

[0132] CAE was used to analyze the stress distribution acting on the die during the manufacture of the cores of specimens No. 4-1 and No. 4-2. Based on the CAE analysis results, the maximum stress value (MPa) generated in the die was calculated.

[0133] The above analysis results show that the maximum stress acts on the corner of the die that forms the first corner of the magnetic yoke. In specimen No. 4-1, the maximum stress is 1009 MPa. In specimen No. 4-2, the maximum stress is 983.2 MPa.

[0134] The above analysis shows that if the radius of curvature of the first corner is larger than that of the second corner, the stress generated at the corner of the die forming the first corner of the yoke can be reduced. It is believed that since a relatively large stress is generated at the corner of the die forming the first corner of the yoke during pressure forming, increasing the radius of curvature of this corner can easily reduce this stress.

[0135] Explanation of reference numerals in the attached figures

[0136] 1 Iron core

[0137] 2. Magnetic yoke

[0138] 21 First page, 22 Second page

[0139] 23 Outer circumferential surface, 24 Inner circumferential surface

[0140] 25 shaft hole

[0141] 31 First corner, 32 Second corner

[0142] 4 teeth

[0143] 40 External Area

[0144] 41 First end face, 42 Second end face

[0145] 421 Periplane, 422 Apoplane

[0146] 43 Side View

[0147] 51 First extended surface, 52 Second extended surface

[0148] 61 First envelope circle, 62 Second envelope circle

[0149] A1, A2 interval

[0150] L1 First Length, L2 Second Length

[0151] T0 First intersection point, T1 First tangent line, T2 Second tangent line, θ Angle

[0152] D1 First Direction, D2 Second Direction

[0153] 7 Stator, 70 Coils, 71 Wiring Group

[0154] 8 Rotary motor, 80 Rotor, 81 Rotating shaft, 82 Housing

[0155] 83 Bearing, 84 Magnet

[0156] 9 Molds

[0157] 91 Stamping Die

[0158] 911 Central Department

[0159] 912 Peripheral part

[0160] 913 Recess, 914 Bottom, 915 Inner side, 916 Outer side

[0161] 917 Through Hole

[0162] 92 Downward punch

[0163] 921 Base, 922 Columnar portion, 923 End face

[0164] 93 Upper Punch

[0165] 931 First end face

[0166] 932 Drum-shaped section, 933 Second end face, 934 Convex section

[0167] 95 powder.

Claims

1. A core for use in a rotary electric motor with axial clearance, comprising: A circular magnetic yoke; and Multiple columnar teeth are arranged at intervals around the axis of the yoke. The magnetic yoke and the plurality of teeth are formed by an integral powder-pressed molding body. The magnetic yoke has the following features: The first surface has a boundary with the plurality of teeth; The second side is the side opposite to the first side; and The outer and inner peripheral surfaces connect the first surface and the second surface. When the core is viewed from a first direction parallel to the axis, each of the plurality of teeth has an outer region located further outward than the first envelope circle formed by the outer peripheral surface.

2. The iron core according to claim 1, wherein, Each of the plurality of teeth has a first end face located at a front end that protrudes from the first surface in a direction parallel to the axis. The deviation of the length from the second face to the first end face of each of the plurality of teeth is less than 0.05 mm.

3. The iron core according to claim 1 or 2, wherein, Each of the plurality of teeth has a first end face located at a front end that protrudes from the first surface in a direction parallel to the axis. The outer region has a second end face that is opposite to the first end face. The second end face is disposed between the extended surface of the second surface and the first end face, and is spaced apart from the extended surface of the second surface.

4. The iron core according to claim 3, wherein, The second end face has: A proximal surface, located between the extension surface of the first surface and the extension surface of the second surface, in a manner connected to the second surface or the outer peripheral surface; and The distal surface is further away from the outer peripheral surface than the proximal surface, and is located on an extended surface away from the second surface.

5. The iron core according to any one of claims 1 to 4, wherein, Each of the plurality of teeth has a first end face located at a front end that protrudes from the first surface in a direction parallel to the axis. The ratio of the second length of the outer region to the first length of each of the plurality of teeth is more than 60% and less than 90%. The first length is the length from the second face to the first end face. The second length is the length of the portion of the outer region located at the position furthest from the axis along the first direction.

6. The iron core according to any one of claims 1 to 5, wherein, When the core is viewed from the first direction, the angle between the first tangent and the second tangent at the first intersection point is less than 90°. The first intersection point is the intersection point of the side surface of the outer region and the first envelope circle. The first tangent is the tangent to the first envelope circle passing through the first intersection point. The second tangent is a tangent to the side of the outer region through the first intersection point.

7. The iron core according to any one of claims 1 to 6, wherein, The first corner formed by the first surface and the outer peripheral surface, and the second corner formed by the first surface and the inner peripheral surface, are respectively rounded.

8. The iron core according to claim 7, wherein, The radius of curvature of the first corner is larger than that of the second corner.

9. The iron core according to any one of claims 1 to 8, wherein, The diameter of the second envelope circle surrounding the plurality of teeth is more than 15% larger than the diameter of the first envelope circle.

10. A rotary electric motor, comprising: Rotor; and The stator is positioned relative to the rotor in the direction along the rotor's axis of rotation. The stator comprises: The iron core according to any one of claims 1 to 9; and A coil, disposed in each of the plurality of teeth in the iron core.

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