Compacted powder, stator core, and axial gap motor

Abstract

To provide a method for producing a green compact capable of reducing chips therein.SOLUTION: A method for producing a green compact includes a step of filling powder in a space composed of a die hole and a lower punch, and a step of making the powder into the green compact with a lower punch and an upper punch. The green compact has a prismatic body, a first plate portion located at a first end of the body, and a second plate portion located at a second end of the body. The body has a left side and a right side. The first plate portion has a first left side and a first right side having an inclined area that extends from a first front surface to a first rear surface. The second plate portion has a second left side and a second right side. The upper punch has a main lower surface for molding the left side, a first sub lower surface for molding the first left side, and a second sub lower surface for molding the second left side. The lower punch has a main upper surface for molding the right side, a first sub upper surface for molding the first right side, and a second sub upper surface for molding the second right side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a powder compact, a method for manufacturing a stator core, and a method for manufacturing an axial gap motor. This application claims priority to Japanese Application No. 2022-187837, filed November 24, 2022, and incorporates the entire disclosure of that Japanese application by reference. [Background technology]

[0002] Patent Document 1 discloses a core piece for constructing a stator core for an axial gap type rotating electric machine. This core piece includes a columnar body extending along the axis of the stator core, a plate-shaped first plate portion provided at a first end of the body, and a plate-shaped second plate portion provided at a second end of the body. Each of the first plate portion and the second plate portion has a protrusion that protrudes outward from the circumferential surface of the body.

[0003] The body, first plate, and second plate that make up such a core piece are integrally molded by compressing powder in a mold having a die, a lower punch, and an upper punch. This molding is achieved by aligning the direction in which the powder is compressed in the mold and the direction in which the core piece, which is a green compact, is extracted from the mold along the diameter of the stator core.

[0004] Generally, a powder compact having the above-described protrusions at both ends of the body cannot be molded by compressing powder in a direction along the axis of the stator core. This is because the protrusions provided at both ends of the body form undercuts that protrude in a direction intersecting the direction in which the powder compact is removed from the die. According to the above-described method for molding a powder compact, even a powder compact having the above-described protrusions at both ends of the body can be manufactured without dividing the components of the die or molding at least one of the body, first plate portion, and second plate portion in a separate die. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2021 / 225049 Summary of the Invention

[0006] A method for producing a powder compact according to the present disclosure includes filling a space defined by a die hole and a lower punch in a die with powder, and compressing the powder filled in the space with the lower punch and an upper punch to form a powder compact. The powder compact includes a prismatic body having a first bottom surface, a second bottom surface opposite the first bottom surface, and multiple side surfaces, a first plate portion provided on the first bottom surface, and a second plate portion provided on the second bottom surface. The multiple side surfaces include a front surface and a rear surface arranged parallel to each other along an axis of the body, a left side surface connecting the front surface and the rear surface, and a right side surface connecting the front surface and the rear surface. The first plate portion has a first protrusion protruding from the body in a direction perpendicular to the axis, a first front surface and a first rear surface arranged parallel to each other along the axis, a first left side surface connecting the first front surface and the first rear surface, and a first right side surface connecting the first front surface and the first rear surface. The first left side surface and the first right side surface have inclined regions such that the distance between them increases from the first front surface to the first rear surface. The second plate portion has a second protrusion protruding from the body in a direction perpendicular to the axis, a second front surface and a second rear surface arranged parallel to each other along the axis, a second left side surface connecting the second front surface and the second rear surface, and a second right side surface connecting the second front surface and the second rear surface. The upper punch has a main lower surface that forms the left side surface of the body, a first sub-lower surface that forms the first left side surface of the first plate portion, and a second sub-lower surface that forms the second left side surface of the second plate portion. The lower punch has a main upper surface that forms the right side surface of the body, a first sub-upper surface that forms the first right side surface of the first plate portion, and a second sub-upper surface that forms the second right side surface of the second plate portion. [Brief explanation of the drawings]

[0007] [Figure 1]FIG. 1 is a perspective view of a powder compact obtained by the method for producing a powder compact according to the first embodiment, as viewed obliquely from the front. [Figure 2] FIG. 2 is a perspective view of a powder compact obtained by the method for producing a powder compact according to the first embodiment, as viewed obliquely from behind. [Figure 3] FIG. 3 is a cross-sectional view of a die used in the method for producing a powder compact according to the first embodiment. [Figure 4] FIG. 4 is a longitudinal cross-sectional view taken along a direction W, showing a body compressed in a mold in the method for producing a powder compact according to the first embodiment. [Figure 5] FIG. 5 is a vertical cross-sectional view taken along the direction W, showing a first plate portion of a powder compact compressed by a die in the method for producing a powder compact according to the first embodiment. [Figure 6] FIG. 6 is a vertical cross-sectional view taken along a direction D, showing a green compact placed in a die during compacting in the method for producing a green compact according to the first embodiment. [Figure 7] FIG. 7 is a plan view showing a stator core for an axial gap motor made of the green compact shown in FIG. [Figure 8] FIG. 8 is a vertical cross-sectional view of an axial gap motor using the stator core of FIG. [Figure 9] FIG. 9 is a vertical cross-sectional view of another axial gap motor using the stator core of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Problem to be solved by this disclosure] It is desirable to mold a green compact having a protrusion as described in the background art so as to minimize chipping or cracking. In the above-described green compact molding method, when a core piece, which is the green compact, forms an annular stator core, the surface that will become the inner peripheral surface is pressed by a lower punch, and the surface that will become the outer peripheral surface is pressed by an upper punch. Because the surface that will become the inner peripheral surface is narrower than the surface that will become the outer peripheral surface, the width of the lower punch is also narrower than the width of the upper punch. In other words, when the green compact is removed from the die, the green compact is locally pressed by the lower punch. As a result, shear stress acts on the green compact, and depending on the shape or dimensions of the green compact, chipping or cracking may occur near the boundary between the area pressed by the lower punch and the area not pressed by the lower punch.

[0009] An object of the present disclosure is to provide a method for manufacturing a powder compact that can reduce the occurrence of damage to the powder compact. Another object of the present disclosure is to provide a method for manufacturing a stator core using the powder compact obtained by the above-mentioned method for manufacturing a powder compact.

[0010] [Effects of this disclosure] The method for producing a powder compact according to the present disclosure can reduce the occurrence of damage to the powder compact.

[0011] [Description of the embodiments of the present disclosure] Embodiments of the present disclosure will be listed and described below.

[0012] <1> A method for producing a powder compact according to an embodiment includes the steps of filling a space defined by a die hole and a lower punch in a die with powder, and compressing the powder filled in the space with the lower punch and the upper punch to form a powder compact. The powder compact includes a prismatic body having a first bottom surface, a second bottom surface opposite the first bottom surface, and multiple side surfaces, a first plate portion provided on the first bottom surface, and a second plate portion provided on the second bottom surface. The multiple side surfaces include a front surface and a rear surface arranged parallel to each other along an axis of the body, a left side surface connecting the front surface and the rear surface, and a right side surface connecting the front surface and the rear surface. The first plate portion has a first protrusion protruding from the body in a direction perpendicular to the axis, a first front surface and a first rear surface arranged parallel to each other along the axis, a first left side surface connecting the first front surface and the first rear surface, and a first right side surface connecting the first front surface and the first rear surface. The first left side surface and the first right side surface have inclined regions such that the distance between them increases from the first front surface to the first rear surface. The second plate portion has a second protrusion protruding from the body in a direction perpendicular to the axis, a second front surface and a second rear surface arranged parallel to each other along the axis, a second left side surface connecting the second front surface and the second rear surface, and a second right side surface connecting the second front surface and the second rear surface. The upper punch has a main lower surface that forms the left side surface of the body, a first sub-lower surface that forms the first left side surface of the first plate portion, and a second sub-lower surface that forms the second left side surface of the second plate portion. The lower punch has a main upper surface that forms the right side surface of the body, a first sub-upper surface that forms the first right side surface of the first plate portion, and a second sub-upper surface that forms the second right side surface of the second plate portion.

[0013] The above-described method for manufacturing a green compact reduces damage to the green compact, such as chipping or cracking. The green compact obtained by this manufacturing method has a shape with a first protrusion and a second protrusion protruding from the body. Despite this shape, the green compact can be molded by pressing the left side, first left side, second left side, right side, first right side, and second right side of the green compact with an upper punch and a lower punch. During molding, the first and second plate portions having the protrusions are arranged such that the left side, first left side, second left side, right side, first right side, and second right side are located above and below the die hole. The front, first front side, second front side, rear side, first rear side, and second rear side are located above and below the die hole. The green compact can be compressed across its entire width by the upper and lower punches. Since the lower punch does not locally press the green compact when it is removed from the die, chipping or cracking of the green compact can be reduced compared to the method for molding a green compact disclosed in Patent Document 1.

[0014] <2> the above <1> In the method for manufacturing a powder compact described in 1, the left side surface and the right side surface may be inclined such that the distance between them increases from the front surface to the rear surface.

[0015] According to the above-described method for manufacturing a green compact, a green compact can be obtained in which the left and right sides of the body are inclined. If the body, as well as the first plate, has an inclined shape, when a coil is provided around the body, it is easy to match the outer shape of the coil with the outer shape of the first plate. In other words, when a magnetic component such as a stator core of a motor is formed using a green compact, the dead space of the motor can be reduced.

[0016] <3> the above <1> or <2> In the method for manufacturing a powder compact described in , the second left side surface and the second right side surface may have an inclined region such that the distance between them increases from the second front surface toward the second rear surface.

[0017] According to the above-described method for manufacturing a green compact, a green compact can be obtained in which not only the first plate portion but also the second left side surface and the second right side surface of the second plate portion are inclined. If the second plate portion also has an inclined surface, the shape of the second plate portion can be easily matched to the shape of the first plate portion. When a coil is provided around the outer periphery of the body, both ends of the coil can be easily held uniformly between the first plate portion and the second plate portion.

[0018] <4> the above <1> from <3> In any one of the methods for manufacturing a powder compact described above, the first protrusion may protrude from the body over an entire circumference around the axis.

[0019] According to the above-described method for manufacturing a powder compact, a powder compact having a shape in which the first protrusion protrudes along the entire circumference of the body can be obtained. When a coil is provided on the outer periphery of the body, the entire circumference of the first end of the coil can be abutted against the first protrusion.

[0020] <5> the above <1> from <4> In any one of the methods for producing a powder compact described above, the second protrusion may protrude from the body over an entire circumference around the axis.

[0021] According to the above-described method for manufacturing a powder compact, a powder compact can be obtained in which the second protrusion protrudes along the entire circumference of the body. When a coil is provided on the outer periphery of the body, the entire circumference of the second end of the coil can be abutted against the second protrusion.

[0022] <6> the above <1> from <5> In any one of the methods for producing a green compact described above, the powder may be a magnetic powder.

[0023] According to the above-described method for producing a powder compact, a powder core such as a stator core of a motor or a core of a reactor can be obtained by forming a powder compact from magnetic powder.

[0024] <7> The method for manufacturing a stator core according to the embodiment is as described above. <1> from <6> and forming an annular stator core by arranging the plurality of powder compacts so that the first left side surface and the first right side surface of adjacent powder compacts face each other in parallel.

[0025] According to the above-described method for manufacturing a stator core, a plurality of the obtained green compacts can be combined into an annular shape to obtain a stator core for, for example, an axial gap motor.

[0026] <8> The manufacturing method of the axial gap motor according to the embodiment includes the steps of: <7> and combining the stator core with a rotor.

[0027] [Details of the embodiments of the present disclosure] A method for manufacturing a powder compact according to an embodiment of the present disclosure will be described below. Prior to describing the method for manufacturing a powder compact, the configuration of the powder compact obtained by this manufacturing method will be described. Next, a method for manufacturing a powder compact will be described. Finally, a stator core using the powder compact, a method for manufacturing the same, and an axial gap motor including the stator core will be described. The same reference numerals in the figures indicate the same or equivalent parts. The sizes of the components shown in each drawing are expressed for the purpose of clarifying the description and do not necessarily represent the actual dimensions.

[0028] <Powder compact> The above-mentioned green compact will be described as an example of a core piece for constructing a stator core for an axial gap motor. The stator core is formed into an annular shape by a plurality of core pieces. As shown in FIGS. 1 and 2, the powder compact 1 includes a body 10, a first plate portion 20, and a second plate portion 30. The body 10 is shaped like a rectangular pillar. The first plate portion 20 is provided at a first end portion of the body 10 in the axial direction. The second plate portion 30 is provided at a second end portion of the body 10 in the axial direction. The first plate portion 20 has a first protrusion 20F, and the second plate portion 30 has a second protrusion 30F. The body 10, the first plate portion 20, and the second plate portion 30 are integrally molded. "Integratedly molded" means that the body 10, the first plate portion 20, and the second plate portion 30 are connected in series by molding, without being mechanically connected using screws or the like or bonded with an adhesive or the like.

[0029] The directions of the powder compact 1 are as follows: The directions of the powder compact 1 are indicated by arrows in Figures 1, 2, and 4 to 6. Figure 7 is referenced for the explanation of the stator core. The direction along the diameter of the stator core 70 in the powder compact 1 is defined as direction X. The direction along the axis of the stator core 70 in the powder compact 1 is defined as direction Z. Direction Z is the direction along the axis of the body 10. The direction perpendicular to both the direction X and the direction Z of the powder compact 1 is defined as the direction Y. In the following description, the inside of the annular stator core is referred to as the front and the outside as the rear, and left and right are defined when viewed from front to rear; however, the outside of the stator core may be referred to as the front and the inside as the rear, and left and right may be defined when viewed from front to rear. The structure of the powder compact will be described in detail below.

[0030] [body] The body 10 is a columnar member extending in the Z direction. Whether the powder compact 1 is used to form a double-stator, single-rotor stator core 70 of an axial gap motor 9 or a single-stator, double-rotor stator core 70 of an axial gap motor 9, the body 10 forms teeth. As shown in FIG. 8, a double-stator, single-rotor axial gap motor 9 is assembled so that one rotor 90 is sandwiched between two stators 7. As shown in FIG. 9, a single-stator, double-rotor axial gap motor 9a is assembled so that one stator 7a is sandwiched between two rotors 90a. Hereinafter, for convenience of explanation, a double-stator, single-rotor configuration may be referred to as DS / SR, and a single-stator, double-rotor configuration may be referred to as SS / DR.

[0031] The body 10 has a prismatic shape. The prismatic shape is, for example, a rectangular prism whose cross-sectional shape when cut along a plane perpendicular to the Z direction is a square. The term "quadrilateral" here refers not only to a strict geometrical quadrangle but also to a shape whose cross-sectional shape is formed by connecting four corners. In other words, it also includes a quadrangle whose cross-sectional shape has been modified in detail, such as a quadrangle whose four corners are rounded by chamfering or whose four corners are linearly chamfered. Quadrilaterals include rectangles and trapezoids. Rectangles include oblongs and squares. Trapezoids include trapezoids whose legs are the same length, such as isosceles trapezoids, as well as right-angled trapezoids. The cross-sectional shape may be uniform in the Z direction. These points also apply to the first plate portion 20 and the second plate portion 30, which will be described later.

[0032] As shown in Figures 1, 2, and 4, one example of the shape of the body 10 is a trapezoidal columnar shape, in which the cross-sectional shape is trapezoidal. The cross-sectional shape of the body 10 is uniform in the Z direction. If the body 10 has a trapezoidal columnar shape, it is easy to configure an annular stator core and ensure a large magnetic path area. It is also easy to reduce the dead space in the powder compact 1, making it easy to construct a stator 7 with a high space factor.

[0033] As shown in FIGS. 1 and 2 , the body 10 has a peripheral surface that connects the first plate portion 20 and the second plate portion 30. The peripheral surface includes a front surface 11, a rear surface 12, a right side surface 13, and a left side surface 14. The front surface 11, the rear surface 12, the right side surface 13, and the left side surface 14 are all flat. The front surface 11 and the rear surface 12 are aligned along the axis of the body 10. The front surface 11 and the rear surface 12 are aligned along direction Z. The front surface 11 and the rear surface 12 are also aligned along direction Y. The front surface 11 and the rear surface 12 face each other parallel to one another. An example of the shape of the front surface 11 and the rear surface 12 is rectangular. The direction from the front surface 11 to the rear surface 12 is the direction along the diameter of the stator core 70. The front surface 11 is closer to the axis of the stator core 70 than the rear surface 12. The dimension of the front surface 11 along direction Y is smaller than the dimension of the rear surface 12 along direction Y. The area of ​​the front surface 11 is smaller than the area of ​​the rear surface 12 .

[0034] The right side surface 13 connects the right sides of the front surface 11 and the rear surface 12. The left side surface 14 connects the left sides of the front surface 11 and the rear surface 12. Both the right side surface 13 and the left side surface 14 have a rectangular shape and the same area. The right side surface 13 and the left side surface 14 are inclined surfaces that intersect non-orthogonally with respect to the direction X. The distance between the right side surface 13 and the left side surface 14 increases as the distance from the front surface 11 to the rear surface 12 increases. The right side surface 13 and the left side surface 14 have the same inclination angle with respect to the direction X. In other words, the right side surface 13 and the left side surface 14 are disposed symmetrically with respect to a line segment along the direction X. The intersection angle between the extension of the right side surface 13 and the extension of the left side surface 14 is, for example, 5° to 40°. If the body 10 also has an inclined surface, when a coil is provided on the outer periphery of the body 10, it is easy to align the outer shape of the coil with the outer shape of the first plate portion 20.

[0035] [First board section] 1, 2, 8, and 9, the first plate portion 20 is provided at a first end portion in the Z direction of the body 10. When the powder compact 1 is used to form a stator core 70 provided in an axial gap motor 9 of DS / SR type, the first plate portion 20 forms a yoke. When the powder compact 1 is used to form a stator core 70 provided in an axial gap motor 9a of SS / DR type, the first plate portion 20a forms a flange portion.

[0036] An example of the shape of the first plate portion 20 is a trapezoidal plate. The trapezoidal plate shape is a trapezoidal cross section obtained by cutting the first plate portion 20 along a plane perpendicular to the Z direction. The cross section is uniform in the Z direction. Note that when the powder compact 1 is used to form a stator core 70 provided in an SS / DR type axial gap motor 9a, the shape of the first plate portion 20a may be a rectangular plate.

[0037] The first plate portion 20 has a first front surface 21, a first rear surface 22, a first right side surface 23, a first left side surface 24, and a first end surface 25. The first front surface 21, the first rear surface 22, the first right side surface 23, the first left side surface 24, and the first end surface 25 are all flat. The first front surface 21 and the first rear surface 22 are aligned along the axis of the body 10. The first front surface 21 and the first rear surface 22 are aligned along direction Z. The first front surface 21 and the first rear surface 22 are also aligned along direction Y. The first front surface 21 and the first rear surface 22 face each other parallel to one another. An example of the shape of the first front surface 21 and the first rear surface 22 is a flat rectangular shape. The direction from the first front surface 21 to the first rear surface 22 is along the diameter of the stator core 70. The first front surface 21 is located closer to the axis of the stator core 70 than the first rear surface 22. The dimension of the first front surface 21 along the direction Y is smaller than the dimension of the first rear surface 22 along the direction Y. The area of ​​the first front surface 21 is smaller than the area of ​​the first rear surface 22.

[0038] The first right side surface 23 connects the right sides of the first front surface 21 and the first rear surface 22. The first left side surface 24 connects the left sides of the first front surface 21 and the first rear surface 22. An example of the first right side surface 23 and the first left side surface 24 is that they both have a rectangular shape and the same area. An example of the first right side surface 23 and the first left side surface 24 is an inclined surface that intersects non-orthogonally with respect to the direction X. The distance between the first right side surface 23 and the first left side surface 24 increases as the distance from the first front surface 21 to the first rear surface 22 increases. The inclination angle of the first right side surface 23 and the first left side surface 24 with respect to the direction X is the same. In other words, the first right side surface 23 and the first left side surface 24 are arranged symmetrically with respect to a line segment along the direction X. A first plate portion 20 having such an inclined surface facilitates the production of a fan-shaped powder compact 1. At least one end of the inclined surfaces of the first right side surface 23 and the first left side surface 24 in the direction X may include a region parallel to the direction X. The parallel regions prevent the corners of the first plate portion 20 from becoming acute. The intersection angle between the extended surface of the first right side surface 23 and the extended surface of the first left side surface 24 is, for example, 5° to 40°. The intersection angle may be the same as or different from the intersection angle between the extended surface of the right side surface 13 and the extended surface of the left side surface 14. In one example of the powder compact 1, the intersection angle between the extended surface of the first right side surface 23 and the extended surface of the first left side surface 24 is the same as the intersection angle between the extended surface of the right side surface 13 and the extended surface of the left side surface 14. The first right side surface 23 and the right side surface 13 are parallel. The first left side surface 24 and the left side surface 14 are parallel. The first end surface 25 is a surface perpendicular to the direction Z. The first end surface 25 constitutes, for example, the bottom surface of the powder compact 1.

[0039] The first plate portion 20 has a first protrusion 20F. The first protrusion 20F protrudes outward from the circumferential surface of the body 10. The first protrusion 20F may protrude outward from the circumferential surface of the body 10 at a portion of the circumferential surface of the body 10. The first protrusion 20F may protrude outward from the circumferential surface of the body 10 over the entire periphery of the circumferential surface of the body 10. In one example, the first protrusion 20F protrudes outward from the circumferential surface of the body 10 over the entire periphery of the circumferential surface of the body 10. The first protrusion 20F is formed in a trapezoidal frame shape. The circumferential surface of this trapezoidal frame-shaped first protrusion 20F forms a first front surface 21, a first rear surface 22, a first right side surface 23, and a first left side surface 24. With this configuration, when a coil is provided on the outer periphery of the body 10, the entire periphery of the first end of the coil can be abutted against the first protrusion 20F. Unlike this example, first protrusion 20F may be configured to protrude outward from the circumferential surface of at least one of front surface 11, rear surface 12, right side surface 13, and left side surface 14 of body 10. In the first protrusion 20F that protrudes outward from a portion of the circumferential surface of body 10, portions of first front surface 21, first rear surface 22, first right side surface 23, and first left side surface 24 may be flush with a portion of the circumferential surface of body 10.

[0040] The protruding length of the first protrusions 20F from the body 10 can be selected as appropriate. When the powder compact 1 is used to form a stator core 70 included in an axial gap motor 9 of DS / SR type, the protruding length of the first protrusions 20F from the circumferential surface of the body 10 is longer than the protruding length of the second protrusions 30F (described later) from the body 10. With this configuration, when a ring-shaped stator core is formed by arranging multiple core pieces in parallel, the first protrusions 20F that form yokes can be brought into contact with each other, and gaps can be provided between the second protrusions 30F that form flanges. When the powder compact 1 is used to form a stator core 70 included in an axial gap motor 9a of SS / DR type, the protruding length of the first protrusions 20F may be the same as the protruding length of the second protrusions 30F (described later) from the circumferential surface of the body 10. The protruding length refers to the length along a direction perpendicular to the circumferential surface of the body 10. When the circumferential surface is curved, the protruding length refers to the length along a normal to the curved surface.

[0041] [Second board] 1, 2, 8, and 9, the second plate portion 30 is provided at a second end portion in direction Z of the body 10. Whether the powder compact 1 is used to construct the stator core 70 provided in the DS / SR type axial gap motor 9 or the SS / DR type axial gap motor 9a, the second plate portions 30, 30a form a flange portion.

[0042] An example of the shape of the second plate portion 30 is a trapezoidal plate. The trapezoidal plate shape is a trapezoidal cross section obtained by cutting the second plate portion 30 along a plane perpendicular to the Z direction. The cross section is uniform in the Z direction. Note that when the powder compact 1 is used to form a stator core 70 provided in an SS / DR type axial gap motor 9a, the shape of the second plate portion 30a may be a rectangular plate.

[0043] The second plate portion 30 has a second front surface 31, a second rear surface 32, a second right side surface 33, a second left side surface 34, and a second end surface 35. The second front surface 31, the second rear surface 32, the second right side surface 33, the second left side surface 34, and the second end surface 35 are all flat. The second front surface 31 and the second rear surface 32 are aligned along the axis of the body 10. The second front surface 31 and the second rear surface 32 are aligned along direction Z. The second front surface 31 and the second rear surface 32 are also aligned along direction Y. The second front surface 31 and the second rear surface 32 face each other parallel to one another. The second front surface 31 is flush with the first front surface 21. The second rear surface 32 is flush with the first rear surface 22. The second front surface 31 and the first front surface 21 do not have to be flush with each other. The second rear surface 32 and the first rear surface 22 do not have to be flush with each other. The second front surface 31 is not flush with the front surface 11. The second rear surface 32 is not flush with the rear surface 12. The second front surface 31 may be flush with the front surface 11. The second rear surface 32 may be flush with the rear surface 12. An example of the shape of the second front surface 31 and the second rear surface 32 is a flat rectangular shape. In an example of the second plate portion 30, the thickness (length along the direction Z) of the second front surface 31 and the second rear surface 32 is thinner than the thickness of the first front surface 21 and the first rear surface 22. However, the thickness of the second front surface 31 and the second rear surface 32 may be the same as the thickness of the first front surface 21 and the first rear surface 22. The direction from the second front surface 31 to the second rear surface 32 is the direction along the diameter of the stator core 70. The second front surface 31 is closer to the axis of the stator core 70 than the second rear surface 32. The dimension of the second front surface 31 along the direction Y is smaller than the dimension of the second rear surface 32 along the direction Y. The area of ​​the second front surface 31 is smaller than the area of ​​the second rear surface 32.

[0044] The second right side surface 33 connects the right sides of the second front surface 31 and the second rear surface 32. The second left side surface 34 connects the left sides of the second front surface 31 and the second rear surface 32. An example of the second right side surface 33 and the second left side surface 34 is that they both have a rectangular shape and the same area. An example of the second right side surface 33 and the second left side surface 34 is an inclined surface that intersects non-orthogonally with the direction X. The distance between the second right side surface 33 and the second left side surface 34 increases as the distance from the second front surface 31 to the second rear surface 32 increases. The second right side surface 33 and the second left side surface 34 have the same inclination angle with respect to the direction X. The second right side surface 33 and the second left side surface 34 are arranged symmetrically with respect to a line segment along the direction X. A second plate portion 30 having such an inclined surface facilitates the production of a fan-shaped powder compact 1. At least one end of the inclined surfaces of the second right side surface 33 and the second left side surface 34 in the direction X may have a region parallel to the direction X. By having a region parallel to the direction X, the corner of the second plate portion 30 at the second rear surface 32 can be prevented from becoming acute. By having regions parallel to the direction X at both ends, the difference in compression ratio during manufacturing between the region including the second front surface 31 of the second plate portion 30 and the region including the second rear surface 32 can be reduced. The intersection angle between the extended surface of the second right side surface 33 and the extended surface of the second left side surface 34 is, for example, 5° to 40°. This intersection angle may be the same as or different from the intersection angle between the extended surface of the right side surface 13 and the extended surface of the left side surface 14. In one example of the powder compact 1, the intersection angle between the extended surface of the second right side surface 33 and the extended surface of the second left side surface 34 is the same as the intersection angle between the extended surface of the right side surface 13 and the extended surface of the left side surface 14. The second right side surface 33 and the right side surface 13 are parallel. The second left side surface 34 and the left side surface 14 are parallel. The second right side surface 33 does not have to be parallel to the first right side surface 23. The second right side surface 33 does not have to be flush with the first right side surface 23. The second left side surface 34 does not have to be parallel to the first left side surface 24. The second left side surface 34 does not have to be flush with the first left side surface 24. The second end surface 35 is a surface perpendicular to the direction Z. The second end surface 35 constitutes, for example, the top surface of the powder compact 1.

[0045] The second plate portion 30 has a second protrusion 30F. The second protrusion 30F protrudes outward from the circumferential surface of the body 10. The second protrusion 30F may protrude outward from the circumferential surface of the body 10 at a portion of the circumferential surface of the body 10. The second protrusion 30F may protrude outward from the circumferential surface of the body 10 over the entire periphery of the circumferential surface of the body 10. In one example, the second protrusion 30F protrudes outward from the circumferential surface of the body 10 over the entire periphery of the circumferential surface of the body 10. The second protrusion 30F is formed in a trapezoidal frame shape. The circumferential surface of the trapezoidal frame-shaped second protrusion 30F forms a second front surface 31, a second rear surface 32, a second right side surface 33, and a second left side surface 34. With this configuration, when a coil is provided on the outer periphery of the body 10, the entire periphery of the second end of the coil can be abutted against the second protrusion 30F. Unlike this example, second protrusion 30F may be configured to protrude outward from the circumferential surface of at least one of front surface 11, rear surface 12, right side surface 13, and left side surface 14 of body 10. In the case of second protrusion 30F that protrudes outward from a portion of the circumferential surface of body 10, portions of second front surface 31, second rear surface 32, second right side surface 33, and second left side surface 34 may be flush with a portion of the circumferential surface of body 10.

[0046] [Material] The green compact 1 is composed of a powder containing magnetic powder. The magnetic powder is composed of a plurality of magnetic particles. An example of the magnetic particles is soft magnetic particles. An example of the green compact 1 is obtained by compression molding soft magnetic powder containing a plurality of soft magnetic particles. The soft magnetic particles include a plurality of iron-based particles made of pure iron or an iron-based alloy. Pure iron refers to iron (Fe) with a purity of 99% by mass or more. The iron-based alloy contains, for example, at least one of silicon (Si) and aluminum (Al), with the remainder consisting of Fe and unavoidable impurities. The iron-based alloy may be one selected from the group consisting of an Fe-Si-based alloy, an Fe-Al-based alloy, and an Fe-Si-Al-based alloy. An example of an Fe-Si-based alloy is silicon steel. An example of an Fe-Si-Al-based alloy is sendust. The green compact 1 may contain a plurality of soft magnetic particles made of different materials. Because the iron-based particles are relatively soft, the soft magnetic particles are easily deformed during molding of the green compact 1. This results in a high density of the green compact 1 and excellent dimensional accuracy. The green compact 1 is composed of an aggregate of multiple coated soft magnetic particles with an insulating coating on the surface of the soft magnetic particles, thereby reducing loss. The green compact 1 may be formed by compression molding a coated soft magnetic powder containing multiple coated soft magnetic particles. If an insulating coating is formed, it is easy to ensure electrical insulation between the particles by the insulating coating. This makes it possible to reduce iron loss in the green compact 1 due to eddy current loss. The soft magnetic particles are as described above. Examples of insulating coatings include phosphate coatings and silica coatings.

[0047] Relative Density The relative density of the powder compact 1 may be 85% or more. A powder compact 1 with a relative density of 85% or more has excellent magnetic properties such as saturation magnetic flux density, and mechanical properties such as strength. The relative density of the powder compact 1 may be 90% or more, or 93% or more. The relative density of the powder compact 1 may be less than 100%. "Relative density" refers to the ratio (%) of the actual density of the powder compact 1 to the true density of the soft magnetic particles that make up the powder compact 1.

[0048] The "relative density of a powder core" refers to the ratio (%) of the density of an actual powder core to the true density of the powder core. The relative density of a powder core can be calculated by [(actual powder core density / true density of powder core) × 100]. The density of an actual powder core can be calculated by immersing the powder core in oil to impregnate it with oil and then calculating [oil-impregnated density × (mass of powder core before oil impregnation / mass of powder core after oil impregnation)]. The oil-impregnated density is (mass of powder core after oil impregnation / volume of powder core after oil impregnation). The density of an actual powder core can be calculated by (mass of powder core before oil impregnation / volume of powder core after oil impregnation). The volume of a powder core after oil impregnation can typically be measured using the liquid displacement method. The true density of a powder core is the theoretical density assuming no voids inside.

[0049] [Relative Density Difference] The difference in relative density between the member with the highest relative density and the member with the lowest relative density among the body 10, the first plate portion 20, and the second plate portion 30 may be 5.0% or less. A powder compact 1 with a small difference in relative density has substantially uniform physical properties, such as magnetic properties, within the powder compact 1. It is expected that the smaller the difference in relative density, the more uniform the physical properties will be. The difference in relative density may be 4.0% or less, or 3.0% or less.

[0050] First Embodiment [Method for manufacturing powder compact] [Mold] The above-described powder compact 1 is molded using a mold 4 shown in FIGS. 3 to 6. First, the mold 4 will be described with reference to FIGS. 3 to 6. Then, each step of the manufacturing method will be described. The mold 4 includes a die 40, an upper punch 50, and a lower punch 60. The die 40 has a vertically extending die hole 40h. The upper punch 50 is configured to be able to move up and down freely within the die hole 40h. The lower punch 60 is configured to be able to move up and down freely within the die hole 40h.

[0051] The directions of the mold 4 are as follows: The directions of the mold 4 are indicated by arrows in Figs. The vertical direction of the die 4 is defined as direction H. Direction H is the direction along the axis of the die hole 40h. Direction H is also the direction along the axes of the upper punch 50 and the lower punch 60. During compaction, direction Y of the powder compact 1 is the same as direction H of the die 4. When looking at the die hole 40h from top to bottom, the direction from the first sub-hole 42h that forms the first plate portion 20 to the second sub-hole 43h that forms the second plate portion 30, or the opposite direction, is defined as direction D. During molding, direction Z of the powder compact 1 is the same direction as direction D of the die 4. When looking at the die hole 40h from top to bottom, the direction perpendicular to or opposite to the direction D is defined as direction W. During compaction, direction X of the powder compact 1 is the same as direction W of the die 4.

[0052] The dimensions of the die 4 or the powder compact 1 in the die 4 along each direction are as follows: The dimension along direction H is the height. The dimension along the direction W is the width. The dimension along direction D is the depth.

[0053] (Thailand) The die 40 has a die hole 40h. The die hole 40h is a through hole that opens to the top and bottom surfaces of the die 40. An upper punch 50 is fitted into the upper part of the die hole 40h. A lower punch 60 is fitted into the lower part of the die hole 40h. The cross-sectional shape of the die hole 40h corresponds to the shape of the powder compact 1. This cross-sectional shape is the shape of the die hole 40h in a cross section perpendicular to the axis of the die hole 40h.

[0054] As shown in Figure 3, the die hole 40h has a main hole 41h, a first sub-hole 42h, and a second sub-hole 43h. The main hole 41h is the region of the die hole 40h that forms the body 10. The first sub-hole 42h is the region of the die hole 40h that forms the first plate portion 20. The second sub-hole 43h is the region of the die hole 40h that forms the second plate portion 30. The boundary between the main hole 41h and the first sub-hole 42h is indicated by a two-dot chain line. The boundary between the main hole 41h and the second sub-hole 43h is indicated by a two-dot chain line.

[0055] The first sub-hole 42h is connected to a first end of the main hole 41h in the direction D. The second sub-hole 43h is connected to a second end of the main hole 41h in the direction D. The main hole 41h, the first sub-hole 42h, and the second sub-hole 43h are connected to one another.

[0056] The cross-sectional shape of the main hole 41h is rectangular. The cross-sectional shape of the first sub-hole 42h is a flattened rectangle. The cross-sectional shape of the second sub-hole 43h is also a flattened rectangle. Here, the rectangular shape includes not only the geometric rectangle as described above, but also rectangles with rounded corners. The rectangle includes oblong and square shapes.

[0057] The front surface 11 is formed by the inner surface 41f of the main hole 41h perpendicular to the direction W. The rear surface 12 is formed by the inner surface 41b of the main hole 41h perpendicular to the direction W. The first front surface 21 is formed by the inner surface 42f of the first sub-hole 42h perpendicular to the direction W. The first rear surface 22 is formed by the inner surface 42b of the first sub-hole 42h perpendicular to the direction W. The second front surface 31 is formed by the inner surface 43f of the second sub-hole 43h perpendicular to the direction W. The second rear surface 32 is formed by the inner surface 43b of the second sub-hole 43h perpendicular to the direction W. The first end surface 25 is formed by the end surface 42e of the first sub-hole 42h perpendicular to the direction D. The second end surface 35 is formed by the end surface 43e of the second sub-hole 43h perpendicular to the direction D.

[0058] In the example shown in FIG. 3, the depths of the main hole 41h, the first subhole 42h, and the second subhole 43h are such that the main hole 41h has the largest depth, the first subhole 42h has the next largest depth, and the second subhole 43h has the smallest depth. In this example, the widths of the main hole 41h, the first subhole 42h, and the second subhole 43h are such that the first subhole 42h has the largest width, the second subhole 43h has the largest width, and the main hole 41h has the smallest width. In the example shown in FIG. 3, the cross-sectional shape of the die hole 40h is H-shaped. Typically, the depth of the main hole 41h is larger than the depths of the first subhole 42h and the second subhole 43h. The depths and widths of the main hole 41h, the first subhole 42h, and the second subhole 43h can be selected arbitrarily without being restricted by this dimensional relationship.

[0059] 3, first sub-holes 42h protrude from both sides of the main hole 41h in the direction W. Second sub-holes 43h protrude from both sides of the main hole 41h in the direction W. However, the first sub-hole 42h may protrude from only one side of the main hole 41h in the direction W. The second sub-hole 43h may protrude from only one side of the main hole 41h in the direction W.

[0060] (upper punch) The upper punch 50 can be driven in the vertical direction relative to the powder compact 1. As shown in FIG. 6 , the upper punch 50 includes a main upper punch 51, a first upper punch 52, and a second upper punch 53. The main upper punch 51 is fitted into the main hole 41h. The first upper punch 52 is fitted into the first sub-hole 42h. The second upper punch 53 is fitted into the second sub-hole 43h. The shape and dimensions of the main upper punch 51 correspond to the shape and dimensions of the main hole 41h. The shape and dimensions of the first upper punch correspond to the shape and dimensions of the first sub-hole 42h. The shape and dimensions of the second upper punch 53 correspond to the shape and dimensions of the second sub-hole 43h. The main upper punch 51 protrudes downward most, followed by the second upper punch 53 and first upper punch 52. The length of protrusion of the first protrusion 20F and the second protrusion 30F from the body 10 can be adjusted by adjusting the amount of downward protrusion of the main upper punch 51, the first upper punch 52, and the second upper punch 53.

[0061] The upper punch 50 has a main lower surface 51b, a first sub-lower surface 52b, and a second sub-lower surface 53b. The main upper punch 51 has the main lower surface 51b. As shown in FIG. 4, the main lower surface 51b forms the left side surface 14 of the body 10. The first upper punch 52 has a first sub-lower surface 52b. As shown in FIG. 5, the first sub-lower surface 52b forms the first left side surface 24. The second upper punch 53 has a second sub-lower surface 53b. As shown in FIG. 6, the second sub-lower surface 53b forms the second left side surface 34. The main lower surface 51b is formed as an inclined surface corresponding to the left side surface 14. The first sub-lower surface 52b is formed as an inclined surface corresponding to the first left side surface 24. The second sub-lower surface 53b is formed as an inclined surface corresponding to the second left side surface 34. These inclined surfaces are arranged so as to intersect non-orthogonally with the direction W. At least one end of each of these inclined surfaces in the direction W may have a surface extending along the direction W. The corner formed by the inclined lower surface of the upper punch 50 and the surface along the axis of the upper punch 50 does not become an acute angle, and damage to the upper punch 50 can be reduced.

[0062] The main upper punch 51, first upper punch 52, and second upper punch 53 used in this example are all configured as a single unit. Two punches selected from the main upper punch 51, first upper punch 52, and second upper punch 53 may be integrated, and the remaining punch may be a punch independent of the two integrated punches. In particular, when the step between the left side surface 14 and the first left side surface 24 and the step between the right side surface 13 and the second right side surface 33 are large, the main upper punch 51 and the first upper punch 52 may be separate punches. Alternatively, the main upper punch 51 and the second upper punch 53 may be separate punches. When the upper punch 50 is divided into multiple punches, multiple boundary lines are indicated by two-dot chain lines in FIG. 6.

[0063] (lower punch) The lower punch 60 can be driven in the vertical direction relative to the powder compact 1. As shown in FIG. 6 , the lower punch 60 includes a main lower punch 61, a first lower punch 62, and a second lower punch 63. The main lower punch 61 is fitted into the main hole 41h. The first lower punch 62 is fitted into the first sub-hole 42h. The second lower punch 63 is fitted into the second sub-hole 43h. The shape and dimensions of the main lower punch 61 correspond to the shape and dimensions of the main hole 41h. The shape and dimensions of the first lower punch 62 correspond to the shape and dimensions of the first sub-hole 42h. The shape and dimensions of the second lower punch 63 correspond to the shape and dimensions of the second sub-hole 43h. The main lower punch 61 protrudes most upward. The second lower punch 63 and the first lower punch 62 protrude upward in sequence. The length of protrusion of the first protrusion 20F and the second protrusion 30F from the body 10 can be adjusted by adjusting the amount of upward protrusion of the main lower punch 61, the first lower punch 62, and the second lower punch 63.

[0064] The lower punch 60 has a main upper surface 61t, a first sub-upper surface 62t, and a second sub-upper surface 63t. The main lower punch 61 has the main upper surface 61t. As shown in FIG. 4, the main upper surface 61t forms the right side surface 13 of the body 10. The first lower punch 62 has a first sub-upper surface 62t. As shown in FIG. 5, the first sub-upper surface 62t forms the first right side surface 23. The second lower punch 63 has a second sub-upper surface 63t. As shown in FIG. 6, the second sub-upper surface 63t forms the second right side surface 33. The main upper surface 61t is formed as an inclined surface corresponding to the right side surface 13. The first sub-upper surface 62t is formed as an inclined surface corresponding to the first right side surface 23. The second sub-upper surface 63t is formed as an inclined surface corresponding to the second right side surface 33. These inclined surfaces are surfaces that are arranged to intersect the direction W non-orthogonally. At least one end of each of these inclined surfaces in the direction W may have a surface that extends along the direction W. The corner formed by the inclined upper surface of the lower punch 60 and the surface along the axis of the lower punch 60 does not become an acute angle, so damage to the lower punch 60 can be reduced.

[0065] The main lower punch 61, first lower punch 62, and second lower punch 63 used in this example are all configured as a single unit. Two punches selected from the main lower punch 61, first lower punch 62, and second lower punch 63 may be integrated, and the remaining punch may be a punch independent of the two integrated punches. In particular, when the step between the left side surface 14 and the first left side surface 24 and the step between the right side surface 13 and the second right side surface 33 are large, the main lower punch 61 and the first lower punch 62 may be separate punches. Alternatively, the main lower punch 61 and the second lower punch 63 may be separate punches. When the lower punch 60 is divided into multiple punches, multiple boundary lines are indicated by two-dot chain lines in FIG. 6.

[0066] The lower punch 60 has the same width and depth as the upper punch 50. The main lower punch 61 has the same width and depth as the main upper punch 51. The first lower punch 62 has the same width and depth as the first upper punch 52. The second lower punch 63 has the same width and depth as the second upper punch 53. Since the lower punch 60 does not locally press the powder compact 1 during compaction, it is possible to suppress the shear stress acting on the powder compact 1.

[0067] (Each step of the manufacturing method) The above-mentioned powder compact 1 is obtained by a method for manufacturing the powder compact 1, which includes a filling step, a molding step, and a demolding step.

[0068] [Filling process] In the filling step, powder is filled into the space defined by the die hole 40h and the lower punch 60 provided in the die 40. The powder may be the soft magnetic powder or coated soft magnetic powder described above. In addition to the soft magnetic powder or coated soft magnetic powder, the powder may also contain a binder or a lubricant. A lubricant may be applied to the inner peripheral surface of the die hole 40h.

[0069] [Molding process] In the compacting step, the powder in the space is compressed by the lower punch 60 and the upper punch 50. The direction in which the powder in the space is compressed is the direction Y of the powder compact 1. The higher the pressure during compaction, the higher the relative density of the produced powder compact 1. The pressure may be, for example, 700 MPa or more, or even 980 MPa or more.

[0070] [Demolding process] In the demolding step, the die 40, the upper punch 50, and the lower punch 60 are moved up and down relative to each other to remove the powder compact 1 from the die hole 40h. At this time, the lower punch 60 does not locally press the powder compact 1, so it is possible to suppress the shear stress acting on the powder compact 1 during demolding. As a result, it is possible to reduce damage such as chipping and cracking of the powder compact 1.

[0071] [Other processes] After the demolding step, the powder compact 1 may be subjected to a heat treatment as needed. For example, by removing distortion in the powder compact 1 through heat treatment, a powder compact 1 with low loss can be manufactured. Alternatively, for example, the binder or lubricant may be removed through heat treatment. When the powder contains the coated soft magnetic particles described above, the heat treatment temperature may be set to, for example, the decomposition temperature of the insulating coating or lower.

[0072] Second Embodiment [Method for manufacturing stator core] A method for manufacturing a stator core 70 according to the second embodiment will be described mainly with reference to FIG. 7 . A plurality of green compacts 1 arranged in an annular shape are used to manufacture the stator core 70 of this embodiment. Each of the plurality of green compacts 1 is obtained by the method for manufacturing a green compact according to the first embodiment. To manufacture the stator core 70, the first right side surface 23 of a first green compact 1a and the first left side surface 24 of a second green compact 1b are brought into contact with each other among the plurality of green compacts 1. The contact between the first right side surface 23 and the first left side surface 24 of adjacent green compacts 1 is repeated. By repeating this process, the plurality of green compacts 1 are combined into an annular shape, and the stator core 70 can be easily obtained. The stator core 70 is used in a DS / SR type axial gap motor 9 shown in FIG.

[0073] The variation in the length between the first end face 25 and the second end face 35 of each powder compact 1 may be 0.1 mm or less. The length between the first end face 25 and the second end face 35 is the maximum length between the first end face 25 and the second end face 35 along the Z direction.

[0074] If the variation in the length between the first end face 25 and the second end face 35 is 0.1 mm or less, the variation in the length is very small. By using a stator core 70 in which the variation in the length between the first end face 25 and the second end face 35 is 0.1 mm or less, an axial gap motor 9 with low noise and vibration can be constructed. The reason for this is as follows. As shown in FIG. 8 , the axial gap motor 9 is arranged so that the stator 7 and the rotor 90 face each other. When the variation in the length of the stator core 70 is small, the variation in the gap between the stator 7 and the rotor 90 is small. This small variation in the gap reduces torque ripple. This small torque ripple makes it difficult for noise and vibration to increase. The variation in the length is determined as follows. For each powder compact 1, the length from the first end face 25 to the second end face 35 is measured. This length is the maximum length of the powder compact 1 along the Z direction. The difference between the maximum and minimum values ​​of the length for each of the multiple powder compacts 1 is calculated. This difference is defined as the variation in the length. The variation in the length between the first end face 25 and the second end face 35 may be 0.05 mm or less, or 0.01 mm or less. The length between the first end face 25 and the second end face 35 is the average of values ​​measured at three or more points using a microgauge.

[0075] <Axial gap motor A using powder compact> An axial gap motor 9 using the powder compact 1 will be described with reference to FIG. 8 . FIG. 8 is a cross-sectional view taken along a plane parallel to the rotation axis 91 of the axial gap motor 9 and including the axis of the stator core. This also applies to an axial gap motor 9a in FIG. 9 , which will be described later. The axial gap motor 9 is a DS / SR configuration including one rotor 90 and two stators 7. In the axial gap motor 9, the rotor 90 and the stators 7 are arranged facing each other along the axis. One rotor 90 is assembled so that it is sandwiched between the two stators 7. Each stator 7 includes multiple powder compacts 1 and multiple coils 80. The multiple powder compacts 1 are arranged in a ring shape. Each of the multiple coils 80 is wound around the body 10 of each powder compact 1. The coils 80 are formed by windings made of a good conductor such as copper. The stator core 70 described above can be used for each stator 7. The axial gap motor 9 can be used as a motor or a generator. The axial gap motor 9 includes a case 92 .

[0076] The case 92 has a cylindrical internal space that houses the stator 7 and rotor 90. The case 92 has a cylindrical portion 921 and two plate portions 922. The cylindrical portion 921 surrounds the outer periphery of the stator 7 and rotor 90. A plate portion 922 is disposed on each end of the cylindrical portion 921. The two plate portions 922 are fixed to both end surfaces of the cylindrical portion 921 so as to sandwich the stator 7 and rotor 90 from the front and back. Both plate portions 922 have a through hole in their center. A bearing 93 is provided in the through hole. The rotating shaft 91 is inserted into the through hole via the bearing 93. The rotating shaft 91 passes through the case 92.

[0077] The rotor 90 includes a magnet 95 and a rotor body (not shown). The rotor 90 is a flat-plate-shaped member. The number of magnets 95 may be multiple or may be one. When the rotor 90 includes multiple magnets 95, the specific number of magnets 95 may be the same as the number of powder compacts 1. The multiple magnets 95 are arranged at equal intervals around the axis of the rotor 90. In this embodiment, each magnet 95 is flat and has a planar shape corresponding to the planar shape of the second end surface 35 of each powder compact 1. Each magnet 95 may be in the shape of a convex lens having a convex surface facing each stator 7. When the rotor 90 includes only one magnet 95, the magnet 95 has an annular shape. In each magnet 95, south and north poles are alternately arranged around the axis. The rotor body supports the multiple magnets 95. The rotor body is an annular member. The rotor body is rotatably supported by a rotating shaft 91. The magnets 95 are arranged at equal intervals around the axis of the rotor body. Each magnet 95 is magnetized in a direction along the axis of the rotating shaft 91. The magnetization directions of adjacent magnets 95 around the axis of the rotor body are opposite to each other. The rotating magnetic field generated by the stator 7 causes the magnets 95 to repeatedly attract and repel each powder compact 1, causing the rotor 90 to rotate.

[0078] The stator 7 is disposed so that the first plate portion 20 of each powder compact 1 faces the corresponding plate portion 922. The second end face 35 of the second plate portion 30 is disposed so as to face the magnet 95 of the rotor 90. When the rotor 90 rotates, the second end face 35 of each powder compact 1 receives magnetic flux from the rotating magnet 95. If the second end face 35 of each powder compact 1 is configured in a convex shape, the noise and vibration of the axial gap motor 9 can be reduced. The reason for this is as follows. By configuring the second end face 35 of each powder compact 1 in a convex shape, sudden changes in the magnetic flux of the magnet 95 received by each powder compact 1 are easily suppressed. Therefore, cogging torque is easily reduced. Since the cogging torque is small, noise and vibration are less likely to increase.

[0079] <Axial gap motor B using powder compact> An axial gap motor 9a will be described with reference to FIG. 9. The axial gap motor 9a differs from the axial gap motor 9 of FIG. 8 mainly in that it is an SS / DR type motor equipped with two rotors 90a and one stator 7a. In the axial gap motor 9a, the rotor 90a and the stator 7a are arranged facing each other in the axial direction. One stator 7a is assembled so that it is sandwiched between the two rotors 90a. The following description will focus on the differences from the axial gap motor 9 of FIG. 8. Description of the same configuration as the axial gap motor 9 of FIG. 8 will be omitted.

[0080] Each rotor 90a includes a rotor body (not shown), a plurality of magnets 95, and a back yoke 98. The rotor body and the plurality of magnets 95 are as described above. The back yoke 98 is provided between the rotor 90a and the plate portion 922. The back yoke 98 is a flat plate-shaped member. The back yoke 98 has the same composition as the powder compact 1 described above. Alternatively, the back yoke 98 is made of laminated steel plates.

[0081] The stator 7a includes a plurality of powder compacts 1c arranged in an annular shape, a coil 80 wound around the body 10 of each powder compact 1c, and a support member that holds the plurality of powder compacts 1c. The support member is not shown. Although simplified in FIG. 9, the first plate portion 20a and the second plate portion 30a of each powder compact 1c have the same configuration. In each powder compact 1c, the protrusion amount of the first protrusion 20F on the first plate portion 20a and the protrusion amount of the second protrusion 30F on the second plate portion 30a are the same. The coil 80 is as shown in the axial gap motor 9 in FIG. 8 described above. The support member holds the plurality of powder compacts 1c so that the intervals between adjacent powder compacts 1c are equal. This support member prevents adjacent powder compacts 1c from contacting each other.

[0082] The present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims. For example, an axial gap motor may have one rotor and one stator. [Explanation of symbols]

[0083] 1, 1c Powder compact 1a First powder compact 1b Second powder compact 10 Body 11 front, 12 rear, 13 right side, 14 left side 20, 20a First plate part 21 First front, 22 First rear, 23 First right side, 24 First left side. 25 First end surface, 20F first protrusion 30, 30a Second plate part 31 2nd front, 32 2nd rear, 33 2nd right side, 34 2nd left side 35 Second end face, 30F second protrusion 4. Mold 40 Die 40h die hole, 41h main hole, 42h first sub-hole, 43h second sub-hole 41f, 41b, 42f, 42b, 43f, 43b inner surfaces 42e, 43e end face 50 Upper Punch 51 Main upper punch, 52 First upper punch, 53 Second upper punch 51b main underside, 52b first sub-underside, 53b second sub-underside 60 Lower Punch 61 Main lower punch, 62 First lower punch, 63 Second lower punch 61t Main top, 62t First sub top, 63t Second sub top 7, 7a stator, 70 stator core, 80 coil 9, 9a Axial gap motor 90a rotor, 91 rotating shaft, 92 case 921 cylindrical portion, 922 plate portion, 93 bearing, 95 magnet, 98 back yoke

Claims

1. A prismatic body having a first base, a second base opposite to the first base, and a plurality of sides, The first plate portion provided on the first bottom surface, It has a second plate portion provided on the second bottom surface, The aforementioned multiple sides are, The front and rear surfaces of the body are arranged parallel to each other along the axis of the body, It has a left side connecting the front and rear surfaces and a right side connecting the front and rear surfaces, The first plate portion is, A first projection extending from the body in a direction perpendicular to the axis, A first front surface and a first rear surface are arranged parallel to each other along the aforementioned axis, It has a first left side surface connecting the first front surface and the first rear surface, and a first right side surface connecting the first front surface and the first rear surface, The first left side and the first right side have inclined regions such that the distance between them increases as you move from the first front to the first rear surface. The second plate portion is, A second projection extending from the body in a direction perpendicular to the axis, A second front surface and a second rear surface are arranged parallel to each other along the aforementioned axis, It has a second left side surface connecting the second front surface and the second rear surface, and a second right side surface connecting the second front surface and the second rear surface, The left side, the first left side, the second left side, the right side, the first right side, and the second right side are pressing surfaces formed by the pressing of the punch of the mold. The aforementioned front surface, the first front surface, the second front surface, the rear surface, the first rear surface, and the second rear surface are sliding surfaces formed by sliding contact with the inner circumferential surface of the die of the mold. Compacted powder.

2. The compacted powder body according to claim 1, wherein the left side and the right side are inclined such that the distance between them increases as you move from the front to the rear.

3. The compacted powder according to claim 1 or claim 2, wherein the second left side and the second right side have regions that are inclined such that the distance between them increases as you move from the second front to the second rear.

4. The compacted powder body according to claim 1 or claim 2, wherein the first projection protrudes from the body over the entire circumference around the shaft.

5. The compacted powder body according to claim 1 or claim 2, wherein the second projection protrudes from the body over the entire circumference around the shaft.

6. The powder forming the compact is a magnetic powder, as described in Claim 1 or Claim 2.

7. comprising a plurality of the compacted powder bodies arranged in a ring, The first left side and the first right side of two adjacent compacted bodies are arranged so that they face each other in parallel. Stator core.

8. The stator core according to claim 7, A rotor combined with the stator core, Axial gap motor.

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