Axial clearance type motor

Abstract

Provided is an axial-gap type motor that allows efficient magnetic flux flow while improving the assemblability of the pressed powder teeth relative to the base yoke. The axial-gap type motor (X) includes a resin bobbin (9) having positioning protrusions (9c) and a base yoke (5) having a plurality of tooth holes (6) and positioning holes (5a). In each tooth hole (6), the circumferential length of the outer end face (6c) of the tooth hole diameter is greater than the circumferential length of the inner end face (6a) of the tooth hole in the radial direction. Each of the plurality of pressed powder teeth (8) has a columnar shape such that the circumferential length of the upper surface (8b) of the pressed powder tooth is greater than the circumferential length of the bottom surface of the pressed powder tooth (8a). The positioning protrusion (9c) is inserted into the positioning hole (5a), and the pressed powder tooth (8) is pressed inward against the base yoke (5) in the radial direction of the stator core (7) such that the bottom surface (8a) of the pressed powder tooth contacts the inner end face (6a) of the tooth hole in the radial direction, and the inclined surface (8c) of the pressed powder tooth contacts the circumferential end face (6c) of the tooth hole.

Description

Technical Field

[0001] This teaching relates to an axial-gap type motor. Background Art

[0002] In a known axial-gap type motor, a rotor including a plurality of magnets and capable of rotating about a rotation axis and a stator including a stator core and stator coils are located in the axial direction of the rotation axis. A known example of such an axial-gap type motor is the axial-gap type motor (hereinafter referred to as an axial-gap type motor) disclosed in Patent Document 1.

[0003] In such an axial-gap type motor, the rotor includes an annular rotor yoke attached to a shaft and a plurality of permanent magnets provided on a surface of the rotor yoke close to the stator. The rotor is located in the axial direction of the rotation axis of the rotor with respect to the stator.

[0004] The stator core of the stator includes an annular base yoke arranged substantially orthogonally to the shaft and a pressed powder iron core tooth provided on a surface of the base yoke close to the rotor. The plurality of teeth extend along the shaft and are arranged around the shaft. Coils are wound around each tooth around the axis. The teeth are fixed to the base yoke by, for example, press fitting or adhesion.

[0005] As in Patent Document 1, for example Figure 1 as shown, each tooth has a triangular shape.

[0006] Citation List

[0007] Patent Documents

[0008] Patent Document 1: International Patent Publication No. 2007 / 114079. Summary of the Invention

[0009] Technical Problem

[0010] For example, from the viewpoint of miniaturization, it is required that an axial-gap type motor having the above configuration has an increased magnetic flux density and an efficient magnetic flux flow. In such a case of increasing the magnetic flux density of the axial-gap type motor, it is preferable to increase the duty factor of the coils wound around the teeth. As disclosed in Patent Document 1, when observing the teeth in the axial direction, in the case where the shape of each tooth is a triangle whose width in the circumferential direction gradually decreases toward the inner side of the stator in the radial direction, the inner side in the radial direction of the gap between adjacent teeth is larger in the circumferential direction than in the case where each tooth has a rectangular shape. Therefore, in the stator, the duty factor of the coils wound around the teeth can be increased. Since each pressed powder iron core tooth that can be formed into an arbitrary shape has the above shape, the magnetic flux density of the axial-gap type motor can be increased.

[0011] In a stator, when the base yoke is made of laminated steel sheets, the base yoke and the pressed powder iron core teeth form different components. Therefore, the teeth are positioned relative to the base yoke by inserting the teeth into tooth holes formed in the base yoke.

[0012] The teeth made of pressed powder iron core are less brittle than the base yoke made of laminated steel sheets. Therefore, when inserting the teeth into the tooth holes, it is necessary to handle the teeth carefully so that scraping or the like does not occur due to contact with the base yoke. This reduces the assemblability of the teeth and the base yoke.

[0013] In the case where the teeth and the base yoke are formed in a shape that forms a gap between the teeth and the base yoke to prevent scraping or the like from occurring in the teeth due to contact with the base yoke, this gap hinders the magnetic flux flowing in the teeth from flowing in the circumferential direction of the base yoke and from the base yoke toward the radially inner side. That is, the gap hinders the magnetic flux from flowing from the teeth to the base yoke. Therefore, the magnetic flux cannot flow effectively between the teeth and the base yoke. Therefore, an axial-gap type motor that allows the magnetic flux to flow efficiently while improving the assemblability of the teeth and the base yoke is required.

[0014] Therefore, the object of the present teaching is to provide an axial-gap type motor that allows the magnetic flux to flow efficiently while improving the assemblability of the teeth and the base yoke.

[0015] Solution to the problem

[0016] The inventors of the present teaching studied the configuration of an axial-gap type motor that allows the magnetic flux to flow efficiently while improving the assemblability of the teeth and the base yoke. Through in-depth research, the inventors of the present teaching arrived at the following configuration.

[0017] An axial-gap type motor according to an embodiment of the present teaching is an axial-gap type motor including: a rotor including a plurality of field magnets and capable of rotating about a rotation axis, the plurality of field magnets being arranged in a circumferential direction; a cylindrical stator core located in the axial direction of the rotation axis with respect to the rotor, the stator core including a base yoke and a plurality of teeth formed of pressed particles and arranged in a circumferential direction around the rotation axis with respect to the base yoke; a plurality of cylindrical resin bobbins, the plurality of teeth being respectively inserted into the resin bobbins; and stator coils wound around each of the plurality of resin bobbins.

[0018] Each resin bobbin includes a bottomed cylindrical side surface having a bottom surface and positioning protrusions protruding axially from the side surface. The base yoke includes a plurality of tooth holes and positioning holes. A plurality of teeth are respectively inserted into the plurality of tooth holes. The positioning holes are located outside or inside the tooth holes in the radial direction and are configured such that the positioning protrusions are inserted into the positioning holes. When the stator core is viewed in the axial direction, each of the plurality of tooth holes extends in the radial direction of the stator core and is shaped such that the circumferential length of the radially outer end face of the tooth hole at the outer end of the corresponding tooth hole in the radial direction is greater than the circumferential length of the radially inner end face of the tooth hole at the inner end of the tooth hole in the radial direction.

[0019] When the plurality of teeth are viewed in the axial direction, each of the plurality of teeth extends in the radial direction of the stator core and has a columnar shape in which the circumferential length of the radially outer end portion of the tooth at the outer end of the tooth in the radial direction is greater than the circumferential length of the radially inner end portion of the tooth at the inner end of the tooth in the radial direction. In a state where the positioning protrusions are inserted into the positioning holes, the positioning protrusions press the teeth radially inward against the base yoke in the radial direction of the stator core, such that the radially inner end portions of the teeth contact the radially inner end faces of the tooth holes, causing the circumferential end portions of the teeth at the ends of each of the teeth in the circumferential direction of the stator core to contact the circumferential end faces of the tooth holes at the ends of the tooth holes in the circumferential direction of the stator core, and the radially outer end portions of the teeth do not contact the radially outer end faces of the tooth holes.

[0020] As described above, the teeth are formed of pressed particles that can be formed into any shape. When viewed in the axial direction, each of the teeth extends in the radial direction of the stator core and is shaped such that the circumferential length of the radially outer end portion of the tooth is greater than the circumferential length of the radially inner end portion of the tooth. A substantially rectangular space is formed between the teeth adjacent to each other in the circumferential direction of the stator core. The stator coil wound around the teeth via the resin bobbin is accommodated in the substantially rectangular space. The space factor of the stator coil with respect to the space is increased by expanding the interval between the radially inner end portions of the teeth, which is the smallest among the intervals between adjacent teeth. That is, compared to the case of using teeth in which the circumferential length of the radially inner end portion of the tooth is equal to the circumferential length of the radially outer end portion of the tooth, the space factor of the stator coil is further increased by setting the circumferential length of the radially inner end portion of the tooth to be smaller than the circumferential length of the radially outer end portion of the tooth.

[0021] When a tooth equipped with a resin bobbin is inserted into a tooth hole, the tooth is positioned in the base yoke by the positioning protrusion of the resin bobbin. At this time, the tooth is pressed inward in the radial direction of the stator core against the base yoke by the positioning protrusion. In each tooth, the radially inner end of the tooth contacts the radially inner end face of the tooth hole, and the circumferentially end of the tooth contacts the circumferentially end face of the tooth hole. That is, in the stator coil, even if the tooth and the base yoke are made of different members, it is unlikely that a gap that hinders the flow of magnetic flux from the tooth in the circumferential direction of the base yoke will occur. Therefore, in the axial-gap type motor, the flow of magnetic flux from the radially inner end and the circumferentially end of each tooth toward the base yoke is not easily hindered.

[0022] On the other hand, in each tooth, the radially outer end of the tooth does not contact the radially outer end face of the tooth hole diameter. That is, in the state where the tooth is inserted into the tooth hole, there is a gap between the radially outer end of the tooth and the radially outer end face of the tooth hole diameter, and therefore, the tooth is not constrained by the tooth hole. With this shape, when the tooth is inserted into the tooth hole, the tooth contacts the radially inner end face of the tooth hole and the circumferentially end face of the tooth hole, so that the force applied to the tooth is released outward in the radial direction. Therefore, when the tooth is inserted into the tooth hole, the friction caused by contact with the base yoke is reduced, and the tooth is positioned relative to the base yoke by the resin bobbin.

[0023] In addition, since the positioning protrusion is provided outside or inside the tooth hole in the radial direction, the flow of magnetic flux occurring in the base yoke between teeth adjacent to each other in the circumferential direction of the stator core is not hindered.

[0024] Therefore, an axial-gap type motor can be provided that allows efficient flow of magnetic flux while improving the assemblability of the tooth and the base yoke.

[0025] On the other hand, the axial-gap type motor according to the present teaching preferably has the following configuration. Each of the positioning holes is continuous with at least a part of the radially outer end face of the tooth hole diameter or at least a part of the radially inner end face of the tooth hole.

[0026] With the above configuration, since the positioning hole is provided outside or inside the tooth hole in the radial direction in the base yoke, the flow of magnetic flux that flows from the tooth in the circumferential direction of the base yoke and has a magnetic flux density higher than the magnetic flux density of the magnetic flux flowing from the tooth in the radial direction of the base yoke is not hindered. The positioning hole is continuous with at least a part of the radially inner end face of the tooth hole or at least a part of the radially outer end face of the tooth hole diameter, and therefore can be formed accurately with respect to the tooth hole. That is, the tooth is configured to be easily and accurately positioned relative to the base yoke by the resin bobbin. Therefore, an axial-gap type motor can be provided that allows efficient flow of magnetic flux while improving the assemblability of the tooth and the base yoke.

[0027] On the other hand, the axial-gap type motor according to the present teaching preferably has the following configuration. The positioning hole is located outside the tooth in the radial direction in the base yoke.

[0028] With the above structure, since the positioning holes are arranged outside the tooth holes in the radial direction in the base yoke, it does not hinder the flow of magnetic flux along the circumferential direction of the base yoke from the teeth and has a magnetic flux density higher than that of the magnetic flux flowing along the radial direction of the base yoke from the teeth. The magnetic flux flowing outward from the teeth along the radial direction of the base yoke is small enough relative to the total magnetic flux flowing from the teeth to the base yoke. Therefore, an axial-gap type motor can be provided that allows efficient flow of magnetic flux while improving the assemblability of the teeth and the base yoke.

[0029] On the other hand, the axial-gap type motor according to the present teachings preferably has the following configuration. In each of the positioning holes, the interval between the outer end face of the tooth diameter and the outer end of the tooth diameter is enlarged by inserting a positioning projection into the positioning hole.

[0030] With the above configuration, the positioning projection enlarges the interval between the outer end of the tooth diameter and the outer end face of the tooth diameter and presses the tooth inward in the radial direction of the stator core against the base yoke. In the stator core, the positioning projection hinders the flow of magnetic flux outward from the teeth along the radial direction of the base yoke. However, since the magnetic flux flowing outward from the teeth along the radial direction of the base yoke is small enough relative to the entire magnetic flux flowing from the teeth to the base yoke, the influence on the flow of magnetic flux can be ignored. On the other hand, in the base yoke, the positioning projection prevents a gap from occurring between the base yoke and each of the radially inner end and the circumferentially end of the tooth, reducing the magnetic resistance, and thus the magnetic flux can flow efficiently. Therefore, an axial-gap type motor can be provided that allows efficient flow of magnetic flux while improving the assemblability of the teeth and the base yoke.

[0031] On the other hand, the axial-gap type motor according to the present teachings preferably has the following configuration. The stator core is molded using resin flowing from the outside in the radial direction to the inside in the radial direction.

[0032] With the above configuration, the tooth inserted into the tooth hole is pressed against the radially inner end face and the circumferentially end face of the tooth hole by the pressure caused by the flow of the resin. Therefore, an axial-gap type motor can be provided that allows efficient flow of magnetic flux while improving the assemblability of the teeth and the base yoke.

[0033] On the other hand, the axial-gap type motor according to the present teachings preferably has the following configuration. Each of the resin winding cylinders covers at least a part of the axial end face of the corresponding tooth located at the end in the axial direction and close to the rotor.

[0034] With the above configuration, the movement of the tooth in the axial direction is suppressed by the resin winding cylinder. That is, the resin winding cylinder prevents the tooth inserted inside the winding cylinder from coming off and maintains a uniform gap with the field magnet. Therefore, an axial-gap type motor can be provided that allows efficient flow of magnetic flux while improving the assemblability of the teeth and the base yoke.

[0035] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the present invention.

[0036] The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0037] It should be further understood that when used in this specification, the terms "comprises", "comprising", or "having" and their variants specify the presence of the stated features, steps, elements, components, and / or their equivalents, but do not preclude the presence or addition of one or more steps, operations, elements, components, and / or their groups.

[0038] It should be further understood that the terms "mounted", "connected", "coupled", and / or their equivalents are used broadly and include both direct and indirect mounting, connection, and coupling. Further, "connected" or "coupled" is not limited to physical or mechanical connection or coupling, but may include direct or indirect connection or coupling.

[0039] Unless defined otherwise, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0040] It will be further understood that terms, such as those defined in a commonly used dictionary, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and this disclosure and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0041] In describing the present invention, it will be understood that several techniques and steps are disclosed. Each of these has its respective advantages and each may also be used in combination with one or more, or in some cases all, of the other disclosed techniques.

[0042] Accordingly, for clarity, this specification will avoid repeating every possible combination of the individual steps in an unnecessary manner. However, the specification and claims should be read with the understanding that such combinations are fully within the scope of the present invention and the claims.

[0043] Embodiments of an axial-gap type motor according to this teaching will be described herein.

[0044] In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that the present invention may be practiced without these specific details.

[0045] This disclosure should be regarded as illustrative of the invention and is not intended to limit the invention to the specific embodiments shown in the following figures or the specification.

[0046] [Axial-gap type motor]

[0047] The axial-gap type motor herein refers to a motor in which a rotor and a stator are located in the axial direction of the rotation axis of the rotor and the rotor rotates about the rotation axis. The rotor includes a plurality of field magnets arranged in the circumferential direction around the rotation axis. The stator includes a plurality of teeth arranged in the circumferential direction around the rotation axis. A stator coil is wound around each of the plurality of teeth. The plurality of field magnets of the rotor and the plurality of teeth of the stator are opposed to each other in the axial direction. Therefore, the axial-gap type motor has a gap (axial gap) in the axial direction between the plurality of field magnets and the plurality of teeth. The axial-gap type motor includes, for example, a motor and a generator.

[0048] [Pressed particles]

[0049] The pressed particles herein refer to fine particles including magnetic material particles. For example, teeth are formed by pressing the pressed particles.

[0050] [Outer radial end of tooth]

[0051] The outer radial end of tooth herein refers to a part of the tooth extending in the radial direction of the stator core, and the outer radial end of tooth is located at the outer end in the radial direction of the tooth. The outer radial end of tooth includes the tooth surface at the outer end in the radial direction of the tooth. The circumferential length of the outer radial end of tooth refers to, for example, the circumferential length of the outermost part of the outer radial end of tooth.

[0052] [Inner radial end of tooth]

[0053] The inner radial end of tooth herein refers to a part of the tooth extending in the radial direction of the stator core, and the inner radial end of tooth is located at the inner end in the radial direction of the tooth. The inner radial end of tooth includes the tooth surface at the inner end in the radial direction of the tooth. The circumferential length of the inner radial end of tooth refers to, for example, the circumferential length of the innermost part of the inner radial end of tooth.

[0054] [Circumferential end of tooth]

[0055] The circumferential end of tooth herein refers to a part of the tooth having a thickness in the circumferential direction of the stator core, and the circumferential end of tooth is located at the end in the circumferential direction of the tooth. The circumferential end of tooth includes the tooth surface at the end in the circumferential direction of the tooth. The radial length of the circumferential end of tooth refers to, for example, the radial length of the circumferential end of tooth from the inner radial end of tooth to the outer radial end of tooth.

[0056] [Outer end face of tooth hole diameter]

[0057] The outer end face of the tooth hole diameter in this article refers to the outer end face of the outer end of the tooth hole formed in the yoke in the radial direction of the yoke, which extends in the radial direction. The circumferential length of the outer end face of the tooth hole diameter refers to, for example, the circumferential length of the yoke at the outermost circumference of the outer end of the tooth hole located in the radial direction.

[0058] [Inner end face of tooth hole diameter]

[0059] The inner end face of the tooth hole diameter in this article refers to the inner end face of the outer end of the tooth hole formed in the yoke in the radial direction of the yoke, which extends in the radial direction. The circumferential length of the inner end of the tooth diameter refers to, for example, the circumferential length of the yoke at the innermost circumference of the inner end of the tooth hole located in the radial direction.

[0060] [Circumferential end face of tooth hole]

[0061] The circumferential end face of the tooth hole in this article refers to the end face of each end in the circumferential direction of the tooth hole formed in the yoke, which has a width in the circumferential direction of the yoke. The radial length of the circumferential end of the tooth hole refers to, for example, the radial length of each end of the tooth hole from the inner end of the tooth hole diameter to the outer end of the tooth hole diameter in the circumferential direction.

[0062] Advantageous effects of the present invention

[0063] According to an embodiment of the present teaching, an axial-gap type motor can be provided that improves the assemblability of the teeth and the yoke while allowing efficient magnetic flux flow. Brief description of the drawings

[0064] Figure 1 Figure 1 is a view of an axial-gap type motor according to an embodiment observed in a first direction.

[0065] Figure 2 Figure 2 is a cross-sectional view taken along line II-II in Figure 1 .

[0066] Figure 3 Figure 3 is a view showing a schematic configuration of the yoke.

[0067] Figure 4A Figure 4A is a perspective view showing a schematic configuration of a pressed powder tooth.

[0068] Figure 4B Figure 4B is a view of the pressed powder tooth observed in the axial direction.

[0069] Figure 5 Figure 5 is a perspective view showing a schematic configuration of a resin bobbin. ​​​​​​​​​​​​

[0070] Figure 6 Figure 6 is a perspective view showing a state in which a pressed powder tooth is inserted into a resin bobbin and a stator coil is wound.

[0071] Figure 7 Figure 7 is a view showing a state in which a resin bobbin accommodating a pressed powder tooth is attached to a base yoke as observed in a first direction.

[0072] Figure 8 Figure 8 is a view showing a state in which a resin bobbin accommodating a pressed powder tooth is attached to a base yoke as observed in a second direction.

[0073] Figure 9 Figure 9 schematically shows a positional relationship between pressed powder teeth adjacent to each other in a circumferential direction.

[0074] Figure 10 Figure 10 is a view showing a state in which a pressed powder tooth is inserted into a tooth hole as observed in a first direction.

[0075] Figure 11 Figure 11 is a view showing a state in which a positioning protrusion is inserted into a positioning hole as observed in a first direction.

[0076] Figure 12 Figure 12 is a partial cross-sectional view showing a positional relationship between a field magnet of a rotor, a resin bobbin, and a pressed powder tooth.

[0077] Figure 13 Figure 13 is a view of a rotor provided in a mold for resin molding as observed in a first direction. DETAILED DESCRIPTION

[0078] Embodiments will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their description will not be repeated. The dimensions of the components in the drawings do not strictly represent the actual dimensions of the components and the dimensional ratios of the components.

[0079] Hereinafter, the direction in which the rotation axis P of the axial-gap type motor X extends will be referred to as the "axial direction". Hereinafter, the radial direction of the stator 2 of the axial-gap type motor X will be referred to as the "radial direction". The direction in which the rotor 1 of the axial-gap type motor X rotates around the rotation axis P will be referred to as the "rotation direction" or the "circumferential direction". The radial direction is a direction orthogonal to the rotation axis P of the axial-gap type motor X.

[0080] ​​​​​​​​​​​​​​​​Hereinafter, the direction in which the stator 2 and the rotor 1 are arranged in sequence in the axial direction is referred to as the first direction. The direction in which the rotor 1 and the stator 2 are arranged in sequence in the axial direction is referred to as the second direction.

[0081] <Overall configuration>

[0082] Reference Figure 1 and Figure 2 , an axial-gap type motor X according to a first embodiment will be described. Figure 1 is a plan view showing a schematic configuration of the axial-gap type motor X. Figure 1 is a view of the stator 2 of the axial-gap type motor X observed in the first direction. Figure 2 is a cross-sectional view showing a cross-section of the axial-gap type motor X taken along line II-II in the radial direction.

[0083] As Figure 2 shown, the axial-gap type motor X according to the present embodiment is, for example, a motor in which the rotor 1 and the stator 2 are arranged in the axial direction of the rotation axis P of the rotor 1 and the rotor 1 rotates around the rotation axis P. The axial-gap type motor X may be a generator.

[0084] The axial-gap type motor X includes a rotor 1 and a stator 2. The rotor 1 and the stator 2 face each other in the axial direction. The rotor 1 and the stator 2 are provided with a predetermined gap G in the axial direction.

[0085] The rotor 1 rotates relative to the stator 2 around the rotation axis P. The rotor 1 includes a rotor yoke 3 and a plurality of field magnets 4.

[0086] The rotor yoke 3 is, for example, a cap-shaped member made of a ferromagnetic steel plate. That is, the rotor yoke 3 includes a bottomed cylindrical rotor yoke protrusion 3a and an annular rotor yoke flange 3b provided to surround the rotor yoke protrusion 3a.

[0087] A rotor shaft (not shown) passes through the rotor yoke protrusion 3a. The rotor shaft is connected to the rotor yoke protrusion 3a. Therefore, the rotor yoke 3 rotates integrally with the rotor shaft. The rotation axis of the rotor shaft coincides with the rotation axis P. The direction in which the rotor yoke protrusion 3a protrudes is the axial direction of the rotation axis P. The rotor yoke protrusion 3a and the rotor yoke flange 3b are integrally formed. In the axial-gap type motor X, the rotor yoke protrusion 3a is located inside an annular stator 2 described later in the radial direction.

[0088] The rotor yoke 3 may have a shape other than the cap shape, such as a disc shape or a cylindrical shape. The rotor yoke 3 may have any shape as long as the rotor yoke can rotate with the rotor shaft while holding the field magnets 4 described later.

[0089] The field magnet 4 is a rectangular flat member. The field magnet 4 is fixed to the rotor yoke flange 3b. In the present embodiment, the field magnet 4 is fixed to the surface of the rotor yoke flange 3b that is in the protruding direction of the rotor yoke projection 3a. On the rotor yoke flange 3b, a plurality of field magnets 4 are arranged at regular intervals in the circumferential direction. Therefore, when the rotor 1 rotates around the rotation axis P, the field magnet 4 also rotates around the rotation axis P.

[0090] The field magnet 4 can be fixed to the rotor yoke flange 3b in any manner such as adhesion, threading, welding, or deposition. The field magnet 4 can be other shapes such as circular, or can be shapes other than plate shapes such as rod-shaped.

[0091] The field magnet 4 generates magnetic flux in the thickness direction. That is, in the present embodiment, the direction of the magnetic flux generated by the field magnet 4 is the axial direction of the rotation axis P in the rotor 1. The direction of the magnetic flux generated by the field magnet 4 can be changed according to the configuration of the motor.

[0092] The stator 2 is integrally configured as a cylinder. The stator 2 and the rotor 1 are arranged in the axial direction of the rotation axis P such that the rotor yoke projection 3a is located inside the stator 2 in the radial direction. The stator 2 includes a base yoke 5, a plurality of pressed powder teeth 8, a resin bobbin 9, and a stator coil 10. In the stator 2 of the present embodiment, the base yoke 5 is a member separated from the plurality of pressed powder teeth 8.

[0093] Reference Figure 3 will describe the base yoke 5 that constitutes the axial-gap type motor X according to the first embodiment. Figure 3 is a plan view showing a schematic configuration of the base yoke 5. The base yoke 5 is formed of a ring-shaped plate-like magnetic material such as an electromagnetic steel sheet, for example. The base yoke 5 can be formed by laminating electromagnetic steel sheets in the thickness direction, or can be made of, for example, pressed powder or amorphous material as long as the base yoke 5 is a magnetic material.

[0094] The base yoke 5 includes a plurality of tooth holes 6 as a plurality of insertion holes arranged in the circumferential direction. In the present embodiment, the base yoke 5 includes the same number of tooth holes 6 as the number of grooves T that are the grooves between adjacent teeth. The pressed powder teeth 8 described later are respectively inserted into the plurality of tooth holes 6.

[0095] When observing the base yoke 5 in the axial direction, the tooth holes 6 extend in the radial direction of the base yoke 5. When observing the base yoke 5 in the axial direction, each tooth hole 6 includes: a tooth hole radially outer end face 6b that is an end face of the base yoke 5 located at the outer end of the tooth hole 6 in the radial direction, a tooth hole radially inner end face 6a that is an end face of the base yoke 5 located at the inner end in the radial direction, and a tooth hole circumferential end face 6c that constitutes the hypotenuse connecting the tooth hole radially outer end face 6b and the tooth hole radially inner end face 6a. When observing the base yoke 5 in the axial direction, in each tooth hole 6, the circumferential length of the tooth hole radially outer end face 6b is greater than the circumferential length of the tooth hole radially inner end face 6a. That is, each tooth hole 6 has a trapezoidal shape, and when observing the base yoke 5 in the axial direction, the width in the circumferential direction of the trapezoidal shape increases toward the outside of the base yoke 5 in the radial direction.

[0096] The tooth hole radially inner end face 6a of each tooth hole 6 has a slit 11. Therefore, the tooth hole 6 opens to the inside of the base yoke 5. The width of each slit 11 in the circumferential direction is smaller than the circumferential length of the tooth hole radially inner end face 6a of the tooth hole 6. In the base yoke 5, the slit 11 can cut off the eddy current generated around the sintered powder tooth 8.

[0097] The base yoke 5 includes a plurality of positioning holes 5a arranged in the circumferential direction. The positioning protrusions 9c of the resin bobbin 9 described later are inserted into the plurality of positioning holes 5a. The base yoke 5 has the same number of positioning holes 5a as the number of tooth holes 6. The positioning holes 5a are located outside the tooth holes 6 in the radial direction. That is, in the state where the sintered powder tooth 8 is inserted into the tooth hole 6, the positioning holes 5a are located outside the sintered powder tooth 8 in the radial direction.

[0098] In the present embodiment, the base yoke 5 includes a positioning hole 5a, and the positioning hole 5a is a rectangular cutout that opens toward the outside of the base yoke 5 in the radial direction and is formed in the tooth hole radially outer end face 6b of the tooth hole 6. The rectangular cutout serving as the positioning hole 5a is positioned to be continuous with at least a part of the tooth hole radially outer end face 6b.

[0099] Reference Figure 4A and Figure 4B , the sintered powder tooth 8 constituting the axial-gap type motor X according to the first embodiment will be described. Figure 4A is a perspective view showing a schematic configuration of the sintered powder tooth 8. Figure 4B is a view of the sintered powder tooth 8 observed in the axial direction. The sintered powder tooth 8 is composed of fine particles including magnetic material particles. Specifically, the sintered powder tooth 8 is composed of sintered particles formed by integrally molding the fine particles with a mold under a predetermined pressure. The sintered powder tooth 8 is arranged relative to the base yoke 5 in the circumferential direction around the rotation axis P. The cylindrical portion including the sintered powder tooth 8 arranged relative to the base yoke 5 in the circumferential direction around the rotation axis P is called a stator core 7.

[0100] The cylindrical stator core 7 includes slots T, each of which is located between adjacent pressed powder teeth 8. The stator coil 10 wound around the pressed powder teeth 8 is received in the slots T. In this embodiment, as Figure 1 shown by the dashed line in Figure 1 , when the stator 2 is viewed in the axial direction along the rotation axis P, each slot T is rectangular. Although Figure 1 shows a slot 37, rectangular slots T are formed between each two adjacent pressed powder teeth 8.

[0101] When viewed in the axial direction, each pressed powder tooth 8 is a columnar member that extends in the radial direction, and in this columnar member, the circumferential length of the tooth radial outer end portion of the pressed powder tooth 8 located at the outer end in the radial direction is greater than the circumferential length of the tooth radial inner end portion of the pressed powder tooth 8 located at the inner end in the radial direction. That is, the pressed powder tooth 8 is a columnar member having a substantially trapezoidal cross-section. Each pressed powder tooth 8 includes a pressed powder tooth bottom surface 8a, a pressed powder tooth upper surface 8b, and a pressed powder tooth inclined surface 8c. The pressed powder tooth bottom surface 8a is the surface of the tooth radial inner end portion that constitutes the short side of the cross-section, the pressed powder tooth upper surface 8b is the surface of the tooth radial outer end portion that constitutes the long side of the cross-section, and the pressed powder tooth inclined surface 8c is the surface of the tooth circumferential end portion that constitutes the hypotenuse connecting the pressed powder tooth bottom surface 8a and the pressed powder tooth upper surface 8b in the cross-section. The cross-sectional shape and cross-sectional area of the pressed powder tooth 8 are the same in the axial direction.

[0102] In each columnar pressed powder tooth 8, at least one of the longitudinal dimension or the transverse dimension of the cross-section may gradually decrease in the axial direction. That is, each pressed powder tooth 8 may have a draft angle in the axial direction.

[0103] Referring to Figure 5 and Figure 6 , the resin winding bobbin 9 that constitutes the axial-gap type motor X according to the first embodiment will be described. Figure 5 is a perspective view showing a schematic configuration of the resin winding bobbin 9. Figure 6 is a perspective view showing a state in which the pressed powder teeth 8 are inserted into the resin winding bobbin 9 and the stator coil 10 is wound. Each of the plurality of pressed powder teeth 8 is provided with a resin winding bobbin 9, and the resin winding bobbin 9 is a cylindrical resin bobbin. The resin winding bobbin 9 can be fixed to the pressed powder tooth 8 by any means such as adhesion, threading, welding, or deposition. The resin winding bobbin 9 is a resin member and covers the pressed powder tooth 8 so as to electrically insulate the pressed powder tooth 8 from the stator coil 10. The resin winding bobbin 9 has a bottomed cylindrical shape that can accommodate the pressed powder tooth 8. Specifically, the resin winding bobbin 9 includes a side surface 9a, a bottom surface 9b, and a positioning projection 9c. In this embodiment, the side surface 9a, the bottom surface 9b, and the positioning projection 9c are integrally formed.

[0104] The side surface 9a is configured to define a compacted powder tooth receiving space A, which has a trapezoidal cross-sectional shape and is capable of receiving a compacted powder tooth 8 having a trapezoidal cross-sectional shape. The bottom surface 9b is located on one side of the resin bobbin 9 in the axial direction of the cylindrical axis with respect to the side surface 9a, and defines one side of the compacted powder tooth receiving space A in the axial direction. The other side of the compacted powder tooth receiving space A in the axial direction is constituted by an opening 9d surrounded by the side surface 9a of the resin bobbin 9. The axial direction coincides with the axial direction of the rotation axis P in the axial-gap type motor X.

[0105] The length of the compacted powder tooth receiving space A in the axial direction is smaller than the length of the compacted powder tooth 8 in the axial direction. Therefore, in a state where the compacted powder tooth 8 is received in the compacted powder tooth receiving space A, the compacted powder tooth 8 protrudes in the axial direction with respect to the side surface 34a.

[0106] The positioning projection 9c is a projection extending in the axial direction from the opening 9d. The positioning projection 9c can be inserted into the positioning hole 5a of the base yoke 5.

[0107] Reference Figure 7 , the stator 2 constituting the axial-gap type motor X according to the first embodiment will be described. Figure 7 is a view of a state in which the resin bobbin 9 that houses the compacted powder tooth 8 is attached to the base yoke 5 as observed in the first direction. Figure 8 is a view of a state in which the resin bobbin 9 that houses the compacted powder tooth 8 is attached to the base yoke 5 as observed in the second direction. As Figure 6 shown, the compacted powder tooth 8 is inserted into the compacted powder tooth receiving space A of the resin bobbin 9 such that the compacted powder tooth 8 is covered by the resin bobbin 9.

[0108] The resin bobbin 9 that houses the compacted powder tooth 8 is disposed with respect to the base yoke 5 such that the opening 9d of the side surface 9a is in contact with the base yoke 5. The bottom surface 9b of the resin bobbin 9 is disposed to face the rotor yoke 3. At this time, the portion of the compacted powder tooth 8 that protrudes outward from the resin bobbin 9 is inserted into the tooth hole 6 of the base yoke 5. The compacted powder tooth 8 inserted into the tooth hole 6 protrudes from the base yoke 5 toward the rotor yoke 3. The portion of the compacted powder tooth 8 that protrudes from the base yoke 5 is received in the side surface 9a. The end surface of the compacted powder tooth 8 in the axial end surface in the axial direction that is close to the rotor yoke 3 is covered by the bottom surface 9b. The positioning projection 9c of the resin bobbin 9 is inserted into the positioning hole 5a of the base yoke 5. Therefore, the movement of the compacted powder tooth 8 in the rotor yoke direction is restricted by the bottom surface 9b, and the compacted powder tooth 8 is positioned with respect to the base yoke 5 by the positioning projection 9c.

[0109] For example, a copper wire as a conductive material is wound around the side surface 9a of the resin bobbin 9. For example, the copper wire constitutes the stator coil 10.

[0110] The stator 2 with the above configuration is resin-molded by insert molding using the resin 12 (see Figure 12 ). In the stator 2, the base yoke 5 and the pressed powder teeth 8 equipped with the stator coil 10 and the resin bobbin 9 are integrally molded with the resin 12. Therefore, in the stator 2, the pressed powder teeth 8, the resin bobbin 9, and the stator coil 10 are fixed to the base yoke 5. The base yoke 5, the pressed powder teeth 8, and the stator coil 10 are insulated by the resin 12.

[0111] The stator 2 is sealed with the resin 12 in a state where the pressed powder teeth 8 are inserted into the tooth holes 6 of the base yoke 5 of the stator 2, so that stress concentration on the base yoke 5 and the pressed powder teeth 8 due to the reaction force generated in the axial-gap type motor X can be suppressed. Therefore, sufficient strength of the brittle pressed powder teeth 8 can be obtained.

[0112] In the stator 2 of the axially gap-type motor X configured as described above, the rotor 1 rotates relative to the stator 2 by the attractive and repulsive forces generated by the magnetic field induced in the pressed powder teeth 8 due to the current flowing in the stator coil 10 and the magnetic field generated by the field magnet 4 of the rotor 1.

[0113] (Pressed powder tooth shape)

[0114] Reference Figure 9 , the positional relationship between the plurality of pressed powder teeth 8 constituting the axial-gap type motor X according to the first embodiment will be described. Figure 9 The positional relationship between the pressed powder teeth 8 adjacent to each other in the circumferential direction is schematically shown. In the axial-gap type motor X having the above configuration, a groove T that is substantially rectangular when viewed in the axial direction is formed between the pressed powder teeth 8 adjacent to each other in the circumferential direction of the base yoke 5. The stator coil 10 wound around the pressed powder teeth 8 via the resin bobbin 9 is accommodated in the groove T.

[0115] The space factor of the stator coil 10 with respect to the groove T is increased by increasing the interval between the bottom surfaces 8a of the pressed powder teeth, which is the smallest among the intervals between the adjacent pressed powder teeth 8. That is, since the pressed powder teeth 8 have a substantially trapezoidal shape when viewed in the axial direction (the circumferential length of the bottom surface 8a of the pressed powder teeth in each axial direction is smaller than the circumferential length of the upper surface 8b of the pressed powder teeth), the space factor of the stator coil 10 in the groove T is larger than that in the case of using pressed powder teeth having a substantially rectangular shape when viewed in the axial direction (the circumferential length of the bottom surface 8a of the pressed powder teeth in each axial direction is equal to the circumferential length of the upper surface 8b of the pressed powder teeth).

[0116] In the axial-gap type motor X having the above configuration, each pressed powder tooth 8 can have a trapezoidal shape having the following dimensional relationship.

[0117] Assume

[0118] Number of slots of stator core 7: S,

[0119] Offset: w,

[0120] Distance from the center of the stator core 7 (rotation axis P) to the bottom surface 8a of the pressed powder tooth: r1, and

[0121] Distance from the center of the stator core 7 (rotation axis P) to the upper surface 8b of the pressed powder tooth: r2,

[0122] The pressed powder tooth 8 may have a trapezoidal shape defined as follows.

[0123] The above dimensions are Figure 9 the dimensions of the pressed powder tooth 8 schematically shown in

[0124] Core height: r1 - r2

[0125] Angle formed by the hypotenuse: 2π / S

[0126] Upper surface length: 2 × (r2 - w / sin(π / S)) × tan(π / S)

[0127] Bottom surface length: 2 × (r1 - w / sin(π / S)) × tan(π / S)

[0128] The trapezoidal pressed powder tooth 8 satisfying the above relationship is inserted into the tooth hole 6 of the base yoke 5 such that the pressed powder tooth inclined surfaces 8c of the pressed powder teeth 8 adjacent to each other in the circumferential direction are parallel. Thus, a slot T can be obtained between the pressed powder tooth inclined surfaces 8c of the pressed powder teeth 8 adjacent to each other in the circumferential direction.

[0129] The expression "parallel" includes not only the case where the pressed powder tooth inclined surfaces 8c of the adjacent pressed powder teeth 8 do not completely intersect each other, but also the case where the angle formed by the pressed powder tooth inclined surfaces 8c of the adjacent pressed powder teeth 8 is less than 90 degrees.

[0130] With the above configuration, the space factor of the stator coil 10 in the stator core 7 increases, so that the number of turns of the copper wire in the same cross-sectional area can be increased. Therefore, the magnetic flux density of the axial-gap type motor X can be improved. In addition, as an advantage of the increase in the space factor of the stator coil 10, the size of the stator coil 10 can be increased, and square wire or flat wire can be wound as the stator coil 10. When the space factor of the stator coil 10 increases, the resistance of the stator coil 10 can be reduced, and the copper loss, which is the cause of the heat generation of the stator coil 10, can also be reduced.

[0131] With the above configuration, although a large winding diameter is required to equalize the resistance of the stator coil 10, an Al coil can also be wound. Therefore, by forming the coil of Al, the weight of the axial-gap type motor X can also be reduced.

[0132] (Positioning of the pressed powder tooth 8 and the tooth hole 6)

[0133] Next, with reference to Figure 10 and Figure 11 , the positioning of the pressed powder tooth 8 inserted into the tooth hole 6 will be described. Figure 10 is a view of the state in which the pressed powder tooth 8 is inserted into the tooth hole 6 as observed in the first direction. The pressed powder tooth 8 is formed to be insertable into the tooth hole 6 of the base yoke 5. Specifically, when each pressed powder tooth 8 is observed in the axial direction, and when the base yoke 5 is observed in the axial direction, the angle formed by one pressed powder tooth inclined surface 8c and another pressed powder tooth inclined surface 8c of the pressed powder tooth 8 is substantially equal to the angle formed by one tooth hole circumferential end surface 6c and another tooth hole circumferential end surface 6c of the tooth hole 6. When each pressed powder tooth 8 is observed in the axial direction, the angle formed by one pressed powder tooth inclined surface 8c and another pressed powder tooth inclined surface 8c of the pressed powder tooth 8 includes a margin that allows the pressed powder tooth 8 to be inserted into the tooth hole 6.

[0134] When each pressed powder tooth 8 is observed in the axial direction, and when the stator core 7 is observed in the axial direction, the circumferential length L4 of the pressed powder tooth bottom surface 8a of the pressed powder tooth 8 is substantially equal to the circumferential length L1 of the tooth hole radially inner end surface 6a of the tooth hole 6. The circumferential length L4 of the pressed powder tooth bottom surface 8a includes a margin that allows the pressed powder tooth 8 to be inserted into the tooth hole 6. On the other hand, when each pressed powder tooth 8 is observed in the axial direction, and when the stator core 7 is observed in the axial direction, the circumferential length L5 of the pressed powder tooth upper surface 8b of the pressed powder tooth 8 is smaller than the circumferential length L2 of the tooth hole radially outer end surface 6b of the tooth hole 6. When each pressed powder tooth 8 is observed in the axial direction, and when the stator core 7 is observed in the axial direction, the radial length L6 from the pressed powder tooth bottom surface 8a to the pressed powder tooth upper surface 8b in the pressed powder tooth 8 is smaller than the radial length L3 from the tooth hole radially inner end surface 6a to the tooth hole radially outer end surface 6b in the tooth hole 6.

[0135] In each pressed powder tooth 8, when the pressed powder tooth inclined surface 8c contacts the tooth hole circumferential end surface 6c through the pressed powder tooth 8 inserted into the tooth hole 6, the pressed powder tooth bottom surface 8a contacts the tooth hole radially inner end surface 6a. At this time, the pressed powder tooth upper surface 8b of the pressed powder tooth 8 does not contact the tooth hole radially outer end surface 6b. That is, there is a gap B between the pressed powder tooth upper surface 8b and the tooth hole radially outer end surface 6b. Therefore, the pressed powder tooth 8 is formed not to be press-fitted into the tooth hole 6.

[0136] When inserting the press - molded powder tooth 8 configured as such into the tooth hole 6, a press - fit is unnecessary. For such a shape, when inserting the press - molded powder tooth 8 into the tooth hole 6, the force applied to the press - molded powder tooth 8 due to the contact between the bottom surface 8a of the press - molded powder tooth and the radially inner end surface 6a of the tooth hole (see the white arrow a1) or the force applied to the press - molded powder tooth 8 due to the contact between the inclined surface 8c of the press - molded powder tooth and the circumferential end surface 6c of the tooth hole (see the white arrow a2) escapes outward in the radial direction (see the white arrow a3). Therefore, the contact pressure between the press - molded powder tooth 8 and the base yoke 5 is reduced. As a result, when inserting the press - molded powder tooth 8 into the tooth hole 6, the friction caused by the contact between the press - molded powder tooth 8 and the base yoke 5 is reduced. Thus, an axial - gap type motor X can be provided that allows efficient magnetic flux flow while improving the assemblability of the press - molded powder tooth 8 and the base yoke 5.

[0137] Figure 11 Fig. is a view of the state where the positioning protrusion 9c is inserted into the positioning hole 5a as observed in the first direction. The positioning protrusion 9c of the resin bobbin 9 attached to the press - molded powder tooth 8 is configured to be inserted into the positioning hole 5a of the base yoke 5 in the state where the press - molded powder tooth 8 is inserted into the tooth hole 6. In the state where the positioning protrusion 9c is inserted into the positioning hole 5a, each positioning protrusion 9c is located between the radially outer end surface 6b of the tooth hole diameter and the upper surface 8b of the press - molded powder tooth. At this time, the positioning protrusion 9c is press - fitted between the radially outer end surface 6b of the tooth hole diameter and the upper surface 8b of the press - molded powder tooth. The press - molded powder tooth 8 is subjected to a force inward in the radial direction (see the white arrow a4) by the elastic force of the press - fitted positioning protrusion 9c. Therefore, the bottom surface 8a of the press - molded powder tooth contacts the radially inner end surface 6a of the tooth hole, and the inclined surface 8c of the press - molded powder tooth contacts the circumferential end surface 6c of the tooth hole. That is, the resin bobbin 9 is configured such that, in the state where the positioning protrusion 9c is inserted into the positioning hole 5a, the press - molded powder tooth 8 presses against the base yoke 5 inward in the radial direction of the stator core 7.

[0138] When observing the press - molded powder tooth 8 in the axial direction, each press - molded powder tooth 8 has a wedge shape in which the circumferential length gradually decreases toward the inside of the stator core 7 in the radial direction. Similarly, when observing the stator core 7 in the axial direction, the bottom surface 8a of each tooth hole 6 for the press - molded powder tooth has a wedge shape in which the circumferential length gradually decreases toward the inside of the stator core. When the inclined surface 8c of the press - molded powder tooth contacts the circumferential end surface 6c of the tooth hole due to the force applied inward in the radial direction toward the inside of the stator core 7 by the positioning protrusion 9c, the inclined surface 8c of the press - molded powder tooth presses against the circumferential end surface 6c of the tooth hole by a force perpendicular to the inclined surface 8c of the press - molded powder tooth. By the action of the wedge, an amplified force is applied to the inclined surface 8c of the press - molded powder tooth to press the press - molded powder tooth 8 against the base yoke 5 inward in the radial direction toward the inside of the stator core 7.

[0139] In each of the compression-molded powder teeth 8 configured in this way, the bottom surface 8a of the compression-molded powder tooth presses against the radially inner end surface 6a of the tooth hole (see the white arrow a6), so that the compression-molded powder tooth 8 is positioned in the radial direction with the bottom surface 8a of the compression-molded powder tooth (which is the inner side in the radial direction of the compression-molded powder tooth 8) as a reference. Each compression-molded powder tooth 8 is positioned in its circumferential direction by pressing the inclined surface 8c of the compression-molded powder tooth against the circumferential end surface 6c of the tooth hole (see the white arrow a5). The inclined surface 8c of each compression-molded powder tooth presses against the circumferential end surface 6c of the tooth hole by a force amplified by the action of the wedge (see the white arrow a5). Therefore, the magnetic reluctance between the inclined surface 8c of the compression-molded powder tooth and the circumferential end surface 6c of the tooth hole is reduced. Therefore, even if the compression-molded powder tooth 8 and the base yoke 5 are composed of different members, the magnetic flux can flow efficiently in the stator core 7.

[0140] In each compression-molded powder tooth 8, the interval B between the upper surface 8b of the compression-molded powder tooth and the radially outer end surface 6b of the tooth hole is enlarged by the positioning projection 9c. The interval between the upper surface 8b of the compression-molded powder tooth and the radially outer end surface 6b of the tooth hole is enlarged to be approximately equal to the radial length of the positioning projection 9c. Therefore, the upper surface 8b of the compression-molded powder tooth and the radially outer end surface 6b do not come into contact due to the insertion of the positioning projection 9c. In the stator core 7, the positioning projection 9c inhibits the magnetic flux from flowing from the compression-molded powder tooth 8 in the radial direction to the outside of the base yoke 5. However, the magnetic flux flowing from the compression-molded powder tooth 8 in the radial direction to the outside of the base yoke 5 is small enough relative to all the magnetic flux flowing from the compression-molded powder tooth 8 to the base yoke 5, and thus does not significantly affect the entire magnetic flux. Since the positioning projection 9c is located outside or inside the tooth hole 6 in the radial direction, the positioning projection 9c does not hinder the magnetic flux from flowing from the compression-molded powder tooth 8 in the circumferential direction to the base yoke 5. Therefore, an axial-gap type motor X can be provided that allows the magnetic flux to flow efficiently while improving the assemblability of the compression-molded powder tooth 8 and the base yoke 5.

[0141] (Positioning the compression-molded powder tooth 8 by the resin bobbin 9)

[0142] Next, with reference to Figure 12 , the positioning of the compression-molded powder tooth 8 in the direction of the rotation axis P by the resin bobbin 9 will be described. Figure 12 is a partial cross-sectional view showing the positional relationship among the field magnet 4 of the rotor 1, the resin bobbin 9, and the compression-molded powder tooth 8. By inserting the positioning projection 9c into the positioning hole 5a, the resin bobbin 9 attached to the compression-molded powder tooth 8 positions the compression-molded powder tooth 8 in the resin bobbin 9 body in the tooth hole 6 in the radial and circumferential directions. The bottom surface 9b of the resin bobbin 9 attached to the compression-molded powder tooth 8 covers at least a part of the end surface of the compression-molded powder tooth 8 in the resin bobbin 9 body, and this end surface of the compression-molded powder tooth 8 is close to the rotor yoke 3.

[0143] In the axial-gap type motor X, the bottom surface 9b faces the field magnet 4 of the rotor 1 in the axial direction. That is, the bottom surface 9b is located between the field magnet 4 and the sintered powder tooth 8. Therefore, even when the sintered powder tooth 8 is subjected to the magnetic attractive force of the field magnet 4 (see the white arrow), the bottom surface 9b restricts the movement of the sintered powder tooth 8 toward the rotor yoke 3. That is, the bottom surface 9b of the resin bobbin 9 prevents the sintered powder tooth 8 from detaching from the resin bobbin 9. The bottom surface 9b of the resin bobbin 9 maintains a uniform axial gap between the field magnet 4 and the sintered powder tooth 8. Therefore, the resin bobbin 9 can restrict the movement of the sintered powder tooth 8 in the radial direction and the circumferential direction of the rotor yoke 3 and the movement of the sintered powder tooth 8 toward the rotor yoke 3 in the tooth hole 6.

[0144] (Positioning the sintered powder tooth 8 by die molding)

[0145] Next, with reference to Figure 13 , the positioning of the sintered powder tooth using the resin 12 will be described. Figure 13 is a view of the rotor 1 provided in the die Y for resin molding as observed in the first direction. The stator 2 including the stator core 7 is molded by the resin 12 in a state where the sintered powder tooth 8 equipped with the stator coil 10 and the resin bobbin 9 is inserted into the tooth hole 6 of the base yoke 5 (see Figure 12 ). The stator 2 is provided inside the die Y. The die Y has at least one injection port Ya for injecting the resin 12 into the die Y, and the injection port Ya is located outside the sintered powder tooth 8 in the radial direction. The resin 12 injected into the die Y from the injection port Ya flows inward in the radial direction of the stator 2 (see the white arrow). By the flow pressure of the resin 12, the sintered powder tooth 8 in the tooth hole 6 is pressed inward against the base yoke 5 in the radial direction of the stator 2. The stator 2 is molded by curing the resin 12 in the flowing state filled in the die Y. The sintered powder tooth 8 is molded by the resin 12 while being pressed against the base yoke 5. Therefore, in the stator 2, the bottom surface 8a of the sintered powder tooth of the sintered powder tooth 8 does not separate from the circumferential end face 6c of the tooth hole of the base yoke 5 due to the pressure caused by flowing the resin 12 into the die Y. Therefore, an axial-gap type motor X can be provided that allows efficient magnetic flux flow while improving the assemblability of the sintered powder tooth 8 and the base yoke 5.

[0146] In addition, the stator 2 is molded by the resin 12 in a state where the sintered powder tooth 8 is inserted into the tooth hole 6 of the base yoke 5 of the stator 2, so that stress concentration on the base yoke 5 and the sintered powder tooth 8 due to the reaction force occurring in the axial-gap type motor X can be suppressed. Therefore, sufficient strength of the fragile sintered powder tooth 8 can be obtained.

[0147] (Other embodiments)

[0148] Embodiments of the present teachings have been described above, but these embodiments are merely examples for implementing the present teachings. Therefore, the present teachings are not limited to the above embodiments, and the embodiments can be modified as needed without departing from the gist of the present teachings.

[0149] In the present embodiment, the positioning hole 5a is located outside the tooth hole 6 in the radial direction of the base yoke 5. Alternatively, the positioning hole may be located inside the tooth hole in the radial direction of the base yoke. The positioning hole may be positioned in the circumferential direction of the tooth hole.

[0150] In the present embodiment, when observing the side surface 9a from the opening portion 9d, each resin bobbin 9 has a positioning projection 9c near the long side of the opening portion 9d. Alternatively, depending on the position of the positioning hole 5a, when observing the side surface 9a from the opening 9d, the positioning projection 9c of each resin bobbin 9 may also be located near the short side of the opening 9d.

[0151] In the present embodiment, the base yoke 5 has the positioning hole 5a as a notch that is at least partially continuous with the outer end surface 6b of the tooth diameter of the tooth hole 6. Alternatively, the base yoke may also have a positioning hole with an independent shape that is not continuous with the outer end surface of the tooth diameter. For example, the base yoke may have a hole that is not continuous with a part of the tooth hole or a notch that is continuous with the outer peripheral end surface of the base yoke as the positioning hole.

[0152] In the present embodiment, the pressed powder tooth 8 is a columnar member having a substantially trapezoidal cross section. Alternatively, the pressed powder tooth may be a columnar member having other cross-sectional shapes. For example, the corner portion of the pressed powder tooth may have a rounded portion or a chamfered portion.

[0153] In the present embodiment, the tooth hole 6 includes the positioning hole 5a and the slit 11. Alternatively, the tooth hole may not include at least one of the positioning hole or the slit.

[0154] In the present embodiment, the resin bobbin 9 includes the positioning projection 9c and the bottom surface 9b. Alternatively, as long as the shape of the resin bobbin can suppress the movement of the pressed powder tooth in the resin bobbin body toward the rotor yoke. Each resin bobbin may include a projection that engages with the pressed powder tooth at one end of the resin bobbin body.

[0155] In the present embodiment, the positioning projection 9c protruding in the cylindrical axis direction of the resin bobbin 9 is inserted into the positioning hole 5a that is a notch of the base yoke 5. Alternatively, the positioning hole portion that is a projection of the base yoke may also be inserted into the positioning projection portion of the hole in the resin bobbin flange that is the resin bobbin. A positioning pin may be inserted into the positioning projection portion of the hole in the resin bobbin flange that is the resin bobbin and the positioning hole portion that is the hole in the base yoke.

[0156] List of Reference Numerals

[0157] X - axis axial clearance type motor

[0158] 1 Rotor

[0159] 2 Stator

[0160] 3 Rotor yoke

[0161] 3a Rotor yoke protrusion

[0162] 3b Rotor yoke flange

[0163] 4 Field magnet

[0164] 5 Base yoke

[0165] 5a Positioning hole

[0166] 6 Tooth hole

[0167] 6a Radial inner end face of tooth hole

[0168] 6b Radial outer end face of tooth hole

[0169] 6c Peripheral outer end face of tooth hole

[0170] 7 Stator core

[0171] 8 Pressed powder tooth

[0172] 8a Bottom surface of pressed powder tooth (radial outer end of tooth)

[0173] 8b Upper surface of pressed powder tooth (radial inner end of tooth)

[0174] 8c Inclined surface of pressed powder tooth (peripheral end of tooth)

[0175] 9 Resin bobbin

[0176] 9a Side surface

[0177] 9b Bottom surface

[0178] 9c Positioning protrusion

[0179] 9d Opening

[0180] 10 Stator coil

[0181] 11 Slit

[0182] G Clearance

[0183] T Groove

[0184] P Axis of rotation

[0185] A Accommodation space for pressed powder teeth

Claims

1. An axial-gap type motor, comprising: a rotor including a plurality of field magnets and rotatable about a rotation axis, the plurality of field magnets being arranged in a circumferential direction; a cylindrical stator core located in an axial direction of the rotation axis with respect to the rotor, the stator core including a base yoke and a plurality of teeth formed of pressed particles and arranged in the circumferential direction around the rotation axis with respect to the base yoke; a plurality of cylindrical resin winding bobbins, the plurality of teeth being respectively inserted into the resin winding bobbins; and a stator coil wound around each of the plurality of resin winding bobbins, wherein, each of the resin winding bobbins includes a bottomed cylindrical side surface having a bottom surface, and a positioning projection protruding from the side surface in the axial direction, the base yoke includes a plurality of tooth holes into which the plurality of teeth are respectively inserted, and a positioning hole located outside or inside the tooth hole in a radial direction and configured such that the positioning projection is inserted into the positioning hole, when the stator core is viewed in the axial direction, each of the plurality of tooth holes extends in the radial direction of the stator core and is shaped such that a circumferential length of a radially outer end surface of the tooth hole at an outer end of the corresponding tooth hole in the radial direction is greater than a circumferential length of a radially inner end surface of the tooth hole at an inner end of the tooth hole in the radial direction, when the plurality of teeth are viewed in the axial direction, each of the plurality of teeth extends in the radial direction of the stator core and has a columnar shape in which a circumferential length of a radially outer end portion of the tooth at an outer end of the tooth in the radial direction is greater than a circumferential length of a radially inner end portion of the tooth at an inner end of the tooth in the radial direction, and in a state where the positioning projection is inserted into the positioning hole, the positioning projection presses the tooth inward in the radial direction of the stator core against the base yoke such that the radially inner end portion of the tooth contacts the radially inner end surface of the tooth hole, causing a circumferential end portion of the tooth at an end of each of the teeth in the circumferential direction of the stator core to contact a circumferential end surface of the tooth hole at an end of the tooth hole in the circumferential direction of the stator core, and the radially outer end portion of the tooth not contacting the radially outer end surface of the tooth hole.

2. The axial-gap type motor according to claim 1, wherein, each of the positioning holes is continuous with at least a part of the radially outer end surface of the tooth hole or at least a part of the radially inner end surface of the tooth hole.

3. The axial-gap type motor according to claim 1 or 2, wherein, the positioning holes are located outside the teeth in the radial direction in the base yoke.

4. The axial-gap type motor according to claim 3, wherein, in each of the positioning holes, a gap between the radially outer end surface of the tooth hole and the radially outer end portion of the tooth is enlarged by inserting the positioning projection into the positioning hole.

5. The axial-gap type motor according to any one of claims 1 to 4, wherein, The stator core is molded using resin that flows from the outside in the radial direction to the inside in the radial direction.

6. The axial-gap type electric motor according to any one of claims 1 to 5, wherein, each of the resin winding bobbins covers at least a part of the axial end face of the corresponding tooth at the end in the axial direction and close to the rotor.

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