Motor

Abstract

A motor according to the present invention comprises: a rotor that can rotate about the central axis; and a stator that faces the rotor in the axial direction. The rotor has a plurality of magnets arranged along the circumferential direction and an annular first ring member for supporting each of the plurality of magnets from the inside in the radial direction. The plurality of magnets have a plurality of first magnets, the magnetization direction of which is the axial direction and a plurality of second magnets, the magnetization direction of which intersects the axial direction. The plurality of first magnets and the plurality of second magnets are each arranged along the circumferential direction in a Halbach array. The first ring member has a plurality of protrusion portions protruding radially outward. Each of the plurality of protrusion portions is disposed spaced apart from each other along the circumferential direction. The one or more magnets have contact portions that contact the protrusions in the circumferential direction.

Description

Motor

[0001] The present invention relates to a motor. This application is based on Japanese Patent Application No. 2024-050321, filed on March 26, 2024, and claims the benefit of priority to that application, the entire contents of which are incorporated herein by reference.

[0002] There is known a motor having a rotor in which a magnet assembly is fixed to a rotor disk, in which main magnets whose magnetization direction is axial and sub-magnets whose magnetization direction is circumferentially arranged alternately in a circumferential direction, a so-called Halbach arrangement (see, for example, Patent Document 1).

[0003] Japanese Patent No. 5108236

[0004] In the motor described in Patent Document 1, a repulsive magnetic field is formed between the main magnets and the sub magnets, so a repulsive force is applied to each of the main magnets and the sub magnets. Therefore, in the rotor assembly process, it is difficult to align the main magnets and the sub magnets with no gaps in the circumferential direction and fix them to the rotor disk, which may increase the number of steps required for rotor assembly.

[0005] In view of the above circumstances, one aspect of the present invention has an object to provide a motor that can suppress an increase in the number of steps required for assembling the rotor.

[0006] One aspect of the motor of the present invention includes a rotor rotatable about a central axis and a stator axially opposed to the rotor. The rotor has a plurality of magnets arranged along a circumferential direction and an annular first ring member supporting each of the magnets from the radially inner side. The magnets include a plurality of first magnets whose magnetization direction is axial, and a plurality of second magnets whose magnetization direction intersects the axial direction. Each of the first magnets and the second magnets is arranged along the circumferential direction in a Halbach array. The first ring member has a plurality of protrusions protruding radially outward. Each of the protrusions is arranged circumferentially at intervals. One or more of the magnets has a contact portion that contacts the protrusion in the circumferential direction.

[0007] According to one aspect of the present invention, an increase in the number of steps required to assemble a rotor in a motor can be suppressed.

[0008] FIG. 1 is a cross-sectional view showing a motor of an embodiment. FIG. 2 is an exploded perspective view showing a rotor of an embodiment. FIG. 3 is a cross-sectional view showing a rotor of an embodiment. FIG. 4 is a schematic view showing a first magnet group of an embodiment. FIG. 5 is a partially enlarged cross-sectional view showing a portion of the rotor of an embodiment. FIG. 6 is a schematic view showing a second magnet group of an embodiment. FIG. 7 is a flowchart showing an assembly process of a rotor of an embodiment. FIG. 8 is a first perspective view showing a first magnet mounting process of an embodiment. FIG. 9 is a second perspective view showing the first magnet mounting process of an embodiment. FIG. 10 is a third perspective view showing the first magnet mounting process of an embodiment. FIG. 11 is a perspective view showing a second magnet mounting process of an embodiment. FIG. 12 is a perspective view showing a second ring member mounting process of an embodiment. FIG. 13 is a perspective view showing a cover member fixing process of an embodiment.

[0009] Hereinafter, motors according to embodiments of the present invention will be described with reference to the drawings. Note that the scope of the present invention is not limited to the following embodiments, and can be modified as desired within the scope of the technical concept of the present invention. In addition, in the following drawings, the scale and number of components may differ from the actual structure in order to make each component easier to understand.

[0010] In the following description, the Z axis is indicated in the figures as appropriate. The Z axis is the direction in which the central axis J of the embodiment described below extends. The central axis J shown in each figure is a virtual axis. In the following description, the direction in which the central axis J extends, i.e., the direction parallel to the Z axis, is referred to as the "axial direction." The radial direction centered on the central axis J is simply referred to as the "radial direction." The circumferential direction centered on the central axis J is simply referred to as the "circumferential direction." The side of the axial direction toward which the arrow of the Z axis points (+Z side) is referred to as the "upper side." The side of the axial direction opposite to the side toward which the arrow of the Z axis points (-Z side) is referred to as the "lower side." Note that the terms "upper side" and "lower side" are simply names used to describe the relative positional relationships of the various parts, and the actual positional relationships may be other than those indicated by these names.

[0011] The circumferential direction is indicated by the arrow θ in each drawing. The side of the circumferential direction toward which the arrow θ points is called the "one circumferential side." The opposite side of the circumferential direction to the side toward which the arrow θ points is called the "other circumferential side." The one circumferential side (+θ side) is the side that moves clockwise around the central axis J when viewed from above. The other circumferential side (-θ side) is the side that moves counterclockwise around the central axis J when viewed from above.

[0012] As shown in FIG. 1 , the motor 10 of this embodiment has a disk shape centered on a central axis J. The motor 10 is a thin motor whose axial dimension is smaller than its radial dimension. The motor 10 is an axial gap motor in which a stator 50 and a rotor 18 face each other in the axial direction with a gap between them. In this embodiment, the rotor 18 includes a first rotor 20 and a second rotor 30. The motor 10 of this embodiment is a single-stator / double-rotor axial gap motor in which the stator 50 is disposed between the first rotor 20 and the second rotor 30. The motor 10 includes the rotor 18, the stator 50, and a case 15.

[0013] The stator 50 has a substantially circular ring shape centered on the central axis J. The stator 50 is disposed above the first rotor 20 and below the second rotor 30. The stator 50 faces the first rotor 20 and the second rotor 30 with a gap therebetween in the axial direction. In other words, the stator 50 faces the rotor 18 in the axial direction. The stator 50 includes a stator case 51, teeth 52, a coil 54, a resin part 57, and a shaft 61.

[0014] The stator case 51 holds the teeth 52, the coil 54, and the resin portion 57. In this embodiment, the stator case 51 is made of resin. The stator case 51 is formed by insert molding using the teeth 52 as insert members. The stator case 51 has a bottom plate 51a, a bottom plate hole 51b, an insulator 51d, an outer cylinder 51f, and an inner cylinder 51g.

[0015] The bottom plate portion 51a has a substantially annular plate shape centered on the central axis J. The plate surface of the bottom plate portion 51a faces the axial direction. The bottom plate portion 51a faces the first rotor 20 in the axial direction with a gap therebetween. The bottom plate portion 51a surrounds the shaft 61 from the radially outer side. The radially inner edge of the bottom plate portion 51a contacts the shaft 61 in the radial direction. The radially outer edge of the bottom plate portion 51a is disposed with a radial gap between it and the case 15.

[0016] The bottom plate holes 51b are holes that penetrate the bottom plate 51a in the axial direction. In this embodiment, the stator case 51 has 12 bottom plate holes 51b. The number of bottom plate holes 51b that the stator case 51 has may be 11 or less, or 13 or more. The bottom plate holes 51b are arranged at approximately equal intervals in the circumferential direction.

[0017] The insulator portion 51d is cylindrical and protrudes upward from the edge of the bottom plate hole 51b of the bottom plate portion 51a. The insulator portion 51d opens upward. The insulator portion 51d insulates the teeth portion 52 from the coil portion 54. The stator case 51 has twelve insulator portions 51d. The insulator portions 51d are arranged at approximately equal intervals in the circumferential direction.

[0018] The outer cylinder portion 51f protrudes upward from the radial outer edge of the bottom plate portion 51a. The outer cylinder portion 51f has a generally cylindrical shape centered on the central axis J. The outer cylinder portion 51f opens upward. The outer cylinder portion 51f is disposed with a radial gap between it and the case 15.

[0019] The inner cylinder portion 51g protrudes upward from the radial inner edge of the bottom plate portion 51a. The inner cylinder portion 51g is generally cylindrical and has a center on the central axis J. The inner cylinder portion 51g is open to the upper side. A shaft 61 passes through the interior of the inner cylinder portion 51g in the axial direction. The inner circumferential surface of the inner cylinder portion 51g is fixed to the shaft 61. In this way, the stator case 51 is fixed to the shaft 61.

[0020] The teeth 52 are columnar and extend in the axial direction. The teeth 52 face the first rotor 20 and the second rotor 30 with a gap in the axial direction. In this embodiment, the stator 50 has twelve teeth 52. Each tooth 52 is disposed inside a different insulator portion 51d. Each tooth 52 is fixed to the inner surface of the insulator portion 51d. The teeth 52 are disposed at approximately equal intervals along the circumferential direction. The upper surface of each tooth 52 is exposed upward from the stator case 51 through an opening in the insulator portion 51d. The lower surface of the teeth 52 is exposed downward from the stator case 51 through the bottom plate hole portion 51b.

[0021] The coil portion 54 is attached to the insulator portion 51d. The coil portion 54 is composed of a coil wound around the outer peripheral surface of the insulator portion 51d. In this embodiment, the stator 50 has 12 coil portions 54. Each coil portion 54 is attached to a different insulator portion 51d. The coil portions 54 are arranged at approximately equal intervals along the circumferential direction. Although not shown, each coil portion 54 is electrically connected to a power supply device (not shown). When current is supplied to each coil portion 54 from the power supply device, each coil portion 54 forms an electromagnet with its magnetic poles facing the axial direction.

[0022] The resin portion 57 has a substantially circular ring shape centered on the central axis J. The resin portion 57 is disposed radially inward of the coil portion 54. The resin portion 57 is made of resin. The resin portion 57 surrounds the shaft 61 from the radially outer side. The resin portion 57 is fixed to a radially inner portion of the bottom plate portion 51a. A plurality of bus bars (not shown) are disposed inside the resin portion 57. Each bus bar electrically connects a power supply device (not shown) to the coil portion 54.

[0023] The shaft 61 has a generally cylindrical shape and extends axially about the central axis J. The shaft 61 is disposed radially inward of the stator case 51. The shaft 61 is fixed to the inner circumferential surface of the inner cylinder portion 51g. The upper end of the shaft 61 is located above the teeth portion 52. The lower end of the shaft 61 is located below the teeth portion 52. In this embodiment, the shaft 61 is made of metal.

[0024] The rotor 18 is rotatable about the central axis J. As described above, in this embodiment, the rotor 18 includes a first rotor 20 and a second rotor 30. The first rotor 20 is disposed below the stator 50. The second rotor 30 is disposed above the stator 50. The first rotor 20 and the second rotor 30 rotate synchronously about the central axis J. In this embodiment, the first rotor 20 and the second rotor 30 can effectively utilize the magnetic flux flowing out from the stator 50 on both sides in the vertical direction, thereby increasing the driving torque of the motor 10. The first rotor 20 includes a holding member 21, a yoke 22, a first magnet group 20a, a first ring member 27, a second ring member 28, and a cover member 29.

[0025] As shown in FIG. 2, the holding member 21 is substantially cylindrical and centered on the central axis J. The holding member 21 holds the yoke 22, the first magnet group 20a, the first ring member 27, and the second ring member 28. The holding member 21 has a bottom wall portion 21a, a peripheral wall portion 21b, an inner wall portion 21d, and a first bearing holding portion 21f. The bottom wall portion 21a is substantially annular and plate-shaped and centered on the central axis J. The plate surface of the bottom wall portion 21a faces the axial direction. As shown in FIG. 1, the bottom wall portion 21a surrounds the shaft 61 from the radially outer side.

[0026] As shown in Fig. 2, the peripheral wall portion 21b protrudes upward from the radial outer edge of the bottom wall portion 21a. The peripheral wall portion 21b is generally cylindrical and centered on the central axis J. The peripheral wall portion 21b is open to the upper side. The inner wall portion 21d protrudes upward from the radial inner edge of the bottom wall portion 21a. The inner wall portion 21d is generally cylindrical and centered on the central axis J. As shown in Fig. 1, the upper end of the inner wall portion 21d is located below the upper end of the first magnet group 20a.

[0027] The first bearing holder 21f has a generally cylindrical shape that protrudes in the axial direction about the central axis J. The first bearing holder 21f is open on both axial sides. A lower portion of the shaft 61 passes through the first bearing holder 21f in the axial direction. The outer peripheral surface of the first bearing holder 21f is connected to the inner peripheral surface of the inner wall portion 21d. The upper end of the first bearing holder 21f is located higher than the upper end of the inner wall portion 21d. A first bearing 71 is attached to the inner peripheral surface of the first bearing holder 21f. The first bearing 71 is annular and centered on the central axis J. In this embodiment, the first bearing 71 is a ball bearing. The first bearing 71 may also be a plain bearing. The inner peripheral surface of the first bearing 71 supports the shaft 61. This allows the first rotor 20 to rotate about the central axis J.

[0028] As shown in Fig. 2, the yoke 22 is in the shape of an annular plate centered on the central axis J. The plate surface of the yoke 22 faces the axial direction. As shown in Fig. 1, the yoke 22 is fixed to the surface of the bottom wall portion 21a facing upward. The yoke 22 is made of a magnetic metal material.

[0029] As shown in FIG. 2, the first magnet group 20a has a substantially annular shape centered on the central axis J. As shown in FIG. 1, the downward-facing surface of the first magnet group 20a contacts the yoke 22 in the axial direction. In this embodiment, the first magnet group 20a is adhesively fixed to the yoke 22 with an adhesive. As described above, the yoke 22 is fixed to the upward-facing surface of the bottom wall portion 21a. As a result, the holding member 21 holds the first magnet group 20a via the yoke 22. As shown in FIG. 3, the first magnet group 20a is arranged radially inward from the peripheral wall portion 21b. The first magnet group 20a is arranged radially outward from the first bearing holding portion 21f. The first magnet group 20a is composed of a plurality of magnets 23. The first rotor 20 includes a plurality of magnets 23. That is, the rotor 18 includes a plurality of magnets 23. In this embodiment, each magnet 23 is a permanent magnet. The magnets 23 are arranged side by side in the circumferential direction. As described above, the holding member 21 holds the first magnet group 20a via the yoke 22. Therefore, the holding member 21 holds each of the plurality of magnets 23. The plurality of magnets 23 includes a plurality of first magnets 24 and a plurality of second magnets 25.

[0030] Each first magnet 24 has a rectangular prism shape that protrudes in the axial direction. When viewed from the axial direction, each first magnet 24 has a trapezoidal shape with a dimension in a direction perpendicular to the radial direction increasing radially outward. The surface of each first magnet 24 facing one circumferential side (+θ side) is positioned closer to one circumferential side as it moves radially outward. The surface of each first magnet 24 facing the other circumferential side (-θ side) is positioned closer to the other circumferential side as it moves radially outward. In this embodiment, the first magnet group 20a includes 14 first magnets 24. The first magnets 24 are arranged at approximately equal intervals along the circumferential direction.

[0031] 4 and 6, the magnetization direction of each magnet 23 is shown imaginarily with an arrow. The direction of the imaginary arrow indicates the direction from the south pole to the north pole of each magnet 23. The magnetic pole of each magnet 23 is such that the side toward which the imaginary arrow points is the north pole, and the side opposite to the side toward which the imaginary arrow points is the south pole. In the following description, the direction of the imaginary arrow, i.e., the direction from the south pole to the north pole of each magnet 23, is referred to as the "magnetization direction." As shown in FIG. 4, the magnetization direction of the first magnet 24 is the axial direction.

[0032] As shown in FIG. 3 , the multiple first magnets 24 include seven first main magnets 24 a and seven second main magnets 24 c. The first main magnets 24 a and the second main magnets 24 c are arranged alternately in the circumferential direction. As shown in FIG. 4 , the magnetization direction of the first main magnets 24 a and the magnetization direction of the second main magnets 24 c are opposite to each other. The magnetization direction of the first main magnets 24 a faces downward. That is, the lower end of the first main magnet 24 a has a north pole, and the upper end of the first main magnet 24 a has a south pole. The magnetization direction of the second main magnets 24 c faces upward. That is, the upper end of the second main magnet 24 c has a north pole, and the lower end of the second main magnet 24 c has a south pole. In the following description, the north pole may be referred to as the first magnetic pole, and the south pole may be referred to as the second magnetic pole.

[0033] In this embodiment, the first main magnet 24a and the second main magnet 24c are magnets of the same shape with their up-down directions facing in opposite directions. In other words, the first main magnet 24a and the second main magnet 24c are magnets of the same shape, but have different surfaces fixed to the yoke 22. Therefore, in this embodiment, the first main magnet 24a and the second main magnet 24c can be made to have a common mold, and the same magnetizing device can be used to magnetize the first main magnet 24a and the second main magnet 24c. This prevents an increase in the number of manufacturing steps and costs for the first magnet 24 compared to when the shapes of the first main magnet 24a and the second main magnet 24c are different. This prevents an increase in the number of manufacturing steps and costs for the rotor 18.

[0034] As shown in FIG. 3 , each second magnet 25 has a rectangular prism shape that protrudes in the axial direction. When viewed in the axial direction, each second magnet 25 has a substantially rectangular shape with its long sides extending radially. In this embodiment, the first magnet group 20a includes 14 second magnets 25. The second magnets 25 are arranged at substantially equal intervals along the circumferential direction. One first magnet 24 is arranged between a pair of second magnets 25 that are arranged adjacent to each other in the circumferential direction. As shown in FIG. 4 , the magnetization direction of each second magnet 25 is the circumferential direction. In other words, the magnetization direction of the second magnets 25 is a direction that intersects with the axial direction.

[0035] As shown in FIG. 3 , the multiple second magnets 25 include seven first auxiliary magnets 25 a and seven second auxiliary magnets 25 c. The first auxiliary magnets 25 a and the second auxiliary magnets 25 c are arranged alternately in the circumferential direction. The surface of the first auxiliary magnet 25 a facing one circumferential side (+θ side) faces the first main magnet 24 a in the circumferential direction, and the surface of the first auxiliary magnet 25 a facing the other circumferential side (−θ side) faces the second main magnet 24 c in the circumferential direction. The surface of the second auxiliary magnet 25 c facing one circumferential side faces the second main magnet 24 c in the circumferential direction, and the surface of the second auxiliary magnet 25 c facing the other circumferential side faces the first main magnet 24 a in the circumferential direction.

[0036] As shown in FIG. 4 , the magnetization direction of the first auxiliary magnet 25a and the magnetization direction of the second auxiliary magnet 25c are opposite to each other. The magnetization direction of the first auxiliary magnet 25a is on the other circumferential side (-θ side). That is, an N pole is formed at the end of the first auxiliary magnet 25a on the other circumferential side, and an S pole is formed at the end of the first auxiliary magnet 25a on one circumferential side (+θ side). The magnetization direction of the second auxiliary magnet 25c is on one circumferential side. That is, an N pole is formed at the end of the second auxiliary magnet 25c on one circumferential side, and an S pole is formed at the end of the second auxiliary magnet 25c on the other circumferential side. As a result, the multiple first magnets 24 and the multiple second magnets 25 are arranged circumferentially in a Halbach array in which the magnetic field strength is stronger on the upper side. Therefore, it is possible to increase the magnetic flux density flowing from the first magnet group 20a into the electromagnets formed in the stator 50, thereby increasing the magnetic force applied to the first magnet group 20a, thereby increasing the output torque of the motor 10.

[0037] In this embodiment, the first and second auxiliary magnets 25a and 25c are magnets of the same shape but with their vertical directions facing in opposite directions. That is, the first and second auxiliary magnets 25a and 25c are magnets of the same shape but with different surfaces fixed to the yoke 22. Therefore, in this embodiment, the first and second auxiliary magnets 25a and 25c can be made to have a common mold, which allows for the use of a common mold for molding the first and second auxiliary magnets 25a and 25c, and a common magnetizing device for magnetizing the first and second auxiliary magnets 25a and 25c. This prevents an increase in the number of steps and costs required to manufacture the second magnet 25 compared to when the shapes of the first and second auxiliary magnets 25a and 25c are different. This prevents an increase in the number of steps and costs required to manufacture the rotor 18.

[0038] As shown in FIG. 5, the multiple second magnets 25 have first surfaces 25e. In the first auxiliary magnet 25a, the first surface 25e faces the other circumferential side (-θ side). In the second auxiliary magnet 25c, the first surface 25e faces one circumferential side (+θ side). As shown in FIG. 4, the first surface 25e of each of the first auxiliary magnet 25a and the second auxiliary magnet 25c has an N pole. In other words, each of the multiple second magnets 25 has a first surface 25e that faces the circumferential direction and has an N pole, i.e., a first magnetic pole. As shown in FIG. 5, a recess 25g is provided on the first surface 25e. In other words, the recess 25g is provided on each of the multiple second magnets 25. Therefore, the recess 25g is provided on the circumferential surface of at least one magnet 23. The recess 25g may be provided on only some of the multiple second magnets 25. In addition, the recess 25 g may be provided in one or more of the first magnets 24 .

[0039] The recess 25g is a recess recessed from the first surface 25e toward the circumferentially inward side of the second magnet 25. The recess 25g is provided on the radially inner portion of the first surface 25e. The recess 25g opens radially inward. In this embodiment, when viewed from the axial direction, the inner surface of the recess 25g is an inclined surface that is positioned circumferentially inward of the second magnet 25 as it extends radially inward. The inner surface of the recess 25g is a contact portion 25h. In the first complementary magnet 25a, the contact portion 25h is provided on the first surface 25e facing the other circumferential side (-θ side). In the second complementary magnet 25c, the contact portion 25h is provided on the first surface 25e facing one circumferential side (+θ side). In this embodiment, each second magnet 25 has a contact portion 25h. Therefore, one or more magnets 23 have a contact portion 25h. When viewed from the axial direction, the recess 25g may have a generally rectangular shape with one inner surface facing radially inward and the other inner surface facing the circumferential direction. In this case, the contact portion 25h is the surface of the two inner surfaces of the recess 25g facing the circumferential direction.

[0040] As shown in Fig. 2, the first ring member 27 has an annular shape surrounding the central axis J. In this embodiment, the first ring member 27 has a substantially circular annular shape centered on the central axis J. As shown in Fig. 3, the first ring member 27 is disposed radially inward of the first magnet group 20a. The first ring member 27 has an annular portion 27a and a protruding portion 27c.

[0041] The annular portion 27a has a substantially circular ring shape centered on the central axis J. The annular portion 27a surrounds the first bearing holder 21f from the radially outer side. The inner circumferential surface of the annular portion 27a faces the first bearing holder 21f in the radial direction. The annular portion 27a may be in contact with the first bearing holder 21f or may face the first bearing holder 21f with a radial gap therebetween. As shown in FIG. 1, the annular portion 27a is fixed to the upper surface of the inner wall portion 21d. That is, the first ring member 27 is fixed to the holder 21. This allows the holder 21 to hold the first ring member 27. As shown in FIG. 3, the outer circumferential surface of the annular portion 27a is in radial contact with the radially inward facing surfaces of each of the multiple magnets 23. The first ring member 27 supports each of the multiple magnets 23 from the radially inner side. This allows the radial position of each magnet 23 to be determined with high precision.

[0042] The protrusions 27c are protrusions that protrude radially outward from the annular portion 27a. The first ring member 27 has a plurality of protrusions 27c. In this embodiment, the first ring member 27 has fourteen protrusions 27c. The protrusions 27c are arranged at intervals along the circumferential direction. The plurality of protrusions 27c includes seven first protrusions 27d and seven second protrusions 27e. The first protrusions 27d and the second protrusions 27e are arranged alternately along the circumferential direction.

[0043] As shown in FIG. 5 , when viewed from the axial direction, the first protrusion 27d has a generally right-angled triangular shape that protrudes radially outward from the annular portion 27a. The first protrusion 27d has an inclined surface that is positioned toward one circumferential side (+θ side) as it extends radially inward. The first protrusion 27d is positioned inside the recess 25g of the first auxiliary magnet 25a. The inclined surface of the first protrusion 27d circumferentially contacts the contact portion 25h of the first auxiliary magnet 25a. That is, the first protrusion 27d circumferentially contacts the contact portion 25h of the first auxiliary magnet 25a. Although not shown, the inclined surface of each first protrusion 27d circumferentially contacts the contact portion 25h of a different first auxiliary magnet 25a. This determines the circumferential position of each first auxiliary magnet 25a relative to the first ring member 27. The surface of the first protrusion 27d facing the other circumferential side (-θ side) comes into circumferential contact with the surface of the second main magnet 24c facing one circumferential side.

[0044] When viewed from the axial direction, the second protrusion 27e has a generally right-angled triangular shape that protrudes radially outward from the annular portion 27a. The second protrusion 27e has an inclined surface that is positioned toward the other circumferential side (-θ side) as it extends radially inward. The second protrusion 27e is positioned inside the recess 25g of the second auxiliary magnet 25c. The inclined surface of the second protrusion 27e contacts the contact portion 25h of the second auxiliary magnet 25c in the circumferential direction. That is, the second protrusion 27e contacts the contact portion 25h of the second auxiliary magnet 25c in the circumferential direction. Although not shown, the inclined surface of each second protrusion 27e contacts the contact portion 25h of a different second auxiliary magnet 25c in the circumferential direction. This determines the circumferential position of each second auxiliary magnet 25c relative to the first ring member 27. As described above, the inclined surfaces of the first protrusions 27d contact the contact portions 25h of the different first auxiliary magnets 25a in the circumferential direction. As a result, each second magnet 25 has a contact portion 25h that contacts the protrusion 27c in the circumferential direction. In other words, one or more magnets 23 have a contact portion 25h that contacts the protrusion 27c in the circumferential direction.

[0045] The surface of the second protrusion 27e facing one circumferential side (+θ side) is in circumferential contact with the surface of the second main magnet 24c facing the other circumferential side. As described above, the surface of the first protrusion 27d facing the other circumferential side (−θ side) is in circumferential contact with the surface of the second main magnet 24c facing one circumferential side. Therefore, the first protrusion 27d and the second protrusion 27e can accurately determine the circumferential position of the second main magnet 24c.

[0046] As shown in FIG. 2 , the second ring member 28 is annular and surrounds the central axis J. In this embodiment, the second ring member 28 has a substantially circular ring shape centered on the central axis J. As shown in FIG. 3 , the second ring member 28 is formed of an annular plate member whose plate surface faces a direction perpendicular to the axial direction. When viewed from the axial direction, the second ring member 28 has a wave shape that oscillates radially in the circumferential direction. The second ring member 28 is elastically deformable in the radial direction. In the radial direction, the second ring member 28 is disposed between each of the multiple magnets 23 and the peripheral wall portion 21b. That is, in the radial direction, the second ring member 28 is disposed between each of the multiple magnets 23 and the holding member 21. The second ring member 28 is in radial contact with the surfaces of each magnet 23 facing radially outward. The second ring member 28 is also in radial contact with the inner circumferential surface of the peripheral wall portion 21b. The second ring member 28 applies an elastic force directed radially inward to each of the plurality of magnets 23. This presses each magnet 23 against the first ring member 27, thereby effectively suppressing variation in the radial position of each magnet 23.

[0047] As shown in Fig. 2, the cover member 29 has a substantially annular plate shape centered on the central axis J. As shown in Fig. 1, the cover member 29 covers the holding member 21, the first magnet group 20a, and the second ring member 28 from above. Although not shown, the cover member 29 is fixed to the holding member 21. In this embodiment, the cover member 29 is fixed to the holding member 21 by fastening members such as screws. The cover member 29 may also be adhesively fixed to the holding member 21 by an adhesive. The cover member 29 contacts each of the multiple magnets 23 in the axial direction. This makes it possible to prevent each magnet 23 from moving in the axial direction.

[0048] In this embodiment, the cover member 29 is made of resin. Therefore, the weight of the cover member 29 can be reduced compared to when the cover member 29 is made of metal. This, in turn, reduces the weight of the rotor 18. The cover member 29 may be made of fiber-reinforced plastic, such as carbon fiber reinforced plastic (CFRP). In this case, the strength of the cover member 29 can be increased while reducing its weight. The cover member 29 may also be made of a non-magnetic metal material, such as aluminum. This increases the strength of the cover member 29, making it easier to reduce its thickness. This reduces the gap between the first magnet group 20a and the teeth 52, thereby increasing the magnetic force applied to the first magnet group 20a. This increases the output torque of the motor 10.

[0049] As described above, the second rotor 30 is disposed above the stator 50. The second rotor 30 includes a retaining member 31, a yoke 22, a second magnet group 30a, a first ring member 27, a second ring member 28, and a cover member 29. In this embodiment, the shapes and arrangements of the components constituting the second rotor 30 are substantially plane-symmetrical to the shapes and arrangements of the components constituting the first rotor 20, with a plane perpendicular to the axial direction as the plane of symmetry. Therefore, in the following description of the second rotor 30, descriptions of the same shapes and arrangements as those of the first rotor 20 may be omitted.

[0050] The holding member 31 is substantially cylindrical and centered on the central axis J. The holding member 31 holds the yoke 22, the second magnet group 30a, the first ring member 27, and the second ring member 28. The holding member 31 has a top wall portion 31a, a peripheral wall portion 31b, an inner wall portion 31d, and a second bearing holding portion 31f. The top wall portion 31a is substantially annular and plate-shaped and centered on the central axis J. The plate surface of the top wall portion 31a faces the axial direction.

[0051] The peripheral wall portion 31b protrudes downward from the radial outer edge of the top wall portion 31a. The peripheral wall portion 31b is generally cylindrical and centered on the central axis J. The peripheral wall portion 31b opens downward. The inner wall portion 31d protrudes downward from the radial inner edge of the top wall portion 31a. The inner wall portion 31d is generally cylindrical and centered on the central axis J.

[0052] The second bearing holder 31f has a generally cylindrical shape that protrudes in the axial direction around the central axis J. The second bearing holder 31f opens downward. The outer peripheral surface of the second bearing holder 31f is connected to the inner wall portion 31d. The second bearing holder 31f has a hole 31g that penetrates the second bearing holder 31f in the axial direction. When viewed from the axial direction, the hole 31g has a generally circular shape centered on the central axis J. A second bearing 72 is attached to the inner peripheral surface of the second bearing holder 31f. The second bearing 72 has an annular shape centered on the central axis J. In this embodiment, the second bearing 72 is a ball bearing. The second bearing 72 may be a plain bearing. The inner peripheral surface of the second bearing 72 supports the shaft 61. This allows the second rotor 30 to rotate around the central axis J.

[0053] The yoke 22 has an annular plate shape centered on the central axis J. The yoke 22 is fixed to the surface of the top wall portion 31a facing downward.

[0054] Although not shown in the drawings, the second magnet group 30a has a substantially annular shape centered on the central axis J. The second magnet group 30a is adhesively fixed to the yoke 22. The holding member 31 holds the second magnet group 30a via the yoke 22. The second magnet group 30a is arranged radially inward from the peripheral wall portion 31b. The second magnet group 30a is arranged radially outward from the second bearing holding portion 31f. The second magnet group 30a is composed of a plurality of magnets 23. In other words, the second rotor 30 has a plurality of magnets 23. In other words, the rotor 18 has a plurality of magnets 23. Although not shown in the drawings, the plurality of magnets 23 are arranged side by side in the circumferential direction. The holding member 31 holds each of the plurality of magnets 23. As shown in FIG. 6 , the plurality of magnets 23 includes a plurality of first magnets 24 and a plurality of second magnets 25.

[0055] Although not shown, in this embodiment, the second magnet group 30a includes 14 first magnets 24. The first magnets 24 are arranged at approximately equal intervals along the circumferential direction. Although not shown, the multiple first magnets 24 include seven first main magnets 24a and seven second main magnets 24c. The magnetization direction of each of the first magnets 24 in the second magnet group 30a is opposite to the magnetization direction of each of the first magnets in the first magnet group 20a. More specifically, the magnetization direction of the first main magnets 24a in the second magnet group 30a is upward. The magnetization direction of the second main magnets 24c in the second magnet group 30a is downward. Although not shown, the first main magnets 24a in the second magnet group 30a are arranged to overlap the first main magnets 24a in the first magnet group 20a in the axial direction. The second main magnets 24c of the second magnet group 30a are arranged so as to overlap with the second main magnets 24c of the first magnet group 20a in the axial direction. Other configurations of the first magnets 24 of the second magnet group 30a are similar to the other configurations of the first magnets 24 of the first magnet group 20a described above.

[0056] Although not shown in the figures, in this embodiment, the second magnet group 30a includes 14 second magnets 25. The second magnets 25 are arranged at approximately equal intervals along the circumferential direction. Although not shown in the figures, the multiple second magnets 25 include seven first auxiliary magnets 25a and seven second auxiliary magnets 25c. The first auxiliary magnets 25a of the second magnet group 30a are arranged to overlap the first auxiliary magnets 25a of the first magnet group 20a in the axial direction. The second auxiliary magnets 25c of the second magnet group 30a are arranged to overlap the second auxiliary magnets 25c of the first magnet group 20a in the axial direction. The magnetization direction of the first auxiliary magnets 25a is oriented toward the other circumferential side (-θ side). The magnetization direction of the second auxiliary magnets 25c is oriented toward one circumferential side (+θ side). As a result, in the second magnet group 30a, the multiple first magnets 24 and the multiple second magnets 25 are arranged circumferentially in a Halbach array, with the magnetic field strength increasing downward. This increases the magnetic flux density flowing from the second magnet group 30a into the electromagnets formed in the stator 50, thereby increasing the magnetic force applied to the second magnet group 30a. This increases the output torque of the motor 10. Other configurations of each second magnet 25 in the second magnet group 30a are similar to those of each second magnet 25 in the first magnet group 20a described above. Specifically, each of the multiple second magnets 25 has a first surface 25e. A recess 25g is provided on the first surface 25e (see FIG. 5). When viewed from the axial direction, the inner surface of the recess 25g is an inclined surface that is positioned circumferentially inward of the second magnet 25 as it extends radially inward. The inner surface of the recess 25g is a contact portion 25h (see FIG. 5). That is, one or more magnets 23 have a contact portion 25h. In this embodiment, each second magnet 25 has a contact portion 25h.

[0057] As shown in FIG. 1 , the first ring member 27 is annular and surrounds the central axis J. In this embodiment, the first ring member 27 is substantially annular and centered on the central axis J. The first ring member 27 surrounds the second bearing holder 31f from the radially outer side. The annular portion 27a is fixed to the lower surface of the inner wall portion 31d. This allows the holder 31 to hold the first ring member 27. The first ring member 27 supports each of the multiple magnets 23 from the radially inner side. This allows the radial position of each magnet 23 to be determined with high precision.

[0058] Although not shown, the protrusions 27c of the first ring member 27 are spaced apart from one another in the circumferential direction. The inclined surfaces of the first protrusions 27d contact the contact portions 25h of the first auxiliary magnets 25a, which are different from each other, in the circumferential direction. The inclined surfaces of the second protrusions 27e contact the contact portions 25h of the second auxiliary magnets 25c, which are different from each other, in the circumferential direction. As a result, each second magnet 25 has a contact portion 25h that contacts the protrusion 27c in the circumferential direction. In other words, one or more magnets 23 have a contact portion 25h that contacts the protrusion 27c in the circumferential direction. This also determines the circumferential positions of the first auxiliary magnets 25a and the second auxiliary magnets 25c relative to the first ring member 27. The other configurations of the first ring member 27 of the second rotor 30 are similar to those of the first ring member 27 of the first rotor 20 described above.

[0059] The second ring member 28 is disposed radially between each of the plurality of magnets 23 and the peripheral wall portion 31b. That is, the second ring member 28 is disposed radially between each of the plurality of magnets 23 and the retaining member 31. The second ring member 28 applies an elastic force directed radially inward to each of the plurality of magnets 23. This presses each magnet 23 against the first ring member 27. Therefore, the radial position of each magnet 23 can be determined with greater precision. Other configurations of the second ring member 28 of the second rotor 30 are similar to those of the second ring member 28 of the first rotor 20 described above.

[0060] According to this embodiment, the rotor 18 includes an annular second ring member 28 that is elastically deformable in the radial direction. The second ring member 28 surrounds the plurality of magnets 23 from the radially outer side and applies a radially inward elastic force to each of the plurality of magnets 23. Therefore, as described above, the radially inward elastic force of the second ring member 28 is applied to each magnet 23, thereby pressing each magnet 23 against the first ring member 27. This allows the radial position of each magnet 23 to be accurately determined, allowing the magnets 23 to be accurately overlapped when viewed circumferentially. This prevents a decrease in the magnetic flux density flowing from the first magnet 24 to the second magnet 25 and the magnetic flux density flowing from the second magnet 25 to the first magnet 24. This effectively increases the magnetic flux density flowing from each of the first magnet group 20a and the second magnet group 30a into the electromagnets formed in the stator 50. This effectively increases the output torque of the motor 10.

[0061] According to this embodiment, the rotor 18 has retaining members 21, 31 that retain the plurality of magnets 23 and the second ring member 28, respectively, and the second ring member 28 is disposed radially between each of the plurality of magnets 23 and the retaining members 21, 31. When the radial position of each magnet 23 is determined by the peripheral wall portions 21b, 31b of the retaining members 21, 31 and the first ring member 27, the radial positional accuracy of each magnet 23 is determined by the shape accuracy of the peripheral wall portions 21b, 31b, the first ring member 27, and each magnet 23. Therefore, in order to accurately determine the radial position of each magnet 23, high shape accuracy is required for the shapes of the peripheral wall portions 21b, 31b, the first ring member 27, and each magnet 23. This may increase the manufacturing costs of these components. In contrast, in the present embodiment, as described above, the magnets 23 are pressed against the first ring member 27 by the elastic force of the second ring member 28, which is elastically deformable in the radial direction, and the radial position of each magnet 23 can be determined with high precision. This prevents the shape precision required of the peripheral wall portions 21b, 31b, the first ring member 27, and each magnet 23 from becoming too high. This prevents an increase in the manufacturing costs of the holding members 21, 31, the first ring member 27, and each magnet 23. This more effectively prevents an increase in the manufacturing cost of the rotor 18.

[0062] The cover member 29 is in the shape of a substantially annular plate centered on the central axis J. The cover member 29 covers the retaining member 31, the second magnet group 30a, and the second ring member 28 from below. The cover member 29 is fixed to the retaining member 31. The cover member 29 contacts each of the multiple magnets 23 in the axial direction. This makes it possible to prevent each magnet 23 from moving in the axial direction. Other configurations of the cover member 29 of the second rotor 30 are similar to those of the cover member 29 of the first rotor 20 described above.

[0063] According to this embodiment, the rotor 18 has a cover member 29 that is fixed to the holding members 21, 31 and that contacts each of the multiple magnets 23 in the axial direction. Therefore, the cover member 29 can prevent each magnet 23 from moving in the axial direction. As a result, even if each magnet 23 comes off the yoke 22 due to vibrations transmitted to each magnet 23 during operation of the motor 10, each magnet 23 can be prevented from falling out of the rotor 18. This can improve the operational stability of the motor 10.

[0064] As shown in FIG. 1 , the case 15 is substantially cylindrical and centered on the central axis J. The case 15 is open on both axial sides. The case 15 surrounds the rotor 18 and the stator 50 from the radially outer side. The lower end of the case 15 is fixed to the peripheral wall portion 21b of the holding member 21. This fixes the case 15 to the first rotor 20. The upper end of the case 15 is fixed to the peripheral wall portion 31b of the holding member 31. This fixes the case 15 to the second rotor 30. As a result, the first rotor 20 and the second rotor 30 are fixed to each other via the case 15. Therefore, the first rotor 20 and the second rotor 30 rotate synchronously around the central axis J.

[0065] Next, the assembly process of the rotor 18 of this embodiment will be described. As shown in FIG. 7 , the assembly process of the rotor 18 includes a first magnet attachment process P01 for attaching the first magnets 24 to the yoke 22, a second magnet attachment process P02 for attaching the second magnets 25 to the yoke 22, a second ring member attachment process P03 for attaching the second ring members 28 to the magnets 23, a magnet fixing process P04 for fixing the magnets 23 to the yoke 22, and a cover member fixing process P05 for fixing the cover member 29 to the holding member 21. In the following description, the term "workers, etc." includes workers and assembly equipment, etc., who perform the tasks in each process. The tasks in each process may be performed by workers alone, by assembly equipment alone, or by both workers and assembly equipment. In the following description, the assembly process of the first rotor 20 will be described, but the second rotor 30 can also be assembled using a similar assembly process.

[0066] In the first magnet attachment process P01, the first magnet 24 is attached to the yoke 22. As shown in FIG. 8 , in the first magnet attachment process P01, a worker first attaches the yoke 22 and the first ring member 27 to a base jig 81. The base jig 81 is plate-shaped and extends in a direction perpendicular to the axial direction. A first hole 81a and a second hole 81e are provided in the base jig 81. The base jig 81 has four positioning pins 81c. The first hole 81a is a hole recessed downward from the upward-facing surface of the base jig 81. When viewed in the axial direction, the first hole 81a has a substantially circular ring shape centered on the central axis J. The outer diameter of the first hole 81a is the same as the outer diameter of the yoke 22. The axial dimension of the first hole 81a is the same as the axial dimension of the yoke 22. An operator places the yoke 22 inside the first hole 81a. This attaches the yoke 22 to the pedestal jig 81. The second hole 81e is a female threaded hole recessed downward from the upward-facing surface of the pedestal jig 81. The second hole 81e is provided radially inward of each of the positioning pins 81c.

[0067] Each positioning pin 81c has a generally cylindrical shape and protrudes upward from the base jig 81. Each positioning pin 81c is fixed to the base jig 81. The positioning pins 81c are arranged at intervals along the circumferential direction. The diameter of a circle centered on the central axis J and tangent to the radial outer edge of each positioning pin 81c is slightly smaller than the inner diameter of the annular portion 27a of the first ring member 27. An operator moves the first ring member 27 from the upper side of the base jig 81 downward and passes each positioning pin 81c through the interior of the first ring member 27. When the first ring member 27 is moved downward until it axially contacts the base jig 81, the first ring member 27 is attached to the base jig 81.

[0068] Next, the worker or the like attaches the first guide jig 83 to the base jig 81. As shown in FIG. 9 , the first guide jig 83 has an annular portion 83a and multiple legs 83d. The annular portion 83a is generally cylindrical and extends axially around the central axis J. When viewed axially, the radial outer edge of the annular portion 83a is positioned slightly radially inward relative to the radial outer edge of the annular portion 27a. Four holes 83b are formed in the annular portion 83a.

[0069] Each hole 83b is a hole that penetrates the annular portion 83a in the axial direction. The holes 83b are spaced apart in the circumferential direction. Different positioning pins 81c are passed through each hole 83b in the axial direction. Each positioning pin 81c is clearance-fitted into the hole 83b. This determines the circumferential and radial positions of the first guide jig 83 relative to the base jig 81. The annular portion 83a is provided with a housing (not shown). The housing is a hole recessed upward from the downward-facing surface of the annular portion 83a. The housing extends around the entire circumference in the circumferential direction. The housing opens radially outward. The first ring member 27 is disposed inside the housing. The annular portion 27a of the first ring member 27 is exposed radially outward from the annular portion 83a.

[0070] The multiple legs 83d are generally rectangular parallelepipeds extending radially outward from the annular portion 83a. In this embodiment, the first guide jig 83 has 14 legs 83d. The legs 83d are arranged at generally equal intervals along the circumferential direction. The circumferential dimension of each leg 83d is the same as the circumferential dimension of the second magnet 25. An insertion hole 83e is provided between a pair of legs 83d arranged adjacent to each other in the circumferential direction. The first guide jig 83 has 14 insertion holes 83e. When viewed in the axial direction, the shape of each insertion hole 83e is the same as the shape of the first magnet 24.

[0071] Next, the worker attaches the first magnet 24 to the yoke 22. The worker first applies adhesive to at least one of the upward-facing surface of the yoke 22 and the downward-facing surface of the first magnet 24. A thermosetting resin such as epoxy resin or silicone resin can be used as the adhesive. Next, the worker inserts the first magnet 24 into the insertion hole 83e until the radially inward-facing surface of the first magnet 24 contacts the first ring member 27, and then attaches the first magnet 24 to the yoke 22. As described above, the shape of each insertion hole 83e is the same as the shape of the first magnet 24 when viewed from the axial direction. Therefore, the circumferential position of each first magnet 24 relative to the yoke 22 and the first ring member 27 can be determined by the circumferential surface of the leg 83d. Furthermore, the radial position of each first magnet 24 can be determined by contacting the radially inward-facing surface of each first magnet 24 with the first ring member 27. Although not shown, as described above, the surface of the first protrusion 27d facing the other circumferential side (-θ side) contacts the surface of the second main magnet 24c facing one circumferential side (+θ side) in the circumferential direction, and the surface of the second protrusion 27e facing one circumferential side contacts the surface of the second main magnet 24c facing the other circumferential side in the circumferential direction. This allows the circumferential position of each second main magnet 24c relative to the yoke 22 and the first ring member 27 to be determined with greater precision. In other words, the simple task of inserting the second main magnet 24c into the insertion hole 83e and bringing the second main magnet 24c into contact with the first protrusion 27d and the second protrusion 27e allows the circumferential position of each second main magnet 24c relative to the yoke 22 and the first ring member 27 to be determined with greater precision. As shown in FIG. 10 , the first magnet attachment process P01 is completed when an operator attaches each first magnet 24 to the yoke 22.

[0072] In the second magnet attachment process P02, the second magnet 25 is attached to the yoke 22. As shown in Figure 11, an operator first removes the first guide jig 83 from the base jig 81, and then attaches the second guide jig 85 to the base jig 81. The second guide jig 85 is substantially circular and centered on the central axis J. The second guide jig 85 is provided with a first hole 85a, a second hole 85b, a third hole 85d, and a fourth hole 85e.

[0073] The first hole portions 85a are circular holes that penetrate the second guide jig 85 in the axial direction. Four first holes 85a are provided in the second guide jig 85. The first holes 85a are provided at intervals in the circumferential direction. Different positioning pins 81c are passed through the first holes 85a in the axial direction. Each positioning pin 81c is loosely fitted into the first hole portion 85a. This determines the circumferential and radial positions of the second guide jig 85 relative to the base jig 81.

[0074] The second hole 85b is a hole that penetrates the second guide jig 85 in the axial direction. When viewed in the axial direction, the second hole 85b is a circular hole centered on the central axis J. Although not shown, when viewed in the axial direction, the second hole 85b overlaps with the second hole 81e provided in the base jig 81. When a screw 88 is passed axially through the second hole 85b and tightened into the second hole 81e, the second guide jig 85 is attached to the base jig 81. At this time, the second guide jig 85 comes into contact with each of the first magnets 24 attached to the yoke 22 in the axial direction.

[0075] The third holes 85d are female-threaded holes that axially penetrate the second guide jig 85. Fourteen third holes 85d are provided in the second guide jig 85. The third holes 85d are provided at approximately equal intervals along the circumferential direction. When viewed from the axial direction, each third hole 85d is located between a pair of first magnets 24 that are arranged adjacent to each other in the circumferential direction.

[0076] The fourth holes 85e are holes that penetrate the second guide jig 85 in the axial direction. When viewed in the axial direction, the fourth holes 85e are generally rectangular with their long sides extending circumferentially. Fourteen fourth holes 85e are provided in the second guide jig 85. Each fourth hole 85e is spaced apart in the circumferential direction. Each fourth hole 85e is located radially outward from the first hole 85a and radially inward from the third hole 85d. When viewed in the axial direction, each fourth hole 85e is located between a pair of first magnets 24 that are adjacent to each other in the circumferential direction. Although not shown, when viewed in the axial direction, each fourth hole 85e overlaps with a different protrusion 27c. This allows an operator or the like to visually recognize each protrusion 27c through each fourth hole 85e. The first protrusion 27d overlaps with a portion on the other circumferential side (-θ side) of the fourth hole 85e. Therefore, the protrusion 27c that can be seen by an operator or the like in the portion on the other circumferential side of the fourth hole 85e is the first protrusion 27d. The second protrusion 27e overlaps with a portion on one circumferential side (+θ side) of the fourth hole 85e. Therefore, the protrusion 27c that can be seen by an operator or the like in the portion on one circumferential side of the fourth hole 85e is the second protrusion 27e.

[0077] Next, the worker attaches the second magnet 25 to the yoke 22. First, the worker applies adhesive to at least one of the upward-facing surface of the yoke 22 and the downward-facing surface of the second magnet 25. Thermosetting resins such as epoxy resin and silicone resin can be used as the adhesive. Next, the worker inserts the second magnet 25 between a pair of first magnets 24 arranged adjacent to each other in the circumferential direction. As described above, the first auxiliary magnet 25a and the second auxiliary magnet 25c are magnets of the same shape but with their top and bottom directions facing in opposite directions. As shown in FIG. 5 , the first surface 25e of the first auxiliary magnet 25a, on which the recess 25g and the contact portion 25h are provided, faces the other circumferential side (−θ side), and the first surface 25e of the second auxiliary magnet 25c, on which the recess 25g and the contact portion 25h are provided, faces the one circumferential side (+θ side). 11 , when the first protrusion 27d is visible in the portion on the other circumferential side of the fourth hole 85e between the pair of first magnets 24, the worker inserts the first auxiliary magnet 25a from the radially outer side between the pair of first magnets 24 with the first surface 25e facing the other circumferential side. In other words, the worker inserts the first auxiliary magnet 25a between the pair of first magnets 24 with the first surface 25e, which allows contact between the first protrusion 27d and the contact portion 25h, facing the other circumferential side. This allows the first auxiliary magnet 25a to be inserted between the pair of first magnets 24 with the magnetization direction of the first auxiliary magnet 25a facing the other circumferential side.

[0078] Furthermore, although not shown, when the second protrusion 27e is visible on one circumferential side (+θ side) of the fourth hole 85e between another pair of first magnets 24, the worker inserts the second auxiliary magnet 25c from the radially outer side between the pair of first magnets 24 with the first surface 25e facing one circumferential side. In other words, the worker inserts the second auxiliary magnet 25c between the pair of first magnets 24 with the first surface 25e, which allows contact between the second protrusion 27e and the contact portion 25h, facing one circumferential side. This allows the second auxiliary magnet 25c to be inserted between the pair of first magnets 24 with the magnetization direction of the second auxiliary magnet 25c facing one circumferential side.

[0079] The worker inserts each second magnet 25 between the first magnets 24 until the contact portion 25h of each second magnet 25 comes into circumferential contact with the protrusion 27c, thereby determining the circumferential and radial positions of each second magnet 25 relative to the yoke 22 and the first ring member 27. In this embodiment, after inserting the second magnets 25 between the first magnets 24, a screw 86 may be tightened into the fourth hole 85e located above the second magnet 25 to press the second magnet 25 against the yoke 22. This prevents the second magnet 25 from moving due to the repulsive force between the second magnet 25 and the first magnet 24, thereby enabling the position of the second magnet 25 to be determined accurately. As shown in FIG. 12 , the worker attaches each second magnet 25 to the yoke 22, completing the second magnet attachment process P02.

[0080] In the second ring member attachment process P03, the second ring member 28 is attached to each magnet 23. The worker, etc., moves the second ring member 28, which is positioned above the base jig 81, downward and attaches the second ring member 28 to the surface of each magnet 23 facing radially outward. As a result, the elastic force of the second ring member 28 facing radially inward is applied to each magnet 23, so that each magnet 23 is pressed against the first ring member 27. Therefore, the radial position of each magnet 23 can be determined with greater precision. Once the worker, etc., has attached the second ring member 28 to each magnet 23, the second ring member attachment process P03 is completed.

[0081] In the magnet fixing process P04, each magnet 23 is fixed to the yoke 22. An operator or the like heats the pedestal jig 81, to which the yoke 22, the multiple magnets 23, the first ring member 27, the second ring member 28, and the second guide jig 85 are attached, in a heating device such as a heating furnace, to harden the adhesive. This adhesively fixes each magnet 23 to the yoke 22. Once each magnet 23 is fixed to the yoke 22, the magnet fixing process P04 is completed.

[0082] In the cover member fixing process P05, the cover member 29 is fixed to the holding member 21. First, the worker removes the yoke 22, the magnets 23, the first ring member 27, and the second ring member 28 from the base jig 81. Next, the worker applies adhesive to at least one of the downward surface of the yoke 22 and the upward surface of the bottom wall portion 21a of the holding member 21, and then adhesively fixes the yoke 22 to the upward surface of the bottom wall portion 21a, as shown in FIG. 13 . Next, the worker moves the cover member 29 from the upper side of the holding member 21 downward to bring the cover member 29 into contact with the holding member 21. Next, the worker fixes the cover member 29 to the holding member 21 using fastening members such as screws (not shown). The worker may adhesively fix the cover member 29 to the holding member 21. The cover member fixing step P05 is completed when the worker fixes the cover member 29 to the holding member 21. When the cover member fixing step P05 is completed, the assembly process of the rotor 18 shown in FIG.

[0083] According to this embodiment, the motor 10 comprises a rotor 18 rotatable about a central axis J, and a stator 50 axially opposed to the rotor 18, the rotor 18 having a plurality of magnets 23 arranged along the circumferential direction and an annular first ring member 27 supporting each of the plurality of magnets 23 from the radially inner side, the plurality of magnets 23 having a plurality of first magnets 24 whose magnetization direction is in the axial direction and a plurality of second magnets 25 whose magnetization direction is in a direction intersecting the axial direction, each of the plurality of first magnets 24 and the plurality of second magnets 25 arranged along the circumferential direction in a Halbach array, the first ring member 27 having a plurality of protrusions 27c protruding radially outward, each of the plurality of protrusions 27c being arranged at intervals from one another along the circumferential direction, and one or more magnets 23 having a contact portion 25h that comes into circumferential contact with the protrusion 27c. Therefore, as described above, in the second magnet attachment step P02, the circumferential and radial positions of the magnets 23 relative to the first ring member 27 can be accurately determined by the simple operation of inserting the second magnets 25, i.e., the magnets 23, between the first magnets 24 until the contact portions 25h of the magnets 23 come into circumferential contact with the protrusions 27c. This prevents an increase in the number of steps required for the second magnet attachment step P02. This also prevents an increase in the number of steps required for assembling the rotor 18.

[0084] Furthermore, in this embodiment, as described above, in the first magnet attachment step P01, the circumferential position of each second main magnet 24c relative to the first ring member 27 can be accurately determined by the simple operation of inserting the second main magnet 24c into the insertion hole 83e of the first guide jig 83 and bringing the second main magnet 24c into contact with the first protrusion 27d and the second protrusion 27e. This makes it possible to prevent an increase in the number of steps required for the first magnet attachment step P01. Therefore, an increase in the number of steps required for assembling the rotor 18 can be more effectively prevented.

[0085] According to this embodiment, the circumferential surface of at least one magnet 23 is provided with a recess 25g that is recessed circumferentially inward and opens radially inward, and the contact portion 25h is the inner surface of the recess 25g. As described above, because the recess 25g opens radially inward, in the second magnet attachment step P02, the contact portion 25h can be easily brought into circumferential contact with the protrusion 27c by simply inserting the second magnet 25, i.e., the magnet 23, between the first magnets 24 from the radially outer side to the radially inner side. This allows the circumferential position of the magnet 23 relative to the first ring member 27 to be easily and accurately determined, thereby more effectively preventing an increase in the number of steps required for the second magnet attachment step P02. Therefore, more effectively preventing an increase in the number of steps required for assembling the rotor 18.

[0086] Furthermore, in this embodiment, recess 25g can be provided only on the radially inner portion of the circumferentially facing surface of second magnet 25, which makes it easier to prevent the circumferential gap between second magnet 25 and first magnet 24 from increasing. This more effectively prevents a decrease in the magnetic flux density flowing from first magnet 24 to second magnet 25 and from second magnet 25 to first magnet 24. This more effectively prevents a decrease in the magnetic flux density flowing from each of first magnet group 20a and second magnet group 30a to the electromagnets formed in stator 50. This more effectively increases the output torque of motor 10.

[0087] According to this embodiment, the recess 25g is provided in each of the multiple second magnets 25. Therefore, as described above, the circumferential position of each second magnet 25 relative to the first ring member 27 can be determined with high precision. This facilitates accurate determination of the circumferential position of each of the multiple magnets 23, thereby making it easier to reduce the circumferential gap between adjacent magnets 23. This effectively prevents a decrease in the magnetic flux density flowing from the first magnet 24 to the second magnet 25 and the magnetic flux density flowing from the second magnet 25 to the first magnet 24. This effectively increases the magnetic flux density flowing from each of the first magnet group 20a and the second magnet group 30a to the electromagnets formed in the stator 50, thereby effectively increasing the magnetic force applied to each of the first magnet group 20a and the second magnet group 30a. This effectively increases the output torque of the motor 10.

[0088] Furthermore, in this embodiment, as described above, the first protrusions 27d and the second protrusions 27e allow the circumferential position of each second main magnet 24c relative to the first ring member 27 to be determined with high precision. This allows the circumferential position of each of the multiple magnets 23 to be determined with high precision. This makes it easier to more suitably reduce the circumferential gap between the magnets 23 that are arranged adjacent to each other in the circumferential direction. This makes it possible to more suitably increase the magnetic flux density flowing from each of the first magnet group 20a and the second magnet group 30a into the electromagnets formed in the stator 50. This makes it possible to more suitably increase the output torque of the motor 10.

[0089] According to this embodiment, each of the plurality of second magnets 25 has a first surface 25e that faces the circumferential direction and has an N pole, i.e., a first magnetic pole, and the recess 25g is provided on the first surface 25e. As described above, the plurality of second magnets 25 includes a first auxiliary magnet 25a whose magnetization direction is oriented toward the other circumferential side (-θ side) and a second auxiliary magnet 25c whose magnetization direction is oriented toward one circumferential side (+θ side). Also, as described above, the first auxiliary magnet 25a and the second auxiliary magnet 25c are magnets of the same shape but with their up-down directions oriented in opposite directions. Therefore, in the second magnet attachment step P02, the first auxiliary magnet 25a and the second auxiliary magnet 25c may be attached to the yoke 22 with the magnetization directions of the first auxiliary magnet 25a and the second auxiliary magnet 25c oriented in opposite directions. In contrast, in the present embodiment, recess 25g is provided on first surface 25e, which constitutes the north pole, i.e., the first magnetic pole, of the circumferentially facing surfaces of second magnet 25. Therefore, as described above, in second magnet attachment step P02, the first auxiliary magnet 25a is attached to yoke 22 with first surface 25e, on which first protrusion 27d and contact portion 25h are capable of contacting, facing the other circumferential side, by a simple operation. Furthermore, the second auxiliary magnet 25c is attached to yoke 22 with first surface 25e, on which second protrusion 27e and contact portion 25h are capable of contacting, facing one circumferential side, by a simple operation. This prevents the second auxiliary magnet 25c from being attached to yoke 22 with the magnetization direction facing the opposite direction. Therefore, an increase in the number of steps in the second magnet attachment process P02 can be more effectively prevented, and an increase in the number of steps in assembling the rotor 18 can be more effectively prevented.

[0090] According to this embodiment, when viewed from the axial direction, each of the multiple second magnets 25 is rectangular, and when viewed from the axial direction, each of the multiple first magnets 24 is trapezoidal, with the dimension in the direction perpendicular to the radial direction increasing radially outward. Therefore, because the shapes of the second magnets 25 and the first magnets 24 are different from each other, it is possible to prevent the second magnets 25 from being mistakenly attached to the position of the yoke 22 where the first magnets 24 are to be attached in the first magnet attachment step P01. This prevents an increase in the number of steps in the first magnet attachment step P01, and therefore more effectively prevents an increase in the number of steps for assembling the rotor 18.

[0091] Furthermore, in this embodiment, the second magnet 25 has a rectangular shape, which makes it easier to manufacture the second magnet 25 than if the second magnet 25 had a trapezoidal shape. Therefore, an increase in the number of steps required to manufacture the rotor 18 can be more effectively suppressed.

[0092] The present invention is not limited to the above-described embodiment, and other configurations and methods may be adopted within the scope of the technical concept of the present invention. For example, the motor may be configured to include only one rotor. In this case, the rotor may be disposed above or below the stator, as long as the rotor and the stator are disposed opposite each other with a gap in the axial direction.

[0093] The first magnet may have a recess and a contact portion on its circumferential surface, and in this case, the first ring member preferably has a protrusion that contacts the contact portion of the first magnet in the circumferential direction. This allows the protrusion to accurately determine the circumferential position of the first magnet. In this case, the second magnet does not need to have a recess or a contact portion.

[0094] The second magnet may be trapezoidal in shape, with the dimension increasing radially outward as viewed from the axial direction. In this case, the first magnet may be trapezoidal in shape, with the dimension increasing radially outward as viewed from the axial direction, or may be rectangular.

[0095] The number of first magnets and the number of second magnets included in each of the first magnet group and the second magnet group may be 13 or less, or may be 15 or more. Furthermore, the number of first magnets included in each of the first magnet group and the second magnet group may be different from each other.

[0096] Although the embodiments of the present invention have been described above, the configurations and combinations thereof in the embodiments are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible without departing from the spirit of the present invention. Furthermore, the present invention is not limited to the embodiments.

[0097] The present technology may be configured as follows: (1) A motor including a rotor rotatable about a central axis and a stator axially facing the rotor, wherein the rotor has a plurality of magnets arranged along a circumferential direction and an annular first ring member supporting each of the plurality of magnets from the radially inner side, wherein the plurality of magnets include a plurality of first magnets whose magnetization direction is axially aligned and a plurality of second magnets whose magnetization direction intersects the axial direction, wherein each of the plurality of first magnets and the plurality of second magnets is arranged along the circumferential direction in a Halbach array, wherein the first ring member has a plurality of protrusions protruding radially outward, wherein each of the plurality of protrusions is arranged at intervals along the circumferential direction, and wherein one or more of the magnets have contact portions that come into circumferential contact with the protrusions. (2) The motor described in (1), wherein a circumferential surface of at least one or more of the magnets is provided with a recess that is recessed circumferentially inward and open radially inward, and wherein the contact portion is an inner surface of the recess. (3) The motor according to (2), wherein the recess is provided in each of the second magnets. (4) The motor according to (2) or (3), wherein each of the second magnets has a first surface facing the circumferential direction and on which a first magnetic pole is formed, and the recess is provided on the first surface. (5) The motor according to any one of (1) to (4), wherein, when viewed from the axial direction, each of the second magnets is rectangular, and when viewed from the axial direction, each of the first magnets is trapezoidal, the dimension in a direction perpendicular to the radial direction increasing radially outward. (6) The motor according to any one of (1) to (5), wherein the rotor has an annular second ring member elastically deformable in the radial direction, and the second ring member surrounds the magnets from the radially outer side and applies an elastic force to each of the magnets that faces radially inward. (7) The motor according to (6), wherein the rotor has a holder that holds the plurality of magnets and the second ring member, and the second ring member is disposed radially between the plurality of magnets and the holder. (8) The motor according to (7), wherein the rotor has a cover member fixed to the holder and in axial contact with the plurality of magnets.

[0098] 10...motor, 18...rotor, 21, 31...holding member, 23...magnet, 24...first magnet, 25...second magnet, 25e...first surface, 25g...recess, 25h...contact portion, 27...first ring member, 27c...protrusion, 28...second ring member, 29...cover member, 50...stator, J...central axis

Claims

1. A motor comprising: a rotor rotatable about a central axis; and a stator axially opposed to the rotor, wherein the rotor has a plurality of magnets arranged circumferentially and a first annular ring member supporting each of the plurality of magnets from the radially inner side, the plurality of magnets including a plurality of first magnets whose magnetization direction is axially aligned and a plurality of second magnets whose magnetization direction intersects the axial direction, the plurality of first magnets and the plurality of second magnets are arranged circumferentially in a Halbach array, the first ring member has a plurality of protrusions protruding radially outward, the plurality of protrusions are arranged circumferentially at intervals, and one or more of the magnets have contact portions that come into circumferential contact with the protrusions.

2. The motor according to claim 1, wherein a recess is provided on the circumferential surface of at least one of the magnets, the recess being recessed inward in the circumferential direction and open to the radially inward, and the contact portion is the inner surface of the recess.

3. The motor according to claim 2, wherein the recess is provided in each of the plurality of second magnets.

4. The motor according to claim 3, wherein each of the plurality of second magnets has a first surface that faces in the circumferential direction and defines a first magnetic pole, and the recess is provided in the first surface.

5. A motor as claimed in any one of claims 1 to 4, wherein, when viewed from the axial direction, each of the plurality of second magnets is rectangular, and when viewed from the axial direction, each of the plurality of first magnets is trapezoidal in shape with dimensions in a direction perpendicular to the radial direction increasing as they extend radially outward.

6. A motor according to any one of claims 1 to 4, wherein the rotor has an annular second ring member that is elastically deformable in the radial direction, the second ring member surrounding the plurality of magnets from the radially outer side and applying an elastic force directed radially inward to each of the plurality of magnets.

7. The motor according to claim 6, wherein the rotor has a retaining member that retains each of the plurality of magnets and the second ring member, and the second ring member is disposed radially between each of the plurality of magnets and the retaining member.

8. The motor according to claim 7, wherein the rotor has a cover member fixed to the holding member and in axial contact with each of the plurality of magnets.

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