Magnetic field generating device and rotating electric machine

Abstract

A field magnet holder provided in a field portion of an electric motor is formed from a non-magnetic material, and a plurality of spacers are arranged with a prescribed spacing in the circumferential direction between an inner wall and an outer wall each formed with a cylindrical shape. Sockets into which permanent magnets are inserted are formed between the spacers in the field magnet holder, and a plurality of said sockets are formed in the circumferential direction. As a result, the permanent magnets can be easily assembled by inserting the permanent magnets into each socket, improving the ease of assembly of a plurality of permanent magnets that are arranged in such a way that the magnetization directions thereof change sequentially at each angle obtained by dividing one electrical angle cycle by a number n of divisions, where the number n of divisions is any integer equal to or greater than 3.

Description

[Technical field]

[0001] The disclosed technology relates to a magnetic field generating device and a rotating electric machine. [Background technology]

[0002] In electric motors and generators, a field magnet in which the north and south poles of permanent magnets are arranged alternately (NS arrangement field magnet) is used. In a field magnet, the magnetic field of one side (inner or outer radial direction) of the arranged permanent magnets is used, but in an NS arrangement field magnet, a magnetic field is generated on both sides of the arranged permanent magnets, and the magnetic field (magnetic energy from the permanent magnets) is not used effectively.

[0003] On the other hand, the field magnet of the permanent magnet array includes, for example, a Halbach array field magnet in which multiple permanent magnets are arranged in order by rotating the direction of the magnetic poles (magnetization direction) by 90° each time. In this Halbach array field magnet, a stronger magnetic field can be generated on one side of the arranged permanent magnets than on the other side, making it possible to effectively utilize the magnetic field generated by the permanent magnets.

[0004] Japanese Patent Application Laid-Open No. 2009-201343 and Japanese Patent Application Laid-Open No. 2010-154688, for example, disclose a field magnet (dual Halbach array field magnet) that can more effectively utilize the magnetic field generated by a permanent magnet by arranging two sets of Halbach magnet arrays facing each other so that their magnetic fields are strengthened. Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, in the Halbach array field magnet used in electric motors, many permanent magnets are arranged in the circumferential direction so that they are in contact with each other (without gaps). Also, the angle between the magnetization directions of adjacent permanent magnets is not 0° (same magnetization direction) or 180° (opposite magnetization directions), but an angle according to the number of divisions (for example, 90°, 72°, 45°, etc.). For this reason, in the Halbach array field magnet, strong repulsive and attractive forces occur in unexpected directions between adjacent permanent magnets, so that assembling the permanent magnets requires time and skill, and there is a demand for improved workability.

[0006] The present disclosure has been made in consideration of the above-mentioned circumstances, and has an object to provide a magnetic field generating device and a rotating electric machine that can improve assembly workability. [Means for solving the problem]

[0007] A first aspect of a magnetic field generating device for achieving the above-mentioned object includes: a field magnet section in which a plurality of permanent magnets are arranged in a circumferential direction with the magnetization direction being changed in sequence by an angle obtained by dividing one electrical angle period by a division number n, where n is any one of integers equal to or greater than 3; a holding member made of a non-magnetic material, having an annular outer peripheral wall whose inner peripheral surface is in contact with the outer peripheral surface of each of the permanent magnets; and a plurality of partition walls each protruding radially inward from the inner surface of the outer peripheral wall in the circumferential direction of the outer peripheral wall, with the permanent magnets being fitted between adjacent partition walls.

[0008] In the magnetic field generator of the first aspect, the field magnet portion is formed by arranging a plurality of permanent magnets in the circumferential direction with the magnetization direction being changed in sequence by an angle obtained by dividing one period of electrical angle by the division number n, where n is any one of integers equal to or greater than 3. The field magnet portion is provided with a holding member made of a nonmagnetic material such as a nonmagnetic substance or synthetic resin, and each of the plurality of permanent magnets is held in the field magnet portion by the holding member.

[0009] Here, the retaining member has a plurality of partitions each protruding radially inward from the inner surface of the outer peripheral wall in the circumferential direction of the annular outer peripheral wall, the inner peripheral surface of which is in contact with the outer peripheral surface of each of the permanent magnets, and between adjacent partitions a permanent magnet is fitted. As a result, the permanent magnets are fitted and positioned between the partitions that are spaced apart in the circumferential direction, and are held by the retaining member and assembled to the field magnet portion, thereby improving the ease of assembly of the permanent magnets to the field magnet portion.

[0010] A second aspect of the magnetic field generating device is the same as the first aspect, in which the retaining member includes an inner circumferential wall whose outer circumferential surface is in contact with the inner circumferential surfaces of each of the permanent magnets and whose outer circumferential surface is connected to the radially inner ends of each of the partitions.

[0011] In the magnetic field generating device according to the second aspect, an inner peripheral wall is provided on the holding member, and each of the permanent magnets is disposed between the inner peripheral wall and the outer peripheral wall. For this reason, it becomes easier to assemble the permanent magnets to the holding member, the assemblability of the field magnet portion can be further improved, and the productivity of the field magnet portion can be improved.

[0012] In the magnetic field generating device according to the third aspect, in the first or second aspect, the thickness dimension d of the partition wall is set according to the length dimension lm of one side along the arrangement direction set in advance as a reference in a cross section along the magnetization direction of the permanent magnet, and the number of divisions n. At this time, a linear array of permanent magnets is applied to the permanent magnet used as a reference for the length dimension lm.

[0013] In the magnetic field generating device according to the fourth aspect, in the third aspect, the thickness dimension d of the partition wall satisfies 0 < d ≦ lm × 1 / (n + 1) × 1.5. Further, in the magnetic field generating device according to the fifth aspect, in the third or fourth aspect, the thickness dimension d of the partition wall satisfies d = lm / (n + 1).

[0014] In the magnetic field generating device according to the sixth aspect, in any one of the first to fifth aspects, an annular member is formed to face each of the permanent magnets of the field magnet portion and is provided so as to be relatively rotatable with respect to the field magnet portion, and a ferromagnetic material that forms a magnetic field with the field magnet portion by the magnetic force of the field magnet portion.

[0015] In the magnetic field generating device according to the sixth aspect, a ferromagnetic material is disposed so as to be relatively rotatable corresponding to the field magnet portion. Thereby, an effective magnetic field can be formed between the permanent magnet of the field magnet portion and the ferromagnetic material.

[0016] In the magnetic field generating device according to the seventh aspect, in any one of the first to fifth aspects, the field magnet portion includes a first field magnet portion in which the plurality of permanent magnets are arranged in the circumferential direction, and a second field magnet portion disposed radially outside the first field magnet portion and integrally rotatable with the first field magnet portion with the plurality of permanent magnets arranged in the circumferential direction, and the holding member includes a first holding member that holds each of the plurality of permanent magnets of the first field magnet portion, and a second holding member that holds each of the plurality of permanent magnets of the second field magnet portion.

[0017] In the magnetic field generator of the seventh aspect, the first field magnet portion and the second field magnet portion are provided in a pair, and the first field magnet portion and the second field magnet portion each include a first holding member and a second holding member. This makes it easier to assemble the permanent magnets to the first field magnet portion and the second field magnet portion when arranging the first field magnet portion and the second field magnet portion in a pair, thereby improving productivity.

[0018] The eighth aspect of the rotating electric machine includes: a field magnet section in which a plurality of permanent magnets are arranged in the circumferential direction with the magnetization direction being changed in sequence by an angle obtained by dividing one electrical angle period by a division number n, where n is any one of integers equal to or greater than three; a retaining member made of a non-magnetic material, having an annular outer peripheral wall whose inner peripheral surface is in contact with the outer peripheral surface of each of the permanent magnets, and a plurality of partition walls each protruding radially inward from the inner surface of the outer peripheral wall in the circumferential direction of the outer peripheral wall, with the permanent magnets inserted between each of the adjacent partition walls; and an armature in which each of the permanent magnets is arranged so as to be rotatable relative to the field magnet section held by the retaining member.

[0019] In the rotating electric machine of the eighth aspect, the field magnet section and the armature are rotated relative to each other. In the field magnet section, a plurality of permanent magnets are arranged in the circumferential direction with the magnetization direction being changed in sequence by an angle obtained by dividing one electrical angle cycle by the division number n, where n is any one of integers equal to or greater than 3. In addition, the field magnet section is provided with a holding member, and each of the plurality of permanent magnets is held by the holding member.

[0020] Here, a non-magnetic material is used for the holding member. The holding member has an annular outer peripheral wall, the outer peripheral surfaces of the permanent magnets abutting against the annular inner peripheral surface, and a plurality of partition walls that protrude radially inward from the inner peripheral surface of the outer peripheral wall in the circumferential direction of the outer peripheral wall, and a permanent magnet is fitted between each adjacent partition wall. This allows the permanent magnets to be fitted between the partition walls that are spaced apart from each other in the circumferential direction of the outer peripheral wall, making it possible to assemble the permanent magnets to the holding member, and facilitating the assembly of the field magnet section, thereby improving the ease of assembly of the field magnet section.

[0021] The rotating electric machine of the ninth aspect is the same as that of the eighth aspect, and includes a ferromagnetic body formed in a circular ring shape facing each of the permanent magnets of the field magnet part, arranged to be rotatable relative to the field magnet part, and having three-phase coils of the armature arranged circumferentially on the surface facing the field magnet part.

[0022] A tenth aspect of the rotating electric machine is the same as that of the eighth aspect, wherein the field magnet section includes a first field magnet section in which the multiple permanent magnets are arranged circumferentially, and a second field magnet section arranged radially outside the first field magnet section and in which the multiple permanent magnets are arranged circumferentially so as to be rotatable integrally with the first field magnet section, the holding member includes a first holding member that holds each of the multiple permanent magnets of the first field magnet section, and a second holding member that holds each of the multiple permanent magnets of the second field magnet section, and the armature has three-phase coils arranged circumferentially between the first field magnet section and the second field magnet section.

[0023] An eleventh aspect of the rotating electric machine is any one of the eighth to tenth aspects, in which the retaining member includes an inner circumferential wall whose outer circumferential surface is in contact with the inner circumferential surfaces of each of the permanent magnets and whose outer circumferential surface is connected to the radially inner ends of each of the partitions.

[0024] A rotating electric machine of a twelfth aspect is any one of the eighth to eleventh aspects, in which a thickness dimension d of the partition wall is set according to a length dimension lm of one side along an arrangement direction set in advance as a reference in a cross section along the magnetization direction of the permanent magnet, and the number of divisions n. In this case, a permanent magnet arranged in a straight line is applied as the reference for the length dimension lm.

[0025] Here, the rotating electric machine of this aspect, in a twelfth aspect which references the ninth aspect, includes that, for a circumferential length dimension Lf of the ferromagnetic body on the field magnet portion side and the number of magnetic poles P of the field magnet portion, the length dimension lm satisfies the relationship Lf=lm×n×P.

[0026] Further, in the rotating electrical machine according to the present aspect, in the twelfth aspect that cites the tenth aspect, regarding the circumferential length dimension Lg of the center Gc of the gap between the first field portion and the second field portion and the number of magnetic poles P of the field portion, the length dimension lm satisfies the relationship Lg = lm × n × P.

[0027] In the rotating electrical machine according to the thirteenth aspect, in the twelfth aspect, the thickness dimension d of the partition wall satisfies 0 < d ≤ lm × 1 / (n + 1) × 1.5. Further, in the rotating electrical machine according to the fourteenth aspect, in the twelfth or thirteenth aspect, the thickness dimension d of the partition wall satisfies d = lm / (n + 1).

Advantages of the Invention

[0028] As described above, according to the magnetic field generating device and the rotating electrical machine of the present disclosure, in the field portion in which the magnetization directions are sequentially changed by an angle obtained by dividing one electrical angle cycle by the division number n, with any one of the integers of 3 or more as the division number n, and a plurality of permanent magnets are arranged in the circumferential direction, the assembly of the plurality of permanent magnets can be facilitated, so that the productivity of the device can be improved.

Brief Description of the Drawings

[0029] [Figure 1] It is a schematic diagram showing a main part of the motor according to the present embodiment. [Diagram 2] It is a schematic diagram showing a Halbach magnet array. [Figure 3A] It is a schematic configuration diagram showing a magnetic field generating portion in which one Halbach magnet array is replaced with a ferromagnetic material in a magnetic field generating portion where two Halbach magnet arrays are opposed. [Figure 3B] It is a schematic configuration diagram showing a magnetic field generating portion where two Halbach magnet arrays are opposed. [Figure 4A] It is a schematic configuration diagram showing a magnetic field generating portion obtained by deforming FIG. 3A. [Figure 4B] It is a schematic configuration diagram showing a magnetic field generating portion obtained by deforming FIG. 3B. [Diagram 5] It is a perspective view showing a field holder according to the present embodiment. [Figure 6]FIG. 2 is a perspective view showing a main part of a field unit according to the embodiment. [Figure 7A] 1 is a graph showing the change in volume ratio and the change in amplitude of the fundamental wave with respect to the spacing dimension of the permanent magnets when n=4. [Figure 7B] 1 is a diagram showing the change in the amplitude ratio of the fifth harmonic component to the fundamental wave component with n=4 versus the spacing dimension of the permanent magnets. [Figure 8A] 1 is a graph showing the change in volume ratio versus spacing dimension of permanent magnets and the change in amplitude of the fundamental wave when n=8. [Figure 8B] 1 is a diagram showing the change in the amplitude ratio of the fifth harmonic component to the fundamental wave component with n=8 versus the spacing dimension of the permanent magnets. [Figure 9] FIG. 11 is a schematic diagram showing a main part of an electric motor according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. FIG. 1 shows, in a plan view seen in the axial direction, a schematic configuration of a main part of a three-phase AC motor (hereinafter, simply referred to as a motor) 10 as a rotating electric machine according to this embodiment.

[0031] 1, electric motor 10 includes rotor 12 having a substantially cylindrical outer shape as a rotor, and a substantially annular (or substantially cylindrical) stator 14 as a stator. In electric motor 10, the central axis of rotor 12 overlaps with the central axis of stator 14, and rotor 12 is accommodated inside stator 14 so as to be capable of relative rotation.

[0032] An annular (or cylindrical) field magnet portion 16 is provided on the outer periphery of the rotor 12. The stator 14 is provided with an annular (or cylindrical) outer tube portion 18 as a ferromagnetic body, and an armature 20, and the outer tube portion 18 has the armature 20 arranged in the circumferential direction on its inner periphery. As a result, in the electric motor 10, the armature 20 faces the radially outer side of the field magnet portion 16 of the rotor 12, and the armature 20 is integrally rotatable relative to the field magnet portion 16.

[0033] In the electric motor 10, a plurality of permanent magnets 22 are arranged in the circumferential direction on the outer periphery of the field magnet portion 16, and in the electric motor 10, a magnetic field generating portion 24 is formed as a magnetic field generating device by the field magnet portion 16 of the rotor 12 and the outer cylinder portion 18 of the stator 14. The magnetic field generating portion 24 forms a magnetic field (magnetic field) between the field magnet portion 16 and the outer cylinder portion 18.

[0034] The armature 20 of the electric motor 10 is provided with a plurality of coils, namely, a U-phase coil 20U, a V-phase coil 20V, and a W-phase coil 20W. A Litz wire is used as the winding of each of the coils 20U, 20V, and 20W (coils 20U to 20W). Each of the coils 20U to 20W is an air-core coil, and each of the coils 20U to 20W is formed by concentrated winding.

[0035] The armature 20 has coils 20U, 20V, and 20W for three phases arranged in a predetermined order along the circumferential direction on the inner circumferential surface of the outer cylinder portion 18. In the electric motor 10, six sets of coils 20U to 20W are used as an example, and the number of slots S of the electric motor 10 is 18. In the electric motor 10, the six sets of coils 20U to 20W are connected in series for each phase, and are arranged in the circumferential direction of the outer cylinder portion 18 in the order of coils 20U, 20V, 20W, 20U, 20V, 20W, ..., for example. Note that the electric motor 10 may use coils 20U', 20V', and 20W' wound in the opposite direction to the coils 20U to 20W and the coils 20U to 20W. In this case, in electric motor 10, coils are arranged in the circumferential direction of outer cylinder portion 18 in the following order: 20U', 20U, 20U', 20V', 20V, 20V', 20W', 20W, 20W', 20U', 20U, . . .

[0036] In the electric motor 10, three-phase (U-phase, V-phase, and W-phase) AC power of a predetermined frequency, in which the phases are shifted from each other by 120° within the range of one electrical angle cycle, is supplied to the coils 20U, 20V, and 20W. As a result, in the electric motor 10, the rotor 12 rotates at a rotation speed according to the frequency of the three-phase AC power supplied to the armature 20 (each of the multiple sets of coils 20U to 20W), and the output shaft 12A is rotated integrally with the rotor 12.

[0037] Here, the field portion 16 of the rotor 12 and the outer cylinder portion 18 of the stator 14 which form the magnetic field generating portion 24 in the electric motor 10 will be described.

[0038] A Halbach magnet array is applied to the field magnet section 16 of the magnetic field generating section 24. Fig. 2 shows a schematic plan view of a single Halbach array field magnet (hereinafter, referred to as a Halbach array field magnet) 26 to which the Halbach magnet array is applied. Figs. 3A and 3B show schematic plan views of magnetic field generating sections 28A and 28B to which the Halbach magnet array is applied, respectively.

[0039] In the drawings, the north pole side of the permanent magnet 22 is indicated by the symbol N, and the south pole side is indicated by the symbol S. In the following description, the magnetization direction of the permanent magnet 22 is indicated by an arrow (solid line arrow) pointing from the south pole side to the north pole side, and the magnetic field lines are indicated by dashed line arrows pointing from the north pole side to the south pole side (from the south pole side to the north pole side within the permanent magnet 22). In the drawings, one direction of the arrangement of the permanent magnets 22 is indicated by an arrow x, and the direction of the magnetic field lines that contribute to torque generation in the Halbach magnet arrangement is indicated by an arrow y.

[0040] As shown in Fig. 2, the Halbach magnet array uses permanent magnets 22 whose cross section along the magnetization direction is substantially rectangular (substantially square, substantially rectangular in three dimensions). In addition, in the Halbach magnet array, the number of divisions n and an angle θ (not shown) based on the number of divisions n are set, and the magnetization direction is changed by the predetermined angle θ, and n permanent magnets 22 according to the number of divisions n are sequentially arranged in a predetermined direction (arrow x direction). In this way, a single Halbach array field magnet 26 (hereinafter simply referred to as the Halbach array field magnet 26) is formed. The angle θ is the angle between the magnetization directions of two adjacent permanent magnets 22 (not shown).

[0041] In the Halbach magnet array, the division number n is an integer equal to or greater than 3, and the angle θ is an angle obtained by dividing one electrical angle period (2π=360°) by the division number n (an integer equal to or greater than 3). In the Halbach array field magnet 26, as an example, the division number n=4, and the angle θ=90° (θ=360° / 4=90°).

[0042] In this Halbach array field magnet 26, permanent magnets 22A, 22B, 22C, and 22D whose magnetization directions are changed by 90° are arranged in order (the arrangement of permanent magnets 22A to 22D is repeated), and the magnetization directions of permanent magnets 22B and 22D on both sides of permanent magnet 22A are directed toward permanent magnet 22A. As a result, in the Halbach array field magnet 26, the magnetic field on one side (the magnetization direction side of permanent magnet 22A) in the direction intersecting the arrangement direction is strengthened, and the strength of the magnetic field on the other side (the opposite side to the magnetization direction of permanent magnet 22A) is suppressed.

[0043] As shown in FIG. 3B, the magnetic field generating unit 28B is a dual Halbach array field magnet in which the Halbach array field magnets 26 (26A, 26B) are arranged in pairs, and in the magnetic field generating unit 28B, the two pairs of Halbach array field magnets 26A, 26B are opposed to each other with a predetermined interval (gap length 2G) between them.

[0044] Specifically, the magnetic field generating unit 28B is formed such that the sides of the Halbach array field magnets 26A and 26B with stronger magnetic fields face each other. In this case, in the magnetic field generating unit 28B, the permanent magnet 22A of one of the Halbach array field magnets 26A and 26B (for example, the Halbach array field magnet 26A) faces the permanent magnet 22C having the same magnetization direction in the other (for example, the Halbach array field magnet 26B).

[0045] That is, the Halbach array field magnets 26A and 26B can be said to be in a state where the magnetization directions of the permanent magnets 22A (or the permanent magnets 22C) are the same, and the permanent magnets 22B and 22D on both sides of the permanent magnet 22A are swapped in the Halbach array field magnet 26B. As a result, in the magnetic field generating unit 28B, a stronger magnetic field is generated between the paired Halbach array field magnets 26A and 26B compared to the case where one Halbach array field magnet 26 is used.

[0046] On the other hand, in the field of electric fields (static electricity), the mirror image method (electrical imaging method) is known. Although not shown, in the mirror image method, the electric field lines between the positive and negative point charges +q and -q facing each other with a predetermined distance (spacing dimension) 2g are plane-symmetric (two-dimensionally, line-symmetric) with the position of distance g, which is the midpoint between the point charges +q and -q, as the symmetry plane. In this state, one of the point charges +q and -q (for example, the point charge -q) is replaced with a conductor (perfect conductor), and the surface of the conductor on the side of the point charge +q is placed at the position of distance g (the midpoint between the point charges +q and -q). As a result, in the mirror image method, the electric field lines between the point charge +q and the conductor become the same as the electric field lines between the midpoint (position of the symmetry plane) between the point charges +q and -q and the point charge +q.

[0047] This mirror image method also applies to magnetic fields by using a ferromagnetic material instead of a conductor. As shown in Fig. 3A, a ferromagnetic body 30 using a ferromagnetic material is disposed in magnetic field generating unit 28A instead of Halbach array field magnet 26B of magnetic field generating unit 28B. The surface of ferromagnetic body 30 on the Halbach array field magnet 26A side is disposed at the gap center Gc, which is the intermediate position between Halbach array field magnets 26A and 26B in magnetic field generating unit 28B.

[0048] For this reason, in the magnetic field generating unit 28A, the gap length between the Halbach array field magnets 26A and the ferromagnetic body 30 is set to a gap length G, while the gap length 2G is the gap length between the Halbach array field magnets 26A and 26B in the magnetic field generating unit 28B. As a result, in the magnetic field generating unit 28A, the magnetic flux distribution between the Halbach array field magnets 26A and the ferromagnetic body 30 is made similar to the magnetic flux portion between the gap center Gc and the Halbach array field magnet 26A in the magnetic field generating unit 28A (dual Halbach array field magnet). In the electric motor 10 and the magnetic field generating unit 24 according to this embodiment, the arrangement of the permanent magnets 22 in the magnetic field generating units 28A and 28B is used as the reference.

[0049] On the other hand, in a dual Halbach magnet arrangement, by deforming each of the permanent magnets 22 so as to satisfy certain conditions and forming the magnetic field generating units 28A and 28B into annular shapes, it is possible to obtain the same effect as that obtained by the dual Halbach magnet arrangement.

[0050] 1, k sets (number of groups k) of permanent magnets 22A-22D are used in magnetic field generating section 24 of electric motor 10, and field magnet section 16 is formed by a Halbach magnet arrangement in which permanent magnets 22A-22D are arranged in sequence in the circumferential direction. As an example, electric motor 10 uses permanent magnets 22A-22D with number of groups k being 8 (8 groups, k=8) in field magnet section 16.

[0051] In each of Fig. 4A and Fig. 4B, a magnetic field generating unit (field magnet) in which permanent magnets 22 are arranged in an annular shape is shown in a plan view as viewed in the axial direction. Fig. 4A shows a magnetic field generating unit 32A corresponding to magnetic field generating unit 28A using one set of Halbach magnet arrays, and Fig. 4B shows a magnetic field generating unit 32B corresponding to magnetic field generating unit 28B using two sets of Halbach magnet arrays (dual Halbach magnet arrays). In the following, to simplify the explanation, the deformed permanent magnets are given the same reference numerals as the permanent magnets 22 before deformation.

[0052] In the Halbach magnet arrangement, n permanent magnets 22 corresponding to the number of divisions n are arranged as one set, and the arrangement of n permanent magnets 22 in the Halbach magnet arrangement corresponds to two poles, N pole and S pole, and the number of magnetic poles P is equivalent to 2 poles. As a result, in the electric motor 10, eight sets of permanent magnets 22A-22D are used in the field magnet section 16, making the total number M of permanent magnets 22 per revolution 32 (M=n×k=32 pieces), and the number of magnetic poles P of the electric motor 10 is 16 poles.

[0053] As shown in FIG. 2, FIG. 3A, and FIG. 3B, the pole pitch τ in the Halbach array field magnet 26 (26A, 26B) is a length along the arrangement direction in a range where the magnetization direction is reversed (a range where the magnetization direction changes by 180°). When the permanent magnets 22 are arranged in close contact with each other, the pole pitch τ is τ=(n×lm) / 2, where n is the number of divisions and lm is the length of one side of the permanent magnet 22 along the arrangement direction. In the magnetic field generating unit 28B, the gap length 2G at which the maximum number of interlinking magnetic fluxes is obtained at the gap center Gc is set in a range of 0.5 to 2.0 times the pole pitch τ (0.5τ≦2G≦2.0τ). The length lm of the permanent magnet 22 is set as a length dimension set in advance as a reference, and the length lm of the permanent magnet 22 is applied to the length of the armature 20 side where the permanent magnet 22 forms a magnetic field in the Halbach array field magnet 26 (26A, 26B).

[0054] Thus, the gap length G, which is the distance between the outer circumferential surface of the Halbach array field magnet 26A (the outer circumferential surface of the permanent magnet 22) and the surface of the ferromagnetic body 30 in the magnetic field generating unit 28A, is set to be in the range of 0.25 to 1.0 times the pole pitch τ (0.25τ≦G≦1.0τ). The gap length G for the division number n is in the range of (0.25×n×lm×1 / 2) to (1.0×n×lm×1 / 2) times the length dimension lm of the permanent magnet 22 (i.e., (0.125×n×lm)≦G≦(0.5×n×lm)). As a result, when the division number n=4, the gap length G is in the range of 0.5 to 2.0 times the length dimension lm of the permanent magnet 22 ((0.5×lm)≦G≦(2.0×lm)).

[0055] In the magnetic field generating unit 28B, when k sets of permanent magnets 22 are arranged in each of the Halbach array field magnets 26A and 26B with the division number n, the length dimension of the gap center Gc along the arrangement direction is k×n×lm=2×k×τ.

[0056] 4B, the Halbach array field magnets 26A, 26B in the magnetic field generating unit 28B are deformed to satisfy a predetermined condition, and the Halbach array field magnets 34A, 34B are formed. In the magnetic field generating unit 32B, the gap center Gc is set as a reference circle, and the Halbach array field magnets 34A, 34B are arranged on either side of the gap center Gc, and in the magnetic field generating unit 32B, the Halbach array field magnets 34A, 34B face each other on either side of the gap 36. In addition, the Halbach array field magnets 34A, 34B are formed by deforming each of the permanent magnets 22 in the Halbach array field magnets 26A, 26B as a reference, and deforming each of the permanent magnets 22 into a sector ring shape (partial ring shape) and arranging them in the circumferential direction.

[0057] Here, the length (circumference) of the gap center Gc is the same for the magnetic field generating unit 32B and the magnetic field generating unit 28B. Also, in the magnetic field generating unit 32B, the distance (gap length) between the Halbach array field magnets 34A, 34B is the same as the gap length 2G in the magnetic field generating unit 28B, and the distance between each of the Halbach array field magnets 34A, 34B and the gap center Gc is the gap length G.

[0058] Furthermore, in the magnetic field generating unit 32B, with regard to the cross-sectional area in the radial cross section, the ratio of the cross-sectional area between the gap center Gc and the Halbach array field magnet 34A to the cross-sectional area between the gap center Gc and the Halbach array field magnet 34B in the gap 36 is set to be similar to the ratio of the cross-sectional area of ​​the Halbach array field magnet 34A to the cross-sectional area of ​​the Halbach array field magnet 34B.

[0059] That is, in a radial cross section of the magnetic field generating unit 32B, the cross-sectional area between the gap center Gc and the Halbach array field magnetic field 34B is area S1, the cross-sectional area between the gap center Gc and the Halbach array field magnetic field 34A is area S2, the cross-sectional area of ​​the Halbach array field magnetic field 34B is area S3, and the cross-sectional area of ​​the Halbach array field magnetic field 34A is area S4. In the magnetic field generating unit 32B, the relationship S2:S1=S4:S3 is satisfied (S1 / S2=S3 / S4).

[0060] In addition, in a radial cross section within a range of a predetermined angle φ (°) (for example, the range of a set of permanent magnets 22A to 22D, the range indicated by the two-dot chain line in FIG. 4B), the cross-sectional area between the gap center Gc and the Halbach array field magnetic field 34B is area Sgo, the cross-sectional area between the gap center Gc and the Halbach array field magnetic field 34A is area Sgi, the cross-sectional area of ​​the Halbach array field magnetic field 34B is area Smo, and the cross-sectional area of ​​the Halbach array field magnetic field 34A is area Smi. The magnetic field generating unit 32B satisfies the relationship Sgi:Sgo=Smi:Smo (Smi / Smo=Sgi / Sgo. Also, Smo / Smi=Sgo / Sgi is satisfied).

[0061] In the magnetic field generating unit 32B thus formed, the inner diameter of the Halbach array field magnet 34A, the outer diameter of the Halbach array field magnet 34A (the inner diameter of the gap 36), the radius of the gap center Gc, the inner diameter of the Halbach array field magnet 34B (the outer diameter of the gap 36), and the outer diameter of the Halbach array field magnet 34B are defined as Rh, Ri, Rco, Rg, and Ro, respectively. In this case, there are relationships such as Ri=(Rco-G) and Rg=(Rco+G).

[0062] In this case, the areas Sgo, Sgi, Smo, and Smi are each expressed by, for example, the following formulas. Sgo = (Rg 2 -Rco 2 )×π×φ / 360 Sgi=(Rco 2 -Ri 2 )×π×φ / 360 Smo = (Ro 2 -Rg 2 )×π×φ / 360 Smi=(Ri 2-Rh 2 )×π×φ / 360

[0063] Furthermore, in the Halbach array field magnets 34A and 34B, similar to the Halbach array field magnets 26A and 26B, the cross section along the magnetization direction of the permanent magnets 22 is a sector ring shape (partial ring shape) that approximates a substantially rectangular shape (substantially square shape). In the magnetic field generating unit 32B, the permanent magnets 22 are each deformed and arranged based on these conditions to provide the same effect as the dual Halbach magnet arrangement as the magnetic field generating unit 28B.

[0064] According to the above-mentioned method of transformation, the length lm along the arrangement direction of the permanent magnets 22 is expressed as follows depending on the type (combination) of the field magnet (field magnet portion 16) and the armature (armature 20).

[0065] In the magnetic field generating unit 28B to which the dual Halbach magnet array is applied, when the permanent magnets 22 are in close contact with each other, the length dimension of the gap center Gc corresponding to one set of permanent magnets 22 is 2×τ=n×lm. In addition, in the magnetic field generating units 28A and 28B, the length dimension lm of the permanent magnet 22 is expressed as lm=2×τ×1 / n (τ=n×lm / 2). In this case, the length dimension lm of the permanent magnet 22 is the same as the length dimension of the permanent magnet 22 (the permanent magnet 22 before deformation) in the Halbach array field magnets 26A and 26B.

[0066] On the other hand, in the magnetic field generating unit 32B to which the dual Halbach magnet arrangement is applied, the length dimension Lc in the circumferential direction of the gap center Gc in the range (range of angle φ) of one set of permanent magnets 22 is Lc=2×π×Rco×φ / 360. Here, if the pole pitch at the gap center Gc is τ, then Lc=2×τ, and if the dimension corresponding to the length along the arrangement direction of the permanent magnets 22 at the gap center Gc is length dimension lm, then Lc=n×lm. Therefore, in the magnetic field generating unit 32B, the length dimension lm=Lc / n corresponds at the gap center Gc. In addition, if the length dimension of the entire circumference of the gap center Gc in the magnetic field generating unit 32B is Lg, the relationship between the length dimension Lg, the number of magnetic poles P, the number of divisions n, and the length dimension lm satisfies the relationship Lg=lm×n×P.

[0067] In addition, in the Halbach array field magnet 34B of the magnetic field generating unit 32B, the length dimension Lo in the circumferential direction of the surface on the gap 36 side is Lo=2×π×Rg×φ / 360. In the Halbach array field magnet 34B, if the pole pitch on the surface on the gap 36 side is τ, then Lo=2×τ. When the permanent magnets 22 are in close contact with each other, if the length dimension lm' along the arrangement direction (circumferential direction) of the permanent magnets 22 on the gap 36 side (magnetic field side) of the Halbach array field magnet 34B is Lo=n×lm', then Lo=n×lm'. Therefore, the permanent magnets 22 on the gap 36 side of the Halbach array field magnet 34B correspond to the length dimension lm'=Lo / n.

[0068] Furthermore, in the Halbach array field magnet 34A of the magnetic field generating unit 32B, the length dimension Li in the circumferential direction of the surface on the gap 36 side (magnetic field side) is Li = 2 × π × Ri × φ / 360. In the Halbach array field magnet 34A, if the pole pitch on the surface on the gap 36 side is τ, then Li = 2 × τ. When the permanent magnets 22 are in close contact with each other, if the length dimension lm" along the arrangement direction of the permanent magnets 22 on the gap 36 side of the Halbach array field magnet 34A is Li = n × lm". Therefore, the permanent magnets 22 on the gap 36 side of the Halbach array field magnet 34A correspond to the length dimension lm" = Li / n.

[0069] 4A, the Halbach array field magnet 34B in the magnetic field generating unit 32B is replaced with a ferromagnetic body 30A. The ferromagnetic body 30A is formed in a circular ring shape with an inner diameter equal to the radius of the gap center Gc, and the inner circumference (inner peripheral surface) of the ferromagnetic body 30A is located at the gap center Gc. As a result, the magnetic field generating unit 32A is equivalent to the magnetic field generating unit 28A deformed into a circular ring shape, and the magnetic field generating unit 32A has the effect of a dual Halbach magnet array like the magnetic field generating unit 28A.

[0070] In addition, in the Halbach array field magnet 34A of the magnetic field generating unit 32A, the circumferential length of the surface of the ferromagnetic body 30A on the gap 36 side is the same as the length Lc. Therefore, if the length of the entire circumference of the ferromagnetic body 30A on the gap 36 side in the magnetic field generating unit 32A is Lf, the relationship between the length Lf, the number of magnetic poles P, the number of divisions n, and the length lm satisfies Lf=lm×n×P.

[0071] Moreover, the magnetic field generating unit 32A has a circumferential length Li=2×τ of the surface on the gap 36 side of the Halbach array field magnet 34A. When the permanent magnets 22 are in close contact with each other, the permanent magnets 22 on the gap 36 side of the Halbach array field magnet 34A correspond to a length lm″=Li / n along the arrangement direction. Furthermore, since the pole pitch τ is set to a range in which the magnetization direction is reversed (a range in which the magnetization direction changes by 180°) in one set of permanent magnets 22 (22A to 22D), when there is a gap between the permanent magnets 22, the pole pitch τ can be said to be a range including this gap.

[0072] Furthermore, in the magnetic field generating unit 32A, the gap length G is in the range of 0.25 to 1.0 times the pole pitch τ (0.25τ≦G≦1.0τ), and the gap length G with respect to the number of divisions n is in the range of (0.125×n×lm) to (0.5×n×lm) times the length dimension lm along the arrangement direction of the permanent magnet 22 ((0.125×n×lm)≦G≦(0.5×n×lm)).

[0073] 1, the magnetic field generating unit 24 of the electric motor 10 has a configuration similar to that of the magnetic field generating unit 32A. A Halbach array field magnet 34A in which permanent magnets 22 are arranged in an annular shape is applied to the field magnet unit 16 of the magnetic field generating unit 24, and a ferromagnetic material is used for the outer cylinder portion 18 of the stator 14 surrounding the field magnet unit 16 (the outer cylinder portion 18 corresponds to the ferromagnetic material 30A). As a result, in the electric motor 10, the magnetic flux distribution between the field magnet unit 16 and the outer cylinder portion 18 is made similar to the magnetic flux portion between the Halbach array field magnet 34A of the magnetic field generating unit 32B and the gap center Gc.

[0074] In such a magnetic field generating section 24, any dimension can be applied to the thickness dimension ly as the dimension along the radial direction of the outer cylinder portion 18. By reducing the thickness dimension ly of the outer cylinder portion 18, the outer diameter dimension of the electric motor 10 can be prevented from increasing, and the output density of the electric motor 10 can be improved. In this case, in the electric motor 10, torque ripple is likely to occur due to magnetic saturation occurring in the outer cylinder portion 18. However, in the field magnet section 16, by applying the Halbach array field magnet 26A, the effect of the Halbach magnet arrangement that torque ripple can be suppressed is obtained.

[0075] Furthermore, by increasing the thickness dimension ly of the outer cylinder portion 18, it becomes more difficult to prevent the outer diameter dimension of the electric motor 10 from increasing, but it is possible to prevent magnetic saturation from occurring in the outer cylinder portion 18, and thus it is possible to effectively suppress torque ripple.

[0076] For this reason, the thickness dimension ly of the outer cylinder portion 18 is preferably the largest dimension at which magnetic flux saturation occurs in the outer cylinder portion 18 (it may be the smallest dimension at which magnetic flux saturation does not occur in the outer cylinder portion 18). This makes it possible to effectively suppress torque ripple while preventing the outer diameter dimension of the motor 10 from becoming large and improving the output density.

[0077] Meanwhile, a field magnet holder 40 is provided as a holding member on the rotor 12 of the electric motor 10. Fig. 5 shows a schematic configuration of the field magnet holder 40 in a perspective view, and Fig. 6 shows a main part of the field magnet portion 16 in a perspective view.

[0078] A non-magnetic material (material having no magnetism) is used for the field holder 40. The non-magnetic material applied to the field holder 40 may be a paramagnetic material, a diamagnetic material, or various resin materials (synthetic resins), and aluminum, various transition metals, and various synthetic resins can be applied to the field holder 40. In this embodiment, carbon fiber reinforced plastics (CFRP) is used for the field holder 40 from the viewpoint of obtaining high strength and toughness as well as enabling weight reduction.

[0079] 5, the field holder 40 includes an inner wall 42 as an inner circumferential wall, and an outer wall 44 as an outer circumferential wall, each of which is formed in a substantially cylindrical shape with a predetermined thickness. In the field holder 40, the outer diameter of the inner wall 42 is smaller than the inner diameter of the outer wall 44, and the field holder 40 is arranged coaxially within the outer wall 44 with the central axis of the inner wall 42 overlapping with the central axis of the outer wall 44. In this embodiment, the dimension of the field holder 40 along the axial direction is the same as the dimension in the direction intersecting the magnetization direction of the permanent magnet 22.

[0080] In the field holder 40, the distance between the outer peripheral surface of the inner wall 42 and the inner peripheral surface of the outer wall 44 is set to be the same as the radial dimension of the deformed permanent magnet 22. As a result, the field holder 40 is formed into a substantially cylindrical shape as a whole, and the field holder 40 is arranged so as to be rotatable integrally with the rotor 12, with the inner peripheral surface of the inner wall 42 being fixed (bonded) to the output shaft 12A of the rotor 12.

[0081] 1, 5 and 6, the field holder 40 is provided with a plurality of spacers 46 as partitions between the inner wall 42 and the outer wall 44, and the inner wall 42, the outer wall 44 and the spacers 46 of the field holder 40 are formed by integral molding of resin. Each of the spacers 46 is aligned along the radial direction of the field holder 40, and the spacers 46 are arranged at predetermined intervals in the circumferential direction of the field holder 40.

[0082] In the field holder 40, the spacers 46 are provided at positions between the adjacent permanent magnets 22, and the spacing between the spacers 46 is approximately the same as the circumferential length of the permanent magnets 22. For example, the spacing dimension between the spacers 46 on the outer wall 44 side along the circumferential direction is the same as the circumferential dimension of the outer circumferential surface of the permanent magnets 22 in the field magnet section 16. Also, the spacing dimension between the spacers 46 on the inner wall 42 side along the circumferential direction is the same as the circumferential length of the inner circumferential surface of the permanent magnets 22 in the field magnet section 16.

[0083] As a result, 32 (k×n) spacers 46 are formed in the field holder 40, and sockets 48, into which the permanent magnets 22 are fitted, are formed in the field holder 40 between adjacent spacers 46, the number of which is the same as the number of permanent magnets 22. The sockets 48 each have an opening cross-sectional shape in a direction (radial direction) intersecting the axial direction of the field holder 40 similar to the cross-sectional shape along the magnetization direction of the permanent magnet 22, and each of the sockets 48 has an opening cross-sectional shape similar to the cross-sectional shape along the magnetization direction of the permanent magnet 22 attached to the field holder 40.

[0084] In the rotor 12 of the electric motor 10, a permanent magnet 22 is inserted into each of the sockets 48 of the field holder 40, and the peripheral surfaces of the inserted permanent magnets are joined by adhesive or the like to the outer peripheral surface of the inner wall 42 of the field holder 40, the inner peripheral surface of the outer wall 44, and the inner surfaces of each spacer 46 (the inner surfaces of the sockets 48).

[0085] On the other hand, in a Halbach magnet array, the spacing between the permanent magnets 22 affects the magnetic field. In the magnetic field generating unit 24, the thickness dimension d, which is the dimension along the circumferential direction of the spacer 46 in the field magnet holder 40, affects the magnetic field generated by the field magnet unit 16.

[0086] Here, in the field holder 40, the thickness dimension d (mm) of the spacer 46 is set according to the length dimension lm (mm) along the arrangement direction of the attached permanent magnet 22 and the number of divisions n. The thickness dimension d of the spacer 46 of the field holder 40 is set so as to satisfy formula (1) from the length dimension lm along the arrangement direction of the permanent magnet 22 and the number of divisions n. 0 <d≦lm×1 / (n+1)×1.5 ···(1) Here, lm×1 / (n+1)×1.5=lm×1.5 / (n+1). In addition, in the field holder 40 formed from a non-magnetic material, the outer wall 44 that is on the outside of the permanent magnets 22 in the magnetic field generating part 24 is included in the area S2, and the spacers 46 between the permanent magnets 22 are included in the area S4.

[0087] In the electric motor 10 configured in this manner, the field magnet portion 16 of the rotor 12 and the outer cylinder portion 18 of the stator 14 form a magnetic field generating portion 24, and the armature 20 (coils 20U to 20W) is disposed in this magnetic field generating portion 24. Therefore, in the electric motor 10, when three-phase AC power of a predetermined voltage is supplied to each of the coils 20U to 20W, the rotor 12 is rotated and the output shaft 12A is rotationally driven. Moreover, the output shaft 12A of the electric motor 10 is rotationally driven at a rotation speed according to the frequency of the three-phase AC power supplied to each of the coils 20U to 20W.

[0088] In the magnetic field generating section 24 of the electric motor 10, the field magnet section 16 is surrounded by an outer cylinder section 18, and the outer cylinder section 18 faces each of the permanent magnets 22 of the field magnet section 16, and the Halbach array field magnet 34A is formed by the multiple permanent magnets 22 in the field magnet section 16. In addition, in the magnetic field generating section 24, the outer cylinder section 18 is disposed at a position corresponding to the gap center Gc of the Halbach array field magnets 34A and 34B in the dual Halbach magnet array with respect to the field magnet section 16, and a ferromagnetic material (ferromagnetic body) is used for the outer cylinder section 18. Therefore, in the magnetic field generating section 24, a magnetic field similar to that (approximate magnetic field) in which a dual Halbach magnet array is applied is formed between the field magnet section 16 and the outer cylinder section 18.

[0089] For this reason, the effect of suppressing torque ripple in the dual Halbach magnet arrangement is properly reproduced in the electric motor 10. As a result, in the electric motor 10, the same effect as that of the dual Halbach array field magnets using the Halbach array field magnets 34A and 34B can be obtained by using one Halbach array field magnet 34A, so that the occurrence of torque ripple is suppressed in the electric motor 10.

[0090] In addition, in the electric motor 10, the outer cylinder portion 18 disposed radially outside the field magnet portion 16 is fixed, so that the outer cylinder portion 18 can function as a housing. This allows the electric motor 10 to be made smaller and have a reduced number of parts, resulting in lower costs and improved output density. Moreover, since the electric motor 10 uses a Halbach magnet array, the number of permanent magnets 22 can be reduced compared to the case where a dual Halbach magnet array is used, resulting in further weight reduction and cost reduction, and effectively improving output density.

[0091] In general, between electric motors whose radial cross sections are similar in shape and whose axial lengths are similar, the output (rotational angular velocity x torque) can be increased in proportion to the cube of the similarity ratio. Since electric motor 10 has more margin in the radial size compared to when a dual Halbach magnet array is applied, electric motor 10 has the potential to increase the output. For this reason, electric motor 10 is expected to achieve a higher output density (output / volume ratio) compared to when a dual Halbach magnet array is applied.

[0092] Furthermore, in the electric motor 10, the coils 20U to 20W are air-core coils, and Litz wire is used for the coils 20U to 20W. In the electric motor 10, the coils 20U to 20W are air-core coils, which suppresses the generation of back electromotive force and makes it possible to suppress heat generation of switching elements in the inverter circuit when performing inverter control. Furthermore, by using Litz wire for the windings of the coils 20U to 20W, it is possible to reduce inductance, and it is possible to effectively suppress heat generation and back electromotive force generated in each of the coils 20U to 20W. As a result, the rated rotation speed of the electric motor 10 can be increased, enabling high rotation speed.

[0093] Furthermore, in the electric motor 10, the outer cylinder portion 18 in which the armature 20 (coils 20U to 20W) is arranged does not rotate, so that the outer cylinder portion 18 can be cooled using cooling means such as cooling fins or cooling pipes, and the armature 20 inside the outer cylinder portion 18 can be cooled together with the outer cylinder portion 18. This allows the electric motor 10 to effectively suppress heat generation, and therefore makes it possible to output a large torque in a short period of time.

[0094] Next, the assembly of the permanent magnets 22 in the field portion 16 of the magnetic field generating unit 24 will be described. In the field magnet portion 16 of the magnetic field generating section 24, a plurality of permanent magnets 22 are arranged in the circumferential direction, and the magnetization directions of adjacent permanent magnets 22 are changed by an angle θ.

[0095] Here, a field magnet holder 40 is used for the field magnet section 16 of the magnetic field generating unit 24, and in the field magnet holder 40, a plurality of spacers 46 are provided between an inner wall 42 and an outer wall 44, and a plurality of sockets 48 are formed into each of which a permanent magnet 22 is fitted. The number of sockets 48 formed is equal to the number of permanent magnets 22 used in the field magnet section 16, and the sockets 48 are arranged in the circumferential direction of the field magnet holder 40. Therefore, the plurality of permanent magnets 22 are assembled to the field magnet section 16 by being sequentially fitted into each of the sockets 48 of the field magnet holder 40 so that the magnetization direction is changed by a predetermined angle θ.

[0096] On the other hand, an attractive force and a repulsive force act between adjacent permanent magnets 22. Also, the magnetization directions of the permanent magnets 22 are shifted by a predetermined angle θ, and adjacent permanent magnets 22 are extremely close to each other. For this reason, when attempting to arrange the permanent magnets 22 in order in the circumferential direction, large attractive and repulsive forces may act between adjacent permanent magnets 22 in the direction of rotating the permanent magnets 22.

[0097] The multiple permanent magnets 22 used in the field magnet section 16 have the same cross-sectional shape along the magnetization direction, and the field magnet holder 40 has as many sockets 48 as the number of permanent magnets 22. Therefore, in the field magnet holder 40, the magnetization direction of the permanent magnets 22 inserted into one socket 48 is determined, and thereby the magnetization directions of the permanent magnets 22 inserted into all of the sockets 48 are determined. In each of the sockets 48, the movement of the permanent magnets 22 is restricted by the inner wall 42, the outer wall 44, and the spacer 46. Furthermore, the attractive and repulsive forces acting between the permanent magnets 22 become weaker as the distance between them increases.

[0098] From this, in the field holder 40, the permanent magnets 22 are fitted into the sockets 48 with one or more spaces between them (one or a predetermined number of spaces), which makes it easy to assemble the permanent magnets 22. For example, as shown in Fig. 6, in the field holder 40, the permanent magnets 22A, 22C, ... are fitted into the corresponding sockets 48 in this order, and then the permanent magnets 22B, 22D, ... are fitted into the empty sockets 48 between the permanent magnets 22A, 22C, ... in that order. This makes it easy to assemble the multiple permanent magnets 22 by arranging them in the circumferential direction, even if a large attractive or repulsive force acts between the permanent magnets 22.

[0099] Furthermore, in the field holder 40, the movement of the permanent magnet 22 fitted in the socket 48 can be restricted by the inner wall 42, the outer wall 44, and the spacer 46. Therefore, in the field holder 40, it is possible to restrict the permanent magnet 22 already fitted in the socket 48 from moving due to the influence of the magnetic force of a new permanent magnet 22 to be fitted in the socket 48. As a result, the field holder 40 can effectively assist in the assembly of the permanent magnet 22.

[0100] Therefore, the field holder 40 can easily assemble each of the multiple permanent magnets 22 even when the multiple permanent magnets 22 are arranged close to each other, and can easily assemble the field section 16 in which the multiple permanent magnets 22 are arranged in the circumferential direction.

[0101] Furthermore, carbon reinforced fiber plastic (CFRP) is used for the field holder 40. Therefore, even if an attractive force and a repulsive force act between adjacent permanent magnets 22 when assembling the permanent magnets 22, the inner wall 42, the outer wall 44 and the spacer 46 do not deform (distortion of the socket 48). This enables the field holder 40 to hold the multiple permanent magnets 22 in a fixed position.

[0102] Further, the permanent magnet 22 fitted into the socket 48 of the field magnet holder 40 is fixed by being adhered to the inner peripheral surface (each surface of the inner wall 42, the outer wall 44, and the spacer 46) of the socket 48 of the field magnet holder 40. Thereby, the permanent magnet 22 is securely fixed to the rotor 12 via the field magnet holder 40.

[0103] Also, in the electric motor 10, when the rotor 12 rotates, a centrifugal force acts on the permanent magnet 22 of the field magnet portion 16. For this reason, as the rotational speed of the electric motor 10 increases, the centrifugal force acting on the permanent magnet 22 increases. At this time, an outer wall 44 is formed on the outer side in the radial direction of the field magnet holder 40, and in the field magnet holder 40, the outer wall 44 is connected to the inner wall 42 by a plurality of spacers 46. For this reason, in the field magnet holder 40, even if a large centrifugal force acts on the permanent magnet 22 due to the rotation of the rotor 12, the outer wall 44 can effectively limit the movement of the permanent magnet 22 outward in the radial direction and can appropriately hold the permanent magnet 22. Thereby, in the electric motor 10, by providing the field magnet holder 40, stable high-speed rotation becomes possible. Moreover, since a carbon reinforced fiber plastic having high strength and toughness is used for the field magnet holder 40, it is possible to surely limit the permanent magnet 22 from shifting due to the centrifugal force and maintain the stable high-speed rotation of the electric motor 10.

[0104] On the other hand, in the Halbach magnet array, the interval between adjacent permanent magnets 22 greatly affects the magnetic field formed by the permanent magnets 22 (field magnet portion 16). In the electric motor 10, the spacer 46 of the field magnet holder 40 slightly opens the interval between adjacent permanent magnets 22, and the interval between adjacent permanent magnets 22 is determined. Also, in the field magnet holder 40, the thickness dimension d of the spacer 46 with respect to the reference length dimension lm is in the range of 0 < d ≤ (lm × 1 / (n + 1)) × 1.5, and the interval dimension w between adjacent permanent magnets 22 is 0 < w ≤ lm × 1 / (n + 1) × 1.5.

[0105] Generally, in a Halbach magnet array, the magnetic flux density at a position a certain distance away from the arranged permanent magnets 22 is affected by the interval (interval dimension w) between adjacent permanent magnets 22, and as the interval between adjacent permanent magnets 22 widens, leakage magnetic flux occurs and the magnetic flux density decreases. This decrease in magnetic flux density causes a decrease in the output torque of the electric motor 10.

[0106] Here, in the Halbach magnet array, the spatial harmonic components of the magnetic flux density distribution at a predetermined position for the permanent magnet 22 are approximately zero when the angle θ=360° / n (n is the number of divisions) and the spacing dimension w between adjacent permanent magnets 22 is 1 / (n+1) (w=lm×1 / (n+1)) of the length dimension lm along the arrangement direction of the permanent magnets 22. For example, when the number of divisions n=4, the spacing dimension w=lm / 5, and the harmonic components of the magnetic flux density distribution at a predetermined position for the permanent magnet 22 are approximately zero.

[0107] 7A shows the amplitude ratio (%) of the fundamental component of the spatial magnetic flux density distribution at the gap center Gc of the dual Halbach magnet array according to the spacing dimension w of the permanent magnets 22 when the angle θ of the magnetization direction of the permanent magnets 22 is 90° (angle θ when the number of divisions n is 4), and the volume ratio (%) of the permanent magnets 22. Also, Fig. 7B shows the amplitude ratio (amplitude ratio %) of the fifth ((n+1)th) harmonic component to the fundamental component of the spatial magnetic flux density distribution according to the spacing dimension w of the permanent magnets 22 at the gap center Gc when the angle θ is 90°.

[0108] The amplitude and volume ratios of the fundamental wave component of the spatial magnetic flux density distribution are based on the spacing dimension w=0, and are the ratios to the amplitude and volume of the fundamental wave component at spacing dimension w=0, and the volume of the permanent magnets 22 decreases as the spacing dimension w increases. 7A and 7B, the length dimension (length dimension along the radial direction) lm as the reference along the arrangement direction of the permanent magnets 22 on the armature 20 side is 10 mm, and the gap length 2G is 1.5 times the length dimension lm (2G=15 mm).

[0109] As shown in Fig. 7A, with respect to the spacing dimension w of the permanent magnets 22, the volume ratio (volume fraction) of the permanent magnets 22 and the amplitude of the fundamental wave are approximately proportional, and as the spacing dimension w of the permanent magnets 22 increases, the volume ratio of the permanent magnets 22 and the ratio of the amplitude of the fundamental wave component decrease.

[0110] In a dual Halbach magnet array, it is known that an (n + 1)-th harmonic component is generated in the magnetic field (in the gap) at an angle θ = 90°. As shown in Fig. 7B, when the spacing dimension w is 2 mm (= lm × 1 / (n + 1)), the ratio (amplitude ratio) of the amplitude of the fifth harmonic component to the amplitude of the fundamental wave component is minimum (substantially zero). From this, it can be considered that the fifth harmonic component disappears at a division number n = 4 and a spacing dimension w = 2 (mm).

[0111] The spacing dimension w = 2 (mm) is 1 / 5 (corresponding to 1 / (n + 1)) with respect to the length dimension lm (mm) of the permanent magnets 22 at a division number n = 4. Also, as shown in Fig. 7A, at a spacing dimension w = 2 mm, the amplitude of the fundamental wave decreases by about 20%.

[0112] Also, as shown in Fig. 7B, in the range where the spacing dimension w of the permanent magnets 22 is up to 3 mm (0 < w ≤ 3), the fifth harmonic component has the same ratio as the fifth harmonic component at w = 0, and no increase in the fifth harmonic component with respect to the fundamental wave component is seen.

[0113] Fig. 8A shows the ratio (%) of the amplitude of the fundamental wave of the spatial magnetic flux density distribution at the center of the gap of the dual Halbach magnet array with respect to the spacing dimension w of the permanent magnets 22 in the case where the angle θ of the magnetization direction of the permanent magnets 22 is 45° (the angle θ for a division number n = 8), and the volume ratio (%) of the permanent magnets 22. Also, Fig. 8B shows the amplitude ratio (amplitude ratio %) of the ninth ((n + 1)-th) harmonic component to the fundamental wave component of the spatial magnetic flux density distribution according to the change in the spacing dimension w of the permanent magnets 22 at the gap center Gc in the case where the angle θ = 45°.

[0114] As shown in FIG. 8A, even when the angle θ=45°, the ratio of the volume of the permanent magnets 22 and the ratio of the fundamental wave amplitude are approximately proportional to the spacing dimension w of the permanent magnets 22, and as the spacing dimension w of the permanent magnets 22 increases, the ratio of the volume of the permanent magnets 22 and the ratio of the fundamental wave amplitude decrease.

[0115] Furthermore, as shown in FIG. 8B, at angle θ=45°, the amplitude ratio is at a minimum (almost zero) when the spacing dimension w is approximately 1 mm (corresponding to lm × 1 / 9), and it can be considered that the ninth harmonic component has almost disappeared at this spacing dimension w ≒ 1 (mm).

[0116] Furthermore, at a spacing dimension w where the 9th harmonic component is deemed to disappear, the amplitude of the fundamental wave is reduced by approximately 10% (see FIG. 8A). The ratio of the amplitude of this fundamental wave becomes the same as the ratio at spacing dimension w=0 when spacing dimension w=1.7 (mm) (corresponding to w=lm×1 / 9×1.5). Therefore, in the range of spacing dimension w of 0≦w≦1.7, it can be deemed that there is no increase in the 9th harmonic component relative to the fundamental wave. The range of this spacing dimension w is up to 1 / 9 (=1 / (n+1)) of the length dimension lm along the arrangement direction of the permanent magnets 22 at angle θ=45° (number of divisions n=8).

[0117] Therefore, the spacing dimension w of the permanent magnets 22 in the Halbach magnet array is preferably 0≦w≦lm×1 / (n+1)×1.5. As a result, in the Halbach magnet array (single Halbach magnet array and dual Halbach magnet array), by setting the spacing dimension w of adjacent permanent magnets 22 in the range of 0≦w≦lm×1 / (n+1)×1.5 (where n is the number of divisions and lm is the length dimension of the permanent magnet 22 along the arrangement direction on the armature 20 side), it is possible to suppress an increase in harmonic components caused by the spacing dimension w of adjacent permanent magnets 22. In addition, by setting the spacing dimension w=lm×1 / (n+1), it is possible to effectively suppress harmonic components.

[0118] In addition, if the thickness dimension d of the spacer 46 provided in the field magnet holder 40 is a dimension of lm×1 / (n + 1)×1.5 (mm) or less (0 < d ≤ lm×1 / (n + 1)×1.5), the increase in harmonic components due to the provision of the spacer 46 can be suppressed. In particular, the field magnet holder 40 can effectively suppress harmonic components by setting the thickness dimension d of the spacer 46 to lm×1 / (n + 1). Therefore, the field magnet holder 40 may be formed with a thickness dimension d within the above range and having a dimension and material that can obtain a desired strength.

[0119] Therefore, the field magnet holder 40 may be formed with a thickness dimension d that satisfies the above conditions. Further, with respect to the cross-sectional area of the radial cross-section in the dual Halbach magnet array, the field magnet holder 40 may be formed such that the ratio of the cross-sectional area between the gap center Gc and the inner radial Halbach magnet array to the cross-sectional area between the gap center Gc and the outer radial Halbach magnet array is the same as the ratio of the cross-sectional area of the inner radial Halbach magnet array to the cross-sectional area of the outer radial Halbach magnet array. At this time, the field magnet holder 40 may be formed such that the spacer 46 is included in the area S4 in the inner radial Halbach magnet array corresponding to the field magnet portion 16, and the thickness dimension d of the spacer 46 of the field magnet holder 40 may be set including the pole pitch τ and the length dimension lm along the arrangement direction of the permanent magnets 22.

[0120] In the embodiment described above, the field magnet holder 40 provided with the spacer 46 corresponding to the number of the inner wall 42, the outer wall 44, and the permanent magnets 22 has been described as an example. However, the holding member may include at least an outer peripheral wall and a partition wall, and the inner peripheral wall may be omitted. In this case, for example, a rotating shaft that becomes the output shaft of the rotor may be applied as the inner peripheral wall of the holding member, and the permanent magnets may be fitted between the partition walls of the holding member with the holding member attached to the rotating shaft to attach the permanent magnets.

[0121] The retaining member may be configured such that the inner peripheral wall is used when the permanent magnet is assembled, but the inner peripheral wall is removed after assembly. Furthermore, the retaining member may be configured such that the movement of the permanent magnet is restricted by the outer peripheral wall and the partition wall, or the outer peripheral wall, the inner peripheral wall and the partition wall, and the outer peripheral wall, the inner peripheral wall and the partition wall may have a shape such as a lattice shape with openings formed in part of them.

[0122] In addition, in the present embodiment, the outer Halbach array field magnet 34A is replaced with the ferromagnetic material 30A in the magnetic field generating unit 32B. However, the magnetic field generating unit may have a configuration in which the radially inner Halbach array field magnet is replaced with a ferromagnetic material.

[0123] Meanwhile, in this embodiment, the magnetic field generating unit 32A is applied to the magnetic field generating unit 24 of the electric motor 10, but the magnetic field generating unit 32B may be applied to the magnetic field generating unit 24. That is, a dual Halbach magnet arrangement may be applied to the rotating electric machine. Fig. 9 shows a schematic configuration of an electric motor 50 according to a modified example in a plan view.

[0124] 9, the magnetic field generating section 52 of the electric motor 50 uses a field magnet section 54A as a first field magnet section to which the Halbach array field magnet 26A is applied, and a field magnet section 54B as a second field magnet section to which the Halbach array field magnet 26B is applied. The field magnet sections 54A and 54B are each formed into a substantially circular ring shape, and the field magnet section 54A is coaxially arranged within the field magnet section 54B with a gap length of 2G between them so that they can rotate together. In the electric motor 50, the armature 20 is arranged between the field magnet section 54A and the field magnet section 54B, and the armature 20 is rotatable relative to the field magnet sections 54A and 54B.

[0125] As a result, in the electric motor 50, when three-phase AC power is supplied to the coils 20U to 20W of the armature 20, the field magnet portions 54A, 54B are rotated integrally relative to the armature 20, and the output shaft 12A is rotationally driven.

[0126] Here, a field magnet holder 56 as a first holding member and a field magnet holder 58 as a second holding member are used for the field magnet portion 54A and the field magnet portion 54B, respectively, and the field magnet holders 56, 58 each have a basic structure similar to that of the field magnet holder 40. That is, the field magnet holder 56 is similar to the field magnet holder 40. Also, the field magnet holder 58 is provided with an inner wall 42A corresponding to the inner wall 42 and an outer wall 44A corresponding to the outer wall 44, a spacer 46 is disposed between the inner wall 42A and the outer wall 44A, and a socket 48A corresponding to the socket 48 is formed.

[0127] In the electric motor 50 configured in this manner, the use of the field holders 56, 58 allows the position of each of the permanent magnets 22 (22A to 22D) to be regulated in each of the field portions 54A, 54B, facilitating the assembly of the permanent magnets 22. This makes the electric motor 50 easy to manufacture, similar to the electric motor 10.

[0128] In the above-described embodiment and modified example, the number of divisions n=4 has been mainly described as an example, but any integer equal to or greater than 3 can be used for the number of divisions n. In addition, in a motor driven by three-phase AC power, from the viewpoint of suppressing torque ripple with greater precision, it is more preferable that the number of divisions n is n=3·k+2 (where k is a positive integer). This makes it possible to effectively suppress torque ripple from occurring in a power supply that uses three-phase AC power.

[0129] In addition, in the present embodiment and the modified example, the electric motors 10 and 50 have been described as examples. However, the rotating electric machine may be a generator that generates three-phase AC power by being rotated. By applying a generator as the rotating electric machine, the output density of the generator can be improved.

[0130] Furthermore, in the present embodiment and the modified example, the electric motors 10 and 50 have been described as examples. However, the rotating electric machine can also be used in a vehicle to operate as a drive source in a powering mode and as a regenerative generator in a deceleration mode (regenerative mode). In this case, even if the direction of the current is reversed when switching between the powering mode and the regenerative mode, the magnetic energy stored in the armature can be suppressed (reduced). Therefore, in the rotating electric machine, the induced voltage generated when the current is switched can be reduced, and therefore the rotating electric machine can be prevented from damaging the drive circuit for driving the rotating electric machine. Moreover, the rotating electric machine can provide a driving characteristic with good response in the vehicle.

[0131] The disclosure of Japanese Patent Application No. 2019-171621 is incorporated herein by reference in its entirety. All publications, patent applications and technical standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application or technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. a field magnet portion in which a plurality of permanent magnets are arranged in a circumferential direction with the magnetization direction being changed in sequence by an angle obtained by dividing one electrical angle cycle by a division number n, the division number n being any one of integers equal to or greater than 3; a retaining member made of a non-magnetic material, the retaining member having an annular outer peripheral wall with an inner peripheral surface against which the outer peripheral surfaces of the permanent magnets abut, and a plurality of partition walls each protruding radially inward from an inner surface of the outer peripheral wall in the circumferential direction of the outer peripheral wall, the adjacent partition walls between which the permanent magnets are fitted; A magnetic field generating device comprising: a thickness dimension d of the partition wall is set according to a length dimension lm of one side along an arrangement direction that is set in advance as a reference in a cross section along the magnetization direction of the permanent magnet, and the number of divisions n, The thickness dimension d of the partition wall is 0<d≦lm×1 / (n+1)×1.5 Fulfill Magnetic field generator.

2. A field magnet section in which a plurality of permanent magnets are arranged in a circumferential direction with the magnetization direction being changed in sequence by an angle obtained by dividing one electrical angle cycle by the division number n, where n is any one of three or more integers; a retaining member made of a non-magnetic material, the retaining member having an annular outer peripheral wall with an inner peripheral surface against which the outer peripheral surfaces of the permanent magnets abut, and a plurality of partition walls each protruding radially inward from an inner surface of the outer peripheral wall in the circumferential direction of the outer peripheral wall, the adjacent partition walls between which the permanent magnets are fitted; A magnetic field generating device comprising: a thickness dimension d of the partition wall is set according to a length dimension lm of one side along an arrangement direction that is set in advance as a reference in a cross section along the magnetization direction of the permanent magnet, and the number of divisions n, The thickness dimension d of the partition wall is d=lm / (n+1) Fulfill Magnetic field generator.

3. 3. The magnetic field generating device according to claim 1 or claim 2, wherein the retaining member includes an inner circumferential wall whose outer circumferential surface is in contact with the inner circumferential surfaces of the permanent magnets and whose outer circumferential surface is connected to the radially inner ends of the partitions.

4. a ferromagnetic body formed in an annular shape facing each of the permanent magnets of the field magnet portion, provided so as to be rotatable relative to the field magnet portion, and forming a magnetic field between the field magnet portion and the ferromagnetic body by a magnetic force of the field magnet portion; The magnetic field generating device according to claim 1 , further comprising:

5. the field magnet portion includes a first field magnet portion in which the plurality of permanent magnets are arranged in a circumferential direction, and a second field magnet portion that is disposed radially outside the first field magnet portion, in which the plurality of permanent magnets are arranged in the circumferential direction, and that is rotatable integrally with the first field magnet portion, The holding member includes a first holding member that holds each of the plurality of permanent magnets of the first field magnet portion, and a second holding member that holds each of the plurality of permanent magnets of the second field magnet portion. The magnetic field generating device according to any one of claims 1 to 3.

6. a field magnet portion in which a plurality of permanent magnets are arranged in a circumferential direction with the magnetization direction being changed in sequence by an angle obtained by dividing one electrical angle cycle by a division number n, the division number n being any one of integers equal to or greater than 3; a retaining member made of a non-magnetic material, the retaining member having an annular outer peripheral wall with an inner peripheral surface against which the outer peripheral surfaces of the permanent magnets abut, and a plurality of partition walls each protruding radially inward from an inner surface of the outer peripheral wall in the circumferential direction of the outer peripheral wall, the adjacent partition walls between which the permanent magnets are fitted; an armature in which each of the permanent magnets is arranged to be rotatable relative to the field magnet portion held by the holding member; A rotating electric machine including: a thickness dimension d of the partition wall is set according to a length dimension lm of one side along an arrangement direction that is set in advance as a reference in a cross section along the magnetization direction of the permanent magnet, and the number of divisions n, The thickness dimension d of the partition wall is 0<d≦lm×1 / (n+1)×1.5 Fulfill Rotating electric motor.

7. A field magnet section in which a plurality of permanent magnets are arranged in a circumferential direction with the magnetization direction being changed in sequence by an angle obtained by dividing one electrical angle cycle by the division number n, where n is any one of three or more integers; a retaining member made of a non-magnetic material, the retaining member having an annular outer peripheral wall with an inner peripheral surface against which the outer peripheral surfaces of the permanent magnets abut, and a plurality of partition walls each protruding radially inward from an inner surface of the outer peripheral wall in the circumferential direction of the outer peripheral wall, the adjacent partition walls between which the permanent magnets are fitted; an armature in which each of the permanent magnets is arranged to be rotatable relative to the field magnet portion held by the holding member; A rotating electric machine including: a thickness dimension d of the partition wall is set according to a length dimension lm of one side along an arrangement direction that is set in advance as a reference in a cross section along the magnetization direction of the permanent magnet, and the number of divisions n, The thickness dimension d of the partition wall is d=lm / (n+1) Fulfill Rotating electric motor.

8. a ferromagnetic body formed in an annular shape facing each of the permanent magnets of the field magnet portion, provided so as to be rotatable relative to the field magnet portion, and having three-phase coils of the armature arranged in a circumferential direction on a surface facing the field magnet portion; The rotating electric machine according to claim 6 or 7, further comprising:

9. the field magnet portion includes a first field magnet portion in which the plurality of permanent magnets are arranged in a circumferential direction, and a second field magnet portion that is disposed radially outside the first field magnet portion, in which the plurality of permanent magnets are arranged in the circumferential direction, and that is rotatable integrally with the first field magnet portion, the holding member includes a first holding member that holds each of the plurality of permanent magnets of the first field magnet portion, and a second holding member that holds each of the plurality of permanent magnets of the second field magnet portion, The armature has three-phase coils arranged in a circumferential direction between the first field portion and the second field portion. The rotating electric machine according to claim 6 or 7.

10. 10. The rotating electric machine according to claim 6, wherein the retaining member includes an inner circumferential wall whose outer circumferential surface is in contact with the inner circumferential surfaces of the permanent magnets and whose outer circumferential surface is connected to the radially inner ends of the partitions.

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