Rotor for electric motor

Abstract

The present invention relates to a rotor for an electric motor, comprising: a rotor core; a plurality of magnet holes provided in the rotor core; and a plurality of permanent magnets disposed in the respective magnet holes. The plurality of magnet bores extend along an axis of the rotor core and are configured to be symmetrical with respect to the d-axis when viewed along the axis. The plurality of magnet holes includes an outermost hole located farthest from the axis and an intermediate hole located alongside the outermost hole in a radial direction of the rotor core. The plurality of permanent magnets includes an outermost main magnet and an auxiliary magnet disposed in the outermost hole, and an intermediate main magnet disposed in the intermediate hole. Here, the auxiliary magnet adjoins the outermost main magnet on a side distant from the d-axis and faces the intermediate main magnet.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a rotor for an electric motor, and particularly to a rotor for an IPM (Interior Permanent Magnet) motor in which permanent magnets are arranged inside a rotor core. Background Art

[0002] In an IPM motor's rotor, multiple permanent magnets form a single rotor pole. The rotor has multiple magnet holes extending along its axis, and the permanent magnets are positioned in these holes. For simplicity, the "electric motor" will sometimes be referred to simply as the "motor," and the "permanent magnet" will sometimes be referred to simply as the "magnet."

[0003] In the rotor disclosed in U.S. Patent Publication No. 2020 / 0412190, two magnets arranged in the circumferential direction of the rotor constitute a rotor pole. In the rotor disclosed in Japanese Patent Application Laid-Open No. 2020-068654 and International Publication No. 2018 / 210577, more magnets constitute a rotor pole. When viewed in the axial direction of the rotor, multiple magnets are arranged in the radial direction of the rotor. In addition, the multiple magnets are configured to be symmetrical with respect to the d-axis when viewed along the axial direction of the rotor. The "d-axis" refers to the main direction of the magnetic flux emitted by a rotor pole. Summary of the Invention

[0004] When viewed along the axis of the rotor, the magnet hole is larger than the magnet. The magnet of the rotor is rectangular when viewed along the axis of the rotor, and the length of the magnet hole in the longitudinal direction is longer than the length of the long side of the rectangle of the magnet. A cavity is left next to the short side of the rectangular magnet. There is also a case where the cavity is filled with resin such as epoxy resin. Both the cavity and the resin are non-magnetic and the magnetic flux does not pass through. This specification provides a technology for configuring other magnets (auxiliary magnets) in the cavity of the magnet hole to adjust the path of the magnetic flux formed by the rotor pole to increase the output torque of the motor.

[0005] A rotor for an electric motor according to one embodiment of the present application includes: a rotor core having a plurality of magnet holes; and a plurality of permanent magnets, each of which is arranged in the plurality of magnet holes. The plurality of magnet holes extend along the axis of the rotor core and are arranged to be symmetrical with respect to the d-axis when viewed along the axis. The plurality of magnet holes include an outermost hole located at a position farthest from the axis and an intermediate hole located next to the outermost hole in the radial direction of the rotor core. The plurality of permanent magnets include an outermost main magnet and an auxiliary magnet arranged in the outermost hole and an intermediate main magnet arranged in the intermediate hole. The auxiliary magnet is adjacent to the outermost main magnet on the side farthest from the d-axis and is opposite to the intermediate main magnet.

[0006] A plurality of permanent magnets arranged symmetrically with respect to the d-axis constitute a rotor pole. In the absence of auxiliary magnets, a gap will be left at the end of the outermost hole (the end on the side far from the d-axis). For ease of explanation, the gap at the end of the outermost hole on the side far from the d-axis is referred to as a distal gap. In existing rotors, the distal gap is filled with non-magnetic materials (including air). Therefore, since a portion of the magnetic flux emitted by the intermediate main magnet bypasses the distal gap, it is far away from the d-axis. On the other hand, in the rotor disclosed in this specification, an auxiliary magnet is arranged in the distal gap. A portion of the magnetic flux emitted by the intermediate main magnet is attracted by the auxiliary magnet and approaches the d-axis. Since the rotor disclosed in this specification can concentrate the magnetic flux of the magnetic pole near the d-axis, the output torque of the motor becomes larger.

[0007] The detailed techniques and further improvements disclosed in this specification will be described in the following “Detailed Description of the Embodiments”. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Hereinafter, features, advantages, technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, in which like reference numerals represent like elements, and in which:

[0009] Figure 1 It is a front view of the motor including the rotor according to the embodiment.

[0010] Figure 2 This is a front view of the rotor of the embodiment (right half only).

[0011] Figure 3 It is the simulation result of the magnetic flux generated in the rotor of the embodiment.

[0012] Figure 4 It is the simulation result of the magnetic flux generated in the rotor of the comparative example.

[0013] Figure 5 This is a diagram comparing the magnetic flux near the far-end gap of the outermost hole.

[0014] Figure 6 It is a front view of the rotor of the first modified example.

[0015] Figure 7 This is a front view of a rotor according to a first modification (a diagram with auxiliary lines added for explaining the arrangement of magnets).

[0016] Figure 8 It is a front view of the rotor of the second modified example.

[0017] Figure 9 It is a front view of the rotor of the third modified example. DETAILED DESCRIPTION

[0018] The rotor according to the embodiment will be described with reference to the drawings. Figure 1 The front view of the motor 2 having the rotor 10 of the embodiment is shown. Here, the front view refers to a view of the rotor 10 viewed along the axis CL of the rotor 10. Figure 1 Only a 1 / 8 sector of the motor 2 is depicted, and the remaining portion is omitted from illustration.

[0019] The motor 2 is an interior permanent magnet (IPM) motor, in which magnets (permanent magnets) are embedded in the rotor core. Hereinafter, the "permanent magnets" are also simply referred to as "magnets."

[0020] The rotor 10 has 8 rotor poles. Figure 1 Only a portion corresponding to one rotor magnetic pole is shown. Since the rotor 10 includes eight rotor magnetic poles, one rotor magnetic pole corresponds to a 45-degree sector of the rotor 10 . Figure 1 The figure shows the range of a rotor pole. As is well known, the boundary between adjacent rotor poles corresponds to the q-axis Aq, and the centerline of the rotor poles corresponds to the d-axis Ad. In other words, the d-axis Ad corresponds to the main direction of the magnetic flux emitted by a rotor pole.

[0021] The motor 2 includes a rotor 10 and a stator 20. The stator 20 includes a plurality of teeth 22 extending toward the rotor 10. Stator coils 24 are wound around slots 23 between adjacent teeth 22.

[0022] The rotor 10 includes a cylindrical rotor core 11 and a plurality of magnets 14R, 14L, 15Ra, 15Rb, 15La, 15Lb, 16R, and 16L. Figure 1 The magnets 14R, 14L, 15Ra, 15Rb, 15La, 15Lb, 16R, and 16L shown in FIG. 1 constitute one rotor magnetic pole. The magnets 14R, 14L, 15Ra, 15Rb, 15La, 15Lb, 16R, and 16L constituting one rotor magnetic pole are arranged so that their polarities face the same direction.

[0023] The rotor core 11 is provided with a plurality of magnet holes 12R, 12L, 13R, and 13L extending along the axis CL. Each magnet is arranged in one of the magnet holes.

[0024] An "R" included in the reference number of a magnet means that the magnet is arranged on the right side of the d-axis Ad, and an "L" included in the reference number of a magnet means that the magnet is arranged on the left side of the d-axis Ad. Similarly, an "R" included in the reference number of a magnet hole means that the magnet hole is arranged on the right side of the d-axis Ad, and an "L" included in the reference number of a magnet hole means that the magnet hole is arranged on the left side of the d-axis Ad.

[0025] like Figure 1As shown, the plurality of magnet holes are arranged line-symmetrically with respect to the d-axis Ad, and the plurality of magnets are also arranged line-symmetrically with respect to the d-axis Ad. Therefore, the following description will focus on the magnet holes and magnets on the right side of the d-axis Ad and their arrangement.

[0026] Magnet holes 12R and 13R are arranged in the radial direction of rotor core 11. Magnet hole 12R is located at the position farthest from axis CL, and magnet hole 13R is located next to magnet hole 12R. For convenience of explanation, magnet hole 12R located farthest from axis CL is referred to as outermost hole 12R. Magnet hole 13R located next to outermost hole 12R in the radial direction of rotor core 11 is referred to as intermediate hole 13R.

[0027] Figure 2 Only the Figure 1 The right side of the rotor core 11 is shown in FIG. Figure 2 In FIG. 1 , in order to better understand the shapes of the outermost hole 12R and the intermediate hole 13R, the magnets 14R, 15Ra, 15Rb, and 16R are depicted with virtual lines.

[0028] Magnets 14R and 16R are placed in the outermost hole 12R, while magnets 15Ra and 15Rb are placed in the middle hole 13R. For ease of explanation, magnet 14R placed in the outermost hole 12R is referred to as the outermost main magnet 14R, and magnet 16R is referred to as the auxiliary magnet 16R. Furthermore, magnets 15Ra and 15Rb placed in the middle hole 13R are referred to as the middle main magnets 15Ra and 15Rb.

[0029] The outermost main magnet 14R has a rectangular shape when viewed along the axis CL and is arranged in the center of the outermost hole 12R. Gaps 12Ra and 12Rb are formed next to the two short sides of the outermost main magnet 14R, and the auxiliary magnet 16R is arranged in the gap 12Ra.

[0030] For ease of explanation, of the gaps 12Ra and 12Rb on either side of the outermost main magnet 14R, the gap 12Ra on the side farther from the d-axis Ad is referred to as the distal gap 12Ra, and the gap 12Rb on the side closer to the d-axis Ad is referred to as the proximal gap 12Rb. The auxiliary magnet 16R is positioned in the distal gap 12Ra. The proximal gap 12Rb is filled with a non-magnetic material (including air).

[0031] The auxiliary magnet 16R is smaller than the outermost main magnet 14R. It adjoins the outermost main magnet 14R on the side farther from the d-axis Ad and faces the intermediate main magnet 15Rb. More specifically, a portion of the auxiliary magnet 16R faces the long side of the intermediate main magnet 15Rb. Furthermore, the auxiliary magnet 16R is positioned between the outer periphery of the rotor core 11 and the intermediate main magnet 15Rb.

[0032] Conventionally, gaps 12Ra and 12Rb were secured on either side of the outermost main magnet 14R, with no magnets placed in these gaps 12Ra and 12Rb. This is for the following reasons. If the outermost main magnet 14R were enlarged to fill the gaps 12Ra and 12Rb, there is a concern that the outermost main magnet 14R would be damaged by the centrifugal force during the rotation of the rotor 10. Furthermore, if the outermost main magnet 14R were formed to conform to the contour of the outermost hole 12R, the cost of magnet manufacturing would increase.

[0033] In the rotor 10 of the embodiment, the outermost main magnet 14R is not enlarged according to the size of the magnet hole 12R, but other magnets (auxiliary magnets 16R) are arranged in the distal gap 12Ra. Since the outermost main magnet 14R is not enlarged, the outermost main magnet 14R does not become fragile relative to the centrifugal force. On the other hand, by arranging the auxiliary magnet 16R in the distal gap 12Ra of the outermost hole 12R, the torque of the motor 2 can be increased. Among them, the strength of the auxiliary magnet 16R is higher than that of the outermost main magnet 14R and the intermediate main magnets 15Ra and 15Rb. By adopting the auxiliary magnet 16R with high strength, the resistance of the rotor 10 to centrifugal force can be improved, and the cost of the rotor 10 can be suppressed.

[0034] Reference Figure 3 5. The reason why the auxiliary magnet 16R can increase the torque of the motor 2 will be described. Figure 3 is the simulation result of the magnetic flux emitted by the magnet of the rotor 10. For comparison, the simulation result of the magnetic flux of the rotor 900 without the auxiliary magnet 16R is shown in FIG. Figure 4 Shown in. Figure 3 and Figure 4 The only difference is the presence or absence of the auxiliary magnet 16R; the other magnet arrangements are the same.

[0035] Figure 5 It is magnified Figure 3 The dotted range Va and Figure 4 The dotted line range Va and Vb are enlarged views of the vicinity of the distal gap. The gap of the rotor (for example, the distal gap 12Ra) is a non-magnetic area, and magnetic flux cannot pass through. In the comparative example ( Figure 5 In Vb), a portion of the magnetic flux emitted by the intermediate main magnet 15Rb does not pass through the distal gap 12Ra and gradually moves away from the d-axis (refer to Figure 5 On the other hand, in the rotor 10 ( Figure 5 In Va), a portion of the magnetic flux emitted by the intermediate main magnet 15Rb is attracted by the auxiliary magnet 16R arranged in the distal gap 12Ra. Figure 5Magnetic flux lines A in Vb transform into magnetic flux lines B in Vb, passing through auxiliary magnet 16R and heading toward the surface of rotor 10. Specifically, a portion of the magnetic flux emitted by intermediate main magnet 15Rb is attracted by auxiliary magnet 16R and drawn toward the d-axis. Auxiliary magnet 16R concentrates the magnetic flux of the rotor poles near the d-axis. This increases the output torque of motor 2.

[0036] In addition, the auxiliary magnet 16R is only arranged in the distal gap 12Ra in the gaps on both sides of the outermost main magnet 14R (the distal gap 12Ra and the proximal gap 12Rb). Compared with the case where an auxiliary magnet is arranged in each of the gaps on both ends of the outermost main magnet 14R, the structure of the embodiment can effectively and flexibly utilize the magnetic flux. In other words, compared with the case where an auxiliary magnet is arranged in each of the gaps on both sides of the outermost main magnet 14R, the structure of the embodiment can achieve high torque while suppressing the amount of magnets. The rotor 10 of the embodiment is obtained by adding the auxiliary magnet 16R to the original gap (the distal gap 12Ra). This structure can increase the design freedom of the rotor (motor).

[0037] The auxiliary magnet 16R is fixed in the outermost hole 12R (the distal end gap 12Ra) by a foaming agent or an adhesive. The foaming agent or the adhesive can alleviate the stress acting between the auxiliary magnet 16R and the rotor core 111 due to the centrifugal force during the rotation of the rotor.

[0038] Figure 6 -9 represents a rotor of a modified example. Figure 6 -9 also goes with Figure 1 Again, only one rotor pole is shown. Figure 6 In Figure 9, the shape of the magnet hole is simplified. Specifically, the gap next to the main magnet is depicted as a triangle. However, the gap next to the main magnet is not limited to a triangle as long as it is smaller than the size of the main magnet. In addition, the auxiliary magnet can be a sintered magnet or a bonded magnet. The strength of the auxiliary magnet can be higher than that of the outermost main magnet and the middle main magnet. Bonded magnets can achieve a magnet with higher strength at a lower cost than sintered magnets.

[0039] (First Modification)

[0040] Figure 6The front view of the rotor 110 of the first variant is shown. In the rotor 110, six magnets (the outermost main magnets 14R, 14L, the intermediate main magnets 15R, 15L, and the auxiliary magnets 16R, 16L) constitute one rotor pole. The magnets 14R, 15R, 16R and the magnets 14L, 15L, 16L are arranged to be line-symmetrical with respect to the d-axis Ad of the rotor pole. The outermost main magnets 14R, 14L are arranged in a V-shape, and the intermediate main magnets 15R, 15L are also arranged in a V-shape. The multiple magnet holes and the multiple magnets that constitute one rotor pole are arranged to be line-symmetrical with respect to the d-axis Ad. The following describes the magnet arrangement on the right side of the d-axis Ad.

[0041] The rotor core 111 is provided with multiple magnet holes. These include an outermost hole 12R, located farthest from the axis CL, and an intermediate hole 13R, located radially adjacent to the outermost hole 12R. An outermost main magnet 14R and an auxiliary magnet 16R are disposed in the outermost hole 12R. When viewed along the axis CL, the outermost main magnet 14R has a rectangular shape. The auxiliary magnet 16R is adjacent to the outermost main magnet 14R on the side farther from the d-axis Ad. The auxiliary magnet 16R is smaller than the outermost main magnet 14R.

[0042] The intermediate main magnet 15R is disposed in the intermediate hole 13R. The auxiliary magnet 16R faces the intermediate main magnet 15R. The auxiliary magnet 16R is disposed between the outer periphery of the rotor core 111 and the intermediate main magnet 15R. The rotor 110 also has the same advantages as the rotor 10 of the embodiment.

[0043] Next, the symmetry of the configuration of the magnet holes and the magnets is explained. The multiple magnet holes are configured to be line-symmetrical with respect to the d-axis Ad. The multiple magnets are also configured to be line-symmetrical with respect to the d-axis Ad. The outermost holes 12R and 12L are configured to be line-symmetrical with respect to the d-axis Ad. In the rotor core 111, the portion between the outermost hole 12R and the outermost hole 12L is called a bridge portion. In other words, a bridge portion is provided between the outermost hole 12R and the outermost hole 12L. Similarly, the intermediate holes 13R and 13L are configured to be line-symmetrical with respect to the d-axis Ad, and a bridge portion is provided between the intermediate holes 13R and 13L.

[0044] Figure 7 This figure shows the front view of the rotor 110 with auxiliary lines (single-dot and double-dot dash lines) added to illustrate the magnet arrangement. The single-dot dash lines overlap the center lines of the outermost main magnets 14R and 14L. The two auxiliary lines overlapping the outermost main magnets 14R and 14L are symmetrical about the d-axis Ad, forming a V-shape. In other words, the outermost main magnets 14R and 14L are arranged in a line-symmetrical V-shape about the d-axis Ad.

[0045] The two-dot chain lines are auxiliary lines that overlap the center lines of the intermediate main magnets 15R and 15L. As indicated by the two two-dot chain lines, the intermediate main magnets 15R and 15L are arranged in a line-symmetrical V-shape with respect to the d-axis Ad. The outermost main magnets 14R and 14L and the intermediate main magnets 15R and 15L form a double V-shape.

[0046] The outermost holes 12R and 12L are also formed in a V-shape that is line-symmetrical with respect to the d-axis Ad. The intermediate holes 13R and 13L are also formed in a V-shape that is line-symmetrical with respect to the d-axis Ad.

[0047] The inner angle of the V-shape formed by the outermost main magnets 14R and 14L ( Figure 7 The angle A1) is larger than the inner angle ( Figure 7 The larger the inner angle A2 of the V-shape formed by the multiple intermediate main magnets 15R and 15L, the greater the tendency of the magnetic flux of the intermediate main magnets 15R (15L) to flow toward the auxiliary magnets 16R (16L). As a result, magnetic flux loss is further reduced, and the output torque of the motor is increased.

[0048] (Second Modification)

[0049] Figure 8 The front view of the rotor 210 of the second variant is shown. In the rotor 210, five magnets (the outermost main magnet 14, the intermediate main magnets 15R and 15L, and the auxiliary magnets 16R and 16L) constitute a rotor pole. The magnets 15R and 16R and the magnets 15L and 16L are arranged to be line-symmetrical with respect to the d-axis Ad of the rotor pole. The magnet 14 is also arranged to be line-symmetrical with respect to the d-axis Ad. The intermediate main magnets 15R and 15L are also arranged in a V shape. The multiple magnet holes and the multiple magnets that constitute a rotor pole are arranged to be line-symmetrical with respect to the d-axis Ad. The following describes the magnet configuration on the right side of the d-axis Ad.

[0050] The rotor core 211 is provided with multiple magnet holes. These include an outermost hole 12, located farthest from the axis CL, and an intermediate hole 13R, located radially adjacent to the outermost hole 12. The outermost hole 12 is provided with an outermost main magnet 14 and an auxiliary magnet 16R. The outermost hole 12 is arranged symmetrically with respect to the d-axis Ad. Therefore, both ends of the outermost hole 12 are located equidistant from the d-axis Ad. The auxiliary magnets 16L and 16R are both adjacent to the outermost main magnet 14 on the side farther from the d-axis Ad.

[0051] The intermediate main magnet 15R is disposed in the intermediate hole 13R. The auxiliary magnet 16R faces the intermediate main magnet 15R. The auxiliary magnet 16R is disposed between the outer periphery of the rotor core 211 and the intermediate main magnet 15R. The rotor 210 also has the same advantages as the rotor 10 of the embodiment.

[0052] (Third Modification)

[0053] Figure 9 This figure shows a front view of the rotor 310 according to the third variant. In the rotor 310, eight magnets (outermost main magnets 14R, 14L, intermediate main magnets 15R, 15L, innermost main magnets 19R, 19L, and auxiliary magnets 16R, 16L) constitute a single rotor pole. The magnets 14R, 15R, 16R, 19R and the magnets 14L, 15L, 16L, 19L are arranged symmetrically with respect to the d-axis Ad of the rotor pole. The outermost main magnets 14R, 14L are arranged in a V-shape, and the intermediate main magnets 15R, 15L are also arranged in a V-shape. The innermost main magnets 19R, 19L are also arranged in a V-shape. The following describes the magnet arrangement to the right of the d-axis Ad.

[0054] The rotor core 311 is provided with multiple magnet holes. These include an outermost hole 12R, located farthest from the axis CL; an intermediate hole 13R, located radially adjacent to the outermost hole 12R; and an innermost hole 18R, located between the intermediate hole 13R and the axis CL. The outermost hole 12R is provided with an outermost main magnet 14R and an auxiliary magnet 16R. When viewed along the axis CL, the outermost main magnet 14R has a rectangular shape. The auxiliary magnet 16R is adjacent to the outermost main magnet 14R on the side farther from the d-axis Ad.

[0055] A middle main magnet 15R is disposed in the middle hole 13R. Auxiliary magnets 16R face the middle main magnets 15R. Auxiliary magnets 16R are disposed between the outer periphery of the rotor core 311 and the middle main magnets 15R. An innermost main magnet 19R is disposed in the innermost hole 18R. The rotor 310 also has the same advantages as the rotor 10 of the embodiment.

[0056] Several features of the rotor introduced in the embodiment are summarized. The multiple magnets shown in the drawings constitute a rotor pole. The auxiliary magnet is adjacent to the outermost main magnet on the side far from the d-axis and is opposite to the middle main magnet. The auxiliary magnet is arranged between the outer periphery of the rotor core and the middle main magnet. The auxiliary magnet is located near the d-axis Ad at the end of the middle main magnet on the side farther from the d-axis Ad. In other words, the auxiliary magnet is located between the end of the middle main magnet on the side farther from the d-axis Ad and the d-axis Ad.

[0057] The auxiliary magnets attract a portion of the magnetic flux emitted by the intermediate main magnets toward the d-axis. This feature concentrates the magnetic flux of the rotor poles near the d-axis, resulting in increased motor torque.

[0058] When viewed along the axis, the outermost main magnet is rectangular, with its long sides extending along the circumference of the rotor and its short sides extending along the radial direction of the rotor. Auxiliary magnets are arranged next to the short sides on the side farther from the d-axis.

[0059] The north poles (south poles) of the plurality of magnets constituting the rotor magnetic poles face the same direction.

[0060] The rotors of other embodiments and other variations may have features of the rotor 110 related to the d-axis symmetry of the arrangement of the magnet holes and magnets ( Figure 7 ).

[0061] The following describes the points of attention related to the technology described in the embodiment. The gaps in the magnet holes can be filled with non-magnetic materials (such as epoxy resin). A small gap can be set between the outermost main magnet and the auxiliary magnet (see Figure 1 There may not be any gap between the outermost main magnet and the auxiliary magnet (see Figure 6 -9).

[0062] The rotor of the embodiment has eight rotor magnetic poles. The technology disclosed in this specification can also be applied to rotors having a number of rotor magnetic poles other than eight.

[0063] In the rotor 110 of the embodiment, the inner angle of the V-shape formed by the plurality of outermost main magnets 14R and 14L is greater than the inner angle of the V-shape formed by the plurality of intermediate main magnets 15R and 15L. When a plurality of other intermediate main magnets are arranged in a V-shape between the intermediate magnet and the axis CL, the inner angle of the V-shape formed by the plurality of other intermediate main magnets can be smaller than or greater than the inner angle of the V-shape formed by the plurality of outermost main magnets 14R and 14L. This is sufficient as long as the inner angle of the V-shape formed by the plurality of intermediate main magnets 15R and 15L adjacent to the outermost main magnets 14R and 14L is smaller than the inner angle of the V-shape formed by the plurality of outermost main magnets 14R and 14L.

[0064] The specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of protection claimed in this application. The technologies described in the scope of protection claimed in this application include technologies obtained by various deformations and changes to the specific examples illustrated above. The technical elements described in this specification or the drawings exert technical usefulness alone or through various combinations, and are not limited to the combinations recorded in the technical solutions at the time of application. In addition, the technologies illustrated in this specification or the drawings can achieve multiple purposes at the same time, and achieving one of the purposes itself has technical usefulness.

Claims

1. A rotor for an electric motor, wherein: include: a rotor core having a plurality of magnet holes; and A plurality of permanent magnets are respectively arranged in the plurality of magnet holes, The plurality of magnet holes extend along the axis of the rotor core and are arranged symmetrically with respect to the d axis when viewed along the axis, the plurality of magnet holes including an outermost hole farthest from the axis and an intermediate hole located beside the outermost hole in the radial direction of the rotor core. The plurality of permanent magnets include an outermost main magnet and an auxiliary magnet arranged in the outermost hole and an intermediate main magnet arranged in the intermediate hole. The auxiliary magnet is adjacent to the outermost main magnet on a side far from the d-axis and is opposed to the intermediate main magnet.

2. The rotor for an electric motor according to claim 1, wherein: The plurality of permanent magnets include a plurality of outermost main magnets and a plurality of intermediate main magnets, The plurality of outermost main magnets are arranged in a line-symmetrical V-shape with respect to the d-axis. The plurality of intermediate main magnets are arranged in a line-symmetrical V-shape with respect to the d-axis.

3. The rotor for an electric motor according to claim 2, wherein: An inner angle of a V-shape formed by the plurality of outermost main magnets is greater than an inner angle of a V-shape formed by the plurality of intermediate main magnets.

4. The rotor for an electric motor according to claim 1, wherein The auxiliary magnet has a strength higher than that of the outermost main magnet and the intermediate main magnet.

5. The rotor for an electric motor according to claim 1, wherein The auxiliary magnet is fixed to the outermost hole by a foaming agent or an adhesive.

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