Rotor

Abstract

To provide a rotor that can improve the demagnetization resistance of a Halbach array magnet.SOLUTION: A permanent magnet 22 of a Halbach array magnet rotor 12 is configured such that the surface side portion of a stator 11 that is likely to receive the magnetic flux φ2 in the opposite direction, which is a cause of demagnetization of the q-axis magnet portion 22q, that is, a portion near the outer surface 22b, which is the portion close to the stator 11 side have at least a high coercive force Hc. As an example, the q-axis magnet portion 22q is configured to have a uniformly high coercive force Hc throughout itself.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a rotor having a permanent magnet.

Background Art

[0002] In a rotor of a motor, there is known a configuration in which a plurality of permanent magnets are arranged on the side surface of a rotor base as magnetic pole portions. The permanent magnets are configured as Halbach array magnets as an example (see, for example, Patent Document 1). By using Halbach array magnets, an improvement in the performance of the motor can be expected.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A Halbach array magnet is a magnet in which a d-axis magnet portion mainly having magnetic flux in the radial direction and a q-axis magnet portion mainly having magnetic flux in the circumferential direction are alternately arranged in the circumferential direction. Further, the d-axis magnet portions on both sides of the q-axis magnet portion have different polarities from each other. Due to such a configuration of the magnet, the magnetic flux emitted from the d-axis magnet portion on one side in the circumferential direction of the q-axis magnet portion returns to the d-axis magnet portion on the other side in the circumferential direction through the stator core or the like on the stator side. A small loop-shaped magnetic path is formed between the permanent magnet of the rotor made of Halbach array magnets and the stator, straddling each other.

[0005] However, in this case, the magnetic flux in the circumferential direction on the stator side is opposite to the magnetic flux in the circumferential direction of the q-axis magnet portion on the rotor side. Since the q-axis magnet portion constituting the Halbach array magnet is arranged close to the stator side, the magnetic flux generated in the opposite direction on the stator side is one of the factors that demagnetize the q-axis magnet portion.

[0006] An object of the present disclosure is to provide a rotor capable of improving the demagnetization resistance performance of a Halbach array magnet.

Means for Solving the Problems

[0007] The rotor for solving the above problems includes a rotor base (21) and a plurality of permanent magnets (22) arranged in the circumferential direction on the side surface (21a) of the rotor base. The permanent magnet is mainly composed of a d-axis magnet portion (22dn, 22ds) in which magnetic flux mainly faces the radial direction and a q-axis magnet portion (22q, 22q1, 22q2) in which magnetic flux mainly faces the circumferential direction, and is alternately arranged in the circumferential direction. The rotor (12) is composed of a Halbach array magnet, and the coercive force (Hc) of at least the surface-side portion (22b) of the q-axis magnet portion of the permanent magnet is set higher than that of the d-axis magnet portion.

[0008] According to the above rotor, the permanent magnet adopting the Halbach array magnet is set such that the coercive force of the surface-side portion of the q-axis magnet portion, that is, the portion close to the stator side, is higher than that of the d-axis magnet portion. If the d-axis magnet portion is set to a generally assumed coercive force, for example, the q-axis magnet portion has a higher coercive force. Therefore, even when receiving the reverse magnetic flux from the stator side, which is a concern as a factor for demagnetization of the q-axis magnet portion, the q-axis magnet portion having a high coercive force can exhibit the desired magnetic performance. That is, the demagnetization resistance performance in the permanent magnet can be improved, and the entire permanent magnet can contribute to exhibiting the desired magnetic performance.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiment for Carrying Out the Invention

[0010] Hereinafter, an embodiment of the rotor will be described. (Configuration of Motor 10) As shown in FIG. 1, the motor 10 of this embodiment includes a stator 11 and a rotor 12. The stator 11 is configured in a substantially annular shape. The stator 11 has, for example, 24-pole coil magnetic pole portions (not shown) in the circumferential direction. Inside the stator 11, the rotor 12 is rotatably arranged. The stator 11 generates a rotating magnetic field for driving the rotation of the rotor 12 based on the energization of its coil magnetic pole portions. The motor 10 of this embodiment is assumed to be applied to a high-speed rotation specification motor with a maximum operating speed of 12,000 [rpm] or more as an example.

[0011] (Configuration of Rotor 12) As shown in FIGS. 1 and 2, the rotor 12 of this embodiment includes a rotor base 21, a permanent magnet 22, and a scattering prevention member 23.

[0012] The rotor base 21 is configured in a substantially cylindrical shape as a whole. The rotor base 21 has a hollow structure considering weight reduction and the like. The axial end portion of the rotor base 21 is integrally configured as an output shaft portion 21x. On the outer surface 21a of the central portion in the axial direction of the rotor base 21, for example, 20 permanent magnets 22 are arranged in the circumferential direction. The outer surface 21a of the rotor base 21 of this embodiment has 20 flat surfaces corresponding to each permanent magnet 22 (see FIG. 3). The rotor 12 has a magnet magnetic pole portion with 20 poles in the circumferential direction.

[0013] The permanent magnet 22 has a substantially rectangular shape. The inner surface 22a of the permanent magnet 22 on the inner diameter side of the rotor 12 is in contact with the outer surface 21a of the rotor base 21. The inner surface 22a of the permanent magnet 22 forms a flat surface and is in contact with the outer surface 21a of the rotor base 21 with the flat surfaces in contact with each other. The outer surface 22b of the permanent magnet 22 on the outer diameter side of the rotor 12 forms a uniform outer peripheral surface of the rotor 12 by all the permanent magnets 22 in the circumferential direction. The side end surfaces 22c on both sides of the permanent magnet 22 in the circumferential direction of the rotor 12 form flat surfaces along the radial direction of the rotor 12. In order to bring its inner surface 22a into contact with the rotor base 21, the permanent magnet 22 has a gap at each of the side end surfaces 22c on both sides with respect to the permanent magnets 22 on both sides in the circumferential direction, or is in contact only at one of the side end surfaces 22c. In each figure, the permanent magnets 22 are depicted as being in contact with each other.

[0014] As shown in FIG. 3, in this embodiment, the permanent magnet 22 is configured as a Halbach array magnet. Specifically, the permanent magnet 22 is divided into three parts with different magnetization patterns in the circumferential direction. The both side portions in the circumferential direction of the permanent magnet 22 are mainly d-axis magnet portions 22dn, 22ds where the magnetic flux is directed in the radial direction. The central portion in the circumferential direction of the permanent magnet 22 is mainly a q-axis magnet portion 22q where the magnetic flux is directed in the circumferential direction and is directed toward the d-axis magnet portions 22dn, 22ds on both sides thereof. The permanent magnet 22 is integrally formed with the d-axis magnet portions 22dn, 22ds and the q-axis magnet portion 22q as one magnetic material.

[0015] At the d-axis magnet portion 22dn on one side in the circumferential direction, an N pole appears on the outer surface 22b of the permanent magnet 22. At the d-axis magnet portion 22ds on the other side in the circumferential direction, an S pole appears on the outer surface 22b of the permanent magnet 22. As the circumferential arrangement pattern of each permanent magnet 22 in the rotor 12, the d-axis magnet portions 22dn of the same poles of the adjacent permanent magnets 22 in the circumferential direction are arranged continuously side by side, and the d-axis magnet portions 22dn of the same poles of the adjacent permanent magnets 22 cooperate with each other to form a magnet pole portion of the same pole.

[0016] Incidentally, regarding the mounting mode of each permanent magnet 22 to the outer surface 21a of the rotor base 21, for example, after mounting one permanent magnet 22 every full circumference or a part of the circumferential direction, the later-mounted permanent magnet 22 is inserted radially between the previously mounted permanent magnets 22. The mounting of each permanent magnet 22 is repeated over the entire circumference of the rotor 12. Further, the radially inner portion 22e of each permanent magnet 22 has inclined surfaces 22f at both circumferential corners, and has a tapered shape that facilitates insertion between the previously mounted permanent magnets 22. Further, each inclined surface 22f is located at the corner of each d-axis magnet portion 22dn, 22ds of the permanent magnet 22. However, since each d-axis magnet portion 22dn, 22ds is magnetized so that its internal magnetic flux inclines along each inclined surface 22f, the influence on the performance of the permanent magnet 22 is small.

[0017] Also, as shown in FIG. 4, the q-axis magnet portion 22q of each permanent magnet 22 of the present embodiment is configured to have a high coercive force Hc. In this case, the q-axis magnet portion 22q has a higher coercive force Hc than the d-axis magnet portions 22dn, 22ds. In other words, the d-axis magnet portions 22dn, 22ds have a relatively low coercive force Hc with respect to the q-axis magnet portion 22q, but this is the coercive force Hc generally assumed in the present embodiment. Further, the q-axis magnet portion 22q of the present embodiment is configured to have a uniformly high coercive force Hc throughout itself.

[0018] As shown in FIG. 2, the scattering prevention member 23 is mounted in a manner that circulates around the rotor 12 along the outer surfaces 22b of a plurality of permanent magnets 22 in the circumferential direction. The scattering prevention member 23 is provided, for example, in a cylindrical shape so as to completely cover the permanent magnet 22. For the scattering prevention member 23, for example, a carbon fiber reinforced resin material (referred to as a CFRP material) is used. A ribbon-shaped material (not shown) of the CFRP material is wound around the permanent magnet 22 of the rotor 12 for several turns, and is wound in one layer or multiple layers. Then, heat curing is performed to produce a cylindrical scattering prevention member 23 that fixes the permanent magnet 22 and prevents scattering.

[0019] (Operation of the present embodiment) The operation of the present embodiment will be described. In the rotor 12 of the present embodiment, the permanent magnet 22 is configured as a Halbach array magnet. As shown in FIG. 4, the magnetic flux that exits from the d-axis magnet portion 22dn on one circumferential side of the q-axis magnet portion 22q passes through a stator core (not shown) on the stator 11 side or the like and returns to the d-axis magnet portion 22ds on the other circumferential side. A small loop-shaped magnetic path is formed across the permanent magnet 22 of the rotor 12 and the stator 11. At this time, the magnetic flux φ2 directed in the circumferential direction on the stator 11 side is opposite to the magnetic flux φ1 directed in the circumferential direction of the q-axis magnet portion 22q on the rotor 12 side. Since the q-axis magnet portion 22q that constitutes the Halbach array magnet is arranged close to the stator 11 side, the magnetic flux φ2 that is generated in the opposite direction on the stator 11 side is one of the factors that demagnetize the q-axis magnet portion 22q.

[0020] In consideration of such concerns, in the permanent magnet 22 of the present embodiment, the q-axis magnet portion 22q has a high coercive force Hc and is configured to improve the demagnetization resistance performance. Therefore, even when receiving the reverse magnetic flux φ2 generated in the stator 11, the q-axis magnet portion 22q can exhibit the desired magnetic properties, and thus the entire permanent magnet 22 can exhibit the desired magnetic properties.

[0021] (Effect of the present embodiment) The effect of the present embodiment will be described. (1) In the permanent magnet 22 of the rotor 12 of the present embodiment that employs a Halbach array magnet, the coercive force Hc of the q-axis magnet portion 22q is set higher than that of the d-axis magnet portions 22dn and 22ds. In the present embodiment, the coercive force Hc is uniformly increased throughout the q-axis magnet portion 22q so as to include the surface side portion of the q-axis magnet portion 22q, that is, the portion near the outer surface 22b which is the portion close to the stator 11 side. If the d-axis magnet portions 22dn and 22ds are set to a generally assumed coercive force Hc, for example, the q-axis magnet portion 22q has a higher coercive force Hc than that. Therefore, even when receiving the reverse magnetic flux φ2 on the stator 11 side, which is a concern as a factor for demagnetization of the q-axis magnet portion 22q, the q-axis magnet portion 22q having a high coercive force Hc can exhibit the desired magnetic properties. That is, the demagnetization resistance performance of the permanent magnet 22 can be improved, and it can contribute to the entire permanent magnet 22 exhibiting the desired magnetic properties.

[0022] (2) The q-axis magnet portion 22q of the permanent magnet 22 is configured to uniformly increase the coercive force Hc not only in the portion near the outer surface 22b, which is the proximity portion to the stator 11 side, but also in its entirety. Therefore, it is easy to fabricate with a single magnetic material.

[0023] (3) As the permanent magnet 22, one integrally formed magnetic material is used in which the q-axis magnet portion 22q is located at the central portion in the circumferential direction, and the d-axis magnet portions 22dn and 22ds are located at both side portions in the circumferential direction, respectively. That is, by using one magnetic material in which the permanent magnets 22 are appropriately combined, it is expected to facilitate the attachment of the permanent magnet 22 to the rotor 12.

[0024] (Modification example) This embodiment can be implemented with the following modifications. This embodiment and the following modification examples can be implemented in combination with each other within a technically non - conflicting range.

[0025] · The above - mentioned various numerical values are examples and may be appropriately changed. · The q - axis magnet portion 22q of the permanent magnet 22 described above is configured to uniformly increase the coercive force Hc not only in the portion near the outer surface 22b, which is the surface - side portion, but also in its entirety. However, it is not limited to this.

[0026] For example, the q - axis magnet portion 22q1 shown in FIG. 5 has two portions: a surface - side portion A1 and a back - side portion A2. The surface - side portion A1 and the back - side portion A2 are made of different magnetic materials and are combined with each other. The coercive force Hc of the surface - side portion A1 is set higher than that of the back - side portion A2 and also higher than that of the d - axis magnet portions 22dn and 22ds. In other words, the back - side portion A2 has a relatively lower coercive force Hc with respect to the surface - side portion A1, but is set to, for example, a generally assumed coercive force Hc. The permanent magnet 22 of this aspect partially has a high coercive force Hc at the surface - side portion A1 of the q - axis magnet portion 22q1 that constitutes the outer surface 22b, which is the proximity portion to the stator 11 side. This is an example of effectively using a magnetic material having a high coercive force Hc.

[0027] Also, for the q-axis magnet portion 22q2 shown in FIG. 6, the coercive force Hc is set to be higher from the central portion B1 toward the peripheral portion B2 of itself. The coercive force Hc of the peripheral portion B2 is set to be higher than that of the d-axis magnet portions 22dn and 22ds. The permanent magnet 22 of this embodiment has a partially higher coercive force Hc at the peripheral portion B2 of the q-axis magnet portion 22q2 that constitutes the outer surface 22b, which is the proximity part to the stator 11 side. In the manufacturing process of the magnetic material including, for example, the addition of dysprosium (Dy), which is a heavy rare earth element that increases its own coercive force, the coercive force Hc of the peripheral portion B2 becomes more likely to be higher than that of the central portion B1. This phenomenon occurs remarkably depending on the size of the magnetic material, etc., and this is an example of a case where it is difficult to obtain a uniform coercive force Hc throughout the magnetic material.

[0028] · The shape of the permanent magnet 22 is an example and may be changed as appropriate. For example, the inclined surface 22f may not be provided on the permanent magnet 22. Also, the inner surface 22a of the permanent magnet 22 may be a circumferential surface. In this case, the shape of the outer surface 21a of the rotor base 21 is also changed accordingly.

[0029] · The scattering prevention member 23 is provided so as to cover the entire permanent magnet 22, but a mode in which a part of the permanent magnet 22 is exposed may also be acceptable. Also, the scattering prevention member 23 may be omitted. · In addition, the configuration of the rotor 12 may be changed as appropriate.

[0030] · Although the rotor 12 is applied to the inner rotor type located radially inside the stator 11, it may be applied to the outer rotor type in which the rotor 12 is located radially outside the stator 11. · Although the rotor 12 and the stator 11 are applied to the radial type in which they face each other in the radial direction, they may be applied to the axial type in which the rotor and the stator face each other in the axial direction.

[0031] (Supplementary Note) The technical idea that can be grasped from the above embodiment and modification examples will be described. (A) A rotor (12) comprising a rotor base (21) and a plurality of permanent magnets (22) arranged in the circumferential direction on the side surface (21a) of the rotor base, wherein the permanent magnets are formed of a Halbach array magnet in which d-axis magnet portions (22dn, 22ds) mainly having magnetic flux in the radial direction and q-axis magnet portions (22q, 22q1, 22q2) mainly having magnetic flux in the circumferential direction are alternately arranged in the circumferential direction, A stator (11) for generating a rotating magnetic field for rotationally driving the rotor A motor (10) comprising: In the rotor, the coercive force (Hc) of at least the surface side portion (22b) of the q-axis magnet portion of the permanent magnet is set higher than that of the d-axis magnet portion. Motor.

Explanation of reference numerals

[0032] 12 Rotor, 21 Rotor base, 21a Outer surface (side surface), 22 Permanent magnet, 22b Outer surface (surface side portion), 22dn, 22ds d-axis magnet portion, 22q, 22q1, 22q2 q-axis magnet portion, Hc Coercive force

Claims

1. A rotor base (21), A plurality of permanent magnets (22) arranged in the circumferential direction on the side surface (21a) of the rotor base, Comprising: The permanent magnet is mainly composed of a d-axis magnet portion (22dn, 22ds) in which magnetic flux is directed in the radial direction and a q-axis magnet portion (22q, 22q1, 22q2) in which magnetic flux is mainly directed in the circumferential direction, and is alternately arranged in the circumferential direction. The rotor (12) is composed of a Halbach array magnet, The coercive force (Hc) of at least the surface side portion (22b) of the q-axis magnet portion of the permanent magnet is set higher than that of the d-axis magnet portion, The q-axis magnet portion (22q1) of the permanent magnet has two portions, a surface side portion (A1) and a back side portion (A2), and the coercive force of the surface side portion is set higher than that of the back side portion, Rotor.

2. A rotor base (21), A plurality of permanent magnets (22) arranged in the circumferential direction on the side surface (21a) of the rotor base, Comprising: The permanent magnet is mainly composed of a d-axis magnet portion (22dn, 22ds) in which magnetic flux is directed in the radial direction and a q-axis magnet portion (22q, 22q1, 22q2) in which magnetic flux is mainly directed in the circumferential direction, and is alternately arranged in the circumferential direction. The rotor (12) is composed of a Halbach array magnet, The coercive force (Hc) of at least the surface side portion (22b) of the q-axis magnet portion of the permanent magnet is set higher than that of the d-axis magnet portion, The q-axis magnet portion (22q2) of the permanent magnet is configured such that the coercive force increases from the central portion (B1) to the peripheral portion (B2), Rotor.

3. The permanent magnet is integrally formed as one magnetic material in which the q-axis magnet portion is located at the circumferential center portion and the d-axis magnet portion is located at both circumferential side portions respectively, The rotor according to Claim 1 or Claim 2.

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