rotor

Abstract

The rotor core is preferably reinforced. [Solution] A rotor having an inner rotor core made of a first magnetic material, and an outer rotor core covering the outer peripheral surface of the inner rotor core and made of a second magnetic material having higher rigidity than the inner rotor core and lower magnetic permeability than the inner rotor core. With the above-described configuration, the inner rotor core can be suitably reinforced by the outer rotor core.

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a rotor.

[0002] In the rotor disclosed in Patent Document 1, a covering member is provided on the outer peripheral surface of the rotor core. The covering member is made of carbon fiber reinforced plastic and is wound around the outer peripheral surface of the rotor core. The covering member reinforces the rotor core. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-052462 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology of Patent Document 1, the covering member is made of a non-magnetic material. Therefore, when this rotor is installed inside the stator, the gap (so-called air gap) between the rotor core, which is made of a magnetic material, and the stator core, which is also made of a magnetic material, becomes wider by the amount of the covering member. This results in a decrease in motor performance. This specification proposes a technology for more appropriately reinforcing the rotor core. [Means for solving the problem]

[0005] The rotor disclosed in this specification has an inner rotor core made of a first magnetic material, and an outer rotor core made of a second magnetic material that covers the outer surface of the inner rotor core and has higher rigidity than the inner rotor core and lower magnetic permeability than the inner rotor core.

[0006] In this rotor, the outer peripheral surface of the inner rotor core is covered by the outer rotor core. The outer rotor core has higher rigidity than the inner rotor core. Therefore, the outer rotor core improves the strength of the rotor core. Furthermore, the outer rotor core is made of a magnetic material with low magnetic permeability and functions as part of the rotor core. Therefore, the gap between the outer rotor core and the stator core becomes the air gap. In this way, the provision of the outer rotor core does not cause the air gap to widen. As described above, this rotor core structure can improve the strength of the rotor core while preventing the air gap from widening. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. [Figure 2] 2 is a cross-sectional view of the rotor core and the stator core of the embodiment, taken along a cross section perpendicular to the axial direction. FIG. [Figure 3] 3 is a cross-sectional view of a rotor core and a stator core of Comparative Example 1 cut along a cross section perpendicular to the axial direction. FIG. [Figure 4] FIG. 10 is a cross-sectional view of a rotor core and a stator core of Comparative Example 2 cut along a cross section perpendicular to the axial direction. [Figure 5] FIG. 10 is a perspective view of a rotor according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0008] In the rotor according to the example disclosed in the present specification, the outer rotor core may have a cylindrical shape, and the inner rotor core may be disposed within a center hole of the outer rotor core in a state in which a tension force is applied from the outer rotor core to the inner rotor core.

[0009] According to this configuration, the outer rotor core can be fixed to the inner rotor core by assembling the inner rotor core into the outer rotor core by shrink fitting, press fitting, or the like.

[0010] In one example rotor disclosed in this specification, the outer rotor core may be made of plate material or wire material wound around the outer peripheral surface of the inner rotor core in a state in which a tension force is applied from the outer rotor core to the inner rotor core.

[0011] According to this configuration, the outer rotor core can be fixed to the inner rotor core by winding a plate material or a wire material around the outer peripheral surface of the inner rotor core.

[0012] The rotor 10 of the embodiment shown in Figure 1 has a shaft 12 and a rotor core 20. The shaft 12 forms the rotating shaft of the motor. The rotor core 20 is fixed to the shaft 12. The rotor core 20 has an inner rotor core 30 and an outer rotor core 40.

[0013] The inner rotor core 30 has a cylindrical shape. The inner rotor core 30 is fixed concentrically to the shaft 12. The inner rotor core 30 is made of a magnetic material having high magnetic permeability (e.g., a soft magnetic material, a hard magnetic material, etc.). For example, the inner rotor core 30 may be made of a laminate in which a plurality of electromagnetic steel plates are stacked in the axial direction of the rotor 10.

[0014] The outer rotor core 40 has a cylindrical shape. The inner rotor core 30 is fixed within a central hole of the outer rotor core 40. The outer rotor core 40 is fixed concentrically to the inner rotor core 30. The outer rotor core 40 covers the outer peripheral surface 30a of the inner rotor core 30. The outer rotor core 40 is made of a magnetic material that has a lower magnetic permeability (H / m) than the inner rotor core 30 and a higher rigidity (N / mm) than the inner rotor core 30. Reducing the magnetic permeability of the outer rotor core 40 broadens the options for magnetic materials that make up the outer rotor core 40, so that a magnetic material with high rigidity can be used as the magnetic material that makes up the outer rotor core 40. Furthermore, the outer rotor core 40 has a higher elastic limit (N / mm) than the inner rotor core 30. 2The elastic limit refers to the limit stress value within the range where the material returns to its original shape even when the load applied to the material is removed.

[0015] As shown in FIG. 2 , the inner rotor core 30 is provided with a plurality of magnet accommodating holes 32 that accommodate magnets 60. Note that the magnets 60 and the magnet accommodating holes 32 are omitted from the perspective views such as FIG. 1 . The magnet accommodating holes 32 are provided at equal angular intervals around the shaft 12. Each magnet accommodating hole 32 extends from one end face to the other end face of the inner rotor core 30 along the axial direction. A magnet 60 is fixed in each magnet accommodating hole 32. In this embodiment, each magnet accommodating hole 32 extends radially to the outer peripheral surface 30 a of the inner rotor core 30. An opening 32 a of each magnet accommodating hole 32 in the outer peripheral surface 30 a is blocked by the outer rotor core 40.

[0016] Next, a method for fixing the outer rotor core 40 to the inner rotor core 30 will be described. Before assembly, the outer diameter of the inner rotor core 30 is larger than the inner diameter of the outer rotor core 40. The inner rotor core 30 is fixed in the center hole of the outer rotor core 40 by shrink fitting or press fitting.

[0017] In shrink fitting, the outer rotor core 40 is heated and thermally expanded so that the inner diameter of the outer rotor core 40 becomes larger than the outer diameter of the inner rotor core 30. In this state, the inner rotor core 30 is inserted into the center hole of the outer rotor core 40, and the outer rotor core 40 is cooled to room temperature. This causes the outer rotor core 40 to thermally contract, and the inner circumferential surface of the outer rotor core 40 comes into contact with the outer circumferential surface 30a of the inner rotor core 30. This fixes the inner rotor core 30 to the outer rotor core 40. In shrink fitting, the inner rotor core 30 is fixed in the center hole of the outer rotor core 40 with a tension force (i.e., pressure along the radial direction) applied from the outer rotor core 40 to the inner rotor core 30.

[0018] In press fitting, the inner rotor core 30 is inserted by pressure into the central hole of the outer rotor core 40. Therefore, the inner rotor core 30 is fixed in the central hole of the outer rotor core 40 in a state where a tension force is applied from the outer rotor core 40 to the inner rotor core 30.

[0019] As described above, in the rotor 10, the outer rotor core 40 is fixed to the inner rotor core 30 in a state in which a tension force is applied from the outer rotor core 40 to the inner rotor core 30. Therefore, the outer rotor core 40 is firmly fixed to the inner rotor core 30. Furthermore, since the outer rotor core 40 has higher rigidity than the inner rotor core 30, the inner rotor core 30 is reinforced by the outer rotor core 40. Therefore, the rotor 10 has high strength and can rotate at a higher rotation speed than conventional rotors.

[0020] FIG. 3 shows, as Comparative Example 1, a rotor in which a reinforcing member 48 made of a non-magnetic material is provided on the outer peripheral surface of the inner rotor core 30. In this case, since the reinforcing member 48 is a non-magnetic material, the gap between the magnetic materials of the rotor core 20 and the stator core 90 (i.e., the substantial air gap) is the gap t2 between the inner rotor core 30 and the stator core 90. In contrast, in the embodiment, the outer rotor core 40 that reinforces the inner rotor core 30 is made of a magnetic material, so as shown in FIG. 2, the air gap is the gap t1 between the outer rotor core 40 and the stator core 90. In this way, in the embodiment, since the outer rotor core 40, which is a reinforcing member, is made of a magnetic material, the air gap can be reduced by the thickness of the outer rotor core 40 compared to FIG. 3. This can improve the performance of the motor.

[0021] FIG. 4 shows a comparative example 2 in which the rotor core 20 is made of a single magnetic material (i.e., a magnetic material with the same magnetic permeability as the inner rotor core 30). In FIG. 3, the magnet accommodating holes 32 do not extend to the outer peripheral surface of the rotor core 20, and the rotor core 20 has bridge portions 22 on the outer peripheral side of each magnet accommodating hole 32. While this configuration provides high strength for the rotor core 20, the magnetic flux generated from the magnets 60 is short-circuited via the bridge portions 22, resulting in reduced motor performance. In contrast, in the rotor 10 of the embodiment, the portions reinforcing the rotor 10 on the outer peripheral side of each magnet accommodating hole 32 (i.e., the portions corresponding to the bridge portions 22) are made of the outer rotor core 40, which has low magnetic permeability, and therefore less magnetic flux is short-circuited via these portions. This improves motor performance.

[0022] In the above-described embodiment, the outer rotor core 40 is formed of a single cylindrical member. However, as shown in FIG. 5( a), the cylindrical outer rotor core 40 may be formed of a plurality of ring-shaped thin plates 41 stacked in the axial direction. Also, as shown in FIG. 5( b), the outer rotor core 40 may be formed of a plate material 42. In FIG. 5( b), a plate material 42 having substantially the same width as the inner rotor core 30 is wound around the outer peripheral surface of the inner rotor core 30. Also, as shown in FIG. 5( c), the outer rotor core 40 may be formed of a wire material 43. In FIG. 5( c), the wire material 43 is repeatedly wound around the outer peripheral surface of the inner rotor core 30 while changing its position in the axial direction. According to the configurations shown in FIGS. 5( a) to 5( c), the outer rotor core 40 can be fixed to the inner rotor core 30 while a tension force is applied from the outer rotor core 40 to the inner rotor core 30, thereby appropriately reinforcing the inner rotor core 30. Furthermore, with the configuration of FIG. 5(b) or FIG. 5(c), the rotor can be manufactured at lower cost than when shrink fitting or the like is used.

[0023] In another example, an outer rotor core (i.e., a member made of a magnetic material with lower magnetic permeability and higher rigidity than the inner rotor core) may be provided on the inner rotor core having the bridge portion 22. With this configuration, the inner rotor core, which has high strength, can be further reinforced by the outer rotor core. In another example, a fixing structure different from that of the above-described embodiment can be used to fix the magnets in the inner rotor core. For example, the outer rotor core may be in contact with a portion of the magnet.

[0024] Although the embodiments have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings simultaneously achieves multiple objectives, and achieving one of these objectives itself has technical utility. [Explanation of symbols]

[0025] 30: inner rotor core, 32: magnet accommodating hole, 40: outer rotor core, 60: magnet

Claims

1. an inner rotor core made of a first magnetic material; an outer rotor core covering an outer peripheral surface of the inner rotor core and made of a second magnetic material having higher rigidity than the inner rotor core and lower magnetic permeability than the inner rotor core; A rotor having

2. the outer rotor core has a cylindrical shape, the inner rotor core is disposed in a center hole of the outer rotor core in a state where a tension force is applied from the outer rotor core to the inner rotor core, The rotor of claim 1.

3. 2. The rotor according to claim 1, wherein the outer rotor core is formed of a plate material or a wire material wound around the outer peripheral surface of the inner rotor core in a state where a tension force is applied from the outer rotor core to the inner rotor core.

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