Rotor

Abstract

This technology provides an improved recyclability of rotors. [Solution] The rotor comprises a rotor core having a hole extending along the axial direction of the rotor, and a slot shape having a cross-sectional shape perpendicular to the axial direction of the hole that extends in a direction intersecting the circumferential direction of the rotor; a permanent magnet disposed in the hole of the rotor core; a spacer member disposed in the hole and adjacent to the permanent magnet from the radially outer side of the rotor; a first adhesive layer disposed between the inner surface of the hole and at least a portion of the side surface of the permanent magnet facing the inner surface, and holding the permanent magnet in the hole; and a second adhesive layer disposed between the inner surface of the hole and at least a portion of the side surface of the spacer member facing the inner surface, and holding the spacer member in the hole.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a rotor of an electric motor.

Background Art

[0002] In the rotor disclosed in Patent Document 1, a permanent magnet is arranged in a magnet insertion hole provided in a rotor core. The magnet insertion hole extends along the axial direction of the rotor. Further, the cross-sectional shape perpendicular to the axial direction of the magnet insertion hole has a slot shape extending in a direction intersecting the circumferential direction of the rotor. In the rotor, a foamed adhesive sheet is arranged between the inner surface extending in a direction intersecting the circumferential direction of the magnet insertion hole and the side surface of the permanent magnet facing the inner surface. The foamed adhesive sheet holds the permanent magnet in the magnet insertion hole.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the rotor of Patent Document 1, demagnetization of the permanent magnet is suppressed by providing a space outside the permanent magnet in the radial direction within the magnet insertion hole. However, due to the centrifugal force caused by the rotation of the rotor, there is a risk that the permanent magnet will move toward the space on the outer side in the radial direction. When the permanent magnet moves to the space on the outer side in the radial direction, the distance between the permanent magnet and the outer periphery of the rotor core becomes smaller, and demagnetization of the permanent magnet is likely to occur.

[0005] Furthermore, in this type of rotor, resin is sometimes injected into the magnet insertion holes of the rotor core, and the injected resin holds the permanent magnets within the magnet insertion holes. Because the space of the magnet insertion holes is filled with resin, the radial outward movement of the permanent magnets due to centrifugal force is suppressed, and demagnetization of the permanent magnets can be suppressed. However, in a configuration in which the permanent magnets are held within the magnet insertion holes by injecting resin, it is difficult to remove the permanent magnets from the magnet insertion holes afterward. For this reason, in such a configuration, for example, it becomes difficult to remove demagnetized permanent magnets with weakened magnetic force from the magnet insertion holes and replace them with new permanent magnets, and the rotor is discarded. This specification provides a technology that can improve the recyclability of rotors. [Means for solving the problem]

[0006] The technology disclosed herein is embodied in a rotor for an electric motor. The rotor comprises a rotor core having a hole extending along the axial direction of the rotor, the cross-sectional shape of the hole perpendicular to the axial direction having a slot shape extending in a direction intersecting the circumferential direction of the rotor; a permanent magnet disposed in the hole of the rotor core; a spacer member disposed in the hole and adjacent to the permanent magnet from the radially outer side of the rotor; a first adhesive layer disposed between the inner surface of the hole and at least a portion of the side surface of the permanent magnet facing the inner surface, and holding the permanent magnet in the hole; and a second adhesive layer disposed between the inner surface of the hole and at least a portion of the side surface of the spacer member facing the inner surface, and holding the spacer member in the hole.

[0007] The rotor described above has a cross-sectional shape that includes a spacer member adjacent to the permanent magnet from the radially outer side of the rotor within a hole extending in a direction intersecting the circumferential direction of the rotor. Therefore, even if centrifugal force is generated by the rotation of the rotor that pushes the permanent magnet radially outward, the movement of the permanent magnet is suppressed by the spacer member, and demagnetization of the permanent magnet is suppressed. Furthermore, in the rotor described above, a first adhesive layer is disposed between the inner surface of the hole and at least a portion of the side surface of the permanent magnet facing that inner surface, and the permanent magnet is held in place within the hole by the first adhesive layer. Furthermore, a second adhesive layer is disposed between the inner surface of the hole and at least a portion of the side surface of the spacer member facing that inner surface, and the spacer member is held in place within the hole by the second adhesive layer. Therefore, compared to conventional techniques in which resin is injected to hold the permanent magnet in the hole, for example, the permanent magnet can be easily removed from the hole, thereby improving the recyclability of the rotor. [Brief explanation of the drawing]

[0008] [Figure 1] This is a side view of a motor unit 10 equipped with a rotor 30 of the embodiment, showing a cross-sectional view of an electric motor 20 parallel to axis C1. [Figure 2] Figure 1 shows a cross-sectional view of the electric motor 20 along line II-II. [Modes for carrying out the invention]

[0009] In one embodiment of this technology, at least a portion of the spacer member may be made of resin.

[0010] With this configuration, for example, the mass of the rotor can be reduced compared to the case where at least a portion of the spacer member is made of ceramic. However, in another embodiment, at least a portion of the spacer member may be made of ceramic, or it may be made of another material that does not have conductivity or magnetism.

[0011] In one embodiment of this technology, at least a portion of the spacer member may be made of a high-coercivity magnet having a higher coercivity than the permanent magnet.

[0012] High-coercivity magnets are less prone to demagnetization than permanent magnets. With this configuration, the demagnetization of permanent magnets can be suppressed by using high-coercivity magnets.

[0013] In one embodiment of this technology, the second adhesive layer may be positioned between the outer surface of the spacer member located radially outward and the inner surface of the hole facing the outer surface.

[0014] The centrifugal force generated by the rotor's rotation pushes the spacer member radially outward. With this configuration, even when centrifugal force is generated on the spacer member, the outer surface of the spacer member is pressed against the inner surface of the hole opposite to the outer surface via the second adhesive layer. Therefore, compared to a configuration where, for example, the second adhesive layer is positioned between the side surface of the spacer member that intersects the rotor's circumferential direction and the inner surface of the hole opposite to that side surface, the spacer member can be held more firmly within the hole.

[0015] In one embodiment of this technology, the rotor may further include a third adhesive layer disposed between the outer surface of the permanent magnet that is located radially outward and the side surface of the spacer member that is opposite to the outer surface.

[0016] With this configuration, even if centrifugal force is generated in the permanent magnet, the outer surface of the permanent magnet is pressed against the side surface of the spacer member facing the outer surface via the third adhesive layer. As a result, the permanent magnet can be held more firmly within the hole.

[0017] (Examples) Figure 1 shows a side view of a motor unit 10 equipped with a rotor 30 of an embodiment. The motor unit 10 is mounted on, for example, an electric vehicle 2 and functions as a prime mover to drive wheels (not shown). In one example, the motor unit 10 is located in the front component (not shown) of the electric vehicle 2. The motor unit 10 comprises a casing 12 and an electric motor 20. The casing 12 houses the electric motor 20. The casing 12 is attached to the electric vehicle 2 via a pair of brackets 14L and 14R.

[0018] The electric motor 20 is electrically connected to the battery 4 of the electric vehicle 2. The electric motor 20 rotates using power supplied from the battery 4. The electric motor 20 includes a shaft 21 that outputs torque. The shaft 21 extends along axis C1 and is rotatably supported about axis C1 by the casing 12. The shaft 21 is mechanically connected to a transmission mechanism unit (not shown). The shaft 21 drives the wheels of the electric vehicle 2 via the transmission mechanism unit.

[0019] The electric motor 20 comprises a stator 22 and a rotor 30. The detailed structure of the electric motor 20 will be described with reference to Figures 1 and 2. Figure 1 shows the cross-sectional shape of the electric motor 20 parallel to axis C1. Figure 2 shows a cross-sectional view of the electric motor 20 along line II-II in Figure 1. That is, Figure 2 shows the cross-sectional shape of the electric motor 20 perpendicular to axis C1.

[0020] The stator 22 comprises a stator core 24 and stator coils 28. The stator coils 28 are attached to the stator core 24 by passing through holes 26 provided in the stator core 24. As shown in Figure 2, the stator core 24 has a cylindrical shape and faces the rotor 30 from the outside in the radial direction D1 of the rotor 30. As shown in Figure 2, the through holes 26 and stator coils 28 are arranged in the stator core 24 at predetermined intervals along the circumferential direction D2 of the rotor 30. The number of stator coils 28 arranged is changed according to the number of phases of the electric motor 20, etc.

[0021] In addition to the shaft 21 described above, the rotor 30 includes a rotor core 32, a first permanent magnet 36, a second permanent magnet 39, and a spacer member 38. The rotor core 32 is provided on the outer peripheral surface of the shaft 21 and has a cylindrical shape. The rotor core 32 is made of a ferromagnetic material. Although not particularly limited, the rotor core 32 of the present embodiment has a structure in which a plurality of electromagnetic steel sheets are laminated along the axis C1. As shown in FIG. 2, the rotor core 32 is provided with a plurality of magnet arrangement portions M1 and M2.

[0022] For example, the magnet arrangement portion M1 is a structure for fixing each of the permanent magnets 36, 39 and the spacer member 38 to the rotor core 32. As shown in FIG. 2, in the rotor 30, two magnet arrangement portions M1 are arranged symmetrically with respect to each other in the circumferential direction D2. The same applies to the magnet arrangement portion M2. In this specification, the structure of the magnet arrangement portion M1 will be mainly described. The pair of magnet arrangement portions M1 and the pair of magnet arrangement portions M2 are arranged on the rotor core 32 at a predetermined interval along the circumferential direction D2. The number of each pair of magnet arrangement portions M1 and M2 to be arranged is changed according to the number of the stator coils 28 and the like.

[0023] As shown in the enlarged view above FIG. 2, in the magnet arrangement portion M1, the first permanent magnet 36, the second permanent magnet 39, the spacer member 38, the first foam sheet L1, the second foam sheet L2, the third foam sheet L3, and the fourth foam sheet L4 are arranged in the hole 34.

[0024] As shown in FIG. 1, the hole 34 extends in the direction of the axis C1 and penetrates the rotor core 32. As shown in FIG. 2, the hole 34 is a space defined by a first inner surface S1 located at the inner end in the radial direction D1 of the hole 34, a second inner surface S2 located at the outer end in the radial direction D1 of the hole 34, a third inner surface S3 and a fourth inner surface S4 connecting the inner surfaces S1 and S2. The third inner surface S3 is located closer to the magnet arrangement portion M2 than the fourth inner surface S4. The third inner surface S3 and the fourth inner surface S4 extend substantially parallel to each other. The distance between the first inner surface S1 and the second inner surface S2 facing each other is longer than the distance between the third inner surface S3 and the fourth inner surface S4 facing each other. The hole 34 extends longer along the radial direction D1 than the circumferential direction D2. As shown in FIG. 2, the hole 34 has a shape bent with respect to the radial direction D1. In a modified example, the hole 34 may extend linearly without being bent with respect to the radial direction D1.

[0025] Inside the radial direction D1, the hole 34 extends in a direction intersecting the radial direction D1. As a result, inside the radial direction D1, the fourth inner surface S4 of the hole 34 is inclined by a first angle A1 with respect to the tangent of the circumferential direction D2. On the other hand, outside the radial direction D1, the hole 34 extends substantially parallel to the radial direction D1. As a result, outside the radial direction D1, the fourth inner surface S4 is inclined by a second angle A2 larger than the first angle A1 with respect to the tangent of the circumferential direction D2. In this embodiment, the second angle A2 is approximately 80 degrees. Thus, the cross-sectional shape of the hole 34 has a slot shape extending in a direction intersecting the circumferential direction D2 of the rotor 30. Since the cross-sectional shape of the hole 34 extends in a direction intersecting the circumferential direction D2, the first permanent magnet 36 can be arranged in the hole 34 so that the longitudinal direction of the first permanent magnet 36 intersects the circumferential direction D2. Thereby, the magnetic flux B1 generated when current flows through the stator coil 28 can be directed toward a permanent magnet (reference numeral omitted) arranged in the second magnet arrangement portion M2. Therefore, the output of the electric motor 20 can be improved. The second angle A2 is not limited to approximately 80 degrees and can be changed according to, for example, the diameter of the rotor core 32, the distance from the adjacent first magnet arrangement portion M1, etc. The second angle A2 may be, for example, 40 degrees or 45 degrees.

[0026] The first permanent magnet 36, positioned within the hole 34, comprises a first side surface W1 located inward in the radial direction D1, a second side surface W2 located outward in the radial direction D1, and third and fourth side surfaces W3 and W4 connecting the respective side surfaces W1 and W2. As shown in the enlarged view of Figure 2, the distance between the opposing first side surface W1 and second side surface W2 is longer than the distance between the opposing third side surface W3 and fourth side surface W4. The first permanent magnet 36 has a rectangular cross-sectional shape extending in the radial direction D1. Also, as shown in Figure 1, the first permanent magnet 36 extends along axis C1.

[0027] A first foam sheet L1 is placed between the third side surface W3 of the first permanent magnet 36 and the third inner surface S3 of the hole 34. The first foam sheet L1 covers a portion of the third side surface W3 of the first permanent magnet 36 and contains a foaming resin. In the manufacturing process of the rotor 30, after the first permanent magnet 36 is placed in the hole 34, the first foam sheet L1 is placed between the third side surface W3 of the first permanent magnet 36 and the third inner surface S3 of the hole 34. Subsequently, upon heating, the foaming resin of the first foam sheet L1 foams up, filling the gap between the third side surface W3 and the third inner surface S3. Further heating causes the surface of the first foam sheet L1 to melt and adhere to the third side surface W3 and the third inner surface S3. In this way, the first foam sheet L1 holds the first permanent magnet 36 in the hole 34. Similarly, the fourth foam sheet L4 also holds the second permanent magnet 39 in the hole 34.

[0028] The spacer member 38 is located between the first permanent magnet 36 and the second inner surface S2. The spacer member 38 is adjacent to the first permanent magnet 36 from the outside in the radial direction D1. The spacer member 38 comprises a fifth side surface W5 located on the inside in the radial direction D1, a sixth side surface W6 located on the outside in the radial direction D1, and seventh and eighth side surfaces W7 and W8 connecting the respective side surfaces W5 and W6. As shown in the enlarged view of Figure 2, the distance between the opposing fifth side surface W5 and sixth side surface W6 is longer than the distance between the opposing seventh side surface W7 and eighth side surface W8. The spacer member 38 has a rectangular cross-sectional shape extending in the radial direction D1. Also, as shown in Figure 1, the spacer member 38 extends along axis C1.

[0029] When current flows through the stator coil 28 of the stator 22, the rotor 30 rotates around the shaft 21 as its axis of rotation, for example in the circumferential direction D2. In this case, a centrifugal force is generated that pushes the first permanent magnet 36 and the spacer member 38 outward in the radial direction D1.

[0030] The spacer member 38 is a member for filling the space outside the radial direction D1 of the first permanent magnet 36. By placing the spacer member 38 in the above space, the first permanent magnet 36 can be positioned inside the radial direction D1. This allows the distance between the first permanent magnet 36 and the outer edge of the rotor core 32 to be increased. In other words, the second side surface W2 of the first permanent magnet 36 can be separated from the ferromagnetic material located between the second inner surface S2 and the outer surface of the rotor core 32. Furthermore, the spacer member 38 suppresses the movement of the first permanent magnet 36 outside the radial direction D1 due to centrifugal force caused by the rotation of the rotor 30. In this way, the spacer member 38 suppresses demagnetization of the first permanent magnet 36. In this embodiment, the spacer member 38 is made of resin. Therefore, the mass of the rotor 30 can be reduced compared to, for example, a configuration in which the spacer member 38 is made of ceramic. In modified examples, the spacer member 38 may be changed according to the shape of the hole 34, and may have a triangular cross-sectional shape, for example. In the case of a spacer member 38 made of resin, the shape of the spacer member 38 can be relatively easily matched to the shape of the hole 34.

[0031] A second foam sheet L2 is placed between the sixth side surface W6 of the spacer member 38 and the second inner surface S2 of the hole 34 facing the sixth side surface W6. The second foam sheet L2 has the same configuration as the first foam sheet L1 described above and holds the spacer member 38 inside the hole 34. When centrifugal force is generated on the spacer member 38, the sixth side surface W6 of the spacer member 38 is pressed against the second inner surface S2 of the hole 34 via the second foam sheet L2. As a result, the spacer member 38 can be held more firmly inside the hole 34.

[0032] Furthermore, a third foam sheet L3 is placed between the second side W2 of the first permanent magnet 36 and the fifth side W5 of the spacer member 38, which is opposite the second side W2. The third foam sheet L3 has the same configuration as the first foam sheet L1 described above. The third foam sheet L3 holds the spacer member 38 within the hole 34. When centrifugal force is generated in the first permanent magnet 36, the second side W2 of the first permanent magnet 36 is pressed against the fifth side W5 of the spacer member 38 via the third foam sheet L3. As a result, the first permanent magnet 36 can be held more firmly within the hole 34.

[0033] (Effects of this embodiment) As described above, in this embodiment, a spacer member 38 is placed in the space outside the radial direction D1 of the first permanent magnet 36, and the first permanent magnet 36 and the spacer member 38 are held in the hole 34 by the foam sheets L1 to L3. Therefore, compared to the conventional technique in which resin is injected to hold the first permanent magnet 36 in the hole 34, the first permanent magnet 36 can be easily removed from the hole 34, for example. The recyclability of the rotor 30 can be improved. In this embodiment, the first foam sheet L1, the second foam sheet L2, and the third foam sheet L3 are examples of the "first adhesive layer," "second adhesive layer," and "third adhesive layer," respectively.

[0034] The specific examples of the technology disclosed herein have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples illustrated above. Modifications of the above embodiments are listed below.

[0035] (Modification 1) The spacer member 38 may be made of a different high-coercivity magnet having a higher coercivity than the first permanent magnet 36, instead of resin. High-coercivity magnets are less prone to demagnetization than the first permanent magnet 36. With this configuration, the spacer member 38 functions as a magnet placed on the rotor core 32, similar to the first permanent magnet 36. This makes it possible to improve the torque output of the electric motor 20. The spacer member 38 is close to the outer edge of the rotor core 32 (in other words, the second inner surface S2 located at the outer end of the hole 34 in the radial direction D1), but because it is made of a high-coercivity magnet, its demagnetization is suppressed. Furthermore, the spacer member 38 made of a high-coercivity magnet can suppress demagnetization of the first permanent magnet 36, similar to the spacer member 38 made of resin or ceramic.

[0036] (Modification 2) The first foam sheet L1 may be placed between the fourth side W4 and the fourth inner surface S4 instead of / in addition to the space between the third side W3 of the first permanent magnet 36 and the third inner surface S3 of the hole 34. Similarly, the fourth foam sheet L4 may be placed between the second permanent magnet 39 and the fourth inner surface S4.

[0037] (Modification 3) The first permanent magnet 36 may be held in the hole 34 by double-sided tape instead of the foam sheets L1 and L3, and the spacer member 38 may be held in the hole 34 by double-sided tape instead of the foam sheets L2 and L3. In this embodiment, the double-sided tape is an example of the "first adhesive layer," "second adhesive layer," and "third adhesive layer."

[0038] The technical elements described herein or in the drawings demonstrate technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated herein or in the drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives constitutes technical usefulness in itself. [Explanation of symbols]

[0039] 2: Electric vehicle, 4: Battery, 10: Motor unit, 12: Casing, 14L: Bracket, 14R: Bracket, 20: Electric motor, 21: Shaft, 22: Stator, 24: Stator core, 26: Through hole, 28: Stator coil, 30: Rotor, 32: Rotor core, 34: Hole, 36: First permanent magnet, 38: Spacer member, 39: Second permanent magnet, A1: First angle, A2: Second angle, B1: Magnetic flux, C1: axis, D1: radial direction, D2: circumferential direction, L1: first foam sheet, L2: second foam sheet, L3: third foam sheet, L4: fourth foam sheet, M1: first magnet arrangement section, M2: second magnet arrangement section, S1: first inner surface, S2: second inner surface, S3: third inner surface, S4: fourth inner surface, W1: first side surface, W2: second side surface, W3: third side surface, W4: fourth side surface, W5: fifth side surface, W6: sixth side surface, W7: seventh side surface, W8: eighth side surface

Claims

1. It is the rotor of an electric motor, A rotor core having a hole extending along the axial direction of the rotor, and the cross-sectional shape of the hole perpendicular to the axial direction having a slot shape extending in a direction intersecting the circumferential direction of the rotor, A permanent magnet disposed in the hole of the rotor core, A spacer member is disposed within the aforementioned hole and is adjacent to the permanent magnet from the radially outer side of the rotor, A first adhesive layer is disposed between the inner surface of the hole and at least a portion of the side surface of the permanent magnet facing the inner surface, and holds the permanent magnet within the hole. A second adhesive layer is disposed between the inner surface of the hole and at least a portion of the side surface of the spacer member facing the inner surface, and holds the spacer member within the hole. Equipped with, Rotor.

2. The rotor according to claim 1, wherein at least a portion of the spacer member is made of resin.

3. The rotor according to claim 1, wherein at least a portion of the spacer member is made of a high-coercivity magnet having a higher coercivity than the permanent magnet.

4. The rotor according to claim 1, wherein the second adhesive layer is disposed between the outer surface of the spacer member located radially outward and the inner surface of the hole facing the outer surface.

5. The rotor according to claim 1, further comprising a third adhesive layer disposed between the outer surface of the permanent magnet that is located radially outward from the side surface and the side surface of the spacer member that is opposite to the outer surface.

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