Rotor

Abstract

The invention relates to a rotor. A rotor of an electric motor includes: a rotor core having a hole extending in an axial direction of the rotor; a permanent magnet disposed in the hole; a spacer member disposed in the hole and adjacent to the permanent magnet on an outer side of the permanent magnet in a radial direction of the rotor; a first adhesive layer configured to hold the permanent magnet in the hole and disposed between an inner surface of the hole and at least a portion of a side surface of the permanent magnet facing the inner surface; and a second adhesive layer configured to hold the spacer member in the hole and disposed between the inner surface and at least a portion of a side surface of the spacer member facing the inner surface. A cross-section of the hole perpendicular to the axial direction has a slot shape extending in a direction intersecting a circumferential direction of the rotor.

Description

Technical Field

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

[0002] In the rotor disclosed in Japanese Unexamined Patent Application Publication No. 2021-100353 (JP 2021-100353 A), permanent magnets are arranged in magnet insertion holes provided in the rotor core. Each magnet insertion hole extends along the axial direction of the rotor. The cross-section of the magnet insertion hole perpendicular to the axial direction has a slot shape extending in a direction intersecting the circumferential direction of the rotor. In the rotor, a foam adhesive sheet is provided between an inner surface extending in a direction intersecting the circumferential direction of the magnet insertion hole and a side surface of the permanent magnet facing the inner surface. The foam adhesive sheet holds the permanent magnet in the magnet insertion hole.

[0003] In the rotor described in JP 2021-100353 A, demagnetization of the permanent magnet is suppressed by providing space in the magnet insertion hole on the radially outer side of the permanent magnet. However, a problem exists: the permanent magnet can move towards the radially outer space due to the centrifugal force caused by the rotation of the rotor. When the permanent magnet moves into the radially outer space, the distance between the permanent magnet and the outer periphery of the rotor core decreases, and demagnetization of the permanent magnet is more likely to occur.

[0004] In this type of rotor, resin is injected into the magnet insertion hole in the rotor core, and the permanent magnet is held in the magnet insertion hole by the injected resin. The space in the magnet insertion hole is filled with resin. Therefore, it is possible to suppress the radial outward movement of the permanent magnet caused by centrifugal force and to suppress the demagnetization of the permanent magnet. However, in the configuration where the permanent magnet is held in the magnet insertion hole by injecting resin, it is difficult to remove the permanent magnet from the magnet insertion hole later. Therefore, in such a configuration, it becomes difficult to remove the permanent magnet, whose magnetic force has been weakened due to demagnetization, from the magnet insertion hole and replace it with a new permanent magnet, and, for example, the rotor is discarded. This disclosure provides a technique that can improve the recyclability of the rotor. Summary of the Invention

[0005] One aspect of this disclosure is a rotor for an electric motor. The rotor includes a rotor core, a permanent magnet, a spacer member, a first adhesive layer, and a second adhesive layer. The rotor core has a hole extending along the axial direction of the rotor. The cross-section of the hole perpendicular to the axial direction has a slot shape extending in a direction intersecting the circumferential direction of the rotor. The permanent magnet is disposed in the hole of the rotor core. The spacer member is disposed in the hole and is adjacent to the permanent magnet on its outer side in the radial direction of the rotor. The first adhesive layer is configured to retain the permanent magnet in the hole. The first adhesive layer is disposed between an inner surface of the hole and at least a portion of a side surface of the permanent magnet facing the inner surface. The second adhesive layer is configured to retain the spacer member in the hole. The second adhesive layer is disposed between an inner surface of the hole and at least a portion of a side surface of the spacer member facing the inner surface.

[0006] The rotor includes a spacer member. The spacer member is adjacent to the permanent magnet on the outside of the permanent magnet in the radial direction of the rotor, within a hole having a cross-sectional shape extending in a direction intersecting the circumferential direction of the rotor. Therefore, even when centrifugal force is generated by the rotation of the rotor, pushing the permanent magnet radially outward, the movement of the permanent magnet is restricted by the spacer member, and demagnetization of the permanent magnet is suppressed. In 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 the permanent magnet is held in the hole by the first adhesive layer. 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 the spacer member is held in the hole by the second adhesive layer. Therefore, compared to techniques that hold the permanent magnet in the hole by injecting resin, it becomes easier, for example, to remove the permanent magnet from the hole, and thus the recyclability of the rotor can be improved. Attached Figure Description

[0007] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, wherein like symbols denote like elements, and wherein:

[0008] Figure 1 A side view of a motor unit 10 including a rotor 30 of one embodiment is shown, which is a cross-sectional view of an electric motor 20 parallel to axis C1; and

[0009] Figure 2 It shows along Figure 1 The cross-sectional view of electric motor 20 taken from line II-II in the figure. Detailed Implementation

[0010] At least a portion of the spacer member may be made of resin.

[0011] Using the construction described above, the rotor mass can be reduced compared to, for example, when at least a portion of the spacer member is made of ceramic. However, in another embodiment, at least a portion of the spacer member can be constructed of ceramic, or at least a portion of the spacer member can be constructed of another material that is neither conductive nor magnetic.

[0012] At least a portion of the spacer may be made of a high coercivity magnet having a higher coercivity than a permanent magnet.

[0013] In highly coercive magnets, demagnetization is less likely to occur compared to permanent magnets. Using the configuration described above, highly coercive magnets can suppress the demagnetization of permanent magnets.

[0014] The second adhesive layer may be disposed between an outer surface located radially outward on one of the multiple side surfaces of the spacer member and an inner surface of a hole facing that outer surface.

[0015] The centrifugal force generated by the rotor's rotation pushes the spacer member radially outward. With the configuration described above, 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 facing that outer surface via a second adhesive layer. Therefore, for example, compared to a configuration where the second adhesive layer is disposed between the side surface of the spacer member intersecting the rotor's circumferential direction and the inner surface of the hole facing that side surface, the spacer member can be securely held in the hole.

[0016] The rotor may also include a third adhesive layer disposed between an outer surface of the permanent magnet located radially outward and a side surface of a spacer member facing that outer surface.

[0017] Using the structure described above, even when centrifugal force is generated on the permanent magnet, the outer surface of the permanent magnet is pressed against the outer-facing side surface of the spacer member via a third adhesive layer. Therefore, the permanent magnet can be held in the hole more securely.

[0018] Implementation Plan

[0019] Figure 1 A side view of a motor unit 10 including a rotor 30 in one embodiment is shown. The motor unit 10 is mounted on, for example, an electric vehicle 2 and serves as a prime mover for driving wheels (not shown). As an example, the motor unit 10 is disposed in a front component (not shown) of the electric vehicle 2. The motor unit 10 includes a housing 12 and an electric motor 20. The housing 12 houses the electric motor 20. The housing 12 is attached to the electric vehicle 2 via a pair of brackets 14L, 14R.

[0020] An electric motor 20 is electrically connected to a battery 4 of an electric vehicle 2. The electric motor 20 rotates using electricity supplied from the battery 4. The electric motor 20 includes a shaft 21 that outputs torque. The shaft 21 extends along an axis C1 and is supported by a housing 12 so that it can rotate about the axis C1. 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.

[0021] The electric motor 20 includes a stator 22 and a rotor 30. (See reference...) Figure 1 and Figure 2 Describe the detailed structure of the electric motor 20. Figure 1 The cross-sectional shape of the electric motor 20 parallel to the axis C1 is shown. Figure 2 It is along Figure 1 The cross-sectional view of electric motor 20 taken from line II-II in the diagram. In other words, Figure 2 The cross-sectional shape of the electric motor 20 perpendicular to axis C1 is shown.

[0022] The stator 22 includes a stator core 24 and a stator coil 28. The stator coil 28 is attached to the stator core 24 by passing through a through-hole 26 provided in the stator core 24. Figure 2 As shown, the stator core 24 has a cylindrical shape and faces the rotor 30 from the outer side of the rotor 30 in the radial direction D1. Figure 2 As shown, through holes 26 and stator coils 28 are arranged at predetermined intervals in the stator core 24 along the circumferential direction D2 of the rotor 30. The number of stator coils 28 provided varies depending on the number of phases of the electric motor 20.

[0023] In addition to the aforementioned shaft 21, the rotor 30 also 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 disposed on the outer peripheral surface of the shaft 21 and has a cylindrical shape. The rotor core 32 is constructed of a ferromagnetic material. Although not particularly limited, the rotor core 32 of this embodiment has a structure in which multiple electromagnetic steel plates are stacked along axis C1. Figure 2 As shown, multiple magnet arrangement sections M1 and M2 are provided in the rotor core 32.

[0024] For example, each magnet arrangement M1 is a structure for fixing each of the permanent magnets 36, 39 and the spacer member 38 in the rotor core 32. Figure 2 As shown, in the rotor 30, two magnet arrangement portions M1 are configured symmetrically to each other in the circumferential direction D2. The same applies to the magnet arrangement portions M2. This specification primarily describes the structure of the magnet arrangement portions M1. A pair of magnet arrangement portions M1 and a pair of magnet arrangement portions M2 are arranged in the rotor core 32 at predetermined intervals along the circumferential direction D2. The number of pairs of magnet arrangement portions M1 and M2 varies depending on the number of stator coils 28, etc.

[0025] like Figure 2 As shown in the enlarged view on the upper side, in the magnet arrangement part M1, the first permanent magnet 36, the second permanent magnet 39, the spacer member 38, the first foaming sheet L1, the second foaming sheet L2, the third foaming sheet L3 and the fourth foaming sheet L4 are arranged in the hole 34.

[0026] like Figure 1 As shown, hole 34 extends in the direction of axis C1 and passes through rotor core 32. Figure 2 As shown, the hole 34 is a space defined by a first inner surface S1 located at the inner end of the hole 34 in the radial direction D1, a second inner surface S2 located at the outer end of the hole 34 in the radial direction D1, and a third inner surface S3 and a fourth inner surface S4 connecting each of the inner surfaces S1 and S2 to each other. The third inner surface S3 is positioned closer to the magnet arrangement 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, which face each other, is longer than the distance between the third inner surface S3 and the fourth inner surface S4, which face each other. The hole 34 extends longer along the radial direction D1 than along the circumferential direction D2. Figure 2 As shown, the hole 34 has a shape that is curved relative to the radial direction D1. In a variation, the hole 34 can extend linearly without being curved relative to the radial direction D1.

[0027] On the inner side of the radial direction D1, the hole 34 extends in a direction intersecting the radial direction D1. Therefore, on the inner side of the radial direction D1, the fourth inner surface S4 of the hole 34 is inclined at a first angle A1 relative to the tangent in the circumferential direction D2. Simultaneously, the hole 34 extends substantially parallel to the radial direction D1 on the outer side of the radial direction D1. Therefore, on the outer side of the radial direction D1, the fourth inner surface S4 is inclined at a second angle A2 greater than the first angle A1 relative to the tangent in the circumferential direction D2. In this embodiment, the second angle A2 is approximately 80 degrees. As described above, the cross-section 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 disposed in the hole 34 such that the longitudinal direction of the first permanent magnet 36 intersects the circumferential direction D2. Therefore, the magnetic flux B1 generated when current flows through the stator coil 28 can be directed to the permanent magnet (reference numerals omitted) disposed in the second magnet arrangement M2. This increases the output of the electric motor 20. The second angle A2 is not limited to approximately 80 degrees, and varies, for example, depending on the diameter of the rotor core 32 or its distance from the adjacent first magnet arrangement M1. For example, the second angle A2 can be 40 degrees or 45 degrees.

[0028] The first permanent magnet 36 disposed in the hole 34 includes a first side surface W1 positioned on the inner side in the radial direction D1, a second side surface W2 positioned on the outer side in the radial direction D1, and a third side surface W3 and a fourth side surface W4 connecting the side surfaces W1 and W2 to each other. Figure 2 As shown in the enlarged view, the distance between the first side surface W1 and the second side surface W2, which face each other, is longer than the distance between the third side surface W3 and the fourth side surface W4, which also face each other. The first permanent magnet 36 has a rectangular cross-section extending in the radial direction D1. Figure 1 As shown, the first permanent magnet 36 extends along the axis C1.

[0029] A first foamed sheet L1 is disposed between the third side surface W3 of the first permanent magnet 36 and the third inner surface S3 of the hole 34. The first foamed sheet L1 covers a portion of the third side surface W3 of the first permanent magnet 36 and contains a foamable resin. During the manufacture of the rotor 30, the first permanent magnet 36 is disposed in the hole 34, and then the first foamed sheet L1 is disposed between the third side surface W3 of the first permanent magnet 36 and the third inner surface S3 of the hole 34. Then, the foamable resin of the first foamed sheet L1 is formed by heating and fills the gap between the third side surface W3 and the third inner surface S3. By heating, the front surface of the first foamed sheet L1 melts and adheres to the third side surface W3 and the third inner surface S3. As described above, the first foamed sheet L1 holds the first permanent magnet 36 in the hole 34. Similarly, a fourth foamed sheet L4 also holds the second permanent magnet 39 in the hole 34.

[0030] Spacer 38 is positioned between the first permanent magnet 36 and the second inner surface S2. Spacer 38 is adjacent to the first permanent magnet 36 on its outer side in the radial direction D1. Spacer 38 includes a fifth side surface W5 positioned on its inner side in the radial direction D1, a sixth side surface W6 positioned on its outer side in the radial direction D1, and a seventh side surface W7 and an eighth side surface W8 connecting side surfaces W5 and W6 to each other. Figure 2 As shown in the enlarged view, the distance between the fifth side surface W5 and the sixth side surface W6, which face each other, is longer than the distance between the seventh side surface W7 and the eighth side surface W8, which face each other. The spacer member 38 has a rectangular cross-section extending in the radial direction D1. (As shown in the enlarged view...) Figure 1 As shown, the spacer member 38 extends along axis C1.

[0031] Here, when current flows through the stator coil 28 of the stator 22, the rotor 30 rotates, for example, about the shaft 21 which serves as the axis of rotation, 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.

[0032] The spacer member 38 is a member used to fill the space on the outer side of the first permanent magnet 36 in the radial direction D1. By providing the spacer member 38 in this space, the first permanent magnet 36 can be positioned on the inner side in the radial direction D1. Therefore, the distance between the first permanent magnet 36 and the outer peripheral edge of the rotor core 32 can be increased. In other words, the second side surface W2 of the first permanent magnet 36 can be spaced apart from the ferromagnetic material of the rotor core 32 positioned between the second inner surface S2 and the outer peripheral surface of the rotor core 32. The spacer member 38 restricts the first permanent magnet 36 from moving outward in the radial direction D1 by the centrifugal force caused by the rotation of the rotor 30. As described above, 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 a construction in which, for example, the spacer member 38 is made of ceramic. In a variation, the spacer member 38 can be varied according to the shape of the hole 34 and can have, for example, a triangular cross-section. When the spacer member 38 is made of resin, the shape of the spacer member 38 can be matched with the shape of the hole 34 in a relatively easy manner.

[0033] The second foam sheet L2 is disposed 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 a similar structure to the first foam sheet L1 and holds the spacer member 38 in 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. Therefore, the spacer member 38 can be held in the hole 34 in a more secure manner.

[0034] A third foam sheet L3 is disposed between the second side surface W2 of the first permanent magnet 36 and the fifth side surface W5 of the spacer member 38 facing the second side surface W2. The third foam sheet L3 has a similar structure to the first foam sheet L1. The third foam sheet L3 holds the spacer member 38 in the hole 34. When centrifugal force is generated on the first permanent magnet 36, the second side surface W2 of the first permanent magnet 36 is pressed against the fifth side surface W5 of the spacer member 38 via the third foam sheet L3. Therefore, the first permanent magnet 36 can be held in the hole 34 in a more secure manner.

[0035] The effect of the implementation plan

[0036] As described above, in this embodiment, the spacer member 38 is disposed in the space on the outer side of the first permanent magnet 36 in the radial direction D1, and the first permanent magnet 36 and the spacer member 38 are held in the hole 34 by each of the foam sheets L1 to L3. Therefore, for example, compared to a technique of holding the first permanent magnet 36 in the hole 34 by injecting resin, the first permanent magnet 36 can be easily removed from the hole 34. This can improve the recyclability of the rotor 30. In this embodiment, the first foam sheet L1, the second foam sheet L2, and the third foam sheet L3 are examples of a "first adhesive layer," a "second adhesive layer," and a "third adhesive layer," respectively.

[0037] Although specific examples of this disclosure have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology disclosed in the claims includes various variations and modifications of the specific examples shown above. Variations of the embodiments are listed below.

[0038] First variant

[0039] The spacer member 38 can be constructed from another high-coercivity magnet, having a higher coercivity than the first permanent magnet 36, instead of resin. In this high-coercivity magnet, demagnetization is less likely to occur compared to the first permanent magnet 36. Using the construction described above, the spacer member 38 serves as a magnet disposed in the rotor core 32, just like the first permanent magnet 36. Therefore, the torque output from the electric motor 20 can be improved. Although the spacer member 38 is located near the outer peripheral edge of the rotor core 32 (in other words, the second inner surface S2 is located in the end of the hole 34 on the outer side in the radial direction D1), demagnetization of the spacer member 38 is suppressed because it is constructed from a high-coercivity magnet. Like the spacer member 38 constructed from resin or ceramic, the spacer member 38 constructed from a high-coercivity magnet can suppress demagnetization of the first permanent magnet 36.

[0040] Second variant

[0041] As an alternative to the first foamed sheet L1 being disposed between the third side surface W3 of the first permanent magnet 36 and the third inner surface S3 of the hole 34, the first foamed sheet L1 can also be disposed between the fourth side surface W4 and the fourth inner surface S4, in addition to the first foamed sheet L1 being disposed between the third side surface W3 of the first permanent magnet 36 and the third inner surface S3 of the hole 34. Similarly, the fourth foamed sheet L4 can also be disposed between the second permanent magnet 39 and the fourth inner surface S4.

[0042] Third variant

[0043] The first permanent magnet 36 can be held in the hole 34 by double-sided tape instead of foam sheets L1 and L3, and the spacer member 38 can be held in the hole 34 by double-sided tape instead of foam sheets L2 and L3. In this embodiment, the double-sided tape is an example of a "first adhesive layer", a "second adhesive layer" and a "third adhesive layer".

[0044] Each technical element described in this specification or drawings demonstrates its technical utility independently or in various combinations, and is not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and are technically useful only by achieving one of those objectives.

Claims

1. A rotor for an electric motor, the rotor being characterized by comprising: A rotor core having a hole extending along the axial direction of the rotor, the hole having a cross section perpendicular to the axial direction, the cross section having a slot shape extending in a direction intersecting the circumferential direction of the rotor; A permanent magnet, wherein the permanent magnet is disposed in the hole of the rotor core; A spacer member is disposed in the hole and is adjacent to the permanent magnet on the outer side of the permanent magnet in the radial direction of the rotor; A first adhesive layer, configured to retain the permanent magnet in the hole, is disposed between an inner surface of the hole and at least a portion of a side surface of the permanent magnet facing the inner surface. and A second adhesive layer, configured to retain the spacer member in the hole, is disposed between an inner surface of the hole and at least a portion of a side surface of the spacer member facing the inner surface.

2. The rotor according to claim 1, characterized in that, At least a portion of the spacer member is made of resin.

3. The rotor according to claim 1, characterized in that, At least a portion of the spacer is composed of a high coercivity magnet, which has a higher coercivity than the permanent magnet.

4. The rotor according to claim 1, characterized in that, The second adhesive layer is disposed on the side surface of the spacer member between the outer surface positioned on the outer side in the radial direction and the inner surface of the hole facing the outer surface.

5. The rotor according to claim 1, characterized in that... It also includes a third adhesive layer disposed on the side surface of the permanent magnet between an outer surface positioned on the outer side in the radial direction and a side surface of the spacer member facing that outer surface.

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