Rotor and electric motor

Abstract

Disclosed is a rotor comprising: a rotor core; a permanent magnet inserted into an insertion hole formed in the rotor core; and a fixing part. The insertion hole has a quadrangular shape when viewed from the axial direction of the rotor core. The permanent magnet includes: a positioning part that contacts an inner surface of the insertion hole to position the permanent magnet with respect to the insertion hole; and four edges that are positioned at four corners of the insertion hole. A chamfered section is formed on at least one edge of the four edges of the permanent magnet. The fixing part is provided in a gap between the chamfered section(s) and the inner surface of the insertion hole.

Description

Rotor and motor

[0001] The present disclosure relates to a rotor and an electric motor.

[0002] Japanese Patent Laid-Open Publication No. 11-98735 discloses a rotor including a rotor core, a permanent magnet inserted into an insertion hole of the rotor core, and an adhesive provided in the gap between the inner surface of the insertion hole and the permanent magnet to fix the permanent magnet to the rotor core.

[0003] A better rotor and motor is needed.

[0004] A first aspect of the present disclosure is a rotor comprising a rotor core having a plurality of electromagnetic steel plates stacked on top of each other, permanent magnets inserted into insertion holes formed in the rotor core, and fixing portions for fixing the rotor core and the permanent magnets, wherein the insertion holes have a rectangular shape when viewed from the axial direction of the rotor core, the permanent magnets have positioning portions that contact the inner surface of the insertion holes to position the permanent magnets relative to the insertion holes, and four corner portions located at the four corners of the insertion holes, at least one of the four corner portions of the permanent magnets has a chamfered portion formed thereon, and the fixing portions are provided in the gaps between each of the chamfered portions and the inner surface of the insertion holes.

[0005] A second aspect of the present disclosure provides an electric motor including the rotor of the first aspect and a stator.

[0006] Fig. 1 is a schematic diagram of an electric motor. Fig. 2 is an enlarged view of a rotor with a portion thereof omitted. Fig. 3 is an explanatory diagram of a permanent magnet according to a first modified example. Fig. 4 is an explanatory diagram of a permanent magnet according to a second modified example.

[0007] In the rotor described above, the gap where the adhesive or other fastening portion is provided (the gap between the inner surface of the insertion hole and the permanent magnet) is formed, for example, in a ring shape surrounding the permanent magnet. In this case, the larger the gap where the fastening portion is provided (the thicker the fastening portion), the greater the peel strength of the fastening portion and the smaller the shear strength of the fastening portion. Therefore, to reliably fix the permanent magnet to the rotor core, the gap (thickness of the fastening portion) needs to be of an appropriate size.

[0008] Furthermore, the larger the gap, the easier it is for the permanent magnet to move within the insertion hole, making it more difficult to accurately position the permanent magnet relative to the insertion hole. If the gap is made smaller to make it easier to position the permanent magnet relative to the insertion hole, the thickness of the fixed portion may become smaller than necessary, and the peel strength of the fixed portion may become excessively small.

[0009] The present disclosure can provide a rotor and an electric motor that can accurately position a permanent magnet with respect to an insertion hole and prevent the peel strength of the fixed portion from becoming excessively small.

[0010] Fig. 1 is a schematic diagram of an electric motor 10. As shown in Fig. 1, the electric motor 10 is an interior permanent magnet motor (IPM motor). The electric motor 10 includes a stator 12 and a rotor 14. The stator 12 is formed in an annular shape. A detailed description of the configuration of the stator 12 will be omitted.

[0011] The rotor 14 has a rotor core 16 and a shaft 18. The rotor core 16 is formed by laminating a plurality of electromagnetic steel plates 20. The rotor core 16 is formed in an annular (ring-shaped) shape. The shaft 18 is fixed to the rotor core 16 in a state where it is inserted into a hole 22 in the center of the rotor core 16.

[0012] A plurality of insertion holes (slots) 24 are formed in the rotor core 16. The plurality of insertion holes 24 are located at the radially outer end (outer periphery) of the rotor core 16. The plurality of insertion holes 24 are arranged at equal intervals in the circumferential direction of the rotor core 16. The plurality of insertion holes 24 are arranged along the outer periphery of the rotor core 16. Each insertion hole 24 penetrates the rotor core 16 (the plurality of electromagnetic steel plates 20) in the axial direction of the rotor 14.

[0013] Fig. 2 is a partially omitted enlarged view of the rotor 14. As shown in Fig. 2, the insertion holes 24 are formed in a quadrangular shape when viewed in the axial direction of the rotor 14. The insertion holes 24 are formed in a rectangular shape when viewed in the axial direction of the rotor 14. In other words, the insertion holes 24 extend in the circumferential direction of the rotor core 16 when viewed in the axial direction of the rotor 14.

[0014] The inner surface 26 of the insertion hole 24 includes two first flat surfaces 26a and two second flat surfaces 26b. The two first flat surfaces 26a are arranged to face each other. When viewed in the axial direction of the rotor 14, the two first flat surfaces 26a form the long sides of the rectangle of the insertion hole 24. The two second flat surfaces 26b are arranged to face each other. When viewed in the axial direction of the rotor 14, the two second flat surfaces 26b form the short sides of the rectangle of the insertion hole 24. When viewed in the axial direction of the rotor 14, the portion connecting the adjacent first flat surfaces 26a and second flat surfaces 26b is curved in an arc shape.

[0015] The size, shape, arrangement, etc. of the insertion holes 24 can be set as appropriate. The insertion holes 24 do not have to pass through the rotor core 16 in the axial direction of the rotor 14. The insertion holes 24 may be formed in a square shape when viewed in the axial direction of the rotor 14. The insertion holes 24 do not have to extend along the circumferential direction of the rotor core 16 when viewed in the axial direction of the rotor 14.

[0016] A permanent magnet 28 is inserted into each insertion hole 24. The permanent magnets 28 are arranged so that their north and south poles are aligned in the radial direction of the rotor core 16. The permanent magnets 28 extend in the axial direction of the rotor 14. The permanent magnets 28 have positioning portions 30 and four corners 32. The positioning portions 30 contact the inner surfaces 26 of the insertion holes 24 to position the permanent magnets 28 relative to the insertion holes 24. The positioning portions 30 include two first positioning flat surfaces 30a and two second positioning flat surfaces 30b.

[0017] The first positioning plane 30a and the first plane 26a face each other. The first positioning plane 30a is in contact with or close to the first plane 26a. In other words, no gap is formed between the first positioning plane 30a and the first plane 26a for providing an adhesive or the like to fix the permanent magnet 28 to the rotor core 16. The second positioning plane 30b and the second plane 26b face each other. The second positioning plane 30b is in contact with or close to the second plane 26b. No gap is formed between the second positioning plane 30b and the second plane 26b for providing an adhesive or the like to fix the permanent magnet 28 to the rotor core 16. This allows the permanent magnet 28 to be positioned in the insertion hole 24 with high precision.

[0018] At least two of the four corners 32 of the permanent magnet 28, which are located diagonally opposite each other, are formed with chamfered portions 34. In this embodiment, each of the four corners 32 of the permanent magnet 28 is formed with a chamfered portion 34. The chamfered portions 34 have flat surfaces. The four corners 32 (chamfered portions 34) of the permanent magnet 28 are located at the four corners of the insertion hole 24. Gaps 36 are formed between the chamfered portions 34 and the inner surface 26 of the insertion hole 24. In this embodiment, four gaps 36 are formed for one permanent magnet 28.

[0019] A fixing portion 38 is provided in each gap 36. The fixing portion 38 fixes the rotor core 16 and the permanent magnet 28. The fixing portion 38 is a chemical fixing portion and has adhesiveness. The fixing portion 38 is formed, for example, from an adhesive. The adhesive is made, for example, from a thermosetting resin. Examples of thermosetting resins include epoxy resin, acrylic resin, phenolic resin, and silicone resin. The adhesive is not limited to the above and can be selected appropriately. The fixing portion 38 is formed, for example, by hardening the adhesive filled in the gap 36. The fixing portion 38 may also be formed from an impregnating material.

[0020] In this embodiment, the adhesive strength of the adhesive portion 38 is S (MPa), and the contact area of ​​the four adhesive portions 38 is A (mm ２ ), and the maximum force acting on the permanent magnet 28 when the rotor core 16 rotates is F (N). In this case, the rotor 14 is formed to satisfy the condition S×A>F. Here, the adhesive force S of the fixing portion 38 is determined in advance by the characteristics of the material (adhesive, etc.) used for the fixing portion 38. The contact area A is the sum of the area where the fixing portion 38 contacts the permanent magnet 28 (chamfered portion 34) and the area where the fixing portion 38 contacts the inner surface 26 of the insertion hole 24. In other words, the contact area A varies depending on the size of the gap 36 (the size of the chamfered portion 34). The maximum force F acting on the permanent magnet 28 when the rotor core 16 rotates is determined, for example, by the specifications (output, rotation speed, etc.) of the electric motor 10.

[0021] If the rotor 14 satisfies the condition S×A>F, peeling of the fixed portions 38 and separation of the permanent magnets 28 from the insertion holes 24 during rotation of the rotor core 16 can be effectively prevented. In this embodiment, the contact area A is set as small as possible within a range that satisfies the condition S×A>F. That is, the size of the chamfered portions 34 is set so that the condition S×A>F is satisfied and the contact area A is minimized. In this case, the size of the chamfered portions 34 can be made as small as possible. That is, the chamfered portions 34 can prevent the first positioning planes (pole faces) 30a of the permanent magnets 28 from becoming excessively small, allowing the rotor 14 to rotate efficiently.

[0022] According to this embodiment, the permanent magnet 28 has a positioning portion 30 that contacts the inner surface 26 of the insertion hole 24 and positions it relative to the insertion hole 24. This prevents the permanent magnet 28 from moving within the insertion hole 24, allowing the permanent magnet 28 to be accurately positioned relative to the insertion hole 24. Furthermore, a chamfered portion 34 is formed on at least one of the four corners 32 of the permanent magnet 28, and the fixing portions 38 are provided in the gaps 36 between each chamfered portion 34 and the inner surface 26 of the insertion hole 24. This prevents the peel strength of the fixing portions 38 from becoming excessively small. This provides a rotor 14 and an electric motor 10 that can accurately position the permanent magnet 28 relative to the insertion hole 24 and prevent the peel strength of the fixing portions 38 from becoming excessively small. This provides a better rotor 14 and an electric motor 10.

[0023] In the rotor 14, a chamfered portion 34 is formed on each of the four corners 32 of the permanent magnet 28. With this simple configuration, the contact area A of the fixing portion 38 (the total area of ​​the fixing portion 38 in contact with the permanent magnet 28 and the fixing portion 38 in contact with the inner surface 26 of the insertion hole 24) can be increased. This allows the permanent magnet 28 to be fixed to the rotor core 16 more effectively.

[0024] Each chamfered portion 34 is a flat surface. With this configuration, the chamfered portions 34 can be easily machined, and the manufacturing cost of the permanent magnet 28 can be reduced.

[0025] The positioning portion 30 includes four positioning planes (first positioning plane 30a and second positioning plane 30b) that face four planes (first plane 26a and second plane 26b) of the inner surface 26 of the insertion hole 24. With this configuration, the permanent magnet 28 can be positioned with respect to the insertion hole 24 with even greater precision.

[0026] The rotor 14 satisfies the condition S×A>F. With this configuration, the permanent magnets 28 can be effectively prevented from coming off the insertion holes 24 when the rotor core 16 rotates.

[0027] This embodiment is not limited to the above-described configuration. FIG. 3 is an explanatory diagram of a permanent magnet 28a according to a first modified example. As shown in FIG. 3, the rotor 14 may include a permanent magnet 28a according to the first modified example instead of the permanent magnet 28. The permanent magnet 28a has a chamfered portion 34 formed only at one of its four corners 32. In this case, the rotor 14 is formed so as to satisfy the condition S×A>F. The size of the chamfered portion 34 is set so as to satisfy the condition S×A>F and minimize the contact area A. Using such a permanent magnet 28a achieves the same effects as using the permanent magnet 28 described above. Furthermore, since the processing of the chamfered portion 34 can be simplified, the manufacturing cost of the permanent magnet 28a can be reduced. Note that FIG. 3 illustrates an example in which the chamfered portion 34 is formed only at one of the four corners 32 of the permanent magnet 28a, which is located radially outward from the rotor core 16. In a first modified example, the chamfered portion 34 may be formed only at one corner 32 of the four corners 32 of the permanent magnet 28 a that is located radially inward of the rotor core 16 .

[0028] FIG. 4 is an explanatory diagram of a permanent magnet 28b according to a second modification. As shown in FIG. 4, the rotor 14 may include a permanent magnet 28b according to the second modification instead of the permanent magnet 28. The permanent magnet 28b has chamfered portions 34 formed only at two diagonally opposite corners 32 of its four corners 32. In this case, the rotor 14 is also formed to satisfy the condition S×A>F. The size of the chamfered portions 34 is set to satisfy the condition S×A>F and minimize the contact area A. Using such a permanent magnet 28b achieves the same effects as using the permanent magnet 28 described above. Furthermore, because the chamfered portions 34 can be more easily machined, the permanent magnet 28b can be manufactured more inexpensively. Furthermore, compared to the permanent magnet 28a according to the first modification, the permanent magnet 28b can be more stably fixed to the rotor core 16, and the contact area A can be easily adjusted.

[0029] The following additional notes are further disclosed regarding the above embodiment.

[0030] (Supplementary Note 1) The present disclosure provides a rotor (14) comprising a rotor core (16) having a plurality of electromagnetic steel plates (20) stacked on top of each other, permanent magnets (28, 28a, 28b) inserted into insertion holes (24) formed in the rotor core, and fixing portions (38) for fixing the rotor core and the permanent magnets, the insertion holes having a rectangular shape when viewed from the axial direction of the rotor core, the permanent magnets having positioning portions (30) that contact an inner surface (26) of the insertion holes to position the permanent magnets relative to the insertion holes, and four corners (32) located at four corners of the insertion holes, at least one of the four corners of the permanent magnets has a chamfered portion (34), and the fixing portions are provided in gaps (36) between each of the chamfered portions and the inner surface of the insertion holes.

[0031] (Supplementary Note 2) In the rotor according to Supplementary Note 1, the chamfered portions may be formed on at least two corners located diagonally out of the four corners of the permanent magnet.

[0032] (Supplementary Note 3) In the rotor according to Supplementary Note 2, the chamfered portions may be formed at each of the four corners of the permanent magnet.

[0033] (Supplementary Note 4) In the rotor according to any one of Supplementary Notes 1 to 3, each of the chamfered portions may be a flat surface.

[0034] (Supplementary Note 5) In the rotor according to any one of Supplementary Notes 1 to 4, the positioning portion may include four positioning flat surfaces (30a, 30b) facing four flat surfaces of the inner surface of the insertion hole.

[0035] (Supplementary Note 6) In the rotor according to any one of Supplementary Notes 1 to 5, the adhesive force of the adhesive portion is S (MPa), and the total contact area of ​​the adhesive portion in contact with the permanent magnet and the contact area with the inner surface of the insertion hole is A (mm ２ ) and the maximum force acting on the permanent magnet during rotation of the rotor core is F (N), the condition S×A>F may be satisfied.

[0036] (Supplementary Note 7) The present disclosure provides an electric motor (10) including the rotor according to any one of Supplementary Notes 1 to 6 and a stator (12).

[0037] Although the present disclosure has been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible in these embodiments without departing from the gist of the present disclosure or the spirit of the present disclosure derived from the content of the claims and their equivalents. These embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical expressions are used in the description of the above-described embodiments.

[0038] REFERENCE SIGNS LIST 10... Electric motor 12... Stator 14... Rotor 16... Rotor core 20... Electromagnetic steel plate 24... Insertion hole 26... Inner surface of insertion hole 26a... First plane 26b... Second plane 28, 28a, 28b... Permanent magnet 30... Positioning portion 30a... First positioning plane 30b... Second positioning plane 32... Corner portion 34... Chamfered portion 36... Gap 38... Fixing portion

Claims

1. A rotor comprising: a rotor core having a plurality of electromagnetic steel plates stacked on top of each other; permanent magnets inserted into insertion holes formed in the rotor core; and fixing portions for fixing the rotor core and the permanent magnets, wherein the insertion holes have a rectangular shape when viewed in the axial direction of the rotor core, and the permanent magnets have positioning portions that contact the inner surface of the insertion holes to position the permanent magnets relative to the insertion holes, and four corners located at the four corners of the insertion holes, wherein at least one of the four corners of the permanent magnets has a chamfered portion, and the fixing portions are provided in the gaps between each of the chamfered portions and the inner surface of the insertion holes.

2. A rotor according to claim 1, wherein the chamfered portions are formed on at least two corners located diagonally out of the four corners of the permanent magnet.

3. A rotor according to claim 2, wherein the chamfered portion is formed at each of the four corners of the permanent magnet.

4. A rotor according to any one of claims 1 to 3, wherein each of said chamfered portions is a flat surface.

5. A rotor according to any one of claims 1 to 4, wherein the positioning portion includes four positioning flat surfaces facing four flat surfaces of the inner surface of the insertion hole.

6. A rotor according to any one of claims 1 to 5, wherein the adhesive force of the adhesive portion is S (MPa), and the total contact area of ​​the adhesive portion in contact with the permanent magnet and the contact area with the inner surface of the insertion hole is A (mm ２ ) and the maximum force acting on the permanent magnet during rotation of the rotor core is F (N), a rotor that satisfies the condition S×A>F.

7. An electric motor comprising: a rotor according to any one of claims 1 to 6; and a stator.

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