Rotating electric machine

Abstract

The invention provides a rotary electric machine which can easily grasp the diffusion direction of a rare earth element and realize reduction of the usage amount of the rare earth element. The rotating electric machine includes: a rotor rotatably provided to a stator and having a rotor core and a plurality of magnets disposed along a rotation direction of the rotor core; and a shaft fixed to the rotor. In a plan view viewed from the axial direction of the shaft, the magnet has a rectangular cross-section comprising a pair of long sides facing each other in the orientation direction thereof and a pair of short sides parallel to the orientation direction. The magnet contains rare earth elements, and the distribution of the rare earth elements is asymmetrical with respect to the center of the rectangular cross section. The magnet is provided with a defect part which is parallel to the orientation direction of the magnet and extends from one of the pair of long sides to the other of the pair of long sides. The defect portion is asymmetrical with respect to the center of the rectangular cross-section in a plan view viewed from the axial direction of the shaft.

Description

Technical Field

[0001] This invention relates to a rotary electric motor. Background Technology

[0002] Previously, in this technical field, for example as described in Patent Document 1, there is a known interior permanent magnet (IPM) motor having a cuboid magnet embedded in a magnet slot. In the IPM motor described in Patent Document 1, the coercivity of the magnet is improved by using rare earth elements such as neodymium as a modifier metal to diffuse across the grain boundaries from the surface of the magnet.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2018-107928 Summary of the Invention

[0004] However, due to the high cost of rare earth elements, there is a desire to reduce their usage from a cost-cutting perspective. To meet this requirement, for example, research is underway on the application of one-sided diffusion to cuboid magnets (see reference). Figure 6 Schemes to reduce the diffusion surface of rare earth elements, such as double-sided diffusion or three-sided diffusion.

[0005] If rare earth elements are allowed to diffuse, their distribution will vary along the diffusion direction from the diffusion surface. For example, in the case of unilateral diffusion, such as... Figure 6 The varying shades of color indicate that the diffused rare earth elements are distributed in a manner that is most concentrated (i.e., highest concentration) on the diffusion surface and least concentrated (i.e., lowest concentration) at locations furthest from the diffusion surface. Therefore, the distribution of rare earth elements is asymmetrical relative to the vertical or horizontal direction of the cuboid magnet. This also occurs when the diffusion surface of rare earth elements, such as in double-sided or triple-sided diffusion, is reduced.

[0006] On the other hand, the external magnetic field incident from the stator side is strongest on the stator side. Therefore, to ensure the required coercivity, the magnets need to be positioned on the rotor core with the surface of highest rare-earth element diffusion (in other words, the surface with the highest heat resistance) facing the stator side. That is, the directionality of the magnets must be ensured. However, the diffusion direction of rare-earth elements in the magnets (in other words, the distribution state of rare-earth elements) cannot be visually identified. Therefore, it is difficult to apply schemes to reduce the diffusion surface of rare-earth elements, resulting in the problem that it is impossible to reduce the amount of rare-earth elements used.

[0007] This invention was made to solve this technical problem, and its purpose is to provide a rotary motor that can easily control the diffusion direction of rare earth elements and reduce the amount of rare earth elements used.

[0008] The rotary electric motor of the present invention comprises: a stator wound with a plurality of coils; a rotor rotatably disposed on the stator and having a rotor core and a plurality of cuboid magnets arranged along the rotation direction of the rotor core; and a shaft fixed to the rotor. The characteristic feature is that, in a top view viewed from the axial direction of the shaft, the magnets have a rectangular cross-section formed by a pair of long sides opposite to each other in the orientation direction of the magnets and a pair of short sides parallel to the orientation direction of the magnets. The magnets contain rare earth elements, the distribution of which is asymmetrical with respect to the center of the rectangular cross-section. A defect is provided on the magnets, parallel to the orientation direction of the magnets and extending from one of the pair of long sides to the other. In a top view viewed from the axial direction of the shaft, the defect is asymmetrical with respect to the center of the rectangular cross-section.

[0009] In the rotary motor of the present invention, the magnet contains rare earth elements, and the distribution of these rare earth elements is asymmetrical with respect to the center of the rectangular cross-section of the magnet. That is, in the rotary motor of the present invention, a magnet that reduces the diffusion area of ​​the rare earth elements can be used. Furthermore, a defect is provided on the magnet, parallel to the magnet's orientation direction and extending from one of the two long sides constituting the rectangular cross-section to the other; in a top view viewed from the axial direction of the shaft, the defect is asymmetrical with respect to the center of the rectangular cross-section.

[0010] Therefore, the diffusion direction (in other words, the distribution state of rare earth elements) in the magnet can be easily determined based on the defect. For example, the placement of the defect can be correlated with the diffusion direction of rare earth elements, and the diffusion direction can be easily determined based on the placement of the defect. Thus, magnets that reduce the diffusion area of ​​rare earth elements can be easily applied to rotating motors, thereby reducing the amount of rare earth elements used. As a result, the cost of magnets and resource risks can be reduced. Furthermore, since the defect is set parallel to the orientation direction of the magnet and extends from one of the two long sides to the other, the influence of the defect placement on the magnetic circuit can be suppressed.

[0011] In the rotary motor of the present invention, the defect is preferably a through hole, a chamfered corner, or a groove provided on the surface of the magnet. This allows the defect to be varied as needed, thus making it easy to control the diffusion direction of rare earth elements in the magnet.

[0012] In the rotary electric motor according to the present invention, the defective portion preferably has a cross-section of the same shape and size in the orientation direction of the magnet. When the defective portion has a cross-section of different shape and size in the orientation direction of the magnet, a step is created in the orientation direction of the magnet, thereby leading to an increase in the demagnetizing field. By forming the defective portion with a cross-section of the same shape and size, this increase in the demagnetizing field can be avoided, thereby suppressing the influence on the magnetic circuit.

[0013] Invention Effects

[0014] According to the present invention, the diffusion direction of rare earth elements can be easily controlled, and the amount of rare earth elements used can be reduced. Attached Figure Description

[0015] Figure 1 This is a schematic top view showing a 1 / 8 scale model of the rotary electric motor involved in the embodiment.

[0016] Figure 2 This is a perspective view showing the magnet of the rotary electric machine according to the embodiment.

[0017] Figure 3 This is a three-dimensional diagram showing a modified example of a magnet.

[0018] Figure 4 This is a three-dimensional diagram showing a modified example of a magnet.

[0019] Figure 5 This is a schematic diagram used to illustrate the problem when the defect is not a through-hole defect.

[0020] Figure 6 This is a schematic diagram illustrating a magnet (single-sided diffusion) used to reduce the diffusion surface of rare earth elements. Detailed Implementation

[0021] Hereinafter, embodiments of the rotary electric motor according to the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are labeled with the same reference numerals, and repeated descriptions are omitted. Furthermore, in the drawings, to facilitate a clearer understanding of the invention, [details omitted]. Figure 1 and Figure 6 The color depth is used to represent the distribution of rare earth elements, but it does not represent the actual distribution.

[0022] Figure 1 This is a schematic top view showing a 1 / 8 scale model of the rotary electric machine involved in the embodiment. Figure 2 This is a perspective view showing the magnet of the rotary electric machine according to the embodiment. (Example) Figure 1As shown, the rotary motor 1 of this embodiment, for example used as a drive source for hybrid electric vehicles or electric vehicles, is an embedded magnet motor (IPM motor) formed by embedding magnets 5 inside the rotor core 30. The rotary motor 1 includes: a stator 2 on which a plurality of coils 6 are wound; a rotor 3 rotatably disposed on the stator 2; and a shaft 4 fixed to the rotor 3.

[0023] The stator 2 has a stator core 20 with a generally annular cross-section and coils 6 wound around the teeth 22 of the stator core 20. The stator core 20 has an annular yoke 21 and a plurality of teeth 22 protruding from the inner circumferential surface of the yoke 21 toward the center of the yoke 21 (i.e., the rotor 3 side). Spaces for housing the coils 6 are formed between adjacent teeth 22. Moreover, the coils 6 are wound around each tooth 22.

[0024] The stator core 20 with this structure is formed, for example, by stacking multiple electromagnetic steel plates having the shape of a yoke 21 and a tooth 22 along the axial direction of the shaft 4.

[0025] The rotor 3 has a rotor core 30 and a plurality of magnets 5 arranged along the rotation direction of the rotor core 30 (in other words, the circumferential direction of the rotor core 30). The rotor core 30 is cylindrical with a central hole. A shaft 4 is inserted into the central hole. The rotor core 30 is formed by stacking a plurality of annular electromagnetic steel plates with a central shaft hole along the axial direction of the shaft 4. The shaft hole constitutes the aforementioned central hole. The thickness of each electromagnetic steel plate is, for example, 0.5 mm or less, but is not limited thereto.

[0026] A plurality of (16 in this embodiment) magnet slots 31 are provided on the rotor core 30 along the circumference of the rotor core 30. The 16 magnet slots 31 are arranged at predetermined intervals along the circumference of the rotor core 30. For example Figure 1 As shown, adjacent magnets are arranged in a U-shape or an inverted U-shape relative to each other using slots 31.

[0027] Furthermore, the aforementioned magnet 5 is embedded in each magnet slot 31. The magnet 5 is a permanent magnet and is rectangular in shape (see reference). Figure 2 Magnet 5 is inserted into magnet slot 31 such that its length direction is parallel to the axial direction of shaft 4 and its N pole faces the stator 2, and is fixed to magnet slot 31 by resin. A thermosetting resin with excellent moldability and heat resistance is used as the resin. Examples of thermosetting resins include epoxy resins and polyimide resins.

[0028] Magnet 5 is a rare-earth magnet containing rare-earth elements. Examples of magnet materials include neodymium magnets, ferrite magnets, Sm-Co magnets, and AlNiCo magnets. The rare-earth elements contained are at least one of the following: heavy rare earth elements (Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) and light rare earth elements (La, Ce, Pr, Nd, Pm, Sm, Eu). Furthermore, the bulk magnets are primarily sintered magnets, heat-worked magnets, and bonded magnets, but are not limited to these. In this embodiment, magnet 5 is formed, for example, by diffusing the aforementioned rare-earth elements from the surface of a neodymium magnet at grain boundaries.

[0029] Furthermore, in this embodiment, any of the methods described above for reducing the diffusion surface of rare earth elements, such as single-sided diffusion, double-sided diffusion, or three-sided diffusion, can be used on the magnet 5. However, the following example is a magnet with single-sided diffusion, such as... Figure 6 The example shown illustrates the diffusion of rare earth elements from one surface (diffusion surface) of a cuboid magnet.

[0030] like Figure 1 As shown, in the top view viewed from the axial direction of axis 4, magnet 5 has a direction determined by the orientation of magnet 5 (reference). Figure 2 The rectangular cross-section 50 is formed by a pair of opposing long sides 51 and a pair of short sides 52 parallel to the orientation direction of the magnet 5 (i.e., a pair of short sides 52 extending along the orientation direction of the magnet 5). Furthermore, since the magnet 5 in this embodiment is cuboid in shape, therefore... Figure 1 As shown, when viewed from the axial direction of axis 4, the cross section of magnet 5, including the upper surface of magnet 5, is entirely rectangular cross section 50.

[0031] Additionally, the orientation of magnet 5 (refer to...) Figure 2 The arrow in the diagram indicates the magnetization direction of magnet 5, which is the orientation direction of NS.

[0032] As described above, since the magnet 5 in this embodiment is a single-sided diffused magnet, the distribution of its rare earth elements is asymmetrical with respect to the center of the rectangular cross-section 50. Specifically, as... Figure 1 The distribution of rare earth elements in magnet 5, indicated by varying shades of color, is shown in the rectangular section 50. Figure 1 The upper surface of magnet 5 is shown in the middle. The axis L1 (reference) is parallel to the orientation direction of magnet 5. Figure 2 ) is symmetrical, but relative to the central axis L2 (reference) which is orthogonal to the orientation direction of magnet 5. Figure 2The distribution of rare earth elements in the magnet 5 is asymmetrical. That is, in the rectangular section 50, the distribution of rare earth elements in the magnet 5 is symmetrical from left to right, but asymmetrical from top to bottom. In addition, the center of the rectangular section 50 is the intersection of the central axis L1 of the rectangular section 50, which is parallel to the orientation direction of the magnet 5, and the central axis L2 of the rectangular section 50, which is orthogonal to the orientation direction of the magnet 5.

[0033] Furthermore, a defect 7 is provided on the magnet 5, which is parallel to the orientation direction of the magnet 5 and extends from one of the two long sides 51 to the other. Moreover, in the top view viewed from the axial direction of the axis 4, the defect 7 is asymmetrical with respect to the center of the rectangular cross-section 50.

[0034] like Figure 1 and Figure 2 As shown, in this embodiment, the defect 7 is a chamfered corner. This chamfered corner is a so-called R-chamfer. More specifically, the chamfered corner is formed to have an inner R by chamfering. That is, the chamfered corner is formed to have a curved surface that is recessed towards the inside of the magnet 5. Furthermore, the chamfered corner extends from one of the pair of long sides 51 to the other in the orientation direction of the magnet 5, so as to penetrate the magnet 5.

[0035] Furthermore, in the top view viewed from the axial direction of axis 4, the chamfered corner is symmetrical with respect to the central axis L2 of the rectangular section 50 orthogonal to the orientation direction of magnet 5, but asymmetrical with respect to the central axis L1 of the rectangular section 50 parallel to the orientation direction of magnet 5. That is, in the rectangular section 50, the chamfered corner is symmetrical vertically, but asymmetrical horizontally.

[0036] Here, for reference Figure 5 The reason why the defective part 7 (the chamfered corner) extends from one of the opposing long sides 51 to the other in the orientation direction of the magnet 5, and that it penetrates the magnet 5 in the orientation direction of the magnet 5, will be explained.

[0037] like Figure 5 As shown, for example, the defect 7a is a chamfered corner, but if it only extends from one of the pair of long sides 51 to the middle (i.e., it does not penetrate the magnet 5 in the orientation direction of the magnet 5), a step is created between the chamfered portion (the portion removed by the chamfering process) and the remaining portion in the orientation direction of the magnet 5. Furthermore, as... Figure 5 As indicated by the dashed arrow, due to this step, the demagnetizing field increases in the remaining portion, thereby affecting the magnetic flux generated by the magnet (refer to the solid arrow). As a result, this causes a problem affecting the magnetic circuit of the rotating motor 1. To suppress the effect on the magnetic circuit, a notch 7 needs to be provided to extend from one of the opposing long sides 51 to the other (i.e., to penetrate the magnet 5 in the orientation direction of the magnet 5).

[0038] Furthermore, to further suppress the influence on this magnetic circuit, the defect 7 preferably has a cross-section of the same shape and size as the magnet 5 in the orientation direction. That is, if the defect has a cross-section of different shape and size in the orientation direction of the magnet, a step is created in that orientation direction, resulting in an increase in the aforementioned demagnetizing field. By forming the defect with a cross-section of the same shape and size, this increase in the demagnetizing field can be avoided, thereby further suppressing the influence on the magnetic circuit. Therefore, in this embodiment, the chamfered corner is formed to have a cross-section of the same shape and size as the magnet 5 in the orientation direction.

[0039] Furthermore, when the defect 7 is parallel to the orientation direction of the magnet 5 and extends from one of the opposing short sides 52 to the other, it also leads to an increase in the demagnetizing field, thereby affecting the magnetic circuit of the rotary motor 1. To avoid this problem, the defect 7 needs to be provided so that it is parallel to the orientation direction of the magnet 5.

[0040] In the rotary motor 1 of this embodiment, the magnet 5 contains rare earth elements, and the distribution of these rare earth elements is asymmetrical with respect to the center of the rectangular cross-section 50 of the magnet 5. That is, in the rotary motor 1 of this embodiment, a magnet that reduces the diffusion area of ​​the rare earth elements can be used. Furthermore, a defect 7 is provided on the magnet 5, parallel to the orientation direction of the magnet 5 and extending from one of the two long sides 51 constituting the rectangular cross-section 50 to the other. In a top view viewed from the axial direction of the axis 4, the defect 7 is asymmetrical with respect to the center of the rectangular cross-section 50. Therefore, the diffusion direction of the rare earth elements in the magnet 5 (in other words, the distribution state of the rare earth elements) can be easily determined based on the defect 7. For example, the placement position of the defect 7 can be correlated with the diffusion direction of the rare earth elements, and the diffusion direction of the rare earth elements can be easily determined based on the placement position of the defect 7.

[0041] Therefore, the magnet 5, which reduces the diffusion area of ​​rare earth elements, can be easily applied to the rotary motor 1, thus enabling a reduction in the amount of rare earth elements used. As a result, it helps to reduce the cost of the magnet 5 and reduce resource risks. Moreover, since the defect 7 is arranged parallel to the orientation direction of the magnet 5 and extends from one of the pair of long sides 51 to the other, the influence of the configuration of the defect 7 on the magnetic circuit can be suppressed.

[0042] In addition to the above, various variations can be considered regarding the defective part 7.

[0043] [Variation Example 1]

[0044] For example, in Figure 3In variant example 1 shown in (a), the defect 7 is a chamfered corner. This chamfered corner is a so-called R-chamfer. More specifically, the chamfered corner is formed to have an outer R by chamfering. That is, the chamfered corner is formed to have a curved surface that expands outward toward the magnet 5. Furthermore, the chamfered corner extends from one of the pair of long sides 51 to the other in the orientation direction of the magnet 5, penetrating the magnet 5. Moreover, in the top view viewed from the axial direction of axis 4, the chamfered corner is asymmetrical with respect to the center of the rectangular section 50.

[0045] [Variation Example 2]

[0046] Furthermore, in Figure 3 In variant example 2 shown in (b), the defect 7 is a chamfered corner, but this chamfered corner is a so-called C-chamfer. That is, the defect 7 is formed by obliquely cutting the corner of the magnet 5. This chamfered corner extends from one of the pair of long sides 51 to the other in the orientation direction of the magnet 5, penetrating the magnet 5. Moreover, in the top view viewed from the axial direction of axis 4, the chamfered corner is asymmetrical with respect to the center of the rectangular section 50.

[0047] [Variation Example 3]

[0048] Furthermore, in Figure 4 In variant example 3 shown in (a), the defect 7 is a groove provided on the surface (upper surface) of the magnet 5. In the top view viewed from the axial direction of axis 4, the groove extends from one of the pair of long sides 51 along the orientation direction of the magnet 5 to the other, penetrating the magnet 5. Moreover, in the top view viewed from the axial direction of axis 4, the groove is asymmetrical with respect to the center of the rectangular cross-section 50.

[0049] More specifically, in the top view viewed from the axial direction of axis 4, the groove is symmetrical with respect to the central axis L2 of the rectangular section 50 orthogonal to the orientation direction of the magnet 5, but asymmetrical with respect to the central axis L1 of the rectangular section 50 parallel to the orientation direction of the magnet 5. That is, in the rectangular section 50, the groove is symmetrical vertically, but asymmetrical horizontally.

[0050] Furthermore, the number of slots is not limited to one; as long as they are asymmetrical with respect to the center of the rectangular cross-section 50, there can be two or more. And, when there are two or more slots, for easier identification, these slots are preferably concentrated on one side of the central axis L1 of the rectangular cross-section 50, which is parallel to the orientation direction of the magnet 5. For example, multiple slots may be arranged only on the left or right side of the central axis L1 of the rectangular cross-section 50, which is parallel to the orientation direction.

[0051] Furthermore, the cross-sectional shape of the groove can be a polygon such as a semi-circle, trapezoid, or rectangle. In addition, the groove can be provided not only on the upper surface of the magnet 5, but also on the bottom or side surface of the magnet 5.

[0052] [Variation Example 4]

[0053] Furthermore, in Figure 4 In variant example 4 shown in (b), the defect 7 is a through hole provided inside the magnet 5. In the top view viewed from the axial direction of the axis 4, the through hole extends from one of the pair of long sides 51 to the other along the orientation direction of the magnet 5, so as to pass through the magnet 5. Moreover, when viewed from the axial direction of the axis 4, the through hole is asymmetrical with respect to the center of the rectangular section 50.

[0054] More specifically, in the top view viewed from the axial direction of axis 4, the through hole is symmetrical with respect to the central axis L2 of the rectangular section 50 orthogonal to the orientation direction of magnet 5, but asymmetrical with respect to the central axis L1 of the rectangular section 50 parallel to the orientation direction of magnet 5. That is, in the rectangular section 50, the through hole is symmetrical vertically, but asymmetrical horizontally.

[0055] Furthermore, the number of through holes is not limited to one; as long as they are asymmetrical with respect to the center of the rectangular cross-section 50, there can be two or more. And, when there are two or more through holes, for easier identification, these through holes are preferably concentrated on one side of the central axis L1 of the rectangular cross-section 50, which is parallel to the orientation direction of the magnet 5. For example, multiple through holes may be arranged only on the left or right side of the central axis L1 of the rectangular cross-section 50, which is parallel to the orientation direction. Furthermore, the cross-sectional shape of the through holes can be a circle, a semi-circle, an ellipse, a triangle, or a rectangle, etc., or a polygon.

[0056] In the above embodiments, an example of an embedded magnet type motor (IPM motor) was given, but the present invention can also be applied to a surface magnet type motor (SPM motor) in which the magnet is disposed on the surface of the rotor core.

[0057] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the above embodiments. Various design changes can be made without departing from the spirit of the present invention as described in the claims.

[0058] Symbol Explanation

[0059] 1-Rotating motor, 2-Stator, 3-Rotor, 4-Shaft, 5-Magnet, 6-Coil, 7-Damaged part, 20-Stator core, 21-Yoke, 22-Tooth, 30-Rotor core, 31-Slot for magnet, 50-Rectangular section, 51-Long side, 52-Short side.

Claims

1. A rotary electric motor comprising: a stator wound with a plurality of coils; a rotor rotatably disposed on the stator and having a rotor core and a plurality of cuboid magnets arranged along the rotation direction of the rotor core; and a shaft fixed to the rotor, characterized in that, In a top view taken from the axial direction of the axis, the magnet has a rectangular cross-section formed by a pair of long sides opposite each other in the orientation direction of the magnet and a pair of short sides parallel to the orientation direction of the magnet. The magnet contains rare earth elements, and the distribution of these rare earth elements is asymmetrical with respect to the center of the rectangular cross-section. The magnet has a defect that is parallel to its orientation direction and extends from one of its two long sides to the other. In a top view taken from the axial direction of the axis, the defect is asymmetrical with respect to the center of the rectangular cross-section.

2. The rotary motor according to claim 1, characterized in that, The defect is a through hole, a chamfered corner, or a groove on the surface of the magnet.

3. The rotary motor according to claim 2, characterized in that, The defective portion has a cross-section of the same shape and size in the orientation direction of the magnet.

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