Permanent magnet-type rotary electric machine

Abstract

The present invention both reduces weight and ensures strength in a rotor core of a permanent magnet-type rotary electric machine. This permanent magnet-type rotary electric machine has a stator and a rotor inward of the stator, wherein: the rotor has a large number of permanent magnets that are arranged so as to extend in the circumferential direction of an outer peripheral part and weight-reducing holes that are each provided to a position straddling a plurality of the permanent magnets at the inner diameter side of the permanent magnets; the weight-reducing holes have a shape which is narrow between the permanent magnets and which widens at the ends of the weight-reducing holes; the number of the weight-reducing holes is equal to the number of the permanent magnets; the permanent magnets and the weight-reducing holes are arranged so as to be shifted by half of the pitch thereof; the curvature of outer diameter-side corner parts of the weight-reducing holes is in the range of R2.28-R3.0; and the curvature of inner diameter-side corner parts thereof is in the range of R1.9-R2.5.

Description

Permanent magnet rotating electric machine

[0001] The present invention relates to a core shape of a permanent magnet rotating electric machine.

[0002] Depending on the application of industrial equipment, permanent magnet rotating electric machines may be required to have low inertia. As a countermeasure, inertia is sometimes reduced by forming lightening holes in a rotor core to reduce the weight of the rotor core.

[0003] An example of a lightening hole is disclosed in Patent Document 1.

[0004] Japanese Patent Application Laid-Open No. 2024-21924

[0005] Patent Document 1 illustrates a shape of a lightening hole for reducing inertia of a rotor core.

[0006] An object of the present invention is to study and provide a more optimal structure based on the structure of Patent Document 1.

[0007] A permanent magnet rotating electric machine comprising a stator and a rotor disposed inside the stator, wherein the rotor includes a plurality of permanent magnets arranged to extend in a circumferential direction of an outer peripheral portion, and a lightening hole provided on an inner diameter side of the permanent magnets at a position straddling a plurality of the permanent magnets, the lightening hole has a shape that is narrower between the permanent magnets and wider at end portions of the lightening hole, the number of the permanent magnets is equal to the number of the lightening holes, the permanent magnets and the lightening holes are arranged offset by a half pitch, a curvature of an outer diameter side corner portion of the lightening hole is in a range of R2.28 to R3.0, and a curvature of an inner diameter side corner portion of the lightening hole is in a range of R1.9 to R2.5.

[0008] According to the present invention, the strength of the rotor core can be ensured while maximizing the size of the lightening holes in the rotor core of the permanent magnet rotating electric machine, so both weight reduction and strength securing can be achieved.

[0009] Further configurations and effects of the present invention will become apparent throughout the following entire specification.

[0010] It is a cross-sectional structural view of a rotor of a permanent magnet rotating electric machine. It is a diagram showing a relationship between a curvature of an outer diameter side corner portion and a safety factor. It is a diagram showing a relationship between a curvature of an outer diameter side corner portion and an area of a lightening hole. It is a diagram in which FIG. 2 and FIG. 3 are superimposed and displayed.

[0011] The embodiments of the present invention will be described below, with reference to the drawings as necessary.

[0012] Figure 1 is a cross-sectional view of the rotor of a permanent magnet type rotating electric machine.

[0013] The rotor in this context is sometimes also called a rotor. It has a stator on the outside of the rotor, which generates a magnetic field using electromagnets, and the rotor rotates due to the magnetic field of the stator's electromagnets and the magnetic field of the rotor's permanent magnets.

[0014] In Patent Document 1, the rotor is referred to as the rotor and the stator as the stator. This basic structure is not only described in Patent Document 1 but is also the basic structure of permanent magnet type rotating electric machines and is therefore publicly known, so a detailed explanation will be omitted.

[0015] The metal part of the rotor is called the rotor core. Inside the rotor core 100, the metal part of the rotor has magnet housing holes 102 for holding permanent magnets 101 and weight-reducing holes 103.

[0016] Figure 1 illustrates a rotor core with 10 magnet housing holes 102, but the number is not limited.

[0017] The magnet storage holes 102 are provided on the outer circumference of the rotor core 100 at intervals from each other in the circumferential direction. As a result, the permanent magnets 101 are held on the outer circumference of the rotor core 100 at intervals from each other in the circumferential direction.

[0018] Furthermore, there are 10 weight-reducing holes 103, and they are spaced apart from each other in the circumferential direction with respect to the rotation axis Ar of the rotor core 100 of the permanent magnet 101 (extending from Ar in the figure toward the viewer in the drawing). The weight-reducing holes 103 are located on the d-axis, that is, in positions that avoid the center of the permanent magnet.

[0019] On the other hand, the weight-reducing hole 103 is located where the center line Ac, which extends radially outward from the rotation axis Ar, coincides with the q-axis of the permanent magnet 101. As a result, the weight-reducing hole 103 is positioned in a highly symmetrical location with respect to the permanent magnet 101.

[0020] This structure can also be described as having permanent magnets and weight-reducing holes positioned with a half-pitch offset.

[0021] The above structure can also be described as a rotor having a large number of permanent magnets arranged circumferentially on its outer circumference, and weight-reducing holes provided on the inner diameter side of the permanent magnets, spanning across multiple permanent magnets. Furthermore, the shape of the weight-reducing holes in Figure 1 can be described as being narrow between the permanent magnets and widening at the ends of the weight-reducing holes.

[0022] The objective of this invention is to maximize the amount of material removed from the rotor core of a permanent magnet type rotating electric machine while ensuring the strength of the rotor core.

[0023] Patent Document 1 does not explicitly disclose numerical values, particularly when the weight-reducing holes have curvature. Therefore, the following describes a technical concept for ensuring the strength of the rotor core while maximizing the weight-reducing holes in the rotor core.

[0024] The rotor core 100 of this embodiment has weight-reducing holes 103. The weight-reducing holes 103 have a weight-reducing hole corner portion 104 on the outer diameter side and a weight-reducing hole corner portion 105 on the inner diameter side.

[0025] Figure 2 shows the relationship between the curvature of the outer diameter corner and the safety factor. The safety factor is an example of an indicator that relates to the risk of rotor core failure, while taking into account a certain margin. As an example, it is desirable for the safety factor to be 1 or greater.

[0026] The triangles in Figure 2 represent the safety factor data for the curvature of the outer diameter side of the weight-reducing hole corner 104. The larger the curvature, the higher the safety factor. The unit of curvature is mm.

[0027] Reading from Figure 2, we can see that the curvature at which the safety factor is 1 occurs when the curvature is 2.28 or greater. Therefore, from the standpoint of safety, a curvature of 2.28 or greater is desirable.

[0028] Figure 3 shows the relationship between the curvature of the outer diameter corner and the area of ​​the weight-reducing holes. The weight-reducing hole area will vary depending on the rotor size, etc., so it is shown as a relative value. For the purpose of reducing the weight of the rotor core, it is desirable that the weight-reducing hole area be 0.945 or larger.

[0029] The circles in Figure 2 represent data on the area of ​​the weight-reducing hole as a function of the curvature of the outer diameter corner portion 104 of the weight-reducing hole. The result shows that the area of ​​the weight-reducing hole improves as the curvature decreases.

[0030] Reading from Figure 3, we can see that the curvature at which the area of ​​the weight-reducing holes is 0.945 or more occurs when the curvature is 3.00 or less. Therefore, from the viewpoint of the weight-reducing hole area, it is desirable for the curvature to be 3.00 or less.

[0031] Figure 4 is a superimposed view of Figures 2 and 3. From Figure 4, it can be seen that the desirable range for curvature is 2.28 to 3.00, based on the results from Figures 2 and 3.

[0032] As described above, in this embodiment, it was found that it is desirable for the curvature of the corner portion of the weight-reducing hole on the outer diameter side to be between 2.28 and 3.00.

[0033] Furthermore, the curvature of the inner diameter cutout corners can be set smaller because less force is applied to them due to centrifugal force compared to the outer side.

[0034] Therefore, we found that the desirable range for the curvature of the inner diameter side of the weight-reducing hole corner is a curvature of 1.9 to 2.5.

[0035] Therefore, overall, the desirable curvature range is 2.28 to 3.00 for the outer diameter corner and 1.9 to 2.5 for the inner diameter corner. By satisfying these conditions, it is possible to achieve both weight reduction and strength in the rotor core of a permanent magnet type rotating electric machine.

[0036] Another desirable example is one where, while satisfying the above range, the curvature of the inner diameter corner is smaller than the curvature of the outer diameter corner. This facilitates design and enables both weight reduction and strength assurance.

[0037] The difference between this embodiment and Embodiment 1 lies in the numerical values ​​of the curvature of the outer diameter corner and the curvature of the inner diameter corner. In this embodiment, the curvature of the outer diameter corner is in the range of 2.35 to 2.8, and the curvature of the inner diameter corner is in the range of 2.1 to 2.4. This embodiment allows for an even better balance between weight reduction and strength assurance in the rotor core of a permanent magnet type rotating electric machine.

[0038] The difference between this embodiment and Embodiment 2 lies in the numerical values ​​of the curvature of the outer diameter corner and the curvature of the inner diameter corner. In this embodiment, the curvature of the outer diameter corner is in the range of 2.3 to 2.7, and the curvature of the inner diameter corner is in the range of 2.0 to 2.3. This embodiment allows for an even better balance between weight reduction and strength assurance in the rotor core of a permanent magnet type rotating electric machine.

[0039] The difference between this embodiment and Embodiment 3 lies in the numerical values ​​of the curvature of the outer diameter corner and the curvature of the inner diameter corner. In this embodiment, the curvature of the outer diameter corner is in the range of 2.4 to 2.7, and the curvature of the inner diameter corner is in the range of 1.9 to 2.2. This embodiment allows for an even better balance between weight reduction and strength assurance in the rotor core of a permanent magnet type rotating electric machine.

[0040] The technical concept of this invention can also be expressed as follows:

[0041] <Part 1> A permanent magnet type rotating electric machine having a stator and a rotor inside the stator, wherein the rotor has a large number of permanent magnets arranged in the circumferential direction on its outer circumference, and weight-reducing holes provided on the inner diameter side of the permanent magnets, spanning multiple permanent magnets, the weight-reducing holes are narrow between the permanent magnets and widen at the ends of the weight-reducing holes, the number of permanent magnets and weight-reducing holes are equal, the permanent magnets and weight-reducing holes are offset by half a pitch, the curvature of the outer diameter side corner of the weight-reducing holes is in the range of R2.28 to R3.0, and the curvature of the inner diameter side corner is in the range of R1.9 to R2.5. <Part 2> The permanent magnet type rotating electric machine according to <Part 1>, wherein the curvature of the inner diameter side corner of the weight-reducing holes is smaller than the curvature of the outer diameter side corner. <Part 3> The permanent magnet type rotating electric machine according to <Part 2>, wherein the curvature of the outer diameter side corner is in the range of R2.35 to R2.8. <4> The permanent magnet type rotating electric machine according to <3>, wherein the curvature of the inner diameter side corner is in the range of R2.1 to R2.4. <5> The permanent magnet type rotating electric machine according to <2>, wherein the curvature of the outer diameter side corner is in the range of R2.3 to R2.7. <6> The permanent magnet type rotating electric machine according to <5>, wherein the curvature of the inner diameter side corner is in the range of R2.0 to R2.3. <7> The permanent magnet type rotating electric machine according to <3>, wherein the curvature of the outer diameter side corner is in the range of R2.4 to R2.7. <8> The permanent magnet type rotating electric machine according to <7>, wherein the curvature of the inner diameter side corner is in the range of R1.9 to R2.2.

[0042] 100: Outer diameter of the rotor core of a permanent magnet type rotating electric machine 101: Permanent magnet 102: Magnet housing hole 103: Lightweight hole in the rotor core 104: Corner of the weight-reducing hole on the outer diameter side 105: Corner of the weight-reducing hole on the inner diameter side

Claims

1. A permanent magnet type rotating electric machine having a stator and a rotor inside the stator, wherein the rotor has a large number of permanent magnets arranged in the circumferential direction on its outer circumference, and weight-reducing holes provided on the inner diameter side of the permanent magnets, spanning across multiple permanent magnets, the weight-reducing holes are narrow between the permanent magnets and widen at their ends, the number of permanent magnets and weight-reducing holes are equal, the permanent magnets and weight-reducing holes are offset by half a pitch, the curvature of the outer diameter side corners of the weight-reducing holes is in the range of R2.28 to R3.0, and the curvature of the inner diameter side corners is in the range of R1.9 to R2.

5.

2. The permanent magnet type rotating electric machine according to claim 1, wherein the curvature of the inner diameter side corner of the weight-reducing hole is smaller than the curvature of the outer diameter side corner.

3. The permanent magnet type rotating electric machine according to claim 2, wherein the curvature of the outer diameter side corner portion is in the range of R2.35 to R2.

8.

4. The permanent magnet type rotating electric machine according to claim 3, wherein the curvature of the inner diameter side corner portion is in the range of R2.1 to R2.

4.

5. The permanent magnet type rotating electric machine according to claim 2, wherein the curvature of the outer diameter side corner portion is in the range of R2.3 to R2.

7.

6. The permanent magnet type rotating electric machine according to claim 5, wherein the curvature of the inner diameter side corner portion is in the range of R2.0 to R2.

3.

7. The permanent magnet type rotating electric machine according to claim 3, wherein the curvature of the outer diameter side corner portion is in the range of R2.4 to R2.

7.

8. The permanent magnet type rotating electric machine according to claim 7, wherein the curvature of the inner diameter side corner portion is in the range of R1.9 to R2.2.

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