Rotating electric machine

Abstract

To provide a rotating electric machine that can alleviate stress concentration while maintaining good torque characteristics. [Solution] This invention is applied to a rotating electric machine comprising a stator having windings and a rotor having permanent magnets and a rotor core, which is rotatably arranged on the stator. The rotor core has multiple magnetic poles formed in the circumferential direction, each composed of multiple permanent magnets. The magnetic poles include a first permanent magnet positioned perpendicular to the d-axis, which is the center of the magnetic pole, and having a shape symmetrical with respect to the d-axis; a second permanent magnet positioned perpendicular to the d-axis on the outer diameter side of the first permanent magnet and having a shape symmetrical with respect to the d-axis; and a third permanent magnet and a fourth permanent magnet positioned on both sides of the circumferential direction relative to the first permanent magnet, inclined with respect to the d-axis and q-axis, such that they approach the q-axis, which is magnetically perpendicular to the d-axis, as they move toward the outer diameter side.

Description

Technical Field

[0001] The present invention relates to a rotating electrical machine.

Background Art

[0002] Patent Document 1 discloses a rotor of a rotating electrical machine including a permanent magnet having a two-layer structure composed of an inner magnet and an outer magnet symmetrically arranged with respect to the d-axis.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

[0004] In the rotor described in Patent Document 1, since the inner magnet and the outer magnet are composed of a plurality of magnets, the torque characteristics can be improved. On the other hand, depending on the shape of the magnet holes and the arrangement of the permanent magnets, stress may concentrate on the outer peripheral portion of the rotor due to centrifugal force during rotation, and the durability of the rotor may deteriorate.

[0005] The present invention has been made in view of such problems, and an object thereof is to provide a rotating electrical machine capable of relaxing stress concentration during rotation while maintaining good torque characteristics.

[0006] According to one aspect of the present invention, a rotating electric machine is provided, comprising a stator having windings, and a rotor having permanent magnets and a rotor core, and rotatably disposed on the stator. The rotor core has multiple magnetic poles formed circumferentially, each composed of multiple permanent magnets. The magnetic poles include a first permanent magnet arranged perpendicular to the d-axis, which is the center of the magnetic pole, and having a shape symmetrical with respect to the d-axis; a second permanent magnet arranged perpendicular to the d-axis on the outer diameter side of the first permanent magnet and having a shape symmetrical with respect to the d-axis; and a third permanent magnet and a fourth permanent magnet arranged on both sides of the circumferential direction relative to the first permanent magnet, inclined with respect to the d-axis and q-axis, such that they approach the q-axis, which is magnetically perpendicular to the d-axis, as they move toward the outer diameter side.

[0007] According to the present invention, the magnetic pole has a two-layer structure consisting of a first layer made up of a second permanent magnet and a second layer made up of a first permanent magnet, a third permanent magnet, and a fourth permanent magnet, with these three permanent magnets arranged in a U-shape in a radial cross-sectional view. This improves the torque of the rotating electric machine. Furthermore, since the first layer, which is close to the outer surface of the rotor, is made up of a single second permanent magnet arranged perpendicular to the d-axis, the concentration of stress due to the centrifugal force of rotation at a single point is suppressed. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view of a rotating electric machine according to an embodiment of the present invention. [Figure 2] Figure 2 is a cross-sectional view of the main part of a rotating electric machine. [Figure 3] Figure 3 is a cross-sectional view of the main part of a rotating electric machine. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings and other documents.

[0010] Figure 1 is a cross-sectional view perpendicular to the axial direction of the rotating electric machine 100 according to an embodiment of the present invention. Figure 2 is a cross-sectional view showing one-quarter of the entire configuration of the rotating electric machine 100. Figure 3 is a cross-sectional view showing one of the magnetic poles 35.

[0011] As shown in Figure 1, the rotating electric machine 100 of this embodiment is configured to include an annular stator 1, a rotor 2 that is concentric with the stator 1 and rotatably arranged with an air gap between it and the stator 1, and a rotating shaft 15 that passes through the center of the rotor 2.

[0012] The rotating electric machine 100 is mounted on an electric vehicle and functions as an electric motor that drives the wheels. It may also be used in devices other than automobiles, such as drive systems for various electrical equipment or industrial machinery.

[0013] The stator 1 comprises an annular stator core 11 and stator windings 10. The stator core 11 is a laminate formed by stacking electrical steel sheets. The stator core 11 has a plurality of teeth 8 that protrude toward the inner circumference and a plurality of slots 9 which are spaces between adjacent teeth 8. The stator windings 10 are arranged in the slots 9.

[0014] The rotor 2 consists of a rotor core 12 and a plurality of permanent magnets 30 mounted on the rotor core 12. A rotating shaft 15 is fixed to the center of the rotor core 12. The rotor core 12 is constructed by laminating electromagnetic steel sheets.

[0015] The rotor core 12 has magnetic poles 35, each composed of multiple permanent magnets 30, arranged at equal intervals in the circumferential direction. In this embodiment, for example, one magnetic pole 35 is composed of four permanent magnets 30, and eight magnetic poles 35 are arranged in the circumferential direction on the rotor core 12.

[0016] Each magnetic pole 35 has a d-axis, which is its magnetic center, at its center, and is adjacent to another magnetic pole 35 with the q-axis, which is magnetically perpendicular to the d-axis, as the boundary. Four magnet holes 40 are formed in the rotor core 12 for each magnetic pole 35, and permanent magnets 30 (first permanent magnet 31 to fourth permanent magnet 34) are fitted into these magnet holes 40 (first magnet hole 41 to fourth magnet hole 44). Each permanent magnet 30 is rectangular in shape.

[0017] Thus, when multiple permanent magnets 30 constitute a single magnetic pole 35, the durability of the rotor core 12 becomes an issue. Specifically, in the rotor core 12, there are areas where the spacing between the permanent magnets 30 and the spacing between the permanent magnets 30 and the outer circumference of the rotor core 12 becomes narrow (shown as A, B, and C in Figure 3; hereafter referred to as "bridge areas"). In particular, when the rotor 2 rotates, outward stress due to centrifugal force is generated in the permanent magnets 30, and if this stress concentrates in such bridge areas, the durability of the rotor 2 may deteriorate.

[0018] Therefore, the rotating electric machine 100 of this embodiment is configured to alleviate stress concentration by the following configuration.

[0019] As shown in Figure 2, the first permanent magnet 31 is positioned such that its longitudinal center lies on the d-axis and is perpendicular to the d-axis. Furthermore, the first permanent magnet 31 is positioned symmetrically with respect to the d-axis.

[0020] The second permanent magnet 32, like the first permanent magnet 31, is positioned so that its longitudinal center lies on the d-axis and is perpendicular to the d-axis. The second permanent magnet 32 ​​is also positioned symmetrically with respect to the d-axis. The second permanent magnet 32 ​​is located on the outer diameter side of the first permanent magnet 31 and is positioned near the outer edge of the rotor 2 (rotor core 12).

[0021] The third permanent magnet 33 is a permanent magnet 30 positioned to the left of the first permanent magnet 31 (towards the rotor's forward rotation direction), and is positioned so that its longitudinal direction is radial. More specifically, the third permanent magnet 33 is positioned at an inclination so that it approaches the q-axis as it approaches the outer diameter, and is positioned so that the angle between the longitudinal direction of the third permanent magnet 33 and the q-axis is less than 90 degrees (an acute angle, e.g., 15 degrees). The inner diameter end of the third permanent magnet 33 is located closer to the d-axis, and the outer diameter end of the third permanent magnet 33 is located closer to the q-axis.

[0022] The fourth permanent magnet 34 is a permanent magnet 30 arranged on the right side (opposite to the rotor reverse rotation direction) with respect to the first permanent magnet 31, and is arranged such that its longitudinal direction is oriented in the radial direction. More specifically, the fourth permanent magnet 34 is arranged to be inclined so as to approach the q-axis as it goes toward the outer diameter side, and is arranged such that the angle formed by the longitudinal direction of the fourth permanent magnet 34 and the q-axis is less than 90 degrees (an acute angle, for example, 15 degrees). The inner diameter side end of the fourth permanent magnet 34 is located closer to the d-axis, and the outer diameter side end of the fourth permanent magnet 34 is located closer to the q-axis.

[0023] The longitudinal direction of each magnet hole 40 is formed to be larger than the length of the longitudinal direction of the permanent magnet 30 inserted into the magnet hole 40. This portion becomes a hole in the rotor core 12 and functions as a flux barrier for the permanent magnet 30.

[0024] The magnetic pole 35 is constituted by a two-layer structure having a first layer (first magnet group) arranged at a position closer to the outer diameter and a second layer (second magnet group) arranged at a position closer to the inner diameter than the first layer. The first layer is constituted by one second permanent magnet 32 and is a layer extending linearly in the circumferential direction. The second layer is constituted by the first permanent magnet 31, the third permanent magnet ३३, and the fourth permanent magnet 34, and is a layer in which these magnets are arranged in a U shape. Thus, by constituting one magnetic pole 35 with four magnets, the magnetic force can be increased.

[0025] As described above, since the magnetic pole 35 of the rotor 2 is constituted by a first layer consisting of one magnet and a second layer consisting of three magnets, the magnet torque can be improved. Further, since the second permanent magnet 32 which is the first layer is arranged on the outer diameter side of the second layer, the salient pole ratio of the magnetic pole 35 can be improved and the reluctance torque can be increased. In the second layer, by the configuration in which three permanent magnets 30 are arranged in a U shape, the magnetic flux centered on the q-axis can also be improved. In this way, the torque of the rotating electrical machine 100 can be increased more than before. <用

[0026] The shape and arrangement of these permanent magnets 30 are set appropriately according to the specifications such as torque required for the rotating electric machine 100, but the following configuration is preferable.

[0027] As shown in Figure 3, a first layer consisting of a second permanent magnet 32 ​​is placed on the outer diameter side of the second layer. The second permanent magnet 32 ​​of this first layer is configured such that the length T2 of the short side in the d-axis direction is smaller than the length T1 of the short side in the d-axis direction of the first permanent magnet 31.

[0028] In this way, by constructing the second permanent magnet 32 ​​of the first layer with a single permanent magnet and making the length of its shorter side smaller than that of the first permanent magnet 31 of the second layer, the mass in the first layer is reduced, and the centrifugal force acting on the first layer when the rotor 2 rotates is reduced.

[0029] Furthermore, by making the length T2 of the short side of the second permanent magnet 32 ​​smaller than the length T1 of the short side of the first permanent magnet 31, the distance Wb between the second permanent magnet 32 ​​and the first permanent magnet 31, that is, the distance between the inner diameter side of the second permanent magnet 32 ​​and the outer diameter side of the first permanent magnet 31, can be increased.

[0030] In this way, by increasing the distance Wb between the second permanent magnet 32 ​​and the first permanent magnet 31 at the magnetic pole 35, the distance between the second permanent magnet 32 ​​and the first permanent magnet 31 can be increased. This makes it possible to alleviate magnetic saturation between the second permanent magnet 32 ​​and the first permanent magnet 31.

[0031] Furthermore, the second layer of the magnetic pole 35 is composed of a first permanent magnet 31, a third permanent magnet 33, and a fourth permanent magnet 34. Therefore, compared to the case where the second layer is composed of, for example, two permanent magnets, the number of bridge sections C increases, and the stress applied to the bridge sections C can be distributed during two rotations of the rotor.

[0032] Furthermore, the distance Wb between the first permanent magnet 31 and the second permanent magnet 32 ​​is set to be greater than the distance Wt between the outer surface of the second permanent magnet 32 ​​and the outer surface of the rotor core 12. This allows the salient pole ratio to be improved by the action of the second permanent magnet 32 ​​at the magnetic pole 35.

[0033] Furthermore, as shown in Figure 3, let Wa1 be the distance between the second permanent magnet 32 ​​and the third permanent magnet 33, and Wa2 be the distance between the second permanent magnet 32 ​​and the fourth permanent magnet 34. Then, let W2 be the distance between adjacent magnetic poles 35, that is, the distance between the third permanent magnet 33 of one magnetic pole 35 and the fourth permanent magnet 34 of the adjacent magnetic pole 35, or the distance between the fourth permanent magnet 34 of one magnetic pole 35 and the third permanent magnet 33 of the adjacent magnetic pole 35.

[0034] The system was configured such that distance W2 is greater than the smallest of these distances Wa1, Wa2, and distance Wb.

[0035] With this configuration, the distance between adjacent magnetic poles 35 can be made sufficiently large, so that the magnetic saturation between the third permanent magnet 33 and the fourth permanent magnet 34 in adjacent magnetic poles 35 can be made smaller than the magnetic saturation between adjacent permanent magnets 30 within one magnetic pole 35, and the salient pole ratio in each magnetic pole 35 can be improved.

[0036] Furthermore, the third permanent magnet 33 and the fourth permanent magnet 34 in the second layer have the same cross-sectional area when viewed in the axial direction, while the cross-sectional area of ​​the second permanent magnet 32 ​​when viewed in the axial direction is made smaller than the cross-sectional areas of the third permanent magnet 33 and the fourth permanent magnet 34 when viewed in the axial direction.

[0037] This configuration reduces the mass of the second permanent magnet 32 ​​in the first layer. Furthermore, the reduced size of the second permanent magnet 32 ​​increases the distance Wa1 between the second permanent magnet 32 ​​and the third permanent magnet 33, and the distance Wa2 between the second permanent magnet 32 ​​and the fourth permanent magnet 34, thereby reducing magnetic saturation between these points.

[0038] Furthermore, as shown in Figure 3, the second permanent magnet 32 ​​has flux barriers 45, which are voids, at both ends in its circumferential direction. These flux barriers 45 are formed to be located on the inner diameter side of the outer edge 32a of the second permanent magnet 32.

[0039] With this configuration, in the bridge section A where stress due to centrifugal force is concentrated on the outer diameter side of the second permanent magnet 32, the flux barrier 45 does not protrude on the outer diameter side of the second permanent magnet 32.

[0040] Furthermore, in the case of the second permanent magnet 32, the thinner the wall thickness (Wt) of the rotor core 12 on its outer diameter side, the closer the second permanent magnet 32 ​​gets to the outer circumference of the rotor core 12, thus improving the magnet torque, but reducing the rigidity accordingly. For this reason, it is desirable to set an appropriate wall thickness considering the torque required for the rotating electric machine 100 and the stress applied to the bridge portion A of the second permanent magnet 32.

[0041] As described above, this embodiment is a rotating electric machine 100 comprising a stator 1 having a stator winding 10, and a rotor 2 having permanent magnets 30 and a rotor core 12 and rotatably arranged on the stator 1. The rotor core 12 has multiple magnetic poles 35 formed in the circumferential direction, each composed of multiple permanent magnets 30. The magnetic poles 35 include a first permanent magnet 31 arranged perpendicular to the d-axis, which is the center of the magnetic poles 35, and having a shape symmetrical with respect to the d-axis; a second permanent magnet 32 ​​arranged perpendicular to the d-axis on the outer diameter side of the first permanent magnet 31 and having a shape symmetrical with respect to the d-axis; and a third permanent magnet 33 and a fourth permanent magnet 34 arranged on both sides in the circumferential direction relative to the first permanent magnet 31, inclined with respect to the d-axis and q-axis so that they approach the q-axis, which is magnetically perpendicular to the d-axis, as they move toward the outer diameter side.

[0042] In this configuration, the first layer, composed of the second permanent magnet 32, and the second layer, arranged in a U-shape by the first permanent magnet 31, the third permanent magnet 33, and the fourth permanent magnet 34, form a two-layer structure in the radial direction, thereby improving the torque of the rotating electric machine 100. Furthermore, since the first layer is composed of a single second permanent magnet 32 ​​perpendicular to the d-axis, the concentration of stress due to the centrifugal force of rotation at a single point is suppressed.

[0043] Furthermore, in this embodiment, the third permanent magnet 33 and the fourth permanent magnet 34 are arranged at an acute angle with respect to the q-axis. This suppresses the circumferential enlargement of the magnetic poles 35 even when the permanent magnet 30 is configured in a U-shape in the second layer, thereby improving the torque of the rotating electric machine 100 without increasing the diameter of the rotor core 12.

[0044] Furthermore, in this embodiment, the first permanent magnet 31 and the second permanent magnet 32 ​​have a rectangular shape with their longer sides perpendicular to the d-axis, and the distance between the first permanent magnet 31 and the second permanent magnet 32 ​​is greater than the distance between the second permanent magnet 32 ​​and the outer circumferential surface of the rotor core 12.

[0045] In this way, by bringing the second permanent magnet 32 ​​closer to the outer circumference of the rotor core 12, the salient pole ratio can be improved, and the reluctance torque can be further increased.

[0046] Furthermore, in this embodiment, the length T1 of the shorter side in the d-axis direction of the first permanent magnet 31 is greater than the length T2 of the shorter side in the d-axis direction of the second permanent magnet 32.

[0047] In this configuration, by increasing the distance Wb between the second permanent magnet 32 ​​and the first permanent magnet 31 at the magnetic pole 35, magnetic saturation between them can be alleviated.

[0048] Furthermore, in this embodiment, for adjacent magnetic poles 35, the distance between the third permanent magnet 33 of one magnetic pole 35 and the fourth permanent magnet 34 of the other magnetic pole 35 is greater than the smallest of the distances between the first permanent magnet 31 and the second permanent magnet 32, the distance between the second permanent magnet 32 ​​and the third permanent magnet 33, and the distance between the second permanent magnet 32 ​​and the fourth permanent magnet 34.

[0049] In this configuration, the distance between adjacent magnetic poles 35 becomes sufficiently large, which reduces magnetic saturation between adjacent magnetic poles 35 and improves the salient pole ratio of the magnetic poles 35, thereby increasing the reluctance torque.

[0050] Furthermore, in this embodiment, the third permanent magnet 33 and the fourth permanent magnet 34 have the same cross-sectional area when viewed in the axial direction, and the cross-sectional area of ​​the second permanent magnet 32 ​​when viewed in the axial direction is smaller than the cross-sectional areas of the third permanent magnet 33 and the fourth permanent magnet 34 when viewed in the axial direction.

[0051] In this configuration, the mass of the second permanent magnet 32 ​​can be reduced, thereby reducing the stress applied to the bridge portion A of the rotor core 12. Furthermore, the distance Wb between the second permanent magnet 32 ​​and the first permanent magnet 31 can be increased, which further mitigates magnetic saturation between them.

[0052] Furthermore, in this embodiment, the rotor core 12 has voids that serve as flux barriers 45 at both ends in the circumferential direction of the second permanent magnet 32, and the flux barriers 45 are formed to be located on the inner diameter side of the outer edge 32a of the second permanent magnet 32.

[0053] In this configuration, since the flux barrier 45 does not protrude to the outer diameter side of the second permanent magnet 32, no localized constriction is formed between it and the outer circumference shape of the rotor core 12, and stress applied to the bridge portion A can be suppressed.

[0054] Although embodiments of the present invention have been described above, these embodiments only represent a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments. [Explanation of Symbols]

[0055] 1: Stator, 2: Rotor, 10: Stator winding, 11: Stator core, 12: Rotor core, 15: Rotating shaft, 30: Permanent magnet, 31: First permanent magnet, 32: Second permanent magnet, 33: Third permanent magnet, 34: Fourth permanent magnet, 35: Magnetic pole, 40: Magnet hole, 45: Flux barrier, 100: Rotating electric machine

Claims

1. A rotating electric machine comprising a stator having windings, and a rotor having permanent magnets and a rotor core, which is rotatably disposed on the stator, The rotor core is configured with multiple permanent magnets, and multiple magnetic poles are formed in the circumferential direction. The aforementioned magnetic poles are A first permanent magnet is positioned perpendicular to the d-axis, which is the center of the magnetic pole, and has a shape symmetrical with respect to the d-axis, A second permanent magnet is positioned on the outer diameter side of the first permanent magnet and perpendicular to the d-axis, and has a shape symmetrical with respect to the d-axis, The device comprises a third permanent magnet and a fourth permanent magnet, which are arranged on both sides in the circumferential direction with respect to the first permanent magnet, and are inclined with respect to the d-axis and the q-axis such that they approach the q-axis, which is magnetically perpendicular to the d-axis, as they move toward the outer diameter side. Rotating electric machine.

2. A rotating electric machine according to claim 1, The third permanent magnet and the fourth permanent magnet are arranged at an acute angle with respect to the q-axis. Rotating electric machine.

3. A rotating electric machine according to claim 1, The first permanent magnet and the second permanent magnet have a rectangular shape with their longer sides perpendicular to the d-axis. The distance between the first permanent magnet and the second permanent magnet is greater than the distance between the second permanent magnet and the outer surface of the rotor core. Rotating electric machine.

4. A rotating electric machine according to claim 3, The length of the shorter side in the d-axis direction of the first permanent magnet is greater than the length of the shorter side in the d-axis direction of the second permanent magnet. Rotating electric machine.

5. A rotating electric machine according to claim 1, In adjacent magnetic poles, the distance between the third permanent magnet of one magnetic pole and the fourth permanent magnet of the other magnetic pole is greater than the smallest of the distances between the first permanent magnet and the second permanent magnet, the distance between the second permanent magnet and the third permanent magnet, and the distance between the second permanent magnet and the fourth permanent magnet. Rotating electric machine.

6. A rotating electric machine according to claim 1, The third permanent magnet and the fourth permanent magnet have the same cross-sectional area when viewed in the axial direction. The axial cross-sectional area of ​​the second permanent magnet is smaller than the axial cross-sectional areas of the third and fourth permanent magnets. Rotating electric machine.

7. A rotating electric machine according to claim 1, The rotor core has voids that serve as flux barriers at both ends in the circumferential direction of the second permanent magnet. The aforementioned void is formed to be located on the inner diameter side of the outer edge of the second permanent magnet. Rotating electric machine.

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