Rotating Electric Machine

Abstract

To provide a rotary electric machine which can suppress deformation of a bridge part due to centrifugal force, and suppress lowering of magnetic flux density due to increase of leakage fluxes without increasing thickness of the bridge part.SOLUTION: A rotor core 21 comprises: first flux barriers 25A formed adjacent to ends on an outer peripheral side of a pair of permanent magnets 23A, 23B, respectively; second flux barriers 25B formed adjacent to ends of an inner peripheral side of the pair of permanent magnets 23A, 23B; outer bridge parts 32 which extends in a circumferential direction along an outer peripheral surface of the rotor core 21 on an outer peripheral side of the first flux barriers 25A; a center bridge part 31 which extends in a radial direction in the second flux barriers 25B to couple the outer peripheral side with the inner peripheral side of the rotor core 21; and a bridging part 33 which passes through the inside of the first flux barriers 25A to couple the outer bridge parts 32 with the inner peripheral part of the rotor core 21.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a rotating electric machine. [Background technology]

[0002] In a conventional rotating electric machine, a rotor core having a pair of magnet holes for arranging a pair of magnets in a V-shape has an outer bridge portion on the outer periphery of the pair of magnet holes and a band-shaped center bridge portion extending in the radial direction between the pair of magnet holes, and these bridge portions are subjected to a large centrifugal force caused by the rotation of the rotor (see Patent Document 1). In the conventional rotating electric machine described in Patent Document 1, a narrow neck portion is provided in the center bridge portion. In the rotating electric machine described in Patent Document 1, the provision of the neck portion results in a phenomenon called notch strengthening, which restricts plasticity at the bottom of the notch (plastic constraint), increasing the strength of the center bridge portion and enabling a high rotation speed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-57958 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the rotating electric machine described in Patent Document 1, when trying to accommodate higher rotation speeds, there were problems in that it became necessary to increase the thickness of the outer bridge section and center bridge section to increase the size of the rotor, and in that the leakage magnetic flux passing through the outer bridge section and center bridge section increased, reducing the magnetic flux density.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a rotating electric machine that can suppress deformation of the bridge portion due to centrifugal force without increasing the thickness of the bridge portion, and can suppress the decrease in magnetic flux density due to an increase in leakage magnetic flux. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the present invention provides a rotating electric machine including a stator in which a plurality of slots in which armature windings are arranged are formed, and a rotor in which a plurality of pairs of permanent magnets arranged in a V-shape widening toward the stator are embedded in a rotor core, the rotor core having first flux barriers formed adjacent to outer circumferential ends of the pair of permanent magnets, second flux barriers formed adjacent to inner circumferential ends of the pair of permanent magnets, an outer bridge portion extending circumferentially along the outer circumferential surface of the rotor core on the outer circumferential side of the first flux barriers, a center bridge portion extending radially within the second flux barrier and connecting the outer circumferential side and the inner circumferential side of the rotor core, and a bridging portion passing through the first flux barrier and connecting the outer bridge portion and an inner circumferential portion of the rotor core. The bridging portion connects a circumferential center portion of the outer bridge portion and a radial center portion of a wall surface of the first flux barrier extending in a radial direction at a position circumferentially facing an end portion of the outer circumferential side of the permanent magnet. It is characterized by: Effect of the Invention

[0007] According to the present invention, it is possible to provide a rotating electric machine that can suppress deformation of the bridge portion due to centrifugal force without increasing the thickness of the bridge portion and can suppress a decrease in magnetic flux density due to an increase in leakage magnetic flux. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of a rotating electric machine according to an embodiment of the present invention, taken along a plane perpendicular to the rotating shaft. [Diagram 2] FIG. 2 is a cross-sectional view of a portion of a rotor for a rotating electrical machine according to an embodiment of the present invention. [Diagram 3] FIG. 3 is an enlarged view of the vicinity of a first flux barrier of a rotor of a rotating electric machine according to one embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing stress distribution due to centrifugal force in a rotating electric machine according to an embodiment of the present invention. [Diagram 5] FIG. 5 is a diagram showing a magnetic flux distribution in a rotating electric machine according to an embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing stress distribution due to centrifugal force in a rotating electric machine according to a comparative example. [Figure 7] FIG. 7 is a diagram showing a magnetic flux distribution in a rotating electric machine according to a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A rotating electric machine according to an embodiment of the present invention includes a stator having a plurality of slots in which an armature winding is arranged, and a rotor having a rotor core in which a plurality of pairs of permanent magnets are embedded, the pairs of permanent magnets being arranged in a V-shape that widens toward the stator, the rotor core having a first flux barrier formed adjacent to the outer peripheral ends of the pair of permanent magnets, a second flux barrier formed adjacent to the inner peripheral ends of the pair of permanent magnets, an outer bridge portion extending circumferentially along the outer peripheral surface of the rotor core on the outer peripheral side of the first flux barrier, a center bridge portion extending radially within the second flux barrier and connecting the outer peripheral side and the inner peripheral side of the rotor core, and a bridging portion passing through the first flux barrier and connecting the outer bridge portion and the inner peripheral part of the rotor core. As a result, the rotating electric machine according to the embodiment of the present invention can suppress deformation of the bridge portion due to centrifugal force without increasing the thickness of the bridge portion, and suppress a decrease in magnetic flux density due to an increase in leakage magnetic flux. EXAMPLES

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a rotating electrical machine according to the present invention will now be described with reference to the drawings.

[0011] 1, a rotating electric machine 1 according to this embodiment is an interior permanent magnet synchronous motor (hereinafter referred to as IPMSM) in which permanent magnets are embedded inside a rotor. The rotating electric machine 1 has performance suitable for installation in, for example, a hybrid vehicle or an electric vehicle.

[0012] The rotating electric machine 1 includes a stator 10 formed in an annular shape and a rotor 20 rotatably housed within the stator 10. The rotor 20 is fixed to a rotating shaft 2 that rotates about an axis O, and rotates integrally with the rotating shaft 2.

[0013] The stator 10 is fixed to a motor case (not shown). The stator 10 includes an annular stator core 11 made of a magnetic material with high magnetic permeability. The stator core 11 is made of electromagnetic steel sheets laminated in the axial direction along the axis of the rotating shaft 2.

[0014] A plurality of stator teeth 12 protruding radially inward are provided along the circumferential direction on stator core 11. A plurality of slots 13, which are groove-like spaces, are formed between circumferentially adjacent stator teeth 12.

[0015] The radial direction refers to a direction perpendicular to the axial direction. The radial inner side refers to a side closer to the rotating shaft 2 in the radial direction, and the radial outer side refers to a side farther from the rotating shaft 2 in the radial direction. The circumferential direction refers to a circumferential direction centered on the rotating shaft 2.

[0016] Three-phase armature windings 14 of W-phase, V-phase, and U-phase are arranged in each slot 13 of stator core 11 along the circumferential direction of stator core 11. Each of the W-phase, V-phase, and U-phase armature windings 14 is distributed around each of stator teeth 12.

[0017] The stator 10 generates a rotating magnetic field that rotates in the circumferential direction when a three-phase AC is supplied to the armature windings 14. The magnetic flux generated by the stator 10 is configured to interlink with the rotor 20. This allows the stator 10 to rotate the rotor 20.

[0018] In FIG. 2, the rotor 20 includes an annular rotor core 21, a plurality of permanent magnet pairs 23, and magnetic pole portions 24.

[0019] Rotor core 21 is made by laminating electromagnetic steel sheets, which are a magnetic material with high magnetic permeability, in the axial direction along the axis of rotating shaft 2. A plurality of slit pairs 22 are formed in rotor core 21 along the circumferential direction of rotor 20. An inner peripheral surface 21B of rotor core 21 is fixed to rotating shaft 2.

[0020] The slit pair 22 is made up of a pair of slits 22A and 22B. The pair of slits 22A and 22B are provided so as to form a V shape that widens from the radially inner side toward the radially outer side, i.e., the stator side.

[0021] Permanent magnets 23A, 23B are fitted into the pair of slits 22A, 22B. The pair of permanent magnets 23A, 23B are arranged in a V-shape expanding from the radially inner side toward the radially outer side, i.e., the stator side, to constitute a permanent magnet pair 23.

[0022] The permanent magnets 23A and 23B are arranged so that the same polarity faces face each other. As a result, a magnetic pole portion 24 having the same polarity as the opposing polarity faces is formed between the permanent magnets 23A and 23B. In this way, the magnetic pole portion 24 is formed as an N magnetic pole or an S magnetic pole depending on the polarity of the permanent magnets 23A and 23B arranged in a V-shape.

[0023] The pair of permanent magnets 23A, 23B are arranged such that the polar faces of the circumferentially adjacent permanent magnet pairs 23 face in opposite directions. As a result, the polarities of the magnetic pole portions 24 adjacent to each other in the circumferential direction are opposite, i.e., the magnetic pole portions 24 are opposite polarity. Therefore, in the rotor 20, the magnetic pole portions 24 of the N pole (indicated as "N" in FIG. 1) and the magnetic pole portions 24 of the S pole (indicated as "S" in FIG. 1) are alternately formed in the circumferential direction.

[0024] In this manner, the rotor 20 has an inverse salient pole structure in which a plurality of permanent magnet pairs 23 are provided, each of which has a pair of permanent magnets 23A, 23B arranged in a V-shape.

[0025] Since the rotating electric machine 1 has the rotor 20 with such an inverse salient pole structure, the inductance in the axial direction (hereinafter referred to as the d-axis direction) passing between the pair of permanent magnets 23A, 23B is smaller than the inductance in the axial direction (hereinafter referred to as the q-axis direction) passing between the circumferentially adjacent permanent magnet pairs 23 and electrically and magnetically perpendicular to the d-axis. Therefore, the inverse salient pole structure can generate a reluctance torque according to the difference between the inductance in the d-axis direction and the inductance in the q-axis direction, in addition to the magnet torque generated by the permanent magnet pair 23. This can improve the torque density in the rotating electric machine 1.

[0026] Furthermore, a first flux barrier 25A and a second flux barrier 25B are formed adjacent to the pair of permanent magnets 23A, 23B in the rotor core 21. The first flux barrier 25A and the second flux barrier 25B are gaps for restricting intrusion of magnetic flux.

[0027] The first flux barrier 25A is formed adjacent to the outer peripheral ends of the pair of permanent magnets 23A, 23B, respectively. The second flux barrier 25B is formed between the pair of permanent magnets 23A, 23B, adjacent to the inner peripheral ends of these permanent magnets 23A, 23B.

[0028] Before the permanent magnets 23A, 23B are fitted into the rotor core 21, the slits 22A, 22B corresponding to the permanent magnets 23A, 23B, respectively, and the first flux barrier 25A and second flux barrier 25B form a continuous, integrated space.

[0029] The rotor core 21 has an outer bridge portion 32 between the first flux barrier 25A and the outer peripheral surface 21A of the rotor core 21. The rotor core 21 also has a band-shaped center bridge portion 31 that passes through the second flux barrier 25B.

[0030] The outer bridge portion 32 extends circumferentially along the outer peripheral surface 21A of the rotor core 21 on the outer peripheral side of the first flux barrier 25A. The center bridge portion 31 extends radially within the second flux barrier 25B and connects the outer peripheral side and the inner peripheral side of the rotor core 21. Here, the outer peripheral side of the rotor core 21 refers to a portion of the rotor core 21 that is radially outward from the second flux barrier 25B. Also, the inner peripheral side of the rotor core 21 refers to a portion of the rotor core 21 that is radially inward from the second flux barrier 25B. Thus, the center bridge portion 31 connects the outer peripheral side and the inner peripheral side of the rotor core 21 across the second flux barrier 25B in the radial direction.

[0031] Here, when the rotor 20 rotates, the centrifugal force acting on the permanent magnets 23A, 23B and the centrifugal force acting on the portions of the rotor core 21 that are outer circumferentially of the permanent magnets 23A, 23B are concentrated on the center bridge portion 31 and the outer bridge portion 32. Therefore, the maximum rotation speed of the rotating electric machine 1 depends on the strength of the center bridge portion 31 and the outer bridge portion 32 of the rotor core 21.

[0032] If the thickness of the center bridge portion 31 and the outer bridge portion 32 is increased in order to increase the strength of the center bridge portion 31 and the outer bridge portion 32, the leakage magnetic flux passing through the center bridge portion 31 and the outer bridge portion 32 increases, resulting in a decrease in magnetic flux density. For this reason, it is desirable to suppress deformation of the bridge portions without increasing the thickness of these bridge portions.

[0033] 2 and 3, the rotor core 21 has a bridging portion 33. The bridging portion 33 passes through the first flux barrier 25A and connects the outer bridge portion 32 to the inner peripheral portion of the rotor core 21. More specifically, the bridging portion 33 connects the outer bridge portion 32 to a wall surface 34 of the rotor core 21. The wall surface 34 extends in the radial direction at a position circumferentially facing the outer peripheral ends of the permanent magnets 23A, 23B of the first flux barrier 25A. The bridging portion 33 extends linearly and is inclined with respect to the radial direction of the rotor 20.

[0034] The outer bridge portion 32 is composed of a first outer bridge portion 32A located on one circumferential side of the connecting position with the bridging portion 33, and a second outer bridge portion 32B located on the other circumferential side of the connecting position with the bridging portion 33. The thickness of the second outer bridge portion 32B is smaller than the thickness of the first outer bridge portion 32A. Here, the thicknesses of the first outer bridge portion 32A and the second outer bridge portion 32B refer to their radial dimensions. In other words, the second outer bridge portion 32B is formed thinner than the first outer bridge portion 32A.

[0035] The circumferential dimensions of the first outer bridge portion 32A and the second outer bridge portion 32B are both set to L1. The radial outer and inner dimensions of the connecting portion with the bridging portion 33 on the wall surface 34 of the rotor core 21 are both set to L2. Therefore, the bridging portion 33 connects the circumferential center of the outer bridge portion 32 and the radial center of the wall surface 34.

[0036] As described above, in the rotating electric machine 1 of this embodiment, the rotor core 21 has, as shown in Figures 2 and 3, a first flux barrier 25A formed adjacent to the outer peripheral ends of a pair of permanent magnets 23A, 23B, a second flux barrier 25B formed adjacent to the inner peripheral ends of the pair of permanent magnets 23A, 23B, an outer bridge portion 32 extending circumferentially along the outer peripheral surface 21A of the rotor core 21 on the outer peripheral side of the first flux barrier 25A, and a center bridge portion 31 extending radially within the second flux barrier 25B and connecting the outer peripheral side and the inner peripheral side of the rotor core 21.

[0037] In the rotating electric machine 1 configured as above, as shown in Fig. 4, the centrifugal force Fc generated when the rotor 20 rotates acts on the pair of permanent magnets 23A, 23B and on the outer peripheral portion 29, which is a portion of the rotor core 21 that is more outer than the permanent magnets 23A, 23B. This centrifugal force Fc is concentrated on the outer bridge portion 32 and the center bridge portion 31, and acts as a tensile stress on the outer bridge portion 32 and the center bridge portion 31. Against this centrifugal force Fc, the center bridge portion 31 exerts a resistance force F1 inward in the radial direction, and the outer bridge portion 32 exerts resistance forces F2 and F3 outward in the circumferential direction.

[0038] The rotating electric machine 1 according to this embodiment has a bridging portion 33 that passes through the first flux barrier 25A so as to connect the outer bridge portion 32 and the inner peripheral portion of the rotor core 21.

[0039] This allows the bridging portions 33 to bear part of the stress acting on the outer bridge portion 32, and the bridging portions 33 can exert resistance forces F4 and F5. As a result, the centrifugal force acting on the rotor core 21 can be distributed to the center bridge portion 31, the outer bridge portion 32, and the bridging portions 33. Therefore, deformation of the bridge portions due to centrifugal force can be suppressed without increasing the thicknesses of the outer bridge portion 32 and the center bridge portion 31.

[0040] Furthermore, since the thickness of the outer bridge portion 32 is not increased, an increase in leakage flux passing through the outer bridge portion 32 can be prevented, and a decrease in magnetic flux density due to an increase in leakage flux can be suppressed.

[0041] As a result, deformation of the bridge portion due to centrifugal force can be suppressed without increasing the thickness of the bridge portion, and a decrease in magnetic flux density due to an increase in leakage magnetic flux can be suppressed.

[0042] 6, the rotor 20A does not have the bridging portion 33, so the stress due to the centrifugal force Fc is entirely borne by the resistance F1 from the center bridge portion 31 and the resistances F2 and F3 from the outer bridge portion 32, and the stress cannot be dispersed. This raises the risk of deformation of the outer bridge portion 32, and if the thickness of the outer bridge portion 32 is increased to suppress deformation, the leakage magnetic flux passing through the outer bridge portion 32 may increase, resulting in a decrease in torque.

[0043] In addition, in the rotating electric machine 1 according to this embodiment, as shown in FIG. 3, the bridging portion 33 connects the outer bridge portion 32 to a wall surface 34 extending radially at a position circumferentially facing the outer peripheral ends of the permanent magnets 23A, 23B in the first flux barrier 25A.

[0044] Therefore, as shown in FIG. 4, part of the stress due to the centrifugal force Fc can be borne by the bridging portion 33 as resistance forces F4, F5, and these resistance forces F4, F5 can be further borne by the wall surface .

[0045] Therefore, the stress that tends to deform the outer bridge portion 32 towards the outer periphery can be borne by the wall surface 34 to which the bridging portion 33 is connected. In addition, since the wall surface 34 to which the bridging portion 33 is connected extends in the radial direction, the stress can be borne by the wall surface 34 without deforming the wall surface 34, and the bridging portion 33 can bear a large stress.

[0046] 6, the rotor 20A does not have the bridging portion 33, so the stress due to the centrifugal force Fc is entirely borne by the resistance F1 from the center bridge portion 31 and the resistances F2 and F3 from the outer bridge portion 32, and the stress cannot be dispersed. As a result, there is a risk that at least one of the center bridge portion 31 and the outer bridge portion 32 will deform.

[0047] In the rotating electric machine 1 according to this embodiment, the outer bridge portion 32 is composed of a first outer bridge portion 32A located on one circumferential side of the connecting position with the bridging portion 33, and a second outer bridge portion 32B located on the other circumferential side of the connecting position with the bridging portion 33. The thickness of the second outer bridge portion 32B is smaller than the thickness of the first outer bridge portion 32A.

[0048] In other words, part of the stress acting on the first outer bridge part 32A and the second outer bridge part 32B can be borne by the bridging part 33, so it is possible to reduce the thickness of the second outer bridge part 32B, which is part of the outer bridge part 32. By reducing the thickness of the second outer bridge part 32B, the amount of leakage magnetic flux passing through the second outer bridge part 32B can be reduced, so the magnetic flux density of the rotor core 21 can be increased, and the torque can be increased.

[0049] More specifically, in the present embodiment shown in FIG. 5, the leakage flux that passed through the first outer bridge portion 32A branches into the second outer bridge portion 32B and the bridging portion 33, and the total number of leakage fluxes passing through the second outer bridge portion 32B and the bridging portion 33 is five. That is, the leakage fluxes passing through the entire outer bridge portion 32 are five. On the other hand, in the rotating electric machine 1A of the comparative example shown in FIG. 7, the leakage fluxes passing through the outer bridge portion 32 of the rotor 20A are six. In this way, in the present embodiment, the leakage flux passing through the outer bridge portion 32 can be reduced more than in the comparative example. By reducing the leakage flux, the magnetic flux density of the air gap A between the stator 10 and the rotor 20 in the rotating electric machine 1 of the present embodiment shown in FIG. 5 is greater than the magnetic flux density of the air gap B between the stator 10 and the rotor 20A in the rotating electric machine 1A of the comparative example shown in FIG. 7.

[0050] Here, since magnetic flux has the tendency to return to its opposing magnetic pole through the shortest path, if the bridging portion 33 is connected to a side closer to the permanent magnets 23A, 23B than to the circumferential center of the outer bridge portion 32, the leakage magnetic flux passing through the bridging portion 33 will increase, which may result in a decrease in torque.

[0051] On the other hand, since the stress acting on the first outer bridge part 32A is distributed between the bridging part 33 and the second outer bridge part 32B, if the bridging part 33 is positioned away from the permanent magnets 23A, 23B from the circumferential center of the outer bridge part 32, the stress acting on the first outer bridge part 32A will become large, and there is a risk that the first outer bridge part 32A will be significantly deformed.

[0052] Therefore, in the rotating electric machine 1 according to this embodiment, the bridging portion 33 connects the circumferential center portion of the outer bridge portion 32 and the radial center portion of the wall surface 34 .

[0053] In this way, by connecting the bridging portion 33 to the circumferential center of the outer bridge portion 32, it is possible to reduce the amount of leakage magnetic flux and distribute stress at the same time. Also, by connecting the bridging portion 33 to the radial center of the wall surface 34, the bridging portion 33 can be disposed at an angle with respect to the radial direction of the rotor core 21, so that the bridging portion 33 can act as a resistance against both the stress acting on the outer bridge portion 32 in the circumferential direction (tensile direction) and the stress acting in the radial direction.

[0054] The rotating electric machine 1 can be suitably used not only as a drive source for hybrid cars and electric cars, but also as a drive source for wind power generation, machine tools, and the like.

[0055] Although an embodiment of the invention has been disclosed, it will be apparent to one of ordinary skill in the art that modifications may be made thereto without departing from the spirit and scope of the invention, and it is intended that all such modifications and equivalents be included in the following claims. [Explanation of symbols]

[0056] 1 Rotating Electric Machine 10 Stator 13 Slots 14 Armature Winding 20 Rotors 21 Rotor core 23A, 23B permanent magnet 25A First Flux Barrier 25B Second Flux Barrier 29 Outer periphery 31 Center Bridge Section 32 Outer bridge section 32A First outer bridge section 32B Second outer bridge section 33 Bridge section 34 Wall

Claims

1. a stator having a plurality of slots in which armature windings are arranged; a rotor having a rotor core in which a plurality of pairs of permanent magnets are embedded, the permanent magnets being arranged in a V-shape that expands toward the stator side, The rotor core is a first flux barrier formed adjacent to each of the outer peripheral ends of the pair of permanent magnets; a second flux barrier formed adjacent to the inner peripheral ends of the pair of permanent magnets; an outer bridge portion extending in a circumferential direction along an outer circumferential surface of the rotor core on an outer circumferential side of the first flux barrier; a center bridge portion extending radially within the second flux barrier and connecting an outer circumferential side and an inner circumferential side of the rotor core; a bridging portion that passes through the first flux barrier and connects the outer bridge portion and an inner circumferential portion of the rotor core, a bridging portion connecting a circumferential center portion of the outer bridge portion and a radial center portion of a wall surface extending radially at a position circumferentially opposite an outer peripheral end portion of the permanent magnet in the first flux barrier.

2. The outer bridge portion is a first outer bridge portion located closer to the pair of permanent magnets in the circumferential direction than a central portion in the circumferential direction; a second outer bridge portion located farther from the pair of permanent magnets in the circumferential direction than a central portion in the circumferential direction, 2. The rotating electric machine according to claim 1, wherein a thickness of the second outer bridge portion is smaller than a thickness of the first outer bridge portion.

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