Rotor

Abstract

A rotor (10) comprises a rotor core (12); and a plurality of magnets (14) that are arranged in the rotation direction of the rotor and that are each embedded in the rotor core. The rotor core has a plurality of housing holes (18) respectively housing the plurality of magnets. A first flux barrier (20) communicating with the housing holes is formed on the rear side of the rotor core in the rotation direction of the rotor relative to the housing holes, and a second flux barrier (22) communicating with the housing holes is formed on the front side of the rotor core in the rotation direction of the rotor relative to the housing holes. The cross-sectional area of the first flux barrier is larger than the cross-sectional area of the second flux barrier.

Description

rotor CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on and claims the benefit of priority from Japanese Patent Application No. 2024-147892, filed on August 29, 2024, the entire contents of which are incorporated herein by reference.

[0002] The technology of the present disclosure relates to a rotor for a rotating electric machine, and more particularly to an embedded magnet rotor.

[0003] Conventionally, an embedded magnet type rotor having a rotor core and a magnet embedded in the rotor core has been known (see, for example, Japanese Patent Application Laid-Open No. 2023-148145).

[0004] As a result of detailed investigations by the inventors, the following problem was discovered. It will be explained below. FIG. 8 shows a conventional rotor disclosed in Japanese Patent Laid-Open Publication No. 2023-148145 (hereinafter referred to as the "conventional rotor" in this specification). The conventional rotor includes a rotor core 112 and a plurality of magnets 114 embedded in the rotor core 112 and aligned in the rotor rotation direction. The rotor core 112 has a plurality of accommodating holes 118 that accommodate the plurality of magnets 114, respectively. A first flux barrier 120 communicating with each accommodating hole 118 is formed on the rear side of each accommodating hole 118 in the rotor core 112 in the rotor rotation direction. A second flux barrier 122 communicating with each accommodating hole 118 is formed on the front side of each accommodating hole 118 in the rotor rotation direction. The cross-sectional area of ​​the first flux barrier 120 is smaller than the cross-sectional area of ​​the second flux barrier 122.

[0005] In a conventional rotor, when the maximum length of the first flux barrier 120 along the tangential direction of the rotor is L1a, the maximum length of the second flux barrier 122 along the tangential direction of the rotor is L2a, the maximum length of the first flux barrier 120 along the radial direction of the rotor is L1b, and the maximum length of the second flux barrier 122 along the radial direction of the rotor is L2b, the following equations (4) and (5) hold: L1a>L2a (4) L1b<L2b (5)

[0006] Although conventional rotors are said to improve drive torque, there is still room for improvement in terms of improving reluctance torque.

[0007] The technique of the present disclosure provides a rotor that can improve reluctance torque compared to conventional rotors.

[0008] The technology disclosed herein is a rotor for a rotating electric machine, comprising a rotor core and a plurality of magnets arranged in the rotational direction of the rotor and each embedded in the rotor core, the rotor core having a plurality of accommodating holes that respectively accommodate the magnets, a first flux barrier communicating with the accommodating holes formed on the rear side of each of the accommodating holes in the rotor core in the rotational direction of the rotor, and a second flux barrier communicating with the accommodating holes formed on the front side of each of the accommodating holes in the rotor core in the rotational direction of the rotor, the cross-sectional area of ​​the first flux barrier being larger than the cross-sectional area of ​​the second flux barrier.

[0009] According to the technique of the present disclosure, a rotor capable of improving reluctance torque compared to conventional rotors is provided.

[0010] FIG. 1 is a plan view of a rotor according to a first embodiment of the disclosed technique; FIG. 2 is an enlarged plan view of a main part of the rotor according to the first embodiment; FIG. 3 is a plan view showing a magnetic path in the rotor according to the first embodiment; FIG. 4 is a graph comparing an example of the relationship between the electrical angle and the reluctance torque for the rotor according to the first embodiment, a conventional rotor, and a rotor according to a comparative example; FIG. 5 is a graph comparing an example of the relationship between the electrical angle and the drive torque for the rotor according to the first embodiment, a conventional rotor, and a rotor according to a comparative example; FIG. 6 is an enlarged plan view of a main part of a rotor according to a second embodiment of the disclosed technique; FIG. 7 is a plan view showing a magnetic path in the rotor according to the second embodiment; FIG. 8 is a plan view showing a magnetic path in the conventional rotor;

[0011] First Embodiment First, a first embodiment of the technology of the present disclosure will be described.

[0012] As shown in FIG. 1 , a rotor 10 according to the first embodiment is an interior permanent magnet (IPM) rotor and is used in an inner rotor brushless motor. A brushless motor is an example of a "rotating electric machine" according to the technology of the present disclosure. The rotor 10 includes a rotor core 12 and a plurality of magnets 14. The plurality of magnets 14 are embedded in the rotor core 12.

[0013] The rotor core 12 is a laminated body formed by stacking a plurality of core sheets in the axial direction of the rotor core 12. An outer peripheral surface 12A of the rotor core 12 is formed in a circular shape when viewed from the axial direction of the rotor core 12.

[0014] The rotor core 12 has an insertion hole 16 and a plurality of accommodating holes 18. The insertion hole 16 and the plurality of accommodating holes 18 penetrate the rotor core 12 in the axial direction. A shaft (not shown) is inserted into the insertion hole 16. The insertion hole 16 is formed in the center of the rotor core 12.

[0015] The multiple accommodating holes 18 are aligned in the circumferential direction of the rotor core 12 along the outer peripheral surface 12A of the rotor core 12. Each accommodating hole 18 is located closer to the outer peripheral surface 12A than the center of the rotor core 12. Since arranging the magnets 14 accommodated in the accommodating holes 18 closer to the stator (not shown) located radially outward of the rotor 10 improves the performance of the brushless motor, the accommodating holes 18 are formed at positions closer to the outer peripheral surface 12A of the rotor core 12. Each accommodating hole 18 is formed linearly along the tangential direction of the rotor core 12.

[0016] Each magnet 14 is housed in a housing hole 18. The magnets 14 are formed in a flat plate shape and extend in a width direction that is tangent to the rotor core 12. Half of each magnet 14 on the outer peripheral surface 12A side is formed by one of the north and south magnetic poles (e.g., north pole), and the other half of each magnet 14 opposite the outer peripheral surface 12A is formed by the other of the north and south magnetic poles (e.g., south pole). The magnetic pole of the other half of each magnet 14 on the outer peripheral surface 12A side (e.g., north pole) of one of the adjacent magnets 14 is set to a different magnetic pole from the magnetic pole of the other half of the adjacent magnet 14 on the outer peripheral surface 12A side (e.g., south pole).

[0017] The arrow R indicates the direction in which the rotor 10 rotates when the rotor 10 receives a rotating magnetic field from the stator. Hereinafter, the leading end side of the arrow R in the direction of rotation of the rotor 10 will be referred to as the "front side of the rotation direction of the rotor 10," and the trailing end side of the arrow R in the direction of rotation of the rotor 10 will be referred to as the "rear side of the rotation direction of the rotor 10."

[0018] A first flux barrier 20 communicating with the accommodating hole 18 is formed on the rear side of each accommodating hole 18 in the rotor core 12 in the direction of rotation of the rotor 10, and a second flux barrier 22 communicating with the accommodating hole 18 is formed on the front side of each accommodating hole 18 in the rotor core 12 in the direction of rotation of the rotor 10. The first flux barrier 20 and the second flux barrier 22 are grooves for ensuring a gap that prevents magnetic flux from passing from the north pole to the south pole of the magnet 14.

[0019] 2, the accommodating hole 18 has an outer surface 18A located radially outward of the rotor 10 relative to the magnet 14, and an inner surface 18B located radially inward of the rotor 10 relative to the magnet 14. The outer surface 18A and the inner surface 18B extend linearly along the tangential direction of the rotor 10.

[0020] The first flux barrier 20 has a first surface 20A connected to the outer surface 18A via a first bent portion 21A, a second surface 20B connected to the inner surface 18B via a second bent portion 21B, and a third surface 20C connected to the second surface 20B via a third bent portion 21C. The first surface 20A extends along the circumferential direction of the rotor 10, the second surface 20B extends along the radial direction of the rotor 10, and the third surface 20C is inclined toward the rear in the direction of rotation of the rotor 10 with respect to the radial direction of the rotor 10. The third surface 20C is connected to the first surface 20A via a fourth bent portion 21D. The first surface 20A is located radially outward of the rotor 10 relative to the second surface 20B and the third surface 20C. The second surface 20B is located forward in the direction of rotation of the rotor 10 relative to the first surface 20A and the third surface 20C. The third surface 20C is located rearward of the second surface 20B in the direction of rotation of the rotor 10 and radially inward of the first surface 20A.

[0021] The second flux barrier 22 has a first surface 22A connected to the outer surface 18A via a first bent portion 23A and a second surface 22B connected to the inner surface 18B via a second bent portion 23B. The first surface 22A extends along the circumferential direction of the rotor 10. The second surface 22B is inclined toward the front in the rotation direction of the rotor 10 with respect to the radial direction of the rotor 10. The second surface 22B is connected to the first surface 22A via a third bent portion 23C. The first surface 22A is located radially outward of the rotor 10 with respect to the second surface 22B.

[0022] The magnet 14 has a first corner 15A and a second corner 15B. The first corner 15A and the second corner 15B are corners located on a diagonal line of the magnet 14. The first corner 15A is the corner of the four corners of the magnet 14 that is closer to the first flux barrier 20 and the outer surface 18A, and the second corner 15B is the corner of the four corners of the magnet 14 that is closer to the second flux barrier 22 and the inner surface 18B. The first corner 15A of the magnet 14 contacts the first bent portion 21A of the first flux barrier 20, and the second corner 15B of the magnet 14 contacts the second bent portion 23B of the second flux barrier 22, thereby positioning the magnet 14 with respect to the rotor core 12.

[0023] Here, the maximum length of the first flux barrier 20 along the tangential direction of the rotor 10 is defined as L1a, the maximum length of the second flux barrier 22 along the tangential direction of the rotor 10 is defined as L2a, the maximum length of the first flux barrier 20 along the radial direction of the rotor 10 is defined as L1b, and the maximum length of the second flux barrier 22 along the radial direction of the rotor 10 is defined as L2b. In this case, the following equations (1) and (2) hold for the first flux barrier 20 and the second flux barrier 22. L1a>L2a (1) L1b>L2b (2)

[0024] As an example, when the above formulas (1) and (2) are satisfied, the cross-sectional area of ​​the first flux barrier 20 is larger than the cross-sectional area of ​​the second flux barrier 22. The cross-sectional areas of the first flux barrier 20 and the second flux barrier 22 are the areas of the cross sections obtained when the rotor 10 is cut in a direction perpendicular to the axial direction of the rotor 10.

[0025] Furthermore, the thickness of the accommodating hole 18 along the radial direction of the rotor 10 is defined as T. In this case, the following equation (3) holds for the first flux barrier 20 and the second flux barrier 22: L1b>T≧L2b (3)

[0026] Furthermore, the line connecting the center between adjacent magnets 14 among the plurality of magnets 14 in the rotation direction of the rotor 10 and the center of the rotor 10 is defined as the inter-pole center line Lc. In this case, the cross-sectional area (in other words, the length L1a) of the first flux barrier 20 is set so that a part of the first flux barrier 20 (specifically, a part of the first flux barrier 20 on the fourth bend portion 21D side) intersects with the inter-pole center line Lc.

[0027] 3 shows the magnetic path of the rotor 10 according to the first embodiment. A stator 30 is disposed radially outward of the rotor 10. The stator 30 has a stator core 32 and a winding 34. The stator core 32 has an annular yoke portion 36 and a plurality of teeth 38 extending from the yoke portion 36 radially inward of the stator 30. The winding 34 is wound around each tooth 38, forming a winding portion 40. A rotating magnetic field is generated by the stator 30 when current is applied to the plurality of winding portions 40 in sequence.

[0028] 3 shows an example in which, for example, tooth portion 38A of the plurality of teeth 38 is located on an extension line of inter-pole center line Lc. Magnetic flux M generated by energizing winding portion 40A, which is wound around tooth portion 38A of the plurality of winding portions 40, passes through rotor core 12 and forms a magnetic path that returns to winding portion 40A from teeth 38B on both sides of tooth portion 38A. The magnetic path includes magnetic paths A and B that pass on the front side of tooth portion 38A in the direction of rotation of rotor 10, and magnetic paths C and D that pass on the rear side of tooth portion 38A in the direction of rotation of rotor 10. Magnetic path A passes on the radially outer side of rotor 10 relative to magnet 14, and magnetic path B passes on the radially inner side of rotor 10 relative to magnet 14. Magnetic path C passes on the radially outer side of rotor 10 relative to magnet 14, and magnetic path D passes on the radially inner side of rotor 10 relative to magnet 14.

[0029] In the first embodiment, the maximum length L2a of the second flux barrier 22 along the tangential direction of the rotor 10 is shorter than the maximum length L1a of the first flux barrier 20 along the tangential direction of the rotor 10, and the maximum length L2b of the second flux barrier 22 along the radial direction of the rotor 10 is shorter than the maximum length L1b of the first flux barrier 20 along the radial direction of the rotor 10 (see FIG. 2 ). Therefore, the length of magnetic path B is longer than the length of magnetic path D. Generally, the shorter the magnetic path, the smaller the loss of magnetic flux and the easier it is for magnetic flux to flow, resulting in a stronger magnetic force due to the magnetic path. However, since the length of magnetic path B is longer than the length of magnetic path D, the magnetic force due to magnetic path B is weaker. On the other hand, the lengths of magnetic paths A and C are the same, and there is no difference between the magnetic forces due to magnetic paths A and C. The sum of the difference between the magnetic force due to magnetic path A and the magnetic force due to magnetic path C and the difference between the magnetic force due to magnetic path B and the magnetic force due to magnetic path D becomes the driving torque that rotates the rotor 10. However, in the first embodiment, there is no difference between the magnetic force due to magnetic path A and the magnetic force due to magnetic path C, so the driving torque is generated by the difference between the magnetic force due to magnetic path B and the magnetic force due to magnetic path D.

[0030] FIG. 4 shows an example of the results of measuring reluctance torque for the rotor 10 according to the first embodiment, a conventional rotor, and a rotor according to a comparative example. The horizontal axis represents electrical angle [deg], and the vertical axis represents reluctance torque [Nm]. The results shown in FIG. 4 are analytical values ​​obtained using analysis software. Graph G1 shows the values ​​for the rotor 10 according to the first embodiment, graph G2 shows the values ​​for the conventional rotor, and graph G3 shows the values ​​for the rotor according to the comparative example in which the first flux barrier 20 and the second flux barrier 22 are symmetrically shaped.

[0031] 4, values ​​are calculated from electrical angles from 0° to 60°, and the average value of the reluctance torque from electrical angles from 0° to 60° is calculated. When the average value of the reluctance torque of the rotor according to the comparative example is set to a reference value (=1), the average value of the reluctance torque of the rotor 10 according to the first embodiment is 1.52 times the reference value, and the average value of the reluctance torque of the conventional rotor is 1.27 times the reference value.

[0032] 4, the result is that the reluctance torque of the rotor 10 according to the first embodiment is higher than the reluctance torque of the conventional rotor and the rotor according to the comparative example. Regarding this result, in the first embodiment, the cross-sectional area of ​​the first flux barrier 20 is larger than the cross-sectional area of ​​the second flux barrier 22, and therefore the length of the magnetic path B passing around the first flux barrier 20 is longer than the length of the magnetic path D passing around the second flux barrier 22. In other words, the length of the magnetic path D is shorter than the length of the magnetic path B, and this can be considered to be the reason why the reluctance torque is improved compared to the conventional rotor and the rotor according to the comparative example.

[0033] The reluctance torque can be measured by the following procedure. First, a brushless motor is prepared in which the magnet 14, which is involved in torque, has been removed from the rotor core 12. An example of a magnet 14 that is not involved in torque is a sensor magnet. Second, current is passed through the stator 30 in the same phase as before the magnet 14 was removed, causing the rotor 10 to rotate. Third, as the torque during rotation of the rotor 10, a measuring instrument combining a torque sensor and a brake is used to detect the torque when a load is applied to the rotor 10 by the brake, as reluctance torque.

[0034] FIG. 5 shows an example of the results of measuring the drive torque for the rotor 10 according to the first embodiment, a conventional rotor, and a rotor according to a comparative example. The horizontal axis represents the electrical angle [deg], and the vertical axis represents the drive torque [Nm]. The results shown in FIG. 5 are analytical values ​​obtained using analysis software. Graph G4 shows the values ​​for the rotor 10 according to the first embodiment, graph G5 shows the values ​​for the conventional rotor, and graph G6 shows the values ​​for the rotor according to the comparative example in which the first flux barrier 20 and the second flux barrier 22 are symmetrically shaped.

[0035] In the example shown in Figure 5, values ​​are calculated from electrical angles from 0° to 60°, and the average value of the drive torque (i.e., motor torque) from electrical angles from 0° to 60° is calculated. When the average value of the drive torque of the rotor according to the comparative example is set to a reference value (= 1), the average value of the drive torque of the rotor 10 according to the first embodiment is 1.04 times the reference value, and the average value of the drive torque of the conventional rotor is 1.02 times the reference value. Thus, in the example shown in Figure 5, the result is that the drive torque of the rotor 10 according to the first embodiment is higher than the drive torque of the conventional rotor and the drive torque of the rotor according to the comparative example.

[0036] The driving torque can be measured by the following procedure. First, a brushless motor is prepared in which the magnet 14 is embedded in the rotor core 12 as usual. Second, current is applied to the stator 30 at a phase that will produce the desired performance as a brushless motor, causing the rotor 10 to rotate. Third, while the rotor 10 is rotating, a measuring device that combines a torque sensor and a brake is used to detect the torque when a load is applied to the rotor 10 by the brake, and this torque is used as the driving torque.

[0037] Next, the effects of the first embodiment will be described.

[0038] As described above in detail, in the first embodiment, the cross-sectional area of ​​the first flux barrier 20 is larger than the cross-sectional area of ​​the second flux barrier 22. As a result, the length of the magnetic path B passing around the first flux barrier 20 is longer than the length of the magnetic path D passing around the second flux barrier 22. In other words, the length of the magnetic path D is shorter than the length of the magnetic path B, which makes it possible to improve the reluctance torque compared to the conventional rotor and the rotor according to the comparative example.

[0039] Furthermore, in the first embodiment, the maximum length L2a of the second flux barrier 22 along the tangential direction of the rotor 10 is shorter than the maximum length L1a of the first flux barrier 20 along the tangential direction of the rotor 10. As a result, the length of magnetic path D is shorter than the length of magnetic path B, and the magnetic flux of magnetic path D flows more easily than the magnetic flux of magnetic path B, thereby further improving the reluctance torque.

[0040] Furthermore, in the first embodiment, the maximum length L2a of the second flux barrier 22 along the tangential direction of the rotor 10 is shorter than the maximum length L1a of the first flux barrier 20 along the tangential direction of the rotor 10, and in addition, the maximum length L2b of the second flux barrier 22 along the radial direction of the rotor 10 is shorter than the maximum length L1b of the first flux barrier 20 along the radial direction of the rotor 10. As a result, the length of magnetic path D becomes even shorter than the length of magnetic path B, and the magnetic flux of magnetic path D flows more easily than the magnetic flux of magnetic path B, thereby further improving the reluctance torque.

[0041] Furthermore, in the first embodiment, the thickness T of the accommodating hole 18 along the radial direction of the rotor 10 is equal to or greater than the maximum length L2b of the second flux barrier 22 along the radial direction of the rotor 10, and is less than the maximum length L1b of the first flux barrier 20 along the radial direction of the rotor 10. This also makes the length of magnetic path D shorter than the length of magnetic path B, which makes it easier for the magnetic flux of magnetic path D to flow than the magnetic flux of magnetic path B, thereby further improving the reluctance torque.

[0042] Furthermore, in the first embodiment, a portion of the first flux barrier 20 intersects with the inter-pole center line Lc that connects the center between adjacent magnets 14 and the center of the rotor 10. This also makes the length of magnetic path D shorter than the length of magnetic path B, making it easier for the magnetic flux of magnetic path D to flow than the magnetic flux of magnetic path B, thereby further improving the reluctance torque.

[0043] In the first embodiment, the first corner 15A of the magnet 14 contacts the first bent portion 21A, and the second corner 15B of the magnet 14 contacts the second bent portion 23B, thereby positioning the magnet 14 with respect to the rotor core 12. This makes it possible to prevent the magnetic flux of the magnet 14 from leaking and the drive torque from decreasing, while also suppressing movement of the magnet 14 in the rotational direction of the rotor 10.

[0044] Next, a modification of the first embodiment will be described.

[0045] The maximum lengths L1a and L1b of the first flux barrier 20 and the maximum lengths L2a and L2b of the second flux barrier 22 vary depending on the width of the magnet 14 in the tangential direction of the rotor 10, the thickness of the magnet 14 in the radial direction of the rotor 10, the length of the magnet 14 in the axial direction of the rotor 10, and the position of the magnet 14 in the radial direction of the rotor 10, and therefore the maximum value of the reluctance torque also varies. Therefore, in the first embodiment, the maximum lengths L1a and L1b of the first flux barrier 20, the maximum lengths L2a and L2b of the second flux barrier 22, the width of the magnet 14 in the tangential direction of the rotor 10, the thickness of the magnet 14 in the radial direction of the rotor 10, the length of the magnet 14 in the axial direction of the rotor 10, and the position of the magnet 14 in the radial direction of the rotor 10 are merely examples.

[0046] Second Embodiment Next, a second embodiment of the technique of the present disclosure will be described.

[0047] In the second embodiment, the configuration of the rotor 10 is modified as follows compared to the first embodiment. That is, in the second embodiment, as shown in Fig. 6 , a first step portion 50 is formed instead of the first bent portion 21A (see Fig. 2) of the first flux barrier 20, and a second step portion 52 is formed instead of the second bent portion 23B (see Fig. 2) of the second flux barrier 22. The first surface 20A of the first flux barrier 20 is connected to the outer surface 18A via the first step portion 50, and the second surface 22B of the second flux barrier 22 is connected to the inner surface 18B via the second step portion 52.

[0048] The first step portion 50 forms a step in the radial direction of the rotor 10 between the outer surface 18A and the first surface 20A of the first flux barrier 20, and the second step portion 52 forms a step in the radial direction of the rotor 10 between the inner surface 18B and the second surface 22B of the second flux barrier 22. The first side surface 14A of the magnet 14 on the first corner portion 15A side comes into contact with the first step portion 50, and the second side surface 14B of the magnet 14 on the second corner portion 15B side comes into contact with the second step portion 52, thereby positioning the magnet 14 with respect to the rotor core 12.

[0049] A first relief groove 54 recessed radially outward of the rotor 10 is formed at the end of the outer surface 18A on the first step portion 50 side, and a second relief groove 56 recessed radially inward of the rotor 10 is formed at the end of the inner surface 18B on the second step portion 52 side. The first relief groove 54 is a relief groove for avoiding interference between the first corner portion 15A of the magnet 14 and the outer surface 18A, and the second relief groove 56 is a relief groove for avoiding interference between the second corner portion 15B of the magnet 14 and the inner surface 18B. The configuration of the second embodiment other than the above is the same as that of the first embodiment.

[0050] Figure 7 shows the magnetic path of the rotor 10 according to the second embodiment. Figure 7 shows an example in which the teeth 38A are located on an extension of the center line of the magnet 14. The driving torque is the sum of the magnet torque and the reluctance torque, but to efficiently generate the magnet torque, the magnetic flux M of the magnet 14 needs to flow efficiently through the teeth 38A. When the teeth 38A are located on an extension of the center line of the magnet 14, magnetic paths E and F are generated in which the magnetic flux flows along the accommodating hole 18. Because magnetic paths E and F do not pass through the teeth 38A, no magnet torque is generated, and the reduction in the magnetic flux flowing through the teeth 38A causes the magnet torque to decrease. Therefore, in general, a first flux barrier 20 and a second flux barrier 22 are provided on both sides of the magnet 14 to make it difficult for magnetic flux to flow, and further, the width of the first bridge portion 58 between the first flux barrier 20 and the outer peripheral surface 12A of the rotor core 12 and the width of the second bridge portion 60 between the second flux barrier 22 and the outer peripheral surface 12A of the rotor core 12 are reduced, thereby reducing the magnetic flux flowing in the magnetic paths E and F.

[0051] The magnetic flux flowing through the magnetic paths E and F generally passes through the rotor core 12, which is made of magnetic material, but if the distance L1 of the first flux barrier 20 separating the two poles of the magnet 14 and the distance L2 of the second flux barrier 22 separating the two poles of the magnet 14 are short, the magnetic flux will pass not only through the rotor core 12 but also through the first flux barrier 20 and the second flux barrier, so it is necessary to ensure that the distance L1 of the first flux barrier 20 and the distance L2 of the second flux barrier 22 are as large as possible.

[0052] Here, if the first flux barrier 20 with the larger cross-sectional area is provided with a first step portion 50, instead of the third bent portion 21C (see FIG. 6 ), that protrudes up to a position where it contacts the first side surface 14A of the magnet 14, the distance L1 of the first flux barrier 22 will be shortened. Therefore, in the second embodiment, the minimum necessary first step portion 50 is provided between the first surface 20A of the first flux barrier 20 and the outer surface 18A of the accommodation hole 18, thereby ensuring a large distance L1 of the first flux barrier 22.

[0053] Furthermore, if the second step portion 52 is formed instead of the first bent portion 23A (see FIG. 6 ) for the second flux barrier 22 with the smaller cross-sectional area, the width of the second bridge portion 60 increases by the amount of the second step portion 52, and the magnetic flux flowing through the magnetic path E increases. Therefore, in the second embodiment, the second step portion 52 is provided between the second surface 22B of the second flux barrier 22 and the inner surface 18B of the accommodating hole 18, thereby ensuring the distance L2 of the second flux barrier 22 while reducing the width of the second bridge portion 60.

[0054] Next, the effects of the second embodiment will be described.

[0055] As described above in detail, in the second embodiment, for the first flux barrier 20 having the larger cross-sectional area, the first step portion 50 is provided between the first surface 20A of the first flux barrier 20 and the outer surface 18A of the accommodating hole 18. This makes it possible to ensure a large distance L1 for the first flux barrier 20, and therefore allows the magnetic flux M of the magnet 14 to flow efficiently to the teeth portion 38A.

[0056] Furthermore, for the second flux barrier 22 with the smaller cross-sectional area, a second step portion 52 is provided between the second surface 22B of the second flux barrier 22 and the inner surface 18B of the accommodating hole 18. This makes it possible to ensure the distance L2 of the second flux barrier 22 while reducing the width of the second bridge portion 60, and therefore allows the magnetic flux M of the magnet 14 to flow efficiently to the teeth portion 38A.

[0057] Furthermore, the first side surface 14A of the magnet 14 contacts the first step portion 50, and the second side surface 14B of the magnet 14 contacts the second step portion 52. Therefore, cracking or chipping of the first corner portion 15A and the second corner portion 15B of the magnet 14 can be suppressed.

[0058] Next, a modification of the second embodiment will be described.

[0059] The maximum lengths L1a and L1b of the first flux barrier 20 and the maximum lengths L2a and L2b of the second flux barrier 22 vary depending on the width of the magnet 14 in the tangential direction of the rotor 10, the thickness of the magnet 14 in the radial direction of the rotor 10, the length of the magnet 14 in the axial direction of the rotor 10, and the position of the magnet 14 in the radial direction of the rotor 10, and therefore the maximum value of the reluctance torque also varies. Therefore, in the second embodiment, the maximum lengths L1a and L1b of the first flux barrier 20, the maximum lengths L2a and L2b of the second flux barrier 22, the width of the magnet 14 in the tangential direction of the rotor 10, the thickness of the magnet 14 in the radial direction of the rotor 10, the length of the magnet 14 in the axial direction of the rotor 10, and the position of the magnet 14 in the radial direction of the rotor 10 are merely examples. Furthermore, the shapes and positions of the first step portion 50 and the second step portion 52 are also merely examples.

[0060] The above describes one embodiment of the technology of the present disclosure, but the present invention is not limited to the above, and it goes without saying that the present invention can be implemented in various modifications within the scope of the gist of the present disclosure.

[0061] The following are supplementary notes regarding the technology of the present disclosure. (Supplementary Note 1) A rotor (10) for a rotating electric machine, comprising: a rotor core (12); and a plurality of magnets (14) lined up in a rotational direction of the rotor and each embedded in the rotor core, the rotor core having a plurality of accommodating holes (18) that accommodate the plurality of magnets, a first flux barrier (20) that communicates with each accommodating hole is formed in the rotor core on the rear side in the rotational direction of the rotor relative to each accommodating hole, and a second flux barrier (22) that communicates with each accommodating hole is formed in the rotor core on the front side in the rotational direction of the rotor relative to each accommodating hole, and a cross-sectional area of ​​the first flux barrier is larger than a cross-sectional area of ​​the second flux barrier. (Supplementary Note 2) The rotor according to Supplementary Note 1, wherein the maximum length of the first flux barrier along the tangential direction of the rotor is L1a, and the maximum length of the second flux barrier along the tangential direction of the rotor is L2a, the following formula (1) holds: L1a>L2a (1). (Supplementary Note 3) The rotor according to Supplementary Note 2, wherein the maximum length of the first flux barrier along the radial direction of the rotor is L1b, and the maximum length of the second flux barrier along the radial direction of the rotor is L2b, the following formula (2) holds: L1b>L2b (2). (Supplementary Note 4) The rotor according to Supplementary Note 3, wherein the thickness of the accommodating hole along the radial direction of the rotor is T, the following formula (3) holds: L1b>T≧L2b (3). (Supplementary Note 5) The rotor according to any one of Supplementary Note 1 to Supplementary Note 4, wherein, when a line connecting a center between adjacent magnets among the plurality of magnets in a rotational direction of the rotor and a center of the rotor is defined as an inter-pole center line (Lc), a part of the first flux barrier intersects the inter-pole center line.(Supplementary Note 6) The rotor according to any one of Supplementary Notes 1 to 5, wherein the accommodating hole has an outer surface (18A) located radially outward of the rotor relative to the magnet, and an inner surface (18B) located radially inward of the rotor relative to the magnet, the first flux barrier has a first surface (20A) connected to the outer surface via a first bent portion (21A), the second flux barrier has a second surface (22B) connected to the inner surface via a second bent portion (23B), and the magnet is positioned with respect to the rotor core by a first corner portion (15A) of the magnet contacting the first bent portion and a second corner portion (15B) of the magnet contacting the second bent portion. (Supplementary Note 7) The rotor according to any one of Supplementary Notes 1 to 5, wherein the accommodating hole has an outer surface located radially outward of the rotor relative to the magnet, and an inner surface located radially inward of the rotor relative to the magnet, the first flux barrier has a first surface connected to the outer surface via a first step portion (50), the second flux barrier has a second surface connected to the inner surface via a second step portion (52), and the magnet is positioned relative to the rotor core by a first side surface (14A) of the magnet contacting the first step portion and a second side surface (14B) of the magnet contacting the second step portion.

Claims

1. A rotor (10) for a rotating electric machine, comprising: a rotor core (12); and a plurality of magnets (14) arranged in a rotational direction of the rotor and each embedded in the rotor core, wherein the rotor core has a plurality of accommodating holes (18) that respectively accommodate the plurality of magnets, a first flux barrier (20) that communicates with each accommodating hole is formed on the rear side of each accommodating hole in the rotor core in the rotational direction of the rotor, and a second flux barrier (22) that communicates with each accommodating hole is formed on the front side of each accommodating hole in the rotor core in the rotational direction of the rotor, wherein the cross-sectional area of ​​the first flux barrier is larger than the cross-sectional area of ​​the second flux barrier.

2. The rotor according to claim 1, wherein the following equation (1) holds: L1a>L2a... (1) where L1a is the maximum length of the first flux barrier along the tangential direction of the rotor, and L2a is the maximum length of the second flux barrier along the tangential direction of the rotor.

3. The rotor according to claim 2, wherein the following (2) holds: L1b>L2b... (2) when the maximum length of the first flux barrier along the radial direction of the rotor is L1b, and L2b is the maximum length of the second flux barrier along the radial direction of the rotor.

4. The rotor according to claim 3, wherein the following formula (3) holds: L1b>T≧L2b (3), where T is the thickness of the accommodation hole along the radial direction of the rotor.

5. A rotor as claimed in any one of claims 1 to 4, wherein, when a line connecting the centre of the rotor and the centre between adjacent magnets among the plurality of magnets in the rotational direction of the rotor is defined as an inter-pole centre line (Lc), a part of the first flux barrier intersects the inter-pole centre line.

6. A rotor as claimed in any one of claims 1 to 5, wherein the accommodating hole has an outer surface (18A) located radially outward of the rotor relative to the magnet, and an inner surface (18B) located radially inward of the rotor relative to the magnet, the first flux barrier has a first surface (20A) connected to the outer surface via a first bent portion (21A), the second flux barrier has a second surface (22B) connected to the inner surface via a second bent portion (23B), and the magnet is positioned relative to the rotor core by a first corner portion (15A) of the magnet contacting the first bent portion and a second corner portion (15B) of the magnet contacting the second bent portion.

7. A rotor as claimed in any one of claims 1 to 5, wherein the accommodating hole has an outer surface located radially outward of the rotor relative to the magnet, and an inner surface located radially inward of the rotor relative to the magnet, the first flux barrier has a first surface connected to the outer surface via a first step portion (50), the second flux barrier has a second surface connected to the inner surface via a second step portion (52), and the magnet is positioned relative to the rotor core by a first side surface (14A) of the magnet contacting the first step portion and a second side surface (14B) of the magnet contacting the second step portion.

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