Rotor for rotating electrical machine

Abstract

Disclosed is a rotating electric machine rotor including: a rotor core in which first magnet holes on the outer side in the radial direction and second magnet holes on the inner side in the radial direction are formed; first permanent magnets in the first magnet holes; and second permanent magnets in the second magnet holes. The rotor core includes: a first region on the outer side from the first magnet holes in the radial direction; a second region between the first magnet holes and the second magnet holes; a third region on the inner side from the second magnet holes in the radial direction; and bridge portions connecting the third region and the second region. When viewed in the axial direction, the separation distance of the second permanent magnets with respect to the first permanent magnets is smaller at a position on the side close to the bridge portions in the circumferential direction than at a position on the side far from the bridge portions in the circumferential direction along the sides of the second permanent magnets on the side facing the first permanent magnets. At least one of the plurality of bridge portions extends radially inwards from the radial direction inner side edge portions of the circumferential direction end portions of the second permanent magnets facing each other in the circumferential direction.

Description

[Technical Field]

[0001] The present disclosure relates to a rotor for a rotating electric machine. [Background technology]

[0002] A technique is known in which multiple permanent magnets are arranged in a two-layer structure on a rotor core. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-54659 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the case of such a two-layer structure (the same applies to three or more layers), if the bridge is made relatively thick to cope with the increased centrifugal force that accompanies the higher rotation speed of the rotating electrical machine, there is a problem that leakage flux through the bridge increases. Also, if the shape of the end of the magnet hole is enlarged by using a relatively large angle R, etc., in order to reduce stress concentration on the bridge, this is likely to be a factor in reducing reluctance torque.

[0005] Therefore, in one aspect, an object of the present disclosure is to enable a rotating electric machine to achieve high rotation speeds while reducing a decrease in reluctance torque and stress concentration on the bridge. [Means for solving the problem]

[0006] According to one aspect, a rotor core is provided with a first magnet hole on the radially outer side and a second magnet hole on the radially inner side; a first permanent magnet in the first magnet hole; a second permanent magnet in the second magnet hole; the rotor core includes a first portion radially outward of the first magnet hole, a second portion passing between the first magnet hole and the second magnet hole and extending on both circumferential sides to the outer peripheral surface of the rotor core, a third portion passing radially inward of the second magnet hole and extending on both circumferential sides to the outer peripheral surface of the rotor core, and a plurality of bridge portions connecting the third portion and the second portion radially inward of the outer peripheral surface of the rotor core, the second permanent magnets include second permanent magnets on the d-axis side located on or near the d-axis, a distance between the second permanent magnet on the d-axis side and the first permanent magnet is smaller, as viewed in the axial direction, at a position closer to at least one bridge portion of the plurality of bridge portions in the circumferential direction along an edge of the second permanent magnet on the d-axis side facing the first permanent magnet than at a position farther from the at least one bridge portion in the circumferential direction; The rotor for a rotating electric machine is provided, wherein the at least one bridge portion extends radially inward beyond a radially inner edge portion of a circumferential end portion of the second permanent magnet on the d-axis side that faces the bridge portion in the circumferential direction. [Effects of the Invention]

[0007] According to one aspect, the present disclosure enables a rotary electric machine to achieve high rotation speed while reducing a decrease in reluctance torque and stress concentration on a bridge. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view schematically showing a cross-sectional structure of a motor according to an embodiment. [Figure 2] 1 is a cross-sectional view of a rotor (a cross-sectional view taken along a plane perpendicular to the axial direction). [Figure 3] FIG. 3 is an enlarged view of a portion relating to one magnetic pole shown in FIG. [Figure 4] FIG. 4 is a further enlarged view of a portion of FIG. 3, illustrating lines for explaining shape features. [Figure 5] 10A and 10B are diagrams illustrating some of the effects of the present embodiment in comparison with a comparative example. [Figure 6]FIG. 10 is an enlarged view of a portion relating to one magnetic pole according to another embodiment. [Figure 7] FIG. 10 is an enlarged view of a portion relating to one magnetic pole according to yet another embodiment. [Figure 8] FIG. 10 is an enlarged view of a portion relating to one magnetic pole according to yet another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Each embodiment will be described in detail below with reference to the accompanying drawings. Note that the dimensional ratios in the drawings are merely examples and are not intended to limit the scope of the invention. In addition, shapes and the like in the drawings may be partially exaggerated for the sake of explanation.

[0010] Fig. 1 is a cross-sectional view that schematically shows the cross-sectional structure of a motor 1 according to one embodiment. Fig. 2 is a cross-sectional view (a cross-sectional view taken along a plane perpendicular to the axial direction) of a rotor 30. Note that in Fig. 2 and other figures, for ease of viewing, reference symbols may be assigned only to some of the parts that exist with the same attribute.

[0011] 1 shows a rotating shaft 12 of a motor 1. In the following description, the axial direction refers to the direction in which the rotating shaft (center of rotation) 12 of the motor 1 extends, and the radial direction refers to the radial direction centered on the rotating shaft 12. Therefore, the radially outer side refers to the side away from the rotating shaft 12, and the radially inner side refers to the side toward the rotating shaft 12. Furthermore, the circumferential direction corresponds to the direction of rotation around the rotating shaft 12.

[0012] The motor 1 may be a motor for driving a vehicle, such as that used in a hybrid vehicle or an electric vehicle, but the motor 1 may also be used for any other purpose.

[0013] The motor 1 is an inner rotor type, and the stator 21 is provided so as to surround the radial outside of the rotor 30. The radial outside of the stator 21 is fixed to the motor housing 10. The stator 21 includes a stator core 211 made of, for example, annular laminated steel plates of a magnetic material, and a plurality of slots (not shown) are formed radially inside the stator core 211, around which the coils 22 are wound.

[0014] The rotor 30 is disposed radially inside the stator 21 .

[0015] The rotor 30 includes a rotor core 32, a rotor shaft 34, end plates 35A and 35B, and permanent magnets 61 and 62.

[0016] The rotor core 32 is fixed to the radially outer surface of the rotor shaft 34 and rotates integrally with the rotor shaft 34. The rotor core 32 has an axial hole 320 (see FIG. 2 ), into which the rotor shaft 34 is fitted. The rotor core 32 may be fixed to the rotor shaft 34 by shrink fitting, press fitting, or the like. For example, the rotor core 32 may be connected to the rotor shaft 34 by a key connection or a spline connection. The rotor shaft 34 is rotatably supported in the motor housing 10 via bearings 14 a and 14 b. The rotor shaft 34 defines the rotary axis 12 of the motor 1.

[0017] The rotor core 32 is formed, for example, from annular laminated steel plates of a magnetic material. Permanent magnets 61, 62 (see FIG. 2) are embedded inside the rotor core 32. That is, the rotor core 32 has magnet holes 321, 322 (see FIG. 2) that penetrate in the axial direction, and the permanent magnets 61, 62 are inserted into and fixed in the magnet holes 321, 322. In a modified example, the rotor core 32 may be formed from a green compact obtained by compressing and solidifying magnetic powder.

[0018] The rotor core 32 is designed to have a circular shape with a first radius r1, and the outer peripheral surface of the rotor core 32 includes portions having the first radius r1 (such as outer peripheral surface portion 328B and portion 328C, which will be described later). In this embodiment, the outer peripheral surface 328 of the rotor core 32 has the first radius r1. Note that in a modified example, the circular shape of the rotor core 32 does not need to be a perfect circle, and may be a circular shape with a partial notch, for example.

[0019] 2, rotor core 32 has a rotationally symmetric shape about rotation axis 12 when viewed in the axial direction. In the example shown in FIG. 2, rotor core 32 has a shape in which each pair of permanent magnets 61, 62 overlaps every 45 degrees of rotation about rotation axis 12.

[0020] The multiple permanent magnets 61, 62 may be made of neodymium or the like. In this embodiment, as an example, as shown in FIG. 2, the multiple permanent magnets 61, 62 are arranged in pairs when viewed in the axial direction. In this case, a common magnetic pole is formed between the pair of permanent magnets 61 and between the pair of permanent magnets 62. The multiple permanent magnets 61, 62 are arranged in a manner such that south poles and north poles appear alternately in the circumferential direction. In this embodiment, the number of magnetic poles is eight, but the number of magnetic poles is arbitrary. In this embodiment, the permanent magnets 61, 62 have the same linear shape when viewed in the axial direction, but may have different shapes. In addition, at least one of the permanent magnets 61, 62 may have an arc-shaped shape when viewed in the axial direction.

[0021] 1 shows the motor 1 having a specific structure, but the structure of the motor 1 is not limited to such a specific structure. For example, in FIG. 1, the rotor shaft 34 is hollow, but it may be solid.

[0022] Next, the rotor core 32 and the permanent magnets 61, 62 will be described in more detail with reference to Figure 3 and subsequent figures. Although the configuration relating to one magnetic pole will be described below, the configurations relating to the other magnetic poles may be similar.

[0023] Figure 3 is an enlarged view of a portion relating to one magnetic pole shown in Figure 2. The configuration relating to one magnetic pole is basically symmetrical with respect to the d-axis (denoted in English as "d-axis" in Figure 3). Hereinafter, the outer circumferential side refers to the side away from the d-axis, and the inner circumferential side refers to the side closer to the d-axis.

[0024] The rotor core 32 is formed with a radially outer magnet hole 321 (hereinafter referred to as a "first magnet hole 321") and a radially inner magnet hole 322 (hereinafter referred to as a "second magnet hole 322").

[0025] The first magnet holes 321 are formed in pairs in a generally V-shape (a generally V-shape that opens radially outward or radially inward). However, in a modified example, the first magnet holes 321 may be formed in pairs in a linear shape, or may be realized by a single linear hole (a linear shape perpendicular to the d-axis). A permanent magnet 61 is provided in each of the first magnet holes 321. A gap may be provided between the first magnet hole 321 and the permanent magnet 61 at both longitudinal ends of the permanent magnet 61. This gap may be hollow or may be filled with resin or the like.

[0026] The second magnet holes 322 are provided radially inward of the first magnet holes 321. Like the first magnet holes 321, the second magnet holes 322 are formed in pairs symmetrical with respect to the d-axis. The second magnet holes 322 on both sides of the d-axis in the circumferential direction extend over a wider range in the circumferential direction than the first magnet holes 321 on both sides of the d-axis in the circumferential direction. A permanent magnet 62 is provided in each of the second magnet holes 322. A gap may be provided between the second magnet holes 322 and the permanent magnet 62 at both longitudinal ends of the permanent magnet 62. This gap may be hollow or may be filled with resin or the like.

[0027] In this embodiment, two second magnet holes 322 are formed on one side of the d-axis in the circumferential direction and two are formed on the other side of the d-axis in the circumferential direction, i.e., a total of four second magnet holes 322 are formed for one magnetic pole.

[0028] By having such a first magnet hole 321 and a second magnet hole 322, the rotor core 32 has three parts 3211, 3212, and 3213 (hereinafter also referred to as the first part 3211, the second part 3212, and the third part 3213) that are connected radially only via bridge portions.

[0029] Specifically, first portion 3211 extends radially outward from first magnet hole 321. First portion 3211 forms part 328A of outer circumferential surface 328 of rotor core 32 (see FIG. 3).

[0030] The second portion 3212 passes between the second magnet hole 322 and the first magnet hole 321, and extends on both circumferential sides to the outer circumferential surface 328 of the rotor core 32. The second portion 3212 forms a part 328B of the outer circumferential surface 328 of the rotor core 32 (hereinafter also referred to as the "outer circumferential surface portion 328B of the second portion 3212") (see FIG. 3) on both circumferential sides of the first portion 3211. The second portion 3212 forms a magnetic path for the q-axis magnetic flux. Specifically, the q-axis magnetic flux flows between the second magnet hole 322 and the first magnet hole 321 from one end (the outer circumferential surface portion 328B on one side) of the second portion 3212 to the other end (the outer circumferential surface portion 328B on the other side).

[0031] The third portion 3213 passes radially inward of the second magnet hole 322 and extends on both circumferential sides to the outer peripheral surface 328 of the rotor core 32. The third portion 3213 forms a part 328C (see FIG. 3) of the outer peripheral surface 328 of the rotor core 32 on both circumferential sides of the second portion 3212.

[0032] In this embodiment, the mass of the third portion 3213 is significantly greater than the mass of the second portion 3212, and the mass of the second portion 3212 is significantly greater than the mass of the first portion 3211.

[0033] Furthermore, the rotor core 32 has these three portions 3211, 3212, and 3213, and thus has a plurality of bridge portions 41, 42, 43, 44, and 45 connecting the three portions 3211, 3212, and 3213.

[0034] The bridge portion 41 (hereinafter referred to as the "first bridge portion 41") supports the first portion 3211 radially outward relative to the second portion 3212. That is, the first bridge portion 41 connects the second portion 3212 and the first portion 3211 and extends in the circumferential direction. The first bridge portions 41 are provided in pairs on both circumferential sides (circumferential outer sides) of the first portion 3211.

[0035] The bridge portion 42 (hereinafter referred to as the "second bridge portion 42") supports the second portion 3212 radially outward relative to the third portion 3213. That is, the second bridge portion 42 connects the third portion 3213 and the second portion 3212 and extends in the circumferential direction. The second bridge portions 42 are provided in pairs on both circumferential sides (circumferential outer sides) of the second portion 3212.

[0036] The bridge portion 43 (hereinafter referred to as the "first center bridge portion 43") supports the first portion 3211 relative to the second portion 3212 on the d axis.

[0037] The bridge portion 44 (hereinafter referred to as the "second center bridge portion 44") supports the second portion 3212 relative to the third portion 3213 on the d axis.

[0038] The bridge portion 45 (hereinafter referred to as the “second intermediate bridge portion 45”) supports the second portion 3212 relative to the third portion 3213 between the two second magnet holes 322.

[0039] Next, the characteristic configuration of this embodiment will be described with reference to Figures 4 and beyond. Figure 4 is a further enlarged view of a portion of Figure 3, illustrating lines for explaining shape features. Figure 5 is a diagram illustrating some of the effects of this embodiment in comparison with a comparative example. In Figure 5, the comparative example is shown on the right and this embodiment is shown on the left, with the flow of q-axis magnetic flux in each shown schematically by arrows R5 and R5'. In the following description of Figures 4 and 5, unless otherwise specified, the second magnet hole 322 and permanent magnet 62 refer to the second magnet hole 322 and permanent magnet 62 on the circumferentially inner side of the second magnet hole 322 and permanent magnet 62 on the circumferentially outer side and the circumferentially inner side.

[0040] In this embodiment, as shown in FIG. 4 , the distance d between the permanent magnet 62 and the permanent magnet 61 is smaller at a circumferential position closer to the second center bridge portion 44 than at a circumferential position farther from the second center bridge portion 44, as viewed in the axial direction, along the side 624 of the permanent magnet 62 that faces the permanent magnet 61. That is, the distance d between the permanent magnet 62 and the permanent magnet 61 is smaller at a circumferentially inner position than at a circumferentially outer position. In FIG. 4 , for ease of distinction, the distance d between the permanent magnet 62 and the permanent magnet 61 is illustrated as d(1) at the circumferentially inner position of the permanent magnet 62 and as d(2) at the circumferentially outer position of the permanent magnet 62. Note that the distance d may be the distance perpendicular to the side 624 of the permanent magnet 62 that faces the permanent magnet 61, as viewed in the axial direction. Here, the separation distance d between the permanent magnets 62 and 61 is the separation distance in a plane perpendicular to the axial direction (i.e., the separation distance in a plane including the paper surface of FIG. 4), and corresponds to the width (magnetic path width) of the second portion 3212. Such a magnitude relationship of the separation distance d is likely to occur when α1<α2, where α1 and α2 are the angles formed by the extension directions of the permanent magnets 61 and 62 with respect to the d axis. Particularly in this embodiment, α1<α2, and α2 is significantly greater than 90 degrees.

[0041] In this case, the permanent magnets 62 in the two adjacent second magnet holes 322 that sandwich the second center bridge portion 44 in the circumferential direction may be arranged so that the side closer to the d-axis in the circumferential direction is located radially outward relative to the side farther from the d-axis. That is, the permanent magnets 62 in the two adjacent second magnet holes 322 that sandwich the second center bridge portion 44 in the circumferential direction may be arranged so that they convex outward in the radial direction. In this case, the volume of the second portion 3212 can be relatively reduced without significantly narrowing the width (magnetic path width) of the second portion 3212 compared to when the permanent magnets 62 are arranged so that they convex inward in the radial direction. As a result, the stress (tensile stress in the radial outward direction) acting on the second center bridge portion 44 and the second intermediate bridge portion 45 due to the centrifugal force generated during rotation of the rotor 30 can be reduced.

[0042] In this embodiment, the second center bridge portions 44 extend radially inward beyond the radially inner edge portions 6211 of the circumferential ends 621 of the circumferentially opposing permanent magnets 62. In other words, when a line segment L2 connecting the radially inner (and circumferentially inner) vertices of two adjacent permanent magnets 62 across the d-axis in the circumferential direction is used as a reference, the second center bridge portions 44 extend radially inward beyond the line segment L2. On the other hand, the second center bridge portions 44 do not extend radially outward beyond the radially outer edge portions 6212 of the circumferential ends 621 of the circumferentially opposing permanent magnets 62. In other words, when a line segment L1 connecting the radially outer (and circumferentially inner) vertices of two adjacent permanent magnets 62 across the d-axis in the circumferential direction is used as a reference, the second center bridge portions 44 do not extend radially outward beyond the line segment L1.

[0043] As described above, in this embodiment, the radial length of the second center bridge portion 44 is significantly longer than the radial width d0 of the permanent magnet 62, and extends radially inward beyond the circumferential end 621 of the permanent magnet 62. In this case, the radii R1 and R2 on both radial sides of the second center bridge portion 44 can be made relatively large, effectively reducing stress concentration (stress concentration due to centrifugal force) at both radial ends of the second center bridge portion 44. In other words, it is possible to reduce the width d1 of the second center bridge portion 44 (and reduce leakage magnetic flux through the second center bridge portion 44) without increasing the stress at both radial ends of the second center bridge portion 44.

[0044] Furthermore, in this embodiment, the second center bridge portion 44' extends radially inward beyond the line segment L2 to increase its radial length. This reduces the disadvantages that tend to occur in a comparative example (see the rotor core 32' in FIG. 5) in which the second center bridge portion 44' extends radially outward beyond the line segment L1 (see FIG. 4) to increase its radial length. Specifically, in the comparative example shown in FIG. 5 in which the second center bridge portion 44' extends radially outward beyond the line segment L1 (see FIG. 4), the width (magnetic path width) of the second portion 3212' is correspondingly smaller. This is because the radial outward extension of the second center bridge portion 44' is accompanied by the radial outward extension of the second magnet hole 322' circumferentially outside it. In this case, the reduced width (magnetic path width) of the second portion 3212' results in a reduction in reluctance torque. In contrast to this, according to the present embodiment, as described above, the radial length of the second center bridge portion 44 is increased without extending the second center bridge portion 44 radially outward from the line segment L1, so that the width (magnetic path width) of the second portion 3212 is not reduced due to the second center bridge portion 44.

[0045] Therefore, according to this embodiment, by increasing the radial length of the second center bridge portion 44, stress concentration on the second center bridge portion 44 can be reduced (and as a result, the motor 1 can be rotated at higher speeds), while effectively preventing a decrease in reluctance torque (a reduction in the width of the second portion 3212) caused by an increase in the radial length of the second center bridge portion 44.

[0046] In this embodiment, the second magnet hole 322 has a first overhang portion 3221 at its end (hereinafter simply referred to as the "circumferential inner end 322-1") that is closer to the second center bridge portion 44 in the circumferential direction. The first overhang portion 3221 extends (overhangs) radially inward of the circumferential inner end 322-1 toward the permanent magnet 62 in the circumferential direction. In this case, the first overhang portion 3221 may overlap the permanent magnet 62 via a portion 3201 of the rotor core 32 when viewed radially. The first overhang portion 3221 is formed in a manner continuing from the radius R2, passes through the radius R3, and terminates at the radius R4 near the apex of the permanent magnet 62 on the radially inner side and circumferentially inner side. The first overhang portion 3221 has the function of reducing an increase in back electromotive force.

[0047] In this embodiment, the second magnet hole 322 has a second overhang portion 3222 at an end portion farther from the second center bridge portion 44 in the circumferential direction (hereinafter simply referred to as the "circumferential outer end portion 322-2"). The second overhang portion 3222 extends (overhangs) radially outward from the circumferential outer end portion 322-2 toward the permanent magnet 62 in the circumferential direction. In this case, the second overhang portion 3222 may overlap the permanent magnet 62 via a portion 3202 of the rotor core 32 when viewed in the radial direction. In this manner, the second overhang portion 3222 may be formed in the common second magnet hole 322 at a position diagonal to the first overhang portion 3221. In this case, the second overhang portion 3222 adds a function (a function of reducing an increase in counter electromotive force) and can effectively reduce an increase in counter electromotive force.

[0048] Note that the second overhang portion 3222 expands the second magnet hole 322 toward the second portion 3212 (i.e., extends the second intermediate bridge portion 45 radially outward beyond the permanent magnet 62), which may reduce the width (magnetic path width) of the second portion 3212 depending on its shape, etc. Therefore, the second overhang portion 3222 is preferably formed in a manner that does not significantly reduce the width (magnetic path width) of the second portion 3212. In particular, in this embodiment, as described above, the separation distance d between the permanent magnet 62 and the permanent magnet 61 is greater at the circumferential outer position of the permanent magnet 62 than at the circumferential inner position of the permanent magnet 62. Therefore, by forming the second overhang portion 3222 at the circumferential outer position of the permanent magnet 62, rather than at the circumferential inner position of the permanent magnet 62, it is easy to ensure the necessary width (magnetic path width) of the second portion 3212.

[0049] In this embodiment, the second magnet hole 322 on the circumferential outer side also has an overhang portion 3223 in a manner that faces the second overhang portion 3222 in the circumferential direction. In this case, the overhang portion 3223 provides an additional function (a function of reducing an increase in counter electromotive force), and the increase in counter electromotive force can be effectively reduced.

[0050] Next, some other embodiments will be described with reference to FIG. 6 and subsequent figures.

[0051] 6 is an enlarged view of a portion relating to one magnetic pole according to another embodiment. In the following description of FIG. 6, unless otherwise specified, the second magnet hole 322A and the permanent magnet 62 refer to the second magnet hole 322A and the permanent magnet 62 on the inner side in the circumferential direction.

[0052] The rotor core 32A according to this embodiment differs from the rotor core 32 according to the above-described embodiment mainly in that the second magnet holes 322 are replaced with second magnet holes 322A. The main difference between the second magnet holes 322A and the second magnet holes 322A is the orientation (angle α2) relative to the second magnet holes 322, and therefore the orientation of the permanent magnets 62 in the second magnet holes 322A differs from that of the above-described embodiment.

[0053] Specifically, in this embodiment, the distance d between the permanent magnet 62 and the permanent magnet 61 is smaller at a circumferential position closer to the second intermediate bridge portion 45A than at a circumferential position farther from the second intermediate bridge portion 45A. That is, the distance d between the permanent magnet 62 and the permanent magnet 61 is larger at a circumferentially inner position than at a circumferentially outer position. This relationship in magnitude of the distance d is likely to occur when α1>α2, where α1 and α2 are the angles formed by the extension directions of the permanent magnets 61 and 62 with respect to the d axis. In particular, in this embodiment, α1>α2 and α2 is 90 degrees or less (or slightly greater than 90 degrees).

[0054] In this embodiment, the second intermediate bridge portion 45A extends radially inward beyond the radially inner edge portions 6221 of the circumferential end portions 622 of the circumferentially opposing permanent magnets 62. In other words, when a line segment L4 connecting the radially inner vertices of two permanent magnets 62 on one circumferential side with respect to the d-axis (and on sides that face each other in the circumferential direction) is used as a reference, the second intermediate bridge portion 45A extends radially inward beyond the line segment L4. On the other hand, the second intermediate bridge portion 45A does not extend radially outward beyond the radially outer edge portions 6221 of the circumferential end portions 622 of the circumferentially opposing permanent magnets 62. In other words, when a line segment L3 connecting the radially outer vertices of two permanent magnets 62 on one circumferential side with respect to the d-axis (and on sides that face each other in the circumferential direction) is used as a reference, the second intermediate bridge portion 45A does not extend radially outward beyond the line segment L3.

[0055] As described above, in this embodiment, the radial length of the second intermediate bridge portion 45A is significantly longer than the radial width d0 of the permanent magnet 62, and extends radially inward beyond the permanent magnet 62. In this case, the radii R11 and R12 of the radially opposite corners of the second intermediate bridge portion 45A can be made relatively large, effectively reducing stress concentration (stress concentration due to centrifugal force) at both radial ends of the second intermediate bridge portion 45A. In other words, the width d10 of the second intermediate bridge portion 45A can be reduced (and leakage magnetic flux through the second intermediate bridge portion 45A can be reduced) without increasing stress at both radial ends of the second intermediate bridge portion 45A.

[0056] Furthermore, in this embodiment, the second intermediate bridge portion 45A is extended radially inward beyond the line segment L4, thereby increasing the radial length of the second intermediate bridge portion 45A. This reduces the inconvenience that would otherwise occur if the second intermediate bridge portion 45A were extended radially outward beyond the line segment L3 (not shown). Specifically, as can be seen from the above-described description shown in FIG. 6 , when the second intermediate bridge portion 45A extends radially outward beyond the line segment L3, the width (magnetic path width) of the second portion 3212A is correspondingly reduced. In this case, the reduced width (magnetic path width) of the second portion 3212A results in a reduction in reluctance torque. In contrast, according to this embodiment, as described above, the second intermediate bridge portion 45A is extended radially inward beyond the line segment L4 without extending radially outward beyond the line segment L3. Therefore, the width (magnetic path width) of the second portion 3212A is not reduced due to the second intermediate bridge portion 45A.

[0057] Therefore, according to this embodiment, by increasing the radial length of the second intermediate bridge portion 45A, stress concentration on the second intermediate bridge portion 45A can be reduced (and as a result, the motor 1 can be rotated at higher speeds), while effectively preventing a decrease in reluctance torque (reduction in the width of the second portion 3212A) caused by an increase in the radial length of the second intermediate bridge portion 45A.

[0058] In this embodiment, the second magnet hole 322A has a first overhang portion 3221A at its end (hereinafter simply referred to as the "circumferential outer end portion 322-3") closer to the second intermediate bridge portion 45A in the circumferential direction. The first overhang portion 3221A extends (overhangs) radially inward of the circumferential outer end portion 322 toward the permanent magnet 62 in the circumferential direction. In this case, the first overhang portion 3221A may overlap the permanent magnet 62 via a portion 3201A of the rotor core 32 when viewed radially. The first overhang portion 3221A is formed in a manner continuing from a radius R12, passes through a radius R13, and terminates at a radius R14 near the apex of the permanent magnet 62 on the radially inner side and circumferentially inner side. The first overhang portion 3221A has the function of reducing an increase in back electromotive force.

[0059] In this embodiment, the second magnet hole 322A has a second overhang portion 3222A at an end portion farther from the second intermediate bridge portion 45A in the circumferential direction (hereinafter also simply referred to as the "circumferential inner end portion 322-4"). The second overhang portion 3222A extends (overhangs) radially outward from the circumferential inner end portion 322-4 toward the permanent magnet 62 in the circumferential direction. In this case, the second overhang portion 3222A may overlap the permanent magnet 62 via a portion 3202A of the rotor core 32 when viewed in the radial direction. In this manner, the second overhang portion 3222A may be formed in the common second magnet hole 322A at a position diagonal to the first overhang portion 3221. In this case, the second overhang portion 3222A adds a function (a function of reducing an increase in counter electromotive force) to effectively reduce an increase in counter electromotive force.

[0060] Note that the second overhang portion 3222A enlarges the second magnet hole 322A toward the second portion 3212A (because the second center bridge portion 44 extends radially outward from the permanent magnet 62), which may reduce the width (magnetic path width) of the second portion 3212A depending on its shape. Therefore, the second overhang portion 3222A is preferably formed in a manner that does not significantly reduce the width (magnetic path width) of the second portion 3212A. In particular, in this embodiment, as described above, the separation distance d between the permanent magnet 62 and the permanent magnet 61 is greater at a position circumferentially inner of the permanent magnet 62 than at a position circumferentially outer of the permanent magnet 62. Therefore, by forming the second overhang portion 3222A at a position circumferentially inner of the permanent magnet 62 rather than at a position circumferentially outer of the permanent magnet 62, it is easy to ensure the required width (magnetic path width) of the second portion 3212A.

[0061] In this embodiment, the second magnet hole 322A on the outer side in the circumferential direction also has an overhang portion 3223A in a manner facing the first overhang portion 3221A in the circumferential direction. In this case, the function of the overhang portion 3223A (the function of reducing an increase in the counter electromotive force) is added, and the increase in the counter electromotive force can be effectively reduced.

[0062] This embodiment also provides the same effects as the above-described embodiment.

[0063] FIG. 7 is an enlarged view of a portion relating to one magnetic pole according to yet another embodiment.

[0064] The rotor core 32B of this embodiment differs from the rotor core 32 of the above-described embodiment mainly in that the circumferentially inner second magnet hole 322 is replaced by a single second magnet hole 322B (hereinafter also referred to as the "central second magnet hole 322B" to distinguish it from the radially outer second magnet hole 322B).As a result, the orientation of the permanent magnet 62B in the central second magnet hole 322B is different from that of the above-described embodiment.

[0065] Specifically, in this embodiment, the distance d between the permanent magnet 62B and the permanent magnet 61 is smaller at a circumferential position closer to the second intermediate bridge portion 45B than at a circumferential position farther from the second intermediate bridge portion 45B (for example, a circumferential position on the d-axis). That is, the distance d between the permanent magnet 62B and the permanent magnet 61 is larger at a circumferentially inner position than at a circumferentially outer position. This relationship in magnitude of the distance d is likely to occur when α1>α2, where α1 and α2 are the angles formed by the extension directions of the permanent magnets 61 and 62B with respect to the d-axis. In particular, in this embodiment, α1>α2 and α2 is equal to or smaller than 90 degrees (or slightly larger than 90 degrees).

[0066] Therefore, in this embodiment, as in the embodiment described above with reference to Figure 6, the second intermediate bridge portion 45B extends radially inward beyond the radially inner edge portion 6221B at the circumferential end portion 622B of the permanent magnet 62B that faces it in the circumferential direction.

[0067] In this embodiment, similarly to the embodiment described above with reference to FIG. 6, a first overhang portion 3221B corresponding to the first overhang portion 3221 and an overhang portion 3223B corresponding to the overhang portion 3223A may be provided.

[0068] This embodiment also achieves the same effects as the above-described embodiments. In the example shown in Fig. 7, one permanent magnet 62B is provided in the central second magnet hole 322B, but instead of one permanent magnet 62B, two or more permanent magnets may be provided lined up in the circumferential direction.

[0069] FIG. 8 is an enlarged view of a portion relating to one magnetic pole according to yet another embodiment.

[0070] The rotor core 32C according to this embodiment differs from the rotor core 32 according to the above-described embodiment in that the second magnet hole 322 on the circumferentially inner side is replaced with a second magnet hole 322C. The second magnet hole 322C differs in that the above-described second overhang portion 3222 is replaced with a second overhang portion 3222C. The arrangement of the second overhang portion 3222C differs from that of the above-described second overhang portion 3222.

[0071] Specifically, the second magnet hole 322C has a second overhang portion 3222C at its end (circumferential outer end) farther from the second center bridge portion 44 in the circumferential direction. The second overhang portion 3222C extends (overhangs) radially inward of the circumferential outer end toward the permanent magnet 62 in the circumferential direction. In this case, the second overhang portion 3222 may overlap the permanent magnet 62 via a portion 3202C of the rotor core 32 when viewed in the radial direction. In this manner, the second overhang portion 3222C may be formed in the second magnet hole 322C on the same radially inner side as the first overhang portion 3221. In this case, the second overhang portion 3222C adds a function (the function of reducing an increase in counter electromotive force) and can effectively reduce an increase in counter electromotive force.

[0072] This embodiment also achieves the same effects as the above-described embodiment. However, in this embodiment, the second overhang portion 3222C is formed radially inward of the second magnet hole 322C in the second intermediate bridge portion 45C, which can be advantageous in that it has no effect on the width (magnetic path width) of the second portion 3212C. However, the second overhang portion 3222C, together with the first overhang portion 3221, can be disadvantageous in that it can obstruct the magnetic path via the third portion 3213C. In other words, in the rotor core 32 according to the above-described embodiment (see FIG. 3), the second overhang portion 3222 is disposed diagonally with respect to the first overhang portion 3221, which can be advantageous in that it does not excessively restrict the magnetic flux emitted from the permanent magnet 62.

[0073] Although each embodiment has been described in detail above, it is not limited to the specific embodiment, and various modifications and changes are possible within the scope of the claims. It is also possible to combine all or a plurality of components of the above-described embodiments. [Explanation of symbols]

[0074] 1····motor (rotating electric machine), 30···rotor, 32, 32A, 32B, 32C···rotor core, 328···outer circumferential surface, 3211···first portion, 3212, 3212A, 3212C···second portion, 3213···third portion, 44···second center bridge portion (at least one bridge portion, center bridge portion), 45A, 45B···second intermediate bridge portion (at least one bridge portion, intermediate bridge portion), 321···first magnet hole, 61 ···Permanent magnet (first permanent magnet), 62···Permanent magnet (second permanent magnet), 322, 322A, 322B, 322C···Second magnet hole, 322-1···Circumferentially inner end (first end), 322-2···Circumferentially outer end (second end), 322-3···Circumferentially outer end (first end), 322-4···Circumferentially inner end (second end), 3221, 3221A···First overhang portion, 3222, 3222A, 3222C···Second overhang portion

Claims

1. a rotor core in which a first magnet hole on the radially outer side and a second magnet hole on the radially inner side are formed; a first permanent magnet in the first magnet hole; a second permanent magnet in the second magnet hole; the rotor core includes a first portion radially outward of the first magnet hole, a second portion passing between the first magnet hole and the second magnet hole and extending on both circumferential sides to the outer peripheral surface of the rotor core, a third portion passing radially inward of the second magnet hole and extending on both circumferential sides to the outer peripheral surface of the rotor core, and a plurality of bridge portions connecting the third portion and the second portion radially inward of the outer peripheral surface of the rotor core, the second permanent magnets include a second permanent magnet on the d-axis side located in the vicinity of the d-axis, the second permanent magnet on the d-axis side located in the vicinity of the d-axis is arranged in such a direction that the side closer to the d-axis in the circumferential direction is positioned radially outward relative to the side farther from the d-axis, a distance between the second permanent magnet on the d-axis side and the first permanent magnet is smaller, as viewed in the axial direction, at a position closer to at least one bridge portion of the plurality of bridge portions in the circumferential direction along an edge of the second permanent magnet on the d-axis side facing the first permanent magnet than at a position farther from the at least one bridge portion in the circumferential direction; The rotor for a rotating electric machine, wherein the at least one bridge portion extends radially inward beyond a radially inner edge portion of a circumferential end portion of the second permanent magnet on the d-axis side opposite in the circumferential direction.

2. 2. The rotor for a rotating electric machine according to claim 1, wherein, for a pair of second permanent magnets in two adjacent second magnet holes that are circumferentially sandwiched between the at least one bridge portion, when a line segment connecting vertices of the pair of second permanent magnets that are radially inward and circumferentially opposite each other is used as a reference, the at least one bridge portion terminates radially inward of the line segment.

3. The second magnet holes and the second magnet holes are provided two by two for each magnetic pole, on each side in the circumferential direction around the d axis, the plurality of bridge portions include a center bridge portion extending in a radial direction passing through the d axis, and an intermediate bridge portion extending at a position spaced apart in a circumferential direction with respect to the d axis, 2. The rotor for a rotating electric machine according to claim 1, wherein the at least one bridge portion is the center bridge portion or the intermediate bridge portion.

4. the at least one bridge portion is the center bridge portion, The rotor for a rotating electric machine according to claim 3 , wherein the second magnet holes and the second permanent magnets are configured symmetrically with respect to a d-axis.

5. A rotor for a rotating electric machine as described in claim 4, wherein the second permanent magnets in the two adjacent second magnet holes circumferentially sandwiching the center bridge portion are each arranged in an orientation such that the side closer to the d-axis in the circumferential direction is positioned radially outward than the side farther from the d-axis.

6. the second magnet hole circumferentially adjacent to the center bridge portion has a first overhang portion at a first end portion on a side closer to the center bridge portion in the circumferential direction, 6. The rotor for a rotating electric machine according to claim 4 or 5, wherein the first overhang portion extends circumferentially radially inward of the first end toward the second permanent magnet in the second magnet hole, and overlaps the second permanent magnet in the second magnet hole when viewed radially.

7. the second magnet hole circumferentially adjacent to the center bridge portion has a second overhang portion at a second end portion on a side farther from the center bridge portion in the circumferential direction, 7. The rotor for a rotating electric machine according to claim 6, wherein the second overhang portion extends circumferentially radially outside the second end toward the second permanent magnet in the second magnet hole and overlaps the second permanent magnet in the second magnet hole when viewed radially.

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