Rotor and motor

Abstract

To provide a rotor and a motor which can secure centrifugal force resistant performance, while suppressing reduction of total torque.SOLUTION: A rotor 30 has a rotor core 20 and a magnetic pole part 10 with one or more pole pairs. The magnetic pole part 10 has a first magnetic pole 21, a second magnetic pole 22, a first bond magnet 31, a second bond magnet 32, a first magnetic path 41, a second magnetic path 42, a third magnetic path 43, a first rib 44, a center rib 45A, a first peripheral rib 45B, and a second peripheral rib 45C. Widths W2 of the center rib 45A, the first peripheral rib 45B, and the second peripheral rib 45C are wider than a width W1 of the first rib 44 and are equal to each other.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a rotor and a motor.

Background Art

[0002] The rotor described in Patent Document 1 includes a cylindrical rotor core, a plurality of magnet rows formed for each magnetic pole, and ribs. Each of the plurality of magnet rows is formed in an arc shape with the same center point that opens toward the outside in the radial direction of the rotor core, and has a plurality of bonded magnets. The ribs are arranged between adjacent bonded magnets in each of the plurality of magnet rows.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The ribs described in Patent Document 1 relieve the stress against the centrifugal force when the rotor rotates, and suppress the breakage of the rotor. By providing the ribs, the strength of the rotor is improved, but the magnetic flux entering the rotor from the outside flows into the ribs. Therefore, the magnetic flux contributing to the reluctance torque decreases, and the reluctance torque decreases. As a result, the efficiency of the motor to which the rotor is applied decreases.

[0005] The present disclosure provides a rotor and a motor capable of ensuring the centrifugal force resistance performance while suppressing the decrease in the total torque.

Means for Solving the Problems

[0006] The rotor (30) of this disclosure has a rotor core (20) and a magnetic pole portion (10) consisting of one or more pole pairs of bonded magnets (31, 32). The rotor core (20) is formed in a cylindrical shape extending along the axis of rotation. The bonded magnets (31, 32) are embedded in the rotor core (20). The magnetic pole portion (10) includes a first magnet hole (21), a second magnet hole (22), a first bonded magnet (31), a second bonded magnet (32), a first magnetic path (41), a second magnetic path (42), a third magnetic path (43), a first rib (44), and three second ribs (45A, 45B, 45C). The first magnet hole (21) is formed in an arc shape that opens radially outward from the rotor core (20) when viewed axially from the rotation axis, and a first bonded magnet is embedded in it as a bonded magnet. The second magnet hole (22) is provided radially inward from the first magnet hole (22) when viewed axially, and is formed in an arc shape that opens radially outward, and a second bonded magnet is embedded in it as a bonded magnet. The first magnetic path (41) is provided radially outward from the first magnet hole (21). The second magnetic path (42) is provided radially inward from the first magnet hole (21) and radially outward from the second magnet hole (22). The third magnetic path (43) is provided radially inward from the second magnet hole (22). The first rib (44) extends along the radially extending magnetic pole centerline (L0), connecting the first magnetic path (41) and the second magnetic path (42), and dividing the first magnet hole (21) into two (21A, 21B) along the circumferential direction of the rotor core (20). The three second ribs (45A, 45B, 45C) connect the second magnetic path (42) and the third magnetic path (43), and divide the second magnet hole (22) into four (22A, 22B, 22C, 22D) along the circumferential direction. The three second ribs (45A, 45B, 45C) include the central rib (45A), the first peripheral rib (45B), and the second peripheral rib (45C). The central rib (45A) extends along the magnetic pole centerline (L0) at the circumferential center of the second magnet hole (22). The first peripheral rib (45B) and the second peripheral rib (45C) are provided on both sides of the central rib (45A) in the circumferential direction. The widths (W2) of the central rib (45A), the first peripheral rib (45B), and the second peripheral rib (45C) are wider than and equal to the width (W1) of the first rib (44).

[0007] When the rotor rotates, centrifugal force acts on it. The second rib supports a larger mass than the first rib, and therefore the second rib must resist a greater centrifugal force than the first rib. When the stress generated in the first and second ribs exceeds the material limit (in other words, the yield point) of the first and second ribs, the first and second ribs undergo plastic deformation. In this disclosure, the width of the second rib, which experiences greater stress than the first rib, is made wider than the width of the first rib, and the number of second ribs is increased compared to the number of first ribs. As a result, the stress generated in the second rib decreases compared to before the width was increased and the number of ribs was increased, improving the strength of the rotor and improving centrifugal force resistance. In addition, since the width of the first rib, which experiences less stress than the second rib, is narrower than the width of the second rib, the magnetic flux flowing to the first rib is suppressed, and the decrease in reluctance torque is suppressed. Furthermore, because the widths of the central rib, the first peripheral rib, and the second peripheral rib are equal, the short circuit from the second magnetic path to the third magnetic path is more uniform compared to when any of them are different. This stabilizes the magnetic flux flow in the second magnetic path and further suppresses the decrease in reluctance torque. Therefore, it is possible to ensure centrifugal force resistance while suppressing the decrease in total torque.

[0008] Furthermore, since the rotor is equipped with bonded magnets as permanent magnets, the generation of eddy currents, which have a significant impact during high-speed rotation, is suppressed, thus also providing the effect of suppressing the deterioration of efficiency during high-speed rotation. [Brief explanation of the drawing]

[0009] [Figure 1] This is a vertical cross-sectional view of the motor according to this embodiment. [Figure 2] This is a vertical cross-sectional view of one magnetic pole of the motor according to this embodiment. [Figure 3] This figure shows the shapes of the first and second bond magnets of the rotor according to this embodiment. [Figure 4] This figure shows the shapes of the first and second bond magnets of the rotor according to this embodiment. [Figure 5] This is a vertical cross-sectional view of one magnetic pole of the motor relating to the first reference example. [Figure 6] This is a vertical cross-sectional view of one magnetic pole of the motor relating to the second reference example. [Figure 7] This figure shows a comparison of magnet torque and reluctance torque according to this embodiment, the first reference example, and the second reference example. [Figure 8] This is a vertical cross-sectional view of one magnetic pole of the rotor according to the second embodiment. [Figure 9] This figure shows the stress distribution in the rotor according to the second embodiment. [Figure 10] This figure shows the stress distribution in the rotor according to the third reference example. [Figure 11] This figure shows the stress distribution in the rotor according to the fourth reference example. [Figure 12] This figure shows the maximum stress values ​​for the second embodiment, the third reference example, and the fourth reference example. [Modes for carrying out the invention]

[0010] (First Embodiment) Hereinafter, exemplary embodiments of the rotor and motor of this disclosure will be described with reference to the drawings. <1-1. Overall Structure> Figure 1 is a vertical cross-sectional view of the motor 100 according to this embodiment, cut in a section perpendicular to the axis of rotation. The motor 100 comprises a rotor 30 and a stator 80. The stator 80 comprises a plurality of teeth 81 and coils 82 wound around the plurality of teeth 81, and is positioned on the outside of the rotor 30.

[0011] The rotor 30 is an embedded magnet type (IPM) and comprises a rotor core 20 and a plurality of magnetic pole portions 10. The plurality of magnetic pole portions 10 are formed for each magnetic pole of the rotor core 20. In this embodiment, the rotor 30 comprises eight magnetic pole portions 10.

[0012] Figs. 2 to 4 are vertical cross-sectional views of one magnetic pole portion 10 of the rotor 30 according to the present embodiment. The magnetic pole portion 10 includes a first magnet hole 21, a second magnet hole 22, a first magnetic path 41, a second magnetic path 42, a bonded third magnetic path 43, a first rib 44, three second ribs 45A, 45B, 45C, a first magnet 31, and a second bonded magnet 32.

[0013] The first magnet hole 21 is formed in an arc shape that opens toward the outside in the radial direction of the rotor core 20 when viewed in the axial direction of the rotation axis of the rotor core 20. Hereinafter, the axial direction of the rotation axis of the rotor core 20 is referred to as the axial direction, the radial direction of the rotor core 20 is referred to as the radial direction, and the circumferential direction of the rotor core 20 is referred to as the circumferential direction.

[0014] The second magnet hole 22 is provided on the inner side in the radial direction than the first magnet hole 21 when viewed in the axial direction. The second magnet hole 22 is formed in an arc shape that opens toward the outside in the radial direction. The first magnetic path 41 is provided on the outer side in the radial direction than the first magnet hole 21. That is, the first magnetic path 41 is provided between the first magnet hole 21 and the outer peripheral edge 250 of the rotor core 20. The second magnetic path 42 is provided on the inner side in the radial direction than the first magnet hole 21 and on the outer side in the radial direction than the second magnet hole 22. The third magnetic path 43 is provided on the inner side in the radial direction than the second magnet hole 22.

[0015] The first rib 44 extends along the magnetic pole center line L0 and connects the first magnetic path 41 and the second magnetic path 42. The magnetic pole center line L0 is a meridian line drawn so as to pass through the center of the magnetic pole from the axis of the rotation axis. The first rib 44 divides the first magnet hole 21 into two third magnet holes 21A and 21B along the circumferential direction. The two third magnet holes 21A and 21B are arranged symmetrically with respect to the magnetic pole center line L0.

[0016] The three second ribs 45A, 45B, 45C connect the second magnetic path 42 and the third magnetic path 43, and divide the second magnet hole 22 into two fourth magnet holes 22A, 22B and two fifth magnet holes 22C, 22D along the circumferential direction. Hereinafter, the three second ribs 45A, 45B, 45C are collectively referred to as the second rib 45.

[0017] The second rib 45 includes a central rib 45A, a first peripheral rib 45B, and a second peripheral rib 45C. The central rib 45A extends along the magnetic pole centerline L0. The first peripheral rib 45B and the second peripheral rib 45C are provided on both sides of the central rib 45A. The first peripheral rib 45B and the second peripheral rib 45C are provided along the magnetic pole centerline L0 at equidistant distances from the magnetic pole centerline L0 in the circumferential direction. That is, the first peripheral rib 45B and the second peripheral rib 45C are arranged symmetrically with respect to the magnetic pole centerline L0.

[0018] The two fourth magnet holes 22A and 22B are arranged symmetrically with respect to the magnetic pole centerline L0 and are located between the first and second peripheral ribs 45B and 45C and the outer edge 250. The two fifth magnet holes 22C and 22D are arranged symmetrically with respect to the magnetic pole centerline L0 and are located between the first and second peripheral ribs 45B and 45C and the central rib 45A.

[0019] The first bonded magnet 31 and the second bonded magnet 32 ​​are formed from a material which is a mixture of magnetic powder and resin. The first bonded magnet 31 and the second bonded magnet 32 ​​are radially oriented toward the orientation center point Pc. The orientation center point Pc is located outside the first magnet hole 21 and on the magnetic pole center line L0. In this embodiment, the orientation center point Pc is located outside the outer peripheral edge 250 and on the magnetic pole center line L0.

[0020] In the pole section 10 shown in Figure 2, the magnetization vectors of the first and second bond magnets 31 and 32 are directed from the inside to the outside in the radial direction. In the pole section 10 adjacent to this pole section 10 (not shown), the magnetization vectors of the first and second bond magnets 31 and 32 are directed from the outside to the inside in the radial direction.

[0021] The first bonded magnet 31 includes two segmented magnets 31A and 31B. One of the two segmented magnets 31A and 31B is embedded in one of the third magnet holes 21A and 21B, and the other of the two segmented magnets 31A and 31B is embedded in the other of the third magnet holes 21A and 21B. Specifically, segmented magnet 31A is filled into the third magnet hole 21A without any gaps so as to be in contact with the inner circumferential surface of the third magnet hole 21A, and segmented magnet 31B is filled into the third magnet hole 21B without any gaps so as to be in contact with the inner circumferential surface of the third magnet hole 21B.

[0022] The second bonded magnet 32 ​​includes two peripheral magnets 32A and 32B and two central magnets 32C and 32D. One of the two peripheral magnets 32A and 32B is embedded in one of the two fourth magnet holes 22A and 22B, and the other peripheral magnet 32A and 32B is embedded in the other fourth magnet hole 22A and 22B. One of the two central magnets 32C and 32D is embedded in one of the two fifth magnet holes 22C and 22D, and the other central magnet 32C and 32D is embedded in the other fifth magnet hole 22C and 22D. Specifically, peripheral magnet 32A is filled into the fourth magnet hole 22A without any gaps so as to be in contact with the inner surface of the fourth magnet hole 22A, and peripheral magnet 32B is filled into the fourth magnet hole 22B without any gaps so as to be in contact with the inner surface of the fourth magnet hole 22B. The central magnet 32C is packed tightly into the fifth magnet hole 22C so as to be in contact with the inner surface of the fifth magnet hole 22C, and the central magnet 32D is packed tightly into the fifth magnet hole 32D so as to be in contact with the inner surface of the fifth magnet hole 32D.

[0023] The first rib 44 has a width W1, and the second rib 45 has a width W2. The width W2 of the second rib 45 is wider than the width W1 of the first rib 44. As the rotor 30 rotates, the rotor core 20 is subjected to centrifugal force. The first rib 44 connects the first magnetic path 41 and the second magnetic path 42, which is located radially inward of the first magnetic path 41. Therefore, stress is generated in the first rib 44 that resists the force that causes the first magnetic path 41 to displace radially outward due to centrifugal force.

[0024] The second rib 45 connects the second magnetic path 42 and the third magnetic path 43, which is located radially inward of the second magnetic path 42. Furthermore, the first magnetic path 41 is connected to the second magnetic path 42 via the first rib 44 as described above. Therefore, stress is generated in the second rib 45 that resists the force that causes the first magnetic path 41 and the second magnetic path 42 to be displaced radially outward due to centrifugal force.

[0025] The second rib 45 needs to withstand a greater centrifugal force than the first rib 44. For this reason, the number of second ribs 45 is set to three, which is more than the number of first ribs 44. In addition, the width W2 of the second rib 45 is set to be larger than the width W1 of the first rib 44.

[0026] Since the width W2 of the second rib 45 is wider than the width W1 of the first rib 44, the stress generated in the second rib 45 decreases compared to before the width W2 was increased. Therefore, the strength of the rotor 30 is improved, and the centrifugal force resistance performance is improved. On the other hand, if the width W1 of the first rib 44 and the width W2 of the second rib 45 are both increased, the amount of magnetic flux entering each rib from the stator 80 to the rotor 30 increases, and the amount of magnetic flux contributing to the reluctance torque Tr decreases. Therefore, by making the width W1 of the first rib 44 narrower than the width W2 of the second rib 45, the decrease in reluctance torque Tr can be suppressed.

[0027] Furthermore, the widths W2 of the central rib 45A, the first peripheral rib 45B, and the second peripheral rib 45C are equal. This configuration, compared to a case where wide and narrow ribs are mixed, results in a more uniform short circuit from the second magnetic path 42 to the third magnetic path 43. As a result, the magnetic flux flow in the second magnetic path 42 becomes more stable, and the decrease in reluctance torque Tr is further suppressed.

[0028] As shown in Figure 3, the second magnetic path 42 comprises a first outer edge 421 and a second outer edge 422. The first outer edge 421 is the radially outer edge of the second magnetic path 42. The second outer edge 422 is the radially inner edge of the second magnetic path 42. The first and second outer edges 421 and 422 are formed in arcs centered on the orientation center point Pc. That is, the width Wa of the second magnetic path 42 in the orientation direction (i.e., the magnetization direction) is constant. Therefore, the magnetic flux entering the rotor 30 from the stator 80 flows easily into the second magnetic path 42, making it easier to secure the reluctance torque Tr.

[0029] Furthermore, the width Wa of the second magnetic path 42 in the orientation direction is greater than the width Wt of the teeth 81. Therefore, the magnetic flux supplied from the teeth 81 flows easily into the second magnetic path 42, ensuring that the amount of magnetic flux flowing through the second magnetic path 42 is secured.

[0030] Furthermore, since the first outer edge 421 and the second outer edge 422 are centered on the orientation center point Pc, the magnetic flux generated from the first and second bonded magnets 31 and 32 is perpendicular to the second magnetic path 42. Therefore, the magnetic flux generated from the first and second bonded magnets 31 and 32 has a component along the magnetic pole center line L0 (the so-called d-axis component in the dq coordinate axis), making it easy to secure the magnet torque Tm.

[0031] Furthermore, the magnetic forces of the first and second bond magnets 31 and 32 are set so that magnetic saturation occurs in the first and second ribs 44 and 45. Therefore, the flow of magnetic flux from the first magnetic path 41 to the second magnetic path 42, and from the second magnetic path 42 to the third magnetic path 43 is suppressed. In other words, the magnetic resistance along the magnetic pole centerline L0 is increased, and the magnetic resistance along the magnetic pole boundary line LL (see Figure 3) is set to be small. As a result, the magnetic flux supplied from the stator 80 to the rotor 30 flows in from near the magnetic pole boundary line LL and out to the stator 80 from near the magnetic pole boundary line LL on the opposite side, making it easier to secure reluctance torque Tr.

[0032] In Figure 4, the dashed line drawn on the second magnet hole 22 represents a virtual arc concentric with the radially outer arc of the second magnet hole 22. The virtual arc is located radially inward of the radially outer arc of the second magnet hole 22 and passes through the end of the second magnet hole 22 on the outer edge 250 side (specifically, the third rounded corner portion 221b, which will be described later).

[0033] As shown in Figure 4, the width Wc of the second magnet hole 22 in the orientation direction expands radially inward as it approaches the magnetic pole centerline L0 from the outer edge 250. Since the width Wc of the second magnet hole 22 does not expand outward, the width Wa of the second magnetic path 42 is kept constant. In other words, by expanding the width Wc radially inward, the second bond magnet 32 ​​is increased while the width Wa remains constant.

[0034] Furthermore, since the width Wb of the third magnetic path 43 in the orientation direction is sufficiently larger on the side closer to the magnetic pole centerline L0 than on the side further from the magnetic pole centerline L0, even if the width Wc is expanded radially inward, the width Wb is maintained and the amount of magnetic flux flowing through the third magnetic path 43 is preserved. In other words, while ensuring the reluctance torque Tr, the magnet torque Tm increases by the amount of the increase in the second bond magnet 32.

[0035] More specifically, the radially inner outer edges of the fourth magnet holes 22A and 22B expand radially inward as they approach the magnetic pole centerline L0 from the outer edge 250. In other words, the orientation width Wc of the fourth magnet holes 22A and 22B expands radially inward as they approach the magnetic pole centerline L0 from the outer edge 250.

[0036] The radially inner outer edges of the fourth magnet holes 22A and 22B have first straight sections 220A and 220B and second straight sections 220C and 220D. The first straight sections 220A and 220B are formed as straight lines parallel to the magnetic pole boundary line LL. The magnetic pole boundary line LL is the boundary line between two adjacent magnetic pole sections 10 and is a straight line passing through the axis of the rotor core 20. The first straight sections 220A and 220B are formed as straight lines extending from the outer peripheral edge 250 side of the fourth magnet holes 22A and 22B (specifically, the third rounded corner section 221b). The second straight sections 220C and 220D are formed as straight lines extending from the first and second peripheral rib 45B and 45C side of the fourth magnet holes 22A and 22B. The first straight section 220A and the second straight section 220C are connected by a smooth curve. The first straight section 220B and the second straight section 220D are connected by a smooth curve.

[0037] The radially inner outer edges of the fifth magnet holes 22C and 22D are formed in an arc shape centered on the orientation center point Pc. That is, the width Wc in the orientation direction of the fifth magnet holes 22C and 22D is formed to be constant.

[0038] As shown in Figure 3, the third magnetic path 43 includes a third outer edge 431. The third outer edge 431 is the radially outer edge of the third magnetic path 43. The third outer edge 431 includes a first outer edge straight section 431aa, 431ab, a second outer edge straight section 431ba, 431bb, and an outer edge arc section 431c. Furthermore, the third magnetic path 43 includes outer edge ends 43a, 43b.

[0039] The outer edge ends 43a and 43b are ends located on the outer edge 250. The first outer edge straight section 431aa extends from the outer edge end 43a. The first outer edge straight section 431ab extends from the outer edge end 43b. The first outer edge straight sections 431aa and 431ab are straight lines parallel to the magnetic pole boundary line LL. The first outer edge straight section 431aa corresponds to the first straight section 220A of the fourth magnet hole 22A, and the first outer edge straight section 431ab corresponds to the first straight section 220B of the fourth magnet hole 22B.

[0040] The second outer edge straight section 431ba is a straight line extending in a direction intersecting the first outer edge straight section 431aa, and is connected to the first outer edge straight section 431aa by a smooth curve. The second outer edge straight section 431bb is a straight line extending in a direction intersecting the first outer edge straight section 431ab, and is connected to the first outer edge straight section 431ab by a smooth curve. The second outer edge straight section 431ba corresponds to the second straight section 220C of the fourth magnet hole 22A, and the second outer edge straight section 431bb corresponds to the second straight section 220D of the fourth magnet hole 22B.

[0041] The width Wb of the third magnetic path 43 in the orientation direction is minimized in the first outer edge straight sections 431aa and 431ab. In the first outer edge straight sections 431aa and 431ab, the width Wb is greater than half the width Wt of the teeth 81. That is, the width Wb of the third magnetic path 43 is greater than half the width Wt of the teeth 81 in all parts.

[0042] As shown in Figure 3, a connecting magnetic path 430 is formed between the first outer edge straight section 431ab and the first outer edge straight section 431aa of the adjacent magnetic pole section 10, connecting the third magnetic paths 43 of the two magnetic pole sections 10. Similarly, a connecting magnetic path 430 is formed between the first outer edge straight section 431aa and the first outer edge straight section 431ab of the adjacent magnetic pole section 10, connecting the third magnetic paths 43 of the two magnetic pole sections 10. The width of these connecting magnetic paths 430 is twice the width Wb of the third magnetic path 43 and is greater than the width Wt of the teeth 81. Therefore, the magnetic flux supplied from the teeth 81 flows easily from the connecting magnetic path 430 to the third magnetic path 43, ensuring a sufficient amount of magnetic flux flows through the third magnetic path 43.

[0043] The outer edge arc portion 431c is the portion of the third outer edge 431 from the first peripheral rib 45B to the second peripheral rib 45C, and is formed in an arc shape centered on the orientation center point Pc. The outer edge arc portion 431c corresponds to the radially inward arc of the fifth magnet holes 22C and 22D.

[0044] In other words, the third outer edge 431 is formed in such a way that it maintains an arc shape, ensures sufficient width Wb of the third magnetic path 43, and maximizes the size of the second bond magnet 32.

[0045] Because the shape of the third outer edge 431 is maintained in an arc shape, much of the magnetic flux generated from the first and second bond magnets 31 and 32 is perpendicular to the third magnetic path 43, making it easier to secure the magnet torque Tm.

[0046] As shown in Figure 4, each of the third magnet holes 21A, 21B, the fourth magnet holes 22A, 22B, and the fifth magnet holes 22C, 22D is provided with four rounded corners. The rounded corners are corners having a curved surface with a predetermined curvature.

[0047] More specifically, each of the third magnet holes 21A and 21B comprises two first rounded corners 211a and 211b and two second rounded corners 212a and 212b. Each of the fourth magnet holes 22A and 22B comprises two third rounded corners 221a and 221b. Each of the fifth magnet holes 22C and 22D comprises two fourth rounded corners 222a and 222b.

[0048] The two first rounded corners 211a and 211b are arranged along the outer edge 250, with the first rounded corner 211b positioned further from the orientation center point Pc than the first rounded corner 211a. The two third rounded corners 221a and 221b are arranged along the outer edge 250, with the third rounded corner 221b positioned further from the orientation center point Pc than the third rounded corner 221a.

[0049] The radius of curvature of the rounded corners located further from the orientation center point Pc among the two first rounded corners 211a, 211b and the two third rounded corners 221a, 221b is larger than the radius of curvature of the rounded corners located closer to the orientation center point Pc. That is, the radius of curvature is larger in the order of third rounded corner 221b, third rounded corner 221a, first rounded corner 211b, and first rounded corner 211a. The larger the radius of curvature of a rounded corner, the gentler the curve of the rounded corner surface.

[0050] The two second rounded corners 212a and 212b are positioned along the first rib 44, with the second rounded corner 212b being positioned further from the orientation center point Pc than the second rounded corner 212a. The two fourth rounded corners 222a and 222b are positioned along the central rib 45A, with the fourth rounded corner 222b being positioned further from the orientation center point Pc than the fourth rounded corner 222a.

[0051] Because the ribs located radially inward support a greater mass than those located radially outward, a larger centrifugal force acts on the radially inward rounded corners compared to the radially outward rounded corners. In this configuration, however, the radially inward rounded corners have a larger radius of curvature than the radially outward rounded corners, thus suppressing stress concentration compared to the case where all rounded corners have the same radius of curvature. Therefore, the centrifugal force resistance of the rotor 30 can be ensured.

[0052] On the other hand, the radially outer rounded corners of the aforementioned rounded corners have a smaller radius of curvature than the radially inner rounded corners. Therefore, compared to the case where all rounded corners have the same radius of curvature, the size of the magnet holes, especially the third magnet holes 21A and 21B, can be secured, and thus the amount of bonded magnets to be embedded in these magnet holes can be secured. Consequently, the magnet torque Tm can be secured, and therefore the torque of the rotor 30 can be secured.

[0053] <1-2. Arrangement of surrounding ribs> Next, with reference to Figure 2, the positions of the first and second peripheral ribs 45B and 45C will be described. The first peripheral rib 45B is located between the first virtual line L1 and the magnetic pole centerline L0. The first peripheral rib 45B is located on the opposite side of the magnetic pole centerline L0 from the third virtual line L3.

[0054] The first virtual line L1 is a straight line passing through the first end P1 and parallel to the magnetic pole centerline L0. The first end P1 is the end of the arc of the first magnet hole 21 (specifically, the third magnet hole 21A) on the side of the second magnetic path 42. The third virtual line L3 is a straight line passing through the third end P3 and parallel to the magnetic pole centerline L0. The third end P3 is the end of the arc of the first magnet hole 21 (specifically, the third magnet hole 21A) on the side of the first magnetic path 41.

[0055] Here, when we say that the first peripheral rib 45B is provided between the first virtual line L1 and the magnetic pole centerline L0, we mean that the first central portion 450B, which is the longitudinal central part of the first peripheral rib 45B, is provided between the first virtual line L1 and the magnetic pole centerline L0, and the entire first peripheral rib 45B does not necessarily have to be provided between the first virtual line L1 and the magnetic pole centerline L0. Similarly, when we say that the first peripheral rib 45B is provided on the side of the third virtual line L3 opposite to the magnetic pole centerline L0, we mean that the first central portion 450B is provided on the side of the third virtual line L3 opposite to the magnetic pole centerline L0, and the entire first peripheral rib 45B does not necessarily have to be provided on the side of the third virtual line L3 opposite to the magnetic pole centerline L0.

[0056] Similarly, the second peripheral rib 45C is provided between the second virtual line L2 and the magnetic pole centerline L0. Furthermore, the second peripheral rib 45C is provided on the opposite side of the magnetic pole centerline L0 from the fourth virtual line L4.

[0057] The second virtual line L2 is a straight line passing through the second end P2 and parallel to the magnetic pole centerline L0. The second end P2 is the end of the arc on the second magnetic path 42 side of the first magnet hole 21 (specifically, the third magnet hole 21B). The fourth virtual line L4 is a straight line passing through the fourth end P4 and parallel to the magnetic pole centerline L0. The fourth end P4 is the end of the arc on the first magnetic path 41 side of the first magnet hole 21 (specifically, the third magnet hole 21B).

[0058] Furthermore, when we say that the second peripheral rib 45C is provided between the second virtual line L2 and the magnetic pole centerline L0, it means that the second central portion 450C, which is the longitudinal central part of the second peripheral rib 45C, is provided between the second virtual line L2 and the magnetic pole centerline L0, and the entire second peripheral rib 45C does not necessarily have to be provided between the second virtual line L2 and the magnetic pole centerline L0. Similarly, when we say that the second peripheral rib 45C is provided on the opposite side of the magnetic pole centerline L0 with respect to the fourth virtual line L4, it means that the second central portion 450C is provided on the opposite side of the magnetic pole centerline L0 with respect to the fourth virtual line L4, and the entire second peripheral rib 45C does not necessarily have to be provided on the opposite side of the magnetic pole centerline L0 with respect to the fourth virtual line L4.

[0059] Thus, by providing the first peripheral rib 45B between the first virtual straight line L1 and the third virtual straight line L3, and the second peripheral rib 45C between the second virtual straight line L2 and the fourth virtual straight line L4, the magnet torque Tm can be maximized. In contrast, with the arrangement of the first peripheral rib 45B and the second peripheral rib 45C in the first and second reference examples, the magnet torque Tm decreases.

[0060] Furthermore, when it is stated that the first peripheral rib 45B is provided between the first virtual straight line L1 and the third virtual straight line L3, it means that the first central section 450B is provided between the first virtual straight line L1 and the third virtual straight line L3, and the entirety of the first peripheral rib 45B does not necessarily have to be provided between the first virtual straight line L1 and the third virtual straight line L3. Also, when it is stated that the second peripheral rib 45C is provided between the second virtual straight line L2 and the fourth virtual straight line L4, it means that the second central section 450C is provided between the second virtual straight line L2 and the fourth virtual straight line L4, and the entirety of the second peripheral rib 45C does not necessarily have to be provided between the second virtual straight line L2 and the fourth virtual straight line L4.

[0061] Figure 5 shows the magnetic pole section 10 according to the first reference example. The first peripheral rib 45B according to the first reference example is provided between the first virtual line L1 and the magnetic pole centerline L0, but not on the opposite side of the magnetic pole centerline L0 with respect to the third virtual line L3. The first peripheral rib 45B according to the first reference example is provided between the third virtual line L3 and the magnetic pole centerline L0. Similarly, the second peripheral rib 45C according to the first reference example is provided between the fourth virtual line L4 and the magnetic pole centerline L0.

[0062] In other words, the first and second peripheral ribs 45B and 45C in the first reference example are positioned closer to the central rib 45A than the first and second peripheral ribs 45B and 45C in this embodiment. As a result, the fourth magnet holes 22A and 22B in the first reference example are larger than the fourth magnet holes 22A and 22B in this embodiment, and the fifth magnet holes 22C and 22D in the first reference example are smaller than the fifth magnet holes 22C and 22D in this embodiment.

[0063] In the first reference example, compared to this embodiment, the central magnets 32C and 32D are smaller, which shortens the length of the central magnets 32C and 32D in the direction perpendicular to the magnetization direction, thus increasing the permeance of the central magnets 32C and 32D. Also, the peripheral magnets 32A and 32B are larger, which length of the peripheral magnets 32A and 32B in the direction perpendicular to the magnetization direction, thus decreasing the permeance of the peripheral magnets 32A and 32B. When the rate of increase in the permeance of the central magnets 32C and 32D is equal to the rate of decrease in the permeance of the peripheral magnets 32A and 32B, the magnet torque Tm in the first reference example is equal to the magnet torque Tm in this embodiment.

[0064] However, as the surrounding magnets 32A and 32B become larger, the nonlinearity of the shapes of the surrounding magnets 32A and 32B increases, so the rate of decrease in the permeance of the surrounding magnets 32A and 32B becomes greater than the rate of increase in the permeance of the central magnets 32C and 32D. Therefore, the overall permeance of the second bonded magnet 32 ​​according to the first reference example is lower than the overall permeance of the second bonded magnet 32 ​​according to this embodiment. Consequently, the magnet torque Tm in the first reference example is lower than the magnet torque Tm in this embodiment.

[0065] Figure 6 shows the magnetic pole section 10 according to the second reference example. The first peripheral rib 45B according to the second reference example is provided on the opposite side of the magnetic pole centerline L0 with respect to the third virtual line L3, but not between the first virtual line L1 and the magnetic pole centerline L0. The first peripheral rib 45B according to the second reference example is provided on the opposite side of the magnetic pole centerline L0 with respect to the first virtual line L1. Similarly, the second peripheral rib 45C according to the second reference example is provided on the opposite side of the magnetic pole centerline L0 with respect to the second virtual line L2.

[0066] In other words, the first and second peripheral ribs 45B and 45C in the second reference example are positioned closer to the outer edge 250 than the first and second peripheral ribs 45B and 45C in the present embodiment. As a result, the fourth magnet holes 22A and 22B in the second reference example are smaller than the fourth magnet holes 22A and 22B in the present embodiment, and the fifth magnet holes 22C and 22D in the second reference example are larger than the fifth magnet holes 22C and 22D in the present embodiment.

[0067] Because the second bond magnet 32 ​​is radially oriented, the closer the first and second peripheral ribs 45B and 45C are to the outer edge 250, the greater the proportion of the magnetic flux supplied from the second bond magnet 32 ​​that passes through the first and second peripheral ribs 45B and 45C. Since the magnetic resistance of the first and second peripheral ribs 45B and 45C is relatively large, the magnet torque Tm decreases as the proportion of magnetic flux passing through the first and second peripheral ribs 45B and 45C increases.

[0068] Figure 7 shows a comparison between this embodiment and the first and second reference examples. The magnetic flux φm of the first reference example when no current is flowing through coil 82 is 3% less than that of this embodiment. Also, the magnetic flux φm of the second reference example at this time is 5.2% less than that of this embodiment. The magnetic flux φm when no current is flowing corresponds to the magnetic flux supplied from the first and second bond magnets 31 and 32.

[0069] Furthermore, the magnet torque Tm of the first reference example when the motor 100 outputs maximum torque is 2.9% lower than that of this embodiment. Also, the magnet torque Tm of the second reference example at this time is 5.1% lower than that of this embodiment. On the other hand, the reluctance torque Tr of the first and second reference examples at this time is approximately the same as that of this embodiment.

[0070] Therefore, by comparing the first and second reference examples with this embodiment, it can be seen that the reluctance torque Tr hardly changes depending on the position of the first and second peripheral ribs 45B and 45C, but the magnet torque Tm does change. Furthermore, it can be seen that the magnet torque Tm can be maximized by providing the first peripheral rib 45B between the first virtual line L1 and the third virtual line L3, and the second peripheral rib 45C between the second virtual line L2 and the fourth virtual line L4, as in this embodiment.

[0071] Furthermore, in this embodiment, the first and second reference examples, the ratio of reluctance torque Tr to total torque T is greater than the ratio of magnet torque Tm to total torque T. Therefore, motor 100 can be said to be a motor that utilizes reluctance torque Tr more than magnet torque Tm.

[0072] <1-3. Effects> The first embodiment described in detail above provides the following effects. (1) When the rotor 30 rotates, centrifugal force acts on the rotor 30. Since the second rib 45 supports a larger mass than the first rib 44, the second rib 45 needs to resist a greater centrifugal force than the first rib 44. When the stress generated in the first rib 44 and the second rib 45 exceeds the material limit of the first rib 44 and the second rib 45, the first rib 44 and the second rib 45 undergo plastic deformation. Therefore, the width W2 of the second rib 45, which needs to resist a greater centrifugal force than the first rib 44, is made wider than the width W1 of the first rib 44, and the number of second ribs 45 is increased compared to the number of first ribs 44. As a result, the stress generated in the second rib 45 is reduced compared to before the width was increased and the number of ribs was increased, thus suppressing plastic deformation of the second rib 45. Consequently, the strength of the rotor 30 is improved, and the centrifugal force resistance performance is improved. Furthermore, since the width W1 of the first rib 44, which experiences less stress than the second rib 45, is narrower than the width W2 of the second rib 45, the magnetic flux flowing to the first rib 44 is suppressed, and the decrease in reluctance torque Tr is suppressed. In addition, since the widths W2 of the central rib 45A, the first peripheral rib 45B, and the second peripheral rib 45C are equal, the short circuit from the second magnetic path 42 to the third magnetic path 43 is made more uniform compared to the case where any of them are different, the flow of magnetic flux in the second magnetic path 42 is stabilized, and the decrease in reluctance torque Tr is further suppressed. Therefore, it is possible to ensure centrifugal force resistance performance while suppressing the decrease in total torque T.

[0073] Furthermore, since the rotor 30 is equipped with bonded magnets as permanent magnets, the generation of eddy currents, which have a significant impact during high-speed rotation, is suppressed, thus also providing the effect of suppressing the deterioration of efficiency during high-speed rotation.

[0074] (2) The first and second bond magnets 31 and 32 are radially oriented toward the orientation center point Pc. Therefore, the closer the positions of the first and second peripheral ribs 45B and 45C are to the outer edge 250, the greater the proportion of the magnetic flux supplied from the second bond magnet 32 ​​that passes through the first and second peripheral ribs 45B and 45C. Since the magnetic resistance of the first and second peripheral ribs 45B and 45C is relatively large, as the proportion of magnetic flux passing through the first and second peripheral ribs 45B and 45C increases, the magnet torque Tm decreases. In contrast, by providing the first and second peripheral ribs 45B and 45C between the first and second virtual lines L1 and L2 and the magnetic pole center line L0, the magnetic flux output from the second bond magnet 32 ​​to the first and second peripheral ribs 45B and 45C is suppressed. Thus, the decrease in magnet torque Tm can be suppressed. Consequently, the decrease in total torque T can be further suppressed.

[0075] (3) When the positions of the first and second peripheral ribs 45B and 45C are brought closer to the magnetic pole centerline L0, the peripheral magnets 32A and 32B, which have a strong nonlinearity, become larger. As a result, the overall permeance of the second bond magnet 32 ​​decreases, and the magnet torque Tm decreases. In contrast, by positioning the first and second peripheral ribs 45B and 45C on the opposite side of the magnetic pole centerline L0 with respect to the third and fourth virtual lines L3 and L4, the decrease in magnet torque Tm can be suppressed.

[0076] (4) By positioning the first peripheral rib 45B between the first virtual line L1 and the third virtual line L3, and the second peripheral rib 45C between the second virtual line L2 and the fourth virtual line L4, the magnet torque Tm can be maximized. Consequently, the total torque T can be maximized.

[0077] (5) Since the first and second outer edges 421 and 422 are arcs with the same center point, the width Wa of the second magnetic path 42 in the orientation direction is constant. Therefore, the magnetic flux entering the rotor 30 from the stator 80 flows more easily into the second magnetic path 42, making it easier to secure the reluctance torque Tr. Also, since the center points of the first and second outer edges 421 and 422 coincide with the orientation center point Pc, the magnetic flux generated from the first and second bond magnets 31 and 32 is perpendicular to the second magnetic path 42. Therefore, it is easier to secure the magnet torque Tm. Consequently, the decrease in the total torque T can be further suppressed.

[0078] (6) The width Wc of the second magnet hole 22 in the orientation direction expands radially inward as it approaches the magnetic pole centerline L0 from the outer edge 250. This makes the second bond magnet 32 ​​larger radially inward compared to the case where the width Wc is constant, and increases the magnet torque Tm. Also, since the width Wc does not expand radially outward, the width Wa of the second magnetic path 42 is maintained, and the amount of magnetic flux flowing through the second magnetic path 42 can be maintained. Furthermore, since the width Wb of the third magnetic path 43 in the orientation direction is sufficiently larger on the side closer to the magnetic pole centerline L0 than on the side further away, even if the width Wc expands radially inward near the magnetic pole centerline L0, the amount of magnetic flux flowing through the third magnetic path 43 can be maintained. Thus, the magnet torque Tm can be increased while ensuring the reluctance torque Tr, and the total torque T can be increased.

[0079] (7) The third outer edge 431 is provided with an outer edge arc portion 431c. This maintains the shape of the third outer edge 431 in an arc shape, so that much of the magnetic flux generated from the first and second bond magnets 31 and 32 is perpendicular to the third magnetic path 43, making it easier to secure the magnet torque Tm.

[0080] (8) The third outer edge 431 is provided with first outer edge straight sections 431aa and 431ab. As a result, in the portion where the width Wb of the third magnetic path 43 is smallest, a connecting magnetic path 430 is formed between two adjacent magnetic pole sections 10, with two third magnetic paths 43 connected. Since the width of the connecting magnetic path 430 is sufficiently larger than the width Wt of the teeth 81, it is easy to secure a reluctance torque Tr. In addition, the radially outer edges of the fourth magnet holes 22A and 22B are formed in an arc shape, and the radially inner edges of the fourth magnet holes 22A and 22B are formed as a combination of straight lines. As a result, compared to the case where the radially outer and inner edges of the fourth magnet holes 22A and 22B are formed in an arc shape, the area of ​​the fourth magnet holes 22A and 22B and the fifth magnet holes 22C and 22D in an axial view is larger, and the amount of second bond magnet 32 ​​filling the second magnet hole 22 is increased. Therefore, the magnet torque Tm can be increased. This, in turn, can increase the total torque T.

[0081] (9) Because the ribs located radially inward support a larger mass than those located radially outward, a greater centrifugal force acts on the radially inward rounded corners compared to the radially outward rounded corners. In this configuration, however, the radially inward rounded corners have a larger radius of curvature than the radially outward rounded corners, thus suppressing stress concentration compared to the case where all rounded corners have the same radius of curvature. Therefore, the centrifugal force resistance of the rotor 30 can be ensured.

[0082] On the other hand, the radially outer rounded corners of the aforementioned rounded corners have a smaller radius of curvature than the radially inner rounded corners. Therefore, compared to the case where all rounded corners have the same radius of curvature, the size of the magnet holes, especially the third magnet holes 21A and 21B, can be secured, and thus the amount of bonded magnets to be embedded in these magnet holes can be secured. Consequently, the magnet torque Tm can be secured, and therefore the torque of the rotor 30 can be secured.

[0083] (10) The width Wa of the second magnetic path 42 is greater than the width Wt of the teeth 81, so that the amount of magnetic flux flowing from the teeth 81 to the second magnetic path 42 can be secured. In addition, a connecting magnetic path 430 is formed between the second bond magnets 32 of two adjacent magnetic pole sections 10 by connecting two third magnetic paths 43. The width of the connecting magnetic path 430 is twice the width Wb of the third magnetic path 43 and is greater than the width Wt of the teeth 81, so that the amount of magnetic flux flowing from the teeth 81 to the connecting magnetic path 430 can be secured. Thus, the reluctance torque Tr can be secured, and consequently, the total torque T of the motor 100 can be secured.

[0084] <1-4. Variations> Next, a modified example of the first embodiment described above will be explained. (a) In the first embodiment, the third outer edge 431 had a first outer edge straight section 431aa, 431ab, a second outer edge straight section 431ba, 431bb, and an outer edge arc section 431c. However, the third outer edge 431 may also have a first outer edge straight section 431aa, 431ab, a first outer edge arc section corresponding to the outer edge arc section 431c, and a second outer edge arc section. The second outer edge arc section is formed in the position of the second outer edge straight section 431ba, 431bb, concentric with the first outer edge arc section, in place of the second outer edge straight section 431ba, 431bb.

[0085] (b) In the first embodiment, the minimum value of the width Wb of the third magnetic path 43 was greater than half the width Wt of the teeth 81, but the minimum value of the width Wb may be equal to the tooth width Wt. (c) In the first embodiment, the radius of curvature r1 of the fourth rounded corner 222b, the radius of curvature r2 of the fourth rounded corner 222a, the radius of curvature r3 of the second rounded corner 212b, and the radius of curvature r4 of the second rounded corner 212a were in the relationship r1>r2>r3>r4, but the relationship r1≧r2≧r3≧r4 may also be present.

[0086] (d) In the first embodiment, the first outer edge 421 and the second outer edge 422 were arcs centered on the orientation center point Pc, that is, the center point of the first outer edge coincided with the orientation center point Pc. However, the first outer edge 421 and the second outer edge 422 may be arcs centered on a first outer edge center point different from the orientation center point Pc, as long as they are points on the magnetic pole center line L0.

[0087] (e) In the first embodiment, the third outer edge 431 was an arc centered on the orientation center point Pc, that is, the center point of the second outer edge coincided with the orientation center point Pc. However, the third outer edge 431 may be an arc centered on a second outer edge center point different from the orientation center point Pc, as long as it is a point on the magnetic pole center line L0. Also, the center point of the arc of the third outer edge 431 may be different from the center points of the arcs of the first outer edge 421 and the second outer edge 422. That is, the center points of the first outer edge, the second outer edge, and the orientation center point Pc may each be different.

[0088] (f) In the first embodiment, the first peripheral rib 45B was provided between the first virtual line L1 and the third virtual line L3. However, the first peripheral rib 45B may be provided on the opposite side of the third virtual line L3 from the first virtual line L1, or it may be provided between the third virtual line L3 and the magnetic pole centerline L0. Also, the second peripheral rib 45C was provided between the second virtual line L2 and the fourth virtual line L4. However, the second peripheral rib 45C may be provided on the opposite side of the fourth virtual line L4 from the second virtual line L2, or it may be provided between the fourth virtual line L4 and the magnetic pole centerline L0. In this way, even if the first and second peripheral ribs 45B and 45C are arranged, the total torque T will be lower than in the first embodiment, but it is possible to realize a rotor that ensures centrifugal force resistance while suppressing the decrease in total torque T.

[0089] (Second Embodiment) <2-1. Differences from the First Embodiment> The second embodiment has the same basic configuration as the first embodiment, so the differences will be explained below. Note that the same reference numerals as in the first embodiment indicate the same components, and refer to the preceding description.

[0090] The three second ribs 45 in the first embodiment described above included a central rib 45A, a first peripheral rib 45B, and a second peripheral rib 45C. In contrast, as shown in Figure 8, the three second ribs 45 in the second embodiment include a central rib 45A, a third peripheral rib 451B, and a fourth peripheral rib 451C. That is, in the second embodiment, the magnetic pole portion 10 includes a third peripheral rib 451B and a fourth peripheral rib 451C instead of the first peripheral rib 45B and the second peripheral rib 45C.

[0091] <2-2. Arrangement of surrounding ribs> The third peripheral rib 451B has a width W2 and, like the first peripheral rib 45B, is located between the first virtual line L1 and the magnetic pole centerline L0. That is, similar to the first peripheral rib 45B, the third central section 452B is located between the first virtual line L1 and the magnetic pole centerline L0. The third central section 452B is the longitudinal central portion of the third peripheral rib 451B.

[0092] Furthermore, the third peripheral rib 451B, like the first peripheral rib 45B, is located on the opposite side of the magnetic pole centerline L0 with respect to the third virtual line L3. That is, similar to the first peripheral rib 45B, the third central section 452B is located on the opposite side of the magnetic pole centerline L0 with respect to the third virtual line L3. Therefore, the third central section 452B is located between the first virtual line L1 and the third virtual line L3.

[0093] The fourth peripheral rib 451C has a width W2 and, like the second peripheral rib 45C, is located between the second virtual line L2 and the magnetic pole centerline L0. That is, similar to the second peripheral rib 45C, the fourth central section 452C is located between the second virtual line L2 and the magnetic pole centerline L0. That is, similar to the second peripheral rib 45C, the fourth central section 452C is located between the second virtual line L2 and the magnetic pole centerline L0. The fourth central section 452C is the longitudinal central portion of the fourth peripheral rib 451C.

[0094] Furthermore, the fourth peripheral rib 451C, like the second peripheral rib 45C, is located on the opposite side of the magnetic pole centerline L0 with respect to the fourth virtual line L4. That is, similar to the second peripheral rib 45C, the fourth central section 452C is located on the opposite side of the magnetic pole centerline L0 with respect to the fourth virtual line L4. Therefore, the fourth peripheral rib 451C is located between the second virtual line L2 and the fourth virtual line L4.

[0095] The third peripheral rib 451B and the fourth peripheral rib 451C are arranged symmetrically with respect to the magnetic pole centerline L0. The third peripheral rib 451B and the fourth peripheral rib 451C are inclined with respect to the magnetic pole centerline L0 so that they gradually approach the magnetic pole centerline L0 as they move from the third magnetic path 43 toward the second magnetic path 42. This inclination of the third peripheral rib 451B and the fourth peripheral rib 451C with respect to the magnetic pole centerline L0 improves the strength of the rotor 30 and enhances its centrifugal force resistance. The magnetic performance of the motor 100 in this embodiment is equivalent to that of the first embodiment.

[0096] The inclination angles of the third peripheral rib 451B and the fourth peripheral rib 451C with respect to the magnetic pole centerline L0 are set to satisfy predetermined conditions. Specifically, the predetermined conditions are that the first intersection Pa and the second intersection Pb are located radially outside the centroid point Pm and radially inside the orientation center point Pc.

[0097] The first intersection point Pa is the intersection of the first rib line LL1 and the magnetic pole centerline L0. The first rib line LL1 is a straight line that passes through the center of the third peripheral rib 451B in the width direction and extends in the longitudinal direction of the third peripheral rib 451B. The second intersection point Pb is the intersection of the second rib line LL2 and the magnetic pole centerline L0. The second rib line LL2 is a straight line that passes through the center of the fourth peripheral rib 451C in the width direction and extends in the longitudinal direction of the fourth peripheral rib 451C. In this embodiment, since the third peripheral rib 451B and the fourth peripheral rib 451C are arranged symmetrically with respect to the magnetic pole centerline L0, the first intersection point Pa and the second intersection point Pb coincide.

[0098] The center of gravity Pm is the center of gravity of the outer region shown by hatching in Figure 8. That is, the center of gravity Pm is the point of application of the resultant force of gravity acting on the mass of the outer region. The outer region is the region radially outside the third magnetic path 43 of the rotor 30. This outer region is the region where the central rib 45A, the third peripheral rib 451B, and the fourth peripheral rib 451C support the mass. In this embodiment, since the magnetic pole section 10 has a symmetrical configuration with respect to the magnetic pole centerline L0, the center of gravity Pm is located on the magnetic pole centerline L0.

[0099] When the inclination angles of the third peripheral rib 451B and the fourth peripheral rib 451C with respect to the magnetic pole centerline L0 are set to satisfy a predetermined condition, the stress generated in the third peripheral rib 451B and the fourth peripheral rib 451C is reduced compared to when the predetermined condition is not satisfied. Therefore, the strength of the rotor 30 is improved, and its centrifugal force resistance is enhanced.

[0100] Figure 9 shows the stress distribution in the magnetic pole portion 10 according to this embodiment. Figure 10 shows the stress distribution in the magnetic pole portion according to the third reference example. Figure 11 shows the stress distribution in the magnetic pole portion according to the fourth reference example. The third reference example is an example in which the first intersection Pa and the second intersection Pb are located radially outside the orientation center point Pc. The fourth reference example is an example in which the first intersection Pa and the second intersection Pb are located radially inside the centroid point Pm.

[0101] In the embodiment shown in Figure 9, the areas of high stress are widespread in the third peripheral rib 451B and the fourth peripheral rib 451C, and no large localized stresses occur. On the other hand, in the third reference example shown in Figure 10, the areas of high stress are narrower in the two peripheral ribs than in this embodiment, and large localized stresses occur. Furthermore, in the fourth reference example shown in Figure 11, the areas of high stress are widespread in the two peripheral ribs to a similar extent as in this embodiment, but areas of even higher stress occur than in this embodiment.

[0102] Figure 12 shows the maximum stress values ​​at the base of the central rib and the base of the peripheral ribs in this embodiment, the third example, and the fourth example. The maximum stress values ​​at the base of the central rib are approximately the same in this embodiment, the third example, and the fourth example. On the other hand, the maximum stress values ​​at the base of the peripheral ribs are smallest in this embodiment. Therefore, when the inclination angle of the peripheral ribs with respect to the magnetic pole centerline L0 is set to satisfy a predetermined condition, the maximum stress values ​​at the peripheral ribs are smaller compared to when the predetermined condition is not satisfied, indicating an improvement in the strength of the rotor 30.

[0103] <2-3. Effects> The second embodiment described in detail above achieves the effects (1) to (10) of the first embodiment, as well as the following effects.

[0104] (11) The third peripheral rib 451B and the fourth peripheral rib 451C are inclined with respect to the magnetic pole centerline L0 so that they gradually approach the magnetic pole centerline L0 as they move from the third magnetic path 43 towards the second magnetic path 42. This reduces the stress generated in the third peripheral rib 451B and the fourth peripheral rib 451C compared to when they are parallel to the magnetic pole centerline L0, thereby improving the centrifugal force resistance of the rotor 30. Consequently, the width W2 of the third peripheral rib 451B and the fourth peripheral rib 451C can be reduced. Therefore, the second magnet hole 22 can be made wider, and the amount of bonded magnets filling the second magnet hole 22 can be increased. As a result, the magnetic torque Tm of the motor 100 can be increased, thus improving the performance of the motor 100.

[0105] (12) By providing the third peripheral rib 451B and the fourth peripheral rib 451C in such a way that the above-mentioned predetermined conditions are met, the stress generated in the third peripheral rib 451B and the fourth peripheral rib 451C can be reduced compared to the case where the above-mentioned predetermined conditions are not met. Consequently, the width W2 of the third peripheral rib 451B and the fourth peripheral rib 451C can be made narrower.

[0106] <2-4. Variations> Next, a modified example of the second embodiment described above will be explained. The second embodiment described above can also be realized by modifying it as shown in (a) to (f), similar to the first embodiment. Furthermore, the second embodiment described above can also be realized by modifying it as follows.

[0107] (g) In the second embodiment, the third peripheral rib 451B and the fourth peripheral rib 451C were provided symmetrically with respect to the magnetic pole centerline L0, but the third peripheral rib 451B and the fourth peripheral rib 451C may be asymmetrical with respect to the magnetic pole centerline L0. In this case, the first intersection point Pa, which is the intersection point of the first rib line LL1 and the magnetic pole centerline L0, and the second intersection point Pb, which is the intersection point of the second rib line LL2 and the magnetic pole centerline L0, do not overlap. However, by having at least one of the first intersection point Pa and the second intersection point Pb located between the centroid point Pm and the orientation center point Pc, the strength of the rotor 30 can be increased and the centrifugal force resistance performance can be improved compared to the case where both the first intersection point Pa and the second intersection point Pb are not located between the centroid point Pm and the orientation center point Pc. Furthermore, the design in which the third peripheral rib 451B and the fourth peripheral rib 451C are asymmetrical with respect to the magnetic pole centerline L0 is desirable when the maximum rotational speed range used differs depending on the rotation direction of the rotor 30.

[0108] (h) In the second embodiment and (g) above, the first intersection Pa and the second intersection Pb may be located on the centroid Pm or on the orientation center Pc. That is, if at least one of the first intersection Pa and the second intersection Pb is located in the line segment from the centroid Pm, which includes the centroid Pm, to the orientation center Pc, which includes the orientation center Pc, the centrifugal force resistance performance of the rotor 30 is improved. [Explanation of Symbols]

[0109] 10...Magnetic pole section, 20...Rotor core, 21...First magnet hole, 22...Second magnet hole, 30...Rotor, 31...First bonded magnet, 32...Second bonded magnet, 41...First magnetic circuit, 42...Second magnetic circuit, 43...Third magnetic circuit, 44...First rib, 45A...Central rib, 45B...First peripheral rib, 45C...Second peripheral rib, 450B...First central section, 450C...Second central section, 451B...Third peripheral rib, 451C...Fourth peripheral rib, 452B...Third central section, 452C...Fourth central section, 80...Stator, 81...Teeth, 82...Coil, 100...Motor.

Claims

1. A rotor comprising a cylindrical rotor core extending along the axis of rotation and bonded magnets embedded in the rotor core, having one or more pole pairs composed of the rotor core and bonded magnets, The aforementioned magnetic pole portion is In an axial view of the rotating shaft, the rotor core is formed in an arc shape that opens radially outward, and the first bonded magnet, which serves as the bonded magnet, is embedded in the first magnet hole, In the axial view, a second magnet hole is provided radially inward from the first magnet hole, is formed in an arc shape that opens radially outward, and has a second bonded magnet embedded in it, which serves as the bonded magnet. A first magnetic path provided radially outward from the first magnet hole, A second magnetic path is provided radially inside the first magnetic hole and radially outside the second magnetic hole, A third magnetic circuit is provided radially inward from the second magnet hole, A first rib extends along the radially extending magnetic pole centerline, connects the first magnetic path and the second magnetic path, and divides the first magnet hole into two along the circumferential direction of the rotor core, It comprises three second ribs that connect the second magnetic path and the third magnetic path, and divide the second magnet hole into four along the circumferential direction, The three second ribs include a central rib extending along the magnetic pole centerline at the circumferential center of the second magnet hole, and first and second peripheral ribs provided on both sides of the central rib in the circumferential direction. The widths of the central rib, the first peripheral rib, and the second peripheral rib are wider than the width of the first rib and equal to each other. Rotor.

2. The first bonded magnet and the second bonded magnet are radially oriented toward an orientation center point located radially outward from the first magnet hole and on the magnetic pole centerline. The first magnet hole has a first end and a second end, which are the ends of the arc on the second magnetic path side. The first peripheral rib is provided between the first end and the first imaginary straight line parallel to the magnetic pole centerline and the magnetic pole centerline, The second peripheral rib is provided between the second end and the magnetic pole centerline, which is a second virtual straight line parallel to the magnetic pole centerline. The rotor according to claim 1.

3. The first peripheral rib and the second peripheral rib are inclined with respect to the magnetic pole centerline so that they gradually approach the magnetic pole centerline as they move from the third magnetic path toward the second magnetic path. The rotor according to claim 1 or 2.

4. The first bonded magnet and the second bonded magnet are radially oriented toward an orientation center point located radially outward from the first magnet hole and on the magnetic pole centerline. The first intersection and / or the second intersection are located (i) on the centroid of the outer region, or (ii) on the orientation center point, or (iii) radially outward from the centroid and radially inward from the orientation center point. The first intersection point is the intersection of the first rib line, which passes through the first peripheral rib and extends in the longitudinal direction of the first peripheral rib, and the magnetic pole center line. The second intersection point is the intersection of the second rib line, which passes through the second peripheral rib and extends in the longitudinal direction of the second peripheral rib, and the magnetic pole center line. The outer region is the region of the rotor that is radially outside the third magnetic path. The rotor according to claim 3.

5. The first bonded magnet and the second bonded magnet are radially oriented toward an orientation center point located radially outward from the first magnet hole and on the magnetic pole centerline. The first magnet hole has a third end and a fourth end, which are the ends of the arc on the first magnetic path side. The first peripheral rib is provided on the opposite side of the magnetic pole centerline with respect to a third virtual straight line that passes through the third end and is parallel to the magnetic pole centerline, The second peripheral rib is provided on the opposite side of the magnetic pole centerline with respect to a fourth virtual line that passes through the fourth end and is parallel to the magnetic pole centerline. The rotor according to claim 1 or 2.

6. The second magnetic path has a first outer edge on the radially outer side and a second outer edge on the radially inner side, The first outer edge and the second outer edge are formed in arcs centered on the center point of the first outer edge on the magnetic pole centerline. The rotor according to claim 1 or 2.

7. The first bonded magnet and the second bonded magnet are radially oriented toward an orientation center point located radially outward from the first magnet hole and on the magnetic pole centerline. The first outer edge center point coincides with the orientation center point. The rotor according to claim 6.

8. The width of the second magnet hole in the orientation direction expands radially inward as it approaches the magnetic pole center line from the outer edge of the rotor core. The rotor according to claim 1 or 2.

9. The third magnetic path has a third outer edge on the radially outer side, The portion of the third outer edge from the first peripheral rib to the second peripheral rib is formed in an arc shape centered on the second outer edge center point on the magnetic pole centerline. The rotor according to claim 1 or 2.

10. The first bonded magnet and the second bonded magnet are radially oriented toward an orientation center point located radially outward from the first magnet hole and on the magnetic pole centerline. The second outer edge center point coincides with the orientation center point. The rotor according to claim 9.

11. The third magnetic path has a third outer edge on the radially outer side, The third outer edge has two outer edge ends on the outer peripheral edge of the rotor core and two straight outer edge portions extending from each of the two outer edge ends, The two outer edge straight sections are formed in a straight line shape parallel to the magnetic pole boundary line, which is the boundary between the adjacent magnetic pole sections. The rotor according to claim 1 or 2.

12. The first bonded magnet and the second bonded magnet are radially oriented toward an orientation center point located radially outward from the first magnet hole and on the magnetic pole centerline. The first magnet hole includes two third magnet holes, The second magnet hole includes two fourth magnet holes located on the outer circumference side of the rotor core and two fifth magnet holes located on the central rib side. Each of the two third magnet holes comprises two first rounded corners arranged along the outer periphery of the rotor core and two second rounded corners arranged along the first rib, Each of the two fourth magnet holes comprises two third rounded corners arranged along the outer edge of the rotor core, Each of the two fifth magnet holes comprises two fourth rounded corners arranged along the central rib, The radius of curvature of the rounded corner portion located further from the orientation center point among the two first rounded corner portions and the two third rounded corner portions is greater than the radius of curvature of the rounded corner portion located closer to the orientation center point. The radius of curvature of the rounded corner portion located further from the orientation center point among the two second rounded corner portions and the two fourth rounded corner portions is greater than the radius of curvature of the rounded corner portion located closer to the orientation center point. The rotor according to claim 1 or 2.

13. A rotor according to claim 1 or 2, A stator having teeth and coils wound around the teeth, The width of the second magnetic path is greater than or equal to the width of the teeth. The width of the third magnetic path is more than half the width of the teeth. Motor.

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