Rotating electric machine

Abstract

The present invention provides a rotating electric machine that can reduce torque ripple and efficiently increase torque. [Solution] In the rotating electric machine 1, the outer circumferential surface of the rotor core 41 has a plurality of partial outer circumferential surfaces 411 formed corresponding to the respective positions of a plurality of magnet insertion holes 44 in the circumferential direction of the rotor 4. Each groove 45 provided on the outer circumferential surface of the rotor core 41 reaches between two adjacent magnet insertion holes 44 in the circumferential direction of the rotor 4. The partial outer circumferential surface 411 has a first curved surface 411a that reaches from the magnetic pole centerline Q to a first reference point A, a second curved surface 411b that reaches from the first reference point A to a second reference point B, and a third curved surface 411c that reaches from the second reference point B to a third reference point C. When the partial outer circumferential surface 411 is viewed along the axis P of the rotor 4, the curvature R3 of the third curved surface 411c is greater than the curvature R2 of the second curved surface 411b.

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses an embedded permanent magnet motor in which, in order to reduce torque ripple, the outer circumferential surface of a rotor core is divided into a plurality of divided outer circumferential surfaces corresponding to permanent magnets, and a radial distance between each divided outer circumferential surface and a stator is made larger at both end portions than at a central portion of the divided outer circumferential surface. The permanent magnets are inserted into magnet insertion holes provided in the rotor core. In a state where the permanent magnets are inserted into the magnet insertion holes, gaps are formed at both circumferential end portions of the magnet insertion holes. The gaps at both circumferential end portions of the magnet insertion holes extend not only to both circumferential sides of the permanent magnets but also to an outer diameter side of the permanent magnets.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] In the conventional embedded permanent magnet motor disclosed in Patent Document 1, the gaps at both circumferential end portions of the magnet insertion holes extend not only to both circumferential sides of the permanent magnets but also to the outer diameter side of the permanent magnets. For this reason, the magnetic flux of the permanent magnets cannot be effectively used for generating torque of the embedded permanent magnet motor, which makes it impossible to efficiently increase the torque.

[0005] The present disclosure solves the problems described above, and an object of the present disclosure is to provide a rotating electrical machine that can reduce torque ripple and can efficiently increase torque.

Means for Solving the Problem

[0006] The rotating electric machine according to this disclosure comprises a cylindrical stator and a rotor arranged coaxially with the stator inside the stator, the rotor being rotatable relative to the stator about the rotor's axis, the rotor having a rotor core with a plurality of magnet insertion holes spaced apart from each other in the circumferential direction of the rotor, and a plurality of permanent magnets arranged in each of the plurality of magnet insertion holes, the outer circumferential surface of the rotor core having a plurality of partial outer circumferential surfaces formed corresponding to the respective positions of the plurality of magnet insertion holes in the circumferential direction of the rotor, the outer circumferential surface of the rotor core having a plurality of grooves formed between the plurality of partial outer circumferential surfaces, each groove reaching between two adjacent magnet insertion holes in the circumferential direction of the rotor, the shape of the partial outer circumferential surface when viewed along the rotor's axis being symmetrical with respect to the magnetic pole center line passing through the center point of the magnet insertion hole in the circumferential direction of the rotor and the rotor's axis, and the partial outer circumferential surface when viewed along the rotor's axis having a section from the magnetic pole center line to the groove, A reference point is established, a second reference point is located closer to the groove than the first reference point, and a third reference point is located at the boundary between the partial outer surface and the groove. The partial outer surface has a first curved surface that extends from the magnetic pole centerline to the first reference point, a second curved surface that extends from the first reference point to the second reference point, and a third curved surface that extends from the second reference point to the third reference point. The second curved surface smoothly connects to the first curved surface at the first reference point, and the third curved surface smoothly connects to the second curved surface at the second reference point, and the inner surface of the stator and the first curved surface The air gap length between the surface is constant in the circumferential direction of the rotor, the air gap length between the inner surface of the stator and the second curved surface widens as the rotor approaches the second reference point from the first reference point in the circumferential direction, the air gap length between the inner surface of the stator and the third curved surface widens as the rotor approaches the third reference point from the second reference point in the circumferential direction, and when viewing the partial outer surface along the axis of the rotor, the curvature of the third curved surface is greater than the curvature of the second curved surface. [Effects of the Invention]

[0007] According to this disclosure, torque ripple can be reduced and torque can be increased efficiently. [Brief explanation of the drawing]

[0008] [Figure 1] This is a partial cross-sectional view showing a rotating electric machine according to Embodiment 1. [Figure 2] Figure 1 is a perspective view showing the rotor. [Figure 3] This is an enlarged front view showing part III of Figure 2. [Figure 4] Figure 3 is a front view of the main components showing the rotor positioned inside the stator. [Figure 5] This is a front view of the main part of the rotor of a comparative example rotating electric machine for comparison with the rotating electric machine in Embodiment 1. [Figure 6] Figure 3 shows a graph illustrating the relationship between magnetic flux density in the air gap and the electrical angle for the rotor of Embodiment 1 and the rotor of the comparative example shown in Figure 5. [Figure 7] This is a front view of the main part showing the rotor of a rotating electric machine according to Embodiment 2. [Figure 8] Figure 7 is a front view of the main components showing the rotor positioned inside the stator. [Figure 9] This graph shows the relationship between magnetic flux density in the air gap and the electrical angle for the rotor of Embodiment 1 shown in Figure 3, the rotor of Embodiment 2 shown in Figure 7, and the rotor of the comparative example shown in Figure 5. [Figure 10] This graph compares the fundamental wave component of the magnetic flux density in the air gap for the rotor of Embodiment 1 shown in Figure 3 and the rotor of Embodiment 2 shown in Figure 7. [Modes for carrying out the invention]

[0009] The embodiments for carrying out the subject matter of this disclosure will be described with reference to the attached figures. In each figure, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations are simplified or omitted as appropriate. The subject matter of this disclosure is not limited to the following embodiments, and any modification of any component of the embodiments or omission of any component of the embodiments is possible without departing from the spirit of this disclosure.

[0010] Embodiment 1. Figure 1 is a partial cross-sectional view showing a rotating electric machine according to Embodiment 1. The rotating electric machine 1 includes a housing 2, a shaft 3, a rotor 4, and a stator 5.

[0011] Housing 2 has a frame 21 and an end plate 22. The frame 21 is a case with an opening 211 formed therein. The end plate 22 is a cover that closes the opening 211. The end plate 22 is attached to the frame 21 with the opening 211 closed.

[0012] Each of the frame 21 and end plate 22 is provided with a through hole for the shaft 3 to pass through. A bearing 23 is positioned in each of the through holes in the frame 21 and end plate 22. The shaft 3 is rotatably supported in the housing 2 via each bearing 23.

[0013] The stator 5 is fixed inside the housing 2, fitted onto the inner circumferential surface of the frame 21. The stator 5 is cylindrical in shape. The stator 5 is positioned coaxially with the shaft 3.

[0014] The stator 5 includes a stator core 51, a stator coil 52, and an insulator 53.

[0015] The stator core 51 is made of a magnetic material. In the present embodiment, the stator core 51 is formed by laminating a plurality of magnetic steel plates in the axial direction of the stator 5. An electrical steel sheet is used as the magnetic steel plate. The stator core 51 has a cylindrical shape. When the stator 5 is fixed inside the housing 2, the outer peripheral surface of the stator core 51 is fitted to the inner peripheral surface of the frame 21.

[0016] The insulator 53 is attached to the stator core 51. The insulator 53 is made of an electrically insulating insulating material.

[0017] The stator coil 52 is attached to the stator core 51 via the insulator 53. This ensures electrical insulation between the stator coil 52 and the stator core 51. In the stator 5, the stator coil 52 can be energized.

[0018] The rotor 4 is disposed inside the stator 5. Further, the rotor 4 is disposed coaxially with the shaft 3 and the stator 5. That is, the axis P of the rotor 4 coincides with the respective axes of the shaft 3 and the stator 5. Furthermore, the rotor 4 is fixed to the shaft 3 inside the housing 2. Accordingly, the rotor 4 is rotatable integrally with the shaft 3 about the axis P of the rotor 4 relative to the housing 2 and the stator 5.

[0019] The rotor 4 includes a rotor core 41, a plurality of permanent magnets 42, and a pair of rotor end plates 43.

[0020] The rotor core 41 is made of a magnetic material. The shaft 3 passes through the rotor core 41. The rotor core 41 is disposed coaxially with the shaft 3 and the stator 5.

[0021] Multiple permanent magnets 42 are embedded inside the rotor core 41. Each permanent magnet 42 is positioned along the axis P of the rotor 4, i.e., across the entire length of the rotor core 41 in the axial direction of the rotor 4.

[0022] A pair of rotor end plates 43 are fixed to the shaft 3. The pair of rotor end plates 43 are positioned on both sides of the rotor core 41 in the axial direction of the rotor 4. The pair of rotor end plates 43 prevent each permanent magnet 42 from coming out of the rotor core 41. Each rotor end plate 43 is made of a non-magnetic material.

[0023] A rotating magnetic field is generated in the stator 5 when the stator coil 52 is energized. Due to the generation of the rotating magnetic field, the rotor 4 rotates together with the shaft 3 with respect to the housing 2 and stator 5, around the axis P of the rotor 4.

[0024] Figure 2 is a perspective view showing the rotor 4 of Figure 1. Figure 3 is an enlarged front view showing part III of Figure 2. The rotor core 41 is provided with a plurality of magnet insertion holes 44. The plurality of magnet insertion holes 44 are provided in the rotor core 41 at intervals from each other in the circumferential direction of the rotor 4. The circumferential direction of the rotor 4 is the direction along the circumference of a circle centered on the axis P of the rotor 4. In this embodiment, the plurality of magnet insertion holes 44 are provided in the rotor core 41 at equal intervals in the circumferential direction of the rotor 4.

[0025] Each magnet insertion hole 44 penetrates the rotor core 41 in the axial direction of the rotor 4. In this embodiment, the shape of each magnet insertion hole 44, when viewed along the axis P of the rotor 4, is rectangular.

[0026] Multiple permanent magnets 42 are arranged one by one in multiple magnet insertion holes 44. As a result, multiple permanent magnets 42 are provided on the rotor core 41 at intervals from each other in the circumferential direction of the rotor 4. In this embodiment, multiple permanent magnets 42 are provided on the rotor core 41 at equal intervals in the circumferential direction of the rotor 4.

[0027] Multiple magnetic poles are formed on the outer circumference of the rotor core 41. These multiple magnetic poles are formed on the outer circumference of the rotor core 41 in accordance with the positions of the multiple permanent magnets 42 in the circumferential direction of the rotor 4.

[0028] Each permanent magnet 42 is arranged without gaps in the magnet insertion hole 44. Therefore, in this embodiment, the shape of each permanent magnet 42 when viewed along the axis P of the rotor 4 is rectangular. The permanent magnets 42 may be fixed to the rotor core 41 by press-fitting into the magnet insertion hole 44, or they may be fixed to the rotor core 41 with an adhesive.

[0029] Each permanent magnet 42 is embedded inside the rotor core 41 by being placed in a magnet insertion hole 44. Therefore, each permanent magnet 42 is provided in the rotor core 41 while being surrounded by it. This increases the permeance coefficient, thereby suppressing self-demagnetization of each permanent magnet 42.

[0030] The outer circumferential surface of the rotor core 41 has a plurality of partial outer circumferential surfaces 411. The plurality of partial outer circumferential surfaces 411 are formed to correspond to the respective positions of the plurality of magnet insertion holes 44 in the circumferential direction of the rotor 4. As a result, the position of each partial outer circumferential surface 411 in the circumferential direction of the rotor 4 coincides with the position of each magnet insertion hole 44 in the circumferential direction of the rotor 4, and also coincides with the position of each magnetic pole in the circumferential direction of the rotor 4.

[0031] The outer circumferential surface of the rotor core 41 is provided with a plurality of grooves 45, each formed between a plurality of partial outer circumferential surfaces 411. Each groove 45 is formed parallel to the axis P of the rotor 4. When the rotor 4 is viewed along the axis P of the rotor 4, each groove 45, as shown in Figure 3, recesses radially inward from the ends of two partial outer circumferential surfaces 411 adjacent to the groove 45, reaching between two adjacent magnet insertion holes 44 in the circumferential direction of the rotor 4. Each of the two adjacent magnet insertion holes 44 in the circumferential direction of the rotor 4 and the groove 45 located between the two magnet insertion holes 44 are separated by a partition wall 41a, which is part of the rotor core 41.

[0032] As shown in Figure 3, the shape of each portion of the outer circumferential surface 411 when viewed along the axis P of the rotor 4 is symmetrical with respect to the magnetic pole centerline Q that passes through the center point of the magnet insertion hole 44 in the circumferential direction of the rotor 4 and the axis P of the rotor 4. The magnetic pole centerline Q is the centerline of each magnetic pole individually set in the rotor 4 for each magnet insertion hole 44. Therefore, the shape of each portion of the outer circumferential surface 411 is symmetrical with respect to the magnetic pole centerline Q set in the magnet insertion hole 44 corresponding to the portion of the outer circumferential surface 411.

[0033] When the rotor 4 is viewed along its axis P, the magnet insertion holes 44 at each magnetic pole are perpendicular to the magnetic pole centerline Q. In each magnet insertion hole 44, the inner surface of the magnet insertion hole 44 that is located on the inside of the rotor 4 in the direction along the magnetic pole centerline Q is the insertion hole reference surface 441 perpendicular to the magnetic pole centerline Q. When the rotor 4 is viewed along its axis P, the position of the bottom surface of the groove 45 located next to the magnet insertion hole 44 is the same as the position of the insertion hole reference surface 441 in the direction along the magnetic pole centerline Q.

[0034] On each portion of the outer circumferential surface 411 of the rotor 4, viewed along the axis P, a first reference point A, a second reference point B, and a third reference point C are set in the section from the magnetic pole centerline Q to the groove 45. The first reference point A is located closer to the groove 45 than the magnetic pole centerline Q. The second reference point B is located closer to the groove 45 than the first reference point A. The third reference point C is located at the boundary between the portion of the outer circumferential surface 411 and the groove 45.

[0035] Each outer surface 411 of the portion has a first curved surface 411a, a second curved surface 411b, and a third curved surface 411c in the section from the magnetic pole centerline Q to the groove 45. The first curved surface 411a is the surface that extends from the magnetic pole centerline Q to the first reference point A. The second curved surface 411b is the surface that extends from the first reference point A to the second reference point B. The third curved surface 411c is the surface that extends from the second reference point B to the third reference point C. The second curved surface 411b smoothly connects to the first curved surface 411a at the first reference point A. The third curved surface 411c smoothly connects to the second curved surface 411b at the second reference point B. When viewed along the axis P of the rotor 4, the shapes of the first curved surface 411a, the second curved surface 411b, and the third curved surface 411c are all arc-shaped.

[0036] When the partial outer surface 411 is viewed along the axis P of the rotor 4, the curvature R2 of the second curved surface 411b is greater than the curvature R1 of the first curved surface 411a. That is, the relationship between the curvature R2 of the second curved surface 411b and the curvature R1 of the first curved surface 411a is R2 > R1. Therefore, when the partial outer surface 411 is viewed along the axis P of the rotor 4, the radius of curvature of the second curved surface 411b is smaller than the radius of curvature of the first curved surface 411a.

[0037] When the partial outer surface 411 is viewed along the axis P of the rotor 4, the curvature R3 of the third curved surface 411c is greater than the curvature R2 of the second curved surface 411b. That is, the relationship between the curvature R3 of the third curved surface 411c and the curvature R2 of the second curved surface 411b is R3 > R2. Therefore, when the partial outer surface 411 is viewed along the axis P of the rotor 4, the radius of curvature of the third curved surface 411c is smaller than the radius of curvature of the second curved surface 411b.

[0038] Each outer surface 411 faces the inner surface of the stator 5 via an air gap. The curvature R1 of the first curved surface 411a is the same as the curvature of the inner surface of the stator 5. As a result, the length of the air gap between the inner surface of the stator 5 and the first curved surface 411a is constant in the circumferential direction of the rotor 4. The air gap length is the dimension of the air gap in the radial direction of the rotor 4. The radial direction of the rotor 4 is along the radius of the circle centered on the axis P of the rotor 4. The fundamental wave component of the magnetic flux that contributes to the torque of the rotating electric machine 1 flows through the first curved surface 411a.

[0039] The air gap length between the inner surface of the stator 5 and the second curved surface 411b widens as the rotor 4 approaches the second reference point B from the position of the first reference point A in the circumferential direction. Similarly, the air gap length between the inner surface of the stator 5 and the third curved surface 411c widens as the rotor 4 approaches the third reference point C from the position of the second reference point B in the circumferential direction. As a result, the magnetic resistance in the air gaps between the second curved surface 411b and the third curved surface 411c and the inner surface of the stator 5 is greater than the magnetic resistance in the air gap between the first curved surface 411a and the inner surface of the stator 5. Therefore, the amount of leakage flux between two adjacent magnetic poles is suppressed, and harmonic flux in the magnetic flux density distribution in the air gap is also suppressed.

[0040] Furthermore, on each of the outer peripheral surfaces 411, the curvature R3 of the third curved surface 411c is greater than the curvature R2 of the second curved surface 411b. As a result, in the rotor 4, the magnetic flux at both ends of the permanent magnets 42 in the circumferential direction of the rotor 4 is more easily guided toward the center of the magnetic poles. Consequently, in the rotor 4, the fundamental wave component of the magnetic flux density contributing to torque increases, and the torque increases. In addition, on each of the outer peripheral surfaces 411, the first curved surface 411a and the third curved surface 411c are continuous via the second curved surface 411b, so the magnetic flux density distribution in the air gap approaches a sinusoidal distribution due to the second curved surface 411b.

[0041] Here, when viewing the partial outer surface 411 along the axis P of the rotor 4, the angle between the line connecting the first reference point A and the axis P of the rotor 4 and the magnetic pole centerline Q is defined as the first angle θ1. Also, when viewing the partial outer surface 411 along the axis P of the rotor 4, the angle between the line connecting the second reference point B and the axis P of the rotor 4 and the magnetic pole centerline Q is defined as the second angle θ2.

[0042] In this case, the first angle θ1 is an angle within the range of 10° ≤ θ1 ≤ 40° in terms of electrical angles. Also, the second angle θ2 is an angle within the range of 43° ≤ θ2 ≤ 55° in terms of electrical angles.

[0043] In rotor 4, as the range of the first curved surface 411a in Figure 3 decreases, that is, as the first angle θ1 decreases, the magnetic flux density distribution in the air gap approaches a sinusoidal distribution. However, as the range of the first curved surface 411a decreases, the fundamental wave component of the magnetic flux density in the air gap decreases, and the torque decreases. However, in rotor 4, even when the first angle θ1 is less than 10°, there is no significant difference in the magnitude of the torque compared to when the first angle θ1 is 10° or greater. Therefore, it is desirable for the first angle θ1 to be 10° or greater in rotor 4. Also, in rotor 4, as the range of the first curved surface 411a increases, the torque ripple increases, so it is desirable for the first angle θ1 to be 40° or less in electrical angle.

[0044] In this embodiment, the first angle θ1 is 10° in electrical angles, and the second angle θ2 is 54° in electrical angles. Figure 3 shows a rotor 4 with the first angle θ1 being 10° in electrical angles and the second angle θ2 being 54° in electrical angles, which is shown as rotor 4a of Embodiment 1.

[0045] Figure 4 is a front view of the main components showing the rotor 4a of Figure 3 positioned inside the stator 5. In Figure 4, the stator coil 52 and insulator 53 of the stator 5 are omitted from the illustration. The stator core 51 has a yoke 511 and a plurality of teeth 512.

[0046] The yoke 511 has a cylindrical shape. The outer surface of the yoke 511 fits into the inner surface of the frame 21. Multiple teeth 512 each protrude radially inward from the yoke 511. The multiple teeth 512 are also spaced apart from each other in the circumferential direction of the stator 5. In this embodiment, the multiple teeth 512 are arranged at equal intervals in the circumferential direction of the stator 5. The stator coil 52 shown in Figure 1 is provided on the multiple teeth 512 via an insulator 53.

[0047] Each tooth 512 has a tooth body portion 512a and a tooth tip portion 512b. The tooth body portion 512a is provided on the inner circumferential surface of the yoke 511. The tooth tip portion 512b is provided at the end of the tooth body portion 512a opposite to the yoke 511 side. Therefore, in the stator core 51, the inner end of each tooth 512 in the radial direction of the stator 5 is the tooth tip portion 512b. The inner circumferential surface of the stator 5 is formed at the tooth tip portion 512b of each tooth 512.

[0048] The dimensions of the tooth tip portion 512b in the circumferential direction of the stator 5 are larger than the dimensions of the tooth body portion 512a in the circumferential direction of the stator 5. As a result, for each tooth 512, both sides of the tooth tip portion 512b in the circumferential direction of the stator 5 protrude outward from the tooth body portion 512a.

[0049] When the stator 5 is viewed along the axis P of the rotor 4a, the angle formed by the two straight lines connecting each side of the tooth tip portion 512b in the circumferential direction of the stator 5 to the axis P of the rotor 4a is defined as the tooth angle θT. In this case, the tooth angle θT is narrower than the electrical angle between the first reference points A set on each of the two adjacent outer peripheral surfaces 411. That is, the relationship between the tooth angle θT and the first angle θ1 is such that, in terms of electrical angles, θT < (180° - 2 × θ1).

[0050] As shown in Figure 4, when the teeth 512 are positioned opposite the groove 45, if magnetic flux flows through the teeth 512 from one of the two partial outer surfaces 411 located on either side of the groove 45 to the other, the magnetic flux that flows between the two partial outer surfaces 411 becomes leakage flux φ1. If the leakage flux φ1 increases, the amount of effective magnetic flux of the permanent magnet 42 decreases, and the torque of the rotating electric machine 1 decreases.

[0051] The air gap length between the first curved surface 411a and the teeth 512 is smaller than the air gap lengths between the second curved surface 411b and the third curved surface 411c and the teeth 512, respectively. Therefore, when the position of the teeth 512 is opposite the groove 45, the amount of leakage magnetic flux φ1 increases when the first curved surface 411a faces the teeth 512.

[0052] In this embodiment, the relationship between the tooth angle θT and the first angle θ1 is such that θT < (180° - 2 × θ1) in electrical angles. As a result, when the position of the tooth 512 is opposite the groove 45, the position of the first curved surface 411a on each of the two partial outer surfaces 411 located on both sides of the groove 45 is away from the position opposite the tooth 512. This suppresses the amount of leakage flux φ1 and increases the torque of the rotating electric machine 1.

[0053] Next, we will compare the rotating electric machine 1 in Embodiment 1 with the rotating electric machine of the comparative example. In the rotating electric machine 1 in Embodiment 1, as described above, a rotor 4a is used in which the first angle θ1 is 10° in electrical angles and the second angle θ2 is 54° in electrical angles.

[0054] Figure 5 is a front view of the main part of the rotor of a comparative example rotating electric machine for comparison with the rotating electric machine 1 in Embodiment 1. Note that Figure 5 corresponds to Figure 3 in Embodiment 1. In the rotor 4b of the comparative example rotating electric machine, the curvature of each portion outer surface 411 when viewed along the axis P of the rotor 4b is the same as the curvature R1 of the first curved surface 411a in Embodiment 1 over the entire range of the portion outer surface 411. Therefore, in the comparative example rotating electric machine, the air gap length between each portion outer surface 411 of the rotor 4b and the inner surface of the stator 5 is constant over the entire range of each portion outer surface 411 in the circumferential direction of the rotor 4b. Other configurations of the comparative example rotating electric machine are the same as in Embodiment 1.

[0055] Figure 6 is a graph showing the relationship between the magnetic flux density φ and the electrical angle θ in the air gap for rotor 4a of Embodiment 1 shown in Figure 3 and rotor 4b of the comparative example shown in Figure 5. Therefore, Figure 6 shows a comparison of the magnetic flux density distribution in the air gap in the circumferential direction of the rotor for rotor 4a of Embodiment 1 and rotor 4b of the comparative example. Figure 6 also shows the relationship between the magnetic flux density φ and the electrical angle θ when the magnetic flux density distribution in the air gap in the circumferential direction of the rotor is a sinusoidal wave S.

[0056] As can be seen from Figure 6, the magnetic flux density distribution in the air gap is closer to a sine wave S in rotor 4a of Embodiment 1 than in rotor 4b of the comparative example. This indicates that torque ripple is reduced in rotor 4a of Embodiment 1 compared to rotor 4b of the comparative example.

[0057] In such a rotating electric machine 1, grooves 45 formed between multiple partial outer surfaces 411 extend to the space between two adjacent magnet insertion holes 44 in the circumferential direction of the rotor 4. When viewed along the axis P of the rotor 4, the partial outer surface 411 has a first reference point A, a second reference point B located closer to the groove 45 than the first reference point A, and a third reference point C located at the boundary between the partial outer surface 411 and the groove 45, in the section from the magnetic pole centerline Q to the groove 45. The partial outer surface 411 has a first curved surface 411a that extends from the magnetic pole centerline Q to the first reference point A, a second curved surface 411b that extends from the first reference point A to the second reference point B, and a third curved surface 411c that extends from the second reference point B to the third reference point C. The second curved surface 411b smoothly connects to the first curved surface 411a at the first reference point A. The third curved surface 411c smoothly connects to the second curved surface 411b at the second reference point B. The air gap length between the inner surface of the stator 5 and the first curved surface 411a is constant in the circumferential direction of the rotor 4. The air gap length between the inner surface of the stator 5 and the second curved surface 411b widens in the circumferential direction of the rotor 4 as it approaches the second reference point B from the position of the first reference point A. The air gap length between the inner surface of the stator 5 and the third curved surface 411c widens in the circumferential direction of the rotor 4 as it approaches the third reference point C from the position of the second reference point B. When the partial outer surface 411 is viewed along the axis P of the rotor 4, the curvature R3 of the third curved surface 411c is greater than the curvature R2 of the second curved surface 411b.

[0058] Therefore, the magnetic flux at both ends of the permanent magnets 42 in the circumferential direction of the rotor 4 can be guided toward the center of the magnetic poles by the third curved surface 411c, and the amount of leakage flux between each magnetic pole can be reduced. In addition, since the groove 45 extends between two adjacent magnet insertion holes 44, the amount of leakage flux between the two permanent magnets 42 placed in the two magnet insertion holes 44 can also be reduced by the magnetic resistance of the groove 45. As a result, the gap between the inner surface of the magnet insertion hole 44 and the permanent magnet 42 can be eliminated as much as possible, and the fundamental wave component of the magnetic flux density in the air gap can be efficiently increased. Demagnetization of the permanent magnets 42 can also be suppressed. Consequently, the magnetic flux of the permanent magnets 42 can be effectively used to generate torque, and the torque of the rotating electric machine 1 can be efficiently increased. Furthermore, the magnetic flux density distribution in the air gap in the circumferential direction of the rotor 4 can be made closer to a sinusoidal distribution by the second curved surface 411b. As a result, torque ripple can be reduced.

[0059] Furthermore, the first angle θ1 is an angle in the range of 10° ≤ θ1 ≤ 40° in electrical angles. In addition, the second angle θ2 is an angle in the range of 43° ≤ θ2 ≤ 55° in electrical angles. Therefore, while bringing the magnetic flux density distribution in the air gap closer to a sinusoidal distribution, the fundamental wave component of the magnetic flux density in the air gap can be increased even more efficiently. Moreover, by setting the second angle θ2 to an angle in the range of 43° ≤ θ2 ≤ 55° in electrical angles, the sixth harmonic component of the torque ripple can be reduced. Thus, torque can be increased even more efficiently while more reliably reducing torque ripple.

[0060] Furthermore, in the magnet insertion holes 44, the inner surface of the magnet insertion hole 44 that is located on the inside of the rotor 4 in the direction along the magnetic pole centerline Q serves as the insertion hole reference surface 441, which is perpendicular to the magnetic pole centerline Q. When the rotor 4 is viewed along its axis P, the position of the bottom surface of the groove 45 located next to the magnet insertion hole 44 is the same as the position of the insertion hole reference surface 441 in the direction along the magnetic pole centerline Q. Therefore, the amount of leakage flux between the two permanent magnets 42, each positioned in the two magnet insertion holes 44, can be more reliably suppressed by the magnetic resistance of the groove 45. This increases the amount of magnetic flux from the permanent magnets 42 that contributes to torque, allowing the magnetic flux of the permanent magnets 42 to be used more effectively in generating torque. Consequently, the torque of the rotating electric machine 1 can be increased more efficiently.

[0061] Furthermore, the relationship between the tooth angle θT and the first angle θ1 is an electrical angle, where θT < (180° - 2 × θ1). Therefore, when the position of the tooth 512 is opposite the groove 45, the position of the first curved surface 411a on each of the two partial outer surfaces 411 located on both sides of the groove 45 can be moved away from the position opposite the tooth 512. This makes it possible to more reliably suppress the amount of leakage magnetic flux between the two permanent magnets 42, each positioned in the two magnet insertion holes 44, and to further increase the torque of the rotating electric machine 1.

[0062] Embodiment 2. Figure 7 is a front view of the main part showing the rotor of a rotating electric machine according to Embodiment 2. Figure 8 is a front view of the main part showing the rotor of Figure 7 positioned inside the stator. Note that Figure 7 corresponds to Figure 3 in Embodiment 1, and Figure 8 corresponds to Figure 4 in Embodiment 1.

[0063] In Embodiment 2, the values ​​of the first angle θ1 and the second angle θ2 are different from the values ​​of the first angle θ1 and the second angle θ2 in Embodiment 1. In Embodiment 2, the first angle θ1 is 30° and the second angle θ2 is 45°. Figures 7 and 8 show a rotor 4 with the first angle θ1 set to 30° and the second angle θ2 set to 45°, which is shown as rotor 4c.

[0064] Therefore, in Embodiment 2, the range of the first curved surface 411a is larger than the range of the first curved surface 411a in Embodiment 1. Also, in Embodiment 2, the range of the second curved surface 411b is smaller than the range of the second curved surface 411b in Embodiment 1. Furthermore, in Embodiment 2, as shown in Figure 8, the relationship between the teeth angle θT and the first angle θ1 is the same as in Embodiment 1, with θT < (180° - 2 × θ1) in terms of electrical angle. Other configurations are the same as in Embodiment 1.

[0065] Figure 9 is a graph showing the relationship between magnetic flux density φ and electrical angle θ in the air gap for rotor 4a of Embodiment 1 shown in Figure 3, rotor 4c of Embodiment 2 shown in Figure 7, and rotor 4b of the comparative example shown in Figure 5. Therefore, Figure 9 shows a comparison of the magnetic flux density distribution in the air gap in the circumferential direction of the rotor for rotor 4a of Embodiment 1, rotor 4c of Embodiment 2, and rotor 4b of the comparative example. Figure 9 also shows the relationship between magnetic flux density φ and electrical angle θ when the magnetic flux density distribution in the air gap in the circumferential direction of the rotor is a sinusoidal wave S.

[0066] As can be seen from Figure 9, the magnetic flux density distribution in the air gap is closer to a sinusoidal wave S in rotor 4c of embodiment 2 than in rotor 4b of comparative example. This indicates that torque ripple is reduced in rotor 4c of embodiment 2 compared to rotor 4b of comparative example.

[0067] Furthermore, as can be seen from Figure 9, the magnetic flux density distribution in the air gap is more divergent from a sinusoidal wave S in the rotor 4c of Embodiment 2 than in the rotor 4a of Embodiment 1. However, in the rotor 4c of Embodiment 2, the range of the first curved surface 411a is larger than that of the first curved surface 411a of Embodiment 1, so the magnetic resistance in the entire air gap is lower than that of the rotor 4a of Embodiment 1. As a result, the fundamental wave component φ0 of the magnetic flux density in the air gap is larger in the rotor 4c of Embodiment 2 than in the rotor 4a of Embodiment 1.

[0068] Figure 10 is a graph comparing the fundamental wave component φ0 of the magnetic flux density in the air gap for the rotor 4a of Embodiment 1 shown in Figure 3 and the rotor 4c of Embodiment 2 shown in Figure 7. As shown in Figure 10, it can be seen that the fundamental wave component φ0 of the magnetic flux density in the air gap is larger in the rotor 4c of Embodiment 2 than in the rotor 4a of Embodiment 1. Therefore, it can be seen that the torque is increased in the rotor 4c of Embodiment 2 compared to the rotor 4a of Embodiment 1.

[0069] Thus, even if the first angle θ1 is set to 30° and the second angle θ2 is set to 45°, torque ripple can be reduced and torque can be increased efficiently.

[0070] In each of the above embodiments, when the rotor 4 is viewed along its axis P, the position of the bottom surface of the groove 45 located next to the magnet insertion hole 44 is the same as the position of the insertion hole reference surface 441 in the direction along the magnetic pole centerline Q. However, the position of the bottom surface of the groove 45 located next to the magnet insertion hole 44 may be located further inside the rotor 4 than the position of the insertion hole reference surface 441 in the direction along the magnetic pole centerline Q. In this way, the amount of leakage flux between the two permanent magnets 42 can be suppressed more reliably by the magnetic resistance of the groove 45, and the torque can be increased more efficiently.

[0071] Furthermore, in each of the above embodiments, the relationship between the tooth angle θT and the first angle θ1 is such that θT < (180° - 2 × θ1) in terms of electrical angle. However, the relationship between the tooth angle θT and the first angle θ1 may also be such that θT ≥ (180° - 2 × θ1) in terms of electrical angle. Even in this case, the third curved surface 411c can guide the magnetic flux at both ends of the permanent magnet 42 toward the center of the magnetic pole, and the amount of leakage magnetic flux between each magnetic pole can be reduced by the groove 45. As a result, the gap between the inner surface of the magnet insertion hole 44 and the permanent magnet 42 can be minimized, and the torque of the rotating electric machine 1 can be increased efficiently. In addition, the magnetic flux density distribution in the air gap in the circumferential direction of the rotor 4 can be made to resemble a sinusoidal distribution by the second curved surface 411b. As a result, torque ripple can be reduced.

[0072] The configurations shown in the embodiments described above are merely examples of the content of this disclosure. The embodiments can be combined with other known technologies. Some parts of the configurations of the embodiments can be omitted or modified without departing from the gist of this disclosure.

[0073] Examples of aspects that may be included in this disclosure are listed below as an addendum. (Note 1) A cylindrical stator, Inside the stator, there is a rotor which is arranged coaxially with the stator. Equipped with, The rotor is rotatable relative to the stator with respect to the axis of the rotor, The rotor comprises a rotor core having a plurality of magnet insertion holes spaced apart from each other in the circumferential direction of the rotor, and a plurality of permanent magnets arranged in each of the plurality of magnet insertion holes. The outer circumferential surface of the rotor core has a plurality of partial outer circumferential surfaces formed in the circumferential direction of the rotor corresponding to the respective positions of the plurality of magnet insertion holes. The outer circumferential surface of the rotor core is provided with a plurality of grooves formed between the plurality of partial outer circumferential surfaces, Each of the grooves extends between two adjacent magnet insertion holes in the circumferential direction of the rotor. The shape of the portion of the outer circumferential surface when viewed along the axis of the rotor is symmetrical with respect to the magnetic pole center line passing through the center point of the magnet insertion hole in the circumferential direction of the rotor and the axis of the rotor. On the outer peripheral surface of the portion of the rotor, when viewed along the axis of the rotor, a first reference point is set in the section from the magnetic pole center line to the groove, a second reference point is set closer to the groove than the first reference point, and a third reference point is set at the boundary between the outer peripheral surface of the portion and the groove. The aforementioned partial outer surface has a first curved surface extending from the magnetic pole centerline to the first reference point, a second curved surface extending from the first reference point to the second reference point, and a third curved surface extending from the second reference point to the third reference point. The second surface is smoothly connected to the first surface at the first reference point. The third surface is smoothly connected to the second surface at the second reference point. The air gap length between the inner circumferential surface of the stator and the first curved surface is constant in the circumferential direction of the rotor. The air gap length between the inner circumferential surface of the stator and the second curved surface widens as the rotor approaches the position of the second reference point from the position of the first reference point in the circumferential direction. The air gap length between the inner circumferential surface of the stator and the third curved surface widens as the rotor approaches the position of the third reference point from the position of the second reference point in the circumferential direction. A rotating electric machine in which, when the partial outer surface is viewed along the axis of the rotor, the curvature of the third curved surface is greater than the curvature of the second curved surface. (Note 2) When viewing the rotor along its axis, let the first angle θ1 be the angle between the straight line connecting the first reference point and the rotor axis and the magnetic pole centerline, and let the second angle θ2 be the angle between the straight line connecting the second reference point and the rotor axis and the magnetic pole centerline. The first angle θ1 is an electrical angle in the range of 10° ≤ θ1 ≤ 40°. The rotating electric machine described in Appendix 1, wherein the second angle θ2 is an electrical angle in the range of 43° ≤ θ2 ≤ 55°. (Note 3) In the magnet insertion hole, the inner surface of the magnet insertion hole that is located on the inside of the rotor in a direction along the magnetic pole center line serves as the insertion hole reference surface perpendicular to the magnetic pole center line. The rotating electric machine as described in Appendix 1 or Appendix 2, wherein, when the rotor is viewed along the axis of the rotor, the position of the bottom surface of the groove adjacent to the magnet insertion hole is the same as the position of the insertion hole reference surface, or is located inside the rotor, in the direction along the magnetic pole center line. (Note 4) The stator has a cylindrical stator core surrounding the rotor, The stator core comprises a cylindrical yoke and a plurality of teeth that protrude radially inward from the yoke and are spaced apart from each other in the circumferential direction of the stator. The inner end of each tooth in the radial direction of the stator is the tooth tip. When the stator is viewed along the axis of the rotor, the angle formed by the two straight lines connecting each of the two sides of the tooth tip portion in the circumferential direction of the stator to the axis of the rotor is defined as the tooth angle θT. When viewing the rotor along its axis, if the angle between the straight line connecting the first reference point and the rotor's axis and the magnetic pole center line is defined as the first angle θ1, The relationship between the tooth angle θT and the first angle θ1 is an electrical angle, and the relationship is θT < (180° - 2 × θ1), as described in any one of the appendices 1 to 3. [Explanation of symbols]

[0074] 1 Rotating electric machine, 4, 4a, 4c Rotor, 5 Stator, 41 Rotor core, 42 Permanent magnet, 44 Magnet insertion hole, 45 Groove, 51 Stator core, 411 Partial outer surface, 411a First curved surface, 411b Second curved surface, 411c Third curved surface, 441 Insertion hole reference surface, 511 Yoke, 512 Teeth, 512b Tip of tooth.

Claims

1. A cylindrical stator, Inside the stator, there is a rotor which is arranged coaxially with the stator. Equipped with, The rotor is rotatable relative to the stator with respect to the axis of the rotor, The rotor comprises a rotor core having a plurality of magnet insertion holes spaced apart from each other in the circumferential direction of the rotor, and a plurality of permanent magnets arranged in each of the plurality of magnet insertion holes. The outer circumferential surface of the rotor core has a plurality of partial outer circumferential surfaces formed in the circumferential direction of the rotor corresponding to the respective positions of the plurality of magnet insertion holes. The outer circumferential surface of the rotor core is provided with a plurality of grooves formed between the plurality of partial outer circumferential surfaces, Each of the grooves extends between two adjacent magnet insertion holes in the circumferential direction of the rotor. The shape of the portion of the outer circumferential surface when viewed along the axis of the rotor is symmetrical with respect to the magnetic pole center line passing through the center point of the magnet insertion hole in the circumferential direction of the rotor and the axis of the rotor. On the outer peripheral surface of the portion of the rotor, when viewed along the axis of the rotor, a first reference point is set in the section from the magnetic pole center line to the groove, a second reference point is set closer to the groove than the first reference point, and a third reference point is set at the boundary between the outer peripheral surface of the portion and the groove. The aforementioned partial outer surface has a first curved surface extending from the magnetic pole centerline to the first reference point, a second curved surface extending from the first reference point to the second reference point, and a third curved surface extending from the second reference point to the third reference point. The second surface is smoothly connected to the first surface at the first reference point. The third surface is smoothly connected to the second surface at the second reference point. The air gap length between the inner circumferential surface of the stator and the first curved surface is constant in the circumferential direction of the rotor. The air gap length between the inner circumferential surface of the stator and the second curved surface widens as the rotor approaches the position of the second reference point from the position of the first reference point in the circumferential direction. The air gap length between the inner circumferential surface of the stator and the third curved surface widens as the rotor approaches the position of the third reference point from the position of the second reference point in the circumferential direction. A rotating electric machine in which, when the partial outer surface is viewed along the axis of the rotor, the curvature of the third curved surface is greater than the curvature of the second curved surface.

2. When viewing the rotor along its axis, let the first angle θ1 be the angle between the line connecting the first reference point and the rotor axis and the magnetic pole centerline, and let the second angle θ2 be the angle between the line connecting the second reference point and the rotor axis and the magnetic pole centerline. The first angle θ1 is an electrical angle in the range of 10° ≤ θ1 ≤ 40°. The rotating electric machine according to claim 1, wherein the second angle θ2 is an electrical angle in the range of 43° ≤ θ2 ≤ 55°.

3. In the magnet insertion hole, the inner surface of the magnet insertion hole that is located on the inside of the rotor in a direction along the magnetic pole centerline serves as the insertion hole reference surface perpendicular to the magnetic pole centerline. The rotating electric machine according to claim 1 or 2, wherein, when the rotor is viewed along the axis of the rotor, the position of the bottom surface of the groove located next to the magnet insertion hole is the same as the position of the insertion hole reference surface, or is located inside the rotor, in the direction along the magnetic pole center line.

4. The stator has a cylindrical stator core surrounding the rotor, The stator core comprises a cylindrical yoke and a plurality of teeth that protrude radially inward from the yoke and are spaced apart from each other in the circumferential direction of the stator. The inner end of each tooth in the radial direction of the stator is the tooth tip. When the stator is viewed along the axis of the rotor, the angle formed by the two straight lines connecting each of the two sides of the tooth tip in the circumferential direction of the stator to the axis of the rotor is defined as the tooth angle θT. When viewing the rotor along its axis, if the angle between the straight line connecting the first reference point and the rotor's axis and the magnetic pole center line is defined as the first angle θ1, The rotating electric machine according to claim 1 or claim 2, wherein the relationship between the tooth angle θT and the first angle θ1 is an electrical angle such that θT < (180° - 2 × θ1).

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