Rotor and rotating electric machine

Abstract

To reduce cogging torque in an embedded magnet type rotor and a rotating electric machine.SOLUTION: Each of a plurality of magnetic pole portions 26 includes a permanent magnet 23 and an outer core portion 25 that is a portion radially outside the permanent magnet 23 in a rotor core 22. A radial outer surface 25a of the outer core portion 25 has an arc shape that approaches the rotation axis L1 of a rotor 20 from the magnetic pole center Ls of the magnetic pole portion 26 toward both sides in the circumferential direction when viewed from the axial direction. The diameter of the rotor core 22 is maximum at the magnetic pole center Ls, a circle having the same diameter as the maximum diameter of the rotor core 22 centered on the rotation axis L1 is defined as a reference circle Ca, and the outer peripheral surface of the rotor core 22 has a maximum displacement portion 31 that is most displaced radially inward from the reference circle Ca at the intersection of the arcuate outer surfaces 25a that are adjacent in the circumferential direction. A displacement amount Lh from the reference circle Ca in the maximum displacement portion 31 is smaller than the maximum thickness Wm of the permanent magnet 23 when the permanent magnet 23 is viewed from the axial direction.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an embedded magnet type rotor and a rotating electric machine. [Background technology]

[0002] For example, Patent Document 1 describes a rotating electric machine that uses an embedded magnet type, so-called IPM type rotor. An embedded magnet type rotor has permanent magnets embedded inside the rotor core. This makes it possible to obtain reluctance torque at the outer core portion located radially outward of the permanent magnets, in addition to magnet torque from the permanent magnets. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4898201 Summary of the Invention [Problem to be solved by the invention]

[0004] The present inventors have been studying a configuration capable of reducing the cogging torque in the above-mentioned embedded permanent magnet rotor. An object of the present invention is to reduce the cogging torque in an embedded permanent magnet rotor and a rotating electric machine. [Means for solving the problem]

[0005] The rotor that solves the above problem is a rotor (20) including a rotor core (22) and a permanent magnet (23) embedded in the rotor core, the rotor (20) including a plurality of magnetic pole portions (26) in a circumferential direction, each of the plurality of magnetic pole portions having the permanent magnet and an outer core portion (25) that is a portion of the rotor core radially outward of the permanent magnet, and a radially outer surface (25a) of the outer core portion is formed on the rotor core from a magnetic pole center (Ls) of the magnetic pole portion toward both sides in the circumferential direction as viewed in the axial direction. The rotor core has an arc shape approaching the rotation axis (L1), the diameter of the rotor core is maximum at the magnetic pole center, and a circle of the same diameter as the maximum diameter of the rotor core centered on the rotation axis is taken as a reference circle (Ca), and the outer peripheral surface of the rotor core has a maximum displacement portion (31) that is displaced the most from the reference circle toward the inner diameter at the intersection of adjacent arc-shaped outer surfaces in the circumferential direction, and the amount of displacement (Lh) from the reference circle at the maximum displacement portion is smaller than the maximum thickness (Wm) of the permanent magnet when viewed in the axial direction.

[0006] The rotating electric machine that solves the above problem includes a stator (10) and the above rotor (20) that is disposed on the inner diameter side of the stator. According to the rotor and rotating electric machine described above, the radial outer surface of the outer core portion is in the shape of an arc approaching the rotation axis of the rotor from the magnetic pole center of the magnetic pole portion toward both sides in the circumferential direction, so that the magnetic poles are smoothly switched. This makes it possible to suppress the cogging torque to a small value. Furthermore, according to this configuration, it is possible to reduce the cogging torque compared to the case where the displacement amount from the reference circle at the maximum displacement portion is greater than the maximum thickness of the permanent magnet. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a configuration diagram of a rotating electric machine having an embedded magnet type rotor according to one embodiment. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4] FIG. [Diagram 5] 4 is a diagram illustrating the characteristics of the rotor in the embodiment; FIG. [Figure 6] 4 is a diagram illustrating the characteristics of the rotor in the embodiment; FIG. [Figure 7] 4 is a diagram illustrating the characteristics of the rotor in the embodiment; FIG. [Figure 8] 3A and 3B are diagrams illustrating characteristics of the rotating electric machine in the same embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] An embodiment of the rotor and the rotating electric machine will be described below. 1 is an embedded magnet type brushless motor. The rotating electric machine M includes a substantially annular stator 10 and a substantially cylindrical rotor 20 rotatably disposed in the radial inner space of the stator 10.

[0009] (Configuration of stator 10) The stator 10 includes a substantially annular stator core 11. The stator core 11 is made of a magnetic metal material. The stator core 11 is formed, for example, by stacking a plurality of electromagnetic steel sheets in the axial direction. The stator core 11 has 12 teeth 12 in this embodiment, which extend radially inward and are arranged at equal intervals in the circumferential direction. That is, the number of slots that can be wound in the stator 10 is 12. The teeth 12 are of the same shape. For example, the radially inner end portion, which is the tip portion, of the teeth 12 is substantially T-shaped. The tip surface 12a of the teeth 12 is in the shape of a circular arc following the outer circumferential surface of the rotor 20.

[0010] The teeth 12 are wound with windings 13 in a concentrated winding manner. The windings 13 are, for example, connected in three phases, and function as U-phase, V-phase, and W-phase, as shown in an example in Fig. 1. When power is supplied to the windings 13, a rotating magnetic field for rotating the rotor 20 is generated in the stator 10. In the stator 10, the outer peripheral surface of the stator core 11 is fixed to the inner peripheral surface of the housing 14.

[0011] (Configuration of rotor 20) The rotor 20 includes a rotating shaft 21 and a substantially cylindrical rotor core 22 into whose center the rotating shaft 21 is fitted. In addition, the rotor 20 includes eight permanent magnets 23 in this embodiment, which are embedded inside the rotor core 22. The rotor core 22 is made of a magnetic metal material. The rotor core 22 is made, for example, by laminating a plurality of electromagnetic steel plates in the axial direction. The rotor 20 is disposed rotatably with respect to the stator 10, with the rotating shaft 21 being supported by a bearing (not shown) provided in the housing 14.

[0012] The rotor core 22 has magnet accommodating holes 24 for accommodating the permanent magnets 23. In this embodiment, eight magnet accommodating holes 24 are provided at equal intervals in the circumferential direction of the rotor core 22. Each magnet accommodating hole 24 has a generally V-shaped folded shape that protrudes radially inward. The magnet accommodating holes 24 have the same shape as each other. The magnet accommodating holes 24 are provided throughout the entire axial direction of the rotor core 22.

[0013] The permanent magnet 23 of this embodiment is, for example, a bonded magnet obtained by molding and solidifying a magnetic material obtained by mixing magnetic powder with resin. That is, the permanent magnet 23 is formed by using the magnet accommodating hole 24 of the rotor core 22 as a molding die, filling the magnet accommodating hole 24 with unsolidified magnetic material by injection molding without gaps, and solidifying the material in the magnet accommodating hole 24 after filling. Therefore, the hole shape of the magnet accommodating hole 24 becomes the outer shape of the permanent magnet 23. Note that, for example, a samarium iron nitrogen (SmFeN) magnet is used as the magnetic powder used for the permanent magnet 23 of this embodiment, but other rare earth magnets, etc. may also be used.

[0014] As shown in FIG. 1, the portion of the rotor core 22 radially outward of the permanent magnets 23, i.e., the portion facing the stator 10, functions as an outer core portion 25 for generating reluctance torque. The rotor 20 has a plurality of magnetic pole portions 26 including the permanent magnets 23 and the outer core portion 25. The number of the magnetic pole portions 26 is the same as the number of the permanent magnets 23, and is eight in this embodiment. That is, the rotor 20 has eight poles. The magnetic pole portions 26 have the same shape as one another. The magnetic pole portions 26 are also disposed at equal intervals in the circumferential direction. As shown in FIG. 1 as an example, each magnetic pole portion 26 functions as an N pole and an S pole. The rotor 20 is configured to generate both magnet torque and reluctance torque from such magnetic pole portions 26.

[0015] (Configuration of magnetic pole portion 26) As shown in FIG. 2, each magnetic pole portion 26 has a magnetic pole center Ls in the circumferential direction. The magnetic pole centers Ls are set at equal intervals from each other in the circumferential direction. In this embodiment, the magnetic pole centers Ls of the eight magnetic pole portions 26 are set at 45° intervals from each other in the circumferential direction. Each magnetic pole portion 26 is adjacent to the adjacent magnetic pole portion 26 in the circumferential direction, with the magnetic pole boundary line Ld as a boundary. Each magnetic pole boundary line Ld is perpendicular to the rotation axis L1 of the rotor 20. The eight magnetic pole boundary lines Ld are set at 45° intervals in the circumferential direction. The angle between adjacent magnetic pole boundaries Ld, i.e., the magnetic pole opening angle θm of the magnetic pole portion 26, is 180° in electrical angle.

[0016] The outer diameter of rotor core 22, i.e., the distance from rotation axis L1 to the outer peripheral surface of rotor core 22, is not uniform in the circumferential direction. Specifically, the outer diameter of rotor core 22 is maximum at each magnetic pole center Ls and minimum at each magnetic pole boundary line Ld. In Figures 1 and 2, a circle having the same diameter as the maximum diameter of rotor core 22 is illustrated as a reference circle Ca. In Figure 2, the diameter of reference circle Ca is D, and the radius of reference circle Ca is D / 2.

[0017] In each magnetic pole portion 26, the outer core portion 25 has an outer surface 25a which is a radially outer surface. The outer surface 25a faces the tip surface 12a of the tooth 12. When viewed from the axial direction, the outer surface 25a is in the shape of an arc centered on a central axis L2. The central axis L2 of the arc defining the outer surface 25a is parallel to the rotation axis L1 of the rotor 20, but does not coincide with the rotation axis L1. The central axis L2 is set within a range surrounded by a reference circle Ca. The radius Da of the arc defining the outer surface 25a is smaller than the radius (D / 2) of the reference circle Ca.

[0018] The portion of the outer peripheral surface of rotor core 22 that is furthest from reference circle Ca is the intersection of circumferentially adjacent outer surfaces 25a, and this intersection is defined as maximum displacement portion 31. In the following description, the distance from reference circle Ca to maximum displacement portion 31 is referred to as the displacement amount Lh of maximum displacement portion 31.

[0019] (Configuration of permanent magnet 23) The permanent magnet 23 has, for example, a generally V-shaped folded shape that protrudes radially inward. More specifically, as shown in Fig. 2, the permanent magnet 23 has a shape in which radially inner ends of a pair of straight portions 23a are connected to each other by a bent portion 23b. The radially outer end of each straight portion 23a is located near the outer circumferential surface of the rotor core 22. The permanent magnet 23 has, for example, a shape that is line-symmetrical with respect to the magnetic pole center Ls. Moreover, each straight portion 23a of each permanent magnet 23 is close to the magnetic pole boundary line Ld.

[0020] The thickness of the straight portion 23a when the permanent magnet 23 is viewed from the axial direction is W1. The thickness of the bent portion 23b when the permanent magnet 23 is viewed from the axial direction is W2. The thickness W1 of the straight portion 23a is the thickness in a direction perpendicular to the extension direction of the straight portion 23a when viewed from the axial direction. The thickness W1 of the straight portion 23a is uniform in the extension direction of the straight portion 23a, for example. Also, for example, the thickness W1 is the same for each straight portion 23a. The thickness W2 of the bent portion 23b is the thickness of the bent portion 23b at the magnetic pole center Ls. In this embodiment, the thickness W1 of the straight portion 23a is thicker than the thickness W2 of the bent portion 23b. That is, the maximum thickness Wm of the permanent magnet 23 when the permanent magnet 23 is viewed from the axial direction is the thickness W1 of the straight portion 23a. In each magnetic pole portion 26, the position of the central axis L2 of the arc defining the outer surface 25a is set to overlap with the bent portion 23b.

[0021] The magnetic pole pitch Lp is the intersection between the extension of the inner surface of each straight portion 23a of the V-shaped permanent magnet 23 and the outer circumferential surface of the rotor core 22. The embedment depth Lm is the distance from the outer circumferential surface of the rotor core 22 to the inner surface of the bent portion 23b at the magnetic pole center Ls. The permanent magnet 23 of this embodiment is set to a deep folded shape such that the embedment depth Lm is larger than the magnetic pole pitch Lp. In other words, the magnet surface of the permanent magnet 23 of this embodiment formed by the inner surfaces of each straight portion 23a and the bent portion 23b is set to be larger than the magnet surface of a known surface magnet type (not shown). In addition, by setting the embedment depth Lm to be large, the bent portion 23b of the permanent magnet 23 is located radially inward and close to the shaft insertion hole 22b into which the rotating shaft 21 is inserted at the center of the rotor core 22. This folded shape of the permanent magnet 23 is just one example, and may be modified as appropriate, such as one with a shallow embedment depth Lm or one with a substantially U-shaped folded shape with a large bent portion 23b.

[0022] 3 and 4, the permanent magnet 23 is configured to partially protrude from the axial end faces 22c, 22d of the rotor core 22, for example. The permanent magnet 23 has an embedded magnet portion 23m in the magnet accommodating hole 24 and protruding portions 23x, 23y protruding from the axial end faces 22c, 22d of the rotor core 22, respectively. Each of the axial end faces 22c, 22d of the rotor core 22 is, for example, a flat surface. The protruding portions 23x, 23y of the permanent magnet 23 can be easily realized by simply providing a recess for forming the protruding portions 23x, 23y in a molding die (not shown) for closing the magnet accommodating hole 24 that opens into the axial end faces 22c, 22d of the rotor core 22.

[0023] The protrusions 23x, 23y are provided, for example, on each of the straight portions 23a and the bent portions 23b. That is, the protrusions 23x, 23y are continuous in a V-shaped path including the straight portions 23a and the bent portions 23b of the permanent magnet 23. The protrusions 23x, 23y are provided on one axial end face 22c and the other axial end face 22d of the rotor core 22, respectively. The protrusions 23x, 23y are provided integrally and continuously with the embedded magnet portion 23m of the permanent magnet 23 located in the magnet accommodating hole 24 of the rotor core 22 using the same material.

[0024] Such protruding portions 23x, 23y of the permanent magnet 23 are the ends of the permanent magnet 23 located at the axial end faces 22c, 22d of the rotor core 22, and function to generate the leakage magnetic flux φb shown in FIG. 3, which is likely to be generated at the ends of the permanent magnet 23, at these locations. In other words, more of the magnetic flux of the embedded magnet portion 23m located in the rotor core 22 of the permanent magnet 23 flows along the radial direction without leaking from the axial end faces 22c, 22d to the outside. More of the magnetic flux becomes effective magnetic flux φa that contributes to the torque of the rotating electric machine M. The protruding portions 23x, 23y are set to have an appropriate protruding amount D1 from the axial end faces 22c, 22d of the rotor core 22 while increasing the effective magnetic flux φa. The protruding amount D1 of the protruding portions 23x, 23y may differ from the illustrated dimensions and the actual dimensions.

[0025] The permanent magnets 23, which are mainly provided inside the magnet accommodating holes 24 of the rotor core 22, are magnetized from the outside of the rotor core 22 using a magnetizing device (not shown) so that the magnets function as intended magnets after the magnetic material has solidified. The permanent magnets 23 are magnetized so that the polarities are alternately different in the circumferential direction of the rotor core 22. Each permanent magnet 23 is also magnetized in its thickness direction.

[0026] The operation of the rotor 20 of the rotating electric machine M of this embodiment will be described. FIG. 5 shows the results of a comparison between the first embodiment, which is the present embodiment, the second embodiment, and a comparative example. The first embodiment is the above embodiment. That is, in the first embodiment, the outer peripheral surface of the rotor core 22 has the above-mentioned configuration, that is, in each magnetic pole portion 26, the outer surface 25a of the outer core portion 25 forms an arc shape centered on the central axis L2. Also, in the first embodiment, the ends of the permanent magnets 23 protrude as protrusions 23x and 23y from axial end faces 22c and 22d on both sides of the rotor core 22, respectively.

[0027] The second embodiment is a configuration in which the protruding portions 23x, 23y of each permanent magnet 23 in the above embodiment are omitted, that is, each permanent magnet 23 does not protrude in the axial direction from the magnet accommodating hole 24. In the second embodiment, the shape of the outer circumferential surface of the rotor core 22 as viewed in the axial direction is the same as that of the first embodiment.

[0028] In the comparative example, the shape of the outer peripheral surface of rotor core 22 as viewed in the axial direction is a circle along reference circle Ca. In addition, in the comparative example, the ends of permanent magnets 23 do not protrude from axial end faces 22c, 22d of rotor core 22.

[0029] FIG. 5 shows the magnitude of the cogging torque generated in the rotating electric machine and the ratio of the torque to the volume of the permanent magnet 23 (torque / magnet volume) in each of the comparative example, the first embodiment, and the second embodiment. The comparison in the figure is a comparison between the first embodiment and the second embodiment when the comparative example is set to 1.0. As shown in the figure, the cogging torque is sufficiently smaller in the first and second embodiments than in the comparative example. Furthermore, the cogging torque in the second embodiment is slightly smaller than that in the first embodiment.

[0030] Fig. 6 shows the relationship between the ratio (Lh / Wm) of the displacement Lh to the maximum thickness Wm of the permanent magnet 23 and the magnitude of the cogging torque. Note that a configuration where the ratio (Lh / Wm) is zero is a comparative configuration where the displacement Lh is zero, that is, the shape of the outer circumferential surface of the rotor core 22 as viewed from the axial direction is a circle along the reference circle Ca. The vertical axis in Fig. 6 represents the cogging torque ratio of 1.0 when the ratio (Lh / Wm) is zero.

[0031] As shown in the figure, the cogging torque ratio is smaller when the ratio (Lh / Wm) is less than 1.0 compared to when the ratio (Lh / Wm) is 1.0 or more. As the ratio (Lh / Wm) decreases from 1.0 to approximately 0.4, the cogging torque ratio decreases quadratically, and when the ratio (Lh / Wm) is approximately 0.4, the cogging torque ratio is at a minimum. As the ratio (Lh / Wm) approaches zero from approximately 0.4, the cogging torque ratio increases quadratically.

[0032] When the ratio (Lh / Wm) is 0.8, the cogging torque ratio is 1.0. In other words, in the range of 0<(Lh / Wm)<0.8, the cogging torque ratio is less than 1.0. Therefore, by setting the ratio (Lh / Wm) within the range of 0<(Lh / Wm)<0.8, it is possible to keep the cogging torque small compared to a comparative configuration in which the displacement amount Lh is zero.

[0033] Furthermore, if the ratio (Lh / Wm) is within the range of 0.33≦(Lh / Wm)≦0.47, the cogging torque ratio is approximately 0.3 or less. In other words, by setting the ratio (Lh / Wm) within the range of 0.33≦(Lh / Wm)≦0.47, it is possible to suppress the cogging torque to approximately 1 / 3 compared to a comparative configuration in which the displacement amount Lh is zero. It is preferable that the ratio (Lh / Wm) is set to 0.4, which minimizes the cogging torque ratio. Furthermore, even when considering manufacturing tolerances, it is preferable that the ratio (Lh / Wm) is set to fall within the range of 0.33≦(Lh / Wm)≦0.47.

[0034] 5, the ratio (torque / magnet volume) of the second embodiment is slightly smaller than that of the comparative example. The ratio (torque / magnet volume) of the first embodiment is approximately the same as that of the comparative example and is larger than that of the second embodiment.

[0035] FIG. 7 shows the relationship between the protruding amount D1 of the protruding parts 23x, 23y and the ratio (torque / magnet volume) in the above embodiment. As shown in the figure, when the protruding amount D1 of the protruding parts 23x, 23y is zero or more, that is, when the protruding parts 23x, 23y are provided, the effective magnetic flux φa increases and the ratio (torque / magnet volume) rises. Even when the protruding amount D1 is zero or more, the ratio (torque / magnet volume) rises for a while and then gradually falls. This is considered to be the result of suppressing the magnet volume small by making the thickness W2 of the bent part 23b thinner than the thickness W1 of the straight part 23a while minimizing the leakage of the magnetic flux of the embedded magnet part 23m of the permanent magnet 23 from the axial end faces 22c, 22d of the rotor core 22. The protruding amount D1 is set to an appropriate value in consideration of the relationship with the ratio (torque / magnet volume) as shown in FIG. Since an increase in the protrusion amount D1 leads to an increase in the weight of the rotor 20 and an increase in the magnetic material of the permanent magnet 23, it is preferable to take this into consideration when setting the protrusion amount D1.

[0036] FIG. 8 shows the relationship between the ratio (Lh / Lg) of the displacement amount Lh to the air gap Lg and the magnitude of the cogging torque. The configuration where the ratio (Lh / Lg) is zero is a comparative configuration where the displacement amount Lh is zero, that is, the shape of the outer circumferential surface of the rotor core 22 as viewed from the axial direction is a circle along the reference circle Ca. The vertical axis in FIG. 8 indicates that the cogging torque ratio when the ratio (Lh / Lg) is zero is 1.0. The air gap Lg shown in FIG. 1 is the difference between the inner radius of the stator 10 and the radius D / 2 of the reference circle Ca. The inner radius of the stator 10 is the distance from the rotation axis L1 to the tip surface 12a of the tooth 12.

[0037] As shown in Fig. 8, as the ratio (Lh / Lg) increases from zero to approximately 0.2, the cogging torque ratio decreases quadratically, and when the ratio (Lh / Lg) is approximately 0.2, the cogging torque ratio is at a minimum. Then, as the ratio (Lh / Lg) increases from approximately 0.2, the cogging torque ratio increases quadratically. When the ratio (Lh / Lg) is greater than zero, the cogging torque ratio is less than 1.0. Therefore, in a configuration in which the displacement amount Lh is greater than zero, it is possible to keep the cogging torque small compared to a comparative configuration in which the displacement amount Lh is zero.

[0038] When the ratio (Lh / Lg) is 1.0 or more, the cogging torque ratio is smaller than when the ratio (Lh / Lg) is less than 1.0. When the ratio (Lh / Lg) is in the range of 1.0≦(Lh / Lg), the cogging torque ratio is 0.5 or less. Therefore, by setting the displacement amount Lh to a value equal to or greater than the air gap Lg, it is possible to halve the cogging torque compared to a comparative configuration in which the displacement amount Lh is zero.

[0039] Furthermore, if the ratio (Lh / Lg) is within the range of 1.67≦(Lh / Lg)≦2.33, the cogging torque ratio is approximately 0.3 or less. That is, by setting the ratio (Lh / Lg) within the range of 1.67≦(Lh / Lg)≦2.33, it is possible to suppress the cogging torque to approximately 1 / 3 compared to a comparative configuration in which the displacement amount Lh is zero. It is preferable that the ratio (Lh / Lg) is set to approximately 0.2, at which the cogging torque ratio is minimized. Furthermore, even when considering manufacturing tolerances, it is preferable that the ratio (Lh / Lg) is set to fall within the range of 1.67≦(Lh / Lg)≦2.33.

[0040] (Relationship between the radius of the reference circle Ca and the maximum thickness Wm of the permanent magnet 23) The inventors also studied the correlation between the ratio (Wm / (D / 2)) of the maximum thickness Wm of the permanent magnet 23 to the radius D / 2 of the reference circle Ca, and the magnet torque.The inventors then obtained the range of the ratio (Wm / (D / 2)) that provides a suitable magnet torque, as shown in the following formula (a).

[0041] -0.0006D+0.1626-0.5 / (D / 2)≦Wm / (D / 2)≦-0.0006D+0.1626+0.5 / (D / 2)…(a) Therefore, the diameter D of the reference circle Ca, that is, the suitable maximum thickness Wm of the permanent magnet 23 relative to the maximum diameter of the rotor core 22 can be easily set from the above formula (a) depending on the specifications of the rotating electric machine M, etc.

[0042] The effects of this embodiment will be described. (1) In the rotor 20, the displacement Lh from the reference circle Ca at the maximum displacement portion 31 is smaller than the maximum thickness Wm of the permanent magnet 23 when viewed from the axial direction. According to this configuration, the radial outer surface 25a of the outer core portion 25 is in the shape of an arc approaching the rotation axis L1 from the magnetic pole center Ls toward both sides in the circumferential direction, so that the magnetic poles are smoothly switched. This makes it possible to suppress the cogging torque to a small value. Furthermore, according to this configuration, it is possible to reduce the cogging torque compared to the case where the displacement Lh from the reference circle Ca at the maximum displacement portion 31 is larger than the maximum thickness Wm of the permanent magnet 23. In the above embodiment, the displacement Lh is changed by changing the radius Da of the arc that defines the outer surface 25a in each magnetic pole portion 26. For example, the larger the radius Da is in each magnetic pole portion 26, the smaller the displacement Lh becomes.

[0043] (2) The permanent magnet 23 has a folded shape that protrudes radially inward. This configuration makes it possible to secure a large surface area of ​​the permanent magnet 23 that faces the outer core portion 25. This makes it possible to improve the magnet torque.

[0044] (3) The axial end faces 22c, 22d of the rotor core 22 are flat. The permanent magnet 23 is configured to have protruding portions 23x, 23y that at least partially protrude from the axial end faces 22c, 22d of the rotor core 22. With this configuration, the ends of the permanent magnet 23 are the protruding portions 23x, 23y, so that leakage magnetic flux φb generated at the ends of the permanent magnet 23 is concentrated at the protruding portions 23x, 23y. In addition, in the embedded magnet portion 23m of the permanent magnet 23 located in the rotor core 22, the path of the magnetic flux that attempts to leak from the axial end faces 22c, 22d of the rotor core 22 exceeds the protruding portions 23x, 23y, so the path length of the magnetic flux is longer. Therefore, the magnetic flux in embedded magnet portion 23m is prevented from leaking from axial end faces 22c, 22d of rotor core 22, and the magnetic flux generated in embedded magnet portion 23m flows radially throughout the entire axial direction within rotor core 22. In this way, most of the magnetic flux generated throughout the entire axial direction of embedded magnet portion 23m becomes effective magnetic flux φa that contributes to the torque of the rotating electric machine M, making it possible to increase the amount of effective magnetic flux φa.

[0045] (4) The ratio (Lh / Wm) of the displacement Lh to the maximum thickness Wm of the permanent magnet 23 is configured to satisfy 0<(Lh / Wm)<0.8. With this configuration, it is possible to suppress the cogging torque to a smaller value compared to a comparative configuration in which the displacement Lh is zero.

[0046] (5) The ratio (Lh / Wm) of the displacement Lh to the maximum thickness Wm of the permanent magnet 23 is configured to satisfy 0.33≦(Lh / Wm)≦0.47. With this configuration, it is possible to reduce the cogging torque to about 1 / 3 compared to a comparative configuration in which the displacement Lh is zero. Even if the ratio (Lh / Wm) deviates from 0.4 due to manufacturing variations, by setting it to fall within the range of 0.33≦(Lh / Wm)≦0.47, it is possible to stably obtain the effect of reducing the cogging torque.

[0047] (6) The displacement Lh is set to be equal to or larger than the air gap Lg, which is the difference between the inner diameter of the stator 10 and the diameter of the reference circle Ca. This configuration makes it possible to reduce the cogging torque compared to a configuration in which the displacement Lh is smaller than the air gap Lg.

[0048] (7) The ratio (Lh / Lg) of the displacement Lh to the air gap Lg is configured to satisfy 1.67≦(Lh / Lg)≦2.33. With this configuration, it is possible to reduce the cogging torque to about one-third compared to a configuration in which the displacement Lh is zero. Even if the ratio (Lh / Lg) deviates from approximately 0.2 due to manufacturing variations, by setting it to fall within the range of 1.67≦(Lh / Lg)≦2.33, it is possible to stably obtain the effect of reducing the cogging torque.

[0049] (8) The number of magnetic pole portions 26 in the rotor 20 is eight, and the number of winding slots in the stator 10 is twelve. With this configuration, it is possible to reduce cogging torque in the rotating electric machine M with eight poles and twelve slots.

[0050] This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction. In the above embodiment, the thickness W1 of the straight portion 23a is greater than the thickness W2 of the bent portion 23b, but this is not limited thereto, and the thickness W1 of the straight portion 23a may be equal to the thickness W2 of the bent portion 23b. Also, the thickness W1 of the straight portion 23a may be thinner than the thickness W2 of the bent portion 23b. In this case, the thickness W2 of the bent portion 23b becomes the maximum thickness Wm of the permanent magnet 23 when viewed from the axial direction.

[0051] The configuration of the protruding portions 23x, 23y at the ends of the permanent magnet 23 protruding from the axial end faces 22c, 22d of the rotor core 22 may be changed as appropriate. For example, the protruding portions 23x, 23y may be partially provided in a V-shaped path including the straight portion 23a and the bent portion 23b of the permanent magnet 23. Also, for example, a configuration in which one of the protruding portions 23x, 23y is omitted may be used. Also, for example, the protruding portion may be partially provided in a thickness direction perpendicular to the extension direction of the V-shaped path of the permanent magnet 23. Also, for example, the protruding amount D1 of the protruding portions 23x, 23y may not be uniform in the extension direction of the V-shaped path of the permanent magnet 23. Also, for example, the protruding portions 23x, 23y of the permanent magnet 23 may be separate from the embedded magnet portion 23m. In this case, the magnet materials of the protruding portions may be different from each other. Furthermore, for example, it is not necessary to provide the protruding portions 23x, 23y protruding from the axial end faces 22c, 22d of the rotor core 22 on all of the permanent magnets 23 arranged in the circumferential direction of the rotor 20.

[0052] The configuration of the permanent magnet 23, such as its shape, is not limited to the above embodiment, and can be appropriately changed according to the configuration of the rotating electric machine M. For example, the shape of the permanent magnet 23 as viewed from the axial direction may be a U-shape or other folded shape that is convex radially inward of the rotor 20. Also, for example, the shape of the permanent magnet 23 as viewed from the axial direction may be a curved shape that is convex radially outward of the rotor 20. Also, for example, the permanent magnet 23 may be substantially rectangular parallelepiped, and the permanent magnet 23 may be arranged so that one side of the permanent magnet 23 is perpendicular to a straight line passing through the rotation axis L1 and the magnetic pole center Ls.

[0053] Furthermore, the number of permanent magnets 23 included in one magnetic pole portion 26 is not limited to one. For example, the bent portion 23b may be omitted from the permanent magnet 23 of the above embodiment, so that the pair of straight portions 23a are separated from each other.

[0054] Although the permanent magnets 23 are formed by injection molding a magnetic material into the magnet accommodating holes 24 of the rotor core 22, the permanent magnets 23 may be manufactured in advance and then inserted and fixed into the magnet accommodating holes 24 of the rotor core 22.

[0055] Although a samarium iron nitrogen (SmFeN) magnet was used for the permanent magnet 23, other rare earth magnets, ferrite, etc. may also be used. Also, although a bonded magnet was used for the permanent magnet 23, a sintered magnet, etc. may also be used.

[0056] Although the rotor core 22 is configured by stacking a plurality of electromagnetic steel plates in the axial direction, it may have another configuration, such as by sintering magnetic powder. Similarly, the stator core 11 is configured by laminating a plurality of electromagnetic steel plates in the axial direction, but may be configured in other ways, such as by sintering magnetic powder.

[0057] The number of poles of the rotor 20, that is, the number of magnetic pole portions 26 and the number of slots of the stator 10 are not limited to those in the above embodiment, and may be changed as appropriate. The N poles and S poles of the rotor 20 shown in FIG. 1 and the U-phase, V-phase and W-phase of the stator 10 shown in FIG. 1 are merely examples and may be changed as appropriate.

[0058] Other than the above, the configuration of the rotor 20 and the configuration of the rotating electric machine M may be changed as appropriate. The embodiments and modified examples disclosed herein are illustrative in all respects, and the present invention is not limited to these examples. That is, the scope of the present invention is defined by the claims, and it is intended to include all modifications within the meaning and scope equivalent to the claims.

[0059] The technical ideas that can be understood from the above-described embodiment and modified examples will be described. (A) A rotor configured to satisfy the following equation using the maximum thickness (Wm) of the permanent magnet, the diameter D of the reference circle Ca, and the radius (D / 2) of the reference circle: -0.0006D+0.1626-0.5 / (D / 2)≦Wm / (D / 2)≦-0.0006D+0.1626+0.5 / (D / 2). With this configuration, it is possible to set the maximum thickness of the permanent magnet that provides an appropriate magnet torque relative to the diameter of the reference circle Ca, i.e., the maximum diameter of the rotor core. [Explanation of symbols]

[0060] M rotating electric machine, 10 stator, 20 rotor, 22 rotor core, 22c, 22d axial end face, 23 permanent magnet, 23x, 23y protrusion, 25 outer core portion, 25a outer surface, 26 magnetic pole portion, 31 maximum displacement portion, Ca reference circle, L1 rotation axis, Lg air gap, Lh displacement amount, Ls magnetic pole center, Wm maximum thickness of permanent magnet.

Claims

1. A rotor core (22); A permanent magnet (23) embedded in the rotor core; A rotor (20) comprising: A plurality of magnetic pole portions (26) are provided in a circumferential direction, Each of the plurality of magnetic pole portions has the permanent magnet and an outer core portion (25) that is a portion of the rotor core radially outward from the permanent magnet, The radial outer surface (25a) of the outer core portion has an arc shape approaching the rotation axis (L1) of the rotor from the magnetic pole center (Ls) of the magnetic pole portion toward both sides in the circumferential direction, as viewed in the axial direction, The diameter of the rotor core is maximum at the magnetic pole center, and a circle having the same diameter as the maximum diameter of the rotor core and centered on the rotation axis is defined as a reference circle (Ca); The outer circumferential surface of the rotor core has a maximum displacement portion (31) that is most displaced from the reference circle toward the inner diameter side at an intersection between the arc-shaped outer surfaces adjacent in the circumferential direction, a displacement (Lh) from the reference circle at the maximum displacement portion is smaller than a maximum thickness (Wm) of the permanent magnet when viewed from the axial direction, The ratio (Lh / Wm) of the displacement amount to the maximum thickness of the permanent magnet is 0.33≦(Lh / Wm)≦0.47 The rotor is configured to satisfy the above.

2. The permanent magnet has a folded shape that is convex toward the inside in the radial direction. The rotor of claim 1 .

3. The axial end faces (22c, 22d) of the rotor core are flat surfaces, The permanent magnet is configured to have a protruding portion (23x, 23y) at least a part of which protrudes from the axial end surface of the rotor core, A rotor according to claim 1 or 2.

4. A stator (10); A rotating electric machine comprising: a rotor (20) according to any one of claims 1 to 3, which is disposed on an inner diameter side of the stator.

5. The displacement amount is set to be equal to or greater than an air gap (Lg) which is a difference between an inner diameter of the stator and a diameter of the reference circle. The rotating electric machine according to claim 4.

6. The ratio (Lh / Lg) of the displacement amount to the air gap is 1.67≦(Lh / Lg)≦2.33 is configured to satisfy The rotating electric machine according to claim 5 .

7. The number of the magnetic pole portions in the rotor is eight, The number of winding slots in the stator is 12. The rotating electric machine according to any one of claims 4 to 6.

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