Rotary electric machine

Abstract

To provide a rotary electric machine capable of suppressing cogging torque.SOLUTION: The rotary electric machine includes a stator 30 positioned radially outward of a rotor. The rotor has a shaft extending axially about a central axis, a rotor core fixed to the shaft, a plurality of magnet sections arranged circumferentially on a radially outward surface of the rotor core, and a magnetic section arranged on a radially outward surface of each magnet section and having a curved outer circumferential surface. The stator has a stator core 31 facing the rotor radially across a gap. The stator core has an annular core back portion, and a plurality of teeth sections 33 arranged along the inner circumferential surface of the core back portion. The tooth section includes a tooth body section 34 extending radially inward from the inner circumferential surface of the core back section, and an umbrella section 35 projecting circumferentially on both sides at the tip of the tooth body section. A groove section 34a extending axially is provided on the surface of the tooth section facing radially inward.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a rotating electric machine. [Background technology]

[0002] In motors having a rotor and a stator, in order to suppress vibration and noise during operation, a configuration has been disclosed in which grooves are provided in the shoes located on both sides of the tip of the body of the stator core to suppress cogging torque (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2019-527016 Summary of the Invention [Problem to be solved by the invention]

[0004] In the motor described above, if the curvature of the outer peripheral surface of the rotor facing the stator is small, the magnetic flux density entering the stator from the rotor tends to change suddenly when the rotor rotates, making it difficult to suppress cogging torque.

[0005] In view of the above circumstances, one aspect of the present invention has an object to provide a rotating electric machine capable of suppressing cogging torque. [Means for solving the problem]

[0006] One aspect of the rotating electric machine of the present invention includes a rotor rotatable about a central axis and a stator positioned radially outward of the rotor. The rotor includes a shaft extending axially about the central axis, a rotor core fixed to the shaft, a plurality of magnet portions arranged circumferentially on the radially outer surface of the rotor core, and a magnetic portion with a curved outer surface provided on the radially outer surface of each of the magnet portions. The stator has a stator core facing the rotor radially across a gap. The stator core has an annular core back portion centered on the central axis and a plurality of teeth portions arranged along the inner peripheral surface of the core back portion. The teeth portions include tooth main portions extending radially inward from the inner peripheral surface of the core back portion and umbrella portions protruding circumferentially on both sides at the tip ends of the tooth main portions. Grooves extending along the axial direction are provided on the radially inward surfaces of the teeth portions. [Effects of the Invention]

[0007] According to one aspect of the present invention, it is possible to provide a rotating electric machine capable of suppressing cogging torque. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a rotating electric machine according to an embodiment. [Figure 2] FIG. 2 is a perspective view showing a part of the rotor of one embodiment. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1, showing the rotating electric machine according to the embodiment. [Figure 4] FIG. 4 is a cross-sectional view showing a part of the stator core of one embodiment. [Figure 5] FIG. 5 is a diagram showing the relationship between the groove width ratio and the cogging torque and motor torque in one embodiment. [Figure 6] FIG. 6 is a cross-sectional view showing a part of a stator core according to a modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] In the following description, the Z axis is shown in the figures where appropriate. The Z axis is the direction in which the central axis J of the rotor in the embodiment described below extends. The central axis J shown in each figure is a virtual axis. In the following description, the direction in which the central axis J extends, i.e., the direction parallel to the Z axis, is referred to as the "axial direction." The radial direction centered on the central axis J is simply referred to as the "radial direction." The circumferential direction centered on the central axis J is simply referred to as the "circumferential direction." The side of the axial direction toward which the arrow of the Z axis points (+Z side) is referred to as the "upper side." The side of the axial direction opposite to the side toward which the arrow of the Z axis points (-Z side) is referred to as the "lower side." Note that the terms "upper side" and "lower side" are simply names used to describe the relative positional relationships of the various parts, and the actual positional relationships may be other than those indicated by these names.

[0010] The circumferential direction is indicated by the arrow θ in each drawing. The side of the circumferential direction toward which the arrow θ points is called the "one circumferential side." The side of the circumferential direction opposite to the side toward which the arrow θ points is called the "other circumferential side." The one circumferential side is the side (+θ side) that moves clockwise around the central axis J when viewed from above (+Z side). The other circumferential side is the side (-θ side) that moves counterclockwise around the central axis J when viewed from above.

[0011] <Embodiment> 1 is a motor attached to a device mounted on a vehicle. The device to which the rotating electric machine 10 is attached may be an automatic transmission or a drive unit that drives an axle of the vehicle. The rotating electric machine 10 includes a housing 11, a rotor 20, a stator 30, a first bearing 15, and a second bearing 16.

[0012] The housing 11 accommodates the rotor 20, the stator 30, the first bearing 15, and the second bearing 16. The housing 11 has a cylindrical portion 12, an upper cover portion 13, and a first bearing holder 14. The cylindrical portion 12 has a cylindrical shape that extends axially around a central axis J. The cylindrical portion 12 is open on the upper side. The cylindrical portion 12 has a side wall portion 12a, a lower wall portion 12b, and a second bearing holder 12c.

[0013] The side wall portion 12a has a cylindrical shape extending in the axial direction around the central axis J. The side wall portion 12a surrounds the rotor 20, the stator 30, the first bearing 15, and the second bearing 16 from the radially outer side. The upper end of the side wall portion 12a is the upper end of the cylindrical portion 12. An opening 12d that opens upward is provided at the upper end of the side wall portion 12a.

[0014] The lower wall portion 12b has an annular plate shape centered on the central axis J. The plate surface of the lower wall portion 12b faces the axial direction. The radially outer end of the lower wall portion 12b is connected to the lower end of the side wall portion 12a. The lower wall portion 12b is provided with a lower wall hole 12e that penetrates the lower wall portion 12b in the axial direction. When viewed in the axial direction, the lower wall hole 12e has a circular shape centered on the central axis J.

[0015] The second bearing retaining portion 12c protrudes upward from the lower wall portion 12b. The second bearing retaining portion 12c is cylindrical and has a center on the central axis J. The second bearing retaining portion 12c opens upward. The inner diameter of the second bearing retaining portion 12c is larger than the inner diameter of the lower wall hole 12e. The second bearing 16 is retained on the inner peripheral surface of the second bearing retaining portion 12c.

[0016] The upper cover part 13 has a disk shape centered on the central axis J. The plate surface of the upper cover part 13 faces the axial direction. The upper cover part 13 is fixed to the upper end of the cylindrical part 12. The upper cover part 13 closes the opening 12d from above.

[0017] The first bearing holder 14 is fixed to a portion of the inner circumferential surface of the side wall portion 12a that is above the rotor 20 and the stator 30. The first bearing holder 14 has a substantially annular shape centered on the central axis J. The first bearing 15 is held on the inner circumferential surface of the first bearing holder 14.

[0018] The rotor 20 is rotatable about a central axis J. The rotor 20 includes a rotor core 21, a plurality of magnet portions 22, a plurality of magnetic portions 23, and a shaft 24.

[0019] The rotor core 21 has a cylindrical shape extending in the axial direction around the central axis J. The rotor core 21 surrounds the shaft 24 from the radially outer side. The rotor core 21 is magnetic. The rotor core 21 is, for example, a laminated steel plate formed by stacking multiple electromagnetic steel plates in the axial direction. As shown in FIG. 2, the rotor core 21 has a polygonal shape when viewed in the axial direction. In this embodiment, the rotor core 21 has a substantially octagonal shape when viewed in the axial direction. The rotor core 21 has multiple hole portions 21a, multiple flat portions 21b, and through holes 21c.

[0020] As shown in FIG. 1, each of the plurality of holes 21a is a hole that penetrates the rotor core 21 in the axial direction. As shown in FIG. 2, when viewed in the axial direction, each of the holes 21a has a substantially circular shape. The holes 21a are arranged at intervals from one another in the circumferential direction. The holes 21a are arranged surrounding the central axis J. In this embodiment, the rotor core 21 has eight holes 21a. By providing the rotor core 21 with a plurality of holes 21a, it is possible to reduce the weight of the rotor core 21 and cut material costs.

[0021] The multiple flat surfaces 21b are radially outer surfaces of the rotor core 21. The flat surfaces 21b are arranged at intervals from one another along the circumferential direction. In this embodiment, the rotor core 21 has eight flat surfaces 21b. Each flat surface 21b has a planar shape that extends in a direction perpendicular to the radial direction. Each flat surface 21b extends in the axial direction over the entire axial length of the rotor core 21. In this embodiment, the axial length of each flat surface 21b is longer than its circumferential length.

[0022] As shown in FIG. 1, the through hole 21c is a hole that penetrates the rotor core 21 in the axial direction. When viewed from the axial direction, the through hole 21c has a circular shape centered on the central axis J. A shaft 24 is inserted into the through hole 21c. The shaft 24 is fixed to the inner circumferential surface of the through hole 21c. In this way, the rotor core 21 is fixed to the shaft 24.

[0023] As shown in FIG. 2 , each of the multiple magnet portions 22 is provided on the flat portion 21b. That is, each of the multiple magnet portions 22 is provided on the radially outer surface of the rotor core 21. In this embodiment, each magnet portion 22 is fixed to the flat portion 21b. Each magnet portion 22 has a plate shape extending in the axial direction. The plate surface of each magnet portion 22 faces the radial direction. In the axial direction, the upper end of each magnet portion 22 is located at the same position as the upper end of the rotor core 21. In the axial direction, the lower end of each magnet portion 22 is located at the same position as the lower end of the rotor core 21. The magnet portions 22 are arranged at intervals from each other in the circumferential direction. In this embodiment, the rotor 20 has eight magnet portions 22. In this embodiment, the rotor 20 has eight poles. The magnetic pole facing radially outward of one magnet portion 22 is different from the magnetic pole facing radially outward of another magnet portion 22 located adjacent to that magnet portion 22 in the circumferential direction.

[0024] As shown in FIG. 1, each of the multiple magnetic portions 23 is provided on the radially outer surface of the magnet portion 22. Each magnetic portion 23 is fixed to the radially outer surface of the magnet portion 22. Each magnetic portion 23 faces the stator 30 at a distance from the stator 30 in the radial direction. As shown in FIG. 2, each magnetic portion 23 has a columnar shape extending in the axial direction. When viewed from the axial direction, each magnetic portion 23 has a substantially semicircular shape protruding radially outward. In the axial direction, the upper end of each magnetic portion 23 is located at the same position as the upper end of the rotor core 21. In the axial direction, the lower end of each magnetic portion 23 is located at the same position as the lower end of the rotor core 21. The magnetic portions 23 are located at intervals from one another in the circumferential direction. In this embodiment, the rotor 20 has eight magnetic portions 23. In this embodiment, the magnetic portions 23 are made of a magnetic material. The magnetic portions 23 are made of a metal material such as iron or steel. Each magnetic portion 23 has a curved surface portion 23a.

[0025] The curved surface portion 23a is a surface of the outer circumferential surface of the magnetic portion 23 that faces radially outward. When viewed from the axial direction, the curved surface portion 23a has a generally arcuate shape that protrudes radially outward. In other words, the outer circumferential surface of the magnetic portion 23 is curved. As shown in FIG. 1, the curved surface portion 23a faces the stator 30 in the radial direction.

[0026] The shaft 24 has a generally cylindrical shape extending in the axial direction around the central axis J. The shaft 24 is passed axially through the through hole 21c of the rotor core 21. The shaft 24 is fixed to the inner circumferential surface of the through hole 21c. An upper portion of the shaft 24 is supported by the first bearing 15. A lower portion of the shaft 24 is supported by the second bearing 16. The shaft 24 is supported by the first bearing 15 and the second bearing 16 so as to be rotatable around the central axis J. This allows the rotor 20 to rotate around the central axis J. The lower end of the shaft 24 protrudes outside the housing 11 through the lower wall hole 12e.

[0027] The first bearing 15 rotatably supports an upper portion of the shaft 24. The second bearing 16 rotatably supports a lower portion of the shaft 24. In this embodiment, the first bearing 15 and the second bearing 16 are ball bearings. The first bearing 15 and the second bearing 16 may be rolling bearings other than ball bearings, or may be plain bearings.

[0028] The stator 30 is located radially outward of the rotor 20. The stator 30 faces the rotor 20 with a radial gap therebetween. The stator 30 is fixed to the inner circumferential surface of the side wall portion 12a. The stator 30 includes a stator core 31, an insulator 37, and a plurality of coils 38.

[0029] The stator core 31 is annular and extends in the axial direction around the central axis J. The stator core 31 faces the rotor 20 in the radial direction via a gap. The stator core 31 is magnetic. The stator core 31 is, for example, a laminated steel plate formed by stacking multiple electromagnetic steel plates in the axial direction. The axial dimension of the stator core 31 is larger than the axial dimension of the rotor 20. That is, the axial dimension of the stator core 31 is larger than the axial dimensions of the rotor core 21, the magnet portion 22, and the magnetic portion 23. Therefore, according to this embodiment, it is easier to reduce the magnetic flux entering the stator core 31 from each of the upper and lower edges of the rotor 20 compared to when the axial dimension of the stator core 31 is smaller than or the same as the axial dimension of the rotor 20. Therefore, when the rotor 20 rotates around the central axis J, it is easier to reduce the fluctuation amount per unit time of the magnetic flux entering the stator core 31 from the rotor 20, thereby suppressing cogging torque. The stator core 31 has a core back portion 32 and a plurality of teeth portions 33 .

[0030] 3, the core back portion 32 has an annular shape centered on the central axis J. The outer peripheral surface of the core back portion 32 is fixed to the inner peripheral surface of the side wall portion 12a. In this way, the stator 30 is fixed to the housing 11.

[0031] Each of the multiple tooth portions 33 extends radially inward from the core back portion 32. Each tooth portion 33 faces the rotor 20 with a radial gap between them. The tooth portions 33 are arranged at intervals along the inner circumferential surface of the core back portion 32. In this embodiment, the stator core 31 has 12 tooth portions 33. Each tooth portion 33 has a tooth main body portion 34 and an umbrella portion 35.

[0032] The tooth main body portions 34 extend radially inward from the inner circumferential surface of the core back portion 32. When viewed in the axial direction, the tooth main body portions 34 have a substantially rectangular shape. As shown in FIG. 4, the radially inward surface of the tooth main body portions 34 has an arc shape centered on the central axis J when viewed in the axial direction. As shown in FIG. 3, the radially inward surface of the tooth main body portions 34 faces the rotor 20 with a radial gap between them. In other words, the radially inner end of the tooth main body portions 34 faces the rotor 20 with a radial gap between them. Grooves 34a are provided in the tooth main body portions 34.

[0033] As shown in FIG. 4 , the grooves 34a are provided on the radially inward surface of the tooth main body 34. That is, the grooves 34a are provided on the radially inward surface of the tooth portion 33. The grooves 34a extend along the axial direction. In this embodiment, the grooves 34a extend from the upper end to the lower end of the radially inward surface of the tooth main body 34. In this embodiment, the grooves 34a are rectangular when viewed from the axial direction. Therefore, according to this embodiment, since the grooves 34a have a simple rectangular shape, the grooves 34a can be easily formed by processing the multiple electromagnetic steel sheets that make up the stator core 31 using a simple processing method such as press working. This prevents increases in the manufacturing process and costs of the stator core 31 and the rotating electric machine 10. The shape of the grooves 34a is not limited to a rectangular shape and may be other shapes, such as a shape in which a semicircular groove is connected to the radially outer side of a rectangular groove, or a triangular shape. The groove portion 34a includes a first groove portion 34b and a second groove portion 34c.

[0034] The first groove portions 34b are provided on one circumferential side (+θ side) of the radially inward surface of the tooth main body portions 34. The second groove portions 34c are provided on the other circumferential side (-θ side) of the radially inward surface of the tooth main body portions 34. When viewed from the axial direction, the first groove portions 34b and the second groove portions 34c have the same shape. The circumferential dimensions of the first groove portions 34b and the second groove portions 34c are the same. In the following description, the circumferential dimensions of the first groove portions 34b and the second groove portions 34c are referred to as groove width W1. The first groove portions 34b and the second groove portions 34c are arranged in positions that are symmetrical to each other with respect to a reference line L that passes through the center of the tooth portion 33 and the central axis J in the circumferential direction.

[0035] The umbrella portions 35 protrude from the radially inner portions of the tooth main bodies 34, i.e., from the tips of the tooth main bodies 34, on both sides in the circumferential direction. This allows the circumferential dimension of the tooth portions 33 to be increased. This therefore increases the magnetic flux entering the tooth portions 33 from the rotor 20 in the circumferential direction, thereby increasing the rotational torque of the rotor 20. The umbrella portions 35 have a first umbrella portion 35a and a second umbrella portion 35b.

[0036] The first umbrella portion 35a protrudes circumferentially in one direction from a side surface facing one circumferential direction (+θ side) of the tip of the tooth main body portion 34. When viewed in the axial direction, the first umbrella portion 35a has a generally triangular shape protruding to one circumferential direction. The surface of the first umbrella portion 35a facing radially inward is arc-shaped with the central axis J as its center. The surface of the first umbrella portion 35a facing radially inward is circumferentially connected to the surface of the tooth main body portion 34 facing radially inward.

[0037] The second umbrella portion 35b protrudes toward the other circumferential side from the side surface of the tip of the tooth main body portion 34 facing the other circumferential side (-θ side). When viewed in the axial direction, the second umbrella portion 35b has a generally triangular shape protruding toward the other circumferential side. The surface of the second umbrella portion 35b facing radially inward is generally arc-shaped, with the center being the central axis J. The surface of the second umbrella portion 35b facing radially inward is connected in the circumferential direction to the surface of the tooth main body portion 34 facing radially inward. The shapes of the first umbrella portion 35a and the second umbrella portion 35b are line-symmetrical with each other, with the reference line L as the axis of symmetry.

[0038] According to this embodiment, as described above, the grooves 34a are provided on the radially inward surface of the tooth main body 34. Therefore, compared to when the grooves 34a are provided on the umbrella portion 35, it is easier to increase the magnetic flux entering the teeth 33 from the rotor 20, and therefore easier to increase the magnetic force applied to the rotor 20. As a result, the rotational torque of the rotor 20 can be increased.

[0039] The first umbrella portion 35a of one tooth portion 33 is circumferentially separated from the second umbrella portion 35b of another tooth portion 33, which is arranged adjacent to the first umbrella portion 35a on one circumferential side (+θ side) of the tooth portion 33, by a gap 50. The gap 50 is a gap between the umbrella portions 35 of the tooth portions 33 that are adjacent to each other in the circumferential direction. A plurality of gaps 50 are provided at intervals along the circumferential direction. In this embodiment, twelve gaps 50 are provided. The gaps 50 are provided between the umbrella portions 35 of the circumferentially adjacent teeth portions 33, which prevents magnetic flux entering the tooth portion 33 from the rotor 20 from leaking to the circumferentially adjacent tooth portion 33 via the circumferentially adjacent umbrella portion 35. This prevents an increase in circumferential variation in the magnetic force applied to the rotor 20 when the rotor 20 rotates around the central axis J. Therefore, the rotation of the rotor 20 around the central axis J can be stabilized.

[0040] When gaps 50 having a lower magnetic permeability than the teeth 33 are provided between circumferentially adjacent teeth 33, the magnetic flux density entering each tooth 33 from the rotor 20 fluctuates during rotation of the rotor 20. This fluctuates the magnetic force applied to the rotor 20, generating cogging torque, which is a pulsation of the motor torque. The frequency and magnitude of the cogging torque correlate with the number of poles and the number of gaps 50 of the rotor 20. The number of times cogging torque occurs in a unit period of one rotation of the rotor 20 is equal to the least common multiple of the number of poles of the magnet portion 22 and the number of gaps 50. As described above, in this embodiment, the number of poles of the magnet portion 22 is eight, and the number of gaps 50 is twelve. Therefore, in this embodiment, cogging torque occurs 24 times in a unit period. The magnitude of the cogging torque decreases as the number of times cogging torque occurs in a unit period increases.

[0041] When the grooves 34a are provided on the radially inward surfaces of the teeth 33, the magnetic permeability of the portions of the teeth 33 where the grooves 34a are provided is substantially reduced. Therefore, by providing the grooves 34a, the number of times that the magnetic flux density entering each tooth 33 from the rotor 20 fluctuates during rotation of the rotor 20 can be increased. This increases the number of times that cogging torque occurs per unit cycle. In this embodiment, each tooth 33 is provided with two grooves, the first groove 34b and the second groove 34c, which is essentially the same as when 36 voids 50 are provided. Therefore, the number of times that cogging torque occurs per unit cycle can be increased to 72, thereby suppressing cogging torque.

[0042] According to this embodiment, the stator 30 includes a stator core 31 that faces the rotor 20 across a gap in the radial direction. The stator core 31 includes an annular core back portion 32 centered on the central axis J and a plurality of teeth 33 arranged along the inner circumferential surface of the core back portion 32. The teeth 33 include tooth main bodies 34 that extend radially inward from the inner circumferential surface of the core back portion 32 and umbrella portions 35 that protrude circumferentially from the tip ends of the tooth main bodies 34. Grooves 34a extending along the axial direction are provided on the radially inward surfaces of the teeth 33. As described above, the magnetic permeability of the portions of the teeth 33 where the grooves 34a are provided can be reduced. As a result, the magnetic flux density that enters the teeth 33 from the rotor 20 when the rotor 20 rotates around the central axis J fluctuates not only in the gaps 50 but also in the grooves 34a, thereby increasing the number of times cogging torque is generated per unit period. Therefore, the cogging torque that occurs when the rotor 20 rotates around the central axis J can be suppressed.

[0043] In this embodiment, the rotor 20 includes a shaft 24 extending axially about the central axis J, a rotor core 21 fixed to the shaft 24, a plurality of magnet portions 22 arranged circumferentially on the radially outer surface of the rotor core 21, and magnetic portions 23 provided on the radially outer surface of each of the magnet portions 22, the outer circumferential surface of each of the magnet portions 22 being curved, i.e., the curved surface portion 23a. As a result, when the rotor 20 rotates around the central axis J, fluctuations in the gap between the teeth 33 and the rotor 20 can be made gentler, thereby reducing the amount of fluctuation per unit time in the magnetic flux density entering each tooth 33 from the rotor 20. As a result, the amount of fluctuation per unit time in the magnetic force applied to the rotor 20 can be reduced, thereby suppressing torque ripple and cogging torque of the rotating electric machine 10.

[0044] Furthermore, in this embodiment, as described above, the magnetic portion 23 is made of a metal material, such as iron or steel, and therefore the curved surface portion 23a of the magnetic portion 23 can be easily formed by a simple processing method, such as press working. Therefore, compared to forming a curved surface on the outer circumferential surface of the magnet portion 22, which is difficult to form a curved shape, an increase in the manufacturing process for the rotor 20 and the rotating electric machine 10 can be suppressed. Furthermore, as described above, the magnetic portion 23 is made of a metal material, such as iron or steel, and therefore the shape accuracy of the curved outer surface of the magnetic portion 23 can be easily improved. Therefore, when the rotor 20 rotates around the central axis J, the fluctuation amount per unit time of the magnetic flux density entering the teeth portion 33 from the rotor 20 can be more effectively reduced. Therefore, the torque ripple and cogging torque of the rotating electric machine 10 can be more effectively suppressed.

[0045] According to this embodiment, when viewed in the axial direction, the radially outer surface of the magnetic portion 23, i.e., the curved surface portion 23a, has an arc shape that protrudes radially outward. Therefore, when the rotor 20 rotates about the central axis J, the fluctuation in the magnetic flux density entering each tooth portion 33 from the rotor 20 can be made curved. Therefore, when the rotor 20 rotates about the central axis J, the amount of fluctuation per unit time in the magnetic flux density entering each tooth portion 33 from the rotor 20 can be more suitably reduced. Therefore, the torque ripple and cogging torque of the rotating electric machine 10 can be more suitably suppressed.

[0046] According to this embodiment, the first groove portions 34b and the second groove portions 34c are arranged at positions symmetrical to each other with respect to the reference line L, which passes through the center of the tooth portion 33 in the circumferential direction and the central axis J. Therefore, cogging torque can be suppressed both when the rotor 20 rotates to one circumferential side (+θ side) and when the rotor 20 rotates to the other circumferential side (−θ side).

[0047] 4, in this embodiment, the groove width W1 is 60% or more and 100% or less of the gap width W2, which is the circumferential dimension of the gap portion 50. In this embodiment, the groove width W1 is approximately 80% of the gap width W2. In the following description, the ratio of the groove width W1 to the gap width W2 is referred to as the groove width ratio W1 / W2.

[0048] The insulators 37 insulate the stator core 31 from the coils 38. The insulators 37 have insulating properties. In this embodiment, the insulators 37 are made of resin. As shown in FIG. 1 , the insulators 37 are attached to each of the plurality of tooth portions 33. Each of the plurality of coils 38 is attached to the tooth portion 33 via the insulators 37. A current is supplied to each of the plurality of coils 38 from an external power source (not shown).

[0049] 5 is a diagram showing the relationship between the groove width ratio W1 / W2 and the cogging torque Tc and motor torque Tm in the rotating electric machine 10 of this embodiment. The horizontal axis of FIG. 5 is the groove width ratio W1 / W2. The vertical axis on the left is the cogging torque Tc. The vertical axis on the right is the motor torque Tm.

[0050] As shown in Figure 5, when the groove width ratio W1 / W2 is 70% or less, the cogging torque Tc decreases rapidly as the groove width ratio W1 / W2 increases. When the groove width ratio W1 / W2 is 70% or less, as the groove width ratio W1 / W2 increases, the circumferential dimension of the portion of the tooth 33 where the magnetic permeability actually decreases increases, thereby reducing the magnetic flux that enters the tooth main body 34 from the rotor 20 via the inner circumferential surface of the groove 34a. This increases the number of times cogging torque occurs per unit cycle, thereby reducing the cogging torque Tc. When the groove width ratio W1 / W2 is 70% or more, the cogging torque Tc increases gradually as the groove width ratio W1 / W2 increases. This is presumably because, as the groove width W1 of the groove 34a increases, the magnetic flux entering the teeth 33 from the inner circumferential surface of the groove 34a increases, causing a gradual increase in the effective magnetic permeability of the teeth 33 where the groove 34a is provided. For these reasons, compared to when no groove 34a is provided in the teeth 33, i.e., when the groove width ratio W1 / W2 is 0%, the cogging torque Tc can be suitably suppressed by providing the groove 34a with a groove width ratio W1 / W2 of 60% or more and 100% or less. Also, as described above, in this embodiment, the groove width ratio W1 / W2 is 80%, so the cogging torque Tc can be suitably suppressed.

[0051] The motor torque Tm decreases gradually as the groove width ratio W1 / W2 increases. This is because the average distance between the radially inward surface of the tooth main body 34 and the rotor 20 increases as the groove width W1 increases. However, since the decrease in motor torque Tm with respect to the groove width ratio W1 / W2 is small, providing the grooves 34a in the teeth 33 can prevent a significant decrease in motor torque Tm. Therefore, according to this embodiment, by setting the groove width ratio W1 / W2 to be 60% or more and 100% or less, a significant decrease in motor torque Tm can be prevented while suppressing the cogging torque Tc.

[0052] <Modification> 6 is a cross-sectional view showing a part of a stator core 231 of a stator 230 according to a modification of the present embodiment. In the following description, the same components as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0053] As shown in FIG. 6 , grooves 234a are provided on the radially inward surface of tooth main body 234 of tooth portion 233 in this modification. In this modification, grooves 234a are semicircular when viewed in the axial direction. Therefore, according to this modification, grooves 234a have a simple semicircular shape, and therefore grooves 234a can be easily formed by processing multiple electromagnetic steel plates that make up stator core 231 using a simple processing method such as press working. This prevents increases in the number of manufacturing steps and manufacturing costs of stator core 231 and rotating electric machine 210. Groove 234a includes first grooves 234b and second grooves 234c.

[0054] The first groove portions 234b are provided on one circumferential side (+θ side) of the radially inward surface of the tooth main body portion 234. The second groove portions 234c are provided on the other circumferential side (-θ side) of the radially inward surface of the tooth main body portion 234. When viewed from the axial direction, the first groove portions 234b and the second groove portions 234c have the same shape. The first groove portions 234b and the second groove portions 234c are arranged in positions that are line-symmetrical to each other with the reference line L as the axis of symmetry.

[0055] In this modification, the groove width W1 is set to be 60% or more and 100% or less of the gap width W2, which is the circumferential dimension of the gap portion 50 in the circumferential direction. In this modification, the groove width W1 is approximately 80% of the gap width W2. The other configurations of the stator 230 of this modification are similar to the other configurations of the stator 30 of the first embodiment.

[0056] In the rotating electric machine 210 of this modified example, the relationship between the groove width ratio W1 / W2 and the cogging torque Tc and motor torque Tm is similar to the relationship between the groove width ratio W1 / W2 and the cogging torque Tc and motor torque Tm of the present embodiment shown in Fig. 5. Therefore, in this modified example, as in the above-described embodiment, by setting the groove width ratio W1 / W2 to be equal to or greater than 60% and equal to or less than 100%, it is possible to suppress a large decrease in motor torque Tm while suitably suppressing cogging torque Tc.

[0057] In this modification, grooves 234a are provided on the radially inward surfaces of the teeth 233. As in the above-described embodiment, the magnetic permeability of the portions of the teeth 233 where the grooves 234a are provided can be reduced, thereby increasing the number of times cogging torque occurs per unit period. This reduces the cogging torque Tc that occurs when the rotor 20 rotates around the central axis J.

[0058] The present invention is not limited to the above-described embodiment, and other configurations and methods may be adopted within the scope of the technical concept of the present invention. For example, the number of teeth of the stator core is not limited to 12, and may be 11 or less, or 13 or more. Furthermore, the stator core may be a stator core used in a rotating electric machine with an outer rotor configuration, in which the stator core is disposed radially inside the rotor and the teeth protrude radially outward.

[0059] Furthermore, the number of magnet portions and the number of magnetic portions that the rotor has are not limited to eight, but may be seven or less, or nine or more.

[0060] The shape of the umbrella portion is not limited to that of the present embodiment, and may be another shape, such as a substantially rectangular shape that protrudes in the circumferential direction when viewed from the axial direction. Also, the umbrella portion may not be provided.

[0061] The configuration of the grooves is not limited to this embodiment, and for example, the number of grooves provided on each tooth may be one, or three or more. The number of grooves provided on each tooth may also be different. However, the grooves are preferably arranged symmetrically with respect to the reference line, and when an odd number of grooves are provided, it is preferable that one groove be positioned so as to overlap the reference line.

[0062] The rotating electric machine to which the present invention is applied is not limited to a motor, and may also be a generator. The application of the rotating electric machine to which the present invention is applied is not particularly limited. For example, the rotating electric machine may be mounted on a vehicle for an application other than rotating an axle, or may be mounted on equipment other than a vehicle. The configurations described above in this specification can be combined as appropriate within a range that does not contradict each other.

[0063] The present technology can be configured as follows. (1) A rotating electric machine comprising: a rotor rotatable about a central axis; and a stator located radially outside the rotor, wherein the rotor has a shaft extending in an axial direction about the central axis; a rotor core fixed to the shaft; a plurality of magnet portions arranged circumferentially on a radially outer surface of the rotor core; and magnetic portions having curved outer surfaces provided on the radially outer surfaces of each of the magnet portions; the stator has a stator core facing the rotor in the radial direction across a gap; the stator core has an annular core back portion centered on the central axis and a plurality of teeth portions arranged along an inner peripheral surface of the core back portion; the teeth portions have tooth main body portions extending radially inward from the inner peripheral surface of the core back portion and umbrella portions protruding circumferentially on both sides at the tip ends of the tooth main body portions; and groove portions extending along the axial direction are provided on the radially inward surfaces of the tooth portions. (2) The rotating electric machine according to (1), wherein the groove is provided on a surface of the tooth body portion facing radially inward. (3) The rotating electric machine according to (1) or (2), wherein, when viewed from the axial direction, the radially outer surface of the magnetic portion has an arc shape that protrudes radially outward. (4) A rotating electric machine described in any one of (1) to (3), wherein the groove portion includes a first groove portion and a second groove portion, and the first groove portion and the second groove portion are arranged at positions symmetrical to each other with a reference line passing through the center of the tooth portion and the central axis in the circumferential direction as the axis of symmetry. (5) A rotating electric machine according to any one of (1) to (4), wherein the dimension of the groove portion in the circumferential direction is 60% or more and 100% or less of the dimension of the gap between the umbrella portions provided on the teeth portions adjacent to each other in the circumferential direction. (6) The rotating electric machine according to any one of (1) to (5), wherein the groove portion has a semicircular shape when viewed in the axial direction. (7) The rotating electric machine according to any one of (1) to (5), wherein the groove portion has a rectangular shape when viewed in the axial direction. (8) The rotating electric machine according to any one of (1) to (7), wherein the axial dimension of the stator core is larger than the axial dimension of the rotor core. [Explanation of symbols]

[0064] 10,210... rotating electric machine, 20... rotor, 21... rotor core, 22... magnet portion, 23... magnetic portion, 24... shaft, 30,230... stator, 31,231... stator core, 32... core back portion, 33,233... teeth portion, 34,234... teeth main body portion, 34a,234a... groove portion, 34b,234b... first groove portion, 34c,234c... second groove portion, 35... umbrella portion, J... central axis, L... reference line

Claims

1. a rotor rotatable about a central axis; a stator positioned radially outside the rotor; Equipped with The rotor is a shaft extending in an axial direction around the central axis; a rotor core fixed to the shaft; a plurality of magnet portions arranged in a circumferential direction on a radially outer surface of the rotor core; a magnetic portion provided on a radially outer surface of each of the plurality of magnet portions, the magnetic portion having a curved outer peripheral surface; and the stator has a stator core that faces the rotor across a gap in the radial direction, the stator core has an annular core back portion centered on the central axis and a plurality of teeth portions arranged along an inner circumferential surface of the core back portion, The tooth portion has a tooth main body portion extending radially inward from an inner circumferential surface of the core back portion, and an umbrella portion protruding on both sides in the circumferential direction at a tip end of the tooth main body portion, A rotating electric machine in which a groove extending along the axial direction is provided on a surface of the tooth portion facing radially inward.

2. The rotating electric machine according to claim 1 , wherein the grooves are provided on surfaces of the tooth main bodies facing radially inward.

3. The rotating electric machine according to claim 2 , wherein the outer peripheral surface of the magnetic portion is arc-shaped and protrudes radially outward when viewed from the axial direction.

4. The groove portion includes a first groove portion and a second groove portion, The rotating electric machine according to claim 3 , wherein the first groove portion and the second groove portion are arranged at positions symmetrical to each other with respect to a reference line passing through the center of the tooth portion and the central axis in the circumferential direction as an axis of symmetry.

5. 5. The rotating electric machine according to claim 3, wherein a dimension of the groove in the circumferential direction is 60% or more and 100% or less of a dimension of a gap between the umbrella portions provided on each of the teeth portions adjacent to each other in the circumferential direction.

6. The rotating electric machine according to claim 5 , wherein the groove portion has a rectangular shape when viewed in the axial direction.

7. The rotating electric machine according to claim 5 , wherein the groove portion has a semicircular shape when viewed in the axial direction.

8. The rotating electric machine according to claim 3 , wherein an axial dimension of the stator core is greater than an axial dimension of the rotor core.

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