Rotating electric machine

Abstract

The invention provides a rotating electrical machine. The rotating electrical machine includes: a rotor capable of rotating about a central axis; and a stator located radially outward of the rotor. The rotor includes: a shaft extending in an axial direction about a central axis; a rotor core fixed to the shaft; a plurality of magnet parts arranged on the radial outer side surface of the rotor core in the circumferential direction; and a magnetic part provided on the radial outer surface of each of the plurality of magnet parts, the outer peripheral surface of the magnetic part being a curved surface. The stator has a stator core facing the rotor with a gap therebetween in the radial direction. The stator core has an annular core back portion and a plurality of tooth portions disposed along an inner circumferential surface of the core back portion. The tooth portion has a tooth main body portion extending radially inward from the inner peripheral surface of the core back portion, and an umbrella-shaped portion protruding toward both sides in the circumferential direction at the tip portion of the tooth main body portion. Grooves extending in the axial direction are provided on the radially inward surfaces of the teeth.

Description

Technical Field

[0001] This invention relates to rotary electric motors. Background Technology

[0002] In motors having a rotor and a stator, in order to suppress vibration and noise during driving, a structure is disclosed in which slots are provided on the protrusions on both sides of the front end of the main body of the stator core to suppress cogging torque (e.g., Patent Document 1).

[0003] Patent Document 1: Japanese Patent Publication No. 2019-527016

[0004] In motors like the one described above, when the curvature of the outer circumferential surface of the rotor opposite the stator is small, the magnetic flux density entering the stator from the rotor tends to change drastically when the rotor rotates, making it sometimes difficult to suppress cogging torque. Summary of the Invention

[0005] In view of the above, one of the objectives of the present invention is to provide a rotary motor capable of suppressing cogging torque.

[0006] One aspect of the present invention provides a rotary electric motor comprising: a rotor capable of rotating about a central axis; and a stator located radially outward of the rotor. The rotor comprises: 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 outward surface of the rotor core; and magnetic portions disposed on the radially outward surfaces of each of the plurality of magnet portions, the outer peripheral surface of the magnetic portion being curved. The stator comprises a stator core opposed to the rotor radially with a gap. The stator core has an annular core back centered on the central axis and a plurality of teeth arranged along the inner peripheral surface of the core back. Each tooth portion has a tooth body portion extending radially inward from the inner peripheral surface of the core back and umbrella-shaped portions protruding circumferentially to both sides at the front end of the tooth body portion. An axially extending groove portion is provided on the radially inward surface of the tooth portion.

[0007] According to one aspect of the present invention, a rotary motor capable of suppressing cogging torque can be provided. Attached Figure Description

[0008] Figure 1 This is a schematic cross-sectional view illustrating one embodiment of a rotary electric motor.

[0009] Figure 2 This is a perspective view showing a portion of a rotor according to one embodiment.

[0010] Figure 3 This illustrates one embodiment of a rotary motor along... Figure 1A cross-sectional view along line III-III.

[0011] Figure 4 This is a cross-sectional view showing a portion of a stator core according to one embodiment.

[0012] Figure 5 This is a graph showing the relationship between the slot width ratio, cogging torque, and motor torque in one embodiment.

[0013] Figure 6 This is a cross-sectional view showing a portion of the stator core of a modified embodiment.

[0014] Label Explanation

[0015] 10, 210: Rotary motor; 20: Rotor; 21: Rotor core; 22: Magnet part; 23: Magnetic part; 24: Shaft; 30, 230: Stator; 31, 231: Stator core; 32: Back of core; 33, 233: Tooth part; 34, 234: Tooth body part; 34a, 234a: Slot part; 34b, 234b: First slot part; 34c; 234c: Second slot part; 35: Umbrella-shaped part; J: Central axis; L: Reference line. Detailed Implementation

[0016] In the following description, the Z-axis is appropriately shown in the figures. 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 an imaginary axis. In the following description, the direction in which the central axis J extends, that is, 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 in which the arrow of the Z-axis in the axial direction points (+Z side) is referred to as the "upper side". The side opposite to the side in which the arrow of the Z-axis in the axial direction points (-Z side) is referred to as the "lower side". In addition, the upper side and the lower side are only names used to describe the relative positional relationship of each part, and the actual configuration relationship may be other than the configuration relationship represented by these names.

[0017] The circumferential direction is represented by an arrow θ in each diagram. The side towards which the arrow θ points in the circumferential direction is called the "circumferential side". The opposite side towards which the arrow θ points in the circumferential direction is called the "circumferential side". The circumferential side is the side that moves clockwise around the central axis J when viewed from above (+Z side) (+θ side). The circumferential side is the side that moves counterclockwise around the central axis J when viewed from above (-θ side).

[0018] <Implementation Method>

[0019] Figure 1The rotary motor 10 shown in this embodiment is a motor installed in equipment such as those mounted on a vehicle. The equipment equipped with the rotary motor 10 can be an automatic transmission or a drive device that drives the axles of a vehicle. The rotary motor 10 includes a housing 11, a rotor 20, a stator 30, a first bearing 15, and a second bearing 16.

[0020] The housing 11 internally houses the rotor 20, stator 30, first bearing 15, and second bearing 16. The housing 11 has a cylindrical portion 12, an upper cover portion 13, and a first bearing retaining portion 14. The cylindrical portion 12 is a cylinder extending axially about a central axis J. The cylindrical portion 12 has an opening at its upper side. The cylindrical portion 12 has a side wall portion 12a, a lower wall portion 12b, and a second bearing retaining portion 12c.

[0021] The sidewall portion 12a is cylindrical, extending axially around the central axis J. The sidewall portion 12a radially surrounds the rotor 20, stator 30, first bearing 15, and second bearing 16. The upper end of the sidewall portion 12a is the upper end of the cylindrical portion 12. An opening 12d is provided at the upper end of the sidewall portion 12a.

[0022] The lower wall portion 12b is in the shape of an annular plate 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. A lower wall hole 12e is provided in the lower wall portion 12b, extending axially through the lower wall portion 12b. When viewed from the axial direction, the lower wall hole 12e is circular in shape centered on the central axis J.

[0023] The second bearing retaining portion 12c protrudes upward from the lower wall portion 12b. The second bearing retaining portion 12c is cylindrical about the central axis J. The second bearing retaining portion 12c has an opening at the top. 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 held on the inner circumferential surface of the second bearing retaining portion 12c.

[0024] The upper cover 13 is a circular plate centered on the central axis J. The plate surface of the upper cover 13 faces the axial direction. The upper cover 13 is fixed to the upper end of the cylindrical part 12. The upper cover 13 closes the opening 12d from the top.

[0025] The first bearing retaining portion 14 is fixed to the portion of the inner circumferential surface of the side wall portion 12a that is higher than the rotor 20 and stator 30. The first bearing retaining portion 14 is approximately annular about the central axis J. The first bearing 15 is held on the inner circumferential surface of the first bearing retaining portion 14.

[0026] The rotor 20 is capable of rotating about the central axis J. The rotor 20 has a rotor core 21, multiple magnets 22, multiple magnetic parts 23, and a shaft 24.

[0027] The rotor core 21 is cylindrical, extending axially around the central axis J. The rotor core 21 radially surrounds the shaft 24. The rotor core 21 is magnetic. The rotor core 21 is, for example, a stacked steel plate constructed by laminating multiple electromagnetic steel plates axially. Figure 2 As shown, when viewed axially, the rotor core 21 has a polygonal shape. In this embodiment, when viewed axially, the rotor core 21 has a roughly octagonal shape. The rotor core 21 has multiple holes 21a, multiple planar portions 21b, and through holes 21c.

[0028] like Figure 1 As shown, the multiple holes 21a are holes that penetrate the rotor core 21 axially. Figure 2 As shown, when viewed axially, each hole 21a is approximately circular. The holes 21a are spaced apart from each other circumferentially. Each hole 21a is arranged surrounding the central axis J. In this embodiment, the rotor core 21 has eight holes 21a. By providing multiple holes 21a in the rotor core 21, it is possible to achieve weight reduction and material cost reduction in the rotor core 21.

[0029] Multiple planar portions 21b are radially outer surfaces of the rotor core 21. The planar portions 21b are arranged at intervals along the circumferential direction. In this embodiment, the rotor core 21 has eight planar portions 21b. Each planar portion 21b is planar, extending in a direction perpendicular to the radial direction. Each planar portion 21b extends axially along the entire axial length of the rotor core 21. In this embodiment, the axial length of the planar portion 21b is longer than its circumferential length.

[0030] like Figure 1 As shown, the through hole 21c is an axial hole that passes through the rotor core 21. When viewed axially, the through hole 21c is circular in shape with the central axis J as the center. 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. Thus, the rotor core 21 is fixed to the shaft 24.

[0031] like Figure 2As shown, multiple magnet portions 22 are respectively disposed on the planar portion 21b. That is, multiple magnet portions 22 are respectively disposed on the radially outer side surface of the rotor core 21. In this embodiment, each magnet portion 22 is fixed to the planar portion 21b. Each magnet portion 22 is plate-shaped and extends axially. The plate surface of each magnet portion 22 faces radially. In the axial direction, the upper end of each magnet portion 22 is disposed 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 disposed at the same position as the lower end of the rotor core 21. The magnet portions 22 are arranged at intervals around each other in the circumferential direction. In this embodiment, the rotor 20 has 8 magnet portions 22. In this embodiment, the rotor 20 has 8 poles. The radially outer magnetic pole of one magnet portion 22 is a different magnetic pole from the radially outer magnetic pole of other magnet portions 22 disposed adjacent to that magnet portion 22 in the circumferential direction.

[0032] like Figure 1 As shown, multiple magnetic parts 23 are respectively disposed on the radially outer surface of the magnet part 22. Each magnetic part 23 is fixed to the radially outer surface of the magnet part 22. Each magnetic part 23 is spaced apart from the stator 30 and is radially opposed to it. Figure 2 As shown, each magnetic part 23 is a columnar shape extending axially. When viewed axially, each magnetic part 23 is a roughly semi-circular shape protruding radially outward. Axially, the upper end of each magnetic part 23 is positioned at the same location as the upper end of the rotor core 21. Axially, the lower end of each magnetic part 23 is positioned at the same location as the lower end of the rotor core 21. The magnetic parts 23 are arranged circumferentially spaced apart from each other. In this embodiment, the rotor 20 has eight magnetic parts 23. In this embodiment, the magnetic parts 23 are made of a magnetic material. For example, the magnetic parts 23 are made of metallic materials such as iron and steel. Each magnetic part 23 has a curved surface 23a.

[0033] The curved surface 23a is the radially outward-facing surface of the outer peripheral surface of the magnetic part 23. When viewed axially, the curved surface 23a presents a roughly arc-shaped appearance protruding radially outward. That is, the outer peripheral surface of the magnetic part 23 is curved. Figure 1 As shown, the curved surface 23a is radially opposed to the stator 30.

[0034] Shaft 24 is approximately cylindrical, extending axially around the central axis J. Shaft 24 passes axially through a through-hole 21c in the rotor core 21. Shaft 24 is fixed to the inner circumferential surface of the through-hole 21c. The upper portion of shaft 24 is supported by a first bearing 15. The lower portion of shaft 24 is supported by a second bearing 16. Shaft 24 is supported by the first bearing 15 and the second bearing 16 to allow it to rotate around the central axis J. Thus, rotor 20 can rotate around the central axis J. The lower end of shaft 24 protrudes outward from the housing 11 through a lower wall hole 12e.

[0035] The first bearing 15 supports the upper portion of the shaft 24 so that it can rotate. The second bearing 16 supports the lower portion of the shaft 24 so that it can rotate. 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 also be rolling bearings other than ball bearings, or they may be sliding bearings.

[0036] The stator 30 is located radially outside the rotor 20. The stator 30 and the rotor 20 are radially opposed to each other with a gap. The stator 30 is fixed to the inner circumferential surface of the side wall portion 12a. The stator 30 has a stator core 31, an insulator 37, and a plurality of coils 38.

[0037] The stator core 31 is annular, extending axially around the central axis J. The stator core 31 and the rotor 20 are radially separated by a gap. The stator core 31 is magnetic. The stator core 31 is, for example, a stacked steel plate constructed by axially stacking multiple electromagnetic steel plates. 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, compared to the case where the axial dimension of the stator core 31 is smaller than or the same as the axial dimension of the rotor 20, it is easier to reduce the magnetic flux entering the stator core 31 from the upper edge and the lower edge of the rotor 20, respectively. Therefore, it is easier to reduce the variation in magnetic flux entering the stator core 31 from the rotor 20 per unit time when the rotor 20 rotates around the central axis J, thus suppressing cogging torque. The stator core 31 has a core back 32 and multiple teeth 33.

[0038] like Figure 3 As shown, the back of the core 32 is annular with the central axis J as its center. The outer circumferential surface of the back of the core 32 is fixed to the inner circumferential surface of the side wall portion 12a. Thus, the stator 30 is fixed to the housing 11.

[0039] Multiple teeth 33 extend radially inward from the back surface 32 of the iron core. Each tooth 33 is radially opposed to the rotor 20 with a gap. The teeth 33 are spaced apart from each other along the inner circumferential surface of the back surface 32 of the iron core. In this embodiment, the stator core 31 has 12 teeth 33. Each tooth 33 has a tooth body portion 34 and an umbrella-shaped portion 35.

[0040] The tooth body 34 extends radially inward from the inner circumferential surface of the back surface 32 of the iron core. Viewed axially, the tooth body 34 has a generally rectangular shape. Figure 4 As shown, when viewed axially, the radially inward-facing surface of the tooth body 34 is an arc centered on the central axis J. Figure 3As shown, the radially inward-facing surface of the tooth body 34 is radially opposed to the rotor 20 with a gap between them. That is, the radially inward end of the tooth body 34 is radially opposed to the rotor 20 with a gap between them. A groove 34a is provided in the tooth body 34.

[0041] like Figure 4 As shown, the groove 34a is provided on the radially inward surface of the tooth body 34. That is, the groove 34a is provided on the radially inward surface of the tooth 33. The groove 34a extends axially. In this embodiment, the groove 34a extends from the upper end to the lower end of the radially inward surface of the tooth body 34. In this embodiment, when viewed axially, the groove 34a is rectangular. Thus, according to this embodiment, the groove 34a is rectangular, which is a simple shape, so the groove 34a can be easily formed by processing the multiple electromagnets constituting the stator core 31 using simple processing methods such as stamping. Therefore, it is possible to suppress the increase in manufacturing time and manufacturing cost of the stator core 31 and the rotary motor 10. In addition, the shape of the groove 34a is not limited to a rectangular shape, and can also be a shape formed by connecting a semi-circular groove to the radially outer side of a rectangular groove, or a triangular shape or other shapes. The groove 34a includes a first groove 34b and a second groove 34c.

[0042] The first groove 34b is located on the circumferential side (+θ side) of the radially inward-facing surface of the tooth body 34. The second groove 34c is located on the circumferential side (-θ side) of the radially inward-facing surface of the tooth body 34. When viewed axially, the shapes of the first groove 34b and the second groove 34c are identical. The circumferential dimensions of the first groove 34b and the second groove 34c are identical. In the following description, the circumferential dimensions of the first groove 34b and the second groove 34c are referred to as the groove width W1. The first groove 34b and the second groove 34c are arranged in a position that is linearly symmetrical about a reference line L, which passes through the circumferential center of the tooth 33 and the central axis J.

[0043] The umbrella-shaped portion 35 protrudes radially inward from the front end of the tooth body portion 34, extending to both sides in the circumferential direction. This increases the circumferential dimension of the tooth portion 33. Consequently, the magnetic flux entering the tooth portion 33 from the rotor 20 can be increased in the circumferential direction, thus improving the rotational torque of the rotor 20. The umbrella-shaped portion 35 has a first umbrella-shaped portion 35a and a second umbrella-shaped portion 35b.

[0044] The first umbrella-shaped portion 35a protrudes circumferentially from the front end of the tooth body portion 34 on the circumferential side (+θ side). When viewed axially, the first umbrella-shaped portion 35a has a roughly triangular shape protruding circumferentially. The radially inward surface of the first umbrella-shaped portion 35a is an arc centered on the central axis J. The radially inward surface of the first umbrella-shaped portion 35a is connected circumferentially to the radially inward surface of the tooth body portion 34.

[0045] The second umbrella-shaped portion 35b protrudes circumferentially from the side of the front end of the tooth body portion 34 facing the other side (-θ side). When viewed axially, the second umbrella-shaped portion 35b has a roughly triangular shape protruding circumferentially. The radially inward surface of the second umbrella-shaped portion 35b is roughly arc-shaped with the central axis J as the center. The radially inward surface of the second umbrella-shaped portion 35b is connected circumferentially to the radially inward surface of the tooth body portion 34. The shapes of the first umbrella-shaped portion 35a and the second umbrella-shaped portion 35b are linearly symmetrical about the reference line L as the axis of symmetry.

[0046] According to this embodiment, as described above, the groove 34a is provided on the radially inward surface of the tooth body portion 34. Therefore, compared to the case where the groove 34a is provided on the umbrella-shaped portion 35, it is easier to increase the magnetic flux entering the tooth portion 33 from the rotor 20, and thus easier to increase the magnetic force applied to the rotor 20. Therefore, it is possible to increase the rotational torque of the rotor 20.

[0047] A first umbrella-shaped portion 35a of one tooth 33 and a second umbrella-shaped portion 35b of another tooth 33 adjacent to it on one circumferential side (+θ side) are circumferentially separated by a gap 50. The gap 50 is the gap between the umbrella-shaped portions 35 of adjacent teeth 33 in the circumferential direction. Multiple gaps 50 are provided at intervals along the circumferential direction. In this embodiment, 12 gaps 50 are provided. Since the gaps 50 are provided between the umbrella-shaped portions 35 of each adjacent tooth 33 in the circumferential direction, the leakage of magnetic flux from the rotor 20 into the tooth 33 through the adjacent umbrella-shaped portions 35 in the circumferential direction can be suppressed. Therefore, the increase in circumferential deviation of the magnetic force applied to the rotor 20 when the rotor 20 rotates around the central axis J can be suppressed. Therefore, the rotation of the rotor 20 around the central axis J can be stabilized.

[0048] When gaps 50 with lower permeability than the teeth 33 are provided between adjacent teeth 33 along the circumferential direction, the magnetic flux density entering each tooth 33 from the rotor 20 changes as the rotor 20 rotates. This causes a change in the magnetic force applied to the rotor 20, resulting in pulsating cogging torque, which is the motor torque. The generation period and magnitude of the cogging torque are related to the number of poles of the rotor 20 and the number of gaps 50. The number of times the cogging torque is generated within a unit cycle of one rotation of the rotor 20 is the least common multiple of the number of poles of the magnet 22 and the number of gaps 50. As described above, in this embodiment, the magnet 22 has 8 poles and the number of gaps 50 is 12. Therefore, in this embodiment, the cogging torque is generated 24 times per unit cycle. The more times the cogging torque is generated per unit cycle, the smaller the magnitude of the cogging torque.

[0049] When a groove 34a is provided on the radially inward surface of the tooth 33, the permeability of the portion of the tooth 33 with the groove 34a substantially decreases. Therefore, by providing the groove 34a, the number of times the magnetic flux density entering each tooth 33 from the rotor 20 changes when the rotor 20 rotates can be increased. This increases the number of times cogging torque is generated per unit cycle. In this embodiment, each tooth 33 has a first groove 34b and a second groove 34c, thus achieving essentially the same result as with the case of 36 gaps 50. Therefore, the number of times cogging torque is generated per unit cycle can be increased to 72 times, thereby suppressing cogging torque.

[0050] According to this embodiment, the stator 30 has a stator core 31 that is radially separated from the rotor 20 by a gap. The stator core 31 has an annular core back 32 centered on the central axis J and a plurality of teeth 33 arranged along the inner circumferential surface of the core back 32. Each tooth 33 has a tooth body portion 34 extending radially inward from the inner circumferential surface of the core back 32 and umbrella-shaped portions 35 protruding circumferentially to both sides at the front end of the tooth body portion 34. A slot portion 34a extending axially is provided on the radially inward surface of the tooth portion 33. As described above, the permeability of the portion of the tooth 33 in which the slot portion 34a is provided can be reduced. As a result, in addition to the gap portion 50, the magnetic flux density entering the tooth portion 33 from the rotor 20 when the rotor 20 rotates around the central axis J also changes in the slot portion 34a, thereby increasing the number of times cogging torque is generated per unit cycle. Therefore, the cogging torque generated when the rotor 20 rotates around the central axis J can be suppressed.

[0051] Furthermore, in this embodiment, the rotor 20 includes: a shaft 24 extending axially about a central axis J; a rotor core 21 fixed to the shaft 24; multiple magnet portions 22 arranged circumferentially on the radially outer surface of the rotor core 21; and magnetic portions 23 disposed on the radially outer surface of each of the multiple magnet portions 22, wherein the outer peripheral surface, i.e., the curved portion 23a, of the magnetic portion 23 is curved. Therefore, when the rotor 20 rotates about the central axis J, the change in the gap between the teeth 33 and the rotor 20 is slowed down, thus reducing the variation in magnetic flux density entering each tooth 33 from the rotor 20 per unit time. Therefore, the variation in the magnetic force applied to the rotor 20 per unit time is reduced, thereby suppressing torque fluctuations and cogging torque in the rotary motor 10.

[0052] Furthermore, in this embodiment, as described above, the magnetic part 23 is made of a metallic material such as iron and steel, so the curved surface 23a of the magnetic part 23 can be easily manufactured using simple processing methods such as stamping. Therefore, compared to the case where a curved surface is manufactured on the outer peripheral surface of the magnet part 22, which is difficult to form a curved shape, the increase in manufacturing time of the rotor 20 and the rotary motor 10 can be suppressed. In addition, as described above, the magnetic part 23 is made of a metallic material such as iron and steel, so it is easy to improve the shape accuracy of the curved surface of the outer surface of the magnetic part 23. Therefore, the variation in magnetic flux density entering the tooth part 33 from the rotor 20 per unit time can be reduced more appropriately when the rotor 20 rotates around the central axis J. Therefore, torque fluctuations and cogging torque of the rotary motor 10 can be suppressed more appropriately.

[0053] According to this embodiment, when viewed axially, the radially outer surface of the magnetic section 23, i.e., the curved surface 23a, is an arc shape protruding radially outward. This allows the variation in magnetic flux density entering each tooth 33 from the rotor 20 as the rotor 20 rotates around the central axis J to be curved. Therefore, the variation in magnetic flux density entering each tooth 33 from the rotor 20 per unit time as the rotor 20 rotates around the central axis J can be reduced more appropriately. Consequently, torque fluctuations and cogging torque of the rotary motor 10 can be more appropriately suppressed.

[0054] According to this embodiment, the first groove portion 34b and the second groove portion 34c are arranged symmetrically about a reference line L, which passes through the circumferential center of the tooth portion 33 and the central axis J. Therefore, cogging torque can be suppressed in either the case where the rotor 20 rotates to one circumferential side (+θ side) or the case where it rotates to the other circumferential side (-θ side).

[0055] like Figure 4As shown, in this embodiment, the groove width W1 is 60% to 100% of the circumferential dimension of the gap portion 50, i.e., the gap width W2. 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 will be referred to as the groove width ratio W1 / W2.

[0056] Insulator 37 insulates the stator core 31 from the coil 38. Insulator 37 has insulating properties. In this embodiment, insulator 37 is made of resin. Figure 1 As shown, insulating elements 37 are respectively mounted on multiple teeth 33. Multiple coils 38 are respectively mounted on the teeth 33 through the insulating elements 37. Current is supplied to the multiple coils 38 by an external power source not shown.

[0057] Figure 5 This is a graph showing the relationship between the slot width ratio W1 / W2 of the rotary motor 10 in this embodiment and the cogging torque Tc and the motor torque Tm. Figure 5 The horizontal axis represents the slot width ratio W1 / W2. The vertical axis on the left represents the cogging torque Tc. The vertical axis on the right represents the motor torque Tm.

[0058] like Figure 5 As shown, within the range where the slot width ratio W1 / W2 is 70% or less, the cogging torque Tc decreases sharply as the slot width ratio W1 / W2 increases. When the slot width ratio W1 / W2 is 70% or less, as the slot width ratio W1 / W2 increases, the circumferential dimension of the portion of the tooth 33 where the permeability is substantially reduced increases, thus reducing the magnetic flux entering the tooth body 34 from the rotor 20 via the inner circumferential surface of the slot 34a. This increases the number of times cogging torque is generated per unit cycle, thereby reducing the cogging torque Tc. Within the range where the slot width ratio W1 / W2 is 70% or more, the cogging torque Tc increases slowly as the slot width ratio W1 / W2 increases. This is presumably because as the slot width W1 of the slot 34a increases, the magnetic flux entering the tooth 33 from the inner circumferential surface of the slot 34a increases, thus the substantial permeability of the portion of the tooth 33 where the slot 34a is located increases slowly. Therefore, compared to the case where the tooth portion 33 does not have a groove portion 34a, i.e., the groove width ratio W1 / W2 is 0%, by providing a groove portion 34a with a groove width ratio W1 / W2 of 60% or more and 100% or less, the tooth cogging torque Tc can be appropriately suppressed. Furthermore, as described above, in this embodiment, the groove width ratio W1 / W2 is 80%, thus the tooth cogging torque Tc can be appropriately suppressed.

[0059] The motor torque Tm decreases slowly as the slot width ratio W1 / W2 increases. This is because the average distance between the radially inward-facing surface of the tooth body 34 and the rotor 20 increases when the slot width W1 increases. However, the decrease in motor torque Tm relative to the slot width ratio W1 / W2 is small, thus suppressing a significant decrease in motor torque Tm caused by the placement of the slot 34a in the tooth 33. Therefore, according to this embodiment, by making the slot width ratio W1 / W2 60% or more and 100% or less, the tooth cogging torque Tc can be suppressed, and a significant decrease in motor torque Tm can be suppressed.

[0060] <Variation Example>

[0061] Figure 6 This is a cross-sectional view showing a portion of the stator core 231 of the stator 230 in a modified example of this embodiment. Furthermore, in the following description, components that are identical in manner to those in the above embodiment are labeled with the same reference numerals, and their descriptions are omitted.

[0062] like Figure 6 As shown, in this modified example, a groove 234a is provided on the radially inward surface of the tooth body portion 234 of the tooth portion 233. In this modified example, the groove 234a is semi-circular when viewed axially. Therefore, according to this modified example, the groove 234a is a semi-circular shape with a simple shape, so the groove 234a can be easily formed by processing the multiple electromagnet plates constituting the stator core 231 using simple processing methods such as stamping. Therefore, it is possible to suppress the increase in manufacturing time and manufacturing cost of the stator core 231 and the rotary motor 210. The groove 234a includes a first groove 234b and a second groove 234c.

[0063] The first groove 234b is located on the circumferential side (+θ side) of the radially inward-facing surface of the tooth body 234. The second groove 234c is located on the other circumferential side (-θ side) of the radially inward-facing surface of the tooth body 234. When viewed axially, the shapes of the first groove 234b and the second groove 234c are identical. The first groove 234b and the second groove 234c are arranged in a position that is linearly symmetrical about the reference line L.

[0064] In this modified example, the slot width W1 is set to be 60% to 100% of the circumferential dimension of the gap portion 50, i.e., the gap width W2. In this modified example, the slot width W1 is approximately 80% of the gap width W2. The other structures of the stator 230 in this modified example are the same as the other structures of the stator 30 in the above-described embodiment.

[0065] The relationship between the slot width ratio W1 / W2 of the rotary electric machine 210 in this variant and the cogging torque Tc and motor torque Tm is as follows: Figure 5The groove width ratio W1 / W2 in this embodiment is related to the cogging torque Tc and the motor torque Tm in the same way. Therefore, in this modified example, similar to the embodiment described above, by making the groove width ratio W1 / W2 60% or more and 100% or less, the cogging torque Tc can be appropriately suppressed, and a significant decrease in the motor torque Tm can be prevented.

[0066] Furthermore, in this modified example, a groove 234a is provided on the radially inward surface of the tooth 233. This reduces the permeability of the portion of the tooth 233 with the groove 234a, similar to the embodiment described above, thus increasing the number of times cogging torque is generated per unit cycle. Therefore, the cogging torque Tc generated when the rotor 20 rotates around the central axis J can be suppressed.

[0067] This invention is not limited to the embodiments described above, and other structures and methods can also be adopted within the scope of the technical concept of this invention. For example, the number of teeth in the stator core is not limited to 12, but can be 11 or less, or 13 or more. In addition, the stator core can also be a stator core for a rotating electric motor with an outer rotor structure that is arranged radially inside the rotor and has teeth protruding radially outward.

[0068] In addition, the number of magnets and magnetic parts in the rotor is not limited to 8, but can be 7 or less, or 9 or more.

[0069] The shape of the umbrella-shaped portion is not limited to this embodiment. For example, it can also be a generally rectangular shape that protrudes circumferentially when viewed from the axial direction, or other shapes. Alternatively, the umbrella-shaped portion may not be provided.

[0070] The structure of the grooves is not limited to this embodiment. For example, the number of grooves provided in each tooth can be one or more. In addition, the number of grooves provided in each tooth can also be different. However, the grooves are preferably arranged linearly symmetrically about the reference line. When an odd number of grooves are provided, it is preferable to place one groove at a position overlapping the reference line.

[0071] The rotary motor using this invention is not limited to a motor, but can also be a generator. The application of the rotary motor using this invention is not particularly limited. For example, the rotary motor can be mounted on a vehicle for purposes other than rotating an axle, or it can be mounted on equipment other than a vehicle. The structures described above can be appropriately combined without contradiction.

[0072] Alternatively, this technology can adopt the following structure.

[0073] (1) A rotary electric motor comprising: a rotor capable of rotating about a central axis; and a stator located radially outside the rotor, the rotor having: 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 disposed on the radially outer surface of each of the plurality of magnet portions, the outer peripheral surface of the magnetic portion being curved, the stator having a stator core opposed to the rotor in the radial direction with a gap, the stator core having an annular core back centered about the central axis and a plurality of teeth disposed along the inner peripheral surface of the core back, the teeth having a tooth body portion extending radially inward from the inner peripheral surface of the core back and an umbrella-shaped portion protruding circumferentially to both sides at the front end of the tooth body portion, and a slot portion extending axially provided on the radially inward surface of the tooth portion.

[0074] (2) The rotary motor according to (1), wherein the groove is provided on the radially inward surface of the tooth body.

[0075] (3) The rotary motor according to (1) or (2), wherein, when viewed from the axial direction, the outer peripheral surface of the magnetic part is in the shape of an arc protruding radially outward.

[0076] (4) A rotary motor according to any one of (1) to (3), wherein the slot includes a first slot and a second slot, the first slot and the second slot being arranged in a position symmetrical about a reference line which passes through the circumferential center of the tooth and the central axis.

[0077] (5) The rotary motor according to any one of (1) to (4), wherein the circumferential dimension of the slot is more than 60% and less than 100% of the dimension of the gap between the umbrella-shaped portions respectively disposed on the circumferentially adjacent teeth.

[0078] (6) The rotary motor according to any one of (1) to (5), wherein the slot is semi-circular when viewed from the axial direction.

[0079] (7) The rotary motor according to any one of (1) to (5), wherein the slot is rectangular when viewed from the axial direction.

[0080] (8) The rotating electric machine according to any one of (1) to (7), wherein the stator core has an axial dimension greater than the rotor core has an axial dimension.

Claims

1. A rotary electric motor, comprising: A rotor that can rotate about a central axis; and The stator is located radially outside the rotor. The rotor has: A shaft that extends axially about the central axis; The rotor core is fixed to the shaft; The magnet section comprises a plurality of magnets arranged circumferentially on the radially outer surface of the rotor core; and A magnetic part is disposed on the radially outer surface of each of the plurality of magnetic parts, and the outer peripheral surface of the magnetic part is curved. The stator has a stator core that is radially opposed to the rotor by a gap. The stator core has an annular core back centered on the central axis and a plurality of teeth arranged along the inner circumferential surface of the core back. The tooth has a tooth body extending radially inward from the inner circumferential surface of the back of the iron core, and umbrella-shaped portions protruding circumferentially to both sides at the front end of the tooth body. A groove extending axially is provided on the radially inward-facing surface of the tooth.

2. The rotary motor according to claim 1, wherein, The groove is provided on the radially inward side of the tooth body.

3. The rotary motor according to claim 2, wherein, When viewed from the axial direction, the outer peripheral surface of the magnetic part is an arc shape that protrudes radially outward.

4. The rotary motor according to claim 3, wherein, The groove portion includes a first groove portion and a second groove portion. The first groove and the second groove are positioned symmetrically about a reference line that passes through the circumferential center of the tooth and the central axis.

5. The rotary motor according to claim 3 or 4, wherein, The circumferential dimension of the groove is more than 60% and less than 100% of the dimension of the gap between the umbrella-shaped portions respectively disposed in the circumferentially adjacent teeth.

6. The rotary electric motor according to claim 5, wherein, When viewed from the axial direction, the groove is rectangular.

7. The rotary electric motor according to claim 5, wherein, When viewed from the axial direction, the groove is semi-circular.

8. The rotary electric motor according to claim 3, wherein, The stator core has a larger axial dimension than the rotor core.

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