Rotor and motor

Abstract

To provide a rotor and a motor that can reduce cogging torque.SOLUTION: A rotor RT includes: ten magnet parts MG; and a rotor core. The ten magnet parts MG are arranged in a circumferential direction around a central axis extending in a vertical direction. The rotor core includes a plurality of magnetic pole parts 61. Each magnet part MG is housed in a magnet arrangement part SP1. The magnet arrangement part SP1 is provided between adjacent ones of the magnetic pole parts 61. A radially outer surface 62 of the magnetic pole part 61 has: an arc part 622; and a peripheral part 624. The arc part 622 has a radius of curvature about the central axis. The peripheral part 624 extends from a circumferential end of the arc part 622. The peripheral part 624 is an arc having a radius of curvature different from that of the arc part 622 or a straight line. The width of the arc part 622 is A. The width of the peripheral part 624 is B. A ratio represented by A / (A+B×2) is 0.64 or more and 0.8 or less. The peripheral part covers a surface of a corner part of a magnet part for which a direction of the central axis is a normal direction.SELECTED DRAWING: Figure 2B

Description

[Technical Field]

[0001] The present invention relates to a rotor and a motor. [Background technology]

[0002] A conventional permanent magnet field rotor includes a laminated core and permanent magnets (see, for example, Patent Document 1). The laminated core has a connecting portion and a magnetic pole portion integrally formed therein. The connecting portion is annular and surrounds the rotating shaft. The magnetic pole portions are sector-shaped, the number of which corresponds to the number of poles. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-156496 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the permanent magnet field rotor described in Patent Document 1 may have a high cogging torque. Although the cogging torque can be reduced by increasing the distance between the rotor and the stator, increasing the distance between the rotor and the stator may also result in a decrease in motor torque.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a rotor and a motor that can reduce cogging torque. [Means for solving the problem]

[0006] An exemplary rotor of the present invention has ten magnet portions and a rotor core. The ten magnet portions are arranged circumferentially around a central axis extending vertically. The rotor core is made of a magnetic material. The rotor core has a plurality of magnetic pole portions. Each of the magnet portions is housed in a magnet arrangement portion. The magnet arrangement portion is provided between adjacent magnetic pole portions. The radially outer surface of each magnetic pole portion has an arc portion and a circumferential portion. The arc portion has a radius of curvature centered on the central axis. The circumferential portion extends from a circumferential end of the arc portion. The circumferential portion is an arc having a different radius of curvature from that of the arc portion, or is linear. The width of the arc portion is defined as A. The width of the circumferential portion is defined as B. The ratio A / (A+B×2) is 0.64 or greater and 0.8 or less. The circumferential portion covers a surface at a corner of each magnet portion that is normal to the direction of the central axis.

[0007] An exemplary motor of the present invention includes the rotor described above and a stator. The stator is disposed radially outward of the rotor. The stator includes a core back portion and a plurality of teeth. The core back portion is arranged annularly along the circumferential direction around the central axis. The plurality of teeth extend radially inward from each of the core back portions. The distance between the radially innermost end of the tooth portion and the radially outermost end of the arc portion is 0.4 mm or more and 0.5 mm or less.

[0008] An exemplary rotor of the present invention has eight magnet portions and a rotor core. The eight magnet portions are arranged circumferentially around a central axis extending vertically. The rotor core is made of a magnetic material. The rotor core has a plurality of magnetic pole portions. Each of the magnet portions is housed in a magnet arrangement portion. The magnet arrangement portion is provided between adjacent magnetic pole portions. The radially outer surface of each magnetic pole portion has an arc portion and a circumferential portion. The arc portion has a radius of curvature centered on the central axis. The circumferential portion extends from a circumferential end of the arc portion. The circumferential portion is an arc having a different radius of curvature from that of the arc portion, or is linear. The width of the arc portion is defined as A. The width of the circumferential portion is defined as B. The ratio A / (A+B×2) is 0.34 or greater and 0.44 or less, or 0.66 or greater and 0.9 or less. [Effects of the Invention]

[0009] According to the exemplary embodiment of the present invention, the cogging torque can be reduced. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view showing the structure of a motor having a rotor according to one embodiment of the present invention. [Figure 2A] FIG. 2A is a plan view showing a rotor and a stator according to one embodiment of the present invention. [Figure 2B] FIG. 2B is an enlarged view of FIG. 2A. [Figure 3] FIG. 3 is a diagram showing the results of a simulation of the relationship between the ratio and the cogging improvement rate and the induced voltage increase rate. [Figure 4] FIG. 4 is a diagram showing the results of a simulation of the relationship between the ratio and the cogging improvement rate and the induced voltage increase rate. [Figure 5] FIG. 5 is a diagram showing the simulation results of the cogging improvement rate when the distance G is changed. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. In the drawings, identical or corresponding parts are designated by the same reference numerals, and their descriptions will not be repeated. For convenience, the present specification may refer to the direction of the motor's central axis AX (see FIG. 1 ) as the up-down direction. For ease of understanding, the X-, Y-, and Z-axes of a three-dimensional Cartesian coordinate system are appropriately indicated in the drawings. The positive direction of the Z-axis indicates the upward direction, and the negative direction of the Z-axis indicates the downward direction. However, the up-down direction, the upward direction, and the downward direction are defined merely for convenience of explanation and do not necessarily correspond to the vertical direction. Furthermore, the up-down direction is defined merely for convenience of explanation and does not limit the orientation of the motor according to the present invention during use or assembly. Furthermore, the direction parallel to the motor's central axis AX will be simply referred to as the "axial direction AD," and the radial and circumferential directions centered on the motor's central axis AX will be simply referred to as the "radial direction RD" and the "circumferential direction CD." Furthermore, "planar view" refers to viewing an object from the axial direction AD. In this specification, "parallel direction" also includes a substantially parallel direction. Furthermore, "upper in the axial direction AD" can be written as "one side in the axial direction AD," and "lower in the axial direction AD" can be written as "the other side in the axial direction AD."

[0012] A motor MT according to an embodiment of the present invention will be described with reference to Figures 1 to 2B. Figure 1 is a cross-sectional view showing the structure of a motor MT having a rotor according to an embodiment of the present invention. The motor MT shown in Figure 1 has 10 or 8 poles and is a 12-slot three-phase motor. The three-phase motor is, for example, a three-phase brushless motor.

[0013] As shown in FIG. 1, the motor MT includes a rotor RT, a stator ST, a rotating shaft SH, a first cover member 1, a first bearing 11, a second cover member 2, a second bearing 21, a substrate SB, and a casing CS.

[0014] The rotor RT is disposed about a central axis AX extending in the vertical direction. In other words, as an example, the motor MT is an inner rotor type motor. The rotor RT rotates around the central axis AX. The rotor RT is disposed radially inward of the stator ST in the RD direction.

[0015] The rotor RT has a magnet portion MG and a rotor core 60. The magnet portion MG is, for example, a permanent magnet. For example, the rotor RT may have a single magnet portion MG in a substantially annular shape, or may have multiple magnet portions MG arranged in the circumferential direction CD. "Substantially annular" means, for example, "substantially circular annular." The number of poles of the magnet portion MG is "10" or "8."

[0016] The rotor core 60 is made of, for example, laminated steel plates in which electromagnetic steel plates are stacked in the axial direction AD. A plurality of magnet portions MG are arranged inside the rotor core 60. In this embodiment, the rotor is a spoke-type rotor.

[0017] The rotating shaft SH is disposed about the central axis AX. The rotating shaft SH is generally cylindrical. The rotating shaft SH is fixed to the rotor core 60. Therefore, the rotating shaft SH rotates together with the rotor RT about the central axis AX.

[0018] The first cover member 1 is disposed at an upper portion of the motor MT in the axial direction AD. The first cover member 1 has a cylindrical first bearing holder 12 and a through hole formed in the center of the first bearing holder 12. The first bearing holder 12 holds a first bearing 11. The rotating shaft SH passes through the through hole. The first bearing 11 rotatably supports the rotating shaft SH. The first bearing 11 is, for example, a rolling bearing.

[0019] The second cover member 2 is disposed at a lower portion of the motor MT in the axial direction AD. The second cover member 2 has a cylindrical second bearing holder 22. The second bearing holder 22 holds a second bearing 21. The second bearing 21 rotatably supports the rotating shaft SH. The second bearing 21 is, for example, a rolling bearing. The first cover member 1 and the second cover member 2 are fixed to a casing CS.

[0020] The stator ST is disposed about a central axis AX extending in the vertical direction. The stator ST faces the magnet portion MG in the radial direction RD. The stator ST has a stator core 7, an insulator 4, and a three-phase winding group 5. Specifically, the three-phase winding group 5 of the stator ST includes a U-phase winding group 5U, a V-phase winding group 5V, and a W-phase winding group 5W.

[0021] The substrate SB is substantially flat. The substrate SB is substantially perpendicular to the axial direction AD. The substrate SB is a printed circuit board with printed wiring and is equipped with various electronic components. The substrate SB faces at least a portion of the stator ST and at least a portion of the rotor RT in the axial direction AD and is disposed substantially horizontally.

[0022] The casing CS accommodates at least a portion of the rotor RT and the stator ST. Specifically, the casing CS has an opening that opens upward in the axial direction AD. The casing CS is a generally cylindrical member with a bottom, and is made of a thermosetting resin. "Regularly cylindrical with a bottom" means, for example, "approximately cylindrical with a bottom." The casing CS is obtained by pouring resin into a mold into which the stator ST is inserted. In other words, the casing CS is a resin-molded product into which the stator ST is inserted. Therefore, the stator ST is fixed by the casing CS. The second bearing holder 22 is fixed to the bottom of the casing CS in the axial direction AD.

[0023] In this embodiment, the casing CS covers at least the outer surface of the stator core 7 in the radial direction RD with resin. Meanwhile, at least the inner surface of the stator core 7 in the radial direction RD is exposed from the casing CS. The casing CS also houses at least a portion of the rotor RT.

[0024] The first cover member 1 is generally plate-shaped. More specifically, it is generally disk-shaped. The first cover member 1 is made of, for example, metal. The first cover member 1 covers an opening of the casing CS above the axial direction AD. The first cover member 1 is fixed to the casing CS. As an example, the casing CS and the first bearing holder 12 are configured as a single member.

[0025] The insulator 4 covers at least a portion of the stator core 7. As an example, the insulator 4 is disposed around the central axis AX and has a generally annular shape. "Regular annular" means, for example, "generally circular ring shape." The insulator 4 is an electrical insulator. The insulator 4 may be formed of a single member or may be formed of multiple individual members. For example, the insulator 4 is a resin molded product into which the stator ST is inserted. The insulator 4 may also have a structure that is separately attached to the stator core 7.

[0026] Next, the rotor RT and the stator ST will be further described with reference to Figures 1, 2A, and 2B. Figure 2A is a plan view showing the rotor RT and the stator ST according to one embodiment of the present invention. Figure 2B is an enlarged view of Figure 2A.

[0027] 2A, the rotor RT has ten magnet portions MG and a rotor core 60. The ten magnet portions MG are arranged in the circumferential direction CD around a central axis AX. The central axis AX extends vertically.

[0028] The rotor core 60 is made of a magnetic material.

[0029] The rotor core 60 has a plurality of magnetic pole portions 61. In this embodiment, the rotor core 60 has ten magnetic pole portions 61. The magnetic pole portions 61 are, for example, fan-shaped. Each magnet portion MG is housed in a magnet arrangement portion SP1. The magnet arrangement portion SP1 is provided between adjacent magnetic pole portions 61. The material of the magnet portions MG is ferrite material.

[0030] The stator ST is disposed radially outward of the rotor RT in the radial direction RD. The stator ST has a plurality of core back portions 72 and a plurality of tooth portions 74. In this embodiment, the stator ST has a stator core 7, which has a plurality of core back portions 72 and a plurality of tooth portions 74. In this embodiment, the stator ST has twelve core back portions 72 and twelve tooth portions 74. The core back portions 72 are arranged annularly along the circumferential direction CD around the central axis AX. The tooth portions 74 extend inward in the radial direction RD from each of the core back portions 72. In this embodiment, the stator ST has a structure in which a plurality of core back portions 72 are arranged circumferentially, but may instead be configured with a single circular core back portion 72.

[0031] As shown in FIG. 2B , the radially outer surface 62 of the magnetic pole portion 61 has an arc portion 622 and two circumferential portions 624. The arc portion 622 has a radius of curvature centered on the central axis AX. The circumferential portions 624 extend from the end of the arc portion 622 in the circumferential direction CD. In this embodiment, the circumferential portion 624 is an arc having a different radius of curvature from that of the arc portion 622. Note that the circumferential portions 624 may be linear.

[0032] Next, with reference to FIGS. 2B and 3, preferred dimensions of the magnetic pole portion 61 for a 12-slot, 10-pole motor MT will be described. In FIG. 2B, A indicates the width of the arc portion 622, and B indicates the width of the circumferential portion 624. FIG. 3 shows the results of a simulation of the relationship between the ratio R and the cogging improvement rate and the induced voltage rise rate. Specifically, FIG. 3 shows the results of a simulation of the 12-slot, 10-pole motor MT shown in FIG. 2A. In FIG. 3, the horizontal axis represents the ratio R, and the vertical axis represents the cogging improvement rate and the induced voltage rise rate. The ratio R is a value expressed as A / (A+B×2), where A is the width of the arc portion 622 and B is the width of the circumferential portion 624. The cogging improvement rate indicates the improvement rate when the median value of the cogging calculation results is used as a reference. The induced voltage rise rate indicates the rise rate of the induced voltage when the ratio R is 0.2.

[0033] As shown in Figure 3, cogging torque is improved when the ratio R is 0.2 to 0.22, 0.34 to 0.42, 0.64 to 0.8, and 0.9 to 0.94. For a 10-pole rotor, the ratio R is preferably 0.34 to 0.42 or 0.64 to 0.8. When the ratio R is 0.34 to 0.42 or 0.64 to 0.8, the cogging torque can be reduced. The ratio R is more preferably 0.64 to 0.8. When the ratio R is 0.64 to 0.8, the induced voltage can be increased. Therefore, a high motor torque can be achieved while reducing the cogging torque. The magnet section MG is preferably made of ferrite. When inexpensive ferrite is used for the magnet section MG, the rotor RT can be used, achieving optimal cogging torque and motor torque.

[0034] Next, with reference to FIG. 4, the preferred dimensions of the magnetic pole portions 61 for a 12-slot, 8-pole motor MT will be described. FIG. 4 is a diagram showing the results of a simulation of the relationship between the ratio R and the cogging improvement rate and the induced voltage rise rate. Specifically, FIG. 4 shows the results of a simulation for a 12-slot, 8-pole motor MT. More specifically, the motor MT used in the simulation has eight magnet portions MG and a rotor core 60. The eight magnet portions MG are arranged in the circumferential direction CD around a central axis AX. The central axis AX extends vertically.

[0035] 1 to 2B, the rotor core 60 has a plurality of magnetic pole portions 61. Each magnet portion MG is housed in a magnet arrangement portion SP1. The magnet arrangement portion SP1 is provided between adjacent magnetic pole portions 61. The magnet portions MG are made of ferrite material. The radially outer surface 62 of the magnetic pole portion 61 has an arc portion 622 and two circumferential portions 624. The arc portion 622 has a radius of curvature centered on the central axis AX. The circumferential portions 624 extend from the ends of the arc portion 622 in the circumferential direction CD. In this embodiment, the circumferential portion 624 is an arc having a different radius of curvature from that of the arc portion 622. Note that the circumferential portion 624 may be linear.

[0036] In Figure 4, the horizontal axis represents ratio R, and the vertical axis represents the cogging improvement rate and the induced voltage increase rate. Ratio R is a value expressed as A / (A+B×2), where A is the width of arc portion 622 and B is the width of peripheral portion 624. The cogging improvement rate indicates the improvement rate when the median value of the cogging calculation results is used as the reference. The induced voltage increase rate indicates the increase rate of induced voltage when ratio R is set to a value of 0.2 as the reference.

[0037] As shown in Figure 4, cogging torque is improved when the ratio R is 0.34 to 0.44 or 0.66 to 0.9. In the case of eight poles, the ratio R is preferably 0.34 to 0.44 or 0.66 to 0.9. When the ratio R is 0.34 to 0.44 or 0.66 to 0.9, the cogging torque can be reduced. The ratio R is more preferably 0.66 to 0.9. When the ratio R is 0.66 to 0.9, the induced voltage can be increased. Therefore, a high motor torque can be used while reducing the cogging torque. The magnet section MG is preferably made of ferrite. When an inexpensive ferrite material is used for the magnet section MG, it can be applied to a rotor RT that optimizes cogging torque and motor torque.

[0038] Next, the cogging improvement rate when the distance G (gap) is changed will be described with reference to Fig. 2B and Fig. 5. Fig. 5 is a diagram showing the simulation results of the cogging improvement rate when the distance G is changed. In detail, Fig. 5 shows the simulation results of the cogging improvement rate when the distance G is changed in a 12-slot, 10-pole motor MT. In Fig. 2B, the distance G indicates the distance between the radial RD innermost end 742 of the tooth portion 74 and the radial RD outermost end 626 of the arc portion 622.

[0039] In Fig. 5, the horizontal axis represents ratio R, and the vertical axis represents the cogging improvement rate. Ratio R is a value expressed as A / (A+B×2), where A is the width of arc portion 622 and B is the width of peripheral portion 624. The cogging improvement rate indicates the improvement rate when the median of the cogging calculation results for each distance G is used as the reference. Fig. 5 shows simulation results for distances G of 0.30 mm, 0.35 mm, 0.40 mm, 0.45 mm, and 0.50 mm.

[0040] As shown in Figure 5, for a 10-pole motor, cogging torque is improved when the ratio R is 0.64 or greater and 0.8 or less, and the distance G is 0.30 mm, 0.35 mm, 0.40 mm, 0.45 mm, or 0.50 mm. For a 10-pole motor, the distance G is preferably 0.4 mm or greater and 0.5 mm or less. When the distance G is 0.4 mm or greater and 0.5 mm or less, the cogging torque can be reduced when the ratio R is 0.64 or greater and 0.8 or less. When the distance G is outside the range of 0.4 mm or greater and 0.5 mm or less, reducing the distance G may cause the rotor and stator to come into contact due to vibration during rotation, while increasing the distance G will result in a decrease in torque.

[0041] The embodiments of the present invention have been described above with reference to the drawings (FIGS. 1 to 5). However, the present invention is not limited to the above-described embodiments and can be embodied in various forms without departing from the spirit of the present invention. The drawings mainly show each component in a schematic manner for ease of understanding, and the thickness, length, number, etc. of each component shown in the drawings may differ from the actual components due to the convenience of creating the drawings. Furthermore, the materials, shapes, dimensions, etc. of each component shown in the above-described embodiments are merely examples and are not particularly limited, and various modifications are possible within a range that does not substantially depart from the effects of the present invention. [Industrial Applicability]

[0042] The present invention can be used in rotors and motors, for example. [Explanation of symbols]

[0043] 60 rotor core 61 Magnetic pole part 62 Radial outer surface 72 Core back part 74 Teeth 622 Arc section 624 Periphery 626 Radial outermost end 742 Radial innermost end AX center axis CD circumferential direction G distance MG magnet part MT motor R ratio RD radial direction RT Rotor SP1 Magnet arrangement part ST stator

Claims

1. Ten magnet portions arranged in a circumferential direction around a central axis extending vertically; A rotor core made of magnetic material and the rotor core has a plurality of magnetic pole portions, Each of the magnet portions is accommodated in a magnet arrangement portion provided between adjacent magnetic pole portions, The radially outer surface of the magnetic pole portion is an arc portion having a radius of curvature centered on the central axis; a peripheral portion that is an arc or a straight line extending from a circumferential end of the arc portion and has a different radius of curvature from the arc portion; and The width of the arcuate portion is A, and the width of the circumferential portion is B, the ratio A / (A+B×2) is equal to or greater than 0.64 and equal to or less than 0.8, The rotor has a peripheral portion that covers a surface at a corner of the magnet portion, the surface having a normal direction that is in the direction of the central axis.

2. 2. The rotor according to claim 1, wherein the material of the magnet portion is a ferrite material.

3. The rotor according to claim 1 or 2; a stator disposed radially outside the rotor; and The stator includes: a core back portion annularly arranged along a circumferential direction around the central axis; a plurality of teeth extending radially inward from each of the core back portions; and A motor in which the distance between the radially innermost end of the tooth portion and the radially outermost end of the arc portion is 0.4 mm or more and 0.5 mm or less.

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