JP2012210105A - Three-phase brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure of motor capable of reducing cogging torque to a plurality of rotor magnets having a different number of poles, and to reduce a manufacturing cost of the motor.SOLUTION: A stator core 221 comprises an annular core back 225; and a plurality of teeth portions 224 disposed in a circumferential direction and extending from the core back 225 toward a rotor magnet. A number of slots of a stator is 15, and a number of poles of the rotor magnet is 10 or 20. The plurality of the teeth portions 224 includes at least one first teeth portion 224a having four recessed portion 61 or four projecting portions which are provided at a position of a mechanical angle 9° and a position of a mechanical angle 3° from a center to both sides in a circumferential direction, on a tip end surface; and at least one second teeth portion 224b having two recessed portions 62 or two projecting portions which are provided at a position of a mechanical angle 6° from the center to both sides in the circumferential direction, on a tip end surface.

Description

  The present invention relates to an electric motor.

Conventionally, various techniques have been proposed for reducing the cogging torque of a motor. The armature of a motor disclosed in Japanese Utility Model Laid-Open No. 5-2551 includes an armature core having a plurality of teeth and an armature coil housed in a slot between the plurality of teeth. Two pseudo slots, which are notches extending in parallel with the rotor shaft, are provided at the tip of the teeth facing the rotor magnetic poles. When the greatest common divisor between the number of rotor magnetic poles P and the number of slots Ns is _nm , in the [{(0, 1, 2,... N _m ) × Ns / n _m } +1] -th tooth, the pseudo slot is The angle difference from the center of the slot is Δθ = 360 / {Ns × m × (n _m +1)}. In the motor, the cogging torque can be reduced by providing the pseudo slot.
Japanese Utility Model Publication No. 5-2551

  By the way, as shown in Japanese Utility Model Laid-Open No. 5-2551, when a recess or the like is provided on the front end surface of the teeth in order to reduce cogging torque, the position of the recess on the front end surface depends on the number of poles of the rotor magnet and the stator It is determined based on the number of slots. If an attempt is made to use a rotor magnet having a different number of poles without changing the number of slots, the optimum position of the recess changes, and the cogging torque cannot be reduced. Moreover, in order to change the position of a recessed part, it becomes necessary to redesign a stator and the manufacturing cost of a motor increases.

  An object of the present invention is to reduce the manufacturing cost of a motor by providing a motor structure capable of reducing cogging torque for a plurality of rotor magnets having different numbers of poles.

  A three-phase brushless motor according to an exemplary first aspect of the present invention includes a stationary part having an annular stator centered on a central axis, and a rotating part having a rotor magnet disposed inside or outside the stator. The stator core of the stator includes an annular core back and a plurality of teeth portions arranged in the circumferential direction and extending from the core back toward the rotor magnet, and the stator has 15 slots. And the number of poles of the rotor magnet is 10 or 20, and the plurality of teeth portions are on the tip surface at a mechanical angle of 3 ° and a mechanical angle of 9 ° on both sides in the circumferential direction from the center of the tip surface. At least one first tooth portion having four provided concave portions or four convex portions, and a tip end surface with a mechanical angle of 6 ° from the center of the tip end surface to both sides in the circumferential direction. Having two recesses or two protrusions provided in a position, including at least one second tooth portion.

  A three-phase brushless motor according to an exemplary second aspect of the present invention includes a stationary portion having an annular stator with a central axis as a center, and a rotating portion having a rotor magnet disposed inside or outside the stator. The stator core of the stator includes an annular core back and a plurality of teeth arranged in the circumferential direction and extending from the core back toward the rotor magnet, and the stator has nine slots. The number of poles of the rotor magnet is 6 or 12, and the plurality of teeth portions are provided on the tip surface at a mechanical angle of 5 ° and a mechanical angle of 15 ° on both sides in the circumferential direction from the center of the tip surface. At least one first tooth portion having four concave portions or four convex portions, and a tip end surface at a mechanical angle of 10 ° on both sides in the circumferential direction from the center of the tip end surface. Comprising at least one second tooth portion, a has two recesses or two protrusions, which kicked.

  According to the present invention, even when the rotor magnet is changed to one having a different number of poles, the cogging torque can be reduced without changing the design of the stator, and the manufacturing cost of the motor can be reduced. .

FIG. 1 is a cross-sectional view of the motor according to the first embodiment. FIG. 2 is a diagram illustrating a magnetization waveform of the rotor magnet. FIG. 3 is a diagram illustrating a magnetization waveform of the rotor magnet. FIG. 4 is a plan view of the stator core. FIG. 5 is a diagram illustrating the first tooth portion. FIG. 6 is a diagram illustrating the first tooth portion. FIG. 7 is a diagram illustrating the second tooth portion. FIG. 8 is a diagram illustrating the second tooth portion. FIG. 9 is a diagram illustrating the cogging torque. FIG. 10 is a diagram showing the counter electromotive voltage of the motor. FIG. 11 is a diagram illustrating the cogging torque. FIG. 12 is a diagram showing the counter electromotive voltage of the motor. FIG. 13 is a plan view of a stator core of the motor according to the second embodiment. FIG. 14 is a diagram illustrating the first tooth portion. FIG. 15 is a diagram illustrating the second tooth portion.

  In the present specification, the upper side in the central axis direction of the motor is simply referred to as “upper side”, and the lower side is simply referred to as “lower side”. The vertical direction in this specification does not indicate the vertical direction when incorporated in an actual device. Further, the circumferential direction around the central axis is simply referred to as “circumferential direction”, and the radial direction around the central axis is simply referred to as “radial direction”.

(First embodiment)
FIG. 1 is a diagram illustrating a motor 1 according to an exemplary first embodiment of the present invention. The motor 1 is a three-phase brushless motor, and is used for, for example, OA (office automation) equipment.

  The motor 1 is an outer rotor type, and includes a stationary part 2 that is a fixed assembly, a rotating part 3 that is a rotating assembly, and an upper ball bearing 41 and a lower ball bearing 42 that are bearing mechanisms. The rotating part 3 is supported so as to be rotatable with respect to the stationary part 2 around the central axis J1 of the motor 1 via the upper ball bearing 41 and the lower ball bearing 42.

  The stationary part 2 includes a base part 21, a stator 22, and a bearing holding part 23. The bearing holding part 23 includes a cylindrical part 231 and a flange part 232. The cylindrical portion 231 is located inside the central hole of the base portion 21 and extends upward. The flange portion 232 extends radially outward from the lower portion of the cylindrical portion 231 and is fixed to the lower surface of the base portion 21. The upper ball bearing 41 is held at the upper part of the inner peripheral surface of the cylindrical portion 231, and the lower ball bearing 42 is held at the lower part. The stator 22 has an annular shape centered on the central axis J1 and is attached to the outer peripheral surface of the cylindrical portion 231. The stator 22 includes a stator core 221 and a coil 223. Stator core 221 is formed by laminating thin silicon steel plates. A coil 223 is formed by winding a conductive wire on each tooth portion 224 of the stator core 221.

  The rotating unit 3 includes a shaft 31, a rotor holder 32, and a rotor magnet 33. The shaft 31 is inserted into the upper ball bearing 41 and the lower ball bearing 42 and is rotatably supported by the upper ball bearing 41 and the lower ball bearing 42. The rotor holder 32 has a substantially cylindrical shape with a lid. The shaft 31 is fixed to the central hole of the lid of the rotor holder 32. The rotor magnet 33 is fixed to the inside of the cylindrical portion of the rotor holder 32 and is located on the radially outer side of the stator 22. The rotor magnet 33 is a continuous annular member. In the present embodiment, the rotor magnet 33 having 10 or 20 magnetic poles (hereinafter referred to as “pole number”) is used. In the motor 1, torque about the central axis J <b> 1 is generated between the rotor magnet 33 and the stator 22 by supplying a three-phase current to the stator 22.

  FIG. 2 is a diagram showing a magnetization waveform on the surface of the rotor magnet 33 facing the teeth portion 224 when the number of poles is 20. As shown in FIG. In FIG. 2, the vertical axis represents the magnetic flux density, and the horizontal axis represents the position of the inner peripheral surface of the rotor magnet 33 as an angle. In the magnetized waveform 51, the magnetic flux density rises steeply toward the right side of FIG. 2 and then maintains a high value. Thereafter, the magnetic flux density falls steeply and maintains a low value, and then rises steeply again. Thus, the magnetization waveform 51 is substantially trapezoidal in the upper and lower sides of the horizontal axis.

  FIG. 3 is a diagram showing a magnetization waveform of the rotor magnet 33 when the number of poles is ten. The magnetization waveform 52 has a substantially trapezoidal shape on the top and bottom of the horizontal axis, similarly to the magnetization waveform 51 shown in FIG.

  FIG. 4 is a plan view of the stator core 221. The stator core 221 includes 15 tooth portions 224a, 224b, 224c, and a core back 225. Hereinafter, the tooth portions 224a, 224b, and 224c are collectively referred to as “teeth portion 224”. Each layer of the laminated steel plates constituting the stator core 221 is a single metal plate that is continuous in the circumferential direction. The core back 225 is annular. The teeth portion 224 extends radially outward from the core back 225. The teeth portions 224 are arranged at an equal pitch in the circumferential direction. In the present embodiment, the number of slot gaps 227 (hereinafter referred to as “slot number”), which is a gap between the teeth portions 224 in the circumferential direction, is fifteen. The mechanical angle (hereinafter referred to as “slot pitch angle”) between the centers of adjacent slot gaps 227 around the central axis J1 is 24 ° (= 360 ° / 15). The mechanical angle of the slot gap 227 is 5.4 °.

  The front end surfaces of the first, second, sixth, seventh, eleventh and twelfth teeth portions 224a (hereinafter referred to as “first teeth portions”) clockwise from the teeth portion 224a located on the upper side in FIG. 60 is provided with four recesses 61. Two concave portions 62 are provided on the tip surface 60 of the third, fifth, eighth, tenth, thirteenth, and fifteenth tooth portions 224b (hereinafter referred to as “second tooth portions”). Further, there is no recess in the tip surface 60 of the fourth, ninth and fourteenth tooth portions 224c (hereinafter referred to as “third tooth portion”). The tip surface 60 of the third tooth portion 224c is a partial cylindrical surface centered on an axis parallel to the center axis J1, more precisely, an axis that is offset from the center axis J1 toward the tip side of the third teeth portion 224c. It is. The distal end surface 60 may be a partial cylindrical surface centered on the central axis J1. In the stator 22, the teeth portion 224 is three-fold rotationally symmetric about the central axis J1. That is, the arrangement of the first tooth portion 224a, the second tooth portion 224b, and the third tooth portion 224c is repeated every 120 °.

  FIG. 5 is an enlarged view of the tip of the first tooth portion 224a. The concave portion 61 of the first tooth portion 224a has a bottom surface 611 and a pair of inclined surfaces 612. However, only a part of the recessed part 61 exists in the circumferential direction both ends of the front end surface 60 of the 1st teeth part 224a. In the front end surface 60, a portion other than the bottom surface 611 may be regarded as a convex portion. The part 613 between the recessed parts 61 among the front end surfaces 60 is a partial cylindrical surface centering on the axis | shaft parallel to the central axis J1. The site | part 613 is the same shape as the front end surface 60 of the 3rd teeth part 224c except for the point that it exists partially. Hereinafter, the part 613 is referred to as a “reference tip surface 613”. The inclined surfaces 612 are located on both sides of the bottom surface 611 in the circumferential direction, and are inclined so as to move away from the central axis J1 as they are separated from the bottom surface 611 in the circumferential direction.

  The angle about the central axis J1 between the radially outer edge and the radially inner edge of the inclined surface 612 is about 1 °. The inclined surface 612 connects the bottom surface 611 and the reference tip surface 613. By providing the inclined surface 612, the magnetic change between the first tooth portion 224a and the rotor magnet 33 can be smoothed. As shown in FIG. 6, the four concave portions 61 are such that the center position of the bottom surface 611 is a mechanical angle A11 (= 3 °) and a mechanical angle A12 (= 9 °) on both sides in the circumferential direction from the center of the tip surface 60. It is provided so that it may become a position. However, “the center of the bottom surface 611” of the recesses 61 at both ends refers to the center of the bottom surface 611 when it is assumed that the entire recess 61 exists. The central pitch angle of the adjacent recesses 61 (hereinafter referred to as “recess pitch angle”) is 6 °.

  The recess pitch angle is calculated by dividing the slot pitch angle of 24 ° by 4 which is a number obtained by dividing the least common multiple 60 of the pole number 20 and the slot number 15 by the slot number 15. The positions of the four concave portions 61 of the first teeth portion 224a are positions where the cogging torque generated in the motor 1 is reduced when the rotor magnet 33 having 20 poles is used.

  FIG. 7 is an enlarged view of the second tooth portion 224b. The concave portion 62 of the second tooth portion 224b has a bottom surface 621 and a pair of inclined surfaces 622. In the front end surface 60, a portion other than the bottom surface 621 may be regarded as a convex portion. Among the front end surfaces 60, the reference front end surfaces 623 that are present on the left and right sides of the recess 62 have a partial cylindrical surface centered on an axis parallel to the central axis J1. The reference front end surface 623 has the same shape as the front end surface 60 of the third tooth portion 224c except that the reference front end surface 623 exists partially.

  The inclined surface 622 connects the bottom surface 621 and the reference tip surface 623, and is inclined so as to move away from the central axis J1 as the distance from the bottom surface 611 in the circumferential direction increases. The angle about the central axis J1 between the radially outer edge and the radially inner edge of the inclined surface 622 is about 1 °. The reference front end surface 623 between the two concave portions 62 exists in a range of (± 4) ° from the center of the front end surface 60 to both sides in the circumferential direction. The reference tip surface 623 may be provided in a range of (± 3) ° from the center of the tip surface 60, for example.

  As shown in FIG. 8, the two concave portions 62 are provided such that the center position of the bottom surface 621 is at a mechanical angle A2 (= 6 °) on both sides in the circumferential direction from the center of the tip surface 60. The recess pitch angle of the bottom surfaces 621 of the two recesses 62 is 12 °. The concave pitch angle is calculated by dividing the slot pitch angle of 24 ° by 2 which is a number obtained by dividing the least common multiple 30 of the pole number 10 and the slot number 15 by the slot number 15. The positions of the two concave portions 62 of the second tooth portion 224b are positions where the cogging torque generated in the motor 1 is reduced when the rotor magnet 33 having ten poles is used.

  FIG. 9 is a diagram showing the result of simulating on a computer the cogging torque of the motor 1 having the stator 22 and a plurality of motors having the stator according to the comparative example. A rotor magnet 33 having 20 poles is used for the motor 1 and the plurality of motors according to the comparative example. In FIG. 9, the change in cogging torque in the motor 1 is indicated by a solid curve 71 connecting triangular dots (ド ッ ト). Similarly to the first tooth portion 224a, the change in cogging torque in the motor of the comparative example in which four concave portions are provided in all the tooth portions is indicated by a dashed curve 72 connecting square dots (■). Similar to the second tooth portion 224b, the change in cogging torque in the motor of the comparative example in which two concave portions are provided in all the tooth portions is indicated by a dashed curve 73 connecting diamond-shaped dots (♦). A change in cogging torque in the motor of the comparative example in which no recess is present in the tooth portion is shown by a solid curve 74 connecting round dots (●).

  When the rotor magnet 33 with the number of poles of 20 is used, as shown by the curve 72, the cogging torque of the motor of the comparative example in which four recesses are provided in the teeth portion is the smallest. The cogging torque of the motor 1 indicated by the curve 71 is approximately 40% smaller than the cogging torque of the motor having no recess indicated by the curve 74. Further, as shown by a curve 73, the cogging torque of the comparative example motor in which two concave portions are provided in the tooth portion is larger than the cogging torque of other motors. This is because the motor indicated by the curve 73 does not have a concave portion arrangement corresponding to the case of the rotor magnet 33 having 20 poles.

  FIG. 10 is a diagram illustrating back electromotive voltages of the motor 1 and a plurality of motors according to the comparative example. The counter electromotive voltage is related to the magnitude of the torque of the motor that is output. In FIG. 10, the same reference numerals and the same dots as those in FIG. As shown in FIG. 10, the counter electromotive voltages of the motor 1 and the plurality of motors according to the comparative example are substantially the same. From the above, it can be seen that in the motor 1, the cogging torque is reduced while maintaining the counter electromotive voltage.

  FIG. 11 is a diagram illustrating another result of simulating the cogging torque of the motor 1 having the stator 22 and a plurality of motors having the stator according to the comparative example, and corresponds to FIG. 9. In FIG. 11, a rotor magnet 33 having ten poles is used for the motor 1 and a plurality of motors according to the comparative example. In this case, as shown by the curve 73, the cogging torque of the motor of the comparative example in which two recesses are provided in the teeth portion is the smallest. As shown by the curve 72, the cogging torque of the comparative example motor in which the four concave portions are provided in the tooth portion is substantially the same as the cogging torque of the comparative example motor having no concave portion shown by the curve 74. The cogging torque of the motor 1 indicated by the curve 71 is approximately 25% smaller than the cogging torque of the motor provided with four recesses and the motor without the recess. As shown in FIG. 12, the counter electromotive voltages of the motor 1 and the plurality of motors according to the comparative example are substantially the same. In the motor 1, it can be seen that even when the rotor magnet 33 having 10 poles is used, the cogging torque is reduced while maintaining the back electromotive voltage.

  As described above, when the cogging torque of the motor of the comparative example in which no recess is present in all the teeth portions is used as a reference, in the motor 1, the rotor magnet 33 having either 20 or 10 poles is used. Even if it exists, a cogging torque can be reduced. As a result, in the motor 1 in which one of the rotor magnet 33 with the number of poles 10 and the rotor magnet 33 with the number of poles of 20 is used, the design of the stator 22 can be made even when the rotor magnet 33 is replaced with the other. The cogging torque can be reduced without changing. As a result, the manufacturing cost of the motor 1 can be reduced.

  The motor 1 according to the first embodiment has been described above. In the motor 1, the stator 22 having the first tooth portion 224 a having the four concave portions 61 and the second tooth portion 224 b having the two concave portions 62 is provided. Thus, the cogging torque can be reduced regardless of whether the number of poles of the rotor magnet 33 is 10 or 20.

(Second Embodiment)
FIG. 13 is a plan view of the stator core 221a of the motor according to the second embodiment. The stator core 221a includes nine teeth portions 226a, 226b, 226c, and a core back 225. Hereinafter, the tooth portions 226a, 226b, and 226c are collectively referred to as “teeth portion 226”. The number of slots of the stator core 221a is nine. In the motor, a rotor magnet 33 having 6 or 12 poles is used. Other structures of the motor are the same as those in the first embodiment. Hereinafter, the same reference numerals are given to the same components. Four concave portions 61 are provided on the distal end surface 60 of the first teeth portion 226a that is the first, fourth, and seventh teeth portions clockwise from the teeth portion 226a located on the upper side of FIG. Two concave portions 62 are provided on the front end surface 60 of the second teeth portion 226b which is the second, fifth and eighth teeth portions. Further, there is no recess in the tip surface 60 of the third tooth portion 226c which is the third, sixth, and ninth tooth portions. The tip surface 60 of the third tooth portion 226c is a partial cylindrical surface centered on an axis parallel to the center axis J1, more precisely, an axis that is offset from the center axis J1 toward the tip side of the third teeth portion 226c. It is. The tip surface 60 may be a partial cylindrical surface centered on the central axis J1. In the stator core 221a, the tooth part 226 is three-fold rotationally symmetric about the central axis J1.

  FIG. 14 is an enlarged view of the first tooth portion 226a. The center position of the four recesses 61 of the first tooth portion 226a is a mechanical angle A31 (= 5 °) position and a mechanical angle A32 (= 15 °) position on both sides in the circumferential direction from the center of the tip surface 60. The recess pitch angle of the recess 61 is 10 °. The recess pitch angle is calculated by dividing the least common multiple 36 of the pole number 12 and the slot number 9 by the slot number 9 and dividing the slot pitch angle 40 ° (= 360 ° / 9) by 4. Is done. The positions of the four recesses 61 of the first teeth portion 226a are positions where the cogging torque generated in the motor is reduced when the rotor magnet 33 having 12 poles is used.

  FIG. 15 is an enlarged view of the second tooth portion 226b. The center position of the two recesses 62 of the second tooth portion 226b is a mechanical angle A4 (= 10 °) from the center of the tip surface 60 to both sides in the circumferential direction, and the recess pitch angle is 20 °. The recess pitch angle is calculated by dividing the slot common angle 18 by the least common multiple 18 of the number of poles 6 and the number of slots 9 by the number of slots 9 and dividing the slot pitch angle 40 °. The positions of the two concave portions 62 of the second tooth portion 226b are positions where cogging torque is reduced when the rotor magnet 33 having six poles is used.

  Also in the second embodiment, by providing the stator 22 having the first tooth portion 226a having the four concave portions 61 and the second tooth portion 226b having the two concave portions 62, either the number of poles of 6 or 12 is provided. It has been confirmed that even when the rotor magnet 33 is used, the cogging torque is reduced. Thereby, the design change of the stator 22 by the change of the rotor magnet 33 becomes unnecessary, and the manufacturing cost of the motor 1 can be reduced.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, You may change variously.

  In the motor 1 according to the first embodiment, depending on the size of the slot gap 227 and the size of the gap between the stator 22 and the rotor magnet 33, a convex portion is provided on the tooth portion 224 instead of the concave portions 61 and 62. Thus, it is known that the cogging torque generated in the motor 1 is reduced. In this case, in the first tooth portion 224a, the four teeth projecting radially outward from the reference tip surface 613 at the mechanical angle of 3 ° and the mechanical angle of 9 ° on both sides in the circumferential direction from the center of the tip surface 60. Protrusions are provided. In the 2nd teeth part 224b, two convex parts are provided in the position of the mechanical angle of 6 degrees from the center of the front end surface 60 to the circumferential direction both sides. When four convex portions are provided, the two convex portions located at both ends do not need to have the same shape as the other two convex portions, and are only a part of the shape of the other two convex portions. Also good.

  Normally, when the first tooth portion 224a is provided with a concave portion, the second tooth portion 224b is also provided with a concave portion, and when the first tooth portion 224a is provided with a convex portion, the second tooth portion 224b is also convex. However, such a combination is not always obtained.

  Also in the second embodiment, four convex portions may be provided on the first tooth portion 226a, and two convex portions may be provided on the second tooth portion 226b. The four convex portions on the first tooth portion 226a are provided at a mechanical angle of 5 ° and a mechanical angle of 15 ° on both sides in the circumferential direction from the center of the tip surface 60. The two convex portions on the second tooth portion 226b are provided at a mechanical angle of 10 ° on both sides in the circumferential direction from the center of the tip surface 60.

  In the first embodiment, since at least one first tooth portion 224a and at least one second tooth portion 224b are provided, the cogging torque can be obtained regardless of whether the number of poles of the rotor magnet 33 is 10 or 20. Can be reduced. For example, the number of the first teeth portions 224a and the second teeth portions 224b may be 3, and the number of the third teeth portions 224c may be 9.

  When the number of the first teeth portions 224a is 5 or less, the cogging torque reduction effect similar to the case of FIG. 4 can be obtained by deepening the concave portions 61. Moreover, even if the width in the circumferential direction of the bottom surface 611 of the recess 61 is increased, the cogging torque reduction effect may be improved. The same applies to the second tooth portion 224b. Of course, the number of the first teeth portions 224a may be 7 or more, and the number of the second teeth portions 224b may be 7 or more. However, considering that the number of teeth portions is an odd number, even if seven first teeth portions 224a and seven second tooth portions 224b are provided, one extra tooth portion is provided, so that at least one third tooth portion 224c is provided. Is preferred.

  Similarly, in the second embodiment, the cogging torque can be reduced by providing at least one first tooth portion 226a and at least one second tooth portion 226b. It is preferable that at least one third tooth portion 224c is provided.

  In the embodiment described above, the teeth portions do not necessarily have to be arranged at an equal pitch in the circumferential direction.

  In the above embodiment, the first teeth portions 224a and 226a and the second teeth portions 224b and 226b may be randomly arranged. However, considering that the motor 1 is a three-phase brushless motor, the teeth portion rotates three times. Symmetry is preferred. The first tooth portion, the second tooth portion, and the third tooth portion can be arranged in various three-fold rotational symmetry other than the arrangement shown in FIGS. 4 and 13. Furthermore, as shown in FIGS. 4 and 13, it is most preferable that the number of the first teeth 224a and the number of the second teeth 224b are the same and the largest.

  If the reference tip surfaces of the first teeth portions 224a and 226a and the second teeth portions 224b and 226b and the tip surfaces 60 of the third teeth portions 224c and 226c in the embodiment are shapes that can be regarded as cylindrical surfaces, It does not have to be strictly cylindrical. If it is a substantially cylindrical surface, for example, it may be a curved surface that becomes an ellipse or another curve when viewed in plan, or may be a combination of multiple types of curved surfaces.

  In the said embodiment, the inclined surfaces 612 and 622 of the recessed parts 61 and 62 may be abbreviate | omitted. When viewed in a plan view, an elliptical or substantially circular groove-shaped recess may be provided. The rotor magnet 33 may be a segment type in which a plurality of magnets are annularly arranged. Even in this case, the magnetization waveform in the circumferential direction is approximately trapezoidal.

  The motor 1 may be an inner rotor type in which the rotor magnet 33 is disposed on the radially inner side of the stator 22. In this case, the tooth portion extends from the core back 225 inward in the radial direction toward the rotor magnet 33. The motor 1 is also suitable as a motor for home appliances that require cost reduction.

  The configurations in the above embodiment and each modification may be combined as appropriate as long as they do not contradict each other.

  The motor according to the present invention can be used as a motor for OA equipment, home appliances, etc., and as a motor for other applications.

DESCRIPTION OF SYMBOLS 1 Motor 2 Static part 3 Rotating part 22 Stator 33 Rotor magnet 51,52 Magnetization waveform 60 Front end surface 61,62 Recessed part 221,221a Stator core 224,226 Teeth part 224a, 226a 1st teeth part 224b, 226b 2nd teeth part 224c , 226c Third tooth portion 225 Core back J1 Central axis

Claims (6)

A stationary part having an annular stator centered on the central axis;
A rotating part having a rotor magnet disposed inside or outside the stator;
With
The stator core of the stator is
An annular core back,
A plurality of teeth portions arranged in the circumferential direction and extending from the core back toward the rotor magnet,
With
The stator has 15 slots, and the rotor magnet has 10 or 20 poles;
The plurality of teeth portions are
At least one first tooth portion having four concave portions or four convex portions provided at a position of a mechanical angle of 3 ° and a mechanical angle of 9 ° on both sides in the circumferential direction from the center of the distal end surface on the distal end surface; ,
At least one second tooth portion having two concave portions or two convex portions provided on the front end surface at a mechanical angle of 6 ° on both sides in the circumferential direction from the center of the front end surface;
Including three-phase brushless motor. A stationary part having an annular stator centered on the central axis;
A rotating part having a rotor magnet disposed inside or outside the stator;
With
The stator core of the stator is
An annular core back,
A plurality of teeth arranged in a circumferential direction and extending from the core back toward the rotor magnet;
With
The stator has 9 slots, and the rotor magnet has 6 or 12 poles;
The plurality of teeth portions are
At least one first tooth portion having four concave portions or four convex portions provided at positions of a mechanical angle of 5 ° and a mechanical angle of 15 ° on both sides in the circumferential direction from the center of the distal surface on the distal surface;
At least one second tooth portion having two concave portions or two convex portions provided on the distal end surface at a mechanical angle of 10 ° on both sides in the circumferential direction from the center of the distal end surface;
Including three-phase brushless motor.   The three-phase brushless motor according to claim 1, wherein the plurality of teeth portions are three-fold rotationally symmetric about the central axis.   4. The device according to claim 1, wherein the plurality of tooth portions further include at least one third tooth portion having a front end surface of a substantially cylindrical surface centered on the central axis or an axis parallel to the central axis. A three-phase brushless motor according to claim 1. The plurality of teeth are three-fold rotationally symmetric about the central axis,
The plurality of teeth portions further include three third teeth portions, each having a substantially cylindrical surface centered on the central axis or an axis parallel to the central axis.
2. The three-phase brushless motor according to claim 1, wherein the number of the at least one first tooth portion and the at least one second tooth portion is 6, respectively. The rotor magnet is a continuous annular member;
The three-phase brushless motor according to claim 5, wherein a magnetization waveform on a surface of the rotor magnet facing the plurality of teeth portions is substantially trapezoidal.

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