JP2019162005A - Brushless motor, and blower - Google Patents

Abstract

To provide a brushless motor in which cogging torque is reduced.SOLUTION: In an outer-rotor type brushless motor to be mounted in a blower, the stator core has a core back surrounding the medial axis annularly, and multiple teeth 212 extending radially outward from the core back. The tooth has multiple small gear teeth 213a, 213b arranged in the hoop direction while facing the rotor 11 in the radial direction, a tooth recess 215 recessed radially inward between small gear teeth adjoining in the hoop direction, and a proximal region 212a provided between the small gear tooth and the core back. At least one of the multiple small gear teeth has a bevelling part 216 at the hoop direction end on the teeth recess side, out of the radial outside facing the radial direction of the magnets 121, 122 of the small gear teeth.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a brushless motor and a blower.

  2. Description of the Related Art Conventionally, a stepping motor having a so-called vernier stator core in which a plurality of small teeth is provided at the tip of a salient pole is known. For example, Patent Document 1 applies a vernier structure to a brushless motor, and further reduces the cogging torque by setting the opening angle of the small teeth provided on the salient pole to 145 ° to 160 ° in electrical angle.

JP 2003-61326 A

  However, when the electrical angle of the small teeth is changed as in Patent Document 1, the circumferential dimension of the stator core teeth (the salient pole in Patent Document 1) changes. Such a change affects the space in which the coil portion is provided in the stator core, and in particular causes a change in the motor torque.

  An object of this invention is to reduce the cogging torque of a brushless motor, without changing the circumferential dimension of teeth.

  An exemplary brushless motor of the present invention is an outer rotor type brushless motor including a rotor that can rotate around a central axis, and a stator that rotationally drives the rotor. The rotor has a plurality of magnets opposed to the stator in the radial direction. The plurality of magnets include a first magnetic pole and a second magnetic pole different from the first magnetic pole. The first magnetic pole and the second magnetic pole are alternately provided in the circumferential direction. The stator includes a stator core and a plurality of coil portions. The stator core includes a core back that annularly surrounds the central axis, and a plurality of teeth that extend radially outward from the core back. Each of the teeth includes a plurality of small teeth arranged in the circumferential direction so as to face the rotor in the radial direction, a tooth recess recessed inward in the radial direction between the small teeth adjacent in the circumferential direction, the small teeth, and the teeth And a base portion provided between the core backs. The coil part provided in each of the teeth includes a conductive wire wound around the base part. At least one of the plurality of small teeth has a chamfered portion at a circumferential end portion on the teeth recess side of a radially outer surface facing the magnet in a radial direction of the small teeth.

  Moreover, the exemplary air blower of this invention is provided with the blade | wing which can be rotated centering | focusing on a center axis | shaft, and said brushless motor which rotates the said blade | wing.

  According to the exemplary brushless motor and the blower of the present invention, the cogging torque of the brushless motor can be reduced without changing the circumferential dimension of the teeth.

FIG. 1 is a perspective view illustrating a configuration example of a ceiling fan. FIG. 2 is a cross-sectional view showing a configuration example of the motor. FIG. 3A is a view of the magnet and the stator core as seen from the axial direction. FIG. 3B is a cross-sectional view of the magnet facing the stator as seen from the circumferential direction. FIG. 4 is an enlarged view of the vicinity of the R chamfered portion viewed from the axial direction. FIG. 5 is an enlarged view of the vicinity of the C chamfered portion as viewed from the axial direction. FIG. 6 is a view of the structure in which the small teeth face the magnet when viewed from the axial direction. FIG. 7A is a graph showing changes in cogging torque tqc with respect to the circumferential angle ratio rθ of the chamfered portion. FIG. 7B is a graph showing a change in torque characteristic Ke with respect to the circumferential angle ratio rθ of the chamfered portion.

  Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings.

  First, in this specification, the rotation axis of the motor 110 of the ceiling fan 100 is referred to as a central axis CA, and a direction parallel to the central axis CA is referred to as an “axial direction”. One of the axial directions from the stator core 21 toward the bearing 3 is referred to as “upward in the axial direction”, and the other of the axial directions from the bearing 3 toward the stator core 21 is referred to as “downward in the axial direction”. On the surface of each component, the surface facing upward in the axial direction is called “upper surface”, and the surface facing downward in the axial direction is called “lower surface”. In each component, an end in the axial direction is referred to as an “axial end”, and a position of the end in the axial direction is referred to as an “axial end”. In particular, the end in the upper axial direction is referred to as the “upper end in the axial direction”, and the position of the upper end in the axial direction is referred to as the “upper end in the axial direction”. Further, the end portion in the axially lower portion is referred to as “axially lower end portion”, and the position of the end portion in the axially lower portion is referred to as “axially lower end”.

  A direction in which a straight line orthogonal to the central axis CA extends is referred to as a “radial direction”. One of the radial directions toward the central axis CA is called “radially inward”, and the other radial direction away from the central axis CA is called “radially outward”. In the side surface of each component, the side surface facing in the radial direction is referred to as “radial side surface”. In particular, a side surface facing radially inward is referred to as a “radial inner surface”, and a side surface facing radially outward is referred to as a “radial outer surface”. In each component, the end portion in the radial direction is referred to as “radial end portion”, and the position of the end portion in the radial direction is referred to as “radial end”. In particular, an end portion in the radially inward direction is referred to as a “radially inner end portion”, and a position of the end portion in the radially inward direction is referred to as a “radial inner end”. Further, the end portion in the radially outward direction is referred to as “radially outer end portion”, and the position of the end portion in the radially outward direction is referred to as “radial outer end”.

  The rotation direction around the central axis CA is referred to as “circumferential direction”. Of the circumferential directions, the counterclockwise direction with respect to the central axis CA when viewed from above in the axial direction is referred to as “circumferential one Rd1”, and the clockwise direction with respect to the central axis CA when viewed from above in the axial direction. The direction is referred to as “the other circumferential direction Rd2”. In the side surface of each component, the side surface facing the circumferential direction is referred to as “circumferential side surface”. In each component, the end in the circumferential direction is referred to as “circumferential end”, and the position of the end in the circumferential direction is referred to as “circumferential end”. In particular, an end portion in one circumferential direction Rd1 is referred to as “circumferential one end portion”, and a position of the end portion in one circumferential direction Rd1 is referred to as “circumferential one end”. Furthermore, the end portion in the other circumferential direction Rd2 is referred to as “the other circumferential end portion”, and the position of the end portion in the other circumferential direction Rd2 is referred to as “the other circumferential end”.

  Note that the names such as the direction, surface, edge, and position thereof described above do not indicate the positional relationship and direction when incorporated in an actual device.

  In this specification, the back electromotive force constant Ke of the motor 110 is used as a value indicating the torque characteristic of the motor 110. Hereinafter, the counter electromotive force constant Ke is referred to as torque characteristic Ke.

<1. Embodiment>
<1-1. Configuration of ceiling fan>
FIG. 1 is a perspective view illustrating a configuration example of the ceiling fan 100. The ceiling fan 100 is a blower device that includes a motor 110 and blades 120. The blade 120 is rotatable on both sides in the circumferential direction around the central axis CA, and is attached to the motor 110. The motor 110 is a brushless DC motor that rotates the blade 120 in one circumferential direction Rd1 or the other circumferential direction Rd2. The number of blades 120 is three in FIG. 1, but is not limited to this example, and may be a single number or a number other than three.

<1-2. Motor configuration>
Next, the configuration of the motor 110 will be described. FIG. 2 is a cross-sectional view illustrating a configuration example of the motor 110. FIG. 2 shows a cross-sectional structure when the motor 110 is cut along a virtual cut surface including the central axis CA.

  In this embodiment, the motor 110 is an outer rotor type brushless DC motor. As shown in FIG. 2, the motor 110 has a rotor 1 that can rotate on both sides in the circumferential direction around a central axis CA that extends in the vertical direction, and drives the rotor 1 to rotate in one circumferential direction Rd1 or the other circumferential direction Rd2. A stator 2 and a bearing 3 are provided.

  As shown in FIG. 2, the rotor 1 includes a rotor core 11, a magnet 12 that faces the stator 2 in the radial direction, an adhesive member 13 that bonds the magnet 12 to the rotor core 11, and a housing 14 that houses the rotor core 11 and the bearing 3. And having. The rotor core 11 is a member that annularly surrounds a central axis CA that extends in the vertical direction. For the rotor core 11, for example, a laminated steel plate in which electromagnetic steel plates or the like are laminated is used. The plurality of magnets 12 are provided on the radially inner side surface of the rotor core 11 and arranged in the circumferential direction on the radially inner side surface. The adhesive member 13 is provided between the rotor core 11 and each magnet 12, and fixes the plurality of magnets 12 to the rotor core 11. The housing 14 has an upper housing part 14a, a cylindrical bearing holder 14b, and a lower housing part 14c. The upper housing portion 14a is annular when viewed from below in the axial direction, and accommodates the rotor core 11 therein. The bearing holder 14b extends axially upward from the inner peripheral edge of the upper housing portion 14a in the radial direction. The bearing 3 is provided inside the bearing holder 14b, and the shaft 24 is inserted therethrough. The lower housing part 14c is attached below the upper housing part 14a in the axial direction and covers the lower end part in the axial direction of the upper housing part 14a. The configuration of the magnet 12 will be described later.

  The stator 2 includes a stator core 21, an insulator 22, a plurality of coil portions 23, and a shaft 24. The stator core 21 is an iron core member using, for example, electromagnetic steel plates laminated in the axial direction, and faces the magnet 12 of the rotor 1 in the radial direction. The insulator 22 is an insulating member using, for example, a resin material, and covers at least a part of the stator core 21. The stator core 21 is provided with a plurality of coil portions 23. Coil portion 23 is provided on each tooth 212 described later in stator core 21 via insulator 22 and includes a conductive wire wound around base 212a described later. The shaft 24 is a cylindrical member extending in the axial direction. A stator core 21 is attached to the shaft 24. The configuration of the stator core 21 will be described later.

  The bearing 3 is attached between the housing 14 of the rotor 1 and the shaft 24, and supports the rotor 1 rotatably with respect to the shaft 24.

<1-3. Magnet and Stator Core>
Next, the magnet 12 and the stator core 21 will be described. FIG. 3A is a view of the magnet 12 and the stator core 21 as seen from the axial direction. FIG. 3B is a cross-sectional view of the magnet 12 facing the stator 2 as seen from the circumferential direction. In FIG. 3A, the insulator 22 and the coil portion 23 are not shown in order to make the configuration easy to see. FIG. 3B shows a cross section taken along line AA of FIG. 3A.

<1-3-1. Magnet configuration>
As shown in FIG. 3B, the magnet 12 faces the stator core 21 of the stator 2 in the radial direction. When viewed from the circumferential direction, the axial length Lma of the magnet 12 is larger than the sum (Lsa + Lmr) of the axial length Lsa of the stator core 21 and the radial length Lmr which is the thickness of the magnet 12 in the radial direction. . By so doing, the magnetic flux flowing directly between the radially inner side surface and the radially outer side surface of the magnet 12 can be suppressed among the magnetic fluxes flowing between the stator core 21 and the rotor 1. Thereby, it can contribute to the improvement of the torque characteristic Ke of the motor 110 and the improvement of efficiency.

  3B, the central position Pm in the axial direction of the magnet 12 and the central position Ps in the axial direction of the stator core 21 are different in the axial direction. In this way, when the stator 2 drives the rotor 1, an axial force can be applied to the rotor 1. Thereby, the vibration in the axial direction of the rotor 1 can be suppressed, and the torque characteristic Ke of the motor 110 can be improved and the efficiency can be improved.

  The magnet 12 is a rare earth sintered magnet such as a neodymium sintered magnet. As described above, the rotor 1 includes the plurality of magnets 12 that are opposed to the stator 2 in the radial direction. The plurality of magnets 12 includes a first magnetic pole and a second magnetic pole that is different from the first magnetic pole. The first magnetic pole and the second magnetic pole are alternately provided in the circumferential direction. The number of the first magnetic poles and the number of the second magnetic poles are 10 in this embodiment, respectively, but are not limited to this example. One of the first magnetic pole and the second magnetic pole is the S pole, and the other is the N pole.

  More specifically, the magnet 12 includes a first magnet 121 having a first magnetic pole and a second magnet 122 having a second magnetic pole. The first magnet 121 and the second magnet 122 are alternately arranged with an interval in the circumferential direction.

<1-3-2. Configuration of stator core>
As shown in FIG. 3A, the stator core 21 includes a core back 211 that annularly surrounds the central axis CA, and a plurality of teeth 212 that extend from the core back 211 in the radial direction. In addition, although the number of the teeth 212 which the stator core 21 has is six in this embodiment, it is not limited to this illustration, A plurality other than six may be sufficient. Each of the teeth 212 includes a plurality of small teeth 213 arranged in the circumferential direction so as to face the rotor 1 in the radial direction, a teeth concave portion 215 recessed inward in the radial direction between the small teeth 213 adjacent in the circumferential direction, and the small teeth 213. And a base 212 a provided between the core backs 211. Each tooth 212 further includes a tip end portion 212b, a connection portion 214, and a chamfered portion 216.

  The base 212a is provided between the tip 212b and the core back 211. The base 212 a extends in the radial direction from the core back 211 and is covered with the insulator 22. The coil part 23 is provided in the base 212a. As described above, the coil portion 23 provided in each of the teeth 212 includes a conductive wire wound around the base portion 212a via the insulator 22. Here, as shown in FIG. 3A, the circumferential angle θc1 between the base portion 212a and the core back 211 on the radially inner side of the base portion 212a, and the small teeth described later on the base portion 212a on the radially outer side of the base portion 212a. The circumferential angle θc2 between the connection portion 214 connecting the 213 to the base portion 212a is preferably the same. A conductive wire having a circular cross section is wound around the base 212a without any gaps. In the present embodiment, the circumferential angles θc1 and θc2 are 120 °, for example. In this way, when the coil portion 23 is provided on the base portion 212a of the tooth 212, it is possible to suppress or prevent turbulence of the conductive wire when the winding of the conductive wire is folded back on the radially outer side and the radially inner side of the coil portion 23. Magnetic flux can be generated efficiently.

  The tip 212b is provided at the radially outer end of the base 212a. More specifically, the tip end portion 212 b has a plurality of small teeth 213, a connection portion 214, and a tooth recess 215.

  A plurality of small teeth 213 are provided at the tip end portion 212b, and are arranged in the circumferential direction so as to face the rotor 1 in the radial direction. In each tooth 212, each small tooth 213 is connected to the base portion 212 a through the connection portion 214. In addition, although the number of the small teeth 213 provided in the front-end | tip part 212b of each tooth | gear 212 is two in this embodiment, it is not limited to this illustration, Three or more may be sufficient. In the following description, among the small teeth 213 adjacent to each other in the circumferential direction at the tip 212b of the same tooth 212, the small tooth 213 positioned on one side Rd1 in the circumferential direction of the tooth recess 215 is referred to as a first small tooth 213a. The small teeth 213 located in the other circumferential direction Rd2 of 215 are referred to as second small teeth 213b.

  With respect to the position of the end of the small tooth 213 in the axial direction, the upper end in the axial direction of the magnet 12 is higher in the axial direction than the upper end in the axial direction of the small tooth 213 in FIG. Further, the lower end in the axial direction of the magnet 12 is lower in the axial direction than the lower end in the axial direction of the small teeth 213 in FIG. 3B. However, the upper end in the axial direction may be the same as the upper end in the axial direction of the small teeth 213, and the lower end in the axial direction may be the same as the lower end in the axial direction of the small teeth 213. . In this way, the axial upper end and the axial lower end of the magnet 12 can be opposed to the small teeth 213 in the radial direction. Therefore, more magnetic flux can be obtained between the stator 2 and the rotor 1.

  Further, the radially outer surface of the small teeth 213 faces radially outward and faces the magnet 12 in the radial direction. The circumferential width Wrb of the base 212a is narrower than the circumferential width Wro of the radially outer surface of the small teeth 213. Further, the radial width Wd of the core back 211 is narrower than the circumferential width Wro of the radially outer surface of the small teeth 213. By so doing, it is possible to sufficiently secure a region around which the conducting wire is wound around the base portion 212a, so that the torque characteristic Ke can be improved and the efficiency of the motor 110 can be improved. In addition, a good magnetic circuit can be formed between the stator core 21 and the rotor 1.

  Next, in each of the teeth 212, the connection portion 214 connects each small tooth 213 to the radially outer end portion of the base portion 212a as described above.

  The teeth recess 215 is provided between the teeth 212 adjacent to each other in the circumferential direction in each of the teeth 212 and is recessed radially inward. It has been confirmed that the size of the tooth recess 215, particularly the radial length Whr and the circumferential length Whc, affects the torque characteristic Ke of the motor 110. The size of the tooth recess 215 will be described later.

  The chamfered portion 216 is a portion obtained by rounding or chamfering the corner of the circumferential end portion on the teeth concave portion 215 side of the radially outer surface of the small teeth 213. The chamfered portion 216 includes at least one of an R chamfered portion 216a and a C chamfered portion 216b. In FIGS. 3A and 6, an R chamfered portion 216 a is provided as an example of the chamfered portion 216 at the circumferential end of each small tooth 213 on the teeth concave portion 215 side.

  The configuration of the stator core 21 is not limited to the above-described embodiment. The configuration of the stator core 21 can be implemented with various modifications without departing from the spirit of the invention.

<1-3-3. Chamfer>
4 and 5 are diagrams for explaining the configuration of the chamfered portion 216. FIG. FIG. 4 is an enlarged view of the vicinity of the R chamfered portion 216a viewed from the axial direction. FIG. 5 is an enlarged view of the vicinity of the C chamfered portion 216b as viewed from the axial direction. 4 and 5, the insulator 22 and the coil portion 23 are not shown in order to make the configuration easy to see. 4 and 5 correspond to a portion surrounded by a broken line in FIG. 3A, for example.

  The chamfered portion 216 is provided at the end portion in the circumferential direction on the tooth recess 215 side of the radially outer surface of the small teeth 213. In other words, each of the plurality of small teeth 213 has a chamfered portion 216 at a circumferential end portion on the teeth concave portion 215 side of the radially outer surface of each small tooth 213. In the present embodiment, the chamfered portion 216 is provided at the end in the circumferential direction of the teeth recesses 215 of all the small teeth 213, but is not limited to this example, and the tooth recesses of some of the small teeth 213. It may be provided at the circumferential end on the 215 side.

  In other words, at least one of the plurality of small teeth 213 has a chamfered portion 216 at the circumferential end portion on the teeth recess 215 side of the radially outer surface facing the magnet 12 of the small teeth 213 in the radial direction. If you do. According to this configuration, the chamfered portion 216 is provided between the radially outer side surface of the small teeth 213 and the circumferential side surface on the teeth concave portion 215 side. Therefore, the cogging torque tqc of the motor 110 can be reduced without changing the circumferential dimension of the teeth 212.

  As shown in FIGS. 4 and 5, the chamfered portion 216 of the first small teeth 213a is preferably symmetrical with the chamfered portion 216 of the second small teeth 213b with respect to the plane Pd. More specifically, the chamfered portion 216 of the small tooth 213 located in the circumferential direction one Rd1 of the teeth concave portion 215 and the chamfered portion 216 of the small tooth 213 located in the other circumferential direction Rd2 of the teeth concave portion 215 are preferably It faces the circumferential direction and is plane symmetric with respect to the plane Pd. That is, the chamfered shape of the same size is formed in the chamfered portion 216 of the first small teeth 213a and the chamfered portion 216 of the second small teeth 213b. The plane Pd passes through the center between the teeth 213 adjacent in the circumferential direction via the tooth recess 215 and includes a central axis CA (see FIG. 6 described later). The plane Pd is parallel to the axial direction and the radial direction.

  As described above, in the small teeth 213 adjacent in the circumferential direction via the tooth recess 215, if the chamfered portion 216 facing in the circumferential direction is plane-symmetric, the cogging torque tqc is obtained even if the rotation direction of the rotor 1 is reversed. Can be similarly reduced. In other words, the cogging torque tqc can be similarly reduced whether the rotor 1 rotates in one circumferential direction Rd1 or the other circumferential direction Rd2.

  However, it is not limited to the illustration of FIG.4 and FIG.5, The chamfering part 216 may be provided in one of the 1st small tooth 213a and the 2nd small tooth 213b.

<1-3-3-1. R chamfer>
Next, a configuration example of the R chamfer 216a will be described. In FIG. 4, the R chamfered portion 216 a is provided as a chamfered portion 216 at a circumferential end portion on the tooth recess 215 side of the radially outer surface of the first small teeth 213 a and the second small teeth 213 b. The chamfered portion 216 is a curved surface that protrudes radially outward and toward the teeth concave portion 215 when viewed in the axial direction. In other words, the R chamfered portion 216a is a curved surface that connects a circumferential end on the teeth recess 215 side of the radially outer surface and a radially outer end of the circumferential side surface on the teeth recess 215 side. . As viewed from the axial direction, the radially outer end portion of the R chamfered portion 216a is connected to the circumferential end portion on the tooth recess 215 side of the radially outer surface of the first small tooth 213a and the second small tooth 213b. Yes. Further, when viewed from the axial direction, the radially inner end portion of the R chamfered portion 216a is connected to the radially outer end portion of the circumferential side surfaces of the first small teeth 213a and the second small teeth 213b on the teeth recess 215 side. Has been.

  As described above, the R chamfered portion 216a is a portion in which a so-called R chamfering is performed on a circumferential end portion on the teeth concave portion 215 side of the radially outer surface of each small tooth 213. When the R chamfered portion 216a is provided on the small teeth 213, the life of the punching die can be made longer than when the C chamfered portion 216b is provided on the small teeth 213. The reason for this is that, in a die for punching, a chamfer connected to one end of a chamfered portion 216 connected to the radially outer surface of the small tooth 213 and a circumferential side surface of the small tooth 213 on the tooth recess 215 side. This is because the portion that forms the other end portion of the portion 216 is likely to have a corner due to wear when forming the C chamfered portion 216b. Accordingly, when the stator core 21 is formed by punching, the portion forming the R chamfered portion 216a of the die for punching is less likely to be worn and deformed than the portion forming the C chamfered portion 216b.

  A more preferable circumferential dimension of the R chamfered portion 216a will be described later.

<1-3-3-2. C chamfer>
Next, a configuration example of the C chamfer 216b will be described. In FIG. 5, a C chamfered portion 216 b is provided as a chamfered portion 216 at a circumferential end portion on the tooth recess 215 side of the radially outer surfaces of the first small teeth 213 a and the second small teeth 213 b. The chamfered portion 216 is a plane that obliquely intersects with the radially outer side surface of the small teeth 213 and the circumferential side surface of the small teeth 213 on the teeth concave portion 215 side when viewed from the axial direction. In other words, the C chamfered portion 216b is a plane that connects the circumferential end on the teeth recess 215 side of the radially outer surface and the radially outer end of the circumferential side surface on the teeth recess 215 side. . When viewed from the axial direction, the radially outer end portion of the C chamfered portion 216b is connected to the circumferential end portion on the tooth recess 215 side of the radially outer surfaces of the first small teeth 213a and the second small teeth 213b. Yes. Further, when viewed from the axial direction, the radially inner end portion of the C chamfered portion 216b is connected to the radially outer end portion of the circumferential side surfaces of the first small teeth 213a and the second small teeth 213b on the teeth recess 215 side. Has been. The normal line of the C chamfered portion 216b is directed outward in the radial direction and toward the teeth concave portion 215 in the circumferential direction.

  As described above, the C chamfered portion 216b is a portion in which a so-called C chamfer is applied to a circumferential end portion on the teeth concave portion 215 side of the radially outer surface of each small tooth 213. When the C chamfered portion 216b is provided, the cogging torque tqc can be reduced with a smaller dimension than when the R chamfered portion 216a is provided, as shown in FIG. 7A described later.

  The radial direction length Yc of the C chamfered portion 216b is preferably larger than the circumferential length Xc from one circumferential end to the other circumferential end of the C chamfered portion 216b. The radial length Yc is the radial direction from the radial inner end to the radial outer end of the C chamfered portion 216b at the circumferential end of the first small teeth 213a and the second small teeth 213b on the teeth recess 215 side. It is the length along. The circumferential length Xc is a length along the circumferential direction from one circumferential end to the other circumferential end of the C chamfered portion 216b at the radially outer ends of the first small teeth 213a and the second small teeth 213b. is there.

  By setting Xc <Yc, it is possible to suppress a decrease in the area of the radially outer surface of the small teeth 213 due to the formation of the C chamfered portion 216b. Accordingly, it is possible to suppress a decrease in the torque characteristic Ke due to the formation of the C chamfered portion 216b. Furthermore, the radial length Yc of the C chamfered portion 216b is made larger than the circumferential length Xc, and the area of the circumferential side surface on the tooth recess 215 side of the small teeth 213 due to the formation of the C chamfered portion 216b is made smaller. Accordingly, the flow of magnetic flux from the magnet 12 to the side surface in the circumferential direction on the tooth recess 215 side of the small teeth 213 can be reduced. Therefore, the effect of reducing the cogging torque tqc due to the formation of the C chamfered portion 216b can be further enhanced.

  In addition, it is not limited to the above-mentioned illustration, The radial direction length Yc of C chamfering part 216b may be the same as the circumferential direction length Xc, and may be smaller than the circumferential direction length Xc. Further, more preferable circumferential dimensions of the C chamfered portion 216b will be described later.

<1-3-4. Teeth recess dimensions>
Next, with reference to FIG.4 and FIG.5, the dimension of the teeth recessed part 215 is demonstrated.

<1-3-4-1. Teeth recess circumferential length>
For example, as shown in FIGS. 4 and 5, the circumferential length Whc of the teeth concave portion 215 is the circumferential direction from the inner side surface in one circumferential direction Rd <b> 1 in the adjacent small teeth 213 forming the teeth concave portion 215. The other is the distance in the circumferential direction to the inner surface of Rd2. In this embodiment, the circumferential length Whc is the distance in the circumferential direction along a virtual peripheral edge 212c (see the broken line in FIGS. 4 and 5) along the outer peripheral edge of the tooth 212 at the radially outer end of the tooth recess 215. Is adopted. More specifically, the circumferential length Whc of the tooth recess 215 is determined by the imaginary direction at the radially outer side of the small tooth 213 located in one circumferential direction Rd1 and the other circumferential direction Rd2 of the small teeth 213 adjacent in the circumferential direction. Of the small teeth 213 located in the other circumferential direction Rd2 among the small teeth 213 adjacent to each other in the circumferential direction in the circumferential direction and the imaginary end portion in the circumferential one Rd1 It is said. Here, the “virtual end portion” refers to the tooth recess 215 in the radially outer surface of the first small teeth 213a and the second small teeth 213b when the chamfered portion 216 is not temporarily provided in the small teeth 213. Means the circumferential end of the side.

  The circumferential length Whc of the tooth recess 215 is preferably larger than the circumferential length Lmc of the magnet 12. In this way, it is possible to suppress the occurrence of a magnetic flux loop that does not contribute to the torque characteristic Ke. This is because, between the first magnetic pole and the second magnetic pole that are alternately provided in the circumferential direction, generation of magnetic flux flowing from one of the two to the other via the small teeth 213 can be suppressed. Therefore, the torque characteristic Ke of the motor 110 can be improved and its output efficiency can be improved.

<1-3-4-2. Teeth recess radial length>
For example, as shown in FIGS. 4 and 5, the radial length Whr of the tooth recess 215 is an imaginary peripheral portion 212 c (see FIG. 4 and FIG. 5) along the outer peripheral edge of the tooth 212 at the radially outer end of the tooth recess 215. The distance in the radial direction from the broken line in FIGS. 4 and 5 to the radially inner end that is the bottom of the tooth recess 215. More specifically, in the present embodiment, the radial length Whr is the maximum distance between the virtual peripheral edge 212c radially outward of the teeth 212 and the radially inner surface of the teeth recess 215. And the radial length at the center in the circumferential direction of the tooth recess 215. However, it is not limited to this illustration, The radial length Whr may be a length that satisfies one of the above two conditions. That is, the radial length Whr is the maximum distance between the virtual peripheral edge 212c and the radially inner surface of the tooth recess 215, but is the radial length at the circumferential center of the teeth recess 215. It does not have to be. Alternatively, the radial length Whr is the radial length at the circumferential center of the tooth recess 215, but is the maximum distance between the virtual peripheral edge 212c and the radially inner surface of the teeth recess 215. It does not have to be.

  The radial length Whr of the tooth recess 215 is preferably larger than the radial length Lmr of the magnet 12. In this way, it is possible to prevent the magnetic resistance between the magnet 12 and the radially inner surface of the tooth recess 215 from becoming too low. Therefore, between the first magnetic pole and the second magnetic pole adjacent to each other in the circumferential direction, a magnetic flux that flows from one of the two to the other via the surface in the radial direction of the tooth recess 215 and the small teeth 213 is generated. It becomes difficult to do. Therefore, it is possible to contribute to the suppression of the occurrence of a magnetic flux loop that does not contribute to the torque characteristic Ke.

<1-3-5. Circumferential dimensions of small teeth facing the magnet>
Next, the circumferential dimension of the small teeth 213 facing the magnet 12 will be described. FIG. 6 is a view of the structure in which the small teeth 213 face the magnet 12 as seen from the axial direction. In FIG. 6, the insulator 22 and the coil portion 23 are not shown in order to make the configuration of the stator core 21 easier to see.

<1-3-5-1. Definition of magnet circumferential dimension>
First, the definitions of the magnet pitch θmp and the magnet outer angle θmo of the magnet 12 will be described with reference to FIG.

  The magnet pitch θmp is a line connecting the circumferential center of the first magnetic pole of the magnet 12 and the central axis CA, as viewed from the axial direction, and the circumferential center of the second magnetic pole adjacent to the first magnetic pole in the circumferential direction. It is an angle in the circumferential direction between the line connecting the central axis CA. In other words, the magnet pitch θmp is a line connecting the center in the circumferential direction of the first magnet 121 and the center axis CA and the line connecting the center in the circumferential direction of the second magnet 122 and the center axis CA as viewed from the axial direction. Is the circumferential angle θmp. In the present embodiment, ten first magnets 121 and ten second magnets 122 are arranged alternately and at equal intervals in the circumferential direction. Therefore, the mechanical angle of the magnet pitch θmp is 18 °. The electrical angle of the magnet pitch θmp is 180 °.

  The magnet outer angle θmo is the circumference of the first magnet 121 arranged next to the line connecting the end of the first magnet 121 in one circumferential direction Rd1 and the central axis CA when viewed from the axial direction and the other circumferential direction Rd2. It is a circumferential angle between the line connecting the end portion in the other direction Rd2 and the central axis CA. In the present embodiment, the mechanical angle of the magnet outer angle θmo is, for example, 50.3 °. In this case, the electrical angle of the magnet outer angle θmo is 503 °.

<1-3-5-2. Definition of circumferential dimensions of small teeth>
Next, the definition of the small tooth opening angle θtp and the small tooth external angle θto of the small teeth 213 will be described with reference to FIG.

  The small tooth opening angle θtp is the center of the circumferential axis of the first small tooth 213a located in one circumferential direction Rd1 of the small teeth 213 adjacent in the circumferential direction and the central axis CA when viewed from the axial direction. And a line connecting the center in the circumferential direction of the second small tooth 213b located in the other circumferential direction Rd2 of the small teeth 213 adjacent in the circumferential direction and the central axis CA. is there. In the present embodiment, the mechanical angle of the small tooth opening angle θtp is, for example, 37.3 °. In this case, the electrical angle of the small tooth opening angle θtp is 373 °.

  The small tooth external angle θto is a line connecting the end of the first small tooth 213a in one circumferential direction Rd1 and the central axis CA and the other circumferential direction Rd2 of the second small tooth 213b in the same tooth 212 when viewed from the axial direction. Is an angle in the circumferential direction between a line connecting the end portion and the central axis CA. In the present embodiment, the mechanical angle of the small tooth external angle θto is, for example, 53.4 °. In this case, the electrical angle of the small tooth external angle θto is 534 °.

<1-3-5-3. Circumferential dimensions of small teeth facing the magnet>
As shown in FIG. 6, the small tooth opening angle θtp is preferably larger than twice the magnet pitch θmp in each of the teeth 212. In this way, since the small teeth 213 facing the first magnetic pole can be secured, a more suitable magnetic circuit can be formed between the stator core 21 and the rotor 1. Therefore, the torque characteristic Ke of the motor 110 can be improved and the output efficiency can be improved.

  Further, the small tooth external angle θto is preferably smaller than three times the magnet pitch θmp in each tooth 212. The reason is that in the circumferential direction, the magnetic pole pitch that can be abutted against the plurality of small teeth 213 of each tooth 212 is three times the magnet pitch θmp, and beyond this, the base of each tooth 212 is exceeded. This is because the reactive magnetic flux that does not intersect with the coil portion 23 provided at 212a increases. Therefore, by preventing the small tooth external angle θto from exceeding three times the magnet pitch θmp, it is possible to prevent an increase in the reactive magnetic flux and to form a good magnetic circuit between the stator core 21 and the rotor 1.

  In each of the teeth 212, the small tooth external angle θto is preferably larger than the magnet external angle θmo. If it carries out like this, in the some small tooth 213 which the teeth 212 which generate | occur | produce a torque, the area matched with three magnetic poles can be brought close to the maximum value. Therefore, a better magnetic circuit can be formed between the rotor 1 and the stator core 21.

<1-3-6. Circumferential dimension of chamfer>
Next, a preferred circumferential dimension of the chamfered portion 216 will be described with reference to FIG. 6 and FIGS. 7A and 7B. In addition, the circumferential direction dimension demonstrated below is a suitable illustration, and does not necessarily limit this invention. FIG. 7A is a graph showing the change in cogging torque tqc with respect to the circumferential angle ratio rθ of the chamfered portion 216. FIG. 7B is a graph showing a change in the torque characteristic Ke with respect to the circumferential angle ratio rθ of the chamfered portion 216. 7A and 7B, a round plot (“Round chamfering”) indicates the characteristic of the R chamfered portion 216a, and a square plot (“Beveling”) indicates the characteristic of the C chamfered portion 216b. .

<1-3-6-1. Definition of circumferential dimensions>
As shown in FIG. 6, the circumferential dimension of the chamfered portion 216 can be represented by a circumferential angle θp. The circumferential angle θp is an angle in the circumferential direction between a line connecting the circumferential end of the chamfered portion 216 and the central axis CA and a line connecting the other circumferential end of the chamfered portion 216 and the central axis CA. is there. Hereinafter, this circumferential angle is referred to as “chamfer angle θp”.

  Further, the circumferential dimension of the small teeth 213 can also be expressed by a circumferential angle {(θto−θti) / 2}. The circumferential angle {(θto−θti) / 2} is a line connecting the circumferential one end of the small tooth 213 and the CA central axis, and a line connecting the circumferential other end of the small tooth 213 and the CA central axis. Is the angle in the circumferential direction between. In the present embodiment, the circumferential angle {(θto−θti) / 2} of the small teeth 213 is obtained by dividing the difference between the small tooth external angle θto and the small tooth internal angle θti by the number of small teeth 213 included in each tooth 212. Is required.

  Furthermore, in the following, the angle ratio {(2 × θp) / (θto−θti) × 100} of the chamfering angle θp of the R chamfered portion 216a to the circumferential angle {(θto−θti) / 2} of the small teeth 213, This is called “circumferential angle ratio rθ”. The circumferential direction angle ratio rθ represents the ratio of the circumferential dimension of the chamfered portion 216 to the small teeth 213 at the radially outer end portion of the small teeth 213 in%.

<1-3-6-2. Circumferential dimension of R chamfer>
First, a preferable circumferential dimension of the R chamfered portion 216a will be described. As shown in FIG. 7A, the cogging torque tqc of the motor 110 shows a high cogging torque tqc when the circumferential angle ratio rθ of the R chamfered portion 216a is 5% or less. On the other hand, for example, when the circumferential angle ratio rθ of the R chamfered portion 216a is 14.3% or more, the cogging torque tqc is 40 [mN · m] or less. Further, as shown in FIG. 7B, the torque characteristic Ke of the motor 110 represented by the counter electromotive force constant decreases as the circumferential angle ratio rθ of the R chamfered portion 216a increases. The decrease rate of the torque characteristic Ke increases with an increase in the circumferential angle ratio rθ of the R chamfered portion 216a. When the circumferential angle ratio rθ of the R chamfered portion 216a is 29.7% or less, the decrease of the torque characteristic Ke The rate is 5% or less.

  Therefore, as shown in FIGS. 7A and 7B, the circumferential angle ratio rθ in the R chamfered portion 216a is preferably 14.3% or more and 29.7% or less. In other words, in the R chamfered portion 216a, as viewed from the axial direction, a line connecting the circumferential end of the chamfered portion 216 and the central axis CA, and a line connecting the other circumferential end of the chamfered portion 216 and the CA central axis. Is preferably between the line connecting the one circumferential end of the small tooth 213 and the CA central axis and the line connecting the other circumferential end of the small tooth 213 and the central axis CA. It is 14.3% to 29.7% of the circumferential angle {(θto−θti) / 2}.

  By setting the circumferential angle ratio rθ in the above range in the R chamfered portion 216a, the cogging torque tqc can be appropriately reduced while suppressing a decrease in the torque characteristic Ke. For example, in FIGS. 7A and 7B, the cogging torque tqc can be set to 40 [mN · m] or less while the rate of decrease in the torque characteristic Ke is suppressed to within 5%. However, in the R chamfered portion 216a, the cogging torque tqc can be set to 40 [mN · m] or less even when the rate of decrease in the torque characteristic Ke is 5% or more, for example. That is, the circumferential angle ratio rθ> 29.7% may be set as long as the rate of decrease in the torque characteristic Ke is allowed.

<1-3-6-3. Circumferential dimension of C chamfer>
First, a more preferable circumferential dimension of the C chamfered portion 216b will be described. As shown in FIG. 7A, the cogging torque tqc of the motor 110 indicates a high cogging torque tqc when the circumferential angle ratio rθ of the C chamfered portion 216b is 5% or less. On the other hand, for example, when the circumferential angle ratio rθ of the C chamfered portion 216b is 12% or more and 32% or less, the cogging torque tqc is 40 [mN · m] or less. Further, as shown in FIG. 7B, the torque characteristic Ke of the motor 110 expressed by the counter electromotive force constant decreases as the circumferential angle ratio rθ of the C chamfered portion 216b increases. The reduction rate of the torque characteristic Ke increases with an increase in the circumferential angle ratio rθ of the R chamfered portion 216a. When the circumferential angle ratio rθ of the R chamfered portion 216a is 24% or less, the reduction rate of the torque characteristic Ke is 5 [%] or less.

  Therefore, as shown in FIGS. 7A and 7B, the circumferential angle ratio rθ in the C chamfered portion 216b is preferably 12% or more and 24% or less. In other words, in the C chamfered portion 216b, as seen from the axial direction, a line connecting the circumferential end of the chamfered portion 216 and the central axis CA is a line connecting the other circumferential end of the chamfered portion 216 and the CA central axis. The circumferential angle θp in the circumferential direction is preferably a line between the one end in the circumferential direction of the small tooth 213 and the CA central axis, and the line connecting the other end in the circumferential direction of the small tooth 213 and the central axis CA. It is 12% or more and 24% or less of the circumferential direction angle {(θto−θti) / 2} in the circumferential direction.

  By setting the circumferential angle ratio rθ in the above range in the C chamfered portion 216b, the cogging torque tqc can be appropriately reduced while suppressing a decrease in the torque characteristic Ke. For example, in FIGS. 7A and 7B, the cogging torque tqc can be set to 40 [mN · m] or less while the rate of decrease in the torque characteristic Ke is suppressed to within 5%.

<2. Other>
The embodiment of the present invention has been described above. The scope of the present invention is not limited to the above-described embodiment. The present invention can be implemented with various modifications without departing from the spirit of the invention. In addition, the items described in the above embodiments can be arbitrarily combined as long as no contradiction occurs.

  For example, in the above-described embodiment, the motor 110 is a brushless DC motor of a fixed shaft type and an outer rotor type that the ceiling fan 100 has in this embodiment. However, the present invention is not limited to these examples, and the motor 110 may be provided in a device other than the ceiling fan 100, may be a shaft rotation type, or may be an inner rotor type. In addition, when the motor 110 is an inner rotor type | mold, the position in the radial direction of the component of the motor 110 may be reversed. For example, when the motor 110 is an inner rotor type, the plurality of teeth 212 extend radially inward from the core back 211.

  The present invention is useful for, for example, a motor having a stator core in which a plurality of small teeth are provided at the tip of a tooth.

  DESCRIPTION OF SYMBOLS 100 ... Ceiling fan, 110 ... Motor, 120 ... Blade, 1 ... Rotor, 11 ... Rotor core, 12 ... Magnet, 121 ... First magnet, 122 ... First 2 magnets, 13 ... adhesive member, 14 ... housing, 14a ... upper housing part, 14b ... bearing holder, 14c ... lower housing part, 2 ... stator, 21 ... Stator core, 211 ... core back, 212 ... teeth, 212a ... base, 212b ... tip, 212c ... virtual peripheral edge of teeth, 213 ... small teeth, 213a ... 1st small tooth, 213b ... 2nd small tooth, 214 ... Connection part, 215 ... Teeth recessed part, 216 ... Chamfered part, 216a ... R chamfered part, 216b ... C chamfered part 2 ... Insulator, 23 ... Coil part, 24 ... Shaft, 3 ... Bearing, CA ... Center axis, Pd ... Plane, Rd1 ... One circumferential direction, Rd2 ... Round Direction, tqc: cogging torque, Ke: torque characteristics (counterelectromotive force constant), Pm: central position in the axial direction of the magnet, Ps: central position in the axial direction of the stator core, θtp. Small tooth opening angle, θto: Small tooth external angle, θmp: Magnet pitch, θmo: Magnet external angle, θc1, θc2: Circumferential angle, θp: Chamfer angle, rθ: Circumference Direction angle ratio, Lma: axial length of magnet, Lmr: radial length of magnet, Lmc: circumferential length of magnet, Lsa: axial length of stator core, Wd · ..Core back Circumferential length of the radial width, Wrb · · · the base of circumferential width, Wro · · · teeth of circumferential width, Whr · · · tooth recess radial width, WHC · · · tooth recess

Claims (11)

An outer rotor type brushless motor comprising: a rotor rotatable about a central axis; and a stator for rotationally driving the rotor,
The rotor has a plurality of magnets facing the stator in the radial direction,
The plurality of magnets include a first magnetic pole and a second magnetic pole different from the first magnetic pole,
The first magnetic pole and the second magnetic pole are alternately provided in the circumferential direction,
The stator has a stator core and a plurality of coil portions,
The stator core has a core back that annularly surrounds the central axis, and a plurality of teeth extending radially outward from the core back,
Each of the teeth includes a plurality of small teeth arranged in the circumferential direction so as to face the rotor in the radial direction, a tooth recess recessed inward in the radial direction between the small teeth adjacent in the circumferential direction, the small teeth, and the teeth A base provided between the core backs,
The coil portion provided in each of the teeth includes a conductive wire wound around the base portion,
A brushless motor in which at least one of the plurality of small teeth has a chamfered portion at a circumferential end portion on the teeth recess side of a radially outer surface facing the magnet in a radial direction of the small teeth. The plurality of small teeth have the chamfered portion at the circumferential end on the teeth concave portion side of the radially outer surface of each small tooth,
The chamfered portion of the small tooth located in one circumferential direction of the teeth concave portion and the chamfered portion of the small tooth located in the other circumferential direction of the tooth concave portion are opposed to each other in the circumferential direction, and the teeth concave portion is interposed therebetween. The brushless motor according to claim 1, wherein the brushless motor passes through a center between the small teeth adjacent in the circumferential direction and is plane-symmetric with respect to a plane including the central axis.   3. The brushless motor according to claim 1, wherein the chamfered portion is a curved surface that protrudes radially outward and toward the teeth concave portion when viewed in the axial direction.   When viewed from the axial direction, the circumferential angle between the line connecting the one end in the circumferential direction of the chamfered portion and the central axis and the line connecting the other end in the circumferential direction of the chamfered portion and the central axis is 14.3% or more and 29.7% of the circumferential angle between a line connecting one end in the circumferential direction of the small tooth and the central axis and a line connecting the other end in the circumferential direction of the small tooth and the central axis The brushless motor according to claim 3, which is not more than%.   The said chamfered part is a plane which cross | intersects the radial direction outer side surface of the said small tooth, and the circumferential direction side surface of the said tooth | gear recessed part side of the said small tooth seeing from an axial direction of Claim 1 or Claim 2. Brushless motor.   The brushless according to claim 5, wherein a radial length from a radially inner end to a radially outer end of the chamfered portion is larger than a circumferential length from one circumferential end to the other circumferential end of the chamfered portion. motor.   When viewed from the axial direction, the circumferential angle between the line connecting the one end in the circumferential direction of the chamfered portion and the central axis and the line connecting the other end in the circumferential direction of the chamfered portion and the central axis is 12% or more and 24% or less of a circumferential angle between a line connecting one end in the circumferential direction of the small tooth and the central axis and a line connecting the other end in the circumferential direction of the small tooth and the central axis The brushless motor according to claim 5 or 6.   The brushless motor according to any one of claims 1 to 7, wherein a radial length of the teeth concave portion is larger than a radial length of the magnet. The small tooth opening angle connects the central axis in the circumferential direction of the first small tooth located at one of the circumferentially adjacent small teeth in the same tooth as viewed from the axial direction. A circumferential angle between a line and a line connecting the center axis of the second small tooth located on the other circumferential side of the small teeth adjacent to the circumferential direction and the central axis,
The small tooth external angle is a line connecting the end of the first small tooth in one circumferential direction and the central axis and the end of the second small tooth in the other circumferential direction as viewed from the axial direction. And a circumferential angle between a line connecting the central axis and the central axis,
The magnet pitch is a line in the circumferential direction of the second magnetic pole adjacent to the first magnetic pole in the circumferential direction and a line connecting the circumferential center of the first magnetic pole of the magnet and the central axis when viewed from the axial direction. A circumferential angle between a center and a line connecting the central axis,
9. In each of the teeth, the small tooth opening angle is larger than twice the magnet pitch, and the small tooth outer angle is smaller than three times the magnet pitch. Brushless motor. The magnet has a first magnet having the first magnetic pole, and a second magnet having the second magnetic pole,
The first magnet and the second magnet are alternately arranged with an interval in the circumferential direction,
The outer angle of the magnet is a line connecting the end of the first magnet in one circumferential direction and the central axis when viewed from the axial direction, and the other circumferential direction of the first magnet disposed next in the other circumferential direction. A circumferential angle between an end and a line connecting the central axis,
The brushless motor according to claim 9, wherein the small tooth external angle is larger than the magnet external angle in each of the teeth. A vane rotatable about a central axis;
A blower comprising: the brushless motor according to any one of claims 1 to 10, wherein the blades are rotated.

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