Patent Publication Number: US-2023155428-A1

Title: Stator core and motor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a U.S. national stage of PCT Application No. PCT/JP2021/016508, filed on Apr. 23, 2021, and with priority under 35 U.S.C. § 119(a) and 35 U.S.C. § 365(b) being claimed from Japanese Application No. 2020-064056, filed Mar. 31, 2020, the entire disclosures of which are hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure relates to a stator core and a motor. 
     BACKGROUND 
     In a claw-pole stepping motor, a stator yoke annularly constructed using a plurality of split yokes is known. In this stator yoke, a plurality of split yokes having pole teeth is arranged in the circumferential direction. Adjacent split yokes are connected and joined by a synthetic resin filled in a gap therebetween. For example, see JP 2012-5161 A. 
     However, in the above configuration, the number of parts increases according to the number of split cores, and the work of assembling the stator yoke becomes difficult. Therefore, the manufacturing process of the stator yoke becomes complicated, and the number of man-hours increases. 
     SUMMARY 
     Example embodiments of the present disclosure provide stator cores each with a simpler configuration. 
     A stator core according to an example embodiment of the present disclosure includes a disk portion and a pole-tooth yoke. The disk portion has a disk shape that extends in a radial direction around a central axis extending in a vertical direction. The pole-tooth yoke is located along a radially outer end of the disk portion. The pole-tooth yoke includes an annular portion and a pole tooth. The annular portion is connected to the radially outer end of the disk portion and extends in a circumferential direction. The pole tooth protrudes to one axial side from the annular portion. The disk portion and the pole-tooth yoke are defined by different members. 
     A motor according to an example embodiment of the present disclosure includes a stator including the above-described stator core and a rotor driven by the stator. The rotor includes a magnet located radially outward of the stator. The stator further includes a coil located radially inward of the pole tooth of the stator core. The coil opposes the magnet in the radial direction via the pole tooth. 
     According to the example embodiments of the stator cores and motors of the present disclosure, it is possible to provide a stator core having a simpler configuration. 
     The above and other elements, features, steps, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a sectional view showing a configuration example of a motor. 
         FIG.  2    is a perspective view of an exemplary stator according to an example embodiment of the present disclosure. 
         FIG.  3    is an exploded perspective view of an example embodiment of a stator according to the present disclosure. 
         FIG.  4 A  is an exploded perspective view of a stator core according to an example embodiment of the present disclosure. 
         FIG.  4 B  is a top view of the stator core according to an example embodiment of the present disclosure. 
         FIG.  5 A  is a top view of a stator core according to a first modification of an example embodiment of the present disclosure. 
         FIG.  5 B  is a developed view of a pole-tooth yoke according to the first modification. 
         FIG.  6 A  is a top view of a stator core according to a second modification of an example embodiment of the present disclosure. 
         FIG.  6 B  is a developed view of a pole-tooth yoke according to the second modification. 
         FIG.  7 A  is an exploded perspective view of a stator core according to a third modification of an example embodiment of the present disclosure. 
         FIG.  7 B  is a perspective view of the stator core according to the third modification. 
         FIG.  8    is a top view of a stator core according to a fourth modification of an example embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Example embodiments of the present disclosure will be described below with reference to the drawings. 
     In the present specification, in a motor  100 , a direction parallel to a central axis CA is referred to by the term “axial direction”, “axial”, or “axially”. In the axial direction, the direction from a flange part  402  of a holding member  400  to a hub  500 , which will be described later, is referred to by the term “upper” or “upward”, and the direction from the hub  500  to the flange part  402  is referred to by the term “lower” or “downward”. In each component, an upper side end is referred to as an “upper end” and a lower side end is referred to as a “lower end”. Further, regarding surfaces of each component, the surface facing upward is referred to as an “upper surface”, and the surface facing downward is referred to as a “lower surface”. 
     The direction orthogonal to the central axis CA is referred to by the term “radial direction”, “radial”, or “radially”. In the radial direction, the direction toward the central axis CA is referred to by the term “radially inward”, and the direction away from the central axis CA is referred to by the term “radially outward”. In each component, a radially inward end is referred to as a “radially inner end”, and a radially outward end is referred to as a “radially outer end”. Further, regarding side surfaces of each component, the side surface directed radially inward is referred to as a “radially inner surface”, and the side surface directed radially outward is referred to as a “radially outer surface”. 
     The direction of rotation about the central axis CA is referred to by the term “circumferential direction”, “circumferential”, or “circumferentially. In each component, an end in the circumferential direction is referred to as a “circumferential end”. Further, one end on a circumferentially one side is referred to as a “first circumferential side end”, and an end on the circumferentially other side is referred to as a “second circumferential side end”. In addition, regarding side surfaces of each component, a side surface directed in the circumferential direction is referred to as a “circumferential side surface”. Further, the side surface directed to the circumferentially one side is referred to as a “circumferentially-one-side surface”, and the side surface directed to the circumferentially other side is referred to as a “circumferentially-other-side surface”. 
     Further, in a later-described stator core  340  that surrounds the central axis CA, a direction in which pole teeth  22  protrude from an annular portion  21  described later in the axial direction is referred to as an “axially one side Da”, and the direction opposite to the axially one side is referred to as an “axially other side Db”. In components of the stator core  340 , an end on the axially one side Da is referred to as an “axially-one-side end”, and an end on the axially other side Db is referred to as an “axially-other-side end”. Further, regarding surfaces of the component of the stator core  340 , the surface directed to the axially one side Da is referred to as an “axially-one-side end surface”, and the surface directed to the axially other side Db is referred to as an “axially-other-side end surface”. 
     Further, in the present specification, an “annular shape” includes not only a shape continuously connected without any cut along the entire circumference in the circumferential direction around the central axis CA but also a shape having one or more cuts in a part of the entire circumference around the central axis CA. The “annular shape” also includes a shape having a closed curve on a curved surface that intersects with the central axis CA around the central axis CA. 
     In the positional relationship between any one of the azimuth, line, and plane and another one of them, the term “parallel” indicates not only a state in which they do not intersect at any point but also a state in which they are substantially parallel. The terms “vertical” and “orthogonal” indicate not only a state in which they intersect at 90 degrees with each other, but also a state in which they are substantially vertical and a state in which they are substantially orthogonal. That is, the terms “parallel”, “vertical”, and “orthogonal” each include a state in which the positional relationship between them has an angular deviation that does not depart from the gist of the present disclosure. 
     It should be noted that the matters described above are not strictly applied when incorporated in an actual device. 
     1. EXAMPLE EMBODIMENT 
       FIG.  1    is a sectional view showing a configuration example of the motor  100 . Note that  FIG.  1    shows the cross-sectional structure of the motor  100  when the motor  100  is cut on a virtual plane including the central axis CA. 
     1-1. Motor 
     The motor  100  is a claw-pole stepping motor in the present example embodiment. As shown in  FIG.  1   , the motor  100  includes a rotor  200 , a stator  300 , the holding member  400 , the hub  500 , and a bearing section  600 . 
     The rotor  200  is driven by the stator  300 . As described above, the motor  100  has the rotor  200 . The rotor  200  is rotatable about the central axis CA that extends in the vertical direction. The rotor  200  has a case  201  and a magnet  202 . The case  201  is a tubular magnetic material in the present example embodiment and holds the magnet  202 . The case  201  can prevent a magnetic flux of the magnet  202  from leaking to the outside of the motor  100 . The magnet  202  is disposed radially outward of the stator  300 . As mentioned above, the rotor  200  has the magnet  202 . The magnet  202  faces the stator  300  in the radial direction and is held on a radially inner surface of the case  201 . 
     The stator  300  drives and rotates the rotor  200  by the magnetic flux generated when power is supplied. The stator  300  surrounds the central axis CA. As described above, the motor  100  includes the stator  300 . In the present example embodiment, the stator  300  has an annular shape centered on the central axis CA. The configuration of the stator  300  will be described later. 
     The holding member  400  holds the stator  300 . The holding member  400  has a columnar part  401  and the flange part  402 . The columnar part  401  extends along the central axis CA in the axial direction. The stator  300  is fixed to a radially outer surface of the columnar part  401 . The columnar part  401  is a columnar shaft which is a rotation axis of the rotor  200  in  FIG.  1   . However, the columnar part  401  is not limited to the example shown in  FIG.  1   . The columnar part  401  may be a tubular shaft or a tubular sleeve through which the columnar shaft passes. The flange part  402  extends radially outward from a lower end of the columnar part  401 . The flange part  402  faces a lower end of the stator  300  in the axial direction. 
     The hub  500  has an annular shape that surrounds the columnar part  401 . The hub  500  is disposed on an upper end of the columnar part  401 . A radially inner end of the hub  500  is fixed to the radially outer surface of the columnar part  401 . The hub  500  faces an upper end of the stator  300  in the axial direction. 
     The bearing section  600  includes a first bearing  601  and a second bearing  602 . 
     A radially inner end of the first bearing  601  is connected to a radially outer portion of the flange part  402  of the holding member  400 . A radially outer end of the first bearing  601  is connected to the radially inner surface of the case  201  at the lower end portion. The first bearing  601  rotatably connects the rotor  200  to the holding member  400  at the lower end portion of the motor  100 . 
     The second bearing  602  is disposed above the first bearing  601 . A radially inner end of the second bearing  602  is connected to a radially outer portion of the hub  500 . A radially outer end of the second bearing  602  is connected to the radially inner surface of the case  201  at the upper end portion. The second bearing  602  rotatably connects the rotor  200  to the holding member  400  via the hub  500  at the upper end portion of the motor  100 . 
     The first bearing  601  and the second bearing  602  are ball bearings in the present example embodiment. However, they are not limited thereto, and at least one of the first bearing  601  and the second bearing  602  may be another type of bearing such as a slide bearing. 
     1-2. Stator 
     Next, the stator  300  will be described with reference to  FIGS.  2  and  3   .  FIG.  2    is a perspective view of the stator  300 .  FIG.  3    is an exploded perspective view of the stator  300 . 
     The stator  300  has a plurality of stator sections  310  arranged in the axial direction. However, the stator  300  is not limited to the example in the present example embodiment, and may have a single stator section  310 . The plurality of stator sections  310  includes a first stator part  311  and a second stator part  312  disposed above the first stator part  311 . In the present example embodiment, the configurations of the first stator part  311  and the second stator part  312  are the same. Therefore, in the following, the configuration of each of the first stator part  311  and the second stator part  312  will be described as a configuration of the stator section  310 . 
     The stator section  310  includes a bobbin  320 , a coil  330 , and the stator core  340 . 
     The bobbin  320  has a cylindrical part  321  extending in the axial direction and a wall  322 . The wall  322  extends in the radial direction from both ends of the cylindrical part  321  in the axial direction. 
     The coil  330  is a member in which a conductive wire is wound around a radially outer surface of the cylindrical part  321  of the bobbin  320  in the circumferential direction. The stator  300  includes the coil  330 . The coil  330  is disposed radially inward of the later-described pole teeth  22  of the stator core  340 , and faces the magnet  202  in the radial direction via the pole teeth  22 . 
     The stator core  340  is a magnetic material and covers the bobbin  320  and the coil  330 . The stator  300  includes the stator core  340 . The stator core  340  has a first stator core  341  and a second stator core  342 . In the present example embodiment, the configurations of the first stator core  341  and the second stator core  342  are the same except that the first stator core  341  is vertically inverted. Therefore, in the following, the configuration of each of the first stator core  341  and the second stator core  342  will be described as a configuration of the stator core  340 . 
     1-2-1. Stator Core 
     The configuration of the stator core  340  will be described with reference to  FIGS.  2  to  4 B .  FIG.  4 A  is an exploded perspective view of the stator core  340  according to the example embodiment.  FIG.  4 B  is a top view of the stator core  340  according to the example embodiment. 
     The stator core  340  has a disk portion  1 , a pole-tooth yoke  2 , and a joint portion  3 . 
     The disk portion  1  has a disk shape that extends in the radial direction around the central axis CA extending in the vertical direction. As described above, the stator core  340  has the disk portion  1 . An opening (no reference sign given) through which the columnar part  401  of the holding member  400  is inserted is formed in the center of the disk portion  1  in the direction perpendicular to the axial direction. The disk portion  1  of the first stator core  341  is disposed below the bobbin  320  and the coil  330 , and covers the lower surface of the bobbin  320 . The disk portion  1  of the second stator core  342  is disposed above the bobbin  320  and the coil  330 , and covers the upper surface of the bobbin  320 . 
     The disk portion  1  has a first protrusion  11 . The first protrusion  11  protrudes radially outward at the radially outer end of the disk portion  1 . More specifically, the disk portion  1  further includes a disk body  10  that surrounds the central axis CA and extends in the radial direction. The first protrusion  11  extends radially outward from a radially outer surface of the disk body  10 . 
     The pole-tooth yoke  2  is disposed along the radially outer end of the disk portion  1 . As described above, the stator core  340  includes the pole-tooth yoke  2 . The pole-tooth yoke  2  has the annular portion  21  and the pole teeth  22 . The annular portion  21  is connected to the radially outer end of the disk portion  1  and extends in the circumferential direction. The pole teeth  22  protrude to the axially one side Da from the annular portion  21 . For example, the annular portion  21  is disposed in the circumferential direction along the radially outer surface of the disk body  10 . The radially inner end of the annular portion  21  is connected to the radially outer surface of the disk body  10 . Further, in the first stator core  341 , the pole teeth  22  protrude upward from the radially outer end of the disk portion  1 . In the second stator core  342 , pole teeth  232  protrude downward from the radially outer end of a disk portion  231 . Further, the pole teeth  22  are disposed radially outward of the bobbin  320  and the coil  330 , and cover at least the radially outer end of the coil  330 . In the present example embodiment, the pole-tooth yoke  2  has a plurality of pole teeth  22 . The plurality of pole teeth  22  is arranged in the circumferential direction along the radially outer end of the disk portion  1 . In the circumferential direction, the pole teeth  22  of the first stator core  341  and the pole teeth  22  of the second stator core  342  are alternately arranged. 
     The disk portion  1  and the pole-tooth yoke  2  are different members. For example, members obtained by separately punching an electromagnetic steel plate can be used for the disk portion  1  and the pole-tooth yoke  2 . The pole-tooth yoke  2 , which is a member different from the disk portion  1 , is placed along and connected to the radially outer end of the disk portion  1 , whereby the stator core  340  in which the pole teeth  22  protrude to the axially one side Da can be obtained. The stator core  340  can be manufactured with a simpler configuration than a configuration in which a stator core is manufactured by, for example, combining multiple split cores. Therefore, the stator core  340  having a simple structure can be provided, and the number of parts of the stator core  340  can be further reduced. 
     The joint portion  3  is a portion of the stator core  340  where the disk portion  1  and the pole-tooth yoke  2  are joined. In the present example embodiment, the joint portion  3  is a welding mark formed by joining the annular portion  21  of the pole-tooth yoke  2  to the radially outer end of the disk portion  1  by welding. Due to welding between the disk portion  1  and the annular portion  21 , the pole-tooth yoke  2  can be more reliably fixed to the radially outer end of the disk portion  1 . Note that the method for joining the disk portion  1  and the annular portion  21  is not limited to the method described in the present example embodiment. For example, the annular portion  21  may be joined to the radially outer end of the disk portion  1  by brazing. That is, the joint portion  3  may be a brazing material used for brazing the annular portion  21  to the radially outer end of the disk portion  1 . For example, any of a silver brazing material, a copper brazing material, an aluminum brazing material, a nickel brazing material, etc. can be used as the brazing material. 
     As shown in  FIGS.  4 A and  4 B , the pole-tooth yoke  2  has an annular shape surrounding the central axis CA while being joined to the radially outer end of the disk portion  1 . Here, the circumferential length of the radially inner end of the annular portion  21  is shorter than that of the radially outer end of the disk portion  1 . Therefore, the pole-tooth yoke  2  has a gap  210  in the circumferential direction. The gap  210  is formed between a first circumferential side end and a second circumferential side end of the annular portion  21 . Thus, even if there is a variation in the circumferential length of the annular portion  21 , the radially inner end of the annular portion  21  can be more reliably brought into contact with the radially outer end of the disk portion  1 . On the other hand, suppose the case where the first circumferential side end of the annular portion  21  contacts the second circumferential side end. In that case, when the circumferential length of the radially inner end of the annular portion is equal to or greater than the circumferential length of the radially outer end of the disk portion  1  due to a dimensional variation, the pole-tooth yoke  2  may not be disposed along the radially outer end of the disk portion  1 . For example, a gap may be formed between the radially outer end of the disk portion  1  and the radially inner end of the annular portion  21 . 
     As shown in  FIG.  4 B , the first protrusion  11  of the disk portion  1  is placed in the gap  210 . In this case, it is preferable that at least one of the first circumferential side end and the second circumferential side end of the annular portion  21  contacts a circumferential end of the first protrusion  11 . With this configuration, the position of the annular portion  21  with respect to the disk portion  1  is determined in the circumferential direction, whereby the pole teeth  22  can be positioned with respect to the disk portion  1  in the circumferential direction. Further, when both ends of the first protrusion  11  in the circumferential direction are in contact with the first circumferential side end and the second circumferential side end of the annular portion  21 , respectively, the movement of the pole-tooth yoke  2  with respect to the disk portion  1  in the circumferential direction can be prevented. That is, circumferential stress exerted on the joint portion  3  can be reduced by fitting the first protrusion  11  into the gap  210 . 
     1-3. Modifications of Stator Core 
     Next, first to fourth modifications of the stator core  340  will be described. In the following, configurations different from the configuration in the abovementioned example embodiment will be described. Further, the same components as those in the abovementioned example embodiment are designated by the same reference numerals, and the description thereof may be omitted. 
     1-3-1. First Modification 
     The first modification of the stator core  340  will be described with reference to  FIGS.  5 A and  5 B .  FIG.  5 A  is a top view of the stator core  340  according to the first modification.  FIG.  5 B  is a developed view of the pole-tooth yoke  2  according to the first modification. 
     In the first modification, the disk portion  1  has a second protrusion  12 . The second protrusion  12  protrudes radially outward at the radially outer end of the disk portion  1 . More specifically, the second protrusion  12  extends radially outward from the radially outer surface of the disk body  10 . The disk portion  1  has a plurality of second protrusions  12  arranged in the circumferential direction. The number of the second protrusions  12  is six in  FIGS.  5 A and  5 B . However, it is not limited to the example shown in  FIGS.  5 A and  5 B , and the number of the second protrusions  12  may be one, or two or more except for six. 
     The pole-tooth yoke  2  has the plurality of pole teeth  22  arranged in the circumferential direction. Each of the second protrusions  12  is disposed in a region between the pole teeth  22  adjacent to each other in the circumferential direction. With this configuration, the movement of the pole-tooth yoke  2  relative to the disk portion  1  in the circumferential direction can be more effectively suppressed or prevented. 
     The second protrusions  12  are placed in all regions between the adjacent pole teeth  22  in the circumferential direction in  FIGS.  5 A and  5 B . However, the present disclosure is not limited to the example shown in  FIGS.  5 A and  5 B , and it is only sufficient that the second protrusion  12  is placed in at least one of the regions between the adjacent pole teeth  22  in the circumferential direction. 
     Preferably, the pole-tooth yoke  2  has pole-tooth recesses  23  as shown in  FIGS.  5 A and  5 B . The pole-tooth recess  23  is recessed in the circumferential direction at the circumferential end of each of the pole teeth  22 . The circumferential end of the second protrusion  12  fits into the pole-tooth recess  23 . With this configuration, the circumferential end of the second protrusion  12  can be fixed to the pole-tooth recess  23  by engagement. Therefore, the fixing strength between the disk portion  1  and the pole-tooth yoke  2  can be increased. 
     Further, the second protrusions  12  are preferably formed at the axially-one-side end of the disk portion  1  on the radially outer surface of the disk portion  1 . Further, the pole-tooth recesses  23  are formed at the circumferential ends on the axially-other-side ends of the pole teeth  22  (that is, at the roots of the pole teeth  22 ). With this configuration, the position of the axially-other-side end of the disk portion  1  in the axial direction can be brought closer to the position of the axially-other-side end of the pole-tooth yoke  2  in the axial direction. That is, the axially-other-side end of the stator core  340  can be further flattened. 
     The pole-tooth recesses  23  are formed at both ends of the pole teeth  22  in the circumferential direction in  FIGS.  5 A and  5 B . However, the present disclosure is not limited to this example, and the pole-tooth recesses  23  may be formed at the first circumferential side ends of the pole teeth  22  without being formed at the second circumferential side ends of the pole teeth  22 . The pole-tooth recess  23  is formed in each pole tooth  22  in  FIGS.  5 A  and  5 B. However, the present disclosure is not limited to this example, and the pole-tooth recess  23  may be formed in at least one of the pole teeth  22 . 
     1-3-2. Second Modification 
     The second modification of the stator core  340  will be described with reference to  FIGS.  6 A and  6 B .  FIG.  6 A  is a top view of the stator core  340  according to the second modification.  FIG.  6 B  is a developed view of the pole-tooth yoke  2  according to the second modification. 
     In the second modification, the disk portion  1  has a third protrusion  13 . The third protrusion  13  protrudes radially outward at the radially outer end of the disk portion  1 . More specifically, the third protrusion  13  extends radially outward from the radially outer surface of the disk body  10 . The disk portion  1  has a plurality of third protrusions  13  arranged in the circumferential direction. The number of the third protrusions  13  is six in  FIGS.  6 A and  6 B . However, it is not limited to the example shown in  FIGS.  6 A and  6 B , and the number of the third protrusions  13  may be one, or two or more except for six. 
     The annular portion  21  of the pole-tooth yoke  2  has holes  24 . In the second modification, the holes  24  pass through the annular portion  21  in the radial direction. However, the present disclosure is not limited to this example, and the holes  24  may be recessed radially outward at the radially inner end of the annular portion  21 . 
     The third protrusions  13  fit into the holes  24 . With this configuration, when the annular portion  21  is joined to the disk portion  1 , the third protrusions  13  fit into the holes  24 , so that the annular portion  21  can be more reliably positioned in the circumferential direction with respect to the disk portion  1 . Further, the third protrusions  13  can be fixed to the annular portion  21  by engagement between the third protrusions  13  and the holes  24 . Therefore, the fixing strength between the disk portion  1  and the pole-tooth yoke  2  can be increased. 
     Preferably, the holes  24  overlap the pole teeth  22  as viewed in the axial direction. For example, as viewed in the axial direction, each hole  24  is formed on the circumferentially other side with respect to the first circumferential side end of the corresponding pole tooth  22  and on the circumferentially one side with respect to the second circumferential side end of the pole tooth  22 . More preferably, the holes  24  overlap the tips of the pole teeth  22  as viewed in the axial direction. Due to the holes  24  being formed at positions including the pole teeth  22  in the circumferential direction, the width in the axial direction between the axially-one-side ends of the holes  24  and the axially-one-side end of the pole-tooth yoke  2  can be further increased. Therefore, a decrease in strength of the pole-tooth yoke  2  due to the formation of the holes  24  in the annular portion  21  can be suppressed. 
     In  FIG.  6 A  and  FIG.  6 B , the holes  24  are formed at all positions overlapping the pole teeth  22  in the circumferential direction, as viewed in the axial direction. However, the present disclosure is not limited to the example shown in  FIGS.  6 A and  6 B , and the hole  24  may be formed on at least one of the positions overlapping the pole teeth  22  in the circumferential direction, as viewed in the axial direction. 
     1-3-3. Third Modification 
     The third modification of the stator core  340  will be described with reference to  FIGS.  7 A and  7 B .  FIG.  7 A  is an exploded perspective view of the stator core  340  according to the third modification.  FIG.  7 B  is a perspective view of the stator core  340  according to the third modification. 
     In the third modification, the disk portion  1  has a flange  14 . The flange  14  extends radially outward at the radially outer end of the disk portion  1 . More specifically, the flange  14  extends radially outward from a lower part of the radially outer surface of the disk body  10 . 
     The pole-tooth yoke  2  is disposed along an upper part of the radially outer surface of the disk body  10 . The radially inner end of the annular portion  21  is connected to the upper part of the radially outer surface of the disk body  10  via the joint portion  3 . The axially-other-side end of the annular portion  21  contacts the axially-one-side end of the flange  14 . With this configuration, when the stator core  340  is manufactured, the position of the pole-tooth yoke  2  with respect to the disk portion  1  in the axial direction can be determined by abutting the pole-tooth yoke  2  against the flange  14  in the axial direction. 
     In  FIGS.  7 A and  7 B , the disk portion  1  has the first protrusion  11  that fits into the gap  210  of the pole-tooth yoke  2 . The first protrusion  11  extends radially outward from the upper part of the radially outer surface of the disk body  10 . The first protrusion  11  is disposed on the axially one side Da with respect to the flange  14 . However, the present disclosure is not limited to the example shown in  FIGS.  7 A and  7 B , and the disk portion  1  may not have the first protrusion  11 . 
     1-3-4. Fourth Modification 
     The fourth modification of the stator core  340  will be described with reference to  FIG.  8   .  FIG.  8    is a top view of the stator core  340  according to the fourth modification. 
     In the fourth modification, the disk portion  1  has a side recess  15 . The side recess  15  is recessed inward in the radial direction on the radially outer surface of the disk portion  1 . In  FIG.  8   , the disk portion  1  has a plurality of side recesses  15 . The two side recesses  15  are formed in the circumferential direction on the radially outer surface of the disk body  10 . However, the present disclosure is not limited to the example shown in  FIG.  8   , and the number of the side recesses  15  may be one or three or more. 
     The annular portion  21  of the pole-tooth yoke  2  has an extension portion  25 . The extension portion  25  extends radially inward at the circumferential end of the annular portion  21 . The extension portion  25  fits into the side recesses  15 . The extension portion  25  can be formed, for example, by bending the circumferential end of the annular portion  21  inward in the radial direction. With this configuration, the annular portion  21  can be more reliably positioned with respect to the disk portion  1  in the circumferential direction. 
     In the fourth modification, the extension portion  25  has a first extension portion  251  and a second extension portion  252 . The first extension portion  251  extends radially inward at the first circumferential side end of the annular portion  21 . The second extension portion  252  extends radially inward at the second circumferential side end of the annular portion  21 . The first extension portion  251  and the second extension portion  252  are fitted into different side recesses  15 . With this configuration, when the annular portion  21  is joined to the disk portion  1 , both ends of the annular portion  21  in the circumferential direction can be fixed to the side recesses  15  of the disk portion  1 , respectively. Therefore, when, for example, the annular portion  21  is joined along the radially outer surface of the disk portion  1 , the annular portion  21  can be joined to the radially outer surface of the disk portion  1  without any gap on the entire circumference. Further, this configuration can prevent the generation of a gap between the annular portion  21  and the disk portion  1 , even if the annular portion  21  bends. However, the present disclosure is not limited to the above example embodiment, and the extension portion  25  may have only one of the first extension portion  251  and the second extension portion  252 . 
     The first to fourth modifications of the example embodiment have been described above. The first to fourth modifications may be implemented individually. Alternatively, a combination of at least two of the first to fourth modifications may be implemented. 
     2. Others 
     The example embodiment of the present disclosure has been described above. Note that the scope of the present disclosure is not limited to the above example embodiment. The present disclosure can be implemented by making various modifications to the abovementioned example embodiment without departing from the gist of the disclosure. In addition, the matters described in the above example embodiment can be arbitrarily combined together, as appropriate, as long as there is no inconsistency. 
     The present disclosure is useful in, for example, a motor including a stator that has a stator core in which pole teeth are disposed radially outward of a coil. 
     While example embodiments of the present disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The scope of the present disclosure, therefore, is to be determined solely by the following claims.