Patent Publication Number: US-2022216742-A1

Title: Stator and motor

Description:
TECHNICAL FIELD 
     The present disclosure relates to stators and motors. 
     BACKGROUND ART 
     Conventionally, there is an inner rotor type stator including an annular stator core formed by coupling a plurality of split cores together (see, for example, Japanese Patent Application Laid-Open No. 2002-95192 (Patent Literature 1)). Each of the plurality of split cores of the stator has a yoke portion extending in the circumferential direction and a tooth portion extending radially inward from the yoke portion. 
     CITATIONS LIST 
     Patent Literature 
     
         
         Patent Literature 1: JP 2002-95192 A 
       
    
     SUMMARY OF INVENTION 
     Technical Problems 
     In the above-described conventional stator, each of the split cores has a protruding portion on one side in the circumferential direction of the yoke portion and a recessed portion on the other side in the circumferential direction of the yoke portion. The split cores are assembled into an annular shape by fitting the protruding portion of one split core into the recessed portion of an adjoining split core. 
     However, in the stator, there is a problem that the adjoining split cores need to be welded to each other at an outer peripheral end of a joint portion between the adjoining split cores in the axial direction of the stator in order to secure the force for fastening the split cores to each other. 
     The present disclosure proposes a stator capable of securing a fastening force between split cores without welding the split cores to each other, and a motor including the stator. 
     Solutions to Problems 
     A stator of the present disclosure includes a stator core including a plurality of split cores arranged in an annular shape. The split cores each include a yoke portion and a tooth portion protruding from the yoke portion in a radial direction of the stator core. The yoke portions of adjoining split cores are connected to each other at joint surfaces of the adjoining split cores, and the joint surfaces are provided with a fitting portion along an axial direction of the stator core from an upper end surface to a lower end surface of the stator core. The fitting portion is provided with a crimped portion. 
     According to the present disclosure, the joint surfaces are provided with the fitting portion that extends along the axial direction of the stator core from the upper end surface to the lower end surface of the stator core, and the crimped portion is provided in the fitting portion. The fitting portion is prastically deformed at the crimped portion, whereby even if dimensional variations occur in the fitting portion due to working of the fitting portion, the fastening force between the split cores can be improved. Therefore, the fastening force between the split cores can be secured without the split cores being welded to each other. In addition, even if the fitting portion has a small shape, the fastening force between the split cores can be secured, so that the length of a contact portion at the fitting portion can be shortened, a possible leakage flux can be reduced, and the efficiency of a motor including the stator can be improved. 
     In addition, in the stator according to one aspect of the present disclosure, the crimped portion is provided in the fitting portion on at least one of the upper end surface and the lower end surface of the stator core. 
     According to the present disclosure, providing a crimped portion in the fitting portion on at least one of the upper end surface and the lower end surface of the stator core allows the fastening force between the split cores to be easily improved. In addition, since distortion due to the crimped portion is limited to at least one of an upper end—side portion and a lower end—side portion of the stator core, influence of iron loss due to the distortion at the crimped portion is small. 
     In the stator according to one aspect of the present disclosure, the crimped portion is provided across the adjoining split cores. 
     According to the present disclosure, providing the crimped portion across the adjoining split cores causes plastic deformation to occur over respective portions of the adjoining split cores that constitute the fitting portion of the adjoining split cores. Thus, the fastening force between the split cores can be improved. 
     In the stator according to one aspect of the present disclosure, the crimped portion is provided across the adjoining split cores in a radial direction of the stator core. 
     According to the present disclosure, providing the crimped portion across the adjoining split cores in the radial direction of the stator core causes plastic deformation to occur radially over respective portions of the adjoining split cores constituting the fitting portion of the adjoining split cores. Thus, the fastening force between the split cores can be improved. 
     In the stator according to one aspect of the present disclosure, the fitting portion includes a protruding portion provided on one side in a circumferential direction of the stator core of the yoke portion of one split core and a recessed portion provided on an opposite side in the circumferential direction of the yoke portion of a split core adjoining to the one split core. Each of the protruding portion and the recessed portion includes two linear portions parallel to each other, each linear portion extending from a joint surface—side end of the linear portion, and an arc portion connecting other ends of the two linear portions. 
     According to the present disclosure, the adjoining split cores can be easily coupled to each other with the protruding portion and the recessed portion each having the two parallel linear portions and the arc portion connecting the other ends of the two linear portions. 
     A motor according to the present disclosure includes any one of the above stators, and a rotor arranged to face the stator in a radial direction. 
     According to the present disclosure, the leakage flux of the stator can be reduced, so that the motor is allowed to have an improved efficiency. 
     According to the present disclosure, it is possible to manufacture a stator including a stator core capable of securing the fastening force between split cores without welding the split cores to each other. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross-sectional view of a motor including a stator according to a first embodiment of the present disclosure. 
         FIG. 2  is a cross-sectional view of the motor taken along line II-II in  FIG. 1 . 
         FIG. 3  is a plan view of a stator core. 
         FIG. 4  is a plan view of a split core constituting the stator core. 
         FIG. 5  is a plan view showing a state in which the split cores are connected. 
         FIG. 6  is an enlarged view of a part including a fitting portion of split cores of Example 1. 
         FIG. 7  is an enlarged view of a part including a fitting portion of split cores of Example 2. 
         FIG. 8  is an enlarged view of a part including a fitting portion of split cores of Example 3. 
         FIG. 9  is an enlarged view of a part including a fitting portion of split cores of Example 4. 
         FIG. 10  is an enlarged view of a part including a fitting portion of split cores of Example 5. 
         FIG. 11  is an enlarged view of a part including a fitting portion of split cores of Example 6. 
         FIG. 12  is a diagram showing a magnetic flux distribution of the stator core. 
         FIG. 13  is a plan view of a split core constituting a stator core of a stator according to a second embodiment of the present disclosure. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments will be described. It should be noted that in the drawings, the same reference numerals represent the same or corresponding parts. In addition, the dimensions on the drawing such as the length, the width, the thickness, and the depth are appropriately changed from the actual scale for clarity and simplification of the drawing, and do not represent the actual relative dimensions. 
     First Embodiment 
       FIG. 1  is a cross-sectional view of a motor  100  including a stator  1  according to a first embodiment of the present disclosure, and shows a cross section of the motor  100  taken along line I-I in  FIG. 2 .  FIG. 2  is a cross-sectional view of the motor  100  taken along line II-II in  FIG. 1 . 
     As shown in  FIG. 1 , the motor  100  is what is called an outer rotor type motor  100 , and includes an annular stator  1  and a rotor  2  arranged to face a radially outer side of the stator  1 . The motor  100  rotationally drives a member such as a fan (not shown) via a shaft  3 . 
     As shown in  FIGS. 1 and 2 , the rotor  2  includes a mold resin  20 , a plurality of back yokes  21 , and a plurality of magnets  22 . 
     The mold resin  20  is formed in a cup shape and covers the stator core  10  of the stator  1 . The mold resin  20  is fixed to the shaft  3  via a coupling member  23 . In this embodiment, bulk molding compound (BMC) is used for the mold resin  20 . 
     The back yokes  21  and the magnets  22  are integrally molded with the mold resin  20 . In the first embodiment, eight back yokes  21  are annularly arranged. Eight magnets  22  are annularly arranged on the radially inner side of the back yokes  21 . Magnets  22  and  22  adjacent to each other in the circumferential direction have different magnetism. 
     The stator  1  includes a stator core  10 , an insulator  11 , and coils  12 . 
     The stator core  10  includes a stack of electromagnetic steel sheets. The stator core  10  includes an annular stator yoke  30  and a plurality of tooth portions  31  protruding radially outward from an outer circumferential surface of the stator yoke  30 . In the first embodiment, 12 tooth portions  31  are arranged at intervals in the circumferential direction. 
     The insulator  11  is attached to each tooth portion  31  of the stator core  10 . The insulator  11  is made of an insulating material such as resin. 
     The coils  12  are wound around the tooth portions  31  of the stator core  10  by concentrated winding via the insulator  11 . Electromagnetic force is generated in the stator core  10  by flowing a current through the coils  12 , and the electromagnetic force rotates the rotor  2  together with the shaft  3 . 
     A mold resin portion  13  integrally molds the stator core  10 , the insulator  11 , and the coils  12 . The mold resin portion  13  is made of, for example, bulk molding compound (BMC). 
     The mold resin portion  13  supports the shaft  3  via a bearing  14 . The mold resin portion  13  is provided with a mount  15  for attaching the motor  100  to another member (not shown). A cover  16  is attached to the mount  15 . The cover  16  covers the rotor  2  to prevent dust, water, and the like from entering. The cover  16  is formed by integrally molding a bearing housing  17  with a mold resin. The cover  16  supports the shaft  3  via a bearing  18 . 
       FIG. 3  is a plan view of the stator core  10 . As shown in  FIG. 3 , the stator core  10  includes a plurality of split cores  40  annularly arranged. The split core  40  includes a yoke portion  41 , which is a radially inner portion, and a tooth portion  31  protruding radially outward from the yoke portion  41 . 
     The  12  split cores  40  are annularly arranged, and the yoke portions  41  of the adjacent split cores  40  are connected to each other to form the stator core  10 . 
       FIG. 4  is a plan view of one of the split cores  40  constituting the stator core  10 . As shown in  FIG. 4 , the yoke portion  41  of the split core  40  includes a protruding portion  41   a  and a recessed portion  41   b  that run along the axial direction of the stator core  10  from an upper end surface to a lower end surface of the split core  40 . The protruding portion  41   a  is provided on one of opposite joint surfaces  43  of the split core, the joint surfaces  43  being arranged in the circumferential direction of the stator core  10 . The recessed portion  41   b  is provided on the other joint surface  43  of the split core. 
     In a plan view, the protruding portion  41   a  of the yoke portion  41  has two linear portions L 11  and L 12  parallel to each other, each extending from its joint surface  43 —side end, and an arc portion C 11  connecting the other ends of the two linear portions L 11  and L 12 . The arc portion C 11  is provided so that the tip (opposite to the joint surface  43 ) of the protruding portion  41   a  bulges. 
     Each of the linear portions L 11  and L 12  forms an angle of 90 degrees with respect to the associated joint surface  43  of the yoke portion  41 . 
     The recessed portion  41   b  of the yoke portion  41  also has two linear portions L 21  and L 22  parallel to each other, each linear portion extending from a joint surface  43 —side end of the linear portion, and an arc portion C 21  connecting the other ends of the two linear portions L 21  and L 22 . The arc portion C 21  is provided so that the side opposite to the joint surface  43  of the recessed portion  41   b  bulges. 
     Each of the linear portions L 21  and L 22  forms an angle of 90 degrees with respect to the associated joint surface  43  of the yoke portion  41 . 
     A crimped portion  47  is provided on the yoke portion  41  of the split core  40 , and a crimped portion  48  is provided on a radially outer portion of the tooth portion  31 . The crimped portions  47  and  48  fix the electromagnetic steel sheets constituting the split core  40  together. 
       FIG. 5  is a plan view showing a state in which two split cores  40  are connected to each other. In  FIG. 5 , L 1  is a center line in the radial direction of each split core  40 . As shown in  FIG. 5 , the protruding portion  41   a  of the yoke portion  41  of one split core  40  and the recessed portion  41   b  of the yoke portion  41  of the other split core  40  are fitted to each other, and the adjacent yoke portions  41  are coupled to each other. The protruding portion  41   a  and the recessed portion  41   b  of the yoke portion  41  constitute a fitting portion  42 . 
     The fitting portion  42  includes the protruding portion  41   a  of the yoke portion  41  of one split core  40  and a peripheral edge portion of the recessed portion  41   b  defining the recessed portion  41   b  in the yoke portion  41  of the other split core  40 . 
     On one joint surface  43  of the yoke portion  41  of one split core  40 , an end of the fitting portion  42  is positioned radially inward from a center P 1  of the joint surface (intersection of a virtual circle VC shown in  FIG. 5  and the joint surface  43 ) between a radially outer end and a radially inner end of the joint surface. The virtual circle VC is a circle centered on the center O 1  of the stator core  10  and passing through the centers P 1  of the joint surfaces  43  of the yoke portions  41  of the split cores  40 . Planes along the joint surfaces  43  of the yoke portions  41  pass through the center O 1  of the stator core  10 . 
     On the other hand, outer circumferential portions of adjacent tooth portions  31  and  31  of the split cores  40  are separated from each other. 
     In this manner, the adjacent yoke portions  41  are connected to each other, and the  12  connected yoke portions  41  constitute the stator yoke  30 . 
     It should be noted that before the adjacent yoke portions  41  are connected to each other, the tooth portion  31  of each split core  40  is covered with a segment of the insulator  11  (shown in  FIGS. 1 and 2 ), and a coil  12  (shown in  FIG. 1 ) is wound around the tooth portion  31  covered with the segment of the insulator  11 . 
     In the stator  1  of the first embodiment, the fitting portion  42  provided in the yoke portions  41  of the adjoining split cores  40  extends in a direction orthogonal to the joint surfaces  43 . 
     Here, as shown in  FIGS. 6 to 11  showing Examples 1 to 6, any one of crimped portions  44 A to  44 G is provided in the fitting portion  42  at the upper end surface and the lower end surface of the stator core  10 . Thus, the fitting portion  42  is plastically deformed, so that the fastening force between the split cores  40  can be improved. In addition, even if the fitting portion  42  has a small shape, since the fastening force between the split cores  40  can be secured by the crimped portion  44 A to  44 G, the length of the contact portion in the fitting portion  42  can be shortened and the leakage flux can be reduced. In addition, since the distortion due to the crimped portion  44 A to  44 G is limited to the upper end side and the lower end side of the stator core  10 , the influence of the iron loss due to the distortion of the crimped portion  44 A to  44 G is small. 
       FIG. 6  shows an enlarged view of a part including the fitting portion  42  of the adjoining split cores  40  of the Example 1. As shown in  FIG. 6 , a thick linear crimped portion  44 A is provided in the protruding portion  41   a  of the fitting portion  42  of the yoke portion  41  such that the crimped portion  44 A has a longitudinal direction along the circumferential direction of the stator core  10 . 
       FIG. 7  shows an enlarged view of a part including the fitting portion  42  of the adjoining split cores  40  of the Example 2. As shown in  FIG. 7 , a circular-shaped crimped portion  44 B is provided in the protruding portion  41   a  of the fitting portion  42  of the adjoining yoke portions  41 . 
       FIG. 8  is an enlarged view of a part including the fitting portion  42  of the adjoining split cores  40  of the Example 3. As shown in  FIG. 8 , a thick linear crimped portion  44  C is provided across the tip portion of the protruding portion  41   a  of one of the adjoining yoke portions  41  and the other of the adjoining yoke portions  41  such that the crimped portion  44 C has a longitudinal direction along the circumferential direction of the stator core  10 . 
       FIG. 9  is an enlarged view of a part including the fitting portion  42  of the adjoining split cores  40  of the Example 4. As shown in  FIG. 9 , a thick linear crimped portion  44 D is provided across the protruding portion  41   a  of one of the adjoining yoke portion  41 , and the other of the adjoining yoke portion  41  on both radial sides of the protruding portion  41   a  such that the crimped portion has a longitudinal direction along the radial direction. 
       FIG. 10  is an enlarged view of a part including the fitting portion of the adjoining split cores  40  of the Example 5. As shown in  FIG. 10 , a thick linear crimped portion  44 E is provided in the protruding portion  41   a  of one of adjoining yoke portions  41  such that the crimped portion  44 E has a longitudinal direction along the radial direction. 
       FIG. 11  is an enlarged view of a part including the fitting portion  42  of the adjoining split cores  40  of the Example 6. As shown in  FIG. 11 , thick linear crimped portions  44 F and  44 G are provided on both radial sides of the recessed portion  41   b  of one of the adjoining yoke portion  41  such that the crimped portions  44 F and  44 G have a longitudinal direction along the circumferential direction of the stator core  10 . 
       FIG. 12  shows a magnetic flux distribution of the stator core  10  obtained by simulation. It should be noted that in  FIG. 12 , the rotor  2  has a configuration for simulation, unlike the configuration in  FIG. 2 . 
     As shown in  FIG. 12 , the magnetic flux density in the fitting portions  42  of the split cores  40  is lower than the magnetic flux density in regions, located on the radially outer side of the fitting portions  42 , of the joint surfaces  43  of the split cores  40 . Therefore, the leakage flux due to the fitting portions  42  can be reduced. 
     According to the stator  1  having the above configuration, the fitting portion  42  is provided on the joint surfaces  43  of the connected yoke portions  41  of the adjoining split cores  40 , and the fitting portion  42  is provided with the crimped portion  44 A to  44 G. The fitting portion is prastically deformed at the crimped portion, whereby even if dimensional variations occur in the fitting portion  42  due to working of the fitting portion, the fastening force between the split cores  40  can be improved. Therefore, the fastening force between the split cores  40  can be secured without the split cores  40  being welded to each other. In addition, even if the fitting portion  42  has a small shape, the fastening force between the split cores  40  can be secured, so that the length of the contact portion at the fitting portion  42  can be shortened and the leakage flux can be reduced, and the efficiency of the motor  100  can be improved. 
     As shown in  FIGS. 6 to 11 , providing the fitting portion  42  with the crimped portion  44 A to  44 G on the upper end surface and the lower end surface of the stator core  10  allows the fastening force between the split cores  40  to be easily improved. 
     As shown in  FIGS. 8 and 9 , since providing the crimped portion  44 C and  44 D across the adjoining split cores  40  causes plastic deformation to occur over the portions constituting the fitting portions  42  of the adjoining split cores  40 , the fastening force between the split cores  40  can be further improved. 
     As shown in  FIG. 9 , since providing the crimped portion  44 D across the adjoining split cores  40  in the radial direction of the stator core  10  causes plastic deformation to occur radially over the portions constituting the fitting portions  42  of the adjoining split cores  40 , the fastening force between the split cores  40  can be further improved. 
     The protruding portion  41   a  of the fitting portion  42  has a shape having two linear portions L 11  and L 12  parallel to each other, each linear portion L 11  and L 12  extending from a joint surface  43 —side end of the linear portion L 11  and L 12 , and an arc portion C 11  connecting the other ends of the two linear portions L 11  and L 12 . The recessed portion  41   b  of the fitting portion  42  has a shape having two linear portions L 21  and L 22  parallel to each other, each linear portion L 21  and L 22  extending from a joint surface  43 —side end of the linear portion L 21  and L 22 , and an arc portion C 21  connecting the other ends of the two linear portions L 21  and L 22 . Due to the shapes of the protruding portion  41   a  and the recess portion  41   b , the protruding portion  41   a  of one split core  40  of the two adjoining split cores  40  can be inserted into the recessed portion  41   b  of the other split core  40  in the circumferential direction of the stator core  10 , and the split cores  40  can be easily coupled to each other. 
     According to the motor  100  having the above configuration, the leakage flux of the stator  1  can be reduced, and the efficiency can be improved. 
     In the first embodiment, in a plan view, the protruding portion  41   a  and the recessed portion  41   b  of the fitting portion  42  each are provided on the associated joint surfaces  43  of the yoke portions  41  in a radial position inside of the virtual circle VC centered on the center O 1  of the stator core  10  and passing through the centers P 1  of the joint surfaces  43  of the yoke portions  41 . However, regardless of the position on the joint surfaces of the yoke portions, the fitting portion has only to be provided on the joint surfaces. 
     In the first embodiment, the protruding portion  41   a  of the fitting portion  42  has a shape having two linear portions L 11  and L 12  parallel to each other, each extending from one end on the joint surface  43  side and an arc portion C 11  connecting the other ends of the two linear portions L 11  and L 12 , and the recessed portion  41   b  of the fitting portion  42  has a shape having two linear portions L 21  and L 22  parallel to each other, each extending from one end on the joint surface  43  side and an arc portion C 21  connecting the other ends of the two linear portions L 21  and L 22 . However, the shapes of the protruding portion and the recessed portion of the fitting portion  42  are not limited thereto. For example, one of the two linear portions parallel to each other of the protruding portion and the recessed portion of the fitting portion may be a curved portion, or two curved portions may be used instead of the two linear portions. Also, polygonal portions may be used instead of the arc portions. 
     Second Embodiment 
       FIG. 13  is a plan view of one of split cores  140  constituting a stator core of a stator according to a second embodiment of the present disclosure. The split core  140  of the stator of the second embodiment has the same configuration as the split core  40  of the stator  1  of the first embodiment except for a fitting portion  142  including a protruding portion  141   a  and a recessed portion  141   b  of a yoke portion  141 , and  FIGS. 1 and 2  will be referred to for describing the stator of the second embodiment. 
     As shown in  FIG. 13 , the yoke portion  141  of the split core  140  includes a protruding portion  141   a  provided on one side in the circumferential direction of the stator core  10  and a recessed portion  141   b  provided on the other side in the circumferential direction. 
     In a plan view, the protruding portion  141   a  of the yoke portion  141  has two linear portions L 31  and L 32  parallel to each other, each extending from a joint surface  143 —side end of the linear portion, and an arc portion C 31  connecting the other ends of the two linear portions L 31  and L 32 . The arc portion C 31  is provided such that a tip side (a side opposite to the joint surface  143 ) of the protruding portion  141   a  bulges. 
     The linear portion L 31  forms an angle of 85 degrees with respect to the associated joint surface  143  located on one side in the circumferential direction of the yoke portion  141 . In addition, the linear portion L 32  forms an angle of 95 degrees with respect to the associated joint surface  143  of the yoke portion  141 . 
     The recessed portion  141   b  of the yoke portion  141  has two linear portions L 41  and L 42  parallel to each other, each extending from a joint surface  143 —side end, and an arc portion C 41  connecting the other ends of the two linear portions L 41  and L 42 . The arc portion C 41  is provided such that a side, opposite to the associated joint surface  143 , of the recessed portion  141   b  bulges. 
     The linear portion L 41  forms an angle of 95 degrees with respect to the associated joint surface  143  located on the other side in the circumferential direction of the yoke portion  141 . In addition, the linear portion L 42  forms an angle of 85 degrees with respect to the associated joint surface  143  of the yoke portion  141 . 
     A crimped portion  147  is provided on the yoke portion  141  of the split core  140 , and a crimped portion  148  is provided on a radially outer portion of a tooth portion  131  of the split core. The crimped portions  147  and  148  integrally fix a plurality of electromagnetic steel sheets constituting the split core  40 . 
     The stator of the second embodiment has the same effects as the stator  1  of the first embodiment. 
     In the stator of the second embodiment, the fitting portion  142  provided in the yoke portion  141  of the split core  140  extends obliquely outward with respect to the direction orthogonal to the joint surface  143 . Thus, since the fit of the fitting portion  142  is less likely to be released by the force acting on the split core  140  in the direction orthogonal to the joint surface  143 , the coupling force between the split cores  140  can be maintained. 
     In the first and second embodiments, the outer rotor type stator  1  and the motor  100  including the stator  1  have been described, but the present invention may be applied to an inner rotor type stator and a motor including the stator. 
     In the first and second embodiments, the yoke portions  41 ,  141  of the annularly arranged split cores  40 ,  140  are connected by the fitting portions  42 ,  142 . The fitting portions are not limited to those shaped as described above, and have only to have a fitting structure provided along the axial direction of the stator core from the upper end surface to the lower end surface of the stator core on the joint surfaces where the yoke portions of the adjoining split cores are connected. 
     Furthermore, the joint surface—side end of the fitting portion is preferably positioned radially inward from the center between the radially outer end and the radially inner end of the joint surface of the yoke portion of the split core. In this case, a part on the side opposite to the joint surface of the fitting portion may be positioned radially outward from a virtual circle centered on the center of the stator core and passing through the center between the radially outer end and the radially inner end of the joint surface. 
     Although specific embodiments of the present disclosure have been described herein, the present disclosure is not limited to the first and second embodiments, and various modifications can be made within the scope of the present disclosure and implemented. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  stator 
               2  rotor 
               3  shaft 
               10  stator core 
               11  insulator 
               12  coil 
               13  mold resin portion 
               14  bearing 
               15  mount 
               16  cover 
               17  bearing housing 
               18  bearing 
               20  mold resin 
               21  back yoke 
               22  magnet 
               23  coupling member 
               30  stator yoke 
               31 ,  131  tooth portion 
               40 ,  140  split core 
               41 ,  141  yoke portion 
               41   a ,  141   a  protruding portion 
               41   b ,  141   b  recessed portion 
               42 ,  142  fitting portion 
               43 ,  143  joint surface 
               44 A to  44 G crimped portion 
               47 ,  48 ,  147 ,  148  crimped portion 
               50  upper insulator portion 
               60  lower insulator portion 
               100  motor 
             L 11 , L 12 , L 21 , L 22 , L 31 , L 32 , L 41 , L 42  linear portion 
             C 11 , C 21 , C 31 , C 41  arc portion