Abstract:
An electrical rotor and stator structure includes at least one stator, at least one rotor and multiple outward pillar structures. The at least one stator includes multiple first magnetic members. Each first magnetic member has a first surface. The at least one rotor is able to be rotated pivotally relative to the at least one stator. The at least one rotor includes multiple second magnetic members. Each second magnetic member has a second surface facing and opposite to the first surface. The multiple outward pillar structures are installed on the second surfaces and the first surfaces.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 101138330 filed in Taiwan, R.O.C. on Oct. 17, 2012, the entire contents of which are hereby incorporated by reference. 
     TECHNICAL FIELD 
     The disclosure relates to an electrical rotor and stator structure, and more particularly to an electrical rotor and stator structure having outward pillar structures on the surfaces of the magnetic members. 
     BACKGROUND 
     In recent years, with the increasing cost of energy, the regulations on energy consumption have been increasingly stringent in every country. Taking energy conservation in the manufacture industry for example, motors are accounted for more than 70 percentages of the overall electricity consumption. Therefore, how to increase the energy efficiency of the motors has become an important issue. Among different motors, the brushless permanent magnet motor offers a simple design that is easy to maintain and has high efficiency. In particular, an axial flux motor (AFM) of the brushless permanent magnet motor is the one having a smaller length-diameter ratio and suitable for thinner design. 
     Magnet is one of key components of the brushless permanent magnet motor that determines the performance and speed thereof. Therefore, methods, that can improve magnets in increasing the energy product, better control of the lines of flux inside the motor and suppressing the flux leakage, can increase the energy efficiency of motors. Hence, the capability of the magnets is a crucial issue in the development of the motors. 
     Among various types of magnets, rare-earth (material) magnets generally are strong permanent magnets made from alloys of rare earth elements. Motors using rare-earth magnet have higher energy product and better torque density, thus to be widely used in the mechanical and electrical applications. 
     However, the cost of rare earth metals has surged almost threefold in recent years. Hence, price of the motors that use rare-earth magnet has risen. Rising price forces the industry to endeavor to design a motor that utilizes less rare-earth magnets and levels up the energy efficiency of the motors. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will become more fully understood from the detailed description given herein below by way of example with reference to the accompanying drawings, and thus does not limit the disclosure, wherein: 
         FIG. 1A  is a perspective view of an electrical rotor and stator structure according to one embodiment of the disclosure. 
         FIG. 1B  is a partially sectional view of a motor with variable axial rotor and stator structure according to one embodiment of the disclosure. 
         FIG. 2A  is a partially enlarged sectional view of an electrical rotor and stator structure according to one embodiment of the disclosure. 
         FIG. 2B  is a partially enlarged sectional view of a motor with variable axial rotor and stator structure according to another embodiment of the disclosure. 
         FIG. 3A  is an enlarged view of an outward pillar structure according to one embodiment of the disclosure. 
         FIG. 3B  to  FIG. 3G  are enlarged views of the outward pillar structure according to other embodiments of the disclosure. 
         FIG. 4A  is a partial schematic layout of the outward pillar structures according to one embodiment of the disclosure. 
         FIG. 4B  is a partial schematic layout of the outward pillar structures according to another embodiment of the disclosure. 
         FIG. 5A  is a partially sectional view of an electrical rotor and stator structure according to another embodiment of the disclosure. 
         FIG. 5B  is a partially sectional view of an electrical rotor and stator structure according to another embodiment of the disclosure. 
         FIG. 6A  is a partially enlarged sectional view of an electrical rotor and stator structure according to another embodiment of the disclosure. 
         FIG. 6B  is a partially enlarged sectional view of an electrical rotor and stator structure according to another embodiment of the disclosure. 
         FIG. 6C  is a partially enlarged sectional view of an electrical rotor and stator structure according to another embodiment of the disclosure. 
         FIG. 7  is the result of the magnetic flux between the rotor and the stator, the radius length of the surface area, and with or without the pillar structure. 
     
    
    
     SUMMARY 
     The disclosure provides an electrical rotor and stator structure comprising at least one stator, at least one rotor and a plurality of outward pillar structures. The at least one stator comprises a plurality of first magnetic members. Each first magnetic member has a first surface. The at least one rotor is adapted to be pivotally rotated relative to the at least one stator. The at least one rotor comprises a plurality of second magnetic members wherein each second magnetic member has a second surface facing and opposite to the first surface. The plurality of outward pillar structures is installed on the second surfaces and the first surfaces. 
     DETAILED DESCRIPTION 
     In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing. 
     Please refer to  FIG. 1A ,  FIG. 1B  and  FIG. 2A ,  FIG. 1A  is a perspective view of an electrical rotor and stator structure according to one embodiment of the disclosure.  FIG. 1B  is a partially sectional view of an electrical rotor and stator structure according to one embodiment of the disclosure.  FIG. 2A  is a partially enlarged sectional view of an electrical rotor and stator structure according to one embodiment of the disclosure. 
     An electrical rotor and stator structure  10  described in the disclosure comprises a stator  11 , a rotor  12  and a plurality of outward pillar structures  13 . 
     The stator  11  comprises a plurality of first magnetic members  111  and a shell body  112 . The first magnetic members  111  are mounted on the shell body  112 . 
     Specifically, in this embodiment, the shell body  112  comprises a first shell  1121  and a second shell  1122 . A gap is arranged between a first shell  1121  and a second shell  1122 . The first magnetic members  111  are mounted on the first shell  1121  and the second shell  1122 . The first magnetic members  111  are located between the first shell  1121  and the second shell  1122 . Each first magnetic member comprises a pole piece  1111  and a coil  1112 . The coil  1112  is wound around the pole piece  1111 . In other word, the first magnetic member  111  is an electromagnet. Moreover, the pole piece  1111  of each first magnetic member  111  has a first surface  1113 . 
     In this embodiment, the material of the pole piece  1111  is soft magnetic composites. The pole piece  1111  may be formed by compressing a mixture of powered magnetic materials containing iron (Fe), silicon (Si), aluminum (Al) and manganese (Mo) into clumps through an insulating binder. The insulating binder may be made of an inorganic material, such as phosphates and oxides. 
     The rotor  12  is pivotally disposed on the stator  11  and may rotate relative to stator  11 . The rotor  12  comprises a plurality of second magnetic members  121 , which are permanent magnets. The rotor also comprises a rotating shaft  122 , rotatable relatively to the shell body  112  as well as located between the first shell  1121  and the second shell  1122 . The second magnetic members  121  are attached to the rotating shaft  122 . The second magnetic members  121  are located between the first magnetic members  111  mounted on the first shell  1121 , and the first magnetic members  111  are mounted on the second shell  1122 . Both the second magnetic members  121  have two second surfaces  1211  opposite to each other. In each second magnetic member  121 , one of the second surfaces  1211  faces to the first surface  1113  of the pole piece  1111  mounted on the first shell  1121 , and the other second surfaces  1211  faces to the first surface  1113  of the pole piece  1111  mounted on the second shell  1122   
     In this embodiment, the second magnetic members  121  are resin-composition magnets, mainly comprising neodymium (Nd), iron (Fe), and boron (B) elements and produced by compression molding. In this embodiment, the second magnetic members  121  do not comprise dysprosium (Dy) element. 
     In this embodiment, the shell body  112  of the stator comprises two shells (the first shell  1121  and the second shell  1122 ), but the disclosure is not limited thereto. In other embodiments, the shell body  112  of the stator  11  may have a single shell, and the first magnetic member  111  exists in one side of the second magnetic member  121 . 
     In this embodiment, the outward pillar structures  13  are installed on the first surfaces  1113  and the second surfaces  1211 . The outward pillar structures may be disposed on the first surfaces  1113  or the second surfaces  1211  and be integrally formed into one piece. The outward pillar structures  13  may increase the magnetic flux density existing between the first surface  1113  of the first magnetic member  111  and the second surface  1211  of the second magnetic member  121 . Thereby, the energy efficiency of the motor that utilizes the electrical rotor and stator structure  10  is increased. 
     In this embodiment, the outward pillar structures  13  on these first surfaces  1113  and the outward pillar structures  13  on the second surfaces  1211  are arranged opposite to each other (namely, opposite setting), as illustrated in  FIG. 2A . Specifically, the opposite setting refers to that when the outward pillar structures  13  on the first surface  1113  is projected on the second surface  1211 , the projected locations thereof are overlapped with the locations of the outward pillar structures  13  on the second surface  1211  completely. 
     In this embodiment, the relative setting of the outward pillar structures  13  on the first surface  1113  and the outward pillar structure  13  on the second surface  1211  is not intended to limit the disclosure. For example, in another embodiment as illustrated in  FIG. 2B , the outward pillar structures  13  on the first surface  1113  and the outward pillar structure  13  on the second surface  1211  are arranged in a staggered setting (namely, an offset arrangement). The staggered setting refers to that when the outward pillar structures  13  on the first surface  1113  is projected on the second surface  1211 , the projected locations thereof fall in between the locations of the outward pillar structures  13  on the second surface  1211 , instead of overlapping with thereof. The staggered setting between the outward pillar structures  13  on the first surface  1113  and the outward pillar structures  13  on the second surface  1211  offer an advantage to the electrical rotor and stator structure  10  during assembly. Specifically, due to the staggered setting, the interference between the outward pillar structures  13  on the first surface  1113  and the outward pillar structures  13  on the second surface  1211  may be avoided. 
     With reference to  FIG. 3A , the outward pillar structure  13  may be of cylindrical shape, such as a circular cylinder, but the disclosure is not limited thereto. In other embodiments, the outward pillar structure  13   a  may be of a triangular prism (as shown in  FIG. 3B ) or the outward pillar structure  13   b  may be a square pillar with right angled edges (as illustrated in  FIG. 3C ). With reference to  FIG. 3D  to  FIG. 3G , in other embodiments of the disclosure, one end of the outward pillar structure  13   c / 13   d / 13   e / 13   f  may be with chamfering and rounded edges  131   c / 131   d / 131   e / 131   f  respectively. Furthermore, in this embodiment, the setting of the outward pillar structures  13  is an array (as shown in  FIG. 4A ). In other embodiments, the setting of the outward pillar structures  13  is a radial layout (as illustrated in  FIG. 4B , namely, arranged radially). However, the setting of the outward pillar structures  13  is not intended to limit the disclosure. 
     With reference to  FIG. 5A ,  FIG. 5A  is a partially sectional view of an electrical rotor and stator structure according to another embodiment of the disclosure. This embodiment is similar to the embodiment of  FIG. 1B , thus only the differences to be addressed. 
     The difference between the electrical rotor and stator structure  10   a  of this embodiment and that in the embodiment illustrated in  FIG. 1B  is that the outward pillar structures  13  are only disposed on the first surfaces  1113 , but not the second surfaces  1211 . However, such a setting of the outward pillar structures  13  still can increase the magnetic flux density between the first surfaces  1113  and the second surfaces  1211  of the electrical rotor and stator structure  10   a . Thereby, the energy efficiency of the motor that utilizes the electrical rotor and stator structure  10   a  is increased. 
     With reference to  FIG. 5B ,  FIG. 5B  is a partially sectional view of an electrical rotor and stator structure according to another embodiment of the disclosure, which is similar to that of  FIG. 1B , thus only the differences to be addressed. 
     The difference between the electrical rotor and stator structure  10   b  of this embodiment and that in the embodiment illustrated in  FIG. 1B  is that the outward pillar structures  13  are only disposed on the second surfaces  1211 , but not the first surfaces  1113 . However, such a setting of the outward pillar structures  13  still can increase the magnetic flux density between the first surfaces  1113  and the second surfaces  1211  of the electrical rotor and stator structure  10   b . Thereby the energy efficiency of the motor that utilizes the electrical rotor and stator structure  10   b  is increased. 
     With reference to  FIG. 6A ,  FIG. 6A  is a partially enlarged sectional view of an electrical rotor and stator structure according to another embodiment of the disclosure. This embodiment is similar to the embodiment of  FIG. 2A , thus only the differences to be addressed. 
     The difference between the outward pillar structure  13  of this embodiment and that in the embodiment illustrated in  FIG. 2A  is that the outward pillar structure  13  inclines from the normal vector L 1  of the first surface  1113  and the normal vector L 2  of the second surface  1211  at an angle θ. The angle θ ranges between −45 to 45 degrees. Specifically, the structured centerline L of the outward pillar structure  13  to the normal vector L 1  of the first surface  1113  and to the normal vector L 2  of the second surface  1211  form an acute angle respectively. The inclined setting of the outward pillar structure  13  with respect to the normal vector L 1  of the first surface  1113  or to the normal vector L 2  of the second surface  1211  may increase the magnetic flux density. In this embodiment, the outward pillar structures  13  are mounted on the first surface  1113  and the second surface  1211  and incline thereof at an angle, but the disclosure is not limited thereto. For example, in another embodiment, only the outward pillar structures  13  on the second surfaces  1211  incline thereof at an angle, as illustrated in  FIG. 6B . Moreover, in still another embodiment, only the outward pillar structures  13  on the first surfaces  1113  incline thereof at an angle, as illustrated in  FIG. 6C . 
     According to various designs of the electrical rotor and stator structure of the embodiments described above, the Maxwell® simulation program is used to calculate the magnetic flux, maximum torque and magnetic flux at the Z axis of the electrical rotor and stator structure of each embodiment of the disclosure and those from prior art for comparison. The data is plotted in  FIG. 7  and listed in Table 1 and Table 2. 
     With reference to  FIG. 7 , the horizontal axis represents the length of the section of the first surface  1113  or the second surface  1211  (millimeter, mm), whereas the vertical axis represents the scale of the magnetic flux (milli-tesla, mTesla). The dashed line is the distribution of the magnetic flux of the electrical rotor and stator structures from prior art having the first surface  1113  and the second surface  1211  without the outward pillar structures  13 . The solid line is the distribution of the magnetic flux of the electrical rotor and stator structures of the embodiments of the disclosure having the first surface  1113  and or second surface  1211  having the outward pillar structures  13 . The outward pillar structures  13  are arranged in setting of a radial layout. Each outward pillar structure  13  is a circular cylinder with an outer diameter of 1.0 mm and 0.5 mm in height. Furthermore, the outward pillar structure  13  incline toward the first surface  1113  or the second surface  1211  at an angle of 30 degrees from the normal vector thereof. According to  FIG. 7 , the average magnetic flux exists in the electrical rotor and stator structure of the embodiment, whose first surfaces  1113  or second surfaces  1211  has the outward pillar structures  13 , (solid line) is greater than that of the electrical rotor and stator structure without the outward pillar structures of prior art (dashed line). Therefore, the results produced by the simulation program prove that installation of the outward pillar structures  13  on the first surfaces  1113  of the first magnetic members  111  or on the second surfaces  1211  of the second magnetic members  121  may improve and increase the magnetic flux in the air gap located between the rotor and stator of the electrical rotor and stator structure. Thereby, the energy efficiency of the motor is increased. 
     A list of data of maximum torque, magnetic flux and magnetic flux in Z axis of different setting of the electrical rotor and stator structure is shown in Table 1. Data of the electrical rotor and stator structure without the outward pillar structures  13  of the prior art is regarded as a control group, The electrical rotor and stator structures of the embodiments 1 to 19 of the disclosure have the outward pillar structures  13  mounted on the second surfaces  1211  at various angles for different embodiments. In addition, the positive value of the angle means that the outward pillar structures  13  incline to the right of the normal vector L 2  of the second surface  1211  and the negative value of the angle represents that the outward pillar structures  13  incline to the left of the normal vector L 2  of the second surface  1211 . Except the differences of the outward pillar structure and equivalent air gap, the rest of conditions are identical among the control group, and the embodiments 1 to 19 of the disclosure. The above-mentioned magnetic flux is defined as that from the first surface  1113  to the second surface  1211 , whereas the magnetic flux in the Z axis represents the portion of magnetic flux from the first surface  1113  to the second surface  1211  in Z axis direction. The definition of the acronym mN-m is milli-newton meters, the unit of torque. 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 Maximum 
                 Magnetic 
                 Magnetic flux 
               
               
                   
                   
                 torque 
                 flux 
                 in Z axis 
               
               
                 Group 
                 Structural feature 
                 (mN-m) 
                 (mTesla) 
                 (mTesla) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Control 
                 No outward pillar structure 
                 316 
                 460 
                 418 
               
               
                 Group 
               
               
                 Embodiment 1 
                 Outward pillar structure at 
                 331 
                 500 
                 463 
               
               
                   
                 −45 degrees 
               
               
                 Embodiment 2 
                 Outward pillar structure at 
                 335 
                 502 
                 465 
               
               
                   
                 −40 degrees 
               
               
                 Embodiment 3 
                 Outward pillar structure at 
                 335 
                 502 
                 466 
               
               
                   
                 −35 degrees 
               
               
                 Embodiment 4 
                 Outward pillar structure at 
                 332 
                 499 
                 463 
               
               
                   
                 −30 degrees 
               
               
                 Embodiment 5 
                 Outward pillar structure at 
                 326 
                 492 
                 456 
               
               
                   
                 −25 degrees 
               
               
                 Embodiment 6 
                 Outward pillar structure at 
                 335 
                 497 
                 461 
               
               
                   
                 −20 degrees 
               
               
                 Embodiment 7 
                 Outward pillar structure at 
                 339 
                 499 
                 463 
               
               
                   
                 −15 degrees 
               
               
                 Embodiment 8 
                 Outward pillar structure at 
                 336 
                 495 
                 459 
               
               
                   
                 −10 degrees 
               
               
                 Embodiment 9 
                 Outward pillar structure at −5 
                 337 
                 495 
                 459 
               
               
                   
                 degrees 
               
               
                 Embodiment 
                 Outward pillar structure at 0 
                 340 
                 496 
                 460 
               
               
                 10 
                 degree 
               
               
                 Embodiment 
                 Outward pillar structure at 5 
                 332 
                 498 
                 462 
               
               
                 11 
                 degrees 
               
               
                 Embodiment 
                 Outward pillar structure at 10 
                 337 
                 496 
                 460 
               
               
                 12 
                 degrees 
               
               
                 Embodiment 
                 Outward pillar structure at 15 
                 333 
                 497 
                 461 
               
               
                 13 
                 degrees 
               
               
                 Embodiment 
                 Outward pillar structure at 20 
                 336 
                 498 
                 462 
               
               
                 14 
                 degrees 
               
               
                 Embodiment 
                 Outward pillar structure at 25 
                 337 
                 494 
                 457 
               
               
                 15 
                 degrees 
               
               
                 Embodiment 
                 Outward pillar structure at 30 
                 338 
                 496 
                 460 
               
               
                 16 
                 degrees 
               
               
                 Embodiment 
                 Outward pillar structure at 35 
                 334 
                 502 
                 465 
               
               
                 17 
                 degrees 
               
               
                 Embodiment 
                 Outward pillar structure at 40 
                 336 
                 500 
                 463 
               
               
                 18 
                 degrees 
               
               
                 Embodiment 
                 Outward pillar structure at 45 
                 338 
                 501 
                 463 
               
               
                 19 
                 degrees 
               
               
                   
               
             
          
         
       
     
     Based on the data in Table 1, the maximum torque, the magnetic flux and the magnetic flux in Z axis of the outward pillar structures  13  of each embodiment are greater than those of the electrical rotor and stator structure of the control group that has no outward pillar structure. Among all, the embodiment has the outward pillar structure  13  at 0 degree(s) producing the upmost maximum torque; at −40, −35, and 35 degrees the highest magnetic flux; and at −35 degrees the highest magnetic flux in Z axis. 
     Table 2 contains a list of data of maximum torque, magnetic flux and magnetic flux in Z axis of different settings of the electrical rotor and stator structure. Data of the electrical rotor and stator structure without the outward pillar structures  13  of the prior art is regarded as a control group. The electrical rotor and stator structures of the embodiments 1 to 19 of the disclosure have the outward pillar structures  13  mounted on both the first surface  1113  and the second surfaces  1211  at various angles for different embodiments. The positive value of the angle means that the outward pillar structures  13  incline to the right of the normal vector L 1  of the first surface  1113  and the outward pillar structures  13  incline to the right of the normal vector L 2  of the second surface  1211 . The negative value of the angle represents that the outward pillar structures  13  incline to the left of the normal vector L 1  of the first surface  1113  and to the left of the normal vector L 2  of the second surface  1211 . Except the differences of the outward pillar structure and equivalent air gap, the rest of conditions are identical among the control group, and the embodiments 1 to 19 of the disclosure. The magnetic flux is defined as that from the first surface  1113  to the second surface  1211 , whereas the magnetic flux in the Z axis represents the portion of magnetic flux from the first surface  1113  to the second surface  1211  in Z axis direction. 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                 Maximum 
                   
                 Magnetic flux 
               
               
                   
                   
                 torque 
                 Magnetic flux 
                 in Z axis 
               
               
                 Group 
                 Structural feature 
                 (mN-m) 
                 (mTesla) 
                 (mTesla) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Control 
                 No outward pillar structure 
                 347 
                 499 
                 456 
               
               
                 Group 
               
               
                 Embodiment 1 
                 Outward pillar structure at 
                 376 
                 595 
                 553 
               
               
                   
                 −45 degrees 
               
               
                 Embodiment 2 
                 Outward pillar structure at 
                 372 
                 592 
                 550 
               
               
                   
                 −40 degrees 
               
               
                 Embodiment 3 
                 Outward pillar structure at 
                 376 
                 586 
                 544 
               
               
                   
                 −35 degrees 
               
               
                 Embodiment 4 
                 Outward pillar structure at 
                 367 
                 581 
                 539 
               
               
                   
                 −30 degrees 
               
               
                 Embodiment 5 
                 Outward pillar structure at 
                 381 
                 588 
                 547 
               
               
                   
                 −25 degree 
               
               
                 Embodiment 6 
                 Outward pillar structure at 
                 384 
                 587 
                 546 
               
               
                   
                 −20 degrees 
               
               
                 Embodiment 7 
                 Outward pillar structure at 
                 374 
                 585 
                 544 
               
               
                   
                 −15 degrees 
               
               
                 Embodiment 8 
                 Outward pillar structure at 
                 374 
                 576 
                 535 
               
               
                   
                 −10 degrees 
               
               
                 Embodiment 9 
                 Outward pillar structure at 
                 378 
                 579 
                 538 
               
               
                   
                 −5 degrees 
               
               
                 Embodiment 
                 Outward pillar structure at 0 
                 369 
                 580 
                 539 
               
               
                 10 
                 degree 
               
               
                 Embodiment 
                 Outward pillar structure at 5 
                 372 
                 581 
                 540 
               
               
                 11 
                 degrees 
               
               
                 Embodiment 
                 Outward pillar structure at 
                 373 
                 583 
                 542 
               
               
                 12 
                 10 degrees 
               
               
                 Embodiment 
                 Outward pillar structure at 
                 359 
                 578 
                 537 
               
               
                 13 
                 15 degrees 
               
               
                 Embodiment 
                 Outward pillar structure at 
                 362 
                 586 
                 545 
               
               
                 14 
                 20 degrees 
               
               
                 Embodiment 
                 Outward pillar structure at 
                 365 
                 588 
                 547 
               
               
                 15 
                 25 degrees 
               
               
                 Embodiment 
                 Outward pillar structure at 
                 376 
                 589 
                 548 
               
               
                 16 
                 30 degree 
               
               
                 Embodiment 
                 Outward pillar structure at 
                 371 
                 587 
                 545 
               
               
                 17 
                 35 degrees 
               
               
                 Embodiment 
                 Outward pillar structure at 
                 373 
                 590 
                 548 
               
               
                 18 
                 40 degrees 
               
               
                 Embodiment 
                 Outward pillar structure at 
                 376 
                 589 
                 546 
               
               
                 19 
                 45 degrees 
               
               
                   
               
             
          
         
       
     
     Based on the data in Table 2, the maximum torque, the magnetic flux and the magnetic flux in Z axis of each embodiment having the outward pillar structures  13  are greater than those of the electrical rotor and stator structure of the control group having no outward pillar structure. Among all, the embodiment has the outward pillar structure  13  at −20 degrees producing the upmost maximum torque; and at −45 degrees the highest magnetic flux and the highest magnetic flux in Z axis. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.