Patent Publication Number: US-2023163645-A1

Title: Motor assembly

Description:
TECHNICAL FIELD 
     The present disclosure relates to a motor assembly. 
     BACKGROUND ART 
     In general, a motor is a device that implements a driving force by an interaction between a stator and a rotor. Basically, overall structures of the stator and the rotor are the same. 
     However, types of motors are distinguished based on a principle that the rotor rotates by the interaction between the stator and the rotor. In addition, the types of motors are also distinguished based on a type or a phase of power applied to a stator coil. In addition, the types of motors are also distinguished based on a method the stator coil is wound. For example, there are a DC variable voltage motor, an AC 3-phase induction motor, and the like. 
     A general structure of the motor will be described. A shaft forming a rotating shaft, the rotor coupled to the shaft, and a stator core fixed inside a housing are arranged, and the stator is installed at a predetermined spacing along a circumference of the rotor. 
     In addition, teeth are arranged on the stator core, and coils are wound around the teeth so as to form a rotating magnetic field and induce an electrical interaction with the rotor to induce rotation of the rotor. 
     Coil winding schemes are divided into concentrated winding and distributed winding. The concentrated winding is a winding scheme in which the coils are concentrated and wound in one slot, and the distributed winding is a winding scheme in which the coils are divided and wound in two or more slots. 
     In the case of the concentrated winding, a copper loss may be reduced while reducing an amount of winding compared to the distributed winding, but a change in magnetic flux density is great and a core loss or an iron loss, that is, a power loss of an iron core increases because the coils are excessively concentrated in the slot. For this reason, the coil wound in the concentrated winding scheme is generally used in a small motor. 
     Recently, a motor used in various home appliances (for example, a hair dryer, a vacuum cleaner, and the like) has undergone various developments for securing ease of assembly, securing a flow path area, and solving a spatial constraint that are required in response to a demand for miniaturization and performance improvement. 
     The cited invention (U.S. Ser. No. 16/011823, published on Dec. 20, 2018) discloses a brushless motor including a C-shaped stator core. The C-shaped stator core forms a protrusion for being in contact with a frame to suppress a radial movement. The C-shaped stator core has a structure that may reduce leakage magnetic flux and have a short magnetic flux path. 
     However, because the C-shaped stator core is composed of two pole arms and a yoke connecting the two pole arms to each other, in order to meet required output of the miniaturized motor, it is necessary to secure a gap between the two pole arms considering a diameter of the coil and the number of turns of the coil. 
     DISCLOSURE 
     Technical Problem 
     Therefore, the present disclosure is to solve the above-mentioned problem. 
     One of various tasks of the present disclosure is to provide a structure that may reduce a weight of a motor and secure a space inside the motor by independently constructing a stator core. 
     One of various tasks of the present disclosure is to provide a C-shaped independent core with an improved structure for increasing an output of a small motor to which the C-shaped independent core is applied. 
     One of various tasks of the present disclosure is to provide a motor assembly including a structure that may secure a slot area for efficiency improvement within a limited diameter when using a C-shaped independent core. 
     One of various tasks of the present disclosure is to provide a motor assembly that may secure a slot width of a C-shaped independent core as a pole shoe with an improved structure is applied thereto. 
     Technical Solutions 
     Various embodiments for solving the problem of the present disclosure provide a motor assembly including a C-shaped independent core with an improved structure that may increase a flux linkage by changing a shape of a pole shoe of the C-shaped independent core, and may secure a slot area. 
     An embodiment of the present disclosure provides a motor assembly including a C-shaped independent core with an improved structure that may secure a slot area of the C-shaped independent core by improving a shape such that a curvature of a yoke of the C-shaped independent core corresponds to a curvature of an inner circumferential surface of a motor housing. 
     An embodiment of the present disclosure provides a motor assembly including a shaft for forming a rotating shaft of a motor, a rotor coupled to the shaft, and a plurality of cores arranged along a circumference of the rotor so as to form a magnetic path, wherein each core includes pole shoes spaced apart from a circumferential surface of the rotor by a predetermined distance and surrounding at least a portion of the circumferential surface of the rotor, wherein each pole shoe has a first surface formed parallel to a radial direction of the rotor, and pole arms respectively extending from the pole shoes outwardly in the radial direction of the rotor, wherein first surfaces formed in respective pole shoes of adjacent cores among the plurality of cores are symmetrical with each other with respect to the radial direction of the rotor. 
     The pole arms may include a first pole arm and a second pole arm spaced apart from the first pole arm to correspond to a width of the core, and the pole shoes may include a first pole shoe formed on one side of the first pole arm and a second pole shoe formed on one side of the second pole arm. The core may further include a connecting portion for connecting the other side of the first pole arm and the other side of the second pole arm to each other. 
     In one example, the motor assembly may further include a motor housing for accommodating the motor therein, and the connecting portion may connect the other side of the first pole arm and the other side of the second pole arm to each other while forming a curvature corresponding to an inner circumferential surface of the motor housing. 
     Each pole shoe may include a second surface extending from one end of the first surface toward each pole arm extending from each pole shoe, and a third surface for forming a curvature corresponding to the circumferential surface of the rotor at the other end of the first surface. 
     Second surfaces of the adjacent cores among the plurality of cores may form a first angle therebetween, a virtual first line extending along the radial direction of the rotor and passing through a center of a space between the first pole shoe and the second pole shoe and a virtual second line extending along the radial direction of the rotor and passing through a center of a space between the first surfaces of the adjacent cores among the plurality of cores may form a second angle therebetween, and the first angle may be greater than the second angle. 
     An angle between a virtual first line extending along the radial direction of the rotor and passing through a center of a space between the first pole shoe and the second pole shoe and a virtual second line extending along the radial direction of the rotor and passing through a center of a space between the first surfaces of the adjacent cores among the plurality of cores may be 60 degrees. 
     In one example, a width of the first surface may be smaller than a width of the pole arm. A coil may be wound on each of the first pole arm and the second pole arm. Alternatively, a coil may be wound on the connecting portion. 
     An embodiment of the present disclosure provides a motor assembly including a shaft for forming a rotating shaft of a motor, a rotor coupled to the shaft, and a plurality of cores arranged along a circumference of the rotor so as to form a magnetic path, wherein each core includes pole shoes spaced apart from a circumferential surface of the rotor by a predetermined distance and surrounding at least a portion of the circumferential surface of the rotor, and pole arms respectively extending from the pole shoes outwardly in a radial direction of the rotor, wherein pole shoes of adjacent cores among the plurality of cores respectively have surfaces symmetrical to each other with respect to a virtual reference line orthogonal to the rotating shaft and parallel to the virtual reference line. 
     The pole arms may include a first pole arm and a second pole arm spaced apart from the first pole arm to correspond to a width of the core, and the pole shoes may include a first pole shoe formed on one side of the first pole arm and a second pole shoe formed on one side of the second pole arm. The core may further include a connecting portion for connecting the other side of the first pole arm and the other side of the second pole arm to each other. 
     In one example, the motor assembly may further include a motor housing for accommodating the motor therein, and the connecting portion may connect the other side of the first pole arm and the other side of the second pole arm to each other while forming a curvature corresponding to an inner circumferential surface of the motor housing. 
     Each of the characteristics of the above-described embodiments may be implemented in combination in other embodiments as long as it is not contradictory or exclusive to other embodiments. 
     In addition, provided is a motor assembly including a shaft for forming a rotating shaft of a motor, a rotor coupled to the shaft, and a plurality of cores arranged along a circumference of the rotor so as to form a magnetic path, wherein each core includes each pole shoe including a first surface parallel to a radial direction of the rotor, a second surface extending from the first surface, and a third surface extending from the first surface and having a curvature corresponding to a circumferential surface of the rotor, each pole arm extending outwardly in the radial direction of the rotor from the second surface, and a connecting portion for connecting the pole shoe and the pole arm to each other, wherein the cores are arranged to be spaced apart from each other, wherein first surfaces of adjacent cores are arranged to be symmetrical with each other with respect to a second line forming a predetermined angle with a virtual first line orthogonal to a rotating shaft of the shaft. 
     In addition, provided is the motor assembly in which the first line passes through a center of a space between the pole shoes of one of the plurality of cores. 
     In addition, provided is the motor assembly in which second surfaces of the adjacent cores form a first angle therebetween, the first line and the second line form a second angle therebetween, and the first angle is greater than the second angle. 
     In addition, provided is the motor assembly in which each core includes a first pole shoe disposed at one side thereof and a second pole shoe disposed at a side thereof opposite to the side where the first pole shoe is disposed. 
     In addition, provided is the motor assembly in which the first pole shoe and the second pole shoe are arranged to be spaced apart from each other. 
     In addition, provided is the motor assembly in which the cores are arranged to be spaced apart from each other at equal spacings. 
     Advantageous Effects 
     According to various embodiments of the present disclosure, as the three-phase C-shaped independent core is used, the leakage flux may be reduced and the short magnetic flux path may be included. In addition, the area between the pole arm and the pole arm for improving the efficiency may be secured within the limited diameter of the motor housing. 
     According to various embodiments of the present disclosure, as the structure of the C-shaped independent core is improved, the slot width of the C-shaped independent core may be increased, and at the same time, the limited space inside the motor housing may be effectively utilized. 
     The effects of the present disclosure are not limited to those described above, and other effects not mentioned will be clearly recognized by those skilled in the art from the description below. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG.  1    is a perspective view of a motor assembly according to an embodiment of the present disclosure. 
         FIG.  2    is an exploded perspective view of a motor assembly according to an embodiment of the present disclosure. 
         FIGS.  3  to  4    are cross-sectional views of a core and a rotor according to an embodiment of the present disclosure. 
     
    
    
     BEST MODE 
     Hereinafter, a specific embodiment of the present disclosure will be described with reference to the drawings. Following detailed description is provided to provide a comprehensive understanding of a method, an apparatus, and/or a system described herein. However, this is merely an example and the present disclosure is not limited thereto. 
     In describing embodiments of the present disclosure, when it is determined that a detailed description of a known technology related to the present disclosure may unnecessarily obscure the gist of the present disclosure, the detailed description will be omitted. In addition, terms to be described later, as terms defined in consideration of functions thereof in the present disclosure, may vary based on intentions of users and operators or customs. Therefore, the definition thereof should be made based on the content throughout this specification. Terms used in the detailed description are for illustrating the embodiments of the present disclosure only, and should not be restrictive. Unless explicitly used otherwise, the singular expression includes the plural expression. Herein, expressions such as “comprising” or “including” are intended to indicate certain features, numbers, steps, operations, elements, and some or combinations thereof, and should not be construed to exclude a presence or a possibility of one or more other features, numbers, steps, operations, elements, or some or combinations thereof other than those described. 
     In addition, in describing components of an embodiment of the present disclosure, terms such as first, second, A, B, (a), (b), and the like may be used. These terms are only for distinguishing the components from other components, and an essence, an order, or a sequence of the corresponding components are not limited by the terms. 
       FIG.  1    is a perspective view of a motor assembly according to an embodiment of the present disclosure, and  FIG.  2    is an exploded perspective view of a motor assembly according to an embodiment of the present disclosure. 
     Hereinafter, a description will be made with reference to  FIGS.  1  and  2   . 
     A motor assembly  1  according to an embodiment of the present disclosure may be used in small household appliances. As an example, the motor assembly  1  may be used in a vacuum cleaner. There are two types of vacuum cleaners: a canister type in which a nozzle for sucking dust and a dust collector for storing the dust are connected to each other with a hose, and a handy type in which the nozzle and the dust collector are formed as a single module. In the case of the handy type, because cleaning is performed while a user grips the entire cleaner module, overall miniaturization and weight reduction of the vacuum cleaner are required. 
     The motor assembly  1  may be applied to the small home appliances to meet the above-mentioned needs. 
     The motor assembly  1  of the present embodiment may include a shroud  10 , an impeller  20 , a diffuser  30 , a housing cover  40 , a core assembly  5 , and a motor housing  60 . 
     The shroud  10  may suck and guide external air. In addition, the shroud  10  may form an upper outer appearance of the motor assembly. 
     The shroud  10  may include a sucking portion  101 , an inclined portion  102 , and a third coupling portion  103 . The sucking portion  101  may be formed in a hollow ring shape at an upper end of the shroud  10 . Because the external air is introduced via the sucking portion  101 , a diameter of the sucking portion  101  may be designed in consideration of a diameter of the impeller  20 . 
     The shroud  10  may include the inclined portion  102  extending while forming a gentle curve from the sucking portion  101 . The inclined portion  102  may be formed in a shape in which a diameter thereof increases from the sucking portion  101  in an axial direction. The inclined portion  102  may form the gentle curve in order to minimize an element that may act as a resistance to a flow of air introduced via the sucking portion  101 . 
     The sucking portion  101  may be formed at one end of the inclined portion  102 , and the third coupling portion  103  may be formed at the other end of the inclined portion  102 . The third coupling portion  103  may extend outwardly in a radial direction from the other end of the inclined portion  102  to have a predetermined thickness. The third coupling portion  103  may be in contact with one surface of a second coupling portion  403  of a housing cover  40  to be described later to allow the shroud  10  and the housing cover  40  to be coupled to each other. In one example, various structures for coupling of the third coupling portion  103  and the second coupling portion  403  may be applied within the thickness of the third coupling portion  103 . 
     The impeller  20  may include a through-hole  20   a , a blade  203 , and an impeller body  201 . The impeller  20  may be installed at one side of a shaft  52 . In more detail, the impeller  20  may be installed at a side opposite to the other side of the shaft  52  where a rotor  53  is installed based on an axial direction of the shaft  52 . 
     As the shaft  52  forming a rotating shaft of a motor is coupled to the through-hole  20   a , the impeller  20  may be fixed at one side of the shaft  52 . The impeller  20  may be fixed to the shaft  52  in various schemes, for example, by a screw fastening scheme. 
     The impeller body  201  may be formed in a shape in which a circumference increases along the axial direction of the shaft  52 . The blade  203  may extend outwardly in the radial direction of the shaft  52  from an outer surface of the impeller body  201 . The blade  203  may be disposed along a longitudinal direction of the impeller body  201 . The blades  203  may be disposed to be spaced apart from each other along a circumferential direction on the outer surface of the impeller body  201 . 
     The impeller  20  of the present embodiment may be formed as a mixed flow impeller that sucks in gas such as air in the axial direction of the shaft  52  and then discharges the gas in an inclined direction between a centrifugal direction and the axial direction. 
     That is, the gas flowing into the shroud  10  via the sucking portion  101  may be guided to the motor housing  60  along the outer surface of the impeller body  201  by rotation of the blade  203 . However, embodiments of the present disclosure are not limited thereto. The impeller  20  may be formed as a centrifugal impeller that sucks in gas in the axial direction and discharges the gas in a centrifugal direction. However, in the following, for convenience of illustration, the case in which the impeller  20  is the mixed flow impeller will be mainly described. 
     The diffuser  30  may include a through-hole  30   a , a fastening hole  30   b,  a diffuser body  301 , and a vane  303 . The diffuser  30  may convert a dynamic pressure of the gas passing through the impeller  20  into a static pressure. 
     The diffuser  30  may be coupled to the shaft  52  by inserting the shaft  52  into the through-hole  30   a , and the diffuser  30  may be disposed between the impeller  20  and the rotor  53 . Therefore, the through-hole  30   a  may be defined at a position in communication with the through-hole  20   a  of the impeller  20  when the impeller  20  and the diffuser  30  are coupled to the shaft  52 . In addition, the fastening hole  30   b  is a component for coupling the diffuser  30  to the housing cover  40 . 
     The diffuser body  301  may be formed in a shape in which a circumference increases along the axial direction of the shaft  52 . The vane  303  may extend outwardly in the radial direction of the shaft  52  from an outer surface of the diffuser body  301 . The vane  303  may be disposed along a longitudinal direction of the diffuser body  301 . The vanes  303  may be disposed to be spaced apart from each other in the circumferential direction on the outer surface of the diffuser body  301 . 
     Based on such structure, the gas flowing into the shroud  10  via the sucking portion  101  may be guided to a space between the shroud  10  and the diffuser  30  by the impeller  20 , and the gas flowing into the space between an inner surface of the shroud  10  and the diffuser  30  may be guided toward the core assembly  5  by the plurality of vanes  303 . 
     The housing cover  40  may include a through-hole  40   a , a fastening hole  40   b,  a second bearing housing  401 , a second bridge  402 , and a second coupling portion  403 . 
     The through-hole  40   a  is a component into which the shaft  52  is inserted. The through-hole  40   a  may be defined at a position in communication with the through-hole  20   a  of the impeller and the through-hole  30   a  of the diffuser when the housing cover  40 , the diffuser  30 , and the impeller  20  are coupled to the shaft  52 . 
     The fastening hole  40   b  is a component for coupling the diffuser  30  and the housing cover  40  to each other. The fastening hole  40   b  may be defined at a position in communication with the fastening hole  30   b  of the diffuser when the diffuser  30  is coupled to the housing cover  40 . 
     The second bearing housing  401  is a component for accommodating therein a second bearing  50  for supporting one side of the shaft  52 . It is preferable that the second bearing housing  401  is disposed at a center of the housing cover  40 . The second bearing  50  may be, for example, a ball bearing, and the shaft  52  may have a step recessed inwardly in the radial direction in the outer surface thereof so as to support the second bearing  50 . Alternatively, in one example, the shaft  52  may have a step protruding outwardly in the radial direction from the outer surface thereof so as to support the second bearing  50 . 
     The second coupling portion  403  extends outwardly in the radial direction of shaft  52  to have a predetermined thickness. One surface of the second coupling portion  403  may be in contact with the third coupling portion  103  of the shroud  10 , and the other surface of the second coupling portion  403  may be in contact with a first coupling portion  601  of the motor housing  60  to couple the shroud  10 , the housing cover  40 , and the motor housing  60  to each other. In one example, various structures for the coupling described above may be applied within the thickness of the second coupling portion  403 . 
     The second bridge  402  connects the second bearing housing  401  and the second coupling portion  403  to each other. A plurality of second bridges  402  may be arranged for structural stability of the housing cover  40 , and may be formed to have a predetermined thickness so as to secure rigidity thereof. 
     When the plurality of second bridges  402  are arranged while having the predetermined thickness, the plurality of second bridges  402  may act as the resistance to the flow of the external air introduced via the sucking portion  101 . Therefore, the second bridge  402  of the present embodiment forms a predetermined inclination along the longitudinal direction of the shaft  52 . As the second bridge  402  is inclined, a portion acting as the resistance to the flow of the external air introduced via the sucking portion  101  may be minimized. In addition, by guiding the flow toward the core assembly  5 , a heat generated as a current flows through a coil  56  may be cooled. 
     In one example, the diffuser  30  may be formed integrally with the housing cover  40 . However, preferably, after being manufactured separately from the housing cover  40 , the diffuser  30  may be fastened with the housing cover  40 . 
     The rotor  53  may surround a portion of the outer surface of the shaft  52 . The shaft  52  may rotate by an electromagnetic interaction between the rotor  53  and the core assembly  5 . As the shaft  52  rotates, the impeller  20  fastened to the shaft  52  may also rotate together with the shaft  52 . As the impeller  20  rotates, the external air may be sucked into the motor assembly  1 . 
     The core assembly  5  may include a core  54 , insulators  55   a  and  55   b , and the coil  56 . It is exemplified that the motor of the present embodiment is a brushless direct current motor (BLDC motor). Therefore, the core assembly  5  of the present embodiment may be disposed outwardly of the rotor  53 . 
     The core  54  is disposed along a circumference of the rotor  53  so as to form a magnetic path, and a plurality of cores may be arranged. The core  54  of the present embodiment is an independent C-shaped core formed by two pole arms that are spaced apart from each other and extend in the radial direction of the shaft  52  and a yoke for connecting the two pole arms to each other. 
     The insulators  55   a  and  55   b  may be coupled to the core  54  to surround the pole arms and the yoke of the core  54  and insulate the core  54  and the coil  56  from each other. The insulators may be formed as a first insulator  55   a  and a second insulator  55   b  so as to be easily assembled to the core  54 . 
     The motor housing  60  may include the first coupling portion  601 , a core support  603 , a first bridge  605 , and a first bearing housing  607 . 
     The first coupling portion  601 , as a component to be coupled to the second coupling portion  403  of the housing cover  40  as described above, may be formed in a hollow ring shape. In addition, the core assembly  5  may be coupled to the motor housing  60  along the axial direction of the shaft  52  while extending through the first coupling portion  601 . 
     The core support  603 , as a component to support the core assembly  5 , may extend along the longitudinal direction of the shaft  52  from the first coupling portion  601 . A seating groove  6033  may be defined in a surface of the core support  603  facing the shaft  52 . The core assembly  5  may be accommodated in the seating groove  6033 . 
     A second hole  6031  may be defined in the core support  603 . The heat generated as the current flows through the coil  56  may be dissipated via the second hole  6031 , or the external air introduced via the sucking portion  101  may be discharged through the second hole  6031  via the core assembly  5 , thereby cooling the core assembly  5 . 
     The first bearing housing  607  is a component in which a first bearing  57  for supporting one side of the shaft  52  is accommodated. Therefore, the first bearing housing  607  is preferably formed at a center of the motor housing  60 . The first bearing  57  may be, for example, the ball bearing. As the first bearing  57  and the second bearing  50  respectively support both sides of the shaft  52 , the shaft  52  may rotate stably. 
     The first bridge  605  connects the first bearing housing  607  and the core support  603  to each other. A plurality of first bridges  605  may be arranged for structural stability of the motor housing  60 , and may be formed to have a predetermined thickness so as to secure rigidity of the second bridge  402 . 
     In addition, the first bridge  605  may have a first hole  6051  defined therein. The first hole  6051  may be defined within the thickness of the first bridge  605 . When the plurality of first bridges  605  are arranged while having the predetermined thickness, the plurality of first bridges  605  may act as the resistance to the flow passing through an interior of the motor housing  60  along the longitudinal direction of the shaft  52 . Therefore, in the first bridge  605  of the present embodiment, the first hole  6051  is defined along a longitudinal direction of the first bridge  605  to minimize a portion acting as the resistance to the flow, and at the same time, secure the rigidity of the motor housing  60 . 
       FIGS.  3  to  4    are cross-sectional views of a core and a rotor according to an embodiment of the present disclosure. Hereinafter, a description will be made with reference to  FIGS.  3  and  4   . 
     The core  54  according to an embodiment of the present disclosure may include a plurality of cores along the circumference of the rotor  53 . In the present drawing, three independent cores along the circumference of the rotor  53  are illustrated. 
     The core  54  may include a first pole shoe  545  and a second pole shoe  547  that are spaced apart from an outer circumferential surface of the rotor  53  by a predetermined distance to surround at least a portion of the outer circumferential surface of the rotor  53  and form a first surface  5471  parallel to the radial direction of the rotor  53 , a first pole arm  541  and a second pole arm  543  extending outwardly in the radial direction of the rotor  53  from the pole shoes  545  and  547 , respectively, and a connecting portion  542  for connecting the first pole arm  541  and the second pole arm  543  to each other. 
     That is, the core  54  of the present embodiment is an independent C-shaped core including the two pole arms, a yoke for connecting the other sides of the pole arms to each other, and the pole shoes respectively formed on one sides of the pole arms. Therefore, the first pole arm  541  and the second pole arm  543  are spaced apart from each other corresponding to a width  54   w  of the core. 
     The pole shoe may be formed of the first surface  5471 , a second surface  5472 , and a third surface  5473 . The first surface  5471  may be formed parallel to the radial direction of the rotor  53 . More specifically, referring to (b) in  FIG.  3   , the first surface  5471  may extend along the radial direction of the rotor  53  and be formed parallel to a virtual second line L 2  passing through a center of the rotor  53 . The second line L 2 , as a virtual reference line orthogonal to the rotating shaft of the shaft, may be defined as a line passing through a center of a space between first surfaces of adjacent cores among the plurality of cores. 
     In addition, a width of the first surface  5471  is preferably smaller than a width of the pole arm. Because when the width of the first surface  5471  is greater than the width of the pole arm, the width of the first surface  5471  should be directed toward the second surface  5472  when considering the predetermined distance at which the pole shoe and the rotor  53  are spaced apart from each other, which may increase leakage flux between the adjacent cores. 
     Accordingly, the width of the first surface  5471  may be smaller than the width of the pole arm, and accordingly, the second surface  5472  may extend from one end of the first surface  5171  toward the pole arm in a straight line. In addition, the third surface  5173  may form a curvature corresponding to the circumferential surface of the rotor  53  at the other end of the first surface  5171 . 
     Relationships between the respective pole shoes and the respective pole arms of the adjacent cores will be described with reference to (b) in  FIG.  3   . The respective first surfaces of the cores may be formed symmetrical with each other with respect to the second line L 2 . More specifically, as the plurality of cores are arranged along the circumference of the rotor, a first pole shoes  545   a  of one of the among the plurality of cores may be disposed adjacent to a second pole shoe  547   b  of one of the remaining cores. Because the plurality of cores have the same shape and configuration, the cores will be distinguished from each other using “a” and “b” below to identify a component of each core. 
     As described above, the first pole shoe  545   a  and the second pole shoe  547   b  are spaced apart from the rotor  53  by the predetermined distance and are disposed adjacent to each other along the circumference of the rotor  53 . A first surface  5471   a  of the first pole shoe may be disposed symmetrically to a first surface  547  lb of the second pole shoe, and, may be preferably parallel to the second line L 2 . As the surfaces parallel to each other and facing each other are formed between the pole shoes of the adjacent cores as described above, the width  54 W of the core may be increased while maintaining a flux linkage between the cores. 
     In addition, a first angle A 1  is formed between a second surface  5472   a  of the first pole shoe and a second surface  5472   b  of the second pole shoe. 
     The first angle A 1  may be larger than a second angle A 2  to be described later. The second angle A 2  may be defined as an angle between a virtual first line L 1  and the second line L 2  extending along the radial direction of the rotor while passing through a center of a space between the first pole shoe  545  of one of the plurality of cores and the second pole shoe  547 . The first line L 1 , as a virtual reference line orthogonal to the rotating shaft of the shaft, may be defined as a line passing through a center of the space between the first pole shoe  545  and the second pole shoe  547  of the cores. 
     In the present embodiment, the second angle A 2  may preferably be 60 degrees. This is because the core of the present embodiment preferably has the three independent cores at equal spacings along the circumference of the rotor. 
     In one example, the connecting portion  542  may connect the other side of the first pole arm  541  and the other side of the second pole arm  543  to each other while forming a curvature corresponding to an inner circumferential surface of the motor housing  60 . As the connecting portion  542  is formed with the curvature corresponding to the inner circumferential surface of the motor housing  60 , the winding area WA of the core  54  may be further secured. In addition, unnecessary gaps that may occur in the connecting portion and the inner circumferential surface of the motor housing when the connecting portion connects the two pole arms to each other in a straight line may be prevented. 
     That is, as in the present embodiment, the connecting portion  542  may form the curvature corresponding to the inner circumferential surface of the motor housing  60 , thereby not only effectively utilizing the inner space of the motor assembly, but also securing the winding area WA of the core. 
     The winding area WA of the core may mean an area of the coil that may be wound on the core. The area of the coil may be defined differently depending on the number of times the coil is wound on the core and a diameter of the coil. However, as described above, it is important to secure the winding area WA within the limited space for the miniaturization of the motor and the improvement of the motor performance. 
     As described above, the motor assembly of the present embodiment discloses the core of the improved structure that may secure the winding area WA. In one example, the winding area WA may be set differently depending on the size of the motor, but in a case of a motor of the same size, a width between the pole arm and the pole arm must be widened in order to increase the winding area WA. 
     In the present embodiment, because the first surfaces of the adjacent pole shoes are symmetrical with each other with respect to the virtual second line L 2  and are formed as parallel surfaces, the core width  54 W may be effectively secured. In addition, as the connecting portion  542  forms the curvature corresponding to the inner circumferential surface of the motor housing  60 , the core width  54 W may be secured. 
     Although various embodiments of the present disclosure have been described in detail above, those with ordinary skill in the technical field to which the present disclosure belongs will understand that various modifications are possible with respect to the above-described embodiments without departing from the scope of the present disclosure. Therefore, the scope of rights of the present disclosure should not be limited to the described embodiments and should be defined by the claims to be described later as well as equivalents thereof.