Patent Publication Number: US-2023140359-A1

Title: Motor assembly and cleaner including same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application PCT/KR2021/007633, filed Jun. 17, 2021, and claims foreign priority to Korean application 10-2020-0093357 filed Jul. 27, 2020, the disclosures of which are incorporated herein by reference in their entireties. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure relates to a motor assembly and a cleaner including the same, and more particularly, to a motor assembly with an improved structure for reducing high-frequency noise and improving its performance by allowing a stator formed as one continuous body to have a limited width ratio of a body area to that of a connection area, and a cleaner including the same. 
     2. Description of Related Art 
     A general motor may be a device that obtains a rotational force from electrical energy, and include a stator and a rotor. The stator and the rotor may electromagnetically interact with each other to rotate the rotor. 
     A motor assembly including the motor may be used in various home appliances by using the rotational force of the motor, and may be used, for example, in a cleaner, a fan, a washing machine, or the like. Among these home appliances, the cleaner may be a device that suctions air on a surface to be cleaned, separates dust or pollutant from the suctioned air, collect the same, and discharges purified air to the outside of its body. 
     The home appliance such as the cleaner has been required to be smaller and lighter and to simultaneously have improved performance, and the motor assembly of the cleaner thus needs to have reduced noise and increased suction power while having a smaller size. 
     In particular, it has been difficult for a small motor assembly having a diameter of 60 mm or less to wind a coil on the stator and assemble the motor assembly, and there has been a need for its structural improvement for smooth air flow from an impeller to an outlet. 
     In addition, a natural frequency of the stator may be formed in a range of a resonance frequency determined by a rotation frequency of the motor assembly, and in this case, high-frequency noise caused by a resonance phenomenon may occur, thus lowering stability of the motor. 
     SUMMARY 
     According to an embodiment of the present disclosure, a motor assembly includes: a rotor rotatable about a rotating shaft; a stator formed as one continuous body, and including a plurality of teeth areas, a plurality of body areas disposed outside the plurality of teeth areas and having a first width, with the plurality of teeth areas extending from the plurality of body areas in a direction toward the rotating shaft, and a plurality of connection areas connecting the plurality of body areas with each other; and a coil wound on each of the plurality of teeth areas, wherein each of the plurality of connection areas includes a bending point having a second width of 0.05 or more and 0.25 or less of the first width, and is in contact with another connection area based on the bending point. 
     In this case, each of the plurality of body areas may be bent twice in the direction toward the rotating shaft. 
     Meanwhile, one connection area among the plurality of connection areas may have a protruding area disposed in an area in contact with another connection area, and another connection area in contact with the one connection area among the plurality of connection areas may have a receiving area positioned opposite to the protruding area and receiving the protruding area. 
     Meanwhile, the motor assembly may be rotataboe at 30,000 to 200,000 revolutions per minute (RPM). 
     Meanwhile, the rotor may have four poles or more of magnet. 
     Meanwhile, the stator may have a diameter of 50 mm or less. 
     Meanwhile, the motor assembly may further include an insulator surrounding the stator, wherein the coil is wound on the insulator. 
     Meanwhile, the motor assembly may further include: an impeller having a plurality of blades and connected to the rotating shaft; and a housing including an outlet configured to discharge air suctioned into the impeller and supporting the stator. 
     In this case, the coil may be suppliable with a three-phase current and be delta-connected, and the outlet may be configured to discharge air to the outside of an outer circumferential surface of the motor assembly. 
     According to another embodiment of the present disclosure, a cleaner includes: a cleaner body; a suction head configured to suction a foreign material on a surface to be cleaned into the cleaner body; and a motor assembly disposed in the cleaner body and configured to provide suction power to the suction head, wherein the motor assembly includes: a rotor rotatable about a rotating shaft; a stator formed as one continuous body, and including a plurality of teeth areas, a plurality of body areas disposed outside the plurality of teeth areas and having a first width, with the plurality of teeth areas extending from the plurality of body areas in a direction toward the rotating shaft, and a plurality of connection areas connecting the plurality of body areas with each other; and a coil wound on each of the plurality of teeth areas, wherein each of the plurality of connection areas includes a bending point having a second width of 0.05 or more and 0.25 or less of the first width, and is in contact with another connection area based on the bending point. 
     In this case, one connection area among the plurality of connection areas may have a protruding area disposed in an area in contact with another connection area, and another connection area in contact with the one connection area among the plurality of connection areas may have a receiving area positioned opposite to the protruding area and receiving the protruding area. 
     Meanwhile, the motor assembly may be rotatable at 30,000 to 200,000 revolutions per minute (RPM). 
     Meanwhile, the stator may have a diameter of 50 mm or less. 
     Meanwhile, the cleaner may further include: an impeller having a plurality of blades and connected to the rotating shaft; and a housing including an outlet to discharge air suctioned into the impeller and supporting the stator. 
     In this case, the coil may be supplied with a three-phase current and be delta-connected, and the outlet may be configured to discharge air to the outside of an outer circumferential surface of the motor assembly. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       above and other aspects, features, and advantages of certain embodiments of the present disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG.  1    is a perspective view of a cleaner including a motor assembly according to an embodiment of the present disclosure. 
         FIG.  2    is a perspective view of the motor assembly according to an embodiment of the present disclosure. 
         FIG.  3    is an exploded perspective view of the motor assembly according to an embodiment of the present disclosure. 
         FIG.  4    is a plan view of a stator before being bent according to an embodiment of the present disclosure. 
         FIG.  5    is an enlarged cross-sectional view of area “A” of  FIG.  4   . 
         FIG.  6    is a table showing a natural frequency of the stator based on a ratio of a first width to a second width. 
         FIG.  7    is a plan view of the stator on which a coil is wound according to an embodiment of the present disclosure. 
         FIG.  8 A  is a view showing a connection method of the coil of the stator. 
         FIG.  8 B  is a view showing the connection method of the coil of the stator. 
         FIG.  9    is a cross-sectional view of the motor assembly according to an embodiment of the present disclosure. 
         FIG.  10    is the cross-sectional view of the motor assembly according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments described below are illustratively provided to assist in understanding of the present disclosure, and it is to be understood that the present disclosure may be variously modified and executed unlike the embodiments described herein. In describing the present disclosure, omitted is a detailed description of a case where it is decided that the detailed description for the known functions or configurations related to the present disclosure may unnecessarily obscure the gist of the present disclosure. Further, the accompanying drawings are not illustrated to scale, and sizes of some of components may be exaggerated to assist in the understanding of the present disclosure. 
     A term used in this specification and the claims is selected in consideration of its function in the present disclosure. However, this term may be changed based on intentions of those skilled in the art to which the present disclosure pertains, legal or technical interpretations, and emergences of new technology. In addition, some terms are arbitrarily selected by the applicant. This term may be interpreted to have the meaning defined in this specification, and if there is no specific definition of the term, it may be interpreted based on a general content of this specification and common technical knowledge in the art. 
     In describing the present disclosure, a sequence of each operation should be understood as non-restrictive unless a preceding operation in the sequence of each operation needs to logically and temporally precede a subsequent operation. That is, except for the above exceptional case, the essence of the present disclosure is not affected even when a process described as the subsequent operation is performed before a process described as the preceding operation, and the scope of the present disclosure should also be defined regardless of the sequences of the operations. 
     In the present disclosure, an expression “have,” “may have,” “include,” “may include” or the like, indicates the existence of a corresponding feature (for example, a numerical value, a function, an operation or a component such as a part), and does not exclude the existence of an additional feature. 
     Terms such as “first,” “second,” and the like, may be used to describe various components, and the components are not to be interpreted to be limited to the terms. These terms may be used to distinguish one component from another component. For example, a “first” component may be named a “second” component and the “second” component may also be similarly named the “first” component, without departing from the scope of the present disclosure. 
     In addition, terms such as “front end,” “rear end,” “upper surface,” “lower surface,” “side surface,” “left side,” “right side,” “upper portion,” “lower portion,” “area,” and the like, used in the present disclosure are defined based on the drawings. The shapes and positions of respective components are not limited to these terms. 
     In addition, this specification describes components necessary for describing each embodiment of the present disclosure, and the present disclosure is not necessarily limited thereto. Accordingly, some components may be changed or omitted, and other components may be added. In addition, the components may be distributed and arranged in different independent devices. 
     Furthermore, the embodiment of the present disclosure is described in detail with reference to the accompanying drawings and the contents shown in the accompanying drawings, and the present disclosure is not limited or restricted to the embodiments. 
     Various embodiments of the present disclosure provide a motor assembly with an improved structure for reducing noise and improving its performance, and a cleaner including the same. 
     According to a motor assembly and a cleaner including the same in various embodiments of the present disclosure, it is possible to reduce noise of the motor assembly and improve its driving performance through disclosed configurations, solve noise problems that occur when the cleaner is driven, and improve its suction power. 
     Hereinafter, the present disclosure is described in more detail with reference to  FIGS.  1  through  10   . 
       FIG.  1    is a perspective view of a stick-type cleaner  1  including a motor assembly  100  according to an embodiment of the present disclosure. 
     Referring to  FIG.  1   , a cleaner including the motor assembly  100  according to an embodiment of the present disclosure may be the stick-type cleaner  1 . However, the present disclosure is not limited thereto, and the motor assembly  100  according to an embodiment of the present disclosure may be applied to various devices. For example, the cleaner  1  according to an embodiment of the present disclosure may be an upright-type or handy-type cleaner. 
     In addition, the motor assembly  100  according to an embodiment of the present disclosure may be applied to various home appliances in addition to the cleaner. Hereinafter, the description exemplifies the stick-type cleaner  1  including the motor assembly  100 . 
     The cleaner  1  may include a cleaner body  10  and a suction head  30 . The cleaner  1  may include a stick  20  connecting the cleaner body  10  and the suction head  30  with each other, and a handle part  40  connected to the cleaner body  10 . 
     The handle part  40  may be a part coupled to the cleaner body  10 , and provided for the user to manipulate the cleaner  1  by holding the handle part. The handle part  40  may include a manipulation device (not shown), and the user may control the cleaner  1 . 
     The suction head  30  may be positioned at a lower portion of the cleaner body  10  and disposed to be in contact with a surface to be cleaned. The suction head  30  may introduce dust or pollutant on the surface to be cleaned into the cleaner body  10  by using suction power generated from the motor assembly  100  in contact with the surface to be cleaned. 
     The cleaner body  10  may include a dust collector  11  and a driving device  12  disposed therein. The dust collector  11  may perform a function of collecting dust by separating a foreign material from air suctioned by the suction head  30 . 
     The driving device  12  may include the motor assembly  100  driving the cleaner  1 . The motor assembly  100  may generate power to generate the suction power inside the cleaner body  1 . 
       FIG.  2    is a perspective view of the motor assembly  100  according to an embodiment of the present disclosure; and  FIG.  3    is an exploded perspective view of the motor assembly  100  according to an embodiment of the present disclosure. 
     Referring to  FIGS.  2  and  3   , the motor assembly  100  may include: a motor including a stator  130 , a rotor  140  and housings  151  and  154 ; an impeller  110  coupled to a rotating shaft  141  of the rotor  140  to generate an air flow; and an impeller cover  120  covering the impeller  110  and guiding air suctioned by the impeller  110 . 
     In addition, although not shown in  FIGS.  2  or  3   , the motor assembly  100  may include a substrate (not shown) controlling the motor assembly  100 . 
     The motor may include the stator  130 , the housings  151  and  154  coupled to the stator  130 , and the rotor  140  rotatably disposed inside the stator  130 . 
     The stator  130  may generate magnetic flux when a current is applied to a coil wound on the stator  130 . The stator  130  may include an insulator  139  surrounding the stator  130 , and a coil  135  may be wound on an outer surface of the insulator  139 . 
     A space for accommodating the rotor  140  may be positioned in a center of the stator  130 . The rotor  140  may electromagnetically interact with the stator  130 . The rotor  140  may include the rotating shaft  141  and bearings  142  and  143 . 
     The rotating shaft  141  may be rotated when the rotor  140  electromagnetically interacts with the stator  130 . 
     The bearings  142  and  143  may include the first bearing  142  coupled to an upper side of the rotating shaft  141  and the second bearing  143  coupled to a lower side of the rotating shaft  141 . 
     The first bearing  142  may be disposed between the first housing  151  and the rotating shaft  141  to support the rotating shaft  141  to be rotated while a rotational axis of the rotating shaft  141  is fixed. 
     The second bearing  143  may be disposed between the second housing  154  and the rotating shaft  141  to support the rotating shaft  141  to be rotated while the rotational axis of the rotating shaft  141  is fixed. 
     The housings  151  and  154  may be coupled to the outside of the stator  130 , and respectively coupled to the bearings  142  and  143  to support the rotating shaft  141  and the stator  130 . The housings  151  and  154  may include the first housing  151  coupled to one side of the stator  130  and the second housing  154  coupled to the other side of the stator  130 . 
     The first housing  151  and the second housing  154  may be coupled with each other while having the rotor  140  and the stator  130  interposed therebetween. The rotor  140  may be disposed inside the stator  130  as the first housing  151  and the second housing  154  are coupled with each other. 
     The first housing  151  may include a first bearing seating part  152  on which the first bearing  142  is seated, and a first coupling part  153  extending in an axial direction and coupled to the second housing  154 . 
     The first housing  151  may have a substantially cylindrical shape, and the first coupling part  153  may extend from the first housing  151  in the axial direction. The plurality of first coupling parts  153  may be spaced apart from each other in a circumferential direction of the first housing  151 . For example, as shown in  FIG.  3   , three first coupling parts  153  may be provided, and the number of the first coupling parts  153  is not limited thereto. 
     The first housing  151  may include an outlet  159  discharging air suctioned into the impeller  110 , and the first housing  151  may guide suctioned air from the impeller  110  to the outlet  159 . The outlet  159  is described in detail with reference to  FIGS.  9  and  10   . 
     The second housing  154  may include a second bearing seating part  155  on which the second bearing  143  is seated and a second coupling part  156  coupled with the first coupling part  153  of the first housing  151 . 
     The number of the second coupling parts  156  may correspond to the number of the first coupling parts  153 . The first coupling part  153  and the second coupling part  156  may be coupled with each other by any of various known methods. For example, the first coupling part  153  and the second coupling part  156  may be screw-coupled with each other by using a bolt  157 . 
     The motor assembly  100  may include the impeller  110  and the impeller cover  120 . The impeller  110  may be coupled to the rotating shaft  141  of the rotor  140  to generate the air flow. The impeller cover  120  may cover the impeller  110 . 
     The impeller  110  may include a shaft coupling part  113  to which the rotating shaft  141  is coupled. The impeller  110  may be rotated together with the rotating shaft  141  when the rotating shaft  141  is mounted into the shaft coupling part  113 . 
     The impeller  110  may include a plurality of blades  111  generating the air flow. 
     The impeller cover  120  or  54  may be spaced apart from the impeller  110  or  53  at a predetermined distance. 
       FIG.  4    is a plan view of the stator  130  before being bent according to an embodiment of the present disclosure. 
     Referring to  FIG.  4   , the stator  130  may be formed as one continuous body, and have a plurality of teeth areas  131 , a plurality of body areas  132 , and a plurality of connection areas  133 . 
     The plurality of teeth areas  131  may be areas extending from the body area  132  in one direction, and the extending one direction may be a direction toward the rotating shaft  141  after being bent. 
     The coil  135  may be wound on the plurality of teeth areas  131 . The plurality of teeth areas  131  may be disposed adjacent to the rotor  140  by extending toward the rotating shaft  141 , and the rotor  140  and the stator  130  may electromagnetically interact with each other by the current flowing in the coil  135  wound on each of the plurality of teeth areas  131 , thereby rotating the rotor  140 . 
     The plurality of body areas  132  may be disposed outside the plurality of teeth areas  131 , support the plurality of teeth areas  131 , and correspond to a yoke area of a general stator. 
     Each of the plurality of body areas  132  may be bent twice in the direction of the rotating shaft  141 . A shape of the stator  130  in which the plurality of connection areas  133  are bent and connected with each other may thus have a polygonal cross-section. 
     For example, as shown in  FIG.  4   , the plurality of body areas  132  may include six areas, and in this case, the bent areas of other body areas  132  adjacent to each other may be connected to each other, and the stator  130  may have a hexagonal or dodecagonal cross-section based on a length of the bent area. 
     The plurality of connection areas  133  may connect the plurality of body areas  132  with each other, and the plurality of connection areas  133  may each include a bending point  138 . In addition, the stator  130  may be formed as one continuous body. 
     The stator  130  may have a structure in which electrical steel sheets forming one continuous body are punched, stacked, and bent for both ends thereof to be connected with each other. The connection area  133  configuring one continuous body together with the plurality of body areas  132  may be positioned between the plurality of body areas  132 . The stator  130  bent into one continuous body may also be referred to as a “chain core type.” 
     In a bending process of the stator  130 , the bending point  138  of the connection area  133  may be bent, and a surface of both ends of the connection area  133  adjacent to the bending point  138  may come into contact with an opposite surface of the other connection area  133 . 
     One connection area  133  in which another adjacent connection area  133  is not positioned among the plurality of connection areas  133  may have a protruding area  136  disposed in an area in contact with another connection area  133 , and another connection area  133  in which another adjacent connection area  133  is not positioned and which is bent to be in contact with the connection area  133  having the protruding area  136  among the plurality of connection areas  133  may be positioned opposite to the protruding area  136  and have a receiving area  137  receiving the protruding area  136 . 
     The protruding area  136  and the receiving area  137  may respectively have concavo-convex shapes to correspond to each other, and when the receiving area  137  receives the protruding area  136 , the two areas may be welded to connect both the ends of the stator  130 . 
     The rotor  140  and rotating shaft  141  of the motor assembly  100  may be rotated at a high speed, generate vibration, and noise may occur here based on a natural frequency of the stator  130  and the number of poles and rotations of the motor. 
     Compared with a structure in which a plurality of discontinuous stator parts are coupled with each other to configure one stator  130 , the stator  130  of the present disclosure may be formed as one continuous body and have a bent structure, thereby preventing damage and lower performance caused by the vibration, and effectively adjusting the natural frequency of the stator  130 . 
     The natural frequency of the stator  130  may be adjusted to prevent a resonance phenomenon of the motor assembly  100 . The natural frequency of the stator  130  may be increased by changing a material of the electrical steel sheet of the stator  130 , by coupling and fixing an additional structure to the stator  130 , or through a reinforcement process. However, there is a limit to a correction range, and it is difficult to avoid the frequency of the high-speed motor. 
     It is possible to adjust a width of the connection area  133  and that of the body area  132  of the stator  130  formed as one continuous body as another method of adjusting the natural frequency of the stator  130 , and the description describes a range of an adjustable width in detail. 
       FIG.  5    is an enlarged cross-sectional view of area “A” of  FIG.  4   ; and  FIG.  6    is a table showing the natural frequency of the stator  130  based on a ratio of a first width H 1  to a second width H 2 . 
     Referring to  FIG.  5   , in a cross-section of the stator  130  in a direction perpendicular to the rotational axis of the rotating shaft  141 , each width of the plurality of body areas  132  may be the first width H 1  and each width of the bending points  138  of the plurality of connection areas  133  may be the second width H 2 . 
     Taking the motor assembly  100  of the cleaner as an example, the motor assembly  100  including the four-pole rotor  140  of the cleaner used for home use may typically have  30 ,000 to 200,000 revolutions per minute (RPM). In this case, the rotation frequency of the motor assembly  100  may be 500 Hz or more and 3,333 Hz or less, and a frequency generation section of electromagnetic induced noise of the motor assembly  100  may be 2,000 Hz to 13,333 Hz. 
     Referring to  FIG.  6   , a result of measuring a natural frequency f 0  of the stator  130  may be confirmed by adjusting the ratio of the first width H 1  to the second width H 2 . 
     When considering a frequency margin of about 10% in a result value of  FIG.  6   , the ratio of the first width H 1  to the second width H 2  to avoid the frequency generation section of the electromagnetic induced noise may be designed to be 25% or less. 
     If the ratio of the first width H 1  to the second width H 2  is 5%, stress applied to the bending point  138  of the plurality of connection areas  133  may be up to 140 MPa in an operation of bending the stator  130  formed as one continuous body. However, the electrical steel sheet which is the material of the stator  130  may have yield stress of around 215 MPa. Therefore, when the ratio of the first width H 1  to the second width H 2  is 5% or less, a safety factor of the stator  130  may thus drop to 50% or less, and the bending point  138  may be cut off in the bending process. Accordingly, a stable lower limit of the ratio of the first width H 1  to the second width H 2  may be set to 5%. 
     Therefore, when the ratio of the first width H 1  to the second width H 2  is in a range of 5% to 25% (i.e., 0.05 to 0.25), the stator  130  may be safely bent, and avoid a resonance frequency section. It is possible to prevent high-frequency noise occurring due to the resonance phenomenon by avoiding the resonance frequency section, and stably control and drive a driving operation of the motor assembly  100 . 
     Although not shown in the experimental result of  FIG.  6   , the motor assembly  100  of the cleaner used for home use may have the revolutions per minute maintained in a similar section even when the rotor  140  included in the motor assembly  100  has two or four poles or more. Therefore, it may be expected that the resonance frequency generation section also does not deviate from a commercial range. 
       FIG.  7    is a plan view of the stator  130  on which the coil  135  is wound according to an embodiment of the present disclosure. 
     Referring to  FIG.  7   , in the cross-section of the stator  130  bent in the direction perpendicular to the rotational axis of the rotating shaft  141 , the stator  130  may have an outer diameter of H 3  mm, and the plurality of teeth of the stator  130  may have an inner width of H 4  mm. 
     The stator  130  included in the motor assembly having a smaller size according to an embodiment of the present disclosure may have outer diameter H 3  of 50 mm or less. 
     In a manufacturing process of the motor, the stator  130  may require a winding process in which a needle of a winding machine winds the coil  135  on the teeth area  131 . In the conventional stator  130 , the electrical steel sheets may be stacked on each other to achieve the stator  130  in a final form, whose both ends are connected with each other, the needle of the winding machine may be disposed in a center of the plurality of teeth areas  131  of the stator  130 , and the needle or the stator  130  may be moved to wind the coil  135 . 
     The plurality of teeth areas  131  of the stator  130  may be six or more for a three-phase motor having four or more poles of the rotor  140 . However, the needle of the winding machine may be required to wind the coil  135  while being moved between the plurality of teeth areas  131 , and the small stator  130  having the outer diameter H 3  of 50 mm or less may thus have a smaller distance H 4  in the center of the plurality of teeth areas  131 . It is difficult for the winding machine to wind the coil  135  on the plurality of teeth areas  131  while being moved between the plurality of teeth areas  131 , and there is thus a limit to make the stator  130  have a smaller size. 
     However, the stator  130  of the present disclosure may be formed in such a manner that the stator  130  is formed by being stacked as one continuous body and bent around the bent part. Therefore, it is possible to sufficiently secure a space between the plurality of teeth areas  131  in an operation before the stator is bent, the needle of the winding machine may easily wind the coil  135 , and this manner may thus be efficiently applied to the small stator  130 . 
       FIGS.  8 A and  8 B  are views each showing a connection method of the coil  135  of the stator  130 . 
     Referring to  FIGS.  8 A and  8 B , the coil  135  according to an embodiment of the present disclosure may be supplied with a three-phase current, and may be Y-connected or delta-connected. 
       FIG.  8 A  shows the Y-connection method in which the three-phase coil  135  wound on the stator  130  of the motor assembly  100  may be Y-connected, and a neutral point may be required at each center of both ends of each coil  135 . The motor assembly  100  using such a connection method may have a structure of  FIG.  9   . 
     On the other hand,  FIG.  8 B  shows the delta connection of the three-phase coil  135  wound on the stator  130  of the motor, and both the ends of the coil are interconnected, thus omitting the neutral point. The motor assembly  100  according to an embodiment of the present disclosure using such a connection method may have a structure of  FIG.  10   . 
       FIGS.  9  and  10    are cross-sectional views of the motor assembly according to an embodiment of the present disclosure. 
     Referring to  FIG.  9   , the motor assembly may further include a neutral member  56 . 
     The neutral member  56  may correspond to the neutral point of the Y-connected three-phase coil  135 . The neutral member may be disposed on an outer circumferential surface of a stator  52 , the stator  52  may thus have a large volume and a greater weight. Therefore, air discharged from an outlet  55  may be discharged toward the neutral member  56 , thus preventing a smooth air flow. 
     Referring to  FIG.  10   , the motor assembly  100  according to an embodiment of the present disclosure may not include the conventional neutral member  56  using the delta connection. In addition, a space where the stator  130  is disposed between the first housing  151  and second housing  154  of the motor assembly  100 , including the stator  130  having a smaller size according to an embodiment of the present disclosure, may have a smaller diameter. 
     As a result, there is no component that obstructs the air flow in an air flow direction of the outlet  159 , and the outlet  159  disposed on an upper part of the stator  130   may discharge air to the outside of an outer circumferential surface of the motor assembly  100 . 
     In addition, there is no component that obstructs the air flow in an air flow direction of the outlet  55 , an amount of air discharged per unit time may thus be increased. Simultaneously, an amount of air introduced into the motor assembly per unit time may also be increased, thus improving performance of the motor assembly. In addition, resistance to the air flow direction may be reduced to reduce the noise. Therefore, noise reduction and further improved performance may be expected for the same power consumption of the motor of the motor assembly  100  and the same revolutions per minute. 
     In the motor assembly  100  according to an embodiment of the present disclosure, the housings  151  and  154  may guide air from the impeller  110  to the outlet  159 . In this case, the outlet  159  may be formed as one body with the first housing  151  disposed on the upper part, and in this case, the first housing  151  may have a diameter of  55  mm or less. 
     The motor assembly  100  including the neutral member  56  shown in  FIG.  9    may have an individual guide structure for guiding air to the outlet  55  positioned below the impeller cover  54  of the impeller  53 . However, the first housing  151  shown in  FIG.  10    may support the stator  130  and include the outlet  159  simultaneously to guide air from the impeller  110  to the outlet  159 . 
     Although the various embodiments of the present disclosure have been individually described hereinabove, the respective embodiments are not necessarily implemented alone, and may also be implemented so that configurations and operations thereof are combined with those of one or more other embodiments. 
     In addition, although the embodiments are shown and described in the present disclosure as above, the present disclosure is not limited to the above mentioned specific embodiments, and may be variously modified by those skilled in the art to which the present disclosure pertains without departing from the gist of the present disclosure as claimed in the accompanying claims. These modifications should also be understood to fall within the scope and spirit of the present disclosure.