Patent Publication Number: US-10326325-B2

Title: Rotor and motor including the same

Description:
This application claims the benefit of U.S. Patent Provisional Application No. 62/215,708, filed on Sep. 8, 2015, Korean Patent Application No. 10-2016-0063069, filed on May 23, 2016, and Korean Patent Application No. 10-2016-0063072, filed on May 23, 2016, which are hereby incorporated by reference as if fully set forth herein. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a rotor and a motor including the same, and more particularly to a rotor that is capable of more efficiently using magnetic flux from magnets and a motor including the same. 
     Discussion of the Related Art 
     A motor is a device that drives a rotor using electromagnetic force generated between the rotor and a stator. Generally, the rotor is rotated relative to the stator. 
     Motors may be used in various devices. For example, a motor may be used as a driving device for rotating the drum of a washing machine. That is, the rotor is connected to a shaft of the drum such that rotation of the rotor is converted into the rotation of the drum to perform washing. 
     The motor, particularly the rotor, used in the washing machine transmits relatively strong force to the drum via the shaft. For this reason, the rigidity of the rotor is critical, and the rotor is required to be highly efficient. 
     A conventional rotor used in the washing machine is generally configured such that a plurality of magnets is fixed to a rotor frame, which is made of an iron plate, in the state of being arranged in the circumferential direction of the rotor frame. That is, the iron plate serves as a rotor core, and performs a back yoke function. However, magnetic flux may leak from the rotor frame, since the rotor frame is made of an iron plate. The magnetic flux may leak outward in the radial direction, and has no relation to the rotation of the rotor. Consequently, it is difficult to provide a high-efficiency motor. 
     In addition, the thickness of the iron plate is relatively large in order to secure the rigidity of the rotor frame. As a result, the weight of the rotor is increased. 
     Therefore, there is a high necessity for a rotor having high efficiency and high output and a motor including the same. 
     Meanwhile, noise may be generated during the rotation of the rotor. In addition, unnecessary vibration may also be generated during rotation of the rotor. The vibration of the rotor may be generated as the result of torque riffle. 
     Therefore, there is a high necessity for a rotor having low noise and vibration and a motor including the same. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a rotor and a motor including the same that substantially obviate one or more in problems due to limitations and disadvantages of the related art. 
     One object of the present invention is to provide a rotor that can be easily manufactured and a motor including the same. 
     Another object of the present invention is to provide a rotor that can be manufactured through a single injection molding process and a motor including the same. 
     Another object of the present invention is to provide a rotor that is capable of minimizing the leakage of magnetic flux, thereby achieving high efficiency and high output and a motor including the same. 
     Another object of the present invention is to provide a rotor that exhibits sufficient rigidity and strength while the weight of the rotor is reduced. 
     Another object of the present invention is to provide a rotor that can be manufactured with reduced material costs and can be easily handled. 
     Another object of the present invention is to provide a rotor having a cooling structure that is capable of limiting the increase in temperature of a stator or cooling the stator. 
     Another object of the present invention is to provide a rotor configured such that rotor cores and magnets are coupled to a rotor frame at uniform intervals. 
     Another object of the present invention is to provide a rotor configured such that rotor cores and magnets are securely coupled to a rotor frame. 
     Another object of the present invention is to provide a rotor configured such that a plurality of magnets is disposed in a spoke arrangement so as to be magnetized inward and outward in the radial direction. 
     A further object of the present invention is to provide a rotor configured such that magnets are entirely magnetized. 
     Additional advantages, objects, and features will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice. The objectives and other advantages may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, in accordance with an aspect of the present invention, a rotor includes a plurality of rotor cores, a plurality of magnets magnetized such that magnetic flux is formed in the circumferential direction, the magnets and the rotor cores being alternately arranged in the circumferential direction, a coupler connected to a shaft, and a rotor frame including a coupler base connected to the coupler, an extension base extending from the coupler base in the radial direction, and a rotary base extending from the extension base in the axial direction of the shaft for supporting the rotor cores and the magnets while surrounding the rotor cores and the magnets, wherein the coupler base, the extension base, and the rotary base are integrally formed by injection molding, and the rotor frame is coupled to the coupler, the rotor cores, and the magnets, and wherein the extension base is provided with crossing ribs that cross in the radial direction. 
     The extension base may include a crossing zone formed between radial inner tips of the crossing ribs and radial outer tips of the crossing ribs. 
     A crossing point of the crossing ribs may be adjacent to the radial inner tips of the crossing ribs. 
     The extension base may be provided with a plurality of radial ribs extending in the radial direction and arranged in the circumferential direction at uniform intervals. 
     A specific one of the radial ribs may extend through the crossing point in the radial direction, and the crossing ribs may be provided between radial ribs formed at circumferentially opposed sides of the specific radial rib. 
     A vertical through part may be formed between each of the crossing ribs and a corresponding one of the radial ribs. 
     Six sections may be formed about the crossing point by the three adjacent radial ribs and the crossing ribs, and the through parts may be formed in four of the sections, excluding two of the sections having the smallest area and located inward in the radial direction. 
     The extension base may include a non-crossing zone located outside the crossing zone in the radial direction and connected to the rotary base. 
     The non-crossing zone may be connected to the rotary base via a step part. 
     The crossing zone and the non-crossing zone may be partitioned by circumferential ribs formed in the circumferential direction. 
     Radial ribs may be continuously connected from the coupler base to the rotary base, and the radial ribs may be arranged in the circumferential direction at uniform intervals. 
     A specific one of the radial ribs may extend through the crossing point of the crossing ribs in the radial direction, and the crossing ribs may be provided between radial ribs formed at circumferentially opposed sides of the specific radial rib. 
     The specific radial rib may extend through the circumferential center of a specific one of the rotor cores, and an adjacent radial rib may extend through the circumferential center of a rotor core that is two cores away from the specific rotor core in the circumferential direction. 
     The non-crossing zone may be provided with a radial rib formed at a middle part between the two adjacent radial ribs so as to extend through the circumferential center of a corresponding one of the rotor cores. 
     The rotor frame may include a reference bottom surface and a reference top surface that define an external shape thereof, and the radial ribs may protrude downward from the reference bottom surface. 
     The radial ribs and the circumferential ribs may protrude upward from the reference top surface. 
     The non-crossing zone may be connected to the rotary base via a step part, and the radial ribs may extend to a radial tip of the rotary base via the step part. 
     The coupler base and the extension base may be partitioned by support ribs formed in the circumferential direction. 
     No vertical through parts may be formed in the coupler base and the non-crossing zone. 
     The rotary base may be formed so as to surround top surfaces, bottom surfaces, and outer circumferential surfaces of the rotor cores and the magnets excluding inner circumferential surfaces of the rotor cores and the magnets that define gaps between the rotor cores and a stator and between the magnets and the stator. 
     In another aspect of the present invention, a rotor includes a plurality of rotor cores, a plurality of magnets magnetized such that magnetic flux is formed in the circumferential direction, the magnets and the rotor cores being alternately arranged in the circumferential direction, a coupler connected to a shaft, and a rotor frame including a coupler base connected to the coupler, an extension base extending from the coupler base in the radial direction, and a rotary base extending from the extension base in the axial direction of the shaft (substantially in the vertically upward direction) for supporting the rotor cores and the magnets while surrounding the rotor cores and the magnets, wherein the coupler base, the extension base, and the rotary base are integrally formed by injection molding, and the rotor frame is coupled to the coupler, the rotor cores, and the magnets, and wherein the extension base includes a heat dissipation zone connected to the coupler base and having a plurality of through parts for heat dissipation and a reinforcement zone connected to the rotary base for increasing the strength of connection with the rotary base. 
     No through parts may be formed in the reinforcement zone. Alternatively, the total area of through parts formed in the reinforcement zone may be smaller than the total area of through parts formed in the heat dissipation zone. 
     The heat dissipation zone and the reinforcement zone may be partitioned by circumferential ribs formed in the circumferential direction. 
     In another aspect of the present invention, a rotor includes a plurality of rotor cores, a plurality of magnets magnetized such that magnetic flux is formed in the circumferential direction, the magnets and the rotor cores being alternately arranged in the circumferential direction, a coupler connected to a shaft, and a rotor frame including a coupler base connected to the coupler, an extension base extending from the coupler base in the radial direction, and a rotary base extending from the extension base in the axial direction of the shaft for supporting the rotor cores and the magnets while surrounding the rotor cores and the magnets. 
     The coupler base, the extension base, and the rotary base may be integrally formed by injection molding, and the rotor frame may be coupled to the coupler, the rotor cores, and the magnets. Consequently, the rotor frame may be very easily manufactured. 
     The rotary base may be formed so as to surround the top surfaces, the bottom surfaces, and the outer circumferential surfaces of the rotor cores and the magnets excluding the inner circumferential surfaces of the rotor cores and the magnets that define gaps between the rotor cores and the stator and between the magnets and the stator. Consequently, it is possible to provide a rotor, particularly an outer type rotor, configured such that the rotor cores and the magnets are more securely coupled to the rotor frame. 
     The rotary base may be formed so as to surround the top surfaces, the bottom surfaces, and the inner circumferential surfaces of the rotor cores and the magnets, excluding the outer circumferential surfaces of the rotor cores and the magnets that define gaps between the rotor cores and the stator and between the magnets and the stator. Consequently, it is possible to provide a rotor, particularly an inner type rotor, configured such that the rotor cores and the magnets are more securely coupled to the rotor frame. 
     The inner circumferential surfaces or the outer circumferential surfaces of the rotor cores and the magnets that define the gap may be exposed outward. That is, the inner circumferential surfaces or the outer circumferential surfaces that define the gap may not be surrounded by the rotor frame. As a result, the gap may be uniform. 
     The inner circumferential surfaces or the outer circumferential surfaces of the rotor cores that define the gap may be exposed outward, and the rotary base may be formed so as to surround the inner circumferential surfaces or the outer circumferential surfaces of the magnets that define the gap. Consequently, one surface of each of the rotor cores that define the gap may not be surrounded by the rotor frame, and one surface of each of the magnets that define the gap may be surrounded by the rotor frame. As a result, the magnets may be supported inward or outward in the radial direction. 
     The circumferential width of each of the magnets may be larger than the radial width of each of the magnets, and the magnets may be magnetized such that magnets provided at opposite sides of a specific rotor core generate magnetic flux in opposite directions. Magnetic flux directed from opposite sides of one rotor core toward the circumferential center of the rotor core may be concentrated in the radial direction through the rotor core. 
     The rotary base may include a lower cover for covering the bottom surfaces of the rotor cores and the magnets, an upper cover for covering the top surfaces of the rotor cores and the magnets, and a side cover extending from the lower cover to the upper cover for covering the inner circumferential surfaces or the outer circumferential surfaces of the rotor cores and the magnets. Consequently, the exposure of the rotor cores and the magnets may be minimized, excluding the parts of the rotor cores and the magnets that define the gap. In addition, most parts of the rotor cores and the magnets may be surrounded by the rotor frame, whereby the rotor cores and the magnets may be securely supported in the rotor frame. 
     The rotor cores may be provided with fixing holes, into which fixing pins provided in an injection mold are inserted to fix the rotor cores in the mold. As a result, the rotor cores may remain in position during injection molding. 
     The lower cover or the upper cover may be provided with cover holes, through which the fixing holes are exposed outward as the result of the fixing pins being separated from the rotor frame after injection molding of the rotor frame. 
     The inner diameter of the cover holes may be larger than the inner diameter of the fixing holes. The reason for this is that a space, in which the lower cover or the upper cover will be formed, must be provided by the fixing pins. 
     The fixing holes may be formed through the rotor cores from the tops to bottoms thereof, and insertion parts, which extend into the fixing holes so as to reach the fixing pins, may be formed at the upper cover or the lower cover located at the side opposite to the cover holes, in which case the cover holes need not be formed. 
     After injection molding, the insertion parts may extend into the fixing holes of the rotor cores, whereby the rotor cores may be more securely fixed in the rotor frame. 
     The rotor cores may be provided with fixing holes, into which fixing pins provided in the injection mold are inserted to fix the rotor cores in the mold, and the fixing pins may be integrally formed with the rotor frame by injection molding of the rotor frame. 
     That is, the fixing pins may be provided so as to support the rotor cores before and after injection molding. The fixing pins may be made of a plastic material in order to minimize the increase in weight of the rotor frame due to the fixing pins. In addition, a process of separating the fixing pins from the rotor frame after injection molding is omitted, whereby it is possible to very easily manufacture the rotor frame. Furthermore, support posts extending through the lower cover and the upper cover may be formed by the fixing pins and the insertion parts. Consequently, it is possible to more securely fix the rotor core than in the case in which only the insertion parts are provided. 
     The fixing pins may include fixing pin insertion parts, which are inserted into the fixing holes, and fixing pin support parts, which support the rotor cores in the mold. The radius of the fixing pin support parts may be larger than the radius of the fixing pin insertion parts. 
     One fixing hole may be formed in each of the rotor cores. Consequently, the rotor cores may be securely fixed in the mold, and the rotor cores may be securely fixed to the rotor frame even after injection molding. 
     Any one of the edge between the lower cover and side cover and the edge between the upper cover and side cover may be provided with edge holes, through which the magnets are exposed outward. 
     The number of edge holes may be equal to the number of magnets. 
     The edge holes may be formed as the result of support seats, for fixing the magnets in the mold in the radial direction of the rotor and the axial direction of the shaft, being separated from the rotor frame after injection molding of the rotor frame. 
     Portions of the bottom surfaces and the side surfaces of the magnets or portions of the top surfaces and the side surfaces of the magnets may be exposed outward through the edge holes. 
     The support seats may be provided to fix the magnets in position. Consequently, the magnets as well as the rotor cores may be fixed in the mold in position, whereby the rotor cores and the magnets may be stably fixed. 
     In addition, the support seats support the magnets in the radial direction while defining a space in which the upper cover or the lower cover will be formed. Consequently, the magnets and rotor cores may be very securely fixed in the radial direction as well as in the vertical direction and the circumferential direction. 
     In another aspect of the present invention, a rotor includes a plurality of rotor cores, a plurality of magnets magnetized such that magnetic flux is formed in the circumferential direction, the magnets and the rotor cores being alternately arranged in the circumferential direction, a coupler connected to a shaft, and a rotor frame including a coupler base connected to the coupler, an extension base extending from the coupler base in the radial direction, and a rotary base extending from the extension base in the axial direction of the shaft for supporting the rotor cores and the magnets while surrounding the rotor cores and the magnets, wherein the coupler base, the extension base, and the rotary base are integrally formed by injection molding, and the rotor frame is coupled to the coupler, the rotor cores, and the magnets, wherein the rotary base includes a lower cover for covering the bottom surfaces of the rotor cores and the magnets, an upper cover for covering the top surfaces of the rotor cores and the magnets, and a side cover extending from the lower cover to the upper cover for covering the inner circumferential surfaces or the outer circumferential surfaces of the rotor cores and the magnets that do not form gaps between the rotor cores and the stator and between the magnets and the stator, wherein the rotor cores are provided with fixing holes, into which fixing pins provided in an injection mold are inserted to fix the rotor cores in the mold during injection molding, and wherein the lower cover or the upper cover is provided with cover holes, through which the fixing holes are exposed outward. 
     The inner diameter of the cover holes may be larger than the inner diameter of the fixing holes such that portions of the top surfaces of the bottom surfaces of the rotor cores around the fixing holes are exposed outward through the cover holes. 
     The fixing holes may be formed through the rotor cores from the tops to bottoms thereof. Insertion parts, which extend into the fixing holes so as to reach the fixing pins, may be formed at the upper cover or the lower cover located at the side opposite to the cover holes, in which case the cover holes need not be formed. 
     The rotor cores may be formed such that the circumferential width of the rotor cores is gradually increased outward in the radial direction from the center of the rotor frame. The magnets may be formed such that the circumferential width of the magnets is uniform outward in the radial direction from the center of the rotor frame, whereby the magnets are in tight contact with adjacent rotor cores. 
     Any one of the edge between the lower cover and side cover and the edge between the upper cover and side cover may be provided with edge holes, through which the magnets are exposed outward. 
     The number of edge holes may be equal to the number of magnets. The edge holes may be formed as the result of support seats, for fixing the magnets in the mold in the radial direction of the rotor and the axial direction of the shaft, being separated from the rotor frame after injection molding of the rotor frame. 
     The cover holes and the edge holes may be provided to form a space in which the rotor cores and the magnets are fixed in the mold during injection molding and the molding material surrounds the rotor cores and the magnets. 
     In another aspect of the present invention, a rotor includes a plurality of rotor cores, a plurality of magnets magnetized such that magnetic flux is formed in the circumferential direction, the magnets and the rotor cores being alternately arranged in the circumferential direction, a coupler connected to a shaft, and a rotor frame including a coupler base connected to the coupler, an extension base extending from the coupler base in the radial direction, and a rotary base extending from the extension base in the axial direction of the shaft (substantially in the vertically upward direction) for supporting the rotor cores and the magnets while surrounding the rotor cores and the magnets, wherein the coupler base, the extension base, and the rotary base are integrally formed by injection molding, and the rotor frame is coupled to the coupler, the rotor cores, and the magnets, wherein the rotary base includes a lower cover for covering the bottom surfaces of the rotor cores and the magnets, an upper cover for covering the top surfaces of the rotor cores and the magnets, and a side cover extending from the lower cover to the upper cover for covering the outer circumferential surfaces of the rotor cores and the magnets that do not form gaps between the rotor cores and the stator and between the magnets and the stator, wherein the rotor cores are provided with fixing holes, into which fixing pins provided in an injection mold are inserted to fix the rotor cores in the mold during injection molding, wherein the lower cover or the upper cover is provided with cover holes, through which the fixing holes are exposed outward, and wherein insertion parts, which extend into the fixing holes so as to reach the fixing pins, may be formed at the upper cover or the lower cover located at the side opposite to the cover holes, in which case the cover holes need not be formed. 
     In another aspect of the present invention, a rotor includes a plurality of rotor cores, a plurality of magnets magnetized such that magnetic flux is formed in the circumferential direction, the magnets and the rotor cores being alternately arranged in the circumferential direction, a coupler connected to a shaft, and a rotor frame including a coupler base connected to the coupler, an extension base extending from the coupler base in the radial direction, and a rotary base extending from the extension base in the axial direction of the shaft (substantially in the vertically upward direction) for supporting the rotor cores and the magnets while surrounding the rotor cores and the magnets, wherein the coupler base, the extension base, and the rotary base are integrally formed by injection molding, and the rotor frame is coupled to the coupler, the rotor cores, and the magnets, wherein the rotary base includes a lower cover for covering the bottom surfaces of the rotor cores and the magnets, an upper cover for covering the top surfaces of the rotor cores and the magnets, and a side cover extending from the lower cover to the upper cover for covering the outer circumferential surfaces of the rotor cores and the magnets that do not form gaps between the rotor cores and the stator and between the magnets and the stator, wherein the rotor cores are provided with fixing holes, into which fixing pins provided in an injection mold are inserted to fix the rotor cores in the mold during injection molding, and wherein the fixing pins are integrally coupled to the rotor frame by injection molding of the rotor frame. 
     In the above embodiments, fixing pins for fixing the rotor cores and the magnets in the mold may be provided at the lower parts of the rotor cores and the magnets. In addition, the fixing pins may be further provided at the upper parts of the rotor cores and the magnets. 
     Some fixing pins (e.g. the lower fixing pins) may be inserted into the fixing holes of the rotor cores so as to fix the rotor cores, and some fixing pins (e.g. the upper fixing pins) may push the top surfaces of the rotor cores so as to fix the rotor cores. Cover holes may be formed in the upper cover and the lower cover of the lower frame by the fixing pins. 
     Portions of the top surfaces of the rotor cores may be exposed outside the rotor frame through the upper cover by the provision of some cover holes (e.g. cover holes formed by the upper fixing pins). Portions of the bottom surfaces of the rotor cores may be exposed outside the rotor frame through the lower cover by the provision of some cover holes (e.g. cover holes formed by the lower fixing pins). 
     The upper fixing pins may support the magnets as well as the rotor cores. That is, one upper fixing pin may simultaneously support one rotor core and a magnet adjacent to the rotor core. On upper fixing pin may simultaneously push a portion of the upper surface of one rotor core and a portion of the upper surface of a magnet adjacent to the rotor core. 
     The lower fixing pins may support the lower parts of the rotor cores, and the support seats may support the lower parts of the magnets. 
     Consequently, the upper and lower parts of the rotor cores and the magnets may be supported in the mold by the upper fixing pins, the lower fixing pins, and the support seats. As a result, the positions and attitudes of the rotor cores and the magnets may be accurately maintained. 
     In another aspect of the present invention, a rotor includes a plurality of rotor cores, a plurality of magnets magnetized such that magnetic flux is formed in the circumferential direction, the magnets and the rotor cores being alternately arranged in the circumferential direction, a coupler connected to a shaft, and a rotor frame formed by injection molding, the rotor frame being integrally coupled to the rotor cores, the magnets, and the coupler, wherein each of the rotor cores includes a pole shoe for defining a gap between each of the rotor cores and a stator and a rotor core body, and the rotor core body is provided with an outer aperture having a radial width greater than a circumferential width such that portions of side surfaces of corresponding ones of the magnets located at opposite sides of each of the rotor cores are exposed. 
     The outer aperture may be formed in each side of the rotor core body in the circumferential direction. 
     An inner aperture may be formed in the rotor core body between the outer apertures. 
     The inner aperture may include a first inner aperture provided inward in the radial direction and a second inner aperture provided outward in the radial direction. 
     The first inner aperture and the second inner aperture may be partitioned by a first core rib. 
     The second inner aperture may be partitioned from the rotor frame outward in the radial direction by a second core rib. 
     The circumferential widths of the first inner aperture and the second inner aperture may be larger than the radial widths of the first inner aperture and the second inner aperture. 
     The circumferential width of the first inner aperture may be smaller than the circumferential width of the second inner aperture. 
     The radial width of the second core rib may be larger than the radial width of the first core rib. 
     The outer aperture and the second inner aperture may be partitioned by the second core rib in the circumferential direction. 
     During injection molding of the rotor frame, support posts may be formed in the outer aperture, the first inner aperture, and the second inner aperture such that the support posts vertically extend through the outer aperture, the first inner aperture, and the second inner aperture to support each of the rotor cores. 
     A fixing hole, into which a fixing pin for fixing each of the rotor cores in the mold during injection molding is inserted, may be formed in the rotor core body between the pole shoe and the inner aperture. 
     After injection molding of the rotor frame, the fixing pin may be separated from the fixing hole, whereby a cover hole may be formed in the rotor frame. 
     The fixing pin may be integrally coupled to the rotor frame by injection molding of the rotor frame. 
     A core coupling part may be formed between the fixing hole and the inner aperture to form each of the rotor cores by stacking. 
     At least two core coupling parts maybe formed outside the fixing hole. 
     In a further aspect of the present invention, a rotor includes a plurality of rotor cores, a plurality of magnets magnetized such that magnetic flux is formed in the circumferential direction, the magnets and the rotor cores being alternately arranged in the circumferential direction, a coupler connected to a shaft, and a rotor frame formed by injection molding, the rotor frame being integrally coupled to the rotor cores, the magnets, and the coupler, wherein each of the rotor cores includes a pole shoe for defining a gap between each of the rotor cores and a stator and a rotor core body, and an outer aperture, by which the side surface formed at the radial tip of each of the magnets does not contact the rotor core body, is formed such that the magnetic flux from the side surfaces of the magnets is concentrated toward the stator in the radial direction via the rotor cores. 
     The outer aperture may be formed in each side of each of the rotor cores in the circumferential direction. 
     An inner aperture may be formed between the outer apertures, the inner aperture being partitioned from the outer apertures in the circumferential direction by a core rib, the inner aperture being provided in each of the rotor cores. 
     The radial width of the inner aperture may be larger than the thickness of the core rib. 
     The features of the above embodiments may be applied in combination with those of other embodiments unless the features are contradictory or exclusive. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the present invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the present invention and together with the description serve to explain the principle of the present invention. In the drawings: 
         FIG. 1  is a view showing a rotor according to an embodiment of the present invention when viewed from above; 
         FIG. 2  is a view showing the rotor of  FIG. 1  when viewed from below; 
         FIG. 3  is a partial sectional view showing a rotor including a rotor core according to an embodiment of the present invention; 
         FIG. 4  is a partial sectional view showing a rotor including a rotor core according to another embodiment of the present invention; 
         FIG. 5  is a view showing the rotor core of  FIG. 4  inserted into an injection mold for a rotor frame; 
         FIG. 6  is a partial sectional view showing a rotary base in the rotor frame; 
         FIG. 7  is a sectional view showing the rotor of  FIG. 1 ; 
         FIG. 8  is a view showing the rotor of  FIG. 1  in the state of being overturned; and 
         FIG. 9  is a view showing the rotor of  FIG. 1  when viewed from above. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
     First, the structure of a rotor that may be applied to an embodiment of the present invention will be described with reference to  FIGS. 1 and 2 . 
     A rotor  100  includes a coupler  200  for transmitting rotational force from the rotor  100  to the outside. The coupler  200  may be connected to a shaft. When the shaft is connected to a drum of a washing machine, the rotational force is transmitted from the rotor  100  to the drum. 
     The coupler  200  may be made of a metal material for high torque and high speed transmission. The coupler  200  may be located in the central part of the rotor  100 . In the case in which the rotor  100  is a rotor of the washing machine, the coupler  200  may be coupled to the shaft through a serrated structure. Consequently, the coupler  200  may also be called a serrated bushing. 
     For rotation of the rotor  100 , a rotating field must be generated by electromagnetic action between the rotor  100  and a stator. To this end, the rotor  100  includes a rotor core  500  and a magnet  400 . 
     In this embodiment, the rotor core  500  and the magnet  400  are disposed so as to be spaced apart from the center of the rotor  100 , i.e. the coupler  200 , in the radial direction. Consequently, a structure for simultaneously rotating the rotor core  500  and the magnet  400  and rotating the coupler  200  is needed. That is, a structure for supporting and integrally coupling the rotor core  500 , the magnet  400 , and the coupler  200  is needed. To this end, in this embodiment, the rotor  100  may include a rotor frame  300 . 
     The rotor core  500 , which forms a magnetic flux path, may be formed by stacking iron sheets. Consequently, the rotor core  500  may be made of a magnetic metal material. The magnet  400  may be made of various materials. Specifically, the magnet  400  may be a ferrite magnet. That is, the magnet  400  may be a permanent magnet. 
     The weight of the rotor  100  is increased due to the weight of the rotor core  500  and the magnet  400 . In addition, it is required for the rotor frame  300 , which simultaneously supports the coupler  200 , the rotor core  500 , and the magnet  400 , to have sufficient rigidity. As a result, the weight of the rotor  100  is further increased due to the weight of the rotor frame  300 . 
     Consequently, it is difficult to reduce the weight of the rotor  100  while satisfying high efficiency, high performance, and required rigidity. This means that it is very desirable to minimize the weight of the rotor  100  as long as the given conditions are satisfied. 
     In this embodiment, the rotor frame  300  may be made of a plastic material in order to prevent the increase in weight of the rotor  100  due to the rotor frame  300 . That is, the rotor frame  300  may be formed by injection molding. The rotor frame  300  may be made of a plastic material not only to reduce the weight of the rotor frame  300  but also to reduce the leakage of magnetic flux through the rotor frame  300 . The reason for this is that magnetic flux readily leaks through a conventional rotor frame, which is made of an iron plate. 
     In addition, the coupler  200 , the rotor core  500 , and the magnet  400  may be fixed to the rotor frame  300  at the time that the rotor frame  300  is injection-molded. That is, the coupler  200 , the rotor core  500 , and the magnet  400  may be inserted into an injection mold, and then a molding material, such as a plastic material, for forming the rotor frame  300  is injected into the injection mold. In other words, the rotor may be formed so as to have a single body by insert molding. Consequently, an additional structure or process for fixing the magnet  400 , the rotor core  500 , and the coupler  200  may not be required. As a result, the rotor  100  may be easily manufactured. 
     The rotor frame  300  may include a coupler base  310  connected to the coupler  200 , an extension base  320  extending from the coupler base  310  in the radial direction, and a rotary base  330  extending from the extension base  320  in the axial direction of the shaft. 
     The rotary base  330  may support the rotor core  500  and the magnet  400  while surrounding the rotor core  500  and the magnet  400 . 
     The rotary base  330  may extend from the radial tip of the extension base  320  substantially in the vertical direction. When the rotor frame  300  is in the state shown in  FIG. 1 , the rotary base  330  may extend vertically downward. Consequently, the coupler base  310  and the extension base  320  may define the top surface of the rotor frame  300 , and the rotary base  330  may define the side surface of the rotor frame  300 . The bottom surface of the rotor frame  300  may have a flat circular container shape due to the bases  310 ,  320 , and  330 . 
     Hereinafter, an embodiment related to the structure of the rotor core  500  and the arrangement between the rotor core  500  and the magnet  400  will be described with reference to  FIG. 3 .  FIG. 3  shows an embodiment of an outer rotor. In addition,  FIG. 3  is a partial horizontal sectional view of the rotor core  500  and the magnet  400 . 
     In this embodiment, the rotor  100  may include a plurality of rotor cores  500  and a plurality of magnets  400 . The rotor cores  500  may be individually formed. In addition, the magnets  400  may be individually formed. Consequently, the rotor cores  500  may be rotor core segments, and the magnets  400  may be magnet segments. 
     Each of the magnets  400  may be magnetized so as to have a single magnetic pole. The magnets  400  and the rotor cores  500  may be alternately arranged in the circumferential direction of the rotor  100 . For example, 48 rotor cores (rotor core segments) and 48 magnets (magnet segments) may be provided. 
     The magnets  400  may generate magnetic flux in various directions. However, magnetic flux for rotating the rotor may be directed to the stator. For example, in the case in which the rotor is an outer rotor, radial magnetic flux directed to the stator, which is located inside the rotor in the radial direction, may be effective. The greater the magnetic flux directed outward in the radial direction of the rotor, therefore, the lower the efficiency of the motor. 
     Magnetic flux is generated by a magnetic material. When the magnetic flux encounters a non-magnetic material during the flow of the magnetic flux, the magnetic flux is distorted. That is, the non-magnetic material may act as magnetic flux resistance, which may be a flux barrier. Consequently, the effective magnetic flux of the magnets  400  may be increased through the magnetic flux resistance. 
     In this embodiment, the rotor cores  500  may be configured so as to concentrate magnetic flux toward the stator. For example, the rotor cores  500  may be configured so as to concentrate magnetic flux inward in the radial direction. In addition, the weight of the rotor cores  500  may be reduced in order to reduce the weight of the rotor  100  and to reduce material costs. 
     Each magnet  400  may be configured such that the radial width of each magnet  400  is larger than the circumferential width thereof. In the case in which the rotational directions constituted by the radial centers of the magnets  400  are the same, therefore, a relatively large number of magnets  400  may be provided. In addition, the area of circumferential side surfaces  410  and  420  of each magnet  400  may be larger than the area of radial side surfaces (a radial inner side surface  430  and a radial outer side surface  440 ) of each magnet  400 . Consequently, the magnets  400  may concentrate magnetic flux to adjacent rotor cores  500 . 
     As shown in  FIG. 3 , each rotor core  500  includes a pole shoe  510  and a rotor core body  530 . The pole shoe  510  is a part that defines a gap between the rotor core and the stator. The pole shoe  510  may extend from the tip of the rotor core body  530  to the circumferentially opposed sides of the rotor core body  530 . In the case in which the rotor is an outer rotor, the pole shoe  510  may extend from the radial inner tip of the rotor core body  530  to the circumferentially opposed sides of the rotor core body  530 . The pole shoe  510  may be formed so as to cover a portion of the radial inner side surface  430  of each adjacent magnet  400 . 
     Each rotor core  500  may include a depression  535  formed in the side opposite to the pole shoe  510  in the radial direction (e.g. in the outside in the radial direction). That is, the depression  535  may be formed in the rotor core body  530 . In the case in which the rotor is an outer rotor, the depression  535  may be formed so as to be depressed inward in the radial direction. Consequently, the volume of each rotor core  500  is reduced by the depression  535 , thereby reducing the weight of the rotor cores  500  and material costs. 
     The depression  535  may be formed so as to expose a portion of the side surface of each magnet  400 . That is, the depression  535  may be formed so as to expose a portion of the circumferential side surface of each magnet  400 . In other words, an exposed surface  410  may be formed at the radial tip of the side surface of each magnet  400  by the depression  535 . 
     The exposed surface  410  may define an aperture  350 . In other words, the exposed surface  410  may be a non-contact surface, which does not contact each rotor core  500 . Consequently, a portion of the side surface of each magnet  400  defines a contact surface  420 , which contacts a corresponding rotor core  500 , and a portion of the side surface of each magnet  400  defines the exposed surface  410 . The exposed surface  410  contacts the rotor frame  300 , which is made of a plastic material. That is, a portion of the rotor frame  300  fills the aperture  350 . Consequently, the rotor frame  300  has a magnetic flux resistance function. That is, the aperture  350  may be formed from the exposed surface  410  in the circumferential direction. 
     The radial width of the exposed surface  410  may be smaller than the radial width of the contact surface  420 . Consequently, magnetic flux is prevented from flowing through the exposed surface  410  in the circumferential direction. In other words, magnetic flux flows to the contact surface  420 , rather than to the exposed surface  410 . As a result, the magnetic flux may be concentrated inward in the radial direction. 
     The depression  535  may be formed so as to be symmetric in the circumferential direction because of the characteristics of the rotor. Consequently, uniform magnetic flux may be formed at opposite sides in the circumferential direction. In addition, vibration may be reduced, since the depression  535  has a symmetric shape. 
     In particular, each rotor core is not located in the circumferential direction between the exposed surface  410  of one magnet and the exposed surface  410  of an adjacent magnet. That is, the apertures may be successively formed in the circumferential direction. In other words, the depression  535  may be formed so as to be further depressed in the radial direction between the exposed surfaces facing each other in the circumferential direction. That is, the aperture defined by the exposed surfaces  410  may extend further inward in the radial direction. Consequently, the aperture  350  is formed between two adjacent magnets so as to have a radial width equal to or larger than the radial width of each exposed surface  410 . 
     The aperture  350  may be configured such that the radial width of the aperture  350  is the largest at the middle between adjacent magnets and is gradually decreased in the circumferential direction. The aperture  350  may have the smallest radial width at the exposed surface  410 . Consequently, it is possible to greatly reduce the generation of magnetic flux from the exposed surface in the circumferential direction. 
     Each rotor core  500  may be formed by stacking. To this end, the rotor core body  530  may be provided with a core coupling part  520  for stacking. In addition, the core coupling part  520  may be provided between the pole shoe  510  and the depression  535 . 
     The core coupling part  520  may be formed in the middle of each rotor core  500  in the circumferential direction. In addition, the inner diameter of the core coupling part  520  may be smaller than the circumferential width and the radial width of the depression  535 . The reason for this is that the core coupling part  520  has a function of reducing the area of each rotor core through which magnetic flux flows as well as a magnetic flux resistance function. If the inner diameter of the core coupling part  520  is increased, the magnetic flux flowing adjacent to the core coupling part  520  is saturated, with the result that the efficiency of each rotor core may be lowered. 
     Some of the molding material may be injected into the core coupling part  520 . As a result, each rotor core  500  may be securely fixed to the rotor frame  300 . 
     The depression  535  may be formed so as to fix each rotor core  500  to the rotor frame  300 . That is, a portion of the rotor frame  300  may be inserted into the depression  535  so as to fix and support each rotor core  500 . In other words, at least some of the molding material for forming the rotor frame may be introduced into the depression  535  during injection molding. 
     Meanwhile, the depression  535  may be formed so as to support each rotor core  500  in the mold. The reason for this is that each rotor core  500  must be located in position during injection molding. To this end, the depression  535  may include a fixing hole  536 , into which a fixing pin  660  (see  FIG. 5 ) for fixing each rotor core  500  in the mold during injection molding is inserted. That is, the fixing hole  536  may be a portion of the depression  535 . 
     The fixing pin  660  may have a circular section. Correspondingly, at least a portion of the fixing hole  536  may be circular. 
     The fixing pin, which is provided in the mold, may be perpendicularly inserted into each rotor core  500 . Subsequently, each rotor core  500  is fixed by the fixing pin. Consequently, the inner circumference of the fixing hole may have an angle of more than 180 degrees. That is, the fixing hole may be formed so as to surround the fixing pin over an angular range of more than 180 degrees. As a result, each rotor core  500  is prevented from being separated in the radial direction of the fixing pin. 
     The depression  535  may be formed over the entire height of each rotor core  500 . That is, the depression  535  may be formed so as to vertically extend through each rotor core  500 . Of course, the fixing hole  536  may be formed so as to vertically extend through each rotor core  500 . However, it is not necessary for the fixing pin to be inserted into the depression  535 , particularly the fixing hole  536 , over the entire height thereof. That is, the fixing pin may be inserted into the fixing hole  536  only to a predetermined height from the bottom of each rotor core  500 . For example, the fixing pin may be inserted into the fixing hole  536  to only half of the height of each rotor core  500 . Consequently, the molding material is not introduced into a portion of the fixing hole corresponding to the fixing pin. On the other hand, the molding material may be introduced into a portion of the fixing hole, into which the fixing pin is not inserted. Consequently, a portion of the fixing hole  536  is filled with the molding material to form a portion of the rotor frame. 
     The depression  535  may include incision parts  540  (   ) formed at opposite sides thereof. The fixing hole  536  may be formed so as to be further depressed from the incision parts  540  in the radial direction. 
     The incision parts  540  may be formed so as to be inclined in the radial direction. Consequently, the incision parts  540  may be inclined incision parts  540 . The circumferential width of each rotor core  500  is gradually increased inward in the radial direction by the incision parts  540 . As a result, magnetic flux may be stably concentrated inward in the radial direction. In addition, the molding material may be more smoothly introduced inward in the radial direction along the inclined incision parts  540 . 
     Meanwhile, the fixing pin must be prevented from falling between the incision parts  540 . Consequently, the circumferential distance between the incision parts  540  at connections with the fixing hole  536  may be smaller than the maximum diameter (inner diameter) of the fixing hole  536 . 
     In this embodiment, as previously described, the molding material may be injected into the depression excluding a portion of the depression (a portion of the fixing hole in which the fixing pin is inserted). The depression is open outward in the radial direction. Consequently, the molding material is injected from the outside in the radial direction to form a side wall of each rotor core  500 , specifically the radial outer side surface  333  of the rotary base  330 . 
     In this embodiment, however, a large amount of molding material is injected into the depression  535 . That is, the injection thickness of the depression  535  is greater than those of other parts. As a result, a portion of the rotor frame corresponding to the depression  535  may shrink when the molding material is cooled after the injection molding is completed. In other words, the side surface of the rotor frame may be nonuniform. Of course, such nonuniformity of the rotor frame may not deteriorate the performance of the rotor. Nevertheless, the nonuniform surface of the rotor frame may be regarded as a product defect. 
     Hereinafter, another embodiment related to the structure of the rotor core  500  and the arrangement between the rotor core  500  and the magnet  400  will be described with reference to  FIG. 4 .  FIG. 4  shows another embodiment of an outer rotor. In addition,  FIG. 4  is a partial horizontal sectional view of the rotor core  500  and the magnet  400 . A detailed description of the construction of this embodiment that is identical to that of the previous embodiment will be omitted. 
     In the rotor core  500  according to this embodiment, magnetic flux may be concentrated in the effective magnetic flux direction, in the same manner as in the rotor core  500  according to the previous embodiment. Furthermore, in this embodiment, injection molding efficiency may be higher than in the previous embodiment, and the rotor core  500  may be more securely fixed to the rotor frame than in the previous embodiment. 
     In this embodiment, a core rib is further included in the depression of the embodiment shown in  FIG. 3 . That is, one side of the depression shown in  FIG. 3  is not surrounded by the core. In this embodiment, however, the depression is completely surrounded by the core. That is, the aperture may be closed by a core rib formed at one side of the depression. A single closed aperture may be provided. Alternatively, a plurality of closed apertures may be provided. The apertures may be arranged in the radial direction. 
     The core rib may extend in the circumferential direction. 
     Each rotor core body  530  may contact the magnets  400  at circumferentially opposed sides thereof. A portion of each circumferential side of the rotor core body  530  may not contact a corresponding one of the magnets  400 . For example, in the case in which the rotor is an outer rotor, a portion of each radial outer side surface of the rotor core body  530  may not contact a corresponding one of the magnets  400 , thereby forming an aperture  350 . 
     In this embodiment, the aperture  350  is formed between each magnet  400  and a corresponding rotor core  500 . The aperture  350  is formed in the outside of the rotor core  500 . Consequently, the aperture  350  may be an outer aperture. The outer aperture is formed in each side of the rotor core  500 . 
     The outer aperture may be defined by the shape of the rotor core body  530 . Each circumferential tip of the rotor core body  530  may be depressed inward in the radial direction, whereby the outer aperture may be formed. 
     The circumferential width of the outer aperture may be smaller than the radial width of the outer aperture. For example, in the case in which the circumferential width of the outer aperture is about 1 mm, the radial width of the outer aperture may be about 3.2 mm. In other words, a length of about 3.2 mm of the circumferential side surface of the magnet  400  may not contact the rotor core  500 , thus forming the aperture. 
     Inner apertures  550  and  560  may be formed between the opposite outer apertures  350 . The inner apertures  550  and  560  may be located in the rotor core body  530 . 
     The inner apertures  550  and  560  may include a first inner aperture  550  and a second inner aperture  560 . The first inner aperture  550  may be located further inward than the second inner aperture  560  in the radial direction. 
     The first inner aperture  550  and the second inner aperture  560  may be partitioned from each other by a first core rib  555 . The second inner aperture  560  may be partitioned from the outside by a second core rib  565 . 
     The radial width of the first core rib  555  may be larger than the radial width of the second core rib  565 . That is, the radial width of the second core rib  565  may be minimized. The reason for this is that the second core rib  565  is provided to form an aperture through which magnetic flux does not flow. In the case in which the radial width of the second core rib  565  is large, magnetic flux is formed through the second core rib  565 , which may reduce efficiency. 
     Consequently, the second core rib  565  may have the minimum radial width that is sufficient to prevent damage by injection pressure and blanking. For example, the radial width of the first core rib  555  may be about 1.5 mm, and the radial width of the second core rib  565  may be about 1.0 mm or less. 
     Meanwhile, the second core rib  565  may extend from the circumferential center thereof to the circumferentially opposed sides thereof. The apertures  350  may be formed in the circumferentially opposed sides of the second core rib  565 . The second core rib  565  may be formed so as to have an approximate arc shape. In addition, the second core rib  565  may have the maximum radius at the circumferential center thereof. This means that the outer apertures  350  formed in the opposite sides of each rotor core  500  and the second inner aperture  560  are partitioned from each other by the second core rib  565 . That is, this means that the radially outermost side of the second inner aperture  560  is located further outward in the radial direction than the radially innermost side of each outer aperture  350 . Even when magnetic flux is formed in the outer apertures  350  in the circumferential direction, therefore, magnetic flux in the circumferential direction may be greatly reduced by the second core rib  565  and the second inner aperture  560 , which are relatively narrow. Consequently, magnetic flux may be concentrated inward in the radial direction. 
     The width or thickness of the second core rib  565  may be uniform. In the case in which the second core rib  565  is arc-shaped, the width or thickness of the second core rib  565  at the circumferential center thereof may be defined as the radial width or thickness of the second core rib  565 . In addition, the width or thickness of the second core rib  565  at the circumferentially opposed sides thereof may be defined as the circumferential width or thickness of the second core rib  565 . 
     The first core rib  555  and the second core rib  565  extend substantially in the circumferential direction. Consequently, magnetic flux flowing in the ribs may be leaking magnetic flux, rather than radial magnetic flux. For this reason, the ribs may have a minimum thickness. The reason for this is that the smaller the width of the ribs, the smaller the space in which magnetic flux can flow. 
     A portion of the rotor frame  300  fills the first inner aperture  550  and the second inner aperture  560 . Consequently, the first inner aperture  550  and the second inner aperture  560  each have a magnetic flux resistance function. The molding material fills the first inner aperture  550  from the top to bottom of the rotor core  500 . In the same manner, the molding material fills the second inner aperture  560  from the top to bottom of the rotor core  500 . 
     Consequently, support posts  351  and  352  may be respectively formed in the first inner aperture  550  and the second inner aperture  560  to support the rotor core while forming a portion of the rotor frame. The support posts may more securely support the rotor core  500  inside the rotor frame. Consequently, the rotor core  500  may be supported in the rotor frame via at least two adjacent support points. 
     In the case in which the first core rib  555  and the second core rib  565  are omitted, this embodiment may be similar to the embodiment shown in  FIG. 3 . In this embodiment, however, the space corresponding to the depression  335  shown in  FIG. 3  is partitioned into at least two spaces. That is, the space corresponding to the depression  335  is partitioned in the radial direction by the first core rib  555 , and the space outside the depression  335  in the radial direction may be partitioned by the second core rib  565 . The molding material may be injected into the partitioned spaces. That is, the molding material may be injected into a plurality of partitioned spaces, rather than into a single large space. As a result, injection molding efficiency may be improved. 
     Meanwhile, the apertures  550  and  560 , which are respectively formed by the first core rib  555  and the second core rib  565 , may reduce the volume of the rotor core  500 . In addition, the apertures  550  and  560  may have a magnetic flux resistance function. Since the apertures  550  and  560  are formed outside in the radial direction, magnetic flux generated by the magnets  400  may be concentrated inward in the radial direction. Of course, in the case in which the rotor is an inner rotor, magnet flux generated by the magnets  400  may be concentrated outward in the radial direction. 
     The molding material is introduced into the apertures  550  and  560 . For this reason, it is necessary for the apertures  550  and  560  not to be deformed during injection molding. This means that the core ribs  555  and  565  must withstand injection pressure and maintain rigidity during injection molding. Consequently, the reduction in the thickness (the radial width) of the core ribs is limited. 
     Specifically, the thickness of the core ribs may be 1.5 mm or less in consideration of magnetic flux saturation. More specifically, the thickness of the core ribs may be 1.0 mm or less. Blanking is performed to form the rotor core. At this time, the core ribs must not be damaged. Consequently, the thickness of the core ribs may be 0.5 mm in consideration of blanking. Of course, the thickness of the core ribs may be reduced further as long as the blanking process is improved or the material for the rotor core is improved. 
     The radial outer tip of the second core rib  565  may be formed so as to have the same radius as the radial outer tip of the magnet. For example, the second core rib  565  may be formed in the shape of an arc that is convex outward in the radial direction. In the same manner, the first core rib  555  may be formed in the shape of an arc that is convex outward in the radial direction. 
     The circumferential width of the first inner aperture  550  may be smaller than the circumferential width of the second inner aperture  560 . In addition, the radial width of the first inner aperture  550  may be smaller than the radial width of the second inner aperture  560 . Furthermore, the circumferential width of each of the apertures  550  and  560  may be larger than the radial width of each of the apertures  550  and  560 . 
     As a result, it is possible to greatly prevent magnetic flux from being formed at the magnet  400 , particularly the radial tip of the magnet  400 , in the circumferential direction. That is, it is possible to concentrate the magnetic flux from the magnet  400  inward in the radial direction through the rotor core  500 . 
     Meanwhile, the molding material is introduced into the first inner aperture  550  and the second inner aperture  560  during injection molding of the rotor frame. That is, the molding material is introduced into the first inner aperture  550  and the second inner aperture  560  from the top to bottom of the first inner aperture  550  and the second inner aperture  560 . The molding material, which becomes a portion of the rotor frame after injection molding, performs a function of supporting the rotor core  500 . Consequently, the rotor frame  300  includes support posts  351  and  352  extending through the apertures  550  and  560  to support the rotor core  500 . 
     The support posts  351  and  352  perform a magnetic flux resistance function and a function of supporting the rotor core  500  such that the rotor core  500  cannot be separated from the rotor frame  300 . 
     A fixing hole  536  may be formed in the rotor core  500 . The fixing hole  536  may be located inside the first inner aperture  550  in the radial direction. In addition, the fixing hole  536  may be circular. 
     A fixing pin for supporting the rotor core  500  in the mold during injection molding of the rotor frame is inserted into the fixing hole  536 . 
     The circumferential width of the fixing hole  536  may be smaller than the circumferential width of the first inner aperture  550 . If the circumferential width of the fixing hole  536  is larger than the circumferential width of the first inner aperture  550 , the radial width of the rotor core  500  at the opposite sides of the fixing hole  536  may be greatly reduced. In this case, magnetic flux saturation may occur. 
     A core coupling part  520  may be formed so as to be adjacent to the fixing hole  536 . A plurality of core coupling parts  520  may be formed around the fixing hole  536 . In particular, one fixing hole  536  may be formed in the circumferential center of the rotor core inside the fixing hole  536  in the radial direction, and two fixing holes  536  may be formed in the left and right sides of the fixing hole  536  in the circumferential direction. 
     In this embodiment, it is difficult to form the core coupling parts  520  in the outside of the rotor core  500  in the radial direction, since the inner apertures  550  and  560  are formed in the outside of the rotor core  500  in the radial direction. In particular, it is difficult to form the core coupling parts  520  in the first core rib  555  and the second core rib  565 , since the widths of the first core rib  555  and the second core rib  565  are small. Consequently, the core coupling parts  520  may be formed around the fixing hole  537  inside the first inner aperture  550  in the radial direction. 
     Hereinafter, the fixing structure of the magnets and the rotor cores and the structure of the rotor frame during injection molding of the rotor frame will be described in detail with reference to  FIGS. 5 and 6 . The rotor frame may be injection-molded as shown in  FIG. 1 . The upper and lower parts of the rotor  100  may be defined based on the state of the rotor  100  shown in  FIG. 1  (the overturned state of the rotor). In addition,  FIGS. 5 and 6  show an example in which the embodiment of the rotor cores shown in  FIG. 3  is applied. 
       FIG. 5  shows the state in which rotor cores  500  and magnets  400  are inserted into a mold, particularly a lower mold  600 . That is, the rotor cores  500  and the magnets  400  are alternately inserted into the mold in the circumferential direction. After the rotor cores  500  and the magnets  400  are inserted, an upper mold may be coupled to the lower mold  600 , and then injection molding may be performed. 
     During injection molding, the rotor cores  500  and the magnets  400  must be prevented from moving in the mold. The axial movement of the rotor cores  500  and the magnets  400  may be prevented by the mold. In addition, the circumferential and radial movement of the rotor cores  500  and the magnets  400  must be prevented. To this end, the mold may be provided with fixing pins for fixing the rotor cores  500  in the mold. In addition, the mold may be provided with support seats  620  for supporting the magnets  400 . 
     Specifically, the rotor cores  500  and the magnets  400  may be surrounded by the rotor frame  300 . That is, top surfaces  570  and  470  and bottom surfaces  571  and  471  of the rotor cores  500  and the magnets  400  may be covered by the rotor frame  300 . In addition, the radial outer side surfaces  440  of the magnets  400 , at which no gap is formed, may be covered by the rotor frame  300 . Of course, in the case in which the rotor is an inner rotor, the radial inner side surfaces of the magnets  400 , at which no gap is formed, may be covered by the rotor frame  300 . 
     First, the rotor cores  500  and the magnets  400  are inserted into the mold  600  such that the radial inner side surfaces of the rotor cores  500  and the magnets  400  contact a gap surface  640  of the mold  600 . Consequently, substantially no molding material is injected into the radial inner side surfaces of the rotor cores  500  and the magnets  400 . In addition, the rotor cores  500  and the magnets  400  are prevented from moving inward in the radial direction in the mold  600  by the gap surface  640  of the mold  600 . 
     In particular, the rotor cores  500  may be located further inward in the radial direction than the magnet  400  due to the pole shoes thereof. Consequently, some molding material may be injected between the rotor cores  500  and the magnets  400  at positions adjacent to the gap. However, the gap surface  640  of the mold  600  may be formed as rotor core gap surfaces  561  and magnet gap surfaces  652  such that the inner circumferential surfaces of the rotor cores  500  and the magnets  400  in the radial direction come into tight contact with the mold  600 . That is, the magnet gap surfaces  652  may protrude further in the radial direction than the rotor core gap surfaces  561  so as to form the gap more uniformly. 
     The rotor cores  500  and the magnets  400  are inserted into the mold such that the bottom surfaces  571  of the rotor cores  500  and the bottom surfaces  471  of the magnets  400  are spaced apart from a first bottom surface  630  of the lower mold  600  by a predetermined height. The molding material is injected into the space between the bottom surfaces  571  and the first bottom surface  630  and between the bottom surfaces  471  and the first bottom surface  630  such that the rotor frame covers the bottom surfaces of the rotor cores  500  and the magnets  400 . 
     In addition, a space is defined on the top surfaces  570  of the rotor cores  500  and the top surfaces  470  and the radial outer side surfaces of the magnets  400 . That is, a space is defined between the lower mold  600  and the upper mold. The molding material is injected into the space such that the rotor frame covers the top surfaces of the rotor cores  500  and the top surfaces and the radial outer side surfaces of the magnets  400 . 
     The lower mold  600  may be provided with fixing pin holes  610 , into which fixing pins  660  may be inserted. The fixing pins  660  may be inserted into the fixing holes  536  of the rotor cores  500 . The rotor cores  500  may be fixed in the mold by the fixing pins. Here, the shape of the fixing pins is critical. The reason for this is that the fixing pins  660  perform a function of spacing the rotor cores  500  upward from the first bottom surface  630  as well as a function of fixing the rotor cores  500 . 
     A second bottom surface  650  is formed at the upper part of the lower mold  600 . The second bottom surface  650  defines the coupler base  410  and the extension base  320  of the rotor frame  300 . In particular, the second bottom surface  650  defines a reference bottom surface  301  of the rotor frame  300 . The second bottom surface  650  may be provided with a plurality of slots. The slots are paths through which the molding material flows to form ribs. 
     The fixing pins  660  may be formed to have a cylindrical shape. In addition, each fixing pin  660  may include lower and upper cylindrical parts  661  and  662  having different radii. The lower cylindrical part  661  is inserted into a corresponding one of the fixing pin holes  610 , and the upper cylindrical part  662  is inserted into the fixing hole  536  of a corresponding one of the rotor cores  500 . The radius of the lower cylindrical part  661  of each fixing pin  660  may be larger than the radius of the upper cylindrical part  662  of each fixing pin  660 . Consequently, a support surface  663  may be formed between the lower cylindrical part  661  and the upper cylindrical part  662 . That is, a support surface  663  for supporting the bottom surface of each rotor core  500  is formed on the top surface of the lower cylindrical part  661 . In other words, the outer diameter of the lower cylindrical part  661  of each fixing pin  660  may be larger than the inner diameter of the fixing hole  536  of a corresponding one of the rotor cores  500 , and the outer diameter of the upper cylindrical part  662  of each fixing pin  660  may be smaller than the inner diameter of the fixing hole  536  of a corresponding one of the rotor cores  500 . 
     When the fixing pin  660  is inserted into the fixing pin hole  610 , the support surface  663  of the fixing pin  660  protrudes upward from the first bottom surface  630 . When the rotor core  500  is located on the support surface  663 , therefore, the bottom surface of the rotor core  500  is vertically spaced apart from the first bottom surface  630 . The molding material is injected into the space to form the bottom surface  332  of the rotary base  330 . 
     Meanwhile, the fixing pin hole  610  is formed in only a portion of the first bottom surface  630 . When the fixing pin is inserted into the fixing pin hole  610 , therefore, the molding material is not injected into the portion of the fixing pin hole  610  corresponding to the fixing pin. As a result, a cover hole  332   a  corresponding to the fixing pin  660  is formed in the bottom surface  332  of the rotary base. The reason for this is that the fixing pin is separated from the rotor frame after injection molding. 
     A portion of the bottom surface of each rotor core  500  and the fixing hole  536  are exposed outward through the cover hole  332   a  due to the difference in radius between the fixing pin  660  and the fixing hole  536 . 
     The fixing pins  660  may be separably coupled to the mold  600 . Alternatively, the fixing pins  660  may be integrally formed at the mold  600 . The rotor cores  500  may be stably supported and fixed in the mold  600  by the fixing pins  660 . The fixing pins  660  may be inserted into the respective rotor cores  500 . 
     It is very important to support the magnets  400  in the mold as well as to support the rotor cores  500  in the mold. To this end, the mold  600  may be provided with support seats  620 . 
     The support seats  620  may support the bottom surfaces and the radial outer side surfaces of the magnets  400 . In addition, the support seats  620  may be configured such that the bottom surfaces of the magnets  400  are located higher than the first bottom surface  630 . The bottom surfaces of the rotor cores  500  and the bottom surfaces of the magnets  400  may be located at the same level by the fixing pins  660  and the support seats  620 . That is, the bottom surfaces of the rotor cores  500  and the bottom surfaces of the magnets  400  may have the same height. 
     The support seats  620  may limit the movement of the magnets outward in the radial direction. When the bottom surfaces of the magnets  400  are supported by the location surfaces  621  of the support seats  620 , the radial outer side surfaces of the magnets  400  may be supported by support parts  622  provided outside the location surfaces  621  in the radial direction. 
     Each of the support parts  622  of the support seats  620  may have a trapezoidal sectional shape. That is, the upper width of each support part  622  may be larger than the lower width of each support part  622 . Consequently, the rotor frames may be more easily separated from the mold after injection molding. 
     After a plurality of magnets  400  and a plurality of rotor cores  500  are inserted into the mold  500  through the fixing pins  660  and the support seats  620 , injection molding may be performed. 
     As the result of injection molding, the rotary frame  330  surrounds the rotor cores and the magnets excluding the inner circumferential surfaces of the rotor cores and the magnets, which define gaps between the rotor cores and the stator and between the magnets and the stator. That is, the rotary frame  330  may be formed so as to surround the top surfaces, the bottom surfaces, and the outer circumferential surfaces of the rotor cores and the magnets. In the case in which the rotor is an inner rotor, the rotary frame  330  surrounds the rotor cores and the magnets excluding the outer circumferential surfaces of the rotor cores and the magnets, which define gaps between the rotor cores and the stator and between the magnets and the stator. 
     The top surface of the rotary frame  330  corresponds to the top surfaces of the rotor cores and the magnets. The bottom surface of the rotary frame  330  corresponds to the bottom surfaces of the rotor cores and the magnets. The radial outer side surface of the rotary frame  330  corresponds to the radial outer side surfaces of the rotor cores and the magnets. Since the top surface, the bottom surface, and the side surface of the rotary frame  330  are formed so as to cover the rotor cores and the magnets, the top surface, the bottom surface, and the side surface of the rotary frame  330  may be an upper cover  331 , a lower cover  332 , and a side cover  333  of the rotary frame  330 . The side cover  333  may extend from the lower cover  332  to the upper cover  331 . 
     The cover holes  332   a  are formed in the lower cover  331 . Portions of the rotor cores  500  are exposed outward through the cover holes  332   a . The cover holes  332   a  are formed by the fixing pins  660 , which support the rotor cores  550  in the mold. In addition, edge holes  333   a  are formed in the lower cover  332  and the side cover  333 . Portions of the bottom surfaces and the side surfaces of the magnets  400  are exposed outward through the edge holes  333   a . The edge holes  333   a  are formed by the support seats  620 , which support the magnets  400  in the mold. Consequently, the upper cover  331 , the lower cover  332 , and the side cover  333  of the rotary frame  330  surround the magnets  400  and the rotor cores  500 , excluding the cover holes  332   a  and the edge holes  333   a . As a result, the magnets  400  and the rotor cores  500  may be securely supported by the rotary frame  330 . 
     Meanwhile, at least one of each magnet  400  and each rotor core  500  may have a fan shape due to the difference between the inner diameter and the outer diameter of each magnet  400  and each rotor core  500 . For example, each magnet  400  may be rectangular, and each rotor core  500  may be fan-shaped. That is, the circumferential width of each rotor core  500  outward in the radial direction is larger than the circumferential width of each rotor core  500  inward in the radial direction. 
     The magnets  400  and the rotor cores  500  may be disposed so as to be in tight contact with each other in the circumferential direction due to the shape of the magnets  400  and the rotor cores  500 . The movement of the magnets  400  and the rotor cores  500  inward in the radial direction in the state in which the magnets  400  and the rotor cores  500  are in tight contact with each other is limited because of the shape characteristics of the magnets  400  and the rotor cores  500 . In this state, the radial outsides of the magnets  400  and the rotor cores  500  are covered by the side cover  333 . Consequently, the movement of the magnets  400  and the rotor cores  500  outward and inward in the radial direction is limited. 
     In addition, the top surfaces and the bottom surfaces of the magnets  400  and the rotor cores  500  are covered by the lower cover  332  and the upper cover  331 . Consequently, the movement of the magnets  400  and the rotor cores  500  upward and downward in the axial direction is limited. 
     As a result, the magnets  400  and the rotor cores  500  may be stably fixed to the rotary base  330 . 
     As previously described, the fixing holes  536  may be formed in the rotor cores  500 . The molding material may be injected into the fixing holes  536 . The lower part of each fixing hole  536  is closed by a corresponding one of the fixing pins  660 , but the upper part of each fixing hole  536  is open. Consequently, the molding material may be injected into the upper parts of the fixing holes  536 . As a result, the molding material forms insertion parts  331   a . The insertion parts  331   a  protrude from the lower cover  332  or the upper cover  331  toward the fixing holes  536 . For example, in the case in which the insertion parts  331   a  are formed through the upper cover  331 , the cover holes  332   a  are formed in the lower cover  332 , rather than in the upper cover  331 . The reason for this is that the insertion parts are formed from the upper cover  331  into the fixing holes  536  to close the fixing holes  536 . For the lower cover  331 , on the other hand, the insertion parts are not formed in the fixing holes  536  due to the fixing pins  660 . 
     The insertion parts  331   a  are integrally formed with the lower cover  332  or the upper cover  331 . As a result, the rotor cores  500  may be securely fixed to the rotor frame  300 . In particular, the radial movement and the circumferential movement of the rotor cores  500  may be limited by the insertion parts  331   a.    
     Meanwhile, the molding material is injected into the apertures formed in the rotor cores  500 . The molding material connects the upper cover  331  and the lower cover  332  to form support posts  350 ,  351 , and  352 . Consequently, the rotor cores  500  may be securely fixed to the rotor frame  300  by the support posts. 
     In particular, the circumferential movement and the radial movement of the rotor cores  500  may be limited by the support posts. 
       FIGS. 5 and 6  show an example in which the mold is provided with fixing pins  660 , and the fixing pins  660  are separated from the rotor frames  300 . In this case, the fixing pins  660  may be repeatedly used. For this reason, each of the fixing pins  660  may be made of a metal material. Traces of the fixing pins  660  may be formed in the rotor frame  300 , and may thus serve as the cover holes  332   a . Of course, traces of the fixing pins  660  due to the height thereof (the insertion length of the fixing pins  660  into the fixing holes  536 ) may be formed as the insertion length of the insertion parts  331   a.    
     Each of the fixing pins may be made of a plastic material, like the rotor frame  300 . That is, the fixing pins may perform a function of fixing the rotor cores  500  in the mold and may constitute a portion of the rotor frame  300  after injection molding. 
     In this case, therefore, the cover holes  332   a  are not formed, and the fixing pins  660  substitute for the cover holes  331   a . That is, the fixing pins  660  are integrally formed with the rotor frame  300  in the state in which the fixing pins  660  are disposed in the rotor cores  500 . In other words, the fixing pins  660  may be integrally coupled to the rotor frame  300  during injection molding of the rotor frame  300 . 
     According to this embodiment, it is easy to manufacture the mold. The reason for this is that it is not easy to integrally form a plurality of fixing pins with the mold. In the case in which the fixing pins, which are repeatedly used, are formed separately from the mold, much effort is required for coupling and separation between the fixing pins and the mold and separation between the fixing pins and the rotor frame. 
     In the case in which the fixing pins  660  constitute a portion of the rotor frame  300 , however, each of the fixing pins  660  may be made of a plastic material, whereby the manufacturing process is simplified. 
     According to this embodiment, therefore, the insertion part  331   a  extending from the upper part of the fixing hole  536  and the fixing pin  660  extending from the lower part of the fixing hole  536  may be simultaneously provided in the fixing hole  536  of each rotor core  500  in the completed rotor frame  300 . Of course, in the case in which the upper mold and the lower mold are reversed, for example, in the case in which injection molding is performed in the state in which the rotor frame  300  is as shown in  FIG. 2 , the fixing pin  660  may extend from the upper part of the fixing hole  536 , and the insertion part  331   a  may extend from the lower part of the fixing hole  536 . 
     In the case in which a sufficient amount of molding material is introduced into the fixing hole  536 , the insertion part  331   a  contacts the fixing pin  660 . Consequently, the insertion part  331   a  and the fixing pin  660  may be coupled to each other, whereby the rotor cores  500  may be more securely coupled to the rotor frame  300 . In this case, the support posts for interconnecting the lower cover  332  and the upper cover  331  may be further formed. 
     Meanwhile, in the case in which the fixing pins  660  are integrally formed with the rotor frame  300 , the fixing pins  660  protrude from the upper cover  331  or the lower cover  332  of the rotor frame  300 . The reason for this is that a portion of each of the fixing pins  660  is inserted into a corresponding one of the fixing pin holes  610  of the mold, and the fixing pins  660  protrude by the insertion length after injection molding. 
     As shown in  FIG. 2 , the lower cover  332  of the rotary base  330  defines the lowermost surface of the rotor frame  300 . In the case in which the fixing pins  660  are provided at the lower cover  332 , therefore, the height of the rotor frame  300  may be increased. On the other hand, the upper cover  331  does not define the uppermost surface of the rotor frame  300 . In the case in which the fixing pins  660  are provided at the upper cover  331 , therefore, the height of the rotor frame  300  is not changed. 
     In the case in which the fixing pins  660  are integrally provided at the rotor frame  300 , therefore, the fixing pins  660  may be provided at the upper cover  331  of the rotor frame  300 , rather than at the lower cover  332  thereof. 
     Meanwhile, in the above embodiment, the rotor cores  500  and the magnets  400  are supported in the lower part of the mold by the fixing pins  660 . In this case, however, the rotor cores  500  and the magnets  400  may not be vertically disposed but may be inclined. That is, the rotor cores  500  and the magnets  400  may be fixed in the rotor frame  300  in the state of being inclined. 
     In order to solve this problem, the fixing pins  660  may be provided at the upper parts as well as the lower parts of the rotor cores  500 . That is, the rotor cores  500  may be supported in the mold on the upper and lower sides of the rotor cores  500 . For example, the fixing pins may be formed at the upper mold. 
     In the above embodiment, the lower fixing pins  660  are inserted into the fixing holes  536  of the rotor cores  500  when the lower parts of the rotor cores  500  are supported. However, the upper fixing pins may support the rotor cores  500  at different positions than the fixing holes  536 . 
     For example, the upper fixing pins may be provided so as to simultaneously push the top surfaces of the rotor cores  500  and the magnets  400 . That is, one upper fixing pin may push one rotor core  500  and one magnet  400  adjacent thereto. 
     In this case, one rotor core  500  and one magnet  400  may be fixed in the mold by the lower fixing pin, the upper fixing pin, and the support seat. Consequently, the magnets and the rotor cores may be manufactured such that the magnets and the rotor cores are vertically fixed. 
     After injection molding, the upper fixing pins are separated from the rotor frame to form the cover holes  331   b , through which portions of the upper surfaces of the rotor cores  500  and the magnets  400  may be exposed outward. 
     That is, since the cover holes  332   a  formed by the lower fixing pins  660  correspond to the fixing holes  536  of the rotor cores  500 , the portions of the bottom surfaces of the rotor cores  500  and the fixing holes  536  are exposed through the cover holes  332   a . Since the cover holes  331   b  formed by the upper fixing pins do not correspond to the fixing holes  536 , however, the fixing holes  536  are not exposed through the cover holes  331   b . Of course, the top surfaces of the rotor cores and/or the top surfaces of the magnets may be exposed outward through the cover holes  331   b.    
     Hereinafter, the structure of the rotor frame  300  according to the embodiment of the present invention will be described with reference to  FIGS. 7 and 8 . 
     Force is applied to the rotor frame in different directions depending on the positional relationship between the coupler  200 , located at the central part of the rotor frame  300 , and the rotor cores  500  and the magnets  400 , located at the outside of the rotor frame  300  in the radial direction. 
     Force may be applied to the rotor frame  300  in the axial direction (the z-axis direction), the radial direction (the y-axis direction), and the circumferential direction (the x-axis direction, i.e. the torque direction). Consequently, the rotor frame  300  may be formed so as to withstand force applied thereto in various directions. The force applied to the rotor frame  300  in various directions may be generated by torque, axial load, and vibration. 
     The rotation of the rotary base  330  is transmitted to the coupler base  310 . At this time, the extension base  320 , which is located between the rotary base  330  and the coupler base  310 , may have low resistance to twisting. For this reason, the extension base  320  may be formed so as to have high resistance to twisting. 
     In addition, the height of the rotary base  330  is different from the height of the coupler base  310 . This means that a force acting to pull the coupler base  310  inward or outward in the radial direction may be generated. For this reason, the extension base  320  may be formed so as to sufficiently withstand force generated from the rotary base  330  in the radial direction. 
     That is, the extension base  320  may be formed so as to sufficiently withstand bending moment as well as twisting. 
     Of course, the thickness of the rotary base  330  may be increased in order to increase rigidity of the extension base  320 . In this case, however, manufacturing costs are increased. In addition, the weight of the rotor is increased, whereby the efficiency of the rotor may be reduced. Consequently, the shape and structure of the extension base  320  are critical in order to reduce material costs and to improve the efficiency of the rotor. 
     The rotor frame  300  may include a plurality of unit zones A arranged in the circumferential direction. The unit zones A may have the same shape and size. That is, the unit zones A may be repeatedly arranged in the circumferential direction to constitute a single rotor frame  300 .  FIG. 8  shows an example of a rotor frame  300  including twelve unit zones A. 
     In this embodiment, crossing ribs  321  are formed at the extension base  320  such that the extension base  320  has the optimal structure. That is, the strength of the extension base  320  may be increased by the crossing ribs  321 . 
     The extension base  320  may include a plurality of zones D arranged in the circumferential direction. The zones D of the extension base  320  may be called sub-zones. The sub-zones D, which have the same shape and size, may be arranged in the circumferential direction to constitute a single extension base  320 . One sub-zone means a zone constituting a portion of the extension base  320  in one unit zone A. That is, one unit zone A includes one sub-zone D of the extension base  320 . 
     The crossing ribs  321  may be formed so as to cross obliquely in each sub-zone D. That is, one crossing rib  321  may extend obliquely and another crossing rib  321  may extend obliquely such that the crossing ribs  321  cross each other. Consequently, a zone between the radius defined by the radial inner tips of the crossing ribs and the radius defined by the radial outer tips of the crossing ribs may be a sub-zone D. Of course, the sub-zone D may be a crossing zone, since the sub-zone D is a zone defined by the crossing ribs. 
     The crossing zone D may withstand force generated between the coupler base  310  and the rotary base  330  in various directions by virtue of the crossing ribs  321 . 
     The crossing ribs  321  cross to form a crossing point B. The crossing point B may be adjacent to the radial inner tips of the crossing ribs  321 . That is, the crossing point B may be located inward in the radial direction from the center radius of the crossing point B. The reason for this is that if the crossing point B is close to the rotary base  330 , the strength of the extension base  320  inward in the radial direction from the crossing point B may be reduced. In other words, the crossing point B may be further spaced apart from the rotary base  330  in consideration of the fact that moment is proportional to moment distance. 
     Meanwhile, the extension base  320  may be provided with a plurality of radial ribs  322  extending in the radial direction and arranged in the circumferential direction at uniform intervals. Each radial rib  322  may extend in the radial direction across a corresponding crossing point B. Each crossing point B may be formed between radial ribs  322  formed at the circumferentially opposed sides thereof. Consequently, one sub-zone or crossing zone D may include three radial ribs  322 . 
     The radial ribs  322  are connected to the circumferential opposite tips of the crossing ribs  321 . That is, the radial ribs  322  are circumferential bases for supporting the crossing ribs  321  in the circumferential direction. Consequently, the radial ribs  322  further prevent the generation of twisting in the sub-zones D. 
     A vertical through part  323  may be formed between one radial rib  322  and an adjacent radial rib  322 . The through part  323  is a passage through which air flows. That is, the through part  323  may be an air through part. 
     The material costs of the rotor frame may be reduced by the provision of the through parts  323 . That is, portions of the extension base  320  having no relation to the rigidity of the extension base  320  may be removed to thus reduce the material costs of the rotor frame. In addition, the through parts  323  dissipate heat generated from the stator. 
     Six sections S 1  to S 6  may be formed about the crossing point B by the three adjacent radial ribs  322  and the crossing ribs  321 . That is, one sub-zone D may be partitioned into six sections S 1  to S 6  about the crossing point B. 
     The through parts  323  may be formed in all of the six sections. As previously described, however, the crossing point B may be biased inward in the radial direction from the radial center of the sub-zone D. Consequently, the areas of the two sections S 5  and S 6  located inside the crossing point B in the radial direction are much smaller than the areas of the other sections. Since the two sections S 5  and S 6  are biased inward in the radial direction, the sections S 5  and S 6  may be located further inward in the radial direction than the coils of the stator. 
     Consequently, the through parts  323  may not be formed in the sections S 5  and S 6  due to the relatively small areas of the sections S 5  and S 6  and the bias of the sections S 5  and S 6  inward in the radial direction. 
     Meanwhile, the sub-zones D may perform a function of dissipating heat from the stator through the through parts  323 . For this reason, the sub-zones D may be heat dissipation zones. 
     The extension base  320  may include non-crossing zones C located outside the sub-zones D in the radial direction. The non-crossing zones C may connect the extension base  320  to the rotary base  330 . In addition, the height of the non-crossing zones C may be different from the height of the rotary base  330  in the vicinity of the rotary base  330 . Consequently, the non-crossing zones C may be formed so as to have high resistance to bending moment, rather than twisting. 
     As a result, the crossing ribs  321  may not extend to the non-crossing zones C. In addition, the through parts  323  may not be formed in the non-crossing zones C, or the size of the through parts  323  formed in the non-crossing zones C may be relatively small. The reason for this is that it is not necessary for the non-crossing zones C, which correspond to the tips of teeth of the stator, to have a heat dissipation function and that the non-crossing zones C may have low resistance to bending moment due to the through parts  323 . 
     Since the non-crossing zones C have high resistance to bending moment, the non-crossing zones C may be reinforcement zones. 
     The crossing zones (heat dissipation zones) D and the non-crossing zones (reinforcement zones) C may be partitioned by circumferential ribs  324  formed in the circumferential direction. 
     The circumferential ribs  324  are connected to the radial tips of the crossing ribs  321 . That is, the circumferential ribs  324  may be radial bases for supporting the crossing ribs  321  in the radial direction. Consequently, the circumferential ribs  324  further prevent the occurrence of twisting in the sub-zones D. 
     Meanwhile, the non-crossing zones C may be provided with radial ribs  325 . The radial ribs  325  may be connected to the radial ribs  322 . That is, the radial ribs  322  may extend to the non-crossing zones C in order to form the radial ribs  325 . One non-crossing zone C may be provided with three radial ribs  325 . 
     The coupler base  310  is also provided with radial ribs  311 . The radial ribs  311  further extend in the radial direction so as to be connected to the radial ribs  322 . 
     Consequently, the rotor frame  300  may be provided with radial ribs  311 ,  322 , and  325 , which continuously extend from the coupler base  310  to the radial tip of the extension base. The radial ribs  311 ,  322 , and  325  may extend to the rotary base  330 . That is, the connections of the rotary base  330  and the extension base  320  via the radial ribs may also be reinforced by the radial ribs. 
     The radial ribs  311 ,  322 , and  325  are passages through which the molding material is uniformly injected into the rotor frame  300 . That is, the ribs are formed so as to correspond to passages through which the molding material is injected into the mold. 
     Meanwhile, specific radial ribs may be formed so as to cross the circumferential centers of the rotor cores  500 . That is, the specific radial ribs may further extend from the circumferential centers of the rotor cores  500  in the radial direction in order to form passages sufficient for injection of the molding material into the fixing holes  536  for supporting the rotor cores  500 . Specifically, the radial ribs crossing the crossing point B may extend further in the radial direction than the centers of the rotor cores  500 . 
     The rotor frame  300 , particularly the coupler base  310  and the extension base  320 , includes a reference bottom surface  301  and a reference top surface  302 , which define the external shape of the rotor frame  300 . That is, the thickness between the reference bottom surface  301  and the reference top surface  302  may be the basic thickness of the coupler base  310  and the extension base  320 . 
     The above ribs may protrude from the reference bottom surface  301  and/or the reference top surface  302 . 
     The radial ribs  311 ,  322 , and  325  may protrude downward from the reference bottom surface  301 . Circumferential ribs or support ribs  312  for partitioning the coupler base  310  and the extension base  320  in the radial direction and the circumferential ribs  324  of the extension base  320  may protrude downward from the reference bottom surface  301 . 
     In addition, the radial ribs  311 ,  322 , and  325  may protrude upward from the reference top surface  302 . Consequently, the vertical width of the radial ribs may be further increased. As a result, the strength of the radial ribs may be further increased. In addition, the ribs perform a blade function of generating air flow, whereby the dissipation of heat through the through part  323  may be more effectively performed. 
     Meanwhile, the extension base  320  is connected to the rotary base  330  via a step part  340 . The step part  340  is provided with radial ribs  341 . As a result, the strength of the step part  340  may be increased. 
     The radial ribs  341  of the step part  340  may be formed as the result of further extension of the radial ribs  325  in the radial direction. The radial ribs  341  extend through the circumferential centers of the rotor cores  500 . Consequently, a sufficient amount of molding material may be injected into the fixing holes  536  through the radial ribs  341 . 
     During injection molding of the rotor frame  300 , a mold injection port  350  (     350   ) may be located in the extension base  320 . In particular, the mold injection port  350  may be provided further outward in the radial direction than the crossing points B. One mold injection port  350  may be formed in each unit zone A. As a result, the molding material may be uniformly injected into the rotor frame. 
     In particular, the mold injection ports  350  may be formed in the radial ribs  322 . The radial ribs are formed so as to be adjacent to the radial ribs forming the crossing points. The molding material injection area around the radial ribs  322  forming the crossing points is relatively small due to the through parts  323 . However, the molding material injection area around the radial ribs  322  adjacent to the radial ribs  322  forming the crossing points is relatively large. Consequently, the molding material may be easily distributed. 
     Meanwhile, the upper fixing pins, the lower fixing pins, and the support seats for supporting the rotor cores and the magnets in the mold may be equally applied to the rotor cores and the magnets shown in  FIGS. 3 and 4 . 
     As is apparent from the above description, the present invention has the effect of providing a rotor that can be easily manufactured and a motor including the same. 
     In addition, the present invention has the effect of providing a rotor that can be manufactured through a single injection molding process and a motor including the same. 
     In addition, the present invention has the effect of providing a rotor that is capable of minimizing the leakage of magnetic flux, thereby achieving high efficiency and high output and a motor including the same. 
     In addition, the present invention has the effect of providing a rotor that exhibits sufficient rigidity and strength while the weight of the rotor is reduced. 
     In addition, the present invention has the effect of providing a rotor that can be manufactured with reduced material costs and can be easily handled. 
     In addition, the present invention has the effect of providing a rotor having a cooling structure that is capable of limiting the increase in temperature of a stator or cooling the stator. 
     In addition, the present invention has the effect of providing a rotor configured such that rotor cores and magnets are coupled to a rotor frame at uniform intervals. 
     In addition, the present invention has the effect of providing a rotor configured such that rotor cores and magnets are securely coupled to a rotor frame. 
     In addition, the present invention has the effect of providing a rotor configured such that a plurality of magnets is disposed in a spoke arrangement so as to be magnetized inward and outward in the radial direction. 
     In addition, the present invention has the effect of providing a rotor configured such that magnets are entirely magnetized. 
     In addition, the present invention has the effect of providing a rotor configured such that fixing pins for fixing rotor cores in an injection mold are injection-molded so as to be integrally coupled to a rotor frame, whereby the rotor is manufactured through a simple manufacturing process. 
     Although the exemplary embodiments have been illustrated and described as above, of course, it will be apparent to those skilled in the art that the embodiments are provided to assist understanding of the present invention and the present invention is not limited to the above described particular embodiments, and various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention, and the modifications and variations should not be understood individually from the viewpoint or scope of the present invention.