Patent Publication Number: US-11658527-B2

Title: Rotor and motor comprising same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application is a Continuation of U.S. patent application Ser. No. 16/081,760, filed on Aug. 31, 2018 (now U.S. Pat. No. 10,910,896, issued on Feb. 2, 2021), which is the National Phase of PCT International Application No. PCT/KR2017/002198, filed on Feb. 28, 2017, which claims priority under 35 U.S.C. 119(a) to Patent Application Nos. 10-2016-0025263, filed in Republic of Korea on Mar. 2, 2016 and 10-2016-0025265, filed in Republic of Korea on Mar. 2, 2016, all of which are hereby expressly incorporated by reference into the present application. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a rotor and a motor including the same. 
     Discussion of the Related Art 
     A motor generates power while a rotor is rotated by an electromagnetic interaction between magnets of the rotor and coils of a stator. 
     A motor includes a housing, a stator, a rotor, and a rotating shaft. The rotor includes a plurality of magnets. The rotor may be classified into an interior permanent magnet (IPM) type rotor in which magnets are inserted into rotor cores and a surface permanent magnet (SPM) type rotor in which magnets are attached onto surfaces of rotor cores. 
     In the SPM type rotor, a plurality of magnets are attached onto surfaces of rotor cores and a steel use stainless (SUS)-based cover is used for protecting the magnets. In a process of attaching the magnets, external surfaces of the rotor cores are coated with an adhesive, the magnets are attached to the rotors, and the adhesive is cured. Next, in a cover assembly process, an adhesive is applied onto the magnets, the magnets are covered by the cover, and the adhesive is cured. However, these processes are very complex, and use of the adhesive and the cover raises a material cost. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to providing a rotor capable of being easily assembled and a motor including the same. 
     In addition, the present invention is also directed to providing a rotor and a motor which are capable of fixing a magnet without an adhesive. 
     In addition, the present invention is also directed to providing a rotor with a reduced weight and a motor including the same. 
     In addition, the present invention is also directed to providing a rotor with a reduced cost and a motor including the same. 
     Objectives to be solved by the present invention will not be limited to the above-described objectives, and objectives which are not described above will be clearly understood by those skilled in the art from the following specification. 
     One aspect of the present invention provides a rotor including a first rotor part and a second rotor part disposed in a shaft direction, wherein the first rotor part includes a first rotor core, a plurality of first magnets disposed on an outer circumferential surface of the first rotor core, and a first holder configured to fix the plurality of first magnets, and the second rotor part includes a second rotor core, a plurality of second magnets disposed on an outer circumferential surface of the second rotor core, and a second holder configured to fix the plurality of second magnets, wherein the first holder includes a plurality of first protrusion parts protruding toward the second rotor part, and the second holder includes a plurality of second protrusion parts protruding toward the first rotor part, and wherein a gap is formed between the first rotor core and the second rotor core. 
     The gap may be in a range of 0.7 mm to 1.5 mm. 
     The first protrusion part and the second protrusion part may be alternately disposed in a radial direction of the rotor. 
     The first holder may include: a first body in a cylindrical shape; a first plate which is connected to the first body and has an annular shape configured to cover an upper surface of the first magnet; and a plurality of first coupling protrusions which protrude from an inner circumferential surface of the first body and are coupled to the first rotor core, wherein the first protrusion part may protrude from a bottom surface of the first coupling protrusion in the shaft direction. 
     The first coupling protrusion may include a coupling part coupled to the outer circumferential surface of the first rotor core and an extension part which connects the coupling part and the first body and fixes the first magnet. 
     The first protrusion part may support the second magnet, and the second protrusion part may support the first magnet. 
     The first plate may include at least one insertion protrusion to be coupled to an upper surface of the first rotor core, and the insertion protrusion is inserted into a coupling hole formed in the first rotor core. 
     A distance between the inner circumferential surface and an outer circumferential surface of the first body may decrease toward a central position between the adjacent first coupling protrusions. 
     The first coupling protrusion may include a through hole formed from the bottom surface of the first coupling protrusion in the shaft direction. 
     Each of the first magnet and the second magnet may include one surface facing the outer circumferential surface of each of the first rotor core and the second rotor core, the other surface facing the one surface, and a plurality of side surfaces connecting the one surface and the other surface, each of the plurality of side surfaces may include a first side surface and a second side surface which are parallel to the shaft direction and a third side surface and a fourth side surface which are perpendicular to the shaft direction, and any one of the first side surface and the second side surface may have a curvature. 
     Another aspect of the present invention provides a motor including: a housing; a stator disposed in the housing; a rotor having one or more features of the above-described rotor; and a rotating shaft passing through a center of the rotor. 
     The gap may be greater than a distance between an outer diameter of the first magnet and the inner circumferential surface of the stator. 
     According to embodiments of the present invention, a rotor assembly process can be simplified. 
     In addition, a weight of a rotor can be reduced, and a cost thereof can be reduced. 
     A variety of useful advantages and effects are not limited to the above-described contents and will be more easily understood when specific embodiments of the present invention are described. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a conceptual view illustrating a motor according to an embodiment of the present invention motor. 
         FIG.  2    is an exploded perspective view illustrating a rotor according to the embodiment of the present invention. 
         FIG.  3 A  is a view illustrating a coupled state of the rotor and a rotating shaft according to the embodiment of the present invention. 
         FIG.  3 B  is a cross-sectional view taken along line C-C′ of  FIG.  3 A . 
         FIG.  4    is a cross-sectional view taken along line A-A′ of  FIG.  3 A . 
         FIG.  5    is a cross-sectional view taken along line B-B′ of  FIG.  3 A . 
         FIG.  6    is a view for describing a gap between a first rotor and a second rotor. 
         FIG.  7    is a view showing a state of a magnet being inserted into the rotor. 
         FIG.  8    is a plan view of  FIG.  7   . 
         FIG.  9    is an enlarged view illustrating portion C of  FIG.  8   . 
         FIG.  10    is a view illustrating a modified embodiment of a holder. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to particular modes of practice, and it is to be appreciated that all changes, equivalents, and substitutes that do not depart from the spirit and technical scope of the present invention are encompassed in the present invention. 
     It will be understood that, although the terms “first,” “second,” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and a second element could similarly be termed a first element without departing from the scope of the present invention. As used herein, the term “and/or” includes at least one or combinations of the associated listed items. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting to the invention. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements, components, and/or groups thereof but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     In a description of the embodiment, in a case in which any one element is described as being formed on (or under) another element, such a description includes both a case in which the two elements are formed to be in direct contact with each other and a case in which the two elements are in indirect contact with each other such that one or more other elements are interposed between the two elements. In addition, when in a case in which one element is described as being formed on (or under) another element, such a description may include a case in which the one element is formed at an upper side or a lower side with respect to another element. 
     Example embodiments of the invention will be described below in more detail with reference to the accompanying drawings. Those components that are the same or are corresponding are rendered the same reference numeral regardless of the figure number, and redundant explanations are omitted. 
       FIG.  1    is a conceptual view illustrating a motor according to an embodiment of the present invention motor. 
     Referring to  FIG.  1   , the motor according to the embodiment of the present invention includes a housing  10  in which a stator  30 , a rotor  20 , and a rotating shaft  70  are disposed. 
     The housing  10  may accommodate the stator  30  and the rotor  20 . The housing  10  may further include a cooling structure (not shown) to easily dissipate internal heat. The cooling structure may be selected from an air cooling structure and a water cooling structure, but the present invention is not limited thereto. 
     The stator  30  may be disposed in an inner space of the housing  10 . The stator  30  may include stator cores  31  and coils  32  wound around the stator cores  31 . 
     The stator  30  may be manufactured using the coils  32  wound around the stator cores  31  which are integrally formed, or using the coils wound around the plurality of divided stator cores and assembled in a cylindrical shape. 
     Busbars  40  may be electrically connected to the coils  32  wound around the stator  30  and include a plurality of terminals for connecting U-, V-, and W-phases. Power terminals of the busbar  40  may be exposed to the outside and electrically connected to an external power source or inverter. 
     The rotor  20  may be disposed to be rotatable with respect to the stator  30 . The rotor  20  may be disposed inside the stator  30 . The rotor  20  may include a first rotor part  21  and a second rotor part  22  which are disposed in a shaft direction (a longitudinal direction of the rotating shaft). The first rotor part  21  and the second rotor part  22  may include rotor cores, magnets, and holders. 
     The rotating shaft  70  may be coupled to a center of the rotor  20 . Accordingly, the rotor  20  may rotate with the rotating shaft  70 . The rotating shaft  70  may be supported by a first bearing  61  disposed at one side of the rotating shaft  70  and a second bearing  62  disposed on the other side thereof. 
     A sensing plate  50  for obtaining position information of the rotor cores may be disposed above the rotor  20 , but the present invention is not limited thereto, and a similar detection device for obtaining the position information may be installed thereabove. 
     For example, the motor according to the embodiment may be an electric power steering (EPS) motor used for an EPS system. Specifically, in the EPS system, an electronic control unit (ECU) may control an inverter to drive the motor according to a traveling condition detected by a speed sensor, a torque angle sensor, a torque sensor, etc. The motor according to the embodiment may be driven by three-phase power supplied by the inverter. However, the motor according to the embodiment is not limited thereto. 
       FIG.  2    is an exploded perspective view illustrating a rotor according to the embodiment of the present invention,  FIG.  3 A  is a view illustrating a coupled state of the rotor and a rotating shaft according to the embodiment of the present invention, and  FIG.  3 B  is a cross-sectional view taken along line C-C′ of  FIG.  3 A . 
     Referring to  FIG.  2   , the rotor  20  according to the embodiment includes the first rotor part  21  and the second rotor part  22  which are disposed in the shaft direction UA. The first rotor part  21  and the second rotor part  22  may respectively include rotor cores  220  and  250 , a plurality of magnets  230  and  260 , and holders  210  and  240  configured to fix the magnets  230  and  260 . The first rotor part  21  and the second rotor part  22  may be formed of the same component and may face each other. 
     The first rotor part  21  may include a first rotor core  220 , a plurality of first magnets  230  disposed on an outer circumferential surface of the first rotor core  220 , and a first holder  210  configured to fix the plurality of first magnets  230 . 
     The first rotor core  220  may have a cylindrical shape and include a plurality of slits  221  formed in the shaft direction. The magnets  230  are disposed in regions  223  divided by the plurality of slits  221 . The first rotor core  220  may be manufactured using a plurality of metal plates stacked in the shaft direction. A central hole  224  and coupling holes  222  may be formed in the first rotor core  220  in the shaft direction. 
     The first holder  210  may include a first body  211  having a hollow cylindrical shape, a first plate  212  connected to the first body  211  and having an annular shape, a plurality of first coupling protrusions  213  protruding from an inner circumferential surface of the first body  211  and coupled to the first rotor core  220 , and first protrusion parts  214  protruding from bottom surfaces of the first coupling protrusions  213  in the shaft direction. 
     The first protrusion part  214  may be defined as a portion protruding from an end of the first body  211  in the shaft direction. That is, the first protrusion parts  214  may protrude toward the second rotor part  22 . Insertion protrusions  212   a  inserted into the coupling holes  222  of the first rotor core  220  may be formed in an inner surface of the first plate  212 . The first plate  212  may cover upper surfaces of the first magnets  230  exposed in the shaft direction. A hole may be formed at a center of the first plate  212 . 
     The second rotor part  22  includes a second rotor core  250 , a plurality of second magnets  260  disposed on an outer circumferential surface of the second rotor core  250 , and a second holder  240  configured to fix the plurality of second magnets  260 . The second holder  240  may include a second body  241  having a hollow cylindrical shape, a second plate  242  connected to the second body and having an annular shape, a plurality of second coupling protrusions  243  protruding from an inner circumferential surface of the second body  241  and coupled to the second rotor core  250 , and second protrusion parts  244  protruding from bottom surfaces of the second coupling protrusions  243  in the shaft direction. The second protrusion parts  244  may protrude toward the first rotor part  21 . 
     Since the first rotor part  21  and the second rotor part  22  are formed of the same component and face each other, a structure of the second rotor part  22  may be the same as that of the first rotor part  21 . 
     Referring to  FIGS.  3 A and  3 B , the first rotor part  21  and the second rotor part  22  may be fixedly pressed against the rotating shaft  70 . Here, the second rotor part  22  may rotate at a predetermined angle with respect to the first rotor part  21  in a circumferential direction and may be coupled to the first rotor part  21 . Therefore, the first protrusion part  214  and the second protrusion part  244  are alternately disposed in a radial direction, and thus a gap between the first rotor part  21  and the second rotor part  22  may be fixed. 
     The first protrusion part  214  of the first rotor part  21  may be disposed on the magnet  260  of the second rotor part  22 . Similarly, the second protrusion part  244  of the second rotor part  22  may be disposed on the magnet  230  of the first rotor part  21 . 
     Here, an angle θ 1  between the first protrusion part  214  and the second protrusion part  244  with respect to a center of the rotating shaft  70  may be in the range of 2° to 10°. In a case in which the angle is less than 2°, the second protrusion part  244  may not support the magnet  230  in the shaft direction, and in a case in which the angle is greater than 10°, a skew angle is large so that rotation of the rotor may not be smooth. 
       FIG.  4    is a cross-sectional view taken along line A-A′ of  FIG.  3 A ,  FIG.  5    is a cross-sectional view taken along line B-B′ of  FIG.  3 A , and  FIG.  6    is a view for describing a gap between a first rotor and a second rotor. 
     Referring to  FIG.  4   , the first protrusion part  214  of the first holder  210  protrudes toward the second rotor part  22 , and referring to  FIG.  5   , the second protrusion part  244  of the second holder  240  protrudes toward the first rotor part  21 . Accordingly, a gap  23  may be formed between the first rotor core  220  and the second rotor core  250 , and a gap  23  may be formed between the first magnet  230  and the second magnet  260 . According to the above-described configuration, an air gap is formed between the first magnet  230  and the second magnet  260  so that magnetic characteristics can be improved. In addition, the rotor core may have a thickness decreased by a thickness corresponding to the gap  23  so that a cost can be reduced. 
     The first protrusion part  214  of the first holder  210  may be in contact with an upper end of the second magnet  260 , and the second protrusion part  244  of the second holder  240  may be in contact with a lower end of the first magnet  230 . Accordingly, the first magnet  230  and the second magnet  260  can be prevented from moving away in the shaft direction. 
     Referring to  FIG.  6   , the first gap  23  between the first rotor part  21  and the second rotor part  22  may be greater than or equal to a first distance W 1  between the first and second magnets  230  and  260  and an inner circumferential surface of the stator  30 . In a case in which the first distance W 1  between the first and second magnets  230  and  260  and the inner circumferential surface of the stator  30  is 0.7 mm, the first gap  23  between the first rotor part  21  and the second rotor part  22  may be in the range of 0.7 mm to 1.5 mm. 
     In a case in which the first gap  23  is less than 0.7 mm, the first gap  23  is less than a distance between an outer diameter of the first and second magnets  230  and  260  and the stator  30 , and thus there is a problem in that a magnetic force may be leaked, and in a case in which the first gap  23  is greater than 1.5 mm, a total height W 2  of the first and the second magnets  230  and  260  is greater than that of the stator, and thus magnetic line loss may occur. Accordingly, a ratio between the first distance W 1  and the first gap  23  may be in the range of 1:1 to 1:2.1. 
       FIG.  7    is a view showing a state of a magnet being inserted into the rotor,  FIG.  8    is a plan view of  FIG.  7   , and  FIG.  9    is an enlarged view illustrating portion C or  FIG.  8   . Hereinafter, the first rotor part will be described mainly, but the description will also be clearly applied to the second rotor part. 
     Referring to  FIG.  7   , the cylindrical shaped first holder  210  is coupled to the first rotor core  220  to form pockets P into which the first magnets  230  are inserted. Conventionally, a magnet is attached to an outer circumferential surface of a rotor core using an adhesive, and is covered by a SUS material using an adhesive, but such a structure has a problem in that a process and manufacturing cost is high. 
     According to the embodiment, since the first magnets  230  are inserted into the pockets P formed by the first holder  210  coupled to the first rotor core  220 , an adhesive for fixing the first magnet  230  may be unnecessary. 
     In addition, as the first holder  210  is formed by injection molding a resin, a cost can be reduced, and since the first coupling protrusion  213  of the first holder  210  is coupled to the slit  221  of the first rotor core  220 , an additional adhesive may be unnecessary. 
     The first magnet  230  incudes one surface  231  facing the outer circumferential surface of the first rotor core  220 , the other surface  232  facing the one surface  231 , and a plurality of side surfaces  233 ,  234 ,  235 , and  236  connecting the one surface  231  and the other surface  232 . The plurality of side surfaces  233 ,  234 ,  235 , and  236  include the first side surface  235  and the second side surface  236  which are parallel to the shaft direction, and the third side surface  233  and the fourth side surface  234  which are perpendicular to the shaft direction. A curvature of the one surface  231  may be different from that of the other surface  232 . Accordingly, a virtual circle in which one surface  231  extends may be greater than a virtual circle in which the other surface  232  extends. 
     Since the remaining surfaces of the first magnet  230  except the third side surface  233  are inserted into the pocket P, the first magnet  230  may be firmly inserted into the pocket P without an adhesive. In addition, a corrosion prevention effect can also be improved. The first magnet  230  and the pocket P may be designed such that a gap is not formed therebetween. 
     Referring to  FIG.  8   , in the first body  211  of the first holder  210 , the plurality of first coupling protrusions  213  may protrude from an inner circumferential surface F 1  toward a center C 1 , a distance between the inner circumferential surface F 1  and an outer circumferential surface F 2  of the first body  211  may decrease toward a central position  211   a  between the adjacent first coupling protrusions  213 . A thickness of the central position  211   a  may be in the range of about 0.1 mm to 0.5 mm or may be 0.3 mm. 
     Referring to  FIG.  9   , the first coupling protrusion  213  may include a coupling part  213   a  coupled to the outer circumferential surface of the first rotor core  220  and an extension part  213   b  connecting the coupling part  213   a  and the first body  211 . A thickness of the extension part  213   b  may decrease from the inner circumferential surface F 1  of the first body  211  toward the coupling part  213   a.    
     The first coupling protrusion  213  may include a through hole  215  passing therethrough from the bottom surface thereof in the shaft direction. In a process in which the first magnet  230  is inserted into the pocket, excessive stresses of the first magnet and/or pocket may occur. The through hole  215  may absorb the stresses occurring at the first magnet  230  and/or pocket. A shape of the through hole  215  may be changed while the stresses are absorbed. The first protrusion part  214  may be disposed to be adjacent to the through hole  215 . 
     The side surface of the first magnet  230  may include a groove  235   a  which is concave from one surface  231  toward the other surface  232 . Accordingly, a side surface of the first magnet may have a section which is not in contact with the extension part  213   b . According to the above-described configuration, the stresses occurring during insertion of the first magnet  230  can be further reduced. 
     The structures of the first protrusion part and the through hole  215  may be variously changed. Referring to  FIG.  10   , the through hole  215   a  may also be formed in the bottom surface of the first coupling protrusion  213 , and the first coupling protrusion  213  may also protrude in the shaft direction to serve as the first protrusion part. 
     Referring to  FIGS.  2 ,  4 , and  7   , in a method of manufacturing a rotor according to the embodiment, first, a resin may be injection-molded to form the first holder  210 , and the first rotor core  220  may be installed in the first holder  210  to form the plurality of pockets P. Next, the first magnets  230  may be inserted into the plurality of pockets P to assemble the first rotor part  21 . 
     The second rotor part  22  may also be assembled by the same method as that of the first rotor part  21 . Next, the rotating shaft  70  may be fixedly inserted into the first rotor part  21  and the second rotor part  22 . Here, as described above, the first gap  23  may be formed between the first rotor part  21  and the second rotor part  22  due to the first protrusion part  214  and the second protrusion part  244 .