Patent Publication Number: US-2016226330-A1

Title: Electric motor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This non-provisional patent application claims priority under 35 U.S.C. §119(a) from Patent Application No. 201510054879.2. filed in The People&#39;s Republic of China on Jan. 30, 2015, and from Patent Application No. 201510738743.3 filed in The People&#39;s Republic of China on Nov. 3, 2015, the entire contents of both are hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     This invention relates to an electric motor and in particular, to a motor having a wound. stator core. 
     BACKGROUND OF THE INVENTION 
     Electric motors are a common source of mechanical power, being used in a wide variety of applications and devices, such as electric fans, washing machines, water pumps etc. Generally, a motor is composed of two parts, namely a rotor and a stator. A one type of motor, the stator is composed of a magnetic core with windings wound around the magnetic core. The rotor may have a permanent magnet. When energized, the windings of the stator generate a magnetic field which interacts with a magnetic field of the rotor to rotate the rotor and in turn drive a load. 
     The magnetic core of a known wound stator is generally formed by stacking a large number of silicon steel sheets or laminations. Each silicon steel sheet is formed by directly punching a thin sheet material. Each silicon steel sheet comprises an annular yoke, and teeth radiating from the yoke part. For a stator used in an outer rotor motor, the teeth radiate outwardly from the yoke. An annular supporting part is formed at a central area of the yoke. The supporting part is used to fixedly connect the stator to other components. The windings are wound around the teeth. Although the manufacturing procedure of the stator core of the existing stator is simple, the punching process use to form the stator laminations generates a large amount of waste material, resulting in a high cost. 
     SUMMARY OF THE INVENTION 
     Hence there is a desire for a motor with a stator having better rate of material utilization. 
     Accordingly, in one aspect thereof, the present invention provides a motor comprising: a support seat, a stator structure and a rotor, wherein the rotor is rotatably mounted on the support seat, and the stator structure comprises: a core, a winding frame covering the core, and windings wound around the winding frame, the core includes a ring-shaped yoke and a plurality of teeth extending outwardly from the yoke, the winding frame comprises an insulating part covering the core and a connecting part within the insulating part to fixedly connect to the support seat. 
     Preferably, each tooth includes a winding portion connected with the yoke and a tip formed at a distal end of the winding portion, the windings are wound around the winding portions, a notch is formed in a connection area between the tip and the winding portion, the tip is partially tilted outwardly before the winding is completed and is pressed to bend inwardly to contact the winding portion after the winding is completed. 
     Preferably, the core is formed by bending material strips, the yoke of the core has through holes, and fastening members are inserted into the through holes to fix the material strips together. 
     Preferably, the core is formed by bending material strips, and tips of the core are welded to fixed the strips together. 
     Preferably, the support seat is formed from a thermally conductive material. 
     Preferably, cooling fins are provided on a side of the support seat facing the stator structure. 
     Preferably, one side of the support seat remote from the stator structure forms a receiving cavity, and a circuit board is received in the receiving cavity. 
     Preferably, the connecting part comprises a ring-shaped base plate extending integrally and radially inwardly from the insulating part, a hollow cylinder extending integrally and axially from an inner edge of the base plate, and a plurality of ribs connected between an outer wall surface of the hollow cylinder and an inner wall surface of the insulating part. 
     Preferably, the base plate of the winding frame has through holes, the support seat is provided with fixing posts corresponding to the through holes, and fixing members pass through the through holes and are fastened in the fixing posts. 
     Preferably, the winding frame is an over-molded integrated structure, the fixing members are integrally fixed at the through holes of the winding frame during the course of forming the winding frame, and distal ends of the fixing members pass through the support seat to connect the stator structure with the support seat. 
     Preferably, the support seat is provided with a positioning post, a step is formed at a top end of the positioning post, the base plate has a positioning hole corresponding to the positioning post, the top end of the positioning post is inserted into the positioning hole, and the stator structure is disposed on the step of the positioning post. 
     Preferably, one of an inner wall surface of the hollow cylinder of the winding frame and an outer wall surface of the sleeve of the support seat forms a protrusion, and the other forms a recess for engaging with the protrusion to circumferentially position the stator structure. 
     Preferably, the insulating part is ring-shaped, the connecting part comprises a plurality of connecting lugs extending inwardly from the ring-shaped insulating part, each connecting lug forms a through hole, the support seat forms a plurality of fixing holes corresponding to the through holes of the winding frame, and fixing members pass through the through holes and are fastened in the fixing holes, respectively, to fix the stator to the support seat. 
     Preferably, the core has connecting arms extending inwardly from the ring-shaped yoke, the connecting part of the winding frame includes connecting lugs extending inwardly from the insulating part, the connecting lugs and the connecting arms correspond respectively and form coaxial through holes, the support seat forms a plurality of fixing holes, and fixing members pass through the through holes and are fastened in the fixing holes of the support seat, respectively. 
     In comparison with the conventional magnetic core, the winding frame of the present invention integrally forms the connecting part within the core to fixedly connect with the support seat, which saves material and reduces the weight of the stator structure and the motor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A preferred embodiment of the invention will now be described, by way of example only, with reference to figures of the accompanying drawings. In the figures, identical structures, elements or parts that appear in more than one figure are generally labeled with a same reference numeral in all the figures in which they appear. Dimensions of components and features shown in the figures are generally chosen for convenience and clarity of presentation and are not necessarily shown to scale. The figures are listed below, 
         FIG. 1  illustrates a stator structure of a motor according to one embodiment of the present invention. 
         FIG. 2  is a plan view of  FIG. 1 . 
         FIG. 3  is an exploded view of  FIG. 1 . 
         FIG. 4  illustrates a winding frame of the stator, viewed from another aspect. 
         FIG. 5  is a perspective, sectional view of the motor according to a preferred embodiment. 
         FIG. 6  through  FIG. 9  illustrate a motor according to another embodiment of the present invention. 
         FIG. 10  and  FIG. 11  illustrate a motor according to further embodiment of the present invention, in which the rotor is removed. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1  through  FIG. 5 , a motor according to one embodiment of the present invention includes a support seat  10 , a stator having a stator structure  20  attached to the support seat  10 , and a rotor  60  ( FIG. 5 ) surrounding the stator structure  20 . 
     A center of the support seat  10  protrudes axially upwardly to form a hollow sleeve  12 , and the hollow sleeve  12  is used to support a bearing or the like for supporting rotation of the rotor. An outer wall surface of a top of the sleeve  12  protrudes outwardly to form a protrusion  14 , for engaging with and positioning the stator structure  20  circumferentially. The protrusion  14  is preferably cylindrical. The support seat  10  is further provided with fixing posts  16  and positioning posts  18 . In this embodiment, there are two fixing posts  16  and two positioning posts  18 , which surround the sleeve  12  and are alternately arranged in a circumferential direction of the sleeve  12 . Each fixing post  16  is formed with a fixing hole  17  therein. The fixing hole  17  may be a round hole or a screw hole for fixed connection with the stator structure  20 . A top end of each positioning post  18  is formed with a step  19  for pre-positioning the stator structure  20  in the axial direction. Preferably, the positioning post  18  is slightly higher than the fixing post  16 , and the step  19  and a top surface of the fixing post  16  are located on substantially the same level. 
     The stator structure  20  comprises a core  22  made of a soft magnetic material, an insulating winding frame  24  wrapped over the core  22 , and windings  25  wound around the core  22 . 
     In this embodiment, the core  22  is of an integrated structure formed by spirally stacking and winding a strip material (i.e. formed by continuously spirally winding the strip material), including an annular yoke  26  and a plurality of teeth  28  that extend radially outwardly from an outer edge of the yoke  26  The yoke  26  is of a hollow cylindrical structure formed by the spiral winding of the strip material. The teeth . 8  are uniformly (non-uniformly in some embodiments) disposed at intervals in a circumferential direction of the yoke  26 . Compared with the traditional circular punching sheet structure, the spirally stacked and wound core  22  generates significantly less waste material, thereby improving the utilization rate of raw materials. In some embodiments, the strip materials can also be bent to form circular sheets, and the circular sheets are stacked in the axial direction of the motor to form the core  22 , which likewise generates substantially less waste material. In this embodiment, a plurality of through holes  27  is formed in the yoke  26 . The through holes  27  may be formed by stacking small holes in the strip materials, which are arranged uniformly (non-uniformly in some embodiments) in the circumferential direction of the yoke  26 . Each through hole  27  penetrates axially through the yoke  26 , and a fastening member, such as a rivet  30 , passes through the through hole  27  to shape the core  22 . In some embodiments, the core  22  can be shaped in other manners, such as, for example, by fixedly connecting tips  34  of the stacked teeth  14  by welding. 
     Each tooth  28  includes a winding portion  32  connected with the yoke  26  and a tip  34  formed at a distal end of the winding portion  32 . The tip  34  extends in the circumferential direction of the motor. A winding slot  36  is formed between adjacent winding portions  32 , a slot opening  38  is formed between adjacent tips  34 , and the windings are wound around the winding portions  32  and disposed in the winding slots  36 . Preferably, a notch  33  is formed in a connection area of the tip  34  and the winding portion  32 . Before formation, the tip  34  is partially tilted outwardly, and the slot opening  38  between the adjacent tips  34  has a large size for facilitating winding. After winding is completed, the tilted part of the tip  34  is pressed to generate plastic deformation to bend inwardly, such that a root of the tip  34  is in tight contact with the winding portion  32 , and a small slot opening is formed between the adjacent tips  34  to reducing cogging torque of the motor. In this embodiment, the notch  33  is only formed in a connection area of the tip  34  and in a single side of the winding portion  32 . Of course, in other embodiments, the notch  33  can be formed in the connection area of the tip  34  and each side of the winding portion  32 . 
     Referring to  FIG. 3  and  FIG. 4 , the winding frame  24  is an integrated structure molded directly over the core  22  from an insulation material, such as plastic or the like. The winding frame  24  comprises a connecting part  40  for assembly, and an insulating part  42  surrounding the connecting part  40 . The insulating part  42  and the core  22  are matched in profile. As shown in  FIG. 5 , preferably, the insulating part  42  covers all outer surfaces of the core  22 , except for outer circumferential surfaces  3 . 5  of the tips  34 , thereby ensuring insulation between the windings and the core  22  when the windings are subsequently wound around the core  22 , and hence avoiding short circuit of the windings. The connecting part  40  is used to fixedly connect with the support seat  10  and includes a base plate  44  integrally extending inward from an inner edge of a bottom end of the insulating part  42 , a hollow cylinder  46  formed on the base plate  44 , and a plurality of ribs  48  extending between the hollow cylinder  46  and the insulating part  42 . 
     The base plate  44  is circular ring shaped. As shown in  FIG. 4 , the base plate  44  forms through holes  45  and positioning holes  43  corresponding to the fixing posts  16  and positioning posts  18  of the support seat  10 , respectively. In this embodiment, the through holes  45  and positioning holes  43  are all located towards an outer edge of the base plate  44 , i.e. a connection area between the base plate  44  and the insulating part  42  and aligned with the inner edge of the stator core  22 . The through holes  45  are round-shaped and have a diameter approximately the same as that of the fixing holes  17  of the fixing posts  17 . The positioning holes  43  are half-round shaped and have a diameter approximately the same as the positioning posts  18 . The hollow cylinder  46  extends axially from an inner edge of the base plate  44 , which has an inner diameter that may be slightly greater than an outer diameter the sleeve  12  of the support seat  10 . As shown in  FIG. 3 , an inner wall surface of a top end of the hollow cylinder  46  forms a. recess  47  for engaging with the protrusion  14  of the sleeve  12 . It is to be understood that the protrusion  14  may also be formed on the inner wall surface of the hollow cylinder  46 , and the recess  47  may be formed in the outer wall surface of the sleeve  12 , or both. The ribs  48  are integrally connected between an outer wall surface of the hollow cylinder  46  and an inner wall surface of the insulating part  42 , and are arranged uniformly in the circumferential direction. Bottom edges of the ribs  48  are integrally connected with the base plate  44 . 
     As shown in  FIG. 5 , on assembly of the stator structure  20  to the support seat  10 , the stator structure  20  and the support seat  10  are circumferentially positioned relative to each other by aligning the recess  47  of the winding frame  24  and the protrusion  14  of the support seat  10 . The sleeve  12  is then inserted into the stator structure  20  in the axial direction. The top ends of the positioning posts  18  are inserted into the positioning holes  43 , the through holes  45  are aligned with the fixing posts  16 , and a bottom surface of the winding frame  24  is disposed on the steps  19  of the positioning posts  18  and positioning surfaces of the fixing posts  16 , such that the stator structure  20  is axially positioned. Finally, fixing members  50  pass through the through holes  45  of the base plate  44  and are then fastened in the fixing holes  17  of the fixing posts  16  of the support seat  10 , such that the stator structure  20  is fixedly connected to the support seat  10 . 
     The fixing members  50  may be screws, rivets or the like. When the fixing members  50  are rivets, the fixing members  50  may be integrally fixed on the winding frame  24  during the course of forming the winding frame  24 , and the fixing holes  17  are round holes passing through the fixing posts  16 . In assembly, the distal ends of the fixing members  50  pass through the fixing posts  16  and are then deformed to fixedly connect the stator structure  20  with the support seat  10 . When the fixing members  50  are screws, a metal piece such as a metal sleeve may be disposed in each through hole  45  when forming the winding frame  24 , which prevents the winding frame  24  from being damaged during assembly. 
     Referring to  FIG. 5 , the rotor  60  includes a shaft  62 , a housing  64  fixed to the rotary shaft  62 , a permanent magnet  66  mounted to an inner surface of a sidewall of the housing  64 . The permanent magnet  66  is opposed to the outer surfaces of the teeth  28  of the core  22 , with an air gap formed there between. The permanent magnet may be a single piece magnet or composed of multiple magnet segments or pieces. The rotary shaft  62  is mounted in the sleeve  12  of the support sleeve  10  through a bearing  68 . Ventilation openings  65  are formed in an end wall of the housing  64  to allow air to flow through the interior of the motor. 
     It is to be understood that the support seat  10  may be formed from a thermally conductive material such as aluminum. As such, the support seat  10  can also provide the heat dissipating function. After the stator structure is mounted to the sleeve  12 , a free end of the sleeve  12  extends outward beyond a free end of the hollow cylinder  46 . The free end of the sleeve  12  is then sealed by a tool having an arc-shaped machining surface, such that the free end of the sleeve  12  generates an outward plastic deformation thus forming a rivet connection with the stator structure. That is, an outer surface of the free end of the sleeve  12  is deformed to press against an edge of the hollow cylinder  46  of the stator structure to prevent the hollow cylinder  46  from becoming disengaged from the free end of the sleeve  12 . As such, the fixing members  50  can be omitted. 
       FIG. 6  through  FIG. 9  illustrates a motor according to another embodiment of the present invention. In this embodiment, a plurality of cooling fins  15  is disposed on an outer surface of the support seat  10 . Preferably, the cooling fins  15  are substantially in a radiating distribution, which facilitates dissipating the heat from the center to the surrounding space. One side of the support seat  10  remote from the stator is concave to form a receiving chamber  70 . The motor further includes a circuit board  72  that is received in the receiving chamber  70 . The winding frame  24  is an integrated structure molded directly over the stator core  22  from an insulation material, such as plastic or the like. The winding frame  24  comprises a connecting part  40  for assembly, and an insulating part  42 . The insulating part  42  and the core  22  are matched in profile. Preferably, the insulating part  42  is ring-shaped, and the connecting part  40  includes a plurality of connecting lugs extending inward from the insulating part  42 . Each connecting lug has a through hole  45 . The support seat  10  is provided with a plurality of fixing posts  16  each defining a fixing hole  17  such as a screw hole therein. A fixing member  50  such as a screw passes through the through hole  45  of the connecting part  40  of the winding frame  24  and is then fastened in the fixing hole  17  of the support seat  10 , so as to fix the stator structure to the support seat  10 . In this embodiment, a motor shaft  13  is fixed to the support seat  10 , and the rotor  60  is rotatably mounted to the shaft  13  via bearings  68 . In this embodiment, the connecting part  40  of the winding frame  24  is implemented as the connecting lugs at the inner side of the insulating part  42 . A length of the connecting lugs may be adjusted according to needs. For example, when the number of stator slats of the motor increases from twelve slots to eighteen slots, the inner diameter of the yoke  26  of the magnetic core  22  and the insulating part  42  of the winding frame  24  usually increases. In this case, by enlarging the size of the connecting part  40 , the connecting part can still match with the original support seat  10 . The core of this embodiment may be formed in the winding manner as described in the previous embodiment. 
       FIG. 10  and  FIG. 11  illustrate a motor according to another embodiment of the present invention. In this embodiment, the stator core  22  uses punched sheets, i.e. each lamination of the core  22  is formed by punching, and the laminations are stacked together. The yoke  26  of each lamination of the magnetic core  22  includes a plurality of connecting arms  262  extending inwardly, and each connecting arm  262  forms a through hole. The insulating winding frame  24  includes upper and lower layers that cover top and bottom surfaces of the stacked core  22 , respectively, to insulate the core  22  from the windings  25 . The insulating winding frame  24  includes a connecting part  40  for assembly and an insulating part  42 . The insulating part  42  and the core  22  are matched in profile. Preferably, the insulating part  42  is ring-shaped, and the connecting part  40  includes a plurality of connecting lugs extending inward from the insulating part  42 . Each connecting lug  40  has a through hole. The through hole of the connecting part  40  is aligned with the through hole of one corresponding connecting arm  262  of the core  22  and a fixing hole of the support seat  10 . The fixing member  50  passes through the respectively through holes and is then fastened in the corresponding fixing hole of the support seat  10 , so as to fix the magnetic core  22  and winding frame  24  to the support seat  10 . The support seat  10  may be formed from a thermally conductive material such as aluminum. As such the support seat  10  can also provide the heat dissipating function. The surface of the support seat  10  may be provided with a cooling fins to increase the heat dissipating surface area. 
     In the stator structure  20  of the present invention, the stator core  22  is formed by bending or winding the strip material, which enhances the material utilization rate and reduces the cogging torque, thus improving the operational stability of the motor. In addition, by forming the integrated winding frame  24  with the over-molding process, the winding frame  24  integrally forms the hollow cylinder  46  within the core  22  to connect with the support seal  10 . In comparison with the conventional stator core which has the central connecting portion connected with the support seat  10 , the core  22  of the present invention saves material and reduces the weight of the stator structure  20  and the motor by forming the winding frame  24  from plastic and connecting the hollow cylinder  46  and the insulating part  42  with the ribs  48 , 
     In the description and claims of the present application, each of the verbs “comprise”, “include”, “contain” and “have”, and variations thereof, are used in an inclusive sense, to specify the presence of the stated item or feature but do not preclude the presence of additional items or features. 
     It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. 
     The embodiments described above are provided by way of example only, and various other modifications will be apparent to persons skilled in the field without departing from the scope of the invention as defined by the appended claims.