Patent Publication Number: US-2016226322-A1

Title: Motor Armature

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This non-provisional patent application claims priority under 35 U.S.C. §119(a) from Patent Application No. 201510050696.3 filed in The People&#39;s Republic of China on Jan. 30, 2015, and from Patent Application No. 201510054879.2 filed in The People&#39;s Republic of China on Jan. 30, 2015, the entire contents of both are hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     This invention relates to motor armatures and in particular, to a stator for an outer rotor motor. 
     BACKGROUND OF THE INVENTION 
     As is known, a motor includes a rotor and a stator that magnetically interact to drive the rotor to rotate, which rotor in turn drives a load. According to the position relationship between the rotor and stator, motors can be classified into inner rotor motor and outer rotor motor. As the name suggests, the outer rotor motor is one in which the rotor surrounds an inner stator. The load such as a fan can be directly disposed on the rotor. Due to the advantages of large rotational inertia and saving copper wires, the outer rotor motors are widely used in ventilators, instruments, range hoods and the like. 
     The stator structure of the conventional outer rotor motor usually includes a core and windings wound around the core. The core is formed by stacking a large quantity of silicon steel sheets, referred to as laminations. Each silicon steel sheet includes an annular yoke and teeth extending radially outwardly from the yoke. The windings are wound around the teeth. For facilitating subsequent winding of the windings, adjacent teeth of the core of the convention stator structure have a large gap there between, i.e. having a large width tooth slot, which results in a large cogging torque and hence affects the motor performance. In addition, in forming this core structure, laminations are punched to form the annular yoke and the spaced teeth. The material parts corresponding to the portions between the teeth and inside the yoke are removed as waste material, which, to a large extent, causes the waste of material. 
     SUMMARY OF THE INVENTION 
     Hence there is a desire for a motor armature which has a reduced cogging torque and increased material utilization rate. 
     Accordingly, in one aspect thereof, the present invention provides a motor armature comprising: a core, comprising an annular yoke and a plurality of teeth extending radially outwardly from an outer edge of the yoke, each of the teeth comprising a winding portion connected with the yoke and a tip formed at a distal end of the winding portion, each tip having circumferential opposite ends extending beyond the winding portion, a slot opening being formed between ends of adjacent tips; and windings wound around the winding portions of the teeth of the core and disposed inside the tips, wherein a slit is formed in each of the teeth on a single circumferential side thereof such that one of said opposite ends of the tip is outwardly tilted relative to the other of said opposite ends in an original position and is bendable inwardly about the slit to a deformed position where a width of the slot opening is less than the width of the slot opening in the original position. 
     Preferably, the slit is formed in an area where the tip and the winding portion are connected. 
     Preferably, the slit extends into the tooth in a circumferential direction of the core and has a depth less than a half of the circumferential width of the winding portion. 
     Alternatively, the slit is formed in the part of the tip that extends beyond the winding portion, and the slit extends outwardly a distance into the tip from an inner surface of the tip. 
     Alternatively, the slit is formed in the winding portion. 
     Preferably, the slit extends into the tooth from an area where the tip and the winding portion are connected and then bends to extend a distance toward an outer surface of the tip. 
     Preferably, when the core is unfold in a circumferential direction, a sum of the widths of the parts of the tip extending beyond the winding portion is greater than a distance between adjacent winding portions. 
     Preferably, the core is formed by spirally winding a strip material. 
     Alternatively, the core is formed by a stack of laminations, and each lamination is bent, with opposite ends of the lamination connected to each other. 
     Alternatively, the core is formed by a stack of punched laminations. 
     Preferably, parts of each of the teeth on opposite sides of the slit form a latching structure. 
     Preferably, the latching structure comprises a latching protrusion formed on one of the tip and winding portion and a latching opening formed in the other of the tip and winding portion. 
     Preferably, the core is fastened together by four weld joints which are located at four ends of an English alphabet X. 
     Preferably, the core is formed by spirally winding a strip material with a starting tooth and an ending tooth, one weld joint is located at an outer circumferential surface of the tip of the starting tooth of the strip material, another weld joint is located at an outer circumferential surface of the tip of the end tooth of the strip material, and the other two weld joints are respectively located at outer circumferential surfaces of the tips of teeth diametrically opposing the starting and end teeth. 
     Alternatively, the core is formed by a stack of laminations each of which is bent from a strip material with a starting tooth and an ending tooth, one weld joint is located at an outer circumferential surface of the tip of the starting tooth of the strip material, another weld joint is located at an outer circumferential surface of the tip of the end tooth of the strip material, and the other two weld joints are respectively located at outer circumferential surfaces of the tips of teeth diametrically opposing the starting and end teeth. 
     According to a second aspect, the present invention provides a method of making a motor armature, the method comprising: providing a strip material which comprises an elongated yoke blank and a plurality of tooth blanks extending from the yoke blank, each tooth blank comprising a linear portion connected to the yoke blank and a tip formed at a distal end of the linear portion, opposite sides of the tip extending beyond the linear portion, a notch being formed in each tooth blank on a single side thereof such that one of said opposite ends of the tip is outwardly tilted relative to the other of said opposite ends; forming a core by spirally winding the strip or by stacking laminations formed by bending the strip, whereby the yoke blank forms an annular yoke, the tooth blanks being stacked to form teeth extending outwardly from the yoke, and the notches form slits in the teeth; and winding windings around the teeth. 
     Preferably, the method further comprises sequentially pressing said one of the opposite ends of the tip outwardly tilted in a clockwise direction or anti-clockwise direction to deform the tilted end of the tip to a deformed position close the slits and narrow a gap between adjacent ends of the tips, after the winding step. 
     Preferably, forming a core further comprises inwardly pressing said one of the opposite ends of the tip outwardly tilted when spirally winding the strip material. 
     In comparison with the conventional motor armature, the tips of the core of the motor armature of the present invention are tilted outward prior to the forming of the core. Therefore, the tips can have a greater width, while ensuring that adjacent tips have the sufficient distance there between for winding of the windings. After the core is formed, the tips of the adjacent teeth form a narrow slot opening which reduces the cogging torque of 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 of an outer rotor motor according to one embodiment of the present invention. 
         FIG. 2  is a plan view of  FIG. 1 . 
         FIG. 3  illustrates a core of the stator of  FIG. 1 , the core being a spiral winding structure. 
         FIG. 4  is a plan view of  FIG. 3 . 
         FIG. 5  illustrates a strip material for forming the core. 
         FIG. 6  is an enlarged view of a part of the strip material. 
         FIG. 7  illustrates the punching step for forming the strip material of  FIG. 5 . 
         FIG. 8  to  FIG. 12  illustrate the strip material according to other embodiments. 
         FIG. 13  illustrates a core blank formed by spirally winding the strip material. 
         FIG. 14  is a plan view of  FIG. 13 . 
         FIG. 15  illustrates the core blank with the windings wound thereon. 
         FIG. 16  illustrates a stator according to a second embodiment of the present invention. 
         FIG. 17  illustrates the core of the stator of  FIG. 16 , the core being a stack of bent strip materials. 
         FIG. 18  illustrates a lamination blank of the core of  FIG. 17 . 
         FIG. 19  illustrates the lamination after the tips have been pressed. 
         FIG. 20  illustrates the core blank formed by stacking the lamination blanks. 
         FIG. 21  illustrates the core blank of  FIG. 20 , with the winding wound thereon. 
         FIG. 22  illustrates a stator according to a third embodiment of the present invention, the core being a stacking structure. 
         FIG. 23  illustrates a punched sheet lamination blank. 
         FIG. 24  illustrates the core blank formed by the punched sheets of  FIG. 23 . 
         FIG. 25  illustrates the core blank of  FIG. 24 , with the windings wound thereon. 
         FIG. 26  is an enlarged view of a part of a strip material for forming a stator core according to a fourth embodiment of the present invention. 
         FIG. 27  illustrates a stator core formed using the strip material of  FIG. 26 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Referring to  FIG. 1  and  FIG. 2 , the stator of the outer rotor motor according to one embodiment of the present invention includes a core  10  made of magnetically conductive material such as iron and windings  20  wound around the core  10 . The core  10  includes an annular yoke  12  and a plurality of teeth  14  extending radially outwardly from an outer edge of the yoke  12 . The windings  20  are wound around the teeth  14  of the core  10 . When appropriately energized, the windings  20  produce alternating magnetic flux which interacts with the rotor so as to drive a load. 
     Referring also to  FIGS. 3 to 5 , in this embodiment, the core  10  includes a plurality of stacked layers made by spirally winding a single piece of strip material  30  to form a unitary structure stator core. The yoke  12  of the core  10  is a hollow cylindrical structure formed by the spiral winding of the strip material  30 . A plurality of grooves  13  is formed in an inner surface of the yoke  12 , which facilitates bending deformation of the strip material  30  during the spiral winding. The grooves  13  extend in an axial direction of the yoke  12  and preferably have a half-round cross-section. Each groove  13  is radially aligned with a corresponding one of the teeth  14 . The teeth  14  are evenly distributed in a circumferential direction of the yoke  12 . Each tooth  14  includes a winding portion  16  connected with the yoke  12  and a tip  18  formed at a distal end of the winding portion  16 . A winding slot  15  is formed between adjacent winding portions  16 . The windings  20  are wound around the winding portions  16  and disposed inside the tips  18 . A circumferential width of the tip  18  is greater than that of the winding portion  16 . Opposite sides of the tip  18  in the circumferential direction extend beyond the winding portion  16 , with a narrow slot opening  19  formed between adjacent tips  18 . In this embodiment, a linear slit  17  is formed in an area where the tip  18  and the winding portion  16  are connected. The slit  17  extends in the width direction of the winding portion  16  and has a depth that is approximately a half of the width of the winding portion  16 . A left half part of the tip  18  is integrally connected with the winding portion  16 , and a right half part of the tip  18  is separated from the winding portion  16  by the slit  17 . 
     Referring also to  FIG. 5  and  FIG. 6 , the strip material  30  for forming the core  10  has a generally elongated form and includes an elongated yoke blank  32  and a plurality of tooth blanks  34  formed on one side of the yoke  32 . A cutout  33  is formed in the other side of the yoke  32 , corresponding to each of the teeth  34 . In a length direction of the strip material  30 , the tooth blanks  34  are spaced apart and arranged parallel to each other. Each tooth blank  34  includes a linear portion  36  and a tip  38  formed at a distal end of the linear portion  36 . The tip  38  is greater than the linear portion  36  in width. Opposite sides of the tip  38  extend beyond the linear portion  36 . A left half part of the tip  38  is integrally connected with and generally perpendicular to the linear portion  38 . A right half part of the tip  38  is tilted outward relative to the left half part, with an angle of greater than 90° formed between the right half part and the linear portion  36 . In this embodiment, a sum of the widths of the opposite sides of the tip  38  extending beyond the linear portion  36  is greater than a distance between adjacent linear portions. Because the right half part is tilted outward, adjacent tips  38  overlap with each other in a direction perpendicular to the length direction of the strip material  30 . A notch  37  is formed in an area where the right half part of the tip  38  and the linear portion  36  are connected. The notch  37  extends in a width direction of the linear portion  36  and has a depth that is approximately half of the width of the linear portion  36 . As such, the right half part of the tip  38  is capable of plastic deformation under an external force and bends toward the linear portion  36  to form a symmetrical structure with the left half part. Alternatively, the depth of the notch  37  is ⅓ of the width of the linear portion  36 , which facilitates the deformation of the tip  38  while not having a large influence on the magnetic path. 
     Referring to  FIG. 13  and  FIG. 14 , the strip material  30  is spirally wound to form a core blank  11 . The yoke  32  experiences plastic deformation to bend spirally to form the yoke  12  of the core  10 . After the yoke  12  is formed, the cutouts  33  are aligned in the axial direction and collectively form the groove  13 . Due to the bending of the yoke  32 , the teeth  34  that were previously parallel to each other now extend radially outward. The linear portions of the tooth blanks  34  are stacked to collectively form the winding portions  16 , and the tips  38  are stacked to collectively form the tips  18 . The left half parts of the tips  18  are integrally connected with the winding portions  16 , and the right half parts are tilted outward. The notches  37  of the tips  38  are aligned to form the slits  17  of the teeth  14 . The slits  17  separate the right half parts of the tips  18  apart from the winding portions  16 , such that the right half parts of the tips  18  are capable of bending relative to the winding portions  16 . Because the teeth  34  extend radially outward, the distance between adjacent winding portions  16  increases gradually in the radially outward direction. The maximum distance, i.e. at the area where the winding portion  16  and the tip  18  are connected, is greater than the widths of the part of the tips  18  extending beyond the winding portions  16 , such that the adjacent tips  18  are spaced from each other in the circumferential direction to facilitate winding of the winding  20 . 
     Preferably, after spirally winding, stacked layers of the core  10  are fastened together by welding. Referring to  FIG. 4 , in this embodiment, adjacent layers of core  10  are fastened together by four weld joints A, B, C and D which are respectively located at four ends of an X. Preferably, one weld joint A is located at the outer circumferential surface of the tip  18  of the starting tooth of the strip material and another welding joint D is located at the outer circumferential surface of the tip of the ending tooth of the strip material. The other two welding joints B and C are respectively located at the outer circumferential surfaces of the tips  18  of teeth diametrically opposing the starting and end teeth. Preferably, the starting tooth and the end tooth are spaced with a width of one tooth in the circumferential direction of the core  10 . 
     After the core blank  11  is formed, the windings  20  are wound around the winding portions  16 . The tips  18  are pressed to inwardly deform the outward-tilting right half parts of the tips  18  to form the stator structure of  FIG. 1 . During winding of the winding portions  20 , as shown in  FIG. 15 , because the right half parts of the tips  18  are outwardly tilted relative to the left half parts, the distance between adjacent tips  18  has a sufficient width to facilitate the winding of the windings  20 . When pressing the tips  18  to inwardly deform, because the outwardly-tilted right half parts and the winding portions  16  have the notches  37  formed there between, only a smaller external force is required to effect the plastic deformation of bending inward, until the tips closely contact the winding portions  16  to substantially eliminate the previously presented slits  17  such that the right half parts and the left half parts are symmetrical with each other. It should be understood that, after the core blank  11  is formed, the outwardly-tilted parts of the tips  18  can first be forced to bend inward to eliminate the slits  17  to form the core of  FIG. 3 , and then the windings  20  are wound to form the stator structure of  FIG. 1 . In comparison, the tips  18  before deformation have a larger distance there between, i.e. the slot opening is larger, which is more advantageous in the winding of the windings  20 . Especially for the small sized core  10 , the outward-tilting of the tips  18  not only facilitates the winding of the windings  20 , but it also ensures the sufficient width of the tips  18  such that the finished core  10  has a narrow slot opening  19 . When winding the windings  20  prior to the deformation of the tips  18 , the slot opening  19  of the core  10  of the present invention can be sized to form an approximately closed slot, and the width of the slot opening  10  can be less than 0.2 mm. The slits  17  are formed on the same single side of the teeth  14 , for example in this embodiment all slits  17  are only formed on the right hand side of the teeth. Therefore, during pressing of the outwardly-tilting part of the tips  38 , it is convenient for a pressing machine to inwardly press the tips sequentially in the clockwise direction of the core  10 . 
     As described above, the core  10  of the stator structure of the present invention is formed by the spiral winding of the strip material  30 . The inner space of the yoke  12  is formed by the spiral winding of the yoke blank  32  instead of punching a core material. In comparison with the conventional circular punched sheet structure, the present stator structure can significantly reduce the waste of material, thus increasing the material utilization rate. In addition, the strip material  30  is in the form of an elongated strip. Therefore, multiple strip materials  30  can be arranged parallel to each other in a single piece of material. As shown in  FIG. 7 , in comparison with the conventional circular punched sheet structure, substantially less material is wasted in between the strip materials  30 , which further increases the material utilization rate. Furthermore, the tip  38  is not a symmetrical structure, with its right half part outwardly tilted relative to its left half part. The adjacent tips  38  overlap in the length direction of the strip material. Therefore, the width of the tip  38  is effectively increased. During the spiral winding of the strip material, the teeth  38  extend radially outward to increase the distance between the tips so that the tips  18  no longer overlap in the circumferential direction. The tips  18  can form a narrow slot opening  19  there between, which effectively reduces the cogging torque of the motor. The slit  17  is formed between the tilted tip  18  and the winding portion  16 , which provides room for subsequent deformation of the tip  18 . 
     In other embodiments, the slit  17  may have another form and position. As shown in  FIG. 8 , and  FIG. 9 , the slit  17   a  and slit  17   b  likewise are defined in the area where the tip  18  and the winding portion  16  are connected and extend in the width direction of the winding portion  16 , but have different shapes. In addition, as shown in  FIG. 10 , the slit  17   c  is defined in the area where the tip  18  and the winding portion  16  are connected and extends in the width direction of the winding portion  16  and then bends to extend outward a distance. The left and right half parts of the tip  18  have a very narrow connecting area there between, which makes the right half part of the tip  18  easier to deform. Further, as shown in  FIG. 11  and  FIG. 12 , the slit  17   d  and slit  17   e  are formed in the tip  18  and the winding portion  16 , respectively. In  FIG. 11 , the slit  17   d  is formed in the part of the tip  18  extending beyond the winding portion  16 , which extends a distance into the tip  18  from an inner surface of the tip  18  in the outward direction. In  FIG. 12 , the slit  17   e  extends perpendicularly a distance into the winding portion  16  from a middle part of the winding portion  16 , and the part of the winding portion  16  outside the slit  17   e  and the entire tip  18  are tilted relative to the part of the winding portion  16  inside the slit  17   e.    
       FIG. 16  illustrates a second embodiment of the stator structure of the present invention. The second embodiment is different from the first embodiment in that the core  40  includes a stack of laminations each of which is formed by a strip material  30  that is bent and deformed into a ring. The length of the strip material  30  is approximately the same as the circumference of the yoke  12 . The strip material  30  is bent such that opposite ends of the strip material  30  are connected to form a circular ring  31 , as shown in  FIG. 18 . The tips  38  of the circular ring  31  are pressed such that the tilt parts of the tips deform to closely contact the winding portions  36 , thus substantially eliminating the notches  37 . The lamination  39  as shown in  FIG. 19  is thus achieved. Stacking the laminations  39  forms the core  40  of the stator structure of the present embodiment, as shown in  FIG. 17 . After the stacking process, the laminations  39  may be fastened together by welding. The stator structure as shown in  FIG. 16  is formed by winding the windings  20  around the core  40 . In addition, it is possible to first stack the circular rings  31  to form the core blank  41  of  FIG. 20 . After the core blank  41  is formed, the windings  20  may be wound as shown in  FIG. 21 , and the tips  18  are then pressed to eliminate the slits  17  to form the stator structure of  FIG. 16 . Alternatively, the tips  18  may be pressed to eliminate the slits  17  to form the core  40  of  FIG. 17  and then the windings  20  are wound to form the stator structure of  FIG. 16 . Therefore, in this embodiment, the stator core  40  may be fabricated in various processes. 
     Different from the first embodiment, in forming the core  40  of the stator structure of this embodiment, the strip material  30  is bent to form the single circular ring  31 , and the circular rings  31  are stacked to form the core  40 . In comparison with the process of spirally winding the strip material  30  to form the core  10 , one more step is added in this embodiment. However, bending to form the circular lamination is easier to control than spirally winding and, therefore, the production efficiency is not reduced. In addition, bending deformation of the strip material  30  can likewise significantly reduce the waste of material, thereby increasing the material utilization rate. The stator structure thus formed likewise has the narrow slot openings  19 , which can effectively reduce the cogging torque. 
       FIG. 22  illustrates a third embodiment of the stator structure of the present invention. In this embodiment, the core  50  includes a stack of punched laminations  60 . Referring also to  FIG. 23 , each punching lamination  60  includes an annular yoke  32  and teeth  34  extending radially outward from the yoke  32 . The yoke  32  is of a complete ring. The notch  37  is formed in the area where the linear portion  36  of each tooth  34  and the tip  38  are connected. The right half part of the tip is tilted outward relative to the left half part. In comparison with the conventional silicon steel sheet, the tip  38  has an increased width. Stacking the punched laminations  60  forms the core blank  51  of  FIG. 24 , with the yokes  32  stacked to form the yoke  12  of the core  50 , the teeth  34  stacked to form the teeth  14  of the core  50 , and the notches  37  aligned to form the slits  17  in the teeth  14 . As shown in  FIG. 25 , the windings  20  are then wound around the teeth  34  and the tips  18  of the teeth  34  are pressed to deform to eliminate the slits  17 , thus forming the stator of this embodiment. Because the tips  38  are tilted outward and hence have the increased width, the slot openings  19  between the tips  18  are narrower, which reduces the cogging torque. 
       FIG. 26  and  FIG. 27  illustrate a stator core according to a fourth embodiment of the present invention. In this embodiment, the stator is formed in the same manner as in the first embodiment, i.e. the core  10  is formed by a strip material  30  spirally wound into a unitary structure, the yoke  12  of the core  10  is a hollow cylindrical structure formed by spirally winding the strip material  30 , and the grooves  13  are formed in the inner surface of the yoke  12 , which facilitate the bending deformation of the strip material  30  during the spiral winding. The differences include: cutouts  33  and through holes  35  are alternately formed in the yoke blank  32  of the strip material  30 , which correspond to the respective tooth blank  34 . These cutouts  33  and through holes  35  form the grooves  13  and mounting holes  15 , respectively. The mounting hole  15  is spaced a distance from an inner edge of the yoke  12 , for allowing a fastener  152  such as a rivet to pass there through to fasten the core  10  together. Preferably, the mounting holes  15  and grooves  13  are spaced apart and evenly distributed in the circumferential direction, with their centers located on central lines of the teeth  14 , respectively. The tip  18  and the winding portion  16  further include a latching structure at the slit  17 . Specifically, in the tooth blank, the end of the winding portion  16  remote from the yoke blank  32  forms a latching opening  362 , and the tip  38  forms a latching protrusion  382  at the notch  37 . After the spiral winding is completed, the tip  18  is pressed to make the outwardly tilt right half part of the tip  18  deform inward such that the latching protrusion  382  of the tip  18  is engaged into the latching opening  362  of the winding portion  16 . The provision of the latching structure of the tip  38  and winding portion  16  at the slit  17  prevents the tip  18  and the winding portion  16  from disengaging from each other. Notches  39  are formed in the yoke  32  of the strip material  30 , corresponding to the respective intervals between the teeth  34 , to facilitate the spiral winding of the strip material  30 . Understandably, the location of the latching protrusion  382  and latching opening  362  is interchangeable, i.e., the latching protrusion  382  may be formed on the winding portion  16  and the latching opening  363  may be formed in the tip  18 . 
     It should be noted that the core structure of the present invention is not limited to be used as a stator for an outer rotor motor, but it can also be used as a rotor for a brush motor. Thus the stator embodiments are used only as examples of a possible motor armature to which the present invention may be applied. 
     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.