Patent Publication Number: US-2007114856-A1

Title: Soft magnetic powder-based stator for use in motor

Description:
FIELD OF THE INVENTION  
      The present invention relates to a soft magnetic powder-based stator for use in a motor, and more particularly, to a soft magnetic powder-based stator for use in a motor, wherein the stator is advantageous of improving performance of a motor and decreasing an amount of a coil used by reducing gaps each between a corresponding tooth and a coil, and of minimizing damage to parts of a manufacturing equipment.  
     BACKGROUND OF THE INVENTION  
      In general, a motor is a device that converts electrical energy into mechanical energy to provide a rotational force. Motors are being widely applied to various industrial fields including electric home appliances and industrial machines. For instance, motors can be applied to compressors, which are installed inside cooling appliances such as air conditioners and refrigerators to restore a refrigerant to a liquid, washing machines, vacuum cleaners, optical disk players, and hard disk drivers of computers.  
      With reference to  FIG. 1 , a conventional motor will be descried hereinafter.  
       FIG. 1  illustrates a sectional view of a conventional motor  10 . The illustrated conventional motor  10  is one exemplary direct current (DC) motor, more particularly, a brushless direct current (BLDC) motor that drives using a non-contact type position detector and a semiconductor device instead of a brush. The conventional motor  10  includes holders  11  and  12 , bearings  11   a  and  12   a , a casing  13 , a stator  14 , teeth  14   b  (refer to  FIG. 2 ), an insulator  14   a , a coil  14   c , a rotor  15 , a plurality of magnets  15   a , and a rotational shaft  16 . The holders  11  and  12  are attached individually to the casing  13  on upper and low sides. In the stator  14 , the teeth  14   b  are affixed to the inner surface of the casing  13  and insulated by the insulator  14   a , and the coil  14   c  is wound around the teeth  14   b . The rotor  15  is installed inside the stator  14  by having a gap therebetween. The magnets  15   a  are inserted into and affixed to the outer surface of the rotor  15 . The rotor  15  rotates due to reciprocal reactions between the magnets  15   a  and a magnetic field produced at the stator  14 . The rotational shaft  16  is affixed to a central part of the rotor  15  and installed to be rotatable by means of the bearings  11   a  and  12   a  of the respective holders  11  and  12 .  
      Referring to  FIG. 2 , the teeth  14   b  of the stator  14  are spaced apart a certain distance from each other along the inner surface of the stator  14  to form a plurality of slots  14   e  inside the stator  14 .  
      As similar to the rotor  15 , the conventional stator  14  for use in a motor is formed by stacking a plurality of silicon steel sheets  14   d  (refer to  FIG. 3 ) over each other. As illustrated in  FIG. 3 , the teeth  14   b  are formed in a quadrature shape from a sectional view. That is, each of the teeth  14   b  has upper and lower surfaces  14   f  and  14   g  and two side surfaces  14   h  in straight lines. Thus, the sectional view of the teeth  14   b  is inevitably in a quadrature shape since the stator  14  is manufactured by stacking the multiple silicon steel sheets  14   d  over each other.  
      However, since the teeth  14   b  of the conventional stator  14  has the quadrature shape from the sectional view, as illustrated in  FIG. 4 , the coil  14   c  wound around the teeth  14   b  insulated by the insulator  14   a  generates gaps G on the surfaces of the teeth  14   b , particularly, the upper and lower surfaces  14   f  and  14   g . The gaps G often cause reduction in the performance of the motor  10  and increase in an amount of the coil  14   c  wound around the individual teeth  14   b . As a result, the loss of the coil  14   c  may be accelerated.  
     SUMMARY OF THE INVENTION  
      It is, therefore, an object of the present invention to provide a soft magnetic powder-based stator for use in a motor, wherein the stator can prevent reduction in performance of a motor by reducing gaps each between a corresponding tooth and a coil, reduce manufacturing costs by decreasing an amount of the coil used, provide a lightweight motor through weight reduction, and minimize damage to parts of a manufacturing equipment.  
      In accordance with a preferred embodiment of the present invention, there is provided a stator for use in a motor. The stator is wound with a coil. The stator includes a main body fixed to the inside of the motor, a plurality of teeth formed to be integrated with the main body and respectively wound with the coil, gap reducers, each of which being formed on upper and lower surfaces of each of the teeth and protruding in a direction to decrease gaps between the upper surface of each of the teeth and the coil and between the lower surface of each of the teeth and the coil, and punch damage barriers, each of which having plane surfaces extending to both sides of each of the gap reducers and connected to both sides of each of the teeth.  
      Preferably, the teeth are formed to have indentations lengthwise on the upper and lower surfaces of the teeth to decrease a volume of the teeth.  
      Preferably, each of the gap reducers is formed in an arc shape to protrude.  
      Preferably, each of the gap reducers is formed to protrude by connecting a straight-line surface portion of each of the gap reducers with curved-line surface portions of each of the gap reducers.  
      Preferably, each of the gap reducers is formed to protrude by connecting straight-line surface portions of each of the gap reducers with each other. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:  
       FIG. 1  illustrates a sectional view of a conventional motor;  
       FIG. 2  illustrates a top view of a stator for use in the conventional motor;  
       FIG. 3  illustrates a sectional view of the stator taken along a line A-A′ illustrated in  FIG. 2 ;  
       FIG. 4  illustrates a sectional view of the conventional stator to describe limitations thereof;  
       FIG. 5  illustrates a sectional view of a motor in accordance with an embodiment of the present invention;  
       FIG. 6  illustrates a top view of a stator used in a motor and formed of soft magnetic powder material in accordance with a first exemplary embodiment of the present invention;  
       FIG. 7  illustrates a sectional view of the stator taken along a line B-B′ illustrated in  FIG. 6 ;  
       FIG. 8  illustrates a sectional view of the stator taken along a line C-C′ illustrated in  FIG. 6 ;  
       FIG. 9  illustrates a sectional view to describe the working of the soft magnetic powder-based stator for use in the motor in accordance with the first exemplary embodiment of the present invention;  
       FIG. 10  illustrates a sectional view to describe the working of a soft magnetic powder-based stator for use in a motor in accordance with a second exemplary embodiment of the present invention;  
       FIG. 11  illustrates a sectional view to describe the working of a soft magnetic powder-based stator for use in a motor in accordance with a third exemplary embodiment of the present invention; and  
       FIGS. 12A and 12B  illustrate sectional views to describe the working of the soft magnetic powder-based stator for use in the motor in accordance with other exemplary embodiments of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that they can be readily implemented by those skilled in the art.  
       FIG. 5  illustrates a sectional view of a motor in accordance with an embodiment of the present invention.  FIG. 6  illustrates a sectional view of a stator used in a motor and formed of a soft magnetic powder material in accordance with a first exemplary embodiment of the present invention.  FIG. 7  illustrates a sectional view of the stator taken along a line B-B′ illustrated in  FIG. 6 . In the motor  200 , the stator  100  is affixed to the inner side of a casing  230  to which holders  210  and  220  are individually attached on both sides. A rotor  240  is affixed to a shaft  250  by having a gap therein. The shaft  250  is installed by means of bearings  211  and  221  of the respective holders  210  and  220 . The stator  100  includes a main body  110 , teeth  120 , gap reducers  130 , and punch damage barriers  140 . The teeth  120  are formed to be integrated with the main body  110 . The gap reducers  130  are placed individually on both upper and lower surfaces of each of the teeth  120 . The punch damage barriers  140  are formed to extend on both sides of each of the gap reducers  130 .  
      The main body  110  is formed in an annular shape and affixed to the inner surface of the casing  130 . The teeth  120  are spaced apart a certain distance from each other on the inner surface of the main body  110 , and formed in an integral structure. In the present embodiment, it is exemplified that the teeth  120  are formed on the inner surface of the main body  110 . However, the teeth  120  can also be formed on the outer surface of the main body  110  depending on motor types and usage.  
      A coil  150  is wound around the individual teeth  120  to generate a magnetic filed, and the gap reducers  130  are individually placed on the upper and lower surfaces of each of the teeth  120 .  
      As illustrated in  FIG. 7 , the gap reducers  130  are formed in the shape of an arc protruding to a direction that reduces gaps between the upper surface of each of the teeth  120  and the coil  150  wound therearound and between the lower surface of each of the teeth  120  and the coil wound therearound. The punch damage barriers  140  are formed to extend to both sides of each of the gap reducers  130 . Each of the punch damage barriers  140  has plane surfaces by extending to both sides of the corresponding gap reducer  130  and being connected to both sides of the corresponding tooth  120 .  
      Referring to  FIG. 8 , the upper and lower surfaces of each of the teeth  120  where the corresponding gap reducer  130  is disposed are indented lengthwise to decrease the volume of the teeth  120  for a lightweight motor.  
      The stator  100  is molded by pressing soft magnetic powder, which includes iron-based particles each coated with a certain material to be electrically insulated from each other.  
      Referring to  FIG. 12A , the gap reducers  130  and the punch damage barriers  140  of the stator  100  are manufactured using a press molding apparatus  300 . In detail, the press molding apparatus  300  includes a molding space  310  designed to have the same shape as the stator  100 . Soft magnetic powder is filled into the molding space  310  and pressed by a pressing member such as a punch  320 , thereby forming the gap reducers  130  and the punch damage barriers  140 . At this time, a lubricant and/or a bonding agent may be added to the soft magnetic powder and pressed together.  FIG. 12A  illustrates the press molding of the gap reducers  130  only for the simplicity of the description.  
      The stator  100  includes a three-dimensional soft magnetic composite (SMC) obtained by pressing the soft magnetic powder, and has a higher degree of freedom as compared with the conventional stator based on silicon steel sheets. Different from the conventional stator having the stack structure of the silicon steel sheets, this high degree of freedom in the three-dimensional structure of the stator  100  allows the formation of the gap reducers  130 .  
      Referring to  FIGS. 5 and 9 , an insulator  160  is attached to the teeth  120  to insulate the teeth  120  and the coil  150  from each other. Those regions of the insulator  160  contacting the gap reducers  130  and the punch damage barriers  140  are formed in a shape substantially the same as the gap reducers  130  and the punch damage barriers  140 .  
      Referring to  FIG. 10 , a gap reducer  170  according to a second exemplary embodiment of the present invention is formed to protrude by connecting a straight-line surface portion of the gap reducer  170  with curved-line surface portions thereof. In the second exemplary embodiment, the straight-line surface portion located at a central region of the target surface of the gap reducer  170  is connected with the curved-line surface portions located at both sides of the straight-line surface portion. In addition to this connection, the protrusion of the gap reducer  170  can also achieved through other various connections between the straight-line surface portions with the curved-line surface portions.  
      Referring to  FIG. 11 , a gap reducer  180  according to a third exemplary embodiment of the present invention is formed to protrude by connecting straight-line surface portions with each other.  
      As similar to the first exemplary embodiment, in the second and third exemplary embodiments, those portions of insulators  171  and  181  contacting the respective gap reducers  170  and  180  and respective punch damage barriers  140  are formed in a shape substantially the same as the gap reducers  170  and  180  and the punch damage barriers  140 .  
      The soft magnetic power-based stator for use in the motor as described above operates as follows.  
      As illustrated in FIGS.  9  to  11 , each of the gap reducers  130 ,  170  and  180  is formed on both upper and lower surfaces of the corresponding tooth  120 , so that gaps each between the upper surface of the corresponding tooth  120  and the coil  150  wound therearound and between the lower surface of the corresponding tooth  120  and the coil  150  wound therearound can be reduced to a greater extent as compared with the conventionally discovered gaps G (see  FIG. 4 ). That is, the teeth  120  are formed to have the width smaller than the height, and thus, when the coil  150  based on a material resistant to a certain degree of bending is wound around the teeth  120 , gaps are produced between the upper surface of each of the teeth  120  and the coil  150  wound therearound and between the lower surface of each of the teeth  120  and the coil wound therearound. However, the gap reducers  130 ,  170  and  180  fill the gaps to thereby reducing sizes of these gaps to a great extent.  
      As illustrated in  FIG. 8 , since the teeth  120  are formed to have the indentations lengthwise, the volume of the teeth  120  can be reduced. This volume reduction helps manufacturing of lightweight motors.  
      As illustrated in  FIG. 12A , the punch damage barriers  140  formed in the stator  100  can dull edge portions  321  of the punch  320 . Hence, even if the punch  320  presses the soft magnetic powder with great strength to manufacture the stator  100 , the punch damage barriers  140  can contribute to improvement in durability of the punch  320 .  
      Meanwhile, as illustrated in  FIG. 12B , for a tooth  410  without punch damage barriers with plane surfaces, gap reducers  420  that protrude in curvature are connected directly to both sides of the tooth  410 . Thus, edge portions  431  of a punch  430  of a press molding apparatus  400  are sharp, and as a result, the edge portions  431  are likely to be damaged when soft magnetic powder is pressed. Accordingly, the punch damage barriers  140  can prevent damage to the punch  320  of the press molding apparatus  300 .  
      Different from the conventional stator  14  (see  FIG. 1 ) formed by stacking the silicon steel sheets  14   d  (see FIG.  3 ) over each other, the soft magnetic powder-based stator  100  for use in the motor  200  allows formation of the gap reducers  130 ,  170  and  180  due to the use of the soft magnetic powder. The gap reducers  130 ,  170  and  180  can reduce the gaps between each of the teeth  120  and the coil  150 . As a result, efficiency of the motor  200  can be improved, thereby further facilitating the performance of the motor  200 .  
      Also, since the coil  150  is disposed close to the individual teeth  120 , an amount of the coil  150  used can be reduced as compared with the amount of the coil  14   c  of the motor  10  (see  FIG. 1 ) having the same number of windings as the coil  150  of the motor  200 . This reduction allows manufacturing of the motor  200  at low cost. Since the teeth  120  are indented lengthwise, the motor  200  can be lightweight. Furthermore, it is possible to minimize damage to those parts of the manufacturing equipment, e.g., the punch  220 .  
      On the basis of various embodiments of the present invention, the performance of the motor can be improved by reducing gaps between each of the teeth and the coil. Also, the manufacturing costs can be reduced by decreasing an amount of the coil used. The decrease in the volume of the teeth allows manufacturing of the lightweight motor, and damage to the parts of the manufacturing equipment can be minimized.  
      While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.