Patent Publication Number: US-2007114862-A1

Title: Motor having stator made of soft magnetic powder material

Description:
FIELD OF THE INVENTION  
      The present invention relates generally to motors having stators made of soft magnetic powder material and, more particularly, to a motor having a stator made of soft magnetic powder material which is constructed such that a cover is easily coupled to the stator without extra coupling members, thus simplifying a process of assembling the cover with the stator.  
     BACKGROUND OF THE INVENTION  
      As well known to those skilled in the art, motors are devices which convert electric energy into mechanical energy to provide rotating force. Such motors are widely used in industrial apparatuses as well as in domestic electronic products. Motors are classified into DC motors and AC motors. A typical motor includes a stator, around which a coil is wound, and a rotor, which is rotatably provided in the stator at a position spaced apart from the inner surface of the stator at a predetermined gap and is rotated by magnetic flux generated in the coil.  
      Meanwhile, in the motor, the stator is fastened to a casing or cover by various methods. With regard to this, a conventional motor will be explained with reference to the attached drawing.  
       FIG. 1  is an exploded view showing critical parts of the conventional motor. As shown in the drawing, in the conventional motor  10 , a shaft  14  is supported by a pair of covers  11  and  12  so as to be rotatable using bearings  14   a  and  14   b , and a stator  13  is fastened between the covers  11  and  12  using a plurality of nuts N and bolts B.  
      The covers  11  and  12  have insert holes  11   a  and  12   a  at positions corresponding to each other such that the bolts B can be inserted through the covers  11  and  12 .  
      Furthermore, a rotor  15 , through the center of which the shaft  14  is fastened, is provided in the stator  13  at a position spaced apart from the inner surface of the stator  13  by a predetermined gap. The stator  13  is formed by layering silicon steel plates having the same shape. Insert holes  13   a  for insertion of the bolts B are formed in the stator  13 .  
      To assemble the conventional motor  10  having the above-mentioned construction, the stator  13  is disposed between the covers  11  and  12  such that the insert holes  11   a ,  12   a  and  13   a  thereof are aligned with each other, and the bolts B are thereafter inserted into the insert holes  11   a ,  12   a  and  13   a  and tightened into the respective nuts N, thus completing the process of assembling the stator  13  and the covers  11  and  12  together.  
      However, in the conventional motor  10 , because the stator  13  is made of layered silicon steel plates having the same shape, the structure for coupling the covers  11  and  12  to the stator  13  is limited, so that the stator  13  and the covers  11  and  12  must be coupled to each other using extra members such as the nuts N and bolts B. Therefore, when the covers  11  and  12  are coupled to the stator  13 , all nuts N and bolts B, which are the coupling members, must be coupled to each other one by one, and the stator  13  and a pair of covers  11  and  12  must be assembled together through a single process. Hence, the insert holes  11   a ,  12   a  and  13   a  of the stator  13  must be aligned all at the same time, thereby making the assembly process inconvenient and reducing the productivity. Furthermore, the production costs are made increased due to the increased expenses for the extra coupling members B and N.  
      Typically, motors have various sizes and structures, for they are used in various products and apparatuses. However, the conventional motor  10  is problematic in that, when it is required to change the standard size of the motor  10 , such as the length and height of the inner space, the stator as well as the covers must be re-engineered.  
     SUMMARY OF THE INVENTION  
      Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a motor having a stator made of soft magnetic powder material in which a process of assembling a cover to the stator is simple, and standard sizes such as the length of the space inside the motor can be easily changed, so that the covers and the stators thereof are compatible with products having different standard sizes, thus reducing the production costs.  
      Another object of the present invention is to provide a motor having a stator made of soft magnetic powder material which is constructed such that a cover can be easily coupled to the stator without requiring extra coupling members, so that the process of assembling the motor is simplified, thereby increasing productivity and reducing the cost of the assembly process and thus the overall production costs.  
      In an aspect, the present invention provides a motor, including: a stator made of compressed soft magnetic powder, with a plurality of bolt holes formed around a circumferential outer surface of an end of the stator; a cover fitted over the end of the stator, with a plurality of coupling position adjustment parts provided around an end of the cover, the coupling position adjustment parts each comprising a plurality of through holes arranged in a direction in which the cover is fitted over the stator; and a plurality of coupling bolts, each of the plurality of coupling bolts being tightened into each of the bolt holes of the stator through the selected through hole of the associated coupling position adjustment part of the cover such that a position at which the cover is coupled to the stator is adjustable.  
      In another aspect, the present invention provides a motor, including: a stator made of compressed soft magnetic powder, with a plurality of coupling position adjustment parts provided around a circumferential outer surface of an end of the stator, the coupling position adjustment parts each comprising a plurality of bolt holes arranged in a longitudinal direction of the stator; a cover fitted over the end of the stator, with a plurality of through holes formed around a circumferential surface of the cover, each of the plurality of through holes being aligned with one of the bolt holes of the associated coupling position adjustment part of the stator; and a plurality of second coupling bolts, each of the plurality of second coupling bolts being tightened into the selected bolt hole of each of the coupling position adjustment parts of the stator through the associated through hole of the cover such that a position at which the cover is coupled to the stator is adjustable.  
      In another aspect, the present invention provides a motor, including: a stator made of compressed soft magnetic powder, with a plurality of coupling protrusions provided around a circumferential outer surface of an end of the stator; and a cover fitted over the end of the stator, with a plurality of coupling position adjustment parts provided around an end of the cover, the coupling position adjustment parts each comprising a plurality of coupling holes arranged in a direction in which the cover is fitted over the stator, each of the plurality of coupling protrusions of the stator being inserted into the selected coupling hole of the associated coupling position adjustment part of the cover such that a position at which the cover is coupled to the stator is adjustable.  
      In another aspect, the present invention provides a motor, including: a stator made of compressed soft magnetic powder, with a plurality of coupling position adjustment parts provided around a circumferential outer surface of an end of the stator, the coupling position adjustment parts each comprising a plurality of coupling holes arranged in a longitudinal direction of the stator; and a cover fitted over the end of the stator, with a plurality of coupling protrusions provided around a circumferential inner surface of the cover, each of the plurality of coupling protrusions inserted into the selected coupling hole of the associated coupling position adjustment part of the stator such that a position at which the cover is coupled to the stator is adjustable.  
      In another aspect, the present invention provides a motor having a stator, to which a cover is coupled. The stator is made of compressed soft magnetic powder and has on an end thereof a plurality of insert protrusions, which are force-fitted into respective insert holes formed in the cover.  
      In another aspect, the present invention provides a motor having a stator, to which a cover is coupled. The stator is made of compressed soft magnetic powder, and a locking groove is formed around a circumferential outer surface of an end of the stator such that a caulking part to be formed by caulking in the cover fitted over the end of the stator is inserted into and locked to the locking groove of the stator. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:  
       FIG. 1  is an exploded view showing critical parts of a motor according to a conventional technique;  
       FIG. 2  is an exploded view showing critical parts of a motor having a stator made of soft magnetic powder material, according to a first embodiment of the present invention;  
       FIGS. 3A and 3B  are views illustrating the assembled motor of  FIG. 2 ;  
       FIG. 4  is an exploded view showing critical parts of a motor having a stator made of soft magnetic powder material, according to a second embodiment of the present invention;  
       FIGS. 5A and 5B  are views illustrating the assembled motor of  FIG. 4 ;  
       FIG. 6  is an exploded view showing critical parts of a motor having a stator made of soft magnetic powder material, according to a third embodiment of the present invention;  
       FIGS. 7A and 7B  are views illustrating the assembled motor of  FIG. 6 ;  
       FIG. 8  is an exploded view showing critical parts of a motor having a stator made of soft magnetic powder material, according to a fourth embodiment of the present invention;  
       FIGS. 9A and 9B  are views illustrating the assembled motor of  FIG. 8 ;  
       FIG. 10  is an exploded view showing critical parts of a motor having a stator made of soft magnetic powder material, according to a fifth embodiment of the present invention; and  
       FIGS. 11A and 11B  are assembled views showing critical parts of a motor having a stator made of soft magnetic powder material, according to a sixth embodiment of the present invention.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings, such that those skilled in the art can easily implement the present invention.  
       FIG. 2  is an exploded view showing critical parts of a motor  100  having a first stator  110  made of soft magnetic powder material, according to a first embodiment of the present invention. As shown in the drawing, the motor  100  according to the first embodiment of the present invention includes the first stator  110 , which is made of compressed soft magnetic powder and has a plurality of bolt holes  111  therein, and first covers  120 , which are fitted over the respective opposite ends of the first stator  110 , and each of which has first coupling position adjustment parts  121  therein. The motor  100  of the first embodiment further includes first coupling bolts  130 , which couple the first covers  120  to the first stator  110 .  
      Teeth (not shown), around each of which a coil (not shown) is wound, are formed on the circumferential inner surface of the first stator  110  at positions spaced apart from each other at regular intervals. Furthermore, a rotor (not shown) is rotatably provided in the first stator  110  at a position spaced apart from the circumferential inner surface of the first stator  110  by a predetermined gap. The several bolt holes  111  are formed in the circumferential outer surface of an end of the first stator  110  at positions spaced apart from each other at regular angular intervals.  
      The bolt holes  111  may be formed in only one end of the first stator  110  to provide a coupling to the first cover  120 . In the present embodiment, the bolt holes  111  are formed in the opposite ends of the first stator  110 , so that the first covers  120  are coupled to the respective opposite ends of the first stator  110  using the first coupling bolts  130  so that the position thereof is adjustable.  
      The first stator  110  is made of compressed soft magnetic powder. The soft magnetic powder mainly comprises iron-based grains. Each grain of the soft magnetic powder is coated with a predetermined material for electrical insulation.  
      To form the first stator  110  using soft magnetic powder through a compression molding process, a compression molding machine, in which a molding cavity having a shape corresponding to the first stator  110  is defined, is provided. Thereafter, soft magnetic powder is charged into the molding cavity and is compressed by a compressing unit such as a press, thus being manufactured into the shape of the first stator  110  having the teeth and the bolt holes  111 . Here, a lubricant and/or binder may be added to the soft magnetic powder before the compressing process is conducted.  
      As such, the first stator  110  comprises a soft magnetic composite (SMC), which has a three-dimensional shape and is manufactured through the process of compressing soft magnetic powder. Thus, a degree of freedom higher than that of the conventional art, which uses silicon steel plates, is achievable. Therefore, the bolt holes  111  can be easily formed, unlike the conventional structure, in which silicon steel plates having the same shape are layered.  
      The first cover  120 , one of which is fitted over each end of the first stator  110 , has therein space sufficient to adjust the depth to which the stator  110  is inserted into the first cover  120 . The first coupling position adjustment parts  121  are formed in the circumferential outer surface of an end of the first cover  120  at positions spaced apart from each other at regular angular intervals.  
      In this embodiment, the first covers  120  comprise a pair of top and bottom covers, which are respectively coupled to the upper and lower ends of the first stator  110 . Each of the top and bottom covers  120  is fitted over one end of the first stator  110  and has the first coupling position adjustment parts  121 , which are formed in the circumferential outer surface of one end of the cover  120  at regular angular intervals.  
      Each first coupling position adjustment part  121  comprises a plurality of through holes  122 , which are arranged in the direction in which the first stator  110  is fitted into the first covers  120 .  
      The number of first coupling bolts  130  is equal to the number of bolt holes  111  formed in the first stator  110 . Furthermore, each first coupling bolt  130  is tightened into each bolt hole  111  of the first stator  110  after passing through the selected through hole  122  of the associated first coupling position adjustment part  121 , thus the position at which each first cover  120  is fastened to the first stator  110  is adjustable.  
      The operation and effect of the above-mentioned motor  100  having the stator made of soft magnetic powder material according to the first embodiment of the present invention will be explained herein below.  
      As shown in  FIGS. 3A and 3B , the first covers  120  are fitted over the respective opposite ends of the first stator  110 . Thereafter, the first coupling bolts  130  are tightened into the respective bolt holes  111  of the first stator  110  via the selected through holes  122  of the respective first coupling position adjustment parts  121 , thus fastening the first covers  120  to the first stator  110 . At this time, each first coupling bolt  130  passes through a selected one of the through holes  122  of the associated first coupling position adjustment part  121 , so that the distance between the first covers  120  can be adjusted to change the length of the space in the motor  100 .  
      In the case where the first coupling position adjustment parts  121 , each of which has four through holes  122 , are provided in each first cover  120 , the length of the motor  100  is adjustable into eight values including the maximum length of the motor  100  shown in  FIG. 3A  and the minimum length of the motor  100  shown in  FIG. 3B .  
       FIG. 4  is an exploded view showing the critical parts of a motor  200  having a second stator  210  made of soft magnetic powder material, according to a second embodiment of the present invention. As shown in the drawing, the motor  200  according to the second embodiment of the present invention includes the second stator  210 , which is made of compressed soft magnetic powder and has a plurality of second coupling position adjustment parts  211  therein, and second covers  220 , which are fitted over the respective opposite ends of the second stator  210 , and each of which has a plurality of through holes  221 . The motor  200  of the second embodiment further includes second coupling bolts  230 , which couple the second covers  220  to the second stator  210 . Hereinafter, the motor  200  according to the second embodiment will be explained in detail, focusing on the differences from the first embodiment.  
      In the second embodiment, the second stator  210  is formed by compressing soft magnetic powder using a compressing machine, so that the second coupling position adjustment parts  211  are formed in the circumferential outer surface of each end of the second stator  210  at positions spaced apart from each other at regular angular intervals.  
      Each second coupling position adjustment part  211  comprises a plurality of bolt holes  212 , which are arranged in the longitudinal direction of the second stator  210 .  
      The second stator  210  has the second coupling position adjustment parts  211  on respective opposite ends thereof, so that the positions at which the second cover  220  is fastened to each end of the second stator  210  using the second coupling bolts  230  are independently adjustable.  
      The motor  200  has the two second covers  220 , which are fitted over respective opposite ends of the second stator  210 . The through holes  221 , each of which is aligned with the selected bolt hole  212  of the associated second coupling position adjustment part  211 , are formed in the circumferential surface of each second cover  220 . In other words, each second cover  220  has a number of through holes  221  equal to the number of second coupling position adjustment parts  211 , which are provided on one end of the second stator  210 .  
      Meanwhile, the motor  200  has several second coupling bolts  230 . Each second coupling bolt  230  is tightened into a selected one of the bolt holes  212  of the associated second coupling position adjustment part  211  after passing through the associated through hole  221 , thus the position at which each second cover  220  is fastened to the second stator  210  is adjustable.  
      The operation and effect of the above-mentioned motor  200  having the stator made of soft magnetic powder material according to the second embodiment of the present invention will be explained herein below.  
      The second covers  220  are fitted over the respective opposite ends of the second stator  210 . Thereafter, the second coupling bolts  230  are tightened into the selected bolt holes  212  of the respective second coupling position adjustment parts  211  via the respective through holes  221  of the second covers  220 , thus fastening the second covers  220  to the second stator  210 . Here, as shown in  FIGS. 5A and 5B , because each second coupling bolt  230  is tightened into a selected one of the bolt holes  212  of the associated second coupling position adjustment part  211 , the length of the inner space of the motor  200  or the overall length of the motor  200  can be adjusted.  
       FIG. 6  is an exploded view showing critical parts of a motor  300  having a third stator  310  made of soft magnetic powder material, according to a third embodiment of the present invention. As illustrated, the motor  300  according to the third embodiment of the present invention includes the third stator  310 , which is made of compressed soft magnetic powder and has a plurality of coupling protrusions  311  therein, and third covers  320 , which are fitted over the respective opposite ends of the third stator  310  and have therein third coupling position adjustment parts  321  to which the respective coupling protrusions  311  are coupled. Hereinafter, the motor  300  according to the third embodiment will be explained in detail, focusing on the differences from the above-mentioned embodiments.  
      In the third embodiment, the third stator  310  is formed by compressing soft magnetic powder using a compressing machine, so that the coupling protrusions  311  can be relatively easily provided on the circumferential outer surface of each end of the third stator  310  at positions spaced apart from each other at regular angular intervals.  
      The motor  300  has the third covers  320 , which are fitted over the respective opposite ends of the third stator  310 . Furthermore, the coupling protrusions  311  are provided on the circumferential outer surface of each end of the third stator  310  such that each third cover  320  can be locked to the coupling protrusions  311  of each end of the third stator  310  using the third coupling position adjustment parts  321  at selected positions thereof.  
      As such, the two third covers  320  are fitted over the respective opposite ends of the third stator  310 . The third coupling position adjustment parts  321  are provided on the circumferential surface of an end of each third cover  320  at positions spaced apart from each other at predetermined angular intervals.  
      Each third coupling position adjustment part  321  comprises a plurality of coupling holes  322 , which are arranged in the direction in which the third stator  310  is inserted into the associated third cover  320 , so that the associated coupling protrusion  311  is inserted into the selected coupling hole  322  such that the position at which the third cover  320  is fastened to the third stator  310  is adjustable.  
      The operation and effect of the above-mentioned motor  300  having the stator made of soft magnetic powder material according to the third embodiment of the present invention will be explained herein below.  
      The third covers  320  are fitted over the respective opposite ends of the third stator  310  such that the coupling protrusions  311  are inserted into the coupling holes  322  of the respective third coupling position adjustment parts  321 , thus the process of assembling the third covers  320  with the third stator  310  is completed. At this time, as shown in  FIGS. 7A and 7B , each coupling protrusion  311  of the third stator  310  is inserted into a selected one of the coupling holes  322  of the associated third coupling position adjustment part  321 . Therefore, the length of the inner space of the motor  300  or the overall length of the motor  300  is adjustable.  
       FIG. 8  is an exploded view showing critical parts of a motor  400  having a fourth stator  410  made of soft magnetic powder material, according to a fourth embodiment of the present invention. As shown in the drawings, the motor  400  according to the fourth embodiment of the present invention includes the fourth stator  410 , which is made of compressed soft magnetic powder and has a plurality of fourth coupling position adjustment parts  411  therein, and fourth covers  420 , which are fitted over the fourth stator  410  and have therein coupling protrusions  421  to be coupled to the respective fourth coupling position adjustment parts  411 . Hereinafter, the motor  400  according to the fourth embodiment will be explained in detail, focusing on the differences with the above-mentioned embodiments.  
      In the fourth embodiment, the fourth stator  410  is formed by compressing soft magnetic powder using a compressing machine, so that the fourth coupling position adjustment parts  411  can be relatively easily provided in the circumferential outer surface of each end of the fourth stator  410  at positions spaced apart from each other at regular angular intervals.  
      Each fourth coupling position adjustment part  411  comprises a plurality of coupling holes  412 , which are arranged in the longitudinal direction of the fourth stator  410 .  
      The fourth stator  410  has the fourth coupling position adjustment parts  411  on opposite ends thereof, so that the positions at which the fourth cover  420  is fastened to each end of the fourth stator  410  using the fourth coupling protrusions  421  are independently adjustable.  
      The motor  400  has the two fourth covers  420 , which are fitted over respective opposite ends of the fourth stator  410 . The coupling protrusions  421 , each of which is inserted into the selected coupling hole  412  of the associated fourth coupling position adjustment part  411 , are provided on the circumferential inner surface of each fourth cover  420 . In other words, each fourth cover  420  has a number of coupling protrusions  421  equal to the number of fourth coupling position adjustment parts  411 , which are provided on one end of the fourth stator  410 .  
      The operation and effect of the above-mentioned motor  400  having the stator made of soft magnetic powder material according to the fourth embodiment of the present invention will be explained herein below.  
      The fourth covers  420  are fitted over the respective opposite ends of the fourth stator  410  such that the coupling protrusions  421  of the fourth covers  420  are inserted into the coupling holes  412  of the respective fourth coupling position adjustment parts  411 , thus the process of assembling the fourth covers  420  with the fourth stator  410  is completed. As shown in  FIGS. 9A and 9B , each coupling protrusion  421  of the fourth covers  420  is inserted into a selected one of the coupling holes  412  of the associated fourth coupling position adjustment part  411 . Therefore, the length of the space in the motor  400  or the overall length of the motor  400  is adjustable.  
      As described above, in the first through fourth embodiments of the present invention, the first through fourth covers  120 ,  220 ,  320  and  420  are respectively coupled to the first through fourth stators  110 ,  210 ,  310  and  410  using the first and second coupling bolts  130  and  230  or the coupling protrusions  311  and  421 , each of which is relatively short. Thus, each of the first through fourth stators  110 ,  210 ,  310  and  410  may be opened only at one end thereof, and the assembly process is simple. Therefore, maintenance is convenient. Furthermore, because the inner space of the motor  100 ,  200 ,  300 ,  400  or the overall length thereof is adjustable, the present invention can easily respond to changes in the standard sizes of motors, and the measurements thereof can be easily changed.  
      In addition, because the first through fourth stators  110 ,  210 ,  310  and  410  are made of compressed soft magnetic powder, the bolt holes  111  and  212 , the coupling protrusions  311  and the coupling holes  412  can be easily formed to couple the first through fourth covers  120 ,  220 ,  320  and  420  to the respective first through fourth stators  110 ,  210 ,  310  and  410 .  
      Hereinafter, the construction of motors according to fifth and sixth embodiments of the present invention will be explained with reference to  FIGS. 10 and 11 .  
       FIG. 10  is an exploded view showing critical parts of the motor  500  having a stator  510  made of soft magnetic powder material, according to the fifth embodiment of the present invention. As shown in the drawing, the motor  500  according to the fifth embodiment of the present invention includes the stator  510 , which is made of compressed soft magnetic powder, and covers  520  and  530 , which are coupled to the respective opposite ends of the stator  510  by a force-fitting method. The motor  500  according to the fifth embodiment further includes a rotor  540 , which is rotatably provided in the stator  510  at a position spaced apart from the inner surface of the stator  510  by a predetermined gap, and a shaft  550 , which is firmly fastened through the central portion of the rotor  540 .  
      Teeth (not shown) for coils (not shown) to be wound thereon are formed on the circumferential inner surface of the stator  510  at positions spaced apart from each other at regular intervals. A plurality of insert protrusions  511  and  512  are provided on the opposite ends of the stator  510  in a direction parallel to the shaft  550 .  
      Meanwhile, a single cover  520  or  530  may be provided on only one end of the stator  510 . In this case, the stator  510  is closed at the other end thereof, and a plurality of insert protrusions  511  or  512  is formed only on the corresponding end of the stator  510 . In the present embodiment, the insert protrusions  511  and  512  are provided on the respective opposite ends of the stator  510 , and the two covers  520  and  530  are coupled to the respective opposite ends of the stator  510  by the force-fitting method using the insert protrusions  511  and  512 .  
      In detail, the covers  520  and  530  comprise the top cover  520  and the bottom cover  530  which are respectively coupled to the upper and lower ends of the stator  510 . The covers  520  and  530 , which are coupled to respective opposite ends of the stator  510 , protect the rotor  540  provided in the stator  510 . The opposite ends of the shaft  550  are rotatably supported by the covers  520  and  530  through bearings  551  and  552 , respectively.  
      In addition, insert holes  521  and  531 , into which the insert protrusions  511  and  512  are respectively fitted, are formed in surfaces of the respective covers  520  and  530 , which face each other based on the stator  510  placed therebetween, that is, face the stator  510 .  
      The operation and effect of the above-mentioned motor  500  having the stator made of soft magnetic powder material according to the fifth embodiment of the present invention will be explained herein below.  
      The insert protrusions  511  and  512  of the stator  510  are respectively force-fitted into the insert holes  521  and  531  of the covers  520  and  530 , so that the covers  520  and  530  are respectively coupled to the opposite ends, that is, to the upper and lower ends of the stator  510 . Here, the rotor  540  is placed beforehand in the stator  510 , and the shaft  550  is supported by the covers  520  and  530  so as to be smoothly rotatable using the bearings  551  and  552 . As such, because the covers  520  and  530  are coupled to the stator  510  by the force-fitting method, the process of assembling them is simplified without requiring extra coupling members such as bolts and nuts.  
      Furthermore, because the stator  510  is made of compressed soft magnetic powder, the insert protrusions  511  and  512  for coupling the covers  520  and  530  to the stator  510  can be formed on the stator  510  relatively easily, unlike the conventional structure, in which silicon steel plates having the same shape are layered.  
       FIGS. 11A and 11B  are assembled views showing critical parts of a motor  600  having a stator  610  made of soft magnetic powder material, according to a sixth embodiment of the present invention. As illustrated, the motor  600  according to the sixth embodiment of the present invention includes the stator  610 , which is made of compressed soft magnetic powder, covers  620  and  630 , which are coupled to the respective opposite ends of the stator  610  by caulking, a rotor (not shown), which is rotatably provided in the stator  610  at a position spaced apart from the inner surface of the stator  610  at a predetermined gap, and a shaft  640 , which is firmly fastened through the central portion of the rotor.  
      In the sixth embodiment, the stator  610  is made of compressed soft magnetic powder in the same manner as that of the fifth embodiment. Thus, locking grooves  611  and  612  can be easily formed around the circumferential outer surfaces of the respective opposite ends of the stator  610 , unlike the conventional structure, in which silicon steel plates having the same shape are layered.  
      Here, only one cover  620  or  630  may be coupled to one end of the stator  610  by caulking. In this embodiment, the stator  610  is closed at the other end thereof, and the covers  620  and  630  are coupled to the respective opposite ends of the stator  610  by caulking. Therefore, the locking grooves  611  and  612  are also formed in the respective opposite ends of the stator  610 .  
      Furthermore, the covers  620  and  630  are coupled to the respective opposite ends of the stator  610  by forming caulking parts  621  and  631 , which protrude into the respective locking grooves  611  and  612 , in the covers  620  and  630  at positions corresponding to the respective locking grooves  611  and  612  when the covers  620  and  630  are fitted over the respective opposite ends of the stator  610 .  
      Each caulking part  621 ,  631  may be formed discontinuously around the cover  620 ,  630 . It is preferable that each caulking part  621 ,  631  be formed around the cover  620 ,  630  into a single body without interruption.  
      The operation and effect of the above-mentioned motor  600  having the stator made of soft magnetic powder material according to the sixth embodiment of the present invention will be explained herein below.  
      While the rotor (not shown) and the shaft  640  are placed in the stator  610 , the covers  620  and  630  are fitted over the respective opposite ends of the stator  610 . Subsequently, portions of the covers  620  and  630  corresponding to the locking grooves  611  and  612  are processed by caulking, thus forming the caulking parts  621  and  631 . As such, because the caulking parts  621  and  631  are formed to be inserted into the respective locking grooves  611  and  612  of the stator  610 , the covers  620  and  630  can be reliably coupled to the respective opposite ends of the stator  610  without requiring extra coupling members such as bolts and nuts.  
      In addition, because the stator  610  is made of compressed soft magnetic powder, locking grooves  611  and  612  can be relatively easily formed in the stator  610 , unlike the conventional structure, in which silicon steel plates having the same shape are layered.  
      Furthermore, in this embodiment, in which the covers  620  and  630  are coupled to the stator  610  by caulking, the distance between the covers  620  and  630  can be adjusted depending on the depths to which the opposite ends of the stator  610  are inserted into the covers  620  and  630 , that is, depending on the caulked positions. Thus, when it is desired to change the length of the motor  600 , it is unnecessary to re-engineer covers  620  and  630  or other elements to respond to new standards, thus markedly reducing the unit cost of production.  
      As described above, the present invention provides a motor having a stator made of soft magnetic powder material in which a process of assembling a cover to the stator is simple, and the standard sizes, such as the length of the space in the motor, can be easily changed, so that, even though products have different standard sizes, the covers and the stators thereof are compatible, thus reducing the unit cost of production.  
      Furthermore, the motor according to the present invention is constructed such that the cover can be easily coupled to the stator without requiring extra coupling members. Therefore, the assembly process is simplified, thus increasing productivity, reducing the cost of the assembly process, and reducing the unit cost of production.  
      Although the preferred embodiments of the motor having a stator made of soft magnetic powder material have been disclosed, these are only illustrative examples. The present invention is not limited to the preferred embodiments. Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.