Patent Publication Number: US-2012025647-A1

Title: Spindle motor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application No. 10-2010-0073929, filed Jul. 30, 2010, entitled “Spindle Motor”, which is hereby incorporated by reference in its entirety into this application. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a spindle motor. 
     2. Description of the Related Art 
     Generally, in spindle motors, when a rotating shaft rotates there is a predetermined contact area between a bearing and the rotating shaft, which ensures a high level of rotational characteristics. Because of these characteristics, spindle motors are widely used as drive units of recording media, such as hard disk drives, optical disk drives (ODD), etc., which need high speed rotation. 
     However, in such a conventional spindle motor, when it rotates at a low speed, a rotor casing may not uniformly rotate due to the clearance between the bearing and the rotating shaft. 
     Hereinafter, the problem of the spindle motor using the conventional technique will be described with reference to  FIG. 1  which is a sectional view showing a conventional spindle motor  100 . As shown in  FIG. 1 , the spindle motor  100  includes a rotor  110  and a stator  120 . The rotor  110  includes a clamp  111 , a rotor casing  112 , a magnet  113  and a rotating shaft  114 . The stator  120  includes a coil  121 , a core  122 , a bearing  123 , a bearing holder  124 , a stopper  125 , a thrust  126 , a support  127 , a PCB (printed circuit board)  128  and a base plate  129 . 
     In detail, in the rotor  110 , the rotating shaft  114  is rotatably supported by the bearing  123  of the stator  120 . 
     The rotor casing  112  is fastened to an end of the rotating shaft  114 . The magnet  113  is attached to an inner surface of the rotor casing  112  at a position corresponding to an armature including the coil  121  and the core  122 . The clamp  111  elastically supports a recording medium placed on the rotor casing  112 . 
     In the stator  120 , the bearing  123  supports the rotating shaft  114  so as to be rotatable. The bearing  123  is fastened in the bearing holder  124  such that the bearing  123  is coaxial with the rotating shaft  114 . 
     The bearing holder  124  supports the bearing  123  inserted thereinto. The armature is fitted over the bearing holder  124  around the rotating shaft  114 . The armature includes the core  122  and the coil  121  which is wound around the core  122  so that external power is applied to the coil  121 , electromagnetic force is generated by interaction between the coil  121  and the magnet  113 . The stopper  125  is provided below the bearing  123  to prevent the rotating shaft  114  inserted into the bearing  123  from being removed from the stator  120 , for example, by the rotational force of the rotor  110 . 
     The thrust  126  prevents the rotating shaft  114  from coming into direct contact with the support  127  when the rotating shaft  114  rotates, thus preventing abrasion. The support  127  functions to support the rotating shaft  114 , the stopper  125  and the thrust  126 . 
     The PCB  128  is mounted on the base plate  129  and supplies external power to the armature. The bearing holder  124  is also mounted to the base plate  129  upright. 
     In the conventional spindle motor having the above-mentioned construction, when electric current is applied to the armature  121  and  122 , the rotating shaft  114  and the rotor casing  112  are integrally rotated by electromagnetic force generated between the armature and the magnet  113 . 
     However, when the rotor casing  112  rotates at a low speed, the rotating shaft  114  cannot uniformly rotate attributable to a clearance between the bearing  123  and the rotating shaft  114 . In other words, the rotating shaft  114  unevenly collides with the inner surface of the bearing  123 , thus making the rotation of the rotor casing  112  unstable. Furthermore, if the spindle motor is used in an optical disk apparatus which can form an image on a rear surface (a label surface) of an optical disk using a laser beam, the quality of the image formed on the label surface of the optical disk may deteriorate. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in an effort to provide a spindle motor which is configured such that when a rotor casing rotates at a low speed, it rotates in a state of being inclined with respect to a stator, thus making uniform rotation of the rotor possible, so that if the spindle motor is used in an optical disk apparatus for forming a label surface on an optical disk, the quality of an image of the label surface of the optical disk can be enhanced. 
     In a spindle motor according to an embodiment of the present invention, a rotor includes a rotor casing provided with a magnet, and a rotating shaft. A stator rotatably supports the rotor. The stator includes an armature facing the magnet. When the rotor casing rotates at a low speed, the rotating shaft rotates in a state of being inclined at a predetermined angle with respect to a vertical direction in which the rotating shaft is upright on the stator. 
     The rotor casing may rotate at low speed, the angle at which the rotating shaft is inclined with respect to the vertical direction ranges from 1° to 15°. 
     The stator may further include a thrust supporting a lower end of the rotating shaft. The thrust is inclined at a predetermined angle from one side to an opposite side thereof with respect to a circumferential direction of the rotating shaft. 
     The angle at which the thrust is inclined may range from 1° to 15°. 
     The stator may include a bearing rotatably supporting the rotating shaft. The bearing may be inserted into a bearing holder so that the bearing is supported by the bearing holder. The bearing holder may have the armature generating an electromagnetic force with the magnet. The bearing holder may be installed upright on a base plate. A printed circuit board may be mounted to the base plate. The printed circuit board may supply external power to the armature. 
     The stator may further include a stopper provided below a lower end of the bearing. The stopper may prevent the rotating shaft inserted into the bearing from being removed from the bearing by rotational force of the rotor. A support may support the rotating shaft. A thrust may prevent the rotating shaft from coming into direct contact with the support when the rotating shaft rotates, thus preventing abrasion between the rotating shaft and the support. The thrust may be inclined at a predetermined angle from one side to an opposite side thereof with respect to a circumferential direction of the rotating shaft. 
     The rotor may include the rotating shaft rotatably supported by the stator. The rotor casing may be fastened to an upper end of the rotating shaft. The magnet may be attached to an inner surface of the rotor casing at a position corresponding to the armature. A clamp may elastically support a recording medium placed on the rotor casing. 
     In a spindle motor according to another embodiment of the present invention, a rotor includes a rotor casing provided with a magnet, and a rotating shaft. A stator includes a bearing rotatably supporting the rotating shaft so that the rotor casing is rotatably supported by the stator. An armature faces the magnet. The rotating shaft rotates in a state of being inclined with respect to a vertical direction in which the rotating shaft is upright on the stator. The bearing is inclined corresponding to the inclined rotating shaft. 
     The rotating shaft and the bearing may be inclined with respect to the vertical direction at an angle ranging from 1° to 15°. 
    
    
     
       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 a sectional view showing a conventional spindle motor; 
         FIG. 2  is a sectional view of a spindle motor, according to a first embodiment of the present invention; and 
         FIG. 3  is a sectional view of a spindle motor, according to a second embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference now should be made to the drawings, in which the same reference numerals are used throughout the different drawings to designate the same or similar components. In the following description, when it is determined that the detailed description of the conventional function and conventional structure would confuse the gist of the present invention, such a description may be omitted. Furthermore, the terms and words used in the specification and claims are not necessarily limited to typical or dictionary meanings, but must be understood to indicate concepts selected by the inventor as the best method of illustrating the present invention, and must be interpreted as having had their meanings and concepts adapted to the scope and sprit of the present invention so that the technology of the present invention could be better understood. 
     Hereinafter, embodiments of a spindle motor according to the present invention will be described in detail with reference to the attached drawings. 
       FIG. 2  is a sectional view of a spindle motor  200 , according to a first embodiment of the present invention. As shown in  FIG. 2 , the spindle motor  200  includes a rotor  210  and a stator  220 . The rotor  210  includes a clamp  211 , a rotor casing  212 , a magnet  213  and a rotating shaft  214 . The stator  220  includes a coil  221 , a core  222 , a bearing  223 , a bearing holder  224 , a stopper  225 , a thrust  226 , a support  227 , a PCB  228  and a base plate  229 . 
     In detail, in the rotor  210 , the rotating shaft  214  is rotatably supported by the bearing  223  of the stator  220 . 
     The rotor casing  212  is fastened to an end of the rotating shaft  214 . The magnet  213  is attached to an inner surface of the rotor casing  212  at a position corresponding to an armature including the coil  221  and the core  222 . 
     The clamp  211  elastically supports a recording medium placed on the rotor casing  212 . 
     In the stator  220 , the bearing  223  supports the rotating shaft  214  so as to be rotatable. The bearing  223  is made of metal and has a cylindrical shape. In addition, the bearing  223  is fastened in the bearing holder  224  such that the axis of the bearing  223  corresponds to that of the rotating shaft  214 . 
     The bearing holder  224  supports the bearing  223  inserted thereinto. The armature is fitted over the bearing holder  224  around the rotating shaft  214 . The armature includes the core  222  and the coil  221  which is wound around the core  222  so that external power is applied to the coil  221 , electromagnetic force is generated by interaction between the coil  221  and the magnet  213 . 
     The stopper  225  is provided below the bearing  223  to prevent the rotating shaft  214  inserted into the bearing  223  from being removed from the stator  220 , for example, by the rotational force of the rotor  210 . 
     The thrust  226  prevents the rotating shaft  214  from coming into direct contact with the support  227  when the rotating shaft  214  rotates, thus preventing abrasion. 
     The support  227  functions to support the rotating shaft  214 , the stopper  225  and the thrust  226 . 
     The PCB  228  is mounted on the base plate  229  and supplies external power to the armature. The bearing holder  224  is also mounted in an upright position to the base plate  229 . 
     In the present invention having the above-mentioned construction, when electric current is applied to the armature  221  and  222 , the rotating shaft  214  and the rotor casing  212  are integrally rotated by electromagnetic force generated between the armature and the magnet  213 . 
     Furthermore, in the first embodiment of the present invention, the thrust  226  is inclined from one side to the opposite side thereof with respect to the circumferential direction of the rotating shaft  214 . Thus, when the rotor casing  212  rotates at low speed, the rotating shaft  214  rotates in a state where it is inclined at a predetermined angle with respect to the bearing  223 , in other words, with respect to the vertical direction in which the rotating shaft  214  is upright to the stator  220 . In the embodiment, the inclined angle of the rotating shaft  214  ranges from 1° to 15°. For this, the thrust  226  is also inclined at an angle ranging from 1° to 15°. Thanks to this structure, even when the rotor casing  212  rotates at low speed, the rotating shaft  214  can rotate uniformly without wobbling attributable to clearance between it and the bearing  223 . 
     Moreover, when the rotor casing  212  rotates at a high speed, the rotor  210  is returned into the upright state by the rotational force. 
       FIG. 3  is a sectional view of a spindle motor  300 , according to a second embodiment of the present invention. As shown in  FIG. 3 , the spindle motor  300  includes a rotor  310  and a stator  320 . The rotor  310  includes a clamp  311 , a rotor casing  312 , a magnet  313  and a rotating shaft  314 . The stator  320  includes a coil  321 , a core  322 , a bearing  323 , a bearing holder  324 , a stopper  325 , a thrust  326 , a support  327 , a PCB  328  and a base  329 . 
     The general construction of the spindle motor  300  according to the second embodiment, excluding the bearing  323 , remains the same as that of the spindle motor  200  according to the first embodiment. In the second embodiment, the bearing  323  is installed in the bearing holder  324  so as to be inclinable along with the rotating shaft  314 . The rotating shaft  314  and the bearing  323  are inclined at an angle ranging from 1° to 15° with respect to the vertical direction in which they are upright to the stator  320 . Thanks to this structure, even when the rotor casing  312  rotates at low speed, the rotating shaft  314  can rotate uniformly without arbitrarily rotating attributable to clearance between it and the bearing  323 . 
     As described above, in a spindle motor according to the present invention, when a rotor casing rotates at low speed, it rotates in a state of being inclined with respect to a stator, thus making uniform rotation of the rotor possible. If the spindle motor is used in an optical disk apparatus for forming a label surface on an optical disk, the quality of the image of the label surface of the optical disk can be enhanced. 
     Although the embodiments of the present invention have been disclosed for illustrative purposes, it will be appreciated that the spindle motor according to the invention is not limited thereto, and 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. 
     Accordingly, any and all modifications, variations or equivalent arrangements should be considered to be within the scope of the invention, and the detailed scope of the invention will be disclosed by the accompanying claims.