Patent Abstract:
A spindle motor includes a rotor including a rotary shaft and magnets, a stator including a bearing, which supports the rotary shaft, and an armature corresponding to the magnets. The rotor is caused to rotate by an electromagnetic force generated by the magnets and the armature. The stator includes a plate having a stepped portion in a portion thereof, which faces the rotary shaft.

Full Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2011-0003709, filed on Jan. 13, 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, in general, to a spindle motor. 
     2. Description of the Related Art 
     In general, a spindle motor can maintain high precision rotation characteristics since a bearing having a rotary shaft therein rotatably supports the rotary shaft. Thanks to this characteristic, the spindle motor is widely used as a driving means of a hard disc drive, an optical disc drive, and other recording media, which are required to rotate at a high speed. 
     This spindle motor generally uses a fluid dynamic bearing, which feeds a certain amount of oil between the rotary shaft and a bearing that supports the rotary shaft, in order to facilitate the rotation of the rotary shaft, and causes dynamic pressure to be generated when the rotary shaft rotates. 
     In particular, entering the 2000s, the shaft system of the spindle motor has experienced an abrupt change whereby a dynamic bearing has been used to substitute for a ball bearing. The dynamic bearing has advantages in that it has little noise, better shock resistance, and a longer lifetime compared to the existing ball bearing. 
     However, due to the trend of the spindle motor for a Hard Disc Drive (HDD) towards a small size and a thin profile, there are many problems in that it becomes difficult to provide the length of the shaft system and thus the reliability of the product decreases. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and the present invention is intended to increase the withdrawal force and product reliability of a spindle motor and realize a thin profile design. 
     In order to achieve the above objects, according to one aspect of the present invention, there is provided a spindle motor including a rotor including a rotary shaft and magnets; a stator including a bearing, which supports the rotary shaft, and an armature corresponding to the magnets. The rotor is caused to rotate by an electromagnetic force generated by the magnets and the armature. The stator includes a plate having a stepped portion in a portion thereof, which faces the rotary shaft. 
     In an exemplary embodiment, the plate may further include a bearing holder, which supports the bearing, and a stepped portion formed toward the bearing holder. 
     In an exemplary embodiment, the plate may have a lower stepped portion formed toward the inner portion thereof, to which the bearing holder is mounted. The height from the upper portion of the plate to the upper portion of a hub is 6.55 mm. 
     In an exemplary embodiment, the plate may have a stepped portion therein, the stepped portion being formed upward to face the armature. 
     In an exemplary embodiment, the plate may have an upper stepped portion formed toward the armature, to which the bearing holder is mounted. The height from the upper portion of the plate to the upper portion of the hub is 5.45 mm. 
     According to the construction of the exemplary embodiments, the plate of the spindle motor according to one exemplary embodiment of the invention provides the axial length of the bearing by forming the stepped portion in the inner portion thereof, which is coupled to the bearing holder  121 , thereby increasing reliability when the motor rotates 
     In addition, since the plate of the spindle motor according to another exemplary embodiment of the invention has the plate with the stepped portion formed toward the armature, it is possible to realize the miniaturization of the motor without decreasing the axial length of the bearing. 
     As described above, in the spindle motor of the invention, the stepped portion is added to the upper or lower portion of the plate  110  such that the shaft system can have a sufficient length, thereby increasing reliability and realizing a small size and a thin profile of the motor. 
    
    
     
       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 when taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a cross-sectional view illustrating a spindle motor according to a first exemplary embodiment of the invention; and 
         FIG. 2  is a cross-sectional view illustrating a spindle motor according to a second exemplary embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in greater detail to a preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to parts that are the same or similar. In describing the present invention, if it is determined that the detailed description on the related known technology would make the gist of the present invention unnecessarily ambiguous, the detailed description will be omitted. 
     Prior to offering the description, it is noted that terms or words expressed in the specification and claims should not be limited to or construed by their conventional or dictionary meanings, but should be understood as meanings and concepts conforming with the technical spirits of the present invention because the inventor can properly define the concepts of terms or words used in order to clarify his/her invention in the best manner. 
       FIG. 1  is a cross-sectional view illustrating a spindle motor according to a first exemplary embodiment of the invention. 
     As shown in  FIG. 1 , the spindle motor  100  of this embodiment includes a plate  110 , a bearing  120 , an armature  130 , a rotary shaft, and a hub  150 . 
     The plate  110  serves to fixedly support the whole part of the spindle motor  100 , and is fixedly provided to a device, such as a Hard Disc Drive (HDD), in which the spindle motor  100  is mounted. Although the plate  110  is made of a light material, such as an aluminum plate or an aluminum alloy plate, it can be made of a steel plate. 
     In addition, the plate  110  has a coupling portion (not shown) protruding therefrom to which the bearing  120  is coupled, and the coupling portion has a coupling hole (not shown) in the central portion. The coupling hole has a diameter the same as the inner diameter of the bearing  120  such that the bearing  120  is fitted thereinto. Here, an adhesive coupling process or the like, which uses an adhesive, can be performed in order to fix the bearing  120  to the coupling portion. Alternatively, it is possible to press the bearing  120  into the coupling hole by applying a predetermined force so that it can be fixedly coupled to the coupling hole. 
     The bearing  120  serves to rotatably support the rotary shaft  140 , and has a generally hollow cylindrical shape, with a fluid dynamic bearing being formed in the inner diameter portion (not shown) that faces the rotary shaft  140 . 
     The armature  130  serves to form an electric field by being induced with external power in order to rotate a hub  150  to which an optical disc is mounted. The armature  130  includes a core  131 , which is formed by stacking a plurality of thin metal plates on one another, and a coil  132 , which is wound around the core  131  a number of times. 
     The core  131  is fixedly mounted to the outer surface of the coupling portion of the plate  110 , and the coil  132  is wound around the core  131 . Here, the coil  132  generates an electric field using current induced from the outside, thereby rotating the hub  150  using an electromagnetic force generated between the coil  132  and magnets  151  of the hub  150 . 
     The rotary shaft  140  serves to axially support the hub  150 , and is fitted into the inner diameter portion of the bearing  120  and is rotatably supported by the bearing  120 . 
     The hub  150  serves to rotate an optical disc (not shown), such as a hard disc, which is mounted thereto, and includes a disc portion (not shown) to which the rotary shaft  140  is fixedly mounted and an annular rim portion (not shown) extending from the distal end of the disc portion. 
     As shown in  FIG. 1 , in the spindle motor  100  according to the first exemplary embodiment of the invention, the plate  111  has a lower stepped portion  111  formed in the inner portion thereof, which is coupled to a bearing holder  121 . The lower stepped portion  111  is stepped downward. 
     The lower stepped portion  111 , which is formed by the stepped-down portion of the plate  110 , increases the axial length of the spindle motor, such that the bearing  120  can be imparted with a sufficient length. 
     That is, the length of the bearing  120  in the vertical direction is increased to as much as the height of the lower stepped portion  111  of the spindle motor  100 . 
     In the spindle motor  100  according to the first exemplary embodiment of the invention, the length A 1  from the upper end of the plate  110  to the upper end of the hub  150  is about 6.55 mm, which is similar to that of a bearing of the related art. However, since the lower stepped portion  111  formed as above provides an additional space in the longitudinal direction of the bearing  120 , the length D 1  of the bearing  120  is increased to as much as the height of the lower stepped portion  111  compared to the length of the bearing of the related art. The spindle motor can achieve a sufficient amount of withdrawal force, and its reliability is excellent. 
       FIG. 2  is a cross-sectional view illustrating a spindle motor  100  according to a second exemplary embodiment of the invention. As shown in  FIG. 2 , a plate  110  has an upper stepped portion  112  that is stepped towards an armature  130 , which is provided above the plate  110 . 
     Since the upper stepped portion  112  is formed such that the plate  110  is stepped upward, the length A 2  from the upper end of the plate  110  to the upper end of the hub  150  is significantly decreased. 
     Specifically, in the spindle motor  100  according to the second exemplary embodiment of the invention, the length A 2  from the upper end of the plate  110  to the upper end of the hub  150  is about 5.45 mm. It can be appreciated that the length A 2  is significantly decreased compared to the length of the spindle motor of the related art, which is about 6.55 mm. 
     Here, the length D 2  of the bearing  120  is the same as that of the bearing of the related art, and thus does not affect the performance of the motor. 
     Therefore, thanks to the upper stepped portion  112  of the plate  110 , it is possible to realize a small size and a thin profile of the motor while maintaining the length D 2  of the bearing  120 . 
     The plate  110  of the spindle motor according to the first exemplary embodiment of the invention having the above-described structure provides the axial length of the bearing  120  by forming the stepped portion in the inner portion thereof, which is coupled to the bearing holder  121 , thereby increasing reliability when the motor rotates. 
     In addition, since the plate  110  of the spindle motor according to the second exemplary embodiment of the invention has the plate  110  with the stepped portion formed toward the armature, it is possible to realize the miniaturization of the motor without decreasing the axial length of the bearing  120 . 
     As described above, in the spindle motor  100  of the invention, the stepped portion is added to the upper or lower portion of the plate  110  such that the shaft system can have a sufficient length, thereby increasing reliability and realizing a small size and a thin profile of the motor. 
     Although preferred embodiments of the present invention have been described for illustrative purposes, those skilled in the art will appreciate that the present invention is not limited thereto, but various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Technology Classification (CPC): 7