Abstract:
A disc clamp and a spindle motor having the same is provided, the disc clamp according to an exemplary embodiment comprising: a disc clamp body; a first disc balancer projected from the disc clamp body in the horizontal direction and configured to have a first thickness; and a second disc balancer bent downwards from an end of the first disc balancer to fix the disc and configured to have a second thickness, wherein an angle between a horizontal surface of the first disc balancer and the second disc balancer is in the range of 92° to 95°.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 12/980,827, filed Dec. 29, 2010, which claims the benefit under 35 U.S.C. §119 of Korean Patent Application No. 10-2009-0132663, filed Dec. 29, 2009, which are hereby incorporated by reference in their entirety. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The present disclosure relates to a disc clamp and a spindle motor having the same. 
         [0004]    2. Description of the Related Art 
         [0005]    Generally, a spindle motor is widely used to rotate a disc at an ultra high speed in an optical disc drive (ODD) and a hard disc drive. 
         [0006]    The spindle motor includes a stator having a core wound with a coil, a rotational axis that rotates with respect to the stator, a yoke arranged at the rotational axis and a rotor having a magnet arranged at the yoke. Further, the rotational axis has a disc clamp fixed thereto, the clamp inhibiting the disc from being detached from the rotational axis that rotates at a high speed. The disc clamp includes a balancer that makes a rotational center of the disc identical to that of a rotational axis. 
         [0007]    A balancer of a general spindle motor is manufactured of a thin plastic material having elasticity in order that the disc is not inserted into the balancer and not extracted from it with ease. 
         [0008]    However, a balancer of the spindle known in the art has a problem that the balancer is broken or damaged as the disc is repeatedly inserted into and extracted from it. 
       BRIEF SUMMARY 
       [0009]    Exemplary aspects of the present disclosure are to substantially solve at least the above problems and/or disadvantages and to provide at least the advantages as mentioned below. Thus, the present invention is to provide a disc clamp into which a disc is not inserted with ease and from which the disc is not extracted with ease and which is neither broken nor damaged with ease even though the disc is repeatedly inserted into and extracted from the disc clamp, and a spindle motor having the same. 
         [0010]    In one aspect of the present disclosure, there may be provided, a disc clamp, comprising: a disc clamp body; a first disc balancer projected from the disc clamp body in the horizontal direction and configured to have a first thickness; and a second disc balancer bent downwards from an end of the first disc balancer to fix the disc and configured to have a second thickness, wherein an angle between a horizontal surface of the first disc balancer and the second disc balancer is in the range of 92° to 95°. 
         [0011]    In some exemplary of the present invention, a balance ratio by the angles of the first and second disc balancers may be in the range of 60 μm to 70 μm, and an insertion force of the disc is in the range of 200 [gf] to 300 [gf]. 
         [0012]    In some exemplary of the present invention, an edge portion where the horizontal surface of the first disc balancer meets an outer surface of the second disc balancer may be formed as a curved surface. In some exemplary of the present invention, a ratio of the first thickness to the second thickness may be in the range of 1.5 to 1.8. 
         [0013]    In other general aspect of the present disclosure, there may be provided a disc clamp, comprising: a disc clamp body; a first disc balancer projected from the disc clamp body in the horizontal direction and configured to have a first thickness; and a second disc balancer bent downwards from an end of the first disc balancer to fix the disc and configured to have a second thickness, wherein a ratio of the first thickness to the second thickness is in the range of 1.5 to 1.8. 
         [0014]    In another general aspect of the present disclosure, there may be provided a spindle motor, comprising: a stator configured to include a bearing housing engaged with a base plate, a bearing inserted into the bearing housing, a core engaged with an outer circumference surface of the bearing housing, and a coil wound around the core; a rotational axis rotatably engaged with the bearing; a rotor configured to include a yoke engaged with the rotational axis, and a magnet fixed inside the yoke and facing the core; and a disc clamp including: a disc clamp body; a first disc balancer projected from the disc clamp body in the horizontal direction and configured to have a first thickness; and a second disc balancer bent downwards from an end of the first disc balancer to fix the disc and configured to have a second thickness, wherein an angle between a horizontal surface of the first disc balancer and the second disc balancer is in the range of 92° to 950°. 
         [0015]    In some exemplary of the present invention, a balance ratio by the angles of the first and second disc balancers may be in the range of 60 μm to 70 μm, and an insertion force of the disc is in the range of 200 [gf] to 300 [gf]. 
         [0016]    In some exemplary of the present invention, an edge portion where the horizontal surface of the first disc balancer meets an upper surface of the second disc balancer may be formed as a curved surface. 
         [0017]    In some exemplary of the present invention, a thickness ratio of the first thickness to the second thickness may be in the range of 1.5 to 1.8. 
         [0018]    The present disclosure has an advantageous effect in that the required disc insertion force, balance performance and enhanced durability can be embodied by changing the thickness ratio of the first and second balance portions of the disc clamp engaged with the rotational axis that rotates at a high speed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a perspective view showing a disc clamp of a spindle motor according to an embodiment of the present disclosure; 
           [0020]      FIG. 2  is a sectional view cut along I-I′ line in  FIG. 1 ; and 
           [0021]      FIG. 3  is a sectional view showing a spindle motor according to another embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    Advantages and features of the present disclosure may be understood more readily by reference to the following detailed description of exemplary embodiments and the accompanying drawings. Thus, the present disclosure is not limited to the exemplary embodiments which will be described below, but may be implemented in other forms. Accordingly, the described aspect is intended to embrace all such alterations, modifications, and variations that fall within the scope and novel idea of the present disclosure. 
         [0023]    Now, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. 
         [0024]      FIG. 1  is a perspective view showing a disc clamp of a spindle motor according to an embodiment of the present disclosure; and  FIG. 2  is a sectional view cut along I-I′ line in  FIG. 1 . 
         [0025]    Referring to  FIGS. 1 and 2 , a disc clamp  100  of a spindle motor  200  includes a disc clamp body  110  having a rotational axis hole  105 , a first disc balancer  120  and a second disc balancer  130 . 
         [0026]    In an embodiment of the present disclosure, an exemplary material for the disc clamp body  110 , the first disc balancer  120  and the second disc balancer  130  may be a synthetic resin such as plastic or metal. 
         [0027]    The first disc balancer  120  is projected or extended from the side of the disc clamp body  110  in the horizontal direction HD defined in  FIG. 2 . 
         [0028]    In an embodiment of the present disclosure, the first disc balancer  120  is formed in a plate shape which has a uniform thickness A. The first disc balancer  120  has an upper surface (or a horizontal surface  122 ) and a bottom surface  124  facing the upper surface  122 . 
         [0029]    The second disc balancer  130  is formed in a plate shape which has a uniform thickness B and is bent or extended from the end of the first disc balancer  120  in the vertical direction VD defined in  FIG. 2 . The second disc balancer  130  formed in a plate shape has an outer side surface  132  and an inner side surface  134  facing the outer side surface  132 . 
         [0030]    An edge where the upper surface  122  of the first disc balancer  120  meets the outer side surface  132  of the second disc balancer  130  is rounded in order that a hole (not shown) of a disc (not shown) which is a data storage medium is easily inserted into the edge. Differently from this, a chamfer portion cut obliquely may be formed at an edge where the upper surface  122  of the first disc balancer  120  meets the outer side surface  132  of the second disc balancer  130 . 
         [0031]    In order that the hole of the disc that is data storage medium is inserted into the second disc balancer  130  of the disc clamp  100  with a required insertion force, the second disc balancer  130  is bent with respect to the first disc balancer  120  in the optimum angle range. 
         [0032]    A bent angle θ formed between the upper surface  122  of the first disc balancer  120  and the outer side surface  132  of the second disc balancer  130  may be from 92.0° to 95.0°, for example. When describing it in a different way, the second disc balancer  130  has an inclined angle θ1 inclined at about 2.0° to 5.0° clockwise with respect to the vertical direction VD. Table 1 includes disc insertion force and disc balance performance data according to a gradient change of the second disc balancer  130  with respect to a vertical direction in an embodiment of the present disclosure. 
         [0000]    
       
         
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Inclined angle (θ1) 
                 Insertion force (gf) 
                 Balance performance (μm) 
               
               
                   
               
             
             
               
                 1.9° 
                 320 gf 
                 60 μm 
               
               
                 2.0° 
                 300 gf 
                 60 μm 
               
               
                 3.0° 
                 260 gf 
                 60 μm 
               
               
                 4.0° 
                 220 gf 
                 60 μm 
               
               
                 5.0° 
                 200 gf 
                 70 μm 
               
               
                 5.1° 
                 180 gf 
                 70 μm 
               
               
                   
               
             
          
         
       
     
         [0033]    In an embodiment of the present disclosure, the insertion force required to insert the hole of the disc into the second disc balancer  130  is generally from about 200 [gf] to about 300 [gf] and the required balance performance is from about 60 μm to about 70 μm. Referring to the Table 1, when the inclined angle θ1 shown in  FIG. 1  is about 1.9°, the balance performance is excellent as 60 μm but the insertion force is about 320 gf which is out of the insertion force range required for a user to insert the disc into the second disc balancer  130 . 
         [0034]    When the inclined angle θ1 is from about 2.0° to about 5.0°, the balance performance is excellent as about 60 μm to about 70 μm, and the insertion force is about 200 gf to about 300 gf, which is included in the required insertion force, too. 
         [0035]    Meanwhile, when the inclined angle 01 is equal to or greater than about 5.1° which exceeds about 5.0°, the balance performance is about 75 μm which is out of the maximum value of the balance performance, about 70 μm, and the insertion force is about 180 gf which is out of the required insertion force. 
         [0036]    According to the Table 1, when the inclined angle θ1 is less than about 2.0°, the insertion force largely increases so that it is difficult for the user to insert the disc into the second disc balancer  130  with ease. Further, when the inclined angle θ1 exceeds about 5.0°, the insertion force is largely decreased and out of the maximum balance performance range. 
         [0037]    Accordingly, when the inclined angle θ1 is about 2.0° to about 5.0°, the disc insertion force and the maximum balance performance of the disc clamp  100  are included in the range set previously. 
         [0038]    Meanwhile, according to an embodiment of the present disclosure, a consideration should be made to the thicknesses of the first disc balancer  120  and the second disc balancer  130  to enhance durability of the first disc balancer  120  as well as the inclined angle θ1 to provide the insertion force required to insert the hole of the disc into the second disc balancer  130 . 
         [0039]    In order to reduce a fatigue fracture of the first disc balancer  120  occurred by a repetitive bending stress that is applied to the first disc balancer  120  during the hole of the disc that is data storage medium is inserted into or extracted from the disc clamp  100  that has the disc clamp body  110 , the first disc balancer  120  and the second disc balancer  130 , the first disc balancer  120  is formed to have a first thickness A and the second disc balancer  130  is formed to have a second thickness B. 
         [0040]    According to an embodiment of the present disclosure, a ratio of the first thickness A of the first disc balancer  120  to the second thickness B of the second disc balancer  130 , A/B, may be about 1.5 to about 1.8. 
         [0041]    Table 2 includes a normal insertion and extraction number and balance performance data according to a thickness ratio of a first thickness A of the first disc balancer  120  to the second thickness B of the second disc balancer  130 , A/B, in accordance with an embodiment of the present disclosure. 
         [0000]    
       
         
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                 Normal insertion and 
                 Balance performance 
               
               
                 Thickness ratio (A/B) 
                 extraction number 
                 (μm) 
               
               
                   
               
             
             
               
                 1.4 
                 About 8,000 times 
                 60 μm 
               
               
                 1.5 
                 10,000 times or more 
                 60 μm 
               
               
                 1.6 
                 10,000 times or more 
                 60 μm 
               
               
                 1.7 
                 10,000 times or more 
                 60 μm 
               
               
                 1.8 
                 10,000 times or more 
                 69 μm 
               
               
                 1.9 
                 10,000 times or more 
                 74 μm 
               
               
                   
               
             
          
         
       
     
         [0042]    In an embodiment of the present disclosure, the second disc balancer  130  should insert and extract the disc about 8,000 times to about 10,000 times. 
         [0043]    Referring to Table 2, when a thickness ratio of a first thickness A of the first disc balancer  120  to a second thickness B of the second disc balancer  130 , A/B, is about 1.4, the balance performance is excellent as about 60 μm but the normal insertion and extraction number is about 8,000 times, which is out of a required durability range. That is, when the thickness ratio A/B is about 1.4, the durability is largely decreased so that the first disc balancer  120  is broken or damaged after inserting and extracting it about 8,000 times. When the thickness ratio of the first thickness A of the first disc balancer  120  to the second thickness B of the second disc balancer  130 , A/B, is about 1.5 to about 1.8, all the balance performances are excellent as about 60 μm, and the normal insertion and extraction number is 10,000 times or more, which shows that the durability is largely enhanced compared with the case that the thickness ratio A/B is about 1.4. 
         [0044]    Meanwhile, when the thickness ratio of the first thickness A of the first disc balancer  120  to the second thickness B of the second disc balancer  130  is about 1.9, the normal insertion and extraction number is 10,000 times or more, too, which shows that the durability is largely enhanced compared with the case that the thickness ration A/B is about 1.4, but the balance performance is about 74 μm, which is out of the maximum balance performance. 
         [0045]    According to the Table 2, when the thickness ratio A/B is less than about 1.4, it does not meet the required durability. Further, when the thickness ratio A/B exceeds about 1.9, it satisfies the required durability but the balance performance is decreased. 
         [0046]    Accordingly, when the thickness ratio A/B is about 1.5 to 1.8, the first disc balancer  120  can satisfy the required durability and balance performance. 
         [0047]      FIG. 3  is a sectional view showing a spindle motor according to another embodiment of the present disclosure. 
         [0048]    Referring to  FIG. 3 , the spindle motor  200  includes a base plate  1 , a rotational axis  10 , a stator  50 , a rotor  60  and a disc clamp  100 . 
         [0049]    The base plate  1  is formed in a plate shape, on which a burring portion  5  is formed, the burring portion being formed by a burring process. The burring portion  5  is formed inwards from the outer side surface of the base plate  1 , for example, to which a bearing housing  30  to be described below is engaged. 
         [0050]    The rotational axis  10  is engaged with a rotor  60  to be described below, and there is formed an axial groove  15  in the bottom of the outer circumference surface of the rotational axis  10 . The bottom end of the rotational axis  10  is processed as a curved surface, for example. 
         [0051]    The stator  50  includes a bearing  20 , a bearing housing  30 , a core  52  and a coil  54 . The stator  50  may further include a washer  40 . The bearing  20  is formed in a cylindrical shape having a hollow that is inserted into the rotational axis  10 . Further, it may be an oil impregnated sintering bearing, for example. 
         [0052]    The washer  40  has a hollow inserted into a portion corresponding to an axial groove  15  of the rotational axis  10 , and the hollow of the washer  40  has a diameter that is smaller than that of the rotational axis  10  and greater than that of the rotational axis  10  corresponds to the axial groove  15 . Accordingly, the washer  40  is touched to the axial groove  15  so that it limits the movement of the rotational axis  10  up and down. The upper surface of the washer is pressed by the bottom of the bearing  20 . 
         [0053]    The bearing housing  30  includes a bottom panel  32  and a side panel  36 . 
         [0054]    The bottom panel  32  is formed in a disc shape, for example, and supports the end portion of the rotational axis  10 . A thrust bearing  38  may be arranged between the bottom of the rotational axis  10  and the bottom panel  10  facing the bottom of the rotational axis  10 . 
         [0055]    The side panel  36  is extended from the bottom panel  32  in the direction facing the rotational axis  10 . In an embodiment of the present disclosure, the side panel  36  is extended in a cylindrical shape along the direction parallel to the rotational axis  10 . 
         [0056]    The core  52  has a structure of a plurality of stacked pieces of iron, and is engaged by being inserted into the side panel  36  of the bearing housing  30 . 
         [0057]    The coil  54  is wound around the core  52  using a winding portion (not shown) formed in the core  52 . 
         [0058]    The rotor  60  includes a yoke  62  and a magnet  64 . 
         [0059]    The yoke  62  is formed in a disc shape, and there is formed a yoke burring portion  61  inserted into the rotational axis  10  at the rotational center. Further, some of the yoke  62  is bent to face the core  52  of the stator  50 . 
         [0060]    The magnet  64  is engaged with the bent portion of the yoke  62 , and the magnet  64  is arranged to face the core  52  of the stator  50 . 
         [0061]    The disc clamp  100  is engaged with the outer circumference surface or the yoke burring portion  61  of the rotational axis  10 , the disc clamp being shown in  FIG. 2  and described above. 
         [0062]    The disc clamp  100  includes the disc clamp body  110 , the first disc balancer  120  and the second disc balancer  130 . 
         [0063]    The disc clamp body  110  includes a rotational axis hole  105  engaged with the yoke burring portion  61 . 
         [0064]    The first disc balancer  120  is projected or extended from the disc clamp body  110  in the horizontal direction. The second disc balancer  130  is bent towards the yoke  60  from the first disc balancer  120 . 
         [0065]    According to an embodiment of the present disclosure, when the first disc balancer  120  has a first thickness A and the second disc balancer  130  has a second thickness B, the thickness ratio of the first disc balancer  120  to the second thickness B of the disc balancer  130 , A/B, may be about 1.5 to about 1.8. 
         [0066]    Further, an inclined angle θ1 of the second disc balancer  130  arranged obliquely clockwise with respect to the vertical direction, may be about 2.0° to about 5.0°, for example. 
         [0067]    In an embodiment of the present disclosure, when the inclined angle is about 2.0° to about 5.0°, the required insertion force of the disc is about 200 [gf] to 300 [gf] and the required balance performance is from 60 μm to 70 μm. 
         [0068]    Further, in an embodiment of the present disclosure, when the thickness ratio A/B is about 1.5 to about 1.8, the first disc balancer  120  can insert and extract disc about 8,000 times to 10,000 times or more so that the required durability can be embodied and the required balance performance can also embodied. 
         [0069]    According to the detailed description above, the required disc insertion force, balance performance and enhanced durability can be embodied by changing the thickness ratio of the first and second balance portions of the disc clamp engaged with the rotational axis that rotates at a high speed. 
         [0070]    Hereinbefore, while the embodiments of the present disclosure are described, they are exemplary ones only and one of ordinary skill in the art may recognize that various alterations and modifications that fall within the scope of the present disclosure may be possible. Accordingly, the true technical protection scope of the present disclosure should be defined by the following claims.