Patent Publication Number: US-2006007601-A1

Title: Base plate and hard disk drive provided therewith

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application claims the priority of Korean Patent Application No. 2004-52602, filed on Jul. 7, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a hard disk drive (HDD), and more particularly, to a base plate that can absorb an external shock transmitted to an actuator, and an HDD containing the base plate.  
      2. Description of Related Art  
       FIG. 1  is an exploded perspective view of a conventional hard disk drive (HDD).  
      Referring to  FIG. 1 , an HDD  10  includes a base plate  11 , a disk  25  which is a data recording medium, a spindle motor  30  which is installed on the base plate  11  and rotates the disk  25 , magnetic heads  41   a  and  41   b  which record and/or reproduce data on/from the disk  25 , an actuator  40  which includes means for moving the magnetic heads  41   a  and  41   b , and a cover plate  20  which is attached to the base plate  11  and protects the disk  25 , the spindle motor  30 , and the actuator  40  on the base plate  11 .  
      The disk  25  is fixedly installed on a rotor of the spindle motor  30  to rotate relative to the base plate  11 . Servo signals indicating positions of data to be recorded on top and bottom surfaces of the disk  25  are previously recorded on tens of thousands of tracks formed along the circumference of the disk  25 .  
      The actuator  40  has an insertion hole into which a protrusion  15  formed on the base plate  11  is inserted, such that the actuator  40  rotates about the protrusion  15  in response to a voice coil motor (VCM)  47 . Further, the actuator  40  includes means for supporting the magnetic heads  41   a  and  41   b . The magnetic head supporting means includes a swing arm  44  and suspensions  43   a  and  43   b  that are installed on the swing arm  44  and elastically bias sliders  42   a  and  42   b  on which the magnetic heads  41   a  and  41   b  are mounted toward the top and bottom surfaces of the disk  25 .  
      In operation, when the HDD  10  is turned on and the disk  25  begins to rotate, a lifting force is generated due to air pressure and the sliders  42   a  and  42   b  are maintained over the surface of the disk  25  at a flying height at which the lifting force generated due to the rotation of the disk  25  is equal to an elastic force of the suspensions  43   a  and  43   b . Accordingly, the magnetic heads  41   a  and  41   b  mounted on the sliders  42   a  and  42   b  record data on the disk  25  or reproduce data from the disk  25  while maintaining a specified distance from the rotating disk  25 .  
      However, the above-described conventional HDD has a drawback. When the conventional HDD  10  is in operation, an external shock may be applied to the HDD  10 . Since the sliders  42   a  and  42   b  on which the magnetic heads  41   a  and  41   b  are mounted fly over the surface of the disk  25  during the operation of the HDD  10 , if an external shock is applied, the sliders  42   a  and  42   b  may collide with the disk  25 , leading to a failure of the HDD  10 . And, even when the sliders  42   a  and  42   b  do not collide with the disk  25 , errors in data recording and reproducing operations may be caused. The external shock is transmitted to the actuator  40  via the base plate  11 . The conventional base plate  11  has no means for absorbing the shock transmitted to the actuator  40 .  
     BRIEF SUMMARY  
      An embodiment of the present invention provides a base plate, which can absorb an external shock transmitted to an actuator, and a hard disk drive (HDD) provided with the base plate.  
      According to an aspect of the present invention, there is provided a base plate on which a disk is rotatably installable and an actuator which transfers data to and/or from the disk is pivotably installable, including a buffer slot formed around an axis to absorb at least some of a shock transmitted to the actuator.  
      The base plate may also include a pair of connecting portions crossing the buffer slot to connect an inner wall of the buffer slot to an outer wall of the buffer slot. The buffer slot may have a circular shape centered around the axis.  
      The plurality of buffer slots may have a concentric-circular shape, and a straight line between the axis and a pair of connecting portions of a buffer slot may not be the same as a straight line connecting the axis and a pair of connecting portions of another buffer slot.  
      The first buffer slot may be close to the axis and a second buffer slot may be farther from the axis than the first buffer slot. A straight line between the axis and a pair of connecting portions of the first buffer slot may intersect perpendicularly a straight line connecting between the axis and a pair of connecting portions of the second buffer slot.  
      According to another aspect of the present invention, there is provided a hard disk drive including: a base plate; and an actuator pivotably installed on the base plate, pivotable about an axis, and supporting on an end portion thereof of a slider on which a magnetic head for recording or reproducing data on a disk is mounted. The a buffer slot is formed around the axis on the base plate to absorb at least some of a shock transmitted to the actuator.  
      According to another aspect of the present invention, there is provided a base plate including: a pivot section to which an actuator is pivotably mountable; and a shock absorbing section which surrounds the pivot section and which includes first and second respective buffer slots, a pair of first connecting portions, and a pair of second connecting portions, the first and second respective buffer slots absorbing at least some of a shock transmitted to the actuator, the first and second connecting portions partially connecting the protrusion to the base plate.  
      According to another aspect of the present invention, there is provided a method of preventing disk failure, including: connecting a pivot protrusion to which an actuator is pivotably mountable to a base plate through plural connecting portions; substantially isolating the pivot protrusion via plural buffer slots between the plural connection portions; and attenuating a shock by absorbing at least some of the shock via the first and second buffer slots and indirectly transmitting the shock to the pivot protrusion through the first and second connecting portions.  
      Additional and/or other aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      These and/or other aspects and advantages of the present invention will become apparent and more readily appreciated from the following detailed description, taken in conjunction with the accompanying drawings of which:  
       FIG. 1  is an exploded perspective view of a conventional hard disk drive (HDD);  
       FIG. 2  is an exploded perspective view of an HDD according to an embodiment of the present invention;  
       FIG. 3  is a plan view of a base plate according to the embodiment of  FIG. 2 ; and  
       FIGS. 4 and 5  are simulation graphs illustrating impulse responses when a virtual impulse is input to a conventional base plate and the base plate according to the embodiment of  FIG. 2 ,  FIG. 4  illustrating an impulse response in an X-direction,  FIG. 5  illustrating an impulse response in a Y-direction. 
    
    
     DETAILED DESCRIPTION OF EMBODIMENT  
      Reference will now be made in detail to an embodiment of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiment is described below in order to explain the present invention by referring to the figures.  
       FIG. 2  is an exploded perspective view of a hard disk drive (HDD) according to an embodiment of the present invention, and  FIG. 3  is a plan view of a base plate according to an embodiment of the present invention.  
      Referring to  FIGS. 2 and 3 , an HDD  100  includes a housing that is formed by attaching a cover plate  110  to a base plate  101  leaving a specified inner space therebetween. A disk  115 , a spindle motor  120 , and an actuator  130  are installed in the housing.  
      The housing includes the base plate  101 , which supports the spindle motor  120  and the actuator  130 , and the cover plate  110 , which is attached to the base plate  101  and protects the disk  115 . The housing may be made of stainless steel or aluminium.  
      The disk  115  is mounted inside the housing. Four or more disks may be mounted in an HDD to increase data storage capacity.  
      The spindle motor  120  rotates the disk  115 , and is fixedly inserted into a receiving hole  109  formed in the base plate  101 . A disk clamp  125  is screwed to a top portion of the spindle motor  120  to prevent the disk  115  from separating.  
      The actuator  130  is used for recording data on the disk  115  or reading out data recorded on the disk  115 , and is pivotably coupled to a protrusion  102  formed on the base plate  101 . The actuator  130  includes a pivot bearing  138  into which the protrusion  102  is inserted, a swing arm  137 , which rotates about the protrusion  102 , first and second respective suspensions  135   a  and  135   b  coupled to a leading end of the swing arm  137 , and first and second respective sliders  132   a  and  132   b , which are respectively supported by the respective suspensions  135   a  and  135   b . Respective first and second magnetic heads  131   a  and  131   b  for recording and reproducing data are mounted on the sliders  132   a  and  132   b , respectively. Further, a voice coil motor (VCM)  139  provides a force for rotating the swing arm  137  about the protrusion  102 . The VCM  139  is controlled by a servo control system, and rotates the swing arm  137  in a direction according to Fleming&#39;s Left Hand Rule due to an interaction between current input to a VCM coil and a magnetic field formed by magnets. Accordingly, the sliders  132   a  and  132   b  attached to leading ends of the respective suspensions  135   a  and  135   b  are moved over the disk  115  toward the spindle motor  120  or an outer periphery of the disk  115 .  
      First and second respective buffer slots  103  and  106  are formed around the protrusion  102 , which is formed on the base plate  101  and functions as a pivot axis of the actuator  130 , so as to absorb a shock transmitted to the actuator  130 . The first and second respective buffer slots  103  and  106  have a concentric-circular shape and are centered around the protrusion  102 . The first slot  103  is closer to the protrusion  102  than the second buffer slot  106 . If the width of the respective buffer slots  103  and  106  is too small, they cannot absorb a shock satisfactorily, and the width of the respective buffer slots  103  and  106  cannot be too large because of structural limitations. Accordingly, the width of the buffer slots  103  and  106  may range from 0.5 to 2.5 mm.  
      A pair of first connecting portions  105  cross the first buffer slot  103  to connect an inner wall of the first buffer slot  103  to an outer wall of the first buffer slot  103 . Further, a pair of second connecting portions  108  cross the second buffer slot  106  to connect an inner wall of the second buffer slot  106  to an outer wall of the second buffer slot  106 . The first and second connecting portions  105  and  108  partially connect the protrusion  102  to the base plate  101 . However, a width of the respective connecting portions  105  and  108  may be as small as possible since an external shock is transmitted via the connecting portions  105  and  108 .  
      The pair of first connecting portions  105  are symmetric with respect to the protrusion  102  on a straight line through the protrusion  102  in a direction Y. The pair of second connecting portions  108  are symmetric with respect to the protrusion  102  on a straight line through the protrusion  102  in a direction X. Consequently, the straight line connecting between the protrusion  102  and the pair of first connecting portions  105  intersects perpendicularly the straight line connecting between the protrusion  102  and the pair of second connecting portions  108 .  
      The protrusion  102  is substantially isolated from the base plate  101  due to the respective first and second buffer slots  103  and  106 , and is restrictively connected to the base plate  101  through the first and second connecting portions  105  and  108 . Accordingly, if an external shock is applied to the HDD  100 , part of the shock is absorbed by the first and second buffer slots  103  and  106 , and as shown by arrows in  FIG. 3 , the external shock cannot directly reach the protrusion  102  but must be indirectly transmitted to the protrusion  102  through the first and second connecting portions  105  and  108 . Thus, the shock is attenuated. As a result, an attenuated shock is transmitted to the actuator  103  as compared with a conventional HDD.  
      For the purpose of verifying the effects of the described embodiment of the present invention, a computer simulation was performed to compare an impulse response of a conventional base plate with an impulse response of the base plate according to the present invention. In detail, a virtual impulse was applied both to the conventional base plate without buffer slots and to the base plate with the first and second buffer slots according to the present invention as shown in  FIG. 3 . Impulse responses of the two base plates at the protrusion were calculated and graphed. The impulse, which is a half-sine wave signal with a peak value of 350 G (1 G=approximately 9800 mm/s 2 ), was applied in a Y-direction (see  FIG. 3 ) during 2 ms.  FIGS. 4 and 5  are graphs illustrating impulse responses obtained through the computer simulation. Especially,  FIG. 4  illustrates an impulse response in an X-direction, and  FIG. 5  illustrates an impulse response in a Y-direction.  
      Referring to  FIG. 4 , the impulse response of the conventional base plate is shown as a solid line and has a peak value of 16.9 G. The impulse response of the base plate with the first and second buffer slots according to the present invention is shown as a dotted line and has a peak value of 15.3 G. Referring to  FIG. 5 , the impulse response of the conventional base plate is shown in a solid line and has a peak value of 392 G, and the impulse response of the base plate with the first and second buffer slots according to the present invention is shown as a dotted line and has a peak value of 366 G.  
      The base plate and the HDD provided with the base plate according to the disclosed embodiment of the present invention can absorb an external shock applied to the HDD more effectively than the conventional art, and accordingly, a weaker shock is transmitted to the actuator. As a result, the risk of failure due to a collision between the slider and the disk is reduced and the possibility of recording and reproducing errors is also reduced.  
      Although an embodiment of the present invention have been shown and described, the present invention is not limited to the described embodiment. Instead, it would be appreciated by those skilled in the art that changes may be made to the embodiment without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.