PATENT ABSTRACT
A magnetic disk device having a magnetic disk for recording information, a spindle motor for driving the magnetic disk for rotation, a magnetic head for reading information from the magnetic disk, a carriage arm for supporting the magnetic disk, a voice coil motor for moving the carriage arm, a loading/unloading mechanism for retracting the carriage arm from a position on the magnetic disk, and a shroud for forming a peripheral wall. The magnetic device includes an air passage positioned between the loading/unloading mechanism and the shroud.

PATENT DESCRIPTION
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application is a continuation of U.S. application Ser. No. 10/287,664, filed Nov. 5, 2002, which is a continuation of U.S. application Ser. No. 09/986,605, filed Nov. 9, 2001, now U.S. Pat. No. 6,560,066, which is a continuation of U.S. application Ser. No. 09/769,362, filed Jan. 26, 2001, now U.S. Pat. No. 6,369,977. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to a magnetic disk device and, more particularly, to a magnetic disk drive which has a high reliability and is capable of reducing windage vibrations of a magnetic head due to turbulent air currents produced by a rotating magnetic disk.  
           [0003]    [0003]FIG. 6 shows a known magnetic disk device  600  disclosed in JP-A No. 2000-156068. The magnetic disk device  600  drives a magnetic disk  11  by way of a spindle motor  12 . A magnetic head for writing information to and reading information from the magnetic disk  11  is supported on the extremity of a suspension  21 . A carriage arm  25  supports the suspension  21 . The carriage arm  25  has a base end fixed to a pivot shaft  20 . A voice coil motor  28  drives the carriage arm  25  for turning. This prior art magnetic disk device  600  is provided with a filter  60  placed on an air passage  61  formed by cutting a portion of a shroud  41 .  
         SUMMARY OF THE INVENTION  
         [0004]    The air passage  61  formed by cutting a portion of the shroud  41  as shown in FIG. 6 often enhances the hydrodynamic vibrations of the magnetic disk  11  generally called disk fluttering  
           [0005]    Accordingly, it is an object of the present invention to provide a magnetic disk device which has a high reliability and is capable of reducing windage vibrations of a magnetic head caused by air currents produced by a rotating magnetic disk.  
           [0006]    With the foregoing object in view, according to a first aspect of the present invention, a magnetic disk device comprises a magnetic disk for recording information, a spindle motor for driving the magnetic disk for rotation, a magnetic head for writing information to and reading information from the magnetic disk, a carriage arm supporting the magnetic head, a voice coil motor for moving the carriage arm, a shroud forming a peripheral wall, a structure forming an air passage extending through a clearance between the voice coil motor and the shroud between a position on the upper side of the carriage arm with respect to the direction of rotation of the magnetic disk and a position on the lower side of the carriage arm with respect to the direction of rotation of the magnetic disk, and a filter placed in the air passage to clean air flowing through the air passage.  
           [0007]    According to a second aspect of the present invention, a magnetic disk device comprises a magnetic disk for recording information, a spindle motor for driving the magnetic disk for rotation, a magnetic head for writing information to and reading information from the magnetic disk, a carriage arm supporting the magnetic head, a voice coil motor for moving the carriage arm, a loading/unloading mechanism for retracting the carriage arm from a position on the magnetic disk, a shroud forming a peripheral wall, and a structure forming an air passage extending through a clearance between the voice coil motor and the shroud between a position on the upper side of the carriage arm with respect to the direction of rotation of the magnetic disk and a position on the lower side of the carriage arm with respect to the direction of rotation of the magnetic disk.  
           [0008]    According to a third aspect of the present invention, a magnetic disk device comprises a magnetic disk for recording information, a spindle motor for driving the magnetic disk for rotation, a magnetic head for writing information to and reading information from the magnetic disk, a carriage arm supporting the magnetic head, a voice coil motor for moving the carriage arm, a loading/unloading mechanism for retracting the carriage arm from a position on the magnetic disk, and a shroud forming a peripheral wall; wherein the rotating direction of the magnetic disk is the same as a direction from the free end of the carriage arm toward the base end of the same. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    The invention disclosed herein will be understood better with reference to the following drawings of which:  
         [0010]    [0010]FIG. 1 is a schematic plan view of a magnetic disk device representing a first embodiment according to the present invention;  
         [0011]    [0011]FIG. 2 is a schematic plan view of a magnetic disk device representing a second embodiment according to the present invention;  
         [0012]    [0012]FIG. 3 is a schematic plan view of a magnetic disk device representing a third embodiment according to the present invention;  
         [0013]    [0013]FIG. 4 is a schematic plan view of a magnetic disk device representing a fourth embodiment according to the present invention;  
         [0014]    [0014]FIG. 5 is a graph showing the results of experiments on pressure variation; and  
         [0015]    [0015]FIG. 6 is a plan view of a prior art magnetic disk device. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    Preferred embodiments of the present invention will be described by way of example with reference to the accompanying drawings.  
         [0017]    First Embodiment  
         [0018]    Referring to FIG. 1, which shows a magnetic disk device  100  representing a first embodiment according to the present invention, a magnetic disk  11  is driven for rotation by a spindle motor  12 . A magnetic head for writing information to and reading information from the magnetic disk  11  is supported on the extremity of a suspension  21  supported on a carriage arm  25 . The carriage arm  25  is capable of turning on a pivot shaft  26 . A voice coil motor  28  drives the carriage arm  25  for turning. The rotating direction of the magnetic disk  11  is the same as a direction from the base end of the suspension  21  toward the extremity of the same. A connector  10  connects input and output signal lines, not shown, extending from the magnetic head supported on the suspension  21  to a control circuit, not shown, which is included in the magnetic disk device  100 . A loading/unloading mechanism  31  in the form of a lumped loading system is disposed so that a tab  32  slides onto the loading/unloading mechanism  31  when the carriage arm  25  is turned to a position outside the magnetic disk  11 .  
         [0019]    A shroud  41  has a wall surrounding the magnetic disk  11 . The shroud  41  and a land  39  form return channels  45   a ,  45   b  and  45   c , i.e., air passages, through which air currents produced when the magnetic disk  11  is rotated flow. A filter  60  for removing dust is placed in the return channel  45   c . The return channel  45   c  is connected to an air passage  50  defined by an extension  42 . Air currents produced when the magnetic disk  11  is rotated flow into the return channel  45   a , flow through the return channels  45   b  and  45   c  and the air passage  50 , and flow outside through an exit  49  formed at a position below the loading/unloading mechanism  31  with respect to the direction of flow of the air currents. The air currents flow also through a space immediately above the loading/unloading mechanism  31  into the air passage  50  and flow outside through the exit  49   b.    
         [0020]    In the magnetic disk device  100 , spaces on the upper and the lower side of the loading/unloading mechanism  31  are connected by the air passage  50 , and a screen  42   b  screens a principal section of the air passage  50  from the magnetic disk  11  so that air flows smoothly downstream to prevent the production of turbulent air currents around the loading/unloading mechanism. Thus, enhancement of windage vibrations of the magnetic head due to turbulent air currents can be prevented and the reliability of the magnetic disk device can be enhanced.  
         [0021]    The fluttering amplitude of the magnetic disk  11  on the magnetic disk device  100  provided with the filter  60  in the return channel  45   b  or  45   c  was smaller by about 27% than that of a magnetic disk on a conventional magnetic disk device provided with an air passage specially for a filter.  
         [0022]    The effect of placing the filter in the return channel in reducing the fluttering amplitude of the magnetic disk  11  is effective not only in magnetic disk devices provided with a loading/unloading mechanism, but also in magnetic disk devices of a CSS (contact start stop) system in which a magnetic head is in sliding contact at the start and stop of rotation of the magnetic disk.  
         [0023]    The filter  60  may be placed in the return channel  45   a  or  45   b . Experiments proved that flutter reduction when the filter  60  is placed at the inlet of the return channel  45   a  was greater by about 10% than those when the filter  60  was placed at other positions. The effect of air on cooling the voice coil motor  28  can be enhanced by placing the filter  60  in the return channel  45   b  between the voice coil motor  28  and the shroud  41 .  
         [0024]    Second Embodiment  
         [0025]    A magnetic disk device  200  representing a second embodiment according to the present invention will be described with reference to FIG. 2, in which parts like or corresponding to those of the magnetic disk device  100  in the first embodiment will be denoted by the same reference numerals and a respect of the description thereof will be omitted.  
         [0026]    The magnetic disk device  200  is provided with a screen  43  to produce smooth air currents around a loading/unloading mechanism  31 . The screen  43  covers a region on one side of the loading/unloading mechanism  31  spaced from the magnetic disk  11 , i.e., on the opposite side of the mechanism  31  from the magnetic disk  11 , and extends into a region on the lower side of the loading/unloading mechanism  31  with respect to the rotating direction of the magnetic disk  11 . A portion  44  of a shroud  41  is shaped so that the width of the air passage  50  decreases gradually.  
         [0027]    The air passage  50  is defined by a portion of the screen  43  on the lower side of the loading/unloading mechanism  31  with respect to the direction of air flow, and the shroud  41 . Air flows through an entrance  49   a  into the air passage  50  and flows outside the air passage  50  through an exit  49   b . The screen  43  is shaped so as to guide air so that air flows smoothly and screens a principal section of the air passage  50  from the magnetic disk  11 . The exit  49   b  is located on a line passing through the center of the magnetic disk  11  and at an angle θ about the center of the magnetic disk  11  measured in the rotating direction of the magnetic disk  11  from a line passing through the center of the magnetic disk  11  and the loading/unloading mechanism  31  (head stroke position). Preferably, the angle θ is in the range of 10° to 30°, more preferably, in the range of 15° to 25°. Turbulent flow of air is produced unavoidably in the vicinity of the exit  49   b , and, if the angle θ is below 10°, the exit  49   b  will be excessively near to the loading/unloading mechanism  31  and turbulent flow of air produced at the exit  49   b  will adversely affect the function of the loading/unloading mechanism  31 . Consequently, the turbulence control effect of the magnetic disk device will be unsatisfactory. When the angle θ is greater than 30°, the shroud  41  is excessively short and the exciting force that causes the magnetic disk  11  to flutter increases.  
         [0028]    In the magnetic disk device  200  in the second embodiment, the screen  43  covers the region on one side of the loading/unloading mechanism  31  spaced from the magnetic disk  11  and extends into the region on the lower side of the loading/unloading mechanism  31  with respect to the rotating direction of the magnetic disk  11 . Therefore, the production of turbulent flow of air by the irregular shape of the loading/unloading mechanism  31  can be prevented and air is able to flow smoothly.  
         [0029]    Since the air currents produced by the rotating magnetic disk  11  flow in a direction opposite the rotating direction of the magnetic disk  11  with respect to the loading/unloading mechanism  31 , the collision of the air currents against the loading/unloading mechanism  31  and the resultant turbulent flow of air can be prevented. Thus, it is possible to prevent the deterioration of the reliability of the magnetic disk device  200  caused by the enhancement of windage vibrations of the magnetic head by the loading/unloading mechanism  31 , the enhancement of exciting force that causes the magnetic disk  11  to flutter, and the unstable loading and unloading operations due to the adverse effect of turbulent flow on the suspension  21  and the carriage arm  25 .  
         [0030]    Third Embodiment  
         [0031]    A magnetic disk device  300  representing a third embodiment according to the present invention will be described with reference to FIG. 3, in which parts like or corresponding to those of the magnetic disk devices  100  and  200  in the first and the second embodiment will be denoted by the same reference numerals, and a repeated description thereof will be omitted.  
         [0032]    The magnetic disk device  300  is basically the same in construction as the magnetic disk device  200  in the second embodiment. The magnetic disk device  300  is provided with a screen  43   a  that extends from the upper side to the lower side of a loading/unloading mechanism  31  to guide air currents more smoothly from the upper side of the loading/unloading mechanism  31  into an air passage  50 . A filter  60  is placed in a passage between an extension  42  and the screen  43   a.    
         [0033]    In the magnetic disk device  300  in the third embodiment, the stability of air currents flowing from the upper side toward the lower side of the loading/unloading mechanism  31  can be enhanced because the screen  43   a  extends from the upper side to the lower side of the loading/unloading mechanism  31 . Experiments show that the screen  43   a  increases flutter reducing effect by about 10%. The filter  60 , similarly to that of the first or the second embodiment, may be disposed in the return channel  45   a  or  45   b.    
         [0034]    Fourth Embodiment  
         [0035]    A magnetic disk device  400  representing a fourth embodiment according to the present invention will be described with reference to FIG. 4, in which parts like or corresponding to those of the magnetic disk devices  100 ,  200  and  300  in the first, the second and the third embodiment will be denoted by the same reference numerals, and a repeated description thereof will be omitted.  
         [0036]    This magnetic disk device  400  drives a magnetic disk  11  by way of a spindle motor  12 . The magnetic disk  11  is rotated in a direction opposite the direction in which the magnetic disks  11  in the first to the third embodiments are rotated; that is, the magnetic disk  11  is rotated in a direction from a loading/unloading mechanism  31  toward a suspension  21 , in a direction from the extremity toward the base end of the suspension  21  or in a direction from a magnetic head toward a carriage arm  25  supporting the suspension  21 .  
         [0037]    In a magnetic disk device of a CSS system, the magnetic disk cannot be turned in the reverse direction because troubles, such as buckling, occur in the gimbals and the suspension of the magnetic disk device when the magnetic disk is rotated in the reverse direction. The magnetic disk device provided with the loading/unloading mechanism  31  is free from such troubles even if the magnetic disk is rotated in the reverse direction.  
         [0038]    A shroud  41  and a land  39  define return channels  45   a ,  45   b  and  45   c  through which air currents produced by a rotating magnetic disk  11  flow. A filter  60  is placed in the return channel  45   c  to filter out dust from the air. An extension  42  connects the return channel  45   c  to an air passage  50 . The filter  60 , similarly to that of the first or the second embodiment, may be placed in the return channel  45   a  or  45   b.    
         [0039]    The air passage  50  is defined by a screen  43   b  disposed on the upper side of the loading/unloading mechanism  31 . Air flows through an entrance  49   a  on the upper side of the loading/unloading mechanism  31  into the air passage  50  and flows out of the air passage  50  through an exit  49   b  on the lower side of the loading/unloading mechanism  31 . The screen  43   b  is shaped so as to guide air so that air flows smoothly, and screens a principal section of the air passage  50  from the magnetic disk  11 . The screen  43   b  is extended on the upper side of the loading/unloading mechanism  31  with respect to the direction of air flow. Air currents produced by the rotating magnetic disk  11  flow through the entrance  49   a  into the air passage  50 , flow out of the air passage  50  through the exit  49   b  and flow through the return channels  45   c ,  45   b  and  45   a.    
         [0040]    [0040]FIG. 5 shows measured ranges of pressure variation at positions at angles 90°, 180° and 270° in the rotating direction of the magnetic disk  11  from a reference line at an angular position of 0° corresponding to the position of the carriage arm  25 . As obvious from FIG. 5, the range of pressure variation decreases with the angle from the reference line. When the magnetic disk  11  is rotated in the direction indicated by the arrow in FIG. 4, the range of pressure variation is the widest in a region between the carriage arm  25  and the exit of the return channel  45   a , extending under an open section of the shroud  41 , i.e., a section between the entrance  49   a  of the passage defined by the shroud  41  and the magnetic disk  11  and a position where the passage defined by the land  39  and the magnetic disk  11  is narrowed. The range of pressure variation is the narrowest in a region around the entrance  49   a  on the upper side of the open section of the shroud  41 .  
         [0041]    Since the head  11  of the magnetic disk device  400  in the fourth embodiment is located at an angular position corresponding to the region around the entrance  49   a  on the upper side of the open section of the shroud  41 , where the range of pressure variation is the narrowest, the windage vibrations of the head  11  can be prevented, thereby to enhance the reliability of the magnetic disk device  400 .  
         [0042]    The mode of variation of the range of pressure variation in a magnetic disk device not provided with any return channels is the same as that shown in FIG. 5. The effect of the magnetic disk device  400  in the fourth embodiment can be attained also in a magnetic disk device not provided with any return channels.  
         [0043]    As apparent from the foregoing description, the magnetic disk device according to the present invention is capable of reducing windage vibrations of the head caused by air currents generated by the rotating magnetic disk, which enhances the reliability of the magnetic disk device.  
         [0044]    Although the invention has been described in its preferred embodiments with a certain degree of particularity, obviously many changes and variations are possible therein. It is therefore to be understood that the present invention may be practiced otherwise than as specifically described herein without departing from the scope and spirit thereof.