Abstract:
A disk apparatus, e.g., a magnetic disk apparatus has a storage medium in the form of a disk which is rotated and accessed, and is designed so as to reduce the occurrence of scratches on the storage medium due to contact between the head and the storage medium while ensuring stable access to the disk-type storage medium. In addition to a main dowel which is provided on a suspension and which supports a magnetic head at a center of the same, an auxiliary dowel is provided on the suspension on the air outflow side relative to the main dowel to limit the tilt of the magnetic head at the time of loading.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a disk apparatus, for example, a magnetic disk apparatus in which a storage medium in the form of a disk is rotated and is accessed.  
         [0003]     2. Description of the Related Art  
         [0004]     Magnetic disk apparatus have found great use as apparatus incorporated in or externally connected to computers. In recent years, magnetic disk apparatus have been incorporated not only in computers in a narrow sense but also in video devices, digital cameras, vehicle navigation devices, etc.  
         [0005]     Magnetic disk apparatus are broadly divided into two types: one called a contact stop/start (CSS) type and one called a load/unload type. In CSS-type magnetic disk apparatus, a magnetic head slider on which a magnetic head for accessing a magnetic disk is fixed (the magnetic head and the magnetic head slider hereinafter referred to, for ease of description, as a magnetic head without being discriminated from each other) is left in a state of being placed on the magnetic disk. When the magnetic disk in a CSS-type magnetic disk apparatus is rotated, the magnetic head is floated by an air flow accompanying the rotation to be is slightly spaced apart from the magnetic disk surface. In this state, the magnetic disk is accessed with the magnetic head.  
         [0006]     In load/unload-type magnetic disk apparatus, the magnetic head is moved to a position off the outer circumference of the magnetic disk and maintained in a standby state at this position when the magnetic disk stops rotating (which moving is called unloading), and is moved onto the magnetic disk after the magnetic disk has started rotating (which moving is called loading).  
         [0007]     The conventional dominating magnetic disk apparatus have been CSS-type magnetic disk apparatus. However, with the increase in the recording density of magnetic disks in recent years, the surface roughness of magnetic disks has become lower to increase the risk of sticking (stiction) fault such that once the magnetic head is brought into contact with the magnetic disk surface, it sticks to the magnetic disk surface.  
         [0008]     With a CSS-type magnetic disk apparatus incorporated in a portable appliance such as a notebook computer, there is a problem that high shock resistance is required of the CSS-type device since the portable appliance is frequently carried, and it is disadvantageous to use the CSS-type device under such a condition since the magnetic head contacts the magnetic disk.  
         [0009]     Because of these problems, load/unload-type magnetic disk apparatus have been widely adopted in recent years. Load/unload-type magnetic disk apparatus can have higher shock resistance in comparison with CSS-type devices because the magnetic head is in the standby position off the magnetic disk when the magnetic disk apparatus is not operating.  
         [0010]     In the case of load/unload-type magnetic disk apparatus, however, a transient operation to load the magnetic head onto the rotating magnetic disk is involved and there is a problem that the magnetic head is liable to contact and damage the magnetic disk during the transient operation.  
         [0011]     The magnetic head is constructed so that a surface of the magnetic head opposite from the floating surface on the magnetic disk side is supported on a projection and the magnetic head is tilted on the projection. Japanese Patent Laid-Open No. 11-250429 discloses a technique of forming this projection at a position offset from a center of the magnetic head on the air flow downstream side. If the projection is formed at such a position, the floating surface of the magnetic head can face easily in a direction on the air flow upstream side to obtain a sufficiently large lifting force. Contact between the magnetic head and the magnetic disk is thereby avoided to reduce the occurrence of scratches on the magnetic disk.  
         [0012]     The technique disclosed in Japanese Patent Laid-Open No. 11-250429 as a technique for obtaining a sufficiently large lifting force by supporting the magnetic head on a projection formed at a position offset from the center of the magnetic head on the air flow downstream side entails a problem that the attitude of the magnetic head is unstable since the projection supporting the magnetic head is set at a position offset from the center of the magnetic head. For example, the magnetic head is floated on the air flow upstream side to excessively tilt the magnetic head. Thus, there is a possibility of a considerable reduction in the stability with which the magnetic disk is accessed with the magnetic head.  
       SUMMARY OF THE INVENTION  
       [0013]     The present invention has been made in view of the above circumstances and provides a disk apparatus capable of reducing the occurrence of scratches on a disk-type storage medium due to contact between the head and the storage medium while ensuring stable access to the storage medium.  
         [0014]     A disk apparatus in accordance with the present invention, in which a storage medium in the form of a disk is rotated and accessed, has: a head which is brought close to the storage medium, and with which the storage medium is accessed; an arm which is rotated to move its tip end portion in a radial direction of the storage medium; a suspension which is provided on the tip end portion of the arm, and which has a first projection; and a gimbal which is attached to the suspension, and through which the head is supported on the first projection at a center of the head, the head being fixed on the gimbal so as to be tiltable on the first projection, wherein the suspension has a second projection at a position adjacent to the first projection and superposed on the head as seen in a direction perpendicular the head.  
         [0015]     Preferably, in the disk apparatus of the present invention, the second projection of the suspension is provided on the air outflow side relative to the first projection.  
         [0016]     Preferably, the second projection is lower in height than the first projection.  
         [0017]     Preferably, in the disk apparatus of the present invention, the second projection has a height such that the tilt of the head on the air inflow side in a state where the head is supported on both the first projection and the second projection is equal to or larger than minus one degree.  
         [0018]     Preferably, in the disk apparatus of the present invention, the arm rotates to move the tip end portion of the arm beyond the outer circumference of the storage medium, the disk apparatus further has a supporting member which supports the arm in a state of having the tip end portion of the arm moved to a position off the storage medium.  
         [0019]     In the disk apparatus of the present invention, the above-described second projection is provided in addition to the first projection corresponding to that provided in the conventional arrangement, thereby maintaining the head in such an attitude that a sufficient lifting force can be obtained, stabilizing the attitude of the head to ensure stable access to the storage medium even when the head is in a state of floating above the storage medium. The disk apparatus of the present invention is suitably applicable to the arrangement having the above-described supporting member, i.e., the load/unload type of disk apparatus. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]      FIG. 1  is a diagram schematically showing a magnetic disk apparatus which is an embodiment of the present invention;  
         [0021]      FIG. 2  is a see-through top view of a conventional head assembly seen from the floating surface side of a magnetic head;  
         [0022]      FIG. 3  is a side view of the conventional head assembly shown in  FIG. 2 , with the floating surface of the magnetic head shown at the top;  
         [0023]      FIG. 4  is a diagram showing the attitude of the magnetic head;  
         [0024]      FIG. 5  is a diagram showing the attitude of the magnetic head;  
         [0025]      FIG. 6  is a see-through top view of a head assembly of a magnetic disk apparatus in an embodiment of the present invention seen from the floating surface side of a magnetic head;  
         [0026]      FIG. 7  is a side view of the head assembly shown in  FIG. 6 , with the floating surface of the magnetic head shown at the top;  
         [0027]      FIG. 8  is a diagram schematically showing the static pitch of the head assembly in the embodiment of the present invention shown in  FIGS. 6 and 7 ; and  
         [0028]      FIG. 9  is a diagram showing the relationship between the value of the static pitch and the rate of occurrence of scratches on the magnetic disk after performing L/UL (loading/unloading) 100k times (100,000 times). 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]     A preferred embodiment of the present invention will be described.  
         [0030]      FIG. 1  is a diagram schematically showing a magnetic disk apparatus which is an embodiment of the present invention.  
         [0031]     In a housing  11  of the magnetic disk apparatus  10  are accommodated a rotating shaft  12 , a magnetic disk  13  attached to the rotating shaft  12 , a swing shaft  14 , a carriage arm  15  which can swing on the swing shaft  14 , a head assembly  16  provided on a carriage arm tip portion, an actuator  17  which drives the carriage arm  15  to cause to swing, and a ramp  18  which is provided in a position off the outer circumference of the magnetic disk  13 , and which supports a projection  161  constituting the head assembly  16  provided at the carriage arm  15  tip when the carriage arm  15  is swung to the position of the ramp  18  so that the projection  161  runs onto the ramp  18 . When an access (read/write) to the magnetic disk  13  is made, the carriage arm  15  is driven and swung by the actuator  17  constituted by a magnetic circuit to position a magnetic head (not shown) provided in the head assembly  16  on a desired one of tracks on the rotating magnetic disk  13 . The magnetic disk  13  is then accessed with the magnetic head. The internal space of the housing  11  is closed with a cover (not shown).  
         [0032]     The structure of the head assembly  16  provided on the tip portion of the carriage arm  15  will be described below. Description will first be made of the structure of a conventional head assembly before the description of the structure of the head assembly in this embodiment.  
         [0033]      FIG. 2  is a see-through top view of a conventional head assembly seen from the floating surface side of a magnetic head.  FIG. 3  is a side view of the conventional head assembly shown in  FIG. 2 , with the floating surface of the magnetic head shown at the top. A combination of a magnetic head in a narrow sense (a portion through which read/write is actually performed) and a head slider on which the magnetic head is fixed is referred to as a magnetic head in this specification, as mentioned above.  
         [0034]     The head assembly  26  shown in  FIGS. 2 and 3  has a projection  261 , a magnetic head  262  (including a slider) a suspension  263  and a gimbal  264 .  
         [0035]     Arrow A shown in  FIGS. 2 and 3  indicates the direction of an air flow caused by the rotation of the magnetic disk  13  (see  FIG. 1 ).  
         [0036]     The projection  261  is fixed on the suspension  263  so as to project from an extreme tip of the suspension  263 . A dowel (projection)  265  is provided on the suspension  263 . The dowel  265  supports the magnetic head  262  by point-to-point contact therebetween, with the gimbal  264  interposed between the dowel  265  and the magnetic head  262 . The dowel  265  is a semispherical projection having a diameter of 285 μm and a height of 55 μm, as shown in  FIG. 3 . The dowel  265  is formed at such a position as to support the magnetic head  262  having a length of 1200 μm at a center of the same, as shown in  FIG. 2 . The suspension  263  is fixed to a tip portion of the carriage arm  15  shown in  FIG. 1 .  
         [0037]     The magnetic head  262  is fixed on the gimbal  264 . The gimbal  264  is attached to the suspension  263 . The magnetic head  262  is provided in such a structure that the magnetic head  262  is fixed to the gimbal  264 , is supported by the dowel  265  with the gimbal  264  interposed between the magnetic head  262  and the dowel  265 , and is tiltable according to factors including the air flow on one central point at which it is supported on the dowel  264 .  
         [0038]      FIGS. 4 and 5  are diagrams showing the attitude of the magnetic head.  
         [0039]      FIG. 4  shows a state in which the tilt of the magnetic head  262  on the air inflow side (a side as seen from the center of the magnetic head  262  in a direction opposite to the direction of arrow A) when the projection  261  is on the ramp  18  (in a static state) is minus (a state in which the air flow-in side of the magnetic head  262  is lowered with respect to a horizontal line (the dot-dash line indicated in  FIG. 4 )).  FIG. 5  shows a state in which the tilt of the magnetic head  262  on the air inflow side (a side as seen from the center of the magnetic head  262  in a direction opposite to the direction of arrow A) when the projection  261  is on the ramp  18  (in a static state) is plus (a state in which the air inflow side of the magnetic head  262  is heightened with respect to the horizontal line (the dot-dash line indicated in  FIG. 4 )). The state shown in  FIG. 4  is expressed as “the static pitch is minus”, and the state shown in  FIG. 5  is expressed as “the static pitch is plus”. When the static pitch is minus as shown in  FIG. 4 , the lifting force produced by the air flow accompanying the rotation of the magnetic disk  13  is small. If the minus value of the static pitch is large, there is a risk of the magnetic head  262  contacting the magnetic disk  13  to scratch the magnetic disk  13  during the loading operation.  
         [0040]     On the other hand, when the static pitch is plus as shown in  FIG. 5 , the lifting force produced by the air flow accompanying the rotation of the magnetic disk  13  is increased to tilt the magnetic head  262  so that the risk of contact of the magnetic head  262  with the magnetic disk  13  is low.  
         [0041]     In the conventional arrangement, the static pitch cannot be controlled so as to be constant and the static pitch varies among magnetic disk apparatus. In a case where the static pitch is minus as shown in  FIG. 4 , the risk of the magnetic disk  13  being scratched is high if the minus value of the static pitch is large.  
         [0042]     The structure of the head assembly of the magnetic disk apparatus in the embodiment of the present invention will now be described.  
         [0043]      FIG. 6  is a see-through top view of the head assembly of the magnetic disk apparatus in the embodiment of the present invention seen from the floating surface side of the magnetic head.  FIG. 7  is a side view of the head assembly shown in  FIG. 6 , with the floating surface of the magnetic head shown at the top.  
         [0044]     The head assembly shown in  FIGS. 6 and 7  has a projection  161 , a magnetic head  162  (including a slider), a suspension  163  and a gimbal  164 . The projection  161 , the magnetic head  162 , the suspension  163  and the gimbal  164  respectively correspond to the projection  261 , the magnetic head  262 , the suspension  263  and the gimbal  264  of the conventional head assembly  26  described above with reference to  FIGS. 2 and 3 . The head assembly in this embodiment is the same as the conventional head assembly shown in  FIGS. 2 and 3  except for a point of difference described below.  
         [0045]     The head assembly  16  shown in  FIGS. 6 and 7  differs from the conventional head assembly shown in  FIGS. 2 and 3  in that an auxiliary dowel  166  is provided in addition to a dowel  165  corresponding to the dowel  265  provided on the suspension  263  constituting the conventional head assembly  26  shown in  FIGS. 2 and 3 . The dowel  165  is provided at such a position as to support the magnetic head  162  at a center of the same, as is that in the conventional head assembly. The size of the dowel  165  is also the same as that in the conventional head assembly. In contrast, the dowel  166  is provided in a forward position (on the air outflow side) in the direction of arrow A relative to the dowel  165 . The distance between centers of the dowel  165  and the auxiliary dowel  166  is 400 μm, as shown in  FIG. 6 . The diameter of the auxiliary dowel  166  is 285 μm, equal to that of the dowel  165 , as shown in  FIG. 7 , but the height of the auxiliary dowel  166  is 47 μm, lower than the height 55 μm of the dowel  165 .  
         [0046]     The static pitch of the magnetic head  162  in a state of being supported on both the dowel  165  and the auxiliary dowel  166  is about minus one degree.  
         [0047]      FIG. 8  is a diagram schematically showing the static pitch of the head assembly in the embodiment of the present invention shown in  FIGS. 6 and 7 .  
         [0048]      FIG. 8  shows the pitch on the plus side. Since the height of the auxiliary dowel  166  existing on the air outflow side (in the direction of arrow) is lower than that of the dowel  165 , there is a possibility of the magnetic head tilting so that the static pitch is minus one degree at the maximum. In some case of the conventional magnetic head device (see  FIGS. 2 and 3 ), the magnetic head tilts so that the static pitch has a minus value largely exceeding minus one degree. In such a case, the lifting force is considerably reduced. In the case of this embodiment, however, a sufficiently large lifting force can be obtained since the static pitch on the minus side is minus one degree at the maximum, thus effectively reducing the possibility of the magnetic head contacting the magnetic disk during the loading operation.  
         [0049]     Description will next be made of the results of an experiment performed to examine the occurrence of scratches on the magnetic disk with respect to loading/unloading (L/UL).  
         [0050]     A plurality of head assemblies are prepared by changing the position at which the auxiliary dowel  166  is provided (the distance between the dowel  165  and the auxiliary dowel  166  (400 μm in the example shown in  FIGS. 6 and 7 ) and the height of the auxiliary dowel  166  (47 μm in the example shown in  FIGS. 6 and 7 ) to change the static pitch. The rate of occurrence of scratches on the magnetic disk after performing loading/unloading 100,000 times (100k times) by moving the magnetic head at a loading/unloading speed of 0.08 m/sec is examined. In the state of being supported on the ramp  18 , the static pitch is maximized on the minus side, that is, the magnetic head is supported by both the dowel  165  and the auxiliary dowel  166  due to the structure of the gimbal  164 . The static pitch in this state can be uniquely determined from the distance between the dowel  165  and the auxiliary dowel  166  and the height of the auxiliary dowel  166  (while the position and height of the dowel  165  are fixed).  
         [0051]      FIG. 9  shows the relationship between the value of the static pitch and the rate of occurrence of scratches on the magnetic disk after performing L/UL (loading/unloading) 100k times (100,000) times.  
         [0052]     It can be understood that when the static pitch is equal to or smaller than minus one degree (on the plus side from minus one degree) the scratch occurrence rate is lower than a tolerance limit.  
         [0053]     While the assumption for the above description is that the magnetic disk apparatus has only one magnetic disk  13  and only one side of the magnetic disk  13  is accessed, the present invention is also applicable to a magnetic disk apparatus in which each of two sides of a magnetic disk is accessed, and to a magnetic disk apparatus in which plural magnetic disks are disposed coaxially with each other and rotated and each magnetic disk is accessed.  
         [0054]     While the above description is made of magnetic disk apparatus, the present invention is applicable not only to magnetic disk apparatus but also to disk apparatus which access other types of storage mediums, e.g., optical disks and magneto-optic disks.