Abstract:
A disk drive includes a casing which houses a disk-shaped recording medium, a drive motor which holds and rotates the recording medium, a head which performs read/write operations, a head actuator movably supporting the head to move the head relative to the recording medium, and a board unit connected to the head actuator. The board unit has a board main body arranged on the inner surface of the casing and at least one capacitor, mounted on the board main body for supplying power to perform a retracting operation for permitting the head actuator to move the head to a retracted position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2004-161421, filed May 31, 2004, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a disk drive having housed therein a disk for use as a recording medium.  
         [0004]     2. Description of the Related Art  
         [0005]     In recent years, disk drives such as magnetic disk drives, optical disk drives, etc. have been widely used as external recording devices or image recording devices for computers.  
         [0006]     A magnetic disk drive, serving as a disk drive, generally has a casing in the shape of a rectangular box. The casing houses a magnetic disk serving as a magnetic recording medium, a spindle motor serving as a drive means for supporting and rotating the magnetic disk, a plurality of magnetic heads for writing information to and reading information from the magnetic disk, a head actuator for movably holding the magnetic heads relative to the magnetic disk, a voice coil motor for pivoting and positioning the head actuator, and a board unit having arranged thereon a head amplifier and the like.  
         [0007]     A printed circuit board that controls the operations of the spindle motor, voice coil motor, and magnetic heads is screwed to the outer surface of the casing with the board unit arranged therebetween. An interface (I/F) connector for connecting the magnetic disk drive to an external device is mounted on an end portion of the printed circuit board.  
         [0008]     Described in Jpn. Pat. Appln. KOKAI Publication No. 2001-210058 discloses a magnetic disk drive in the form of a thin card which can be loaded into a card slot of a personal computer, for example. The card-shaped magnetic disk drive of this type is required to be made thinner and smaller than a conventional one. To meet this requirement, various components are mounted on a plate-shaped base, a support frame is fixed on the peripheral edge of the base, and a plate-shaped top cover is attached to the support frame. Further, a printed circuit board is arranged on the backside of the base, and an I/F connector on the printed circuit board is positioned and held by means of a dedicated fixing member on the support frame.  
         [0009]     Furthermore, miniaturization of magnetic disk drives these days is being promoted so that they can be used as recording devices for a wider variety of electronic devices, especially for smaller-sized electronic devices. For example, in a magnetic disk drive having housed therein a disk whose diameter is one inch or more, a printed circuit board, which is so arranged as to overlap the surface of a casing, can be made smaller than the area of the casing surface. However, in a magnetic disk drive having housed therein a disk whose diameter is one inch or less, a printed circuit board is required to be made small due to miniaturization of a casing. Accordingly, the setting space on a printed circuit board is reduced, which makes it difficult to mount a plurality of electronic components thereon. Generally, a magnetic disk drive is provided with a capacitor for a retracting operation which stores electric charge to move the magnetic heads to the retreated position when the power is unexpectedly turned off. Since the capacitor is comparatively large in capacity and dimensions, it becomes difficult to mount the capacitor on a printed circuit board, and the entire magnetic disk drive including the printed circuit board is prevented from being reduced in thickness.  
       BRIEF SUMMARY OF THE INVENTION  
       [0010]     According to an aspect of the invention, a disk drive comprises: a casing; a disk-shaped recording medium arranged in the casing; a drive motor which is arranged in the casing and which holds and rotates the recording medium; a head which performs information processing for the recording medium; a head actuator arranged in the casing and movably supporting the head to move the head relative to the recording medium; a board unit arranged in the casing and connected to the head actuator; and a control circuit board arranged to face an outer surface of the casing and connected to the board unit. The board unit includes a board main body arranged on an inner surface of the casing and at least one capacitor, mounted on the board main body, for supplying power to permit the head actuator to move the head to a retracted position. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0011]     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.  
         [0012]      FIG. 1  is a perspective view showing an hard disk drive (hereinafter referred as an HDD) according to a first embodiment of the present invention;  
         [0013]      FIG. 2  is an exploded perspective view showing the HDD;  
         [0014]      FIG. 3  is a plan view of a casing and the internal structure of the HDD;  
         [0015]      FIG. 4  is a perspective view showing the HDD when viewed from the side of a control circuit board;  
         [0016]      FIG. 5  is a cross-sectional view of the HDD taken along a line V-V in  FIG. 1 ;  
         [0017]      FIG. 6  is an expanded plan view of a board unit of the HDD;  
         [0018]      FIG. 7  is a cross-sectional view of the board unit taken along line VII-VII of  FIG. 6  with the first shell  10   a  and the control circuit board  12  added thereto;  
         [0019]      FIG. 8  is a cross-sectional view showing a board unit of an HDD according to a second embodiment of the present invention taken along line VIII-VIII of  FIG. 9  with the first shell  10   a  and the control circuit board  12  added thereto; and  
         [0020]      FIG. 9  is an exploded plan view of the board unit of the HDD according to the second embodiment. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     Referring to the accompanying drawings, an HDD according to a first embodiment of the present invention will be described in detail.  
         [0022]     As shown in  FIGS. 1 and 2 , the HDD comprises a casing  10  substantially in the shape of a rectangular box that houses various components, which will be mentioned later, and a rectangular control circuit board  12  that is so arranged as to overlap an outer surface of the casing  10 . The casing  10  and the control circuit board  12  have a length L of 32 mm and a width W of 24 mm, and a thickness T, including the thicknesses of the casing and the control circuit board, of 3 mm to 6 mm. The thickness T is set to be approximately 3.3 mm or 5 mm depending on the number of disks to be housed in the casing  10 .  
         [0023]     As shown in  FIG. 2  to  FIG. 5 , the casing  10  includes first and second shells  10   a  and  10   b , which have substantially equal dimensions. The first and second shells  10   a  and  10   b  are formed of a metal and have a rectangular structure with sidewalls on their respective peripheral edge portions. The first and second shells  10   a  and  10   b  are so arranged as to face each other with their peripheral edge portions (e.g. sidewalls) in contact with each other. A belt-shaped sealing member  16  is wound around the peripheral edge portions of the first and second shells  10   a  and  10   b  so that the peripheral edge portions are secured connected to each other and the interior region between the shells are sealed. In this way, the casing  10  in the shape of a rectangular box is configured.  
         [0024]     The bottom surface of the first shell  10   a  configures a rectangular mount surface  11 . Four corners of the casing  10 , including the corners of the mount surface  11 , are rounded, forming circular arcs. As a result, the sealing member  16  wound around the peripheral edge portions of the casing  10  is prevented from being damaged by the corners of the casing, and deterioration of airtightness due to release or unsticking of the sealing member  16  is prevented.  
         [0025]     A plurality of support posts  18  are arranged on the peripheral edge portions at the inside of the casing  10 . Each support post  18  has a proximal end that is fixed to the inner surface of the first shell  10   a , and is substantially perpendicular to the inner surface of the first shell. The mount surface  11  is provided with screw holes at positions corresponding to the respective support posts  18 , which extend into the inside of the support posts.  
         [0026]     The casing  10  houses a magnetic disk  20  having a diameter of, e.g., 0.85 inches and serving as an information recording medium, a spindle motor  22  serving as a drive motor for holding and rotating the magnetic disk, a magnetic head  24  for writing information to and reading information from the magnetic disk, a carriage  26  for movably holding the magnetic head relative to the magnetic disk  20 , a voice coil motor (referred to as VCM, hereinafter)  28  for pivoting and positioning the carriage, a ramp load mechanism  30  for unloading the magnetic head to a position away from the magnetic disk and holding the magnetic head thereat when the magnetic head is moved to the outer peripheral portion of the magnetic disk, an electromagnetic latch  32  for holding the carriage in a retreated position, and a board unit  34  mounted with a head amplifier and the like.  
         [0027]     The spindle motor  22  is mounted on the first shell  10   a . The spindle motor  22  has a spindle  36  that is fixed to the inner surface of the first shell  10   a , and is substantially perpendicular to the inner surface. The extended end of the spindle  36  is fixed to the second shell  10   b  by a fixing screw  37  that is screwed into the second shell from outside. Thus, the spindle  36  is supported by the first and second shells  10   a  and  10   b  from both sides.  
         [0028]     A bearing, not shown, rotatably supports a rotor on the spindle  36 . The end portion of the rotor on the side of the second shell  10   b  constitutes a columnar hub  43 , on which the magnetic disk  20  is coaxially fitted. A clamp ring  44  in the form of a ring is fitted on the end portion of the hub  43 , thereby holding the inner peripheral portion of the magnetic disk  20 . Thus, the magnetic disk  20  is fixed to the rotor and rotatable integrally with the rotor.  
         [0029]     A ring-shaped permanent magnet, not shown, is fixed to the end portion of the rotor on the side of the first shell  10   a  such that the permanent magnet is coaxial with the rotor. The spindle motor  22  has a stator core attached to the first shell  10   a , and a plurality of coils wound around the stator core. The stator core and the coils are located outside the permanent magnet with a gap arranged therebetween.  
         [0030]     The carriage  26 , which constitutes a head actuator, is provided with a bearing assembly  52  that is fixed to the inner surface of the first shell  10   a . The bearing assembly  52  has a pivot  53  that is perpendicularly fixed to the inner surface of the first shell  10   a , and a cylindrical hub  54  that is rotatably supported by the pivot  53  using a pair of bearings. The extended end of the pivot  53  is fixed to the second shell  10   b  by a fixing screw  56  that is screwed into the second shell from outside. Thus, the pivot  53  is supported by the first and second shells  10   a  and  10   b  from both sides. The bearing assembly  52  serving as a bearing unit is arranged collaterally with the spindle motor  22  along the longitudinal direction of the casing  10 .  
         [0031]     The carriage  26  is provided with arms  58  extending from the hub  54 , suspensions  60  in the form of an elongated plate extending from the respective distal ends of the arms, and a support frame  62  extending from the hub  54  in a direction opposite to the extending direction of the arms. The extended end of each suspension  60  supports the magnetic head  24  through a gimbal portion, not shown. A predetermined head load, brought about by spring force of the suspension  60 , is applied to the magnetic head  24  in a direction toward the surface of the magnetic disk  20 . A voice coil  64 , constituting the VCM  28 , is fixed to the support frame  62 .  
         [0032]     The VCM  28 , which rotates the carriage  26  around the bearing assembly  52 , includes a pair of yokes  63  which are fixed to the first shell  10   a  and face each other with a gap provided therebetween, and a magnet, not shown, which is fixed to the inner surface of one of the yokes and faces the voice coil  64 . When the voice coil  64  is energized, the carriage  26  pivots between the retreated position shown in  FIG. 3  and the operating position located over the surface of the magnetic disk  20 . Thereupon, the magnetic head  24  is positioned on a desired track of the magnetic disk  20 . The electromagnetic latch  32 , which is fixed to the first shell  10   a , latches the carriage  26  in the retreated position, thereby preventing the carriage  26  from moving from the retreated position to the operating position when the HDD is subjected to external force such as shock.  
         [0033]     The ramp load mechanism  30  includes a ramp member  70  that is fixed to the inner surface of the first shell  10   a  and faces the outer peripheral portion of the magnetic disk  20 , and a tab  72  that extends from the distal end of each suspension  60  and serves as an engaging member. The ramp member  70  is formed by bending a plate member and has ramp surfaces  73  with which the tabs  72  can engage. When the carriage  26  rotates from the inner peripheral portion of the magnetic disk  20  to the retreated position located outside of the outer peripheral portion of the magnetic disk, the tabs  72  engage with the ramp surfaces  73  of the ramp member  70 . Thereafter, the tabs  72  are pulled up by the inclination of the ramp surfaces, whereupon the magnetic heads  24  are unloaded. When the carriage  26  rotates to the retreated position, the tabs  72  are supported on the ramp surfaces  73  of the ramp member  70 , and the magnetic head  24  is kept at a distance from the surface of the magnetic disk  20 .  
         [0034]     As shown in  FIG. 2 ,  FIG. 3 ,  FIG. 6 , and  FIG. 7 , the board unit  34  has a board main body  40  and a main flexible printed circuit board (referred to as main FPC, hereinafter)  41  which extends from the board main body. The board main body  40  and the main FPC are integrally formed of a flexible printed circuit board. The board main body  40  has a base portion  40   a  and a cover portion  40   b  which are substantially of the same shape. Both ends of the base portion  40   a  and the cover portion  40   b  are provided with through holes  42  through which the support posts  18  can be passed.  
         [0035]     On the inner surface of the base portion  40   a  are mounted a head amplifier  46  and a plurality of, for example, six capacitors  47 , for a retracting operation. The head amplifier  46  is formed of a substantially rectangular bare chip, and has a height of approximately 0.4 mm. Each capacitor  47  is configured by, for example, a rectangular tantalum capacitor with its height made higher than that of the head amplifier  46 , or set to be approximately 0.8 mm. The outer surface of the capacitor  47  is covered with resin. The six capacitors  47  are so arranged around the head amplifier  46  as to enclose the head amplifier.  
         [0036]     The six capacitors  47  function as capacitors for a retracting operation, and store electric charge when the HDD is operated, and drive the head actuator using the stored electric charge to move the magnetic head  24  to the retreated position when the power is unexpectedly turned off. Each capacitor  47  has its capacity set to be, for example, 10 μF, and the total capacity of the six capacitors  47  comes to 60 μF. It is desired that the total capacity of the capacitors  47  be set to be more than or equal to 50 μF.  
         [0037]     On the cover portion  40   b  of the board main body  40  are provided a plurality of connection terminals  48   a  which are connected to the head amplifier  46  respectively, and a plurality of connection terminals  48   b  which are connected to the capacitors  47  respectively. A connector  34   c  is mounted on the cover portion  40   b  to overlap the connection terminals  48   a ,  48   b  and connected thereto.  
         [0038]     The board main body  40  is folded along the portion  40   d  (see  FIGS. 6 and 9 ) so that the backs of the cover portion  40   b  and base portion  40   a  are facing each other. The board main body  40  is fixed to a predetermined position on the first shell  10   a  by making the support posts  18  pass through the through holes  42  with the cover portion  40   b  facing the inner surface of the first shell  10   a . The connector  34   c  arranged on the cover portion  40   b  is at least partially positioned on and opposed to the head amplifier  46  with the base portion  40   a  and cover portion  40   b  sandwiched therebetween. The connector  34   c  is exposed to the mount surface  11  of the first shell  10   a  through an opening formed in the first shell  10   a.    
         [0039]     The main FPC  41  extends from the base portion  40   a , and the extended end thereof is provided with a plurality of connection pads  45 . The extended end of the main FPC  41  is connected to the carriage  26  at the vicinity of the bearing assembly  52 , and the connection pads  45  are electrically connected to the magnetic heads  24  through a cable, not shown, arranged on the arms  58  and suspensions  60 .  
         [0040]     As shown in  FIG. 2 ,  FIG. 4 , and  FIG. 7 , the control circuit board  12  formed of a printed circuit board is of a rectangular shape whose length and width are substantially equal to those of the mount surface  11  of the casing  10 . The mount surface  11  has a circular convex surface  70   a  corresponding to the spindle motor  22  and a circular convex surface  70   b  corresponding to the bearing assembly  52 . The control circuit board  12  is provided with circular openings  72   a ,  72   b  corresponding to the convex surfaces  70   a ,  70   b , respectively. The control circuit board  12  has its four corners cut off obliquely such that the respective cut-off lines define angles of 45 degrees relative to the respective sides of the circuit board  12 , forming cut-off portions  77 .  
         [0041]     A plurality of electronic components  74  and a connector  71  are mounted on the inner surface of the control circuit board  12  which faces the casing  10 . A flexible printed circuit board  76  for electrically connecting the HDD to an external device is connected to the control circuit board  12 . The flexible printed circuit board  76  is drawn from one of the short sides of the control circuit board  12 , and is provided with a plurality of connecting terminals  75  at the extended end thereof.  
         [0042]     The thus-formed control circuit board  12  is arranged to overlap the mount surface  11  of the casing  10 , and fixed to the first shell  10   a  using a plurality of screws. At this time, the four sides of the control circuit board  12  mate with the four sides of the mount surface  11 . The convex surfaces  70   a ,  70   b  formed on the mount surface  11  are arranged within the openings  72   a ,  72   b  of the control circuit board  12 . The connector  71  mounted on the control circuit board  12  is connected to the connector  34   c  of the board unit  34 .  
         [0043]     The cut-off portions  77  formed at the four corners of the control circuit board  12  correspond to the four corners of the mount surface  11 , respectively. Thus, the four corners of the mount surface  11  are exposed to the exterior without being covered by the control circuit board  12 . The four corners of the casing  10  including the exposed four corners of the mount surface  11  constitute holding potions  78  for holding the casing  10  without coming into contact with the control circuit board  12 .  
         [0044]     According to thus configured HDD, the capacitors  47  for a retracting operation are mounted on the board unit  34  within the casing  10 . Thus, the capacitors  47 , which are comparatively large in dimensions and capacity, are not required to be mounted on the control circuit board  12 , which can miniaturize the control circuit board as well as reduce the thickness thereof. Accordingly, an HDD that is further miniaturized and used as a recording device for a wider variety of electronic devices can be realized. The card-shaped, portable HDD constructed in this manner can be used as a recording device for various electronic devices such as cellular phones, digital cameras, video cameras, personal digital assistants (PDA), etc.  
         [0045]     The capacitors  47  are arranged around the head amplifier  46  and have a height higher than that of the head amplifier. Therefore, if any external force acts on the casing  10 , or when the connectors  34   c  and  71  are connected, the capacitors  47  can protect the head amplifier  46 , and prevent the head amplifier from being affected by the impact.  
         [0046]     As shown in  FIG. 8  and  FIG. 9 , according to an HDD of the second embodiment of the present invention, the board main body  40  of the board unit  34  further has a second cover portion  40   c  in addition to the base portion  40   a  and cover portion  40   b . The second cover portion  40   c  is formed of a flexible printed circuit board overlying and at least partially contacting the base portion  40   a , and has a shape substantially similar to that of the base portion. The second cover portion  40   c  has a pair of leg sections  80  that extend outward, and the extended end  80   a  of each leg section is provided with a through hole  42 . Two capacitors  82  for a retracting operation are mounted on the second cover portion  40   c . The capacitors  82  are configured by tantalum capacitors with their capacities set to be, for example, 68 μF, 47 μF. Instead of the capacitors  82 , an electric double layer capacitor of larger capacity may be arranged.  
         [0047]     The second cover portion  40   c  is turned, facing the base portion  40   a . The pair of the leg sections  80  are folded, forming the “L” shape, and are fixed to the first shell  10   a  by making the support posts  18  pass through the through holes  42  of the extended ends  80   a . The capacitors  82  mounted on the second cover portion  40   c  face the capacitors  47  and head amplifier  46  mounted on the base portion  40   a.    
         [0048]     In the thus-configured second embodiment, advantages similar to those obtained in the first embodiment can be obtained. Furthermore, according to the second embodiment, a larger electric charge for a retracting operation can be secured by arranging further capacitors  82 , which can move the magnetic heads to the retreated position easily when the power is turned off. Furthermore, the capacitors  82  can surely prevent the head amplifier  46  from being affected by impact.  
         [0049]     The second embodiment shares the other configurations of the HDD with the first embodiment. Therefore, like reference numerals are used to designate like portions of the two embodiments, and a detailed description of those portions is omitted.  
         [0050]     The present invention is not limited directly to the embodiments described above, and various changes or modifications may be effected therein without departing from the scope of the invention. Further, various inventions may be made by suitably combining a plurality of components described in connection with the foregoing embodiments. For example, some of the components according to the foregoing embodiments may be omitted. Furthermore, the components according to the different embodiments may be combined as required.  
         [0051]     For example, the number of capacitors for a retracting operation can be increased or decreased according to need. The number of magnetic disk and that of magnetic heads are not restricted to one, and can be increased according to need. The diameter of the magnetic disk is not restricted to 0.85 inches, and can be 1.8 inches or 2.5 inches. Further, the present invention is not limited to magnetic disk drives, and may be also applied to any other disk drives, such as optical disk drive.