Patent Abstract:
An assembly structure low in height and suitable for downsizing and for high hermeticity sealing in a micro hard disk drive is provided. Burrings projecting toward a top cover and having an internal thread cut are formed on a base plate where the top cover is screw-fastened to the base plate, the base plate accommodating a functional unit such as a disk and a head. Burrings are formed extendedly upward on flat portions of recesses at certain corners of the top cover. These burrings have a diameter larger than that of the burrings of the base plate. The burrings of the base plate are fitted into the burrings to be screw-fastened with top cover fastening screws. After attaching the top cover to the base plate, a covering seal is applied to cover the respective top faces of the top cover, base plate, and the top cover screws.

Full Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to disk drives and, more particularly, to a small disk drive low in height and excellent in sealing properties. 
     Various types of portable recording mediums are provided for various devices including personal computers (PC) and digital cameras to store data. Efforts have been made in recent years to provide recording media having a small size and a large storage capacity. For example, a small, portable magnetic disk drive has been proposed. This proposed disk drive has a new assembly construction based on the Compact Flash® commercially available from SanDisk Corporation, i.e., one of standard small memory cards. 
     A large-capacity miniature hard magnetic disk drive conforming to the standard of Compact Flash Type 2 is provided with a one-inch diameter magnetic disk having a storage capacity of 1 GB, and has a weight on the order of only 16 g. The PC card to be used in combination with the disk drive, similarly to the disk drive, is based on standards such as the standards of Compact Flash Type 2. The disk drive can be inserted in the PC card. 
     This portable, miniature hard disk drive is provided, in addition to the magnetic disk (disk) for storing data, a spindle motor for rotating the disk, a read/write head for writing and reading data to and from the disk, and an actuator for moving the read/write head in a direction along a radius of the disk. Functional components including a disk, a spindle motor, a read/write head and an actuator of such a miniature hard disk drive having compact construction are formed very minutely. Japanese Patent Laid-open No. 2002-15553 (pp. 5-6, FIGS. 3 and 4) discloses the assembly structure of a small disk drive, which meets Compact Flash standards. 
     BRIEF SUMMARY OF THE INVENTION 
     In order to meet the Compact Flash standards, micro hard disk drives have limitation of height and restriction on mechanism elements and fasteners for a case. Accordingly, this needs an assembly structure suitable for downsizing. When foreign particles such as dust are entrapped into the device, they cause a head crush to lead to a critical defect. Therefore, there is a demand for a sealing structure having good sealing properties. 
     A feature of the present invention is to provide a small disk drive that is low in height and is readily assembled. 
     Another feature of the invention is to provide a small disk drive having an enhanced hermetic structure. 
     In accordance with an aspect of the present invention, a disk drive comprises: a functional unit including a disk as an information storage medium; a case for containing the functional unit; and a cover for covering the functional unit contained in the case; wherein the case is provided with a burring having an internal thread cut on its inner wall and projecting toward the cover, the burring being formed on a region at which the cover is attached to the case; and the cover is screw-fastened at the burring. 
     The cover has a flat portion in a recess formed on a region at which the cover is screw-fastened to the case, and the burring is fitted into a hole formed on the flat portion to be screw-fastened. 
     Alternatively, the cover has a flat portion in a recess formed on a region at which the cover is screw-fastened to the case; the flat portion in the recess is provided with a burring having a diameter larger than that of the burring of the case and projecting in the projecting direction of the burring of the case; and the burring of the case is fitted into the burring of the cover to be screw-fastened. 
     Top faces of the case, the cover, and the fastening regions are covered with a seal; and the fastening regions on a bottom face of the case are covered with seals. Each of the seals may preferably be an adhesive tape. 
     In accordance with another aspect of the invention, a disk drive comprises: a disk; a head; a cable plate for holding a connector to which a cable for transmitting a signal from the head is connected; a case for containing the disk, the head, and the cable plate; and a cover for covering the disk, the head, and the cable plate contained in the case; wherein the case is provided with a first burring having an internal thread cut on its inner wall and projecting toward the cover, the first burring being formed on a region at which the cable plate is attached to the case; the cable plate is screw-fastened at the first burring; the case is provided with a second burring having an internal thread cut on its inner wall and projecting toward the cover, the second burring being formed on a region at which the cover is attached to the case; and the cover is screw-fastened at the second burring. 
     The cover has a flat portion in a recess formed on a region at which the cover is screw-fastened to the case; and the second burring is fitted into a hole formed on the flat portion to be screw-fastened. 
     Alternatively, the cover has a flat portion in a recess formed on a region at which the cover is screw-fastened to the case; the flat portion in the recess is provided with a third burring having a diameter larger than that of the second burring and projecting in the projecting direction of the second burring; and the second burring is fitted into the third burring to be screw-fastened. 
     Top faces of the case, the cover, and the fastening regions are covered with a seal, and the fastening regions on a bottom face of the case are covered with seals. Each of the seals may preferably be an adhesive tape. 
     In accordance with another aspect of the invention, a disk drive comprises: a functional unit including a disk as an information storage medium; a case for containing the functional unit; a cover for covering the functional unit contained in the case; a wiring board at one of whose edges a connector is disposed, the wiring board being attached to the case; and a shock-absorbing member for covering sides of the case other than a side at which the connector is disposed; wherein the case is provided with a burring having an internal thread cut on its inner wall and projecting toward the cover, the burring being formed on a region at which the cover is attached to the case; and the cover is screw-fastened at the burring. 
     In accordance with another aspect of the invention, a disk drive comprises: a bottom cover; a wiring board at one of whose edges a connector is disposed, the wiring board being contained in the bottom cover; a base plate disposed on the wiring board in such a fashion that the connector is located at one side thereof; a disk and a head contained in the base plate; a top cover for covering a top face of the base plate; and a shock-absorbing member for covering sides of the base plate other than the side at which the connector is located; wherein the base plate is provided with a burring having an internal thread cut on its inner wall and projecting toward the top cover, the burring being formed on a region at which the top cover is screw-fastened; and the top cover is screw-fastened at the burring. 
     In accordance with another aspect of this invention, the magnetic disk drive comprises: a bottom cover; a wiring board at one of whose edges a first connector is disposed, the wiring board being contained in the bottom cover; a base plate disposed on the wiring board in such a fashion that the first connector is located at one side thereof; a magnetic disk and a head contained in the base plate; a cable plate for holding a second connector to which a cable for transmitting a signal from the head is connected; a top cover for covering top faces of the magnetic disk, the head, and the cable plate; and a frame bumper for covering sides of the base plate other than the side at which the first connector is located, the frame bumper being a shock-absorbing member; wherein the base plate is provided with a first burring having an internal thread cut on its inner wall and projecting toward the top cover, the first burring being formed on a region at which the cable plate is attached to the base plate; the cable plate is screw-fastened at the first burring; the base plate is provided with a second burring having an internal thread cut on its inner wall and projecting in the direction of the top cover, the burring being formed on a region at which the top cover is attached to the base plate; and the top cover is screw-fastened at the second burring. 
     According to embodiments of present invention, it is possible to provide a small disk drive which is low in height and is readily assembled. Further, it is possible to provide a small disk drive having a sealing structure improved in hermeticity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing an internal structure of a disk drive according to one embodiment of the present invention. 
         FIG. 2  is a perspective view showing a state in which a top cover is attached to the disk drive of  FIG. 1 . 
         FIG. 3  is a sectional view taken along line A-A of  FIG. 2 . 
         FIG. 4  is an exploded perspective view showing an assembly structure of the disk drive according to the embodiment of the present invention. 
         FIG. 5  is a top view showing the internal structure of the dirk drive according to the 
         FIG. 6  is a diagram showing a position relationship between a base plate and an FC plate according to the embodiment of the present invention. 
         FIG. 7  is an enlarged view showing part of  FIG. 6 . 
         FIG. 8  is a diagram for explaining a process of attaching the FC plate to the base plate according to the embodiment of the present invention. 
         FIG. 9A to 9D  are diagrams showing a sealing structure according to the embodiment of the present invention. 
         FIG. 10  is a sectional view taken along line B-B of  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 4  shows an assembly structure of a disk drive  1  according to one embodiment of the invention, and  FIG. 1  is a perspective view showing the disk drive  1  obtained by assembling components, with a top cover  33  removed. The disk drive  1  in this embodiment is a storage medium conforming to the Compact Flash Type 2 standards, and a portable precision device includes a functional unit  10 , i.e., a built-in recording/reproducing unit for recording and reproducing data, and a card assembly  20  including circuits for driving and controlling the functional unit  10  and data input/output operation. The functional unit  10 , the card assembly  20  and the like are contained in a case. The card assembly  20  includes a wiring board  21  provided on one side thereof with a connector (interface connector)  22  meeting function and construction having a form factor specified by Compact Flash Type 2 standards. 
     The functional unit  10  includes a magnetic disk (disk)  11 , i.e., a data storage medium, supported for rotation; an actuator assembly  12  supporting on its tip part a read/write head for reading data from and writing data to the magnetic disk  11 ; a VCM assembly  13  including a VCM coil and a VCM magnet; a top clamp  14  for clamping the magnetic disk  11  mounted on a spindle motor, not shown; a ramp mechanism  15  for supporting the read/write head when the read/write head is retracted from the magnetic disk  11 ; and a latching mechanism  16 , such as a magnetic latch or an inertia latch, for holding the read/write head on the ramp mechanism  15  when the disk drive  1  is inoperative. 
     A case includes a frame bumper  30  having a form factor specified by the Compact Flash Type 2 standards, and formed of an elastic member as a shock-absorbing member (cushioning member), a bottom cover  31  for supporting the components of the disk drive  1 , a shallow, box-shaped base plate  32  containing the components of the functional unit  10 , and a top cover  33  for covering the functional unit  10  contained in the base plate  32 . 
     Bottom cover fastening screws  34  are passed through the bottom cover  31 , the card assembly  20  and the frame bumper  30 , and are screwed in threaded holes formed in the base plate  32  to fasten together the bottom cover  31 , the card assembly  20 , the frame bumper  30  and the base plate  32 . The top cover  33  is fastened to the base plate  32  with top cover fastening screws  35 . A burring into which the bottom cover fastening screw  34  is extendedly screwed is formed at each of four corners of the base plate  32  toward the bottom cover. A burring  321  into which the top cover fastening screw  35  is screwed is extendedly formed toward the top cover at each of the positions (at a flat portion in a step) at which the top cover  33  is screwed, each of the burrings being internally threaded on its inner wall. 
     A burring  331  is formed extendedly upward on a flat portion in a recess formed on each of three corners of the top cover  33  by pressing. The burring  331  has a diameter larger than that of the burring  321  of the base plate so that the burring  321  of the base plate  32  is fitted thereinto. A covering seal  36  is provided for covering gaps between edges of the top cover  33  and the base plate  32  and heads of the top cover screws  35  after the top cover  33  is attached to the base plate  32 . 
     Although the burrings  331  are formed on the top cover  33  in this embodiment, the burrings  331  may be omitted and replaced by holes. 
     The base plate  32  has hitherto been an aluminum casting made by die casting aluminum. Aluminum castings formed by die casting have very low shock resistance. This embodiment employs the frame bumper  30  formed of a shock absorbing material instead of a cast frame. The base plate  32  can be formed by processing a metal sheet by press working, and the shock-absorbing frame bumper  30  is used instead of thick parts formed by casting. Thus, the base plate  32  can be manufactured at a low manufacturing cost. 
     Each of the burrings of the base plate  32  is formed by boring a hole for forming the burring, followed by scraping using a rod-shaped tool having a diameter identical with a desired diameter of the burring with the hole being used as a base point. On an inner wall of each of the burrings, an internal thread is cut so as to provide the bottom cover fastening screw  34  and the top cover fastening screw  35  into the burrings. The number of ridges of the internal thread formed on the base plate  32  is insufficiently provided due to the small thickness of the base plate, but it is possible to increase the number of ridges of the internal thread by providing the burrings. A height of the burring  321  is lower than the flat portion of a periphery of the base plate  32 . As a result of forming the burrings, such components for fastening the bottom cover fastening screw  34  and the top cover fastening screw  35  as nuts are unnecessary. 
     A plurality of bosses  323  are formed on a bottom face of a corner of the base plate  2  by pressing, the bosses  323  being used for pressing and fixing a bracket for holding a filter. On a bottom of a corner diagonal to the formerly mentioned corner of the base plate  2 , a plurality of bosses (not shown in  FIG. 4 , but shown in  FIG. 8 ) are formed to be used for positioning a lower yoke of the VCM when fixing the same. 
       FIG. 2  shows a state in which the tope cover  33  covers the base plate  32 . The burrings  321  of the base plate  32  are fitted into the burrings  331  of the top cover  33 . Therefore, the top cover  33  is positioned accurately with respect to the base plate, and the top cover fastening screws  35  are screwed in the state where the top cover  33  is thus positioned. 
       FIG. 3  is a cross-sectional view taken along line A-A of  FIG. 2 , wherein the top cover fastening screw  35  is screwed. From  FIG. 3 , it is understood that the burring  321  of the base plate  32  is fitted into the burring  331  of the top cover  33 , and the top cover fastening screw  35  is screwed into the burring  321  of the base plate  32 . Here, flat portions of the base plate  32  and the top cover  33  and heads of the top cover fastening screws  35  are substantially level with one another. 
     Since the base plate  32  is formed by pressing, an edge of the pressed portion is curved. Accordingly, in the case where the burring is not formed on the base plate  32 , it is difficult to position the top cover  33  on the base plate  32 , thereby deteriorating working efficiency. Further, a gap may be undesirably defined between the base plate  32  and the edges of the top cover  33  after the screw-fastening. In this embodiment, the burrings solve the above problems. 
     Referring to  FIG. 1 , the frame bumper  30  makes use of a space produced by the alteration in the base plate  32  and has a function of a shock-absorbing member, the frame bumper being a molded component having a side slot which is required to be in conformity with the Compact Flash Type-2 standards. This molded component is formed from a thermoplastic elastomer such as a polyester elastomer and has a moderate elasticity as well as an excellent dimensional stability after molding. 
     The frame bumper  30  is designed to be larger than the base plate  32 . For example, a periphery of the frame bumper  30  is larger than that of the base plate  32  by about 0.5 to 1 mm and is substantially level with the surface of the connector  22 . Corners of the frame bumper  30  are increased in thickness taking into consideration that the impact is most liable to be given on the corners. By thus covering the periphery (side in the two dimensional directions of the external form) with the frame bumper  30  and the connector  22 , it is possible to protect the disk drive  1  from the side impact. 
     Shown in  FIG. 5  is a top face of the disk drive  1  with the top cover  33  removed. Signals from/to the read/write head are transmitted by an FC (flex cable)  18 . The FC  18  is connected to an FC substrate near the actuator assembly  12  as well as to the connector near an FC plate  17  and is movable in accordance with the rotation of the actuator assembly  12 . In the case where the attachment position of the FC plate  17  is in error, such erroneous positioning affects the movement of the FC  18  or, in the worst situation, the FC  18  can be brought into contact with the actuator assembly  12  or the magnetic disk  11  in rotation. Therefore, it is necessary to accurately position the FC plate  17  on the base plate  32 . 
       FIG. 6  is a diagram for explaining the attachment of the FC plate  17  to the base plate  32  according to the specific embodiment of the present invention.  FIG. 7  is a partially enlarged view. Burrings  322  are formed on the base plate  32  at the attachment positions of the FC plate  17 , and an internal thread is cut on an inner wall of each of the burrings  322 . Holes having a diameter larger than that of the burrings  322  are formed in the FC plate  17 . 
     First, the FC plate  17  is positioned in such a manner that the burrings  322  of the base plate  32  penetrate through the holes of the FC plate  17 . Then screws  19  are fastened in directions indicated by arrows and in the order of (1) and (2) shown in  FIG. 8 , thereby fixing the FC plate  17  to the base plate  32  in such a fashion that the FC plate  17  is in contact with a wall of the base plate, i.e., to the accurate position. Further, since the FC plate  17  is positioned on the flat surface of the base plate  32  at roots of the burrings  32  (see  FIG. 7 ), a dimensional accuracy in height is also improved. 
     Referring back to  FIG. 5 , the bracket  40  for holding the filter is disposed at one corner nearer to the disk  11  and the connecter  22  of the disk drive  1  and along an outer periphery of the disk  11 . The filter is cased in the bracket  40  as being in the shape of an arch. The bracket  40  has a plurality of grooves formed at its bottom and is pressed into the bosses  323  (see  FIG. 1 ) formed on the base plate  32 , so that the bracket  40  is fixed to the base plate  32  using the grooves. 
     Shown in  FIG. 9A  is a top face of the disk drive  1  in a state where the top cover  33  is attached to the base plate  32  with the top cover fastening screws  35 . A slight gap may be in some cases generated between the base plate  32  and the edges of the top cover  33 . In order to prevent the entry of foreign matters such as dust from the gap, the covering seal  36  is applied on the disk drive  1  in such a fashion as to cover the whole top face as shown in  FIG. 9B . Referring to  FIG. 10  showing a section taken along line B-B of  FIG. 9B , since the flat portion of the base plate  32 , the flat portion of the top cover  33 , and the heads of the top cover screws  35  are substantially level with one another, it is possible to stick the covering seal  36  without a gap. Thus, the hermeticity is improved. 
       FIG. 9C  is a bottom view of the base plate  32 . A screw seal  37  is applied on each of the flat portions (for screwing) of a rear face of the base plate  32  at which the burrings are formed and a flat portion at which the actuator assembly  12  is pivotally mounted as shown in  FIG. 9D . As the covering seal  36  and the screw seals  37 , an adhesive tape is appropriately used because it is sufficiently thin, less bulky in height, easily stripped off, and easily reapplied. 
     It is to be understood that the above description is intended to be illustrative and not restrictive. Many embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.

Technology Classification (CPC): 6