Abstract:
A disk drive includes a housing having a base and a cover fixed to the cover, a disk rotatably mounted in the housing and having a plurality of tracks, a head for reading/writing data on the disk, and an actuator for moving the head across the tracks of the disk. The cover is composed of a molded resin and a metal sheet integrally embedded in the molded resin.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates generally to a magnetic disk drive, and more particularly to a cover structure of the magnetic disk drive.  
           [0003]    2. Description of the Related Art  
           [0004]    In a magnetic disk drive for a computer, a contact start and stop (CSS) system is generally adopted as the relation between a magnetic head and a magnetic disk. This system is such that while the disk is in rotation, the head is kept flying above the disk at a microscopic height owing to the balance between a flying force applied to the head by an air flow generated by high-speed rotation of the disk and an elastic force of a suspension pressing the head on the disk. When the disk rotation is stopped, the head is moved to a contact zone formed on the disk and comes into contact with the disk at the contact zone. While the disk is at rest, the head and the disk are kept in contact with each other.  
           [0005]    As mentioned above, the head is kept flying above the disk at a microscopic height during rotation of the disk. Accordingly, there is a possibility of head crash or the like due to dust or the like even in a small amount. To cope with this problem, the magnetic disk and the magnetic head for reading/writing data on the disk are enclosed in a sealed housing (disk enclosure). The housing is composed of a base and a cover fixed through a packing to the base by a plurality of screws. The cover of a conventional magnetic disk drive is a cast cover manufactured primarily by aluminum die casting. A metal sheet is mounted on the cover to reduce noise.  
           [0006]    However, it is difficult to manufacture an aluminum cast cover having a complicated shape with good accuracy. It is accordingly considered to use a resin for the cover material because of its good moldability, thereby realizing a complicated shape. However, such a resin-only cover is inferior in electromagnetic shielding effect to a metal cover, causing a possibility of malfunction or the like of the disk drive due to external electromagnetic waves. Further, the resin-only cover is lighter in weight than the metal cover, causing an increase in noise from the disk drive. Thus, the resin-only cover is not satisfactory in noise reduction. Further, the resin-only cover is prone to charge static electricity, so that there is a high possibility of IC crash, head crash, etc. due to the static electricity. It is therefore necessary to provide protection against static electricity.  
           [0007]    In the conventional magnetic disk drive, a printed wiring board on which a control circuit or the like for the disk drive is exposed to the outside of the housing. Accordingly, there is a possibility that electromagnetic waves generated from the printed wiring board have adverse effects on the surroundings, e.g., an adverse effect on a pacemaker used by a heat handicapped person and an adverse effect on an unborn child in a pregnant woman.  
         SUMMARY OF THE INVENTION  
         [0008]    It is therefore an object of the present invention to provide a disk drive having a resin cover which can provide electromagnetic protection and reduce noise from the disk drive.  
           [0009]    In accordance with an aspect of the present invention, there is provided a disk drive comprising a housing having a base and a cover fixed to said base; a disk rotatably mounted in said housing and having a plurality of tracks; a head for reading/writing data on said disk; and an actuator for moving said head across said tracks of said disk; wherein said cover is composed of a molded resin and a metal sheet integrally embedded in said molded resin.  
           [0010]    The cover is secured to the base by a plurality of screws. Preferably, the metal sheet of the cover is exposed at a portion where the screws are located. The metal sheet is a copper sheet or a steel sheet. The metal sheet may be formed as a meshed sheet. In this case, a bonding strength between the metal sheet and the molded resin can be improved. Preferably, a noise absorbing member such as a polyurethane sheet is attached to the cover.  
           [0011]    In accordance with another aspect of the present invention, there is provided a disk drive comprising a housing having a base and a first cover fixed to said base; a disk rotatably mounted in said housing and having a plurality of tracks; a head for reading/writing data on said disk; an actuator for moving said head across said tracks of said disk; and a printed wiring board mounted below said base, on which a drive circuit is mounted; and a second cover fixed to said base so as to cover said printed wiring board; each of said first and second covers being composed of a molded resin and a metal sheet integrally embedded in said molded resin.  
           [0012]    The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing some preferred embodiments of the invention.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1A is a sectional view of a magnetic disk drive according to a first preferred embodiment of the present invention;  
         [0014]    [0014]FIG. 1B is a plan view of the magnetic disk drive shown in FIG. lA;  
         [0015]    [0015]FIG. 2 is a perspective view of the magnetic disk drive with its cover removed;  
         [0016]    [0016]FIG. 3 is a sectional view of a magnetic disk drive according to a second preferred embodiment of the present invention;  
         [0017]    [0017]FIG. 4A is a sectional view of a magnetic disk drive according to a third preferred embodiment of the present invention;  
         [0018]    [0018]FIG. 4B is a plan view of the magnetic disk drive shown in FIG. 4A;  
         [0019]    [0019]FIG. 5 is a sectional view of a magnetic disk drive according to a fourth preferred embodiment of the present invention; and  
         [0020]    [0020]FIG. 6 is a sectional view of a magnetic disk drive according to a fifth preferred embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]    Various preferred embodiments of the present invention will now be described with reference to the drawings. Throughout the drawings, substantially the same parts are denoted by the same reference numerals. Referring to FIG. 1A, there is shown a sectional view of a magnetic disk drive according to a first preferred embodiment of the present invention. FIG. 1B is a plan view of the magnetic disk drive shown in FIG. 1A. Reference numeral  2 A denotes a housing of the magnetic disk drive. The housing  2 A includes a base  4  and a cover  6 A fixed to the base  4  by a plurality of screws  14 . A packing  12  is interposed between the base  4  and the cover  6 A to seal the housing  2 A.  
         [0022]    The base  4  is formed of aluminum, for example. The cover  6 A is composed of a molded resin  8  of polycarbonate, for example, and a solid metal sheet  10  integrally embedded in the molded resin  8 . The metal sheet  10  is formed preferably of copper, but it may be formed of steel. The metal sheet  10  is formed by deep drawing of a metal into the shape of the cover  6 A. The cover  6 A is formed by first placing the metal sheet  10  preliminarily formed into a predetermined shape by pressing, casting, etc. into a given mold and next pouring a molten resin into the mold to thereby integrate the metal sheet  10  with the molded resin  8 .  
         [0023]    The cover  6 A is characterized in that the copper sheet  10  is integrally embedded in the molded resin  8  to obtain an electromagnetic shielding effect. Further, since the metal sheet  10  is laminated in the molded resin  8 , a damping effect is also obtained to contribute to a reduction in noise generated from the disk drive. In the case of using a steel sheet as the metal sheet  10 , the weight of the cover  6 A itself becomes larger than that in the case of using a copper sheet, so that the damping effect is improved, but the electromagnetic shielding effect is somewhat reduced as compared with the case of using a copper sheet. Further, in the case that only the electromagnetic shielding effect is intended, an aluminum sheet may be used as the metal sheet  10 .  
         [0024]    The configuration of the magnetic disk drive according to this preferred embodiment will now be described in brief with reference to FIGS. 1A and 2. A shaft  22  is fixed to the base  4 , and a spindle hub  16  is provided on the shaft  22  so as to be rotatably driven by a DC motor. A plurality of magnetic disks  18  and spacers  20  are mounted on the spindle hub  16  in such a manner as to be alternately stacked. That is, the plural magnetic disks  18  are fixedly mounted on the spindle hub  16  by securing a disk clamp  23  to the spindle hub  16  by a plurality of screws  24 , and are equally spaced a given distance by the spacers  20 . A screw  26  is fixed to the shaft  22  from the upper side of the cover  6 A.  
         [0025]    Referring to FIG. 2, reference numeral  28  denotes a rotary actuator consisting of an actuator arm assembly  30  and a magnetic circuit  32 . The actuator arm assembly  30  is rotatably mounted on a shaft  34  fixed to the base  4 . The actuator arm assembly  30  includes an actuator block  40  rotatably mounted on the shaft  34  through a pair of bearings  36  and  38 , a plurality of actuator arms  42  extending from the actuator block  40  in one direction, and a plurality of suspensions  46  fixedly connected to the actuator arms  42 . A magnetic head  44  is mounted on a front end portion of each suspension  46 .  
         [0026]    As shown in FIG. 1A, a coil  48  is supported on the opposite side of the actuator arms  42  with respect to the shaft  34 . The magnetic circuit  32  includes an upper yoke  50 , an upper magnet  52  fixed to the upper yoke  50 , a lower yoke  54 , and a lower magnet  56  fixed to the lower yoke  54 . As shown in FIG. 1A, the coil  48  is inserted in a gap of the magnetic circuit  32  to constitute a voice coil motor (VCM)  60 . A screw  64  is threadedly engaged into the shaft  34  from the upper side of the cover  6 A.  
         [0027]    Reference numeral  62  denotes a flexible printed circuit board (FPC) for supplying write signals to the magnetic heads  44  and taking read signals from the magnetic heads  44 . The flexible printed circuit board  62  is fixed at its one end to the side surface of the actuator block  40 . As shown in FIG. 1A, a printed wiring board  66  on which a drive circuit such as a control circuit is mounted is provided outside the housing  2 A under the base  4 .  
         [0028]    The molded resin  8  of the cover  6 A preferably contains carbon or the like to have conductivity to some extent. Further, the metal sheet  10  is preferably exposed at its outer peripheral portion where the cover  6 A is secured to the base  4  by the screws  14 . With this configuration, static electricity in the molded resin  8  can be passed to the base  4  through the screws  14  securing the cover  6 A to the base  4 , thereby preventing charging of static electricity in the cover  6 A.  
         [0029]    [0029]FIG. 3 is a sectional view of a magnetic disk drive according to a second preferred embodiment of the present invention. Reference numeral  2 B denotes a housing composed of a base  4  and a cover  6 B fixed to the base  4 . The cover  6 B is composed of a molded resin  8  and a meshed copper sheet  10 ′ integrally embedded in the molded resin  8 . The meshed copper sheet  10 ′ is formed by deep drawing into the shape of the cover  6 B. By embedding the meshed copper sheet  10 ′ in the molded resin  8 , a bonding strength between the molded resin  8  and the meshed copper sheet  10 ′ can be improved. The other configuration of this preferred embodiment is similar to that of the first preferred embodiment shown in FIG. 1A, so the description thereof will be omitted herein.  
         [0030]    [0030]FIG. 4A is a sectional view of a magnetic disk drive according to a third preferred embodiment of the present invention, and FIG. 4B is a plan view of the magnetic disk drive shown in FIG. 4A. Reference numeral  2 C denotes a housing composed of a base  4  and a cover  6 C fixed to the base  4 . The cover  6 C is composed of a molded resin  8  and a solid metal sheet  10  integrally embedded in the molded resin  8  like the first preferred embodiment. The metal sheet  10  is formed of copper or steel.  
         [0031]    In this preferred embodiment, a noise absorbing sheet  68  such as a polyurethane sheet is attached to the outer surface of the cover  6 C. The noise absorbing sheet  68  can contribute to a further reduction in noise from the disk drive. The other configuration of this preferred embodiment is similar to that of the first preferred embodiment, so the description thereof will be omitted herein.  
         [0032]    Referring to FIG. 5, there is shown a sectional view of a magnetic disk drive according to a fourth preferred embodiment of the present invention. The magnetic disk drive according to this preferred embodiment includes another cover  70 A for covering a printed wiring board  66  in addition to a housing  2 A composed of a base  4  and a cover  6 A similar to that of the first preferred embodiment. The cover  70 A is fixed through a packing  76  to the base  4  by a plurality of screws  78 . The cover  70 A is composed of a molded resin  72  and a solid metal sheet  74  integrally embedded in the molded resin  72  like the cover  6 A. The metal sheet  74  is formed of copper or steel. The solid metal sheet  74  may be replaced by a meshed metal sheet.  
         [0033]    The printed wiring board  66  on which a drive circuit is mounted is covered with the cover  70 A having the metal sheet  74 . Accordingly, electromagnetic waves generated from the drive circuit can be shielded by the cover  70 A, thereby reducing the leakage of the electromagnetic waves from the disk drive. Recently, attention has just been given to adverse effects of electromagnetic waves on the human body. For example, it tis desirable to minimize an adverse effect of electromagnetic waves on a pacemaker used by a heart handicapped person and an adverse effect of electromagnetic waves on a pregnant woman.  
         [0034]    In view of these circumstances, this preferred embodiment is intended to reduce the adverse effects of electromagnetic waves from a magnetic disk drive installed in a mobile computer such as a notebook personal computer when it is used especially by the above persons. Furthermore, the cover  70 A can also shield external electromagnetic waves, thereby preventing a malfunction of the disk drive due to the external electromagnetic waves to improve the reliability of the disk drive. The other configuration of this preferred embodiment is similar to that of the first preferred embodiment, so the description thereof will be omitted herein.  
         [0035]    Referring to FIG. 6, there is shown a sectional view of a magnetic disk drive according to a fifth preferred embodiment of the present invention. A cover  70 B in this preferred embodiment is configured by attaching a noise absorbing sheet  80  such as a polyurethane sheet to the cover  70 A in the fourth preferred embodiment shown in FIG. 5. A cover  6 C in this preferred embodiment is similar to the cover  6 C in the third preferred embodiment shown in FIG. 4A. By using a steel sheet as each of the metal sheets  10  and  74 , the weight of each of the covers  6 C and  70 B can be increased as compared with the case of using a copper sheet, thereby improving a damping effect.  
         [0036]    The noise absorbing sheets  68  and  70  respectively attached to the outer surfaces of the covers  6 C and  70 B function to reduce noise from the disk drive. Accordingly, in combination with the damping effect by the steel sheets  10  and  74 , the noise from the disk drive can be further reduced. The other configuration of this preferred embodiment is similar to that of the first preferred embodiment, so the description thereof will be omitted herein.  
         [0037]    According to the present invention, it is possible to provide a disk drive having a resin cover which can improve electromagnetic protection characteristics and reduce noise from the disk drive.