Abstract:
A disk drive has an actuator supported for turning, and supporting magnetic heads for reading and writing data from and to a recording disk and a voice coil for driving the actuator. Plates are disposed near the voice coil so as to cover part of the voice coil. A hard disk drive capable of detachably combined with a PC card is formed by assembling separate component parts including a functional unit including a disk, a base plate holding the functional unit, a frame bumper disposed in a middle part of the assembly and serving as a shock-absorbing member, a card assembly provided with a connector to be connected to the slot of a PC card, and a top cover covering the functional unit held on the base plate. The frame bumper receives lateral shocks that act on the side surfaces of the hard disk drive.

Description:
PRIORITY PATENT APPLICATION  
         [0001]    This application claims priority to Japanese Patent Application No. JP2002-311350 (Hitachi Global Storage Technologies Docket No. JP920020171US1), filed on Oct. 25, 2002, and entitled “Disk Drive and Actuator”.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Technical Field  
           [0003]    The present invention relates to a disk drive for driving, for example, a hard disk. More particularly, the present invention relates to a disk drive provided with an actuator for writing and reading data to and from a recording disk.  
           [0004]    2. Description of the Related Art  
           [0005]    A disk drive, such as a hard disk drive, is used prevalently as a principal data storage means for a computer. The disk drive includes a case called a disk enclosure, and one or more of recording disks for recording data. The recording disk or recording disks are supported for rotation on a spindle fixed to the case, and are driven for rotation by a spindle motor. An actuator for reading and writing data from and to the recording disk is disposed near the recording disk.  
           [0006]    The actuator is supported for turning by a bearing on a pivot shaft fixed to the case of the disk drive. The actuator has an arm extending on one side of the pivot shaft, and a magnetic head supported on a free end part of the arm. A coil support extends on the other side of the pivot shaft, and a voice coil included in a voice coil motor (VCM) is mounted on the coil support.  
           [0007]    A stator included in the VCM is disposed opposite to the voice coil mounted on the actuator. A magnetic field created between the stator and the VCM is varied to drive the actuator for turning on the pivot shaft. Consequently, the magnetic head mounted on the free end part of the arm of the actuator moves along the surface of the recording disk to access a desired track in the surface of the recording disk for reading or writing data from or to the recording disk.  
           [0008]    The recording capacity of the disk drive has progressively increased in recent years, and the enhancement of speed of operations for reading and writing data from and to the recording disk has been required. Although the enhancement of data processing speed, i.e., the data read/write speed of the magnetic head, is naturally important, it is important to enhance the mechanical turning speed of the actuator in making the magnetic head access (seek) a desired track on the recording disk. Thus, it is preferable that the actuator has a small moment of inertia and an intense current is supplied to the voice coil to turn the actuator at a high speed so that the magnetic head is able to access a desired track on the surface of the recording disk quickly.  
           [0009]    One prior art technique discloses making an actuator access a desired track on a recording medium controls the operation of the actuator in moving the actuator substantially along a radius of a recording medium by a VCM. This technique makes the actuator access a desired tack on a recording medium, but does not mention any effective technique for preventing the increase of seek time necessary for the actuator to access a desired track.  
         SUMMARY OF THE INVENTION  
         [0010]    In a conventional disk drive, the higher the intensity of current supplied to the voice coil, the higher is the turning speed of the actuator. However, the design of the voice coil sets an upper limit to the current that can be supplied to the voice coil. Usually, a current on the order of 1.6 A is used for energizing the voice coil. When a current on the order of 1.6 A is supplied to the voice coil, the voice coil generates heat and the resistance of the voice coil increases. Consequently, the current supplied to the voice coil decreases as the magnetic head is moved continuously over the recording disk for a seek operation, and seek time increases. In particular, increase in seek time affects data processing time significantly in a server that operates a 3 in. diameter recording disk at 10,000 rpm or a 2.5 in. diameter recording disk at 15,000 rpm to process a large amount of data.  
           [0011]    The present invention has been made in view of the prior art technical problems and it is therefore an object of the present invention to provide a disk drive capable of preventing the increase of seek time and of reducing data processing time. The present invention provides a disk drive including an actuator provided with a coil, and characterized by a plate disposed near the coil so as to cover part of the coil. The plate disposed near the coil so as to cover part of the coil is able to suppress the increase of the resistance due to the rise of the temperature of the coil and hence a sufficient current can be supplied to the coil. The plate serves as a heat-radiating plate. Preferably, the plate is disposed near a pivot shaft supporting the actuator. When the plate is thus disposed, the increase of the moment of inertia of the actuator can be limited to the least extent.  
           [0012]    A plurality of the plates may be arranged. The use of the plurality of plates increases the amount of absorbed heat among that generated by the coil. Preferably, the plurality of plates is disposed on the opposite sides of the coil. The plate may be with grooves in its surface, which increases the rate of heat radiation from the plate and reduces the weight of the plate. The plate may be formed in a shape having a rectangular or wavy cross section.  
           [0013]    A disk drive according to the present invention is characterized by a heat-radiating member disposed near a pivot shaft supporting an actuator. This construction of the disk drive suppresses the increase of the resistance due to the rise of the temperature of the coil, and limits the increase of the moment of inertia of the actuator to the least extent. The heat-radiating member may be formed integrally with the pivot shaft supporting the actuator. The heat-radiating member may adhesively bonded to the pivot shaft supporting the actuator.  
           [0014]    An actuator according to the present invention comprises a head, a support member supported for turning on a pivot shaft, a coil, and a plate disposed near the coil so as to cover part of the coil. Thus, the increase of the resistance due to the rise of the temperature of the coil can be suppressed.  
           [0015]    An actuator according to the present invention comprises a head, a support member supported for rotation on a pivot shaft, a coil, and a heat-radiating member disposed near the pivot shaft. Thus, the increase of the resistance due to rise of the temperature of the coil can be suppressed, and the heat-radiating member thus disposed limits the increase of the moment of inertia of the actuator to the least extent.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 is a perspective view of a hard disk device to which one embodiment of the present invention is applied.  
         [0017]    [0017]FIG. 2 is a perspective view of an actuator applied to one embodiment of the present invention.  
         [0018]    [0018]FIG. 3 shows a part, including a voice coil, of the actuator, in which FIG. 3( a ) is a sectional view taken on line Y-Y′ in FIG. 2, and FIG. 3( b ) is a sectional view taken on line Z-Z′ in FIG. 2.  
         [0019]    [0019]FIG. 4 is a graph comparatively showing currents that flowed through voice coils when seek speed was 50 iops.  
         [0020]    [0020]FIG. 5 is a graph comparatively showing currents that flowed through voice coils when seek speed was 150 iops.  
         [0021]    [0021]FIG. 6 is a view of assistance in explaining a surface shape of a plate.  
         [0022]    [0022]FIG. 7 is a view of assistance in explaining other surface shapes of plates.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]    Embodiments of the present invention are described below with reference to the accompanying drawings. FIG. 1 shows a hard disk drive (disk drive)  20  in one embodiment according to the present invention. The hard disk drive  20  is built in or externally connected to a PC (personal computer). The hard disk drive  20  operates for data reading and writing operations according to instructions given by the PC, i.e., a host device.  
         [0024]    The hard disk drive  20  includes a predetermined number of recording disks (disk mediums, data recording mediums)  12 , an actuator  30 , and a disk enclosure (case)  11  holding the recording disks  12  and the actuator  30  therein. The disk enclosure  11  has a base  13  having the shape of a bottomed box having an open upper side, and a cover, not shown, closing the open upper side of the base  13 .  
         [0025]    The recording disks  12  are nonvolatile recording medium, such as magnetic disks or the like. The recording disks  12  are mounted on a spindle  10  supported on the base  13 . The predetermined number of recording disks  12  are stacked in layers on the spindle  10 . The spindle  10  includes integrally an in-hub type spindle motor (disk driving device), not shown. The spindle motor drives the recording disks  12  for rotation about the axis of the spindle  10  at a predetermined rotating speed.  
         [0026]    The actuator  30  has a middle part supported on a pivot shaft  31  for turning relative to the base  13 . The actuator  30  is able to turn on the pivot shaft  31  in a plane corresponding to the surface of the recording disk  12 . The actuator  30  has arms  37  extending on one side of the pivot shaft  31 , suspension arms  38  projecting from the free ends of the arms  37 , and a pair of magnetic heads  32  supported on the suspension arms  38 . The pair of magnetic heads  32  faces the upper and the lower surface, respectively, of the recording disk  12 .  
         [0027]    A pair of coil support arms  34 A and  34 B extend on the other side of the pivot shaft  31  in a shape substantially resembling the letter V or U. The coil support arms  34 A and  34 B hold a voice coil  33  consisting of a predetermined number of complete turns of wire.  
         [0028]    An upper stator  40 U and a lower stator  40 L for creating a magnetic field together with the voice coil  33  are disposed so as to correspond to the voice coil  33  of the actuator  30  and are attached to the base  13 . The voice coil  33  and the stators  40 U and  40 L constitute a VCM, i.e., a driving device for driving the actuator  30  for turning. Current supplied to the voice coil  33  is controlled to vary the magnetic field created by the voice coil  33  and the stators  40 U and  40 L to turn the actuator  30 . The actuator  30  is thus driven by the VCM for turning on the pivot shaft  31 . Consequently, the magnetic heads  32  are moved substantially along a radius of the recording disk  12  for a seek operation to positions corresponding to desired tracks on the recording disk  12 , and read data recorded on the recording disk  12  or write data to the recording disk  12 .  
         [0029]    [0029]FIG. 2 shows the actuator  30  in this embodiment. Referring to FIG. 2, the actuator  30  has plates  36  formed by processing a 0.3 mm thick aluminum flat plate. The plates  36  are placed on a side surface  35 A, on the side of the voice coil  33 , of a hub  35  so as to extend substantially in parallel to a plane including the voice coil  33 . The plates  36  cover a part, in the vicinity of the hub  35 , of a region in which the voice coil  33  is disposed.  
         [0030]    The voice coil  33  has a substantially rectangular shape, and a plane including the voice coil  33  is perpendicular to the pivot shaft  31 . The plates  36  cover one side  33 A, on the side of the hub  35 , of the voice coil  33  substantially entirely.  
         [0031]    [0031]FIG. 3 includes sectional views showing a part, including the voice coil  33 , of the actuator  30 . FIG. 3( a ) is a sectional view taken on line Y-Y′ in FIG. 2, and FIG. 3( b ) is a sectional view taken on line Z-Z′ in FIG. 2. As shown in FIG. 3, the upper stator  40 U and lower stator  40 L are disposed close to the voice coil  33  on the upper and the lower side, respectively, of the voice coil  33 . Two sides  33 B and  33 C, extending toward the pivot shaft  31 , of the voice coil  33  are effective in generating a torque for turning the actuator  30 . Therefore, the stators  40 U and  40 L extend only in a region in which the two sides  33 B and  33 C, extending toward the pivot shaft  31 , of the voice coil  33  move as shown in FIG. 3( b ), and do not extend in regions in which a side  33 A, near the hub  35 , of the voice coil  33  and a side  33 D, remote from the hub  35 , of the voice coil  33  as shown in FIG. 3( a ). The plates  36  are disposed near the hub  35  in a space between the stators  40 U and  40 L, including the side  33 A of the voice coil  33  close to a plane including the voice coil  33  with respect to a direction perpendicular to the plane including the voice coil  33 . The two plates  36  are disposed on the upper and the lower side, respectively, with respect to a direction perpendicular to the plane including the voice coil  33 .  
         [0032]    When a voltage is applied to the voice coil  33 , the actuator  33  turns. Consequently, the magnetic heads  32  move substantially along a radius of the recording disk  12  for a seek operation to positions corresponding to a desired tracks on the recording disk  12 . A current on the order of 1.6 A flows through the voice coil  33  and the voice coil  33  generates heat owing to the agency of its resistance and the temperature of the voice coil  33  rises. Consequently, the resistance of the voice coil  33  increases, the current flowing through the voice coil  33  decreases and the magnetic heads  32  cannot moved at a desired seek speed.  
         [0033]    In the actuator  30  in this embodiment, the plates  36  are disposed close to a plane including the voice coil  33  with respect to a direction perpendicular to the plane including the voice coil  33  so as to cover the side  33 A, on the side of the hub  35 , of the coil  33  substantially entirely. Therefore, heat generated by the side  33 A, near the hub  35 , of the voice coil  33  is radiated toward and absorbed by the plates  36 . Thus, the temperature of the voice coil  33  decreases.  
         [0034]    Heat generated by the voice coil  33  is transferred through the side  33 A near the hub  35  to the plates  36 , and the plates  36  dissipate the absorbed heat. Thus, the heat generated by the voice coil  33  can efficiently be dissipated.  
         [0035]    The actuator  30  was moved at a seek speed of  50  iops (input output per second) for experimental operations. Whereas the voice coil  33  was heated at 45.3° C. when the plates  36  were removed, the voice coil  33  was heated at 35.7° C. when the actuator  30  was provided with the plates  36 . When the actuator  30  was moved at a seek speed of 150 iops, the temperature of the voice coil  33  was 81.3° C. when the plates  36  were removed and was 69.3° C. when the actuator  30  was provided with the plates  36 .  
         [0036]    [0036]FIGS. 4 and 5 are graphs showing the results of mean seek time simulation, in which the actuator with the plates  36  and an actuator without the plates  36  were operated at different seek speeds. FIGS. 4 and 5 show the variation of currents that flowed through the voice coils  33  with time when the actuator  30  was moved for seek operation relative to the recording disk  12  at seek speeds of 50 iops and 150 iops, respectively. In FIGS. 4 and 5, current is measured on the vertical axis and time is measured on the horizontal axis.  
         [0037]    It is known from FIGS. 4 and 5 that the reduction of the current flowing through the voice coil  33  can be suppressed in both the case where the seek speed is 50 iops and the case where the seek speed is 150 iops. When the actuator was moved at a seek speed of 50 iops, seek time was 5.44580 ms when the plates  36  were removed, and seek time was 5.29332 ms when the actuator  30  was provided with the plates  36 . Thus, the use of the plates  36  reduced seek time by 3.1%. When the actuator was moved at a speed of 150 iops, seek time was 5.788669 ms when the plates  36  were removed, and seek time was 5.67490 ms when the actuator  30  was provided with the plates  36 . Thus, the use of the plates  36  reduced seek time by 2.2%.  
         [0038]    The plates  36  are placed on the side surface  35 A, on the side of the voice coil  33 , of the hub  35 . Since the plates  36  are placed on the hub  35  near the axis of turning of the actuator  30 , the increase of the moment of inertia of the actuator  30  can be limited to the least extent. Thus, the turning performance of the actuator  30  is not deteriorated, and the effect of the plates  36  on extending the seek time can be limited to the least extent. Preferably, the plates  36  are formed of a metal having a small specific gravity, such as aluminum or a magnesium alloy.  
         [0039]    The plates  36  are spaced 0.5 mm apart from the voice coil  33 . The heat absorbing effect and heat absorbing efficiency of the plates  36  enhance when the plates  36  are disposed closer to the voice coil  33 . Preferably, the plates  36  are disposed so as to come into contact with the voice coil  33 .  
         [0040]    On the other hand, the heat capacity of the plates  36  can be increased, the amount of heat generated by the voice coil  33  and absorbed by the plates  36  can be increased and the amount of heat dissipated from the plates  36  can be increased by increasing the surface area of the plates  36 , and the effect of cooling the voice coil  33  can be enhanced. However, the weight of the plates  36  and the moment of inertia of the actuator increase when the surface area of the plates  36  is increased. Therefore, an optimum value must selectively be determined through the comparative consideration of the effect of the plates  36  on cooling the voice coil  33  and that of the same on increasing the moment of inertia of the actuator  30 .  
         [0041]    [0041]FIG. 6 shows the shape of the surface of the plate  36 . As shown in FIG. 6, the plate  36  is provided in its surface with grooves  36 A. The formation of the grooves  36 A the surface of the plate  36  increases the surface area of the plate  36  and reduces the weight of the plate  36 , which reduces the moment of inertia of the actuator  30 . The grooves  36 A may be extended in any direction. The arrangement of the grooves  36 A in a high density is effective in increasing the amount of heat absorbed from the voice coil  33  and the amount of heat dissipated.  
         [0042]    [0042]FIG. 7 shows other possible surface shapes of the plate  36 . The plate may have a rectangular cross section or a wavy cross section as shown in FIG. 7 for the same effect. The body of the actuator  30  is formed of aluminum by extrusion molding. The plates  36  are formed integrally with the body of the actuator  30 . When the plates  36  are formed integrally with the body of the actuator  30 , heat absorbed by the plates  36  is transferred to the body of the actuator  30  and the heat is dissipated from the body of the actuator  30 , which enhances the effect of cooling the voice coil  33 .  
         [0043]    The plates  36  may be bonded to the body of the actuator  30  with an adhesive. The adhesive bonding of the plates  36  to the body of the actuator  30  improves productivity when the plates  36  have a complicated cross section, such as a rectangular cross section or a wavy cross section. It is preferable to use an adhesive having a high heat conductivity for bonding the plates  36  to the body of the actuator  30 .  
         [0044]    The embodiment of the present invention is capable of suppressing the rise of the temperature of the voice coil and of preventing the excessive increase of the resistance of the voice coil  33 . Therefore, a sufficient current can be supplied to the voice coil  33  and quick data access can be achieved without increase in seek-time. The present invention is particularly effective in making a server that processes a large amount of data at a high data processing speed achieve quick data access.  
         [0045]    As apparent from the foregoing description, according to the present invention, increase in seek time is prevented, and data processing time is reduced.