Patent Publication Number: US-2007121252-A1

Title: Actuator and hard disk drive having the same

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a hard disk drive. More particularly, the present invention relates to an actuator of a hard disk drive.  
      2. Description of the Related Art  
      As one of the information storage devices of a computer, a hard disk drive (HDD) reproduces data stored on a disk or records data onto the disk using a read/write head. To this end, a head of the HDD reads or writes the data from or onto a recording surface the disk while the disk is rotating and the head is spaced a predetermined distance from the recording surface of the disk. The head itself is moved to a desired position over the recording surface of the disk by an actuator.  
       FIG. 1  is a perspective view of a conventional HDD. Referring to  FIG. 1 , the conventional HDD includes a disk  10  for storing data, a spindle motor  20  for rotating the disk  10 , and an actuator  30  for moving a read/write head  34  to a desired position over the disk  10  to record and reproduce data onto and from the disk  10 . The actuator  30  includes a swing arm  32  rotatably coupled to an actuator pivot  31 , a suspension  33  installed at an end portion of the swing arm  32  and supporting the head  34  as biased toward the recording surface of the disk  10 , and a voice coil motor (VCM, not all of which is shown) for rotating the swing arm  32  about an axis of the pivot  31 . The VCM includes a VCM coil  37  wound along a coil support member  36  provided at a read end portion of the swing arm  32  and magnets  50  respectively disposed above (not shown) and below the VCM coil  37 .  
      The VCM rotates the swing arm  32  in a direction according to Fleming&#39;s left hand rule due to the flow of current through the VCM coil  37  and the magnetic field formed by the magnets  50 . That is, when the power to the HDD is turned on and the disk  10  starts to rotate at a constant angular velocity Ω, the VCM rotates the swing arm  32  in a predetermined direction, for example, counterclockwise, to move the head  34  above the recording surface of the disk  10 . The head  34  is maintained at a predetermined height above the surface of the disk  10  by a lift force generated by the disk  10  that is rotating. In this state, the head  34  follows a particular track T of the disk  10  to record data onto the recording surface of the disk  10  or reproduce data stored on the recording surface of the disk  10 .  
      In the meantime, when the power is turned off and the disk  10  stops rotating, the VCM rotates the swing arm  32  in the opposite direction, for example, clockwise. Accordingly, the head  34  is moved off of the recording surface of the disk  10  and is parked on a ramp  60  located radially outwardly of the disk  10 . More specifically, a lift tab  35  protrudes from the end of the suspension  33 . The lift tab  35  moves along the ramp  60  and is ultimately set on a support surface of the ramp  60  to park the head  34 .  
      In the HDD as described above, numerous sources of resistance affect the rotation of the swing arm  32 . For example, the pivot  31  of the actuator offers resistance in the direction of rotation of the swing arm  32 , a printed circuit ribbon  70  attached to the side of the swing arm  32  offers resistance corresponding to the flexibility of the ribbon, and the ramp  60  and the lift tab  35  create friction that resists the rotation of the swing arm  32 . Thus, the VCM needs to supply a rotational force to the swing arm  32  that is great enough to overcome these resistances. However, the need to keep the drive apparatus compact imposes a limit on the maximum output of the VCM.  
      Alternatively, a relatively high drive current can be supplied to the VCM coil  37  to attain the required dynamic characteristic of the actuator  30  such as rapid response. However, with this solution, the power consumption of the actuator  30  is high and its operating efficiency is thus correspondingly low. Moreover, the circuit board which provides power to the HDD needs to be redesigned so as to be suitable for handling a large amount of current.  
      In addition, after the head  34  is parked on the ramp  60 , the head  34  may nonetheless be separated from the ramp  60  and moved above the disk  10  by shock applied to the HDD. At this time, a lift force is not applied to the head  34  by the disk  10  because the disk  10  is not rotating. As a result, the head  34  can collide with the recording surface of the disk  10  and become damaged, thereby permanently damaging the HDD or making it impossible to reproduce data recorded on the disk  10 .  
     SUMMARY OF THE INVENTION  
      An object of the present invention is to overcome one or more of the problems, limitations and disadvantages of the conventional hard disk drive.  
      A more specific object of the present invention is to provide a rotatable actuator having an improved dynamic characteristic, and a hard disk drive including the same.  
      Another object of the present invention is to provide a hard disk drive that is shock resistant, and an actuator that provides the hard disk drive with an anti-shock characteristic.  
      Still another object of the present invention is to provide a hard disk drive that can park its read/write head rapidly and yet does not require an overly complex power circuit to supply current to the voice coil motor coil to rapidly park the read/write head.  
      According to an aspect of the present invention, an actuator of a hard disk drive includes a swing arm having an axis or rotation, a suspension extending from a distal end of the swing arm, a read/write head mounted on the suspension, a coil support fixed to a proximate end of the swing arm so as to rotate with the swing arm and to which a voice coil motor coil is wound, a respective magnet disposed above and/or below the voice coil motor coil as facing the voice coil motor coil, and at least one retract magnetic member of a magnetic material fixed to the coil support and attracted to the magnet. Each retract magnetic member arrives close to the magnet when the swing arm is rotated clockwise or counterclockwise about its axis of rotation.  
      According to another aspect of the present invention, a hard disk drive comprises at least one disk for storing information, a spindle motor to which the disk is mounted for rotating the disk which is installed thereon, and an actuator including a retract magnetic member. The heard disk drive may also include a ramp on which the read/write head of the actuator is parked when not in use. Preferably, the retract magnetic member is fixed to the coil support of the actuator at a position spaced from a permanent magnet in a direction opposite to the direction in which the swing arm rotates from a loaded state to an unloaded state. Accordingly, the swing arm is biased by a magnetic force of attraction between the retract magnet member and the magnet during the unloading operation in which the end of the suspension is moved along a ramp to park the read/write head.  
      The ramp has a support surface that receives an end of the suspension when the swing arm is rotated in a direction that moves the read/write head off of the disk. That is, the ramp supports the suspension to park the read/write head. Preferably, the support surface includes a first inclined section that first receives the suspension during the unloading operation, and a second section extending from the inclined section parallel to the surface of the disk. The support surface may also have a second inclined section connected to the second section and inclined in a direction opposite to that in which the first inclined section extends away from the disk, and a stop accommodation section connected to the second inclined section and extending parallel to the second section.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments thereof made with reference to the attached drawings in which:  
       FIG. 1  is a perspective view of conventional HDD;  
       FIG. 2  is a plan view of an HDD according to the present invention, in which the read/write head of the HDD is in a loaded state;  
       FIG. 3  is a plan view of the actuator of the HDD of  FIG. 2 , in which a tab of the suspension that supports the read/write head is starting to move onto a ramp of the HDD;  
       FIG. 4  is a similar view, but shows the read/write head parked on the ramp;  
       FIG. 5  is an enlarged plan view of part of the actuator of the HDD according to the present invention, when the read/write head parked on the ramp as shown in  FIG. 4 ; and  
       FIG. 6  is a sectional view of the ramp  60  and shows rotational resistance, drive torque, bias rotational force, and overall torque according to the position of the lift tab on the ramp. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Referring to  FIG. 2 , a hard disk drive (HDD) according to the present invention includes at least one disk  110  for storing data, a spindle motor  120  for rotating the disk  110  at a constant angular velocity Ω, and an actuator  130  including a read/write head  134  to record and reproduce data onto and from a recording surface of the disk  110 . The recording surface of the disk  110  refers to that region where information is effectively stored on the surface of the disk and does not constitute the entire surface of the disk  110 . In particular, an inner peripheral region of the disk  110  (bounded by ID in  FIG. 2 ) is reserved for use in attaching the disk  110  to the spindle motor  120  whereas an outer peripheral region of the disk  110  (bounded by OD) is reserved for the parking of the head  134  when the HDD is not in use.  
      The HDD also includes a base  101 , and the spindle motor  120  is mounted to the base  101 . In addition to the read/write head  134 , the actuator  130  includes an actuator pivot  131  disposed on the base  101 , a swing arm  132  for moving the read/write head  134  over the disk, a suspension  133 , a coil support member  136  disposed at a proximate end portion of the swing arm  132 , and a VCM coil  137  of a voice coil motor (VCM). The swing arm  132  is rotatably supported by the actuator pivot  131 . The suspension  133  is coupled to a distal end of the swing arm  132 , and supports the read/write head  134  so as to be biased toward a recording surface of the disk  110 . The VCM coil  137  is assembled to the coil support member  136  coupled to the rear end portion of the swing arm  132 .  
      The VCM rotates the swing arm  132  in a direction according to Fleming&#39;s left hand rule due to current flowing through the VCM coil  137  and a magnetic field formed by magnets  150 . The magnets  150  are respectively disposed above and below the VCM coil  137  and face the VCM coil  137 . A yoke  155  disposed on the base  101  supports the magnets  150 . Each magnet  150  has the shape of an arc whose curvature corresponds to the trajectory of the VCM coil  137  with the swing arm  132 . Each magnet  150  may comprise a first magnetic pole piece  150 L at the left-hand side of the yoke  155  and a second magnetic pole piece  15 OR at the right-hand side of the yoke which have almost equal lengths direction in the direction of rotation of the swing arm  132 . The first and second magnetic pole pieces  150 L and  15 OR are disposed close to each other and have opposite polarities. The VCM coil  137  is located in a region of magnetic flux formed by the magnet  150  and is forced in a clockwise or counterclockwise direction in the region of magnetic flux according to the direction of the current flowing through the VCM coil  137 .  
      The coil support member  136  has a main body to which the VCM coil  137  is mounted, and an extension  138  that protrudes from the front of the main body at a certain angle. At least one magnetic retracting member  140  is disposed on the extension  138  adjacent the magnet  150 . Each magnetic retracting member  140  is formed of a magnetic material to coact with the magnet  150 , i.e., to be attracted to the magnet  150 . The magnetic retracting member  140  may be cylindrical (pin-shaped) or semi-spherical (mound-shaped) and may be fixed to the extension  138  in a hole formed in the extension  138 . In any case, the magnet  150  exerts a strong magnetic force of attraction on the retract magnetic member  140  when the magnetic retracting member  140  is moved to within a predetermined distance from the magnet  150  as the actuator  130  rotates. At this time, the magnetic force acts to bias the actuator  130 , thereby contributing to the unloading operation of the actuator  130  as will be described in more detail later.  
      A flexible printed circuit ribbon  170  is connected to one side of the actuator  130 . The actuator  130  is moved toward the disk  110  in a loading operation and away from the disk  110  in an unloading operation by an operation signal and a stop signal, respectively, transmitted through the flexible printed circuit ribbon  170 . The flexible printed circuit ribbon  170 , in turn, receives a controlled drive signal or power from a circuit board (not shown) disposed beneath the base  101 . To this end, a bracket  171  bridges the connection between the flexible printed circuit ribbon  170  and the circuit board. The bracket  171  is mounted to the base  101  adjacent a corner of the base  101 .  
      Also, a cover  102  is coupled to the base  101  to form a space therewith in which the spindle motor  120  and the actuator  130  are situated. The base  101  and the cover  102  prevent foreign material from penetrating into the space to protect the parts accommodated therein. The base  101  and the cover  102  also block drive noise so that the noise is not transferred to the outside.  
      When power to the HDD is turned on and the disk  110  starts to rotate, the VCM rotates the swing arm  132  in one direction, for example, counterclockwise, to position the head  134  (loading operation) above the recording surface of the disk  110 . The head  134  is raised off of the recording surface by a lift force generated by the rotating disk  110  and is thereby maintained at a predetermined height above the surface of the disk  110 . In this state, the head  134  follows a particular track on the disk  110  to write data onto the recording surface of the disk  110  or read the data stored on the recording surface of the disk  110 . On the other hand, the disk  110  stops rotating when the power is turned off. At this time, the VCM rotates the swing arm  132  in the reverse direction, for example, clockwise, so that the head  134  is moved from the recording surface of the disk  110  (unloading). The head  134  is parked on the ramp  160  which is located radially outwardly of the disk  110 .  
       FIGS. 2, 3  and  4  show an operating sequence of the actuator. In  FIG. 2 , the head  134  is loaded as located adjacent the inner peripheral portion of the disk  110 . In  FIG. 3 , the unloading operation of the actuator  130  starts. At this time, the read/write head  134  is located at the outer peripheral region of the disk  110 .  FIG. 4  shows the head  134  parked on the ramp  160 .  
      More specifically, as shown in  FIG. 3 , the swing arm  132  is rotated clockwise over a first angle θ 1  from the position shown in  FIG. 2 . Hence, the lift tab  135  at the tip of the swing arm  132  contacts the ramp  160  and moves up onto a guide surface of the ramp  160 . At this time, though, a bearing (not shown) supporting the actuator pivot  131  offers resistance to the swing arm  132  in a direction opposite to that of the rotation of the swing arm  132 . Furthermore, the guide surface of the ramp  160  and the lift tab  135  create friction corresponding to the pressure by which the suspension  133  urges the lift tab  135  against the guide surface of the ramp  160 . The friction also opposes the rotation of the swing arm  132 . Nonetheless, according to the present invention, the magnetic retracting member  140  rotating with the swing arm  132  is brought close to the magnet  150 . Thus, a force of attraction is exerted by the magnet  150  on the magnetic retracting member  140  to assist the unloading operation, i.e., to bias the arm  132  in its direction of rotation towards the ramp  160 . Accordingly, a desired rotational force can be applied to the swing arm  132  while the actuator remains relatively simple and compact and without the need to provide a relatively great amount of power to the VCM.  
      The distance between the magnetic retracting member  140  and the magnet  150  greatly affects the bias applied to the swing arm  132  in its direction of rotation. For example, the distance between the magnetic retracting member  140  and the magnet  150  is rather great in the loading state shown in  FIG. 2 . Accordingly, the force of attraction between the magnetic retracting member  140  and the magnet  150  is correspondingly weak. Thus, in the loading state, the amount of bias applied to the swing arm  132  by the magnetic retracting member  140  is negligible. Accordingly, the magnetic retracting member  140  will not cause any tracking errors to occur.  
      As shown in  FIG. 3 , when unloading operation is initiated, a strong magnetic force of attraction occurs between the magnetic retracting member  140  and the magnet  150  because the magnetic retracting member  140  is disposed close to the magnet  150 . The location or shape of the magnet  150  is designed, considering the trajectory of the magnetic retracting member  140  along with the swing arm  132 , to ensure that a sufficient amount force is exerted on the swing arm  132  at the initiation of the unloading operation, i.e., when the ramp  160  starts to offer resistance to the rotation of the swing arm  132 . For example, the magnet  150  can be made as thick as the space between the base  101  and the cover  102  permits. Also, adding magnetic retracting members  140  can increase the amount of bias applied to the swing arm  132  without the need to alter the shape or size of the magnet  150 . Therefore, as shown in  FIGS. 2-5 , at least two retract magnetic members  140  are provided.  
      Moreover, the weight or position(s) of the magnetic retracting member(s)  140  can be used to balance the swing arm  132  with respect to its axis of rotation, i.e., with respect to the actuator pivot  131 . The balancing of the actuator in this way can be used to correct the posture of the actuator so that the actuator lies in a plane perpendicular to its axis of rotation. By doing so, the resistance offered by the actuator to the swing arm in its directions of rotation is minimized, i.e., the driving efficiency of the actuator and its dynamic characteristic during loading/unloading are enhanced.  
      After the loading operation is initiated, the swing arm  132  is rotated over a second angle θ 2  to set lift tab  135  on the ramp  160  and thereby complete the unloading operation, as shown in  FIG. 4 . At this time, the magnetic retracting member  140  is preferably located at a position closest to the magnet  150 . For example, the magnetic retracting member  140  is juxtaposed with the magnet  150 . Therefore, the magnetic retracting member  140  is held in place by the magnet  150  so that any unintended rotation of the swing arm  132  can be prevented.  
      Referring now to  FIG. 5 , a latch can be provided at the rear of the actuator  130 . The latch includes a protrusion  139  extending from the coil support member  136  and defining a notch therewith, a latch lever  181  comprising a hook, and a latch pivot  185  supporting the latch lever  181  so as to be rotatable in clockwise/counterclockwise directions. The hook of the latch lever  181  extends into the notch to engage the protrusion  139  and thereby lock the swing arm  132  in place when the read/write head  134  is parked. Thus, the latch prevents unintended rotation of the swing arm  132  from the unloaded position shown in  FIG. 4 . On the other hand, a suitable mechanism (not shown) is provided to rotate the latch lever  181  clockwise to release the hook of the latch lever  181  from the protrusion  139  when the power to the HDD is turned on to initiate the loading operation.  
      Again, referring to  FIG. 5 , a lock magnetic locking member  145  can be provided to also hold the swing arm  132  in place when the read/write head  134  is parked. The magnetic locking member  145  is of a magnetic material, and preferably is cylindrical (pin-shaped) or semi-spherical (mound-shaped). The lock magnetic member  145  is disposed at a position at which it will be sufficiently attracted to the magnet  150  when the read/write head  134  is parked. For example, the magnetic locking member  145  is disposed on the protrusion  139 , and a portion  151  of the magnet  150  protrudes from the main body of the magnet  150  to a location corresponding to the position at which the protrusion  139  arrives when the read/write head  134  is parked. Thus, a magnetic force generated by the protruding portion  151  of the magnet  150  acts on the magnetic locking member  145  so that the magnetic locking member  145  and hence, the sing arm  132 , cannot be arbitrarily rotated around the pivot shaft  131  when the swing arm  132  has been unloaded. Also, the exact position and/or mass of the locking magnetic member  145  can be designed to balance the actuator like the retract magnetic member  140 .  
       FIG. 6  shows the ramp  160  and the lift tab  135  in section as the lift tab  135  is guided by the ramp  160 . Note, in  FIG. 6 , lift tabs  135  are shown at the upper and lower surfaces of the ramp  160 . That is, the present invention also applies to an HDD in which the disk  110  has recording surfaces at each of its upper and lower surfaces, and the actuator  130  has read/write heads  134  associated with the recording surfaces respectively.  
      Still referring to  FIG. 6 , the support surface of the ramp  160  includes a plurality of contiguous sections for guiding the lift tab  135  so that the lift tab  135  is safely accommodated on the ramp  160  without the actuator  130  colliding with the disk  110 . The support surface includes a first inclined section  161  provided at a location where the lift tab  135  first arrives when the read/write head  134  is moved off of the recording surface of the disk  110  and inclined at a predetermined angle in a direction away from the surface of the disk  110 , a horizontal section  163  connected to the first inclined section  161  and extending parallel to the disk  110  (horizontally) in a plane spaced from that in which the surface of the disk  110  lies, a second inclined section  165  connected to the horizontal extension surface  163  and inclined in a direction opposite to that in which the first inclined surface  161  extends away from the disk, and a stop accommodation section  167  connected to the second inclined section  165  and extending parallel to the surface of the disk (horizontally).  
       FIG. 6  also shows the resistance exerted on the lift tab  135 , the driving torque generated by the VCM, the bias force generated on the swing arm  132  by the retract magnetic member  140 , and the overall torque on the swing arm  132  which is the sum of the driving torque and the bias force, according to the position of the lift tab  135  on the ramp  160 . In addition to the friction between the lift tab  135  and the ramp  160 , the resistance exerted on the lift tab  135  includes the resistance offered by the actuator pivot  131 . However, the variations in the resistance as the lift tab  135  is displaced are mainly the result of variations in the friction between the ramp  160  and the lift tab  135 .  
      That is, the amount of elastic deformation of the suspension  133  biasing the read/write head  134  towards the disk  110  gradually increases as the lift tab  135  moves along the first inclined section  161 . Accordingly, the friction acting on the lift tab  135  and the overall resistance reflecting the same gradually increase. As shown in graph (a) of  FIG. 6 , the resistance in the direction of rotation increases almost linearly as the lift tab  135  moves along the first inclined section  161  (section L 1  of the graph). On the other hand, the friction acting on the lift tab  135  and the overall resistance reflecting the same are maintained almost constant as the lift tab  135  moves along the horizontal section  163  (section L 2  of the graph) because the elastic deformation amount of the suspension  133  is maintained constant while the lift tab  135  is guided by the horizontal section  163 . The elastic deformation of the suspension  133  decreases sharply when the lift tab  135  leaves the horizontal section  163  and enters the second inclined section  165 . Accordingly, the overall resistance suddenly drops when the lift tab  135  arrives at the second inclined section  165 . The lift tab  135  moves smoothly across the second inclined surface  165  because the force exerted by the suspension  133  on the lift tab  135  has a component parallel to the second inclined section  165 . The overall resistance to the progression of the lift tab  135  along the ramp  160  decreases to a value close to “0” as the lift tab  135  traverses the second inclined section  165  (section L 3  of the graph). Finally, the overall resistance increases drastically as the lift tab  135  leaves the second inclined section  165  and arrives on the stop accommodation section  167  because, unlike with the second inclined section  165 , the force exerted by the suspension  133  does not help move the lift tab  135  along the horizontal stop accommodation section  167 . Subsequently, the overall resistance acting on the lift tab  135  is maintained almost constant as the lift tab  135  moves along the stop accommodation section  167  (section L 4  of the graph).  
      Graph (b) of  FIG. 6  shows a profile of the driving torque generated by the VCM. The driving torque can be increased linearly in correspondence with the linear increase in the friction generated between the lift tab  135  and the ramp  160  as the lift tab  135  moves along the first inclined section  161 . However, the maximum driving torque T max  that the VCM can produce, at a point in time corresponding to point P in graph (b), is limited to a specific amount according to the design specifications of the VCM. Thus, the overall resistance exceeds the maximum driving torque at some point as the lift tab  135  is moving along the first inclined section  161 , e.g., at the point in time represented by point P in section L 1  of graph (a).  
      Graph (c) of  FIG. 6  shows a profile of the bias in the direction of rotation applied to the swing arm  132  by the magnetic retracting member  140  of the present invention. The magnitude of the bias gradually increases as the unloading operation gets underway and sharply increases as the lift tab  135  moves along the first inclined section  161  (section L 1  of graph (a)). The magnitude of the bias becomes almost equivalent to the maximum overall resistance offered against the rotation of the swing arm  132 . In the present embodiment, the maximum bias T b  is applied after the lift tab  135  has traversed the first inclined surface  161  where the friction between the lift tab  135  and the ramp  160  is at its greatest. At this time, the magnetic retracting member  140  and the magnet  150  are relatively close to each other so that the magnetic force of attraction therebetween is relatively strong. On the other hand, as indicated by the dashed portion of the plot in the graph, the is negligible while the actuator  130  is in a loading state so as to not affect the tracking of the read/write head  134 .  
      Graph (d) of  FIG. 6  shows the sum of the driving torque of the VCM and the bias exerted by the magnetic retracting member  140  on the swing arm  132  (solid line plot) as superimposed on the overall resistance offered against the rotation of the swing arm  132  (dashed line plot). As can be seen from this figure, the magnitude of the overall torque is greater the resistance offered against the swing arm  132  in parking the read/write head  134 .  
      In the hard disk drive according to the present invention, the load exerted by the suspension  133  must prevent the head  134  from inadvertently flying off of the surface of the disk  110 , i.e., the suspension must provide the hard disk drive with an anti-shock characteristic. In the conventional hard disk drive, the anti-shock characteristic compromises the unloading operation. On the other hand, according to the present invention, the magnetic retracting member  140  biases the swing arm in its direction of rotation during unloading. Accordingly, the unloading operation is readily carried out even though the load exerted by the suspension  133  to press the read/write head  134  toward the surface of the disk  110  is great enough to provide the hard disk drive with a significant anti-shock characteristic.  
      In addition, the read/write head of a hard disk drive must be rapidly moved off of the disk to a parking-position in an emergency, e.g., when power to the drive is suddenly discontinued or the hard disk drive is carelessly dropped. Otherwise, a head slap may occur in which the read/write head collides with the surface of the disk. As the result of a head slap, the disk may be damaged to such an extent that data stored on the disk can not be reproduced, or the head itself may be so damaged that it can no longer function. The read/write head could be rapidly parked by designing the power supply circuit to supply the actuator with a large amount of available current in the case of an emergency. Such a solution would require a relatively complex power supply circuit. According to the present invention, however, the unloading operation is enhanced by the magnetic retracting member  140  so that it can be carried out in a minimal amount of time without the need for an overly complex power supply circuit. Therefore, a hard disk drive according to the present invention is particularly durable and reliable.  
      Also, according to the present invention, the magnetic retracting member  140  and the magnetic locking member  145  may be formed of a relatively heavy metallic magnetic material. Therefore, the retract magnetic member  140  and/or the magnetic locking member  145  can be used to balance the actuator. Thus, the present invention enhances the dynamic characteristic of the hard disk drive.  
      Furthermore, the magnetic retracting member  140  can be readily introduced into existing hard disk drives. Accordingly, the costs of implementing the present invention are minimal.  
      Finally, although the present invention has been particularly shown and described with reference to the preferred embodiments thereof, the present invention is not so limited. For example, the magnetic retracting member  140  has been shown and described as disposed to one side of the VCM coil so as to bias the swing arm in the unloading direction. However, the magnetic retracting member  140  can be instead disposed at the other side of the VCM coil to bias the swing arm in the loading direction for the purpose of providing the hard disk drive with a rapid response characteristic. Therefore, various changes in the form and details of the disclosed embodiments are seen to be within the true spirit and scope of the invention as defined by the appended claims.