Abstract:
A head actuator supports a head slider and designed to swing around a support shaft over first and second swinging ranges adjacent each other. A restraint member is designed to restrain the swinging movement of the head actuator from separating from the first swinging range toward the second swinging range. A restriction member is designed to restrict the swinging movement of the head actuator from separating from the second swinging range toward the first swinging range. The second swinging range is excluded from the actual swinging range of the head actuator when the restraint member operates. The swinging range of the head actuator can thus be reduced or narrowed. Likewise, the first swinging range is excluded from the actual swinging range of the head actuator when the restriction member operates. The swinging range of the head actuator can thus be reduced or narrowed.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a recording disk drive designed to manage information based on a recording medium such as a hard disk (HD), for example.  
         [0003]     2. Description of the Prior Art  
         [0004]     A so-called load/unload mechanism is well known in the technical field of hard disk drives (HDDs). A head suspension is incorporated within a hard disk drive. The head suspension is designed to support a head slider at the tip end. When a magnetic recording disk stops rotating, the head slider moves to a position outside the outer periphery of the magnetic recording disk. The head suspension is supported on a ramp member located at a position outside the magnetic recording disk. The head slider is in this manner prevented from contact with the magnetic recording disk when the magnetic recording disk stays still.  
         [0005]     A latch mechanism is disclosed in Japanese Patent Application Publication No. 2002-313040, for example. The latch mechanism is designed to restrain the swinging movement of the head actuator inducing the movement of the head suspension. If an impact is applied to the hard disk drive at rest, the head suspension is reliably held on the ramp member. The head slider is prevented from falling from the ramp member toward the surface of the magnetic recording disk, so that the magnetic head and the magnetic recording disk are prevented from suffering from damages.  
         [0006]     The head slider is kept away from the surface of the magnetic recording disk during the rotation of the magnetic recording disk. If a seek error occurs in the hard disk drive, for example, the hard disk drive first operates to move the head slider to a position outside the outermost recording track. The target recording track is subsequently sought again. The head suspension thus slides on the ramp member during the movement of the head slider. The ramp member suffers from abrasion due to the sliding movement of the head suspension. The aforementioned latch mechanism cannot prevent the sliding movement of the head suspension.  
       SUMMARY OF THE INVENTION  
       [0007]     It is accordingly an object of the present invention to provide a recording disk drive capable of suppressing an unnecessary swinging movement of a head actuator.  
         [0008]     According to a first aspect of the present invention, there is provided a recording disk drive comprising: a recording disk; a head slider related to the recording disk; a head actuator supporting the head slider and designed to swing around a support shaft over first and second swinging ranges adjacent each other; a restraint member designed to restrain the swinging movement of the head actuator from separating from the first swinging range toward the second swinging range; and a restriction member designed to restrict the swinging movement of the head actuator from separating from the second swinging range toward the first swinging range.  
         [0009]     The restraint member serves to keep the head actuator within the first swinging range in the recording disk drive. The second swinging range is excluded from the actual swinging range of the head actuator when the restraint member operates. The swinging range of the head actuator can thus be reduced or narrowed. Likewise, the restriction member serves to keep the head actuator within the second swinging range. The first swinging range is excluded from the actual swinging range of the head actuator when the restriction member operates. The swinging range of the head actuator can thus be reduced or narrowed. In any cases, the swinging movement of the head actuator can be suppressed.  
         [0010]     The head slider may be held at a position outside the outermost recording track on the recording disk when the head actuator swings over the first swinging range. In this case, the head slider is kept out of the outermost recording track, so that the head slider is reliably prevented from contacting with the recording disk. On the other hand, the head slider may be held at a position inside the outer periphery of the recording disk when the head actuator swings over the second swinging range. In this case, the head slider cannot move to a position outside the outer periphery of the recording disk. The head slider can be held on or above the recording disk during the rotation of the recording disk.  
         [0011]     The restraint member may comprise a stop designed to move along a movement path extending in parallel with the support shaft. The head actuator moves along a plane perpendicular to the support shaft during the swinging movement of the head actuator. The stop may collide against the head actuator along the plane so as to restrain the swinging movement of the head actuator. Since the movement path of the head actuator is set perpendicular to the movement path of the stop, no driving force is applied to the stop along the movement path of the stop even when the head actuator collides against the stop. The stop fails to move.  
         [0012]     The restriction member may comprise a stop designed to move along a movement path extending in parallel with the support shaft. The stop may collide against the head actuator along the plane so as to restrain the swinging movement of the head actuator. Since the movement path of the head actuator is set perpendicular to the movement path of the stop, no driving force is applied to the stop along the movement path of the stop even when the head actuator collides against the stop. The stop fails to move. Here, the stop of the restraint member may also serve as the stop of the restriction member. In this case, a collision piece may be fixed to the head actuator. The collision piece is designed to move across the movement path of the stop when the head actuator swings.  
         [0013]     The recording disk drive may further comprise: a swinging member designed to swing around a rotation shaft and having an arm member extending in a first direction from the rotation shaft, said swinging member supporting the stop at the tip end of the arm member; a driven piece integral to the swinging member and extending in a second direction opposite to the first direction; and a drive source designed to generate the movement of the driven piece around the rotation shaft.  
         [0014]     When the collision piece collides against the stop, the impact of the collision is received on the rotation shaft through the arm member. In this case, no driving force is applied to the stop along the movement path. The stop fails to move. No impact is transmitted to the drive source if the swinging member is prevented from swinging in this manner. The drive source can thus be protected enough from impact of collision. An electromagnetic solenoid may be employed as the drive source, for example. A depression may be formed on the arm member so as to allow the movement of the collision piece between the stop and the rotation shaft.  
         [0015]     According to a second aspect of the present invention, there is provided a recording disk drive comprising: a recording disk; a ramp member located at a position outside the recording disk; a head slider related to the recording disk; a head actuator supporting the head slider and designed to swing around a support shaft from a first swinging range, where the head actuator is contacted with the ramp member, to a second swinging range, where the head actuator separates from the ramp member; and a restriction member designed to restrict the swinging movement of the head actuator from separating from the second swinging range toward the first swinging range.  
         [0016]     The first swinging range is excluded from the actual swinging range of the head actuator when the restriction member operates. The swinging range of the head actuator can thus be reduced or narrowed. The head slider cannot move to a position outside the outer periphery of the recording disk. The head actuator is prevented from contacting with the ramp member. Abrasion caused by the sliding movement of the head actuator can thus be avoided in the ramp member.  
         [0017]     The restriction member may comprise a stop designed to move along a movement path extending in parallel with the support shaft. The stop may collide against the head actuator along the plane so as to restrain the swinging movement of the head actuator. Since the movement path of the head actuator is set perpendicular to the movement path of the stop, no driving force is applied to the stop along the movement path of the stop even when the head actuator collides against the stop. The stop fails to move.  
         [0018]     The recording disk drive may further comprise a restraint member designed to restrain the swinging movement of the head actuator from separating from the first swinging range toward the second swinging range. The second swinging range is excluded from the actual swinging range of the head actuator when the restraint member operates. The head slider cannot move to a position inside the outermost recording track. The head slider is prevented from contacting with the recording disk.  
         [0019]     The restraint member may comprise a stop designed to move along a movement path extending in parallel with the support shaft. The head actuator moves along a plane perpendicular to the support shaft during the swinging movement of the head actuator. The stop may collide against the head actuator along the plane so as to restrain the swinging movement of the head actuator. Since the movement path of the head actuator is set perpendicular to the movement path of the stop, no driving force is applied to the stop along the movement path of the stop even when the head actuator collides against the stop. The stop fails to move. Here, the stop of the restraint member may also serve as the stop of the restriction member. In this case, a collision piece may be fixed to the head actuator. The collision piece is designed to move across the movement path of the stop when the head actuator swings.  
         [0020]     The recording disk drive may further comprise: a swinging member designed to swing around a rotation shaft and having an arm member extending in a first direction from the rotation shaft, said swinging member supporting the stop at the tip end of the arm member; a driven piece integral to the swinging member and extending in a second direction opposite to the first direction; and a drive source designed to generate the movement of the driven piece around the rotation shaft.  
         [0021]     When the collision piece collides against the stop, the impact of the collision is received on the rotation shaft through the arm member. In this case, no driving force is applied to the stop along the movement path. The stop fails to move. No impact is transmitted to the drive source if the swinging member is prevented from swinging in this manner. The drive source can thus be protected enough from impact of collision. An electromagnetic solenoid may be employed as the drive source, for example. A depression may be formed on the arm member so as to allow the movement of the collision piece between the stop and the rotation shaft. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     The above and other objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments in conjunction with the accompanying drawings, wherein:  
         [0023]      FIG. 1  is a plan view schematically illustrating the structure of a hard disk drive as an example of a recording disk drive according to the present invention;  
         [0024]      FIG. 2  is a plan view of the hard disk drive for illustrating the swinging range of a head actuator;  
         [0025]      FIG. 3  is an enlarged perspective view schematically illustrating the structure of a restraint mechanism according to a specific example;  
         [0026]      FIG. 4  is an enlarged perspective view schematically illustrating the structure of the restraint mechanism when a stop is positioned out of an operating position;  
         [0027]      FIG. 5  is a plan view of the hard disk drive for illustrating the stop receiving the movement of a collision piece on the head actuator within a first swinging range;  
         [0028]      FIG. 6  is an enlarged perspective view of the restraint mechanism for illustrating the collision piece colliding against the stop within a first movable range;  
         [0029]      FIG. 7  is a plan view of the hard disk drive for illustrating the stop receiving the movement of the collision piece on the head actuator within a second swinging range;  
         [0030]      FIG. 8  is an enlarged perspective view of the restraint mechanism for illustrating the collision piece colliding against the stop within a second movable range;  
         [0031]      FIG. 9  is an enlarged perspective view schematically illustrating the structure of a restraint mechanism according to another example; and  
         [0032]      FIG. 10  is an enlarged perspective view schematically illustrating the structure of the restraint mechanism when a stop is positioned out of an operating position. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0033]      FIG. 1  schematically illustrates the inner structure of a hard disk drive (HDD)  11  as an example of a recording disk drive or storage device according to a first embodiment of the present invention. The hard disk drive  11  includes a box-shaped main enclosure  12  defining an inner space of a flat parallelepiped, for example. At least one magnetic recording disk  13  as a recording medium is incorporated in the main enclosure  12 . The magnetic recording disk or disks  13  is mounted on the driving shaft of a spindle motor  14 . The spindle motor  14  is allowed to drive the magnetic recording disk or disks  13  for rotation at a higher revolution speed such as 7,200 rpm, 10,000 rpm, or the like, for example. A cover, not shown, is coupled to the main enclosure  12  so as to define the closed inner space between the main enclosure  12  and the cover itself.  
         [0034]     A data zone  17  is defined over the front and back surfaces of the individual magnetic recording disk  13  between an innermost recording track  15  and an outermost recording track  16 . Concentric recording circles or tracks are defined within the data zone  17 . No magnetic information is recorded on a marginal zone or non-data zone inside the innermost recording track  15 . Likewise, no magnetic information is recorded on a marginal zone or non-data zone outside the outermost recording track  16 .  
         [0035]     A head actuator  18  is also incorporated in the inner space of the main enclosure  12 . The head actuator  18  includes an actuator block  21 . The actuator block  21  is coupled to a vertical support shaft  19  for relative rotation. Rigid actuator arms  22  are defined in the actuator block  21  so as to extend in the horizontal direction from the vertical support shaft  19 . The actuator block  21  may be made of aluminum. Molding process may be employed to form the actuator block  21 .  
         [0036]     Elastic suspensions  23  are fixed to the corresponding tip ends of the actuator arms  22  so as to further extend in the forward direction from the actuator arms  22 . A flying head slider  24  is attached to the tip end of the elastic suspension  23 . The flying head slider  24  is cantilevered on the elastic suspension  23  based on the action of a gimbal spring, not shown.  
         [0037]     An electromagnetic transducer, not shown, is mounted on the flying head slider  24 . The electromagnetic transducer may include a write element and a read element. The write element may include a thin film magnetic head designed to write magnetic bit data into the magnetic recording disk  13  by utilizing a magnetic field induced at a thin film coil pattern. The read element may include a giant magnetoresistive (GMR) element or a tunnel-junction magnetoresistive (TMR) element designed to discriminate magnetic bit data on the magnetic recording disk  13  by utilizing variation in the electric resistance of a spin valve film or a tunnel-junction film, for example.  
         [0038]     The elastic suspension  23  serves to urge the flying head slider  24  toward the surface of the magnetic recording disk  13 . When the magnetic recording disk  13  rotates, the flying head slider  24  is allowed to receive airflow generated along the rotating magnetic recording disk  13 . The airflow serves to generate a positive pressure or lift on the flying head slider  24 . The flying head slider  24  is thus allowed to keep flying above the surface of the magnetic recording disk  13  during the rotation of the magnetic recording disk  13  at a higher stability established by the balance between the urging force of the elastic suspension  23  and the lift.  
         [0039]     When the head actuator  18  is driven to swing about the vertical support shaft  19  during the flight of the flying head slider  24 , the flying head slider  24  is allowed to move along the radial direction of the magnetic recording disk  13 . This radial movement allows the electromagnetic transducer on the flying head slider  24  to cross the data zone  17  between the innermost recording track  15  and the outermost recording track  16 . The flying head slider  24  can thus be positioned right above a target recording track on the magnetic recording disk  13 . A power source  25  such as a voice coil motor (VCM) may be employed to realize the swinging movement of the head actuator  18 , for example.  
         [0040]     A load tab  26  is attached to the front or tip end of the elastic suspension  23  so as to further extend in the forward direction from the elastic suspension  23 . The load tab  26  is allowed to move in the radial direction of the magnetic recording disk  13  based on the swinging movement of the head actuator  18 . A ramp member  27  is located at a position outside the magnetic recording disk  13  on the movement path of the load tab  26 . The ramp member  27  brings the tip end to a position inside the outer periphery of the magnetic recording disk  13 , so that the tip end of the ramp member  27  is opposed to the non-data zone outside the outermost recording track  16 . The combination of the load tab  26  and the ramp member  27  establishes a so-called load/unload mechanism as described later in detail. The ramp member  27  may be made of a hard plastic material, for example. Molding process may be employed to from the ramp member  27 .  
         [0041]     As shown in  FIG. 2 , the swinging range of the head actuator  18  is divided into first and second swinging ranges  28 ,  29  adjacent each other. When the head actuator  18  is positioned within the first swinging range  28  around the support shaft  19 , the load tab  26  is received on the ramp member  27 . The flying head slider  24  is kept away from the magnetic recording disk  13  against the urging force from the elastic suspension  23  and the negative pressure caused on the flying head slider  24  by the airflow. The flying head slider  24  is thus prevented from contact with the magnetic recording disk  13  even without generation of a lift on the flying head slider  24 . When the head actuator  18  swings within the first swinging range  28 , the load tab  26  keeps in contact with the ramp member  27 . The flying head slider  24  is maintained at a location at least outside the outermost recording track  16  on the magnetic recording disk  13 .  
         [0042]     When the head actuator  18  swings around the support shaft  19  from the first swinging range  28  to the second swinging range  29 , the load tab  26  takes off from the ramp member  27 . The rotating magnetic recording disk  13  serves to generate airflow acting on the flying head slider  24 . The flying head slider  24  thus keeps flying above the surface of the magnetic recording disk  13  as described above. The electromagnetic transducer can be positioned right above a target recording track. The write and read operations of magnetic information are effected. When the head actuator  18  swings within the second swinging range  29 , the flying head slider  24  is kept at least inside the outer periphery of the magnetic recording disk  13 .  
         [0043]     A restraint mechanism  31  is related to the head actuator  18 . The restraint mechanism  31  includes a collision piece  32  formed on the actuator block  21 . The collision piece  32  may extend from the support shaft  19  along the horizontal direction in a direction opposite to the actuator arms  22 . When the actuator block  21  swings around the support shaft  19 , the collision piece  32  traces an arc orbit around the support shaft  19 . When the head actuator  18  swings within the first swinging range  28 , the collision piece  32  moves within a first movable range  33 . When the head actuator  18  swings within the second swinging range  29 , the collision piece  32  moves within a second movable range  34 .  
         [0044]     As shown in  FIGS. 1 and 3 , the restraint mechanism  31  further includes a swinging member  36  designed to swing around a rotation shaft  35  extending in the horizontal direction. The rotation shaft  35  may tightly be fitted into a hole defined in the main enclosure  12 , for example. A spacer, not shown, may be interposed between the rotation shaft  35  and the inner wall surface of the main enclosure  12 .  
         [0045]     An arm  38  is formed on the swinging member  36 . The arm  38  is allowed to extend along the horizontal direction in a first direction  37  from the rotation shaft  35 . A stop  39  is coupled to the tip end of the arm  38 . When the swinging member  36  swings around the rotation shaft  35 , the stop  39  moves in the vertical direction along an arc orbit around the rotation shaft  35 . A movement path  41  of the stop  39  is in this manner established in parallel with the support shaft  19 . The movement path  41  of the stop  39  intersects with the first movable range  33  of the collision piece  32 . The swinging member  36  may be made of a resin material, for example. Molding process may be employed to form the swinging member  36 . The stop  39  may be made of an elastic material such as rubber.  
         [0046]     A driven piece  43  is formed on the swinging member  36 . The driven piece  43  extends in a second direction  42  opposite to the first direction  37  along the horizontal direction. The driven piece  43  is integral to the swinging member  36 . A columnar or prismatic permanent magnet  44  is incorporated in the driven piece  43 . The permanent magnet  44  extends in the vertical direction. The magnetization is established in the permanent magnet  44  in the vertical direction. An electromagnetic solenoid  45  as a drive source is related to the permanent magnet  44 . The electromagnetic solenoid  45  includes a columnar or prismatic core  45   a . The core  45   a  is press-fitted into a hole defined in the bottom plate of the main enclosure  12 , for example. A coil  45   b  is wound around the core  45   a  in the electromagnetic solenoid  45 . Lead wires  46  are connected to the coil  45   b . The lead wires  46  penetrate through through holes defined in the bottom plate of the main enclosure  12 , so that the lead wires  46  are connected to a printed circuit board unit, not shown, located at the back of the hard disk drive  11 . Electric power is supplied to the coil  45   b  through the lead wires  46 ,  46 .  
         [0047]     The magnetic flux of the permanent magnet  44  acts on the magnetic body such as the core  45   a . Since the core  45   a  is fixed on the main enclosure  12 , the permanent magnet  44  is drawn to the core  45   a . The driven piece  43  contacts the core  45   a . The stop  39  is thus positioned at the highest position, namely an operating position. The stop  39  is positioned in the first movable range  33  adjacent the second movable range  34 . A depression  47  is formed on the arm  38 . The depression  47  allows the movement of the collision piece  43  within the second movable range  34 .  
         [0048]     On the other hand, when electric current is supplied to the coil  45   b , a magnetic flux circulates through the coil  45   b . The magnetic flux passes through the core  45   a . The same magnetic pole is established at opposed positions on the core  45   a  and the permanent magnet  44 , so that the permanent magnet  44  reacts against the core  45   a . Since the core  45   a  is fixed on the main enclosure  12 , the permanent magnet  44  along with the driven piece  43  is distanced away from the electromagnetic solenoid  45 . As shown in  FIG. 4 , the swinging member  36  thus swings around the rotation shaft  35 . The stop  39  is in this manner forced to move to the lowest position, namely an inoperative position, from the operating position. When the tip end of the arm  38  touches the bottom plate of the main enclosure  12 , the swinging member  36  stops swinging. As long as electric current is sufficiently supplied to the coil  45   b , the stop  39  is kept at the inoperative position.  
         [0049]     As shown in  FIG. 5 , the load tab  26  is kept on the ramp member  27  in the hard disk drive  11  at rest. The permanent magnet  44  generates a magnetic field establishing an attraction to keep the stop  39  at the operating position. When the head actuator  18  swings over the first swinging range  28  toward the second swinging range  29 , the collision piece  32  moves over the first movable range  33  toward the second movable range  34 . In this case, the collision piece  32  collides against the stop  39  before the collision piece  32  deviates from the first movable range  33 . The movement of the collision piece  32  is thus restrained. The head actuator  18  is accordingly prevented from entering the second swinging range  29 . The swinging movement of the head actuator  18  is in this manner restrained. The load tab  26  is thus kept on the ramp member  27 . The restraint mechanism  31  functions as a restraint member according to the present invention.  
         [0050]     As shown in  FIG. 6 , the collision piece  32  collides against the stop  39  in the horizontal direction, for example. The impact of the collision is received on the rotation shaft  35  through the arm  38 . Since the movement path  41  of the stop  39  is established in the vertical direction as described above, no driving force is applied to the stop  39  along the movement path  41 . The stop  39  is thus prevented from moving. The swinging movement of the swinging member  36  is in this manner prevented. No impact is transmitted to the electromagnetic solenoid  45 . The electromagnetic solenoid  45  can sufficiently be protected from impact of collision.  
         [0051]     Now, assume that the hard disk drive  11  starts operating. The hard disk drive  11  receives an instruction signal for starting the operation. The magnetic recording disk  13  starts rotating. Electric current is subsequently supplied to the coil  45   b . The stop  39  is positioned at the inoperative position as described above. When the head actuator  18  swings toward the second swinging range  29  from the first swinging range  28 , the collision piece  32  moves into the second movable range  34  from the first movable range  33 . The collision piece  32  enters the second movable range  34  across the movement path  41  of the stop  39 . The head actuator  18  concurrently enters the second swinging range  29 . The load tab  26  takes off from the ramp member  27 . As shown in  FIG. 7 , the flying head slider  24  keeps flying above the surface of the magnetic recording disk  13  based on the rotation of the magnetic recording disk  13 . When the hard disk drive  11  confirms the separation of the load tab  26  from the ramp member  27 , the supply of the electric current is terminated for the coil  45   b . The attraction of the permanent magnet  44  serves to bring the stop  39  back to the operating position.  
         [0052]     The stop  39  is kept at the operating position based on the attraction from the permanent magnet  44  during the operation of the hard disk drive  11 . If the head actuator  18  is driven to swing toward the first swinging range  28  over the second swinging range  29 , the collision piece  32  moves toward the first movable range  33  over the second movable range  34 . In this case, the collision piece  32  collides against the stop  39  before the collision piece  32  deviates from the second movable range  34 , as shown in  FIG. 7 . The movement of the collision piece  32  is thus restrained. The head actuator  18  thus cannot enter the first swinging range  28 . The load tab  26  is prevented from contacting with the ramp member  27 . Abrasion is accordingly prevented on the ramp member  27 . The restraint mechanism  31  in this manner functions as a restriction member according to the present invention.  
         [0053]     As shown in  FIG. 8 , the collision piece  32  collides against the stop  39  in the horizontal direction in the hard disk drive  11 . The impact of the collision is received on the rotation shaft  35  through the arm  38 . Since the movement path  41  of the stop  39  is established in the vertical direction as described above, no driving force is applied to the stop  39  along the movement path  41 . The stop  39  is thus prevented from moving. The swinging movement of the swinging member  36  is in this manner prevented. No impact is transmitted to the electromagnetic solenoid  45 . The electromagnetic solenoid  45  can sufficiently be protected from impact of collision.  
         [0054]     Now, assume that the hard disk drive  11  finishes the operation. The hard disk drive  11  receives the instruction signal for the completion of the operation. Electric current is at once supplied to the coil  45   b . The stop  39  is thus positioned at the inoperative position as described above. When the head actuator  18  swings toward the first swinging range  28  from the second swinging range  29 , the collision piece  32  moves toward the first movable range  33  from the second movable range  34 . The collision piece  32  enters the first movable range  33  across the movement path  41  of the stop  39 . The head actuator concurrently enters the first swinging range  28 . The load tab  26  contacts the ramp member  27 . When the load tab  26  is received on the ramp member  27 , the supply of the electric current is terminated for the coil  45   b . The attraction from the permanent magnet  44  serves to bring the stop  39  back to the operating position. The magnetic recording disk  13  then stops rotating.  
         [0055]     As shown in  FIGS. 9 and 10 , the lowest position of the stop  39  may correspond to the operating position while the highest position may correspond to the inoperative position in the restraint mechanism  31 . In this case, a magnetic body or bar magnet  48  may be located at a position opposed to the permanent magnet  44 . The bar magnet  48  may be fixed to the main enclosure  12 . The bar magnet  48  generates a magnetic field stronger than that of the core  45   a  of the electromagnetic solenoid  45 . Like reference numerals are attached to structure and components equivalent to those of the aforementioned embodiment.  
         [0056]     The bar magnet  48  generates a magnetic attraction applied to the permanent magnet  44  at the intensity stronger than that of the magnetic attraction induced between the permanent magnet  44  and the core  45   a . The permanent magnet  44  is thus attracted to the bar magnet  48 . The driven piece  43  contacts with the bar magnet  48 . The stop  39  is in this manner positioned at the lowest or operating position. The stop  39  is positioned in the first movable range  33  of the collision piece  32 . In this case, the swinging movement of the head actuator  18 , namely the movement of the collision piece  32  is prevented in the aforementioned manner.  
         [0057]     On the other hand, when electric current is supplied to the coil  45   b , a magnetic flux circulates through the coil  45   b . The magnetic flux passes through the core  45   a . Here, the different magnetic poles are established at opposed positions on the core  45   a  and the permanent magnet  44 , so that the core  45   a  effects the attraction on the permanent magnet  44  at the intensity stronger than the bar magnet  48 . The permanent magnet  44  is thus attracted to the core  45   a . Since the core  45   a  is fixed to the main enclosure  12 , the permanent magnet  44  namely the driven piece  43  is attracted to the electromagnetic solenoid  45 . The driven piece  43  contacts with the core  45   a . The stop  39  moves to the highest or inoperative position. As long as electric current is sufficiently supplied to the coil  45   b , the stop  39  is kept at the inoperative position. When the supply of the electric current is stopped for the coil  45   b , the stop  39  is moved to the operating position from the inoperative position based on the attraction from the permanent magnet  44 .  
         [0058]     Otherwise, a pin made of iron may be employed in place of the bar magnet  48 , for example. In this case, electric current is supplied to the coil  45   b  in the direction opposite to the flow of electric current in the aforementioned case. When a magnetic flux is induced at the coil  45   b , the same magnetic pole is established at opposed positions on the core  45   a  and the permanent magnet  44 . The core  45   a  reacts against the permanent magnet  44 , so that the driven piece  43  is moved toward the pin based on the attraction of the permanent magnet  44 . The stop  39  is kept at the operating position. When the flow of the electric current is reversed in the coil  45   b , the different magnetic poles are established at opposed positions on the core  45   a  and the permanent magnet  44 . The core  45   a  generates a magnetic attraction applied to the permanent magnet  44  at the intensity stronger than that of the magnetic attraction induced between the permanent magnet  44  and the pin. The driven piece  43  is thus attracted to the core  45   a  based on the attraction of the permanent magnet  44 . The stop  39  moves to the inoperative position from the operating position. The pin may be integral to the yoke of the voice coil motor as the power source  25 , for example.