Abstract:
A disk apparatus has a rotatable actuator adapted to magnetically latch in a predetermined stop position when the disk apparatus is not operating. The actuator rotates about a rotating or swinging shaft and includes a coil arm having a latch magnet. The coil arm is adapted to pass between opposing permanent magnets when the actuator rotates about the rotating or swinging shaft. When the actuator is in the stop position, the latch magnet is outside of the area between the permanent magnets, therefore generating a repulsive force between the latch magnet and permanent magnets, inducing the actuator to magnetically latch. When the disk apparatus is operating, the latch magnet travels between the permanent magnets, resulting in opposing repulsive magnetic forces having equal magnitudes which cancel each other, maintaining the actuator&#39;s attitude without rotating it. In this manner, the latch magnet does not interfere with the operation of the actuator, and locks the actuator in a stop or park condition when the disk apparatus is not operating.

Description:
The present invention generally relates to an actuator arm adapted to drive a head in a disk apparatus, and more particularly, to a latch mechanism adapted to hold the actuator arm in a predetermined position during non-operation of the disk apparatus. 
     BACKGROUND OF THE INVENTION 
     A disk apparatus for recording and reproducing information to or from a disk medium must to avoid wear which results from contact between the head slider and the disk surface. Therefore, a contact-start-stop (CSS) system is employed in which, during non-operation of the disk apparatus, the head is in contact with the disk surface, and during operation of the disk apparatus, namely, during recording or reproducing operations, the head floats above the rotating disk surface. 
     In a disk apparatus employing the CSS system, the head slider includes a head element to record or reproduce information to or from a disk which floats away from the rotating disk surface during operation of the disk drive by receiving air flow generated by rotation of the disk. When information is recorded or reproduced, the head slider moves while floating above the rotating disk surface and is then placed over a predetermined track of the disk. When the disk apparatus is in the non-operating condition, the head slider is placed within the CSS zone provided on the disk surface. Moreover, when the disk apparatus is in the non-operating condition, since the disk is not rotating, air flow for floating the head slider is not generated and the head slider is in contact with the CSS zone. 
     If the disk apparatus receives a shock when the head slider is in contact with the CSS zone, the head slider may move to the data zone and cause damage, namely, a destruction of data or a disabling of the data reading or writing operation. In recent years, with reduction of size, such a disk apparatus has been used in portable devices such as note-sized personal computers. Such a disk apparatus is often placed in a condition where it may easily receive an external shock. Therefore, high durability against shock is one of the performance characteristics required for a disk apparatus. 
     Therefore, a latch mechanism has been provided so that the actuator is fixed in the stop position when the disk apparatus is in the non-operating condition. By providing the latch mechanism, if the disk apparatus receives a certain degree of shock, the head slider does not move to the data zone and thereby the disk and data can be protected. 
     FIGS.  1 ( a ) and  1 ( b ) illustrate a structure of the latch mechanism of the related art. A voice coil  51  is mounted at the rear end surface of an actuator  22  which supports a head slider  4 ,. The voice coil  51  is placed within magnetic fields generated by an upper permanent magnet  54  provided at the lower surface of an upper yoke  52 , and a lower permanent magnet  55  provided at the upper surface of lower yoke  53 . A voice coil motor (VCM)  23  which rotates the actuator  22  includes the voice coil  51 , upper and lower yokes  52 ,  53  and permanent magnets  54 ,  55  or the like. 
     A latch magnet  11  is provided in the area outside the magnetic field of the rear end surface of the actuator  22 . Moreover, opposing dowels  12  are provided which sandwich the plane of motion of the latch magnet  11 . The dowels are located at the lower surface of upper yoke  52  and at the upper surface of the lower yoke  53 . The dowels  12  are generally formed by pressing the yokes  52 ,  53 . 
     According to this structure, when the head slider  4  stops in a CSS zone  31  of a disk  1 , the latch magnet  11  is proximal to the dowels  12  and magnetic force attracts the latch magnet  11  toward the dowels  12 . As a result, a counterclockwise torque is generated in the actuator  22  and thereby the actuator  22  is energized or biased in the counterclockwise direction. Therefore, when the head slider  4  receives a shock when it is in contact with the CSS zone  31 , it is prevented from moving to data zone  32 . 
     In order to realize a highly reliable latch mechanism, the actuator  22  must be energized or biased toward the CSS zone  31  by an intensive torque. In the latch mechanism illustrated in FIG. 1, the magnetic force of latch magnet  11  must be intensified to attain a strong latch force. However, when the magnetic force of the latch magnet  11  is raised, a significant attracting force is generated between the dowels  12  and the latch magnet  11  even during seek operations, resulting in an influence on the seek control. As a result, the seek control becomes difficult and the processing speed is decreased. Moreover, when an intensified magnetic force of the latch magnet  11  is required, it also requires enlargement of the latch magnet  11 . Since the latch magnet  11  illustrated in FIG. 1 is provided at the far end of the rotating shaft of the actuator  22 , enlargement of latch magnet  11  requires a large rotating inertia of the actuator  22  to release the latch. Thereby, the load on VCM  23  becomes large and power consumption also becomes large. 
     As a solution to the problems explained above, a latch mechanism utilizing a solenoid and a mechanical latch mechanism utilizing air pressure generated by rotation of the disk medium have been proposed, but these mechanisms require the addition of expensive parts, thereby increasing cost. 
     It is therefore a first object of the present invention to improve the shock resistance of a disk apparatus. 
     It is a second object of the present invention to provide a disk apparatus which assures high speed operation. 
     It is a third object of the present invention to provide a low cost disk apparatus. 
     It is a fourth object of the present invention to provide a latch mechanism having a simplified structure. 
     It is a fifth object of the present invention to provide a latch mechanism having a large latching force. 
     SUMMARY OF THE INVENTION 
     In a latch mechanism used for a disk apparatus of the present invention, a latch force is obtained from a latch magnet attached to an actuator. The latch magnet passes through a magnetic field generated by two permanent magnets of a voice coil motor (VCM), with a rotating or swinging shaft of the actuator defining a center of rotation. According to this structure, a magnetic force in the rotating direction of the actuator can be generated between the latch magnet and the permanent magnets of the VCM when the actuator is in certain locations. The magnetic force working on the permanent magnets is higher than the magnetic force working between the metal piece and magnet of the related art. Therefore, an intensive latch force can be obtained from this magnetic force to improve the shock resistance of the disk apparatus. In addition, the latch mechanism has a simplified structure which does not require additional parts and therefore a low cost disk apparatus can be realized. Moreover, the latch magnet can be located proximal to the rotating shaft of the actuator, thereby decreasing the rotational inertia of the actuator. Accordingly, the load required for the VCM drive the actuator is alleviated to realize reduction of power consumption and high speed seeking. 
     Moreover, when the direction of the magnetic flux of the latch magnet is parallel to the direction of the magnetic flux generated by the permanent magnets of the VCM, and the head slider is resting on the CSS zone, it is preferable that the latch magnet be placed at least partially outside of the magnetic field of the permanent magnets. According to this structure, when the disk is in the non-operating condition and a latching of the actuator is required, a magnetic force in the direction of rotation of the actuator is generated between the latch magnet and the permanent magnets, and an intensive latch force can be obtained from this lateral magnetic force. 
     Moreover, when the head slider is located at a position furthest from the CSS zone in the movable range of the actuator, it is preferable for the latch magnet to be placed in the magnetic field of the permanent magnets. According to this structure, a magnetic force is not generated between the permanent magnets and the latch magnet during the seek operation, and therefore such a magnetic force does not influence the seek control. Therefore, high speed seek control may be realized. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above mentioned and other features of this invention and the manner of obtaining them will become more apparent, and the invention itself will be best understood with reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, in which: 
     FIG.  1 ( a ) is a plan view of a magnetic disk apparatus of the prior art; 
     FIG.  1 ( b ) is a back side view of a VCM of the prior art; 
     FIG.  2 ( a ) is a perspective view of a disk drive which has a first embodiment of the present invention; 
     FIG.  2 ( b ) is a plan view of the actuator illustrated in FIG.  2 ( a ); FIG.  3 ( a ) is a plan view of the disk apparatus of FIG.  2 ( a ) in an operating condition; 
     FIG.  3 ( b ) is a back-side view of the VCM illustrated in FIG.  3 ( a ); 
     FIG.  4 ( a ) is a plan view of the disk apparatus FIG.  2 ( a ) in a non-operating condition; 
     FIG.  4 ( b ) is a back-side view of the VCM illustrated in FIG.  4 ( a ); 
     FIG.  5 ( a ) is a perspective view of a coil arm having an auxiliary mechanism; 
     FIG.  5 ( b ) is a cross-sectional view along the line A—A of FIG.  5 ( a ); 
     FIG.  6 ( a ) is a cross-sectional view of an auxiliary mechanism which adjusts the stopping position by screw; 
     FIG.  6 ( b ) is a plan view of an auxiliary mechanism which adjusts the stopping position with an elliptical plate; 
     FIG.  7 ( a ) is a plan view of a disk apparatus which has a second embodiment of the present invention shown in an operating condition; 
     FIG.  7 ( b ) is a back-side view of the VCM illustrated in FIG.  7 ( a ); 
     FIG.  8 ( a ) is a plan view of the disk apparatus of FIG.  7 ( a ) in the non-operating condition; and 
     FIG.  8 ( b ) is a back-side view of the VCM illustrated in FIG.  8 ( a ). 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS.  2 ( a ) and  2 ( b ) illustrate a disk drive of the first embodiment of the present invention. FIG.  2 ( a ) is a perspective view of a disk drive in the condition that the cover (not illustrated) is removed, and FIG.  2 ( b ) is a plan view of an actuator. 
     The disk drive illustrated in FIGS.  2 ( a ) and  2 ( b ) includes, within an enclosure consisting of a cover (not illustrated) and a base  42 , a disk  1  such as a magnetic disk or the like as the data recording medium, a spindle motor  2  to drive the disk  1  to rotate, an actuator  22  on which a head slider  4  is mounted, and a voice coil motor (VCM)  23  to drive the actuator  22  to swing back and forth around an axis. 
     The disk  1  is fixed to a rotor of the spindle motor  2 . When the disk drive is operating, the disk  1  is driven to rotate around the spindle shaft of the spindle motor  2 , and is also driven to stop when the disk drive is in non-operating condition. On the surface of the disk  1 , a data zone  32  where the tracks on which data and servo information are recorded are arranged concentrically, and a stop area or CSS zone  31  in which the head slider  4  is placed when the disk drive is in the non-operating condition are provided. Here, the CSS zone  31  is provided at the internal circumference of the disk  1 , but it may also be provided at the external circumference. In this embodiment, three disks are mounted, but the number of disks to be mounted is not limited thereto. 
     The actuator  22  is formed of aluminum and is provided with a head arm  25  and a coil arm  26 . The actuator  22  is engaged with a rotating or swinging shaft  21  and is adapted to freely swing, namely, the actuator  22  can rotate about the rotating or swinging shaft  21 . The head arm  25  and coil arm  26  are arranged respectively on opposite sides of the rotating or swinging shaft  21 . Here, the coil arm  26  and head arm  25  are integrated at the time of formation. 
     The coil arm  26  is composed of an outer arm  26 ( b ) and an inner arm  26 ( a ). 
     At the end portion of head arm  25 , a suspension  27  is mounted to give a spring pressure to the head slider  4 . 
     The head slider  4  is provided opposed to a surface of the disk  1  and is connected to control means (not illustrated) with a head wire  41  or the like. The head slider  4  records the data supplied from the control means (not illustrated) to the tracks on the surface of disk  1 , and is also provided with a head element (not illustrated) to read the data recorded in the tracks and then send this data to the control means (not illustrated). When the disk drive is not in operation, the head slider  4  is in contact with the CSS zone  31  provided on the inner area of disk  1 . When the disk drive is in the operating condition, the head slider  4  floats above on the surface of the rotating disk  1 . Usually, a head slider is provided for each surface of each disk, and the head sliders move in unison. 
     The VCM  23  is composed of a voice coil  51  mounted on the coil arm  26 , an upper yoke  52  and a lower yoke  53 , a permanent magnet  54  deposited at the lower surface of the upper yoke  52 , and a permanent magnet  55  deposited on the upper surface of the lower yoke  53 . To the voice coil  51 , a drive current is supplied from the control means (not illustrated). The coil arm  26  is arranged in the space between by the upper yoke  52  and the lower yoke  53 . In this embodiment, a permanent magnet is provided for both the upper and the lower yokes  52 ,  53 , but a permanent magnet may be provided to only one of them. 
     A stopper  5  is provided around a pole  6  provided between the upper yoke  52  and the lower yoke  53 . The stopper  5  is formed of an elastic material. If for any reason the VCM  23  operates uncontrollably during operation, the coil arm  26  contacts the stopper  5  to forcibly stop the swinging operation of the actuator  22 . With the stopper  5 , the actuator  22  is protected from collision with the spindle motor  2  and the other mechanisms forming the apparatus. 
     As illustrated in FIG.  2 ( b ), the outer arm  26   b  of the coil arm  26  of the X actuator  22  includes a latch magnet  11 . The latch magnet  11  has a circular shape and is located in a hole provided in the outer arm  26   b  and is also fixed by a bonding agent. The latch magnet  11  has a diameter of 1.5 mm and a height of 1.2 mm and also has a magnetic flux which is inverted in relation to the magnetic field generated by the permanent magnets  54 ,  55 . 
     FIGS.  3 ( a ),  3 ( b ),  4 ( a ) and  4 ( b ) and FIG. 4 illustrate the operation of the actuator of the present invention. In FIGS.  3 ( a ) and  3 ( b ), the disk drive is in the operating condition, while in FIGS.  4 ( a ) and  4 ( b ), the disk drive is in the non-operating condition. 
     First, operation of the actuator  22  when the disk drive is in the operating condition will be explained. 
     As FIG.  3 ( a ) illustrates, when the disk drive is in the operating condition, the head slider  4  mounted to the surface of the head suspension  27  opposing the disk  1  is located at a position within the data zone  32  of the disk  1 . The head element (not illustrated) mounted on the head slider  4  performs the data recording and reproducing operation to and from the tracks of the data zone  32 . Moreover, the head slider  4  floats above the surface of the disk  1  by receiving air flow generated when the disk  1  rotates. In this case, the latch magnet  11  is placed in the area between the permanent magnets  54 ,  55  as illustrated in FIG.  3 ( b ). In the present embodiment, the movable range of the actuator  22  is set so that the latch magnet  11  does not enter the area between the permanent magnets  54 ,  55 , where upper permanent magnet  54  is polarized to S pole and the lower permanent magnet  55  to N pole. The direction of the magnetic flux in the latch magnet  11  is the same as the direction of magnetic flux generated by the permanent magnets  54 ,  55 , namely, the end portion of the latch magnet  11  opposing the upper permanent magnet  54  is polarized to the N pole, and the end portion of the latch magnet  11  opposing the lower permanent magnet  55  is polarized to the S pole. Therefore, the latch magnet  11  receives a lower direction force F 1  from the upper permanent magnet  54 , and also receives an upper direction force F 2  from the lower permanent magnet  55 . However, F 1  and F 2  are identical in amplitude but are different by 180 degrees in direction and therefore, these forces cancel each other. As a result, when the latch magnet  11  is placed in the magnetic field, it does not receive any net magnetic force from the magnetic field. Therefore, the actuator  22  maintains a stabilized attitude. 
     Next, operation of the actuator arm when the disk drive is in the non-operating condition will be explained. 
     When the disk drive is in the non-operating condition, the head slider  4  is located, as illustrated in the plan view of FIG.  4 ( a ), at the position within the CSS zone  31  provided at the internal circumference of the disk  1 . Moreover, the rotation of the disk  1  is stopped and the head slider  4  is in contact with the disk  1 . As illustrated in FIG.  4 ( b ), the latch magnet  11  is located at least partially outside the magnetic field generated by the permanent magnets  54 ,  55 . The entire latch magnet  11  or only a part of the latch magnet  11  may be located outside of the magnetic field. When the latch magnet  11  is located in this position, the latch magnet  11  receives right lower diagonal force F 3  from the upper permanent magnet  54 , and receives a right upper diagonal force F 4 , which is equal in amplitude to the right lower diagonal force F 3 , from the lower permanent magnet  55 . The forces F 3  and F 4  include force vectors in the vertical direction F 3   V , F 4   V  and the horizontal direction F 3   H , F 4   H . The vertical components F 3   V , F 4   V , of F 3  and F 4  effectively cancel each other and do not place rotational force on the actuator. However, the horizontal components F 3   H , F 4   H  are in the lateral direction between the permanent magnets. Therefore, the latch magnet  11  creates a magnetic force in the horizontal direction away from the permanent magnets  54 ,  55 . As a result, a torque to rotate the actuator  22  is generated, and thereby the actuator  22  is activated in the counterclockwise direction in FIG.  4 ( a ). When the actuator  22  is in contact with the stopper  5 , the head slider  4  stops when it is placed on the CSS zone  31 . If the disk drive receives a shock in this condition, since the actuator  22  is activated in the direction inversed or opposite from the data zone  32 , the head slider  4  is prevented from moving toward the data zone  32 , and thereby the data zone  32  can be protected. 
     According to the latch mechanism explained above, an intensified torque to latch the actuator  22  is generated by the magnetic force generated between the permanent magnets  54 ,  55  and thereby shock resistance can be improved. Also, since additional parts and complicated structure are not required, an intensified latch force can be obtained at a lower cost. In addition, since the latch magnet  11  does not generate torque when the disk drive is in the operating condition, the actuator  22  can be driven at a high speed. 
     In order to latch the actuator  22 , at least a part of the latch magnet  11  must be located partially outside of the magnetic field of the permanent magnets  54 ,  55  when the head slider  4  is located within the CSS zone  31 . Therefore, the latch magnet  11  is provided at an opposite position of the actuator  22  depending on the position of CSS zone  31 . In the disk drive explained above, the CSS zone  31  is provided at the internal circumference side of the disk  1  and the latch magnet  11  is located on the outer arm  26   b . The CSS zone  31  may be provided at the external circumference side of the disk  1  and in such a disk drive, the latch magnet  11  would be located on the inner arm  26   a.    
     In the first embodiment explained above, an auxiliary mechanism may be provided to generate an intensified torque for the latching purpose. The auxiliary mechanism will be explained below with reference to FIGS.  5 ( a ),  5 ( b ) and FIGS.  6 ( a ),  6 ( b ). 
     First, the auxiliary mechanism illustrated in FIGS.  5 ( a ) and  5 ( b ) will be explained. FIG.  5 ( a ) is perspective view of the coil arm  26 , while FIG.  5 ( b ) is a cross-sectional view along the line A—A of FIG.  5 ( a ). 
     On the base  42 , a projection  43  integrally formed to the base  42  is provided. An iron piece  44  is also mounted on the projection  43 . When the head slider  4  is located on the CSS zone  31 , the distance between iron piece  44  and latch magnet  11  is such that an attracting force toward the iron piece  44  is generated on the latch magnet  11 . As a result, a torque for isolating the actuator  22  from the data zone  32  is generated. According to the structure illustrated in FIGS.  5 ( a ) and  5 ( b ), the attracting force generated between the iron piece  44  and latch magnet  11  is added to further intensify the torque. 
     It is also possible to provide a mechanism to adjust the torque in the auxiliary mechanism of FIGS.  5 ( a ) and  5 ( b ). FIGS.  6 ( a ) and  6 ( b ) are cross-sectional views along the line crossing the coil arm  25 , illustrating auxiliary mechanisms adapted to adjust the torque. 
     FIG.  6 ( a ) illustrates an iron screw  45  which is provided as the auxiliary mechanism to the projection  43  provided on the base  42  (not shown). The screw  45  can be moved in the direction parallel to the rotating surface of the actuator  22 . Depending on the position of the screw  45 , the distance between the latch magnet  11  and the end portion of the screw  45  changes, causing the magnetic force generated between the latch magnet  11  and the screw  45  to change. Therefore, the torque required to rotate the actuator  22  can be adjusted depending on the position of the screw  45 . 
     In FIG.  6 ( b ), an elliptical plate  46  formed of iron material is provided as the auxiliary mechanism at the upper surface of the projection  43  provided on the base  42  (not shown). The elliptical plate  46  is adapted to rotate about a shaft in the same direction as the rotating or swinging shaft  21  (shown in FIG.  2 ( a )) of the actuator  22 . Depending on the rotating angle of the elliptical plate  46 , the distance between the elliptical plate  46  and the latch magnet  11  changes, causing the magnetic force between the latch magnet  11  and the elliptical plate  46  to change. Therefore, the torque for rotating the actuator  22  can be adjusted depending on the rotating angle of the elliptical plate  46 . 
     FIG.  7 ( a ) illustrates an actuator  22  according to the second embodiment of the present invention. In FIGS.  7 ( a ) and  7 ( b ), the disk drive is in the operating condition, while in FIGS.  8 ( a ) and  8 ( b ), the disk drive is in the non-operating condition. 
     In this embodiment, the direction of the magnetic flux of the latch magnet  11  is Inverted from that of the magnetic flux generated by the permanent magnets  54 ,  55 , and the latch magnet  11  is provided on the inner arm  26   a  of the actuator  22 . 
     First, operation of the actuator  22  when the disk drive is in the operating condition will be explained. 
     When the disk drive is in the operating condition, the head slider  4  is located, as illustrated in FIG.  7 ( a ), on the data zone  32  of the disk  1 , and the head element (not illustrated) mounted to the head slider  4  reads or writes data from or to the tracks on the data zone  32 . Moreover, the head slider  4  receives air flow generated by rotation of the disk  1  causing the head slider  4  to float above the surface of the disk  1 . In this case, the latch magnet  11  is placed, as illustrated in FIG.  7 ( b ), outside of the area between the permanent magnets  54 ,  55 . In this embodiment, the movable range of the actuator  22  is set so that the latch magnet  11  is not located in the area between the permanent magnets  54 ,  55  in both the operating or non-operating condition. The direction of the magnetic flux on the latch magnet  11  is different by 180 degrees from the magnetic flux generated by the spaced permanent magnets  54 ,  55 . Namely, the upper end of the latch magnet  11  is polarized as the N pole, while the lower end is polarized as the S pole. Here, an attracting force is generated between the latch magnet  11  and permanent magnets  54 ,  55 , but this attracting force may be neglected by providing sufficient distance between the latch magnet  11  and permanent magnets  54 ,  55 . 
     Next, operation of the actuator  22  when the disk drive is in the nonoperating condition will be explained. 
     When the disk drive is in the non-operating condition, the head slider  4  is located, as illustrated in FIG.  8 ( a ), on the CSS zone  31  provided within the internal circumference of the disk  1 . Moreover, the latch magnet  11  is most approximated, as illustrated in FIG.  8 ( b ), to the magnetic field generated by the permanent magnets  54 ,  55 . When the latch magnet  11  is located in this position, it receives a right upper diagonal-attractive force F 5  from the upper permanent magnet  54 , as illustrated in FIG.  8 ( b ) and also a right lower diagonal-attractive force F 6 , which is equal in amplitude to F 5  from the lower permanent magnet  55 . The forces F 5  and F 6  can be defined in terms of their respective vertical direction elements F 5   V , F 6   V  and horizontal direction elements F 5   H , F 6   H . The vertical components F 5   V , F 6   V  of F 5  and F 6  do not move the actuator laterally. However, the horizontal elements F 5   H , F 6   H  of F 5  and F 6  do create such a force. Therefore, the latch magnet  11  is drawn by magnetic force in the horizontal direction in the direction of the permanent magnets  54 ,  55 . As a result, a torque for latching the actuator  22  is generated and thereby the actuator  22  is activated in the clockwise direction as illustrated in FIG.  8 ( a ). The actuator  22  is placed in contact with the stopper  5  and the head slider  4  stops when it is placed in the CSS zone  31 . If the disk apparatus receives a shock in this condition, since the actuator  22  is activated in the direction inversed or opposite from the data zone  32 , the head slider  4  is impeded from moving toward the data zone  32 . Thereby, the data zone  32  can be protected. 
     According to this latch mechanism, first, an intensified torque for latching the actuator  22  is generated by the magnetic force generated between the permanent magnets  54 ,  55  and the latch magnet  11 , and thereby shock resistance can be improved. Second, since additional parts and complicated structure are not required, an intensified latch force can be obtained at a low cost. 
     In the second embodiment, when the head slider  4  is located in the CSS zone  31 , the latch magnet  11  must be close to the permanent magnets  54 ,  55 . Even in the second embodiment, the latch magnet  11  is provided at the appropriate position of the actuator  22  depending on the position of the CSS zone  31 . In the second embodiment, the CSS zone  31  is provided in the internal circumference side of the disk  1  and the latch magnet  11  is provided in the inner arm  26   a . The CSS zone  31  may also be provided at the external or outside circumference side of the disk  1  and in such a disk apparatus, the latch magnet  11  is provided on the outer arm  26   b.    
     In the present invention, the latch magnet  11  is arranged on the periphery of the magnetic field generated by the permanent magnets  54 ,  55 . According to this structure, the rotational inertia of the actuator  22  becomes small, processing time can be curtailed and power consumption can also be reduced. 
     Moreover, the direction of the magnetic flux generated by the latch magnet  11  is parallel to the magnetic flux in the magnetic field generated by the permanent magnets  54 ,  55 . Moreover, the latch magnet  11  is located outside of the magnetic field of the permanent magnets  54 ,  55  when the head slider  4  is located on the stop area or CSS zone  31 . Thereby, an intensified magnetic force is generated between the latch magnet  11  and the permanent magnets  54 ,  55 . As a result, an intensified latch force can be obtained and reliability is much improved. Moreover, it is no longer required to individually provide a member to attract the latch magnet  11  and the latch mechanism can be simplified. As a result, a reduction in size and a lower cost can be realized. 
     While the principles of the invention have been described above in connection with a specific apparatus and applications, it is to be understood that this description is made only by way of example and not as a limitation on the scope of the invention.