Patent Publication Number: US-2004052002-A1

Title: Voice coil motor for a hard disk drive

Description:
BACKGROUND INFORMATION  
       [0001] The present invention relates to magnetic hard disk drives. More specifically, the present invention relates to a method of assembling actuator driving mechanisms.  
       [0002] In the art today, different methods are utilized to improve recording density of hard disk drives. FIG. 1 provides an illustration of a typical disk drive. The typical disk drive has a head gimbal assembly (HGA) configured to read from and write to a magnetic hard disk  101 . The HGA and the magnetic hard disk  101  are mounted to the base  102  of a main board  103 . The disk  101  is rotated relative to the base  102  by a spindle motor  104 . The HGA typically includes an actuator arm  105  and a load beam  106 . The HGA supports and positions a magnetic read/write slider  107  above the magnetic hard disk  101 . The HGA is rotated relative to the base  102  along the axis of a bearing assembly  108 . The HGA is rotated by a magnetic field generated between a yoke  109  and a magnetic block  110 . A relay flexible printed circuit  111  connects a board unit  112  to the magnetic read/write slider  107 . A cover  113  protects the hard drive components as they operate. Often, the cover is attached by a set of screws  114 .  
       [0003]FIG. 2 provides an illustration of a head actuator mechanism as configured in the prior art. The HGA, in this embodiment including an actuator arm  105  and a loadbeam  106 , are coupled to an actuator driving mechanism. In one embodiment, more than one HGA are coupled to the actuator driving mechanism. The actuator driving mechanism can include a driving coil  201 , also called a voice coil, attached to a coil holding frame  202 . The magnetic field generated by the yoke  109  and magnetic block  110  acts upon the driving coil  201  causing the coil holding frame  202 , and by extension the HGA, to move. The HGA and actuator driving mechanism pivot around the bearing assembly  108 . A spacer  203  separates each HGA and actuator driving mechanism from the other HGA&#39;s and driving mechanisms on the bearing assembly  108 .  
       [0004]FIG. 3 provides an illustration of the assembled head actuator mechanism. The loadbeam  107  is coupled to actuator arm  108  to form the HGA. The driving coil  201  is coupled to the coil holding frame  202  to form the actuator driving mechanism. The HGA is bonded to the actuator driving mechanism. The entire head actuator mechanism pivots on the bearing assembly.  
       [0005]FIG. 4 provides an illustration of a driving coil  201  as it passes through a magnetic field. The driving coil  201  and the coil holding frame  202  pass through a magnetic field  401  created by the yoke  109  and the magnetic block  110  coupled to the base  102 . An electric current is sent through the driving coil  201 , creating a second magnetic field. The two magnetic fields interact causing the driving coil  201 , as well as the frame  202  holding the driving coil  201 , to move. The movement of the holding frame forces the head gimbal assembly to move in the same tangential direction.  
       [0006] The current design of the actuator driving mechanism has a number of drawbacks. Coupling the driving coil to the frame, as well as coupling the frame to the HGA, leaves numerous opportunities for the driving coil to become damaged. Distortion caused by the expansion and contraction due to the difference in thermal expansion coefficients of the plastic bobbins and the metallic coil may lead to a major resonance mode affecting the positioning of the transducer head on the magnetic disc. Additionally, the current magnet and yoke construction occupies a great deal of space.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0007]FIG. 1 provides an illustration of a typical disk drive.  
     [0008]FIG. 2 provides an illustration of a head actuator mechanism as configured in the prior art.  
     [0009]FIG. 3 provides an illustration of the assembled head actuator mechanism.  
     [0010]FIG. 4 provides an illustration of a driving coil as it passes through a magnetic field.  
     [0011]FIG. 5 illustrates one embodiment of an actuator driving mechanism as constructed in the present invention.  
     [0012]FIG. 6 illustrates in an exploded view one embodiment of the head actuator mechanism.  
     [0013]FIG. 7 illustrates in a perspective view one embodiment of the head actuator mechanism.  
     [0014]FIG. 8 illustrates in a perspective view one embodiment of the assembled hard disk drive.  
     [0015]FIG. 9 illustrates in a top view one embodiment of the assembled hard disk drive.  
    
    
     DETAILED DESCRIPTION  
     [0016] An actuator driving mechanism and a method of manufacture for that mechanism are disclosed. In one embodiment, the actuator driving mechanism includes a statically located stator generating a variable magnetic field to act upon a mobile rotator generating a permanent magnetic field. In a further embodiment, the stator includes a set of driving coils to generate the variable magnetic field and the rotator includes a permanent magnet coupled to a holding frame.  
     [0017]FIG. 5 illustrates one embodiment of an actuator driving mechanism as constructed in the present invention. In one embodiment, a statically located stator generates a variable magnetic field that acts on a rotator having a permanent magnetic field, causing the rotator to move tangentially to an axis of a pivot assembly attached to one end of the rotator. In one embodiment, the stator is a driving coil  501  with multiple windings. In a further embodiment, the individual windings are placed on either side of the rotator, the windings attached to an inner enclosure of the hard disk drive base. A current is passed through the driving coils  501  to create a first magnetic field. In an alternate embodiment, a single driving coil is positioned to one side of the rotator, the magnetic field varied by controlling the current flow through the single coil  501 . The first magnetic field acts upon a second magnetic field generated by the rotator. The magnitude of the first magnetic field can be altered adjusting the current through the driving coils  501 . In one embodiment, reversing the flow of current through the driving coils  501  reverses the direction of the rotator. In an alternate embodiment, each coil is set up to create a magnetic field in an opposing direction from the magnetic field created by the other coil. The coil that is given current depends on which direction the holding frame is to be moved. In one embodiment, the rotator includes a permanent magnet  502  and a holding frame  503 . In a further embodiment, the holding frame  503  is made of plastic by injection molding.  
     [0018]FIG. 6 illustrates in an exploded view one embodiment of the head actuator mechanism. In one embodiment, the actuator driving mechanism includes a stator and a rotator. In a further embodiment, the rotator includes a permanent magnet  502  coupled to a holding frame  503 . The stator includes a driving coil  501  positioned on either side of the permanent magnet and the holding frame  503 . In one embodiment, the HGA includes an actuator arm  105  coupled to a loadbeam  106 . In a further embodiment, the actuator arm  105  is coupled to the loadbeam  106  by laser welding. In this embodiment, the magnetic read/write head  107  is coupled to the end of the loadbeam. A relay flexible printed circuit  111  allows a board unit  112  to control the magnetic read/write head  107 .  
     [0019]FIG. 7 illustrates in a perspective view one embodiment of the head actuator mechanism. In one embodiment, the actuator driving mechanism is coupled directly to the HGA. The stator of the actuator driving mechanism causes the rotator of the actuator driving mechanism to move in a tangential direction around a pivot assembly. The tangential movement of the rotator causes the HGA to move in the same tangential direction on the opposite side of the pivot assembly.  
     [0020]FIG. 8 illustrates in a perspective view one embodiment of the assembled hard disk drive. The pivot assembly  108  couples the actuator driving mechanism and the HGA to the disk drive base  102 . As part of the actuator driving mechanism, driving coils  501  are positioned on either side of the rotator. In one embodiment, the driving coils  501  are attached to an inner enclosure of the base  102 . The driving coils  501  act upon the frame  502 , causing the rotator and the HGA to pivot around the pivot assembly  108 . The HGA moves the magnetic read/write head  107  in a radial direction along the magnetic disk. FIG. 9 illustrates in a top view one embodiment of the assembled hard disk drive.  
     [0021] Although several embodiments are specifically illustrated and described herein, it will be appreciated that modifications and variations of the present invention are covered by the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention.